10+ years is not sufficient for proper, large scale, longitudinal research, particularly as they have not been in common use for 10+ years. They were used by small numbers up until quite recently.
Where are the large scale, longitudinal studies for air fresheners, hairspray, deodorants etc.? New products arrive on the market every day without these studies. Should we be alarmed?
Your point on the risks of action vs inaction, while valid, presupposes that the rights of the smoker trump the rights of a non-smoker. In your list of risks you have ignored the fact that the long term impact of secondhand vaping cannot be known at this point, thus exposing bystanders may potentially be dangerous.
Vaping is not smoking. Risk assessment is to do with risk, not rights. If you want to talk about a balance of rights then the balance is between your right to avoid a tiny theoretical risk versus a smoker's right to use whatever means available to quit, and so avoid the well evidenced 50% chance of early death.
The CDC disagrees with your statement that young people who are vaping are already smokers. The US Surgeon General also believes exposure to vaping is bad for children. Both views based on research.
CDC study is discussed on p87 of the PHE report. They point out that CDC have failed to differentiate between ever use, occasional use and regular use. They also failed to acknowledge that over the period of the study, youth smoking prevalence continued to fall.
The Surgeon General's report is roundly demolished in detail here by Clive Bates, ex-director of ASH. He calls it truly terrible – a heady mix of emotive propaganda and a completely warped and one-sided account of the science built on a lack of insight into youth behaviors and no knowledge of the tobacco and nicotine market or its consumers. He's not wrong.
The general standard of ecig research coming from the US is absolutely shocking and is in large part responsible for the rapid growth of the erroneous belief that vaping is as dangerous as, or more dangerous than, smoking. It was this shift in beliefs, including amongst smokers, that motivated PHE to produce their report.
While e-cigs pollute the air less than tobacco products, they still release nicotine and particulate matter into the air. Other studies have shown that cotinine (our bodies metabolise nicotine into cotinine) can be found in the blood of passive vapers.
See p 64 of the report. They release approx 1/10 the level of nicotine as a cigarette but, because there is no side stream vape, actual levels are much lower. Cotinine levels in non-smoking, non-vaping partners of vapers were found to be about the same as you get from eating a tomato. PHE acknowledge that vaping releases some nicotine into the air but still conclude there is no cause for concern.
The 'particulate' thing is almost as funny as the popcorn lung rubbish (except neither are funny really as they scare smokers away from switching). When considering 'particulates' you need to think about whether they are solid or liquid because those will behave differently. You also need to consider the toxicity of the fine particles. If you are worried about 'particulates' as a blanket category, I hope you never boil a kettle or have a shower!
There's a very good discussion on the topic here, again by Clive Bates. There's also this article by Michael Siegel, which shows clearly how much bias there is in research in this area.
if vaping turns out to be dangerous to passive vapers, I am more at risk from vaping than smoking as I can completely avoid being in an enclosed area with smokers. I cannot do the same for vapers.
I'm not so sure about that, given that smokers' breath and THS on their clothing is now considered a health risk. Current evidence suggests you are at more risk from being near smokers after they have come in from having a fag than you are being around someone who is vaping indoors.
Therefore, until more conclusive evidence exists, why potentially put the health of non-vapers at risk in the same way as was done to non-smokers? Why not err on the side of caution by learning from the mistakes of the past?
But it's not 'in the same way' is it? Vaping is not smoking. There is no smoke. Second hand vape is far more like air fresheners, cleaning products, cosmetics etc. in terms of potential harm profile. I ask again, why are you not demanding large scale longitudinal studies for these products?
We've already discussed what 'erring on the side of caution' means. It means fewer smokers switch and so more of them die early. Around 96,000 preventable deaths each year.