I have never heard an accomplished grower who didn't claim that cigarette smoke is bad for the plants. From what I understand, if the plant senses enough smoke in the air, it will close it stomata for a few minutes or perhaps even hours. Plants use the stomata to breath and transpire and other important stuff, so it's like putting the plant on pause for that length of time. There are also those who say tabacco smoke is way more poisonous to plants than humans, and those who claim that tobacco conatins a common plant virus that can get on your hands and infect your plants.