Maternal exposure to multi-wall carbon nanotubes does not induce embryo-fetal developmental toxicity in rats

Background: Although the potential risk of carbon nanotubes (CNTs) to humans has recently increased due to expanding production and widespread use, the potential adverse effects of CNTs on embryo-fetal development have not yet been determined. METHODS: This study investigated the potential effects of multi-wall CNTs (MWCNTs) on pregnant dams and embryo-fetal development in rats. MWCNTs were administered to pregnant rats by gavage at 0, 40, 200, and 1,000mg/kg/day. All dams were subjected to Cesarean section on day 20 of gestation, and the fetuses were examined for any morphological abnormalities. RESULTS: All animals survived to the end of the study. A decrease in thymus weight was observed in the high dose group in a dose-dependent manner. However, maternal body weight, food consumption, and oxidant-antioxidant balance in the liver were not affected by treatment with MWCNTs. No treatment-related differences in gestation index, fetal deaths, fetal and placental weights, or sex ratio were observed between the groups. Morphological examinations of the fetuses demonstrated no significant difference in incidences of abnormalities between the groups. CONCLUSIONS: The results show that repeated oral doses of MWCNTs during pregnancy induces minimal maternal toxicity and no embryo-fetal toxicity at 1,000mg/kg/day in rats. The no-observed-adverse-effect level of MWCNTs is considered to be 200mg/kg/day for dams and 1,000mg/kg/day for embryo-fetal development. In this study, the dosing formulation was not analyzed to determine the degree of reaggregation (or not), nor were blood levels of CNT's measured in the dosed animals to verify or characterize absorption.