In 2006, a former Russian spy was allegedly murdered using Polonium -210. This radioactive chemical is also found in cigarette smoke, a fact at least one tobacco company was aware of in 1964.
Proctor, R.N. "Puffing on Polonium." The New York Times. 01 Dec. 2006. Web.
http://www.nytimes.com/2006/12/01/opinion/01proctor.html?ex=1166590800&en=ad9fa6ba36fdf6ab&ei=5070
"Polonium-210 In Tobacco Smoke As A Tracer For Particle Deposition And Movement In Human Lungs." Truth Tobacco Industry Documents, 15 Apr. 1964.
"Exposure Of Cigarette Smokers To Polonium-210." Truth Tobacco Industry Documents, 1964. Report.
Hager, JH. "Telephone Conversation, R. K. Heimann, This Date." Truth Tobacco Industry Documents, 09 June 1967. Letter.
Pedersen, PM. "Filter Cigarettes For Removing Polonium From The Smoke, Interview With Mr. Nelson Stewart On September 23, 1964." Truth Tobacco Industry Documents, 25 Sept. 1964. Letter.