Perry Charley has spent nearly 40 years trying to heal his land.

Charley, a 62-year-old political and social activist, has lived his entire life on Navajo territory in New Mexico, and he speaks of its beauty with both reverence and melancholy. In the 1940s, just before he was born, a uranium mining boom swept across the Navajo Nation and other parts of the western United States, and soon accelerated as the US looked to expand its nuclear weapons program during the Cold War. The economic opportunities at first seemed bright for the Navajo, though they didn't fully understand the scope of the industry, or the risks it entailed.

"We saw an opportunity for money, for jobs. We saw an opportunity to make life a little better," says Charley, who works as an administrator at Diné College in Arizona. "We didn't know the nature of this element called uranium. We had no names for it. We didn't know what it was."

The mines closed in the 1980s, but their toxic legacy lives on in the Navajo Nation. Radioactive waste contaminated soil and water supplies, and many of those living nearby were afflicted with cancer and other chronic health problems. US authorities launched an extensive cleanup program in 2007, though the process has been costly and slow, and hundreds of abandoned mines and contaminated areas remain untouched.

Determining liability for the damages has also proven difficult, as many of the mining companies that once operated in the region have since gone out of business. But now, the government has taken a major first step: last week, the US Justice Department announced that energy company Anadarko Petroleum Corp. has agreed to pay $5.15 billion to clean up widespread contamination and pollution caused by Kerr-McGee, a Texas-based subsidiary with a long history of toxic business practices. Over the course of 85 years, Kerr-McGee's factories spread deadly chemicals and pollutants in several regions across the US — including the Navajo Nation — but prosecutors argued that the company avoided liability by spinning off its operations into a chemical company that later declared bankruptcy.