Air quality has been implicated by researchers in Europe and the U.S. as a factor in mortality rates associated with COVID-19 in some areas. Chronic inflammatory disorders and other pre-existing conditions that exacerbate the risk of death from COVID-19 are also adversely impacted by long-term exposure to air pollution.

Harvard University researchers examined the potential link between long-term average exposure to fine particulate matter (PM2.5) and an increased risk of COVID-19 deaths in the U.S., based on data from about 3,000 counties through April 4, 2020. Modeling analyses focused on county-level COVID-19 deaths as the outcome and county-level long-term average of PM2.5 as the exposure.

An increase of only 1 μg/m3 in PM2.5 was observed to be associated with a statistically significant 15% increase in the COVID-19 death rate. The indication that long-term exposure to air pollution increases vulnerability to experiencing the most severe COVID-19 outcomes is consistent with the known relationship between PM2.5 exposure and many of the cardiovascular and respiratory comorbidities that dramatically increase the risk of death in COVID-19 patients. A small increase in long-term exposure to PM2.5 leads to a large increase in COVID-19 death rates, with the magnitude of increase 20 times that observed for PM2.5 and all-cause mortality.

A similar study conducted by researchers from the University of Siena, Italy, and Aarhus University, Denmark, also points to high levels of air pollution in northern Italy as an agent in the high level of COVID-19 fatalities recorded in that area. Despite a recent drop in pollution levels stemming from restricted population mobility and commercial activity, the COVID-19 mortality rate is up to 12% in the northern part of Italy but only about 4.5% in the rest of the country.

The researchers analyzed data from the NASA Aura satellite, which has demonstrated very high levels of air pollution across the Lombardy and Emilia Romagna regions, and from the European Environment Agency Air Quality Index, which tracks particulate, ozone, sulfur dioxide and nitrogen dioxide concentrations. When combined with a review of experimental and epidemiological studies, the research indicates that residents of areas with high levels of pollutant are more prone to develop chronic respiratory conditions and susceptible to infectious agents, such as the coronavirus responsible for COVID-19.

The findings should be used to inform policies that encourage populations with high pollution exposure to take extra precautions and to allocate extra resources to reduce the risk of adverse outcomes from COVID-19.

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