Characterization of maternal influence on teratogenicity: An assessment ofdevelopmental toxicity studies for the herbicide cyanazine

The contribution of maternal toxicity to the teratogenic effects of the her bicide cyanazine has been assessed to determine whether it may be a hazard to development. Eye defects such as anophthalmia and microphthalmia were ob served in rat fetuses and pups. Maternal toxicity was determined from body weight data and clinical signs. Two approaches were used. First, the timing of maternal toxicity was correlated with the specific period of gestation during which the observed fetal defect was most likely to have occurred. Se cond, individual dams, as well as mean values for each group, were evaluate d. The data at the individual level, i.e., in dams with affected litters, d id not support conclusions based on the group means. instead, it is suggest ed that the developmental effects were not a direct result of maternal toxi city of cyanazine. Data fi om a rabbit developmental toxicity study support ed the findings from the Fischer 344 rat studies. The strategy employed may thus enable direct toxicity to the fetus to be distinguished from; develop mental toxicity arising as a secondary consequence of maternal toxicity.