An hour spent smoking a hookah, or water pipe, delivers as much carbon monoxide to the user as smoking a pack of cigarettes, HealthDay News reported Jan 3.

Hookah smoking has become a popular alternative to cigarette smoking in recent years, particularly among college students, but, "This is not the risk-free activity they think it is," said study co-author S. Katherine Hammond of the University of California at Berkeley.

Hammond's study only looked at carbon monoxide, not other hazards of smoking. But Thomas Eissenberg of Virginia Commonwealth University, who also has studied hookah use, said smoking a water pipe for 46 minutes produces 36 times more tar than smoking a cigarette for five minutes. And smoking tobacco through hookahs, like cigarettes, can be addictive.

Hammond's findings were published in a letter in the Jan. 2, 2008 issue of the Journal of the American Medical Association.