Particulate matter air pollution exposure, distance to road, and incident lung cancer in the nurses' health study cohort

Background: A body of literature has suggested an elevated risk of lung cancer associated with particulate matter and traffic-related pollutants. Objective: We examined the relation of lung cancer incidence with long-term residential exposures to ambient particulate matter and residential distance to roadway, as a proxy for trafficrelated exposures. Methods: For participants in the Nurses' Health Study, a nationwide prospective cohort of women, we estimated 72-month average exposures to PM_2.5, PM_2.5-10, and PM₁₀ and residential distance to road. Follow-up for incident cases of lung cancer occurred from 1994 through 2010. Cox proportional hazards models were adjusted for potential confounders. Effect modification by smoking status was examined. Results: During 1,510,027 person-years, 2,155 incident cases of lung cancer were observed among 103,650 participants. In fully adjusted models, a 10-μg/m³ increase in 72-month average PM₁₀ [hazard ratio (HR) = 1.04; 95% CI: 0.95, 1.14], PM_2.5 (HR = 1.06; 95% CI: 0.91, 1.25), or PM_2.5-10 (HR = 1.05; 95% CI: 0.92, 1.20) was positively associated with lung cancer. When the cohort was restricted to never-smokers and to former smokers who had quit at least 10 years before, the associations appeared to increase and were strongest for PM_2.5 (PM₁₀: HR = 1.15; 95% CI: 1.00, 1.32; PM_2.5: HR = 1.37; 95% CI: 1.06, 1.77; PM_2.5-10: HR = 1.11; 95% CI: 0.90, 1.37). Results were most elevated when restricted to the most prevalent subtype, adenocarcinomas. Risks with roadway proximity were less consistent. Conclusions: Our findings support those from other studies indicating increased risk of incident lung cancer associated with ambient PM exposures, especially among never- and long-term former smokers.