Young adults who smoked water pipes in hookah（水烟袋） bars had elevated levels of nicotine, cotinine, tobacco-related cancer-causing agents, and volatile organic compounds (VOC) in their urine, and this may increase their risk for cancer and other chronic diseases, according to a study published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research. "This study reports systemic intake of tobacco-specific nitrosamines and VOCs after a typical water pipe-smoking session in a hookah bar setting, thus making the findings generalizable to most water pipe users in the United States," said Gideon St.Helen, Ph.D., postdoctoral fellow in the Division of Clinical Pharmacology and the Center for Tobacco Control Research and Education at the University of California, San Francisco.

After a single evening of water pipe smoking in a hookah bar, young men and women had in their urine a 73-fold increase in nicotine; fourfold increase in cotinine; twofold increase in NNAL, a breakdown product of a tobacco-specific nitrosamine, NNK, which can cause lung and pancreatic cancers; and 14 to 91 percent increase in the breakdown products of VOC such as benzene（苯） and acrolein that are known to cause cancer and cardiovascular and respiratory diseases.

"There was also a substantial increase in nicotine levels, which raises concerns about the potential addictiveness of water pipe smoking and possible effects on the developing brains of children and youths who use water pipes," added St.Helen. "Water pipe smoking is generally perceived to be a safe alternative to cigarette smoking, even for children and youths. Our study shows that water pipe use, particularly chronic use, is not risk-free."

St.Helen and colleagues recruited 55 healthy, experienced water pipe smokers, ages 18 to 48 years, to the study. Participants were instructed to refrain from（避免） any type of smoking for a week.

At the end of this period they provided a "before" urine sample and smoked water pipes at a hookah bar of their choice in the San Francisco Bay area. Soon after the visit, they provided the "after" urine sample, and filled a form to provide detailed information on their smoking session including total time spent smoking, number of bowls smoked, and number of shared users. They also provided a first-voided urine sample the next morning, which helped researchers estimate the clearance of the tobacco-related chemicals of interest.

The study participants spent on average 74 minutes smoking water pipes and smoked an average 0.6 bowls of water pipe tobacco per person.