FaktowoBananas are radioactive. And that's not a problem
Every banana contains a trace of radioactive potassium-40. Physicists even use it as a tongue-in-cheek unit of radiation dose.
Bananas are rich in potassium. About 0.012 per cent of all potassium on Earth is the isotope potassium-40, which is radioactive. Since a banana contains potassium, it contains potassium-40 too.
An average banana has an activity of about 15 becquerels – that is, 15 nuclear decays per second. That sounds alarming, but it corresponds to a dose of about 0.1 microsievert. For comparison: a chest X-ray is roughly 100 microsieverts, and a flight across the Atlantic about 40.
The banana unit
Nuclear physicists came up with a half-joking ‘banana equivalent dose’ to explain to non-specialists how small some radiation doses are. Living near a nuclear power plant for a year amounts, on this scale, to roughly the same as eating a few bananas.
Importantly, the body keeps its potassium level constant. When we eat a banana, the excess potassium – and with it potassium-40 – is excreted. So it is not possible to ‘accumulate’ bananas in the body.
Not just bananas
Potassium-40 is found in potatoes, beans, nuts and in ourselves. An adult's body contains enough of it for several thousand decays to occur in it every second. We are, in the literal sense, slightly radioactive – and everything is fine.
- UNSCEAR, “Sources and Effects of Ionizing Radiation”, raport dla Zgromadzenia Ogólnego ONZ, tom I, 2008
- Eisenbud M., Gesell T., “Environmental Radioactivity from Natural, Industrial and Military Sources”, wyd. 4, Academic Press, 1997
- Health Physics Society, “Radiation Basics – Natural Background Radiation”, materiały informacyjne
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