*cides aren't the only thing to worry about. There are things to make it heavier, like lead dust, to make it feel more tacky(best case just sugar), to make it smell better, and whatnot else. None of which are good to inhale.
Vapes aren't that much better, containing different groups of chemicals you wouldn't want to inhale directly, or not in the concentrations used in vaping.
I don't know exactly, because I don't smoke/vape that much, and my experiences with what is offered in shops is mostly limited to some small resort town in Colorado, sometimes San Jose, CA, Austin, TX(no 'shopping' there), Hamburg, Germany,(no shopping there either, just strange vapes with 10-OH-HHC(P)), Rotterdam, NL, and finally Georgia, the country at the Black Sea, no shopping there, either, and couldn't read it anyways because of their most weird alphabet, but it has been good, no regrets so far.
So my 'knowledge' about that stuff is a patchwork of what I've read in the media, concerning the region/changing legislature/over time, and personal experience, be it by consuming it itself, or just smelling it from afar and thinking for myself 'I'd never touch that crap with a ten foot pole!'
I can say that I feel safest with Colorados model, which basically amounts to that all the stuff has to be tested before it is allowed to be sold legally, be it in shops, or online. Not halfassed shit like in the Netherlands, where it is only decriminalized, and the 'Coffeeshops' pay taxes for 'not drunken coffee', while the supply chain is still VERBOTEN and shrugged off, or the recent German model, which is shitty in similar ways, and doesn't even allow 'Coffee-shops'. Georgia, the country? They also messed the supply-chain and shop-thing up, or decided not to bother at all. Just consuming and maybe up to hand full of plants for personal use is legal, and that's it.
Which means anywhere not following Colorados mandatory testing model has a black market, and thus the potential 'quality problems' which they bring with them.
Vapes aren't that much better, containing different groups of chemicals you wouldn't want to inhale directly, or not in the concentrations used in vaping.