Risk of nonaccidental and cardiovascular mortality in relation to long-term exposure to low concentrations of fine particulate matter: a Canadian national-level cohort study.
BACKGROUND
Few cohort studies have evaluated the risk of mortality associated with long-term exposure to fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM(2.5))]. This is the first national-level cohort study to investigate these risks in Canada.


OBJECTIVE
We investigated the association between long-term exposure to ambient PM(2.5) and cardiovascular mortality in nonimmigrant Canadian adults.


METHODS
We assigned estimates of exposure to ambient PM(2.5) derived from satellite observations to a cohort of 2.1 million Canadian adults who in 1991 were among the 20% of the population mandated to provide detailed census data. We identified deaths occurring between 1991 and 2001 through record linkage. We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for available individual-level and contextual covariates using both standard Cox proportional survival models and nested, spatial random-effects survival models.


RESULTS
Using standard Cox models, we calculated HRs of 1.15 (95% CI: 1.13, 1.16) from nonaccidental causes and 1.31 (95% CI: 1.27, 1.35) from ischemic heart disease for each 10-μg/m(3) increase in concentrations of PM(2.5). Using spatial random-effects models controlling for the same variables, we calculated HRs of 1.10 (95% CI: 1.05, 1.15) and 1.30 (95% CI: 1.18, 1.43), respectively. We found similar associations between nonaccidental mortality and PM2.5 based on satellite-derived estimates and ground-based measurements in a subanalysis of subjects in 11 cities.


CONCLUSIONS
In this large national cohort of nonimmigrant Canadians, mortality was associated with long-term exposure to PM(2.5). Associations were observed with exposures to PM(2.5) at concentrations that were predominantly lower (mean, 8.7 μg/m(3); interquartile range, 6.2 μg/m(3)) than those reported previously.
Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada. daniel.crouse@hc-sc.gc.ca
Dan L
DL
Crouse
Paul A
PA
Peters
Aaron
A
van Donkelaar
Mark S
MS
Goldberg
Paul J
PJ
Villeneuve
Orly
O
Brion
Saeeda
S
Khan
Dominic Odwa
DO
Atari
Michael
M
Jerrett
C Arden
CA
Pope
Michael
M
Brauer
Jeffrey R
JR
Brook
Randall V
RV
Martin
David
D
Stieb
Richard T
RT
Burnett
D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000633:toxicity*; D002170:Canada / Q000453:epidemiology; D002318:Cardiovascular Diseases / Q000401:mortality*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010316:Particle Size; D012307:Risk Factors; D012959:Socioeconomic Factors
D000393:Air Pollutants