Registration Dossier

Diss Factsheets

Toxicological information

Repeated dose toxicity: inhalation

Currently viewing:

Administrative data

Endpoint:
chronic toxicity: inhalation
Remarks:
combined repeated dose and carcinogenicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
0981-01-28 to 1983-01-14
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods
Remarks:
NTP standard protocol, cancer bioassay with limited dose range

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1986

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Methyl methacrylate
EC Number:
201-297-1
EC Name:
Methyl methacrylate
Cas Number:
80-62-6
Molecular formula:
C5H8O2
IUPAC Name:
methyl methacrylate
Test material form:
liquid
Specific details on test material used for the study:
- Name of test material (as cited in study report): methyl methacrylate
- Molecular weight (if other than submission substance): 100.1
- Smiles notation (if other than submission substance):
- Physical state: liquid
- Analytical purity: > 99.8 %
- Purity test date: several times throughout the test
- Stability under test conditions: stable
- Other: stabilised commercila grad material

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals or test system and environmental conditions:
Feed:
NIH 07 Rat and Mouse Ration (Zeigler Bros., Gardners, PA); until 4/23/81 and aft.er 5/8/81.
Wayne LAB BLOX" from 4/23/81 to 5/8/81. Available ad libitum except during exposure

Bedding: None
Water: Automatie wate ring system (Edstrom Industries, Waterford, Wll; available ad libitum

Cages: Stainless steel wire cages (Lab Products, Inc., Rochelle Park, NJ)

Animals per cage: 1

Animal room envoronment:
Temp: 72° -79° F;
humidity: 45%-65%;
fluorescent light: 12 h/d;
20 room air changes/h

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
air
Remarks on MMAD:
MMAD / GSD: vapour
Details on inhalation exposure:
Methyl methacrylate was pumped from a stainless steel reservoir to a vaporizer by a stable micrometering pump with adjustable drift-free pump rates. The vaporizer was heated to 50° ± 2° C, and the
study material vapor, along with an air stream, entered thetest chamber.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Methyl methacrylate concentrations were monitored on-line twice during each exposure hour, initially by a photoionization detector and later by gas chromatographic analysis
Duration of treatment / exposure:
2 years
Frequency of treatment:
6 h / day, 5 d / wk
Doses / concentrationsopen allclose all
Dose / conc.:
0 ppm
Remarks:
males/females
Dose / conc.:
250 ppm
Remarks:
females
Dose / conc.:
500 ppm
Remarks:
males/females
Dose / conc.:
1 000 ppm
Remarks:
males
No. of animals per sex per dose:
50
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: random (table)
- Dose selection rationale: Based on the results of several preliminary studies up to 90 d duration
Positive control:
no

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: 2/d

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at weighing

BODY WEIGHT: Yes
- Time schedule for examinations: weekly for the first 13 weeks, monthly afterwards

FOOD CONSUMPTION, FOOD EFFICIENCY and WATER CONSUMPTION: no data
HAEMATOLOGY, CLINICAL CHEMISTRY, URINALYSIS, NEUROBEHAVIOURAL EXAMINATION: No data
Sacrifice and pathology:
Grosspathology (necropsy) and histologic examination:
Necropsy and histologic examination performed on all animals; the following tissues were examined:
- gross lesions and tissue masses
- regional lymph nodes
- mandibular lymph node
- sternebrae including marrow,
- thyroid gland, parathyroids
- small intestine
- rectum
- colon
- liver
- mammary gland
- prostate/testes/epididymis or ovaries/uterus
- Iungs and mainstem bronchi
- nasal cavity and turbinates
- skin
- heart,
- esophagus
- stomach
- salivary gland,
- brain,
- hymus
- trachea
- pancreas
- spleen
- kidneys
- adrenal glands
- urinary bladder
- pituitary gland
- preputial or clitoral gland
- tracheobronchial lymph nodes
Statistics:
Data Recording: Data were recorded in the Carcinogenesis Bioassay Data System (Linhart et al., 1974). The data elements include descriptive information on the chemicals, animals, experimental design, survival, body weight, and individual pathologic results, as recommended by the International Union Against Cancer (Berenblum, 1969).

Survival Analyses: The probability of survival was estimated by the product-limit procedure of Kaplan and Meier (1958).
Statistical analyses for a possible dose-related effect on survival used the method of Cox (1972) for testing two groups for equality and Tarone's (1975) life table test for a dose-related trend.

Analysis of Tumor lncidence: Three statistical methods are used to analyze tumor incidence data. The two that adjust for intercurrent mortality employ the classical method for combining
contingency tables developed by Mantel and Haenszel (1959). Tests of significance included pairwise comparisons of high dose and low dose groups with controls and tests for overall doseresponse trends.

Results and discussion

Results of examinations

Clinical signs:
not specified
Mortality:
mortality observed, non-treatment-related
Description (incidence):
No significant differences in survival were observed between any groups of either sex.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Mean body weights of 1000-ppm male rats were 5%-10% lower than those of the controls after week 81. Mean body weights of 500-ppm female rats were 6%-11%l ower than those of the controls after week 73.
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:
effects observed, non-treatment-related
Description (incidence and severity):
A statistically significant positive trend in the incidence of mononuclear cell leukemia occurred in female rats exposed to 500-ppm (incidence of 22%, 26% and 40% for the control, 250 ppm and 500 ppm groups, respectively). However, life table analysis, which can be regarded as more appropriate for life-threatening lesions, showed no difference. The incidence of mononuclear cell leukemia in the three groups of male rats was not statistically different by life table analysis.
Clinical biochemistry 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
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Nasal Cavity and Olfactory Sensory Epithelium:
Serious and suppurative inflammation and degeneration of the olfactory epithelium in the nasal cavity were observed at increased incidences in exposed male and female rats relative to controls. Serous inflammation was characterized by noncellular mucus in the lumen of the posterior region of the nasal cavity.
Suppurative inflammation was characterized by an infiltration of neutrophils and varying numbers of mononuclear cells into the mucosa and submucosa of the nasal turbinates and wall of the nasal cavity. Degeneration of the olfactory epithelium was characterized by a loss of sensory neuroepithelial cells from the epithelium (atrophy) and, in the most severely affected areas, replacement by respiratory epithelium (metaplasia). This degeneration was accompanied by variable atrophy of the nerve bundles in the submucosa.

Lung: Alveolar macrophages were observed at increased incidences in exposed male and female rats. The severity in all groups was considered minimal. Focal or multifocal fibrosis was observed at an increased incidence in 500- ppm female rats.
Histopathological findings: neoplastic:
no effects observed
Description (incidence and severity):
Pituitary Gland: Pituitary gland adenomas or carcinomas (combined) in male rats occurred with a significant negative trend, and the incidence in the 1,000 ppm group was significantly lower than that in the controls . The
incidences of pituitary gland adenomas in the three groups of female rats were not different statistically.
Preputial Gland: Preputial gland adenomas and carcinomas occurred in male rats with a significant negative trend, and the incidence in the high dose group was significantly lower than that in the controls .

Hematopoietic System: Mononuclear cell leukemia in female rats occurred with a significant positive trend, and the incidence in the 500-ppm group was significantly greater than that in the controls by the incidental tumor test but not by life table analysis. The latter test procedure is generally considered more appropriate for life-threatening lesions. The incidences of mononuclear cell leukemia in the three groups of male rats were not statistically different by life table analysis.

The mononuclear cell leukemia in female rats in the control and dosed groups was classified according to the extent of involvement of the spleen and its advancement to other organs. The following criteria were used:
Stage 1. Spleen not enlarged or only slightly enlarged with small numbers of neoplastic mononuclear cells in the red pulp; no or very few mononuclear cells in the liver sinusoids. No identifiable neoplastic cells in other organs.
Stage 2. Spleen moderately enlarged with moderate to large numbers of mononuclear cells in the red pulp; architectural features including lymphoid follicles and periarteriolar lymphocytic sheaths remain intact. Minimal to moderate involvement of the liver. Mononuclear cells may be evident in blood vessels in other organs, but aggregates/masses of neoplastic cells generally limited to spleen and liver.

Stage 3. Advance disease with multiple organ involvement. Spleen usually markedly enlarged with effacement of normal architectural features by accumulated neoplastic cells. Liver moderately to markedly enlarged and nodular; hepatic parenchyma shows variable degenerative changes associated with the accumulation of neoplastic cells. Accumulations of neoplastic mononuclear cells in other organs including
lung, lymph nodes, kidney, brain, and adrenal gland.

According to these criteria, there were no differences in the character of the mononuclear cell leukemia found in the dosed female rats and the controls.

Effect levels

open allclose all
Dose descriptor:
LOAEC
Remarks:
for local effects in the URT (no NOAEC identified)
Effect level:
250 ppm
Based on:
test mat.
Sex:
female
Basis for effect level:
other: Histopathology (Irritation)
Key result
Dose descriptor:
NOAEC
Remarks:
for systemic effects
Effect level:
500 ppm
Based on:
test mat.
Sex:
female
Basis for effect level:
other: Gross pathology, Histopathology (organ effects)
Dose descriptor:
NOAEC
Effect level:
1 000 ppm
Based on:
test mat.
Sex:
male
Basis for effect level:
other: Gross pathology, Histopathology (organs)

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Mortality: No difference in survival between treated and untreated groups.

Histopathology:

Site / Lesion

Males

Control

[0 ppm]

Low. Conc.

[500 ppm]

High Conc.

[1000 ppm]

Nasal Cavity /

           Serous inflammation

           Suppurative inflammation

 

 0/50

11/50

 

37/50

21/50

 

44/50

30/50

Olfactory sensory epithelium /

           Degeneration

 

 7/50

 

39/50

 

42/50

Lung /

           Alveolar macrophages

           Focal or multifocal fibrosis

 

 6/49

 6/49

 

20/49

 6/49

 

16/50

 5/50

 

 

 

 

Site / Lesion

Females

Control

[0 ppm]

Low. Conc.

[250 ppm]

High Conc.

[500 ppm]

Nasal Cavity /

           Serous inflammation

           Suppurative inflammation

 

4/50

7/50

 

17/50

12/50

 

32/50

12/50

Olfactory sensory epithelium /

           Degeneration

 

2/50

 

39/50

 

44/50

Lung /

           Alveolar macrophages

           Focal or multifocal fibrosis

 

9/50

1/50

 

14/50

 2/50

 

16/50

 7/50

 

No histopathological findings other than local findings in the respiratory tract. Systemic histopathological effects, as for example in the brain in females particularly at 2000 ppm and above in the subchronic range finding study (Batelle, 1980), are absent in this 104 week study.

Body weight: Mean body weight gain was reduced in females at 500 ppm resulting in 6 -11% lower body weights after week 73 and in males at 1000 ppm which were 5 -10 % lower than controls after week 81.

There was no treatment-related increase in tumour incidence.

Applicant's summary and conclusion

Conclusions:
The primary finding in this study was inflammation of rat nasal cavity as well as olfactory epithelial degeneration at all exposure levels in male and female rats. For local effects the LOAEC was 250 ppm in this study while a NOAEC could not be found. 
In contrast to the 90 d range finding study with histopathological changes in females at exposures of 1000 ppm and above (Battelle, 1980), no other significant histopathological changes were reported in male and female rats after 104-week exposures to MMA vapour in this study. Based on this a NOEC for systemic effects of 500 ppm is derived.
Executive summary:

In this104-week study with groups of 50 animals each, male rats were treated with MMA vapour by whole-body exposure to 500 or 1000 ppm while female rats were exposed to 250 or 500 ppm. Control animals were only treated with air.

The primary finding was inflammation of rat nasal cavity as well as olfactory epithelial degeneration at all exposure levels in male and female rats. For local effects the LOAEC was 250 ppm in this study while a NOAEC could not be found. 

No other significant histopathological changes were reported in male and female rats after 104-week exposures to MMA vapour in this study. Based on this a NOEC for systemic effects of 500 ppm is derived.

Male and female rat body weights were lower at the 1000 ppm (5-10%) and 500 ppm (6-11%) exposure levels, respectively, presumably due to reduced food consumption due to nasal irritation and damage of olfactory epithelium. While food consumption was not recorded in this study this association is confirmed by two other studies, the developmental toxicity study with MMA with reduced food consumption and reduced body weight gain at concentrations higher than 99 ppm (Solomon, 1993) and a subchronic inhalation study with methacrylic acid where there was also an association of irritative effects in the nose and reduced food consumption and reduced body weight gain (BASF, 2008). Consequently, reduced body weight gain, while clearly treatment-related - is considered to be secondary to the local effects in the nose and not the result of true systemic toxicity.