Synthetic compounds known as "forever chemicals" because they never break down in the environment can actually be destroyed — by beheading.
Scientists discovered a simple destruction technique that works on 10 types of these chemicals, known as per- and polyfluoroalkyl substances (PFAS). Researchers hope that the method will expose weaknesses in even more PFAS-class substances, leading to paths for removing these chemicals from drinking water easily and cheaply.
The researchers published their findings in the journal Science on Aug. 18.
Forever chemicals, everywhere
PFAS compounds are found in a huge variety of products: from food packaging to shampoos to non-stick cookware and electronics. The chemicals consist of a head, often containing charged oxygen molecules, and a tail of carbon and fluorine atoms, which are joined by a bond that nothing in nature can break. As a result, PFAS compounds persist in low levels in soil, air, water and even human blood samples, according to the Environmental Protection Agency (EPA). Researchers are still working to understand the health effects of PFAS exposure, but the chemicals may interfere with the body's hormones, raise cholesterol levels, affect fertility and increase the risk of certain cancers, according to the EPA.
Related: What are PFAS?
PFAS chemicals pass through water treatment plants unaltered, and current clean-up methods are prohibitively expensive, Tasha Stoiber, an environmental chemist at the Environmental Working Group, a nonprofit organization that tracks environmental contamination, told Science. Stoiber was not involved in the new study. Filtering them and sticking PFAS chemicals in landfills just raises the risk that they'll leach out later, and other clean-up methods often produce harmful byproducts that require complicated steps to break down.
Chemists at the University of California, Los Angeles and Northwestern University took a simpler approach — targeting the molecules' heads with a chemical guillotine. Charged oxygen molecules are reactive with other chemicals, so Northwestern University chemist William Dichtel and doctoral student Brittany Trang decided to go after this weak spot.
The researchers used a common solvent, dimethyl sulfoxide (DMSO), because previous EPA research had hinted that PFAS slowly degrades when exposed to DMSO. Testing different recipes at different temperatures, Dichtel and his colleagues discovered that the fastest way to take PFAS down was to heat the "forever chemical" to boiling along with DMSO and lye, or sodium hydroxide — a common chemical found in many types of soap.
"That triggered all these reactions, and it started spitting out fluorine atoms from these compounds to form fluoride, which is the safest form of fluorine," Dichtel said in a statement. "Although carbon-fluorine bonds are super-strong, that charged head group is the Achilles' heel."
Cleaning up the water
Fluoride is safe for humans in small amounts and is often added to drinking water to help prevent tooth decay. The other byproducts of the reaction are carbon dioxide and formic acid, which is a chemical used for defense by some species of ants and is low in toxicity — the acid is even sometimes added to animal feed to reduce bacterial growth without harming livestock.
Because the new method doesn’t produce harmful chemicals, it could be used to clean drinking water, Trang told Science. PFAS compounds could be filtered away and then beheaded separately, leaving behind only harmless chemicals to dispose of.
The method can clean up any PFAS compounds containing oxygen-rich carboxylic acid heads, the researchers found. That doesn't cover all classes of PFAS, but Dichtel and his colleagues are hopeful that their method might inspire new means of attacking more resistant PFAS chemicals.
Originally published on Live Science.
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.