The poison they say he was killed with is polonium 210. However, the half life (how fast it decays) is only about 5 - 6 months. Arafat died in 2004. That means its impossible to show he died from polinium 210 poisoning, but that won't stop people from saying he was killed by it.
Ex-FM Lieberman: Firebomb attack in Jerusalem a reminder that norm is Arab terror against Jews (Haar
from the article: French, Swiss investigators to visit West Bank for Arafat death probe