Diacetyl, a flavouring chemical linked to cases of severe respiratory disease, was found in more than 75% of flavoured electronic cigarettes and refill liquids tested by researchers at Harvard TH Chan School of Public Health. Two other potentially harmful related compounds were also found in many of the tested flavours, which included varieties with potential appeal to young people such as Cotton Candy, Fruit Squirts, and Cupcake.
The US Occupational Safety and Health Administration and the flavouring industry have warned workers about diacetyl because of the association between inhaling this chemical and the debilitating respiratory disease bronchiolitis obliterans, colloquially termed “Popcorn Lung” because it first appeared in workers who inhaled artificial butter flavor in microwave popcorn processing facilities.
“Recognition of the hazards associated with inhaling flavouring chemicals started with ‘Popcorn Lung’ over a decade ago. However, diacetyl and other related flavouring chemicals are used in many other flavours beyond butter-flavoured popcorn, including fruit flavours, alcohol flavours, and, we learned in our study, candy flavoured e-cigarettes,” said lead author Joseph Allen, assistant professor of exposure assessment science.
There are currently more than 7,000 varieties of flavoured e-cigarettes and e-juice (liquid containing nicotine that is used in refillable devices) on the market. Although the popularity and use of e-cigarettes continues to increase, there is a lack of data on their potential health effects. E-cigarettes are not currently regulated, but the US Food and Drug Administration (FDA) has issued a proposed rule to include e-cigarettes under its authority to regulate certain tobacco and nicotine-containing products.
Allen and colleagues tested 51 types of flavoured e-cigarettes and liquids sold by leading brands for the presence of diacetyl, acetoin, and 2,3-pentanedione, two related flavouring compounds that are listed as “high priority,” (they may pose a respiratory hazard in the workplace) by the Flavour and Extract Manufacturers Association. Each e-cigarette was inserted into a sealed chamber attached to a lab-built device that drew air through the e-cigarette for eight seconds at a time with a resting period of 15 or 30 second between each draw. The air stream was then analysed.
At least one of the three chemicals was detected in 47 of the 51 flavours tested. Diacetyl was detected above the laboratory limit of detection in 39 of the flavours tested. Acetoin and 2,3-pentanedione were detected in 46 and 23 and of the flavours, respectively.
“Since most of the health concerns about e-cigarettes have focused on nicotine, there is still much we do not know about e-cigarettes. 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,” said study co-author David Christiani, Elkan Blout professor of environmental genetics.
Background: There are over 7,000 e-cigarette flavors currently marketed. Flavoring chemicals gained notoriety in the early 2000’s when inhalation exposure of the flavoring chemical diacetyl was found to be associated with a disease that became known as “Popcorn Lung.” There has been limited research on flavoring chemicals in e-cigarettes.
Objective: To determine if the flavoring chemical diacetyl, and two other high-priority flavoring chemicals 2,3-pentanedione, and acetoin, are present in a convenience sample of flavored e-cigarettes.
Methods: We selected 51 types of flavored e-cigarettes sold by leading e-cigarette brands and flavors we deemed were appealing to youth. E-cigarette contents were fully discharged and the air stream was captured and analyzed for total mass of diacetyl, 2,3-pentanedione, and acetoin, according to OSHA Method 1012.
Results: At least one flavoring chemical was detected in 47 of 51 unique flavors tested. Diacetyl was detected above the laboratory limit of detection 39 of the 51 flavors tested, ranging from < limit of qualification (LOQ) to 239 μg/e-cigarette. 2,3-pentanedione and acetoin were detected in 23 and 46 of the 51 flavors tested at concentrations up to 64 and 529 μg/e-cigarette, respectively.
Conclusion: Due to the associations between diacetyl, bronchiolitis obliterans and other severe respiratory diseases observed in workers, urgent action is recommended to further evaluate this potentially widespread exposure via flavored e-cigarettes.