Metal content is negligible unless you dry hit. No one likes that so it's pretty much a self-limiting problem.
Flavoring compounds, though... there are liquids out there that contain diacetyl (a "buttery" flavoring). It's relatively common in foods, but is known specifically to cause issues when heated and inhaled.
ETA: I just saw that this is mentioned in the article.
> Any one of those components could be harmful.
Yep. The best harm reduction strategy at the moment seems to be to stick to well-known and establish manufacturers of eliquid.
That name rang a bell; diacetyl is the compound behind "popcorn lung", so called because its use for its buttery taste in microwave popcorn was common but is damaging to the lungs if the fumes were inhaled; e.g. https://nyti.ms/2h7ls4G. Interesting to see that it's being used as a vaping flavorant.
https://en.m.wikipedia.org/wiki/Bronchiolitis_obliterans#Dia...
I... I... need get to bed.
I assumed when people were talking about metal content, they were referring to metal vapors from the heating elements or something, but I'll admit that I don't know enough about this, or what a dry hit is vs. normal use, or how we know when metal vapors or whatever are/aren't a concern.
(I feel so old right now, hah!)
The only study I've seen that shows that heavy metals in vapor is an issue used conditions that are unlikely to occur in "real life" because of this. The argument seems to be that one could become accustomed to it through the cravings associated with nicotine withdrawal, but I honestly find that unlikely. In reality, you'd burn your coil up in short order, and if you can afford a new coil you'd have been buying more liquid in the first place.
https://www.jhsph.edu/news/news-releases/2017/study-toxic-me...
"For their study, the researchers selected five leading brands of so-called first generation e-cigarettes, which are referred to as cig-a-likes because they resemble traditional cigarettes. (Newer ones look like small cassette recorders with a mouthpiece. In the newer devices the liquid is added from a dispenser prior to use. In contrast, the liquid in first generation e-cigs is stored in the cartridge together with the coil, which increases the liquid’s exposure to the coil even in the absence of heating.) The five brands are sold across the United States in big-box retail stores, convenience stores and gas stations, as well as online. Three of the five brands constituted 71 percent of total market share in 2015. If a brand came in more than one flavor, the researchers chose one flavor for consistency’s sake."
Almost no one uses this piece of junk cig-a-likes. Try and find a person using one on the street, compared to people using proper high powered mods, which their "market share" statistic most certainly does not include.
"This study was funded by the Institute for Global Tobacco Control, Johns Hopkins School of Public Health."
Shocking.
I have yet to read a negative study that does not contain obvious blatant lies.
Who do you expect to investigate tobacco products, if not the institute of tobacco control at America's #1 medical college?
edit: also, if your "high power mod" still uses a nichrome heating element, you will have the same problems. Chemistry is chemistry.
71% of the market of product sold in big-box retail stores, convenience stores and gas stations, as well as online. That market is perhaps 10% (that's being generous) of the overall ecig market, because those tiny things suck.
I'm less worried about metal leeching in higher end mods, the juice doesn't sit for months on end with significant surface area touching metal as the juice is typically vaped in << 24 hours, and the physical designs are quite different.
That said, there is still an element of unknown risk, both with the metals used, as well as the wicking materials, but it seems reasonable to expect high end products where they have better margins and more concern with reputation to put much more emphasis on safety and quality.
EDIT:
I think I will have to eat some crow, after doing some googling it seems there are in fact thorough real studies being performed on real world equipment:
https://ehp.niehs.nih.gov/ehp2175/
I mostly just skimmed this article, figuring out whether these detected levels are beyond what is considered "safe" or how they compare to both regular cigarettes and background environmental exposure I suppose would be nice to know, but based on this article I am going to change my stance to believe that yes, in fact I am exposing myself to heavy metals even when using a high end mod. I think I'm going to do some more research later as I would expect this report would have gotten a fair amount of publicity in the enthusiast community, will be interesting to see how honest their reaction is to this.
We're talking about exposures to ten micrograms in various e-liquids, versus 7,000 micrograms for smokers. On a daily basis, in both cases.
Even more curious, traditional smoking has not been shown to be a risk factor for bronchiolitis.[2] Should those flavors be avoided? Yeah, but I honestly wouldn't get hysterical over it. We're talking about fractions of micrograms in the end product. You certainly are exposed to far more diacetyl in second-hand smoke than a vaper is exposed to in a day, on average, in liquids that contain this flavoring.
FYI: I quit smoking completely using e-cigarettes, and quit using e-cigarettes last year. I wrapped my own coils and built my own atomizers at one point, so I'm probably biased, but the numbers speak for themselves.
To say nothing of my opinion on the hysteria over nicotine, which has never been shown to have strong reinforcing properties in any study. Nicotine, by itself, has simply never been shown to be more addictive than caffeine.[3]
[1] http://onlinelibrary.wiley.com/doi/10.1002/tox.20153/abstrac...
[2] http://www.tandfonline.com/doi/abs/10.3109/10408444.2014.882...
But as other people here said - diacetyl / popcorn lung has been known on the popular vaping scene for almost a decade now. Not to speak in absolute terms but I think it would be hard to find a retailer these days that carries any liquid with diacetyl in it.
Maybe there aren't enough regulations around vaping ingredients? If so, the solution is to regulate it (much like food). In the meantime, it's up to the buyer to find reliable suppliers who use good ingredients. This isn't impossible.