Does Polluted Air Increase COVID-19 Severity? A Critical Review of the Evidence and Proposals to Clarify a Potentially Dramatic Interaction

André Almeida (), Diana Neves, Sofia Silvério Serra and Thierry E. Mertens
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André Almeida: Department of Internal Medicine 4, Centro Clínico Académico de Lisboa, Unidade Local de Saúde São José, Rua António José Serrano, 1150-199 Lisbon, Portugal
Diana Neves: Department of Infectious Diseases, Hospital Garcia da Orta, Avenida Torrado da Silva, 2805-267 Almada, Portugal
Sofia Silvério Serra: NOVA Medical School, Universidade Nova de Lisboa, Campo dos Mártires da Pátria 130, 1169-056 Lisbon, Portugal
Thierry E. Mertens: Institute of Hygiene and Tropical Medicine, Rua da Junqueira 100, 1349-009 Lisbon, Portugal

World, 2025, vol. 6, issue 4, 1-20

Abstract: Several broad ecological analyses have been conducted, mostly in urban settings in Europe and North America, suggesting that air pollution may be associated with greater severity of SARS-CoV-2 infection. Following the identification of possible measurement and confounding biases, we review published studies using alternative study designs, whose main finding was a crude association between COVID-19 severity and PM 2.5 long-term exposure. These preliminary studies are lacking adequate control for confounders and data for other major pollutants. Their results are inconsistent regarding short-term exposures, and virtually all were from high-income countries, limiting their generalizability. We consider the role of alternative study designs in elucidating further such a potential association, by using individual baseline and health outcome data and epidemiological methods to control for potential confounders. To further investigate the role of air pollution in COVID-19 severity between early 2020 and late 2021, we propose to design retrospectively case–control and case-crossover studies using data from public health and air pollution registries, as these may represent the best compromise between validity, reproducibility, and cost. Public health and air pollution registries may provide adequate data sources in industrialized countries and some middle-income countries, facilitating the study of air pollution and COVID-19.

Keywords: COVID-19; air pollution; epidemiology and environment; review literature (search for similar items in EconPapers)
JEL-codes: G15 G17 G18 L21 L22 L25 L26 Q42 Q43 Q47 Q48 R51 R52 R58 (search for similar items in EconPapers)
Date: 2025
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