(CNN NEWSOURCE) Researchers say a flavoring chemical linked to severe respiratory disease can be found in most e-cigarettes.
The Harvard University study says more than 75 percent of flavored e-cigarettes contain diacetyl.
That chemical has been linked to a debilitating respiratory disease known as "popcorn lung.”
The disease first appeared in workers who inhaled artificial butter flavoring from microwave popcorn.
The study also found two related, potentially harmful compounds in many of the tested flavors.
The study's authors say the findings show that there's much to be learned about the dangers of e-cigarettes.