What does "we can't chew our air" mean?

It means that "at least our air is not very polluted." "Chew our air" is an exaggeration for effect (or hyperbole).

Got it. Thank you.
But I failed to understand why "can't chew our air" can mean "at least our air is not very polluted."
Chew? Chew air? It makes no sense to me in the context of Chinese language.

I think it is just a very over-dramatic way. Of saying that the air has so much garbage in it, or so many impurities. That one can basically taste it. Or would be "chewing it". I know it is disgusting to think about. But the writer did get their point across with their hyperbole. So by them saying "can't chew our air" was an effective way for them to stress how disgusting they think it is to have polluted air. And imply that by not being able to "chew it". Would mean it was clean, or unpolluted air.

could it possibly be not JUST that the air is polluted, and you can taste it , but that the air is so thick with pollution you could chew it. a bit like when we have a very strong coffee, we make jokes about standing the spoon up in it.

Ori - you know better than to ask a question like this without context!

China has a air pollution problem. Is your question from a discussion about this?

Otherwise, it's an idiom that simply could mean "wasting time" or "working in vain."

Yes. Americans were commenting on the thick smog that covered 1.3 million square kilometers of China.