I have terrible allergies, and poor air quality makes them worse. I have seen the direct impact of bad air.
As a child, we lived in Sao Paulo, Brazil, and we would often drive to Rio. On the way home, as we came off the mountain and descended into the pollution of the city, I would become physically ill—my allergies couldn't handle the congestion.
When in a heavily-polluted city, I still suffer the consequences.