Hey Mr. Geiger Counter, Tally Me Banana

Incidentally this is post 425, 5²×17. The last one was 424, 2³×53.

Anyway I discovered something awesome. Namely, the thing called "Banana Equivalent Dose". See, bananas are mildly radioactive, due to a small amount of potassium-40 isotope incorporated in their structure (tissues tend to incorporate radioactive isotopes as easily as nonradioactive ones, that's why carbon-14 dating works on any organic material).

Specifically, eating one banana exposes you to roughly 0.1 μSv (a tenth of a microsievert) of radiation. This fact leads to the banana-based method of expressing radiation exposures. E.g., living within 50 miles of a nuclear power plant exposes you to half a banana per year of radiation. Living that close to a coal power plant exposes you to three bananas. Yep, coal power plants expose you to six times as much radiation as nuclear ones—nuclear plants are set up to keep radiation from getting out, while coal plants are just fires (coal contains a minuscule quantity of radioactive material, mainly uranium, barium, thorium and the same potassium isotope as in bananas).

It seems a Brazil nut (which also contains—holy Marie Curie, Batman!—radium) is four bananas worth of radioactivity. Living on the Colorado plateau, I get about 12 bananas of radiation a day just from the elevated background radiation, over and above the 100 bananas one absorbs from normal background radiation. You get 400 bananas from an airline flight (the higher you go, the more radiation there is).

A chest x-ray is only 200 bananas, while a chest CT scan is a whopping 58,000 bananas—and incidentally, spending an hour at Chernobyl in 2010 is 60,000 bananas, so go easy on the CT scans. Interestingly, living in a building mainly made of minerals (brick, stone, concrete, etc.) will give you 700 bananas a year; living ten miles from Three Mile Island at the time of the accident gave you 800 bananas, or the equivalent of 4 chest x-rays.

The maximum yearly dose permitted to US radiation workers, by law, is half a million bananas. A full million bananas is the smallest radiation dose clearly linked to increased cancer rate; 4 million bananas' exposure in a short time will cause symptoms of radiation poisoning. 20 million bananas is severe radiation poisoning, the sometimes-fatal kind; 40 million is usually fatal but is survivable with prompt treatment. The fatal dose even with treatment is 80 million bananas.

I really shouldn't be having as much fun with this as I am.