Diacetyl, a flavouring chemical found in some e-cigarettes, has been linked to cases of the severe respiratory disease bronchiolitis obliterans or “popcorn lung”, according to research published in Environmental Health Perspectives
on 8 December 2015.
Two other flavouring compounds — acetoin, and 2,3-pentanedione — were found that the US Flavour and Extract Manufacturers Association says pose a potential respiratory hazard in the workplace. The chemicals were found in the cotton candy, fruit squirts and cupcake varieties.
Joseph Allen from the Harvard TH Chan School of Public Health led the team of researchers who tested 51 types of flavoured e-cigarettes and liquids sold by leading brands for the presence of diacetyl, acetoin, and 2,3-pentanedione.
Each e-cigarette was put into a sealed chamber 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 air stream was then analysed for the flavouring compounds.
They found that at least one of the three chemicals being tested for was found in 47 of the samples. Diacetyl was detected above the laboratory limit of detection in 39 of the flavours tested. Acetoin was found in 46 flavours and 2,3-pentanedione in 23 samples.
“Our findings confirm the presence of diacetyl and other high priority flavoring chemicals in flavoured e-cigarettes. Due to the associations between diacetyl, bronchiolitis obliterans and other severe respiratory diseases among workers inhaling heated vapours containing diacetyl, urgent action is recommended to further evaluate the extent of this new exposure to diacetyl and related flavouring compounds in e-cigarettes,” the researchers say.
 Allen JG, Flanigan SS, LeBlanc M et al. Flavoring chemicals in e-cigarettes: diacetyl, 2,3-pentanedione, and acetoin in a sample of 51 products, including fruit-, candy-, and cocktail-flavored e-cigarettes. Environmental Health Perspectives 2015. doi: 10.1289/ehp.1510185