The metabolites of organophosphorus pesticides in urine as an indicator of occupational exposure

Abstract

The differences in the degree in workers’ exposure to organophosphorus pesticides during the spraying of an apple‐orchard were assessed from the urinary content of metabolites: dimethyl phosphorothiolate potassium salt (DMPThK) for Demeton‐S‐methyl and dimethyl phosphorothionate and phosphorodithioate potassium salts (DMTPK and DMDTPK) for Azinphos‐methyl and Methidathion. The highest median concentrations of the metabolites in the urine samples collected after two to three days of work with the pesticides were determined in the mixers preparing pesticide solutions: DMPThK 83ng cm‐3 (N = 7) after exposure to Demeton‐S‐methyl; DMTPK 2040 and DMDTPK <20n gcm‐3 (N =7) after exposure to Azinphos‐methyl; DMTPK 501 and DMDTPK 88 ng cm‐3 (N = 6) after exposure to Methidathion. The applicators (sprayers) were the second most exposed group: DMPThK 30 ng cm‐3 (N = 6) after exposure to Demeton‐S‐methyl; DMTPK 433 and DMDTPK <20 ng cm‐3 (N = 7) after exposure to Azinphos‐methyl; DMTPK 45 and DMDTPK <20 ng cm‐3 (N = 16) after exposure to Methidathion. The median concentrations in the other orchard employees (N = 5–8) were always ≤50 ng cm‐3. Mean decrease/increase in pre‐exposure cholinesterase activity in whole blood and plasma (to 20%) gave no indication of different organophosphorus pesticide absorption in different groups of workers. The concentration of specific metabolites is an early, direct, more reliable and more sensitive indicator of subtle differences in occupational exposure which should initiate well‐timed and more efficient measures for the protection of workers’ health.