© Mark Blinch / Reuters
More than 75 percent of flavored electronic cigarettes and their refill cartridges contain the chemical diacetyl, which is linked to a disease known as 'popcorn lung', a new study by the Harvard T.H. Chan School of Public Health has shown.

The name "popcorn lung" comes from the disease's origin in microwave popcorn processing plants, where workers breathed in artificial butter flavorings. Now cases of bronchiolitis obliterans, the scientific name for the devastating disease, could arise from e-cigarette use, according to the study, which was funded through a government grant from the National Institutes of Health and National Institute of Environmental Health Sciences Center.

"Recognition of the hazards associated with inhaling flavoring chemicals started with 'popcorn lung' over a decade ago. However, diacetyl and other related flavoring chemicals are used in many other flavors beyond butter-flavored popcorn, including fruit flavors, alcohol flavors, and, we learned in our study, candy-flavored e-cigarettes," Joseph Allen, assistant professor of exposure assessment sciences and lead author of the study, told the Harvard Gazette.

In deciding which chemical flavorings to test, Allen and the rest of the team targeted those they figured were most likely to entice children. Flavors such as cotton candy, 'Fruit Squirts', and cupcake were some of the 51 types used in e-cigarette tests.

Each e-cig was placed inside a sealed compartment, from which a "lab-built device" was attached to suck out air for eight seconds, allowing 15 to 30 second breaks in between. The resulting air stream was analyzed for diacetyl and two other chemicals ruled as "high priority" in terms of their risk of respiratory hazard in the workplace by the Flavor and Extract Manufacturers Association.

Diacetyl was found in 39 of the 51 tests, while the other two chemicals - acetoin and 2,3-pentanedione - were present in 46 and 23 cases, respectively.

There are over 7,000 kinds of flavored e-cigarettes and accompanying e-liquids on the market today. While the Food and Drug Administration (FDA) does not currently regulate them, the agency has offered to, saying the e-products, which are marketed to counter traditional smoking habits, could fall under the same rules as tobacco products.

"Since most of the health concerns about e-cigarettes have focused on nicotine, there is still much we do not know about e-cigarettes," said David Christiani, a professor of environmental genetics and co-author of the study. "In addition to containing varying levels of the addictive substance nicotine, they also contain other cancer-causing chemicals, such as formaldehyde, and as our study shows, flavoring chemicals that can cause lung damage."