Exposure to the organophosphate diazinon: data from a human volunteer study with oral and dermal doses

Biological monitoring of occupational exposure to diazinon is possible by the determination of blood cholinesterase activity and by the measurement of metabolites in urine. However, there is little data to aid in the interpretation of results. This study gave oral (11 microg kg(-1) (36 nmol kg(-1)) body weight) and occluded dermal (100 mg (329 micromol)) doses of diazinon to five volunteers and analysed blood and urine samples for plasma and erythrocyte cholinesterase and urinary dialkyl phosphate (DAP) metabolites of diazinon: diethyl phosphate (DEP) and diethyl thiophosphate (DETP). Following oral and dermal exposure, peak urinary DAP levels occurred at 2 and 12 h, respectively. The apparent urinary elimination half-lives of DAP metabolites following oral and dermal exposure were approximately 2 and 9 h, respectively. Approximately 60% of the oral dose and 1% of the dermal dose was excreted as urinary DAP metabolites, with 90% of the dermal dose being recovered from the skin surface. On a group basis, there was no statistically significant mean depression in plasma or erythrocyte cholinesterase when compared with pre-exposure levels for either dosing experiment. The observed elimination kinetics of diazinon metabolites suggest a biological monitoring strategy for occupational exposure to diazinon based on urine samples collected at the end of shift.