We live in the South, where the air is always humid, and in the summer, it is hot and humid, and just walking out the door causes perspiration on your face and arms, even when it is early in the morning. Some days, it is almost like trying to breathe underwater.
When I go back out to Idaho to visit family there, I can breathe so much better, and the air is fresh and pure.
Huntsville (AL) is down in a valley, and so the quality of the air is even worse because of that. The early settlers here were told by the Indians who lived out here, that the air was "poison", and they camped in the hills surrounding the valley and not in the valley itself.
And that was way before there was any kind of industry here that was actually polluting the air, it was just mainly because the air here was stagnant.
And the mosquitoes are horrific here ! Worse than anywhere I have ever lived in all of my life ! I am not sure what it is about the air that facilitates mosquito propagation, but something sure does.
The mosquito-spraying truck goes up and down the streets several times each week in the summer to try and help keep the population at bay; but I don't think that it does a whole lot of good.