According to a report recently published by WebMD, a new study found high fluorine levels from a sampling of 231 cosmetic products purchased in the U.S. and Canada from retailers such as Ulta Beauty, Sephora, Target, and Bed Bath & Beyond. Three-quarters of waterproof mascara samples contained high fluorine concentrations, as did nearly two-thirds of foundations and liquid lipsticks, and more than half of the eye and lip products tested.

Fluorine indicates the presence of per- and polyfluoroalkyl substances, commonly known as PFAS. But since these chemicals are not listed in the ingredients on the product labels an general lack of regulation of toxic chemicals in consumer products, it makes it difficult for consumers to look out for them.

Researchers have linked PFAS exposure to increased cholesterol levels, increased risk of kidney and testicular cancer, changes in liver enzymes, decreased vaccine response in children, and a higher risk of high blood pressure or preeclampsia in pregnant women, impaired immune function, certain cancers, increased risks of diabetes, obesity and endocrine disruption. In short, they appear to be harmful to every major organ system in the human body.

PFAS are a class of chemicals used in a variety of consumer products, such as nonstick cookware, stain-resistant carpeting, and water-repellent clothing, according to the CDC. They are added to cosmetics to make the products more durable and spreadable.

Says study co-author Tom Bruton, PhD, senior scientist at the Green Science Policy Institute in Berkeley, CA: “The concerning thing about cosmetics is that these are products that you’re applying to your skin and face every day, so there’s the skin absorption route that’s of concern, but also incidental ingestion of cosmetics is also a concern as well.”

Researchers found higher levels of fluorine in products commonly advertised as “water-proof”, “water-resistant” or “long-lasting.” But there is obviously a potential long term health trade-off when cosmetic companies try to meet the needs of consumers looking for makeup that is long lasting.