"Look at my spinach. That is the sand from the mine. The yellow one in the soil - it's destroying everything," said Thabo Ngubane as he tended his small allotment in Soweto.
In Johannesburg, tens of thousands of poor people like him spend their lives in the shadow of vast mine dumps, exposing them to toxic substances such as arsenic, lead and uranium. The gold rush from 1886 that caused the imposing slag heaps to spring up saw many investors and miners become fabulously wealthy.
The same was not true of those who lived and worked near the pits, and were exposed to dangerous cocktails of dust and chemicals.
More than 200 mounds of earth contaminated with heavy metals, notably uranium, lie within sight of the country's commercial capital, according to the Harvard International Human Rights Clinic.
They include the one close to where 50-year-old Ngubane tends his vegetables in Snake Park in the north of the Soweto township.
"When there is heavy rains, all the mine waste comes here and erodes everything," he said.
"This month, 22 of my baby pigs died... I think it's because of the mine."
When the waste comes into contact with water, oxidation causes an extremely dangerous solution to form.
The company responsible for the slag heap built a storage pool to allow contaminated water to evaporate in an effort to protect the neighbouring homes from pollution.