BIOLOGICAL MONITORING OF WORKERS OCCUPATIONALLY EXPOSED TO ORGANOPHOSPHORUS PESTICIDES

This paper describes the development and use of a biological monitorin g method for assessing exposure to organophosphorus pesticides. The me thod is used to determine the concentration of six dialkyl phosphates and phosphorothioates (dimethyl phosphate, diethyl phosphate, O,O-dime thyl phosphorothioate, O,O-diethyl phosphorothioate, O,O-dimethyl phos phorodithioate and O,O-diethyl phosphorodithioate) in urine. The metho d 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 be en applied to the analysis of over 400 urine samples obtained from 140 workers with potential occupational exposure to organo-phosphorus pes ticides during various agricultural activities, sheep dipping or pesti cide formulation. Wherever possible, blood samples were taken for meas urement of red blood cell and plasma cholinesterase activity. The resu lts show that in over 300 instances where blood samples were also obta ined, urinary dialkyl phosphate metabolites could be detected even tho ugh there was no depression of red cell or plasma cholinesterase activ ity. Formulation workers had higher urinary metabolite levels (express ed as nmoles metabolite per mmole creatinine) than any of the other gr oups 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 metabol ites described is useful for monitoring occupational exposure to organ ophosphorus pesticides and is capable of detecting low levels of expos ure not detectable by depression of cholinesterase activity.