I have been to LA, and yes the pollution is bad there. In other areas, it's not so bad.
H_TeXMeX_H, than I respectfully suggest that you have never been to the Bay Area (Silicon Valley, San Jose, Santa Clara, etc) during the summer. I used to be a private pilot and live and fly in the Bay Area. When I started taking my lessons, more than 25 years ago, you could get out of the pollution around 3,500 feet. When I stopped flying, about 15 years ago, it took over 6,000 feet to climb out of the "brown haze" over the South Bay... During the warmer months air pollution is a very large and real problem. This can also happen during the colder months, but without the inversion and hopefully some rain, air quality is usually better.