Water-pipe smokers may face the same health risks as cigarettes.
"Using a water pipe to smoke tobacco is not a safe alternative to cigarette smoking," the U.N. health agency said in a seven-page document on the practice. "Contrary to ancient lore and popular belief, the smoke that emerges from a water pipe contains numerous toxicants known to cause lung cancer, heart disease and other diseases."
The WHO "advisory note" warned that using water pipes to consume the tobacco, which is commonly a mixed with molasses and fruit flavors, usually exposes a person to more smoke over a longer period of time than do cigarettes. Preliminary research indicates that hookah smoking poses many of the same dangers as cigarettes and may involve "some unique health risks," the agency said.
A hookah is a bowl connected to a vase of water with a long tube and mouthpiece. The tobacco sits inside the bowl with a layer of foil and a hot coal on top. The tobacco is never lit, instead heated by the charcoal, which smokers say produces a vapor different from smoke.
The hookah, used for centuries in North Africa, the Middle East and Central and South Asia, has become increasingly popular in the United States, Europe and Brazil, particularly among college students and young adults.
WHO says the trend is partly due to "unfounded assumptions" of its safety, and misleading commercial marketing.
The agency said a person can inhale more than 100 times more smoke in a hookah session than in a single cigarette. By delivering nicotine, the water pipe can cause addiction.
"None of the accessories have been demonstrated to reduce smokers' exposure to toxins or risk of tobacco-related disease and death," WHO said.
While further research is required, the health body said those exposed to secondhand hookah smoke appeared to be at risk of the same diseases as those exposed to cigarettes. WHO warned that hookah smoke could also increase the risk of adverse effects during pregnancy.