Radioactive Horses and Hot Weasels: Taming Radon at Hagerman Fossil Beds

Fossils from Hagerman Fossil Beds National Monument in Idaho carry an unusual hazard: they give off radon. It has troubled the monument's paleontology collection ever since the monument was founded in 1988.

Why the fossils are "hot"

The region's geology, combined with the way fossils form, left excessive uranium locked in Hagerman's fossils. As uranium decays it produces radon, a radioactive, colorless, odorless gas. How radioactive a fossil is depends on where it was deposited.

The fossils' radioactivity was well studied, but radon stayed a known problem for the staff who care for the collection. Offices and storerooms regularly exceeded the Environmental Protection Agency's limit of 4 picocuries per liter of air (pCi/L). High exposure can cause serious illness, including lung cancer. Earlier recommendations reduced exposure but never solved the problem.

Fossils in storage cabinets. NPS photo / Alex Kim.

A new building, a new study

When the collection moved into a new building in 2021, staff seized the chance to study the problem properly. Using Wi-Fi and Bluetooth sensors read through iPad apps, they logged hourly radon levels in every room and in individual storage cabinets, gathering more than thirty days of data for each.

Because fresh air dilutes radon and makes it less dangerous, experiments from August to December 2022 compared three approaches:

The idea was not new, but it was the first time comprehensive data had been collected in the building to standardize monitoring and permanently improve conditions.

The fix

• Energy recovery ventilation (ERV). Other museums, including the Arizona Museum of Natural History, use ERV systems to improve air and cut radon exposure. On the strength of the study, managers funded designs for one at Hagerman, and the data helped engineers tailor it — cutting costs and speeding up air replacement.
• Simple measures. Keeping temperature and humidity within set ranges, storing small fossils in airtight containers, and organizing cabinets by taxonomic family — giving the "hot" horses their own aisle — all helped.
• New procedures. Standard operating procedures were written for the collection, and weekly monitoring continues.

Part of a fossilized horse skull. NPS photo / Karina Rapp.

Lessons for "rad" museums

Long-term data can justify building changes and special construction for radioactive fossils and other hazardous objects, guide management and set storage standards. Monitoring equipment, mitigation systems, environmental controls and simple storage fixes can all make collections safer and easier to use for staff and the public, while saving money. A detailed technical paper was planned for later in 2024.

Sources

Based on "Radioactive Horses and Hot Weasels: Solving an Age-Old Problem at Hagerman Fossil Beds with Science," Hagerman Fossil Beds National Monument, National Park Service; a work of the United States government in the public domain.