Paraquat (Pesticides)

Food Safety Commission of Japan (FSCJ) conducted a risk assessment of a bipyridinium herbicide, paraquat (CAS No. 1910-42-5), based on results from various studies. Major adverse effects of paraquat in experimental animals were observed in body weight (suppressed weight gain), lungs (increased weight, alveolar epithelium hyperplasia, and pneumonia), kidneys (renal tubule dilatation) and eyes (cataract in rats and dogs). The effects on the lung were considered to be the most critical endpoints in the assessment. Neither carcinogenicity, effects on fertility, teratogenicity, genotoxicity, or immunotoxicity was observed. FSCJ reasonably concluded no obvious concern of paraquat-residue in foods to yield neurotoxicity through human dietary exposure, as long as paraquat is applied following the registered standard use of the pesticide. The lowest no-observed-adverse-effect level (NOAEL) obtained from all the studies was 0.45 mg paraquat ion(*)/kg bw per day in one-year chronic toxicity study in dogs. FSCJ specified an acceptable daily intake (ADI) of 0.0045 mg paraquat ion/kg bw per day by applying a safety factor of 100 to the NOAEL. FSCJ judged these effects also as the end-point of the acute reference dose (ARfD). The lowest NOAEL was 0.45 mg paraquat ion/kg bw per day in one-year chronic toxicity study in dogs. For potential adverse effects of a single oral administration of paraquat, FSCJ specified an ARfD to be 0.0045 mg paraquat ion/kg bw by applying a safety factor of 100 to the NOAEL.