A string of toxic pollution hotspots has been uncovered across Cumbria and Lancashire, with high levels of the banned cancer-causing “forever chemical” Pfos detected in rivers and groundwater at 25 sites.

The contamination, spread across a large area, was uncovered by Watershed Investigations and the Guardian after a freedom of information request revealed high concentrations of Pfos in Environment Agency samples taken in January 2025.

Pfos is a type of per- and polyfluoroalkyl substance (Pfas), known as “forever chemicals” because they take hundreds or thousands of years to degrade. They are widely used in consumer products and some have been linked to a range of serious health problems.