Maddy,

That’s an interesting paper, although I wouldn’t make too much of it, and nor, it seems, would its authors (my emphasis added):

Airway inflammation and emphysema were more common in marijuana smokers than in nonsmokers and tobacco-only smokers, although variable interobserver agreement and concomitant cigarette smoking among the marijuana-smoking cohort limits our ability to draw strong conclusions.

That said, I doubt if most people who smoke marijuana (there are always gummies, vapes, etc.) expect that the smoking would do them much good. Still, it does no harm to warn of a possible risk, and indeed it may do some good. The more information that is out there the better, assuming it is honest (anti-vaping activists have not covered themselves with glory in this respect).

Of course, an increased risk of emphysema or airway inflammation shouldn’t be used as a reason to ban marijuana for adult consumption. Caveat emptor and all that. It’s also no reason to slap onerous taxes on weed (the same can be said about the larcenous taxes so often imposed on cigarettes, which should be cut).