New research has reported a link between elevated blood levels of perfluooctane sulfate (PFOS) and increased risk of liver cancer. The study is the first to directly associate exposure from this “forever chemical” to liver cancer in humans.
There are thousands of different chemicals under the umbrella of per- and polyfluoroalkyl substances, or PFAS. These substances are often informally referred to as “forever chemicals” because they can persist in the environment for decades.
For much of the 20th century PFAS chemicals were used in a broad variety of manufacturing contexts. However, over the past 20 years an increasing body of evidence has revealed exposure to PFAS can contribute to a number of deleterious health effects, from low birth weight to hypothyroidism.
Following on from animal and lab-based studies suggesting PFAS exposure is potentially damaging to liver cells, this new research offers the first robust investigation into the relationship between the chemicals and liver cancer in humans.
The power of this new research is in its leveraging of data from a multi-decade health study following more than 200,000 people since the early 1990s. This allowed the researchers to look at historic blood levels of PFAS in subjects years before they presented with cancer.
“Part of the reason there has been few human studies is because you need the right samples,” explained Veronica Wendy Setiawan, an author on the new study. “When you are looking at an environmental exposure, you need samples from well before a diagnosis because it takes time for cancer to develop.”
Several types of PFAS were found in blood samples from subjects who ultimately went on to develop liver cancer. But one particular chemical stood out, perfluooctane sulfate (also known as PFOS). Those subjects with the highest blood levels of PFOS were 4.5 times more likely to develop liver cancer compared to the group with the lowest PFOS blood levels.
The study also homed in on some potential mechanisms by which PFOS exposure could be causing liver cancer. Four particular metabolites were found to link PFOS levels with liver cancer: “glucose, butyric acid (a short chain fatty acid), α-Ketoisovaleric acid (a branched-chain α-keto acid), and 7α-Hydroxy-3-oxo-4-cholestenoate (a bile acid).”
“We believe our work is providing important insights into the long-term health effects that these chemicals have on human health, especially with respect to how they can damage normal liver function,” explained lead researcher on the project Leda Chatzi. “This study fills an important gap in our understanding of the true consequences of exposure to these chemicals.”
The new findings come just days after another study found levels of PFAS in rainwater often exceed new safety limits set by the Environmental Protection Authority (EPA). That research called for a global phase-out of PFAS from all manufacturing contexts as soon as possible. An expert committee formed by the United Nations to review persistent pollutants in 2019 also called for the elimination of all use of PFAS chemicals to, “protect human health and the environment from its harmful impacts.”
The new study was published in the journal JHEP Reports.
Source: Keck School of Medicine
