I was in Beijing a few weeks ago when the AQI was in the mid to high 200s. While it looked nasty, what really surprised me was that I couldn't really sense that I was breathing polluted air – it didn't smell bad and it wasn't difficult to inhale. The only indicator that I was breathing bad air was the cough I developed after a week in the city. I attributed it to a traveling cold but it quickly went away when I returned to the relatively clean Manhattan air.
We've had up to 700+ this year in Beijing. The "standard", almost everyday 200+ makes it hard to do any sport... 700 was barely breathable.
The situation here really deserves attention such as the one in Singapore it getting right now.
