There is accumulating evidence that air pollution causes lung cancer. Still, questions remain about exposure misclassification, the components of air pollution responsible, and the histological subtypes of lung cancer that might be produced.
We investigated lung cancer incidence in relation to long-term exposure to three ambient air pollutants and proximity to major roads, using a Canadian population-based case-control study. We compared 2,390 incident, histologically confirmed lung cancer cases with 3,507 population controls in eight Canadian provinces from 1994 to 1997. We developed spatiotemporal models for the whole country to estimate annual residential exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) over a 20-year exposure period. We carried out a subanalysis in urban centers, using exposures derived from fixed-site air pollution monitors, and also examined traffic proximity measures. Hierarchical logistic regression models incorporated a comprehensive set of individual and geographic covariates.
The increase in lung cancer incidence (expressed as fully adjusted odds ratios [ORs]) was 1.29 (95% confidence interval = 0.95–1.76) with a ten-unit increase in PM2.5 (μg/m3), 1.11 (1.00–1.24) with a ten-unit increase in NO2 (ppb), and 1.09 (0.85–1.39) with a ten-unit increase in O3 (ppb). The urban monitor-based subanalyses generally supported the national results, with larger associations for NO2 (OR = 1.34; 1.07–1.69) per 10 ppb increase. No dose-response trends were observed, and no clear relationships were found for specific histological cancer subtypes. There was the suggestion of increased risk among those living within 100 m of highways, but not among those living near major roads.
Lung cancer incidence in this Canadian study was increased most strongly with NO2 and PM2.5 exposure. Further investigation is needed into possible effects of O3 on development of lung cancer.
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From the aSchool of Population and Public Health, University of British Columbia, Vancouver, BC, Canada; bOccupational Cancer Research Centre, Cancer Care Ontario, Ontario, Canada; cScience Integration Division, Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada, Ottawa, Canada; and dDepartment of Sociology, University of British Columbia, Vancouver, BC, Canada.
Original funding for the National Enhanced Cancer Surveillance System was provided through the Government of Canada’s Action Plan on Health and the Environment. The Michael Smith Foundation for Health Research (MSFHR) and Canadian Institute for Health Research (CIHR) supported P.H. through a UBC Bridge Strategic Training Fellowship, a Senior Graduate Studentship, and a Frederick Banting and Charles Best Canada Graduate Scholarship. MSFHR and CIHR supported R.M.C. through Investigator Awards.
The authors declare no conflicts of interest.
Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com). This content is not peer-reviewed or copy-edited; it is the sole responsibility of the author.
Correspondence: Perry Hystad, School of Population and Public Health, University of British Columbia, 2206 East Mall Vancouver, BC, V6T 1Z3 Canada. E-mail: firstname.lastname@example.org.
Received September 8, 2012
Accepted January 25, 2013