The sounds of children playing baseball has been silenced at one ball field in this western North Dakota city. Officials fear the ground itself is simply too unsafe.
The ballpark, one of two in this town of about 700 people, is covered with crushed gravel containing erionite, a mineral found in the chalky white rock mined from the nearby Killdeer Mountains.
The rock, used for decades on everything from gravel roads to flower beds, contains fibers that can collect in the lungs of people who breathe it, health officials say.
Steve Way, a federal Environmental Protection Agency coordinator, said studies have shown that erionite causes cancer in lab rats, though the mineral is not regulated by his agency.
Erionite is found in at least a dozen states in the West, but Way said he did not know of another area in the U.S. that uses it "at the same magnitude" as Dunn County.
The mineral also has been found in gravel mines in Stark and Slope counties, in southwestern North Dakota. Officials there also have been asked not to use the gravel.
"We definitely should be looking at this for health concerns," Way told a group of about 60 residents at a meeting Tuesday night in Killdeer.
Killdeer Mayor Dan Dolechek said the ballpark was shuttered as a precaution, and the county voluntarily quit using gravel from the Killdeer Mountains until studies are completed. But many residents are more worried about road maintenance than the risk of cancer from the gravel.
State Rep. Shirley Meyer told federal and state officials at the meeting that Dunn County now will have to look outside its borders for gravel, a potentially costly change.
"It seems to me like you're making a mountain out of a molehill with what little data you have," Meyer told EPA and state officials. "The taxpayers in this county are having a tough time trying to swallow this."
Federal and state officials have been testing rocks and airborne samples from Dunn County over the past two years. But they say more tests, including tests on humans, are needed.
The EPA said it wants to test local residents who have had long-term exposure to erionite, and is looking for volunteers. Way said testing would continue through the spring, with results of the study completed in about 18 months.
"I'm 80 years old and it hasn't killed me yet," said Milton Johnson, who ranches in the Killdeer Mountains. "They can test my lungs if they want — I've been breathing it all my life."
Gary Jepson, another rancher in the area, called the worries over erionite "one of those sky-is-falling kind of deals."
State geologist Ed Murphy, who notified the EPA of the erionite in the region two years ago, said the county officials are trying to balance one health concern against another.
"We're looking at long-term health problems caused by erionite and somebody getting killed on the roads out there — you've got to keep something on the roads to keep them safe," Murphy said.
In the nation of Turkey, erionite has been linked to mesothelioma, an incurable form of lung cancer commonly associated with asbestos exposure, health officials say.
Erionite found in North Dakota differs slightly than the mineral found in Turkey, where it's a known carcinogen, Murphy said. Erionite in the state is more calcium based; the mineral in Turkey is sodium based, he said.
Western North Dakota could have "hundreds of miles" of roads paved with gravel containing erionite, Murphy said. Paving them with asphalt would be too costly, state officials say.
The bright white appearance of the rock mined from the Killdeer Mountains is the reason Deb Harsche puts it in her flower beds.
"It looks nice — I haven't had any problems with it so far," she said. "Every white gravel road you see around here, that's what's on it.
"If it is determined to be cancer-causing, then what?" she asked.
Way, of the EPA, said the agency wasn't looking that far ahead.
"I don't have an answer," he said.