Air pollution exposures from multiple point sources and risk of incident chronic obstructive pulmonary disease (COPD) and asthma

Background: Exposure to environmental air pollutants exacerbates respiratory illness, but prospective studies of disease incidence are uncommon. Further, attempts to estimate effects from multiple point sources have rarely been undertaken. The current study examined risk of incident chronic obstructive pulmonary disease (COPD) and asthma in association with emissions of multiple air pollutants from point pollution sources in Australia. Methods: We analyzed prospective cohort data from the Australian Longitudinal Study on Women's Health. Women from three age-cohorts (N = 35,755) were followed for up to 21 years for incident COPD and asthma. Exposures were measured from the National Pollutant Inventory and included carbon monoxide, nitrogen oxides, sulfur dioxide, and particulate matter (PM2.5 and PM10). We identified inverse-distance weighted emissions in kilograms that women experienced over time from point sources within 10 km of their residences. Cox proportional hazards regression models examined risk of self-reported doctor-diagnosed COPD and asthma in association with pollutant exposures and covariates. Results: New COPD cases numbered 3616 (11.5%) and new asthma cases numbered 2725 (9.4%). Participants were exposed to an average of 47-59 sites with air pollution emissions within 10 km of their residences. Fossil fuel electricity generation and mining made the largest contributions to air pollution but hundreds of other types of emissions also occurred. Controlling for covariates, all five air pollutants modeled individually were significantly associated with risk of COPD. Modeled jointly, only sulfur dioxide (SO2) remained significantly associated with COPD (HR = 1.038, 95% CI = 1.010-1.067), although the five pollutants were highly correlated (r = 0.89). None of the pollutants were significantly associated with adult onset asthma. Cohort-specific analyses indicated that COPD risk was significantly associated with SO2 exposure for younger (HR = 1.021, CI = 1.001-1.047), middle-age (HR = 1.019, CI = 1.004-1.034) and older cohorts (HR = 1.025, CI = 1.004-1.047). Conclusions: Multiple exposure sources and pollutants contributed to COPD risk, including electricity generation and mining but extending to many industrial processes. The results highlight the importance of policy efforts and technological improvements to reduce harmful air pollution emissions across the industrial landscape.