Toxicologic studies in a fatal overdose of 2,4-D, MCPP, and chlorpyrifos.

A death due to ingestion of 2,4-dichlorophenoxyacetic acid (2,4-D), 2-(2-methyl-4-chlorophenoxy) propionic acid (MCPP), and phosphorothioic acid O,O-diethyl O-(3,5,6-trichloro-2-pyridinyl)ester (chlorpyrifos) is reported. The clinical course, dose ingested, and plasma levels of the chemicals were compatible with previous fatalities due to the chlorophenoxyacetic acids. Chlorpyrifos concentrations and tissue cholinesterase and in esterase inhibitions indicated the presence of the organophosphate and its biochemical effect, but few cholinergic signs were observed clinically. Lymphocytic neurotoxic esterase activity was decreased for a limited period of time after ingestion. Postmortem nervous tissue neurotoxic esterase was also decreased. This association has not been demonstrated before in man. HPLC and GC/NPD methods for measuring chlorophenoxy acetic acids and chlorpyrifos, respectively, are presented.