Ambient PM2.5 exposure and rapid spread of COVID-19 in the United States

It has been posited that populations being exposed to long-term air pollution aremore susceptible to COVID-19. Evidence is emerging that long-termexposure to ambient PM2.5 (particulate matter with aerodynamic diameter 2.5 mu m or less) associates with higher COVID-19 mortality rates, but whether it also associates with the speed at which the disease is capable of spreading in a population is unknown. Here, we establish the association between long-term exposure to ambient PM2.5 in the United States (US) and COVID-19 basic reproduction ratio R-0-a dimensionless epidemicmeasure of the rapidity of disease spread through a population. We inferred state-level R-0 values using a state-of-the-art susceptible, exposed, infected, and recovered (SEIR) model initialized with COVID19 epidemiological data corresponding to the periodMarch 2-April 30. This period was characterized by a rapid surge in COVID-19 cases across the US states, implementation of strict social distancing measures, and a significant drop in outdoor air pollution. We find that an increase of 1 mu g/m(3) in PM2.5 levels belowcurrent national ambient air quality standards associates with an increase of 0.25 in R-0 (95% CI: 0.048-0.447). A 10% increase in secondary inorganic composition, sulfate-nitrate-ammonium, in PM2.5 associates with similar to 10% increase in R-0 by 0.22 (95% CI: 0.083-0.352), and presence of black carbon (soot) in the ambient environment moderates this relationship. We considered several potential confounding factors in our analysis, including gaseous air pollutants and socio-economical and meteorological conditions. Our results underscore two policy implications - first, regulatory standards need to be better guided by exploring the concentration-response relationships near the lower end of the PM2.5 air quality distribution; and second, pollution regulations need to be continually enforced for combustion emissions that largely determine secondary inorganic aerosol formation. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

It has been suggested that long-term exposure to air pollution, particularly PM2.5, can increase susceptibility to COVID-19. Studies have shown that higher levels of PM2.5 and secondary inorganic composition are associated with increased COVID-19 transmission rates, highlighting the importance of regulating pollution levels to control the spread of the disease.