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The website sales pitches for a popular e-cigarette feature huge puffs of cotton candy, and words that conjure images of carnivals and state fairs.

But a study published Tuesday notes that these candied confections have a downside: Many of the best-selling flavorings include a toxic chemical that has long been associated with serious lung problems.

The Environmental Health Perspectives, a journal published by the National Institute of Environmental Health Sciences, says that some companies hide the presence of the flavoring chemical, known as diacetyl, as well as other potentially harmful artificial flavorings.


Diacetyl was first recognized as a respiratory hazard more than 10 years ago after it appeared in workers who breathed in artificial butter flavor in microwave popcorn plants. The illness came to be known as “Popcorn Lung.” It can be severe and irreversible, with some sufferers requiring lung transplants.

Both the Occupational Safety and Health Administration, which oversees workplace safety, have worked to raise awareness of the potential for harm, which is strongest when the chemical is heated.


“You have a similar pathway,” said Joseph Allen, an assistant professor of exposure assessment science at the Harvard T.H. Chan School of Public Health and the lead author of the federally funded study. “You have heated, flavored chemicals that are directly inhaled. Diacetyl and other related flavoring chemicals are used in many other flavors, including fruit flavors, alcohol flavors, and, as we learned in our study, candy flavored e-cigarettes.”

There are more than 7,000 flavors available for e-cigarettes. Most are mixed with nicotine and sold in cartridges. The mixture is heated, turned into a vapor, then inhaled. The emission from e-cigarettes includes a vapor and aerosol component.

Many of the flavors seem designed to appeal to children and young adults — with names like Cupcake, Fruit Squirts, Waikiki Watermelon, Tutti Frutti, Oatmeal Cookie, and Alien Blood.

Their popularity is growing. The Centers for Disease Control and Prevention said earlier this year that in a survey, 2 million high-school students reported using e-cigarettes at least once in the month before the survey. The World Health Organization reported that in 2013, more than $3 billion was spent on e-cigarettes in the United States alone. It predicts that sales will increase seventeenfold in 15 years.

Allen and his colleagues selected 51 flavors from a variety of manufacturers and distributors. Each e-cigarette was put in a sealed chamber and attached to a device that drew air through the e-cigarette for eight seconds at a time, with a resting period of 15 or 30 seconds between each draw. The researchers then analyzed the air stream.

They found that diacetyl was present in 39 of the 51 flavors, even those made by the companies that researchers had called before the test.

“We specifically looked at the packaging and at the website to see if any of the sellers were providing warnings,” Allen said. “We asked two companies specifically, and they said ‘No,’ they did not have diacetyl in it. But we tested them and, in fact, they did.”

Two other chemicals of concern, acetoin and 2,3-pentanedoine, were detected in some of the flavors, as well. Allen and his colleagues found that no flavor packaging came with warnings about potential dangers from diacetyl or other flavorings that OSHA has said may pose a hazard.

David Ozonoff, a professor of environmental health at Boston University’s School of Public Health, said he was alarmed by the study.

“I think the discovery that there is diacetyl and a structurally similar compound in [e-cigarettes] is a giant red flag,” he said. “If this is happening, then a huge exposure hazard has slipped through the cracks — and the cracks are pretty big if something like this can slip through them. I believe the [Food and Drug Administration] should take immediate action as if this were an emergency, which it is.”

Read more: Experts debate: How tightly should e-cigarettes be regulated?

The FDA has proposed regulating e-cigarettes, but its proposal has been the subject of much lobbying. It is now in the hands of the White House Office of Management and Budget, which must weigh in on the matter.

A spokesman for the American Vaping Association was not available for comment. A spokesman for the Flavor and Extract Manufacturers Association of the United States referred a reporter to the group’s website, which notes that “e-cigarette manufacturers and marketers should take appropriate action to assure the safety of their flavor ingredients used in e-cigarettes.”