Understanding the link between COVID-19 Mortality and Air Pollution

As we mourn and reflect on the more than 300,000 lives that have been lost to COVID-19 in the United States, we can also take stock of what the latest science shows us about the disease. We already know that during this pandemic, people living in areas with unhealthy levels of air pollution are facing multiple threats to their lung health at once. Now, emerging research is shedding light on the links between air pollution and severe illness from COVID-19 -- underscoring the critical need to ensure healthy air for all.

Hazardous Air Pollutants and COVID-19

In a U.S.-based study released in September 2020, researchers at the SUNY College of Environmental Science and Forestry looked at the relationship between chronic exposure to hazardous air pollution and the COVID-19 death rate. Hazardous air pollutants, like formaldehyde, asbestos and mercury, are known or suspected to cause cancer, birth defects, impaired lung function and other serious health harms. These toxic pollutants come from a variety of sources, including coal-fired power plants and other industry, households, vehicles, and wildfires.

The researchers found that an increase in exposure to hazardous air pollutants is associated with a 9% increase in death among patients with COVID-19. They made sure that this increase was really caused by the hazardous air pollutants, not by differences in wealth, other health reasons, or exposure to other types of air pollution. Essentially, the higher the air pollution index, the more it correlated to poor health outcomes due to COVID-19. The likely reason: these pollutants cause respiratory stress, thereby increasing vulnerability to severe illness from COVID-19. 

Particle Pollution and COVID-19 Worldwide

In December 2020, a second study tried to determine the how much of COVID-19 mortality is because of long-term exposure to fine particle pollution. Utilizing a mix of epidemiological data, satellite data and other monitoring information from around the world, the researchers estimated that, on average, 15% of worldwide deaths from COVID-19 may be linked to chronic exposure to air pollution. 

This study breaks down results by region and by country. For example, the study’s estimates show that air pollution contributed to 27% of COVID-19 deaths in China, 18% in the United States, 15% in Mexico, 14% in the United Kingdom, 6% in Israel, and just 1% in New Zealand. The researchers also distinguished between fossil-fuel related air pollution and other sources of human-caused air pollution. In the U.S., 15% of COVID-19 mortality is specifically attributable to fossil fuel-related air pollution, showing that fossil fuel-related air pollution contributes significantly to overall U.S. air emissions. 

Particle Pollution and COVID-19 in the U.S.

In a third study, researchers from the Harvard T.H. Chan School of Public Health and the Dana-Farber Cancer Institute also looked at the impact of long-term exposure to fine particle pollution on COVID-19 death rates. They examined 3,089 counties, accounting for 98% of the United States’ population. The researchers found that just a small increase (1 microgram per cubic meter) in long-term average exposure to fine particle pollution is associated with an 11% increase in the COVID-19 death rate for that county.  

The study identified several other important predictors of the death rate, including population density, days since the first COVID-19 case was reported, median household income, percent of owner-occupied housing, percent of the adult population with less than high school education, age distribution, and percent of Black residents. Adding to the evidence on the connection between racial disparities, air pollution and COVID-19, the researchers found a 49% increase in the COVID-19 death rate in counties with elevated fine particle pollution and that had a higher Black population. 

Nitrogen Dioxide and COVID-19

Researchers from Emory University conducted a nationwide study published in September 2020 looking at long-term county-level exposures to nitrogen dioxide, fine particle pollution and ozone; county-level COVID-19 case-fatality rates; and county-level COVID-19 mortality rates in the U.S. The researchers found links between exposure to nitrogen dioxide and increased rates of dying from COVID-19[DVV7] . 

Nitrogen dioxide is an air pollutant that comes from traffic and power plants. According to the study, a 4.6 parts per billion increase of nitrogen dioxide in the air was associated with 11.3% and 16.2% increases in COVID-19 case-fatality and mortality rate, respectively. The researchers argue that a 4.6 parts per billion reduction in long-term exposure to nitrogen dioxide would have prevented over 14,000 COVID-19 deaths among those who tested positive for the virus. 

The researchers also observed a marginally significant association between fine particle exposure and COVID case-fatality rate.

These findings may help identify susceptible and high-risk populations, especially those living in areas with historically high nitrogen dioxide pollution, including the metropolitan areas in New York, New Jersey, California, and Arizona. 

To learn more about the Lung Association’s latest resources on the COVID-19 pandemic, visit Lung.org/COVID-19. 

To join the Lung Association’s advocacy efforts to ensure clean air for all, visit Lung.org/healthyair.