Background: We previously showed that apricot sulfurization workers (ASW) are exposed to high concentrations of SO2, resulting in an asthma-like syndrome. The aim of this study was to evaluate whether oxidative stress plays a role in the pathogenesis of asthma-like syndrome due to the high concentrations of SO2 exposure in agricultural environment. Methods: Serum antioxidant enzyme activities and malondialdehyde (MDA) concentrations, which are markers of lipid peroxidation, and pulmonary function tests (PFT) were measured in 40 volunteer ASW and compared to 20 healthy control subjects. Results: The superoxide dismutase (SOD, 2.2 +/- 0.6 vs. 3.2 +/- 0.7 U/m), glutathione peroxidase (GSH-Px, 0.6 +/- 0.3 vs. 1.1 +/- 0.3 U/m) and catalase (107.6 +/- 27.4 vs. 152.6 +/- 14.3 k/l) activities in ASW were significantly (p < 0.0001) lower than controls, whereas the malondialdehyde concentration (4.1 +/- 0.9 vs. 1.9 +/- 5.3 nmol/l) was higher in ASW (p < 0.0001). ASW had significant decreases in pulmonary function parameters after exposure. Conclusion: These results show that occupational exposure to high concentrations of SO2 enhances oxidative stress and lipid peroxidation may be considered as a new mechanism of SO2-induced bronchoconstriction. (C) 2003 Elsevier Science B.V. All rights reserved.