Commute Patterns, Residential Traffic-Related Air Pollution, and Lung Cancer Risk in the Prospective UK Biobank Cohort Study

Background:: Commuting exposes millions of people to lung carcinogens from traffic-related air pollution (TRAP). In the United Kingdom (UK) Biobank cohort study, we investigated associations between commute patterns, residential nitrogen dioxide concentrations (NO2; a surrogate for TRAP), and lung cancer risk. Methods: We analyzed 234,124 employed participants at baseline (2006-2010). Subjects were cross-classified into exclusive categories of commute mode (automobile, public transportation, walking, cycling, active mixture, and other mixture) and frequency (regular:1-4, often:≥5 work-bound trips/week). Annual average residential NO2 concentrations in were estimated with land use regression. Multivariable Cox regression was used to estimate associations between commute patterns, NO2 quartiles, and lung cancer. Findings: There were 493 incident lung cancer cases diagnosed over an average 7-year follow-up. Compared to regular automobile use, commuting often by public transportation was associated with increased lung cancer risk (hazard ratio (HR)=1·58, 95% confidence intervals (CI):1·08-2·33). Additionally, we found a positive exposure-response relationship with residential NO2 (HR Q2 =1·21, 95%CI:0·90-1·62; HR Q3 =1·48, 95%CI:1·10-1·99; HR Q4 =1·58, 95%CI:1·13-2·23; p-trend=3·1x10-3 ). The public transportation association was observed among those with higher NO2 (p-interaction=0·02). Other commute categories were not significantly associated with risk. Interpretation: Commuters residing in high-NO2 areas who often use public transportation could have elevated lung cancer risk, possibly from traversing high-TRAP microenvironments. These preliminary results require replication and refinement to determine which, if any, component of public transportation is associated with lung cancer. Funding: Intramural support from the National Cancer Institute and funding from Wellcome Trust, Medical Research Council, UK Department of Health, Scottish Government, Welsh Assembly Government, British Heart Foundation, and Diabetes United Kingdom. Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: The UK Biobank study was approved by the National Information Governance Board for Health and Social Care and the NHS North West Multicenter Research Ethics Committee.