Remember "Popcorn Lung," the severe respiratory illness linked to the artificial ingredients in microwave popcorn?
It made headlines 15 years ago when former workers in a microwave popcorn plant in Missouri fell sick with the irreversible disease.
Now obliterative bronchiolitis, as it's officially known, is in the news again.
VIDEO: What Science Says About E-Cigs So Far
Some of the same suspect chemicals - in particular diacetyl - that were used to make artificial butter have turned up in e-cigarettes, posing a pulmonary threat to a whole new group of people.
And these chemical compounds are not found in nicotine, the most-studied substance when it comes to the health dangers of tobacco use. They're found in the flavorings added to e-cigs, according to new research – flavors like "Cupcake" and "Cotton Candy" that disproportionately appeal to young people.
Those are just two of over 7,000 flavor varieties of e-cigarettes.
BLOG: Five Must-Knows About E-Cigarettes
"Recognition of the hazards associated with inhaling flavoring chemicals started with ‘Popcorn Lung," lead author Joseph Allen said in a release.' However, diacetyl and other related flavoring chemicals are used in many other flavors beyond butter-flavored popcorn, including ... candy flavored e-cigarettes." Worth noting: several leading microwave popcorn brands have since pulled diacetyl from their formulas.
In analyzing 51 different flavored e-cigarettes, Allen and his team found at least one of three top toxins - diacetyl, acetoin and 2,3-pentanedione - in 47 of the e-cigs. Not only that, the amount of diacetyl in 39 of the e-cigs exceeded the amount that was able to be detected by the laboratory.
The use of e-cigarettes in the United States has surged in recent years. An estimated 10 percent of U.S. adults engage in the habit, reports Reuters. That's up from a mere 2.6 percent of adults in 2013.
Vaping May Make Lungs More Vulnerable To Infection
The highest rates of usage are among young adults - the same group that might find flavored e-cigs most appealing. As many as 22 percent of adults between the ages of 18 and 24 have tried e-cigs, according to a government survey.
Vaping, or the practice of smoking e-cigarettes, has been touted as a healthier alternative to conventional smoking, but there is not enough research yet to support that claim.
"There is still much we do not know about e-cigarettes," study coauthor David Christiani said in the release.