Millions of tonnes of treated sewage sludge is spread on farmland across the UK every year despite containing forever chemicals, microplastics and toxic waste, and experts say the outdated current regulations are not fit for purpose.

An investigation by the Guardian and Watershed has identified England’s sludge-spreading hotspots and shown where the practice could be damaging rivers.

Sludge – the solid matter left over after sewage treatment – is laden with Pfas “forever chemicals”, flame retardants, pharmaceuticals, microplastics, and toxic waste from homes and industry. Water companies rebrand it as biosolids and give or sell it to farmers as a nutrient-rich fertiliser.