Although chronic obstructive pulmonary disease (COPD) is attributed predominantly to tobacco smoke, occupational exposures are also suspected risk factors for COPD. Estimating the proportion of COPD attributable to occupation is thus an important public health need.A randomly selected sample of 2,061 US residents aged 55-75 yrs completed telephone interviews covering respiratory health, general health status and occupational history. Occupational exposure during the longest-held job was determined by selfreported exposure to vapours, gas, dust or fumes and through a job exposure matrix. COPD was defined by self-reported physician9s diagnosis.After adjusting for smoking status and demography, the odds ratio for COPD related to self-reported occupational exposure was 2.0 (95% confidence interval (CI) 1.6-2.5), resulting in an adjusted population attributable risk (PAR) of 20% (95% CI 13-27%). The adjusted odds ratio based on the job exposure matrix was 1.6 (95% CI 1.1-2.5) for high and 1.4 (95% CI 1.1-1.9) for intermediate probability of occupational dust exposure; the associated PAR was 9% (95% CI 3-15%). A narrower definition of COPD, excluding chronic bronchitis, was associated with a PAR based on reported occupational exposure of 31% (95% CI 19-41%).Past occupational exposures significantly increased the likelihood of chronic obstructive pulmonary disease, independent of the effects of smoking. Given that one in five cases of chronic obstructive pulmonary disease may be attributable to occupational exposures, clinicians and health policy-makers should address this potential avenue of chronic obstructive pulmonary disease causation and its prevention.

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Background: The contribution of occupational exposures to chronic obstructive pulmonary disease (COPD) and, in particular, their potential interaction with cigarette smoking remains underappreciated. Methods: Data from the FLOW study of 1202 subjects with COPD (of which 742 had disease classified as stage II or above by Global Obstructive Lung Disease (GOLD) criteria) and 302 referent subjects matched by age, sex and race recruited from a large managed care organisation were analysed. Occupational exposures were assessed using two methods: self-reported exposure to vapours, gas, dust or fumes on the longest held job (VGDF) and a job exposure matrix (JEM) for probability of exposure based on occupation. Multivariate analysis was used to control for age, sex, race and smoking history. The odds ratio (OR) and adjusted population attributable fraction (PAF) associated with occupational exposure were calculated. Results: VGDF exposure was associated with an increased risk of COPD (OR 2.11; 95% CI 1.59 to 2.82) and a PAF of 31% (95% CI 22% to 39%). The risk associated with high probability of workplace exposure by JEM was similar (OR 2.27; 95% CI 1.46 to 3.52), although the PAF was lower (13%; 95% CI 8% to 18%). These estimates were not substantively different when the analysis was limited to COPD GOLD stage II or above. Joint exposure to both smoking and occupational factors markedly increased the risk of COPD (OR 14.1; 95% CI 9.33 to 21.2). Conclusions: Workplace exposures are strongly associated with an increased risk of COPD. On a population level, prevention of both smoking and occupational exposure, and especially both together, is needed to prevent the global burden of disease.

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