E-cigarette Vapors with Common Ingredients Cause Lung Irritation and Mucus

David Palenski
24th January, 2024

Image Source: Natural Science News, 2024

Have you ever been in a cloud of vapor from an e-cigarette and wondered just how harmless that mist is? (Just think about it, those plumes are pretty ubiquitous nowadays.) Well, it turns out that the supposedly 'safe' components in e-cigarettes – we're talking about propylene glycol (PG) and vegetable glycerin (VG), by the way – might not be as benign as once thought, especially when inhaled. Now, before we get into the nitty-gritty, let's get one thing out of the way. Nicotine and the various flavors added to e-cigarettes are already known to cause some trouble in the airways. But what about the substances primarily used to deliver them into your lungs? That's where things get interesting (and concerning). Researchers (the clever folks over at the Department of Internal Medicine at the University of Kansas Medical Center, to be specific) decided to take a peek at what happens when human bronchial cells and sheep (yes, the fluffy farm animals) are exposed to aerosols composed just of PG and VG. Why does this matter, you ask? (Well, these components are essentially the bread and butter of e-liquid bases, making up nearly the whole concoction in many e-cigs.) Now picture this: human bronchial epithelial cells are sitting cozy at an air-liquid interface (ALI) – think of it as a petri dish where cells get a taste of being in a lung environment. These cells are exposed to a 50/50 PG/VG e-cig cocktail for seven whole days while being observed with the scientific equivalent of a hawk-eye. And what did they find? A statutory warning for our airways in the making. (Makes you think twice about taking a puff, right?) Turns out, after the seven-day hangout with PG/VG aerosols, the cells showed a significant downturn in some pretty important ion channels, like the cystic fibrosis transmembrane conductance regulator (CFTR). As a sidenote, CFTR is quite the VIP in making sure our mucus stays the consistency of say, a light syrup, rather than a sticky sludge. Ion channels aside, the inflammation markers were through the roof; interleukin-6 (IL6), interleukin-8 (IL8), and matrix metalloproteinase-9 (MMP9) were having a field day. Think of inflammation markers as tell-tale signs that your body's not particularly happy. Oh, and the mucus-related protein MUC5AC? Way more of it. But curiously, while MUC5AC was crashing the party, MUC5B was heading out the back door, leading to an imbalance one might say is... not ideal. (Too much MUC5AC, and not enough MUC5B, are like having too much mustard and not enough ketchup on a burger – it's all about balance, folks.) If that wasn't enough, some of the cells literally lost their defining features – becoming less like themselves and more like... well, not lung cells (a cell identity crisis, if there was ever one). And those hair-like projections called cilia that sweep debris out of your lungs? Fewer and slower. (And nobody wants lazy janitors when it comes to keeping lungs clean.) But let's move on from cells in a dish to the live-action scenario: sheep. You'd think life in the pasture keeps them away from vaping concerns, but not so fast. The sheep were exposed to the same PG/VG e-cigarette aerosols, and guess what? Their airway mucus became thick and stubborn – think more molasses than water – and the activity of MMP-9, a kind of molecular scissor that typically helps keep mucus in check, went up. So what's the gist of all this scientific sleuthing? (Besides the fact that sheep can get caught up in vaping research?) These innocent-seeming PG/VG vapors seem to get a little rebellious when they hit the airways, causing inflammation, mixed-up mucus production, lacklustre lung cell performance, and in living, breathing sheep – a mucus Matryoshka, becoming denser and denser. Now, despite their reputation for being the 'less harmful' smoking alternative, e-cigarettes, or at least the PG/VG duo, appear to be stirring up trouble in ways that might keep our lungs guessing, and not in a fun way. This research is essentially poking holes in the safety net that many vaping enthusiasts have been hanging on to. E-cigarettes and their aerosols containing PG/VG are likely, according to this evidence, not the airway-friendly alternatives they've been billed as. So the next time you see a puff of e-cig vapor, or consider taking one yourself, you might just ponder – are they truly the benign puffs we've been told? Or is our respiratory health secretly getting vaped away?

Medicine Health Biotech

References

Main Study

1) The combination of propylene glycol and vegetable glycerin e-cigarette aerosols induces airway inflammation and mucus hyperconcentration.

Published 23rd January, 2024

https://doi.org/10.1038/s41598-024-52317-8

References

Main Study

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