Reproductive toxicology of inhaled styrene oxide in rats and rabbits

Experiments were performed to evaluate reproductive and developmental toxicology in rats and rabbits exposed to styrene oxide by inhalation. Female rats were exposed to 100 or 300 ppm styrene oxide or to filtered air for 7 h/day, 5 days/week for 3 weeks. Extensive mortality occurred in rats that received prolonged exposure to 100 ppm styrene oxide while 300 ppm was rapidly lethal. As a result exposures were terminated in this latter group and the group was eliminated from further study. The rats of the 0 and 100 ppm groups were then mated and exposed to 0 or 100 ppm styrene oxide daily through 18 days of gestation (dg). Female rabbits were artificially inseminated and exposed for 7 h daily to 0, 15, or 50 ppm styrene oxide through 24 dg. Both of these lower concentrations used for exposure of the rabbits produced mortality of does. The rats were killed at 20 dg and the rabbits at 30 dg. Pregnant animals were examined for toxic changes including altered tissue weights and histopathologic effects. Litters were evaluated using several measures of embryotoxicity, and live fetuses were examined for external, visceral, and skeletal malformations. Exposure during gestation appeared to increase preimplantation loss in rats, and tended to increase the incidence of resorptions in rabbits. In both species, fetal weights and crown-rump lengths were reduced by gestational exposure. The incidences of ossification defects of the sternebrae aned occipital bones were increased by gestational exposure of rats to styrene oxide. These results indicate that inhalation exposures at these concentrations produce reproductive and development toxicity, as well as maternal toxicity.