Hookah sessions loaded with toxicants.

• Position: Smoking

Though cigarette smoking rates are falling, more people are smoking tobacco from-hookahs--communal pipes that enable users to draw tobacco smoke through water. A meta-analysis--a mathematical summary of previously published data--led by the University of Pittsburgh (Pa.) School of Medicine shows that hookah smokers are inhaling a large load of toxicants.

The research team discovered that, compared with a single cigarette, one hookah session delivers approximately 125 times the smoke, 25 times the tar, 10 times the carbon monoxide, and 2.5 times the nicotine.

"Our results show that hookah tobacco smoking poses real health concerns and that it should be monitored more closely than it is currently," says lead author Brian A. Primack, assistant vice chancellor in the School of the Health Sciences. "For example, hookah smoking was not included in the 2015 Youth Risk Behavior Surveillance Survey System questionnaire, which assesses cigarette smoking, chewing tobacco, electronic cigarettes, and many other forms of substance abuse."

Primack and his coauthors note that comparing a hookah smoking session to smoking a single cigarette is a complex process because of the differences in smoking patterns. A frequent cigarette smoker may smoke 20 cigarettes per day, while a frequent hookah smoker may participate in a few sessions each day.

"It's not...