“Forever chemicals” are in our drinking water sources, sea foam and spray, rain and groundwater, sea ice, and even human blood – so now efforts are increasing to detect, remove and destroy them. With increasing evidence linking per- and polyfluoroalkyl substances (PFAS) with cancers, birth defects and negative effects on the immune systems of humans and animals, pressure is growing to restrict these handy waterproofing chemicals that are in everything from Teflon pans and medical devices to cosmetics and pizza boxes. According to Nijhuis Saur industries, which has built more than 80 technologies to treat forever chemicals such as the banned or restricted PFOS, PFOA and PFHxS, these PFAS are difficult and expensive to remove and destroy. “They are called the forever chemicals, because they cannot be removed easily, they don’t break down very easily, so they will persist forever,” said Wilbert Menkveld, chief technology officer, at the Aquatech Amsterdam conference. “And we are talking about very small concentrations: one nanogram per litre is like one glass of cola in a million tankers.” Even when they have been banned, it is hard to get rid of their lingering traces: water cleanups must deal with different concentrations of pollutants and national limits. In the UK, there is a guideline of 100 nanograms per litre for individual PFAS in drinking water, while in EU countries such as the Netherlands, the public health institute RIVM advises a maximum of 4.4ng/l. Similar limits have been proposed for six of the chemicals this year by the United States Environmental Protection Agency in a “toxicity index”. While the EU is working on a broader ban on the chemicals, many are already in the environment. There were no limits for wastewater, said Menkveld. Dr David Megson, a senior lecturer in chemistry and environmental forensics at Manchester Metropolitan University, said some pollutants were not even being tested for, there was no standard testing protocol for many compounds, and legislation was lagging. “There is no consistency in approach, especially on a global level,” he said. “The US have committed to doing a studies and testing, within Europe there’s a lot going on – in Sweden in particular – and five years ago in the UK we were really behind the ball. People are doing more routine monitoring, but the number of PFAS we need to be worried about has gone from two, to 17, to 47 and now we could have 14,000. By the time a two-year monitoring programme has been performed, it’s almost obsolete.” According to journalists and academics contributing to the Forever Pollution Project, there are 20 manufacturing facilities and more than 2,100 sites in Europe that “can be considered PFAS hotspots”. Last year, Chemours, DuPont and Corteva agreed to pay $1.185bn to settle liability claims from American public water systems over PFAS contamination. The chemical company 3M has agreed to settle similar lawsuits in America, while the government of Flanders and 3M announced a €571m remediation agreement last year, and the Dutch government wants to hold the firm liable for pollution linked to a Westerschelde factory. But even with the cash, cleanups are complex. The type of treatment currently being used depends on whether the pollutants are short- or long-chain chemicals, as well as their combination and whether the aim is to separate them from the water or also to destroy them. “The longer the chain is, the better it absorbs; short chains are quite hard to reach, so you need a very selective [technology],” said Menkveld. “You can concentrate PFAS, but you have to have a destruction technology at the end.” The most feasible and developed technologies, according to a review he cited by Blue Tech Research in March, include nanofiltration or reverse osmosis, using a special membrane to separate out larger particles from drinking water. Granular activated carbon filtration is another method – although you need to treat the carbon before it can be reused, put in landfill or destroyed – and there are also pricier ion exchange resins to separate and concentrate out the pollutant. Conventional treatments such as coagulation – adding another chemical to help purify the water – remove only limited amounts, but advanced coagulation using a reactor can do more, leaving PFAS in a sludge. The options to destroy this concentrated waste include low-energy electrochemical oxidation, supercritical water oxidation – which requires high temperature, pressure and specialist operators – and expensive, high-temperature incineration at more than 1,400C. “You need to have different solutions each and every time,” said Menkveld. Scientists are working on more techniques. Dr Madeleine Bussemaker, a senior lecturer in chemical engineering at the University of Surrey, wants to start a first commercial pilot for an ultrasound method, sonolysis, that can completely degrade the strong carbon-fluorine bonds of PFAS into relatively harmless carbon dioxide and fluoride. “We have seen that ultrasound works with other organics or different cell concentrations: the next step is going to the bigger scale and employing it in real life,” she said. “An American study has shown hydrofluorocarbons around the incineration location: you don’t want to create another pollution stream that you have to deal with later. Sonolysis breaks down those bonds using sound waves.” But experts are calling for more work globally. In the UK, bodies such as the Royal Society of Chemistry have urged more action, while the Health and Safety Executive issued new recommendations in April. In Europe, the implementation of a new drinking water directive and a proposed PFAS ban are looming. “Funding, legislation and awareness all go hand in hand,” said Bussemaker. “One of the most alarming things for me is that in order to find a blood sample that does not have PFAS in it, one study had to get blood from [1948-1951 American] Korean war soldiers … it’s not going to go away on its own.”