Birds’ eggs show just how serious a problem river pollution remains in the UK’s former industrial heartlands, according to a new study.

Scientists analysed the eggs of Eurasian Dippers living in 33 rivers in South Wales, comparing the eggs of birds living along urban waterways with those of their rural peers. The city-dwellers’ eggs contained large amounts of several harmful chemicals – in some cases four times higher than their country cousins, and approaching levels known to cause permanent damage.