If you spent time in the museum collectibles building at the South Rim of the Grand Canyon over the past two decades, you may have been exposed to unsafe levels of radiation.

Three five-gallon containers brimming with uranium ore were stored in the building, next to a taxidermy exhibit where tours sometimes stopped for presentations.

Here’s what you should know.

What is radiation?

Ionized radiation is the emission of energy, or high-speed particles, in the form of invisible rays. Radiation occurs naturally in amounts of about 300 millirems per year at sea level. Ambient levels at the Grand Canyon are higher due to the altitude and geology. 

Natural dosages are safe for humans. However, intense exposures from radioactive material may damage cells, leading over time to medical issues.

What factors affect contamination levels?

Dosage depends on how much radiation is emitted, how close a person is to the source, for how long, and what the individual is wearing.

What’s considered unsafe?

Radiation exposure is measured in a number of ways, and the danger depends on the age of the person and the type of radiation.

The Nuclear Regulatory Commission has established a general public limit of 2 millirems in one hour for adults, or 100 millirems in a single year. Limits for children are one-tenth that due to higher vulnerability. 

What are the risks of exposure?

Acute radiation poisoning may lead to immediate vomiting and other symptoms. It can also be fatal.

Lesser exposures may eventually cause cancers.

RELATED:  Are uranium mines near the Grand Canyon hazardous to wildlife?

How is radiation contamination treated?

There are no antidotes, but chemical therapies can purge some radioactive substances from the body. Decontamination is followed by long-term medical screening.

What should I do if I may have been exposed?

A number of federal agencies — the Department of Energy, Nuclear Regulatory Commission and Environmental Protection Agency — regulate industries that use radioactive substances with strict protocols for monitoring, reporting and addressing incidents.

However, there appears to be little guidance on how to address a possible past exposure for members of the public over a long period of time.

In the Grand Canyon incident, it is unclear how many people may have been exposed, and to what extent. Officials with the National Park Service and OSHA said they are investigating the incident, and stressed that there is no ongoing danger at the building.

Sources: Online materials of OSHA, the NRC, and U.S. National Library of Medicine.

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