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(8tra)t It has been hypothesized that air pollution can increase an individual’s susceptibility to COVID-19. Our study sought to investigate if short-term exposure to a high average level of Air Quality Index (AQI), ozone (O 3 ), particulate matter (PM 2.5 , PM 10 ), sulfur dioxide (SO 2 ), carbon monoxide (CO), and nitrogen dioxide (NO 2 ) are risk factors for death from COVID-19. We conducted an unmatched case-control study to compare the risk of mortality among reported COVID-19 cases within metropolitan statistical areas in Indiana from March 31, 2020, to December 31, 2020 ( N = 53,459). Air pollution concentration data at the county level were retrieved from the U.S. Environmental Protection Agency. Pollutant concentrations for the 90 days before disease development were averaged. Data were analyzed using stepwise logistic regression accounting for median air temperature, race, ethnicity, and preexisting conditions as confounders. At the population level, individuals who were exposed to a greater average of PM 2.5 in the 90 days before the development of COVID-19 had an increased risk of death: OR = 2.16, 95% confidence interval (CI) [1.12, 18.57]. Individuals with chronic lung disease had an increased risk of death in relation to PM 10 : OR = 2.72, 95% CI [1.15, 6.43]. Short-term exposure to particulate matter may serve as a risk factor for COVID-19 mortality. Keywords: COVID-19, air pollution, Indiana, particulate matter Air Pollution and COVID-19 Mortality: A Case-Control Study of COVID-19 Cases Reported in Indiana in 2020
Anna E. Heilers, MPH, CPH Indiana Department of Health Sarah A. Bennett Indiana Department of Health
Because air quality can be regulated through policy, the regulation of air pollution could play a key role in preventing excess morbidity and mortality from COVID-19 (Xu et al., 2022). We conducted an unmatched case-control study to assess short-term air pollution and approximate the risk of COVID-19 mortality. As more comprehen- sive data are now available for COVID-19 cases from 2020, we sought to contribute a more complete assessment of the potential impact of air pollution on COVID-19 mortal- ity in Indiana. Methods An unmatched case-control study was con- ducted comparing the risk of mortality among reported COVID-19 cases within metropolitan statistical areas (MSAs) in Indi- ana between March 31, 2020, and December 31, 2020 ( N = 53,459), in relation to short- term air pollution exposure. Short-term air pollution exposure was defined as a 90-day mean exposure concentration. Data analysis was conducted in SAS 9.4 via IUanyWare Citrix Receiver, Microsoft Oce Excel, and R-4.2.1 via RStudio Desktop 2022.07.2+576. COVID-19 data used for our study were compiled within the National Electronic Dis- ease Surveillance System (NEDSS), Indiana’s infectious disease surveillance system. Pol- lutant data files from the U.S. Environmental Protection Agency were used to obtain mea- sures of air pollution and air temperature. Using a systematic approach, air pollution and COVID-19 case data were integrated and stratified to retain COVID-19 cases within counties associated with MSAs and within the specified time frame. The 90-day analysis period for assess- ing short-term exposure to air pollutants was determined by referencing valid dates of first symptom onset with the preceding
Introduction In 2020, the third leading cause of death in Indiana was COVID-19 (Centers for Disease Control and Prevention, 2024). Since 2020, preliminary studies have demonstrated a rela- tionship between COVID-19 incidence, hospi- talization, and mortality with elevated levels of air pollution (Copat et al., 2020; Zang et al., 2022). Elevated levels of air pollutants have been shown to increase the risk of developing chronic conditions, including chronic lung diseases such as chronic obstructive pulmo- nary disease (COPD) and asthma (Weaver et al., 2022). As chronic conditions are risk fac- tors for severe COVID-19 outcomes, research-
ers have theorized that long-term exposure to pollutants, which increases the risk of developing chronic respiratory diseases in a population, could also lead to increased risk of COVID-19 in these populations (Weaver et al., 2022). Researchers have also theorized that short-term air pollution exposure could lead to an increased risk of mortality through immunological mechanisms and reduced viral clearance (Karan et al., 2020). Additionally, several studies have identified the presence of SARS-CoV-2 in particulate matter pollution, suggesting particulate matter pollution might act as a carrier of viral particles into the respi- ratory tract (Meo et al., 2021).
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