Physiological response to organophosphate residues in field workers.

The physiologic response of 21 male agricultural field workers exposed to foliage-borne Guthion residues was monitored during routine peach-thinning operations in a northern California orchard. Surveillance included daily venipuncture and urine collection to determine whole blood cholinesterase (CHE) activity and level of dialkylphosphate excretion for 3 baseline (nonexposed) and 5 normal work days. Foliage samples were obtained to measure dislodgeable and total Guthion residues. A decrease in group-mean CHE activity by 15% over the surveillance period was found. Apart from one worker who showed a consistent decrease in CHE activity, reaching a maximum of 30% below baseline at the end of the work week, daily changes in individual CHE activity were erratic. Group-mean dialkylphosphate excretion levels provided a semiquantitative indication of exposure to Guthion. Medical examination before and after the exposure period revealed an absence of clinical signs of organophosphate intoxication.