Many UK rivers run clear and look healthy, but they contain an extraordinary mix of common pharmaceuticals and chemicals that harm fish.

Early results from tests of river water at more than 2,300 locations by the environmental charity Earthwatch in September have revealed the widespread presence of caffeine and nicotine, as well as common anti-depressants, antibiotics, anti-inflammatories and painkillers.

Many of the pharmaceuticals, with the exception of the painkiller Tramadol (found in 45% of samples), were found at concentrations that Earthwatch says “present a risk to aquatic life”.

Its report states that 100% of the 92 samples so far analysed contained caffeine, 30% the anti-depressant venlafaxine, and 18% the garden pesticide acetamiprid. The analysis is being conducted by Imperial College London.

The tests also measured levels of nutrients derived from sewage discharges, and agricultural and urban run-off. This revealed the county with the worst water quality in England was Rutland and the best was Northumberland. The best water in Wales was found in West Glamorgan and the worst in South Glamorgan. The cleanest rivers in Scotland were in Kircudbrightshire and the worst in Aberdeenshire. Read more at earthwatch.org.uk