Associations of Outdoor Air Pollution With Incidence of Cancers Other Than Lung Cancer in a Large US Prospective Cohort

ABSTRACT Outdoor air pollution, including particulate matter (PM), is a Group 1 carcinogen based on evidence for lung cancer; however, evidence for other cancers is limited. Further research on cancer incidence rather than mortality endpoints is needed as well as examinations in non‐smokers. In the Cancer Prevention Study‐II Nutrition Cohort, annual predictions of particulate and gaseous pollutant concentrations were assigned to residential addresses. Extended Cox regression estimated hazard ratios (HR) and 95% confidence intervals (CI) for associations of pre‐diagnosis pollutants with risk of all incident non‐lung cancers and 20 cancer sites with detailed adjustment for confounding variables. There were 28,008 incident cancers identified among the 108,002 participants followed from 1992 to 2017. There were no statistically significant associations with fine particulates (PM 2.5 ) overall or among never smokers. There were elevated HRs with coarse particulates (PM 10‐2.5 ) for uterine and cervical cancer incidence, though CIs were wide, and an association with ER‐ breast cancers (HR = 1.16; 95% CI 1.03–1.30). There were also weak positive associations of gaseous pollutants in never smokers with colorectal cancer (sulfur dioxide HR = 1.08; 95% CI 1.01–1.16), kidney cancer (carbon monoxide HR = 1.17; 95% CI 1.00–1.37), and melanoma of the skin (ozone HR = 1.11; 95% CI 0.99–1.25). Overall, these findings indicate few positive associations of ambient air pollutants with cancer incidence beyond lung cancer. The observed associations were low magnitude and stronger in never smokers. Larger pooled studies are needed to validate these associations with rare subtypes and non‐smokers, and cancer survival research is needed to clarify differences in mortality and incidence studies.