University of Oulu

Lavigne E, Ryti N, Gasparrini A, et al. Thorax 2023;78:459–466.

Short-term exposure to ambient air pollution and individual emergency department visits for COVID-19 : a case-crossover study in Canada

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Author: Lavigne, Eric1,2; Ryti, Niilo3; Gasparrini, Antonio4,5,6;
Organizations: 1Air Sectors Assessment and Exposure Science Division, Health Canada, Ottawa, Ontario, Canada
2School of Epidemiology & Public Health, University of Ottawa, Ottawa, Ontario, Canada
3Center for Environmental and Respiratory Health Research (CERH), University of Oulu, Oulu, Finland
4Department of Public Health Environments and Society, London School of Hygiene & Tropical Medicine, London, UK
5Centre for Statistical Methodology, London School of Hygiene & Tropical Medicine, London, UK
6Centre on Climate Change and Planetary Health, London School of Hygiene & Tropical Medicine, London, UK
7Department of Statistics, Computer Science and Applications "G. Parenti", University of Florence, Florence, Italy
8Department of Epidemiology, Biostatistics, and Occupational Health, McGill University Montreal, Montreal, Quebec, Canada
9Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
10Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
11Public Health Ontario, Toronto, Ontario, Canada
12Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada
13Child Health Evaluative Sciences, The Hospital For Sick Children, Toronto, Ontario, Canada
14Department of Chemical Engineering, University of Toronto, Toronto, Ontario, Canada
15Environment and Climate Change Canada Montreal Office, Montreal, Ontario, Canada
16National Microbiology Laboratory, Public Health Agency of Canada, Saint-Hyacinthe, Ontario, Canada
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.4 MB)
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Language: English
Published: BMJ, 2023
Publish Date: 2023-05-30


Background: Ambient air pollution is thought to contribute to increased risk of COVID-19, but the evidence is controversial.

Objective: To evaluate the associations between short-term variations in outdoor concentrations of ambient air pollution and COVID-19 emergency department (ED) visits.

Methods: We conducted a case-crossover study of 78 255 COVID-19 ED visits in Alberta and Ontario, Canada between 1 March 2020 and 31 March 2021. Daily air pollution data (ie, fine particulate matter with diameter less than 2.5 µm (PM2.5), nitrogen dioxide (NO₂) and ozone were assigned to individual case of COVID-19 in 10 km × 10 km grid resolution. Conditional logistic regression was used to estimate associations between air pollution and ED visits for COVID-19.

Results: Cumulative ambient exposure over 0–3 days to PM2.5 (OR 1.010; 95% CI 1.004 to 1.015, per 6.2 µg/m³) and NO₂ (OR 1.021; 95% CI 1.015 to 1.028, per 7.7 ppb) concentrations were associated with ED visits for COVID-19. We found that the association between PM2.5 and COVID-19 ED visits was stronger among those hospitalised following an ED visit, as a measure of disease severity, (OR 1.023; 95% CI 1.015 to 1.031) compared with those not hospitalised (OR 0.992; 95% CI 0.980 to 1.004) (p value for effect modification=0.04).

Conclusions: We found associations between short-term exposure to ambient air pollutants and COVID-19 ED visits. Exposure to air pollution may also lead to more severe COVID-19 disease.

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Series: Thorax
ISSN: 0040-6376
ISSN-E: 1468-3296
ISSN-L: 0040-6376
Volume: 78
Issue: 5
Pages: 459 - 466
DOI: 10.1136/thoraxjnl-2021-217602
Type of Publication: A1 Journal article – refereed
Field of Science: 3142 Public health care science, environmental and occupational health
Funding: This study was supported by Addressing Air Pollution Horizontal Initiative program of Health Canada. AG was supported by the Medical Research Council-UK (Grant ID: MR/R013349/1).
Copyright information: © Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY. Published by BMJ.