01.09.2017

Do you know the "Banana equivalent dose"?

A banana contains naturally occuring radioactive material in <br /> the form of potassium-40 (Photo: Creative Commons License)

A banana contains naturally occuring radioactive material in
the form of potassium-40 (Photo: Creative Commons License)

Banana equivalent dose (BED) is an informal measurement of ionizing radiation exposure, intended as a general educational example to compare a dose of radioactivity to the dose one is exposed to by eating one average-sized banana. Bananas contain naturally occurring radioactive isotopes, particularly potassium-40 (40K).

One BED is often correlated to 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 meant to inform the public about the existence of very low levels of natural radioactivity within natural food and is not a formally adopted dose measurement.

The origins of the concept are uncertain, but one early mention can be found on the RadSafe nuclear safety mailing list in 1995, where Gary Mansfield of the Lawrence Livermore National Laboratory mentions that he has found the "banana equivalent dose" "very useful in attempting to explain infinitesimal doses (and corresponding infinitesimal risks) to members of the public". A value of 9.82×10−8 sieverts or about 0.1 μSv was suggested for a 150-gram banana.

The banana equivalent dose is an informal measurement, so any equivalences are necessarily approximate, but it has been found useful as a way to inform the public about relative radiation risks. The radiation exposure from consuming a banana is approximately 1% of the average daily exposure to radiation, which is 100 banana equivalent doses. 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).

Have a look at Randall Munroe's chart of radiaton doses here. It gives a nice visual overview of radiation levels.

Do you also know a Mickey, a Wiffle or a Jiffy? There is more to come in our next Synergy newsletter.

Source: From Wikipedia, the free encyclopedia