Cities across the state are grappling with how to regulate the use and sale of electronic cigarettes, a relatively new technology that is exploding in popularity.

E-cigarettes are battery-powered devices that convert liquid nicotine and propylene glycol and/or vegetable glycerin into a mist or vapor that’s inhaled. The user then breathes out steam that looks like smoke. E-cigarettes contain no tobacco and are marketed as an alternative way of consuming nicotine.

Duarte has just passed an urgency ordinance to adopt a moratorium on smoke shops that sell vapor, or e-cigarettes, tobacco and smoking paraphernalia. In the past 18 months the number of smoke shops in the city has doubled to six and inquiries have been pouring in the past few months for shops that specialize in vapor cigarettes, city officials said.

“Our main concern if this were a trend that were to continue, we want to make sure it’s properly regulated,” said Craig Hensley, Duarte’s community development director.

The city will be focused on zoning issues and such shops to schools. State law prohibits the sale of electronic cigarettes to anyone younger than 18.

E-cigarette or vapor retailers have been popping up all over Southern California in the past year and a half with a high concentration in Orange County, and several recently opened in the San Gabriel Valley.

Monrovia has issued a licence for one e-cigarette store, and the city has had about six inquiries this year, according to the city.

Pasadena’s two shops have both opened within the last month.

Benjamin Ocampo, owner of the The Vape Supply Company on North Hill Avenue in Pasadena, said he was going for a lounge-like atmosphere with taupe-colored walls, a long wooden bar and booth-style seating. Customers can purchase low- to high-end devices and sit and “vape” at the juice bar. The most popular flavor is watermelon mint, staffers said.

Marco Malfitano, 44, of Pasadena, said he vapes “anywhere and everywhere.” A 30-year cigarette smoker, Malfitano said the devices helped him quit.

He said some local bars and restaurants are “vape-friendly” because they are educated about it, while others will ask him to step outside because they have a no-smoking policy. He said he’ll try to explain that it is not smoke but vapor or steam, but he’ll gladly step outside with cigarette smokers.

E-cigarette use is now being debated at the state level, with a bill introduced by state Senate Majority Leader Ellen M. Corbett. D-Fremont, to regulate e-cigarettes as a tobacco product and prohibit their use in all smoke-free zones.

Corbett pointed to a UC Riverside study that found concentrations of silver, iron, aluminum and other metals in e-cigarettes were the same or higher than in conventional cigarette smoke, which is known to cause breathing problems and disease.

E-cigarettes are banned in many countries, including Brazil and Panama, and New Jersey is the first state to ban their use in public places.

Dr. Michael Siegel, a tobacco control specialist at Boston University School of Public Health who advocated for smoke-free laws in California and Massachusetts, said research shows e-cigarettes are safer than real cigarettes, although more research is needed.

Siegel said since there is no tobacco or combustion in an e-cigarette, there is no secondhand smoke.

However, he said, the propylene glycol or vegetable glycerine heated to create the vapor has very low levels of formaldehyde, a chemical found in carpeting or upholstery.

“My view of public health regulations is that in order for the government to intervene there needs to be evidence that behavior is causing a public harm,” Siegel said. “I don’t think it’s justifiable for the government to start banning things without having any evidence that electronic cigarettes are causing any significant damage in exposure.”

The reason these policies have gotten support, Siegel said, is that people have not been able to separate cigarettes from e-cigarettes.

Malfitano said he wouldn’t be surprised if Corbett’s bill to restrict e-cigarette use is passed into law.

“Most people don’t know what it is,” he said. “If I had to smoke outdoors, that’s fine with me. It’s not going to stop me from doing it.”

Joseph Ocampo, 30, who works at The Vape Supply Co. with his brother Benjamin, said the social stigma of smoking has prevented him from vaping in public places.

“I wouldn’t go into McDonald’s and start doing it,” he said. “It’s not something that’s socially accepted.”