Ghana Gold

Galamsey also causes serious environmental problems and water pollution. Many mining operators are now focusing their efforts on the rivers themselves, using specialist imported machinery to suck up mud from the river bed. This is then treated with chemicals, including poisons such as cyanide, lead and mercury, to extract the gold before the waste is deposited back into the rivers. Aside from the dreadful consequences this has for aquatic life, the toxins are absorbed by humans because fish is a necessary food source and the rivers are often the only source of water for drinking and bathing. Dozens of people have died and hundreds more have been poisoned because of the after effects. 
http://www.aljazeera.com/programmes/africainvestigates/2011/11/2011113071310331931.html