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      Examining the Shape of the Association between Low Levels of Fine Particulate Matter and Mortality across Three Cycles of the Canadian Census Health and Environment Cohort

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          Abstract

          Background:

          Ambient fine particulate air pollution with aerodynamic diameter 2.5 μ m ( PM 2.5 ) is an important contributor to the global burden of disease. Information on the shape of the concentration–response relationship at low concentrations is critical for estimating this burden, setting air quality standards, and in benefits assessments.

          Objectives:

          We examined the concentration–response relationship between PM 2.5 and nonaccidental mortality in three Canadian Census Health and Environment Cohorts (CanCHECs) based on the 1991, 1996, and 2001 census cycles linked to mobility and mortality data.

          Methods:

          Census respondents were linked with death records through 2016, resulting in 8.5 million adults, 150 million years of follow-up, and 1.5 million deaths. Using annual mailing address, we assigned time-varying contextual variables and 3-y moving-average ambient PM 2.5 at a 1 × 1 km spatial resolution from 1988 to 2015. We ran Cox proportional hazards models for PM 2.5 adjusted for eight subject-level indicators of socioeconomic status, seven contextual covariates, ozone, nitrogen dioxide, and combined oxidative potential. We used three statistical methods to examine the shape of the concentration–response relationship between PM 2.5 and nonaccidental mortality.

          Results:

          The mean 3-y annual average estimate of PM 2.5 exposure ranged from 6.7 to 8.0 μ g / m 3 over the three cohorts. We estimated a hazard ratio (HR) of 1.053 [95% confidence interval (CI): 1.041, 1.065] per 10 - μ g / m 3 change in PM 2.5 after pooling the three cohort-specific hazard ratios, with some variation between cohorts (1.041 for the 1991 and 1996 cohorts and 1.084 for the 2001 cohort). We observed a supralinear association in all three cohorts. The lower bound of the 95% CIs exceeded unity for all concentrations in the 1991 cohort, for concentrations above 2 μ g / m 3 in the 1996 cohort, and above 5 μ g / m 3 in the 2001 cohort.

          Discussion:

          In a very large population-based cohort with up to 25 y of follow-up, PM 2.5 was associated with nonaccidental mortality at concentrations as low as 5 μ g / m 3 . https://doi.org/10.1289/EHP5204

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          Most cited references30

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          A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010

          The Lancet, 380(9859), 2224-2260
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            Is Open Access

            Global estimates of mortality associated with long-term exposure to outdoor fine particulate matter

            Significance Exposure to outdoor concentrations of fine particulate matter is considered a leading global health concern, largely based on estimates of excess deaths using information integrating exposure and risk from several particle sources (outdoor and indoor air pollution and passive/active smoking). Such integration requires strong assumptions about equal toxicity per total inhaled dose. We relax these assumptions to build risk models examining exposure and risk information restricted to cohort studies of outdoor air pollution, now covering much of the global concentration range. Our estimates are severalfold larger than previous calculations, suggesting that outdoor particulate air pollution is an even more important population health risk factor than previously thought.
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              Effects of long-term exposure to air pollution on natural-cause mortality: an analysis of 22 European cohorts within the multicentre ESCAPE project

              Few studies on long-term exposure to air pollution and mortality have been reported from Europe. Within the multicentre European Study of Cohorts for Air Pollution Effects (ESCAPE), we aimed to investigate the association between natural-cause mortality and long-term exposure to several air pollutants. We used data from 22 European cohort studies, which created a total study population of 367,251 participants. All cohorts were general population samples, although some were restricted to one sex only. With a strictly standardised protocol, we assessed residential exposure to air pollutants as annual average concentrations of particulate matter (PM) with diameters of less than 2.5 μm (PM2.5), less than 10 μm (PM10), and between 10 μm and 2.5 μm (PMcoarse), PM2.5 absorbance, and annual average concentrations of nitrogen oxides (NO2 and NOx), with land use regression models. We also investigated two traffic intensity variables-traffic intensity on the nearest road (vehicles per day) and total traffic load on all major roads within a 100 m buffer. We did cohort-specific statistical analyses using confounder models with increasing adjustment for confounder variables, and Cox proportional hazards models with a common protocol. We obtained pooled effect estimates through a random-effects meta-analysis. The total study population consisted of 367,251 participants who contributed 5,118,039 person-years at risk (average follow-up 13.9 years), of whom 29,076 died from a natural cause during follow-up. A significantly increased hazard ratio (HR) for PM2.5 of 1.07 (95% CI 1.02-1.13) per 5 μg/m(3) was recorded. No heterogeneity was noted between individual cohort effect estimates (I(2) p value=0.95). HRs for PM2.5 remained significantly raised even when we included only participants exposed to pollutant concentrations lower than the European annual mean limit value of 25 μg/m(3) (HR 1.06, 95% CI 1.00-1.12) or below 20 μg/m(3) (1.07, 1.01-1.13). Long-term exposure to fine particulate air pollution was associated with natural-cause mortality, even within concentration ranges well below the present European annual mean limit value. European Community's Seventh Framework Program (FP7/2007-2011). Copyright © 2014 Elsevier Ltd. All rights reserved.
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                Author and article information

                Journal
                Environ Health Perspect
                Environ. Health Perspect
                EHP
                Environmental Health Perspectives
                Environmental Health Perspectives
                0091-6765
                1552-9924
                22 October 2019
                October 2019
                : 127
                : 10
                : 107008
                Affiliations
                [1 ]Health Analysis Division, Statistics Canada , Ottawa, Ontario, Canada
                [2 ]Department of Sociology, University of New Brunswick , Fredericton, New Brunswick, Canada
                [3 ]New Brunswick Institute for Research, Data, and Training, Fredericton, New Brunswick, Canada
                [4 ]Dalla Lana School of Public Health, University of Toronto , Toronto, Ontario, Canada
                [5 ]School of Population and Public Health, University of British Columbia , Vancouver, British Columbia, Canada
                [6 ]College of Public Health and Human Sciences, Oregon State University , Corvallis, Oregon, USA
                [7 ]Department of Physics and Atmospheric Science, Dalhousie University , Halifax, Nova Scotia, Canada
                [8 ]Harvard-Smithsonian Center for Astrophysics , Cambridge, Massachusetts, USA
                [9 ]Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri, United States
                [10 ]Department of Epidemiology, Biostatistics & Occupational Health, McGill University , Montreal, Quebec, Canada
                [11 ]Air Health Science Division, Health Canada , Ottawa, Ontario, Canada
                [12 ]Population Studies Division, Health Canada , Ottawa, Ontario, Canada
                Author notes
                Address correspondence to Dan L Crouse, PhD, Dept. of Sociology, University of New Brunswick, 9 Macaulay Lane, Tilley Hall, Room 20, Fredericton, New Brunswick, Canada E3B 5A3. Telephone: (506) 458-7436. Email: Dlcrouse@ 123456gmail.com
                Article
                EHP5204
                10.1289/EHP5204
                6867181
                31638837
                f7ff4a3b-32d8-457f-a033-b4457e9f6261

                EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted.

                History
                : 15 February 2019
                : 18 September 2019
                : 18 September 2019
                Categories
                Research

                Public health
                Public health

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