Scientists have found another way we are exposed to ‘forever chemicals’: through our skin

In early April, the Environmental Protection Agency for the first time set a limit on these “forever chemicals” in drinking water, after mounting evidence that chemicals in contaminated water can pose a health risk to people, even at the smallest observable exposure levels. Per- and polyfluoroalkyl substances, or PFAS, are a man-made class of thousands of carbon-fluorine bonded compounds designed to make products and coatings that repel grease, water, oil and heat. PFAS are known as ‘forever chemicals’ and can persist in the environment for centuries.

It is known that PFAS can enter the body through contaminated food and water, as well as by breathing in polluted air. But it was previously thought that PFAS could not penetrate the skin barrier. This study adds to the limited body of evidence showing that dermal exposure to PFAS can lead to dermal absorption.

Waterproof cosmetics such as mascara, long-lasting matte lipstick and waterproof clothing are examples of products containing PFAS that can be absorbed through the skin, says Graham Peaslee, a professor of physics at the University of Notre Dame who regularly tests for PFAS in everyday products. Peaslee was not involved in the investigation. The chemicals are found in hundreds of household, personal care and beauty products – including cosmetics, water-repellent clothing, hand sanitizers and other products that direct contact with human skin. PFAS have generally been linked to various types of cancer, infertility, high cholesterol, low birth weight, and adverse effects on the liver, thyroid, and immune system.

The new study extends the results of a single-human study that mixed PFOA with sunscreen and applied to the skin, concluding that PFAS could be absorbed through the skin. Using cultured human skin models – which mimic real skin – researchers examined the absorption potential of 17 commonly used synthetic ‘forever chemicals’. Researchers then assessed the amount that crosses the skin barrier and enters the bloodstream, the totals that are only absorbed through the skin, and the totals that are not absorbed at all.

The results showed that compounds with shorter carbon chains had higher absorption rates into the bloodstream than compounds with longer chains. Harrad, professor of environmental chemistry at the University of Birmingham, explained that it is easier for smaller chemicals to penetrate the skin barrier and then accumulate in the blood.

“It suggests that the lower molecular weight (PFAS) introduced as a replacement for PFOA, for example, is more easily absorbed through the skin.”

Perfluoro-n-pentanoic acid (PFPEA), a compound with five carbon chains, was almost 60 percent absorbed into the blood through the skin. While perfluorobutane sulfonate (PFBS), a compound with four carbon chains, was almost 50 percent absorbed into the bloodstream.

Still other nine-carbon compounds, such as perfluorononane sulfonate (PFNS), did not penetrate the bloodstream at all.

But researchers predict that longer carbon chains may still eventually reach the bloodstream with more time after being absorbed through the skin. In the 36 hours of the study, only about 14 percent of the perfluorooctanoic acid (PFOA), which has eight carbons, was absorbed into the bloodstream, but more than 38 percent was absorbed into the skin. Nearly 70 percent of the PFNS was absorbed into the skin, although none entered the blood.

“We think it’s unlikely that it’s going the other way: it’s not coming out of your skin. It’s more likely that it’s going through,” Harrad said. The amount that’s transferred through the skin depends on the amount of product used, the concentration of PFAS and the type of PFAS in the product.

Cosmetic products containing PFAS that are applied directly to the skin can penetrate the skin more quickly than fabrics and clothing containing PFAS, because the latter products require the PFAS to be released from the product material before it can be absorbed into the skin through the skin. sweat or oil, Harrad said.

“We are constantly surrounded by consumer products that intentionally or unintentionally contain things we probably shouldn’t use,” Peaslee says. Absorption could be increased in thin skin areas such as the neck, groin and armpits, he said.

But Peaslee — who says the main source of PFAS exposure is through drinking water — isn’t sure what portion of exposure might come through skin contact.

“We cover ourselves in this stuff every day, so the long-term prognosis is that a lot of this stuff can pass through the skin and in surprising amounts,” Peaslee said.

Katie Pelch, an environmental health scientist at the Natural Resources Defense Council, an advocacy group, said the study raises concerns about routine showering and bathing in contaminated water and swimming in water with high levels of PFAS.

The study examines the same range of chemicals associated with immune, hormonal and developmental effects, as well as various cancers. Pelch says the type of exposure does not change the potential health risks once PFAS enters the body.

“These chemicals are not metabolized by your body, so they don’t change when they go through our mouth, into our digestive system or into our blood,” Pelch said.

There are only eight states that have taken action to restrict PFAS in personal care products. The study examined five chemicals covered by the EPA’s new drinking water standard.

Harrad says the next step in the research is to expose cultured human skin models to various consumer products containing PFAS and monitor absorption. For consumers, he suggests avoiding cosmetic products containing PFAS and looking for PFAS-free products.

He said people need to “push for awareness of what is actually going into products and be an actively conscious consumer of these things.”