Registration Dossier

Administrative data

Key value for chemical safety assessment

Effects on fertility

Description of key information

Wang, 2020, Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test (OECD 422). Wistar rat, whole body inhalation: 0, 8, 25, 75 ppm. NOAEL for systemic (F0 and F1 and neonatal toxicity for F1) = 75 ppm. LOAEL for port of entry effects (F0/F1) animals = 8 ppm.

Coder, 2021, Extended One-Generation Reproductive Toxicity study OECD 443, rats, whole body inhalation: 0, 4, 12, 30 ppm, LOAEL (local adverse effects) for F0and F1males and females = 4 ppm; NOAEL for F0and F1male and female (systemic toxicity) = 30 ppm

Link to relevant study records

Referenceopen allclose all

Endpoint:
extended one-generation reproductive toxicity - basic test design (Cohorts 1A, and 1B without extension)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
29-Jul-2019 - 20-Nov-2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
according to guideline
Guideline:
OECD Guideline 443 (Extended One-Generation Reproductive Toxicity Study)
Qualifier:
according to guideline
Guideline:
EU Method B.56 (Extended One-Generation Reproductive Toxicity Study)
GLP compliance:
yes (incl. QA statement)
Limit test:
no
Justification for study design:
SPECIFICATION OF STUDY DESIGN FOR EXTENDED ONE-GENERATION REPRODUCTION TOXICITY STUDY WITH JUSTIFICATIONS:

- Premating exposure duration for parental (P0) animals: 10 weeks (according to ECHA Guidance, the starting point for deciding on the length of premating exposure period should be ten weeks to cover the full spermatogenesis and folliculogenesis before the mating, allowing meaningful assessment of the effects on fertility)
- Basis for dose level selection: preliminary dose range finder (the highest dose level shall aim to induce some toxicity to allow comparison of effect levels and effects of reproductive toxicity with those of systemic toxicity)
- exclusion of extension of Cohort 1B (the conditions to include the extension of Cohort 1B are currently not met (please also refer to the summary of effects observed depicted below)
- Termination time for F2: not applicable
- exclusion of developmental neurotoxicity Cohorts 2A and 2B (No triggers for the inclusion of Cohorts 2A and 2B (developmental neurotoxicity) were identified, please also refer to the summary of effects observed depicted below)
- exclusion of developmental immunotoxicity Cohort 3 (No triggers for the inclusion of Cohort 3 (developmental immunotoxicity) were identified, please also refer to the summary of effects observed depicted below)
- Route of administration: inhalation (gas)
- Other considerations, e.g. on choice of species, strain, vehicle and number of animals: not applicable


Background information used to conclude on the study design:
- Uses and exposure assessment for professional workers and consumers: no consumer uses identified, several professional uses identified, which do not lead to significant exposure
- Genotoxicity: the substance has been shown to be not genotoxic (negative results in a bacterial reverse mutation assay (Ames test); negative results in an multiple-endpoint mutagenesis test with Chinese hamster ovary cells; negatvie results In an in vivo Mammalian Chromosome Aberration Assay; and in conclusion no classification as mutagenic)
- Bioaccumulaiton: there are no indications that an extended exposure durcation is needed to reach the steady state kinetics, as the substance has been shown to have a very low potential for bioaccumulation in aquatic and terrestrial organisms. The very low Bioconcentration factor (BCF = 3.2), derived based on an octanol-water coefficient of only -0.71 (BASF, 1988), clearly shows that persistence of the test substance in environmental compartments or organisms can be ruled out.
- Repeated-dose toxicity: The olfactory sensory cell is highly sensitive to the toxic effects of DMA, with minor lesions being produced in rodents even at the current threshold limit value of 10 ppm. A LOAEC can be set at 10 ppm (18.7 mg/m³), since only a few animals were affected with slight alterations.
- Neurotoxicity: there is no data avaialble which rises a concern for dimethylamine and its potential to induce neurotoxicity (please also refer to the summary of effects observed depicted below)
- Immunotoxicity: there is no data avaialble which rises a concern for dimethylamine and its potential to induce immunotoxicity (please also refer to the summary of effects observed depicted below)
- Endocrine effects and modes of action: there is no data available which rises a concern for dimethylamine and its potential to induce endocrine effects (please also refer to the summary of effects observed depicted below). The available repeated dose toxicity and reproductive toxicity studies do not provide indication of endocrine disrupting modes of action. Furthermore, no data rising concerns related to endocrine disruption is available which is derived from in vivo assays, from non-animal approaches for prediction to (endocrine disrupting modes of action, from eco-toxicity testing for predicting endocrine (disrupting) modes of action.

The available results for dimethylamine and its read-across substances can be summarised as follows:
The results of two chronic inhalation studies and two recent GLP guideline developmental studies showed that the target substance does not to produce adverse effects on reproductive organs or tissues and therefore no concern exists in relation with reproductive performance. In details, the toxicity of Dimethylamine was investigated in F-344 rats and B6C3F1 mice following a one-year inhalation exposure to 0, 10, 50, or 175 ppm (Buckley et al., 1985). After 6 or 12 month exposure period, animals were sacrificed and their organs and tissues, including reproductive organs, were examined for gross abnormalities. Any gross lesions were then collected and examined histopathologically. The only treatment-related changes were concentration-related lesions in the nasal passages: the respiratory epithelium and olfactory epithelium. The study results were confirmed by another chronic two-year inhalation study in F-344 rats (Gross et al., 1987). The only treatment-related lesions were abnormalities related to destruction of the nasal tissues. In the OECD 414 drinking water study conducted with Dimethyl hydrochloride (CAS 506-59-2) and rats, the NOAEL for maternal toxicity was 300 mg/kg bw/d, mid dose, based on decreased food consumption and salivation after treatment in the high dose dams (1000 mg/kg bw/d) (BASF, 2009). No test substance-related and/or biologically relevant differences with regard to conception rate, mean number of corpora lutea, implantation sites, pre- and postimplantation loss and resorptions (total, early and late) were observed. At necropsy, no test substance-related findings were observed in the dams. Reproductive organs examined grossly were similar to those of controls. The NOAEL for prenatal developmental toxicity was 1000 mg/kg bw/d because there was no evidence of an adverse effect of the test compound on fetal morphology. In the OECD 414 inhalation study with Dimethylamine and rabbits, there were no treatment-related effects on reproductive performance and morphology and histology of reproductive organs of dams (WIL Research, 2016). Gravid uterine weights in all treatment groups were similar to controls. Intrauterine growth and survival were unaffected by test substance exposure at all exposure levels. Parameters evaluated included post implantation loss, live litter size, mean fetal body weights, and fetal sex ratios. Mean numbers of corpora lutea and implantation sites were similar across all groups.
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL : Dimethylamine (CAS No. 124-40-3)
- Source (i.e. manufacturer or supplier) and lot/batch number of test material: Airgas Specialty Products
- Purity: pure

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Kept in a controlled temperature area set to maintain 18 °C to 24 °C
- Stability of the test material under the storage conditions provided by the Sponsor: The test substance is considered to be stable under the storage conditions provided by the Sponsor.
- Stability and homogeneity of the test material in the vehicle/solvent under test conditions (e.g. in the exposure medium) and during storage: see below
- Stability in the medium, i.e. sensitivity of the test material to hydrolysis and/or photolysis: see lebow
- Solubility and stability of the test material in the solvent/vehicle and the exposure medium: see below
- Reactivity of the test material with the incubation material used (e.g. plastic ware): not specified

Exposure Atmosphere Homogeneity Assessment
Homogeneity of exposure atmospheres was evaluated during the method development phase of the study. Four test locations and a reference location were used for sampling. Samples were collected and analyzed on the GC as rapidly as possible alternating from the reference and test location. For each location, the measured concentration was calculated as a percent difference from the reference location. Homogeneity was performed in triplicate for each test substance chamber. Based on mean differences from the reference location, spatial homogeneity was considered acceptable for all exposure chambers. Temporal stability was evaluated using the concentrations from the reference location. The variability during the homogeneity evaluation was acceptable for all exposure chambers. The generation and exposure trial performed before the start of animal exposure also demonstrated acceptable concentration stability for each exposure chambers.

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing (e.g. warming, grinding): yes - heated up tp 50 °C (For the test substance-treated groups, a gaseous exposure was generated from the primary cylinder. The exposure atmospheres were characterized by analyzed exposure concentrations using a gas chromatograph. Neat test substance (1,000,000 ppm) was delivered from the original cylinder to a 25-L Tedlar® bag using a 2-stage regulator (Matheson; Montgomeryville, PA). The neat test substance bag was placed into a box that was heated to approximately 50°C using an Omega® heat tape controlled, J-type thermocouple, and temperature controller (Model No. CN370, Omega Engineering, Inc.; Stamford, CT).
- Preliminary purification step (if any): not applicable
- Final concentration of a dissolved solid, stock liquid or gel: 0 ppm, 4 ppm, 12 ppm or 30 ppm

OTHER SPECIFICS
- Receipt Date: 15 Oct 2018
- Physical Description: Clear, colorless gas
Species:
rat
Strain:
Crj: CD(SD)
Remarks:
Crl:CD(SD)
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Crl:CD(SD) rats were received from Charles River Laboratories, Inc., Raleigh, NC
- Females (if applicable) nulliparous and non-pregnant: [yes]
- Age at study initiation: approximately 6 weeks old
- Weight at study initiation: between 167 and 280 g at the initiation of exposure
- Fasting period before study: none (Food and water were withheld during the exposure periods.)
- Housing: On arrival (F0) or following weaning (F1), animals were group housed (2 to 3 animals of the same sex) until cohabitation. During cohabitation, the animals were paired for mating in the home cage of the male. Following the breeding period, animals were individually housed. Animals were housed in solid-bottom cages containing appropriate bedding equipped with an automatic watering valve.
- Use of restrainers for preventing ingestion (if dermal): yes/no
- Diet (e.g. ad libitum): PMI Nutrition International, LLC Certified Rodent LabDiet® 5002 (meal) was provided ad libitum throughout the study, except during designated procedures.
- Water (e.g. ad libitum): Municipal tap water after treatment by reverse osmosis was freely available to each animal via an automatic watering system, except during designated procedures. Water bottles were provided, if required. [Animals were housed in solid-bottom cages containing appropriate bedding equipped with an automatic watering valve.]
- Acclimation period: After receipt at the Testing Facility, the Crl:CD(SD) rats were acclimated prior to initiation of dosing.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 68 °F to 78 °F (20 °C to 26 °C)
- Humidity (%): 30 % to 70 %
- Air changes (per hr): Ten or greater air changes per hour with 100 % fresh air (no air recirculation) were maintained in the animal rooms.
- Photoperiod (hrs dark / hrs light): 12-hour light/12-hour dark cycle
IN-LIFE DATES: From: 12 Jul 2019 To: 17 Mar 2020

Upon receipt, each animal was identified using a subcutaneously implanted electronic identification chip (BMDS system). Offspring were identified by tattoo markings applied to the digits after parturition and by microchip starting from PND 21. Pups selected for the F1 generation retained the dam number, followed by a hyphen "-" and the digit tattoo marking (i.e., 9999 01).

Animals were separated during designated procedures/activities. Each cage was clearly labeled with a color-coded cage card indicating study, group, animal, cage number(s), dosage level, and sex. Cages were arranged on the racks in group order.

Enrichment devices were provided to all animals as appropriate throughout the study for environmental enrichment and to aid in maintaining the animals’ oral health.

Animals were socially housed for psychological/environmental enrichment and were provided with environmental enrichment as appropriate to aid in maintaining the animals’ oral health.
Route of administration:
inhalation: gas
Type of inhalation exposure (if applicable):
whole body
Vehicle:
air
Remarks:
Filtered, humidified air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus:
For the filtered air control group, dry compressed air was mixed to achieve a similar humidity, airflow, and/or oxygen content to that in the test substance-exposed groups.
For the test substance-treated groups, a gaseous exposure was generated from the primary cylinder.
The exposure atmospheres were characterized by analyzed exposure concentrations using a gas chromatograph.

Exposure Atmosphere Generation Methods
For the atmosphere generation and exposure setup used for test substance exposures neat test substance (1,000,000 ppm) was delivered from
the original cylinder to a 25-L Tedlar® bag using a 2-stage regulator (Matheson; Montgomeryville, PA). The neat test substance bag was placed into a box that was heated to approximately 50°C using an Omega® heat tape controlled, J-type thermocouple, and temperature controller (Model No. CN370, Omega Engineering, Inc.; Stamford, CT).
Generation bags (250,000 ppm) were prepared by injecting 2 L of the neat test substance into a 10-L Tedlar® bag that was filled with 6 L of nitrogen. The volume of compressed nitrogen was measured using a dry test meter (DTM-200A, Elster American Meter Co.; Nebraska City, NE).
The generation bags were placed into a sealed polycarbonate box, one for each test substance chamber. The box was heated to approximately 35°C using a heat pad, J-type thermocouple, and Omega® temperature controller (Model No. 370). Using a regulator (model no. 8802K, Coilhose
Pneumatics; East Brunswick, NJ) and a Dwyer rotameter-type flowmeter (Model No. VFB-69-BV), dry compressed air was added to pressurize the generation box. A Dwyer Magnehelic® Indicating Transmitter pressure gauge was used to monitor the box pressure. The positive pressure within the box forced the test substance in the generation bag to be delivered to the chamber inlet using a flowmeter (Model No. 10, Barnant Co. / Gilmont Instruments; Barrington, IL) and needle valve. The gas entered the exposure chamber inlet via 1/8” Teflon tubing where it mixed with dilution supply air prior to entering the exposure chamber.

- Method of holding animals in test chamber: as it is a whole body inhalation procedure, the animals were kept freely in the exposure chamber. Exposures will be conducted using four 2000-L glass and stainless-steel whole-body exposure chambers. One chamber will be dedicated for the filtered air group (0 ppm, Group 1) and one chamber will be dedicated for each of the three test substance-exposed groups.
- Source and rate of air: dry compressed air (supplied from a breathing quality in-house compressed air source); moreover, air supplied to the whole-body chambers was provided from the Inhalation Department HEPA and charcoal-filtered, temperature- and humidity-controlled supply air source.
- Method of conditioning air: braught to a tmeperature of 35 °C
- System of generating particulates/aerosols: not applicable
- Temperature, humidity, pressure in air chamber: 35 °C; the control chamber was placed under positive pressure to prevent any further potential contamination from the test substance; the other chambers will be operated under dynamic conditions and at a slight negative pressure.
- Air flow rate: as such as the below mentionned air change range
- Air change rate: a minimum of 12 air changes per hour
- Method of particle size determination: not applicable
- Treatment of exhaust air: All chambers exhaust was directed to the facility exhaust system, which consists of redundant exhaust blowers preceded by activated-charcoal and HEPA-filtration units.

TEST ATMOSPHERE
- Brief description of analytical method used: Test substance concentration within the exposure chambers were sampled and analyzed at
approximately 60-minute intervals using a gas chromatograph (GC, Model No. 7890B, Agilent Technologies Inc.; Santa Clara, CA). Samples were collected from the approximate animal-breathing zone of the exposure chamber via 1/8-inch Teflon® tubing. Sampling of the exposure chambers occurred under the control of Chromeleon data acquisition software (version 7.2, ThermoFisher Scientific, Waltham, MA), sampling and analyses were performed as follows. The program controls an external multi-position valve (Cheminert®, Model No. 19P-0105L, Valco Instruments Co., Inc. Houston, TX) that permitted sequential sampling from the exposure room and each exposure chamber. Gas sampling injection onto the chromatography column occurred via an internal gas-sampling valve with a sample loop, the chromatogram was displayed and the area under the sample peak was calculated and stored. The Chromeleon program used an equation based on the GC calibration curve to calculate the measured concentration in ppm. WINH then acquired the calculated concentration to monitor and report values.
- Samples taken from breathing zone: yes (Samples were collected from the approximate animal-breathing zone of the exposure chamber via 1/8-inch Teflon® tubing.)

Administration of Test Material:
F0 males were exposed for 6 hours daily for 70 consecutive days prior to mating and continuing through the day prior to euthanasia. F0 females were exposed for 6 hours daily for 70 consecutive days prior to mating and continuing throughout mating, gestation, and lactation, through the day prior to euthanasia. For females with evidence of mating, exposures during gestation were conducted up to and including Gestation Day 20, at which time exposure was suspended through Lactation Day 4, to avoid confounding effects on parturition and nursing behavior. Exposures resumed on Lactation Day 5 and continued until 1 day prior to scheduled euthanasia. For females with evidence of mating that failed to deliver, exposures were resumed on Postmating Day 25. The offspring selected for the F1 generation began exposure following weaning until the day prior to euthanasia (PND 91 [Cohort 1A] or following the reproductive assessment [Cohort 1B]). All animals were exposed at approximately the same time each day.
Details on mating procedure:
- M/F ratio per cage: 1:1 [During cohabitation, the animals were paired for mating in the home cage of the male.]
- Length of cohabitation: 14 days
- Proof of pregnancy: [either vaginal plug or sperm in vaginal smear] referred to as [day 0] of pregnancy
- After ... days of unsuccessful pairing replacement of first male by another male with proven fertility.: not conducted
- Further matings after two unsuccessful attempts: [no / yes (explain)] not specified
- After successful mating each pregnant female was caged (how): Following the breeding period, animals were individually housed.
- Any other deviations from standard protocol:

Breeding Procedures
The F0 animals were paired on a 1:1 basis within each treatment group after 70 days of exposure. Positive evidence of mating was confirmed by the presence of a vaginal copulatory plug or the presence of sperm in a vaginal lavage. If evidence of mating was not apparent after 14 days, the animals were separated, with no further opportunity for mating. Animals cohabited over a 12 hour dark cycle were considered to have been paired for 1 day.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The exposure atmospheres were characterized by analyzed exposure concentrations using a gas chromatograph.
The Overall Mean Exposure Concentrations - F0 Generation (number of exposures = 137) were 0, 4.3 (+/- 0.89), 11.9 (+/- 0.89) and 30.7 (+/- 2.24) ppm
The Overall Mean Exposure Concentrations - F1 Generation (number of exposures = 113) were 0, 4.2 (+/- 0.80), 11.9 (+/- 1.36) and 31.1 (+/- 3.62) ppm
Duration of treatment / exposure:
6 hours
Frequency of treatment:
daily for 70 consequtive days prior to mating and continuing throughout mating, gestation, and lactation, through the day prior to euthanasia [For females with evidence of mating, exposures during gestation were conducted up to and including Gestation Day 20, at which time exposure was suspended through Lactation Day 4, to avoid confounding effects on parturition and nursing behavior. Exposures resumed on Lactation Day 5 and continued until 1 day prior to scheduled euthanasia. For females with evidence of mating that failed to deliver, exposures were resumed on Postmating Day 25. The offspring selected for the F1 generation began exposure following weaning until the day prior to euthanasia (PND 91 [Cohort 1A] or following the reproductive assessment [Cohort 1B]).]
Details on study schedule:
Control (filtered air) and test substance atmospheres were administered as a daily, 6-hour, whole body inhalation exposure. To accommodate protocol-specified activities, exposures were staggered as necessary.
Prior to each exposure, the selected animals were transferred to appropriate caging and transported to the exposure room. Following completion of daily exposures, the animals were returned to their home cages. Food and water were withheld during the exposure periods.
For the filtered air control group, dry compressed air was mixed to achieve a similar humidity, airflow, and/or oxygen content to that in the test substance-exposed groups.
For the test substance-treated groups, a gaseous exposure was generated from the primary cylinder.

- F1 parental animals not mated until [...] weeks after selected from the F1 litters.
- Selection of parents from F1 generation when pups were [4] days of age.
- Age at mating of the mated animals in the study: [between 90 and 120 days of age]

To reduce variability among the F1 litters, 8 pups/litter, 4 pups/sex when possible, were randomly selected on PND 4. Standardization of litter size was not performed on litters with fewer than 8 pups.
For the F1 generation, 2 F1 pups/sex/litter from all available litters (≥ 20 litters/group) were randomly selected prior to weaning and were assigned to the following cohorts: Cohorts 1A and 1B were assigned to reproductive/developmental toxicity testing. Animals assigned to Cohort 1B were maintained on study for breeding when the animals were between 90 and 120 days of age. Assignment of same-sex littermates to a particular cohort was avoided whenever possible. In addition, if there were an insufficient number of pups to fill a designated cohort, the following prioritization plan was used (highest to lowest priority): Cohort 1A, Cohort 1B.
Dose / conc.:
0 ppm
Dose / conc.:
4 ppm
Dose / conc.:
12 ppm
Dose / conc.:
30 ppm
No. of animals per sex per dose:
24 rats/sex/group
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: The exposure concentrations were determined from results of previous studies and were provided by the Sponsor. In a previous modified OECD 422 rat study (Wang, 2020), dimethylamine was administered via whole-body inhalation exposure at 8, 25, and 75 ppm in F0 male and female rats during the premating, mating, gestation, and lactation periods. In addition, F1 rats were exposed to the same concentrations from PND 28–40. Systemic toxicity was limited to lower body weights and body weight gains in the F1 generation, and only at the 75 ppm exposure concentration. Histopathological examination revealed dimethylamine-related adverse findings at all exposure levels in both the F0 and F1 generations. At the same dimethylamine exposure levels, nasal cavity injury was more prominent in F1 animals. In the F0 generation, lesions were restricted to Level II of the nasal cavity in all test substance-exposure groups. For F1 animals in the 8 and 25 ppm exposure groups, histological findings were generally limited to nasal cavity Level II and included respiratory and transitional epithelial degeneration and/or mixed cell inflammation, without ulceration. These findings were considered locally adverse based on the concurrent presence of inflammation and degeneration or regeneration. In the 75 ppm groups, the changes were consistently observed at multiple nasal cavity levels and ulceration was prominent at Level II. Based on these histopathological findings, the 75 ppm exposure level was considered excessive for an extended one-generation reproductive study and dose levels of 4, 12 and 30 ppm were selected.
- Rationale for animal assignment (if not random): F0 animals were assigned to groups by a stratified randomization scheme designed to achieve similar group mean body weights. Males and females were randomized separately. Animals in poor health or at extremes of body weight range were not assigned to groups.

To reduce variability among the F1 litters, 8 pups/litter, 4 pups/sex when possible, were randomly selected on PND 4. Standardization of litter size was not performed on litters with fewer than 8 pups.
For the F1 generation, 2 F1 pups/sex/litter from all available litters (≥20 litters/group) were randomly selected prior to weaning and were assigned to the following cohorts: Cohorts 1A and 1B were assigned to reproductive/developmental toxicity testing. Animals assigned to Cohort 1B were maintained on study for breeding when the animals were between 90 and 120 days of age. Assignment of same-sex littermates to a particular cohort was avoided whenever possible. In addition, if there were an insufficient number of pups to fill a designated cohort, the following prioritization plan was used (highest to lowest priority): Cohort 1A, Cohort 1B.

- Fasting period before blood sampling for clinical biochemistry: Animals were fasted overnight prior to blood collection.
Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Throughout the study, animals were observed for general health/mortality and moribundity twice daily, once in the morning and once in the afternoon. Animals were not removed from cage during observation, unless necessary for identification or confirmation of possible findings.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: The animals were removed from the cage, and a detailed clinical observation was performed once daily throughout the study. During the exposure period, these observations were performed prior to exposure. On exposure days, clinical observations were also recorded 0.5- 3 hours postexposure.
During social housing, some observations (e.g., fecal observations) may not have been attributable to an individual animal.

BODY WEIGHT: Yes
- Time schedule for examinations: Animals were weighed individually twice weekly throughout the study and prior to the scheduled necropsy. Once evidence of mating was observed, female body weights were recorded on Gestation Days 0, 4, 7, 11, 14, 17, and 20 and on Lactation Days 1, 4, 7, 11, 14, 21, and 28. A fasted weight was recorded on the day of necropsy. Terminal body weights were not collected from animals found dead.

FOOD CONSUMPTION:
Food consumption was quantitatively measured weekly throughout the study, except during the mating period. Once evidence of mating was observed, female food consumption was recorded on Gestation Days 0, 4, 7, 11, 14, 17, and 20 and Lactation Days 1, 4, 7, 14, 21, and 28. Food efficiency (body weight gained as a percentage of food consumed) was calculated and reported.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

OTHER:
Sample Collection for Clinical Pathology was conducted in Week 19.
Animals were fasted overnight prior to blood collection.
Urine was collected overnight using metabolism cages.
Blood samples for hematology and serum chemistry were collected from the jugular vein.
Blood samples for coagulation parameters were collected by necropsy personnel from the inferior vena cava at the time of euthanasia from animals euthanized via carbon dioxide inhalation.
K2EDTA was used for the anticoagulant on samples collected for hematology.
Sodium citrate was used for samples collected for clotting determinations.
Samples for serum chemistry were collected without anticoagulants.

Hematology
Blood samples were analyzed for the following parameters:
Total leukocyte count (WBC); Erythrocyte count (RBC); Hemoglobin (HGB); Hematocrit (HCT); Mean corpuscular volume (MCV); Mean corpuscular hemoglobin (MCH); Mean corpuscular hemoglobin concentration (MCHC); Platelet count (Platelet); Reticulocyte count; Percent (RETIC); Absolute (RETIC Absolute), Differential leukocyte count: - Percent and absolute; -Neutrophil (NEU); -Lymphocyte (LYMPH)
-Monocyte (MONO); -Eosinophil (EOS); -Basophil (BASO); -Large unstained cell (LUC); Red cell distribution width (RDW); Hemoglobin distribution width (HDW); Platelet estimate; Red cell morphology (RBC Morphology)

Coagulation
Blood samples were processed for plasma, and the plasma was analyzed for the following parameters: Activated partial thromboplastin time (APTT), Prothrombin time (PT).

Serum Chemistry
Blood samples were processed for serum, and the serum was analyzed for the following parameters: Albumin; Total protein; Globulin [by calculation]; Albumin/globulin ratio (A/G Ratio) [by calculation];Total bilirubin (Total BILI); Urea nitrogen; Creatinine; Alkaline phosphatase (ALP); Alanine aminotransferase (ALT); Aspartate aminotransferase (AST); Gamma glutamyltransferase (GGT); Glucose; Total cholesterol (Cholesterol); Calcium; Chloride; Phosphorus; Potassium; Sodium; Sorbitol dehydrogenase (SDH); Triglycerides (Triglyceride); Bile acid; Appearance

Urinalysis
Urine samples were processed and analyzed for the following parameters: Specific gravity (SG); pH; Urobilinogen (URO); Total volume (TVOL); Color (COL); Clarity (CLA); Protein (PRO); Glucose (GLU) ; Ketones (KET); Microscopy of sediment; Bilirubin (BIL); Occult blood (BLD); Leukocytes (LEU)
Oestrous cyclicity (parental animals):
Slides of the daily Vaginal lavages were evaluated microscopically to determine estrous cycle stage of each F0 female for 14 days prior to cohabitation and continuing until evidence of mating was observed or until the end of the mating period. The average cycle length was calculated for complete estrous cycles (i.e., the total number of returns to metestrus [M] or diestrus [D] from estrus [E] or proestrus [P], beginning 14 days prior to initiation of the mating period and continuing until the detection of evidence of mating). Estrous cycle length was determined by counting the number of days from the first M or D in a cycle to the first M or D in a subsequent cycle. The cycle during which evidence of mating was observed for a given animal was not included in the mean individual estrous cycle length calculation. Vaginal lavages were also performed on the day of necropsy to determine the stage of the estrous cycle.
At the end of the study, the overall pattern of each female was characterized as regularly cycling, irregularly cycling, not cycling, or insufficient data.
Sperm parameters (parental animals):
Parameters examined in [all/P/F1/F2] male parental generations:
[testis weight, epididymis weight, daily sperm production, sperm count in testes, sperm count in epididymides, enumeration of cauda epididymal sperm reserve, sperm motility, sperm morphology, other:]

Sperm Evaluations
Immediately upon euthanasia, the reproductive tract of each male was exposed via a ventral mid line incision. The right cauda epididymis was excised and weighed. An incision was made in the distal region of the right cauda epididymis, and it was then placed in Dulbecco's phosphate buffered saline (maintained at approximately 37 °C) with 10 mg/mL BSA. After a minimum 10 minute incubation period, a sample of sperm was loaded onto a slide with a 100 µm chamber depth for determination of sperm motility. Because sperm motility can be affected by temperature shock, all pipettes, slides, and diluents were warmed in an incubator, and motility determinations were performed under constant temperature (approximately 37 °C). Analysis of a minimum of 200 motile and nonmotile spermatozoa per animal (if possible) in all groups was performed by the analyzer.
The motility score (percent) for motile (showing motion only) and progressively motile (showing net forward motion) sperm was reported:
Percent Motile (or Progressively Motile) Sperm = (Number of Motile (or Progressively Motile) Sperm/ Total Number of Sperm Counted) * 100

The right epididymis was then placed in modified Davidson’s solution for subsequent microscopic examination. Sperm morphology was evaluated by light microscopy via a modification of the wet mount evaluation technique (Linder et al., 1992). Abnormal forms of sperm (double heads, double tails, microcephalic, or megacephalic, etc.) from a differential count of 200 spermatozoa per animal, if possible, were recorded.
The left testis and cauda epididymis from all males were weighed, stored frozen, homogenized, and analyzed for determination of homogenization resistant spermatid count and calculation of sperm production rate (Blazak et al., 1985). An aliquot of each sample was added to a solution containing a DNA specific fluorescent dye (the dye stains DNA that is present in the head of the sperm). For analysis, each sample was mixed, and an aliquot was placed on a slide with a 20 µm chamber depth. Illumination from a xenon lamp within the analyzer allowed for the visualization and quantitation of the sperm. A minimum of 200 cells, if possible, or up to 20 fields were counted for each sample. The sperm production rate was calculated as follows:
Sperm Production Rate = (No. of Sperm Per Gram of Tissue/ 6.1. days)
* where 6.1 days is the rate of turnover of the germinal epithelium
Litter observations:
STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: [yes]
- If yes, maximum of 8 pups/litter (4]/sex/litter as nearly as possible); excess pups were killed and discarded.

PARAMETERS EXAMINED
The following parameters were examined in [F1 / F2 / F3] offspring:
[number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities, anogenital distance (AGD), pup weight on the day of AGD, presence of nipples/areolae in male pups, other. Particular attention should be paid to the external reproductive genitals which should be examined for signs of altered development; gross evaluation of external genitalia]
- Viability: Litters were observed for general health/mortality and moribundity twice daily, once in the morning and once in the afternoon. A daily record of litter size was maintained. Animals were not removed from cage during observation, unless necessary for identification or confirmation of possible findings.
- Observations: The animals were removed from the cage, and a detailed clinical observation was performed on PND 1, 4, 7, 14, 21, and 28. Any abnormalities in nesting and nursing behavior were recorded
- Sex Determination: Pups were individually sexed on PND 0, 4, 14, 21, and 28.
- Body Weights: Pups were weighed individually on PND 1, 4 (before culling), 7, 14, 21, and 28.

Preweaning Developmental Landmarks
Anogenital Distance: The anogenital distance of all pups was measured on PND 1. Anogenital distance was defined as the distance from the caudal margin of the anus to the caudal margin of the genital tubercle (Gallavan et al., 1999).
Assessment of Areolas/Nipple Anlagen: On PND 13, all male pups were evaluated for the presence of thoracic nipples/areola (Gray et al., 1999). The number of nipples was recorded.

Thyroid Hormone Analysis
Sample Collection: Blood samples for thyroid hormone analyses were collected (on PND4 and PND 28; each time prior to 1200 hours in order to avoid normal diurnal fluctuation in thyroid hormone levels) via cardiac puncture of animals anesthetized by inhalation of isoflurane (PND 4 culled pups) or via the jugular vein (PND 28 nonselected pups) into tubes without anticoagulants.
Details on samples collected on PND4: Samples were collected from culled pups and pooled by litter until a total of 10 samples/dosage level were obtained. To the extent possible, samples from the first 10 litters at each dosage level with sufficient numbers of culled pups were used.
Details on samples collected on PND28: Samples collected from nonselected pups (10/sex/group).
Sample Processing: Blood samples were maintained at room temperature and allowed to clot. Serum was isolated in a refrigerated centrifuge and stored in a freezer set to maintain a target of -70 °C.
Sample Analysis: Blood samples were analyzed for the followingparameters: Thyroxine (Total T4); Thyroid Stimulating Hormone (TSH)
Samples to be analyzed for T4 were transferred to the Charles River Ashland Bioanalytical Chemistry Department; analyses were performed using a validated UHPLC/MS/MS assay. Samples to be analyzed for TSH were transferred to the Charles River Ashland ADME/DMPK Department; analyses were performed using a qualified radioimmunoassay.

F1 Developmental Landmarks
Balanopreputial Separation: Each male was observed for balanopreputial separation beginning on PND 35 (Korenbrot et al., 1977). Examination of the males was continued daily until balanopreputial separation was present, and the age of attainment was recorded. Body weights were recorded at the age of attainment of this landmark. Any abnormalities of genital organs (e.g., persistent preputial threads) were noted.
Vaginal Patency: Each female was observed for vaginal perforation beginning on PND 25 (Adams et al., 1985). Examination of the females was continued daily until vaginal patency was present, and the age of attainment was recorded. Body weights were recorded at the age of attainment of this landmark. Any abnormalities of genital organs (e.g., persistent vaginal threads) were noted.

GROSS EXAMINATION OF DEAD PUPS:
[yes] : Moribund pups will be euthanized by an intraperitoneal injection of sodium pentobarbital. Stillborn pups, pups found dead and any pups that are euthanized in extremis will be dissected (including the heart and brain examined by a mid-coronal slice) by a technique described by Stuckhardt and Poppe.6 If a skeletal anomaly is suspected, the pups will be eviscerated, cleared, and stained with Alizarin Red S as described by Dawson7 and examined. Cannibalized pups will be discarded without necropsy. Any findings will be recorded as either developmental variations
or malformations. Representative specimens with malformations may be preserved in 10 % neutral-buffered formalin at the discretion of the Study Director.

ASSESSMENT OF DEVELOPMENTAL NEUROTOXICITY:

ASSESSMENT OF DEVELOPMENTAL IMMUNOTOXICITY:
Postmortem examinations (parental animals):
SACRIFICE
- Male animals: All surviving animals [describe when, e.g. as soon as possible after the last litters in each generation were produced.]
- Maternal animals: All surviving animals [describe when, e.g. after the last litter of each generation was weaned.]

Unscheduled Death: A necropsy was conducted for animals that died on study, and specified tissues were saved. For females that delivered, the number of former implantation sites were recorded.
Scheduled Euthanasia: All surviving animals, including females that failed to deliver, were euthanized by carbon dioxide inhalation.

GROSS NECROPSY
- Gross necropsy consisted of [external and internal examinations including the cervical, thoracic, and abdominal viscera.]
All animals were subjected to a complete necropsy examination, which included examination of the external surface, all orifices, the cranial cavity, the external surfaces of the brain and spinal cord, and the thoracic, abdominal, and pelvic cavities, including viscera. Special attention was paid to the organs of the reproductive system. The numbers of former implantation sites were recorded for females that delivered. The number of unaccounted-for sites was calculated for each female by subtracting the number of pups born from the number of former implantation sites observed. For females that failed to deliver, a pregnancy status was determined, and specific emphasis was placed on anatomic or pathologic findings that may have interfered with pregnancy.

HISTOPATHOLOGY / ORGAN WEIGTHS
The tissues indicated below were collected, prepared for microscopic examination and weighed, respectively.
Representative samples of the tissues indicated below were collected from all animals and preserved in 10% neutral buffered formalin, unless otherwise indicated.
Tissues examined: Adrenals (2); Aorta; Bone with marrow (sternebrae); Brain; Coagulating glands (2); Eyes with optic nerve (2); Gastrointestinal tract (Esophagus; Stomach; Duodenum; Peyer’s Patches; Jejunum; Ileum; Cecum; Colon; Rectum); Heart; Kidneys (2); Lacrimal/Harderian glands; Liver (sections of 2 lobes); Lymph node; Axillary (2); Mandibular (2); Mesenteric; Levator ani and bulbocavernosus (LABC) muscle group ; Larynx; Lungs (including bronchi, fixed by inflation with fixative); Nasal cavities with turbinates; Ovariesb and oviduct (2); Pancreas; Peripheral nerve (sciatic); Pituitary; Pharynx; Prostate; Mandibular salivary glands (2); Seminal vesicles (2); Skeletal muscle (quadriceps); Skin with mammary gland; Spinal cord (cervical); Spleen; Testes with epididymides (2) and vas deferens; Thymus; Thyroids (with parathyroids if present [2]); Trachea; Urinary bladder; Uterus with cervix and vagina; All gross lesions (all groups)

The organs indicated below were weighed at necropsy for all scheduled euthanasia animals. Organ weights were not recorded for animals found dead. Paired organs were weighed together, unless otherwise noted. Organ to body weight ratio (using the terminal body weight) and organ to brain weight ratios were calculated.
Organs examined: Adrenal glands; Brain; Epididymidesa (total and cauda); Heart; Kidneys; Levator ani and bulbocavernosus (LABC) muscle group; Liver; Lungs; Ovaries; Pituitary gland; Prostate gland;
Seminal vesicles with coagulating glands (with accessory fluids); Spleen; Testes; Thyroids with parathyroids; Thymus gland; Uterus with oviducts and cervix

Histology
Ovarian tissues for quantitative assessment were processed at PAI Durham. All other tissues were processed at the Testing Facility. Tissues listed above from all animals in the control and high-dose groups and from all animals found dead, as well as nasal section Level II and gross lesions from all animals in all groups, and reproductive organs (ovaries, oviducts, uterus, cervix, and vagina of females; testes, epididymides, prostate gland, seminal vesicles, coagulating glands, and levator ani/bulbocavernosus [LABC] muscle group of males) of all animals suspected of reduced fertility (e.g., those that failed to mate, conceive, sire or deliver healthy offspring, or for which estrous cyclicity or sperm number, motility or morphology were affected) were embedded in paraffin, sectioned, mounted on glass slides, and stained with hematoxylin and eosin. Processing of the testes, epididymides, and ovaries were performed as noted below.
Sections of 2–4 microns of the testis (transverse) and epididymis (longitudinal) were stained with PAS and hematoxylin staining in addition to the routine hematoxylin and eosin (H&E) staining. Testes and epididymides from males that were found dead were stained with H&E only. The following regions of the epididymis were embedded in paraffin: caput, corpus, and cauda; the vas deferens was examined when possible.
Five (5) sections were taken approximately 100 µm apart from the inner third of each ovary from any F0 females suspected of reduced fertility, e.g., those that failed to mate, conceive, sire or deliver healthy offspring, or for which estrous cyclicity or sperm number, motility or morphology were affected. In addition, a single section was taken from remaining F0 females for a qualitative bilateral evaluation of each ovary. For females found dead, a single section from each ovary was qualitatively evaluated.

Histopathology
Pathological evaluation was performed by a board-certified veterinary pathologist. Tissues were selected for microscopic examination from all animals in the control and high dose groups and from all animals found dead. Nasal section level two and gross lesions were examined from all animals in all groups.
In addition, reproductive organs (ovaries, oviducts, uterus, cervix, and vagina of females; testes, epididymides, prostate gland, seminal vesicles, coagulating glands, and levator ani/bulbocavernosus [LABC] muscle group of males) of all animals suspected of reduced fertility (e.g., those that failed to mate, conceive, sire or deliver healthy offspring, or for which estrous cyclicity or sperm number, motility or morphology were affected) were subjected to a histopathologic evaluation.
Histopathological examination of the testis included a qualitative assessment of the stages of spermatogenesis (Russell et al., 1990). For males that survived to the scheduled necropsy, microscopic evaluation included a qualitative assessment of the relationships between spermatogonia, spermatocytes, spermatids, and spermatozoa seen in cross-sections of the seminiferous tubules. The progression of these cellular associations defines the cycle of spermatogenesis. In addition, sections of both testes were examined for the presence of degenerative changes (e.g., vacuolation of the germinal epithelium, a preponderance of Sertoli cells, sperm stasis, inflammatory changes, mineralization, and fibrosis).
For any F0 female suspected of reduced fertility, e.g., those that failed to mate, conceive, sire or deliver healthy offspring, or for which estrous cyclicity or sperm number, motility or morphology were affected, a quantitative histopathologic evaluation of multiple sections was conducted. This examination included enumeration of the total number of primordial follicles (Bolon et al., 1997; Bucci et al., 1997; Picut et al., 2008).
Postmortem examinations (offspring):
SACRIFICE
- The F1 offspring not selected as parental animals and all F2 offspring were sacrificed at [Study Days 134-137] days of age.
- These animals were subjected to postmortem examinations (macroscopic and/or microscopic examination) as follows:

LItters - Unscheduled Deaths: A necropsy was conducted for animals that died on study, and specified tissues were saved.
If necessary, for humane reasons, animals were euthanized as per Testing Facility SOPs. These animals underwent necropsy, and specified tissues were retained.
Intact offspring that were found dead or euthanized for humane reasons during PND 0–4 were necropsied using a fresh dissection technique, which included examination of the heart and major vessels (Stuckhardt and Poppe, 1984). Pups with external abnormalities that would warrant further skeletal examination were eviscerated and stained for subsequent skeletal evaluation (Dawson, 1926). Findings were recorded as developmental variations or malformations, as appropriate. A gross necropsy was performed on any pup found dead after PND 4.

Litters . Scheduled Euthanasia: On PND 4, culled pups were euthanized by exsanguination (those pups used for blood/thyroid collection) or an intraperitoneal injection of sodium pentobarbital.
On PND 28, nonselected pups were euthanized by carbon dioxide inhalation.

Litters: Terminal procedures were conducted on PND 4 for Groups 1-4 (No. of animals: 119; 94, 126 and 105, respectively) and on PND 28 for groups 1-4 (No. of animals: 99, 79, 98 and 75, respectively).

LITTERS - GROSS NECROPSY
- Gross necropsy consisted of [external and internal examinations including the cervical, thoracic, and abdominal viscera.]
On PND 4, 1 culled pup/sex/litter was subjected to a complete necropsy examination. Pups were necropsied using a fresh dissection technique, which included examination of the heart and major vessels (Stuckhardt and Poppe, 1984). All remaining culled pups were discarded without examination.
On PND 28, nonselected pups were subjected to a complete necropsy examination, with emphasis on developmental morphology and organs of the reproductive system.

LITTERS - HISTOPATHOLOGY / ORGAN WEIGTHS
The tissues indicated below were collected rom 1 culled pup/sex/litter on PND 4 and preserved in 10% neutral buffered formalin, prepared for microscopic examination and weighed, respectively.
Tissues examined: Trachea (with thyroid gland); All gross lesions
Representative samples of the tissues identified below were collected from 1 nonselected F1 pup/sex/litter on PND 28 and preserved in 10 % neutral buffered formalin:
Brain; Liver; Nasal cavities with turbinates; Ovaries (2); Skin with mammary gland, Spleen Testes (2); Thymus; Thyroids; All gross lesions

Representative specimens with malformations and gross lesions from offspring found dead or euthanized for humane reasons were preserved in 10 % neutral buffered formalin.

The organs ispecified below were weighed at necropsy from 1 nonselected F1 pup/sex/litter on PND 28. Organ to body weight ratio (using the terminal body weight) and organ to brain weight ratios were calculated.
Organs examined: Brain; Liver; Spleen; Thymus; Thyroid

F1 Cohort 1A: Terminal procedures were conducted on PND 91 for Groups 1-4 (No. of animals: 20 males and 20 females for group 1-3 and 19 males and 19 females for group 4) and for Males on PND 133-140 (No. of animals: 23, 20, 22 and 19, respectively) and for Females on Gestation Day 15d (No. of animals: 24, 21, 23 and 19, respectively).

F1 Cohort 1A:
Unscheduled Deaths: A necropsy was conducted for animals that died on study, and specified tissues were saved.
Scheduled Euthanasia: All surviving animals were euthanized by exsanguination following isoflurane inhalation.

F1 Cohort 1A - GROSS NECROPSY
- Gross necropsy consisted of [external and internal examinations including the cervical, thoracic, and abdominal viscera.]
All animals were subjected to a complete necropsy examination, which included examination of the external surface, all orifices, the cranial cavity, the external surfaces of the brain and spinal cord, and the thoracic, abdominal, and pelvic cavities, including viscera. Special attention was paid to the organs of the reproductive system.
Cohort 1B females were subjected to a laparohysterectomy and macroscopic examination (animals with evidence of mating or appearing to be gravid). The number of corpora lutea on each ovary were recorded and the number of viable and nonviable embryos, early resorptions, and the total number of implantations was recorded, if possible. Uteri with no macroscopic evidence of implantation were opened and subsequently placed in 10% ammonium sulfide solution for detection of early implantation loss (Salewski, 1964).

F1 Cohort 1A - HISTOPATHOLOGY / ORGAN WEIGTHS
The organs indicated below were weighed at necropsy for all scheduled euthanasia animals. Organ weights were not recorded for animals found dead. Paired organs were weighed together, unless otherwise noted. Organ to body weight ratio (using the terminal body weight) and organ to brain weight ratios were calculated.
Organs examined: Adrenal glands, Brain; Epididymides (total and cauda); Heart, Kidneys, Levator ani and bulbocavernosus (LABC) muscle group, Liver, Lungs, Ovaries, Pituitary gland, Prostate gland,
Seminal vesicles with coagulating glands (with accessory fluids), Spleen, Testes, Thyroids with parathyroids, Thymus gland, Uterus with oviducts and cervix

Representative samples of the tissues identified below were collected from all animals and preserved in 10% neutral buffered formalin:
Adrenal glands (2); Aorta; Bone with marrow (sternebrae); Brain; Coagulating glands (2); Eyes with optic nerve (2), Gastrointestinal tract (Esophagus, Stomach, Duodenum, Peyer’s Patches, Jejunum, Ileum, Cecum, Colon, Rectum, Heart, Kidneys (2), Lacrimal/Harderian glands, Levator ani and bulbocavernosus (LABC) muscle group, Liver (section of 2 lobes), Lungs (including bronchi, fixed by
inflation with fixative), Lymph node (axillary [2], mandibular [2], and mesenteric); Ovariesb and oviducts (2); Pancreas; Peripheral nerve (tibial); Pituitary; Prostate; Mandibular salivary gland (2), Seminal vesicles (2); Skeletal muscle (rectus femoris), Skin with mammary gland and subcutis, Spinal cord (cervical, thoracic, lumbar), Spleen, Testes with epididymides (2) and vas deferens, Tongue, Thymus, Thyroids (with parathyroids if present [2]), Trachea, Urinary bladder, Uterus with cervix and vagina, All gross lesions (all groups)

Histology:
Ovarian tissues for quantitative assessment were processed at PAI Durham. All other tissues were processed at the Testing Facility. Tissues enlisted above from F1 animals in Cohort 1A in the control and high-dose groups and from all animals found dead, as well as nasal section level two and gross lesions from all animals in all groups, and reproductive organs (ovaries, oviducts, uterus, cervix, and vagina of females; testes, epididymides, prostate gland, seminal vesicles, coagulating glands, and levator ani/bulbocavernosus [LABC] muscle group of males) of all animals suspected of reduced fertility (e.g., those that failed to mate, conceive, sire or deliver healthy offspring, or for which estrous cyclicity or sperm number, motility or morphology were affected) were embedded in paraffin, sectioned, mounted on glass slides, and stained with hematoxylin and eosin. Processing of the testes, epididymides, and ovaries were performed as noted below.
Sections of 2–4 microns of the testis (transverse) and epididymis (longitudinal) were stained with PAS and hematoxylin staining in addition to the routine hematoxylin and eosin (H&E) staining. Testes and epididymides from males that were found dead were stained with H&E only. The following regions of the epididymis were embedded in paraffin: caput, corpus, and cauda; the vas deferens was examined when possible.
Five (5) sections were taken approximately 100 µm apart from the inner third of each ovary from all F1 Cohort 1A females at the scheduled termination. In addition, a single section was taken from all F1 Cohort 1A females for a qualitative bilateral evaluation of each ovary.
The coagulating glands, ovaries, pituitary gland, prostate gland, seminal vesicles, testes with epididymides, uterus with cervix and vagina, and gross lesions from Cohort 1B animals were processed to the block stage (in paraffin).

Histopathology (Cohort 1A)
Pathological evaluation was performed by a board-certified veterinary pathologist. Tissues enlisted above for microscopic examination were evaluated from all animals in the control and high dose groups and from all animals found dead. Nasal section level two and gross lesions were examined from all animals in all groups.
In addition, reproductive organs of all animals suspected of reduced fertility, e.g., those that failed to mate, conceive, sire or deliver healthy offspring, or for which estrous cyclicity or sperm number, motility or morphology were affected, were subjected to a histopathologic evaluation.
Histopathological examination of the testis included a qualitative assessment of the stages of spermatogenesis (Russell et al., 1990). For males that survived to the scheduled necropsy, microscopic evaluation included a qualitative assessment of the relationships between spermatogonia, spermatocytes, spermatids, and spermatozoa seen in cross-sections of the seminiferous tubules. The progression of these cellular associations defines the cycle of spermatogenesis. In addition, sections of both testes were examined for the presence of degenerative changes (e.g., vacuolation of the germinal epithelium, a preponderance of Sertoli cells, sperm stasis, inflammatory changes, mineralization, and fibrosis). When possible, sections of the rete testis were examined in the F1 Cohort 1A males.
For all F1 Cohort 1A females in the control and high-dose groups at scheduled termination, a quantitative histopathologic evaluation of multiple sections was conducted. This examination included enumeration of the total number of primordial follicles primordial follicles (Bolon et al., 1997; Bucci et al., 1997; Picut et al., 2008).
For the F1 Cohort 1A females, a tiered approach was used for the evaluation of ovarian follicle counts. A quantitative evaluation of primordial and primary follicles (combined) and corpora lutea were performed on 1 of 5 sections from each of the control and high exposure group animals, as a screening measure for potential adverse effects. If any 1 of the mean counts of the high-exposure level group differed by more than 10% of the corresponding count of the control group, then the quantitative evaluation was extended to include all 5 sections of ovary per animal, as a more definitive measure for potential adverse effects. If the results were equivocal, the quantitative evaluation was performed on the low- and mid-exposure groups for F1 females in Cohort 1A.
Statistics:
Each mean was presented with the standard deviation (S.D.) and the number of animals or cages (N) used to calculate the mean. Where applicable, the litter was used as the experimental unit. Due to the use of significant figures and the different rounding conventions inherent in the types of software used, the means, standard deviations, and coefficients of variation on the summary and individual tables may differ slightly. Therefore, the use of reported individual values to calculate subsequent parameters or means will, in some instances, yield minor variations from those listed in the report data tables. Data obtained from nongravid animals were excluded from statistical analyses following the mating period. Statistical analyses were not performed on F0 female weekly food or body weight data after 1 or more animals had entered the gestation phase or remained in the lactation phase.
All statistical tests were performed using WTDMS™ unless otherwise noted. Analyses were conducted using two tailed tests (except as noted otherwise) for minimum significance levels of 1 % and 5 %, comparing each test substance exposed group to the control group by sex.
Clinical signs:
no effects observed
Description (incidence and severity):
No test substance-related clinical findings were noted for F0 animals in the 4, 12, and 30 ppm groups at the detailed clinical observations and at 0.5-3 hours postexposure. Clinical observations noted in the test substance-exposed groups occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not exposure-related.
Dermal irritation (if dermal study):
not examined
Mortality:
mortality observed, non-treatment-related
Description (incidence):
In the 30 ppm group, 1 male (Animal No. 5997) was found dead on Study Day 46 and 1 female (Animal No. 6100) was found dead on Study Day 133. Although both animals had test substance-related microscopic lesions in the nasal cavity that were similar to those described in other animals in this group examined at scheduled necropsy, a specific cause of death was not determined based on microscopic examination. These deaths were deemed unlikely to be test substance related based on the lack of any other evidence of systemic toxicity at this dosage level.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
weekly bodyweights: No test substance related effects on mean body weights, body weight gains, and cumulative body weight gains were noted in the 4, 12, and 30 ppm groups. The values in the test substance exposed groups were generally comparable to the control group values for the pre-mating period (females) or the entire generation (males).
Sporadic statistically significant values were observed in a non-toxicologically relevant manner, or in a non exposure related manner and were considered incidental.

Body weight during Gestation: Mean maternal body weights, body weight gains, and cumulative body weight gains were unaffected by test substance exposure during gestation. Differences between the control, 4, 12, and 30 ppm groups were slight and not statistically significant.

Body weights during Lactation: Mean maternal body weights, body weight gains, and cumulative body weight gains were unaffected by test substance exposure during lactation. Sporadic statistically significant values were observed in a non-toxicologically relevant manner, or in a non exposure related manner and were considered incidental.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
weekly Food consumption, evaluated as g/animal/day, and food efficiency in the 4, 12, and 30 ppm groups was unaffected by test substance exposure. The values in the test substance exposed groups were generally comparable to the control group values for the pre-mating period (females) or the entire generation (males). Sporadic statistically significant values were observed in a non-toxicologically relevant manner, or in a non exposure related manner and were considered incidental.

Food consumption during gestation: Mean maternal food consumption, evaluated as g/animal/day and g/kg/day, and food efficiency were unaffected by test substance exposure during gestation. Differences between the control, 4, 12, and 30 ppm groups were slight and not statistically significant.

Food consumption during lactation: Mean maternal food consumption, evaluated as g/animal/day, and food efficiency were unaffected by test substance exposure during lactation. Differences between the control, 4, 12, and 30 ppm groups were slight and not statistically significant. Sporadic statistically significant values were observed transiently, in a non-toxicologically relevant manner, or in a non exposure related manner and were considered incidental.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Description (incidence and severity):
Haematology: There were no test substance-related effects on hematology parameters. A statistically significantly lower mean % basophil value was noted for males in the 30 ppm group; however, the magnitude of the change was minimal. Other differences from the control group were slight and not statistically significant.
Coagulation: There were no test substance-related effects on coagulation parameters. Differences from the control group were slight and not statistically significant.
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
There were no test substance-related effects on serum chemistry parameters. A statistically significantly lower mean urea nitrogen value was noted for females in the 30 ppm group; however, this was attributed to the lower values for 2 females. Other differences from the control group were slight and not statistically significant.
Endocrine findings:
no effects observed
Description (incidence and severity):
Thyroid hormone Analysis:
Higher T4 levels noted for F0 males (54.8% and 87.9% respectively) and F0 females (68.7 and 65.3 % respectively) in the 12 and 30 ppm groups were considered incidental based on the lack of a dose response (females), atypically low control group mean values in comparison with Charles River Historical Control Data, and the lack of an effect on TSH levels in both males and females.
In addition, mean values across all treated groups were within the range of the Historical Control Data. In the control group, only 5 and 6 (of 10) samples were available for analysis (due to insufficient serum quantity), for both males and females, which may have contributed to the noted differences. Lastly, there were no noted differences in thyroid organ weights or corresponding changes in thyroid histopathology and given the lack of any correlating findings, and because an increase in thyroid hormones is generally not considered toxicologically relevant, these changes were considered likely to be unrelated to test substance administration.
Urinalysis findings:
no effects observed
Description (incidence and severity):
There were no test substance-related effects on urinalysis parameters. Differences from the control group were slight and not statistically significant.
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Dimethylamine was associated with microscopic findings in the nasal cavity (level II) at ≥ 4 ppm in males and females of the F0 generation. There was a dose-related increase in incidence and/or severity of respiratory epithelial hyperplasia and transitional epithelial hyperplasia in males and females, and mixed cell inflammation in the males. The mixed cell inflammation was similar in females at 4 and 12 ppm and at a higher incidence in the 30 ppm group.
Histologically, the transitional and respiratory epithelial hyperplasia was characterized by focal to multifocal increased numbers of cells and disorganization. There was loss or clustering of goblet cells and/or decreased cilia in the affected respiratory epithelium. Inflammation, when present, was associated with the hyperplasia and included variable numbers of neutrophils, lymphocytes, and plasma cells. These histologic lesions were considered locally adverse at ≥ 4 ppm based on the presence of inflammation and epithelial hyperplasia.
Other microscopic findings observed were considered incidental, of the nature commonly observed in this strain and age of rats, and/or were of similar incidence and severity in control and treated animals and, therefore, were considered unrelated to administration of dimethylamine. One female in the 30 ppm group (Animal No. 6036) had an incidental mammary adenocarcinoma, which correlated grossly with the subcutaneous mass. This tumor was deemed incidental because of the single occurrence and known spontaneous occurrence in young Sprague Dawley rats (Kuzutani et al., 2012; Oishi et al., 1995).
In the F0 generation, there were nine pairs of males and females with suspected reduced fertility. The suspected reduced fertility was not associated with dimethylamine-related histologic findings. Three pairs were in Group 2 (4 ppm), one pair in Group 3 (12 ppm), and five pairs in Group 4 (30 ppm). Of these, 3 females (Animal No. 6088 in Group 2; 6087 in Group 4; and 6131 in Group 4) had histologic findings in the ovary consistent with early reproductive senescence (increased numbers of atretic follicles, decreased numbers of corpora lutea), which can be occasionally seen in this age of rat (Vidal, 2017). The cause of the suspected reduced fertility in the other animals was not determined by light microscopic evaluation.
F0 generation females with suspected reduced fertility had quantitative counts of primordial/small growing ovarian follicles performed. Primordial/small growing ovarian follicular counts of these animals were similar to values obtained from the F1 Cohort 1A control females (155.95 ± 53.8). Dimethylamine exposure did not have any effect on the number of primordial/small growing ovarian follicles in these F0 animals.
Histopathological findings: neoplastic:
not examined
Other effects:
no effects observed
Reproductive function: oestrous cycle:
no effects observed
Description (incidence and severity):
not further specified
Reproductive function: sperm measures:
no effects observed
Description (incidence and severity):
No test substance related effects were observed on F0 sperm parameters (mean testicular and epididymal sperm numbers and sperm production rate, motility, progressive motility, and morphology) in males at any dosage concentration. Differences from the control group were slight and were not statistically significant.
Reproductive performance:
no effects observed
Description (incidence and severity):
A decrease in male and female fertility and copulation/conception was noted in the 30 ppm group, where 5 of 24 mating pairs (Female Nos. 6036, 6060, 6084, 6087, and 6131 and Male Nos. 5955, 5957, 5968, 5969, and 6016) did not produce a litter; differences from the control group were not statistically significant. There were no macroscopic or microscopic lesions to account for reduced fertility in any of the listed animals, with the exception of 2 females in the 30 ppm group that exhibited abnormal estrous cycles (≥ 6 consecutive days of estrus, Nos. 6087 and 6131) and had histologic findings in the ovary consistent with early reproductive senescence (increased numbers of atretic follicles, decreased numbers of corpora lutea), which can be occasionally seen in this age of rat (Vidal, 2017); these observations were hence considered incidental and unrelated to dimethylamine administration. Male No. 5968, which did not sire a litter with the first female (No. 6084), was also paired with a second female (No. 6062) and successfully sired a litter.
In addition, 3 and 1 mating pairs in the 4 and 12 ppm groups also did not sire a litter, but these findings were considered unrelated to dimethylamine exposure, based on the lack of a dose response. Based on the lower male and female fertility in the 30 ppm group, F1 animals assigned to Cohort 1B for follow-up reproductive assessments were bred to obtain reproductive performance data for the F1 generation.
There were no effects of test substance exposure on reproductive performance in the 4 and 12 ppm groups and the mean numbers of days between pairing and coitus in the test substance exposed groups were comparable to the control group value. The mean lengths of estrous cycles in these groups were also comparable to the control group value. None of these differences were statistically significant.
Gestation length / parturition:
No test substance related effects were noted on mean gestation lengths or the process of parturition at any dosage concentration. Mean F0 gestation lengths in the test substance exposed groups were comparable to the control group value. Differences were slight and were not statistically significant. The mean gestation lengths in the 4, 12, and 30 ppm groups were 22.0, 22.0, and 22.0 days, respectively, compared to mean gestation lengths of 22.1 days in the concurrent control group and 21.9 days in the Charles River Ashland historical control data. No signs of dystocia were noted at any dosage/exposure level.
Dose descriptor:
NOAEC
Remarks:
systemic toxicity
Effect level:
30 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Absence of any systemically adverse effects in either generation (F0 and F1 males and females) during the study
Dose descriptor:
LOAEC
Remarks:
local effects
Effect level:
4 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Dose descriptor:
NOAEC
Remarks:
reproductive toxicity
Effect level:
30 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Based on the lack of any evidence of reproductive toxicity at any exposure level following the evaluation of reproductive performance, sperm measurements, and estrous cyclicity
Clinical signs:
not specified
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Dermal irritation (if dermal study):
not examined
Mortality:
not specified
Description (incidence):
please refer to observations described in the fields for F1 (Cohort 1A).
Body weight and weight changes:
no effects observed
Description (incidence and severity):
Maternal Body Weights during Gestation (Cohort 1B). Mean maternal body weights, body weight gains, and cumulative body weight gains were unaffected by test substance exposure during gestation. Differences between the control, 4, 12, and 30 ppm groups were slight and not statistically significant.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
Maternal Food Consumption and Food Efficiency during Gestation (Cohort 1B): Mean maternal food consumption, evaluated as g/animal/day, and food efficiency were unaffected by test substance exposure during gestation. Differences between the control, 4, 12, and 30 ppm groups were slight and not statistically significant.
Food efficiency:
not specified
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Water consumption and compound intake (if drinking water study):
not specified
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Ophthalmological findings:
not specified
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Haematological findings:
not specified
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Clinical biochemistry findings:
not specified
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Endocrine findings:
no effects observed
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Urinalysis findings:
not specified
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
Cohort 1A: No dimethylamine-related organ weight changes were noted. Statistically significantly higher mean left cauda epididymal weights were noted at 12 and 30 ppm; however, mean values were within the historical control data range, and a significant increase in weight was not observed in the contralateral right cauda epididymis. In addition, there was no effect on cauda epididymal weights for animals in Cohort 1B (see Section 8.4.16.2). Therefore, this finding was not considered to be related to dimethylamine administration. There were isolated organ weight values that were statistically different from their respective controls. There were, however, no patterns, trends, or correlating data to suggest these values were toxicologically relevant. Thus, the organ weight differences observed were considered incidental and unrelated to administration of dimethylamine.
Cohort 1B: No dimethylamine-related organ weight changes were noted in the males of Cohort 1B. Organ weights were not collected from females as they were in gestation.
Gross pathological findings:
no effects observed
Description (incidence and severity):
Cohort 1A: No dimethylamine-related gross findings were noted. The gross findings observed were considered incidental, of the nature commonly observed in this strain and age of rats, and/or were of similar incidence in control and treated animals and, therefore, were considered unrelated to administration of dimethylamine.
Cohort 1B: No dimethylamine-related gross findings were noted. The gross findings observed were considered incidental, of the nature commonly observed in this strain and age of rats, and/or were of similar incidence in control and treated animals and, therefore, were considered unrelated to administration of dimethylamine.
Neuropathological findings:
not specified
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Dimethylamine-related microscopic findings are summarized in Text Table 33 (please refer to field 'Any other information on results (incl. tables).
Dimethylamine was associated with microscopic findings in the nasal cavity (level II) in all test substance groups for males and females of the F1 Cohort 1A. There was a dose-related increase in incidence and/or severity of respiratory epithelial hyperplasia, transitional epithelial hyperplasia, vacuolar degeneration of the respiratory epithelium, and vacuolar degeneration of the transitional epithelium in males and females at ≥ 4 ppm. Inflammation was similar in all dose groups in males and showed a slightly increased incidence at 12 and 30 ppm in females compared to 4 ppm.
Dimethylamine-related lesions included minimal to moderate hyperplasia of the respiratory and transitional epithelium, minimal to mild mixed cell inflammation, and minimal vacuolar degeneration of the respiratory epithelium, and minimal to mild vacuolar degeneration of the transitional epithelium.
Histologically, the epithelial hyperplasia and inflammation were as described for the F0 generation animals (See Section 8.2.14.). The vacuolar degeneration was characterized by a single to few, round to irregular, variably sized cytoplasmic vacuoles and disorganized epithelium.
Other microscopic findings observed were considered incidental, of the nature commonly observed in this strain and age of rats, and/or were of similar incidence and severity in control and treated animals and, therefore, were considered unrelated to dimethylamine exposure. There were no dimethylamine-related effects on primordial/small growing ovarian follicle counts between control and 30 ppm F1 females from Cohort 1A. Any variation in counts between those groups was due to normal biological variability.
Histopathological findings: neoplastic:
no effects observed
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Other effects:
no effects observed
Description (incidence and severity):
please refer to observations described in the fields for F1 (Cohort 1A).
Reproductive function: oestrous cycle:
not specified
Reproductive function: sperm measures:
not specified
Reproductive performance:
no effects observed
Description (incidence and severity):
Reproductive Performance (Cohort 1B): No test substance related effects on F1 reproductive performance were observed at any exposure concentration. No statistically significant differences were noted between the control and test substance exposed groups. Males that did not sire a litter numbered 0, 2, 1, and 1 in the control, 4, 12, and 30 ppm groups, respectively. Females that had evidence of mating but were nongravid numbered 0, 1, 1, and 1 in the same respective groups.
The mean numbers of days between pairing and coitus in the test substance-exposed groups were comparable to the control group value. The statistically significantly higher precoital interval noted in the 4 ppm group was attributed to a single mating pair in this group that had a precoital interval of 12 days, and successfully produced a litter. The mean lengths of estrous cycles in these groups were also comparable to the control group value. None of these differences were statistically significant.
Dose descriptor:
NOAEL
Remarks:
reproductive toxicity
Effect level:
30 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: lack of any evidence of reproductive toxicity at any exposure level following the evaluation of reproductive performance, sperm measurements, and estrous cyclicity in the F0 and Final Report Laboratory Project ID 00235551 Page 69 F1 generations
Dose descriptor:
NOAEL
Remarks:
systemic toxicity
Effect level:
30 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
other: absence of any systemically adverse effects in either generation (F0 and F1 males and females) during the study
Dose descriptor:
LOAEL
Remarks:
local effects
Effect level:
4 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: observation of locally adverse histologic lesions at all exposure levels
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
F1 Generation Following Weaning: No test substance related clinical findings were noted during the generation at the detailed clinical observations or at 0.5-3 hours postexposure observations. Findings noted in the test substance exposed groups occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not exposure related.
Dermal irritation (if dermal study):
not examined
Mortality / viability:
mortality observed, non-treatment-related
Description (incidence and severity):
F1 Generation Following Weaning: One F1 generation Cohort 1B male (Animal No. 6077-05) at 12 ppm was found dead on PND 63. No remarkable clinical or macroscopic findings were noted for this male. No other mortality or moribundity was noted at the higher exposure level 30 ppm; therefore, this single death was considered incidental and not attributed to test substance exposure.
All other F1 parental animals in the control, 4, 12, and 30 ppm groups survived to the scheduled necropsy.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
F1 Generation Following Weaning: No test substance related effects on mean body weights, body weight gains, and cumulative body weight gains were noted in the 4, 12, and 30 ppm groups. The values in the test substance exposed groups were generally comparable to the control group values for the premating period (females) or the entire generation (males). Statistically significant differences from the control group were discordant in direction of change, transient, and/or did not occur in a dose related manner.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
F1 Generation Following Weaning: Food consumption, evaluated as g/animal/day, and food efficiency in the 4, 12, and 30 ppm groups were unaffected by test substance exposure. The values in the test substance exposed groups were generally comparable to the control group values for the pre-mating period (females) or the entire generation (males). Statistically significant differences from the control group were discordant in direction of change, transient, and/or did not occur in a dose related manner.
Food efficiency:
no effects observed
Description (incidence and severity):
F1 Generation following Weaning: Food consumption, evaluated as g/animal/day, and food efficiency in the 4, 12, and 30 ppm groups were unaffected by test substance exposure. The values in the test substance exposed groups were generally comparable to the control group values for the pre-mating period (females) or the entire generation (males). Statistically significant differences from the control group were discordant in direction of change, transient, and/or did not occur in a dose related manner.
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Description (incidence and severity):
Cohort 1A: There were no test substance-related effects on hematology parameters. Statistically significantly higher mean red cell distribution width values were noted for females in the 12 and 30 ppm groups; however, the magnitudes of change were small, and the mean values were comparable to males in the control, 4, 12 and 30 ppm groups. The statistically significant differences were ascribed to the atypically low control group value for females, rather than an effect of dimethylamine exposure. All other differences from the control group were slight and not statistically significant.
There were no test substance-related effects on coagulation parameters. Differences from the control group were slight and not statistically significant.
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
Cohort 1A: There were no test substance-related effects on serum chemistry parameters. Differences from the control group were slight and not statistically significant.
Urinalysis findings:
no effects observed
Description (incidence and severity):
Cohort 1A: There were no test substance-related effects on urinalysis parameters. Differences from the control group were slight and not statistically significant.
Sexual maturation:
no effects observed
Description (incidence and severity):
Balanopreputial separation: Mean ages of attainment of balanopreputial separation and mean body weights at the age of attainment were unaffected by test substance exposure. The mean ages of attainment of balanopreputial separation were 45.0, 45.5, and 44.8 days in the 4, 12, and 30 ppm groups, respectively, when compared to 45.6 in the control group. Mean body weights at the age of attainment were 242.7 g, 247.9 g, and 242.5 g in the same respective groups compared to 255.1 g in the control group. None of the differences from the control group were statistically significant.
Vaginal Patency: Mean ages of attainment of vaginal patency and mean body weights at the age of attainment were unaffected by test substance exposure. The mean ages of attainment of vaginal patency were 34.1, 34.5, and 34.4 days in the 4, 12, and 30 ppm groups, respectively, when compared to 34.1 days in the control group. Mean body weights at the age of attainment were 128.1 g, 129.9 g, and 129.8 g in the same respective groups compared to 132.9 g in the control group. None of the differences from the control group were statistically significant.
Anogenital distance (AGD):
no effects observed
Description (incidence and severity):
F1 Generation before weaning: The anogenital distances (absolute, relative to pup body weight, and relative to the cube root of pup body weight) in the 4, 12, and 30 ppm groups were comparable to the control group values. Differences from the control group were slight and not statistically significant.
Nipple retention in male pups:
no effects observed
Description (incidence and severity):
Areolae/nipple anlagen in the F1 male pups was unaffected by parental exposure to the test substance when evaluated on PND 12. The test substance treated group values were not statistically different from the control group values.
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Terminal body weights for males were comparable across all groups. No test substance related effects on organ weights (absolute, relative to final body weight, and relative to brain weight) were observed for F1 pups on PND 28 at any exposure concentration when the test substance exposed groups were compared to the control group. A statistically significantly higher mean thymus weight relative to final body weight was noted for males in the 30 ppm group; however, mean absolute and relative to brain weight thymus weights were not affected.
Terminal body weights for females in the 4, 12 and 30 ppm groups were 5.2 %, 9.4 % and 7.5 % lower respectively than the control group; differences were statistically significant at 12 ppm only. Although non-dose responsive, these differences were considered to be a consequence of the lower mean body weight gains noted across all test substance groups during PND 21-28 and were considered test substance related but nonadverse based on the transient nature of the change. A statistically significantly lower mean brain weight was noted for females in the 4 ppm group; however, this did not occur in a dose-related manner. Other differences from the control group were slight and not statistically significant.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Unscheduled Deaths
Twenty (8), 25 (8), 8 (4), and 7 (4) pups (litters) in the control, 4, 12, and 30 ppm groups, respectively, were found dead or euthanized in extremis from PND 0 through the selection of the F1 generation. No internal findings that could be attributed to parental test substance exposure were noted at the necropsies of pups that were found dead or euthanized in extremis. Aside from the presence or absence of milk in the stomach, no internal findings were noted for pups in the test substance-exposed groups. Pup No. 6041-05 in the control group had malformations of hemimelia (both hindlimbs, consisting of short femurs), claw absent (all digits of both hindlimbs, consisting of absent phalanges), and bent tail (distal).

PND 4 Culled Pups
No internal findings that could be attributed to parental exposure with the test substance were noted at the necropsy of culled pups euthanized on PND 4. No internal findings were noted.

PND 28 Nonselected Pups
No internal findings that could be attributed to parental exposure to the test substance were noted at the necropsy of pups euthanized on PND 28. Pup No. 6035-09 in the 12 ppm group had a kidney cyst and dilated renal pelvis and Pup No. 6111-02 in the 30 ppm group had a kidney cyst; however, these findings were noted for single animals in each group. No other internal findings were noted. No other internal findings were noted.

PND 28 Pups Selected for Hormone Analysis
At the PND 28 necropsy of F1 weanlings selected for organ weights, no test substance-related internal findings were observed at any exposure concentration. Internal findings in the test substance-exposed groups were limited to a small eye (left), liver (all lobes), spleen and thymus for Pup No. 6032-06 in the 12 ppm group; however, these findings were noted for a single pup and were not noted in an exposure-related manner. Pup No. 6065-13 in the control group had multiple cysts on the kidney. No other internal findings were noted.
Histopathological findings:
effects observed, treatment-related
Description (incidence and severity):
Dimethylamine was associated with microscopic findings in the nasal cavity (level II) in all test substance groups for males and females of the F1 Cohort 1A. There was a dose-related increase in incidence and/or severity of respiratory epithelial hyperplasia, transitional epithelial hyperplasia, vacuolar degeneration of the respiratory epithelium, and vacuolar degeneration of the transitional epithelium in males and females at ≥ 4 ppm. Inflammation was similar in all dose groups in males and showed a slightly increased incidence at 12 and 30 ppm in females compared to 4 ppm.
Dimethylamine-related lesions included minimal to moderate hyperplasia of the respiratory and transitional epithelium, minimal to mild mixed cell inflammation, and minimal vacuolar degeneration of the respiratory epithelium, and minimal to mild vacuolar degeneration of the transitional epithelium.
Histologically, the epithelial hyperplasia and inflammation were as described for the F0 generation animals (See Section 8.2.14.). The vacuolar degeneration was characterized by a single to few, round to irregular, variably sized cytoplasmic vacuoles and disorganized epithelium.
Other microscopic findings observed were considered incidental, of the nature commonly observed in this strain and age of rats, and/or were of similar incidence and severity in control and treated animals and, therefore, were considered unrelated to dimethylamine exposure.
There were no dimethylamine-related effects on primordial/small growing ovarian follicle counts between control and 30 ppm F1 females from Cohort 1A. Any variation in counts between those groups was due to normal biological variability.
Other effects:
no effects observed
Description (incidence and severity):
Gestation Day 15 Laparohysterectomy:
Mean numbers of corpora lutea, implantation sites, and intrauterine survival of the F2 embryos were unaffected by test substance exposure to F1 animals at exposure concentrations of 4, 12, and 30 ppm. No statistically significant differences from the control group were noted. Intrauterine parameters evaluated included mean litter proportions of postimplantation loss and mean numbers and litter proportions of viable embryos.
Behaviour (functional findings):
not examined
Developmental immunotoxicity:
not examined
F1 Gerneation prior to weaning:
PND 0 Litter Data and Postnatal Survival:
The mean number of pups born, live litter size, percentage of males per litter at birth, and postnatal survival between birth and PND 0 (relative to number born), PND 0–1, 1–4 (pre selection), 4 (post-selection)–7, 7–14, 14–21, 21-28, and from birth to PND 4 (pre-selection) and PND 4 (post-selection)–28 were unaffected by the test substance at all dosage concentrations. Differences from the control group were slight, were not statistically significant, and/or did not occur in an exposure related manner.
Observations:
The general physical condition (defined as the occurrence and severity of clinical findings) of all F1 pups in this study was unaffected by test substance exposure. Nineteen (8), 25 (8), 8 (4), and 7 (4) pups (litters) in the control, 4, 12, and 30 ppm groups, respectively, were found dead or euthanized in extremis. Six (6), 9 (4), 3 (3), and 3 (3) pups (litters) in the same respective groups were missing and presumed to have been cannibalized.
Offspring Body Weights:
Mean male and female pup body weights and body weight changes in the 4, 12, and 30 ppm groups were unaffected by parental test substance exposure generally throughout the postnatal period. Lower mean body weight gains were noted across all test substance exposure groups during PND 21-28 resulting in mean pup body weights that were 3.3 to 6.1 % lower than the control group on PND 28 for both males and females; differences were dose responsive for females only. Based on the low magnitude of the noted differences, and the transient nature of the deficits versus controls (recovery was noted for both males and females by PND 35), these differences were considered test substance related, but nonadverse.

Thyroid Hormone Analysis
PND 4 Culled Pups
No test substance-related effects were noted for culled pups on PND 4 at any exposure level. Differences from the control group were slight and not statistically significant.
PND 28 Pups Selected for Hormone Analysis
No test substance-related effects were noted for pups on PND 28 at any exposure level. A statistically significantly higher mean TSH value was noted for females in the 12 ppm group; however, this did not occur in a dose-related manner. Other differences from the control group were slight and not statistically significant.

Estrous Cycle data (Cohort 1A):
The mean ages at the first occurrence of estrus in the 4, 12, and 30 ppm groups (35.8, 36.3, and 36.4 days, respectively) were generally comparable to the control group (36.0 days). In addition, the duration from vaginal opening to first estrus in these same respective groups (2.8, 2.9, and 2.8 days) was generally comparable to the control group (2.7 days). None of the differences were statistically significant.
The mean lengths of estrous cycles in the test substance-treated groups from PND 75-91 were also comparable to the control group value. None of these differences were statistically significant.

Sperm Evaluations (Cohort 1A):
No test substance related effects were observed on F1 sperm parameters (mean testicular and epididymal sperm numbers and sperm production rate, motility, progressive motility, and morphology) in males at any exposure concentration. Differences from the control group were slight and were not statistically significant.

Thyroid Hormone Analysis (Cohort 1A):
There were no test substance-related effects on thyroid hormones in F1 Cohort1A pups on PND 91. Differences from the control group were slight and not statistically significant.
Dose descriptor:
NOAEC
Remarks:
for neonatal and developmental toxicity
Generation:
F1
Effect level:
30 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Absence of any effects during the preweaning period
Dose descriptor:
LOAEC
Remarks:
local effects
Generation:
F1
Effect level:
4 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Dose descriptor:
NOAEC
Remarks:
reproductive toxicity
Generation:
F1
Effect level:
30 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Based on the lack of any evidence of reproductive toxicity at any exposure level following the evaluation of reproductive performance, sperm measurements, and estrous cyclicity
Reproductive effects observed:
no

Reproductive performance (Fo-Generation):

F0male and female reproductive parameters are presented in the following table.

Results of F0Reproductive Performance

Parameter

Dosage Level (mg/kg/day)

CRL HCa

Mean (Range)

0

4

12

30

Male Mating Index (%)

100.0

100.0

100.0

100.0

96.2 (86.7-100.0)

Female Mating Index (%)

100.0

100.0

100.0

100.0

96.7 (86.7-100.0)

Male Fertility Index (%)

100.0

87.5

95.8

82.6

89.0 (70.0-100.0)

Female Fertility Index (%)

100.0

87.5

95.8

79.2

89.3 (70.0-100.0)

Male Copulation Index (%)

100.0

87.5

95.8

82.6

93.2 (70.0-100.0)

Female Conception Index (%)

100.0

87.5

95.8

79.2

93.1 (70.0-100.0)

Estrous Cycle Length (days)

4.3

4.3

4.2

4.5

4.6 (3.9-7.6)

Pre-Coital Interval (days)

2.5

2.3

2.8

2.1

3.0 (1.8-4.7)

a Charles River Ashland historical control data.

Dimethylamine-related microscopic findings are summarized in the following Table:
Summary of Microscopic Findings – F0Generation

 

Males

Females

Group

1

2

3

4

1

2

3

4

Target Exposure Concentration (ppm)

0

4

12

30

0

4

12

30

No. Animals Examined

24

24

24

23

24

24

24

23

Nasal Level II (No. Examined)

24

24

24

23

24

24

24

23

Hyperplasia, Respiratory Epithelium

(0)a

(6)

(24)

(20)

(0)

(5)

(12)

(21)

     Minimal

0

6

15

9

0

4

10

13

     Mild

0

0

9

8

0

1

2

7

     Moderate

0

0

0

3

0

0

0

1

Hyperplasia, Transitional Epithelium

(0)

(14)

(23)

(22)

(0)

(15)

(15)

(23)

     Minimal

0

11

13

7

0

14

12

9

     Mild

0

3

6

7

0

1

3

12

     Moderate

0

0

4

8

0

0

0

2

Inflammation, mixed cell

(2)

(11)

(16)

(22)

(4)

(16)

(16)

(23)

     Minimal

2

11

16

22

4

15

16

23

     Mild

0

0

0

0

0

1

0

0

a  Numbers in parentheses represent the number of animals with the finding.

Text Table - Ovarian Primordial/Small Growing Ovarian Follicle Counts – F0 Generation

 Animal No.  Group

Target Exposure

Concentration (ppm)

Total Primordial/Small Growing

Ovarian Follicles

 
 6088  2  4  246
6055  2  4  112
 6082  2  4  61
 6108  3  12  187
 6084  4  30  102
 6060  4  30  169
 6087  4  30  186
 6131  4  30  154
 6036  4  30  162

Reproductive Performance Cohort 1B

F1male and female reproductive parameters are presented in the following table:
Results of F1Reproductive Performance

Parameter

Dosage Level (mg/kg/day)

CRL HCa

Mean (Range)

0

4

12

30

Male Mating Index (%)

100.0

95.0

100.0

100.0

96.2 (86.7-100.0)

Female Mating Index (%)

100.0

95.2

100.0

100.0

96.7 (86.7-100.0)

Male Fertility Index (%)

100.0

90.0

95.5

94.7

89.0 (70.0-100.0)

Female Fertility Index (%)

100.0

90.5

95.7

94.7

89.3 (70.0-100.0)

Male Copulation Index (%)

100.0

94.7

95.5

94.7

93.2 (70.0-100.0)

Female Conception Index (%)

100.0

95.0

95.7

94.7

93.1 (70.0-100.0)

Estrous Cycle Length (days)

4.0

4.1

4.1

4.2

4.6 (3.9-7.6)

Pre-Coital Interval (days)

2.4

3.8*

2.7

2.7

3.0 (1.8-4.7)

a Charles River Ashland historical control data

* Significantly different from the control group at 0.05

Histopathology (Cohort 1A)

Dimethylamine-related microscopic findings are summarized in the following table:

Summary of Microscopic Findings – F1Generation Cohort 1A

 

Males

Females

Group

1

2

3

4

1

2

3

4

Target Exposure Concentration (ppm)

0

4

12

30

0

4

12

30

No. Animals Examined

20

20

20

19

20

20

18

19

Nasal Level II (No. Examined)

20

20

20

19

20

20

18

19

Hyperplasia, Respiratory Epithelium

(0)a

(19)

(18)

(18)

(0)

(8)

(16)

(17)

     Minimal

0

9

1

3

0

8

9

4

     Mild

0

10

15

9

0

0

5

12

     Moderate

0

0

2

6

0

0

2

1

Hyperplasia, Transitional Epithelium

(0)

(20)

(19)

(19)

(0)

(14)

(18)

(17)

     Minimal

0

8

1

2

0

13

7

4

     Mild

0

11

16

8

0

1

8

9

     Moderate

0

1

2

9

0

0

3

4

Inflammation, mixed cell

(1)

(18)

(19)

(18)

(0)

(13)

(17)

(17)

     Minimal

1

16

19

17

0

13

17

17

     Mild

0

2

0

1

0

0

0

0

Vacuolar degeneration, Respiratory Epithelium

(0)

(6)

(4)

(9)

(0)

(3)

(6)

(12)

     Minimal

0

6

4

9

0

3

6

12

Vacuolar degeneration, Transitional Epithelium

(0)

(16)

(17)

(18)

(0)

(5)

(11)

(19)

     Minimal

0

16

17

17

0

5

11

19

     Mild

0

0

0

1

0

0

0

0

a  Numbers in parentheses represent the number of animals with the finding.      

 

Text Table - Ovarian Primordial/Small Growing Ovarian Follicle Counts – F1 Generation Cohort 1A

      females
 Group  1  4
 Target Exposure Concentration (ppm)  0  30
 No. Animals per Group  20  19
      Primordial/Small Growing Ovarian Follicles
 Mean  155.950  147.368
 Standard Deviation  53.834  51.234

DISCUSSION

The objective of this study was to evaluate the potential adverse effects of the test substance on reproduction in an extended one-generation study. This included evaluation of life stages not covered by other types of toxicity studies and test for effects that may occur as a result of pre- and postnatal chemical exposure.

Dose levels for the current study (4, 12 and 30 ppm) were selected based on a previous rat study (Wang, 2020, 00235550) where dimethylamine was administered via whole-body inhalation to F0male and female rats at 8, 25, and 75 ppm during the premating, mating, gestation, and lactation periods. F1male and female rats on the same study were exposed to the same concentrations from weaning (PND 28) through PND 40. While systemic toxicity was limited to lower body weights and body weight gains in the F1generation (only at the 75 ppm level), dose limiting locally adverse histopathological lesions were noted for both F0and F1animals on this study and the 75 ppm exposure level was considered excessive for an extended one-generation reproductive study.

In the current study, at 30 ppm, the highest exposure level tested, lower F0 male and female fertility and copulation/conception indices were observed in comparison with the control group. Five (5) of 24 mating pairs in the 30 ppm group did not produce a litter as opposed to the control group where 100 % of the mating pairs produced a litter. There were no correlating effects on estrous cyclicity, gestation lengths, the process of parturition or on sperm morphology, or histopathology of the reproductive organs. The mean number of days between pairing and coitus were comparable across all groups and there were no effects on F0 reproductive performance at 4 and 12 ppm. Based on these findings, F1 animals assigned to Cohort 1B for follow-up reproductive assessments were bred to obtain reproductive performance data for the F1 generation. All procedures for F1 animals assigned to Cohort 1B breeding were generally the same as those for the F0 generation, with the exception that F1females were euthanized in mid-gestation, on Gestation Day 15 because there were no observations related to the process of parturition or gestation lengths in the F0 generation nor any effects on F1 pup birth weights or survival, and hence further assessments of the same endpoints in the next generation were not warranted. Upon evaluation, there were no test substance‑related effects observed in the F1 generation at any exposure concentration. Mean mating, fertility and conception/copulation indices were comparable between the control and test substance‑exposed groups, as were the mean numbers of days between pairing and coitus. Mean estrous cycle lengths were also comparable to the control group value. Thus, based on the lack of any effects on reproductive performance of the F1generation, it was concluded that the lower male and female fertility, copulation and conception indices noted for animals in the 30 ppm group in the F0generation were likely incidental and hence unrelated to test substance exposure.

Higher T4 levels noted for F0 males and females in the 12 and 30 ppm groups were considered incidental based on the lack of a dose response (females), atypically low control group mean values in comparison with Charles River Historical Control Data, and the lack of an effect on TSH levels in both males and females. In addition, only 5 and 6 (of 10) samples were available for analysis (due to insufficient serum quantity) for both male and female control groups which may have contributed to the noted differences. Lastly, there were no noted differences in thyroid organ weights or corresponding changes in thyroid histopathology and given the lack of any correlating findings, these changes were considered likely to be unrelated to test substance administration.

Dimethylamine exposure was associated with microscopic findings in the nasal cavity (level II) of F0 generation and F1 Cohort 1A males and females at all exposure concentrations. There was transitional and/or respiratory epithelial hyperplasia and mixed inflammation in both generations, along with vacuolar degeneration of the transitional and/or respiratory epithelium of the F1 Cohort 1A animals. These histologic lesions were considered locally adverse at all exposure concentrations based on the presence of inflammation and epithelial hyperplasia.

With the exception of the abovementioned effects, there were no other changes noted on this study. Parental and neonatal survival, and all other systemic, reproductive and terminal endpoints in the F0 and F1 generations were unaffected by dimethylamine administration via whole body inhalation to Crl:CD(SD) rats at 4, 12 and 30ppm.

Conclusions:
Dimethylamine exposure was associated with locally adverse histologic lesions at all exposure levels. Thus, an exposure level of 4 ppm was considered to be the lowest-observed-adverse-effect level (LOAEL) for locally adverse effects for F0 and F1males and females when dimethylamine was administered via whole body inhalation.
In the absence of any systemically adverse effects in either generation (F0 and F1males and females) during the study, an exposure level of 30 ppm, the highest exposure level evaluated, was considered to be the no-observed-adverse-effect level (NOAEL) for F0 and F1male and female systemic toxicity when dimethylamine was administered via whole body inhalation to Crl:CD(SD) rats.
Based on the lack of any effects F1offspring during the preweaning period, an exposure level of 30 ppm was considered to be the NOAEL for F1 neonatal and developmental toxicity. Based on the lack of any evidence of reproductive toxicity at any exposure level following the evaluation of reproductive performance, sperm measurements, and estrous cyclicity in the F0 and F1 generations, the NOAEL for F0 and F1 reproductive toxicity was also considered to be 30 ppm, the highest exposure level evaluated.
Executive summary:

The objective of this study was to evaluate the potential adverse effects of the test substance dimethylamine on reproduction in an extended one-generation study. This included evaluation of life stages not covered by other types of toxicity studies and tested for effects that may occur as a result of pre- and postnatal chemical exposure.

The study design was as follows: Group 1 - 0 ppm DMA (Filtered Air), Group 2 - 4 ppm DMA, Group 3 - 12 ppm Dimethylamine, Group 4 - 30 ppm DMA (Each of the four groups contained 24 Males and Females).

Animals in the parental (F0) generation were exposed via whole-body inhalation for 6 hours daily for 70 consecutive days prior to mating and continuing through the day prior to euthanasia. Maternal exposure was suspended from Gestation Day 20 through Lactation Day 4 to prevent confounding effects on parturition and maternal nursing and nesting behavior. The offspring in the F1 generation were potentially exposed in utero and through nursing during lactation. The offspring selected to constitute the F1 generation were exposed beginning at weaning (PND 28) and continuing until the day prior to euthanasia. Due to observation of lower mean fertility and copulation/conception indices for F0 males and females (see below), F1 animals assigned to Cohort 1B for follow-up reproductive assessments were bred to obtain reproductive performance data for the F1 generation. All procedures for F1 animals assigned to Cohort 1B breeding were generally the same as those for the F0 generation, with the exception that F1 females were euthanized in mid-gestation, on Gestation Day 15, because there were no observations related to the process of parturition or gestation lengths in the F0 generation nor any effects on F1 pup birth weights or survival, and hence further assessments of the same endpoints in the next generation were not warranted. F1 males were euthanized following examination of females with evidence of mating.

The following parameters and end points were evaluated in this study: clinical signs, body weights, body weight gains, food consumption, estrous cycles, reproductive performance, parturition, litter viability and survival, pre- and postweaning developmental landmarks, thyroid hormones, clinical pathology, gross necropsy findings, sperm parameters, organ weights, and histopathologic examinations.

Target exposure concentrations were 4, 12 and 30 ppm. Overall mean analyzed exposure concentrations were 4.3, 11.9 and 30.7 ppm for the F1 generation and 4.2, 11.9 and 31.1 ppm for the F1 generation.

F0Generation: There were no test substance-related effects on survival at any exposure level. One male and one female each in the 30 ppm group were found dead on Study Day 46 and 113, respectively. Although both animals had test substance-related microscopic lesions in the nasal cavity that were similar to those described in other animals in this group examined at scheduled necropsy, a specific cause of death was not determined based on microscopic examination. These deaths were deemed unlikely to be test substance related based on the lack of any other evidence of systemic toxicity at this dosage level. All other F0 animals survived to the scheduled necropsies, and there were no test substance-related clinical observations, or any effects on mean body weights, body weight gains, food consumption or food efficiency during the study.

In the F0generation, lower male and female fertility and copulation/conception indices were observed in the 30 ppm group, when compared to the control group. Five (5) of 24 mating pairs in the 30 ppm group did not produce a litter as opposed to the control group where 100 % of the mating pairs produced a litter. There were, however, no correlating effects on estrous cyclicity, gestation lengths, the process of parturition or on sperm morphology, or histopathology of the reproductive organs. The mean number of days between pairing and coitus were also comparable across all groups. There were no effects on F0 reproductive performance at 4 and 12 ppm.

Increased T4 levels were noted for males and females in the 12 and 30 ppm groups; differences from the control group were statistically significant. However, due to lack of other correlating changes in the levels of TSH, thyroid organ weight, or thyroid histopathology in the F0 generation, and the lack of any effects on thyroid endpoints in the F1 generation, these changes were considered likely to be incidental and not related to test substance administration.

There were no test substance-related gross macroscopic findings or any changes in clinical pathology parameters (hematology, coagulation, serum chemistry, and urinalysis) noted for F0 animals at any exposure level.

Dimethylamine exposure was associated with microscopic findings in the nasal cavity (level II) of F0 animals at ≥ 4 ppm. There was a dose-related increase in incidence and/or severity of respiratory epithelial hyperplasia and transitional epithelial hyperplasia in males and females, and mixed cell inflammation in the males. The mixed cell inflammation was similar in females at 4 and 12 ppm and at a higher incidence in the 30 ppm group. Histologically, the transitional and respiratory epithelial hyperplasia was characterized by focal to multifocal increased numbers of cells and disorganization. There was loss or clustering of goblet cells and/or decreased cilia in the affected respiratory epithelium. Inflammation, when present, was associated with the hyperplasia and included variable numbers of neutrophils, lymphocytes, and plasma cells. These histologic lesions were considered locally adverse at all exposure levels based on the presence of inflammation and epithelial hyperplasia.

F1Generation: F1 postnatal survival was unaffected by test substance exposure at all exposure levels. In addition, pup birth weights and the general physical condition of F1 pups during the pre-weaning period were unaffected by test substance exposure. Mean pup body weights and body weight gains were comparable across all groups, including in the period immediately following re-initiation of maternal test substance exposures on PND 5. There were also no substance-related effects on serum levels of thyroid hormones for F1 pups (on PND 4 and 28) or any effects on preweaning developmental landmarks (anogenital distance, areolae/nipple retention) at any exposure level in the F1 generation.

Following weaning, there were no test substance-related effects on survival in the F1 generation at any exposure level. One male in the 12 ppm group was found dead on PND 63; there were no remarkable clinical or macroscopic findings noted for this male and given the lack of mortality at the 30 ppm, this death was considered incidental and unrelated to test substance exposure. All other F1 animals survived to the scheduled necropsies, and there were no test substance-related clinical observations, or any effects on mean body weights, body weight gains, food consumption or food efficiency during the generation. There were also no substance-related effects on post weaning developmental landmarks (vaginal patency, onset of estrus or balanopreputial separation), serum levels of thyroid hormones, gross macroscopic findings, estrous cyclicity, sperm parameters, or clinical pathology parameters at any exposure level for F1 males and females (Cohort 1A, PND 90).

Microscopic findings related to test substance exposure in F1 Cohort 1A animals were similar to the F0 generation. In the nasal cavity (level II) of animals exposed to ≥ 4 ppm, a dose-related increase in incidence and/or severity of respiratory epithelial hyperplasia, transitional epithelial hyperplasia, vacuolar degeneration of the respiratory epithelium, and vacuolar degeneration of the transitional epithelium was noted in males and females. Inflammation was similar in all dose groups in males and showed a slightly increased incidence at 12 and 30 ppm in females compared to 4 ppm. Similar to the F0 generation, these findings were considered locally adverse at all exposure levels based on the presence of inflammation and epithelial hyperplasia. There were no test substance-related effects on primordial/small growing follicles in F1 Cohort 1A females on PND 90.

Due to observation of lower mean fertility and copulation/conception indices for F0 males and females, F1 animals assigned to Cohort 1B for follow-up reproductive assessments were bred to obtain reproductive performance data for the F1 generation. There were no test substance related effects on reproductive performance. Male and female mating, fertility, and copulation and conception indices, estrous cyclicity and the number of days between pairing and coitus were comparable across all exposure levels. Mean numbers of corpora lutea, implantation sites and viable embryos were similar across all exposure levels. Based on the lack of any effects on reproductive performance of the F1 generation, it was concluded that the lower male and female fertility and copulation/conception indices noted for animals in the 30 ppm group in the F0 generation were spurious and unrelated to test substance exposures.

In conclusion, dimethylamine exposure was associated with locally adverse histologic lesions at all exposure levels. Thus, an exposure level of 4 ppm was considered to be the lowest-observed-adverse-effect level (LOAEL) for locally adverse effects for F0 and F1 males and females when dimethylamine was administered via whole body inhalation.

In the absence of any systemically adverse effects in either generation (F0 and F1males and females) during the study, an exposure level of 30 ppm, the highest exposure level evaluated, was considered to be the no-observed-adverse-effect level (NOAEL) for F0 and F1male and female systemic toxicity when dimethylamine was administered via whole body inhalation to Crl:CD(SD) rats.

Based on the lack of any effects F1 offspring during the preweaning period, an exposure level of 30 ppm was considered to be the NOAEL for F1 neonatal and developmental toxicity. Based on the lack of any evidence of reproductive toxicity at any exposure level following the evaluation of reproductive performance, sperm measurements, and estrous cyclicity in the F0 and F1 generations, the NOAEL for F0 and F1reproductive toxicity was also considered to be 30 ppm, the highest exposure level evaluated.

Endpoint:
screening for reproductive / developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
23-Jan-2019 - 04-Aug-2020
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose for cross-reference:
reference to other study
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Version / remarks:
29 July 2016
Deviations:
yes
Remarks:
several slight deviations in Atmosphere Generation & Exposure, Husbandry, In-life Observations, Measurements & Evaluations, Laboratory Evaluations & Postmortem and Pathology (all are considered not to have had impact the overall integrity of the study);
GLP compliance:
yes (incl. QA statement)
Limit test:
no
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source (i.e. manufacturer or supplier) and lot/batch number of test material: Airgas Specialty Products

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Kept in a controlled temperature area set to maintain 18 °C to 24 °C

OTHER SPECIFICS
- The Sponsor and/or Supplier provided to the Testing Facility documentation of the identity, strength, purity, composition, and stability for the test substance. A Certificate of Conformance was provided to the Testing Facility.
Species:
rat
Strain:
Crj: CD(SD)
Remarks:
Crl:CD(SD)
Details on species / strain selection:
Crl:CD(SD)
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, NC
- Females nulliparous and non-pregnant: yes
- Age at study initiation: (P) approximately 11 wks
- Weight at study initiation: between 220 and 423 g at the initiation of exposure
- Fasting period before study: not applicable
- Housing: Animals were housed in an animal colony room during nonexposure periods. In detail, on arrival (F0) or following selection (F1), animals were group housed (up to 3 animals of the same sex) until cohabitation or euthanasia. At initiation of cohabitation, F0 males were assigned to individual home cages and then F0 animals were paired for mating in the home cage of the male. Following the breeding period, F0 animals were individually housed. Animals were housed in solid-bottom cages containing appropriate bedding equipped with an automatic watering valve throughout the study. Animals were separated during designated procedures/activities. Each cage was clearly labeled with a color-coded cage card indicating study, group, animal, cage number(s), dosage level, and sex. Cages were arranged on the racks in group order. Animals were maintained in accordance with the Guide for the Care and Use of Laboratory Animals. The animal facilities at Charles River Ashland are accredited by AAALAC International
- Diet: PMI Nutrition International, LLC Certified Rodent LabDiet® 5002 was provided ad libitum throughout the study, except during designated procedures. Food was withheld during the animal exposure periods.
- Water: Municipal tap water after treatment by reverse osmosis was freely available to each animal via an automatic watering system, except during inhalation exposure procedures. Water was withheld during the animal exposure periods.
- Acclimation period: at least 7 days prior to initiation of exposure
- Animal identification: Upon receipt, each animal was identified using a subcutaneously implanted electronic identification chip (BMDS system). Offspring were identified by tattoo markings applied to the digits after parturition and by microchip at weaning.
- Animal Enrichment: Animals were socially housed for psychological/environmental enrichment and were provided with environmental enrichment as appropriate to aid in maintaining the animals’ oral health.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 68 °F to 78 °F (20 °C to 26 °C)
- Humidity (%): 30 % to 70 %
- Air changes (per hr): Ten or greater air changes per hour with 100 % fresh air (no air recirculation) were maintained in the animal rooms
- Photoperiod (hrs dark / hrs light): 12-hour light/12-hour dark

IN-LIFE DATES: From: 24 Jan 2019 (Animal Arrival) To: 13 May 2019
Route of administration:
inhalation: gas
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: Humidified, filtered air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Exposures were conducted in four, 2000-L stainless-steel and glass whole-body exposure chambers. One chamber was used for the filtered air control group and 1 chamber was used for each test substance group. The chambers were operated under dynamic conditions, at a slight negative pressure, and with a minimum of 12 air changes per hour.
- Method of holding animals in test chamber: Animals were individually housed in standard exposure batteries of appropriate size for the whole-body exposure chamber in use.
- Source and rate of air: Air supplied to the whole-body chambers was provided from an in-house compressed nitrogen source and a HEPA- and charcoal-filtered, temperature- and humidity-controlled supply air source. All whole-body chamber exhaust passed through the facility exhaust system, which consists of redundant exhaust blowers preceded by activated-charcoal and HEPA-filtration units
Test substance atmospheres were generated by releasing neat test substance gas from the cylinder. The cylinder was heated to maintain pressure within the cylinder. The test substance gas was directed to a manifold. Test substance gas was directed to the chamber inlet, where it mixed with dilution supply air to achieve the desired atmosphere concentration.
- Method of conditioning air: not specified
- System of generating particulates/aerosols: not applicable
- Temperature, humidity, pressure in air chamber: The mean temperature and relative humidity of the exposure atmospheres were to be 69 °F to 75 °F (19 °C to 25 °C) and 30 % to 70 %, respectively. Oxygen content of the exposure atmospheres was measured during the method development phase and was 20.9 % for all groups.
- Air flow rate: between 453 and 464 Liters/min
- Air change rate: not specified
- Method of particle size determination: not applicable
- Treatment of exhaust air: All whole-body chamber exhaust passed through the facility exhaust system, which consists of redundant exhaust blowers preceded by activated-charcoal and HEPA-filtration units.

TEST ATMOSPHERE
- Brief description of analytical method used: Analyzed exposure concentrations were determined at approximately 60-minute intervals using a gas chromatograph
- Samples taken from breathing zone: yes (An external multi-position valve permitted sequential sampling from the exposure room and each exposure chamber. Gas sampling injection onto the chromatography column occurred via an internal gas sampling valve with a sample loop, the chromatograph was displayed, and the area under the sample peak was calculated and stored. An ln quadratic equation based on the gas chromatograph calibration curve(s) was used to calculate the measured concentration in ppm.)

VEHICLE (if applicable)
- Justification for use and choice of vehicle: air
- Composition of vehicle: not specified
- Type and concentration of dispersant aid (if powder): not applicable
- Concentration of test material in vehicle: not specified
- Lot/batch no. of vehicle (if required): not required
- Purity of vehicle: no details given
For exposure of the control group (Group 1, 0 ppm), humidified supply air was delivered to the chamber from the facility air supply source. To provide a comparable oxygen level in the control chamber to that as within the test substance chambers, compressed nitrogen was delivered to the inlet of the control exposure chamber at a flow rate similar to that used in the high-exposure group, where it mixed with supply air.
Details on mating procedure:
- M/F ratio per cage: 1:1
- Length of cohabitation: for a maximum of 14 days
- Proof of pregnancy: vaginal copulatory plug or the presence of sperm in a vaginal lavage referred to as day 0 of pregnancy
- After successful mating each pregnant female was caged: individually
- Any other deviations from standard protocol: none in the context of mating
Vaginal lavages were performed daily during the mating period until evidence of mating was observed. If evidence of mating was not apparent after 14 days, the animals were separated, with no further opportunity for mating. Animals cohabited over a 12-hour dark cycle were considered to have been paired for 1 day.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analyzed exposure concentrations were determined at approximately 60-minute intervals using a gas chromatograph.
Samples were collected from the approximate animal-breathing zone of the exposure chamber. An external multi-position valve permitted sequential sampling from the exposure room and each exposure chamber. Gas sampling injection onto the chromatography column occurred via an internal gas sampling valve with a sample loop, the chromatograph was displayed, and the area under the sample peak was calculated and stored. An ln quadratic equation based on the gas chromatograph calibration curve(s) was used to calculate the measured concentration in ppm.
Duration of treatment / exposure:
Males: 14 days prior to mating and continuing throughout mating for a total of 28 days
Females: 14 days prior to mating and continuing through Gestation Day 20, exposure resumed on Lactation Day 5 and continued until Lactation Day 28 for a total of 58–65 days
F1 pups: directly exposed from Postnatal Day (PND) 28–40
Frequency of treatment:
6 hours/day
Details on study schedule:
Parturition: The day parturition was initiated was designated Lactation Day 0 (Postnatal Day [PND] 0 for pups). During the period of expected parturition, females were observed twice daily for initiation and completion of parturition and for dystocia or other difficulties. All females were allowed to deliver naturally. Beginning on the day parturition was initiated, the numbers of stillborn and live pups were recorded. Individual gestation length was calculated using the date delivery was first observed.
Dose / conc.:
0 ppm
Remarks:
Control (filtered air)
Dose / conc.:
8 ppm
Dose / conc.:
25 ppm
Dose / conc.:
75 ppm
No. of animals per sex per dose:
10
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale:
Justification of Route and Exposure Levels
The route of administration was whole-body inhalation exposure because inhalation would be a likely route of unintended human exposure.
The dosage levels were determined from results of a previous tolerability/range finding study. In that study, DMA was administered via whole-body inhalation exposure to up to 250 ppm in rats for 14 days (6 hours per day). No test substance-related adverse clinical signs, body weight, or food consumption effects were noted at any exposure level. However, at the histopathology evaluation, degeneration of the transitional and respiratory epithelium, multifocal mixed inflammation, and ulceration with bone atrophy of the nasoturbinates and maxilloturbinates were noted at ≥ 50 ppm. Changes were noted in an exposure-dependent manner and were of minimal grade at the low-exposure level (50 ppm). Based on the corrosive nature of DMA gas and the findings from the previous tolerability/range finding study, port of entry effects were expected in the current study. Therefore, exposure levels of 8, 25, and 75 ppm were selected for the current study.

- Rationale for animal assignment: Animals were assigned to groups by a stratified randomization scheme designed to achieve similar group mean body weights. Males and females were randomized separately. Animals with physical abnormalities, at extremes of body weight range, or not exhibiting normal, 4- to 5-day estrous cycles were not assigned to groups.
- Fasting period before blood sampling for clinical biochemistry: Animals were fasted overnight prior to blood collection
- Other: Animals were housed in an animal colony room during nonexposure periods. Prior to each exposure, the animals were transferred to exposure caging, transported to the exposure room, exposed for the requisite duration, transported back to the colony room, and returned to their home cages. Food and water were withheld during the animal exposure periods.
Prior to exposure, females were evaluated for estrous cyclicity during the pretest period and any females that failed to exhibit normal 4-5 day estrous cycles (e.g., EDDDE), during the pretest period, were excluded from the study; therefore, the extra females were included to yield at least 10 females per group. Given the possibility of nongravid animals, unexpected deaths, total litter losses, or test substance-related moribundity and/or mortality, this was an appropriate number of animals to obtain a sample size of 8 at termination.
Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Throughout the study, animals were observed for general health/mortality and moribundity twice daily, once in the morning and once in the afternoon. Animals were not removed from cage during observation, unless necessary for identification or confirmation of possible findings

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: The animals were removed from the cage, and a detailed clinical observation was performed once daily throughout the study. During the exposure period, these observations were performed prior to exposure. On exposure days, clinical observations were also recorded 0.5–3 hours following completion of exposure.
During social housing, some observations (e.g., fecal observations) may not have been attributable to an individual animal.

BODY WEIGHT: Yes
- Time schedule for examinations: Animals were weighed individually weekly throughout the study and prior to the scheduled necropsy. Once evidence of mating was observed, female body weights were recorded on Gestation Days 0, 4, 7, 11, 14, 17, and 20 and Lactation Days 1, 4, 7, 10, 13, 17, 21, 25, and 28. A fasted weight was recorded on the day of necropsy.

FOOD CONSUMPTION:
Food consumption was quantitatively measured weekly until cohabitation. Once evidence of mating was observed, female food consumption was recorded on Gestation Days 0, 4, 7, 11, 14, 17, and 20 and Lactation Days 1, 4, 7, 10, 13, 17, 21, 25, and 28.

WATER CONSUMPTION: No

OTHER:
Sample Collection
Animals were fasted overnight prior to blood collection. Blood samples for hematology and serum chemistry were collected from the jugular vein. Blood samples for coagulation parameters were collected by necropsy personnel from the inferior vena cava of animals anesthetized by inhalation of isoflurane and euthanized by exsanguination.
K2EDTA was used for the anticoagulant on samples collected for hematology. Sodium citrate was used for samples collected for clotting determinations. Samples for serum chemistry were collected without anticoagulants.

Hematology
Blood samples were analyzed for the parameters: Differential leukocyte count (-Percent and absolute; -Neutrophil (NEU); -Lymphocyte (LYMPH), -Monocyte (MONO), -Eosinophil (EOS), -Basophil (BASO), -Large unstained cell (LUC)), Erythrocyte count (RBC); Hemoglobin (HGB); Hemoglobin distribution width (HDW), Hematocrit (HCT), Mean corpuscular hemoglobin (MCH), Mean corpuscular volume (MCV), Mean corpuscular hemoglobin concentration (MCHC), Platelet count (Platelet), Red cell distribution width (RDW), Reticulocyte count, Percent (RETIC), Absolute (RETIC Absolute), Total leukocyte count (WBC), Platelet estimatea, Red cell morphology (RBC Morphology).

Coagulation
Blood samples were processed for plasma, and the plasma was analyzed for: Activated partial thromboplastin time (APTT), Fibrinogen, Prothrombin time (PT).

Serum Chemistry
Blood samples were processed for serum, and the serum was analyzed for: Alanine aminotransferase (ALT), Albumin, Albumin/globulin ratio (A/G Ratio) [by calculation], Alkaline phosphatase (ALP), Aspartate aminotransferase (AST), Bile Acids, Calcium, Chloride, Creatinine, Gamma glutamyltransferase (GGT), Globulin [by calculation], Glucose, Phosphorus, Potassium, Sodium, Sorbitol dehydrogenase (SDH), Total bilirubin (Total BILI), Total cholesterol (Cholesterol), Total protein, Triglycerides (Triglyceride), Urea nitrogen, Appearance

Thyroid Hormone Analysis
Sample Collection: Blood samples for thyroid hormone analyses were collected from the jugular vein into tubes without anticoagulants.
Sample Processing: Blood samples were maintained at room temperature and allowed to clot. Serum was isolated in a refrigerated centrifuge and stored in a freezer set to maintain a target of -70 °C.
Sample Analysis: Blood samples were analyzed for Thyroxine (Total T4). Samples to be analyzed for T4 were transferred to the Charles River Ashland Bioanalytical Chemistry Department; analyses were performed using a validated UHPLC/MS/MS assay.
Oestrous cyclicity (parental animals):
For all females, vaginal lavages were performed daily for 2 weeks prior to randomization and continuing until evidence of mating was observed or until the end of the mating period. The slides were microscopically examined to determine the stage of the estrous cycle. The average cycle length was calculated for complete estrous cycles (i.e., the total number of returns to metestrus [M] or diestrus [D] from estrus [E] or proestrus [P] for 14 consecutive days before cohabitation and until the detection of evidence of mating). Estrous cycle length was determined by counting the number of days from the first M or D in a cycle to the first M or D in a subsequent cycle. The cycle during which evidence of mating was observed for a given animal was not included in the individual mean estrous cycle length calculation. Vaginal lavages were also performed on the day of necropsy to determine the stage of the estrous cycle.
Sperm parameters (parental animals):
not specified
Litter observations:
STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: yes
- If yes, maximum of 8 pups/litter (4/sex/litter as nearly as possible); excess pups were killed and discarded.
Following completion of delivery, all pups will be individually identified by tattoo markings applied on the digits. To reduce variability among the litters, eight pups from each litter, of equal sex distribution (if possible), will be randomly selected on PND 4. Culled pups will be used for thyroid hormone assessments. Culled pups not selected for blood collection will be euthanized by an intraperitoneal injection of sodium pentobarbital and discarded appropriately.

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring: number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities, anogenital distance (AGD), pup weight on the day of AGD, presence of nipples/areolae in male pups. Particular attention should be paid to the external reproductive genitals which should be examined for signs of altered development; gross evaluation of external genitalia

GROSS EXAMINATION OF DEAD PUPS:
yes, for external and internal abnormalities

LItter observation after birth until PND28
Moribundity:
Litters were observed for general health/mortality and moribundity twice daily, once in the morning and once in the afternoon. A daily record of litter size was maintained. Animals were not removed from cage during observation, unless necessary for identification or confirmation of possible findings.

Observations
Clinical observations were performed on PND 1, 4, 7, 10, 13, 17, 21, 25, and 28.

Sex Determination
Pups were individually sexed on PND 0, 4, 13, and 28.

Body Weights
Pups were weighed individually on PND 1, 4, 7, 10, 13, 17, 21, 25, and 28.

Preweaning Developmental Landmarks
Anogenital Distance: The anogenital distance of all pups was measured on PND 1. Anogenital distance was defined as the distance from the caudal margin of the anus to the caudal margin of the genital tubercle.
Assessment of Areolas/Nipple Anlagen: On PND 13, all male pups were evaluated for the presence of nipples/areolae. The number of nipples was recorded.

Thyroid Hormone Analysis
Sample Collection: Blood samples for thyroid hormone analyses were collected via cardiac puncture (PND 4) or vena cava (PND 28) from animals anesthetized with isoflurane into tubes without anticoagulants. Samples were collected on PND 4 (at least 2/litter) and on PND 28 (1/sex/litter).
Sample Processing: Blood samples were maintained at room temperature and allowed to clot. Serum was isolated in a refrigerated centrifuge and stored in a freezer set to maintain a target of -70 °C.
Sample Analysis: Blood samples were analyzed for Thyroxine (Total T4).
Samples to be analyzed for T4 were transferred to the Charles River Ashland Bioanalytical Chemistry Department; analyses were performed using a validated UHPLC/MS/MS assay.
Postmortem examinations (parental animals):
SACRIFICE
- Male animals: All surviving animals on Study Day 28
- Maternal animals: All surviving animals on Lactation Day 29

Unscheduled Deaths: No animals died during the course of the study; therefore, no animals were examined.
Scheduled Euthanasia: All animals, including females that failed to deliver, were anesthetized by inhalation of isoflurane followed by euthanasia by exsanguination.

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.
Males were subjected to necropsy on day 28; females were subjected to necropsy on Lactation day 29. On these days organ weights were determined and tissues were collected and subsequently subject to histological and histopathogical examinations.
Animals were subjected to a complete necropsy examination, which included examination of the external surface, all orifices, the cranial cavity, the external surface of the brain, and the thoracic, abdominal, and pelvic cavities, including viscera. The numbers of implantation sites and former implantation sites were recorded for females that delivered or had macroscopic evidence of implantation. The number of unaccounted-for sites was calculated for each female by subtracting the number of pups born from the number of former implantation sites observed. Uteri of females without macroscopic evidence of implantation were opened and placed in 10 % ammonium sulfide solution for detection of early implantation loss.

HISTOPATHOLOGY / ORGAN WEIGHTS
Representative samples of the tissues were collected from all animals and preserved in 10 % neutral buffered formalin, unless otherwise indicated.
The following tissues were collected: Adrenal glands (2), Aorta, Bone with marrow (sternebrae), Brain, Coagulating glands (2), Eyes with optic nerve (2), Gastrointestinal tract, Esophagus, Stomach, Duodenum, Peyer’s Patches, Jejunum, Ileum, Cecum, Colon, Rectum, Heart, Kidneys (2), Liver (sections of 2 lobes), Lymph node, Axillary (2), Mandibular (2), Mesenteric, Lungs (including bronchi, fixed by inflation with fixative), Nasal cavities with turbinates, Ovaries and oviducts (2), Pancreas, Peripheral nerve (sciatic)c, Pituitary gland, Prostate gland, Salivary gland (mandibular [2]), Seminal vesicles (2), Skeletal muscle (quadriceps), Skin with mammary gland, Spinal cord (cervical), Spleen, Testes with epididymides (2) and vas deferens, Thymus gland, Thyroids (with parathyroids, if present [2]), Trachea, Urinary bladder, Uterus with cervix and vagina, All gross lesions.

Organ Weights
The organs were weighed at necropsy for all scheduled euthanasia animals. Paired organs were weighed together, unless otherwise indicated. Organ to body weight ratio (using the terminal body weight) and organ to brain weight ratios were calculated.
The following organs were weighted: Adrenal glands, Brain, Epididymides, Heart, Kidneys, Liver, Lungs, Ovaries (with oviducts), Pituitary gland, Prostate gland, Seminal vesicle (with coagulating gland and fluid), Spleen, Testes, Thymus gland, Thyroids (with parathyroids).

Histology
Tissue trimming was performed at the Testing Facility. Tissues from all animals were embedded in paraffin, sectioned, mounted on glass slides, and stained with hematoxylin and eosin. In addition, PAS staining was used for the testes and epididymides.

Histopathology
Pathological evaluation was performed by a board-certified veterinary pathologist. Tissues for microscopic examination were evaluated from all animals.
Postmortem examinations (offspring):
SACRIFICE
- The F1 offspring were sacrificed at PND40 days of age.
- These animals were subjected to postmortem examinations (macroscopic and/or microscopic examination) as follows: all F1 animals at PND28

Unscheduled Deaths
A necropsy was conducted for animals that died on study, and specified tissues were saved. Intact offspring that were found dead during PND 0–4 were necropsied using a fresh dissection technique, which included examination of the heart and major vessels. Findings were recorded as developmental variations or malformations, as appropriate. A gross necropsy was performed on any pup found dead after PND 4.

Scheduled Euthanasia
On PND 28, animals were euthanized by carbon dioxide inhalation (animals not selected for blood collection) or were anesthetized by inhalation of isoflurane and euthanized by exsanguination (animals selected for blood collection).

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.
On PND 28, 1 pup/sex/litter was subjected to a complete necropsy examination, with emphasis on developmental morphology and organs of the reproductive system. All other animals were discarded without examination.

HISTOPATHOLOGY / ORGAN WEIGTHS
At the time of necropsy, the following tissues and organs will be collected and placed in 10% neutral-buffered formalin (except as noted):

Organ Weights
The organs were weighed at necropsy from 1 pup/sex/litter at the scheduled euthanasia. Paired organs were weighed together, unless otherwise indicated. Organ to body weight ratio (using the terminal body weight) and organ to brain weight ratios were calculated.
The following organs were weighted: Adrenal glands, Brain, Epididymides, Heart, Kidneys, Liver, Lungs, Ovaries (with oviducts), Pituitary gland,Prostate gland, Seminal vesicle (with coagulating gland and fluid), Spleen, Testes, Thymus, Thyroid (with parathyroids).

Tissue Collection and Preservation
Representative samples of the Thyroid (with parathyroids), the Nasal cavities with turbinates and all gross lesions (all groups) were collected from 1 pup/sex/litter at the scheduled euthanasia and preserved in 10 % neutral buffered formalin.

Histology
Tissue trimming was performed at the Testing Facility. Tissues (Lungs (including bronchi, fixed by inflation with fixative), Nasal cavities with turbinates and all gross lesions (all groups)) from all animals were embedded in paraffin, sectioned, mounted on glass slides, and stained with hematoxylin and eosin.

Histopathology
Pathological evaluation was performed by a board-certified veterinary pathologist. Tissues identified above for microscopic examination were evaluated from all animals.
Statistics:
Each mean was presented with the standard deviation (S.D.) and the number of animals or cages (N) used to calculate the mean. Where applicable, the litter was used as the experimental unit.
All statistical tests for the following parameters were performed using WTDMS™. Analyses were conducted using two-tailed tests (except as noted otherwise) for minimum significance levels of 1% and 5%, comparing each test substance-treated group to the control group by sex.
Parental mating, fertility, copulation, and conception indices were analyzed using the Chi-square test with Yates’ correction factor. Parental and offspring body weights and body weight changes, parental food consumption, estrous cycle lengths, precoital intervals, gestation lengths, former implantation sites, unaccounted-for sites, live litter size on PND0, numbers of pups born, abs. & rel. organ weights, clinical pathology values, thyroid hormone values, anogenital distance (abs. & rel. to the cube root of bw), no. of nipples/areolae, and FOB data values were subjected to a parametric one-way ANOVA to determine intergroup differences. If the ANOVA revealed significant (p < 0.05) intergroup variance, Dunnett's test was used to compare the test substance-treated groups to the control group. FOB parameters that yielded scalar or descriptive data were analyzed using Fisher’s Exact Test. Mean litter proportions of postnatal survival and pup sexes at birth (% of males/litter) were subjected to the Kruskal-Wallis nonparametric ANOVA to determine intergroup differences. If the nonparametric ANOVA revealed significant (p < 0.05) intergroup variance, Dunn’s test was used to compare the test substance-treated groups to the control group.
The locomotor activity ambulatory & total counts data were statistically analyzed using SAS Software for Windows, Release 9.4 (SAS Institute Inc., Cary, NC) or later. All statistical tests were conducted at the 5% significance level. All pairwise comparisons were performed two-sided.
Reproductive indices:
Male copulation, female conception, male, and female mating and fertility indices of the treated groups are compared to the control group using the Chi-square test with Yates’ correction factor.

MALE (FEMALE) MATING INDEX (%) = (NO. OF MALES (FEMALES) WITH EVIDENCE OF MATING (OR CONFIRMED PREGNANCY)/ TOTAL NO. OF MALES (FEMALES) USED FOR MATING) * 100

MALE FERTILITY INDEX (%) = (NO. OF MALES SIRING A LITTER/ TOTAL NO. OF MALES USED FOR MATING) * 100

FEMALE FERTILITY INDEX (%) = (NO. OF FEMALES WITH CONFIRMED PREGNANCY / TOTAL NO. OF FEMALES USED FOR MATING) * 100

MALE COPULATION INDEX (%) = (NO. OF MALES SIRING A LITTER / NO. OF MALES WITH EVIDENCE OF MATING (OR FEMALES CONFIRMED PREGNANT)) * 100

FEMALE CONCEPTION INDEX (%) = (NO. OF FEMALES WITH CONFIRMED PREGNANCY / NO. OF FEMALES WITH EVIDENCE OF MATING (OR CONFIRMED PREGNANCY)) * 100
Clinical signs:
no effects observed
Description (incidence and severity):
All F0 males and females in the control, 8, 25, and 75 ppm groups survived to the scheduled necropsies. There were no test substance-related clinical observations noted at the weekly examinations or 0.5–3 hours following the completion of exposure. Findings noted in the test substance-exposed groups, including hair loss, scabbing or red material on various body surfaces, occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not exposure-related.
Dermal irritation (if dermal study):
not examined
Mortality:
no mortality observed
Description (incidence):
All F0 males and females in the control, 8, 25, and 75 ppm groups survived to the scheduled necropsies.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
Males, Females premating and Females during gestation: Mean body weights and body weight gains in the 8, 25, and 75 ppm group males were unaffected by test substance exposure throughout the study. None of the differences from the control group were statistically significant.
Females during lactation: Mean body weights and body weight gains in the 8, 25, and 75 ppm groups were unaffected by test substance administration during lactation. The only statistically significant difference from the control group was a lower mean body weight gain in the 75 ppm group females during Lactation Days 1–4 (when females were not being exposed to the test substance). When the overall lactation exposure period (Lactation Days 4-28) was evaluated, body weight change in the 75 mg/kg/day group was comparable to the control group.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
Males: Mean food consumption, evaluated as g/animal/day, in the 8, 25, and 75 ppm group males was similar to that in the control group throughout the study. No statistically significant differences were observed.
Females premating: Mean food consumption, evaluated as g/animal/day, in the 8, 25, and 75 ppm group females was unaffected by test substance administration during the premating period. None of the differences from the control group were statistically significant.
Females during Gestation: Mean maternal food consumption, evaluated as g/animal/day, in the 8, 25, and 75 ppm groups was unaffected by test substance administration during gestation. The only statistically significant differences from the control group were higher mean food consumption (31.5 % compared to control) in the 25 ppm group during Gestation Days 17–20, resulting in higher mean food consumption when the entire gestation exposure period (Gestation Days 0–20) was evaluated. However, this effect is not dose dependent and not considered to be of toxicological significance.
Females during Lactation: Mean maternal food consumption, evaluated as g/animal/day, in the 8, 25, and 75 ppm groups was unaffected by test substance administration.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Description (incidence and severity):
Haematology:
There were no test substance-related effects on hematology parameters. The only statistically significant difference from the control group values (lower [2.9 %] mean corpuscular hemoglobin concentration in the 25 ppm group females) did not occur in an exposure-related manner and was of minimal magnitude. Therefore, this finding was considered to be the result of normal biological variation and not considered to be of toxicological significance.

Coagulation:
There were no test substance-related effects on coagulation parameters. The only statistically significant difference from the control group values (faster [14.7 %] activated prothrombin time in the 75 ppm group females) was of minimal magnitude. Therefore, this finding was considered to be the result of normal biological variation and not considered to be of toxicological significance.
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
There were no test substance-related effects on serum chemistry. The only statistically significant difference from the control group was a slightly higher sodium level [1.4 %] in the 25 ppm group males. There was no exposure-response relationship, and the change was of minimal magnitude. This difference from the control group was considered to be the result of normal biological variation and not considered to be of toxicological significance.
Endocrine findings:
no effects observed
Description (incidence and severity):
There were no test substance-related effects on thyroid hormone values in the F0 males at any dosage level. Differences from the control group were considered to be the result of normal biological variation and were not considered to be of toxicological significance.
Urinalysis findings:
not examined
Behaviour (functional findings):
no effects observed
Description (incidence and severity):
Functional Observational Battery:
Home cage parameters; Handling parameters, Open field parameters, Sensory Observations, Neuromuscular parameters and Physiological parameters were unaffected by test substance administration. There were no statistically significant differences for the test substance-treated groups when compared to the control group during Study Day 27 (males) or on Lactation Day 28 (females).
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Test substance-related microscopic findings were noted in the nasal cavity (Level II) of the 8, 25, and 75 ppm F0 group males and females.
Test substance-related lesions within Level II of the nasal cavity included minimal or mild hyperplasia of the respiratory and transitional epithelium and minimal or mild mixed cell inflammation.
The transitional and respiratory epithelial hyperplasia was characterized by a focal disorganized, thickened epithelial surface. There was loss or clustering of goblet cells and absence of cilia in the affected respiratory epithelium. In some animals the hyperplasia was associated with mixed cell inflammation characterized by the presence of variable numbers of neutrophils, lymphocytes, and plasma cells.
There were no other test substance-related histologic changes. Remaining histologic changes were considered to be incidental findings or related to some aspect of experimental manipulation other than exposure to the test substance. There was no test substance-related alteration in the prevalence, severity, or histologic character of those incidental tissue alterations.
Histopathological findings: neoplastic:
not specified
Other effects:
no effects observed
Description (incidence and severity):
Motor Activity:
Motor activity patterns (total activity as well as ambulatory activity counts) in F0 animals were unaffected by test substance exposure at all concentrations when evaluated on Study Day 27 (males) or on Lactation Day 28 (females). Values obtained from the 6 subintervals evaluated (0–10, 11–20, 21–30, 31–40, 41–50 and 51–60 minutes) and the overall 60-minute test session values were comparable to the concurrent control values and the Charles River Ashland historical control data. Differences from the control group were slight, not statistically significant, within the Charles River Ashland historical control data ranges, and/or did not occur in an exposure-related manner. No remarkable shifts in the pattern of habituation occurred in any of the test substance-exposed groups when the F0 animals were evaluated.
Reproductive function: oestrous cycle:
no effects observed
Description (incidence and severity):
No test substance-related effects on reproductive performance were observed at any exposure level. No statistically significant differences were noted between the control and test substance-exposed groups. Two males each in the control and 8 ppm groups, respectively, did not sire a litter. Two females each in these same groups were determined to be nongravid. The mean numbers of days between pairing and coitus in the test substance-exposed groups were similar to the control group value. The mean lengths of estrous cycles in these groups were also similar to the control group value. None of these differences were statistically significant.
Reproductive function: sperm measures:
not specified
Reproductive performance:
no effects observed
Description (incidence and severity):
No test substance-related effects on reproductive performance were observed at any exposure level. No statistically significant differences were noted between the control and test substance-exposed groups. Two males each in the control and 8 ppm groups, respectively, did not sire a litter. Two females each in these same groups were determined to be nongravid. The mean numbers of days between pairing and coitus in the test substance-exposed groups were similar to the control group value. The mean lengths of estrous cycles in these groups were also similar to the control group value. None of these differences were statistically significant.
Gestation length and Parturition:
Mean gestation lengths in the 8, 25, and 75 ppm groups were similar to those in the control group. No statistically significant differences were noted. No signs of dystocia were noted in these groups.

Dose descriptor:
NOAEL
Effect level:
75 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: systemic and reproductive toxicity
Dose descriptor:
LOAEL
Effect level:
8 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: based on test substance-related adverse port of entry findings, consisting of respiratory epithelial hyperplasia and mixed cell type inflammation, and/or ulceration noted in all exposure levels.
Clinical signs:
not examined
Dermal irritation (if dermal study):
not examined
Mortality:
not examined
Body weight and weight changes:
not examined
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Endocrine findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not examined
Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
not examined
Reproductive performance:
not examined
Clinical signs:
no effects observed
Description (incidence and severity):
There were no test substance-related clinical observations noted at the daily examinations or 0.5–3 hours following the completion of exposure. Findings noted in the test substance-exposed groups, including scabbing or red material on various body surfaces, occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not exposure-related.
Dermal irritation (if dermal study):
not examined
Mortality / viability:
no mortality observed
Description (incidence and severity):
All F1 males and females in the control, 8, 25, and 75 ppm groups survived to the scheduled necropsies.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
Mean F1 body weight gains in the 75 ppm group males and females were occasionally lower than the control group during the exposure period, resulting in slight lower mean body weight gains
when the entire exposure period (PND 28–40) was evaluated. The difference was statistically significant for males on PND 35–36. As a result, mean absolute body weights were up to 5.0 % and 6.3 % lower for these males and females, respectively, compared to the control group during the exposure; the differences were not statistically significant.
Mean F1 body weight and body weight gains in the 8 and 25 ppm group males and females were generally comparable to the control group throughout the exposure period (PND 28–40). The only statistically significant differences from the control group were higher mean body weight gains in the 8 and 25 ppm group males during PND 30–31. There was no exposure-response relationship.
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Sexual maturation:
not examined
Anogenital distance (AGD):
no effects observed
Description (incidence and severity):
The anogenital distances (absolute, relative to pup body weight, and relative to the cube root of pup body weight) in the 8, 25, and 75 ppm groups were similar to the control group values.
Differences from the control group were slight and not statistically significant.
Nipple retention in male pups:
no effects observed
Description (incidence and severity):
Areolae/nipple anlagen in the F1 male pups was unaffected by parental administration of the test substance when evaluated on PND 13. The test substance-treated group values were not statistically different from the control group values.
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
There were no test substance-related alterations in organ weights. Some organ weight differences in the 75 ppm F1 group males were statistically significant when compared to the control group. These included the kidney weights (males, absolute and relative to brain weight). The changes were minimal (11 % higher). Therefore, these organ weight differences were considered incidental.
Gross pathological findings:
no effects observed
Description (incidence and severity):
Review of the gross necropsy observations revealed no observations that were considered to be associated with exposure to the test substance.
Histopathological findings:
effects observed, treatment-related
Description (incidence and severity):
Test substance-related microscopic findings were noted in the nasal cavity (Level I, II, III, and/or IV) of the 8, 25, and 75 ppm F1 group male and females.
Test substance-related lesions observed at Levels I through IV were more prominent at Level II and included minimal to marked degeneration of the respiratory, mild to severe degeneration of the transitional epithelium, and minimal to moderate mixed cell inflammation. The degeneration of the transitional and respiratory epithelium was characterized by a disorganized epithelium (Levels I through IV) composed of enlarged, usually vacuolated cells (Levels I through III).
There was loss or clustering of goblet cells and absence of cilia in the affected respiratory epithelium. In some animals, the degeneration was associated with ulceration and mixed cell inflammation characterized by the presence of variable numbers of neutrophils, lymphocytes, and plasma cells. Ulcerated surfaces were often covered with a serofibrinous or serocellular exudate and in some areas the adjacent epithelial extended across the defect.
Other effects:
no effects observed
Behaviour (functional findings):
not examined
Developmental immunotoxicity:
not examined
Dose descriptor:
NOAEL
Generation:
F1
Effect level:
75 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: systemic and neonatal toxicity
Dose descriptor:
LOAEL
Generation:
F1
Effect level:
8 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: based on adverse port of entry findings in respiratory epithelial
Clinical signs:
not examined
Dermal irritation (if dermal study):
not examined
Mortality / viability:
not examined
Body weight and weight changes:
not examined
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Sexual maturation:
not examined
Anogenital distance (AGD):
not examined
Nipple retention in male pups:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Histopathological findings:
not examined
Other effects:
not examined
Behaviour (functional findings):
not examined
Developmental immunotoxicity:
not examined
Reproductive effects observed:
no

DISCUSSION

The objective of this study was to provide preliminary information on the potential adverse effects of the test substance, Dimethylamine (DMA) on male and female reproduction within the scope of a screening study. This encompassed gonadal function, mating behavior, conception, parturition, and lactation of the F0 generation, and the development of F1 offspring from conception through day 40 of postnatal life. In addition, the F1 pups were directly exposed to DMA for 2 weeks following weaning.

All F0 animals survived to the scheduled necropsies. There were no test substance-related systemic and reproductive toxicity noted at 8, 25, and 75 ppm in the F0 generation.

Test substance-related lesions within Level II of the nasal cavity in the 8, 25, and 75 ppm group F0 males and females consisted of minimal or mild transitional and/or respiratory epithelial hyperplasia and mixed cell type inflammation in all test substance exposure groups. Although no systemic adverse effects were noted at any exposure level, local effects that were restricted to Level II of the nasal cavity, not associated with clinical signs, were considered adverse at 75 ppm due to the known corrosive nature of DMA gas.

There were no test substance-related findings at any exposure level in F1 pups during pre-weaning period (PND 0 -28). However, after the initiation of exposure on the F1 generation animals (PND 28-40), slightly lower mean body weight gains were noted in the 75 ppm group F1 males and females occasionally during the exposure period (PND 28–40; statistically significant in males on PND 35-36), resulting in mean absolute body weights that were up to 5.0 % and 6.3 % lower for these males and females, respectively, compared to the control group during the exposure period; the difference was not statistically significant.

Transitional epithelial degeneration and/or ulceration, respiratory epithelial degeneration, and/or mixed cell inflammation were noted in all F1 test substance-exposure groups on PND 40. At 8 and 25 ppm, findings were generally limited to nasal cavity Level II and there was no ulceration or associated clinical signs; therefore, the changes were considered nonadverse. In contrast to the F0 generation, F1 generation initiated exposure at a much younger age and changes in the F1 animals at 75 ppm were consistently observed at multiple levels, and ulceration was prominent at Level II; the F1 animals also had body weight effects. Based on the corrosive nature of DMA gas and the findings from the previous tolerability/range finding study, port of entry effects were expected in the current study. Therefore, the nasal cavity microscopic findings in these groups were considered adverse.

Conclusions:
In conclusion, no systemic and reproductive toxicity was noted in the F0 generation at exposure up to 75 ppm (the highest level tested). Therefore, the no-observed-adverse-effect level for F0 male and female systemic and reproductive toxicity was 75 ppm. Based on test substance-related adverse port of entry findings, consisting of respiratory epithelial hyperplasia and mixed cell type inflammation, and/or ulceration noted in all exposure levels the LOAEL for port of entry effects for F0 generation was 8 ppm.
No systemic and neonatal toxicity were noted in the F1 generation animals, therefore the NOAEL for systemic and neonatal toxicity for F1 generation was 75 ppm. Similar to F0 generation, adverse port of entry findings in respiratory epithelial were noted in F1 animals; therefore, the LOAEL for port of entry effects for F1 animals was 8 ppm.
Executive summary:

The objective of this study was to provide preliminary information on the potential adverse effects of the test substance, Dimethylamine (DMA), on male and female reproduction within the scope of an OECD 422 study. This encompassed gonadal function, mating behavior, conception, parturition, and lactation of the F0 generation, and the development of F1 offspring from conception through day 40 of postnatal life. In addition, the F1 pups were directly exposed to DMA for 2 weeks following weaning.
The study design was as follows:
Group 1 - Treatment: Filtered Air - Exposure Level: 0 ppm - Number of males: 10 - Number of females: 10
Group 2 - Treatment: Dimethylamine - Exposure Level: 8 ppm - Number of males: 10 - Number of females: 10
Group 3 - Treatment: Dimethylamine - Exposure Level: 25 ppm - Number of males: 10 - Number of females: 10
Group 4 - Treatment: Dimethylamine - Exposure Level: 75 ppm - Number of males: 10 - Number of females: 10

Animals were exposed via whole-body inhalation for 6 hours daily. Males were exposed for 14 days prior to mating and continuing throughout mating for a total of 28 days. Females were exposed for 14 days prior to mating and continuing through Gestation Day 20; exposure resumed on Lactation Day 5 and continued until Lactation Day 28 for a total of 58–65 days. Selected F1 pups were directly exposed from Postnatal Day (PND) 28–40.
The following parameters and end points were evaluated in this study: clinical signs, body weights, body weight gains, food consumption, estrous cycles, reproductive performance, parturition, litter viability and survival, anogenital distance, areolae/nipple anlagen, neurobehavior, thyroid hormones, clinical pathology, gross necropsy findings, organ weights, and histopathologic examinations.
Analyzed F0 mean exposure concentrations were 0.1, 9.2, 26.9, and 75.9 ppm in the control, 8, 25, and 75 ppm groups, respectively. Analyzed F1 mean exposure concentrations were 0.0, 7.6, 25.2, and 73.9 ppm in the same respective groups during PND 28-40. On Study Days 3 and 4, non-zero concentrations of DMA were noted in the control chamber. Because no test substance was being directed to the control system, and the chambers were under ambient conditions on these 2 exposure days, there should have been no DMA in the chamber. Therefore, although the reason of non-zero values in the control chamber could not be determined, carryover within the gas chromatogram/sampling setup was suspected to be the cause. The non-zero values were included in the daily average (and study mean as 0.1 ppm) for the control group. No detection of test substance was noted for the rest of the exposure period.
All F0 animals survived to the scheduled necropsies. There were no test substance-related clinical observations noted at the daily examinations or 0.5–3 hours following the completion of exposure at 8, 25, and 75 ppm.
No test substance-related effects were noted on mean body weights, body weight changes, or food consumption throughout the F0 generation at any exposure level.
No test substance-related effects on F0 reproductive performance (male and female mating and fertility, male copulation, and female conception indices) were observed at any exposure level.
The mean numbers of days between pairing and coitus and estrous cycle lengths in the test substance-exposed groups were similar to the control group value. There were no test substance-related effects on mean gestation lengths or the process of parturition at any exposure level.
No test substance-related effects were noted on the functional observational battery or motor activity in the F0 males on Study Day 27 or F0 females on Lactation Day 28.
Hematology, coagulation, and serum chemistry parameters in the 8, 25, and 75 ppm group F0 males and females and mean T4 levels in the F0 males were unaffected by test substance exposure.
There were no test substance-related macroscopic findings or effects on organ weights noted at the scheduled F0 necropsies at any exposure level.
Test substance-related lesions within Level II of the nasal cavity in the 8, 25, and 75 ppm group F0 males and females consisted of minimal or mild transitional and/or respiratory epithelial hyperplasia and mixed cell type inflammation in all test substance exposure groups. Although no systemic adverse effects were noted at any exposure level, based on the corrosive nature of DMA gas and the findings from the previous tolerability/range-finding study, port of entry effects were expected in the current study. Therefore, local effects that were restricted to Level II of the nasal cavity, not associated with clinical signs, were considered adverse at 75 ppm.
The mean number of F1 pups born, live litter size on PND 0, postnatal survival, percentage of males at birth, general physical condition of the pups, anogenital distance, and areola/nipple anlagen in the 8, 25, and 75 ppm groups were unaffected by parental exposure to the test substance. Lower mean body weight gain was noted in the 75 ppm group females at the end of the preweaning period (PND 25–29). No other effects on F1 pup body weights or body weight gains were noted at any exposure level during the preweaning period.
There were no test substance-related macroscopic findings at any exposure level in F1 pups that were found dead or at the scheduled necropsy and no effects on F1 organ weights on PND 28.
All F1 animals selected for direct exposure survived to the scheduled necropsy. There were no test substance-related clinical observations noted at the daily examinations or 0.5–3 hours following the completion of exposure at 8, 25, and 75 ppm.
Slightly lower mean body weight gains were noted in the 75 ppm group F1 males and females occasionally during the exposure period (PND 28–40), resulting in mean absolute body weights that were up to 5.0% and 6.3% lower for these males and females, respectively, compared to the control group during the exposure period; due to the low magnitude of the changes, the lower body weight gains were considered nonadverse. No test substance-related effects on mean body weights or body weight gains were noted in the F1 pups at 8 and 25 ppm.
There were no test substance-related macroscopic findings or effects on organ weights on PND 40 at any exposure level. Transitional epithelial degeneration and/or ulceration, respiratory epithelial degeneration, and/or mixed cell inflammation were noted in all F1 test substance-exposure groups on PND 40. At 8 and 25 ppm, findings were generally limited to nasal cavity Level II and there was no ulceration or associated clinical signs; therefore, the changes were considered nonadverse. At 75 ppm, changes were consistently observed at multiple levels, ulceration was prominent at Level II. Based on the corrosive nature of DMA gas and the findings from the previous tolerability/range finding study, port of entry effects were expected in the current study. Therefore, the nasal cavity microscopic findings in these groups were considered adverse.
In conclusion, no systemic and reproductive toxicity was noted in the F0 generation at exposure up to 75 ppm (the highest level tested). Therefore, the no-observed-adverse-effect level for F0 male and female systemic and reproductive toxicity was 75 ppm. Based on test substance-related adverse port of entry findings, consisting of respiratory epithelial hyperplasia and mixed cell type inflammation, and/or ulceration noted in all exposure levels the LOAEL for port of entry effects for F0 generation was 8 ppm.
No systemic and neonatal toxicity were noted in the F1 generation animals, therefore the NOAEL for systemic and neonatal toxicity for F1 generation was 75 ppm. Similar to F0 generation, adverse port of entry findings in respiratory epithelial were noted in F1 animals; therefore, the LOAEL for port of entry effects for F1 animals was 8 ppm.

Effect on fertility: via oral route
Endpoint conclusion:
no study available
Effect on fertility: via inhalation route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEC
30 ppm
Study duration:
subchronic
Experimental exposure time per week (hours/week):
42
Species:
rat
Effect on fertility: via dermal route
Endpoint conclusion:
no study available
Additional information

A combined repeated dose toxicity test with a reproductive / developmental toxictiy test has been conducted in rats via the inhalation route of exposure (Wang, 2020). The objective of this study was to provide preliminary information on the potential adverse effects of the test substance, Dimethylamine (DMA), on male and female reproduction within the scope of an OECD 422 study. This encompassed gonadal function, mating behavior, conception, parturition, and lactation of the F0 generation, and the development of F1 offspring from conception through day 40 of postnatal life. In addition, the F1 pups were directly exposed to DMA for 2 weeks following weaning.
The study design was as follows: Group 1 - 0 ppm DMA (= Filtered Air), Group 2 - 8 ppm DMA, Group 3 - 25 ppm DMA, Group 4 - 75 ppm DMA (Each group contained 10 males and females). Animals were exposed via whole-body inhalation for 6 hours daily. Males were exposed for 14 days prior to mating and continuing throughout mating for a total of 28 days. Females were exposed for 14 days prior to mating and continuing through Gestation Day 20; exposure resumed on Lactation Day 5 and continued until Lactation Day 28 for a total of 58–65 days. Selected F1 pups were directly exposed from Postnatal Day (PND) 28–40.
The following parameters and end points were evaluated in this study: clinical signs, body weights, body weight gains, food consumption, estrous cycles, reproductive performance, parturition, litter viability and survival, anogenital distance, areolae/nipple anlagen, neurobehavior, thyroid hormones, clinical pathology, gross necropsy findings, organ weights, and histopathologic examinations.
Analyzed F0 mean exposure concentrations were 0.1, 9.2, 26.9, and 75.9 ppm in the control, 8, 25, and 75 ppm groups, respectively. Analyzed F1 mean exposure concentrations were 0.0, 7.6, 25.2, and 73.9 ppm in the same respective groups during PND 28-40. On Study Days 3 and 4, non-zero concentrations of DMA were noted in the control chamber. Because no test substance was being directed to the control system, and the chambers were under ambient conditions on these 2 exposure days, there should have been no DMA in the chamber. Therefore, although the reason of non-zero values in the control chamber could not be determined, carryover within the gas chromatogram/sampling setup was suspected to be the cause. The non-zero values were included in the daily average (and study mean as 0.1 ppm) for the control group. No detection of test substance was noted for the rest of the exposure period.
All F0 animals survived to the scheduled necropsies. There were no test substance-related clinical observations noted at the daily examinations or 0.5–3 hours following the completion of exposure at 8, 25, and 75 ppm. No test substance-related effects were noted on mean body weights, body weight changes, or food consumption throughout the F0 generation at any exposure level. No test substance-related effects on F0 reproductive performance (male and female mating and fertility, male copulation, and female conception indices) were observed at any exposure level.
The mean numbers of days between pairing and coitus and estrous cycle lengths in the test substance-exposed groups were similar to the control group value. There were no test substance-related effects on mean gestation lengths or the process of parturition at any exposure level. No test substance-related effects were noted on the functional observational battery or motor activity in the F0 males on Study Day 27 or F0 females on Lactation Day 28. Hematology, coagulation, and serum chemistry parameters in the 8, 25, and 75 ppm group F0 males and females and mean T4 levels in the F0 males were unaffected by test substance exposure.
There were no test substance-related macroscopic findings or effects on organ weights noted at the scheduled F0 necropsies at any exposure level. Test substance-related lesions within Level II of the nasal cavity in the 8, 25, and 75 ppm group F0 males and females consisted of minimal or mild transitional and/or respiratory epithelial hyperplasia and mixed cell type inflammation in all test substance exposure groups. Although no systemic adverse effects were noted at any exposure level, based on the corrosive nature of DMA gas and the findings from the previous tolerability/range-finding study, port of entry effects were expected in the current study. Therefore, local effects that were restricted to Level II of the nasal cavity, not associated with clinical signs, were considered adverse at 75 ppm.
The mean number of F1 pups born, live litter size on PND 0, postnatal survival, percentage of males at birth, general physical condition of the pups, anogenital distance, and areola/nipple anlagen in the 8, 25, and 75 ppm groups were unaffected by parental exposure to the test substance. Lower mean body weight gain was noted in the 75 ppm group females at the end of the preweaning period (PND 25–29). No other effects on F1 pup body weights or body weight gains were noted at any exposure level during the preweaning period. There were no test substance-related macroscopic findings at any exposure level in F1 pups that were found dead or at the scheduled necropsy and no effects on F1 organ weights on PND 28. All F1 animals selected for direct exposure survived to the scheduled necropsy. There were no test substance-related clinical observations noted at the daily examinations or 0.5–3 hours following the completion of exposure at 8, 25, and 75 ppm. Slightly lower mean body weight gains were noted in the 75 ppm group F1 males and females occasionally during the exposure period (PND 28–40), resulting in mean absolute body weights that were up to 5.0 % and 6.3 % lower for these males and females, respectively, compared to the control group during the exposure period; due to the low magnitude of the changes, the lower body weight gains were considered nonadverse. No test substance-related effects on mean body weights or body weight gains were noted in the F1 pups at 8 and 25 ppm.
There were no test substance-related macroscopic findings or effects on organ weights on PND 40 at any exposure level. Transitional epithelial degeneration and/or ulceration, respiratory epithelial degeneration, and/or mixed cell inflammation were noted in all F1 test substance-exposure groups on PND 40. At 8 and 25 ppm, findings were generally limited to nasal cavity Level II and there was no ulceration or associated clinical signs; therefore, the changes were considered nonadverse. At 75 ppm, changes were consistently observed at multiple levels, ulceration was prominent at Level II. Based on the corrosive nature of DMA gas and the findings from the previous tolerability/range finding study, port of entry effects were expected in the current study. Therefore, the nasal cavity microscopic findings in these groups were considered adverse.
In conclusion, no systemic and reproductive toxicity was noted in the F0 generation at exposure up to 75 ppm (the highest level tested). Therefore, the no-observed-adverse-effect level for F0 male and female systemic and reproductive toxicity was 75 ppm. Based on test substance-related adverse port of entry findings, consisting of respiratory epithelial hyperplasia and mixed cell type inflammation, and/or ulceration noted in all exposure levels the LOAEL for port of entry effects for F0 generation was 8 ppm.
No systemic and neonatal toxicity were noted in the F1 generation animals, therefore the NOAEL for systemic and neonatal toxicity for F1 generation was 75 ppm. Similar to F0 generation, adverse port of entry findings in respiratory epithelial were noted in F1 animals; therefore, the LOAEL for port of entry effects for F1 animals was 8 ppm.

An Extended One-generation Reproductive Toxictiy test has been conducted in rats via the inhalation route of exposure (Coder, 2021). The objective of this study was to evaluate the potential adverse effects of the test substance on reproduction in an extended one-generation study. This included evaluation of life stages not covered by other types of toxicity studies and tested for effects that may occur as a result of pre- and postnatal chemical exposure.

The study design was as follows: Group 1 - 0 ppm DMA (Filtered Air), Group 2 - 4 ppm DMA, Group 3 - 12 ppm DMA, Group 4 - 30 ppm DMA (Each group contained 24 males and 24 females). Animals in the parental (F0) generation were exposed via whole-body inhalation for 6 hours daily for 70 consecutive days prior to mating and continuing through the day prior to euthanasia. Maternal exposure was suspended from Gestation Day 20 through Lactation Day 4 to prevent confounding effects on parturition and maternal nursing and nesting behavior. The offspring in the F1generation were potentially exposed in utero and through nursing during lactation. The offspring selected to constitute the F1 generation were exposed beginning at weaning (PND 28) and continuing until the day prior to euthanasia. Due to observation of lower mean fertility and copulation/conception indices for F0 males and females (see below), F1 animals assigned to Cohort 1B for follow-up reproductive assessments were bred to obtain reproductive performance data for the F1 generation. All procedures for F1 animals assigned to Cohort 1B breeding were generally the same as those for the F0 generation, with the exception that F1 females were euthanized in mid-gestation, on Gestation Day 15, because there were no observations related to the process of parturition or gestation lengths in the F0 generation nor any effects on F1 pup birth weights or survival, and hence further assessments of the same endpoints in the next generation were not warranted. F1 males were euthanized following examination of females with evidence of mating.

The following parameters and end points were evaluated in this study: clinical signs, body weights, body weight gains, food consumption, estrous cycles, reproductive performance, parturition, litter viability and survival, pre- and postweaning developmental landmarks, thyroid hormones, clinical pathology, gross necropsy findings, sperm parameters, organ weights, and histopathologic examinations.

Target exposure concentrations were 4, 12 and 30 ppm. Overall mean analyzed exposure concentrations were 4.3, 11.9 and 30.7 ppm for the F1 generation and 4.2, 11.9 and 31.1 ppm for the F1 generation.

F0Generation: There were no test substance-related effects on survival at any exposure level. One male and one female each in the 30 ppm group were found dead on Study Day 46 and 113, respectively. Although both animals had test substance-related microscopic lesions in the nasal cavity that were similar to those described in other animals in this group examined at scheduled necropsy, a specific cause of death was not determined based on microscopic examination. These deaths were deemed unlikely to be test substance related based on the lack of any other evidence of systemic toxicity at this dosage level. All other F0 animals survived to the scheduled necropsies, and there were no test substance-related clinical observations, or any effects on mean body weights, body weight gains, food consumption or food efficiency during the study.

In the F0 generation, lower male and female fertility and copulation/conception indices were observed in the 30 ppm group, when compared to the control group. Five (5) of 24 mating pairs in the 30 ppm group did not produce a litter as opposed to the control group where 100 % of the mating pairs produced a litter. There were, however, no correlating effects on estrous cyclicity, gestation lengths, the process of parturition or on sperm morphology, or histopathology of the reproductive organs. The mean number of days between pairing and coitus were also comparable across all groups.There were no effects on F0 reproductive performance at 4 and 12 ppm.

Increased T4 levels were noted for males and females in the 12 and 30 ppm groups; differences from the control group were statistically significant. However, due to lack of other correlating changes in the levels of TSH, thyroid organ weight, or thyroid histopathology in the F0generation, and the lack of any effects on thyroid endpoints in the F1 generation, these changes were considered likely to be incidental and not related to test substance administration.

There were no test substance-related gross macroscopic findings or any changes in clinical pathology parameters (hematology, coagulation, serum chemistry, and urinalysis) noted for F0 animals at any exposure level.

Dimethylamine exposure was associated with microscopic findings in the nasal cavity (level II) of F0 animals at ≥ 4 ppm. There was a dose-related increase in incidence and/or severity of respiratory epithelial hyperplasia and transitional epithelial hyperplasia in males and females, and mixed cell inflammation in the males. The mixed cell inflammation was similar in females at 4 and 12 ppm and at a higher incidence in the 30 ppm group. Histologically, the transitional and respiratory epithelial hyperplasia was characterized by focal to multifocal increased numbers of cells and disorganization. There was loss or clustering of goblet cells and/or decreased cilia in the affected respiratory epithelium. Inflammation, when present, was associated with the hyperplasia and included variable numbers of neutrophils, lymphocytes, and plasma cells. These histologic lesions were considered locally adverse at all exposure levels based on the presence of inflammation and epithelial hyperplasia.

F1 Generation: F1 postnatal survival was unaffected by test substance exposure at all exposure levels. In addition, pup birth weights and the general physical condition of F1 pups during the pre-weaning period were unaffected by test substance exposure. Mean pup body weights and body weight gains were comparable across all groups, including in the period immediately following re-initiation of maternal test substance exposures on PND 5. There were also no substance-related effects on serum levels of thyroid hormones for F1 pups (on PND 4 and 28) or any effects on preweaning developmental landmarks (anogenital distance, areolae/nipple retention) at any exposure level in the F1 generation.

Following weaning, there were no test substance-related effects on survival in the F1generation at any exposure level. One male in the 12 ppm group was found dead on PND 63; there were no remarkable clinical or macroscopic findings noted for this male and given the lack of mortality at the 30 ppm, this death was considered incidental and unrelated to test substance exposure. All other F1 animals survived to the scheduled necropsies, and there were no test substance-related clinical observations, or any effects on mean body weights, body weight gains, food consumption or food efficiency during the generation. There were also no substance-related effects on post weaning developmental landmarks (vaginal patency, onset of estrus or balanopreputial separation), serum levels of thyroid hormones, gross macroscopic findings, estrous cyclicity, sperm parameters, or clinical pathology parameters at any exposure level for F1 males and females (Cohort 1A, PND 90).

Microscopic findings related to test substance exposure in F1 Cohort 1A animals were similar to the F0 generation. In the nasal cavity (level II) of animals exposed to ≥ 4 ppm, a dose-related increase in incidence and/or severity of respiratory epithelial hyperplasia, transitional epithelial hyperplasia, vacuolar degeneration of the respiratory epithelium, and vacuolar degeneration of the transitional epithelium was noted in males and females. Inflammation was similar in all dose groups in males and showed a slightly increased incidence at 12 and 30 ppm in females compared to 4 ppm. Similar to the F0 generation, these findings were considered locally adverse at all exposure levels based on the presence of inflammation and epithelial hyperplasia. There were no test substance-related effects on primordial/small growing follicles in F1 Cohort 1A females on PND 90.

Due to observation of lower mean fertility and copulation/conception indices for F0 males and females, F1 animals assigned to Cohort 1B for follow-up reproductive assessments were bred to obtain reproductive performance data for the F1 generation. There were no test substance related effects on reproductive performance. Male and female mating, fertility, and copulation and conception indices, estrous cyclicity and the number of days between pairing and coitus were comparable across all exposure levels. Mean numbers of corpora lutea, implantation sites and viable embryos were similar across all exposure levels. Based on the lack of any effects on reproductive performance of the F1generation, it was concluded that the lower male and female fertility and copulation/conception indices noted for animals in the 30 ppm group in the F0 generation were spurious and unrelated to test substance exposures.

In conclusion, dimethylamine exposure was associated with locally adverse histologic lesions at all exposure levels. Thus, an exposure level of 4 ppm was considered to be the lowest-observed-adverse-effect level (LOAEL) for locally adverse effects for F0 and F1males and females when dimethylamine was administered via whole body inhalation.

In the absence of any systemically adverse effects in either generation (F0 and F1males and females) during the study, an exposure level of 30 ppm, the highest exposure level evaluated, was considered to be the no-observed-adverse-effect level (NOAEL) for F0 and F1male and female systemic toxicity when dimethylamine was administered via whole body inhalation to Crl:CD(SD) rats.

Based on the lack of any effects F1 offspring during the preweaning period, an exposure level of 30 ppm was considered to be the NOAEL for F1 neonatal and developmental toxicity. Based on the lack of any evidence of reproductive toxicity at any exposure level following the evaluation of reproductive performance, sperm measurements, and estrous cyclicity in the F0 and F1 generations, the NOAEL for F0 and F1 reproductive toxicity was also considered to be 30 ppm, the highest exposure level evaluated.

Effects on developmental toxicity

Description of key information

BASF AG (2009): the study with rats and DMA hydrochloride, test concentrations: 100, 300 and 1000 mg/kg bw. A NOAEL for maternal toxicity was 300 mg/kg bw and a NOAEL for developmental toxicity, including teratogenicity was 1000 mg/kg bw.

WIL Research (2016): There were no test substance-related effects on intrauterine growth, survival, and fetal morphology at any exposure concentration; therefore, the NOAEC for embryo/fetal development was 250 ppm for rabbits.

Link to relevant study records

Referenceopen allclose all

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
13 Feb 2008 - 17 Mar 2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Qualifier:
according to guideline
Guideline:
other: Corrigendum to ECC Directive 2004/73/EC, Part B
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes (incl. QA statement)
Limit test:
yes
Species:
rat
Strain:
Wistar
Details on test animals or test system and environmental conditions:
Time-mated Wistar rats (Crl:WI[Han]) were supplied by Charles River Laboratories, Research Models and Services, Germany GmbH at an age of about 10-15 weeks. Only animals free from clinical signs of disease were used for the investigations.
The animals were paired by the breeder and supplied on GD 0 (= detection of vaginal plug/sperm). After arrival, they were randomly allocated to the test groups by withdrawal from the transport box at random and placed in to a random distribution of groups. After randomization the rats were identified uniquely by ear tattoo.
Reason for species selection: The Crl:WI(Han) strain was selected since extensive experience is available on Wistar rats. This specific strain has been proven to be sensitive to substances with a teratogenic potential.

Acclimatization period: from arrival to GD 6. (so from Day GD 0 to GD 6)

Housing: singly from GD 0-20 in type M III Makrolon cages supplied by BECKER & CO., Castrop-Rauxel, Germany (floor area about 800 cm²).
Bedding: Lignocel FS 14 fibres, dustfree bedding, supplied by SSNIFF, Soest, Germany
Enrichment: wooden gnawing blocks (Typ NGM E-022, supplied by Abedd® Lab. and Vet. Service GmbH, Vienna, Austria).

Accomodation: in fully air-conditioned rooms (central air conditioning)
Temperature: 20-24°C
relative humidity: 30-70%.
Air change rate: 10 times per hour.
The light cycle rhythm was 12 hours light from 6:00 a.m. to 6:00 p.m. and 12 hours darkness from 6:00 p.m. to 6:00 a.m.

Before the study started, the animal room was completely disinfected using a disinfector ("AUTEX" fully automatic, formalin-ammonia-based terminal disinfection). In general, each week the walls and the floor were cleaned with water containing about 0.5% Mikro-Quat (supplied by Ecolab Deutschland GmbH, Hanau, Germany).
Food: ground Kliba maintenance diet mouse/rat “GLP” supplied by PROVIMI KLIBA SA (Kaiseraugst, Switzerland).
Food: available ad libitum throughout the study (from the day of supply to the day of necropsy),
Drinking water: available from water bottles ad libitum

The food used in the study was assayed for chemical and for microbiological contaminants.
The drinking water was regularly assayed for chemical contaminants.
Bedding and the enrichment were regularly assayed for contaminants (chlorinated hydrocarbons and heavy metals).

Based on the pregnant animals the body weight on day 0 varied between 142.5-191.3 g.
Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
The oral route was selected since this has proven to be suitable for the detection of a toxicological hazard.
A standard dose volume of 10 mL/kg body weight was used for each group.
The calculation of the volume administered was based on the most recent individual body weight.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Tested by various analyses:
• the stability of the test substance solutions was demonstrated over a period of 10 days at room temperature
• The results of the analyses of the test substance solutions in drinking water confirmed the correctness of the prepared concentrations. Generally, the analytical values of the samples corresponded to the expected values within the limits of the analytical method, i.e. were above 90% and below 110% of the nominal concentrations (see PART III; Supplement); except two deviant values in test groups 1 and 2. One deviant value in the samples from the study beginning (test group 2 = 88.8%) and one deviant value in the samples from the end of the study (test group 1 = 80.5%) were considered as outliers with respect to precision and accuracy of the analytical method. As no effects of toxicological concern were observed even at 1000 mg/kg bw/d, these minor deviations had virtually no effect on the quality of the study
Duration of treatment / exposure:
administration from gestational day (GD) 6 through GD 19 = from implantation to one day prior to the expected day of parturition
Frequency of treatment:
once daily
Duration of test:
terminal sacrifice on GD 20
Dose / conc.:
100 mg/kg bw/day (nominal)
Remarks:
nominal in water
Dose / conc.:
300 mg/kg bw/day (nominal)
Remarks:
nominal in water
Dose / conc.:
1 000 mg/kg bw/day (nominal)
Remarks:
nominal in water
No. of animals per sex per dose:
25 time-mated female Wistar rats per group
Control animals:
yes, concurrent vehicle
Maternal examinations:
Food consumption and body weights of the animals checked regularly (GD 0, 1, 3, 6, 8, 10, 13, 15, 17, 19 and 20).
Mortality: a check was made twice a day on working days or once a day on Saturdays, Sundays or on public holidays (GD 0-20).
Clinical symptoms: a cage-side examination was conducted at least once daily for any signs of morbidity, pertinent behavioral changes and signs of overt toxicity. If such signs occurred, the animals were examined several times daily (GD 0-20).
gross pathology (including weight determinations of the unopened uterus and the placentae).

Sacrifice of the animals on GD 20, then necropsied and assessed by gross pathology.
The uteri and the ovaries were removed and the following data were recorded:
- Weight of the unopened uterus*
- Number of corpora lutea
- Number and distribution of implantation sites classified as:
• live fetuses
• dead implantations:
a) early resorptions (only decidual or placental tissues visible or according to SALEWSKI (Salewski, 1964) from uteri from apparently non pregnant animals and the empty uterus horn in the case of single horn pregnancy)
b) late resorptions (embryonic or fetal tissue in addition to placental tissue visible)
c) dead fetuses (hypoxaemic fetuses which did not breathe spontaneously after the uterus had been opened)
Ovaries and uterine content:
For each dam, corpora lutea were counted and number and distribution of implantation sites (differentiated by resorptions, live and dead fetuses) were determined
Fetal examinations:
Examinations of the fetuses after dissection from the uterus At necropsy each fetus was weighed, sexed, and external tissues and all orifices were examined macroscopically. The sex was determined by observing the distance between the anus and the base of the genital tubercle and was later confirmed by internal examination, in all fetuses designated for soft tissue examination. If there were discrepancies between the "external" and the "internal" sex of a fetus, the fetus was finally sexed according to the internal sex.

Furthermore, the viability of the fetuses and the condition of placentae, umbilical cords, fetal membranes, and fluids were examined. Individual placental weights were recorded. Thereafter, the fetuses were sacrificed by subcutaneous injection of a pentobarbital (Narcoren®; dose: 0.1 mL/fetus). After these examinations, approximately one half of the fetuses per dam were eviscerated, skinned and placed in ethanol, the other half was placed in Harrison’s fluid for fixation.

Soft tissue examination of the fetuses
The fetuses fixed in Harrison’s fluid were examined for any visceral findings according to the method of BARROW and TAYLOR (Barrow and Taylor, 1969). After this examination these fetuses were discarded.

Skeletal examination of the fetuses
The skeletons of the fetuses fixed in ethanol were stained according to a modified method of KIMMEL and TRAMMELL (Kimmel and Trammell, 1981). Thereafter, the skeletons of these fetuses were examined under a stereomicroscope. After this examination the stained fetal skeletons were retained individually.

Classifications based on terms and definitions proposed by CHAHOUD et al. and SOLECKI et al. (Chahoud et al., 1999; Solecki et al., 2001; Solecki et al., 2003):
- Malformation = A permanent structural change that is likely to adversely affect the survival or health.
- Variation = A change that occurs also in fetuses of control animals and is unlikely to adversely affect the survival or health. This includes delays in growth or morphogenesis that has otherwise followed a normal pattern of development.

Moreover, the term "unclassified observation" was used for those fetal findings, which could not be classified as malformations or variations.
All fetal findings were listed in tables according to these classifications.
Statistics:
The conception rate (in %) was calculated according to the following formula:
(number of pregnant animals x 100)/number of fertilized animals
The preimplantation loss (in %) was calculated according to the following formula:
((number of corpora lutea – number of implantations) x 100) / number of corpora lutea
The postimplantation loss (in %) was calculated according to the following formula:
((number of implantations – number of live fetuses) x 100)) / number of implantations

DUNNETT-test (twosided)
FISHER'S EXACT test (one-sided)
WILCOXON-test (onesided)
Details on maternal toxic effects:
Maternal toxic effects:yes. Remark: salivation, reduced food consumption, yellowish discolored urine,

Details on maternal toxic effects:
There were no test substance-related mortalities in any of the female animals in any of the groups.
The mean food consumption of the high-dose dams (1000 mg/kg bw/d) was statistically significantly reduced between GD 6 to 8 (14% below control) and GD 8 to 10 (12% below control; see Fig. 4.2.1.3.1.). However, on the following days the food consumption of the high-dose rats became comparable to control. The average food consumption of the highdose dams during the treatment phase (GD 6-19) was less than 4% below the control value. The impaired food consumption is considered to be related to treatment. The food consumption of the females of test groups 1 and 2 (100 and 300 mg/kg bw/d) was unaffected and did not show any statistically significant or biologically relevant differences in comparison to the controls.
Mean body weight and mean body weight gain of low-, mid- and high-dose animals (100; 300 and 1000 mg/kg bw/d) were similar to those of the concurrent controls. All differences observed in these groups during the pretreatment and the treatment period were without biological relevance and reflected the normal variation inherent in the strain of rats used in the present experiment.
The mean gravid uterus weight of the dams of test groups 1; 2 and 3 (100; 300 and 1000 mg/kg bw/d) were comparable to the control and not affected by treatment.
At necropsy, no test substance-related findings were observed in the dams of test groups 0 - 3 (0; 100; 300 and 1000 mg/kg bw/d). One animal of test group 2 showed a diaphragmatic hernia (No. 56). This observation was not considered to be associated to the test compound

The conception rate reached 96% in the control group as well as in test group 1 (100 mg/kg bw/d), 92% in test group 2 (300 mg/kg bw/d) and 100% in test group 3 (1000 mg/kg bw/d). As all presumed pregnant rats had implantation sites at necropsy, a sufficient number of dams were available for the purpose of the study.
No test substance-related and/or biologically relevant differences with regard to conception rate, mean number of corpora lutea, implantation sites, pre- and postimplantation loss and resorptions (total, early and late) were observed

Test group 3 (1000 mg/kg bw/d)
Dams
• Salivation after treatment in 25 dams
• Statistically significant impairment of food consumption between GD 6-8 and GD 8-10.

All animals of the low-, mid- and high-dose groups showed yellowish discoloured urine what has been considered to be treatment-related. Discoloured urine occurred from GD 8 onwards and persisted until the end of the study. This urine discolouration was a sign of systemic availability of the test substance rather than being an adverse effect. It happened most likely due to the excreted test compound or its metabolite(s).
Dose descriptor:
NOAEL
Effect level:
300 mg/kg bw/day (nominal)
Basis for effect level:
other: maternal toxicity
Remarks on result:
other: see Remarks
Remarks:
based on decreased food consumption and salivation after treatment
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day
Basis for effect level:
other: developmental toxicity
Remarks on result:
other: see Remarks
Remarks:
because no evidence of an adverse effect of the test compound on fetal morphology
Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects. Remark: up to 1000 mg/kg bw /day

Details on embryotoxic / teratogenic effects:
The sex distribution of the fetuses in test groups 1-3 (100; 300 and 1000 mg/kg bw/d) was comparable to the control fetuses. Observable differences were without biological relevance.
The mean placental weights of dose group 1 and 2 (100 and 300 mg/kg bw/d) were similar to the corresponding control. The mean placental weight of the male fetuses of dose group 3 (1000 mg/kg bw/d) was statistically significantly reduced (about 19% below the concurrent control value) but clearly in the range of the historical control data (PART III, Supplement). Therefore, the observed differences were not considered to be biologically relevant and without relation to dosing.
The mean fetal weights were not influenced by the test substance administration and did not show any biologically relevant differences between the test substance-treated groups and the control. The observable differences between the groups reflect the usual fluctuation for this parameter.
External malformations were recorded for one fetus in the control, for four fetuses in the lowdose group (100 mg/kg bw/d) and for four fetuses in the mid-dose group; (300 mg/kg bw/d; Tab. 4.3.2.1.1). Since two low-dose (100 mg/kg bw/d) fetuses of the same litter (dam no. 35) showed gastroschisis and two mid-dose (300 mg/kg bw/d) fetuses of the same litter (dam No. 58) had a menigocele it is reasonable to consider a spontaneous background in single animals rather than a test substance-induced effect. Furthermore, these findings did not show a relation to dosing (Tab. 4.3.2.1.2.). All other findings were incidental or can be found in the historical control data (PART III, Supplement).
No external variations were observed.
No unclassified external observations were recorded.

Soft tissue malformations were recorded for three fetuses in the low-dose group (100 mg/kg bw/d) and for three fetuses in the mid-dose group; (300 mg/kg bw/d; Tab. 4.3.3.1.1.). Since the low- (100 mg/kg bw/d) and the mid-dose (300 mg/kg bw/d) fetuses belonged to the same litters (dam no. 35 and dam no. 58, respectively) and with regard to the findings of the external observation, it is reasonable to consider a spontaneous background in single animals rather than a test substance-induced effect due to a missing dose-response relationship (Tab. 4.3.3.1.2.).

Fetuses
• No test substance-related adverse effects Test group 2 (300 mg/kg bw/d)
• No test substance-related adverse effects on dams, gestational parameters or fetuses Test group 1 (100 mg/kg bw/d)
• No test substance-related adverse effects on dams, gestational parameters or fetuses
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Embryotoxic / teratogenic effects:no effects
Abnormalities:
not specified
Developmental effects observed:
not specified

Malformations of the fetuses: cleft palate, gastroschisis, exencephaly, mandibular micrognathia, malrotated limb (bilateral hindlimb) meningocele.

Soft tissue malformations:

Fetus with multiple visceral malformations: short intestine, large uterus horns (reaching to the middle of the kidneys), enlarged ovaries, persistent truncus arteriosus, heart: muscular ventricular septum defect, anophthalmia (bilateral),

Fetus with multiple visceral malformations: absent subclavian, persistent truncus arteriosus, heart: muscular ventricular septum defect, anophthalmia (bilateral),

anophthalmia (left)

Soft tissue variation:

Four soft tissue variations were detected, i.e. dilated cerebral ventricle, short innominate and uni- or bilateral dilation of renal pelvis and ureter. Dilated cerebral ventricle and short innominate occurred only in the male fetus 35-07 of the low-dose group and the male fetus 58-05 of the mid-dose group in addition to external, soft tissue and skeletal malformations. Uni- or bilateral dilation of renal pelvis and ureter were seen in several fetuses of all test groups including the control. These findings were considered to be incidental because they did not show a relation to dosing. (Tab. 4.3.3.2.1.). In addition, they can be found in the historical control data (PART III, Supplement) in comparable or even higher incidences.

Fetal skeletal malformations:

Skeletal malformations were noted in fetuses of test groups 1 and 2 (100 and 300 mg/kg bw/d; Tab. 4.3.4.1.1.). No dose-response relationship was observed (Tab. 4.3.4.1.2.). Based on the rate of affected fetuses per litter, the incidence of skeletal malformations was comparable to the historical control data (PART III, Supplement).

Fetal skeletal variations:

For all test groups, skeletal variations of different bone structures were observed, with or without effects on corresponding cartilages. The observed skeletal variations were related to several parts of fetal skeletons and appeared without a relation to dosing (Tab. 4.3.4.2.1.). Based on the rate of affected fetuses per litter, the incidence of skeletal variations was comparable to the historical control data (PART III, Supplement).

Fetal skeletal unclassified cartilage observation:

Two isolated cartilage findings without impact on the respective bone structures, which were designated as unclassified cartilage observations, were noted in all test groups or only in test group 2. These cartilage findings, i.e. bipartite processus xiphoideus and notched manubrium were related to the sternum. An association to the test substance is not assumed because the incidences of both observations were within the historical control range (PART III, Supplement).

Conclusions:
Thus, the oral administration of Dimethylamine hydrochloride to pregnant Wistar rats had no effect on morphology of offspring at any dose level tested (100; 300 and 1000 mg/kg bw/d). The recorded incidences did not suggest a treatment-relationship, but reflected the usual biological variation inherent in the strain of rats used for this experiment.
In conclusion, the no observed adverse effect level (NOAEL) for maternal toxicity is 300 mg/kg bw/d based on decreased food consumption and salivation after treatment in the highdose dams (1000 mg/kg bw/d). The no observed adverse effect level (NOAEL) for prenatal developmental toxicity is 1000 mg/kg bw/d because there was no evidence of an adverse effect of the test compound on fetal morphology.
Executive summary:

Dimethylamine hydrochloride was administered to pregnant Wistar rats daily by gavage from implantation (GD 6) to one day prior to the expected day of parturition (GD 19). The test substance did not cause any mortality. Test substance-related relevant clinical effects were only seen in the high-dose dams (1000 mg/kg bw/d), i.e. salivation after treatment and decreased food consumption, although the latter did not affect body weight, body weight gain, net body weight gain and uterus weight. At necropsy, no test substance related findings were noted in any of the dams. The temporary salivation was likely to be induced by the taste of the test substance or by local irritation of the upper digestive tract. It was not considered to be a sign of systemic toxicity. All animals of the low-, mid- and high-dose groups showed yellowish discoloured urine which occurred from GD 8 onwards and persisted until the end of the study. The urine discolouration was a sign of systemic availability of the test substance and happened most likely due to the excreted test compound or its metabolite(s). This finding has been considered to be treatment-related but was not assessed as an adverse effect. No differences of toxicological relevance between the control and the dose groups were determined for reproductive parameters such as conception rate, mean number of corpora lutea, mean number of implantations, pre- and postimplantation losses, live fetuses and fetal sex ratio. Examination of the fetuses revealed incidental fetal external, soft tissue and skeletal malformations in individual litters of the low- and the mid-dose groups as well as the control. Since malformations only occurred in one litter of the low- and one litter of the mid-dose group, it is reasonable to consider a spontaneous background in single animals rather than a test substance-induced effect. A consistent pattern and a dose-response relationship were missing. Thus, a test substance-related effect on ontogeny is not assumed. No external variation was noted. Four soft tissue and a broad range of skeletal variations occurred in every test group including the control. All of these variations are documented at a comparable frequency in the historical control data (Part III, Supplement). A spontaneous origin is also assumed for the unclassified cartilage observations, which were recorded for fetuses of all dose-groups including the control. Character as well as distribution of all of these findings did not suggest a relation to treatment. In summary, there was no evidence of an adverse effect of Dimethylamine hydrochloride on fetal morphology at any dose level tested.

Thus, the oral administration of Dimethylamine hydrochloride to pregnant Wistar rats had no effect on morphology of offspring at any dose level tested (100; 300 and 1000 mg/kg bw/d). The recorded incidences did not suggest a treatment-relationship, but reflected the usual biological variation inherent in the strain of rats used for this experiment. In conclusion, the no observed adverse effect level (NOAEL) for maternal toxicity is 300 mg/kg bw/d based on decreased food consumption and salivation after treatment in the highdose dams (1000 mg/kg bw/d). The no observed adverse effect level (NOAEL) for prenatal developmental toxicity is 1000 mg/kg bw/d because there was no evidence of an adverse effect of the test compound on fetal morphology.

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)
Deviations:
no
GLP compliance:
yes
Remarks:
US EPA EPA GLP Standards 40 CFR Part 160 and 40 CFR Part 792 (16-Oct-1989 and 18-Sep-1989, respectively) and the OECD Principles of GLP [C(97) 186/Final] (26-Nov-1997)
Limit test:
no
Species:
rabbit
Strain:
New Zealand White
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Strain: New Zealand White [Hra:(NZW)SPF]
- Source: Covance Research Products, Inc., Greenfield, IN
- Age at study initiation: approximately 6 months old upon receipt.
- Weight at study initiation: Body weight values ranged from 2900 g to 3878 g on gestation day 0.
- Fasting period before study: no, food was withheld only during exposure periods.
- Housing: Upon arrival, all rabbits were housed individually in clean, stainless steel cages suspended above ground corncob bedding (Pel O’Cobs®; The Andersons, Cob Products Division, Maumee, OH). During exposure period, animals were individually housed in stainless steel wire mesh caging.
- Diet (e.g. ad libitum): The basal diet: PMI Nutrition International, LLC Certified Rabbit LabDiet® 5322. The basal diet was offered in 25-g increments 3 times per day on the day of arrival and in increased amounts over the next few days, until the animals gradually achieved ad libitum status prior to the exposure period; basal diet was offered ad libitum throughout the study, except during the exposure periods when food was withheld.

Kale (1 leaf at each occasion) was provided to each animal daily for environmental enrichment and to aid in maintaining the animal's gastrointestinal health, beginning upon animal receipt and continuing throughout the duration of the study. Kale present in the cage was discarded at the time of providing a new leaf.
Use of non-certified kale did not have an adverse impact on the quality or integrity of the data or the outcome of the study as kale is commonly regarded as safe and is intended for human consumption.

- Water (e.g. ad libitum): Municipal water. Reverse osmosis purified (on site) drinking water, delivered by an automatic watering system, was provided ad libitum throughout the study, except during the exposure periods when water was withheld.
- Acclimation period: not specified. However, it is reported that animals were received on gestation day 3 or 4 and the exposure started from gestation day 7.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19°C ± 3° (66°F ± 5°F)
- Humidity (%): 50% ± 20%,
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES:
21-Sep-2015 to 13-Oct-2015 (Test substance exposure period (Phase I))
02-Nov-2015 to 24-Nov-2015 (Test substance exposure period (Phase II))
Route of administration:
inhalation: gas
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: humidified filtered air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Exposures were conducted using four 1500-L glass and stainless steel whole-body exposure chambers. One 1500-L chamber was dedicated to the filtered-air control group and three 1500-L chambers were dedicated to each of the 3 exposure levels. One chamber was dedicated for each group for the duration of the study. Chamber supply air was provided from a HEPA- and charcoal-filtered, temperature- and humidity-controlled source. All exposure chamber exhaust passed through the facility exhaust system that included charcoal- and HEPA-filtration units.

- Method of holding animals in test chamber: Animals were individually housed in stainless steel wire mesh caging and food and water were withheld during the exposure periods. Animals were housed in a normal animal colony room during non-exposure hours. Prior to each exposure, the animals were transferred to exposure caging and transported to the exposure room. Animals were then exposed for the requisite duration and returned to their home cages in the animal colony room. Animals were housed individually in standard exposure batteries of appropriate size for the whole-body chamber in use during exposure periods. To ensure a similar exposure for all animals, the exposure batteries were rotated daily amongst 3 chamber positions.

- Source and rate of air: Test substance atmosphere was generated by releasing test substance gas (1,000,000 ppm) from the original cylinder. The gas cylinder was heated using heating pads controlled by temperature controllers and J-Type thermocouples. A 2 stage regulator with pressure gauges was used to control test substance flow from the cylinder to a needle valve through 1/8-inch stainless steel tubing. Test substance from the regulator was delivered to a manifold system equipped with a pressure gauge to monitor manifold pressure. The manifold delivery line was heated using a heat tape with a temperature controller and a J Type thermocouple. The manifold was used to distribute test substance to each exposure chamber through 1/8-inch Teflon® tubing. The test substance gas flow to the manifold was controlled using a needle valve and metered using rotameter-type flowmeters.

- Temperature, humidity, pressure in air chamber: Temperature, relative humidity, chamber ventilation rate, and negative pressure within the exposure chambers were continually monitored and recorded approximately every 45 minutes during the 6-hour exposure periods. The mean temperature and mean relative humidity were to be between 16°C to 22°C and 30% to 70%, respectively.

- Air flow rate: Chamber airflow rates were monitored using a sharp edge orifice meter and Dwyer Magnehelic® Indicating Transmitter pressure gauge (Dwyer Instruments, Inc.; Michigan City, IN). Each gauge was calibrated for conversion from pressure to airflow in standard liters per minute through the use of a Fox Gas Mass Flowmeter Transmitter (Model FT2, Fox Thermal Instruments; Marina, CA).

- Air change rate: at least 12 air changes per hour.

- Treatment of exhaust air: Test substance gas was directed to the chamber inlet through a 3-way valve where it was mixed and diluted with facility dilution supply air. The 3-way valve was used to divert the flow of the test substance gas from the chamber directly to facility exhaust, if necessary. The test substance delivery lines from the 3-way bypass valve to the chamber inlet were 1/4 inch stainless-steel tubing heated using a heat tape with temperature controllers and J-Type thermocouples.
- Oxygen content was measured during the method development phase and was 20.9% for all chambers.

TEST ATMOSPHERE
- Brief description of analytical method used: GC
- Samples taken from breathing zone: yes.

VEHICLE (if applicable)
The control substance used for exposure of the control group (Group 1) was humidified, filtered air.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Due to the use of a single cylinder of test substance for generation of all test substance atmospheres, nominal concentrations were not calculated. Test substance usage was documented in the study records.

Analyzed exposure concentrations were determined at approximately 45-minute intervals using an appropriate gas chromatography (GC) method. Samples were collected from the approximate animal breathing zone of each exposure chamber via 1/8-inch Teflon® tubing. Exposure atmosphere samples were collected automatically using an external multi position valve. Gas sample injection into the chromatography column occurred via an internal gas-sampling valve with a sample loop. The chromatograph was displayed, the area under the sample peak was calculated and stored, and the concentration in parts per million (ppm) was calculated.
Duration of treatment / exposure:
6 hours per day
Frequency of treatment:
once a day
Duration of test:
during gestation days 7-28
Dose / conc.:
0 ppm (analytical)
Remarks:
Due to the use of a single cylinder of test substance for generation of all test substance atmospheres, nominal concentrations were not calculated. Test substance usage was documented in the study records.
Dose / conc.:
50 ppm (analytical)
Remarks:
Due to the use of a single cylinder of test substance for generation of all test substance atmospheres, nominal concentrations were not calculated. Test substance usage was documented in the study records.
Dose / conc.:
100 ppm (analytical)
Remarks:
Due to the use of a single cylinder of test substance for generation of all test substance atmospheres, nominal concentrations were not calculated. Test substance usage was documented in the study records.
Dose / conc.:
250 ppm (analytical)
Remarks:
Due to the use of a single cylinder of test substance for generation of all test substance atmospheres, nominal concentrations were not calculated. Test substance usage was documented in the study records.
No. of animals per sex per dose:
24
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: pre-test:
In WIL 235503 (Weinberg, 2015), nonpregnant rabbits were exposed to 50, 100, 150, 300, and 700 ppm of the test substance atmospheres for 6-hours (whole-body) per day for 10 consecutive days. Exposure of 700 ppm was not tolerated and the animals were euthanized prior to the end of the first day of exposure. On study day 1, observations of labored respiration were noted at the 300 ppm exposure concentration, but all rabbits survived and this observation was not noted following the first day of exposure. There were no gross observations at necropsy from the rabbits that survived to scheduled euthanasia. Based on these data, exposure concentrations of 50, 150, 200, and 250 ppm were selected for a range-finding study in pregnant rabbits (Charlap, 2015, WIL-235501). All animals survived to scheduled euthanasia. Decreased respiration was noted in animals at the approximate mid-point of exposure observation from 150 ppm through 250 ppm (highest exposure concentration). Additional observations at the approximate mid-point of exposure observation included clear nasal discharge in the 250 ppm group and wet clear material around the nose in the 150 ppm group (although only a single incidence) through the 250 ppm group. Clear material around the mouth was also noted in 200 and 250 ppm groups. Observations at 1 2 hours following exposure included rales in the 200 and 250 ppm groups and clear material around the nose in the 150, 200, and 250 ppm groups. Body weight and food consumption data were generally comparable across groups.
Based on these data, target exposure concentrations of 0, 50, 100, and 250 ppm were selected for this definitive study.

- Rationale for animal assignment (if not random): each animal judged to be in good health and meeting acceptable gestation day 0 body weight requirements was selected for use in the computerized randomization procedure based on body weight stratification in a block design.
Separate randomizations were conducted for Phases I and II. Replacement animals were arbitrarily assigned based on body weight prior to the initiation of exposure

- Other: the study was conducted in two phases:
The number of animals selected for this study (24 females/group) was based on the United States EPA Health Effects Test Guidelines: OPPTS 870.3700, Prenatal Development Toxicity Study, Aug-1998 and the OECD Guidelines for the Testing of Chemicals Guideline 414, Prenatal Developmental Toxicity Study, Jan 2001, which recommend evaluation of approximately 20 females with implantation sites at necropsy. Given the possibility of nongravid animals, unexpected deaths, or treatment-related moribundity and/or mortality, this was an appropriate number of animals to obtain a sample size of 20 at termination. In addition, due to limitation of exposure chamber size, only 12 rabbits could be placed into each exposure chamber; therefore, 24 rabbits was the maximum number of animals per group that could be placed on study to allow completion of the study in 2 phases.
Fifty-two time-mated female New Zealand White rabbits were received in good health from Covance Research Products, Inc., Greenfield, IN, on 18-Sep-2015 (first shipment; Phase I). An additional 52 rabbits of the same strain were received from the same supplier on 30-Oct-2015 (second shipment; Phase II). The time-mated rabbits were received on gestation day 3 or 4; a breeding record was provided by the supplier and is maintained in the study records.
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All rabbits were observed twice daily, once in the morning and once in the afternoon, for moribundity and mortality.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Individual clinical observations were recorded daily from the day of receipt through gestation day 29 (prior to exposure during the treatment period). Animals were also observed for signs of toxicity at the approximate midpoint of exposure and 1-2 hours following exposure. The absence or presence of findings was recorded for individual animals at observations conducted 1-2 hours following exposure. Only significant findings were recorded at the approximate midpoint of exposure.

BODY WEIGHT: Yes
- Time schedule for examinations: Individual maternal body weights were recorded on gestation days 0 (by supplier under conditions that were not compliant with GLPs, but in accordance with the supplier’s SOPs), 4, and 7-29 (daily). Group mean body weights were calculated for each of these days. Mean body weight changes were calculated for each corresponding interval and also for gestation days 7-10, 10-13, 13-20, 20-29, and 7-29.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
Individual food consumption was recorded on gestation days 4-29.
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes. Food intake was reported as g/animal/day and g/kg/day for the corresponding body weight change intervals.
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data

POST-MORTEM EXAMINATIONS: Yes
The laparohysterectomies and macroscopic examinations were performed blind to treatment group.
- Sacrifice on gestation day 29
- Organs examined: The thoracic, abdominal, and pelvic cavities were opened by a ventral mid line incision, and the contents were examined.

OTHER: Ocular Irritation Observations
Examination of ocular irritation in both eyes of all animals was performed on gestation day 3 or 4 (day of animal receipt) and gestation day 28 in accordance with the method of Draize (1965) and was facilitated by use of a direct ophthalmoscope, as necessary. Sodium fluorescein was used to aid in revealing possible corneal injury at all examinations.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
The thoracic, abdominal, and pelvic cavities were opened by a ventral mid line incision, and the contents were examined. In all instances, the postmortem findings were correlated with the antemortem observations, and any abnormalities were recorded. The uterus and ovaries were then exposed and excised.
Examinations included:
The number of corpora lutea on each ovary was recorded. The trimmed uterus was weighed and opened, and the number and location of all fetuses, early and late resorptions, and the total number of implantation sites were recorded. The placentae were also examined. The individual uterine distribution of implantation sites was documented using the following procedure. All implantation sites, including resorptions, were numbered in consecutive order beginning with the left distal to the left proximal uterine horn, noting the position of the cervix, and continuing from the right proximal to the right distal uterine horn.
- Gravid uterus weight: Yes
Gravid uterine weight was collected and net body weight (the gestation day 29 body weight exclusive of the weight of the uterus and contents) and net body weight change (the gestation day 0 29 body weight change exclusive of the weight of the uterus and contents) were calculated and presented for each gravid female at the scheduled laparohysterectomy.

- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: Uteri with no macroscopic evidence of implantation were opened and subsequently placed in 10% ammonium sulfide solution for detection of early implantation loss (Salewski, 1964).
Maternal tissues were preserved in 10% neutral buffered formalin for possible future histopathologic examination only as indicated by the gross findings. Representative sections of corresponding organs from a sufficient number of control animals were retained for comparison. The carcass of each female was then discarded.
Fetal examinations:
- External examinations: Yes: [all per litter]: each viable fetus
Fetal examinations were performed blind to exposure group. Each viable fetus was examined externally, individually weighed, euthanized by a subcutaneous injection of sodium pentobarbital in the scapular region, and tagged for identification. Fetal tags contained the WIL Research study number, the female number, and the fetus number. The detailed external examination of each fetus included, but was not limited to, an examination of the eyes, palate, and external orifices, and each finding was recorded. Crown rump measurements, degrees of autolysis and gross examinations, if possible, were recorded for late resorptions, and the tissues were discarded.

- Soft tissue examinations: Yes: [all per litter]: each viable fetus
Each viable fetus was subjected to a visceral examination using a modification of the Stuckhardt and Poppe fresh dissection technique to include the heart and major blood vessels (Stuckhardt and Poppe, 1984). The sex of each fetus was determined by internal examination. Fetal kidneys were examined and graded for renal papillae development (Woo and Hoar, 1972).

- Skeletal examinations: Yes: [all per litter]
Following fixation in alcohol, each fetus was stained with Alizarin Red S (Dawson, 1926) and Alcian Blue (Inouye, 1976). Fetuses were then examined for skeletal malformations and developmental variations.

- Head examinations: Yes: [half per litter]
Heads from approximately one half of the fetuses in each litter were placed in Harrison’s fixative for subsequent soft tissue examination by the Wilson sectioning technique (Wilson, 1965). The heads from the remaining one half of the fetuses were examined by a midcoronal slice. All carcasses were eviscerated and fixed in 100% ethyl alcohol.
Statistics:
All statistical tests were performed using WTDMS™ unless otherwise noted. Analyses were conducted using two tailed tests (except as noted otherwise) for minimum significance levels of 1% and 5%, comparing each test substance exposed group to the control group. Each mean was presented with the standard deviation (S.D.), standard error (S.E.), and the number of animals (N) used to calculate the mean. Data obtained from nongravid animals were excluded from statistical analyses.
Maternal body weights (absolute and net), body weight changes (absolute and net), and food consumption, gravid uterine weights, numbers of corpora lutea, implantation sites, and viable fetuses, and fetal body weights (separately by sex and combined) were subjected to a parametric one way ANOVA (Snedecor and Cochran, 1980) to determine intergroup differences. If the ANOVA revealed significant (p<0.05) intergroup variance, Dunnett's test (Dunnett, 1964) was used to compare the test substance exposed groups to the control group. Mean litter proportions (percent per litter) of prenatal data (viable and nonviable fetuses, early and late resorptions, total resorptions, pre and post implantation loss, and fetal sex distribution), total fetal malformations and developmental variations (external, visceral, skeletal, and combined), and each particular external, visceral, and skeletal malformation or variation were subjected to the Kruskal Wallis nonparametric ANOVA test (Kruskal and Wallis, 1952) to determine intergroup differences. If the nonparametric ANOVA revealed significant (p<0.05) intergroup variance, Dunn’s test (Dunn, 1964) was used to compare the test substance exposed groups to the control group.
Indices:
Intrauterine data were summarized using 2 methods of calculation:
- Postimplantation Loss/Litter based on 1) group mean litter basis and on 2) proportional litter basis (in %);
- Sum of postimplantation losses per group was calculated based on proportional litter basis (please see below table 1).

The fetal developmental findings were summarized by: 1) presenting the incidence of a given finding both as the number of fetuses and the number of litters available for examination in the group; and 2) considering the litter as the basic unit for comparison and calculating the number of affected fetuses in a litter on a proportional basis as presented in table 2 (please see below).
Details on maternal toxic effects:
Maternal toxic effects:yes. Remark: the higher incidence clinical observations (rales, elevated head, and clear material findings), mean body weight losses, and lower food consumption in the 250 ppm group.

Details on maternal toxic effects:
All females in the control and test substance-exposed groups survived to the scheduled necropsy on gestation day 29.
Test substance-related adverse rales were noted in 250 ppm group at the daily examinations and at 1-2 hours following exposure throughout the exposure period. An increase in the incidence of elevated head and clear material around the mouth was noted at the approximate mid-point of each daily exposure for the 250 ppm group throughout the exposure period compared to the control group. Clear material around the eyes was noted primarily for the 250 ppm group at 1-2 hours following exposure and at the daily examinations beginning on gestation day 14 and continuing through euthanasia. Clear material around the nose was noted for all test substance-exposed groups at 1-2 hours following exposure throughout the exposure period; this finding was also noted for the majority of females in the 250 ppm group at the daily examinations and the mid-point of exposure.
Other clinical findings, including brown, red, and or yellow material on various body surfaces (nose and/or anogenital region), occurred infrequently and/or in a manner that was not exposure-related.

A test substance-related significant (p<0.01) mean body weight loss was noted in the 250 ppm group during the gestation day 7-10 interval compared to a mean body weight gain in the control group. Mean body weight gains in the 250 ppm group were similar to the control group throughout the remainder of the treatment period (gestation days 10-29). The initial mean body weight loss resulted in a significantly (p<0.05) lower mean body weight gain for the entire exposure period (gestation day 7-29) at 250 ppm. However, the mean body weight loss was not of sufficient magnitude to result in a lower mean body weight at the end of the exposure period. In addition, a larger mean net body weight loss (not statistically significant) was noted in the 250 ppm group when compared to the control group. Mean net body weight and gravid uterine weight in this group were similar to the control group.
Mean maternal body weights, body weight gains, net body weights, net body weight gains, and gravid uterine weights in the 50 and 100 ppm groups were unaffected by test substance exposure. Differences from the control group were slight and not statistically significant, with the following exception. A significantly (p<0.05) higher mean body weight gain was noted in the 100 ppm group during gestation day 21-22. This difference was transient and not dose-responsive.

Test substance-related lower mean food consumption (g/animal/day and g/kg/day) was noted in the 250 ppm group during the first 5 days of exposure (gestation days 7-12; differences were generally significant [p<0.05 or p<0.01]). For the remainder of the exposure period slightly lower mean food consumption was noted for the 250 ppm group compared to the control group; differences were significant (p<0.05) during gestation days 19-20 and 20-21 (g/animal/day only). Lower mean food consumption noted in the 250 ppm group correlated to lower mean body weight gains during the exposure period.
Food consumption, evaluated as g/animal/day and g/kg/day, in the 50 and 100 ppm groups was unaffected by test substance exposure. Differences from the control group were slight and not statistically significant.

Details on ocular irritation observations, maternal necropsy data and on laparohysterectomy on gestation day 29 are presented below in the "Any other information on results incl.tables".
Dose descriptor:
NOAEC
Effect level:
100 ppm (analytical)
Based on:
test mat.
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEC
Effect level:
250 ppm (analytical)
Based on:
test mat.
Basis for effect level:
other: developmental toxicity
Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects. Remark: no statistically significant malformations or developmental variations were atributed to the test substance.

Details on embryotoxic / teratogenic effects:
The numbers of fetuses (litters) available for morphological evaluation were 209(21), 191(22), 211(23), and 195(21) in the control, 50, 100, and 250 ppm groups, respectively. Malformations were observed in 7(7), 3(3), 7(4), and 6(3) fetuses (litters) in these same respective exposure groups and were considered spontaneous in origin. When the total malformations and developmental variations were evaluated on a proportional basis, no statistically significant differences from the control group were noted. Fetal malformations and developmental variations, when observed in the test substance exposed groups, occurred infrequently or at a frequency similar to that in the control group, did not occur in an exposure-related manner, and/or were within the WIL Research historical control data ranges (Appendix F). Based on these data, no fetal malformations or developmental variations were attributed to the test substance.

Dose descriptor:
NOAEC
Effect level:
250 ppm (analytical)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Embryotoxic / teratogenic effects:no effects.
Abnormalities:
not specified
Developmental effects observed:
not specified

The overall mean analyzed concentrations for each group during Phases I and II are presented below:

Table 1. Mean Analyzed Exposure Concentration (Phase I)

Exposure System:

1

2

3

4

Target Concentration (ppm):

0

50

100

250

Study Mean Concentration (ppm):

0

50

103

251

Standard Deviation:

0.0

5.4

4.3

7.9

N:

23

23

23

23

 

Table 2. Mean Analyzed Exposure Concentration (Phase II)

Exposure System:

1

2

3

4

Target Concentration (ppm):

0

50

100

250

Study Mean Concentration (ppm):

0

50

100

247

Standard Deviation:

0.0

3.0

2.7

7.2

N:

23

23

23

23

Maternal data

Ocular Irritation Observations

There were no test substance-related effects on the eyes for any animals. There were some animals that were noted with conjunctival hyperemia/congestion or corneal opacity in the test substance groups. However, the findings were noted in a manner that was not exposure-related, occurred in single animals, and/or occurred at a similar incidence in the control group or during the pre-exposure assessment on gestation day 3 or 4.

 

At the scheduled necropsy on gestation day 29, no test substancerelated internal findings were observed at any exposure level. Macroscopic findings observed in the test substanceexposed groups occurred infrequently, at similar frequencies in the control group, and/or in a manner that was not exposurerelated. All females were gravid with the exception of 3, 2, 1, and 3 female(s) in the control, 50, 100, and 250 ppm groups, respectively.

 

Gestation Day 29 Laparohysterectomy

Intrauterine growth and survival were unaffected by test substance exposure at exposure levels of 50, 100, and 250 ppm. Parameters evaluated included post implantation loss, live litter size, mean fetal body weights, and fetal sex ratios. Mean numbers of corpora lutea and implantation sites were similar across all groups. Mean litter proportions of pre-implantation loss were higher in the test substance-exposed groups (9.9%, 10.5%, and 7.7% for the 50, 100, and 250 ppm groups, respectively) compared to the control group (2.3%) but were not consider test substance-related because the initiation of exposure started after implantation and the values in the test substance groups were similar to the WIL Research historical control mean (8.1 ± 2.95% per litter; Appendix F). All other differences from the control group were slight and not statistically significant.

 

Fetal morphological data

The numbers of fetuses (litters) available for morphological evaluation were 209(21), 191(22), 211(23), and 195(21) in the control, 50, 100, and 250 ppm groups, respectively. Malformations were observed in 7(7), 3(3), 7(4), and 6(3) fetuses (litters) in these same respective dosage groups and were considered spontaneous in origin.

 

External Malformations and Variations

External malformations were limited to 2 fetuses in the 100 ppm group and 1 fetus in the 250 ppm group. Fetus nos. 3178-02 and 3178-07 in the 100 ppm group were noted with disseminated subcutaneous hemorrhage. In the 250 ppm group, fetus no. 5220-09 was noted with a short tail; skeletally, this finding consisted of absent, fused, small, and misshapen caudal vertebra. These malformations were noted in single fetuses or litters and/or in a manner that was not exposure-related, and therefore were not considered test substancerelated.

There were no external developmental variations noted for fetuses at any exposure level.

 

Visceral Malformations and Variations

Visceral malformations were observed in 7(7), 3(3), 1(1), and 3(2) fetuses (litters) in the control, 50, 100, and 250 ppm groups, respectively. A visceral malformation of diaphragmatic hernia (portion of left lobe of liver and stomach protruded into the thoracic cavity though an opening in the diaphragm) was noted for 2 fetuses(nos. 5220-06 and 5220-09) from the same litter in the 250 ppm group. The incidence of this malformation at 250 ppm(1.2% per litter) was slightly outside of the WIL Research historical data range (0% to 1.0% per litter; Appendix F). However, the incidence was not statistically significant when compared to the concurrent control group, diaphragmatic hernia has been previously observed in 2 fetuses from 1 control group in the WIL Research historical control data (version 4.3 full), and this finding is the second most common visceral malformation observed in the WIL Research historical control data (Appendix F). In addition, no other effects on fetal morphology were observed in the 250 ppm group. Therefore, the 2 diaphragmatic hernias observed in a single litter in the 250 ppm group were not considered to be test substance-related.

Lobular agenesis of the lungs (right accessory lobe absent) was noted for 6(6), 2(2), 1(1), and 1(1) fetuses (litters) in the control, 50, 100, and 250 ppm groups, respectively. An enlarged heart (all chambers), interventricular septal defect (an opening in the anterior portion of the septum), and misshapen papillary muscles were noted for fetus no. 5214-01 in the 50 ppm group. The aforementioned visceral malformations were not consisted test substance-related because they occurred in single fetuses, similarly in the control group, and/or in a manner that was not dose-related. Fetus no. 5232-09 in the control group was noted with folded retina.

No test item-related visceral developmental variations were noted. Findings observed in the test itemtreated groups were noted infrequently, similarly in the control group, were not observed in a dose-related manner, the differences in the mean litter proportions were not statistically significant compared to the concurrent control group, and/or the values were within the ranges of the WIL Research historical control data (Appendix F).Red fluid abdominal cavity was noted for a single fetus (no. 5214-01) in the 50 ppm group. This finding was not classified as either a malformation or developmental variation, was not included on the summary tables, and was not considered to be test substance-related because it occurred in single fetus and in a manner that was not exposure-related. Skeletal Malformations and Variations Skeletal malformations were noted for 4(2) and 4(3) fetuses (litters) in the 100 and 250 ppm groups, respectively. Fetus no. 3156-10 in the 100 ppm group and fetus nos. 3168-03 and 5220-06 in the 250 ppm group were noted with vertebral anomalies without associated rib anomalies(absent, extra, fused, mal positioned, or mal proportioned arches or fused, extra, misshapen, mal positioned, or mal proportioned centrum). Fetus nos. 3156-04 and 5235-01 in the 100 ppm group and fetus no. 3168-08 in the 250 ppm group were noted with vertebral central anomalies(bipartite, fused, mal positioned, or mal proportioned centrum). Fetus no. 3156-13 in the 100 ppm group was noted with severely maligned sternebra(e). Fetus no. 5194-02 in the 250 ppm group was noted with a rib anomaly (forked rib and mal positioned costal cartilage) and costal cartilage anomaly (right costal cartilage no. 7 bifurcates, rejoins and associates with sternum in normal no. 7 position). The aforementioned malformations were noted in a single fetus and/or mean litter proportions were within the WIL Research historical control data ranges(Appendix F)and therefore they were not considered test substancerelated. No test substance-related skeletal developmental variations were noted. Findings observed in the test substanceexposed groups were noted infrequently, similarly in the control group, were not observed in an exposure-related manner, the differences in the mean litter proportions were not statistically significant compared to the concurrent control group, and/or the values were within the ranges of the WIL Research historical control data (Appendix F).

Conclusions:
Based on the higher incidence clinical observations (rales, elevated head, and clear material findings), mean body weight losses, and lower food consumption in the 250 ppm group, an exposure level of 100 ppm was considered to be the no observed adverse effect concentration (NOAEC) for maternal toxicity. There were no test substance-related effects on intrauterine growth, survival, and fetal morphology at any exposure concentration; therefore, the NOAEC for embryo/fetal development was 250 ppm when dimethylamine was administered via whole body inhalation exposure for 6 hours per day from gestation days 7 through 28 to time-mated New Zealand White rabbits.
Executive summary:

The objectives of the study were to determine the potential of the test substance, dimethylamine, to induce developmental toxicity after maternal exposure from implantation to 1 day prior to expected parturition, to characterize maternal toxicity at the exposure levels tested, and to determine a no-observed-adverse-effect concentration (NOAEC) for maternal toxicity and developmental toxicity (WIL Research, 2016).

Dimethylamine (DMA) was administered via whole-body inhalation exposure to 3 groups of 24 time-mated female New Zealand White [Hra:(NZW)] rabbits for 6 hours per day from gestation days 7 through 28. Target exposure concentrations were 50, 100, and 250 ppm for Groups 2, 3, and 4, respectively. A concurrent control group (Group 1) composed of 24 time-mated females was exposed to humidified, filtered air on a comparable regimen. Due to limitation of exposure chamber size, only 12 rabbits could be placed into each exposure chamber; therefore, this study was conducted in 2 phases, with 12 animals/group in each phase. The females were approximately 6 months of age at the initiation of dose administration. All animals were observed twice daily for mortality and moribundity. Clinical observations, body weights, and food consumption were recorded at appropriate intervals. The eyes of all animals were examined for ocular irritation on gestation day 3or 4 (day of animal receipt) and gestation day 28. On gestation day 29, a laparohysterectomy was performed on each female. The uteri, placentae, and ovaries were examined, and the numbers of fetuses, early and late resorptions, total implantations, and corpora lutea were recorded. Gravid uterine weights were recorded, and net body weights and net body weight changes were calculated. The fetuses were weighed, sexed, and examined for external, visceral, and skeletal malformations and developmental variations.

All females in the control and test substance-exposed groups survived to the scheduled necropsy on gestation day 29.

Rales were noted in 250 ppm group at the daily examinations and at 12 hours following exposure throughout the exposure period. An increase in the incidence of elevated head was also noted in the 250 ppm group at the mid-point of exposure throughout the exposure period. Clear material around the eyes, mouth, and nose were noted at the daily examinations, approximate mid-point of each daily exposure, and/or 12 hours following exposure for the 250 ppm group throughout the exposure period compared to the control group. The aforementioned clinical observations at 250 ppm were considered test substance-related and adverse. In addition, test substance-related clear material around the nose was noted for 50 and 100 ppm groups at 12 hours following exposure throughout the exposure period. In the absence of other signs of toxicity at 50 and 100 ppm, and because the material findings did not persist to the daily examinations, they were not considered adverse at these exposure levels.

Test substance-related mean body weight losses were noted in the 250 ppm group during gestation days 7-10 compared to mean body weight gains in the control group. Corresponding lower mean food consumption was noted in this group generally throughout the exposure period. The initial mean body weight losses in the 250 ppm group were not of sufficient magnitude to result in lower mean body weight at the end of the exposure period. A mean net body weight loss was noted in the 250 ppm group. Mean maternal body weights, net body weights, and gravid uterine weights in all test substance-exposed groups and mean body weight gains and net body weight changes in the 50 and 100 ppm groups were unaffected by test substance exposure.

There were no remarkable ocular or macroscopic findings in any exposure group.

Intrauterine growth, survival, and fetal morphology (external, visceral, and skeletal) were unaffected by test substance exposure at all exposure levels.

Based on the higher incidence clinical observations (rales, elevated head, and clear material findings), mean body weight losses, and lower food consumption in the 250 ppm group, an exposure level of 100 ppm was considered to be the noobservedadverseeffect concentration (NOAEC) for maternal toxicity. There were no test substance-related effects on intrauterine growth, survival, and fetal morphology at any exposure concentration; therefore, the NOAEC for embryo/fetal development was 250 ppm when dimethylamine was administered via wholebody inhalation exposure for 6 hours per day from gestation days 7 through 28 to time-mated New Zealand White rabbits.

Effect on developmental toxicity: via oral route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
1 000 mg/kg bw/day
Study duration:
subacute
Species:
rat
Quality of whole database:
The overal quality of the database is high because two GLP guideline studies available: in one species (rat - oral adminstration of DMA-HCl) and in second species (rabbit - DMA administered via inhalation).
Effect on developmental toxicity: via inhalation route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEC
461 mg/m³
Study duration:
subacute
Experimental exposure time per week (hours/week):
42
Species:
rabbit
Quality of whole database:
The overal quality of the database is high because two GLP guideline studies available: in one species (rat - oral adminsitration of DMA-HCl) and in second species (rabbit - DMA administered via inhalation).
Effect on developmental toxicity: via dermal route
Endpoint conclusion:
no study available
Additional information

Oral developmental toxicity study in one species (rats)

In a GLP OECD 414 study, Dimethylamine hydrochloride was administered to pregnant Wistar rats daily by gavage from implantation (GD 6) to one day prior to the expected day of parturition (GD 19) (BASF AG, 2009). The test substance did not cause any mortality. Test substance-related relevant clinical effects were only seen in the high-dose dams (1000 mg/kg bw/d), i.e. salivation after treatment and decreased food consumption, although the latter did not affect body weight, body weight gain, net body weight gain and uterus weight. At necropsy, no test substance related findings were noted in any of the dams. The temporary salivation was likely to be induced by the taste of the test substance or by local irritation of the upper digestive tract. It was not considered to be a sign of systemic toxicity. All animals of the low-, mid- and high-dose groups showed yellowish discoloured urine which occurred from GD 8 onwards and persisted until the end of the study. The urine discoloration was a sign of systemic availability of the test substance and happened most likely due to the excreted test compound or its metabolite(s). This finding has been considered to be treatment-related but was not assessed as an adverse effect. No differences of toxicological relevance between the control and the dose groups were determined for reproductive parameters such as conception rate, mean number of corpora lutea, mean number of implantations, pre- and postimplantation losses, live fetuses and fetal sex ratio. Examination of the fetuses revealed incidental fetal external, soft tissue and skeletal malformations in individual litters of the low- and the mid-dose groups as well as the control. Since malformations only occurred in one litter of the low- and one litter of the mid-dose group, it is reasonable to consider a spontaneous background in single animals rather than a test substance-induced effect. A consistent pattern and a dose-response relationship were missing. Thus, a test substance-related effect on ontogeny is not assumed. No external variation was noted. Four soft tissue and a broad range of skeletal variations occurred in every test group including the control. All of these variations are documented at a comparable frequency in the historical control data. A spontaneous origin is also assumed for the unclassified cartilage observations, which were recorded for fetuses of all dose-groups including the control. Character as well as distribution of all of these findings did not suggest a relation to treatment. In summary, there was no evidence of an adverse effect of Dimethylamine hydrochloride on fetal morphology at any dose level tested.

Thus, the oral administration of Dimethylamine hydrochloride to pregnant Wistar rats had no effect on morphology of offspring at any dose level tested (100; 300 and 1000 mg/kg bw/d). The recorded incidences did not suggest a treatment-relationship, but reflected the usual biological variation inherent in the strain of rats used for this experiment. In conclusion, the no observed adverse effect level (NOAEL) for maternal toxicity is 300 mg/kg bw/d based on decreased food consumption and salivation after treatment in the high dose dams (1000 mg/kg bw/d). The no observed adverse effect level (NOAEL) for prenatal developmental toxicity is 1000 mg/kg bw/d because there was no evidence of an adverse effect of the test compound on fetal morphology.

In a supporting study performed in mice (CD-1) by Guest and Varma (1991), maternal and fetal effects were investigated after administration of DMA as hydrochloric salt via intraperitoneal injection (11.3, 45.1, 112.7, 225.4 mg/kg bw, duration 17 days). The number of resorbed and dead fetuses were equally distributed across all doses of DMA, but the highest dose (225,4 mg/kg bw) caused a not significant increased number of dead fetuses and a significant higher number of resorptions. None of the amines (MMA, DMA, TMA) caused a significant increase in external, internal organ, or skeletal abnormalities, but all three possess a teratogenic potential in varying degrees. They reported a significant increase of mortality and number of dead fetuses at the highest dose of 225,4 mg/kg bw; a significant decrease of fetal body weight at 112,7 and 225,4 mg/kg bw. In vitro, all three methylamines produced concentration-dependent decreases in yolk-sac diameter, crown-rump length, head length, and fetal survival; developmental score and somite number also exhibited a similar concentration-dependent decrease. The effect of all the three methylamines was more marked on the head length than on crown-rump length and yolk-sac diameter. The development of yolk-sac circulation was severely affected at 112.7 mg/kg bw DMA. The colour of the yolk sac of DMA-treated embryos was paler than control and there appeared to be a decrease in flow rather than vascularization. The external appearance of the embryos was not affected by low concentrations of methylamines, but at higher concentrations (> 0,5 mM), there appeared a disproportionate retardation in the forelimb and branchial bar development relative to the development of other organs.All three methylamines produced concentration-dependent decreases in embryo RNA, DNA and proteins; the relative order of toxicity was the same as in vivo, namely TMA> DMA > MMA. DMA inhibits development of mouse embryos in culture and acts as endogenous teratogen under certain conditions. From the above, it was considered that reproductive/developmental toxicity NOAEL is 112.7 mg/kg/day for delivered pups.

Inhalation developmental toxicity study in second species (rabbits)

The objectives of the study were to determine the potential of the test substance, dimethylamine, to induce developmental toxicity after maternal exposure from implantation to 1 day priod to expected parturition, to characterize maternal toxicity at the exposure levels tested, and to determine a no-observed-adverse-effect concentration (NOAEC) for maternal toxicity and developmental toxicity (WIL Reseach, 2016). Dimethylamine (DMA) was administered via whole-body inhalation exposure to 3 groups of 24 time-mated female New Zealand White [Hra:(NZW)] rabbits for 6 hours per day from gestation days 7 through 28. Target exposure concentrations were 50, 100, and 250 ppm for Groups 2, 3, and 4, respectively. A concurrent control group (Group 1) composed of 24 time-mated females was exposed to humidified, filtered air on a comparable regimen. Due to limitation of exposure chamber size, only 12 rabbits could be placed into each exposure chamber; therefore, this study was conducted in 2 phases, with 12 animals/group in each phase. The females were approximately 6 months of age at the initiation of dose administration. All animals were observed twice daily for mortality and moribundity. Clinical observations, body weights, and food consumption were recorded at appropriate intervals. The eyes of all animals were examined for ocular irritation on gestation day 3or 4 (day of animal receipt) and gestation day 28. On gestation day 29, a laparohysterectomy was performed on each female. The uteri, placentae, and ovaries were examined, and the numbers of fetuses, early and late resorptions, total implantations, and corpora lutea were recorded. Gravid uterine weights were recorded, and net body weights and net body weight changes were calculated. The fetuses were weighed, sexed, and examined for external, visceral, and skeletal malformations and developmental variations.

All females in the control and test substance-exposed groups survived to the scheduled necropsy on gestation day 29.

Rales were noted in 250 ppm group at the daily examinations and at 1‑2 hours following exposure throughout the exposure period. An increase in the incidence of elevated head was also noted in the 250 ppm group at the mid-point of exposure throughout the exposure period. Clear material around the eyes, mouth, and nose were noted at the daily examinations, approximate mid-point of each daily exposure, and/or 1‑2 hours following exposure for the 250 ppm group throughout the exposure period compared to the control group. The aforementioned clinical observations at 250 ppm were considered test substance-related and adverse. In addition, test substance-related clear material around the nose was noted for 50 and 100 ppm groups at 1‑2 hours following exposure throughout the exposure period. In the absence of other signs of toxicity at 50 and 100 ppm, and because the material findings did not persist to the daily examinations, they were not considered adverse at these exposure levels.

Test substance-related mean body weight losses were noted in the 250 ppm group during gestation days 7-10 compared to mean body weight gains in the control group. Corresponding lower mean food consumption was noted in this group generally throughout the exposure period. The initial mean body weight losses in the 250 ppm group were not of sufficient magnitude to result in lower mean body weight at the end of the exposure period. A mean net body weight loss was noted in the 250 ppm group. Mean maternal body weights, net body weights, and gravid uterine weights in all test substance-exposed groups and mean body weight gains and net body weight changes in the 50 and 100 ppm groups were unaffected by test substance exposure.

There were no remarkable ocular or macroscopic findings in any exposure group.

Intrauterine growth, survival, and fetal morphology (external, visceral, and skeletal) were unaffected by test substance exposure at all exposure levels.

Based on the higher incidence clinical observations (rales, elevated head, and clear material findings), mean body weight losses, and lower food consumption in the 250 ppm group, an exposure level of 100 ppm was considered to be the no‑observed‑adverse‑effect concentration (NOAEC) for maternal toxicity. There were no test substance-related effects on intrauterine growth, survival, and fetal morphology at any exposure concentration; therefore, the NOAEC for embryo/fetal development was 250 ppm when dimethylamine was administered via whole‑body inhalation exposure for 6 hours per day from gestation days 7 through 28 to time-mated New Zealand White rabbits.

The concentration in ppm was converted into mg/m³ according to the formula presented in the section 3.1.2.3.2. of ECHA guidance on the Application of Regulation (EC) No. 1272/2008 (2015):

mg/m³ = (MW x ppm)/ 24.45, where MW is molecular weight and 24.45 mg/m³ is the volume of ideal gas by 25 °C. MW of Dimethylamine is 45.08 g/mol.

mg/m³ = (45.08 x 250 ppm) / 24.45 = 461 mg/m³.


Justification for selection of Effect on developmental toxicity: via oral route:
The only developmental toxicity study by oral route available.

Justification for selection of Effect on developmental toxicity: via inhalation route:
Recent developmental toxicity study in second species (rabbit).

Justification for selection of Effect on developmental toxicity: via dermal route:
No study is selected since a recent inhalation developmental toxicity study in second species (rabbit) is available. NOAEL for dermal route can be estimated using route-to-route extrapolation procedure.

Justification for classification or non-classification

Since no developmental toxicity to fetuses of rats have been shown up to a concentration of 1000 mg DMA hydrochloride/ kg bw/day, and no developmental toxicity to fetuses of rabbits have been shown up to a concentration of 461 mg DMA/m³, DMA is considered not to possess an embryo/fetotoxicity including teratogenic potential.

Also the results obtained from the dams, indicate that the maternal toxicity starts at doses above 300 mg/kg bw/day dose level below that of developmental toxicity. Therefore, the classification is not warranted according to the criteria of EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulations No 1272/2008.

Additional information