Polonium-210 is an isotope of polonium. It undergoes alpha decay to stable 206Pb with a half-life of 138.376 days, the longest of all naturally occurring polonium isotopes. First identified in 1898, and also marking the discovery of the element polonium, 210Po is generated in the decay chain of uranium-238 and radium-226. 210Po is a prominent contaminant in the environment, mostly affecting seafood and tobacco. It is also extremely toxic to humans as a result of its intense radioactivity.