this is a major health threat -- one that mariette liefferink has been warning of for years.he is calling for someone to take responsibility. >> for 120 years of gold mining, we do feel that the mines should put something back into the communities. as you can see, they're busy. to remediate the land, and to put something back into communities. >> but that's easier said than done. many of the area's mining firms have moved away. mine owners want nothing to do with their predecessors' pollution. >> it is something that happened due to the previous mining activities. at this point in time, this companies that mine at the time are nowhere to be found. hence, the responsibility has reverted back to the state. >> time is running out. toxic water is collecting in the minds, uranium and other toxins from the rock. johannesburg itself is threatened. researchers say drinking water in the metropolitan area could be contaminated in two or three years' time. >> we don't want to underestimate this problem. to act on it and to work on it. since the democratic government, we have since moved