Exposure to air pollution and COVID-19 mortality in the United States

Background: United States government scientistsestimate that COVID-19 may kill between 100,000 and 240,000 Americans. The majority of the pre-existing conditions that increase the risk of death for COVID-19 are the same diseases that are affected by long-term exposure to air pollution. We investigate whether long-term average exposure to fine particulate matter (PM2.5) increases the risk of COVID-19 deaths in the United States.
https://projects.iq.harvard.edu/pm_and_covid_mortality.pdf