Background: Most studies on the association between lung cancer and air pollution have investigated mortality. There have been few studies of lung cancer incidence.
Methods: We used data from the ongoing Netherlands Cohort Study on Diet and Cancer for 114,378 subjects with follow-up from September 1986 to December 1997. Exposure to black smoke, nitrogen dioxide (NO2), sulfur dioxide (SO2), and particulate matter ≤2.5 μm (PM2.5) and traffic intensity variables (intensity on nearest road, intensity in a 100 m buffer, and an indicator variable for living close to a major road) were estimated at the home address. We conducted Cox proportional hazard analyses in the full cohort adjusting for age, sex, smoking status, and area-level socioeconomic status. We also carried out case-cohort analyses using more potential confounders on a subset of study participants for whom complete information from the baseline questionnaire had been processed.
Results: Adjusted analyses included 1940 cases for the full cohort and 1295 cases for the case-cohort analysis. Relative risks (RRs) for the overall air pollution concentrations were slightly below unity, and for the traffic variables RRs were slightly elevated. Risk was elevated among people who never smoked cigarettes (40,114 participants; 252 cases), with RRs of 1.47 (95% confidence interval = 1.01–2.16) for overall black smoke concentration, 1.11 (0.88–1.41) for traffic intensity on nearest road, and 1.55 (0.98–2.43) for living near a major road.
Conclusions: We found evidence for an association of exposure to black smoke and traffic with lung cancer incidence in people who had never smoked. No associations were found for the full cohort, or for other categories of smoking.
From the aInstitute for Risk Assessment Sciences, Division Environmental Epidemiology, Utrecht University, Utrecht, The Netherlands; bDepartment of Epidemiology, Maastricht University, Maastricht, The Netherlands; cTNO Quality of Life, Department of Food and Chemical Risk Analysis, Zeist, The Netherlands; dCentre for Environmental Health Research, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands; ePublic and Environmental Research Unit, London School of Hygiene and Tropical Medicine, London, United Kingdom; and fJulius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
Submitted 12 December 2007; accepted 26 February 2008; posted 14 July 2008.
Research was conducted under contract to the Health Effects Institute (HEI) (research grant 01-2), an organization jointly funded by the United States Environmental Protection Agency (EPA) and certain motor vehicle and engine manufacturers. The Netherlands Cohort Study on Diet and Cancer was supported by the Dutch Cancer Society.
The contents of this article do not necessarily reflect the views of HEI, or its sponsors, nor do they necessarily reflect the views and policies of EPA or motor vehicle and engine manufacturers.
Correspondence: Bert Brunekreef, Institute for Risk Assessment Sciences, Division Environmental Epidemiology, Utrecht University, P.O. Box 80178, 3508 TD Utrecht, The Netherlands. E-mail: firstname.lastname@example.org.