Banana equivalent dose

A banana contains naturally occurring radioactive material in the form of potassium-40.

Banana Equivalent Dose (BED) is an informal expression of ionizing radiation exposure, intended as a general educational example to indicate the potential dose due to naturally occurring radioactive isotopes by eating one average-sized banana. One BED is often taken as 0.1 µSv, however, in practice this dose is not cumulative, as the principal radioactive component is excreted to maintain metabolic equilibrium. The BED is only an indicative concept meant to show the existence of very low levels of natural radioactivity within a natural food and is not a formally adopted dose quantity.
For example, the radiation exposure from consuming a banana is approximately 1% of the average daily exposure to radiation, which is 100 banana equivalent doses (BED). The maximum permitted radiation leakage for a nuclear power plant is equivalent to 2,500 BED (250 μSv) per year, while a chest CT scan delivers 70,000 BED (7 mSv). A lethal dose of radiation is approximately 35,000,000 BED (3500 mSv). A person living 16 kilometres (10 mi) from the Three Mile Island nuclear reactor received an average of 800 BED of exposure to radiation during the 1979 accident.[1]


1 History
2 Source of radioactivity
3 Radiation from other foods
4 See also
5 References
6 External links

The concept probably originated on the RadSafe nuclear safety mailing list in 1995,[original research?] where a value of 9.82×10−8 sieverts or about 0.1 μSv was suggested for a 150-gram banana.[2]
Although this unit is not formally adopted, the use of the word “equivalent” may still cause confusion. Properly, any dose quantity, which is a measure of the health effect of radiation on the whole body, is known as an “effective” dose. Equivalent doses only relate to specific organs of the body.
Source of radioactivity[edit]

Approximate doses of radiation in sieverts, ranging from trivial to lethal

The major natural source of radioactivity in plant tissue is potassium: 0.0117% of the naturally occurring potassium is the unstable isotope potassium-40 (40K). This isotope decays with a half-life of about 1.25 billion years (4×1016 seconds), and therefore the radioactivity of natural potassium is about 31 Bq/g – meaning that, in one gram of the element, about 31 atoms will decay every second.[3][4] Plants naturally contain radioactive carbon-14 (14C), but in a banana containing 15