We previously showed that apricot sulfurization workers are exposed to high concentrations of sulfur dioxide (SO2) resulting in an asthmalike syndrome. The aim of this study was to investigate whether pre-treatment of ipratropium bromide protects bronchoconstriction induced by SO2 exposure during apricot sulfurization processes that causes asthma-like syndrome. Firstly, pulmonary function tests were measured before and immediately after SO2 exposure due to processes of apricot sulfurization in 21 healthy volunteer apricot sulfurization workers who did not use any medication in apricot farms. One week later, same measurements were repeated in the same workers when they were working in same farm but they were administered two puffs of ipratropium bromide (20 mu g per dose) before 30 min second SO2 exposure for protection Of SO2-induced bronchoconstriction. Occupational SO2 exposure caused significant decrement in forced vital capacity (FVC), forced expiratory volume (FEVI) and forced mid-expiratory flow rate (FEF25-75%) in the worker and these decrements were prevented by ipratropium bromide given 30 min before SO2 exposure. This result suggests that pre-treatment of ipratropium bromide protects SO2-induced bronchoconstriction in healthy worker during apricot sulfurization processes that causes asthma-like syndrome in agricultural environment. (c) 2005 Elsevier Ltd. All rights reserved.