Neurotoxicity of halogenated O-phenyl O-alkyl alkylphosphonothioates.

Twenty-seven halogenated organophosphorus esters were tested for neurotoxicity in adult hens. Fourteen compounds were overtly neurotoxic, including eight of the eleven methylphosphonothioates, three of seven ethylphosphonothioates, and three of six phosphoramidates, one of which was the commercial herbicide DMPA. Neurotoxic activity varied both with the number of halogen substituents on the phenyl group, and with the identity of the 4-phenyl halogen. Neurotoxic activity also varied with the alkyl group involved in the P-C or P-N bond, and with the identity of the O-alkyl group.