hookah isnt less harmful, than cigarrettes ...
there was a test of a german chemistry student, who checked everything in a labor, with his own hookah (an egypt one) and al fakher tobacco.
the result was, that every drag on the hookah contained 5x more nicotin, than a cigarrette. but you blow 90% of it out with the smoke and some nicotin was in the water.
all in all 1 hookah session is the same as smoking a cigarrette. but mostly you smoke with some other ppl (its like sharing a cigarrette with 1 or 2 friends
) and you smoke longer...
the arab tests made some years ago said hookah is 50x as harmful as cigarrettes. but they took about 20g of tobacco for a normal clay bowl and smoked it with ql-coals. they dragged it with a apparat, what dragged like a vacuum cleaner. so the tobacco scorched ... no one would be able to smoke like this ^^