The risk of asthma in relation to occupational exposures: a case-control study from a Swedish city

The purpose of this study was to estimate the risk of adult asthma in relation to certain occupational exposures. The study was designed as a case-control study in Göteborg, including 321 subjects with asthma, born between 1926 and 1970. Controls (n=1,459) were randomly selected from the same area from registers of the 1986 population. Questionnaire information was collected in 1996, and included occupational exposures and smoking habits. Odds ratios were calculated for exposure before asthma onset, stratified by sex and age-class. The highest risks for asthma were associated with exposure to grain dust (odds ratio (OR) 4.2, 95% confidence interval (CI) 1.6-10.7) and flour dust (OR 2.8, 95% CI 1.1-7.2). Among males, significantly increased risks were observed after exposure to flour dust, welding fumes, man-made mineral fibres, and solvents. Among females, increased risks for asthma were associated with exposures to paper dust and textile dust. In logistic regression models controlling for age, smoking, sex and interacting exposures, increased risks were seen for welding fumes (OR 2.0, 95% CI 15-3.4), man-made mineral fibres (OR 2.6, 95% CI 1.4-7.3) and solvents (OR 2.2, 95% CI 1.2-3.2). The fraction of asthma attributed to occupational exposures after adjusting for sex, smoking and age was 11% (95% CI 7-14%). In conclusion, exposure to welding fumes, man-made mineral fibres, solvents and textile dust is associated with increased risk for asthma.