Hookah

Hookah is a pipe used to smoke Shisha, a combination of tobacco and fruit or vegetable that is heated and the smoke is filtered through water. Hookah smoking delivers the addictive drug nicotine and the smoke from a hookah (or waterpipe) is at least as toxic as, or more toxic than cigarette smoke. Due to the variety of flavors like mint, cherry, and licorice, along with exotic paraphernalia, and social use at hookah bars, there has been an increase in popularity with people who don’t already smoke cigarettes and younger people in the United States.
Health risks:

A typical one-hour session of hookah smoking exposes the user to 100 to 200 times the volume of smoke inhaled from a single cigarette.
Hookah smoking has been associated with lung, mouth, and other cancers
Hookah smokers are more prone to experience heart disease and respiratory infections
Substances used to heat the tobacco also produces carbon monoxide, heavy metals, and cancer causing chemicals creating additional health hazards
Sharing the hookah mouthpiece has been associated with mouth and other infections including herpes, tuberculosis, and hepatitis.

References:

http://www.ct.gov/dph/lib/dph/hems/tobacco/tobacco_products.pdf

http://www.who.int/tobacco/global_interaction/tobreg/waterpipe/en/index.html obtained July 15, 2009

WHO Study Group on Tobacco Product Regulation. Advisory note: Waterpipe Tobacco Smoking: Health Effects, Research Needs and Recommended Actions by Regulators. World Health Organization, 2005.