Short-term exposure to air pollution and COVID-19 mortality with susceptibility factors: a case-crossover study for Cook County, Illinois

Abstract

BACKGROUND AND AIM: Evidence on individual-level association between exposure to aerodynamic diameter 2·5µm (PM2·5) and ozone (O3) and coronavirus 2019 (COVID-19) mortality is lacking. Susceptibility to air pollution-related COVID-19 mortality is unknown. METHODS: With individual mortality records of 8020 deaths from COVID-19 (January, 2020–February, 2021) confirmed by medical examiners in Cook County, Illinois, we conducted time-stratified case-crossover analysis to link COVID-19 mortality and inverse-distance weighting interpolated PM2·5 and O3 at geocoded location of death. We further adjusted for viral transmission, temperature, relative humidity, and residual temporal confounding over the course of the pandemic. We conducted stratification analyses by age, sex, race/ethnicity, the number of comorbid conditions, age-adjusted Charlson Comorbidity Index, ZIP code-level poverty rate, and accessibility to adult intensive care unit (ICU) beds. RESULTS:Averages of daily pollution levels assigned to cases and self-controls were 8·6 µg/m3 for PM2·5 and 18·7µg/m3 for O3. An interquartile range (IQR) increase (5·11µg/m3) in three-week PM2·5 was associated with a 34·1% [95% confidence interval (CI): 9·2, 64·6%] increase of COVID-19 mortality. This association was higher for those aged ≥65 years (vs. those aged 65 years), Black, non-Hispanic White (vs. Hispanic White), and those with less comorbid conditions. An IQR increase (7·52 µg/m3) in O3 on two days before the death was associated with a 5·0% (-2·7, 13·3%) increase of COVID-19 mortality. The mortality increase for non-Hispanic White was a 14·0% (0·7, 28·9%), which was higher than for Hispanic White. The mortality increase was also higher for those with more comorbid conditions. The association between the air pollutants and COVID-19 mortality was stronger for areas with lower poverty rate and higher accessibility to ICU beds. CONCLUSIONS:Short-term exposure to air pollution below national air quality standards may immediately increase COVID-19 mortality. This increase may be unequal by demographics, pre-existing conditions, area-level poverty, and access to healthcare. KEYWORDS: Air pollution, COVID-19, susceptibility, environmental justice, case-crossover design, individual-level association