The Wildlife and Countryside Link (WCL) looked at the prevalence of five chemical cocktails known to have toxic impacts for wildlife which include PFAS forever chemicals, pesticides and pharmaceuticals.
The chemicals were found in 814 river and lake sites (out of 1,006 sites with data) and 805 groundwater sites (out of 1,086 sites with data) across England.
Over half of these sites contained three or more dangerous chemicals, which, in specific combinations, are known to have increased harmful impacts on a range of species including amphibians, fish, insects, nitrogen-fixing bacteria and algae.
Identified detrimental effects included reduced growth, cell function, impacts on embryos and lower survival rates. However, any potential human health implications, for example through contact via bathing or recreation, remain unknown.
WCL, alongside a group of other environmental charities, has urged the government to take a much more ambitious approach to regulating chemicals in Britain's public water bodies.
Their calls include asking the government to regularly monitor for the presence of the chemicals alongside new legal protections, which include requiring assessments of potential hazardous chemical mixture impacts before any new substances are allowed on the market.
Richard Benwell, WCL CEO, said: "A harmful chemical cocktail is being stirred up in UK rivers, putting wildlife and public health at risk. Government regulates and monitors chemicals individually, ignoring the cocktail effect.
"But our research shows that toxic combinations of pesticides, pharmaceuticals and forever chemicals are polluting rivers up and down the country. The new Chemicals Strategy must make sure harmful substances are regulated not just for individual risks, but for their effects in combination."
Rob Collins, director of policy at the Rivers Trust, said: "We need to stop pumping poison into our rivers. Hazardous chemicals are flowing into our waters, derived from every aspect of our lives.
"On the small-scale from the toiletries, food packaging, clothing and other goods we use individually, to large-scale industrial, medical and food production, we are creating an ever-growing chemical cocktail in our rivers.
"The fact that these known toxic chemical combinations are found so widely across the country is deeply worrying. And that's just the tip of the iceberg. Unless we act now we'll see increasingly contaminated water, less wildlife in our rivers and ocean, and this raises implications for human health as well."
A range of five known toxic chemical cocktails was looked for in Environment Agency data.
The levels of these contaminants in rivers were typically much lower than in the laboratory studies looking into their effects. But individually, each of these chemicals are known to impact wildlife at concentrations lower than those reported in these studies.
Alongside other measures, WCL called for increased funding for the Environment Agency's river monitoring programme.
