Objective: The aim of this study was to elucidate further whether occupational exposure to non-sensitising air pollution at workplaces increases the risk of adult onset asthma.
Methods: One hundred and twenty persons with asthma diagnosed by general practitioners, aged 20-65 years, were compared with 446 referents matched for age and gender and living in the same community as the cases. Information about occupation, exposure to specific allergens, smoking habits, dwellings and atopy was obtained from a postal questionnaire. The subjects' occupations were categorised as clean or polluted, based on the judgement of the referents on their respective occupations.
Results: Three years or more of work in air-polluted workplaces resulted in an odds ratio of 1.7 (95% confidence interval 1.0-2.7). Stratification of the material on smoking habits, gender or atopy did not alter the results, nor did exclusion of subjects exposed to specific allergens of statistical significance in this material, e.g. flour dust. Smoking per se did not bring any risk of asthma. Working in buildings affected by dampness and mould brought a fourfold significant risk.
Conclusion: In this study occupational exposure to unspecific air pollution at workplaces was associated with an increased risk of adult-onset asthma.