• Chen Chen, John Wang, Jeff Kwong, JinHee Kim, Aaron van Donkelaar, Randall V Martin, Perry Hystad, Yushan Su, Eric Lavigne, Megan Kirby-McGregor, Jay S Kaufman, Tarik Benmarhnia, and Hong Chen.
• Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California San Diego, La Jolla, Calif.; Public Health Ontario (Wang, Kwong, Kim, H. Chen); ICES Central (Kwong, H. Chen); Dalla Lana School of Public Health (Kwong, Kim, H. Chen), and Department of Family and Community Medicine (Kwong), University of Toronto, Toronto, Ont.; Department of Energy, Environmental, and Chemical Engineering (van Donkelaar, Martin), Washington University in St. Louis, St. Louis, Mo.; College of Public Health and Human Studies (Hystad), Oregon State University, Corvallis, Ore.; Ontario Ministry of the Environment (Su), Conservation and Parks, Toronto, Ont.; Environmental Health Science and Research Bureau (Lavigne, H. Chen), Health Canada, Ottawa, Ont.; Department of Epidemiology and Biostatistics and Occupational Health (Kirby-McGregor, Kaufman), McGill University, Montréal, Que. chc048@ucsd.edu hong.chen@hc-sc.gc.ca.
• CMAJ. 2022 May 24; 194 (20): E693-E700.

BackgroundThe tremendous global health burden related to COVID-19 means that identifying determinants of COVID-19 severity is important for prevention and intervention. We aimed to explore long-term exposure to ambient air pollution as a potential contributor to COVID-19 severity, given its known impact on the respiratory system.MethodsWe used a cohort of all people with confirmed SARS-CoV-2 infection, aged 20 years and older and not residing in a long-term care facility in Ontario, Canada, during 2020. We evaluated the association between long-term exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ground-level ozone (O3), and risk of COVID-19-related hospital admission, intensive care unit (ICU) admission and death. We ascertained individuals' long-term exposures to each air pollutant based on their residence from 2015 to 2019. We used logistic regression and adjusted for confounders and selection bias using various individual and contextual covariates obtained through data linkage.ResultsAmong the 151 105 people with confirmed SARS-CoV-2 infection in Ontario in 2020, we observed 8630 hospital admissions, 1912 ICU admissions and 2137 deaths related to COVID-19. For each interquartile range increase in exposure to PM2.5 (1.70 μg/m3), we estimated odds ratios of 1.06 (95% confidence interval [CI] 1.01-1.12), 1.09 (95% CI 0.98-1.21) and 1.00 (95% CI 0.90-1.11) for hospital admission, ICU admission and death, respectively. Estimates were smaller for NO2. We also estimated odds ratios of 1.15 (95% CI 1.06-1.23), 1.30 (95% CI 1.12-1.50) and 1.18 (95% CI 1.02-1.36) per interquartile range increase of 5.14 ppb in O3 for hospital admission, ICU admission and death, respectively.InterpretationChronic exposure to air pollution may contribute to severe outcomes after SARS-CoV-2 infection, particularly exposure to O3.© 2022 CMA Impact Inc. or its licensors.

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