Chlorpyrifos: Hazard assessment based on a review of the effects of short-term and long-term exposure in animals and humans

Analyses of potential dietary exposure to chlorpyrifos residues were conducted by the Department of Pesticide Regulation (DPR). Potential acute dietary ingestion of chlorpyrifos for all labelled uses was based on the 95th percentile of user-day exposures. Margins of safety (MOSs) for potential acute dietary exposure to chlorpyrifos residues were based on a no-observed-effect level (NOEL) for cholinergic signs in a human study, and ranged from 52 to 205 for all population subgroups. MOSS for potential chronic dietary exposure to chlorpyrifos residues were based on a NOEL for inhibition of brain cholinesterase activity in rats and dogs, and ranged from 2198 to 8065 for all population subgroups. The limitations on toxicity, consumption and residue data are discussed, with the assumptions necessitated by those limitations.