Analysis of official data shows toxic "forever chemicals" have been found in the tissues and organs of dolphins, otters, porpoises, fish and birds across the UK.

Man-made chemicals called PFAS, known as "forever chemicals" because they do not degrade, are used in a wide range of consumer products and industrial processes, some of which have been linked to serious illnesses in humans and animals, including cancer. PFAS have been found to widely contaminate water and soil and are thought to be in the blood of everyone on the planet.

Watershed Investigations, the Marine Conservation Society and the Guardian obtained official data from more than 1,000 animals, revealing widespread contamination with a range of PFAS, particularly PFOS and PFOA, which were the longest studied, found to be toxic and now banned. However, there are more than 10,000 types of PFAS, and the toxic effects of most of them are poorly understood.

Environmental Quality Standards for PFOS stipulate that PFAS levels in fish tissue must not exceed 9 micrograms per kilogram (9.1 μg/kg) to protect top predators and people who eat fish from bioaccumulation of PFAS in the body, but 12% Fish in the fish dataset exceeded the threshold, with fish such as flounder and cockroaches having levels as high as 34 micrograms/kg and 41 micrograms/kg respectively.

If this threshold were true for all species, almost half of the animals sampled would exceed it. Many believe this limit is too high, and the EU is considering cutting the threshold to 0.077 μg/kg. If this method is applied, 92% of animals will exceed the threshold.

Data plotted on a watershed pollution map showed much higher levels of pollution for many animals, particularly predators higher up the food chain. Otters have levels as high as 9,962 μg/kg, harbor porpoises have levels as high as 2,420 μg/kg, gray seals have levels as high as 357 μg/kg, and dolphins have levels as high as 78 μg/kg. Contents in gannet eggs are as high as 158 micrograms/kg and in vulture livers are as high as 104 micrograms/kg.

Major sources of PFAS contamination include airports, military sites and chemical manufacturers. A study last year by Cardiff University showed that concentrations of PFOA were found in otters around a chemical factory that had used large amounts of PFOA in its processing in the past, with concentrations getting lower the further away from where the otters were found. Watershed and the Guardian revealed that wastewater discharged from the plant in 2023 contained high levels of PFOA.

Other sources include wastewater treatment plants, fire stations and fire training facilities, metal companies, pulp and paper mills, leather and textile manufacturers, energy and industrial facilities, and waste sites, including historic and permitted landfills. Old landfills built along rivers and coasts are known to leach harmful materials into the water.