Residents here fear the wind most. When it blows, fine particles from these man-made dumps are carried up into the air and deposited on to residents’ homes. It is no ordinary dust, either: the residue of decades of mining, it can contain traces of everything from copper and lead to cyanide and arsenic.

“During August and September, the dust is terrible. You stop cleaning the floor after a while. It’s just useless,” says Plaatjies.

In the local clinic, respiratory cases such as tuberculosis and asthma are ubiquitous across all age groups, says Musa Mbatha, chairman of the clinic’s civic committee. Rashes and skins diseases are commonplace, too.

“People can’t afford to buy food every day, so they leave the food and it gets contaminated,” Mbatha adds. “The government said that it would do a survey of the health impacts of the mining dust, but until today it hasn’t happened.”

An even more dangerous pollutant is lurking in Johannesburg’s mine dumps, however: radioactive waste. According to one university study, an estimated 600,000 metric tonnes of radioactive uranium are buried in waste rock in and around Johannesburg – around three times what was exported during the Cold War. 

“[Johannesburg] is undoubtedly the most uranium-contaminated city in the world,” says Dr Antony Turton, a professor at the University of Free State’s Centre for Environmental Management.

Uranium naturally occurs in reefs alongside gold, meaning the two are often excavated at the same time. For every tonne of gold mined in the Witwatersrand gold fields – the southern sections of which border western Johannesburg –between 10 and 100 tonnes of uranium were also mined.

“For most of the gold mines, uranium was merely a waste product and therefore dumped without being recovered. Those tailing disposal facilities therefore have a relatively high uranium concentration today,” Turton says.

Without the proper precautions in place, ore-bearing uranium leaches from the tailings and enters as run-off into surrounding streams and wetlands. A similar process occurs in abandoned mines underground, with polluted water seeping through porous rock as the mines flood.

Despite its vast reserves of groundwater, Johannesburg pumps most of its drinking water from Lesotho – more than 380km away – because its own water reserves are too polluted.

Mine waste is also removed illegally from tailings for use in the manufacture of bricks and for other construction purposes, some environment groups allege. Potentially, the physical infrastructure of Johannesburg could be becoming radioactive as well.

The release of uranium in dust form can be exacerbated by the re-mining of tailings – a process that happens in various locations across the city. The companies involved in this re-mining maintain that they are providing an environmental service by removing waste and depositing it in modern tailings that are better regulated.

David van Wyk, chief researcher at the Bench Marks Foundation, a church-funded non-profit based in Johannesburg, is sceptical about mining companies’ environmental practices. “When the uranium price is very low, the mining companies simply dump it. That’s why the dust is yellow. We call it ‘yellow cake’,” he says.

Bench Marks, which receives support from UK charity Christian Aid, is mid-way through a three-year impact assessment of pollution levels in an around Johannesburg’s Soweto district. By systematically tracking air and water contamination, Bench Marks hopes to provide a scientific basis for the alleged health impacts of the tailings………http://www.theguardian.com/cities/2015/jul/06/radioactive-city-how-johannesburgs-townships-are-paying-for-its-mining-past