2-amino-2-methylpropanol

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Principles of method if other than guideline:

- Principle of test: The objective of this study was to determine the toxicity via inhalation exposure of AMP administered by nose-only inhalation during/ after five consecutive daily exposures
- Short description of test conditions: The rats were exposed to three dose levels of test article (700, 1400, and 2000 mg/m3) for six hours per day.
- Parameters analysed / observed:Experimental endpoints consisted of moribundity/mortality and cage-side clinical observations (pre- and post-exposure); body weights; food consumption; clinical pathology parameters (clinical chemistry and hematology); organ weights; and necropsy and histopathological evaluations (lungs, liver, kidney, spleen, adrenals, heart, nasal turbinates, and gross lesions).

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-amino-2-methylpropanol

EC Number:

204-709-8

EC Name:

2-amino-2-methylpropanol

Cas Number:

124-68-5

Molecular formula:

C4H11NO

IUPAC Name:

2-amino-2-methylpropan-1-ol

Details on test material:

The test article was identified in this study as follows:
[14C]-AMP (molecular weight = 91.1 g/mol; specific activity = 25 mCi/mmol)


[14C]-AMP was provided by The Dow Chemical Company prepared in three formulations, identified in this study as follows:

1. AMP (Batch No. TA074801Z1) – Contains 94.85 mg AMP/g and 0.27 mg 14C-AMP/g, for a total calculated value of 95.12 mg AMP/g (Paste)

2. 40% aqueous solution (w/v, pH 9.5) prepared from AMP - Contains 0.26 mg 14C-AMP/g (Liquid)

3. Control Lotion B with pure AMP (Lot BP200500759.06) – Contains 40 mg AMP/g and 0.26 mg 14C-AMP/g, for a total calculated value of 40.26 mg AMP/g (equivalent to the level of AMP in cosmetic lotions)


Pure AMP, 40% aqueous, and Neat Control Lotion B formulations were evaluated for radiochemical concentration, which was determined to be, respectively, 79.3, 86.2, or 87.6% in a first shipment of formulations, and 80.3, 88.9, or 92.4% in a second shipment of formulations.

Specific details on test material used for the study:

AMP-REGULAR™ - industrial grade

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

Twenty-two (22) male and 22 female Sprague–Dawley derived rats [Crl:CD®(CD)BR] were obtained from Wilmington, MA-based Charles River Laboratories’ facility in Stone Ridge, NY, and were received at IITRI on October 26, 2016. One day after receipt, weights of animals ranged from 183 to 219 g for males and 152 to 182 g for females. The rats were approximately seven weeks old at arrival (date of birth of September 5, 2016) and approximately eight weeks old at the initiation of dosing.
During the one-week quarantine period, the rats were observed daily for mortality or evidence of moribundity. Before being released from quarantine, the animals were carefully examined (hand-held physical examination) to ensure their health and suitability as test subjects. The rats were released from quarantine on November 2, 2016. Group Assignment and Identification: Animals were randomized with a computerized body weight stratification procedure that produced similar group mean body weight values (not exceeding ±20%) on November 1, 2016, using ToxData®. The animals were randomized into four groups. Each animal selected for the study received a permanent identification number by permanent marker on the tail at the time of randomization. Extra animals not selected for the study were used as training animals. All cages were identified by project number, study number, animal number, dose group, and sex. Cage cards were color-coded by study group.
Food and Water: The rats were provided with Certified Global 18% Protein Rodent Diet [2018C; Teklad Laboratory Animal Diets, Envigo; Madison, WI]. City of Chicago water was supplied by means of an in-cage automatic watering system. No known contaminants that would have interfered with the outcome of the study were present in the food or water of the animals. Reports for the food and water analyses are maintained with facility records. The animals did not have access to food or water during inhalation exposures or to food during the scheduled fasting periods.

Housing and Environment: During quarantine and non-exposure periods of the treatment phase, rats were double-housed in polycarbonate “shoe-box” cages (10 ½” × 19” × 8”) lined with autoclaved absorbent hardwood chip bedding. The cages were equipped with automatic feeding and watering systems. Racks and cages were sanitized following group assignment.
Temperature and relative humidity (%RH) values were recorded once daily during quarantine and twice daily during the treatment period of the study. Recorded values ranged from 21°C to 22°C and from 35% to 51% RH. Fluorescent lighting in the animal room was provided on a cycle of 12 hours of light followed by 12 hours of darkness.
Restraint and Acclimation to Restraint: During the inhalation exposures, the animals were restrained in nose-only holding tubes (CH Technologies, USA; Westwood, NJ). Following confirmation of the correct animal number, each tube was placed in a pre-designated port of the inhalation exposure chamber. Animal placement for each exposure is documented in the study records. Processes for animal tube loading and unloading and tube insertion and removal from the chamber manifold were performed according to laboratory standard operating procedures that are designed to minimize stress to the rats. The rats were observed frequently while restrained to ensure that they remained in the tubes and were not in danger of injury or death. At the end of each exposure, when the chamber was purged of the test substance, the tubes with the animals were removed. The rats were removed from the tubes, observed, and returned to their home cages. The holding tubes were sanitized after each use.
To condition the animals to placement and restraint in nose-only holding tubes and to reduce stress during the exposure phase, the animals were placed in the holding tubes for varying lengths of time on weekdays (but not on any intervening weekend) prior to the start of exposure to the test substance according to the following schedule: 1.5 hours on Day -5; 3 hours on Day -2; and 4.5 hours on Day -1 (October 28 and 31 and November 1, 2016, respectively).
Animal Welfare: The study complied with all applicable sections of the Animal Welfare Act (AWA; Title 9, Code of Federal Regulations), the Public Health Service (PHS) Policy on Humane Care and Use of Laboratory Animals (National Institute of Health’s Office of Laboratory Animal Welfare, 2015), and the Guide for the Care and Use of Laboratory Animals (National Research Council, 2011). To the extent possible, procedures used in this study were designed to avoid or minimize discomfort, stress, and pain to the animals.

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

water

Remarks:

The test article was diluted to 10% with ASTM water by weight and was used as an aerosolized aqueous solution.

Mass median aerodynamic diameter (MMAD):

>= 0.74 - <= 1.65 µm

Remarks on MMAD:

Particle Size Distribution: Mean MMAD values in test atmosphere were 1.10, 0.93, and 1.26 μm for Groups 2-4, respectively. GSD ranges in the test atmosphere were 1.67-1.95, 1.53-1.85, and 1.55-2.07 for Groups 2-4, respectively.

Details on inhalation exposure:

Test Atmosphere Concentration: Overall mean test atmosphere concentrations were 0.697 ± 0.0812, 1.614 ± 0.0986, and 2.004 ± 0.1211 mg/L for Groups 2-4, respectively.
Temperature and Humidity: Overall mean chamber temperatures were 21.8, 21.6, 21.9, and 21.3°C for Groups 1-4, respectively. Overall mean humidity levels were 14.4, 99.9, 99.9, and 99.9% for Groups 1-4, respectively; the elevated relative humidity values for Groups 2-4 were due to the aqueous nature of the dosing formulations.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Impinger Analysis: One test atmosphere sample was collected per two hours of exposure (three samples per 6-hour exposure). Chamber aerosol/vapor test atmosphere concentration was monitored with a serially connected train of two impingers, each containing 20 mL of a naphthyl isothiocyanate trapping solution. Samples from each impinger were combined and brought to volume (50 mL) with isopropyl alcohol. These samples were collected at a constant flow rate equal to the port flow of the delivery tube, and the total volume of air sampled was measured with a dry-gas meter. The concentrations of the samples were quantified by chemical analysis at IITRI.
Aerosol Particle Size Distribution: Aerosol particle size distribution was determined once per day for Groups 2-4 with a quartz crystal microbalance (QCM) cascade impactor (California Measurements Inc.; Sierra Madre, CA) equipped with 10 stages to collect size-segregated samples. The mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were calculated from the mass accumulated on each collection stage of the QCM.
Aerosol Concentration: Aerosol concentration was monitored with a real-time aerosol sensor (model #pDR-1000AN; MIE Inc., Bedford, MA). The sensor was employed as a real-time indicator of short-term changes in aerosol concentration and was used in guiding laboratory personnel if concentration excursions were encountered.

Duration of treatment / exposure:

Experimental Design: The rats were exposed to three levels of test article (700, 1400, and 2000 mg/m3) for six hours per day for five days. The first day of exposure was November 2, 2016, and the final day of exposure was November 6, 2016 (Day 5). All study animals were euthanized on November 7, 2016.
Inhalation Exposure Methods
1. Inhalation Exposure Laboratory: The study was conducted in Chambers 1-4 of Laboratory VIII. This laboratory is equipped with 64-port, flow-past-type nose-only inhalation exposure chambers (manufactured by Lab Products Inc.; Seaford, DE). A schematic diagram of the inhalation exposure system is provided in Figure 1.
Air for test atmosphere generation was of breathable quality and was filtered with a compressed air filter and a carbon absorber. The test atmosphere inlet and exhaust configurations provided a uniform and continuous stream of fresh test atmosphere to the animals undergoing exposure. During exposure, the animals were held in clear plastic restraining devices (holding tubes; see Section II.C.5) attached to the chamber at the ports.
2. Test Atmosphere Generation: The test atmosphere was generated via aerosolization of the test (10% aqueous solution of AMP-REGULAR™) article using a Pari LC Plus nebulizer (Pari Respiratory Equipment, Inc.; Midlothian, VA). The test article was dispensed into the nebulizer reservoir as needed by means of a syringe. The resulting test atmosphere entered the nose-only inhalation exposure chamber. The exhaust from the exposure chamber was moved through a high efficiency particulate air (HEPA) filter by a ring compressor and exhausted outside the building. Inlet and exhaust flows to and from the chamber were controlled and continuously monitored by rotameters.

Frequency of treatment:

six hours per day for five days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

700 mg/m³ air (nominal)

Remarks:

achieved: 697 mg/m3

Doses / concentrations 2

Dose / conc.:

1 400 mg/m³ air (nominal)

Remarks:

achieved: 1614 mg/m3

Doses / concentrations 3

Dose / conc.:

2 000 mg/m³ air (nominal)

Remarks:

achieved: 2004 mg/m3

No. of animals per sex per dose:

5

Control animals:

yes, sham-exposed

Details on study design:

The rats ( 5 male and 5 female per dose group) were exposed to three levels of test article (700, 1400, and 2000 mg/m3) for six hours per day for five days.

Examinations

Observations and examinations performed and frequency:

Moribundity/Mortality Observations: Rats were observed for mortality and evidence of moribundity at least once daily prior to the initiation of dosing and at least twice daily during the treatment period. Mortality/moribundity checks were separated by a minimum of four hours, as appropriate.
Physical Examinations/Clinical Observations: Upon initiation of inhalation exposure, animals were observed regularly during exposure to correct any potential emergency conditions while in the holding tubes and to monitor for signs of toxicity (documented manually). Additionally, all surviving study animals were observed at least twice daily (before exposure and within an hour after exposure termination) for clinical signs (documented electronically in ToxData®). Observations included but were not limited to changes in the skin and fur, eyes, and mucous membranes; effects on the respiratory, circulatory, autonomic, and central nervous systems; and effects on somatomotor activity and behavior pattern. Particular attention was devoted to the observation of tremors, convulsions, salivation, diarrhea, lethargy, sleep, and coma. Any animals in possibly moribund condition were identified for further monitoring and possible euthanasia.
Body Weights and Body Weight Changes: Animals were weighed one day after receipt; on the day of randomization; and on Study Days 1, 3, and 5. All study animals were fasted overnight and also weighed on Day 6 prior to scheduled necropsy.
Food Consumption: Average food consumption per cage (due to the study animals being double-housed) was recorded on the same schedule as body weights.
Clinical Pathology: Samples were collected for analysis of clinical pathology parameters from all animals prior to scheduled euthanasia on Day 6. Animals were fasted overnight prior to blood collection. Blood samples for hematology and clinical chemistry were obtained from the retro-orbital plexus under anesthesia with 70% CO2/30% O2. The following clinical pathology parameters were evaluated:
a. Hematology: Hematology blood samples were collected into tubes containing EDTA as the anticoagulant. Blood smears were prepared from fresh blood and stained with Wright–Giemsa stain for manual differential leukocyte counts but were to be evaluated only if requested by the Sponsor. The parameters listed below were evaluated using an ADVIA 120 Hematology System Analyzer (Siemens Healthcare Diagnostics; Tarrytown, NY).
Differential white blood cell count (absolute and relative)
Erythrocyte count
Hematocrit
Hemoglobin
Mean corpuscular hemoglobin
Mean corpuscular hemoglobin concentration
Mean corpuscular volume
Platelet count
Reticulocyte count (absolute and relative)
Total white blood cell count

Clinical Chemistry: Clinical chemistry blood samples were collected into tubes, allowed to clot, centrifuged to obtain serum, and assayed on the day of collection. The parameters listed below were evaluated using a Beckman Coulter AU480 Clinical System (Beckman Coulter, Inc.; Brea, CA).
Alanine aminotransferase
Creatinine
Albumin
Gamma-glutamyl transpeptidase
Albumin/globulin ratio (calculated)
Globulin (calculated)
Alkaline phosphatase
Glucose
Aspartate aminotransferase
Inorganic phosphorus
Bilirubin (total)
Lactate dehydrogenase
Blood urea nitrogen
Potassium
Calcium
Protein (total)
Chloride
Sodium
Cholesterol
Triglycerides

Sacrifice and pathology:

Postmortem Procedures
1. Necropsy, Organ Weights, Tissue Analysis, and Gross Pathology: A complete necropsy was scheduled for all animals on Day 6. Prior to necropsy, the rats were fasted overnight. Animals were euthanized by an overdose of an intraperitoneal injection of sodium pentobarbital and exsanguinated.
At scheduled necropsy, the external surface of the body; all orifices; and the cranial, thoracic, and peritoneal cavities and their contents were examined, and any lesions or abnormal conditions (gross pathologic findings) were recorded. Complete necropsies were performed in the presence/under the supervision of a pathologist.
The tissues listed in the table below were collected and fixed in 10% neutral buffered formalin with the following exceptions: The eyes (with optic nerves) were fixed in Davidson’s solution; the testes and epididymides were fixed in modified
Davidson’s solution; and the bone marrow smear was fixed in methanol. The brain, paired kidneys, liver, adrenals, testes, ovaries, and paired lungs were weighed, and organ-to-body weight ratios were calculated using the fasted body weight for each animal.
Adrenal gland (paired)
Animal Identification (tail)1
Aorta
Bone, femur
Bone, sternum
Bone marrow, femur
Bone marrow, sternum
Bone marrow smear (femur)
Brain
Cervix
Epididymis (paired)
Esophagus
Eye (paired)
Gross lesion (if any)
Harderian gland (paired)
Heart
Kidney (paired)
Large intestine, cecum
Large intestine, colon
Large intestine, rectum
Liver
Lung (paired)
Lymph node, mandibular
Lymph node, mesenteric
Mammary gland (females)
Mass (if any)
Nasal cavity and turbinates2
Nerve, optic (paired)
Nerve, sciatic
Ovary (paired)
Pancreas
Parathyroid gland (paired)3
Pituitary gland
Prostate gland
Salivary gland (paired)
Seminal vesicle (paired)
Skeletal muscle
Skin (ventral abdomen)
Small intestine, duodenum
Small intestine, ileum
Small intestine, jejunum
Spinal cord, cervical
Spinal cord, lumbar
Spinal cord, thoracic
Spleen
Stomach
Testis (paired)
Thymus
Thyroid gland (paired)
Trachea
Urinary bladder
Uterus
Vagina
Zymbal gland (paired)3
1 The tail with the identification number of each animal was collected but not processed.
2 Per the request of the Sponsor, as noted in Protocol Amendment No. 2.
3 Due to size constraints, these organs were only evaluated when present in normal sections.
Histopathology: Protocol-specified tissues required for microscopic evaluation (lungs, liver, kidney, spleen, adrenals, heart, and gross lesions) from animals in Groups 1 and 4 (Air Control and High Dose, respectively); liver and gross lesions on the skin (mostly on the nose) from animals in Groups 2 and 3 (Low and Mid Dose, respectively), as noted in Protocol Amendment No. 1; and nasal turbinates from all animals, as noted in Protocol Amendment No. 2 were trimmed, processed routinely, embedded in paraffin, and stained with hematoxylin and eosin by Charles River Laboratories, Pathology Associates, Illinois. Light microscopic evaluation was conducted by a board-certified veterinary pathologist on the protocol-specified tissues.

Statistics:

Statistical Procedures: Descriptive statistics (mean and standard deviation) were calculated, and data were analyzed for statistical significance for body weight/body weight change, clinical pathology (clinical chemistry and hematology), and organ weight/organ-to-body weight ratio data using the ToxData® system. If a data set was normally distributed and of equal variance, statistical comparisons were conducted using a one-way analysis of variance (ANOVA), with post hoc comparisons made (if necessary) using Dunnett’s test. If normality and/or equal variance failed for a data set, statistical comparisons were conducted using nonparametric Kruskal–Wallis ANOVA, with post hoc comparisons made (if necessary) using Dunn’s test. A minimum significance level of p < 0.05 was used for the statistical comparisons in this study.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Test article-related clinical observation of scabbing (head and/or forelimb) due to irritation (burning) caused by the test article:
High- and Mid-dose: all animals.
Low-dose: one rat/sex

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight loss occurred in high- and mid-dose males (-5%) and females (-4%) over 5 days.
At the low-dose, body weight gain was slightly lower in both sexes by a few grams, not reaching statistical or toxicological relevance.

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

2-fold increased monocyte count in Mid and High dose males and females were considered treatment-related.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Increased aspartate aminotransferase (+76% to +129%) and slightly decreased albumin (-9% to -17%) in the Mid and High dose males and females were considered treatment-related.

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:

effects observed, treatment-related

Description (incidence and severity):

Statistically significant effects on adrenal (Group 4 males); liver (Group 3 and 4 males and females); and kidney (Group 3 and 4 females) absolute and/or relative weights were recorded.

Considering histopathology data and the decreased terminal body weight, the only biologically relevant change was increased absolute liver weight:
+8% in high-dose males,
+11% and +14% in mid- and high-dose females.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Skin crusts (thick hard black regions, predominantly on the nose) were observed in all mid- and high-dose animals, and in one low-dose female.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

High Dose: microscopic findings were noted in skin, nasal cavities and liver of 9/10 to 10/10 animals:
- skin: minimal epidermal hyperplasia, mild to moderate mixed cell infiltrates, and mild to marked necrosis and ulceration
- nasal cavities: mild to severe atrophy of goblet cells, minimal to mild atrophy of olfactory epithelium, minimal to mild epithelium hyperplasia, minimal to moderate mixed cell infiltrates, minimal to moderate squamous metaplasia of respiratory epithelium, mild to moderate ulceration of turbinates
- liver: minimal vacuolation

Mid Dose: microscopic findings were noted in skin, nasal cavities and liver of 8/10 to 10/10 animals:
- skin: minimal to marked serocellular crusts, minimal epidermal hyperplasia, mild to moderate mixed cell infiltrates, and mild to marked necrosis and ulceration
- nasal cavities: mild to marked atrophy of goblet cells, minimal to mild atrophy of olfactory epithelium, minimal to mild epithelium hyperplasia, minimal to moderate mixed cell infiltrates, minimal to moderate squamous metaplasia of respiratory epithelium, minimal to mild ulceration of turbinates
- liver: minimal to mild vacuolation

Low Dose: microscopic findings were noted in nasal cavities of 10/10 animals, and skin and liver of 1/10 animal:
- skin: moderate serocellular crusts, minimal necrosis and ulceration
- nasal cavities: minimal to moderate atrophy of goblet cells, minimal to mild atrophy of olfactory epithelium, mild epithelium hyperplasia, minimal to mild mixed cell infiltrates, minimal to mild squamous metaplasia of respiratory epithelium, minimal ulceration of turbinates
- liver: minimal vacuolation, also noted in one control

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Effect levels

1

Dose descriptor:

other: Maximum tolerated dose (MTD)

Effect level:

>= 700 - < 1 400 mg/m³ air (nominal)

Sex:

male/female

Basis for effect level:

body weight and weight gain

2

Key result

Dose descriptor:

LOAEC

Effect level:

<= 700 mg/m³ air (nominal)

Sex:

male/female

Basis for effect level:

clinical signs

dermal irritation

gross pathology

histopathology: non-neoplastic

Remarks on result:

other: local effects (skin/respiratory tract corrosion)

3

Key result

Dose descriptor:

LOEC

Effect level:

1 400 mg/m³ air (nominal)

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Remarks on result:

other: systemic effects (liver)

4

Key result

Dose descriptor:

NOEC

Effect level:

700 mg/m³ air (nominal)

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Remarks on result:

other: systemic effects (liver)

Target system / organ toxicity

Critical effects observed:

yes

Lowest effective dose / conc.:

700 mg/m³ air (nominal)

System:

respiratory system: upper respiratory tract

Organ:

nasal cavity

Treatment related:

yes

Dose response relationship:

yes

Any other information on results incl. tables

Target organs in order of decreasing sensitivity: respiratory tract >> skin > liver.

Effects on respiratory tract and skin are attributable to the alkaline nature of the test item (see executive summary).

Incidence of treatment-related microscopic liver effects compared to local toxicity (summarized)

Sex	Male				Female
Airborne concentration (mg/m3)	0	700	1400	2000	0	700	1400	2000
# rats examined	5	5	5	5	5	5	5	5
Liver reversible systemic toxicity (vacuolation)	0	0	3 (minimal)	5 (minimal)	1 (minimal)	1 (minimal)	5 (minimal to mild)	4 (minimal)
Skin irreversible local toxicity (necrosis and/or ulceration)	0	0	5 (mild to marked)	5 (mild to marked)	0	1 (minimal)	5 (moderate to marked)	5 (mild to marked)
Respiratory tract irreversible local toxicity (ulceration in turbinates)	0	2 (minimal)	3 (minimal to mild)	3 (mild to moderate)	0	0	2 (minimal to mild)	3 (mild to moderate)

Bold type indicates the effects judged to be treatment related.

Applicant's summary and conclusion

Conclusions:

In rats exposed nose-only, 6h/day for 5 days to a 10% solution of AMP-REGULAR, the LOAEC was 700 mg/m3 in both sexes. The maximum tolerated dose ranged >=700 to <1400 mg/m3 in both sexes. Target organs in order of decreasing sensitivity were: respiratory tract >> skin > liver. Effects on respiratory tract and skin were due to the alkaline test item (estimated pH for 10% aqueous solution: 11.9).

Executive summary:

The objective of this study was to determine the toxicity via inhalation exposure of AMP administered by nose-only inhalation during five consecutive daily exposures. The following effcets were noted in rats exposed to the test aerosol (MMAD ranging 0.74-1.65 µm, 10% AMP solution in water) for six hours per day:

• 2000 mg/m3: skin scabbing (burns from test item) in all animals. Slight body weight loss in both sexes. Increased monocyte counts and aspartate aminotransferase and slightly decreased albumin in both sexes. 8% (males) to 14% (females) higher liver weight. Skin crusts (thick hard black regions, predominantly on the nose) in all animals. Microscopic findings in almost all animals: 1) nasal cavities: mild to severe atrophy of goblet cells, minimal to mild atrophy of olfactory epithelium, minimal to mild epithelium hyperplasia, minimal to moderate mixed cell infiltrates, minimal to moderate squamous metaplasia of respiratory epithelium, mild to moderate ulceration of turbinates. 2) skin: minimal epidermal hyperplasia, mild to moderate mixed cell infiltrates, and mild to marked necrosis and ulceration. 3) Liver: minimal vacuolation.


• 1400 mg/m3: skin scabbing in all animals. Slight body weight loss in both sexes. 2-fold increased monocyte counts and aspartate aminotransferase and slightly decreased albumin in both sexes. 11% (females) higher liver weight. Skin crusts in all animals. Microscopic findings in almost all animals: 1) nasal cavities (maximum severity "marked"), 2) skin (maximum severity "marked") and 3) liver (maximum severity "mild").


• 700 mg/m3: Skin scabbing and/or crusts in 1 rat/sex. Microscopic findings in nasal cavities in all animals (maximum severity "moderate"). In a single animal, skin lesions (maximum severity "moderate") and liver lesions (minimal vacuolation, also noted in one control).

Below conclusions were drawn post-report by the registrant:

1) The test article was a 10% solution in water and its pH was not indicated. As is, AMP is alkaline (industrial-grade: pKa = 9.74). Based on Fernandes, 2023 [see IUCLID § 4.20: pH = 0.3309 ln(Concentration in % w/w) + 11.548], pH of industrial-grade AMP solutions at 10 % AMP w/w would be 12.3. This confirms that the observed skin and respiratory tract lesions represent corrosive effects. (local toxicity).

2) Based on corrosion to skin/respiratory tract, the local LOAEC was <=700 mg/m3 in both sexes. Based on minimal liver vacuolation (unsure whether the minimal grade also observed in one control female can even be considered adverse), the systemic NOEC and LOEC were 700 and 1400 mg/m3 in both sexes, resp. Minimal liver vacuolation being typically a reversible effect, STOT classification is not required. Considering 4-5% weight loss over only 5 days, the maximum tolerated dose ranged >=700 to <1400 mg/m3 in both sexes.

3) This study shows that the most sensitive toxic effect upon inhalation of high airborne concentrations of non-neutralised AMP is not liver toxicity (which was minimal) but pH-related local corrosion of respiratory tract and skin. Thus, liver toxicity can be avoided by keeping concentrations below corrosive ones.