Huge volumes of sewage sludge, also known as biosolids but which is essentially human excrement and industrial waste, are spread on UK fields every year. It is regulated by the Environment Agency and treated by the water companies before being sold to farmers, but many substances are not removed by the processes. Analysis of official figures by Watershed and the Guardian shows that the total amount of sludge produced for spreading has increased from 790,923 tonnes to 819,001 tonnes between 2012 and 2023. In that time, the amount of land it is spread on has increased by 12% from 135,637 hectares to 151,921 hectares, with most of it spread on agricultural land.
The Environment Agency is supposed to police the sludge but in practice this is not happening, whistleblowers from the agency told Watershed and the Guardian.
Sewage sludge spread on farmland is contaminating soils, water and potentially the food chain with “forever chemicals”.
Watershed Investigations and the Guardian obtained samples of treated sewage sludge destined to be spread on land from five different catchments, and found levels of PFAS (per- and polyfluoroalkyl substances) forever chemicals that would not be considered safe on allotments, as well as levels of flame-retardant chemicals described by experts as “exceptionally high”.
Dr David Megson, a forensic environmental scientist from Manchester Metropolitan University, said the “concentration of PFAS in the sludge samples poses a cause of concern. Concentrations of PFOS in all samples were greater than the recommended limit for an allotments site (2.7μg/kg). Uptake of PFAS in fruit and vegetables is poorly understood, but recent research has concluded that consumption of crops is a significant and underappreciated pathway for human exposure to PFAS.”
Prof Hans Peter Arp, an environmental chemist at the Norwegian University of Science and Technology, said he found the concentrations of flame retardants, used to coat materials to prevent them catching fire, “exceptionally high … Norway would consider 500μg/kg as contaminated, but these sludges range from 8,000 to 12,000μg/kg. I suspect the cause is fire-proof textile and/or textile manufacturing.”
The water industry wants to see the back of PFAS. A spokesperson for trade body Water UK said: “We want to see PFAS banned and the development of a national plan to remove it from the environment which should be paid for by manufacturers. In the meantime, water companies are exploring alternatives to spreading sludge to land on a precautionary basis.”
PFAS in sludge has created enormous problems for farmers in the US. In 2016, in Maine, high levels of PFAS were detected in milk from a dairy farm and investigations revealed that the source was sludge applied to the farmland as fertiliser. About 78 farms across Maine have been identified with PFAS contamination and drinking water sources have been polluted.