I found that out the HARD way! My whole garden began to die off, with brown splotches on the leaves... I had to take the leaves to a co-op place to get a diagnosis... I was told that tobacco has a nasty fungus on the leaves...and my smoking and then even touching my plants had been my undoing! They called it Tobacco Mosiac, and it's highly contagious in the garden! I lost the whole thing in less than 10 days. No way to stop it. And then there was this little tidbit of infornation: I have successfully poisoned my soil for some time with that fungus now! If you smoke, don't step on your cigarette butts and then walk into your garden. ALWAYS: Wash your hands before you touch anything after smoking! Man that fungus really bites!