Respiratory symptoms and lung-function changes with exposure to five substances in aluminium smelters

Objectives: To determine whether exposure to five different occupational substances contributes to respiratory symptoms in aluminium smelter workers. Methods: A cross-sectional survey of 1,615 male employees of two Australian aluminium smelters was conducted in 1995. Subjects underwent spirometry ad were asked about respiratory symptoms and the relationship of those symptoms to work. Their job histories were combined with a task exposure matrix to produce individual quantitative measures of cumulative exposure to fluoride, sulphur dioxide, inspirable dust, the benzene-soluble fraction of coal tar pitch volatiles (BSF), and oil mist. Results: After adjusting for smoking and age, we found that subjects with the highest cumulative exposure to fluoride ( >0.16 mg/m(3) years) and inspirable dust ( >2.9 mg/m(3) years) were two to four times more likely to report work-related wheeze and chest tightness than were unexposed subjects. Lower prevalence ratios for the same symptoms were seen with sulphur dioxide and BSF. Levels of lung function decreased slightly with exposure to oil mist, but not with cumulative exposure to other substances. Conclusions: This study suggests that the relevant causative agents for respiratory symptoms in aluminium smelters are fluoride and inspirable dust.