We read with interest the article by Allen et al. in which the authors reported the presence of diacetyl and 2,3-pentanedione in e-cigarette vapors and concluded that “[d]ue 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.” As part of their analysis, it was suggested that the occupational exposure limits (OELs) that have been proposed for these compounds may not be health protective for most e-cigarette users.

We support efforts to characterize the composition of e-cigarette vapors and believe that such research is necessary to fully assess the potential health risks, if any, associated with use of these products.