Harmful chemicals found in drinking water systems may increase the risk for severe COVID-19. A recent study by Harvard University researchers found that elevated levels of these harmful contaminants in COVID-19 patients increased their likelihood to be admitted to intensive care units or die.

According to the Dayton Daily News, a group of these chemicals, collectively called PFAS, attacks the lungs in a similar fashion to the coronavirus. The Harvard scientists studied blood plasma samples from 323 people in Denmark who had COVID-19 and measured their PFAS levels to see what effect the “forever chemicals” had on the course of the disease.

These compounds are known as “forever chemicals” because they do not fully degrade, according to The Conversation. The Centers for Disease Control and Prevention has stated that PFASs concentrate in various organs, tissues, and cells of the body and can cause immunotoxicity, testicular and kidney cancer, liver damage, decreased fertility, and thyroid disease.

Now, researchers are investigating their role in worsening COVID-19 outcomes.

One PFAS in particular, PFBA, was found to double the risk of infection because it builds up in the lungs, where COVID-19 commonly attacks. According to an article in Harvard T.H. Chan School of Public Health newsletter, PFASs have water and grease resistant properties and are used in nonstick cookware, waterproof clothing, food packaging, and firefighting foams.

The Harvard researchers found that those Danish patients with “higher PFBA levels had higher odds of being hospitalized, winding up in intensive care and dying than those with lower levels of the chemical,” according to the news report.

The authors suggested that more research is needed to determine the effect of elevated exposure to environmental toxins and poor COVID-19 outcomes.