Researchers have confirmed a link between liver-cancer risk and exposure to man-made chemicals.
PFAS, or "forever chemicals," are thought to cause health problems, including developmental delays.
People with high levels of PFAS in their blood may be 41/2 times more likely to get liver cancer.
Exposure to chemicals used in nonstick cookware and long-lasting makeup has been linked to elevated liver-cancer risk, researchers at the University of Southern California found.
Scientists have theorized that man-made "forever chemicals," also known as PFAS, were harmful to the liver, based on extensive animal studies and a few analyses involving humans.
But studying cancer risk in humans has proved tricky. It comes with a unique set of challenges, as many factors can affect overall risk, and it would be unethical to expose people to potential carcinogens.
The new study from USC's Keck School of Medicine, published on Monday in JHEP Reports, is the first to use human samples to confirm a link between PFAS exposure and liver-cancer risk.
The team at Keck had access to blood and tissue samples from more than 200,000 people living in Los Angeles and Hawaii, thanks to a previous collaboration between the medical school and the University of Hawaii.
Within that population, the research team found 50 participants who eventually developed liver cancer, a news release from Keck said. Analysis of blood samples taken prior to these people's cancer diagnoses showed relatively high levels of certain PFAS chemicals.
There are different types of PFAS, or per- and polyfluoroalkyl substances. PFOA and PFOS are some of the oldest and most well-studied kinds. PFOS had the strongest association with liver-cancer risk in this particular study.
People in the top 10% of PFOS exposure were 41/2 times more likely to develop liver cancer compared to people with the lowest levels of PFOS in their blood, the researchers found. To prove the association, the research team compared the 50 people who developed liver cancer with a similar sample of 50 people who did not develop the disease.
The team said it's possible that PFOS interferes with normal liver function, which causes a buildup of fat that can progress to nonalcoholic fatty liver disease, or NAFLD. More research is needed to determine exactly what that disruption looks like and when it happens.
Rates of NAFLD have been rising globally in recent years, and the disease is expected to affect 30% of all adults in the US by 2030, according to a 2018 study published in the journal Hepatology. By then, scientists predict that NAFLD will become the leading reason for liver transplants, Insider previously reported.
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