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Toxicological information

Developmental toxicity / teratogenicity

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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:
other: Method and result sufficient described, similar to OECD-guideline 414, GLP.

Data source

Reference
Title:
Unnamed
Year:
1991
Report Date:
1991

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed

Test animals

Species:
rat
Strain:
other: Crl:CDBR
Details on test animals 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 / concentrations
Remarks:
Doses / Concentrations:
ca. 0.41, 1.2, 4.8, 8.3 mg/L (corresponding to 99, 304, 1178, 2028 ppm)
Basis:
analytical conc.
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

Maternal developmental toxicity

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)

Dose descriptor:
LOEC
Effect level:
ca. 0.41 mg/L air (analytical)
Basis for effect level:
other: maternal toxicity

Results (fetuses)

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
Effect level:
>= 8.3 mg/L air (analytical)
Basis for effect level:
other: fetotoxicity
Dose descriptor:
NOAEC
Effect level:
>= 8.3 mg/L air (analytical)
Basis for effect level:
other: teratogenicity

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

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