Particulate matter air pollution components and risk for lung cancer

Background: Particulate matter (PM) air pollution is a human lung carcinogen; however, the components responsible have not been identified. We assessed the associations between PM components and lung cancer incidence. Methods: We used data from 14 cohort studies in eight European countries. We geocoded baseline addresses and assessed air pollution with land-use regression models for eight elements (Cu, Fe, K, Ni, S, Si, V and Zn) in size fractions of PM_2.5 and PM₁₀. We used Cox regression models with adjustment for potential confounders for cohort-specific analyses and random effect models for meta-analysis. Results: The 245,782 cohort members contributed 3,229,220person-years at risk. During follow-up (mean, 13.1 years), 1878 incident cases of lung cancer were diagnosed. In the meta-analyses, elevated hazard ratios (HRs) for lung cancer were associated with all elements except V; none was statistically significant. In analyses restricted to participants who did not change residence during follow-up, statistically significant associations were found for PM_2.5 Cu (HR, 1.25; 95% CI, 1.01-1.53 per 5 ng/m³), PM₁₀ Zn (1.28; 1.02-1.59 per 20 ng/m³), PM₁₀ S (1.58; 1.03-2.44 per 200 ng/m³), PM₁₀ Ni (1.59; 1.12-2.26 per 2 ng/m³) and PM₁₀ K (1.17; 1.02-1.33 per 100 ng/m³). In two-pollutant models, associations between PM₁₀ and PM_2.5 and lung cancer were largely explained by PM_2.5 S. Conclusions: This study indicates that the association between PM in air pollution and lung cancer can be attributed to various PM components and sources. PM containing S and Ni might be particularly important.