Vissa 'för alltid kemikalier' kan absorberas genom vår hud.

Forever chemicals are everywhere. 

They’re in school uniforms, food packaging, cosmetics and personal care products (SNE: 11/18/22; SN: 6/4/19; SN: 6/15/21). They seep into our food and drinking water. And now new research suggests that some can move through the skin, posing yet another avenue through which humans are intimately exposed to these chemicals, which have been linked to harmful health issues. 

When 3-D human skin models were exposed to per- and polyfluoroalkyl substances, or PFAS, the chemicals could cross the skin barrier, environmental chemists from the University of Birmingham in England report in the June Environment International. That suggests the compounds can be absorbed through the skin and may even travel into the bloodstream. 

PFAS are a collection of thousands of human-made chemical compounds. They get their ‘forever’ nickname from their almost unbreakable bonds between carbon and fluorine atoms. Consumers have encountered these chemicals since companies began mass-producing them in the 1940s and using them for everything from nonstick pans to stain- and water-repellent fabrics. But after decades of making living better, research has begun to show the chemicals are harmful to our bodies, difficult to degrade and pervasive in the environment (SN: 11/29/22).  

In the United States, most people are exposed to PFAS through food packaging, indoor dust and ingestion of contaminated drinking water. The PFAS levels were so concerning in drinking water that in June 2022, the U.S. Environmental Protection Agency set guidelines and limits to help reduce human consumption. 

Past research suggested that skin absorption was a possible route of exposure, too. But studies have been limited and data sparse. One study, for instance, found that one type of PFAS was able to penetrate rat skin. But “the skin of a rat does not directly mimic human skin,” says environmental chemist Stuart Harrad.

In the new study, Harrad, Oddný Ragnarsdóttir and Mohamed Abdallah studied 17 PFAS that are in various products that come in contact with human skin. In the lab, the researchers dissolved each PFAS chemical in methanol. They then applied 500 nanograms per square centimeter of the chemicals to models made from lab-grown human epidermis cells for up to 36 hours. 

For each PFAS, the researchers analyzed three things: how much of the chemical crossed the skin barrier, the totals absorbed only within the skin surface, and the amount that wasn’t absorbed.  

Of the 17 PFAS, 11 were able to cross the skin barrier. But ones with only four to seven carbon atoms appeared to be absorbed more readily than PFAS with more carbon atoms. For instance, roughly 59 percent of perfluoropentanoic acid (PFPeA) and 49 percent of perfluorobutane sulfonate (PFBS) entered the skin and penetrated to a fluid representing blood in the body. These shorter PFAS were developed as safer alternatives to the original forever chemicals but are proving to also be problematic. 

“We cannot say with 100 percent certainty that [PFAS] will end up in the bloodstream,” says Ragnarsdóttir, now at the University of Iceland in Reykjavik. “But they have still managed to enter the skin — which is the first step in the process of dermal permeation.” 

While the experiments show that model skin can absorb PFAS, that might not accurately represent the behavior of skin in a real-life scenario, says Miriam Diamond, an environmental scientist at the University of Toronto, who was not involved in the study. And skin is thicker in some places, like the soles of our feet, and thinner in others, like the genital area, so there will be differences in absorption depending on where the PFAS exposure is, she says.  

In addition, the doses used in the experiments were higher than people would likely be exposed to in their normal lives, Ragnarsdóttir says. (The dosage was chosen in order to more easily track the movement of the chemicals.)  

Even so, she says, consumers need to be increasingly aware of PFAS in the clothing and personal care products they use on the skin. “We wear our clothes for hours during the day, so if you’re wearing something with PFAS, it’s a source of exposure.”