Using old lists of potentially contaminated structures, federal and Navajo scientists have fanned out to rural reaches of the 27,000 square mile reservation  which includes swaths of Arizona, New Mexico and Utah  to measure levels of radium, a decay product of uranium that can cause lung cancer. Of 113 structures assessed so far, 27 contained radiation levels that were above normal.

Image There were a lot of things people werent told about the plight of Navajos and uranium mining, Stephen B. Etsitty said. Credit... Kevin Moloney for The New York Times

“In these situations, you have contamination in somebody’s yard or in their house,” said Harry Allen, the E.P.A.’s section chief for emergency response in San Francisco who is helping lead the government’s efforts. “To us, that is somewhat urgent.”

Many structures that showed high levels of radiation were vacant; some families had already moved out after hearing stories of contamination in their homes. But eight homes still had people living in them, and the E.P.A. and Navajo officials have worked to convince residents that it would be unsafe to stay.

“People had been told they were living in contaminated structures, but nobody ever did anything about it,” said Will Duncan, an environmental scientist who has been the E.P.A.’s main representative on the reservation. “They would tell us, ‘We don’t believe you are going to follow through.’ ”

But with a budget of nearly $8 million, the E.P.A. has demolished all 27 contaminated structures and has begun building ones to replace those that had been occupied. Typically, the agency pays a Navajo contracting company to construct a log cabin or a traditional hogan in the structure’s stead, depending on the wishes of the occupants. Mr. Allen said the cost, including temporarily relocating residents, ran approximately $260,000 per dwelling and took about eight months.

The agency also offers $50,000 to those who choose not to have an old home rebuilt.

Lillie Lane, a public information officer with the Navajo Nation E.P.A. who has acted as a liaison between the federal government and tribal members, said the program held practical and symbolic importance given the history of uranium mining here.

Ms. Lane described the difficulty of watching families, particularly elders, leaving homes they had lived in for years. She told of coming upon two old miners who died before their contaminated homes could be rebuilt. “In Navajo, a home is considered sacred,” she said. “But if the foundation or the rocks are not safe, we have to do this work.”