Water companies selling sludge fertiliser containing banned ‘forever chemical’ to farmers

PFAS - or ‘forever chemicals’ as they have been dubbed for their refusal to break down in the environment and human bodies - are a family of around 10,000 chemicals used in a huge range of consumer products, from cookware and cosmetics, furniture and food packaging, to a wide array of industrial processes.

For years, DEFRA and its regulatory agencies, along with the water industry, have been carrying out the National Chemicals Investigation Programme (CIP), which is intended to investigate risks posed by chemicals, including PFAS, in wastewater discharges. 

Last year, the programme published a report on biosolids - also known as sewage sludge - which is a by-product of the sewage treatment process that is often sold to farmers as a fertiliser for its rich nutrient content. Industry figures suggest that 170,000 truckloads - or 3.5 million tonnes - of biosolids are spread on agricultural land in the UK each year. 

An ENDS Report investigation has extracted and analysed the data behind the CIP biosolid report, revealing that PFOS - a type of PFAS which has been banned in the UK, and is linked to a range of diseases in humans, including kidney cancer, testicular cancer, hormone-related diseases, and fertility issues - has been found in high levels in sludge samples from England. 

There is no official regulatory standard for how much PFAS is considered safe in biosolids. As such, under current rules in England, water companies which sell biosolid fertiliser to farmers are not obliged to test for PFAS, or anything other than heavy metals and a limited number of other chemicals. 

However, emerging research has led scientists in the US - where sewage sludge contamination has seen farms forced to close - to conclude that PFOS concentrations in soil higher than one part per billion (ppb) can be absorbed into the roots and shoots of plants grown in it at a level that breaches the US Environmental Protection Agency (EPA)'s daily exposure limit for humans. The 1ppb risk threshold is currently in draft sludge regulation for a county in Pennsylvania.   

The highest test result analysed by ENDS comes from a Thames Water-operated sewage treatment centre in Crawley, near Gatwick Airport. It recorded a PFOS level of 135ppb in one sludge sample, a striking 135 times higher than the 1ppb risk threshold. ENDS has been unable to determine the location of the farms that the Crawley sludge treatment centre supplies. 

Crawley’s top reading was the highest recorded by a margin, but when all samples were averaged, every single sludge treatment centre sampled for the CIP programme recorded average PFOS concentrations above 1ppb. 

Sludge is a concentrated substance, and can be expected to dilute to a certain extent once applied to soil. However, with PFOS - and other types of PFAS - known to bioaccumulate, experts have warned that if multiple applications of contaminated sludge are made to fields over the years, dilution cannot be relied upon to make PFAS-contaminated sludge safer.

The authors of the CIP biosolid report concluded that it is “highly likely” that biosolids will be a source of PFOS into the environment, adding that the risk “may be great at some locations or at particular times”. 

When approached for a comment, Thames Water deferred to the industry body Water UK to comment. A Water UK spokesperson said: “The use of bioresources on agricultural land is long established and highly regulated. Compliance is 99.8% according to the Environment Agency’s 2023 Environmental Performance Assessment.”

The Environment Agency has emphasised that findings from the CIP report are being used to design “a new sludge investigation”, which will include chemical sampling at a range of sludge treatment centres, including Thames Water’s Crawley centre.

In the US state of Maine, the practice of sludge spreading has been banned after officials discovered high levels of PFAS in water, crops, cattle and soil on farms where sludge had been spread. The discovery of PFAS contamination on some of these farms has been so bad that it has seen farmers put out of business, and as of this year, the Maine Organic Farmers and Gardeners Association has announced it is suing the US Environmental Protection Agency (EPA) for allegedly failing to regulate the spread of PFAS-contaminated sludge.

Adam Nordell, who had to stop working his land and leave his Maine farm after exceedingly high levels of PFAS-contamination were discovered as a result of historic sludge spreading, described the 135ppb reading from the sludge sample in Crawley STC as “terrifying”. 

He added that it presents “an untenable risk to the farmers, to the farm workers, to people who live near the farms who are drinking water and breathing dust that blows off the farm”.

Dr. Steven Lasee, a consultant ecological toxicologist in the US and the lead author on the scientific paper which led authorities in Pennsylvania to request he calculate risk thresholds said: “These chemicals don't break down, and they don't move tremendously in soil, especially PFOS, so it's likely going to stay in the first 10 feet of the soil, where it's completely available for plant uptake.”

Lasee also said that crops impacted by PFAS are a major route by which the chemicals can contaminate livestock, where they can continue to bioaccumulate. According to wildlife charity WWF, 40% of the UK’s most productive agricultural land is used to grow wheat and barley for farm animals, rather than people. 

Speaking on the condition of anonymity, a water industry source said that in their experience, there is simply “no appetite” in the industry to look closer at the issue of PFAS-contaminated sludge. 

“What I find is that people are typically just very proud of having run the process by the regulations in front of them,” they said. “And that's how it goes: ‘We do a great job of really good testing of all the things we’re supposed to test for’. People aren't interested in looking beyond that; they're just doing the job, nothing more, nothing less.”

Campaigners are urging the government to take a precautionary approach to regulating the use of the product, and require water companies to test sludge for PFAS before it is sold to farmers. 

George Monbiot, the writer and environmentalist who is also one of the three founders of the campaign group Fighting Dirty, which recently attempted to sue the Environment Agency over its approach to sludge regulation, said the “neglect of this issue is astounding”. 

He continued: “Farmers are being deceived about the contents of sewage sludge by the water companies, who continue to market it as safe. Consumers have no idea what they are eating. Ministers and regulators are looking the other way. 

“This is a creeping environmental and public health crisis, which will become harder to address and harder to reverse the longer it goes on. We need immediate action. DEFRA must step up now to prevent a nationwide Dark Waters scandal.”

An Environment Agency spokesperson said: “The global science on PFAS is evolving rapidly and we continue to develop our scientific understanding. 

“That’s why we are collaborating with several partners, including water companies, to improve our evidence base and are working with government to inform future decisions on the management and use of sludge.”

A DEFRA spokesperson said: “This government recently announced a rapid review of the Environmental Improvement Plan to deliver on our legally binding targets to save nature. This includes how best to manage chemicals, including the risks posed by PFAS. 

“We are also working with the Environment Agency to assess the regulatory framework for sludge.”