We could just ... not give police tear gas. That is a decision we could make. A state or city could make that decision, and remove it from inventory.
Maybe police do not actually need area-denial weaponry present at every public gathering. Maybe "people are throwing bottles at us, therefore tear gas" need not be the standard playbook.
The medical research on the _safety_ of CS gas suggests a spectrum from "unknown" to "probably dangerous, particularly the way it actually used": https://www.propublica.org/article/tear-gas-is-way-more-dangerous-than-police-let-on-especially-during-the-coronavirus-pandemic https://med.umn.edu/news/u-m-study-shows-little-research-available-long-term-effects-tear-gas-use
I had less luck finding studies about its _effectiveness_ of CS gas for the presumed goals of police forces: officer safety and encouraging compliance with dispersal order. I found a lot of quotes from police along the lines of "well, the only alternative is bashing people with batons" One study of the introduction of CS spray in UK police forces (for personal protection, not crowd control) did not find a clear win: https://doi.org/10.1108/13639510010343065
Anecdotally, we might look at the current situation at LA, or that a few years ago in Minneapolis, and note that CS gas was not effective in reducing crowd antagonism, even if it does move people from one place to another.