Experts dispute Grand Canyon safety manager’s claim that radiation posed risk to public

Corrections & Clarifications: A previous version of this story misstated the primary type of radioactive particles emitted by uranium. It emits almost exclusively alpha particles.

GRAND CANYON NATIONAL PARK, Ariz. – It’s no cause for alarm. That’s what some experts said about a Grand Canyon safety manager’s allegation that thousands of people may have been exposed to dangerous radiation for nearly two decades inside a National Park building.

At issue are three buckets of stones believed to be uranium specimens, that were collected decades ago and stored from 2000 to 2018 in a museum collections building that was sometimes visited by tourists and students, as well as employees.

Elston “Swede” Stephenson, federal health and safety manager at the South Rim, recently fired off letters warning colleagues, members of Congress and media that untold numbers of people may have been endangered, yet National Park Service officials struck a “secrecy pact” and did not notify the public.

Stephenson based his assertion on radioactivity readings gathered by Park Service officials, which appeared to be hundreds of times higher than thresholds set by the government for exposure to radiation.

The U.S. Occupational Safety and Health Administration and the Arizona Bureau of Radiation Control are investigating the matter with the Park Service, and have declined to comment on Stephenson’s assertion. Instead, they say readings at the building – taken after the contents of the buckets were dumped into a defunct uranium mine -show no danger.

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As the controversy went viral this week, however, a number of experts declared that uranium is simply not a threat to humans, and questioned either the radiation readings taken by the Park Service or Stephenson’s interpretation of that data.

“It’s just a bucket of rocks,” declared Craig Little, a health physicist who worked 25 years at the Oak Ridge National Laboratory and now serves as a consultant at uranium producing facilities. “I wouldn’t line my baby’s crib with it, but…”.

Little and Modi Wetzler, a chemistry professor at Clemson University who studies nuclear waste, said there are three types of radiation, and uranium ore emits almost exclusively the least-dangerous alpha particles.

Wetzler said alpha particles are hazardous if inhaled or swallowed, but not externally dangerous because they can be absorbed and rendered harmless by a sheet of paper, a few inches of air, or a person’s outer layer of dead skin.

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“The safety manager doesn’t know what he’s talking about,” said Wetzler. “Uranium ore would have a (radiation) value of zero. Either that, or it’s not ore and there’s some communication problem.”.

Wexler later revised his criticism, acknowledging when uranium is stored for many years in closed containers “it is possible radioactivity would have built up,” though not to the level described.

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Little offered a different theory. He and other experts in the Health Physics Society suspect Park Service employees who measured radiation levels near the buckets may have misread the results by a magnitude of 1,000.

For example, the Park Service report shows radioactivity at “13.9 mR/hr” near the buckets, referring to milliroentgens per hour. While that would be dangerously high, he added, uranium could not possibly cause such a reading.

“It’s not even a regulated material,” Little said, adding that the only danger is if someone swallowed the mineral or inhaled it.

Others who claimed expertise fired off emails and social media posts expressing outrage at what they called a “scare story” or “fake news.” The report circulated so widely that the Hualapai Tribe issued a news release Tuesday clarifying that its resort known as Grand Canyon West “is NOT part of Grand Canyon National Park.”.

Stephenson said while he is not a uranium scientist he checked his calculations with experts. Moreover, he noted, National Park employees were fearful enough that they removed the buckets by lifting them with a mop handle, and OSHA technicians wore full protective gear when they visited the building.

Given all those factors, Stephenson said, he had an obligation to alert Grand Canyon employees and the public when Park Service administrators failed to do it.

State and federal officials have said they do not expect to complete their inquiry until spring.

Meantime, the mystery of what was in three 5-gallon paint buckets, where the materials came from, and whether the rocks presented a threat remains unsolved.

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What is clear is that the problem was isolated to a single building at the canyon. It presented no danger to the overwhelming majority of visitors.

And, even in that building, authorities say there is no remaining evidence of radioactivity beyond natural background levels.

Follow Dennis Wagner on Twitter: @azrover.

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