This story was originally published by The Guardian and appears here as part of the Climate Desk collaboration.

Anti-fogging sprays and cloths often used to prevent condensation on eyeglasses from wearing a mask or on face shields may contain high levels of potentially toxic PFAS “forever chemicals,” according to a new study led by Duke University.

Researchers tested four of the top-rated anti-fogging sprays as well as five top-rated anti-fogging cloths sold by Amazon. In all nine products, experts found fluorotelomer alcohols (FTOHs) and fluorotelomer ethoxylates (FTEOs), two types of per- and polyfluorinated alkyl substances (PFAS).

PFAS have been dubbed as forever chemicals due to their longevity in the environment.

“Our tests show the sprays contain up to 20.7 milligrams of PFAS per millilitre of solution, which is a pretty high concentration,” said study lead Nicholas Herkert, a postdoctoral researcher at Duke’s Nicholas School of the Environment.

Exposure to some PFAs — perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in particular — have been linked to cancer, thyroid disease, fertility complications and other health problems.

Herkert noted that FTOHs and FTEOs have not been studied extensively, so scientists do not know what health risks they could pose, but research currently suggests that FTOHs inhaled or absorbed through the skin could break down in the body and become toxic, long-lasting PFAs.

The FTEOs used in all four anti-fogging sprays were also analyzed in the new study and exhibited substantial cell-altering toxicity and conversion to fat cells during lab tests, said Herkert.

“It’s disturbing to think that products people have been using on a daily basis to help keep themselves safe during the COVID pandemic may be exposing them to a different risk,” said Heather Stapleton, a distinguished professor of environmental chemistry and health at Duke.

Stapleton initiated the study after reviewing the ingredients in a bottle of anti-fogging spray she bought for her nine-year-old daughter.

“It’s disturbing to think that products people have been using on a daily basis to help keep themselves safe during the COVID pandemic may be exposing them to a different risk,” said Duke professor Heather Stapleton. #PFAS #ForeverChemicals

Stapleton noted that the other eight products did not have their ingredients listed, making it virtually impossible to tell if they contained toxic chemicals until they were analyzed using equipment from her research laboratory.

This study, conducted by Herkert and Stapleton with researchers from Duke University, Wayne State University, and the University of North Carolina at Charlotte, is only the second ever to focus on FTEOS. The researchers published their peer-reviewed study on Jan. 5 in the journal Environmental Science & Technology.

Herkert and Stapleton said that more research would be needed to expand on initial findings, with larger studies involving tests on living organisms being the next step. Studies that include a larger sample size of sprays and cloths could also help identify other unknown chemicals being used in these products.

“Because of COVID, more people than ever, including many medical professionals and other first-responders, are using these sprays and cloths to keep their glasses from fogging up when they wear masks or face shields,” said Stapleton. “They deserve to know what’s in the products they’re using.”