In article , Michael
Green writes
Bananas and Brazil nuts concentrate radioactive Potassium (and
Polomium in the case of Brazil nuts). Why?

According to sites on the web its Radium that Brazil Nuts concentrate.
That would make sense - Brazil Nuts are known for concentrating
Strontium and Barium, and Radium is chemically similar to those
elements.

Brazil Nuts are high in Selenium. I don't recall anything about the
chemistry of Polonium, but from its position in the periodic table I'd
expect similarities to that of Selenium.

Bananas concentrate Potassium. From the point of view of a Banana's
metabolism the differences between radioactive and other isotopes of
Potassium is negligible.

So it seems likely that the concentration of Radium and Polonium by
Brazil Nuts is a side effect of the concentration of Barium, Strontium
and Selenium, and the concentration of radioactive Potassium by bananas
is a side effect of the concentration of Potassium in general.
--
Stewart Robert Hinsley