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At last, good news about PFAS 'forever chemicals' removal

Published: Thursday, August 18, 2022 - 1:29pm
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In June, the U.S. Environmental Protection Agency issued four health advisories for PFAS in drinking water, and Arizona officials found alarming levels of the pervasive toxins in a Prescott restaurant's water supply.

Now, new research published in the journal Science offers hope for taking the "forever" out of these "forever chemicals."

Lead author Brittany Trang of Northwestern University performed the experiments as part of her dissertation research. She said it required doing the opposite of what most of her colleagues do.

"Most synthetic organic chemists are taking two molecules and squishing them together to make one big molecule — like taking two Legos and putting them together to make one thing that is larger. But instead, what we are doing is kind of smashing the Lego to bits and looking at what was left to figure out how it fell apart," she said.

Per- and polyfluoroalkyl substances, or PFAS, are held together by the strongest bond in organic chemistry. But they have an Achilles' heel — a charged end which, like a hair tie taken off a braid, allows the chemical to unravel.

That means readily available chemicals and relatively low temperatures can break down the largest group of PFAS — perfluorocarboxylic acids (PFCAs) — into harmless substances.

PFCAs include PFOA (perfluorooctanoic acid, used in textiles, firefighting foam and sealants), PFBA (perfluorobutanoic acid, used in stain-resistant fabrics, paper food packaging and carpets) and the common pollutant GenX (HFPO-DA, used in cabling, nonstick cookware and cell phones), which was originally intended as a replacement for PFOA when that chemical came under scrutiny.

"The fundamental knowledge of how these materials degrade is probably the single most important thing coming out of this study," said senior author William Dichtel of Northwestern University's Department of Chemistry.

That knowledge provides a roadmap to guide future PFAS research and cleanup efforts.

But understanding the chemistry at work required quantum mechanics and a whole lot of computer processing power.

"Experimentally, you can take A and end up with B. But how does that happen? Is it one step? Is it two steps? Or, as we found, is it, like, 50 steps?" said co-author Ken Houk of UCLA's Department of Chemistry and Biochemistry.

PFAS entered the world of manufacturing in the 1940s and quickly rose to popularity in a variety of products for their nonstick, water-resistant and firefighting capabilities.

Their tendency to stay stable for thousands of years and accumulate in ecosystems have earned them the nickname "forever chemicals."

Unfortunately, studies link even small amounts of PFAS to numerous adverse health effects, including thyroid disease, liver damage and several cancers.

Worse, PFAS turn up all over the world in soil, water, air, animals and crops. A report by the Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey found PFAS in the blood of 97% of Americans.

Experts have seen some success removing PFAS from water, which then raises the question of what to do with it afterward. Storing PFAS in landfills ultimately leads to it leaching into soil and groundwater. Burning can release it into the air.

Previous efforts to break down PFAS required high pressures and temperatures — around 800 Fahrenheit — and left behind a toxic byproduct that itself required disposal.

The new method heats the PFAS to less than 250 F in ambient pressure. It uses the solvent dimethyl sulfoxide and a common regent, sodium hydroxide, and leaves behind only fluoride ions and small carbon-containing products, many of which occur in nature.

Science Sustainability Water