I notice a difference when I'm out of LA, Kell, which is what I'm assuming you're asking about.
I've lived in LA all my life and didn't leave much until I was out of college. San Francisco, Seattle, Salzburg, Chicago - I notice a difference in my breathing even though my FEV1's are 98%.
Smog causes asthma for people with NORMAL lungs (the rate of asthma in LA is very high). So you can imagine how much it helps those with poor lungs.
This is why I'm hoping to go to grad school in SF and move to Seattle one day.