Here is a listing of some of the cities in the US with the most polluted air, Los Angeles takes the 'least-breathable' award...http://gizmodo.com/who-is-breathing-the-worst-air-in-america-1569834891
I used to get sick whenever we went to Disneyland-headache,nausea-took me a long time to figure out it was the smog making me sick....