For those who don’t know, PFAS are a category of so-called Forever Chemicals:
- They can be found in many everyday products – outdoor clothing and equipment, textiles, paints, food packaging, photographic coatings, non-stick coatings on cookware as well as fire-fighting foam.
- They can have harmful effects on human and animal health and stay in the environment and in our bodies for long periods of time where they can increase in concentration. They are often referred to as “forever chemicals”.
- Some PFAS have been linked to an increased risk of cancer, high cholesterol, reproductive disorders, hormonal disruption (also known as endocrine disruption) and weakening of the immune system.
- Human and environmental exposure to PFAS can arise from contaminated water and food, PFAS-containing consumer products, household dust and air as well as the reuse of PFAS contaminated sewage sludge as fertiliser resulting in PFAS pollution in soil and crops.
The most recent headline that drew attention was the fact that even the rain is contaminated with this shit.
This is one of the many forms of cleanup we need to do, if we want to take our reliance on nature, not to mention public health, seriously. As with plastic (which is now eaten by several kinds of bacteria), there’s been a fear that these PFAS will continue building up indefinitely, bringing new, and potentially devastating health problems to all life on Earth. That’s still a valid concern, in my opinion, but now researchers at UCLA and Northwestern have developed a method to break down at least some of these chemicals.
Northwestern chemistry professor William Dichtel and doctoral student Brittany Trang noticed that while PFAS molecules contain a long “tail” of stubborn carbon-fluorine bonds, their “head” group often contains charged oxygen atoms, which react strongly with other molecules. Dichtel’s team built a chemical guillotine by heating the PFAS in water with dimethyl sulfoxide, also known as DMSO, and sodium hydroxide, or lye, which lopped off the head and left behind an exposed, reactive tail.
“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. “Although carbon-fluorine bonds are super-strong, that charged head group is the Achilles’ heel.”
But the experiments revealed another surprise: The molecules didn’t seem to be falling apart the way conventional wisdom said they should.
To solve this mystery, Dichtel and Trang shared their data with collaborators Houk and Tianjin University student Yuli Li, who was working in Houk’s group remotely from China during the pandemic. The researchers had expected the PFAS molecules would disintegrate one carbon atom at a time, but Li and Houk ran computer simulations that showed two or three carbon molecules peeled off the molecules simultaneously, just as Dichtel and Tang had observed experimentally.
The simulations also showed the only byproducts should be fluoride — often added to drinking water to prevent tooth decay — carbon dioxide and formic acid, which is not harmful. Dichtel and Trang confirmed these predicted byproducts in further experiments.
“This proved to be a very complex set of calculations that challenged the most modern quantum mechanical methods and fastest computers available to us,” Houk said. “Quantum mechanics is the mathematical method that simulates all of chemistry, but only in the last decade have we been able to take on large mechanistic problems like this, evaluating all the possibilities and determining which one can happen at the observed rate.”
Li, Houk said, has mastered these computational methods, and he worked long distance with Trang to solve the fundamental but practically significant problem.
The current work degraded 10 types of perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl ether carboxylic acids (PFECAs), including perfluorooctanoic acid (PFOA). The researchers believe their method will work for most PFAS that contain carboxylic acids and hope it will help identify weak spots in other classes of PFAS. They hope these encouraging results will lead to further research that tests methods for eradicating the thousands of other types of PFAS.
This is good news. As with plastic pollution, having the means to destroy these chemicals is not a substitute for cutting off the source of the pollution, but every bit of cleanup that we know is possible reinforces the fact that we can make things better. Our vast collective knowledge really does mean that we can change what we do and how we do it. I also like that the ingredients required are ones that should be accessible to any nation on Earth, so it won’t require expensive, high-tech facilities. This seems like something that pretty much any water treatment plant in the world could set up, for a pretty reasonable cost. Just a couple weeks ago, it was looking like we were gonna be stuck with PFAS in our food, water, and bodies. It may be that you and I, dear reader, will never be rid of the stuff, but we’re very close to having the means to stop the buildup, even if we can’t yet force corporations to stop making it. I want to end with a quote from near the beginning of the press release, because I find the potential scalability of this reaction very encouraging:
In a paper published today in the journal Science, the researchers show that in water heated to just 176 to 248 degrees Fahrenheit, common, inexpensive solvents and reagents severed molecular bonds in PFAS that are among the strongest known and initiated a chemical reaction that “gradually nibbled away at the molecule” until it was gone, said UCLA distinguished research professor and co-corresponding author Kendall Houk.
The simple technology, the comparatively low temperatures and the lack of harmful byproducts mean there is no limit to how much water can be processed at once, Houk added. The technology could eventually make it easier for water treatment plants to remove PFAS from drinking water.
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