Significantly more Americans are using electronic-cigarettes and other vaporizing devices than a year ago, but most of those consumers are also smoking conventional cigarettes, according to a new Reuters/Ipsos poll.

The findings support evidence that smokers are using both traditional tobacco products and e-cigarettes to deliver nicotine, rather than giving up traditional cigarettes altogether. Researchers are studying many questions about the potential benefits and dangers of e-cigarettes and U.S. health regulators are still working on their first set of rules governing the products.

In the meantime, proponents of vaping, as the practice is called, have argued that e-cigarettes and vaporizer represent a safer alternative to tobacco products, which have been proven to contribute to lung cancer and other diseases.

About 10 percent of U.S. adults now vape, according to the online Reuters/Ipsos poll of 5,679 Americans conducted between May 19 and June 4. That's almost four times higher than a U.S. government estimate that 2.6 percent of adults used e-cigarettes in 2013.

About 15 percent of poll participants under the age of 40 now vape. In 2013, 18.8 percent of those 18 to 24 and 20.1 percent of those 25 to 44 smoked cigarettes, according to the government data.

E-cigarettes are metal tubes that heat liquids typically laced with nicotine and deliver vapor when inhaled. Almost 70 percent of current users started in the last year alone, and about three quarters of them also smoke cigarettes, according to the poll.

The surge in use comes as conventional cigarette smoking has declined in the United States to about 19 percent of adults, prompting tobacco companies like Altria Group Inc, Lorillard Inc and Reynolds American Inc to rush into the e-cigarette market.

Reynolds' Vuse brand, helped by its national rollout to 100,000 retail outlets, has captured almost 36 percent of the U.S. market to become the No. 1 e-cigarette. It passed Lorillard's Blu eCigs, which had 22.7 percent, according to Nielsen data.

At the same time, the number of U.S. vape shops has risen to at least 15,000 from virtually none a few years ago, according to recent industry estimates.

Wells Fargo Securities analyst Bonnie Herzog estimates the entire U.S. market for "vapor devices" will grow to $3.5 billion by the end of the year, from $2.5 billion in 2014. More than half of that will be vapor tanks and personal vaporizer, which typically have a stronger battery and can use nicotine liquid in thousands of flavors.

TRYING TO QUIT

Almost half of users surveyed said they were motivated to use the devices because of friends or family, while almost 40 percent said they were persuaded by the ability to smoke indoors and the lower cost over time. The credibility interval, a measure of the poll's accuracy, was plus or minus 1.5 percentage points for all poll participants and 5.2 percentage points for questions specific to the 463 e-smokers in the poll.

About 80 percent of vapers said using the devices was "a good way to help people quit smoking," according to the poll. By contrast, fewer than 40 percent of all adults surveyed felt that way.

Many are like Emily Deppe of Utah, who wants to quit smoking before she gets pregnant. She learned about the devices from a neighbor.

Deppe, 37, believes the devices are less harmful than cigarettes. They satisfy her urge to hold a cigarette, but can be used in more places than cigarettes and don't make her clothes smell like smoke.

U.S. companies are barred from explicitly marketing the products as smoking cessation devices, though e-cigarettes have already made a dent in sales of nicotine patches and gums that are meant to help smokers quit, according to research group Euromonitor. U.S. sales of nicotine replacement therapies rose 0.2 percent to $900 million in 2014, according to Euromonitor.

Euromonitor expects U.S. sales to drop this year by the same amount because of the increased use of vaping devices and a shrinking population of smokers.

Mike Morgan, works in IT for a telecommunications company. The 48-year-old Kentucky man knew he needed to quit his pack a day habit, but it wasn't until his mother died two years ago of cancer that he decided to try electronic cigarettes.

"You don’t get the great big burst of nicotine you get with a cigarette, but at this point, it satisfies my cravings," said Morgan, who now uses a vaping device about 10 to 15 times a day and eventually wants to quit.

Vapers were twice as likely as the general population to think the devices are "healthier than the traditional cigarettes” but they were also more likely to say someone could become "addicted to e-smoking."

"I definitely think it is better," said Seth Hunt, 45, who started vaping about six months ago after a doctor told him he needed to quit smoking.

The New Jersey man said he feels significantly better now that he puffs the device about 150 times a day instead of smoking, but his family would like him to quit that too.

"I'm waiting to see, but for now, I think it is better than cigarettes," he said.