"U.N. Body Alarmed Over Mining Waste Disasters"

"Some of the worst mining disasters do not happen in mines.

They take place at dams.

After minerals are extracted from mines, there are waste materials — including sand, rock and chemicals. They're known as "tailings" and are permanently stored in dams constructed of earth, rock-fill or concrete.

But the dams can fail — from chemical erosion caused by the tailings and from disasters like floods and earthquakes. And the toll can be devastating."

Jose Olivares reports for NPR December 2, 2017.