Urban Air Pollution May Enhance COVID-19 Case-Fatality and Mortality Rates in the United States

BACKGROUND The novel human coronavirus disease 2019(COVID-19)pandemic has claimed more than 600,000 lives worldwide,causing tremendous public health,social,and economic damages.Although the risk factors of COVID-19 are still under investigation,environmental factors,such as urban air pollution,may play an important role in increasing population susceptibility to COVID-19 pathogenesis.METHODS We conducted a cross-sectional nationwide study using zero-inflated negative binomial models to estimate the association between longterm(2010–2016)county-level exposures to NO2,PM2.5,and O3 and county-level COVID-19 case-fatality and mortality rates in the United States.We used both single-and multi-pollutant models and controlled for spatial trends and a comprehensive set of potential confounders,including state-level test positive rate,county-level health care capacity,phase of epidemic,population mobility,population density,sociodemographics,socioeconomic status,race and ethnicity,behavioral risk factors,and meteorology.RESULTS From January 22,2020,to July 17,2020,3,659,828 COVID-19 cases and 138,552 deaths were reported in 3,076 US counties,with an overall observed case-fatality rate of 3.8%.County-level average NO2 concentrations were positively associated with both COVID-19 case-fatality rate and mortality rate in single-,bi-,and tri-pollutant models.When adjusted for co-pollutants,per interquartile-range(IQR)increase in NO2(4.6 ppb),COVID-19 case-fatality rate and mortality rate were associated with an increase of 11.3%(95%CI 4.9%–18.2%)and 16.2%(95%CI 8.7%–24.0%),respectively.We did not observe significant associations between COVID-19 case-fatality rate and long-term exposure to PM2.5 or O3,although per IQR increase in PM2.5(2.6 mg/m3)was marginally associated,with a 14.9%(95%CI 0.0%–31.9%)increase in COVID-19 mortality rate when adjusted for co-pollutants.DISCUSSION Long-term exposure to NO2,which largely arises from urban combustion sources such as traffic,may enhance susceptibility to severe COVID-19 outcomes,independent of long-termPM2.5 and O3 exposure.The results support targeted public health actions to protect residents from COVID-19 in heavily polluted regions with historically high NO2 levels.Continuation of current efforts to lower traffic emissions and ambient air pollution may be an important component of reducing population-level risk of COVID-19 case fatality and mortality.