Radioactive uranium stored at the Grand Canyon from 2000 to 2018 may have exposed tourists and employees to harmful radiation, according to the park’s health and safety manager, a whistleblower.

Elston "Swede" Stephenson alleged that three five-gallon buckets of uranium sat in a museum collections building at the park starting in 2000, according to a report posted Monday by AZcentral.

The article includes Stephenson’s 45-slide presentation, which he created to document his findings. He estimated that adults may have been exposed to 140 times the radiation levels deemed safe by the Nuclear Regulatory Commission (NRC). Children exposed to the uranium potentially experienced 1,400 times the safe limit.

The room where the buckets were stored is located next to a taxidermy exhibit that was frequented by tourists, including children. Stephenson said any radiation contamination that reached the exhibits may have caused harmful exposure to children within seconds, and adults within a half-minute.

Radiation levels right next to the uranium were measured at 13.9 milliroentgen per hour, according to a report from the Park Service's regional safety manager. That is about seven times the safe limit recommended by the NRC. However, the same report also found that the radiation levels dropped to zero beyond a five-foot radius of the buckets.

On February 11, Stephenson alerted acting Interior Secretary David Bernhardt and Deputy Inspector General Mary Kendall to the problem in an email. "Respectfully, it was not only immoral not to let Our People know,” he wrote, “but I could not longer risk my (health and safety) certification by letting this go any longer."

At Stephenson’s request, technicians moved the uranium from the building on June 18, 2018, and transported it to Orphan Mine, located two miles from Grand Canyon Village. Footage shows that the team used store-bought dishwashing gloves to handle the buckets, and moved the rocks onto a truck with a mop handle.

Emily Davis, a spokesperson for Grand Canyon National Park, said that Stephenson’s claim would be investigated by the Occupational Safety and Health Administration and the Arizona Department of Health Services.

"There is no current risk to the park employees or public," Davis told AZcentral. "The information I have is that the rocks were removed, and there's no danger."

According to Stephenson, the buckets of ore were discovered in March 2018 by the teenage son of a park employee, described as a “Geiger counter enthusiast.” He noticed high readings on his counter in the basement storage room at Museum Collections Building (2C), located in Grand Canyon Village.

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Stephenson claims he was alerted to the problem during a safety audit. Calling it “bad mojo,” he requested help from National Parks specialists, who ultimately removed the uranium in June.

Stephenson said he decided to go public with the information after failing to persuade National Parks Service management to issue a warning to those who might suffer health consequences due to radiation exposure. Radiation contamination puts people at a heightened risk of developing cancer, especially if the exposure happened while they were children.

It is not yet clear at this time whether anyone visiting Grand Canyon Village between 2000 and 2018 was exposed to dangerous levels from the buckets of ore.