Almost 500 different chemicals, some of which are banned, have been found in various mixtures across all 171 river and groundwater catchments tested in England in 2024, according to data from the Environment Agency, analysed by the Guardian and Watershed Investigations.
More than half of them are classified as very toxic, toxic or harmful to aquatic life, according to the European Chemicals Agency (ECHA), and a banned, carcinogenic “forever chemical” was among 20 “substances of very high concern” found.
“What this shows is that the way we monitor and manage chemicals in our rivers is completely unfit for purpose,” said Alistair Boxall, professor in environmental science at the University of York.
“Although it depends on the concentrations, a lot of these are very toxic. We know they target algae, invertebrates and fish. If you’ve got a mixture of a few hundred substances, they are potentially working together and exacerbating the effect,” explained Boxall.
Environmental groups have called chemical pollution the silent killer in our waterways. The world has lost 83% of its freshwater aquatic life in 50 years and in UK waters, the sturgeon and the burbot have vanished and Atlantic salmon is endangered.
“Our invertebrate monitoring shows clear evidence of significant chemical impact across all the 100-plus rivers we monitor,” said the WildFish CEO, Nick Measham. “It ties together chemical presence with widespread ecological impact. It makes poo in rivers look like a second-order problem.”
Neonicotinoid pesticides are banned in the UK and EU for use on all outdoor crops because of the high risk to pollinators. However, the data shows all three banned neonics across 29 river and groundwater catchments, including thiamethoxam, which the UK government has continued to allow for sugar beet crops. The Environment Agency said policies were being changed to prevent this use.
Another neonic, imidacloprid, is still legally used as a flea treatment for dogs and cats, which experts say is nonsensical.
“Imidacloprid is like novichok for insects,” said Dave Goulson, professor of biology at Sussex University.
“A single teaspoon of this pesticide is enough to deliver a lethal dose to 1.25 billion honey bees. It’s concerning that our rivers should be awash with a potent insecticide.”
The majority is found downstream of sewage outlets, suggesting that they are coming primarily from owners washing their pets and bedding at home. These chemicals are more toxic to insects than vertebrates, but there are health concerns and research in Switzerland found neonics in the cerebral spinal fluid of children.
The most widespread chemicals found are classic markers of road runoff, where pollutants from car exhaust pipes and tyres, for example, build up on roads and then get washed into streams and rivers when it rains. Fluoranthene, which is very toxic to aquatic life, and pyrene, were found in 80% of water catchments. Both are substances of very high concern because they are persistent, bioaccumulative and toxic, meaning they don’t break down easily and can build up in our bodies.
“I found fluoranthene at levels over 100 times above the maximum allowable concentration in samples of runoff from the M6,” said Jo Bradley, a former Environment Agency officer who heads the Stormwater Shepherds nonprofit. She says road runoff often exceeds statutory standards.
“National Highways identified fluoranthene and pyrene as potentially significant pollutants way back in 2002, so it is desperately sad that they have not delivered treatment schemes at their highway outfalls to control this pollution in the last 20 years.”
National Highways says it is “committed to improving water quality, and our water quality plan sets out a high-level programme of work to address all our high-risk outfalls by 2030.”
Farm runoff was another major source of contamination, with approximately 30% of the substances commonly used as insecticides, fungicides, pesticides and medicines for livestock. Around 34% of substances detected are pharmaceuticals, caffeine and sweeteners, which are probably discharging from sewage treatment works.
Sewage is the main reason the Medway catchment fails to meet good status followed by agriculture, according to the Environment Agency. Together with the Tees estuary, it has the highest number of different chemicals in its waters. The highest concentrations of the recreational drug ketamine was found here, as well as of an insecticide used to control aphids on crops.
“We have parts of the River Medway that are no-go areas, where the river is devoid of life and we don’t fish there,” said Ian Tucker, of the Royal Tunbridge Wells Angling Society.
Sewage works could install tertiary treatment to remove many chemicals, but it is expensive.
“We’ve had a lack of investment in wastewater treatment and we’ve not progressed to removing chemicals,” said Chris Gardner at the South East Rivers Trust. “We need a regulator to drive improvements.”
Water UK, the water industry body, points out that water companies are not responsible for these pollutants being in the water system and supports a “polluter pays” principle.
“Water companies want to invest nearly £12bn to stop sewage spills from storm overflows and remove chemicals during the treatment process,” a Water UK spokesperson said. “We now need Ofwat to approve these plans in full so we can get on with it. However, prevention is better than cure and we need greater action from government and other sectors to stop this material entering the environment in the first place.”
In the country’s chemical manufacturing capital, the Tees estuary, the site of a series of crustacean mass die-offs in 2021, seven out of the top 10 highest sum concentration chemicals found are very toxic, toxic or harmful to aquatic life. For example, the highest levels found in all the samples in England is of a pesticide that is 200 times over the predicted no-effect concentration and is very harmful to aquatic life.
“As this study confirms, the extent of chemical pollution of our waterways is staggering, impacting upon aquatic life and raising implications for human health”, said Rob Collins, of the Rivers Trust. “It is imperative that we see a robust chemicals strategy from the government as a matter of urgency, where tackling chemical pollution at source is prioritised.”
An Environment Agency spokesperson said: “Our analytical techniques are highly sensitive and allow us to detect over 1,500 compounds at low levels to support our work on managing chemical risks in the environment. This testing is specifically targeted at sites where we want to better understand the chemical risk.
“We are working closely with other regulators and the water industry on a series of chemical investigation programmes to better understand how chemical compounds affect our water environment.”
But experts remain concerned.
“The big picture is that from conception we’re all being exposed to a cocktail of synthetic toxins,” warned Goulson. “The impact of the mixtures is totally unknown … and it’s inescapable.”
