Flowering plants can transfer radiocesium from soils to honey bees, who can then concentrate the contaminant in honey. ARX0NT/ISTOCK

Fallout from nuclear bomb tests in the 1950s and ’60s is showing up in U.S. honey, according to a new study. Although the levels of radioactivity aren’t dangerous, they may have been much higher in the 1970s and ’80s, researchers say.

“It’s really quite incredible,” says Daniel Richter, a soil scientist at Duke University not involved with the work. The study, he says, shows that the fallout “is still out there and disguising itself as a major nutrient.”

In the wake of World War II, the United States, the former Soviet Union, and other countries detonated hundreds of nuclear warheads in aboveground tests. The bombs ejected radiocesium—a radioactive form of the element cesium—into the upper atmosphere, and winds dispersed it around the world before it fell out of the skies in microscopic particles. The spread wasn’t uniform, however. For example, far more fallout dusted the U.S. east coast, thanks to regional wind and rainfall patterns.