Per- and polyfluoroalkyl substances (PFAS) are a group of manufactured chemicals containing 9,000 different compounds that have been around since the 1940s. PFAS do not break down and accumulate in the environment and human body over time. The substances persist for long periods of time, hence the nickname "forever chemicals." They are linked to severe health effects such as cancer, hormone disruptions, weakened immune systems, and low birth weights. The toxic chemicals are found in various everyday consumer products, including non-stick cookware, pizza boxes, stain repellants—and even cosmetics, according to a new study published last week in the journal Environmental Science and Technology Letters.

More than half of all cosmetics tested in the study contained high levels of toxic Per- and polyfluoroalkyl substances (PFAS), reports Mathew Daly for the Associated Press. The study is the first to screen cosmetics for the total amount of PFAS present in make-up.

University of Notre Dame researchers tested 231 frequently-used makeup products, including liquid foundation, concealer, blush, lipsticks, and mascara, reports Tom Perkins for the Guardian. Approximately 82 percent of waterproof mascaras, 63 percent of foundations, and 62 percent of liquid lipsticks contained at least 0.384 micrograms of fluorine per square centimeter of product spread out, reports Maria Temming for Science News. After analyzing 29 cosmetics containing the highest amounts of PFAS, these products were found to contain four chemicals that further break down into other highly toxic PFAS, such as perfluorooctanoic acid, which can cause cancer and low infant birth weights, per Science News.

"Moreover, the types of products that tested positive for high levels of fluorine—and thus likely to contain PFAS—are often used close to and around the eyes and lips," Whitney Bowe, a dermatologist at the Icahn School of Medicine, who was not part of the study, tells CNN's Sandee LaMotte.

A table showing the percentage of cosmetics tested containing high levels of fluorine
Various products tested contained high levels of fluorine (Green Science Policy Institute)

The eyes, skin, and lips are vulnerable to absorption of the toxic chemicals. PFAS are absorbed through thin mucus membranes close to the mouth and tear ducts. Lipstick is more likely to be accidentally ingested, and wearers may consume up to several pounds of the cosmetic throughout their lives, explains study co-author Graham Peaslee, a physicist at the University of Notre Dame, in a statement. Besides direct exposure through makeup, PFAS can end up in drinking water after being washed off the skin, Science News reports.

PFAS are added to cosmetics to increase their long-term wearability and make skin appear shimmery and smooth, CNN reports. The compounds increase durability, product consistency and water resistance. Because PFAS do not breakdown in water, cosmetics designed to stay on longer or marketed as "wear-resistant," "long-lasting," and "waterproof" contained the highest levels of the chemicals, the Guardian reports. However, the researchers were unsure if cosmetic companies are aware that their products are infused with fluorine.

It's not clear whether the brands are actually saying 'Give us PFAS to use in our products or asking for a thickener, for example, or something functional without paying too much attention to what's in it," says study co-author Tom Bruton, a chemist at the Green Science Policy Institute, to the Guardian.

In 88 percent of all tested products, the label did not disclose PFAS to the consumer, making it almost impossible to avoid the toxins, reports CNN.

While half the makeup tested contained PFAS, the other half did not, which demonstrates that products can be manufactured without the chemicals, the Guardian reports.

Elizabeth Gamillo is a science journalist based in Milwaukee, Wisconsin. She has written for Science magazine as their 2018 AAAS Diverse Voices in Science Journalism Intern.