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(The Hill) — Millions of students in the U.S. and Canada are being exposed to toxic “forever chemicals” through the uniforms they wear every day, a new study finds.

The exposure to these compounds — also called per- and polyfluoroalkyl substances (PFAS) — lies in the “stain-resistant” technology often marketed as an advantage in the fabrics.

The scientists behind Wednesday’s study, published in Environmental Science & Technology, said they detected PFAS in uniforms from all the popular brands that they tested.

“PFAS don’t belong in any clothing, but their use in school uniforms is particularly concerning,” senior author Marta Venier, a professor of environmental chemistry at Indiana University, said in a statement.

“School uniforms are worn directly on the skin for up to eight hours per day by children, who are particularly vulnerable to harm,” Venier added.

Known for their ability to persist in the human body and the environment, PFAS are notorious for their presence in firefighting foams and industrial discharge. These cancer-linked compounds are also key ingredients in many household items, such as nonstick pans, cosmetics and waterproof hiking clothes.

But most school uniforms tested in Wednesday’s study contained PFAS concentrations as high as those in outdoor apparel, the researchers found. 

In total, the scientists said they analyzed 72 children’s textiles marketed as stain-resistant in the U.S. and Canada in 2020 and 2021.

While they predominantly focused on uniforms, they also sampled other fabrics that come into contact with children, such as snowsuits, bibs, sweatshirts and stroller covers.

PFAS are often added to textiles due to their ability to prevent stains, making them particularly useful for school uniforms, according to the study.

The scientists first screened for total fluorine, which is an initial indicator of the possible presence of PFAS. They then performed targeted analyses for 49 types of PFAS, of which there are thousands. 

The researchers detected PFAS in all products from both the U.S. and Canadian markets, determining that the most common offender was a “fluorotelomer alcohol” known as FTOH.

Total PFAS levels of school uniforms were significantly higher than those of bibs, hats, stroller covers and swimsuits, but comparable to those found in outdoor apparel, the authors determined.

Uniforms made of 100-percent cotton tended to have higher concentrations of PFAS than those of synthetic blends, according to the study. Cotton, which naturally attracts water, likely needs additional PFAS treatment to reach a desired stain-resistant state, the authors explained.

“What was surprising about this group of samples was the high detection frequency of PFAS in the garments required for children to wear,” study co-author Graham Peaslee, a professor of physics at Notre Dame, said in a statement.

“Children are a vulnerable population when it comes to chemicals of concern, and nobody knows these textiles are being treated with PFAS and other toxic chemicals,” Peaslee added.

About a quarter of U.S. and Canadian school-aged children were wearing uniforms as of 2018, the authors noted, citing data from Statista. That same year, about one-fifth of U.S. public schools required students to wear uniforms, the researchers added, referring to a report from the National Center for Education Statistics.

PFAS in treated uniforms could end up in children’s bodies through skin absorption, as well as from eating with unwashed hands and hand-to-mouth behaviors often exhibited by younger children, the scientists warned.

The main type of PFAS found in the uniforms, FTOH, also poses an inhalation risk, according to the study.

PFAS-treated uniforms remain a source of potential contamination in the environment when they are worn, laundered, discarded or recycled, the authors explained.

Part of the problem, according to Peaslee, is that “there is no consumer option to purchase clothing that can be washed instead of clothing that comes coated with chemicals to reduce stains.”

Peaslee, whose novel method for detecting fluorine was integral to the study, called for increasing textile labeling so that consumers can make the informed decision “to pick garments that were not treated with chemicals for their children.”

Both New York and California have recently advanced bills that would phase out PFAS from textiles, including school uniforms, the authors noted. New York’s S6291A and California’s AB-1817 have both passed through their state legislatures and are awaiting signatures from their respective governors.

“I don’t know any parent who values stain repellency over their child’s health,” co-author Miriam Diamond, a professor of environmental chemistry at the University of Toronto, said in a statement.

Co-author Arlene Blum, executive director of Berkeley, Calif.-based Green Science Policy Institute, echoed these sentiments, stressing that manufacturers should “prevent harm by moving away from PFAS as soon as possible.” 

“To protect our children and future generations, the whole class of PFAS should be eliminated from school uniforms and all other products where they are not essential,” Blum added.