Smoking hookah, a type of flavored tobacco, is quickly becoming more popular in the United States. Now a new study from San Diego State University reports it could lead to an increase in cases of leukemia.

Researchers found that hookah smoke doubles exposure to the dangerous carcinogen benzene, which numerous studies show is responsible for several types of deadly cancers, including leukemia.

Benzene is a toxic element found in tobacco and charcoal that the U.S. National Toxicology Program classifies as a Group 1 carcinogen, meaning it’s been proven to cause cancer in humans. The World Health Organization (WHO) has reported there is no safe level of exposure for the chemical.

The study, published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research, analyzed the levels of S phenylmercapturic acid (SPMA), a metabolite of benzene, from urine samples of 105 hookah smokers and 103 nonsmokers. Samples were taken both the morning of and the morning after participants attended an event at a hookah lounge or a private home.

Results showed the amount of SPMA in hookah smokers increased 4.2-fold after smoking hookah tobacco at a lounge and increased 1.9-fold after smoking in a private home.

The non-smoking participants also showed a 2.6-fold increase in benzene intake.

Study author Dr. Nada Kassem, associate director at the Center for Behavioral Epidemiology and Community Health at San Diego State University, told FoxNews.com she wasn’t surprised to find the benzene increase in non-smokers in the study.

“Non-smokers who socialize with hookah smokers also inhale large quantities of charcoal combustion-generated toxic and carcinogenic emissions,” she said. “Benzene is present in both tobacco smoke and burning charcoal emissions.”

Hookah smoking is unique because it involves burning charcoal to heat tobacco that generates smoke that the user inhales.

Kassem said the major conflict behind the study is that so many hookah smokers don’t realize the adverse health effects. It’s widely accepted by the public that the drug is safer than cigarettes for several reasons, which include:

Smoking process: “Hookah tobacco smoke is passed through water before it is inhaled, leading to the conclusion that water dissolves the toxic chemicals found in hookah tobacco smoke,” she said.

Smoke temperature: “Hookah smoke becomes cooler when passed through water giving the impression that it is not harmful,” Kassem said.

Flavoring: “The sweet aroma of flavored hookah tobacco smoke leads to an illusion that the it is harmless,” Kassem said. “Hookah tobacco is manufactured with numerous flavors like apple, strawberry, vanilla and mint, possibly making it more attractive to smoke.”

Packaging: Packages of hookah tobacco portray large images of fruits that may create a false impression that it is less harmful than other tobacco products, according to Kassem. They also showcase misleading ingredient statements, claiming hookah contains no tar and very little nicotine. “These labels may mask the adverse health consequences of smoking hookah tobacco,” Kassem said.

Lack of regulations: Hookah lounges are not required to display health warnings on the harms of smoking hookah tobacco in their venues or on menus.

Lack of education: “There are very few comprehensive health education programs in schools, colleges and communities at the national level on the harmful effects of hookah use,” she said.

“Because there is no safe level of exposure to benzene, our results call for regulatory actions to limit toxicants including benzene in hookah tobacco and charcoal products,” she said.

Kassem added that health professionals need to raise awareness about the dangers of smoking hookah.

The researchers also tested for other carcinogenic substances present in the body after smoking hookah and results will be published at a later date.