Re: How harmful is smoking hookah?
A quick note about nicotine being "poisonous".
Talking about something being poisonous only makes sense within the context of time/dosage exposures and insofar as smoking concerned nicotine toxicity isn't really an issue. Smoking high nicotine tobaccos is not somehow more dangerous then smoking low nicotine products and how much nicotine you absorb into your blood stream is mainly a matter of how rather then what you smoke.
What is an issue the matter of addiction and it is dubious for the reasons I've cited before so those interested should check out the stuff i've cited on the issue.
What is dangerous about smoking are the solid particulates in the smoke stream, the tar and CO. All of those things can be dealt with by common sense use of coals, moderation and smoking method.