Investigators have found toxic pollution hotspots across Cumbria and Lancashire.
High levels of the banned chemical PFOS appeared at 25 river and groundwater sites.
Watershed Investigations and the Guardian uncovered the contamination through a freedom of information request.
The Environment Agency collected the samples in January 2025.
PFOS belongs to the PFAS group of “forever chemicals”.
These substances persist for centuries and accumulate in the environment.
Some link them to cancer and other serious health problems.
One site showed groundwater contamination of 3,840ng/l.
Many sites exceeded the 100ng/l drinking water guideline for combined PFAS.
The pollution affects an area with strong wildlife and landscape protections.
A business owner discovered their private well was contaminated in 2021.
They stopped drinking the water immediately after an unofficial warning.
They said authorities offered no practical help or clear advice.
Westmorland and Furness council confirmed the supply switched to mains water.
It said it continues to manage the case to protect public safety.
The Environment Agency stated that councils hold responsibility for private supplies.
It said it notified national health and water bodies in 2025.
A 2025 agency report listed possible sources of the pollution.
These include a paper mill in Beetham that previously used PFAS.
Land spreading of contaminated paper pulp may have polluted soils.
Historical and active landfills also pose a risk.
Sewage works, fire stations and caravan park discharges remain potential contributors.
The mill now operates under a new company, Pelta Medical Papers.
The firm said it no longer uses PFAS and complies with current regulations.
Administrators for the former operator did not comment.
The government has published a new PFAS action plan.
It proposes tighter land guidance and consultation on drinking water limits.
Water UK called for a complete ban.
Environmental groups criticised the plan for lacking binding phase-out dates.
About 33,000 private water supplies exist in England.
Regulators warn that climate change and pollution increase their vulnerability.
Campaigners say the UK must rapidly replace PFAS with safer alternatives.
