Registration Dossier

Diss Factsheets

Toxicological information

Developmental toxicity / teratogenicity

Currently viewing:

Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1991
Report date:
1991

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
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:
Methyl methacrylate (CAS 80-62-6)
Purity= 99.9 %
colorless, volatile liquid

Test animals

Species:
rat
Strain:
other: Crl:CDBR
Details on test animals or test system and environmental conditions:
Nulliparous female rats, weighing 183-240 grams upon arrival.
AGE AT TIME OF MATING: 88-95 days. 
ACCLIMATION PRIOR TO MATING: 7 days 
SOURCE: Charles River Breeding Laboratories Inc., Kingston, NY.
Animals were housed individually, except during mating, in suspended stainless-steel cages (7" x 8" x 13.5"). During exposures, females were housed individually in suspended stainless-steel, wire mesh cages (6" x 7" x 11"). Temperature range was 23 ± 2°C and the relative humidity ranged from 40-60% during cohabitation and 63-80% during the exposure and post-exposure periods. Food (Certified Purina Rodent Chow #5002) and filtered tap water were available ad libitum except during exposures. A photoperiod of 12 hrs dark/ 12 hrs light was maintained.

Administration / exposure

Route of administration:
inhalation
Type of inhalation exposure (if applicable):
whole body
Vehicle:
unchanged (no vehicle)
Details on exposure:
The test material exposure concentrations were generated by metering the test material with calibrated Fluid Metering Pumps (Fluid Matering Inc., Oyster Bay, NY) into 500 mL three-necked round bottom flasks (Lab Glass Inc., Vineland, NJ).
Exposures were whole body and were conducted in 2000 L stainless steel, glass and Plexiglas® chambers. Cage positions within the chamber were rotated daily. The temperature and relative humidity within the chambers during exposure were 22-24°C and 55-67%, respective.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The concentration of the test substance in the chambers was determined by the use of a Miran gas analyzer attached to a strip chart recorder. A probe was placed into the center of the chamber and the chamber atmosphere was drawn into the Miran A1 gas analyzer at a rate of 9.5 L/min. Each chamber was analyzed initially within 40 min. of the end of the t99 to insure that each chamber was within the accepted target range. Subsequently, each chamber was sampled every 120 min. A range of  plus or minus 10% of the target chamber concentration was maintained by making minor adjustments on the generator pump delivery rates whenever necessary.
Details on mating procedure:
Females were mated with males overnight (one male:one female) and the presence of sperm in the vaginal smear was considered  gestation day 0. Mated females were exposed via inhalation to the test material for 6 hrs/day on gestation days 6 through 15 and then sacrificed on day 20.  
Duration of treatment / exposure:
6 - 15 day of gestation
Frequency of treatment:
6 hours/day
Duration of test:
20 d (dams were euthanized on gestation day 20)
Doses / concentrationsopen allclose all
Dose / conc.:
99 ppm
Remarks:
corresponding to 412 mg/m3 or 0.41 mg/L
Dose / conc.:
304 ppm
Remarks:
corresponding to1285 mg/m3 or 1.29 mg/L
Dose / conc.:
1 178 ppm
Remarks:
corresponding to 4900 mg/m3 or 4.9 mg/L
Dose / conc.:
2 028 ppm
Remarks:
corresponding to 8436 mg/m3 or 8.44 mg/L
No. of animals per sex per dose:
27 animals per group exposed; 22-25 pregnant  females per exposure group.
Control animals:
yes, sham-exposed
Details on study design:
- Other: The strain was selected because background development toxicity data exists as Rohm and Haas Company on this rat strain. The test material was given by inhalation since the respiratory route is a potential route of human exposure.

Examinations

Maternal examinations:
Maternal body weights were recorded on GD 0, 6, 8, 10, 13, 16 and 20. Food consumption was measured for GD intervals 0-6, 6-10, 10-16 and 16-20. Animals were observed daily for behavioral changes.
Ovaries and uterine content:
On GD 20, all dams were asphyxiated with carbon dioxide, the thoracic and abdominal cavities were examined and the uterus was removed and weighed, and corpora lutea, implantation sites and resorptions were counted. The number of fetuses per litter was counted and position inside the uterus recorded. The uteri of apparently non pregnant rats were stained with a 10% ammonium sulfide solution to detect very early resorptions. All fetuses were weighed, examined for external alterations and the sex of each fetus was determined. 
Fetal examinations:
One half of the fetuses from each litter were examined for visceral alterations using the Staples' technique. Head alterations were recorded for these fetuses examined for soft tissue alterations using the technique of Barrow and Taylor (1969, J. Morphol., 127: 291-306). The carcasses of all fetuses  were stained with alizarin red S and examined for skeletal alterations. 
Statistics:
For the purpose of statistical evaluation, the litter was considered the experimental unit for fetal parameters. Pregnancy rate, clinical signs, maternal deaths, gross necropsy findings  and liters with total resorptions were statistically analyzed using the  Fisher's exact test. Maternal body weight data and feed consumption values were statistically analyzed using Dunnett's test when the one-way ANOVA was significant. The number of implantations, live fetuses, resorptions, corpora lutea, mean fetal body weight/litter, and incidence of fetal alterations were statistically analyzed using the Mann-Whitney U test. When more than 75% ties occurred, then Fisher's exact test was used in place of the Mann-Whitney U test to detect significant differences between groups.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
no effects observed
Description (incidence and severity):
The only clinical sign noted was a minimal increase in the incidence of scant feces at 2028 ppm.
Dermal irritation (if dermal study):
not examined
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Treatment-elated decreases on maternal body weight and feed consumption were noted at all exposure levels. The decreases in maternal body weight at 99 and 304 ppm were minimal and transient since they occurred only during the first 2 days of exposure and returned to control values by the next weighing period. The body weight and feed consumption values returned to control values for all groups during the post exposure period (GD 16-20). At 1178 and 2028 ppm, treatment-related effects included losses in maternal body and/or decreased body weight gain throughout the exposure period (GD 6 - 16) and decreased corrected maternal body weight gain.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Treatment related decrease waere noted on feed consumption between days 6-10 G at all exposure levels teasted. Decteases in feed consumption continued between days 6-10 G at 304, 1178, and 2028 ppm. Feed consumption of all treated groups returend to control value during post-treatment period (days 16-20 G)
Gross pathological findings:
no effects observed

Maternal developmental toxicity

Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
no effects observed
Details on maternal toxic effects:
Details on maternal toxic effects:
No animals died and no treatment-related clinical signs were noted for the dams in the 99, 304 or 1178 ppm groups. Scant feces was noted in the 2028 ppm group throughout the exposure period (GD 6-15). Treatment-related decreases on maternal body weight and feed consumption were noted at all exposure levels. The decreases in maternal body weight at 99 and 304 ppm were minimal and transient since they occurred only during the first 2 days of exposure and returned to control values by the  next weighing period. The body weight and feed consumption values returned to control values for all groups during the post exposure period  (GD 16-20). At 1178 and 2028 ppm, treatment-related effects included losses in maternal body and/or decreased body weight gain throughout the exposure period (GD 6 - 16) and decreased corrected maternal body weight gain. The gross necropsy evaluations did not indicate any treatment-related effects and there were no treatment-related differences between the control and treated groups in any reproductive parameter.  

Effect levels (maternal animals)

open allclose all
Dose descriptor:
LOEC
Remarks:
maternal toxicity
Effect level:
ca. 0.41 mg/L air (analytical)
Based on:
test mat.
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEC
Remarks:
maternal toxicity
Effect level:
8.44 mg/L air (analytical)
Based on:
test mat.
Remarks on result:
other: no adverse effects observed

Maternal abnormalities

Abnormalities:
no effects observed

Results (fetuses)

Fetal body weight changes:
no effects observed
Reduction in number of live offspring:
no effects observed
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
no effects observed
External malformations:
effects observed, non-treatment-related
Description (incidence and severity):
No treatment-related increase were detected in the type of external, visceral, or skeletal malformations.
Spontaneous malformations detected in the study included duplicated hypothalamus in a control fetus, hydrocephaly in a fetus at 304 ppm and an omphalocele in one fetus and enlarged adrenal glands in two fetuses at 1178 ppm was not considered to be treatment related as at 2028 ppm no increase was observed.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
The significant increase in skeletal developmental variations at 1178 ppm was not detected at 2028 ppm, the highest doese tested. The slightly, not statistically significant number of fetuses with partial or unossified sternebra at 304 ppm was not considered a result of treatment since no dose response was demonstrated.
Visceral malformations:
no effects observed
Other effects:
not specified
Details on embryotoxic / teratogenic effects:
Details on embryotoxic / teratogenic effects:
 Fetal body weight was not affected by exposure to MMA vapors. The fetal external, visceral and skeletal examinations did not show any treatment related effects.

Effect levels (fetuses)

open allclose all
Dose descriptor:
NOAEC
Remarks:
fetotoxicity
Effect level:
8.44 mg/L air (analytical)
Based on:
test mat.
Sex:
male/female
Remarks on result:
other: corresponding to 2028 ppm; no substance related effects observed
Key result
Dose descriptor:
NOAEC
Remarks:
teratogenicity
Effect level:
8.44 mg/L air (analytical)
Based on:
test mat.
Sex:
male/female
Remarks on result:
other: corresponding to 2028 ppm; no substance related effects observed

Fetal abnormalities

Abnormalities:
no effects observed

Overall developmental toxicity

Developmental effects observed:
no

Any other information on results incl. tables

Mean measured concentrations (± SD) within the chambers for the 0, 100, 300, 1200 and 2000 ppm groups were 98.8 (±3.4), 304.4 (±9.1), 1178.1  (±69.1) and 2028.2 (±107.3) ppm, respectively.

Applicant's summary and conclusion

Conclusions:
Exposure by inhalation to methyl methacrylate concentrations up to 8.44 mg/L (2028 ppm) resulted in no embryo or fetal toxicity or malformations even at exposure levels that resulted in maternal toxicity.
Executive summary:

In a developmental toxicity study (1991) acc. OECD 414 by inhalation on CRl: CD Br rats pregnant rats were exposed to methyl methacrylate at concentrations of 0 (control), 99, 304, 1178 and 2028 ppm on days 6-15 of gestation. A maternal no observed level was not demonstrated since losses in maternal body weight or decreases in maternal body weight gain and decreases in maternal feed consumption were noted at all exposure levels tested. No embryo or fetal toxicity was evodent and no increase in the incidence of malformations or variations was noted at exposure levels up to and including 2028 ppm. Therefore toxicity to the conceptus was not evident even at expsoure levels that resulted in overt maternal toxicity.