In short, while available research points towards these things being safer, we really don't know what that margin is. Even if it's, say, 10 times safer, if vaping explodes to more than 10x the current smoking population then net harm could still be increased. Or not! But that's my point: we really don't know.
Personally, I don't think they should be outlawed. I think fruit flavors should be banned just like they are in cigarettes, and I think anti-smoking education campaigns need to ramp up their message to include vaping as a "no, just don't ever even start" part of the effort, and e-cigs should be required to only be marketed as aids for quitting smoking.
[0]https://pediatrics.aappublications.org/content/141/4/e201735...
Compared to what? Harm isn't measured in a vacuum. In the comparisons that make sense (e.g. vaping vs smoking american cigarettes) vaping is in fact damn near harmless in comparison, even if harmless is not the term I'd use for a vasodilator as potent as nicotine.
All of these "well we don't know vaping is harmless" monologues are coming from bad faith where you compare it to breathing "air" or something. Even that comparison doesn't really work because city air can itself be on the order of harm of a smoking habit—wouldn't it be funny if simply existing in SF turned out worse for your lung health than vaping?
https://www.washington.edu/news/2019/08/13/air-pollution-can...
So... of course we don't know what the harm of these things are, but we do know the harm of cigarette smoking, a factor that seems repeatedly absent from calls for regulations of vaping. Why aren't people banning cigarettes?
I also don't see how comparing vaping to not vaping is a bad faith argument. If smoking causes lung cancer at 13 to 23 times the rate as not smoking, it would seem important to compare vaping's rate to both of these, along with any other health effects. It's one (albeit imperfect) baseline. Sometimes, as in the case of living in a polluted city, the baseline varies and should be controlled for in studies. You yourself emphasized relative harm. So comparing harm of doing something to that of not doing it is exactly what you would want in order to get that relative relationship.
More on pollution-- maybe living with air pollution is worse than vaping, but then living that way and vaping would be worse still. Again, there's that relative harm again. These studies have been done with traditional cigarettes, showing living in pollution increased lung disease but smoking then increases it even more, again all relative (in most studies) to "never smokers". An important piece of research to find out for vaping as well.
Finally you put a straw man up against my arguments when you talk about banning hypocrisy: I don't advocate banning it, and you're right that it seems a silly conversation to talk about banning vaping if you're not thinking about the same for cigarettes. For my part, I generally want vaping to be treated on par with cigarettes, excepting I think it should be marketed as a quitting method, not an alternate life-long choice.
I totally get where you're coming from and am sympathetic to this argument, but I don't agree with it. We have learned a great deal from decades of research in to the harms of cigarette smoking, and have drawn some uncontroversial conclusions about why smoking causes so many health problems. We also can be reasonably sure that vaporizing nicotine does not create those same harmful conditions. I'm not saying anyone knows the long term implications of vaping, but "no one knows what will happen" is not a strong argument to me. As it stands, I think we have every reason to believe that smoking cigarettes is drastically more harmful than vaping.
Should this apply to vodka and other liquors as well?
Your point about certain populations of drinkers being able to indulge without obvious adverse health outcomes is also applicable to users of vaporized nicotine. And again it is worth pointing out that alcohol is significantly more harmful than nicotine.
I would be curious to see any research that supports the idea that flavored vape products are primarily appealing to underage users. I suspect there aren't many teenagers opting for scotch as their drink of choice, but I am certain there are plenty of adults who prefer a rum punch, peach white claw, jameson and ginger ale, or a glass of wine (it's made from grape juice for god's sake, brazenly targeting the children!), etc.
Just to pick an obviously stupid example, I could chug a can of soda (or seltzer, if you prefer) in one go. It would contain around 2.2g of CO2. If you put that 2.2g of CO2 in my lungs, I would be dead. (Well, you would have to keep it there. It would at least be very painful.)
Or to pick another obviously stupid example, I could drink enough alcohol to kill myself. In most situations, I would vomit or pass out before I got to the fatal dose. But instead, I could give myself an alcohol enema and just die (which does happen, from time to time). So, delivery matters absolutely.
For the non-obvious examples we (at least) need data. If you are putting “high” concentrations of a chemical (for some appropriate definition of “high”) in your lungs you will want some good safety data. For ingestion we already have an FDA approval process. You may disagree with the methodology, but at least it’s there.
Hence dosage for injections/sublingual delivery is much lower than dosage for normal pills to swallow.
My opinion: keep the nicotine for tobacco-flavored pods as a smoking cessation tool; otherwise drop the nicotine and go for a La Croix-style strategy.
"Nicotine causes catecholamine release both locally and systemically leading to an increase in heart rate, blood pressure and cardiac contractility. It reduces blood flow in cutaneous and coronary vessels; and increases blood flow in the skeletal muscles. Due to restricted myocardial oxygen delivery there is reduced cardiac work. In a study, chewing a low dose (4 mg) of nicotine gum by healthy nonsmokers blunted the increase in coronary blood flow that occurs with increased heart rate produced by cardiac pacing. Thus, persistent stimulation by nicotine can contribute to Coronary Vascular Disease by producing acute myocardial ischemia. In the presence of coronary disease, myocardial dysfunction can be worsened."
"Nicotine alters the structural and functional characteristics of vascular smooth muscle and endothelial cells. It enhances release of the basic fibroblast growth factor and inhibits production of transforming growth factor-β1. These effects lead to increased DNA synthesis, mitogenic activity, endothelial proliferation and increases atherosclerotic plaque formation. Neovascularization stimulated by nicotine can help progression of atherosclerotic plaques. These effects lead to myointimal thickening and atherogenic and ischemic changes, increasing the incidence of hypertension and cardiovascular disorders."
"Nicotine plays a role in the development of emphysema in smokers, by decreasing elastin in the lung parenchyma and increasing the alveolar volume."
"The simultaneous effect of bronchoconstriction and apnea increases the tracheal tension and causes several respiratory disorders."
"Nicotine use has been associated with Gastro Esophageal Reflux Disorder (GERD) and peptic ulcer disease (PUD)."
"Nicotine has been known to be immunosuppressive through central and peripheral mechanisms. It impairs antigen and receptor mediated signal transduction in the lymphoid system leading to decreased immunological response."
"Nicotine promotes pathologic angiogenesis and retinal neovascularization in murine models. It causes age-related macular degeneration in mice."
"There is synergistic relationship between nicotine and glucose metabolism which increases the risk of diabetes mellitus. This might cause accelerated cataract formation."
"Nitrous oxide liberated from parasympathetico-nergic nerves plays a pivotal role in generating immediate penile vasodilatation and corpus cavernosum relaxation, and NO derived from endothelial cells contributes to maintaining penile erection. Nicotine causes impairment of NO synthesis. This may lead to loss of penile erections and erectile dysfunction."
"Nicotine affects the ovaries and alters the production of oocytes in various animal studies. Nicotine-treated oocytes appeared nonspherical with rough surface and torn and irregular zona-pellucida. Nicotine also caused disturbed oocyte maturation. There is a decreased blood flow to the oviducts and thus impaired fertilization."
"Various animal studies show retarded fetal growth and lower birth weight when treated perinatally with nicotine. The lower levels of ACTH and cortisol due to nicotine are probable reasons for the incidence of lower birth weight in the newborns."
"Nicotine adversely affects many organs as shown in human and animal studies. Its biological effects are widespread and extend to all systems of the body including cardiovascular, respiratory, renal and reproductive systems. Nicotine has also been found to be carcinogenic in several studies. It promotes tumorigenesis by affecting cell proliferation, angiogenesis and apoptotic pathways. It causes resistance to the chemotherapeutic agents."
It's not controversial to say smoking is bad for you. But that's always been not because of nicotine, but all the other substances you inhale when smoking, some of which are known to interact with nicotine. What's controversial is whether nicotine itself is bad for you, in isolation, and it's of interest to people taking it in the form of chewing gums, or more recently, vaping.
Here's Gwern with a bunch of papers arguing that nicotine isn't more addictive than coffee and doesn't cause cancer, and the whole thing is just confusion: https://www.gwern.net/Nicotine#addictiveness.
I don't mind more regulation here, absolutely make sure it's safe and find a set of ingredients that cause the least amount of harm to humans. Why is vaping perceived as so dangerous? Compared with cigarettes its damn near harmless. I don't get it.