Researchers disagree about whether or not e-cigarettes can help smokers quit, but with nearly 500 brands now available, e-cigarettes appear to be here to stay.

The e-cigarette market is on fire as more and more people try using the devices to “vape” liquid nicotine.

A new study from the University of California, San Diego, published in Tobacco Control, finds that an average of 10 new e-cigarette brands and 240 new e-liquid flavors appeared on the market each month from 2012 to 2014. As of January 2014, there were 466 e-cigarette brands sold online and more than 7,700 flavors.

The researchers found that older brands were more likely to make claims that e-cigarettes are healthier or more affordable than traditional cigarettes. They were also more apt to insist that e-cigarettes are a good way to quit smoking. Newer brands were less likely to make such claims and more likely to focus instead on their selection of flavors or devices.

“It almost seems that newer brands don’t want to be compared to cigarettes, which are associated with the image of cancer,” said lead author Shu-Hong Zhu, Ph.D., a professor of family and preventive medicine and director of the Center for Research and Interventions in Tobacco Control at UC San Diego, in a press statement.

Zhu’s team says they support the Food and Drug Administration’s proposed rules to make e-cigarette companies list their ingredients and nicotine strengths, and take other measures to ensure their devices are safe. But they say that any rules that are too strict might favor brands with strong financial support that are owned by big tobacco companies. The most important goal in regulating e-cigarettes, they said, should be to reduce the number of people smoking traditional cigarettes.

“Obviously, tobacco companies would be more concerned with protecting cigarette market share than smaller e-cigarette companies,” Zhu said.

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A 2013 report estimated that there are about 2.5 million e-cigarette smokers in the U.S. and 45 million traditional cigarette smokers. Nearly 30 million Europeans are using e-cigarettes, according to another study published in Tobacco Control. Those under 25 were more than three times as likely to have smoked an e-cigarette than those over 55.

“E-cigarettes are very popular, especially among younger people,” said Dr. Michael Steinberg, who heads the Tobacco Dependence Program at Rutgers University.

Steinberg said that many people use e-cigarettes in places that have banned traditional cigarettes, which has created apprehension about indoor air quality and the safety of non-smokers nearby. There are many concerns about the safety of e-cigarettes for those smoking them, too, he said.

“The problem is we don’t yet know about their long-term safety,” Steinberg said. “It is probably the case that since they do not contain combusted tobacco, they are likely less harmful than smoking cigarettes. However, less harmful does not equate to safe.”

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Thus far, research has been mixed on whether e-cigarettes can help people quit traditional smoking. Some people smoke them instead of traditional cigarettes with no intention of stopping, while others use them as a way to “step down” from traditional smoking.

Lawrence Phillips, an emeritus professor at the London School of Economics, recently said at a conference sponsored by the Decision Analysis Society at the Institute for Operations Research and the Management Sciences that e-cigarettes shouldn’t be classified as tobacco products, but rather as devices for fighting nicotine addiction.

Another recent survey found that 85 percent of e-cigarette users were vaping as a means to quit smoking. Last month, a study from the UK, published in Addiction, found that smokers looking to quit without professional help were 60 percent more successful if they used e-cigarettes, as opposed to relying on willpower or over-the-counter nicotine replacement therapies.

Dr. Andrew Nickels, author of another recent study on the health claims made by e-cigarette companies published in Annals of Allergy, Asthma, and Immunology, said there has not been enough research to show that using e-cigarettes is an effective way to kick tobacco smoking.

“Despite the apparent optimism surrounding e-cigarettes … there just simply is not enough evidence to suggest that consumers should use e-cigarettes for this purpose,” Nickels said in a statement.

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Steinberg agrees that there is little evidence that e-cigarettes work as a smoking cessation tool.

“Most of what we have to date are self-reports from e-cigarette users themselves, but these are clearly a biased group who had a positive experience. We don’t hear from those who tried the e-cigarette to quit smoking and did not succeed,” said Steinberg, who said he has seen many people in his program who have failed at using e-cigarettes as a way to quit.