An evaluation of the collapse of a waste dam at a Chinese state-owned copper mine in Zambia may have released 30 times more toxic sludge into the environment than previously reported. At least 1.5 million tons of the poisonous substance escaped when a reservoir failed at the Sino-Metals Leach Zambia mine near the northern city of Kitwe in February, findings from the company hired to assess the environmental damage showed. Bloomberg's Ondiro Oganga reports. -------- More on Bloomberg Television