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Chemicals Linked to Lung Disease Have Been Found in More Vaping Liquids

A Harvard study found 92 percent of the flavors tested contained one of the three chemicals.

Vapers have more than impending government regulation to worry about. A flavoring chemical linked to serious lung disease can be found in even more e-liquid flavors than previously thought, according to new research from Harvard.

Diacetyl is a chemical commonly used in food flavoring, giving products a creamy, smooth taste and finish. Eating something that contains diacetyl is considered harmless, but there are serious risks associated with inhaling the chemical (at least in a factory setting, we don't yet know for sure about the effects of vaping it).


Diacetyl is frequently found in flavored e-liquids, particularly dessert flavors like caramel or vanilla, as are its "sister chemicals" acetyl propionyl and acetoin, which are very similar to diacetyl and often used as substitutes. A study published last year specifically testing sweet-flavored e-liquids found 74 percent contained diacetyl, acetyl propionyl, or both. Now, a Harvard study published Tuesday in Environmental Health Perspectives, shows the chemical is common even in less-obvious flavors, including watermelon, menthol, and even plain tobacco-flavored e-juices.

"A lot of people think it ends with butter flavors," said Joseph Allen, a Harvard researcher in environmental health and the lead author of the study. "But in fact if you look at where diacetyl and other flavoring compounds are used, it's a really eye-opening list of flavorings that you wouldn't think it'd be in."

Allen and his colleagues tested the vapor from 51 unique flavors of e-liquid for the presence of diacetyl, acetyl propionyl, and acetoin. They found at least one of the three chemicals in 92 percent of the flavors, some with levels as high as 239 micrograms per e-cigarette.

E-liquids come in more than 7,000 flavors, so the researchers honed in on flavors they believed would be appealing to kids and adolescents—cupcake, pineapple punch, and something called "alien blood," for example—to highlight the potential risk to young consumers.

But the news will likely cause concern for the vaping community at large, which has been discussing the potential risks of diacetyl for the last seven years. Three vapers even recently filed a class action lawsuit against a major e-liquid manufacturer, claiming it lied to consumers about the levels of diacetyl and acetyl propionyl in its products.

The problem, Allen said, is that because e-cigarettes are currently unregulated, it's near-impossible for consumers to get accurate information about what's in their e-juice. Combined with a lack of scientific studies on the effects of vaping means consumers are treading unchartered territory, with their health potentially on the line.

"The consumer doesn't have the information to make informed decisions," Allen said over the phone. "The flavoring industry is giving warnings to workers who are handling these chemicals and have the potential to inhale them, but we don't see these warnings given to users of flavored e-cigarettes."

Some vapers try to avoid these chemicals by ditching dessert flavors and seeking out liquids that are labelled diacetyl-free, but this new research pokes major holes in that strategy. Not only did it show that diacetyl isn't limited to dessert flavors, but it also showed a great deal of variance within brands, indicating how difficult it is to be sure a flavor is truly diacetyl-free. Whether you go for "Crunch Berry" or "Peace Pipe," until we have more information, no flavor can be guaranteed safe.