Urban Air Pollution May Make COVID-19 More Deadly

Another study links pollution to worse coronavirus outcomes.

Brown Layer of Los Angeles Smog
steinphoto / Getty Images

New research reveals that air pollution might be having a deadly impact on coronavirus in the United States.

A study published in the journal The Innovation suggests that long-term exposure to urban air pollution can make COVID-19 more severe for some people.

"Both long-term and short-term exposure to air pollution has been associated with direct and indirect systemic impact on the human body by enhancing oxidative stress, acute inflammation, and respiratory infection risk," said co-first author Donghai Liang of Emory University, in a statement.

For the study, researchers analyzed specific urban air pollutants including fine particulate matter, nitrogen dioxide (NO2), and ozone, in more than 3,000 counties in the U.S. from January to July. They investigated both the case-fatality rate (the number of deaths among people who are diagnosed with COVID-19) and the mortality rate (the number of COVID-19 deaths in the U.S. population). 

Of the pollutants that the researchers studied, NO2 had the strongest correlation with raising someone’s risk of death from the coronavirus. A 4.6 parts per billion (ppb) increase of NO2 in the air was associated with an 11.3% increase in COVID-19 case fatality and a 16.2% increase in COVID-19 mortality rate.

Researchers found that a 4.6 ppb reduction in long-term exposure to NO2 would have prevented 14,672 deaths in those who tested positive for the coronavirus.

"Long-term exposure to urban air pollution, especially nitrogen dioxide, might enhance populations' susceptibility to severe COVID-19 death outcomes," said Liang. "It's essential to deliver this message to public health practitioners and policymakers in order for them to consider protecting vulnerable populations that lived in historically high NO2 pollution including the metropolitan areas in the state of New York, New Jersey, California, and Arizona."

Air pollution does not affect people equally, the researchers point out. "People with lower income and people of color often face higher exposure to ambient air pollution and may experience a more significant impact from the pollutants," notes the statement. Communities located by highways and industrial sites, for exmaple, are especially vulnerable to air pollution.

"The continuations and expansions of current efforts to lower traffic emissions and ambient air pollution might be an important component of reducing the population-level risk of COVID-19 case-fatality and mortality in the United States," said Liang.

Earlier Pollution Research

This is only the latest study to link air pollution to more serious COVID-19 risks.

A study published earlier in September found that COVID-19 can be more serious, and sometimes more deadly, in areas with a specific type of industrial emission called hazardous air pollutants, or HAPs.

The Environmental Protection Agency (EPA) defines HAPs as “those known to cause cancer and other serious health impacts.” They are often prevalent in areas with certain industrial facilities. Under the Clean Air Act, industrial facilities are required to regulate these pollutants.

The study, published in the journal Environmental Research Letters, found the correlations in rural counties in Louisiana as well as highly populated areas in New York. These communities have had disproportionately high death rates due to the virus.

Researchers analyzed COVID-19 death rates and air pollution in more than 3,000 counties to look at pollution’s effect on respiratory hazard index. (The respiratory hazard index is an EPA measurement of how pollutants affect health and breathing.) They found a strong correlation.

“We find that an increase in the respiratory hazard index is associated with a 9% increase in COVID-19 mortality,” the authors write. “These findings help us to understand variation in US-based COVID-19 mortality rates, reinforce existing research linking air pollution to mortality, and emphasize the importance of regulatory efforts to limit air pollution exposure risk.”