This review critically evaluates the recent scientific literature relevant to occupational risk factors for chronic obstructive pulmonary disease (COPD) and chronic bronchitis. The 2003 American Thoracic Society statement on the occupational contribution to the burden of airway disease synthesized relevant data on this topic through 1999. Since 2000, 14 separate studies have published values or provide data that allow estimation of the population attributable risk per cent (PAR%) for the proportion of chronic bronchitis or COPD due to work-related factors. Based on data since 2000, the median PAR% value for both chronic bronchitis and COPD is 15%. A number of additional studies have been published that underscore the association between specific occupational exposures and airflow obstruction. In addition, data are emerging that indicate the extent to which COPD is a cause of work disability; limited data raise the possibility that among those with occupational COPD, disability may be even more prominent. This review supports previous analyses concluding that there is a causal association between work-related exposures and COPD.