The South Gauteng High Court Tuesday in South Africa continued hearing a case against mining company Anglo American South Africa on allegations of lead poisoning. Zambian communities brought the class action lawsuit after it was discovered that the town of Kabwe, Zambia contains the “world’s most toxic lead mine” called the Broken Hill mine.

The 12-day hearing is now on its fourth day. The court must decide whether to certify the class action and allow it to proceed. Amnesty International, the South African Litigation Centre, and several UN experts have been admitted as joint amici curiae. They informed the court of “international business standards,” and focused on the country’s duty to “regulate the conduct of its companies.”

The South African Litigation Centre’s Socio-Economic Rights Lead Brigadier Siachitema highlighted the human rights implications of the case, stating:

This case is not just another class action. Its certification is important not only to the people of Kabwe but to anyone who suffered human rights abuses as a result of transboundary corporate conduct by a South African company. South African courts have the power to level the imbalance and close the accountability gap that exists in practice.

Anglo American South Africa allegedly “operated and managed” the mine between 1925 and 1974, which contributed a large share of the contamination to the environment of the local Zambian community. The lead mine’s nearly half a century-long operations led to a “massive” level of soil contamination in Kabwe. Zambian officials discovered that soil lead levels in Kabwe were as much as ten times that of recommended safe levels. As such, childhood lead poisoning in Kabwe–especially in children younger than three–is among the highest in the world. Pregnant women also face a high risk of lead poisoning.