OWYHEE, Nev. (AP) — The Shoshone-Paiute Tribes of the Duck Valley Indian Reservation have long grappled with contaminants embedded in the land and water.

For decades, the tribes suspected that widespread illness and deaths from cancer are tied to two buildings owned and operated by the U.S. Bureau of Indian Affairs. Fuel, herbicides and other chemicals spilled onto the dirt floors of the now-shuttered or demolished structures.

Earlier this year, the BIA discovered a decades-old document with a passing mention of Agent Orange that suggests the government might have been more involved in contaminating the land than previously known, this time around the irrigation canals. The community is still waiting to get answers.

Sacred land, now contaminated

Owyhee is the sole town on the reservation where snow-capped mountains loom over a valley of scattered homes and ranches, nearly 100 miles (161 kilometers) from any stoplights. Bookended by deep Nevada canyons and flat Idaho plains, the valley is home to “Sho-Pais,” whose ancestors were confined there by the federal government.

For generations, the legacy and livelihood of residents have centered around raising cattle year-round. Many of the 1,800 or so residents still use the same medicinal plans and practice the same ceremonies as their relatives buried under them.

Representatives from the BIA and the U.S. Environmental Protection Agency visited the reservation as recently as Aug. 7 to talk about the contamination and review the report that mentioned Agent Orange. Action can’t come soon enough for tribal members who say the federal government’s past cleanup attempts have lacked urgency and direction.

“People are dying. And I don’t know what they’re waiting for,” said tribal Chairman Brian Mason.

First spills, then potential sprays

Historically, most of the environmental dangers at Owyhee have been traced to two BIA buildings that have since closed or been demolished.

Back in 1985, at the now-abandoned irrigation shop, some 8,000 gallons of heating oil leaked from a pipeline next to a two-lane highway that acts as the area’s main road. Samples taken from sump, soil and floor drains around the building revealed a mix of the hazardous chemicals that were stored inside, including waste oil, arsenic, copper, lead and cadmium, along with the two herbicides that make up Agent Orange.

Racheal Thacker, a pesticides and solid waste technician with the tribes, said residents at the time were likely unaware of the dangers related to handling the chemicals stored there. Back then, she said, the workers employed by the BIA didn’t have the expertise or resources to identify pollutants in the ground.

In 1995, the EPA ordered the BIA to stop discharging gasoline, batteries and other fluids onto the dirt floor of the maintenance building, saying the practice was improper, threatened the groundwater supply and could endanger tribal members’ health. The disposal practice had long-lasting effects. The building has since been demolished and is fenced off.

In its statement to the AP, the BIA said it has extensively studied the soil and groundwater on the reservation since 1999 and cleaned up wells used for drinking water. The agency also said any petroleum in the soil is safe and it’s working with the tribe on other remedial actions.

Link between toxins and deaths from cancer

To the community, there’s a clear link between past contaminants and the pronounced number of cancer cases and other illnesses.

Mason validated those beliefs in an announcement earlier this year. He stood at a podium and declared — without caveats — that the BIA further poisoned the tribes’ land. Agent Orange chemicals were sprayed extensively by the canals, he said, and demanded the government take quick action.

Health experts say it’s nearly impossible to say with certainty that the environment factored into cancer diagnoses and deaths — especially without robust data.

The tribal health clinic has logged more than 500 illnesses since 1992 that could be cancer, and is trying to break down the reservation’s data to determine what were the most common types. A switch in recent years from paper to electronic filing means the records are likely incomplete.

Even if the BIA is able to account for the time, frequency, concentration and volume of herbicides sprayed on the reservation, that wouldn’t be enough to prove a cause, experts say. Genetics, lifestyle and other factors often combine to form a diagnosis.

“Bottom line is it’s really, really complicated even to establish among things we already sort of know about,” said Lauren Teras, the senior scientific director of epidemiology research at the American Cancer Society.

Mason has called for a study that would give tribal members a better idea of the extent that chemicals could have been sprayed, and the effect on the tribes’ land and its residents. He said that might provide tribal members a pathway to seek payment from the federal government.