As with all living things on earth, potassium-containing bananas emit radioactivity at very low levels occurring naturally from potassium-40 (40K or K-40),[22] which is one of several isotopes of potassium.[23][24] The banana equivalent dose of radiation was developed in 1995 as a simple teaching-tool to educate the public about the natural, small amount of K-40 radiation occurring in every human and in common foods.[25][26] The K-40 in a banana emits about 15 becquerels or 0.1 micro-sieverts (units of radioactivity exposure),[27] an amount that does not add to the total body radiation dose when a banana is consumed.[22][26]

This is because the radiation exposure from consuming one banana is only 1% of the average daily exposure to radiation, 50 times less than a typical dental x-ray and 400 times less than taking a commercial flight across the United States.