Effects of maternal exposure to toluene during pregnancy on mouse embryos and fetuses.

Female mice 11 weeks of age (ICR Strain) with vaginal plugs were divided into three groups. Two groups were exposed to 100 or 1,000 ppm of toluene and the other group was exposed to air in the exposure chamber of six hours every day from the 1st to 17th day of gestation. On the 18th day of gestation, two thirds of the mice in each group were sacrificed and their uteri were examined from implantation and resorption sites. The fetuses were weighed and external examinations for malformations were performed. Skeletal preparations stained with alizarin red S were also examined. To compare the postnatal growth of pups in the three groups, the rest of the mice in each group were delivered. Results were as follows. 1. Incidence of resorbed fetuses in the 100ppm and 1,000ppm toluene exposed groups was increased when compared with the control group, but the difference was not statistically significant. 2. No significant difference was observed in the number of implantation sites, mean live or dead fetuses and mean fetal body weight among the three groups. 3. External malformations were found at a low frequency, and no difference was seen among the three groups. 4. Body weight gains, and periods of eye or ear-opening, weaning, full incidence of body hair and coordinated walking of pups showed no differences among the groups. 5. Incidence of skeletal abnormalities was low, except for extra 14th ribs and rudimentary 14th ribs. The high incidence of extra 14th ribs in the 1,000ppm toluene exposed group suggested the possible teratogenicity of toluene.