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So Kaste and his colleagues—including one of his undergrads—collected 122 samples of locally produced, raw honey from across the eastern United States and tested them for radiocesium.

In both data sets, the researchers found that radiocesium levels had declined sharply since the 1960s—a similar trend that likely occurred in honey.

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.

Radiocesium is soluble in water, and plants can mistake it for potassium, a vital nutrient that shares similar chemical properties.

To see whether plants continue to take up this nuclear contaminant, James Kaste, a geologist at the College of William & Mary in Williamsburg, Virginia, gave his undergraduate students an assignment: Bring back local foods from their spring break destinations to test for radiocesium.