In early April, the Environmental Protection Agency set its first limits on these “forever chemicals” in drinking water, following growing evidence that chemicals in contaminated water can pose health risks to people, even at the lowest detectable levels. Per- and polyfluoroalkyl substances, or PFAS, are a man-made class of thousands of carbon-fluorine bonded 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 breathing polluted air. But it was previously believed that PFAS were unable to penetrate the skin barrier. This study adds to the limited evidence that proves that skin exposure to PFAS can lead to skin absorption.
Graham Peaslee, a physics professor at the University of Notre Dame who frequently tests for PFAS in everyday products, said 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. Peaslee was not involved in the study. These chemicals are found in hundreds of household, personal care and beauty products — including cosmetics, water-repellent clothing, hand sanitizers and other products that harm the skin. 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.
New Study The results of a single human subject study in which PFOA was mixed with sunscreen and applied to the skin led to the conclusion that PFAS can be absorbed by the skin. Using cultured human skin models — which mimic real skin — researchers examined the absorption capacity of 17 commonly used synthetic “forever chemicals.” The researchers then assessed the amount that crossed the skin barrier into the bloodstream, the total amount that was absorbed only into the skin and the total amount that was not absorbed at all.
The results found that compounds with shorter carbon chains had a higher percentage of absorption into the bloodstream than those with longer chains. Harrad, a professor of environmental chemistry at the University of Birmingham, explained that shorter chemicals have an easier time penetrating the skin barrier, then accumulating in the blood.
“This suggests that the low molecular weight [PFAS] For example, those that were introduced as alternatives to PFOA are more easily absorbed through the skin.”
Perfluoro-n-pentanoic acid (PFPeA), a compound with a five-carbon chain, is absorbed from the skin into the blood by about 60 percent, while perfluorobutane sulfonate (PFBS), a compound with a four-carbon chain, is absorbed into the bloodstream by about 50 percent.
However, other nine-carbon compounds, such as perfluoronenone sulfonate (PFNS), did not enter the bloodstream.
But the researchers speculate that longer-chain carbons may enter the bloodstream over longer periods of time, even after being absorbed through the skin. Over the 36 hours monitored in the study, only 14 percent of perfluorooctanoic acid (PFOA), which has eight carbons, was absorbed into the bloodstream, but more than 38 percent was absorbed into the skin. About 70 percent of PFNS was absorbed into the skin, although none entered the blood.
“We think it's unlikely to go back in the other direction: It's not going to come out of your skin. It's more likely to move through,” Harrad said. The amount that is transferred through the skin depends on the amount of product used, the concentration of PFAS, and the type of PFAS in the product.
Harrad said PFAS-containing cosmetic products that are applied directly to the skin may penetrate the skin faster than PFAS-containing clothing and apparel, because in PFAS-containing products, the PFAS has to be released from the product ingredients before they can be absorbed into the skin through sweat or oil.
“We are constantly surrounded by consumer products that intentionally or unintentionally contain things we probably shouldn't be using,” Peaslee said. He added that absorption may be increased in areas with thinner skin, such as the neck, groin and armpits.
But Peaslee — who says the primary source of exposure to PFAS is drinking water — is unsure how much exposure might occur through skin contact.
“We cover ourselves with this substance every day, so the long-term prognosis is that a lot of this substance may be moving through the skin, and at astonishing rates,” Peaslee said.
Katie Pelch, an environmental health scientist at the Natural Resources Defense Council, an advocacy group, said the study raises concerns about regularly bathing and showering in contaminated water, as well as swimming in water with high levels of PFAS.
The studies examined the same series of chemicals linked to 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 enter the body.
“These chemicals are not metabolized by your body, so if they enter our mouth, digestive system or our blood, they don't undergo any changes,” Pelech said.
There are only eight states that have taken action to ban PFAS in personal care products. The study examined five chemicals included in 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 that contain PFAS and monitor absorption. For consumers, he suggests avoiding cosmetic products containing PFAS and looking for PFAS-free items.
He said people “need to raise their awareness about what's actually being used in products and to actively become aware consumers about these things.”