E-cigarettes have arrived in the life of the American teenager.

Use of the devices among middle- and high school students tripled from 2013 to 2014, according to federal data released on Thursday, bringing the share of high school students who use them to 13 percent — more than smoke traditional cigarettes. The sharp rise, together with a substantial increase in the use of hookah pipes, led to 400,000 additional young people using a tobacco product in 2014, the first increase in years, though researchers pointed out it fell within the margin of error. About a quarter of all high school students and 8 percent of middle school students — 4.6 million young people altogether — used tobacco in some form last year.

The numbers came as a surprise and seemed to pitch policy makers into uncharted territory. The Food and Drug Administration took its first tentative step toward regulating e-cigarettes last year, but the process is slow and many experts worry that habits are forming far faster than rules are being written. Because e-cigarettes are so new, little is known about their long-term health effects, leaving regulators scrambling to gather data.

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