Biological monitoring of workers occupationally exposed to organophosphorus pesticides

Abstract

AbstractThis paper describes the development and use of a biological monitoring method for assessing exposure to organophosphorus pesticides. The method is used to determine the concentration of six dialkyl phosphates and phosphoro‐thioates (dimethyl phosphate, diethyl phosphate, O,O‐dimethyl phosphorothioate, O,O‐diethyl phosphorothioate, O,O‐dimethyl phosphorodithioate and O,O‐diethyl phosphorodithioate) in urine. The method involves the azeotropic distillation of urine, derivatisation of the residue with pentafluorobenzylbromide followed by high resolution gas chromatography with flame photometric detection.The technique has been applied to the analysis of over 400 urine samples obtained from 140 workers with potential occupational exposure to organophosphorus pesticides during various agricultural activities, sheep dipping or pesticide formulation. Wherever possible, blood samples were taken for measurement of red blood cell and plasma cholinesterase activity. The results show that in over 300 instances where blood samples were also obtained, urinary dialkyl phosphate metabolites could be detected even though there was no depression of red cell or plasma cholinesterase activity. Formulation workers had higher urinary metabolite levels (expressed as nmoles metabolite per mmole creatinine) than any of the other groups studied and were the only group where a significant reduction in cholinesterase activity was also seen.The results discussed here show that the method for the analysis of urinary dialkyl phosphate metabolites described is useful for monitoring occupational exposure to organophosphorus pesticides and is capable of detecting low levels of exposure not detectable by depression of cholinesterase activity.