With tobacco smoke claiming a life every six seconds, the tar-free, electronic alternative could help prevent much of the cancer, heart and lung disease and strokes caused by the toxins in traditional cigarettes, the 50-odd experts wrote to World Health Organisation chief Margaret Chan.
E-cigarettes "could be among the most significant health innovations of the 21st century, perhaps saving hundreds of millions of lives," the group said.
They urged "courageous leadership" from the WHO in guiding global and national approaches to e-cigarettes, which are banned in some countries like Brazil and Singapore and face increasingly strict restrictions in other countries amid uncertainty about their long-term health effects.
This would compel member countries to ban advertising and use of the gadgets in public places, and to impose sin taxes.
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"It would be unethical and harmful to inhibit the option to switch to tobacco harm-reduction products" like e-cigarettes, said the letter, a copy of which was given to AFP.
The WHO is working on recommendations for e-cigarette regulation, to be presented to a meeting of member governments in October.
Some fear its use and often unrestricted promotion could glamorise an addictive habit, and hook non-smoking teenagers on nicotine.