Thioether excretion in urine of applicators exposed to 1,3-dichloropropene: a comparison with urinary mercapturic acid excretion

The excretion of thioethers in urine of applicators occupationally exposed to the soil fumigant 1,3-dichloropropene (DCP) was determined by the thioether assay. The mercapturic acid metabolite of E-1,3-dichloropropene, N-acetyl-S-(E-3-chloropropenyl-2-)-L-cysteine (E-DCP-MA), was the reference compound in the thioether assay. The mean recovery of E-DCP-MA was 58.5% (coefficient of variation (CV) 9%, n = 4). In non-exposed men mean background of urinary thioethers was 6.05 mmol SH/mol creatinine (n = 56). In applicators exposed to soil fumigants containing DCP, urinary excretion of thioethers followed first order elimination kinetics. Urinary half lives of elimination of thioethers were 8.0 (SD 2.5) hours based on excretion rates and 9.5 (SD 3.1) hours based on creatinine excretion. The urinary half life of elimination of thioethers was almost twofold higher compared with half lives of elimination of the mercapturic acids of Z- and E-1,3-dichloropropene. The post- minus pre-shift thioether concentrations in urine and the cumulative urinary thioether excretions correlated well with exposure to DCP. In urine samples the mean thioether concentration was 1.38 higher than mean DCP mercapturic acid concentration. This suggests the presence of unidentified thioether metabolite(s) due to exposure to soil fumigants containing DCP. According to the present data, an eight hour time weighted average exposure to the Dutch occupational exposure limit of 5 mg/m(3) DCP results in a post- minus pre-shift thioether concentration of 9.6 mmol SH/mol creatinine (95% confidence interval (95%CI) 7.4-11.8 mmol SH/mon creatinine) and in a cumulative thioether excretion of 139 micromol SH (95% CI 120-157 micromol SH). It is concluded that the thioether assay can be used to assess comparatively high levels of exposure to DCP.