Ozone and Particulate Air Pollution in Summertime America 2014

If the map is colored green it is either healthy, slightly less than unhealthy, or there is no instruments  measuring air pollution in the area.
Yellow, orange, and red signify unhealthy air.

Air Pollution in America June 18, 2014

Animated Air Pollution in America June 18, 2014

Source:

California's Central Valley Ozone PM2.5

California's Central Valley, a.k.a. The Salad Bowl of the World, also collects and generates enormous  amounts of unhealthy ozone and fine particulate pollution.
This AIRNow animated map shows a one days cycle of these dangerous pollutants.
Just left-of-center near the bottom of the map and just above Los Angeles is the southern edge of the Central Valley.
Much of the air entering the valley began as relatively fresh sea air off of the Pacific. As the air traveled through San Fransisco and San Jose, it began picking up pollution from those metro areas then flowed to the bottom of the valley, accumulating more pollutants.The Valley's pollution then spills over the Tehachapi Mountains, the site of many wind turbines, into the high deserts north of Los Angeles.
This is a normal cycle of air mixing and pollution generation for this area

Ozone in US Cities
AIRNow

Toxic Ozone and Fine Particle Air Pollution in US.

Below is an animated color coded map of ozone and fine particulate air pollution as it goes through its forecast cycle. Areas colored warmer than green signify unhealthy levels of listed pollutants.

Source: http://airnow.gov