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Occupational mould exposure and respiratory disease morbidity among BC lumber mill workers Ronald, Lisa Anne

Abstract

Background: Previous studies have found woodworkers to be at an increased risk for nonmalignant respiratory disease (NMRD) compared to control populations, and mould exposure has been suggested as a possible cause of NMRD in woodworkers. The main objectives of this thesis were to develop a predictive model of mould exposure among BC lumber mill workers and to assess the risk of NMRD associated with mould exposure within a cohort of BC lumber mill workers. Methods: In the first study, multivariate linear regression modeling was applied to 223 personal samples of B-(l,3)-glucan (a marker of mould exposure) collected at four BC lumber mills, to produce a predictive model of mould exposure among workers. In the second study, quantitative exposure values derived from the predictive model were assigned retrospectively to a cohort of 11,200 BC lumber mill workers (employed at one of fourteen BC mills between 1979 and 1994 for at least one year) to develop cumulative exposure estimates. Morbidity was assessed using hospital discharge records (April 1, 1985 and July 31, 1997) obtained from the BC linked Health Database. Exposure gradients among hospitalrzation rates for any NMRD (ICD9=460-519), chronic obstructive pulmonary disease (COPD, ICD9=490- 92, 496) and asthma (ICD9=493) were assessed using Poisson regression, with workers in low exposure categories acting as the reference population. Results: A total of 1097 cases of any NMRD, 256 cases of COPD and 97 cases of asthma were included in analyses. After controlling for age, calendar period and race (and employment in Western Red Cedar mills for asthma analyses), there was evidence of an increase in COPD risk among high and moderate exposed workers at no exposure lagging and lagging up to 5 years. There was some evidence of a link between exposure and asthma, though no clear trends were apparent, and no evidence of a link with any respiratory disease. Conclusion: This study provided evidence of a link between cumulative mould exposure and hospitalrzation due to COPD among woodworkers. Further studies with greater power and better control of possible conflunders are needed to fully assess dose-response relationships between mould exposure and NMRD morbidity among BC woodworkers.

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