N 34 11.586,W 117 19.414,Andy Jackson Flight Park, San
Bernardino, CA, USA

http://www.environmentamerica.org/home/reports/report-archives/clean-air/clean-air/danger-in-the-air-unhealthy-air-days-in-2010-and-2011

Of large metropolitan areas, or those with populations over 1
million people, Riverside-San Bernardino, California suffered the worst smog
pollution in 2010 by far, with 41 more days than the area in second place: Los
Angeles-Long Beach, CA.

State-by-state rankings of smog in 2010: Across the state of California, there
were 135 days in 2010, or more than a third of the year, when at least part of
the state experienced smog levels exceeding the health standard.