I live in a region with a very severe air pollution problem -- the worst day you remember is nothing compared to the typical winter day here, trust me on this. 200 µg/m³ of PM2.5 is a pretty average winter day, and in evenings it goes up to 1000 µg/m³, and sometimes even higher.
(The yearly average WHO recommendation for PM2.5 is no more than 5 µg/m³; in my neighbourhood the yearly average is around 150 µg/m³).
There are also high levels of chemical gaseous pollutants which nobody has bothered to measure properly over the past decade -- last time the gas monitoring worked at all, it showed persistent levels of 120-200 µg/m³ of NO₂ and 200-800 µg/m³ of SO₂, among many other pollutants (there are definitely high levels of at least H₂S, HCl, Cl, and HF).
In the warm period (which is short -- no longer than 4 months per year) it's much better, although chemical pollutants caused by heavy industry are very high all year round.
Yes, everybody has sore throats all the time, you often hear coughing even if nobody around you is sick, and I curse my fate for being born to this every single day. Yet the average life expectancy is "only" 10 years shorter compared to rich Western countries, and we have so many other problems (like high levels of smoking, high alcohol consumption, high levels of saturated animal fat in historically popular home foods, etc) that I very much doubt removing air pollution will improve it by much.
We definitely have never seen any healthcare system collapse or anything like that, and our COVID situation also wasn't any worse than anywhere else. I personally don't know anyone who suffered any noticeable long-term effects.