Oral (drinking water) developmental toxicity study of ammonium perchlorate in New Zealand White rabbits.

This developmental toxicity study was conducted to evaluate the embryo-fetal toxicity and teratogenic potential of ammonium perchlorate in New Zealand White [Hra:(NZW)SPF] rabbits. Pregnant rabbits were given continual access to ammonium perchlorate in drinking water at target doses of 0, 0.1, 1.0, 10.0, 30.0, and 100.0 mg/kg-day on gestation days 6 through 28. The actual consumed doses in the study were 0, 0.1, 0.9, 10.4, 30.3, and 102.3 mg/kg-day. The rabbits were sacrificed on gestation day 29, and fetuses were examined for developmental alterations. In addition, blood was collected from does for determination of serum thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) levels and the thyroid was subjected to histopathologic examination. No maternal deaths were attributed to perchlorate exposure. Ammonium perchlorate as high as 100.0 mg/kg-day did not affect caesarean sectioning or litter parameters studied, and all values were found to be within the historical ranges of the laboratory. The litter averages for corpora lutea, implantations, litter sizes, live and dead fetuses, percent dead or resorbed conceptuses, and fetal body weights were comparable and also did not differ significantly in the six dose groups. All placentae appeared normal and no dam had a litter consisting of only resorbed conceptuses. The maternal thyroid was the target organ for ammonium perchlorate in this study. Increased incidence of thyroid follicular hypertrophy was observed in does treated with > or =10 mg/kg-day perchlorate and significantly decreased T4 was observed in does treated with > or =30 mg/kg-day. Based on these data, the maternal no-observable-adverse-effect level (NOAEL) for ammonium perchlorate was 1.0 mg/kg-day. The developmental NOAEL for ammonium perchlorate was found to be 100.0 mg/kg-day for rabbits.