Some ‘forever chemicals’ can be absorbed through our skin

PFAS are a collection of thousands of man-made chemical compounds. They get their nickname ‘forever’ from their almost unbreakable bonds between the carbon and fluorine atoms. Consumers have encountered these chemicals since companies began mass-producing them in the 1940s and using them in everything from non-stick pans to stain- and water-resistant fabrics. But after decades of making life better, research is beginning to show that chemicals are harmful to our bodies, difficult to degrade, and widespread in the environment.SN: 29.11.22).

In the United States, most people are exposed to PFAS through food packaging, indoor dust, and ingestion of contaminated drinking water. Levels of PFAS were of such concern in drinking water that in June 2022, the US Environmental Protection Agency established guidelines and limits to help reduce human consumption.

Past research suggested that skin absorption was also a possible route of exposure. But studies have been limited and data scarce. One study, for example, found that one type of PFAS was able to penetrate mouse skin. But “mouse skin doesn’t directly mimic human skin,” says environmental chemist Stuart Harrad.

In the new study, Harrad, Oddný Ragnarsdóttir and Mohamed Abdallah studied 17 PFASs that are in various products that come into 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 chemical to models made from human epidermal cells grown in the lab for up to 36 hours.

For each PFAS, the researchers analyzed three things: how much of the chemical crossed the skin barrier, the total absorbed just within the skin’s surface, and the amount that was not absorbed.

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

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

While the experiments show that the model’s skin can absorb PFAS, it may not accurately represent the skin’s behavior 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 might be exposed to in their normal lives, says Ragnarsdóttir. (The dose was chosen to more easily track the movement of the chemicals.)

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