Journal Article

Risk estimates of mortality attributed to low concentrations of ambient fine particulate matter in the Canadian community health survey cohort

Brauer, Michael, Pinault, Lauren, Burnett, Richard T., Tjepkema, Michael, Chen, Hong, van Donkelaar, Aaron, Crouse, Daniel L., Weichenthal, Scott, Martin, Randall V.

2016

Overview

Background Understanding the shape of the relationship between long-term exposure to ambient fine particulate matter (PM 2.5 ) concentrations and health risks is critical for health impact and risk assessment. Studies evaluating the health risks of exposure to low concentrations of PM 2.5 are limited. Further, many existing studies lack individual-level information on potentially important behavioural confounding factors. Methods A prospective cohort study was conducted among a subset of participants in a cohort that linked respondents of the Canadian Community Health Survey to mortality ( n  = 299,500) with satellite-derived ambient PM2.5 estimates. Participants enrolled between 2000 and 2008 were followed to date of death or December 31, 2011. Cox proportional hazards models were used to estimate hazard ratios (HRs) for mortality attributed to PM 2.5 exposure, adjusted for individual-level and contextual covariates, including smoking behaviour and body mass index (BMI). Results Approximately 26,300 non-accidental deaths, of which 32.5 % were due to circulatory disease and 9.1 % were due to respiratory disease, occurred during the follow-up period. Ambient PM 2.5 exposures were relatively low (mean = 6.3 μg/m 3 ), yet each 10 μg/m 3 increase in exposure was associated with increased risks of non-accidental (HR = 1.26; 95 % CI: 1.19-1.34), circulatory disease (HR = 1.19; 95 % CI: 1.07–1.31), and respiratory disease mortality (HR = 1.52; 95 % CI: 1.26–1.84) in fully adjusted models. Higher hazard ratios were observed for respiratory mortality among respondents who never smoked (HR = 1.97; 95 % CI: 1.24–3.13 vs. HR = 1.45; 95 % CI: 1.17–1.79 for ever smokers), and among obese (BMI ≥ 30) respondents (HR = 1.76; 95 % CI: 1.15-2.69 vs. HR = 1.41; 95 % CI: 1.04–1.91 for normal weight respondents), though differences between groups were not statistically significant. A threshold analysis for non-accidental mortality estimated a threshold concentration of 0 μg/m 3 (+95 % CI = 4.5 μg/m 3 ). Conclusions Increased risks of non-accidental, circulatory, and respiratory mortality were observed even at very low concentrations of ambient PM 2.5 . HRs were generally greater than most literature values, and adjusting for behavioural covariates served to reduce HR estimates slightly.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V
• Subject: Air Pollutants - adverse effects / Air Pollution - statistics & numerical data / Body mass index / Canada / Cardiovascular Diseases - mortality / Cohort Studies / Databases, Factual / Earth and Environmental Science / Environment / Environmental Exposure - adverse effects / Environmental Health / Exposure / Health aspects / Health risks / Humans / Influence / Mortality / Occupational Medicine/Industrial Medicine / Particles / Particulate matter / Particulate Matter - adverse effects / Prospective Studies / Public Health / Respiratory diseases / Respiratory tract diseases / Respiratory Tract Diseases - mortality / Risk Assessment / Risk factors / Statistics as Topic / Time Factors