Sequential cholinesterase tests and symptoms for monitoring organophosphate absorption in field workers and in persons exposed to pesticide spray drift

Pre-season, in-season and post-season cholinesterase (ChE) levels (Ellman method) were monitored in 36 field workers (sprayers, field hands, leaf inspectors) from 3 kibbutzim and 25 residents from the same kibbutzim. Small and presumably inconsequential in-season reductions in plasma and whole blood ChE activity were seen in field workers and residents exposed to spray drift, but not in non-exposed residents. Intra- and inter-individual variability in plasma and whole blood ChE activities were within 'normal' ranges (e.g., less than 30% inhibition), but the variability (intra- and inter-individual) was greater in the field workers compared with residents. Daily logs from the infirmary of one kibbutz for 1 month recorded an excess of complaints (respiratory tract, eye irritation, headache) in residents on days when organophosphates were sprayed from aircraft compared to days when other or no pesticides were sprayed. The findings provide some indications of the utility and the level of sensitivity of plasma ChE for monitoring field workers, and possibly residents exposed to drift. Selective semi-routine examinations of alkylphosphates in urine together with the assessment of health effects are recommended to determine whether or not ChE monitoring is needed on a routine basis, or should be replaced by alkylphosphate monitoring.