A Thames21 charity citizen science project helps track plastic pollution in the capital’s river

On a pale-blue Sunday morning on the foreshore of the River Thames, 40 people are searching for what others have tried to lose. Dotted across a 250-metre stretch under Hammersmith Bridge, they are combing through layers of silt, seashells and dirty driftwood to find one of the river’s most stubborn problems: wet wipes.

“People come and walk here and it looks just like mud, at a distance,” says the organiser, Dr Felicity Rhodes. “And then you get closer in and see.”