COVID-19 Pandemic
Wildfire-related air pollution and COVID-19 outcomes: a systematic review of population-based studies Olufunmilayo Arogbokun Knutson* Olufunmilayo Arogbokun Knutson Arogbokun Knutson Arogbokun Knutson University of St. Thomas, Morrison Family College of Health
Background: Wildfires have increased in frequency and intensity in recent years, coinciding with the COVID-19 pandemic. Some studies have examined associations between wildfire-related air pollution and COVID-19 outcomes, but epidemiologic studies accounting for key confounders are limited in the literature.
Methods: We conducted a systematic review of population-based studies examining wildfire-attributable air pollution and COVID-19 outcomes. PubMed and Scopus were searched through June 10, 2025 and reviewers independently screened titles and abstracts and reviewed full texts. Eligible studies evaluated pollution specifically attributed to wildfires and reported COVID-19 cases, hospitalizations, or deaths. Findings were synthesized descriptively across studies by design, exposure definition, outcomes, analytic methods, and covariate adjustment.
Results: Of 996 records screened, 24 studies met inclusion criteria. Studies were conducted globally, including Brazil, Australia, South Africa, and the United States. Most analyses focused on daily COVID-19 cases and/or deaths and used ecological designs with population-level exposure and outcome data from surveillance systems. Common analytic methods included Poisson and negative binomial regression and correlation analyses. Approximately half of studies adjusted for covariates, primarily atmospheric variables, while few accounted for sociodemographic confounders. Several studies reported positive associations between wildfire-related fine particulate matter and COVID-19 outcomes.
Conclusions: Evidence suggests associations between wildfire-related air pollution and adverse COVID-19 outcomes; however, limited adjustment for key confounders constrains causal inference. This review provides the synthesis of population health studies on wildfire pollution and COVID-19. Future epidemiologic research should incorporate pertinent sociodemographic confounders to better characterize health impacts as wildfire frequency increases.