I agree with everything that has been said. I know that methane (not from the cigarettes) is harmful to orchids as evidenced by the Miami collector who won a judgment against the city of Miami for destroying his orchids. Similarly the ethylene gas given off by ripening fruit does have an effect on plants (not sure about orchids) but it was noticed that ethylene gas lights in the 1880's made plants around them grow differently- faster in most cases. I would imagine that unless it is bags and bags of tomatoes the effect might be minimal. I know to ripen my fruit using the ethylene gas from a banana I have to enclose the fruit in a paper bag with the banana.
I would also make you like ksriramkumar said to wash your hands. I have heard numerous reports about tobacco mosaic virus being spread that way.
As for the smoking I am not trying to preach at all so please don't take it this way but in the United States (not sure where you are) most if not all states have tobacco cessation programs that are paid for out of the tobacco settlement money. After registering for a card (there are some age restrictions) you can get free medical care related to smoking cessation, free medications including pills and patches to quit smoking and individual or group counseling to do so. Most people are totally unaware of the program including most of the doctors I have talked to about as a medical student.