Mining’s toxic timebomb: dams full of poisonous waste are dotted around the world. What happens when they burst?

The aftermath of the tailings dam collapse at the Chinese state-owned Sino-Metals Leach copper mine near Chambishi. Photograph: Richard Kille/AP

As soon as the barrier broke, a flood of poison brought death to the river. Gushing through the fragile wall built to hold back mining waste in Zambia’s copper belt in February 2025, more than 50m cubic litres of acid and heavy metals poured into the Chambishi stream – a tributary of the Kafue River, the country’s longest waterway.

Thousands of lifeless fish rose to the surface as a plume of acid floated downriver, leaving dead crocodiles and other wildlife in its wake.