Background Airborne exposures at the workplace are believed to be associated with lung function decline. However, results from longitudinal studies are conflicting.

Methods Participants from two general population-based cohorts, the Copenhagen City Heart Study and the Copenhagen General Population Study, with at least two lung function measurements were followed for an average of 9 years, range 3–27 years. Occupational exposure was assigned to each year of follow-up between two lung function measurements by a job exposure matrix. Associations between mean occupational exposure per year and mean annual decline in forced expiratory volume in 1 second (FEV1) were investigated using linear mixed effects models according to cohort and time period (1976–1990 and 2003–2015). We adjusted for sex, height, weight, education, baseline FEV1, and pack-years of smoking per year during follow-up.

Results A total of 16,144 individuals were included (mean age 48 years and 43% male). Occupational exposure to mineral dusts, biological dusts, gases & fumes, and a composite category were not associated with FEV1 decline in analyses with dichotomized exposure. In analyses with an indexed measure of exposure, gases & fumes were associated with a FEV1 change of -5.8 mL/unit/year (95% confidence interval:-10.8; -2.3) during 1976–1990, but not during 2001–2015.

Conclusion In two cohorts from the Danish general population, occupational exposure to dusts, gases, and fumes was not associated with excess lung function decline in recent years but might have been of importance decades ago.