California is the second state to raise the legal age for purchasing tobacco products from 18 to 21. A similar law went into effect in Hawaii on Jan. 1. Paul J. Richards/AFP/Getty Images hide caption

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E-cigarettes work by heating up a fluid that contains the drug nicotine, producing a vapor that users inhale. The devices are most popular among young adults, ages 18 to 24, a federal survey indicates. iStockphoto hide caption

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Most E-Cigarette Users Are Current And Ex-Smokers, Not Newbies
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Vapor from an e-cigarette obscures the user's face in a London coffee bar. Dan Kitwood/Getty Images hide caption

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E-Cigarettes Can Churn Out High Levels Of Formaldehyde
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Jonathan Franzen, pictured here at The New Yorker Festival Fiction Night in 2009, won the National Book Award for his third novel, The Corrections. Joe Kohen/Getty Images hide caption

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A woman tries electronic cigarettes at a store in Miami. Joe Raedle/Getty Images hide caption

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FDA Moves To Regulate Increasingly Popular E-Cigarettes
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