Polonium 210 and how dangerous can it be

If ingested, it is lethal in extremely small doses. Less than 1 gram (0.04 ounces) of the silver powder is sufficient to kill. A 2007 study by radiation experts from Britain's Health Protection Agency concluded that once polonium-210 is deposited in the bloodstream, its potent effects are nearly impossible to stop. A poisoning victim would experience multiple organ failure as alpha radiation particles bombard the liver, kidneys and bone marrow from within. The symptoms shown by Litvinenko — nausea, hair loss, throat swelling and pallor — are also typical.

Polonium makes a good weapon. Its large alpha particles of radiation do not penetrate the skin and don't set off radiation detectors, so it is relatively easy to smuggle across international borders. Polonium can be ingested through a wound or inhaled — but the surest method would be to have the victim consume it in food or drink. Litvinenko drank tea laced with polonium during a meeting at a luxury London hotel.

https://in.news.yahoo.com/the-poison-that-killed-sunanda-pushkar--all-you-need-to-know-about-polonium-210-053603842.html