The greatest danger of tailings ponds is dam failure, with the most publicized failure in the U.S. being the failure of a coal slurry dam in the West Virginia Buffalo Creek Flood of 1972, which killed 125 people; other collapses include the Ok Tedi environmental disaster in New Guinea, which destroyed the fishery of the Ok Tedi River. On average, worldwide, there is one big accident involving a tailings dam each year.
Other disasters caused by tailings dam failures are, the 2000 Baia Mare cyanide spill and the Ajka alumina plant accident. In 2015, the iron ore tailings dam failure at the Germano mine complex in Minas Gerais, Brazil, was the country's biggest environmental disaster. The dam breach caused the death of 19 people due to flooding of tailings slime downstream and affected some 400 km of the Doce river system with toxic effluence and out into the Atlantic Ocean.