By Stephanie Stahl

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PHILADELPHIA (CBS) — The FDA is expected to announce its expected ban on the sale of most flavored E-cigarettes in tens of thousands of convenience stores and gas stations across the country.

The crackdown comes as federal health officials say flavored E-cigarettes can be very addictive and they’ve become hugely popular with minors.

It’s now estimated that 3.5 million children are vaping, that’s up 1 million young users since last year.

The research shows E-cig use has increased 77 percent among high schoolers and nearly 50 percent for students in middle school this year.

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“I now have good reason to believe that it’s reached nothing short of an epidemic proportion of growth,” FDA Commissioner Scott Gottlieb said.

Studies have shown E-cigs can potentially release significant amounts of toxic chemicals — a concern for still developing adolescent brains, which are also more vulnerable to nicotine addiction.

“I don’t really think about it,” high school sophomore Kyler Kristopaitis said. “It’s just advertised as being healthier than smoking cigarettes.”

In September, the FDA set a 60-day deadline for several major E-cigarette companies to prove they could keep E-cigarettes away from kids.

“Everyone does it, like everyone,” Kyler said. “Every time I go to the bathroom there’s someone doing it.”

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The FDA is also considering online restrictions, including having age-verification requirements for those sales.

Part of the concern is that many E-cigarette users are likely to become addicted to nicotine and some could end up on regular cigarettes — a product that kills half of its long-term users.

Doctors say the long-term health consequences of vaping are not known. E-cig companies say they can help adults stop smoking real cigarettes and that they’re not intended for kids.

Stephanie Stahl