Researchers monitored carbon monoxide in the breath of the participants both before and after the experiment using a machine designed to detect if people are smokers.
The findings were published in a letter in the Jan. 2 issue of the Journal of the American Medical Association.
The exhaled carbon monoxide in participants was an average of 42 parts per million, higher than that reported in cigarette smokers (17 parts per million). The study also found that carbon monoxide levels grew in the room where the subjects smoked hookahs and might reach environmentally unhealthy levels, as determined by the federal government, during longer sessions.
Hammond said she can't directly compare hookah use to the smoking of cigarettes, which house thousands of toxic chemicals. And, she said, it's hard to know exactly what hookah use will mean in terms of higher risk of lung or heart disease.
Hookahs "may not give you lung cancer but may compromise your health in other ways," she said.
Thomas Eissenberg, an associate professor of psychology at Virginia Commonwealth University who studies hookah use, said research has suggested that smoking a water pipe for 45 minutes produces 36 times more tar than smoking a cigarette for five minutes. Tar -- or "nicotine-free, dry particulate matter" -- contains the cancer-causing constituents of the smoke, although it's not clear if water pipe tar is different from cigarette tar, he said.
"Occasional water pipe tobacco smoking may carry its own health risks, and it may also be dangerous, because it can lead to daily water pipe use, regular cigarette smoking, or both," he said.
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