| This dissertation is a result of an epidemiological prospective cohort study carried out among apprentice welders at four vocational teaching institutions in welding profession in the Montreal region, for the purpose of: (1) assessing the respiratory health of students, before starting welding, such as respiratory symptoms suggestive of asthma, lung function and bronchial responsiveness as well as immunological sensitization to common allergens and to metals; (2) providing a reassessment of the respiratory health of these same students as well as an assessment of the incidence of systemic symptoms suggestive of metal fume fever (MFF) after being exposed to welding fumes; (3) estimating the association between MFF and the incidence of bronchial hyperresponsiveness (BHR) and/or the presence of welding-related respiratory symptoms suggestive of occupational asthma (OA); (4) determining whether atopy, immunological sensitization to metals encountered in the welding environment, smoking and a personal history of asthma, are associated with an increased level of BHR or welding-related respiratory symptoms suggestive of OA; and (5) determining the relationship between exposure to metal oxide fumes and the outcome variables, i.e., MFF, immunological sensitization to metals, welding-related respiratory symptoms suggestive of OA and BHR.; The undertaken study consisted of an initial pre-exposure assessment survey and two follow-up reassessment surveys that took place between September 1998 and June 2001. During these surveys a series of tests were carried out. These included a respiratory symptom questionnaire as well as a systemic symptom questionnaire, skin prick tests, spirometry and methacholine challenge tests. Industrial hygiene sampling for welding fumes in the breathing zone of these students was also performed. The overall results of the epidemiological study are presented in three interrelated manuscripts.; The first manuscript describes in detail the underlying methodology. In addition, it provides incidence figures, which are lacking in the reviewed literature, for the outcomes of interest described afterwards. The second manuscript determined the incidence of bronchial hyperresponsiveness (BHR) and the increase in airway obstruction from baseline values. The third manuscript confirmed our earlier findings (1) of a strong association between welding-related MFF and welding-related respiratory symptoms suggestive of OA. (Abstract shortened by UMI.)... |
