A cohort study of traffic-related air pollution and mortality in Toronto, Ontario, Canada.
BACKGROUND
Chronic exposure to traffic-related air pollution (TRAP) may contribute to premature mortality, but few studies to date have addressed this topic.


OBJECTIVE
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 < or = 2.5 microm (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.
Jerrett
Michael
M
Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, Berkeley, California 94720-7360, USA. jerrett@berkeley.edu
Finkelstein
Murray M
MM
Brook
Jeffrey R
JR
Arain
M Altaf
MA
Kanaroglou
Palvos
P
Stieb
Dave M
DM
Gilbert
Nicolas L
NL
Verma
Dave
D
Finkelstein
Norm
N
Chapman
Kenneth R
KR
Sears
Malcolm R
MR
D000393:Air Pollutants / Q000633:toxicity*; D002319:Cardiovascular System / Q000187:drug effects; D015331:Cohort Studies; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008168:Lung / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D009864:Ontario; D010126:Ozone / Q000633:toxicity; D052638:Particulate Matter / Q000633:toxicity; D012140:Respiratory Tract Diseases / Q000453:epidemiology / Q000401:mortality*; D012907:Smoking; D001335:Vehicle Emissions / Q000032:analysis*
D000393:Air Pollutants; D052638:Particulate Matter; D001335:Vehicle Emissions; D010126:Ozone