i read so much arguing about this before and how harmful it is especially cigarettes. they were saying if you smoke around or even touch a plant after touching tobacco you can give it some disease and kill it. now heres the thing i smoke like a chimney in my room my grow box intakes nothing but stagnant ass cigarette and pot smoke all day long. my plants arent dead and been growing pretty damn nice in my opinion. although it could be the cause of some minor problems im not sure but they dont seem to mind it to much. check the link in the signature and look at the pictures you be the judge on how harmful it is

i think im more harmful to my plants by all the trimming i do to keep them small and bushy lol. oh i also handle my plants and touch them multiple times daily