A woman and her dog walk past a partially flooded street on Sept. 26, 2023, in Ocean Springs, Miss. Ricky Carioti/The Washington Post file

For years, scientists have worried about “forever chemicals,” substances used to make hundreds of household items that have been linked by research to a wide range of health problems. In response, a growing number of companies have pledged not to use the chemicals, and regulators have increasingly taken aim at them.

But even as work continues to phase out the substances, scientists are beginning to focus on new types that are far more widespread than earlier realized – prompting worries about undetected health risks.

A growing body of research has raised concerns about a forever chemical known as TFA, which is short for trifluoroacetic acid and has been found in increasing amounts in rainwater, groundwater and drinking water.

The chemical has a composition that scientists say may make it especially hard to filter, although scientists lack consensus on whether it poses a human health risk.

“The situation is that we have TFA in all the drinking water. You are drinking it right now. Everyone’s drinking it,” said David Behringer, an environmental consultant who works extensively with refrigerants and propellants in Germany.

Recently released research by the Pesticide Action Network Europe, an organization that advocates against the use of pesticides, found strikingly high levels of TFA contamination in 23 surface and six groundwater samples from 10 European Union countries. The researchers found that the TFA levels were 70 times higher than those of other, better-known forever chemicals in the water.

Forever chemicals, also known as PFAS or per- and polyfluoroalkyl substances, are a class of compounds companies developed to give different products their resistant and repellent properties. They earned the nickname “forever chemicals” because of their extreme durability: They take years to break down in nature. The persistent chemicals are found in hundreds of household items – including nonstick cookware, fast-food wrappers and dental floss – and are used to make products and coatings that repel grease, water, oil and heat.

TFA comes from a variety of products, but its prevalence is growing in large part because of its use in modern refrigerators and heating and cooling systems – an unintended side effect of efforts to make these appliances more climate-friendly. And because it has a simpler molecular structure than other PFAS, it may be harder to detect and filter.

“A bigger chunky molecule, obviously it’s easier to filter out, but the very short ones, it’s just going to slip through,” Behringer said. “It takes a lot of effort to get TFA out of the water.”

WHERE ARE CONCENTRATIONS OF TFA FOUND?

Growing levels of these compounds have been found across the globe, according to experts, though scientists in countries including Germany and Belgium have been leading recent research into its concentrations.

But where are they coming from? Refrigerants and foam-blowing agents used in air conditioning, aerosol sprays and heat pumps account for most of the TFA entering the atmosphere, Behringer said, while many pesticides, which are directly deposited into the ground, degrade into TFA.

Some hydrofluoroolefins refrigerants, also known as HFOs – like those prevalent in European passenger car air conditioners – fully degrade into TFA, Behringer said.

Products that could degrade into TFA include dyes, pharmaceuticals and cosmetic foaming items. There are chemicals in some pharmaceuticals, used to ensure medicine doesn’t break down before reaching its intended destination, that breaks down into TFA, said Katie Pelch, an environmental health scientist at the Natural Resources Defense Council, an advocacy group.

In medicines, fluorine and other halogens are added to make the chemical a bit more stable “so that the digestive system doesn’t tear it up before it gets to where it needs to be in your body,” Pelch said. As some pharmaceuticals that contain fluorine break down, it can enter wastewater as TFA.

WHY ARE CONCENTRATIONS OF TFA SURGING?

Ironically, an effort to phase out compounds that warm the planet and thin the ozone layer has fueled TFA concentrations.

The Montreal Protocol, an international treaty adopted in 1987, phased out the production of chlorofluorocarbons, or CFCs, which depleted the ozone layer. But the more ozone-friendly gases that followed, hydrofluorocarbons (HFCs), are potent greenhouse gases that warm the planet.

The most recent climate-friendly alternatives to HFCs for cooling air conditioners, heat pumps and refrigerators, HFOs, do not deplete ozone and have a lower global warming potential, but some break down into TFA.

Emily Best, a program manager at the Environmental Coalition on Standards, an international nongovernmental organization in Brussels, said the Montreal Protocol solved one problem but created another. As HFOs degrade and are converted to TFA in the atmosphere, they return to the surface through rain and other precipitation or dust, Behringer said.

“We strongly assume that whatever rains down as TFA stems from emissions into the air, and that’s usually only refrigerants and foam-blowing agents,” Behringer said.

Recent studies found abundant TFA concentrations in indoor and outdoor dust, freshwater invertebrates, precipitation, and drinking water. A recent rainwater test conducted by the Ecology Center in Michigan, an environmental advocacy organization, and community partners from Detroit, Dearborn and Ann Arbor, Mich., found PFAS in each sample, with TFA levels contributing the most to total PFAS concentrations at each site.

Filtering TFA from the environment could pose an extra challenge because the compound’s small size allows it to spread farther and faster, Pelch said.

Overall, Pelch said, TFA is “not being widely monitored and there are no regulations in the U.S.”

WHAT DO EXPERTS KNOW ABOUT POTENTIAL HARMS?

PFAS in general have been linked to several kinds of cancer; infertility; high cholesterol; low birth weights; and negative effects on the liver, thyroid and immune system. By contrast, there is limited information about the impact of TFA on human health.

Scientists are still working to determine whether TFA accumulates in the body. Some reports suggest that TFA’s ability to bind to protein in the body could help it accumulate in the blood. Meanwhile, other experts have said the chemicals that degrade into TFA clear the body quickly.

The Environmental Protection Agency does not currently regulate TFA. In an email, EPA spokesperson Remmington Belford said officials are “prepared to proactively manage emergent risks” and conduct scientific research on TFA. The agency pointed to a 2022 report by the United Nations that described its potential impacts, which said that increasing TFA concentrations are “not expected to pose a significant risk to humans or the environment at present.”

There have been some efforts to address TFA. In Germany, for example, the Federal Office for Chemicals proposed listing it as a reproductive toxicant under the U.N. Globally Harmonized System of Classification and Labeling of Chemicals, which would mean it could be internationally recognized for its potential harm. If it were listed, the European Chemicals Agency (ECHA) would provide guidelines about how to classify and communicate the chemical’s impact on human health and the environment.

The ECHA, which oversees the safe use of chemicals in the E.U., classified TFA as a substance that causes severe skin burns and eye damage and is harmful to aquatic life with long-lasting effects. A report by the Health and Safety Executive in Britain identified it as having “a potential concern for developmental toxicity.” The report cites a study that found TFA and other chemicals might cause rare abnormalities in rabbit offspring.

Pelch worries that chronic exposure to TFA could lead to health risks.

“If you’re still getting exposed every single day through your drinking water or through your air, or through the products that you use, there’s still a really good chance that your exposure is building up and accumulating in your body,” Pelch said.