Boilermaker construction workers are exposed to combustion particulates fom multiple sources. They construct, maintain and repair boilers at power plants which bum oil, coal or natural gas, as well as boilers at trash incinerators burning waste and at paper mills which bum tree bark and sap. Given the evidence of both acute cross-shift and short-term decrements in lung function in boilermakers following occupational exposure to combustion particulates, we sought to determine whether exposure is associated with an annual loss in lung function. As part of an ongoing investigation of the health effects of boilermakers, we conducted a longitudinal study of lung function among 118 boilermaker construction workers exposed to combustion particulates. Exposure during a two-year study was assessed with a detailed work history questionnaire. Spirometry measurements were performed annually to prospectively assess lung function decline. A generalized estimating equation (GEE) approach was used to account for the repeated measures design. We found a robust association between FEV1 and the number of hours worked at gas-fired plants during the previous year, as well as an association with having ever worked at a gas fired plant during the previous year. The association between FEV, and hours worked at a gas-fired plant was -9.8 mls/1 00 hours worked (95% C1 -16.0, -3.5) after adjustment for age, baseline FEV1 and cigarette smoking status. The adjusted association between FEV1 and "ever worked" at a gas-fired plant was -99.7 mls (95%C1 -154.8, -44.5). There was also evidence of a negative association between hours worked at oil and coal-fired plants and annual FEV1, as well as a significant negative association between "ever worked" at an oil or coal-fired plant and reduced FEV1. These data suggest an association between annual lung function and working at gas-fired, as well coal-fired and oil-fired plants. These results should be replicated with further followup of this cohort, as well as other cohorts of boilermaker construction workers.