BOISE, Idaho (AP) — A land exchange between the U.S. and an Idaho agribusiness will expand a giant toxic waste pile next to tribal land and harm tribal members, an eastern Idaho tribe said in a lawsuit.

The Shoshone-Bannock Tribes in the lawsuit filed in federal court Friday seek to block the land exchange between the U.S. Bureau of Land Management and Idaho-based J.R. Simplot Company.

The tribes say the Blackrock Land Exchange approved last summer violates environmental laws and an 1868 treaty. The lawsuit said the exchange will expand phosphogypsum stacks next to the tribes’ reservation.

The stacks are waste from fertilizer production and contain small amounts of naturally occurring radium and uranium. The stacks also can release large concentrations of radon gas.

The tribes said an environmental impact statement intended to identify potential problems was poorly done and violated various environmental laws that will lead to air and water pollution at the tribes' 840-square-mile (2,200-square-kilometer) Fort Hall Reservation.

The tribes said existing phosphogypsum stacks are polluting the Portneuf River that flows through the Reservation.

"Wind also carries fine particles of radioactive material from the gypsum stacks to the Reservation and toward the cities of Chubbuck and Pocatello,” the lawsuit states. “The (environmental impact study) does not adequately evaluate the health impacts, both physical and mental, that result from living adjacent to one of the nation’s most hazardous toxic sites.”

The tribes also said the deal privatizes land previously subject to the treaty that promised access to traditional activities such as hunting and fishing on lands outside the reservation.

The U.S. Justice Department, which defends federal agencies in lawsuits, didn’t respond Wednesday to a request for comment sent through its online media inquiry portal.

The deal has Simplot receiving 719 acres (290 hectares) adjacent to its existing gypsum storage area and phosphate facility, called the Simplot Pocatello Don Plant in Pocatello. The heavily polluted site was listed as part of a Superfund site in 1990 because of past phosphate processing operations. Phosphate is mined in giant open pits in the region and then taken to plants to be processed.

In exchange, the bureau received 667 acres (270 hectares) of Simplot's private land in the Blackrock and Caddy Canyon area about 9 miles (14 kilometers) southeast of Pocatello. It's considered a prime recreation area and also key habitat for wildlife.

The lawsuit notes that Idaho's Congressional delegation in 2018, at the request of Simplot, proposed legislation to circumvent environmental studies and mandate approval of the land exchange. However, the legislation didn't advance out of a committee.

Under President Donald Trump, the U.S. Environmental Protection Agency has slashed support for some programs and regulatory protections benefiting disadvantaged communities. His budgets have proposed killing or cutting funds to enforce regulations promoting environmental justice — fair treatment of racial minorities and low-income residents who live near polluting industries and are disproportionately exposed to contamination — although Congress has continued most of the spending.

Phosphate mining is a major business in southeastern Idaho, where phosphate ore is turned into fertilizer needed by farmers to grow food. Simplot started mining in the area about 80 years ago.

Simplot is a privately-held multinational agricultural company engaged in a wide array of activities that include seed production, farming, ranching, frozen-food processing and gene editing.

Simplot spokesman Josh Jordan, in an email to The Associated Press on Wednesday, didn't address specifics in the tribes' lawsuit but said the company has invested millions of dollars at its plant in Pocatello to improve the environment. He also said the plant is a major community employer, with just under 400 workers.

“This facility provides nutrients needed to grow the crops that help maintain food security in North America,” Jordan said.