In 1938, chemist Roy J. Plunkett stumbled across a substance that would change the world forever. He was experimenting with refrigerant gases when he noticed that one compound had transformed into a white, waxy solid. It had extraordinary properties, being impervious to heat and chemical degradation and also extremely slippery.
Today, we know this chemical as Teflon, and produce more than 200,000 tonnes of the stuff every year. It is used in everything from non-stick frying pans to medical catheters. Though undoubtedly useful, Teflon was also the first of a group called perfluoroalkyl and polyfluoroalkyl substances (PFAS), better known as forever chemicals.
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Almost as soon as Teflon was invented, concerns were raised about its potential impacts on the environment and our bodies (it is worth noting, though, that these days, using non-stick cookware is probably safe as the pans are heat-treated and donāt release any nasties unless they are left on a high heat for a long time). Today, the world is finally getting to grips with just how dangerous forever chemicals can be to our health ā and dealing with the problem head on. In January, the US Environmental Protection Agency (EPA) added nine forever chemicals to its list of hazardous constituents. And last month, the US imposed its first ever limits on levels of PFAS in drinking water, in a belated bid to reduce exposure to these ubiquitous chemicals. But what risks do they actually pose and what should we be doing to remove them from our lives? Researchers face a huge challenge in finding the answers, but are starting to make real headway.
What are forever chemicals?
PFAS are a diverse group of about 16,000 artificial chemicals used in a vast array of products. What they all have in common are fluorine atoms attached to carbon atoms. To qualify as one of the PFAS, a molecule must contain at least one āfully fluorinatedā methyl or methylene group ā a carbon atom with all its available bonds occupied by a fluorine.
The name āforever chemicalsā is derived from the fact that they are incredibly stable, immensely heat tolerant, resistant to chemical degradation and also thoroughly repellent to water and oils. This combination of properties makes them useful in all sorts of applications, from non-stick cookware to outdoor clothing, stain-resistant furniture and carpets, food packaging, personal care products, paints, varnishes and firefighting foams.
But it also means that when they inevitably leak into the wild, they hang around for a long, long time ā hundreds or even thousands of years, according to at ETH Zurich in Switzerland. PFAS pollution has been , and outdoor air, and has ā it can cause suppressed immunity and reproductive issues in some animals, even at tiny concentrations.
An estimated 98 per cent of the US population have detectable concentrations of forever chemicals in their blood
These chemicals are also found in , , and . A study last year . Unsurprisingly, they are also present in the human body. āAn estimated 98 per cent of the US population have detectable concentrations of PFAS in their blood,ā says at Johns Hopkins University in Maryland. Not only do we drink them and inhale them, we also eat them in food that has been wrapped in PFAS-containing packaging, grown in PFAS-contaminated soil or caught in PFAS-contaminated water. They are eventually excreted in urine, but only slowly: in the human body, they take between a few months to five years to halve in concentration. Being so ubiquitous, rates of excretion canāt keep up with rates of acquisition, so the older we get, the higher our PFAS load tends to be.
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Being so stable and inert, the prevailing view was that these chemicals couldnāt do much harm. That is no longer the case, says at the Food Packaging Forum in Zurich, a non-profit organisation governed by independent scientists. While human enzymes canāt degrade them, PFAS can interact with biological systems by binding to cell receptors and other proteins and hence disrupt metabolism, she says, and there is ample data that certain , , and more. āThereās increasing evidence that there are toxic effects on a variety of levels,ā says Prasse.
PFAS are already regulated to a degree. Two of the ones about which the most is known ā perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) ā have been included in the Stockholm Convention on Persistent Organic Pollutants, which severely restricts their use. Others are being considered for inclusion, says at the University of New South Wales in Sydney. Many countries have limits on the amount of PFAS allowable in food and drinking water.
But these measures are akin to shutting the stable door after the horse has bolted. In 2022, at Stockholm University in Sweden and his colleagues found that , and that this probably applies to many other PFAS too.
More recent research by OāCarroll found that a . That doesnāt necessarily translate into unsafe drinking water, as many water treatment plants remove some PFAS. But OāCarroll points out that drinking water standards usually cover only a fraction of the 16,000 PFAS that are out there. Canada, for example, has one of the ā no more than 30 nanograms of all PFAS combined per litre ā but only monitors 18 of these chemicals.
Regulating forever chemicals
As a result, the US government recently announced in drinking and waste water. Two powerful US agencies are also stepping up their efforts to phase out PFAS and the EU is attempting to ban them outright.
One major mover and shaker is the EPA, which recently put after studies showed that no level of exposure to PFOS and PFOA is safe. It has also added nine PFAS to its list of hazardous constituents, the first step on a potentially torturous path to designate them as hazardous waste and hence strictly regulate their manufacture, use and disposal. āIt appears the EPA is moving more aggressively to get PFAS out of our environment,ā says , at Verisk, a New Jersey-based company that advises its clients on emerging risks.
To be listed as a hazardous constituent, scientific studies must show that the chemical is toxic, cancer-causing, leads to changes in DNA or causes developmental abnormalities in humans or other animals. āIn the case of PFAS, unfortunately, several of these criteria are met,ā says Prasse.
Are forever chemicals harmful to our health?
The question of what these chemicals actually do to our health is complicated. For ethical reasons, you canāt expose a certain population to PFAS and others to a placebo. Instead, EPA scientists assessed the peer-reviewed literature on PFAS, including data from human epidemiology and animal studies, which together attempt to draw connections between exposure to PFAS and health problems ā for example, by measuring vaccine responses in children versus the levels of certain PFAS in their blood.
Among the nine chemicals that the EPA decided to take action against was PFOA, which was widely used for decades in furniture, clothing and food packaging before its use was restricted globally in 2019 under the Stockholm Convention. The EPA concluded that . They also experience a . Studies on monkeys, rats and mice found similar problems, plus kidney toxicity, liver and pancreatic cancer and congenital conditions. The EPA published similarly detailed reviews of eight other PFAS.
āI think the step that the EPA is taking is in the right direction,ā says Prasse. āBut I think it is important to consider that this can only be the tip of the iceberg, and that thereās much more work needed to deal with this issue.ā
For instance, the big question on everyoneās lips is what level of exposure leads to what harms ā a question that is challenging to answer. It is very hard to say what levels of PFAS are safe, says Prasse. āI would say we want to have as low levels as possible.ā
Another agency on the warpath is the US Food and Drug Administration (FDA). In February, it announced that greaseproof food packaging containing certain PFAS was no longer on sale in the US after the completion of a voluntary phase-out.
What products contain forever chemicals?
Food packaging is a significant source of PFAS in the human body. Earlier this year, Geueke and her colleagues , mostly added to paper, plastic and coated metal as barriers against moisture and grease. It is already well-established that PFAS migrate out of packaging into food and hence into the body, says Geueke.
Inevitably, PFAS manufacturers are pushing back. In 2023, five European nations in the EU and affiliated countries. In response, 13 PFAS producers are mounting a ā¬20-million-a-year lobbying campaign to water down the proposals, according to in Brussels, Belgium.
There are ways to replace PFAS with other chemicals, but whether they are safer is an open question. For instance, one option is to create similar compounds that use chlorine atoms in place of some of the fluorines, but according to at Sapienza University of Rome in Italy, we . Attempts to replace PFAS could lead to cases of āregrettable substitutionā where one toxic chemical is superseded by something worse, says Scoblete.
Replacement wonāt solve the problem of legacy PFAS already in the environment either. There are measures that we can take to reduce our exposure (see āHow to avoid forever chemicalsā, left), but to solve the problem for good, PFAS need to be detected, and, if possible, destroyed.
How to get rid of forever chemicals
Detection of PFAS in environmental samples is improving. The current gold standard method concentrates water samples and then applies gas chromatography and mass spectrometry to identify 18 PFAS at parts-per-trillion levels. The method is āelegant and ultra-sensitiveā, according to at the University of Connecticut, but is also expensive, time consuming, only applicable to water samples and restricted to the lab. āThere is a strong demand for rapid, accessible, low-cost PFAS detection methods,ā says Lei. There has been a and that can also test biological samples including blood, milk, meat and eggs, he says. Such research āpaves the way towards a healthier future for humanityā, says Lei.
PFAS can also be removed. They can be filtered or adsorbed out of water and washed from soil, says at Marquette University in Wisconsin. The problem is, these methods are also expensive and energy intensive. Cleaning up PFAS in drinking water in the US alone would cost trillions of dollars and create a huge carbon footprint, according to Wang. Thankfully, innovation is afoot. Bioremediation ā using living organisms to remove PFAS from the wild ā looks promising, according to at Stockholm University. She and her university colleague have shown that and rapidly reduce their levels in the water. The plants can then be harvested.
New ways of detecting forever chemicals pave the way for a healthier future for humanity
But then what? Dealing with PFAS once they have been collected is another slippery issue. Incineration can destroy them, but is risky as it creates more unknown PFAS and may release them into the environment. Putting them in landfill risks them leaching out all over again.
But various new treatment methods are in the pipeline. Last year, for example, the US military began testing a method to destroy PFAS with superheated water. Nevertheless, most methods require a lot of energy and may produce toxic by-products, says at the University of Illinois Chicago.
Bioremediation may again be our answer. Gregerās experiments with aquatic plants show that some are able to partially degrade PFAS using a process called enzyme-catalysed oxidative humification, though they donāt break the stubborn carbon-fluorine bond. Some bacterial enzymes, however, can. At the University of Minnesota, is working on , and artificially evolving them to be more efficient. āPFAS are not forever,ā says Wackett.
Until that proves true, though, we are going to have to live with the legacy of that serendipitous, slippery discovery in 1938. And so will future generations. āItās doubtful weād be able to remove all PFAS,ā says OāCarroll. āItās pervasive.ā
How to avoid forever chemicals
Human exposure to perfluoroalkyl and polyfluoroalkyl substances (PFAS), also known as forever chemicals, which have been linked to numerous health problems, comes through many routes (see main story). Some are unavoidable if you wear clothes, have furniture or carpets or use consumer household products. But others can be swerved.
Food is a major source of exposure. The two things to be most wary of are greaseproof fast-food packaging ā paper wrappers, pizza boxes, cardboard cartons ā and bags of microwaveable popcorn, says Birgit Geueke at the Food Packaging Forum in Zurich, Switzerland.
Nowadays, the use of non-stick cookware is likely to pose no risk because it is heat-treated in the factory and so doesn't release any PFAS unless left on a high heat for extended periods, says Geueke.
Tap water is another important but mitigable source. Carsten Prasse at Johns Hopkins University in Maryland recommends using certified filters on taps or in water jugs.
Bottled water isn't necessarily the answer, says Denis O'Carroll at the University of New South Wales in Sydney. "It doesn't mean that they've done anything differently than what comes out of the tap."
There is no guarantee that these lifestyle changes will significantly reduce PFAS exposure. "I don't think we know enough to really say which exposure pathway is the most problematic one. I would say at this point all exposures are concerning," says Prasse.
There is, however, hope that PFAS can be scrubbed from the human body. A recent . Cholestyramine works by binding to cholesterol-rich bile acids in the gut and preventing them from being absorbed. PFAS are excreted in bile acids, but are mostly reabsorbed before being expelled in faeces ā it appears that cholestyramine significantly increases the efficiency of PFAS excretion by this route. The results are "groundbreaking", according to the study authors.
