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Haze behind Denver's City and County Building on the afternoon of Thursday, Oct. 31, 2019. (Jesse Paul, The Colorado Sun)

Living in a community with higher rates of air pollution may be associated with a greater risk of coronavirus infection, hospitalization and death, according to a study released Thursday by the Colorado Department of Public Health and Environment.

The study also finds that there is a greater risk of coronavirus infection and severe outcomes in communities with larger proportions of people of color, higher numbers of essential workers, and higher rates of mobility.

While not yet formally peer reviewed, the research reinforces one of the most consistent findings throughout the pandemic — that inequity within Colorado and across the nation means the burden of the virus falls very differently on different communities.

“This study for us really underscores that higher rates of underlying health conditions, air pollution and worse COVID-19 outcomes go hand-in-hand with the disproportionate impact on communities of color,” said Kristy Richardson, Colorado’s state toxicologist and one of the authors of the study. CDPHE statistical analysts Kevin Berg and Paul Romer Present are also authors on the report.

But the study’s findings were also delivered with a note of caution. Richardson said measuring air pollution at the local level is difficult because there are not enough monitoring stations spread across the state. As a result, the study looked at four models that can be used to estimate fine-particle air pollution at the census-tract level. But census tracts can vary widely in size, from as small as a neighborhood in an urban area to as large as a whole rural county.

In analyses using three of the models, and taking into account things like the age of people living in the census tracts, the study found that an increase in air pollution was associated with an increase in the risk of coronavirus infection, hospitalization and death. But the results were only statistically significant for one of the models — one developed by the Environmental Protection Agency.


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In the fourth model, the researchers found a non-statistically significant negative association — meaning an increase in air pollution was associated with lower COVID-19 risk.

Overall, it means the researchers can’t be conclusive about how air pollution impacts coronavirus cases.

“What we found in general is that long-term exposure to fine particles is associated with more COVID-19 infections, hospitalizations and deaths,” Richardson said. “But we don’t have enough localized pollution data to really be certain about that relationship.”

The researchers plan to submit the study for publication in a peer-reviewed journal. The study was informally reviewed by researchers at Harvard University who have conducted a similar study, as well as experts at Colorado universities.

More clear in the study is the disproportionate impact COVID-19 has on communities of color.

The researchers found that census tracts with larger proportions of Black residents were associated with a 4% greater relative risk of coronavirus infection and a 7% greater relative risk of hospitalization due to COVID-19. Census tracts with larger proportions of non-Black people of color — a group primarily made up of Hispanic Coloradans — have a 31% higher risk of infection, a 44% higher risk of hospitalization and a 59% higher risk of death.

The study also showed greater risks for neighborhoods with more essential workers and with higher levels of mobility — typically an indicator of people who cannot work from home.

Richardson said it’s difficult to disentangle all the variables. Due to social inequities, communities of color often have higher rates of chronic illness. People of color are also more likely to be essential workers and less likely to be able to work from home.

But she said the research provides valuable insight for health officials looking to use pandemic-blunting resources where they are most needed. And she said the study also shows the value in setting up more pollution-monitoring stations, something echoed by CDPHE executive director Jill Hunsaker Ryan in a statement.

“Centuries of structural discrimination in the U.S. housing system mean people of color and low-income populations often live near busy highways and industrial areas where pollution is worse,” Hunsaker Ryan said. “The resulting disproportionate harm to these communities is documented in many studies. We’ll accelerate our efforts to implement additional monitoring in areas that have higher levels of air pollution and will continue to do everything we can to ensure an equitable pandemic response.”

John Ingold is a co-founder of The Colorado Sun and a reporter currently specializing in health care coverage. Born and raised in Colorado Springs, John spent 18 years working at The Denver Post. Prior to that, he held internships at the Rocky Ford Daily Gazette, the Colorado Springs...