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Michael Jerrett,¹ Murray M. Finkelstein,² Jeffrey R. Brook,³ M. Altaf Arain,⁴ Palvos Kanaroglou,⁴ Dave M. Stieb,⁵ Nicolas L. Gilbert,⁵ Dave Verma,⁶ Norm Finkelstein,⁴ Kenneth R. Chapman,⁷ and Malcolm R. Sears⁸

¹Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, Berkeley, California, USA; ²Department of Family and Community Medicine, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; ³Meteorological Services, Environment Canada, Toronto, Ontario, Canada; ⁴School of Geography and Earth Science, McMaster University, Hamilton, Ontario, Canada; ⁵Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada; ⁶Program in Occupational Health & Environmental Medicine, McMaster University, Hamilton, Ontario, Canada; ⁷Division of Respirology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada; ⁸Division of Respirology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada

Abstract
Background: Chronic exposure to traffic-related air pollution (TRAP) may contribute to premature mortality, but few studies to date have addressed this topic.

Objectives: In this study we assessed the association between TRAP and mortality in Toronto, Ontario, Canada.

Methods: We collected nitrogen dioxide samples over two seasons using duplicate two-sided Ogawa passive diffusion samplers at 143 locations across Toronto. We calibrated land use regressions to predict NO₂ exposure on a fine scale within Toronto. We used interpolations to predict levels of particulate matter with aerodynamic diameter ≤ 2.5 µm (PM_2.5) and ozone levels. We assigned predicted pollution exposures to 2,360 subjects from a respiratory clinic, and abstracted health data on these subjects from medical billings, lung function tests, and diagnoses by pulmonologists. We tracked mortality between 1992 and 2002. We used standard and multilevel Cox proportional hazard models to test associations between air pollution and mortality.

Results: After controlling for age, sex, lung function, obesity, smoking, and neighborhood deprivation, we observed a 17% increase in all-cause mortality and a 40% increase in circulatory mortality from an exposure contrast across the interquartile range of 4 ppb NO₂. We observed no significant associations with other pollutants.

Conclusions: Exposure to TRAP was significantly associated with increased all-cause and circulatory mortality in this cohort. A high prevalence of cardiopulmonary disease in the cohort probably limits inference of the findings to populations with a substantial proportion of susceptible individuals.

Key words: air pollution, GIS, mortality, nitrogen dioxide, traffic air pollution, Toronto. Environ Health Perspect 117:772–777 (2009) . doi:10.1289/ehp.11533 available via http://dx.doi.org/ [Online 5 January 2009]

Address correspondence to M. Jerrett, University of California, Berkeley, School of Public Health, Division of Environmental Health Sciences, 50 University Hall, Berkeley, CA 94720-7360 USA. Telephone: (510) 725-9991. Fax: (510) 642-5815. E-mail: jerrett@berkeley.edu

Supplemental Material is available online at http://www.ehponline.org/members/2009/11533/suppl.pdf

This work was funded by Canadian Institutes of Health Research grant MOP-64463.

The authors declare they have no competing financial interests.

Received 2 April 2008 ; accepted 5 January 2009.