A simple mix of soap and solvent could help destroy 'eternal chemicals'

There is finally hope for a simple and inexpensive way to destroy a class of ubiquitous environmental toxins found in shampoos, fast food wrappers and fire fighting foams. A common ingredient in soap, mixed with water and an organic solvent, readily degrades per- and polyfluoroalkyl substances (PFAS), commonly referred to as "eternal chemicals" because they can remain in the environment for decades. according to a new study. The blend doesn't work on all PFAS compounds, but related approaches could offer communities an inexpensive way to rid soils and drinking water of contaminants that currently put millions of people at risk of cancer and other diseases.

"It's encouraging and promising," says Tasha Stoiber, an environmental chemist with the Environmental Working Group, a US-based nonprofit that tracks the issue closely. Current methods for collecting and processing PFAS compounds exist, she says. "But it's incredibly expensive."

PFAS contain chains of carbon atoms attached to fluorine atoms, which bind together so tightly that it is almost impossible to separate them. The compounds repel oil and water and can withstand friction and high temperatures, making them very popular in industry. They accumulate in soils, water supplies and even in living tissue. In the United States alone, there are nearly 3,000 PFAS contaminated sites, from landfills to rivers and groundwater supplies. Numerous studies have shown that they are toxic in trace amounts. Compounds have been implicated in kidney and liver cancer, thyroid disease, decreased immune response, and infant and fetal growth problems.

Communities around the world have tried to filter out these chemicals or destroy them. Simply filtering them doesn't solve the problem, Stoiber notes, because if they're landfilled, the chemicals can then leak out. And current techniques for destroying PFAS, such as incineration, can require large amounts of energy, very high temperatures, and millions of dollars.

Two years ago, researchers at the U.S. Environmental Protection Agency came across a better approach. When they put a PFAS compound in a common solvent called DMSO as part of a toxicity study, the PFAS compound began to degrade.

The new study builds on that work. Researchers led by William Dichtel and Brittany Trang, chemists at Northwestern University, studied many recipes involving DMSO. A little solvent was combined with sodium hydroxide, a common component of soap, in water. When the team heated the mixture to boiling temperature, it readily degraded one of the largest subsets of PFAS compounds.

The PFAS compounds in question, used in fire-fighting foams and the production of non-stick coatings, contain a chemical group called carboxylic acid, a small group of carbon, oxygen and hydrogen atoms. Computer calculations by colleagues at the University of California, Los Angeles revealed that DMSO removes the carboxylic acid group. "Once that happens, the entire molecule collapses in a cascade of reactions," says Dichtel.

What's left, Trang says, is mostly easily captured fluorine ions and a mixture of harmless, natural byproducts containing carbon and oxygen, his team reports today in Science.< /p>

About 40% of PFAS compounds contain carboxylic acid groups and could therefore potentially be degraded by the new approach, Trang says. Although it has not yet been field tested, she adds that the most likely strategy would be to use conventional means to filter the PFAS chemicals, for example from drinking water, and then treat them outside. website.

However, the method does not work on all types of PFAS. Compounds used in flame retardants and batteries, for example, contain a sulfonate group instead of a carboxylic acid group and do not break down with this approach. Still, the new work, says Stoiber, offers hope that other researchers will be able to find sweet recipes to also rip those chemicals away forever.