It is well-recognized that workplace exposures importantly contribute to the burden of asthma, but the role of some agents needs to be clarified. The aims of the thesis are to evaluate the relationships between occupational exposure to cleaning products and asthma, and to study the impact and the control of the healthy worker effect bias, in the Epidemiological study on the Genetics and Environment of Asthma (EGEA, 2047 subjects including 1477 adults with data regarding occupations).Exposure to cleaning products was estimated by an expert assessment and a job-exposure matrix. In women, current asthma was associated with exposure to decalcifiers (OR=2.4 (1.1-5.3)), and to sprays (2.9 (1.0-8.1)) and ammonia (3.1 (1.2-7.8)) in personal care workers. Decalcifiers and ammonia are irritants. Exposure to cleaning products was associated with severe asthma, and asthma without allergic sensitization. Two analyses underlined the important impact of the healthy worker effect in asthma. A healthy worker hire effect was observed in subjects with severe asthma in childhood. Using a marginal structural model, we studied the effect of occupational exposure on asthma clinical expression over a lifetime, while controlling for the healthy worker effect bias. Elevated risks of asthma were observed, not only for known asthmagens, but also for other agents which role in asthma is less established, including irritants (1.6 (1.0-2.4)). The results are consistent with a role of irritants in work-related asthma. They support a broader use of causal inference approaches, to control the healthy worker effect bias in studies of occupational risk factors.
