True, but I imagine in an environment in which the vast majority of people smoke, the ones who don't will probably still passively inhale a lot more toxins than if no one smoked at all - making the effect size in direct comparison with smokers seem weaker than we know today it really is.

I believe social media and phone use could have a similar dynamic - like the kids said themselves, it's more a "collective action" than an individual problem.

That was what I was trying to get at with that analogy.