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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 Oct 1978 - 03 Jan 1979
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline (OECD 408) with acceptable restrictions (missing neurological and ophthalmological checks; no post observation period)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1981
Report date:
1981

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)
Deviations:
yes
Remarks:
missing neurological and ophthalmological checks
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Methyl acrylate
EC Number:
202-500-6
EC Name:
Methyl acrylate
Cas Number:
96-33-3
Molecular formula:
C4H6O2
IUPAC Name:
methyl acrylate
Details on test material:
- Name of test material: Methyl acrylate
- Physical state: liquid
- Analytical purity: 99.7 %
- Impurities: methyl acetate 0.1 % ; methyl propionate 0.1 % ; ethyl acrylate, 0.07 % ; methyl methacrylate 0.01 % .
- Stability under test conditions: inconsistent information about the presence of polymerisation inhibitors

Test animals

Species:
rat
Strain:
other: CDF-Fischer 344
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Wilmington, USA
- Age at study initiation: 4 weeks
- Weight at study initiation: males: 80 - 102 g (mean: 91.5 g); females: 69 - 89 g (mean: 78.7 g)
- Housing: single
- Diet (e.g. ad libitum): ground Purina Laboratory Chow , Ralston Purina Company, St . Louis, USA
- Water (e.g. ad libitum): not specified
- Acclimation period: two weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22+- 2
- Humidity (%): 40 - 60
- Air changes (per hr): ca. 12
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: drinking water
Vehicle:
unchanged (no vehicle)
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
To check the initial concentrations of methyl acrylate in the drinking water solutions, analyses were conducted on complete sets of samples (1/sex/dose) prepared on five different days during the course of the study and on a set of the male test solutions prepared another day. The samples were taken from the freshly mixed stock solutions after the individual water bottles were filled and were immediately prepared for analysis. The means ± S.D. of the % of target concentrations obtained from analyses of the 11 samples at each dose were 97±19, 99±8 and 103±7 for respective dose levels of 1, 5 and 20 mg/kg/day. All analyses of water solutions for methyl acrylate were performed by GC/FID.
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
continuous
Doses / concentrations
Remarks:
Doses / Concentrations:
1; 5; 20 mg/kg bw
Basis:
nominal in water
No. of animals per sex per dose:
15
Control animals:
yes, concurrent no treatment
Details on study design:
Post-exposure period: none
- Dose selection rationale: Based on results of palatability and tolerance studies (Dow Chemical, unpublished data, 1981).

Examinations

Observations and examinations performed and frequency:
Rats were observed daily during the work week for signs of toxicity and changes in demeanor. Food and water consumption examinations were similar to those outlined in OECD 408.
Sacrifice and pathology:
As outlined in OECD 408.
Other examinations:
Clinical chemistry, hematology, urinalysis, gross and microscopic evaluation of tissues were similar to that outlined in OECD 408 with the following exceptions: platelet count, clotting time, serum electrolytes, cholesterol, and creatinine were not measured.
Statistics:
Data on body weights, food and water consumption, clinical biochemistries, hematological parameters (except white cell differential count), urine specific gravities, fasted body weights, and absolute (g) and relative (g/100g body weight) organ weights were evaluated by a one-way analysis of variance; differences between experimental group(s) and the corresponding controls were examined using Dunnett's test, p<0 .05 (Steel and Torrie, 1960). Outlying values for body weights and food and water consumption data were identified using the sequential outlier test of Grubbs (1969), p<0.02 (two-sided), and were excluded from the calculations for the respective groups.
Steel RGD & Torrie HH (1960). Principles and Procedures of Statistics. McGraw-Hill Book Company, Inc., N.Y., pp. 101-105, 11-112
Grubbs FE (1969). Technometrics 2(1)

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
No signs of toxicity were noted upon daily observation of the rats. All rats survived the 13-week test period.


BODY WEIGHT AND WEIGHT GAIN
Although there were no statistically significant differences between treated and control mean body weights, slight, dose-related decreases in weight gain were noted for both sexes receiving 5 or 20 mg/kg bw/day. The decreases at 5 mg/kg bw/day were so minimal that they are judged to be of
negligible significance.

FOOD CONSUMPTION
Concerning food consumption very small but statistically significant decreases occurred in males at 5 and 20 mg/kg bw/day for the 69-75 day interval and females at 20 mg/kg bw/day for the 62-68 day period. These random decreases are considered to be a reflection of normal variation.


WATER CONSUMPTION
Water consumption data shows decreased intake in males and females at the highest dose. The decreases in males were apparent during the last half of the test period, with statistically significant differences in seven of the last 11 measurements. Statistically significant decreases in water intake of females at the highest dose occurred at eight of the last 19 measurements (last 2/3 of the test period). In general, water intake for the 1 and 5 mg/kg bw/day groups was comparable to controls.


HAEMATOLOGY
Hematologic data were similar for treated and control groups. The single case of a statistically significant difference was an increase in packed cell volume (PCV) of females at 20 mg/kg bw/day. This increase was not accompanied by similar changes in other erythroid parameters and is considered to be a sporadic occurrence unrelated to treatment.


CLINICAL CHEMISTRY

Concerning clinical biochemical determinations statistically significant decreases in alkaline phosphatase activity (AP) were noted for all groups of treated females. However, the differences were very slight and were not proportional to dose; furthermore, decreases in AP are not indicative of a toxicological effect. The statistically significant increase in total protein of males at the lowest dose was not considered to be associated with treatment due to its isolated occurrence and lack of a dose-response relationship.

URINALYSIS
Urinalyses showed a statistically significant increase in specific gravity of the 20 mg/kg bw/day females when measured at 79 days. A repeat of urinalyses at 84 days to evaluate the reproducibility of this observation again showed a slight increase for females in the 20 mg/kg bw/day group, although the difference was not statistically significant from the control mean. Specific gravity of treated male rats was not different from controls at either the 79 or 84 day sampling times. Other urinalysis parameters were similar for control and treated groups.

ORGAN WEIGHTS
The only statistically significant difference in terminal organ weights was an increase in mean relative kidney weight of female rats receiving the highest dose. The absolute weight (g) was also slightly higher than the control mean, but the difference was not statistically significant. All other organ weights of treated groups were similar to controls. The slight decreases in mean body weight gains of males at the 5 and 20 mg/kg bw/day doses are apparent in the fasted terminal body weights of these groups.


GROSS PATHOLOGY
Gross examination at necropsy revealed only spontaneous lesions commonly observed in rats of this age and strain.


HISTOPATHOLOGY: NON-NEOPLASTIC
All alterations were typical of those occurring spontaneously in rats of this age and strain. The kidneys of male rats at the highest dose showed an increase in severity of a spontaneous renal disease normally seen in Fischer 344 rats. This alteration, characterized by dilated renal tubules with eosinophilic cast formation, was observed in six of 10 males examined from the 20 mg/kg bw/day dose and in two of 10 male controls. This observation was also noted in two of 10 females at the highest dose and in none of the female controls. All other lesions observed histopathologically occurred with similar frequency and severity in treated and control rats.





Effect levels

open allclose all
Key result
Dose descriptor:
NOAEL
Effect level:
5 other: mg/kg
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects were observed at this concentration
Key result
Dose descriptor:
LOAEL
Effect level:
20 other: mg/kg
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Effects on kidney weight

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Average body weight gain:
males:
0 mg/kg 1 mg/kg 5 mg/kg 20 mg/kg
204 g 202 g 197 g 192 g
222 % 222 % 216 % 209 %
females:
0 mg/kg 1 mg/kg 5 mg/kg 20 mg/kg
89 g 91 g 86 g 83 g
116 % 115 % 108 % 104 %


Kidney weights:
males:
0 mg/kg 1 mg/kg 5 mg/kg 20 mg/kg
2.05 g 2.06 g 1.99 g 2.03 g
0.74 g/100g 0.75 g/100g 0.74 g/100g 0.76 g/100g
females:
0 mg/kg 1 mg/kg 5 mg/kg 20 mg/kg
1.22 g 1.25 g 1.24 g 1.26 g
0.79 g/100g 0.79 g/100g 0.80 g/100g 0.83 g/100g*

*statistically significant

Discussion:

Although differences in treated and control mean body weights were not statistically significant, ingestion of the 20 mg/kg bw/day dose of methyl acrylate resulted in slight decreases in weight gain of male and female rats. The decreases in water consumption of both sexes at the highest dose are believed to be due to unpalatability of water solutions containing methyl acrylate. The specific gravity of urine was increased in female rats given 20 mg/kg bw/day, probably as a result of decreased water consumption. However, the mean relative kidney weight of the 20 mg/kg bw/day females was slightly increased, and both sexes at the highest dose showed an increased incidence of the spontaneous renal disease that occurs normally in CDF Fischer 344 rats and is characterized by dilated renal tubules and eosinophilic cast formation. Hence, the test material may have had some slight effect on kidneys when given at a dose of 20 mg/kg bw/day.

In conclusion, doses up to 20 mg/kg bw/day of methyl acrylate did not produce frank toxicity on any organ upon ingestion by rats in their drinking water for 13 weeks, even though concentrations providing the highest dose were unpalatable. The no-observable effect level (NOEL), based on the effects seen at the 20 mg/kg bw/day dose level in this study, was determined to be 5 mg/kg bw/day for male and female CDF Fischer 344 rats.


Applicant's summary and conclusion