Within- and between-city contrasts in nitrogen dioxide and mortality in 10 Canadian cities; a subset of the Canadian Census Health and Environment Cohort (CanCHEC)

• Published in: Journal of exposure science & environmental epidemiology Vol. 25; no. 5; pp. 482 - 489
• Main Authors: Crouse, Dan L, Peters, Paul A, Villeneuve, Paul J, Proux, Marc-Olivier, Shin, Hwashin H, Goldberg, Mark S, Johnson, Markey, Wheeler, Amanda J, Allen, Ryan W, Atari, Dominic Odwa, Jerrett, Michael, Brauer, Michael, Brook, Jeffrey R, Cakmak, Sabit, Burnett, Richard T
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.09.2015; Nature Publishing Group
• Subjects: 692/700/478/174; 704/172/169/896; Adult; Aged; Aged, 80 and over; Air Pollutants - adverse effects; Air Pollutants - analysis; Air pollution; Air Pollution - adverse effects; Analysis; Canada; Cardiovascular diseases; Cardiovascular Diseases - chemically induced; Cardiovascular Diseases - mortality; Cause of Death; Cities; Cohort Studies; Environmental Monitoring; Epidemiology; Exposure; Female; Health aspects; Humans; Land use; Male; Medicine; Medicine & Public Health; Middle Aged; Mortality; Nitrogen dioxide; Nitrogen Dioxide - adverse effects; Nitrogen Dioxide - analysis; Original; original-article; Proportional Hazards Models; Regression Analysis; Respiratory diseases; Respiratory Tract Diseases - chemically induced; Respiratory Tract Diseases - mortality; Urban Population; Canada; epidemiology; criteria pollutants; exposure modelling
• ISSN: 1559-0631; 1559-064X; 1559-064X
• DOI: 10.1038/jes.2014.89

The independent and joint effects of within- and between-city contrasts in air pollution on mortality have been investigated rarely. To examine the differential effects of between- versus within-city contrasts in pollution exposure, we used both ambient measurements and land use regression models to assess associations with mortality and exposure to nitrogen dioxide (NO 2 ) among ~735,600 adults in 10 of the largest Canadian cities. We estimated exposure contrasts partitioned into within- and between-city contrasts, and the sum of these as overall exposures, for every year from 1984 to 2006. Residential histories allowed us to follow subjects annually during the study period. We calculated hazard ratios (HRs) adjusted for many personal and contextual variables. In fully-adjusted, random-effects models, we found positive associations between overall NO 2 exposures and mortality from non-accidental causes (HR per 5 p.p.b.: 1.05; 95% confidence interval (CI): 1.03–1.07), cardiovascular disease (HR per 5 p.p.b.: 1.04; 95% CI: 1.01–1.06), ischaemic heart disease (HR per 5 p.p.b.: 1.05; 95% CI: 1.02–1.08) and respiratory disease (HR per 5 p.p.b.: 1.04; 95% CI: 0.99–1.08), but not from cerebrovascular disease (HR per 5 p.p.b.: 1.01; 95% CI: 0.96–1.06). We found that most of these associations were determined by within-city contrasts, as opposed to by between-city contrasts in NO 2 . Our results suggest that variation in NO 2 concentrations within a city may represent a more toxic mixture of pollution than variation between cities.