Air Pollution Linked to Increased Risk of Death From COVID-19 in U.S., Harvard Study Finds

People living in areas with high levels of air pollution may be particularly vulnerable to COVID-19 and could have an increased risk of dying from the disease, research suggests.

The results come from the first nationwide study examining the relationship between long-term exposure to PM2.5—tiny inhalable particles measuring 2.5 micrometers or smaller that are emitted by various sources such as vehicles and power plants—and COVID-19 death rates, which was conducted by scientists at Harvard University.

The team found statistically significant evidence suggesting that an increase of 1 microgram per cubic meter in PM2.5 is associated with a 15 percent increase in the COVID-19 mortality rate, according to a study submitted to The New England Journal of Medicine for review.

The researchers say that a small increase in long-term exposure to PM2.5 leads to a large increase in the COVID-19 death rate. A person who has lived for many years in an area with high PM2.5 is more likely to die from the disease than someone else living in another area where PM2.5 levels are one microgram per cubic meter lower.

Government scientists have estimated that the novel coronavirus could claim the lives of between 100,000 and 240,000 Americans, many of whom will have pre-existing medical conditions.

Given that COVID-19 is a respiratory illness, most of the underlying conditions that increase the risk of death from the illness are the same conditions that are affected by long-term exposure to air pollution, the researchers say.

Numerous studies have linked long-term exposure to PM2.5 with a variety of health outcomes, including premature death in people with heart or lung disease, non-fatal heart attacks, irregular heartbeats, aggravated asthma, decreased lung function, and respiratory problems such as inflammation, airway irritations, coughing, or difficulty breathing.

These health problems arise from long-term exposure to fine particulate matter, such as PM2.5— tiny particles or liquid droplets in the atmosphere that can be inhaled. A Global Burden of Disease study published in 2016 found that 5.5 million people die prematurely around the world every year as a result of air pollution.

For the latest study, the researchers collected data on COVID-19 deaths and exposure to PM2.5 from more than 3,000 counties in the United States, roughly 98 percent of the population, up to April 4. They adjusted their findings to take into account various factors that could affect the results such as "population size, hospital beds, number of individuals tested, weather, and socioeconomic and behavioral variables including, but not limited to obesity and smoking."

"The results of this paper suggest that long-term exposure to air pollution increases vulnerability to experiencing the most severe COVID-19 outcomes," the authors wrote in the study. "These findings align 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."

"They are also consistent with findings that air pollution exposure dramatically increased the risk of death during the Severe Acute Respiratory Syndrome (SARS) outbreak in 2003, which is caused by another type of coronavirus," the authors said.

According to the authors, the latest results highlight the importance of continuing to enforce existing air pollution regulations during the pandemic.

Los Angeles, air pollution
The buildings of downtown Los Angeles are partially obscured in the late afternoon on November 5, 2019 as seen from Pasadena, California. Mario Tama/Getty Images

"On Thursday, March 26, 2020 the U.S. Environmental Protection Agency announced a sweeping relaxation of environmental rules in response to the coronavirus pandemic, allowing power plants, factories and other facilities to determine for themselves if they are able to meet legal requirements on reporting air and water pollution," the authors wrote in the study.

"We hypothesize that because long-term exposure to PM2.5 adversely affects the respiratory and cardiovascular system, it can also exacerbate the severity of the COVID-19 infection symptoms and may increase the risk of death in COVID-19 patients," they said.

Failing to enforce existing air pollution regulations could increase the number of deaths from COVID-19 in the country, they argue, as well as the number of people requiring hospitalization, placing a further burden on the health system.

Finally, the researchers say that areas with higher levels of PM2.5 may need to prepare for more serious cases of COVID-19 compared to those with cleaner air.

John R. Balmes, a spokesman for the American Lung Association and a professor of medicine at University of California, San Francisco, who was not involved in the latest research, said the findings have particular relevance for health care in low-income and minority-dominated neighborhoods, where levels of harmful pollutants tend to be higher.

"We need to make sure that hospitals taking care of folks who are more vulnerable and with even greater air pollution exposure have the resources they need," Balmes told The New York Times.

Air Pollution Linked to Increased Risk of Death From COVID-19 in U.S., Harvard Study Finds | Health