Strontium unit

The strontium unit is a unit used to measure the amount of radioactivity from strontium-90, a chemical found in nuclear fallout, in a subject's body; as the human body mistakes the substance for calcium and incorporates it into the skeleton, its presence is very common. One strontium unit is equal to one picocurie from strontium-90 per gram of calcium (37 becquerels per kilogram) in the subject's skeleton.

The United States National Academy of Sciences holds that the maximum safe measure of strontium-90 in a person is one hundred strontium units (3700 Bq/kg). The average American is estimated to have three to four strontium units.

The strontium unit was formerly known briefly as the sunshine unit, a term promoted by the United States Department of Defense until public ridicule brought about its disuse.