From Greenland to West Virginia, cancer cases have been linked to exposure to the group of chemicals known as PFAS.
Now, a new study is going one step further to try to explain how some of these PFAS compounds, a family of thousands of synthetic chemicals that have been used for decades in everything from food packaging to nonstick cookware, might cause cancer on a molecular level.
PFAS, short for “per- and polyfluoroalkyl substances,” are known for building up in the body and persisting in the environment, giving them the nickname “forever chemicals.” They’ve caused widespread alarm after turning up in the drinking water of dozens of cities in the US, in some food items, in soil, and in people: In 2015, the National Health and Nutrition Examination Survey found PFAS in the blood of 97% of Americans. Last week, the EPA disclosed it “has multiple criminal investigations underway concerning PFAS-related pollution.”
Some of these chemicals have been associated with health effects like altered metabolism and fertility, birth defects, obesity, diabetes — and cancer. Elevated body levels of the chemical PFOA, one type of PFAS chemical, were associated with a greater risk of non-Hodgkin’s lymphoma and kidney, testicular, prostate, and ovarian cancers, according to a massive study of 70,000 people living in the Mid-Ohio Valley. The drinking water there was contaminated with PFOA, which the chemical company DuPont used to make Teflon, as dramatized in the 2019 film Dark Waters.
Other studies have found links between PFAS chemicals and breast and liver cancers.
Still, those links don’t necessarily mean that PFAS chemicals cause the diseases they’re associated with. Public health organizations have stopped short of labeling the chemicals as clear carcinogens.
The new study, published Wednesday, tried to establish possible mechanisms underlying those links. Researchers summarized the existing evidence about PFAS chemicals that can act like established cancer-causing chemicals. The mechanisms include different ways the compounds disrupt biological activity, such as by changing DNA, weakening the immune system, inducing chronic inflammation, causing cells to proliferate, or altering normal communication between cells.
The researchers looked for evidence of 10 such carcinogenic traits in animal, cell, and human studies of roughly two dozen PFAS chemicals. “We found that every single one of them exhibited at least one of the key characteristics” of carcinogens, said toxicologist Alexis Temkin of the advocacy group Environmental Working Group, which conducted the study with researchers from Indiana University. It was published in the International Journal of Environmental Research and Public Health.
For chemicals that have been around for decades — like DuPont’s PFOA and PFOS, which used to be in 3M’s Scotchgard stain repellent — there is a stronger body of research linking them to diseases like non-Hodgkin’s lymphoma and breast and kidney cancer. The new study found that PFOA and PFOS had up to five characteristics of carcinogens each.
That connection is backed up by other scientific agencies: The International Agency for Research on Cancer classifies PFOA as a possible human carcinogen, and the EPA says PFOA and PFOS may be linked to cancer.
In contrast, less research has been done on some of the other chemicals in this family, particularly those that have replaced PFOA and PFOS since DuPont and 3M began phasing them out more than a decade ago (both chemicals are no longer made in the US). Whereas the older chemicals had longer chains of fluorinated carbons, these newer ones have shorter chains, which the chemical companies claim makes them safer for health and the environment.
Some of these newer chemicals do not have enough data behind them yet to indicate if they cause cancer, while others do have early evidence of carcinogenic-like behavior, the new paper reported.
In animal studies, GenX, a PFOA replacement in Teflon that was introduced by DuPont in 2009, has been found to affect hormone activity.
“Some of the replacement chemicals are not necessarily safer alternatives, and so the best thing to do is really to prevent exposure,” Temkin said.
Jamie DeWitt, an associate professor of pharmacology and toxicology at East Carolina University who was not involved in the study, noted that lots of compounds can have characteristics in common with carcinogens without actually causing cancer. “But the more they exhibit, the greater the likelihood they can or could cause cancer,” she told BuzzFeed News.
“There’s the potential for cancer, not just from one compound but from several,” she added.
David Savitz, an epidemiologist at Brown University who helped lead the study of people who lived near the DuPont facility in West Virginia, said that the findings added more weight to previous studies that have found PFAS chemicals are likely to be carcinogenic. “These efforts to bring the toxicology and epidemiology evidence together are important and needed to fully appreciate the public health significance of PFAS exposure,” he said by email.
This story has been updated to reflect that the journal published the study on Wednesday. A link to the study has been added.