The World Health Organization is calling for major regulations on the e-cigarette industry, including a ban on indoor smoking.
The UN agency says e-cigarette smoke -- also known as vapor -- increases levels of toxins in the air, including nicotine.
"Existing evidence shows that e-cigarette aerosol is not merely 'water vapor' as is often claimed in the marketing of these products," it said, though acknowledged that e-cigarettes were generally not as bad for smokers and bystanders as traditional cigarettes.
The WHO called for standardized regulations that would restrict advertising efforts and prohibit the industry from making unproven health claims for e-cigarettes.
The industry -- worth an estimated $3 billion per year -- markets e-cigarettes as a less-toxic product that can help smokers quit. But the WHO maintained there was no scientific proof showing the products helped people stop smoking.
The WHO is worried that current marketing techniques could encourage non-smoking youth to try e-cigarettes. It suggested banning candy and fruit-flavored e-cigarette products to ensure kids weren't tempted.
The e-cigarette industry has grown since 2005 to encompass 450 brands made by 'Big Tobacco' and small independents.
Based on research from 2013, nearly half of smokers and ex-smokers in the U.S. have tried e-cigarettes, but only 4% use the products on a regular basis.
WHO members will be discussing regulatory options for e-cigarettes in mid-October at a meeting in Moscow.