(E)-2-methoxy-4-(prop-1-enyl)phenol

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From September 20, 2011 to February 07, 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Reference 2

Reference Type:

other company data

Title:

Unnamed

Year:

2013

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

(E)-2-methoxy-4-(prop-1-enyl)phenol

EC Number:

227-678-2

EC Name:

(E)-2-methoxy-4-(prop-1-enyl)phenol

Cas Number:

5932-68-3

Molecular formula:

C10H12O2

IUPAC Name:

2-methoxy-4-prop-1-en-1-ylphenol

Test material form:

liquid

Details on test material:

- Physical state: Clear pale yellow liquid

Specific details on test material used for the study:

- Storage condition of test material: Stored at room temperature and was considered stable under these conditions

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, NC.
- Age at study initiation: Approximately 7 weeks
- Weight at study initiation: 187-240 g for males; 149-184 g for females at randomization
- Housing: Animals were housed individually in clean, stainless steel, wire-mesh cages suspended above cage-board.
- Diet: Basal diet; PMI Nutrition International, LLC, Certified Rodent LabDiet® 5002 (meal), ad libitum
- Water: Reverse osmosis-treated (on-site) drinking water, ad libitum
- Food and water were withheld during each daily exposure period.
- Acclimation period: 16 days

ENVIRONMENTAL CONDITIONS
- Temperature: 70.4-71.5 °F (21.3-21.9 °C)
- Humidity: 36.6-52.6 %
- Air changes: 10 fresh air changes per hour
- Photoperiod: 12 h dark / 12 h light

IN-LIFE DATES: From: September 20, 2011 To: February 07, 2012

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

clean air

Mass median aerodynamic diameter (MMAD):

>= 1.3 - <= 2.2 µm

Remarks on MMAD:

Mean MMAD: 1.4, 1.3 and 2.2 µm for 1, 10 and 100 mg/m3, respectively
Mean GSD: 3.59, 4.00 and 2.30 for 1, 10 and 100 mg/m3, respectively

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 7.9-L conventional nose-only exposure systems with synthetic rubber grommets in exposure ports to engage animal holding tubes.
- Method of holding animals in test chamber: To perform nose-only exposure, it is necessary to restrain the rats in specially designed nose-only holding tubes. The 6-hour period of restraint was necessary to achieve the exposure duration.
- Source and rate of air: HEPA- and charcoal-filtered air source (WIL Research Inhalation Department supply air source) or breathing-quality in-house compressed air source.
- Method of conditioning air: Charcoal- and HEPA-filters
- System of generating aerosols: Aerosolized test substance was generated using a Collison nebulizer.
- Temperature, humidity in air chamber: Mean temperature ranged from 20-21 °C and the mean relative humidity ranged from 43-56 %.
- Air flow rate: Daily mean ventilation rate ranged from 44.3-47.9 liters per minute (LPM).
- Method of particle size determination: Aerosol particle size determinations were conducted for each test substance exposure system using a 7-stage stainless steel cascade impactor.
- Treatment of exhaust air: All test substance atmosphere exposure system exhaust passed through a Solberg canister filter prior to entering the facility exhaust system, which consisted of redundant exhaust blowers proceeded by charcoal- and HEPA-filters.

TEST ATMOSPHERE
- Brief description of analytical method used:
Nominal exposure concentrations: Due to the small amount of test substance that was required for the study, a nominal concentration was not calculated.
Actual exposure concentrations: Actual aerosol mass concentrations of the test atmospheres for exposure systems 1, 3, and 4 (control, 10 and 100 mg/m3) were determined using standard gravimetric methods. Due to the volatility of the test material, standard gravimetric methods cannot be used for the analysis of the atmosphere in the Group 2 exposure system.
Analysed exposure concentrations: Analysed exposure concentrations of the total test material (combined vapour and aerosol) within exposure system 2 were determined at approximately 60-minute intervals using an appropriate gas chromatography (GC) method and were expressed as mg/m3.
- Samples taken from breathing zone: Yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

A sample of the test substance was collected from prior to the initiation of exposure for purity and concentration analyses. Analyses of purity and stability were performed using a similar method from a sample collected at the end of the exposure period. All analyses were conducted using a gas chromatography method with flame ionization detection.
Results: Analyses conducted for a sample of the test substance collected prior to exposure initiation resulted in a purity of 90.8%. Following the completion of the exposure phase, another sample was collected that resulted in a purity of 89.3%. Comparison of these purity data indicated that the test substance was stable (98.3% of the initial test substance concentration after up to 34 days), based on the acceptance criteria for stability (i.e., the mean post-storage concentration was not <90% of the pre-storage value).
Mean exposure concentrations were 1.28, 9.8 and 98 mg/m3 for the target exposure concentrations 1, 10 and 100 mg/m3, respectively.

Duration of treatment / exposure:

2 weeks

Frequency of treatment:

6 hours per day, 5 days per week for 2 weeks (10 total exposures)

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

1 mg/m³ air (nominal)

Remarks:

0.15 ppm

Doses / concentrations 2

Dose / conc.:

10 mg/m³ air (nominal)

Remarks:

1.5 ppm

Doses / concentrations 3

Dose / conc.:

100 mg/m³ air (nominal)

Remarks:

14.9 ppm

No. of animals per sex per dose:

10

Control animals:

other: filtered air (control group)

Details on study design:

- Dose selection rationale: Prior to exposure of animals for the main study, preliminary animal exposures were conducted at 750 and then at 300 mg/m3 (89.4 and 44.7 ppm, respectively) for three days to assess tolerability of the test substance. At 750 mg/m3, the animals were observed to have decreased body weights over the 3-day exposure period (-14 and -10% for males and females, respectively, compared to day 0) and significant clinical observations included rales and laboured respiration in 1/3 males and 2/3 females. At 300 mg/m3, the mean body weight was decreased by 8% and 3 % compared to the study day 0 values for males and females, respectively. Therefore, one third of the lowest concentration tested in the preliminary exposures, 100 mg/m3 (i.e.14.9 ppm), was chosen as the high exposure level for the main two-week study.
- Rationale for animal assignment: Animals judged suitable for assignment to the study were selected for use in a computerized randomization procedure based on body weight stratification in a block design.

Positive control:

None

Examinations

Observations and examinations performed and frequency:

CLINICAL OBSERVATIONS: Yes
- Time schedule: Clinical examinations were performed daily, prior to exposure, during exposure (at the approximate midpoint for visible signs of animals in nose-only exposure restraint tubes), and 0 to 1 h following the end of exposure. The absence or presence of findings was recorded for individual animals at observations conducted prior to exposure and following the end of exposure. Only significant findings were recorded at the approximate midpoint of exposure observations. On non-exposure days, the animals were observed once daily.
- Survival: All animals were observed twice daily, once in the morning and once in the afternoon, for mortality and moribundity, except on the days of the scheduled necropsy.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Detailed physical examinations were conducted on all animals during pretest prior to randomization, at the time of randomization prior to group assignment, and approximately weekly during the exposure period, including prior to the scheduled necropsy. Observations conducted prior to exposure were not performed on days when detailed physical examinations were conducted, provided they were conducted prior to
exposure.

BODY WEIGHT: Yes
- Time schedule for examinations: Individual body weights were recorded during the pretest period, at randomization, prior to the first exposure, and twice weekly during the exposure period (prior to the first and last exposure each 5-day exposure week) including the day before the first scheduled day of necropsy (nonfasted).
- Mean body weights and mean body weight changes were calculated for the corresponding intervals. Final body weights (fasted) were recorded on the day of the scheduled necropsy.

FOOD CONSUMPTION:
- Individual food consumption was recorded during the pretest period (prior to randomization) and twice weekly during the exposure period. Food intake was calculated as g/animal/day for the corresponding body weight intervals.

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY AND CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Blood samples for clinical pathology evaluations (haematology and serum chemistry) were collected at the scheduled necropsy (study day 12).
- Anaesthetic used for blood collection: Yes; Blood was collected for haematology and standard serum chemistry evaluations via the retro-orbital sinus and for coagulation parameters via the vena cava from animals anesthetized by inhalation of isoflurane at the scheduled necropsy. (inhalation of isoflurane)
- Animals fasted: Yes; animals were fasted overnight prior to blood collection.
- How many animals: Blood samples for clinical pathology evaluations (haematology and serum chemistry) were collected from all animals, and blood samples for coagulation evaluations were collected from 5 animals/sex/group (Subgroup 1).
- Parameters checked:
HAEMATOLOGY AND COAGULATION: Total leukocyte count (WBC), Erythrocyte count (RBC), Haemoglobin (HGB), Haematocrit (HCT), Mean corpuscular volume (MCV), Mean corpuscular haemoglobin (MCH), Mean corpuscular haemoglobin concentration (MCHC), Platelet count (PLATELET), Prothrombin time (PT), Activated partial thromboplastin time (APTT), Reticulocyte count Percent (RETIC), Absolute (RETIC ABSOLUTE), Mean Platelet Volume (MPV), Red cell distribution width (RDW), Haemoglobin Distribution Width (HDW), Differential leukocyte count - Percent and absolute (Neutrophil (NEU), Lymphocyte (LYMPH),Monocyte (MONO), Eosinophil (EOS), Basophil (BASO), Large unstained cell (LUC)), Platelet estimate, Red cell morphology (RBC Morphology)
CLINICAL CHEMISTRY: 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, Triglycerides (Triglyceride), Sorbitol dehydrogenase (SDH) and Lactate dehydrogenase (LDH)

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes; Animals were anesthetized by isoflurane inhalation and euthanized by exsanguination. For 5 animals/sex/group (BALF animals), a BAL was performed on the lungs as soon as possible after exsanguination and after completion of the BAL, all BALF animals were subjected to necropsy. The necropsies included, but were not limited to, examination of the external surface, all orifices, and the cranial, thoracic, abdominal, and pelvic cavities, including viscera. Tissues or gross lesions were not collected from the BALF animals (Subgroup 2).

HISTOPATHOLOGY: Yes; the following tissues and organs were collected from the histopathology animals (remaining 5 animals/sex/group; Subgroup 1) and placed in 10 % neutral-buffered formalin for examination:
Adrenals (2), Aorta, Bone with marrow, Femur (with joint)[a], Sternebrae, Bone marrow smear (from femur), Brain with olfactory blub - Cerebrum level 1, Cerebrum level 2 , Cerebellum with medulla/pons, Cervix, Epididymides (2)[b], Eyes with optic nerve (2) [c], Gastrointestinal tract, Oesophagus, Stomach, Duodenum, Jejunum, Ileum, Cecum, Colon, Rectum, Harderian glands (2), Heart, Kidneys (2), Lacrimal gland (exorbital [2]), Larynx, Liver (sections of 2 lobes), Lungs (including bronchi, fixed by constant pressure inflation with fixative), Lymph nodes - Auricular (2 [if visible]), Axillary (2), Bronchial (if visible), Mandibular (2), Mediastinal and bronchial (if visible), Mesenteric, Mammary glands (females only) [d], Nasal cavity (with turbinates) [e], Olfactory bulbs [e], Ovaries with oviducts (2) [f], Pancreas, Peripheral nerve (sciatic), Peyer’s patches, Pharynx, Pituitary, Prostate, Salivary glands (mandibular [2]), Seminal vesicles (2), Skeletal muscle (rectus femoris), Skin, Spinal cord (cervical, lumbar, thoracic), Spleen, Testes (2), Thymus, Thyroid (with parathyroids [2]) [f], Tongue, Trachea, Urinary bladder, Uterus, Vagina and Gross lesions

a = Bone marrow smears were obtained at scheduled necropsy from the femur, but not placed in formalin; slides were not examined.
b = Fixed in Bouin’s solution
c = Fixed in Davidson’s solution
d = A corresponding section of skin was taken from the same anatomical area for males.
e = Following the collection of the appropriate protocol-specified tissues, the entire head was removed and preserved (olfactory bulbs were severed from the brain and remained in the skull). Following decalcification, 6 cross-sections of the nasal cavities were prepared for microscopic examination in accordance with the method described by Morgan (1991) and Mery et al. (1994).
f = Oviducts and parathyroids were examined microscopically when in the plane of section and in all cases where a gross lesion was present.

After fixation, lungs with bronchi, bronchus associated lymphoid tissues [BALT], nasal tissues, nasal-associated lymphoid tissue [NALT], larynx, trachea, mediastinal and bronchial lymph nodes, and gross lesions) were trimmed. Trimmed tissues were processed into paraffin blocks, sectioned at 4 to 8 microns, mounted on glass microscope slides, and stained with haematoxylin and eosin. Microscopic examination of the lungs with bronchi, BALT, nasal tissues, NALT, larynx, trachea, mediastinal and bronchial lymph nodes, and gross lesions were performed for 5 animals/sex/group (Subgroup 1) not assigned for the BAL at the scheduled necropsy.

ORGAN WEIGHTS
The following organs were weighed from all animals at the scheduled necropsy:
Adrenals, Brain, Heart, Kidneys, Liver, Lungs (prior to inflation with fixative), Ovaries with oviducts, Spleen, Testes, Thymus, Thyroid with parathyroids*

Paired organs were weighed together. Designated (*) organs were weighed after fixation. Organ to final body weight and organ to brain weight ratios were calculated.

Other examinations:

Bronchoalveolar lavage fluid (BALF) clinical pathology and serum and BALF cytokine evaluation:
Prior to the scheduled necropsy, the animals were fasted overnight. At the time of necropsy, the 5 animals/sex/group selected for serum cytokine evaluations (Subgroup 2) were anesthetized by inhalation of isoflurane. Blood samples were collected from the vena cava into tubes containing no anticoagulant. A bronchoalveolar lavage (BAL) was performed on the lungs of 5 animals/sex/group (Subgroup 2) at the scheduled necropsy (study day 12).

BALF chemistry and cytology
The following parameters were evaluated:
Total and differential cell counts for: Alveolar macrophages, Neutrophils, Lymphocytes, Eosinophils, Basophils
Lactate dehydrogenase (LDH), Total protein, Alkaline Phosphatase

Serum and BALF cytokine evaluations
The following cytokines were evaluated:
TNF-α, IL-5, IL-10, ICAM-1, IFN-γ, IL-4, TGF-β, MCP-1, IL-1β, IL-13, MIP-2, RANTES

TNF = Tumour necrosis factor, IFN = Interferon, IL = Interleukin, TGF = Transforming growth factor, MIP = Macrophage inflammatory protein, ICAM = Intracellular adhesion molecule, MCP = Macrophage chemotactic protein, RANTES = Regulated upon activation, normal T-cell expressed, and presumably secreted.

Statistics:

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. Due to the use of significant figures and the different rounding conventions inherent in the types of software used, the means and standard deviations 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.

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-treated group to the control group by sex.

Body weight, body weight change, food consumption, clinical pathology data including BALF total protein, lactate dehydrogenase, alkaline phosphatase, and cytology parameters (with the exception of gamma glutamyltransferase), and organ weight data were subjected to a parametric one-way ANOVA (Snedecor and Cochran, 1980) to determine intergroup differences. If the ANOVA revealed statistically significant (p<0.05) intergroup variance, Dunnett's test (Dunnett, 1964) was used to compare the test substance-treated groups to the control group. Gamma glutamyltransferase values under range were assigned a value of 0.1 (half the lower limit of quantitation) for statistical analysis and reporting. Gamma glutamyltransferase data were subjected to the Kruskal-Wallis nonparametric ANOVA test (Kruskal and Wallis, 1952) to determine intergroup differences. If the ANOVA revealed significance (p<0.05), Dunn’s test (Dunn, 1964) was used to compare the test substance-treated groups to the control group.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

There were no test substance-related clinical observations. All clinical findings in the test substance-treated groups were noted with similar incidence in the control group, were limited to single animals, were not noted in a dose-related manner and/or were common findings for laboratory rats of this age and strain.

Mortality:

no mortality observed

Description (incidence):

All animals survived to the scheduled necropsy

Body weight and weight changes:

no effects observed

Description (incidence and severity):

- There were no toxicologically significant effects on body weights.
- Transient lower body weight gains were present in the 100 mg/m3 group males and females during the exposure period, reaching statistical significance during study days 0 to 4 and/or 7 to 11. Statistically significantly lower cumulative body weight gains were recorded for the 100 mg/m3 group males from study day 0 to 11. Although lower cumulative body weight gains were noted in the 100 mg/m3 group females by the end of the study, the values were not statistically significant.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

- There were no toxicologically significant effects on food consumption.
- Transient slightly lower food consumption was noted for the 100 mg/m3 group males and females during the exposure period. Although the differences were statistically significant compared to the control group from study days 0 to 4 and/or 7 to 11, these effects on food consumption were sporadic and not considered toxicologically relevant.

Food efficiency:

not specified

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

There were no clear test substance-related differences in haematology parameters when compared to the control group. Reticulocyte counts were slightly lower in the 1, 10, and 100 mg/m3 group females and 100 mg/m3 group males when compared to the control group; however, a relationship with test substance administration was not established due to the lack of dose response in females.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

There were no test substance-related differences in serum clinical chemistry parameters when compared to the control group. Alanine aminotransferase (ALT) was slightly lower in the 100 mg/m3 group males when compared to the control group; however, decreases in ALT have no known toxicological meaning, and this difference was considered to be incidental.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

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 were statistically significant when compared to the control group but were considered to be a result of a test substance-related effect on final body weight. For the 100 mg/m3 group males, mean adrenal gland weights (absolute and relative to brain weight) were lower, but the mean adrenal gland to body weight ratio was not statistically significantly lower. The mean final body weight was lower for this group, and this contributed to the lower adrenal gland weight values. Mean liver weights (absolute and relative to final body and brain weights) were also lower for the 100 mg/m3 group males, but these were affected by the lower final body weights in this male group. The mean liver weight relative to final body weight, which is a more appropriate permutation of the liver weight parameters, was very similar to the value in the 1 mg/m3 group indicating that there really were no differences in these relative weights. Adrenal gland, liver, and final body weights were not significantly altered in the 100 mg/m3 group females. Additionally, the adrenal gland weight values fell within the historical control reference ranges and there were no test substance-related microscopic changes in the livers of the 100 mg/m3 group males.

Gross pathological findings:

no effects observed

Description (incidence and severity):

There were no test substance-related macroscopic findings at the scheduled necropsy. All macroscopic findings noted were considered to be spontaneous and/or incidental in nature and unrelated to test substance exposure.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

- Test substance-related microscopic findings were present in the nasal cavity of males and females exposed to the test substance, but not in the larynx, trachea, lung, liver, or kidney. Nasal cavity changes tended to be more frequent in anterior portions of the nasal cavity (nasal levels II and III) and were also more frequent in males than in females.
Epithelial inflammation and degeneration were most prominent at nasal levels II (1, 10, and 100 mg/m3 group males and females) and III (1, 10, and 100 mg/m3 group males and 100 mg/m3 group females) and showed reduced incidence and severity in the posterior nasal levels (IV, V, and/or VI) in the 1, 10, and/or 100 mg/m3 group males and 10 and/or 100 mg/m3 group females.
- There were no other test substance-related histologic changes. The nasal-associated lymphoid tissue (NALT) and bronchial-associated lymphoid tissue (BALT) were unaffected by test substance exposure. 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:

no effects observed

Other effects:

not specified

Effect levels

Key result

Dose descriptor:

LOAEL

Effect level:

1 mg/m³ air (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

other: histologic changes indicative of localized irritation of the epithelia in the nasal cavity (upper airways) at all exposure levels. Therefore, a no-observed-effect level (NOEL) could not be determined for this study.

Target system / organ toxicity

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

1 mg/m³ air (nominal)

System:

respiratory system: upper respiratory tract

Organ:

nasal cavity

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

yes

Any other information on results incl. tables

None

Applicant's summary and conclusion

Conclusions:

Results showed histologic changes indicative of localized irritation of the epithelia in the nasal cavity (upper airways) at all exposure levels up to 100 mg/m3. There were no test substance-related microscopic effects in the lower respiratory tract tissues (lungs, trachea, or larynx) or in the liver and kidneys, and there were no toxicologically significant effects on BALF cytokine levels. Therefore a NOEL could not be determined for this study and the LOAEL is 1 mg/m3, based on the microscopic findings in the nasal tissues at all exposure levels.

Executive summary:

In a repeated dose toxicity study conducted according to the OECD Guideline 412 and in compliance with GLP, test material was administered by inhalation-aerosol to groups of Sprague-Dawley rats (10 animals/sex/dose) at the concentrations of 1, 10 and 100 mg/m³(0.15, 1.5, and 14.9 ppm, respectively) for 6 hours per day, 5 days per week for 2 weeks (10 total exposures). A concurrent control group was exposed to humidified, filtered air on a comparable regimen. Examinations during the study included: mortality, clinical observation, body weight change, food consumption, laboratory investigations: haematology, blood clinical chemistry, Bronchoalveolar lavage fluid (BALF) clinical pathology and serum and BALF cytokine evaluation, gross pathology, organ weights and histopathology.

 

Prior to the main study, a preliminary 3-day exposure (6 hours/day) was run at 750 and 300 mg/m3 (89.4 and 44.7 ppm, respectively) to allow selection of appropriate exposure concentrations. At 750 mg/m3, the animals were observed to have decreased body weights over the 3-day exposure period (-14 and -10% for males and females, respectively, compared to day 0) and significant clinical observations included rales and laboured respiration in 1/3 males and 2/3 females. At 300 mg/m3, the mean body weight was decreased by 8% and 3 % compared to the study day 0 values for males and females, respectively. At both concentrations, no animals died. Therefore, one third of the lowest concentration tested in the preliminary exposures, 100 mg/m3 (i.e.14.9 ppm), was chosen as the high exposure level for the main two-week study.

 

There were no test substance related effects on survival, clinical observations, haematology, coagulation, bronchoalveolar lavage clinical chemistry or cytology, serum cytokines, macroscopic findings, or organ weights. There were no toxicologically significant effects on body weight gain, food consumption, or BALF cytokine levels. The only test substance-related changes in BALF cytokine levels were the lower concentrations of sICAM in the 10 and 100 mg/m3group animals and lower concentrations of RANTES in the 100 mg/m3 group animals. No test substance-related microscopic findings were observed in the lungs, trachea, larynx, liver, or kidneys. Portal of entry effects suggestive of irritation were present in the nasal cavity of males and females exposed to test material. Epithelial inflammation and degeneration of the nasal cavity were noted in the 1, 10, and 100 mg/m3 group males and females. A dose-relationship was evident as higher incidences and severity of degeneration and subacute inflammation in males and females affecting transitional epithelium (nasal level II) at the 10 and 100 mg/m3 exposure levels, compared with effects at the 1 mg/m3 exposure. Based on severity and combined incidences for males and females, a similar test substance-relationship was evident for subacute inflammation of the respiratory epithelium at nasal level III. The findings were most prominent at nasal levels II and III and showed reduced incidence and severity in the posterior nasal levels (IV-VI), and were generally more frequent in males than in females at all exposure and nasal cavity levels. All nasal cavity findings were minimal to mild in severity and would be considered reversible with removal of the irritant. 

 

Results showed histologic changes indicative of localized irritation of the epithelia in the nasal cavity (upper airways) at all exposure levels up to 100 mg/m³. There were no test substance-related microscopic effects in the lower respiratory tract tissues (lungs, trachea, or larynx) or in the liver and kidneys, and there were no toxicologically significant effects on BALF cytokine levels.

 

Therefore a NOEL could not be determined for this study and the LOAEL is 1 mg/m³, based on the microscopic findings in the nasal tissues at all exposure level.

 

Based on the nasal irritation, test material is classified as H335: May cause respiratory irritation according to the Regulation (EC) No. 1272/2008 (CLP).

 

This study is considered as acceptable and satisfies the requirement for repeated dose inhalation toxicity endpoint.