Does vaping cause popcorn lung?

According to Cancer Research UK, there is little to no evidence that using e-cigarettes will result in "Popcorn Lung" (bronchiolitis obliterans). In 2015, a few studies caused a media frenzy when they published results stating that there was a link between breathing in a chemical called diacetyl and Popcorn Lung. However, the cluster of people affected by this very rare lung condition were factory workers in a a popcorn factory. The illness was not related to the use of e-cigarettes. 

Nevertheless, as a safety precaution, vaping companies and flavor manufacturers have since completely eliminated diacetyl from their products. In 2016 the UK completely banned diacetyl under the EU Tobacco Products Directive (TPD). Today most vape juices are completely diacetyl-free while others may contain diacetyl in levels hundreds of times lower than in cigarette smoke.