While fewer American teens are lighting up cigarettes, more of them are vaping instead, a new report shows.

At the same time, marijuana use has held steady as it remains more popular than cigarettes and, in a piece of good news, misuse of opioid painkillers like OxyContin has actually dropped among adolescents.

In 2017, more than 1 in 4 high school seniors said they've vaped during the past year -- and most apparently don't know they're toying with a potentially addictive product.

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Nearly 28 percent of 12th graders reported trying an e-cigarette or other vaping device in 2016, according to results from the 2017 Monitoring the Future survey, sponsored by the U.S. National Institute on Drug Abuse (NIDA).

But when asked what they'd inhaled while vaping, about 52 percent of high school seniors responded "just flavoring." Only 33 percent said they'd inhaled vapor that contains nicotine.

"They don't even realize that what they're using is a tobacco product," said Erika Sward, assistant vice president of the American Lung Association.

E-cigarettes contain fewer harmful chemicals than traditional tobacco products, and might prove useful in helping adults quit smoking, said NIDA Deputy Director Dr. Wilson Compton.

But "that's a very different story when you're talking about youths who may not have used any other tobacco product," Compton pointed out. "Instead of this being a tradeoff, this could be an entree into what we know can be a lifelong, extraordinarily harmful habit. Kids that start with vaping do transition to smoked tobacco more often than those who've never used e-cigarettes."

Sward said the survey results "really underscore why aggressive action from the [U.S.] Food and Drug Administration is required" regarding regulation of e-cigarettes.

But the FDA announced in July that it would delay its review of vaping products that are already on the market for another five years, Sward noted.

"That delay of five years really locks in all of the products that are currently on the market that have flavorings and appeal to children," Sward said. "[The] FDA's decision to delay true oversight is going to have significant consequences."

The survey had more positive news when it came to teen smoking and prescription painkiller abuse.

Just over 4 percent of high school seniors reported smoking cigarettes on a daily basis, down more than 24 percent from 1997, the survey showed.

The decrease in teen cigarette smoking is "a remarkable public health story over the last 20 years. In a single generation, we've had just a huge impact," Compton said.

However, more 12th graders now report daily marijuana use (almost 6 percent) than tobacco smoking, the survey found.

But teens are dipping into prescription pain medications much less often. Past-year misuse declined to just over 4 percent, down from a peak of 9.5 percent in 2004.

The decrease in painkiller abuse likely is tied to the overall response to America's opioid crisis, Compton said. Fewer opioid prescriptions are being written in an effort to stem the tide of abuse that has claimed thousands of lives, and that means there are fewer pills available for misuse.

There's evidence in the survey to support this theory. Only 36 percent of high school seniors said these drugs are easily available, compared to more than 54 percent in 2010.

Marijuana use is about the same as it was in 2015, with around 24 percent of teenagers trying pot at least once within the past year, the survey revealed.

This may not seem like a win, but it actually is, Compton said. There's been no increase in teens using pot, even though marijuana legalization is spreading state-by-state across the nation.

"Despite very permissive attitudes by youth and a lack of concern about the harms of marijuana, the rates really haven't gone up," Compton said. "The fact they haven't gone up is a bit of a surprise for most of us."

There's also been a leveling off in binge drinking -- having five or more drinks in a row within the past two weeks, the survey showed.

Overall, more than 43,700 students participated in this year's survey, which since 1975 has measured how teens report their drug, alcohol and cigarette use.