. 2021 Oct 8:375:n2368.

doi: 10.1136/bmj.n2368.

Changes in exposure to ambient fine particulate matter after relocating and long term survival in Canada: quasi-experimental study

Hong Chen^{1

2

3

4}, Jay S Kaufman^{5

6}, Toyib Olaniyan⁷, Lauren Pinault⁷, Michael Tjepkema⁷, Li Chen¹, Aaron van Donkelaar⁸, Randall V Martin⁹, Perry Hystad¹⁰, Chen Chen¹¹, Megan Kirby-McGregor⁵, Li Bai³, Richard T Burnett¹², Tarik Benmarhnia^{13

14}

Affiliations

¹ Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada hong.chen@hc-sc.gc.ca.
² Public Health Ontario, Toronto, ON, Canada.
³ ICES, Toronto, ON, Canada.
⁴ Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
⁵ Department of Epidemiology and Biostatistics, McGill University, Montreal, QC, Canada.
⁶ Institute for Health and Social Policy, McGill University, Montreal, QC, Canada.
⁷ Health Analysis Division, Statistics Canada, Ottawa, ON, Canada.
⁸ Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada.
⁹ Department of Energy, Environment and Chemical Engineering, Washington University, St Louis, MO, USA.
¹⁰ College of Public Health and Human Sciences, Oregon State University, Corvallis, OR, USA.
¹¹ Department of Family Medicine and Public Health, University of California, San Diego, La Jolla, CA, USA hong.chen@hc-sc.gc.ca.
¹² Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada.
¹³ Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.
¹⁴ Department of Family Medicine and Public Health, University of California, San Diego, La Jolla, CA, USA.

PMID: 34625469
PMCID: PMC8498990
DOI: 10.1136/bmj.n2368

Changes in exposure to ambient fine particulate matter after relocating and long term survival in Canada: quasi-experimental study

Hong Chen et al. BMJ. 2021.

. 2021 Oct 8:375:n2368.

doi: 10.1136/bmj.n2368.

Authors

Affiliations

¹ Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada hong.chen@hc-sc.gc.ca.
² Public Health Ontario, Toronto, ON, Canada.
³ ICES, Toronto, ON, Canada.
⁴ Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
⁵ Department of Epidemiology and Biostatistics, McGill University, Montreal, QC, Canada.
⁶ Institute for Health and Social Policy, McGill University, Montreal, QC, Canada.
⁷ Health Analysis Division, Statistics Canada, Ottawa, ON, Canada.
⁸ Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada.
⁹ Department of Energy, Environment and Chemical Engineering, Washington University, St Louis, MO, USA.
¹⁰ College of Public Health and Human Sciences, Oregon State University, Corvallis, OR, USA.
¹¹ Department of Family Medicine and Public Health, University of California, San Diego, La Jolla, CA, USA hong.chen@hc-sc.gc.ca.
¹² Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON, K1A 0K9, Canada.
¹³ Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.
¹⁴ Department of Family Medicine and Public Health, University of California, San Diego, La Jolla, CA, USA.

PMID: 34625469
PMCID: PMC8498990
DOI: 10.1136/bmj.n2368

Abstract

Objective: To investigate the association between changes in long term residential exposure to ambient fine particulate matter (PM_2.5) and premature mortality in Canada.

Design: Population based quasi-experimental study.

Setting: Canada.

Participants: 663 100 respondents to the 1996, 2001, and 2006 Canadian censuses aged 25-89 years who had consistently lived in areas with either high or low PM_2.5 levels over five years preceding census day and moved during the ensuing five years.

Interventions: Changes in long term exposure to PM_2.5 arising from residential mobility.

Main outcome measures: The primary outcome was deaths from natural causes. Secondary outcomes were deaths from any cardiometabolic cause, any respiratory cause, and any cancer cause. All outcomes were obtained from the national vital statistics database.

Results: Using a propensity score matching technique with numerous personal, socioeconomic, health, and environment related covariates, each participant who moved to a different PM_2.5 area was matched with up to three participants who moved within the same PM_2.5 area. In the matched groups that moved from high to intermediate or low PM_2.5 areas, residential mobility was associated with a decline in annual PM_2.5 exposure from 10.6 μg/m³ to 7.4 and 5.0 μg/m³, respectively. Conversely, in the matched groups that moved from low to intermediate or high PM_2.5 areas, annual PM_2.5 increased from 4.6 μg/m³ to 6.7 and 9.2 μg/m³. Five years after moving, individuals who experienced a reduction in exposure to PM_2.5 from high to intermediate levels showed a 6.8% (95% confidence interval 1.7% to 11.7%) reduction in mortality (2510 deaths in 56 025 v 4925 deaths in 101 960). A greater decline in mortality occurred among those exposed to a larger reduction in PM_2.5. Increased mortality was found with exposure to PM_2.5 from low to high levels, and to a lesser degree from low to intermediate levels. Furthermore, the decreases in PM_2.5 exposure were most strongly associated with reductions in cardiometabolic deaths, whereas the increases in PM_2.5 exposure were mostly related to respiratory deaths. No strong evidence was found for the changes in PM_2.5 exposure with cancer related deaths.

Conclusions: In Canada, decreases in PM_2.5 were associated with lower mortality, whereas increases in PM_2.5 were associated with higher mortality. These results were observed at PM_2.5 levels considerably lower than many other countries, providing support for continuously improving air quality.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/disclosure-of-interest/ and declare: support from funded by Health Canada for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Figures

**Fig 1**
Flowchart of cohort creation. *Based on thirds of annual mean fine particulate matter (PM_2.5) in cohort. CanCHEC=Canadian Census Health and Environment Cohort

**Fig 2**
Sensitivity analysis of associations between changes in residential fine particulate matter (PM_2.5) and risk of disease related mortality when moving from (a) high to intermediate, (b) high to low, (c) low to intermediate, and (d) low to high PM_2.5 areas in Canada, 1997 to 2016

**Fig 3**
Estimated associations between changes in residential fine particulate matter (PM_2.5) and risk of cause specific mortality when moving from (a) high to intermediate, (b) high to low, (c) low to intermediate, and (d) low to high PM_2.5 areas in Canada, 1997 to 2016

See this image and copyright information in PMC

Comment in

Cut particulate air pollution, save lives.
Pereira G. Pereira G. BMJ. 2021 Oct 20;375:n2561. doi: 10.1136/bmj.n2561. BMJ. 2021. PMID: 34670803 No abstract available.

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Changes in exposure to ambient fine particulate matter after relocating and long term survival in Canada: quasi-experimental study

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Changes in exposure to ambient fine particulate matter after relocating and long term survival in Canada: quasi-experimental study

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Abstract

Conflict of interest statement

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