In early April, the Environmental Protection Agency for the first time set a limit on these “permanent chemicals” in drinking water, following growing evidence that chemicals in contaminated water may pose a risk to human health, even at the lowest detectable exposure levels. Per- and polyfluoroalkyl substances, or PFAS, are an artificial class of thousands of carbon-fluorine-related compounds developed to make products and coatings that repel grease, water, oil and heat. Known as “forever chemicals,” PFAS 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 inhaling polluted air. But it was previously thought that PFAS were unable to cross the skin barrier. This study adds to the limited body of evidence that dermal exposure to PFAS can lead to dermal absorption.
Waterproof cosmetics like mascara, long-wear matte lipsticks and waterproof clothing are examples of products containing PFAS that could be absorbed through the skin, said Graham Peaslee, a physics professor at the University of Notre Dame who frequently tests everyday products for PFAS. Peaslee was not involved in the study. The chemicals are found in hundreds of household, personal care and beauty products, including cosmetics, water-repellent clothing, hand sanitizers and other products that make direct contact with human skin. PFAS in general have been linked to several types of cancer, infertility, high cholesterol, low birth weight, and negative effects on the liver, thyroid, and immune system.
The new study extends the results of a single human subject study who mixed PFOA with sunscreen and applied it to the skin, concluding that PFAS could be absorbed through the skin. Using human skin culture models – which mimic real skin – the researchers examined the absorption potential of 17 commonly used synthetic “forever chemicals.” The researchers then assessed the amount that crosses the skin barrier into the bloodstream, the totals only absorbed through the skin, and the totals that are not absorbed at all.
The results revealed that compounds with shorter carbon chains had higher absorption percentages 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 build up in the blood.
“This suggests that (low molecular weight) PFASs that have been introduced as substitutes for PFOA, for example, are more easily absorbed through the skin.”
Perfluoro-n-pentanoic acid (PFPeA), a five-carbon chain compound, was absorbed almost 60% from the skin into the blood. While perfluorobutane sulfonate (PFBS), a four-carbon chain compound, had almost 50 percent absorption into the bloodstream.
Yet other nine-carbon compounds, like perfluorononane sulfonate (PFNS), did not enter the bloodstream at all.
But researchers predict that longer-chain carbons could potentially enter the bloodstream longer after being absorbed through the skin. During the 36 hours covered by the study, only about 14 percent of perfluorooctanoic acid (PFOA), which contains eight carbons, was absorbed into the bloodstream, but more than 38 percent was absorbed through the skin . Nearly 70 percent of the PFNS was absorbed through the skin, but none entered the bloodstream.
“We think it’s unlikely to come back the other way: it won’t come out of your skin. It’s more likely to transfer,” Harrad said. The amount transferred through the skin depends on the amount of product used, the concentration of PFAS, and the type of PFAS present in the product.
Cosmetic products containing PFAS that are directly applied to the skin may penetrate the skin more quickly than fabrics and clothing containing PFAS because, in the latter products, the PFAS would first be released from the product material before being released. able to be absorbed by the skin. sweat or oils, Harrad said.
“We are continually surrounded by consumer products that, intentionally or not, contain elements that we probably shouldn’t use,” Peaslee said. Absorption could be increased in thin skin areas like the neck, groin and armpits, he said.
But Peaslee — who says the primary source of PFAS exposure is drinking water — isn’t sure what fraction of exposures may come from skin contact.
“We slather ourselves in this stuff every day, so the long-term prognosis is that a lot of this stuff can pass through the skin and at surprising rates,” 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 as well as swimming in water containing high levels of PFAS.
The study looks at the same suite of chemicals associated with effects on the immune system, hormones and development, as well as various cancers. Pelch says the type of exposure doesn’t change the potential health risks once PFAS enter the body.
“These chemicals are not metabolized by your body, so they are not changed if they get into our mouth, into our digestive system or if they get into our blood,” Pelch said.
Only eight states have taken action to restrict PFAS in personal care products. Five chemicals covered by the EPA’s new drinking water standard were examined in the study.
Harrad says the next step in research involves exposing cultured human skin models to different consumer products containing PFAS and monitoring their absorption. For consumers, he suggests avoiding cosmetic products containing PFAS and looking for items that are PFAS-free.
He said people need to “push to be aware of what is actually used in products and be an actively conscious consumer of those things.”