You have, what?, 1/40th the polonium in the brush that you did back in 1992?
Anyway, legal answer: what you have is an amount of polonium that is produced in extremely small amounts, and is considered by the NRC to be an exempt quantity for regulatory purposes.
http://www.nrc.gov/reading-rm/doc-co.../polonium.html
So just throw it away. Or keep it. Whatever you want.