Toxic “forever chemicals” have been discovered in the Solent at concentrations up to 13 times the safe threshold for coastal waters, according to a new study that also found many samples failed tests for combined toxicity even when individual chemicals were below legal limits.
The contamination, detected in soil, water and throughout the marine food chain, has raised urgent questions about the adequacy of current regulations, which scientists say overlook the cumulative effect of multiple per- and polyfluoroalkyl substances (PFAS) present together in the environment.
Solent contamination levels alarm scientists
Researchers from the University of Portsmouth and the Marine Conservation Society analysed government data, testing at water utilities, and their own samples from a dozen species of fish, seaweed and invertebrates across the Solent strait – the crucial waterway running between the Isle of Wight and the mainland. In some locations, PFAS pollution was measured at 13 times the recognised safe threshold for coastal waters.
While certain individual chemicals remained below existing legal limits, far more samples failed a newer European Union test for combined toxicity, which weighs the relative potency of PFAS when they occur together. Professor Alex Ford, a biologist at the University of Portsmouth and a study author, said: “Looking at chemicals one at a time misses the bigger picture.”
The scale of the issue extends well beyond the Solent. The study noted that all but seven of English surface waters tested fail the combined EU test, and that a number of remote lochs and burns in Scotland would also be in breach. “I don’t think our story is specific to the Solent,” Ford added. “I think we would see a pattern all around the UK.”
What are PFAS and why do they pose such a risk?
Per- and polyfluoroalkyl substances – PFAS – are a large family of synthetic chemicals used for their exceptional durability and resistance to heat, water and grease. They are found in a vast array of everyday products: non-stick cookware, food packaging, waterproof clothing, carpets and firefighting foams. Their chemical stability, which makes them so useful in industry and manufacturing, also makes them extraordinarily persistent. PFAS do not break down easily and can remain in the environment for thousands of years, earning them the moniker “forever chemicals”.
Over decades of widespread use, these compounds have accumulated in water, soil and living organisms. Scientific evidence has linked them to a range of serious health problems in humans, including increased risks of testicular, kidney and thyroid cancers, liver damage, high cholesterol, thyroid disease, immune system suppression, fertility problems and developmental defects in unborn children. Wildlife is equally affected: PFAS have been found in harbour porpoises, otters, seabirds and other iconic UK species, with documented harm to immune function, blood and liver function, neurological development and reproduction.
Because PFAS do not degrade, they move through ecosystems and accumulate up the food chain. The Solent study detected the chemicals in the livers of harbour porpoises at levels above existing safe legal limits for individual compounds. Researchers also highlighted emerging evidence that seaweed can act as a significant reservoir – one compound, perfluorobutanoic acid (PFBA), was found in seaweed at concentrations more than 6,000 times higher than in the surrounding water, pointing to a potential pathway for PFAS to enter the food web.
Sources and pathways of pollution
The study identified several routes by which PFAS enter the Solent. Primary among them is treated effluent from wastewater treatment plants operated by Southern Water in Portsmouth and Fareham. Current wastewater treatment systems are not designed to remove PFAS, meaning the chemicals pass through the treatment process and are discharged directly into the waterway.
In addition, researchers mapped 194 combined sewer overflow (CSO) outfalls in the vicinity. CSOs release untreated sewage and stormwater during heavy rain, and studies have shown that PFAS concentrations can rise sharply after such discharges – with eight different PFAS compounds detected post-discharge compared with just one before in some instances.
More than 500 historic landfill sites near the Solent are also believed to be contributing to the pollution, as PFAS leach out of old waste deposits over time. Military sites in the area, where PFAS-containing firefighting foams (aqueous film-forming foam, or AFFF) have historically been used, represent another likely source.
Regulatory response and calls for action
The UK government published its first PFAS Plan in February 2026, setting out a framework to understand where these chemicals originate, how they spread and how to reduce public and environmental exposure. Initiatives include expanded monitoring, commissioned research on wildlife impacts, and a consultation on setting statutory limits for PFAS in drinking water. The government has also indicated it will issue a final opinion on restricting PFAS in firefighting foam.
However, critics argue the plan falls short of what is needed. The Marine Conservation Society, which funded the Solent study, said the proposals lack decisive action. Calum Duncan, the charity’s head of policy, warned: “It’s not good enough to plan to have a plan. We urgently need action and we have this once-in-a-generation opportunity with the water reform process to get on and do that.”
A Southern Water spokesperson acknowledged the challenge, telling researchers: “Tackling the presence of these chemicals is a challenge for society as a whole. The most sustainable solution is to meet the problem at source … and keep [the chemicals] out of pipes and the environment in the first place.” The company agreed on the need for new legislation “to restrict or ban certain chemicals”.
Professor Ford echoed that view, noting that water companies lack the capacity to treat these compounds effectively. “This is one thing I don’t necessarily pin on the water companies because they don’t have the capacity to treat these compounds,” he said. “That’s why they should be banned at source.”
The European Union is moving towards a blanket ban on PFAS under its REACH chemicals regulation, covering more than 10,000 substances, with exemptions only for critical uses such as medicine. The proposal is expected to enter into force in 2027 or 2028. In the UK, two specific PFAS – Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) – are already banned, and the government has signalled its intention to reform UK REACH to align more closely with EU regulations and enable faster chemical protections.
