External and internal exposure of winegrowers spraying methyl parathion

Organophosphates, used in agriculture, are readily absorbed through the skin. We investigated the relationship between dermal and inhalative methyl parathion exposure and the plasma levels. Twenty-three healthy winegrowers sprayed the insecticide for 50 min. Fluorescent brilliant sulfoflavin was added to the spraying fluids and filter papers were fixed on the subjects. The filter papers were used to evaluate the amount of brilliant sulfoflavine on the unprotected skin fluorometrically. Inhalative exposure was measured with personal air sampler. Plasma concentrations of methyl parathion and its metabolite methyl paraoxon were determined with gas chromatography. Cholinesterase activity in serum and erythrocytes was measured before and after exposure. Some winegrowers wore protective clothes, none protective gloves. Dermal exposure ranged up to 12,044 μg, inhalative to 22 μg. Maximum plasma concentration of methyl parathion was 12.1 μg/l. Methyl paraoxon was not detectable. Cholinesterase activity did not decrease. Dermal exposure correlated with the methyl parathion plasma level (Spearman's ρ = 0.72, p < 0.001). In conclusion, dermal exposure exceeded inhalative exposure considerably. Measuring dermal deposition with the brilliant sulfoflavin technique may provide a good estimate of the internal load with methyl parathion. Preventive measures should be improved as toxic effects of repeated exposure to low doses of methyl parathion cannot be excluded.