Defining challenge: conference covers the options for PFAS

Estimates of the number of synthetic fluorinated organic chemicals vary. At Environment Analyst’s 2022 Groundwater conference alone – held online on 12 May – estimates of Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) ranged from 4000-9000, indicating just one aspect of the difficulties faced by policy makers. 

Conference chair Jane Thrasher, senior consultant in land quality at Jacobs, noted that the first monitoring report from the Office of Environmental Protection (OEP) concludes the country needs more monitoring and pushes for a more ambitious look at emerging contaminants and persistent chemicals, and in particular better monitoring of PFAS.

"Without that the government can’t understand their effects in the environment," she said.

Thrasher pointed out that there are more than 4000 synthetic fluorinated organic chemicals which are persistent, mobile, bioaccumulative and toxic – but there is limited information on toxicity of individual substances. "They have a huge diversity of uses – repellents for oil, water and stains, temperature and chemical resistance, and as surfactants. They are useful in fire-fighting foams, as mist suppressants and in chrome plating."

The standard definition of PFAS is from the OECD 2021: fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom – i.e at least one -CF2- or -CF3- moiety in their structure.  Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the most commonly regulated; both have eight fluorinated carbons.

"We are hearing a lot more about fluorotelomers which have eight carbon atoms but with only six fluorinated with two hydrogens, which are used as substitutes. But there are important, more obscure ones like the 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), a main component in fire-fighting foams, which is not included in test suites but used in firefighting, and tests have found it. It is more complicated the more you investigate," says Thrasher. "Another is 6:2 FTS fluorotelomer and fluoropolymers – with side chains of PFAS."

A key question that needs to be addressed, said Thrasher, is: "Where do you draw the line between precursors and things we are finding?"

Precursors are used on the manufacture of the chemicals, and there is a wide diversity of them. They degrade to a more limited range of arrowhead substances and stable precursors, which are hydrophobic (not mixing in or with water) and oleophobic – lacking affinity with oils. Examples include short chain perfluoroalkyl acids (PFAAs) like perfluorobutanoic acid (PFBA) and perfluorobutanesulfonic acid (PFBS), which have four carbons, are more water soluble and highly mobile, but are less bio accumulative in humans and biota.

There is limited toxicity and other fate and transport information on the majority of PFAS, but the US Environmental Protection Agency has put together a road map of data gathering that must be undertaken over the next five years. 

The Environment Agency is monitoring 44 PFAS in groundwater. 

There are now data for 75 non-targeted groundwater locations. Forty-four PFAS were analysed, 24 PFAS detected, and Thrasher says: "It’s not just PFOS and PFOA we are looking at. They were not the highest concentrations. The most frequently found and at higher concentrations were fluorotelomers, FTS 6a and cyclic PFecHS. which is found in hydraulic fluids.

"We have to look for the right PFAS compounds and be sure when we are looking that the results are representative of the media we are trying to sample. With the ubiquity of daily use – the risk of cross contamination is high."

PFAS policy

So where does this leave UK policy on PFAS? Ed Latter, chemicals policy team leader at Defra, referred to the UK Chemicals Strategy, which was most recently committed to in 2018 as part of the government’s 25-year environment action plan, replacing the previous, 1999 version. "It is in development but sets our priorities and actions for more sustainable and safer chemicals for present and future generations."

Defra’s vision, according to Latter, is: "To restore and enhance the environment for the next generation by making our air purer, our water cleaner, our land greener and our food more sustainable." He referred in particular to Goal 9: "We will make sure that chemicals are safely used and managed and that the levels of harmful chemicals entering the environment are significantly reduced."

Latter stressed that one of the challenges for regulation is that it needs to keep pace with innovation. The chemicals industry is expected to double globally by 2030, leaving an ongoing contamination legacy. Persistent harmful chemicals continue to build up and are responsible for biodiversity loss and threats to human health. 

"Government will set out a clear framework for making policy and [will] provide clarity and reassurance on the UK direction on regulations and how to amend for emerging risk," Latter said. "We have the main tool of UK REACH. We are working across the government on a UK-wide strategy. We are working on stakeholder workshops. There was a ministerial round table in April led by Jo Churchill MP."

Major themes in the strategy include setting out a vision for 2040 and the type of chemical environment we hope to live in; tackling priority and future chemical risks; driving innovation and sustainable chemistry; creating a regulatory framework; managing chemicals through the life cycle and international collaboration.

Latter defined PFAS as a group of over 9000 synthetic chemical substances in the - CF2 – CF3 aliphatic group that are persistent due to their strong C—F bonds. He said that most PFOA or PFOS studies have indicated reproductive, developmental, liver, kidney and immunological effects and tumours in laboratory animals.

Defra and EA are working on PFAS, he confirmed, assessing the levels occurring in the environment, with data collected in England and new analytical methods being developed.

"We are working with industry to assess the risks of PFAS produced in the UK, and are identifying current and legacy uses and mapping potential sources. We are looking at river catchment and water company investigations to understand sources to sewer and wastewater treatment options and also engaging with partners internationally."

Latter produced a long list of PFAS uses in the UK including aqueous film forming, foams, fire suppressants, metal finishing and plating, hydraulic fluid, fluoropolymer production, paper products, packaging, semiconductor manufacturing, textiles, leather, carpets and furniture.

"The number of active PFAS in the UK is in the hundreds. There is complexity in the exact number, and exact use and a risk from imported products.

"There is existing legislation and regulation. PFOS and PFAS are under the Stockholm Convention. Some Gen X and PFBS are under EU Reach – and retained under UK law," he explained.

Regulatory management options analysis

Last year the Environment Agency, HSE and Defra started work on the Regulatory Management Options Analysis (RMOA), looking in more detail at how PFAS should be managed in the UK. It is part of the UK REACH Work Programme 2021-22, with EA and HSE looking at risks and measures to address them.

"The aim is to document the existing regulatory landscape around the concern, identify which regulatory action or actions might be needed to resolve the concern and highlight any key areas of uncertainty in the available information," said Latter.

The outcome, he added, may involve grouping approaches. "We are identifying regulatory actions and highlighting key areas of uncertainty in available information. The results are due in the summer. Grouping could reduce the risk of regrettable substitution, but this approach could [also] result in unintended consequences.

"The pros are a reduced risk of regrettable substitution and reduced evidence requirements, but substance-by-substance assessment is not always practical. If you reduce a substance it could get replaced by an equally bad substance. You have to take environmental trade-offs and look at things in a broader environmental context.

"The cons are that you may capture a chemical that has a net benefit, but it doesn’t prevent regrettable substitution with chemicals outside the grouping.

"There are many possible approaches which could be applied. The two basic approaches are looking at properties or risk management. Up to 40 different groups have been identified."

European policy and PFAS remediation

Dorte Harrekilde, chief consultant and European PFAS Network lead at Ramboll, based in Denmark, outlined the various policy approaches of European countries, adding that there should be some convergence around the EU Drinking Water Directive, with compliance set for 2023.

Some countries don’t have laws covering contaminated soil, explained Harrekilde, but some have publicly financed investigations and remediation. Currently most EU countries have PFAS limits for drinking water, groundwater and soil, but they differ between countries.

Harrekilde illustrated how Denmark treated PFAS with a case from the Korsør fire training school. High levels had been detected at a waste-water treatment centre, which was linked back to the school. After intensive investigations involving the state, and analysing grass, cow meat and blood samples, the local municipality took out an injunction whereby the treated water had to meet the current drinking water quality criteria.

The treatment train involved a sedimentation tank, an oil separator, ion exchange resins and treatment with supercritical water oxidation.

Treatment trains have to be used to deal properly with PFAS, Harrekilde said. The aqueous category requires treatment including activated carbon, which has been around for a while, but a high volume has to be used, and there can be difficulties with short chain PFAS. An alternative is ion exchange resin, which can be more effective than active carbon, and the two can also be combined. Other techniques include reverse osmosis and nano-filtration, which Harrekilde said, can be quite expensive. Foam fractionation is increasingly used in Nordic countries. This involves bubbling air through water. PFAS collects in the bubbles. The steps can be repeated, making for an efficient process.

Soil treatment technologies are more mature and feasible than water treatment approaches. One of the oldest treatment methods – dig and dump – can lead to leachate problems, but other more successful approaches include stabilisation and soil mixing. Soil washing is also a mature technology, but accessibility present issues, as can clay soils. Several companies are working on destructive techniques, including thermal treatments and experimental electrochemical oxidation methods.

So although PFAS are proliferating and presenting substantial challenges, there are grounds for optimism, according to Harrekilde, who concluded that there is a lot of research underway and new technologies can be expected to emerge.