“Forever chemicals” are an increasing threat to the future of human life on earth. These chemicals are synthetic, manufactured, and are extremely difficult to get rid of. They affect our well-being, and that of the natural world. Scientists are working on ways to try and clean them up.

     There are more than 9,000 different types of synthetic per- and poly-fluoroalkyl substances (PFAS). They are used to make everything from fire-fighting foam to the non-stick coating on cooking pans (see the picture above). Nicknamed “forever chemicals”, PFAS’s are persistent and ubiquitous: They have been found in rainwater, drinking water, soilwildlife, and humans.

     A recent UK and Europe-wide investigation, led by Le Monde, and Watershed Investigations, identified over 2,100 “hotspots” thought to be contaminated with levels of PFAS hazardous to health; hazardous is defined as more than 100 nanograms per litre. An example is perfluorooctanoic acid, which is classified by the International Agency for Research on Cancer (IARC) as a possible carcinogen. Certain other compounds have been banned internationally through the Stockholm Convention on Persistent Organic Pollutants. However, with so many “forever chemicals” already in the environment, efforts to clean them up do not come easily, or cheaply. A recent report from ChemSec, a Sweden-based non-profit that advocates for safer chemicals, found that the global societal costs – including remediation – of PFAS chemicals amount to €16tn ($17tn/£13.8tn) per year.

     “I think all of this is fixable. It’s just a matter of cost,” says Ian Cousins, a professor of environmental chemistry at Stockholm University. “There are treatment technologies that work for legacy PFAS’s. You can, in principle, clean up a very contaminated site – if you have all the money in the world. But where’s the money going to come from? We need technologies that are low cost, and low energy.”

     PFAS’s in water could be cleaned up with filters. They work but, because PFAS’s include such a diverse group of chemical compounds, making filters that can remove them all is a huge challenge, says Andrew Knight, a chemist at US government-funded Sandia National Laboratories. He is working with a team of chemists and material scientists to design a filtration system able to capture a wide range of PFAS’s.

     Then there is the question of waste. If PFAS’s can be successfully filtered out of the water, you are left with waste material containing a high concentration of PFAS’s. “Enabling some sort of degradation would be critical,” says Knight who notes that any new filtration economy needs to allow for customers to send contaminated filters away for proper disposal. Usually, says Knight, any remaining concentrate goes to landfill or energy-intensive incineration. Many PFAS’s are designed to be thermally stable and heat resistant – Teflon can withstand temperatures of up to 260C (500F) – and Knight explains that the burning of longer-chain PFAS’s releases short-chain PFAS’s into the air that could be more mobile and move through soil, into groundwater and through water systems – ending up right back in drinking water. There are energy efficient ways to use filters but, at the moment, there aren’t any energy efficient ways to destroy PFAS’s. There’s no magical solution, right now.

     Electrochemical and photochemical techniques have been used by scientists at the University of British Columbia to “zap” PFAS’s that’s been trapped onto a reusable silica-based material. While another team at the University of California, Riverside, are using “deep UV” – extremely low wavelengths (below 220nm) of ultraviolet light – to break PFAS down under ambient conditions without producing secondary waste.

     Soil remediation is necessary at heavily contaminated sites. One strategy is to pump activated carbon into the soil that binds PFAS’s in situ to prevent leaks into groundwater – this has been done in Australia, for example, but there are no long-term studies of this technique yet. Another option is to dig out contaminated soil and clean it, using different washing methods, but the remaining water still has to be purified, either with filters or UV radiation.

     Some academics are looking to nature for inspiration – and microbes could offer a biological solution. At Princetown University in 2019, researchers found that Acidimicrobium bacterium A6 removed 60% of PFAS’s in lab vials over 100 days of observation. However, the Princetown study hasn’t been replicated, so more research is required. 

     While some remediation technologies look promising, they shouldn’t be an excuse to keep producing PFAS. That will need government intervention if we are ever to catch up with the problem we have created. We have to do something about the currently existing problem of PFAS’s, but the overall solution is to stop their production and use, as far as possible.             One thought that might motivate us to increase our efforts in this direction is that some PFAS’s have been shown to affect the ability to reproduce, in all species, including us.

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