Background Occupational air pollution exposures have been consistently associated with increased lung cancer risk. Few studies have examined the association of long term air pollution in the general population. Aims To determine if long term ambient exposures to particulate matter (PM) PM2.5, PM10 and PM2.5-10 are associated with an increased risk of lung cancer among women in the Nurses' Health Study (NHS), a US-wide prospective cohort study. Methods Lung cancer cases from 1988 through 2010 were identified through biennial questionnaires and confirmed through medical reports. Information on time varying covariates including age, region of US, smoking, alcohol intake, BMI, physical activity, and area-level socioeconomic status was available. A spatio-temporal statistical model using monitor, meteorological, and other geographic data estimated PM exposures for the three size fractions for each month at each residential address for each participant between 1988 and 2007. Analyses were restricted to women living within metropolitan statistical areas. Results Among 88,033 women, 1,548 cases of lung cancer were identified. Using 10 year cumulative average exposure, the fully adjusted hazard ratio for lung cancer was 1.16 (95%CI: 1.04,1.30) for PM10,1.27 (95%CI: 1.09,1.49) for PM2.5-10, and 1.14 (95%CI: 0.94,1.40) for PM2.5. Stratified results showed lower risks for current smokers and higher risks among former and never smokers, though the sample size for never smokers was limited (107 cases). Specifically, for never smokers the HRs were 1.20,1.37,1.15 for PM10, PM2.5-10, and PM2.5, respectively. Conclusions Among this cohort of US women, long-term particulate matter exposures were associated with increased lung cancer risk. Although a small number of cases, the risk appears strongest among never smokers.
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