Almost 30 million people across Europe now use e-cigarettes, according to a Reuters News story.
The people who use these devices are most likely to be aged between 15 and 24. They are most likely to smoke tobacco regularly while trying to quit.
The rising number of e-cigarette users has led to a staggering growth in the availability of these products, with about 10 new brands coming to market every month.
Writing in the journal Tobacco Control, researchers in the U.S. said their findings underlined the size and speed of growth in the market for e-cigarettes, and the need for more research into their potential risks and benefits.