Though he no longer lives there, Mumba grew up in Chingola — his dad worked as a miner before becoming a Pentecostal minister. Knowing that his community was suffering, he felt he had to do something, so he travelled some 250 miles north from his home in Lusaka to investigate. What he saw startled him, particularly when it came to the Kafue — the river was barren, even at his favorite fishing spot.

“It gave me an awakening as to what was happening,” he says. “It brought this feeling like something has to be done about this. It should not and could not go on.”

The Nchanga mine, which has been in operation for nearly a century, has always been a fixture in Chingola. Indeed, the city was established in the 1940s to support the complex, which includes the world’s second largest open pit mine, along with several underground mines, a smelter, a sulfuric acid plant, a tailings dam, and a refinery.

But locals say that while they have long lived alongside Nchanga, things changed for the worse in 2004. That’s when Vedanta Resources, which is headquartered in the United Kingdom, purchased a controlling stake in Konkola Copper Mines (KCM), which operates the Chingola mine. Soon, copper, iron, cobalt, and dissolved sulfates were detected in local waterways at levels far above legal thresholds. Locals began suffering headaches, nose bleeds, rashes, burns, and other health impacts. In 2006, the river ran bright blue due to contamination. City residents sued Konkola in Zambia that year but ultimately lost after several years of litigation.

When, Mumba learned of this painful history in 2013, he knew he had to hold Vedanta to account, but he didn’t know where to start. So he did what so many of us do in these situations — he turned to the Internet and started searching for people who could help.

“I decided to try and get in touch with as many NGOs and law firms as possible to bring attention to this issue,” he says. “I must have written to maybe close to 100 of them.”

This effort, which Mumba describes as essentially a shot in the dark, paid off. One of the law firms he reached out to, the UK-based Leigh Day, wrote back. And two weeks later, attorney Oliver Holland was in Zambia to learn more and see how they might make a case against Vedanta in UK court.

It wouldn’t be easy. First, Leigh Day had to figure out what had happened with the Zambian court case and why it hadn’t succeeded. Then they had to confirm that those impacted most by the pollution — residents of four villages in Chingola — were on board with filing a new lawsuit.

Mumba played a major role supporting that effort, facilitating discussions between Leigh Day and community members. He also helped collect blood samples for analysis, overcoming rumors spread by KCM that the samples would be sold, rather than used for the case. He helped obtain witnesses to testify against the company. And he persevered through attempts to stop him, including a 2017 arrest during a meeting with villagers — by police who arrived in a KCM vehicle.

“I think my time being there and building that trust with the community contributed to the success and brought us to where we ended up,” he says.

Where they ended up was with a 2015 lawsuit in the UK, and ultimately a 2019 supreme court ruling that Vedanta, as a controlling stakeholder in Nchanga, could be held liable in UK court for the environmental damage wrought by the Nchanga copper mine. It was a landmark decision, the first time the British supreme court had held that a UK-based company could be held accountable for the actions of a subsidiary acting outside of Britain.

It was a major moment for Mumba as well, the culmination of six year’s work that had pulled him away from his day job running an orphanage in Lusaka with his wife, and took him away from his wife and children.

“It was an ecstatic feeling for me,” he says of the moment he learned they had won. “I cannot quite put it into words.”

The decision has already reverberated within Chingola. In 2021, Vedanta settled with the 2,000-plus Chingola residents who brought the UK lawsuit for an undisclosed amount. Since the settlement, Mumba says that Vedanta and other mining companies operating in the area have been engaging more responsibly with locals. Several other communities have also approached him regarding similar experiences with polluting industries. Muma has been acting an advisor and intermediary with mining companies as they figure out next steps. He was cautious not to say more, lest he jeopardize their efforts.

The impact of the UK court ruling has extended beyond Chingola as well. In 2021, a British court permitted a lawsuit by 42,500 Nigerian residents to proceed in the UK against Shell Global for contamination of their land and groundwater by oil spills in the Niger Delta, relying on the precedent set in the case.

For his leadership in holding Vendata Resources to account, Mumba was awarded the prestigious Goldman Environmental Prize earlier this month, along with five other activists from around the world.