Diacetyl is a flavor chemical that is commonly added to the nicotine liquid used in “vape juices” for e-cigarettes. In high doses, diacetyl is also known to cause a potentially deadly lung disease.
The link between diacetyl and lung disease was discovered when a group of popcorn factory workers were all diagnosed with the same rare disease — bronchiolitis obliterans — during the 1990s.
The disease was nicknamed “Popcorn Lung.” It is an irreversible and progressive condition in which scar tissue grows in the lungs. It causes wheezing, fatigue, shortness of breath, and it can be fatal.
Vaping advocates point out that a few puffs on an e-cigarette is a lot different from spending years breathing diacetyl in the air of a popcorn factory.
The problem is that vape juice may have hundreds of different flavor additives, with different concentrations and toxicities — and it is almost impossible for e-cigarette users to find out what is in the liquid.
And while flavor additives are relatively safe in food that is eaten, very few flavor additives have been tested for safety when they are routinely breathed into the lungs.
According to Amanda Dickinson, a developmental biologist at Virginia Commonwealth University:
Just because vanilla flavor or crème flavor is okay in your cookies doesn’t mean it’s okay when you heat it and then inhale it. It seems that it’s a roll of the dice.”
Dickinson’s studies have already demonstrated potential safety hazards associated with breathing diacetyl, for example.
She co-authored a recent study that tested the effects of 6 different vape liquids on tadpoles. The flavors that correlated with birth defects were citrus or fruity flavors.
The researchers said the problem may not be fruity or creamy flavor additives themselves, but the complexity of the chemical combination.
For example, 20% percent of tadpoles exposed to a flavor called “strawberry, almond, caramel, vanilla, biscuit, Vienna cream” had birth defects. Another 70% of tadpoles exposed to the e-cigarette flavor “cereal, berries, cream, citrus” developed facial deformities. The study suggests that toxicity increases when the liquid has more chemicals.