How to Destroy a “Chemical Forever” PFAS
Scientists Discover Ways to Eliminate Perfluoroalkyl and Polyfluoroalkyl Substances, But This Growing Global Health Problem Isn’t Going Away Anytime Soon
PFAS chemicals seemed like a good idea at first. As Teflon, they made pots easier to clean from the 1940s. They made waterproof jackets and stain-resistant carpets. Food packaging, fire-fighting foam, and even makeup looked better with perfluoroalkyl and polyfluoroalkyl substances.
Then the tests started to detect PFAS in people’s blood.
Today, PFAS are ubiquitous in soil, dust, and drinking water around the world. Studies suggest they are in 98% of American bodieswhere they have been associated with health problems including thyroid disease, liver damage, and kidney and testicular cancer. There is now more than 9,000 types of the PFAS.
They are often called “eternal chemicals” because the same properties that make them so useful also make sure they don’t decompose in the wild.
Scientists are working on methods to capture these man-made chemicals and destroy them, but it’s not straightforward.
The latest breakthroughpublished on August 18, 2022 in the journal Science, shows how a class of PFAS can be broken down into mostly harmless components using sodium hydroxide, or lye, an inexpensive compound used in soap. It is not an immediate solution to this vast problem, but it offers new perspectives.
How do PFAS pass from everyday products into water, soil and possibly humans?
There are two main routes of exposure to PFAS entering humans: drinking water and food consumption.
PFAS can enter the soil through land application of biosolids, i.e. sludge from wastewater treatment, and can leach out of landfills. If contaminated biosolids are applied to agricultural fields as fertilizerPFAS can enter water and crops and vegetables.
For example, livestock can consume PFAS through the crops they eat and the water they drink. There have been cases reported in Michigan, Maine and New Mexico high levels of PFAS in cattle and dairy cows. The magnitude of the potential risk to humans is still largely unknown.
Scientists in our group at Michigan State University are working on materials added to soil that might prevent plants from taking up PFAS, but it would leave PFAS in the soil.
The problem is that these chemicals are everywhere, and there are no natural process in water or soil which decomposes them. Many consumer products are laden with PFAS, including makeup, dental floss, guitar strings, and ski wax.
How do remediation projects eliminate PFAS contamination now?
Methods exist to filter them out of the water. Chemicals will stick to activated carbon, for example. But these methods are expensive for large-scale projects and the chemicals still need to be disposed of.
For example, near an old military base near Sacramento, California, there is a huge reservoir of activated carbon that absorbs approximately 1,500 gallons of contaminated groundwater per minute, filters it and then pumps it underground. This sanitation project cost over $3 millionbut it prevents PFAS from spreading into the drinking water used by the community.
Filtering is just one step. Once the PFAS is captured, you have to get rid of the PFAS-laden activated carbons, and the PFAS is still moving. If you bury contaminated materials in a landfill or elsewhere, the PFAS will eventually leach out. That is why it is essential to find ways to destroy it.
What are the most promising methods scientists have found to break down PFAS?
The most common method of destroying PFAS is incineration, but most PFAS are remarkably resistant to combustion. This is why they are in fire fighting foams.
PFAS have several fluorine atoms attached to a carbon atom, and the bond between carbon and fluorine is one of the strongest. Normally to burn something you have to break the bond, but fluorine resists the breaking of carbon.
Most PFAS will completely decompose at incineration temperatures of approximately 1,500 degrees Celsius (2,730 degrees Fahrenheit), but it uses a lot of energy and suitable incinerators are rare.
There are several other experimental techniques that show promise, but have not been scaled up to handle large amounts of chemicals.
A group in Battelle has developed supercritical water oxidation to destroy PFAS. High temperatures and pressures change the state of water, accelerating chemistry in ways that can destroy hazardous substances. However, scaling remains a challenge.
The method described in the new paper, led by Northwestern scientists, shows promise for what they’ve learned about how to break down PFAS. It will not go through industrial processing and it uses dimethyl sulfoxideor DMSO, but these results will guide future discoveries about what might work.
What are we likely to see in the future?
Much will depend on what we learn about the main source of human exposure to PFAS.
If exposure is primarily from drinking water, there are other potential methods. It is possible that it will eventually be destroyed at the household level with electrochemical methods, but there are also potential risks to be understood, such as the conversion of common substances such as chloride into more toxic by-products.
The big challenge in sanitation is to make sure we don’t make the problem worse by releasing other gases or creating harmful chemicals. Humans have a long history of trying to solve problems and make things worse. Refrigerators are a prime example.
Freon, a chlorofluorocarbon, was the solution to replace toxic and flammable ammonia in refrigerators, but it caused stratospheric ozone depletion. It has been replaced by hydrofluorocarbons, which contribute to climate change.
If there’s a lesson to be learned, it’s that we need to think about the full life cycle of products. How long do we really need chemicals to last?
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