A chemical e-liquid linked to the “popcorn lung” harms the cells of the respiratory tract


In 2007, health officials in California revealed that many workers at local flavor factories suffered from a rare and potentially fatal lung disease called bronchiolitis obliterans, later dubbed “Popcorn lung”. Disease, which scars the air sacs of the lungs and makes breathing difficult, due to exposure to diacetyl, a yellow chemical used to give microwave popcorn its buttery flavor. Now this chemical is at the center of a new study revealing that it is also harmful in vape liquids.

“Why don’t e-cig users get the same warnings?

In the to study, published Friday in Scientific reports, researchers at the TH Chan School of Public Health at Harvard show that diacetyl, together with a similar chemical called 2,3-pentanedione, can impair lung function when inhaled. Flavoring chemicals are found in over 90% of flavored electronic cigarettes on the market, and of these chemicals, diacetyl is the most common, according to the authors. 2,3-Pentanedione is used as a substitute in e-liquids, they add, possibly because diacetyl is associated with the lung of popcorn. The European Union diacetyl prohibited in vaping liquids in 2016.

Diacetyl, a compound used to impart a buttery flavor, has been implicated in “popcorn lung” cases among flavor factory workers.Unsplash / Christian Wiediger

While these chemicals are considered safe ingredients to take in food, the history of diacetyl strongly suggests that it is not safe to breathe, especially not in the form of a vape. Flavor factory workers now receive warnings about the dangers of inhaling flavoring chemicals, noted lead co-author Joseph Allen, Ph.D., who asked, “Why don’t e-cig users get the same warnings? “

Allen and another lead co-author, Quan Lu, Ph.D., led a team that studied what these chemicals do in the human lung. Rather than experimenting on real humans, they used normal human bronchial epithelial cells – the ones lining the lung – in a system closely mimicking a living human airway.

They found that exposing their man-made airways to chemicals for 24 hours significantly reduced the lung’s usual number of cilia, the finger-like protrusions that protrude from the surface of lung cells to sweep away mucus and others. dirt away from the lung and through the mouth. Eyelashes, which can also be damaged by smoking, are often considered the lungs’ first line of defense against large irritating particles, which can be expelled. Normally, 50 to 75 percent of the cells lining the airways have cilia.

The finger-shaped cilia of the lung epithelial cells sweep away the particles to keep the lung clear. Wikipedia

Taking a closer look at the genomes of these chemically exposed cells, the team found that 163 genes were regulated differently after exposure to diacetyl; ditto for 568 genes after exposure to 2,3-pentanedione. Exposure to these chemicals via e-cigarettes for just 24 hours, the team concludes, alters the genes of airway cells, hampering their ability to sweep away particles.

It can’t be good, especially at the epidemic scale that teens are using vapers. Originally marketed as a way to help people quit smoking – a claim that has some scientific support – vaping has been adopted as a new hobby for teenagers. Much of its immense popularity has been attributed to the fact that e-liquids are so tasty and appealing to children. Concerned San Francisco voters have decided to ban flavored vape products in june 2018 for this reason, although the continued rise in popularity shows that few other cities have followed suit. Other studies showing the cell-damaging effects of other e-liquid chemicals imparting cinnamon and buttery flavors exist, although the evidence has not been sufficient to stem the vaping wave.

The vaping industry itself complicates research, which has conducted its own studies on the usefulness of vaping flavors in quitting smoking.

The biggest concern about vaping’s skyrocketing popularity is that the science just can’t keep up. Scientists need to study whether vaping is addictive, a ‘gateway drug’ and has long-term effects, but between its introduction into society and its overwhelmingly enthusiastic adoption, there hasn’t been enough time to find out.


Aron M. Newman

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