New Delhi, Sep 12 (IANS): With e-cigarette usage increasing among the youth, the World Health Organisation Thursday called on countries to frame regulatory guidelines to keep a tab on their usage.

WHO representative Angela Patt said the size of the e-cigarette market will increase rapidly in coming years, and currently there is little research on the health impact of the long-term use of e-cigarettes.

"The market of e-cigarette has increased to $3 billion in the past 12 months, and it is being said that the inevitable future of tobacco lies in e-cigarette," said Patt, while speaking at the International Conference on Public Health Priorities in the 21st Century.

She said the sale of e-cigarette had doubled in the US, and big tobacco companies are investing in it.

E-cigarette is an electronic nicotine delivery system (ENDS) meant to simulate and substitute tobacco smoking.

"The tobacco industry is projecting it as a "safe" and "healthy" substitute for cigarettes, but there is no research evidence on the health impact of their long term usage," she said.

"Tobacco companies are targeting youth and women by adding the notion of glamour, luxury and freedom to the e-cigarette. Countries must frame regulatory guidelines to advise consumers not to use it," she said.