Have you brought up the polonium argument yet? I'm lazy, so I'm just copying and pasting this from another post of mine.

Originally Posted by graph
Cancer is a very dangerous thing, and there have been arguments back and forth about what is worse. Keep in mind, while tar has shown to be one of many contributing factors in lung cancer, what has shown to be more prevalent in causing any type of cancer is radioactivity. Tobacco industries use polonium-210, which is a radioactive substance, to grow tobacco plants. While the FDA says that polonium-210 was shown to have no negative side affects while ingesting plants grown using the radioactive substance, it is still inconclusive if smoking such plant can cause lung cancer. Also, keep in mind cannabis users don't smoke leaves, but the bud, which contains 33% less tar, and cannabis does not narrow the air passages in the lungs like tobacco.
Your buddy is dead wrong, ppl get cancer for cigarrets because of the fact that the government has growers grow the tobacco in some kind of soil that has small amounts of radioactivity, I wich I could remember the soruce, if any has heard of this post it.
Tobacco crops are fertilized with calcium phosphate fertilizers derived from the mineral apatite which does contain traces of radium, polonium 210 and lead 210. When the tobacco is growing these particles get trapped and concentrated on the leaf. Polonium 210 is the only ingredient in tobacco tar that has been proven to cause cancers in lab animals by itself.

http://www.acsa2000.net/HealthAlert/...e_tobacco.html
http://www.ukcia.org/research/cancer2.htm
http://nepenthes.lycaeum.org/Drugs/T...ancer.rad.html
http://en.wikipedia.org/wiki/Health_...obacco_smoking