title: 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).
abstract: 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 (NO2) 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 NO2 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 NO2. Our results suggest that variation in NO2 concentrations within a city may represent a more toxic mixture of pollution than variation between cities.
authors.affiliation: Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada.
authors.forename: Dan L
authors.initials: DL
authors.lastname: Crouse
authors.affiliation: 1] Health Analysis Division, Statistics Canada, Ottawa, Ontario, Canada [2] Department of Sociology, University of New Brunswick, Fredericton, New Brunswick, Canada.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Peters
authors.affiliation: Institute of Health Science, Technology and Policy, Carleton University, Ottawa, Ontario, Canada.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Villeneuve
authors.affiliation: Health Analysis Division, Statistics Canada, Ottawa, Ontario, Canada.
authors.forename: Marc-Olivier
authors.initials: MO
authors.lastname: Proux
authors.affiliation: Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada.
authors.forename: Hwashin H
authors.initials: HH
authors.lastname: Shin
authors.affiliation: 1] Department of Medicine, McGill University, Montreal, Québec, Canada [2] Division of Clinical Epidemiology, McGill University Health Centre, Montreal, Québec, Canada.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Goldberg
authors.affiliation: Air Health Science Division, Health Canada, Ottawa, Ontario, Canada.
authors.forename: Markey
authors.initials: M
authors.lastname: Johnson
authors.affiliation: Air Health Science Division, Health Canada, Ottawa, Ontario, Canada.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Wheeler
authors.affiliation: Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Allen
authors.affiliation: Faculty of Arts & Science, Nipissing University, North Bay, Ontario, Canada.
authors.forename: Dominic Odwa
authors.initials: DO
authors.lastname: Atari
authors.affiliation: School of Public Health, University of California, Berkeley, California, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Jerrett
authors.affiliation: School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Brauer
authors.affiliation: 1] Air Quality Research Division, Environment Canada, Toronto, Ontario, Canada [2] Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Brook
authors.affiliation: Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada.
authors.forename: Sabit
authors.initials: S
authors.lastname: Cakmak
authors.affiliation: Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada.
authors.forename: Richard T
authors.initials: RT
authors.lastname: Burnett
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000009:adverse effects* / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects*; D002170:Canada; D002318:Cardiovascular Diseases / Q000139:chemically induced / Q000401:mortality*; D002423:Cause of Death; D002947:Cities; D015331:Cohort Studies; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009026:Mortality; D009585:Nitrogen Dioxide / Q000009:adverse effects* / Q000032:analysis; D016016:Proportional Hazards Models; D012044:Regression Analysis; D012140:Respiratory Tract Diseases / Q000139:chemically induced / Q000401:mortality*; D014505:Urban Population
chemical_list: D000393:Air Pollutants; D009585:Nitrogen Dioxide