Read the full article by XiaoZhi Lim (Nature)
“This February, the European Chemicals Agency (ECHA) in Helsinki published a proposal that could lead to the world’s largest-ever clampdown on chemicals production. The plan, put forward by environmental agencies in five countries — Denmark, Germany, the Netherlands, Norway and Sweden — would heavily restrict the manufacture of more than 12,000 substances, collectively known as forever chemicals.
These chemicals, per- and poly-fluoroalkyl substances (PFASs), are all around us. They coat non-stick cookware, smartphone screens, weatherproof clothing and stain-resistant textiles. They are also used in microchips, jet engines, cars, batteries, medical devices and refrigeration systems.
PFASs are extraordinarily useful. Their fluorine-swaddled carbon chains let grease and water slide off textiles, and they protect industrial equipment from corrosion and heat damage. But their strong carbon–fluorine bonds cannot be broken apart by natural processes. So after PFASs escape from factories, homes and vehicles into the environment1, they add to a forever-growing pollution problem. The February proposal estimates that tens of thousands of tonnes of these chemicals escape annually in Europe alone.
Several PFASs are now known to be toxic. They have been linked to cancers and damage to immune systems, and are now banned under national and international laws. Most PFASs, however, have not yet undergone toxicology assessments or been linked to health harms. But officials at the agencies that submitted the plan to the ECHA say their persistence means they will inevitably build up until as-yet unknown safe thresholds are crossed.
‘We see that there is an unacceptable risk now,’ says Richard Luit, a policy adviser at the Dutch National Institute for Public Health and the Environment in Bilthoven.
There’s no prospect of an instant ban. The ECHA is consulting on the idea before it takes a position. European legislators are unlikely to have a plan to vote on before 2025, and even the current proposal offers grace periods — of more than a decade in some cases — to allow manufacturers to develop alternative materials or systems. Several permanent exemptions are also offered (including for fluorinated drugs, such as Prozac, and for materials used to calibrate scientific instruments).
But taken as a whole, the idea is to shrink PFAS use to a minimum. ‘We are asking society to make quite a shift,’ says Luit. ‘We are asking to reverse all of it, go back to the drawing table and invent alternative solutions.’
Change is already under way for consumer use of PFASs. The notoriety of the toxic examples has pushed more than 100 companies and brands, including Apple, to pledge to phase out PFASs, even before it’s clear whether other materials can do the same job.
For industrial users, however, the idea of life without PFASs is a more shocking prospect. So February’s proposal has ignited debate about which uses of fluorinated chemicals the world could leave behind — and which must stay.
Three forms of forever
A peculiarity with fluorinated compounds, researchers say, is that some kill, whereas others are safe enough for use in medical products. ‘Fluorine compounds are really, really, incredibly strange in this regard,’ says Mark McLinden, a chemical engineer at the US National Institute of Standards and Technology in Boulder, Colorado. ‘Certain fluorine compounds are incredibly toxic. And then you have things like [the gas] R134a, which is benign enough that you’re shooting it directly into your lungs in asthma inhalers’.
Forever chemicals come in three distinct forms (see ‘Fluorinated world’). The notoriously toxic kinds are fluorosurfactants. These molecules resemble those in soap, made of two parts: carbon chains with fluorine atoms wrapped around them, that repel everything, and a water-loving portion at one end of the chains that allows the molecules to dissolve in water.
After some of these molecules were linked to serious health harms and widespread water pollution, individual substances were banned or severely restricted internationally: first PFOS (perfluorooctanesulfonic acid) in 2009, then PFOA (perfluorooctanoic acid) in 2019, and, last year, PFHxS (perfluorohexanesulfonic acid). Manufacturers have moved on to other fluorosurfactants, many of which lack toxicity studies.
The February proposal suggests phasing out all the fluorosurfactants at once to avoid ‘regrettable’ substitutions, says Jona Schulze, a staff scientist at the German Environment Agency in Dessau-Roßlau.
But the proposal goes further than that. The five agencies behind it have adopted the Organisation for Economic Co-operation and Development’s definition of PFASs: any molecule with a carbon atom in a chain that’s bonded to two fluorine atoms (or, if at the end of the chain, three). Restrictions under this expansive definition cover the other two kinds of forever chemicals.
There are the fluoropolymers, the plastic-like form that most consumers encounter. The most famous example is Teflon, or polytetrafluoroethylene (PTFE), long carbon chains wrapped in fluorine atoms. A Teflon-based coating makes frying pans non-stick; in medical products, it helps catheters to glide through the body, safeguards implants from deterioration, and, coated on the inside of bottles and blister packs, prevents drugs from interacting with their glass or foil containers. Stain-resistant textiles use a variant of this structure, in which fluorine-wrapped side chains hang off a main carbon chain.
The third category of PFASs is made up of small, light fluorocarbon molecules that generally exist as gases or liquids. R134a, the asthma-inhaler propellant, is also a common refrigerant in refrigerators and mobile air-conditioning systems, for instance. Sensitive equipment that is prone to overheating, such as servers in a data centre, can be submerged in fluorocarbon fluids that cool the apparatus without shorting its circuits or running the risk of fire.
Although fluoropolymers and fluorocarbons haven’t been shown to harm consumers directly, the problems come when they’re produced and when their useful lives end. Fluoropolymers are created using toxic fluorosurfactants, which pollute water and soil around fluoropolymer plants worldwide. Some researchers also suspect that fluoropolymers might, during their long lifetimes, shed fragments small enough to be ingested, as is known to happen with microplastics (Nature 593, 22–25; 2021). As for the fluorocarbons, some are powerful greenhouse gases, and others break up into a small-molecule PFAS that is now accumulating in water.
‘If no action is taken, at some point the societal costs due to continued use are likely to exceed the costs which are now associated with their restriction,’ says Schulze.
The electric-car conundrum
To see all three forms of PFAS in one product, look no further than cars. Their air-conditioning systems use a fluorocarbon refrigerant, the hydraulic fluids usually contain fluorosurfactant additives that prevent corrosion, the painted chassis probably has a weatherproof fluoropolymer coating, and the seats are usually covered in a stain-resistant fluorinated textile.
Electric vehicles are even more reliant on fluoromaterials because of their lithium-ion batteries. These batteries get their high energy density, and therefore range, by operating at relatively high voltages, explains Gao Liu, a chemist at Lawrence Berkeley National Laboratory in Berkeley, California. The metallic content in their cathodes is usually a powder that must be bound together with a material that can withstand the high voltage. In the 1990s, that was PTFE; today, battery makers use a cheaper fluoropolymer called polyvinylidene fluoride (PVDF), containing half the fluorine.
Smaller fluorinated molecules have become crucial, too. Adding them to battery electrolytes allows a protective layer of lithium fluoride to form on the electrodes, improving performance and extending lifetime by preventing cracks, says Cheng Zhang, a chemist at the University of Queensland in Brisbane, Australia. This area has become a battleground for battery manufacturers, who are developing cocktails of fluorinated additives.
Liu has developed a fluorine-free binder, but it works only for a lower-voltage battery such as one based on lithium iron phosphate. These batteries do have advantages: they last longer and don’t use critical minerals such as cobalt, nickel or manganese, important factors to consider as battery production ramps up in the fight against climate change, Liu says. But even though lithium iron phosphate batteries would work for stationary storage and already power half of Chinese electric vehicles, they might not be cost-effective for long-range vehicles.
‘The whole field needs to look into better chemistries,’ says Liu. ‘The reason we switch to batteries is to protect the environment. It doesn’t make sense to invent something that’s dirtier than before.’
The magic of fluorine: myth or fact?
Industries that have known nothing but fluorine chemistry need to break away from believing in its magic, says Martin Scheringer, an environmental scientist at the Swiss Federal Institute of Technology in Zurich (ETHZ). ‘PFASs are a block to innovation,’ he says, pointing to the example of firefighting foams. Despite making foams from PFOS for decades, the multinational technology company 3M managed to create fluorine-free firefighting foam in 2002, but only after PFOS became a high-profile pollutant. Many other industries now need to make similar breakthroughs. ‘We need lots of materials that have not been invented that are fluorine-free,’ Scheringer says.
In December, 3M announced it would stop making all its fluorochemical products — including fluoropolymers and fluorocarbon gases and liquids — by 2025, but did not say what would take their place. This June, it reached a $10-billion settlement to pay to clean fluorosurfactants from drinking water in parts of the United States, although it faces other unresolved lawsuits.
For the moment, most of the funding granted to PFAS topics relates to cleaning up pollution, and neither of the huge government-funded European Union or US programmes to boost clean energy or the manufacture of semiconductor chips specify the need to find alternatives to PFASs. ‘We should channel more of the funding to the research that will find new solutions,’ says Jonatan Kleimark, an adviser at ChemSec, a non-profit organization based in Gothenburg, Sweden, that advocates for safer chemicals.
Eason and Wan are trying to find ways to manufacture fluoropolymers without using toxic fluorosurfactants. If that can be achieved, Eason argues, it should be fine to continue using fluoropolymers where they cannot be substituted, provided that recycling at the end of their life is also resolved. But Eason recognizes the problem of persistence with fluoropolymers. ‘The ECHA proposal has made everyone realize they have to do something different,’ he says. ‘In my view, a responsible company should be looking to minimize the use of fluorinated materials.’
The officials who proposed the ban say that they welcome proposals from manufacturers to extend producer responsibility and develop closed-loop systems for recycling fluorochemicals. ‘They have to provide the information and step forward,’ says Heggelund. But he is highly sceptical, noting the low rates of plastic recycling. And if fluoropolymers could be made without toxic surfactants, then manufacturers should have done it from the start instead of reacting to regulation, he says.
The ECHA is collecting feedback on the proposal until the end of September. After that, it will revise the plan and carry out a techno-economic assessment to evaluate the costs and benefits for society.
The agency is the only one in the world contemplating such comprehensive PFAS restrictions. But enacting a ban would send a signal to the rest of the world about the acceptability of the chemicals. Zhanyun Wang, an environmental scientist at ETHZ, thinks that the proposal will spur innovative research for applications that don’t have obvious alternatives to fluorinated chemicals. And for those that do, Wang hopes the proposal and market changes that follow could act as a ‘lighthouse’, as he puts it: showing industries around the world how to ditch forever chemicals for good.”