People who smoke water pipes in hookah bars may be exposing themselves to nicotine and cancer-causing agents, according to a recent study.

Researchers found that young adults who smoked water pipes in hookah bars had elevated levels of nicotine, cotinine, tobacco-related cancer-causing agents, and volatile organic compounds (VOC) in their urine. This could increase their risk for cancer and other chronic diseases.

"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," Gideon St.Helen, researcher and postdoctoral fellow in the Division of Clinical Pharmacology and the Center for Tobacco Control Research and Education at the University of California, San Francisco, said in a statement.

For the study, researchers examined 55 healthy, experienced water pip smokers, ages 18 to 48 years. They were instructed to refrain from 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.

Researchers found that the elevated levels of nicotine, cotinine, and NNAL, which were detected immediately after the water pipe-smoking session, remained significantly elevated in the next-day urine samples, compared with the "before" samples: Nicotine was 10.4-fold higher; cotinine, 3.2-fold; and NNAL, 2.2-fold.

In the results, water pipe-smoking duration correlated significantly with the increase in post-exposure urine nicotine levels, and number of bowls smoked per person significantly correlated with the increase in post-exposure and next-day urine cotinine levels, respectively. The average increase in nicotine levels was comparable to levels obtained after smoking at least one cigarette, explained St.Helen.

The findings were recently published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.