Bakersfield tops the list for having the most unhealthy days from airborne particles spewed by highway traffic, diesel trucks, farm equipment and fireplaces, the American Lung Association’s State of the Air 2016 report says
The California Central Valley (look on a map) is flat and for the most part bare land. Nature picking up dirt and moving it elsewhere would be the most likely cause of any airborne particles.
Another study to provide the legislature a reason to restrict the freedoms of the citizens of California (they want to do away with fireplaces, and it appears farms).
A large portion of Bakersfield’s dirty air is pushed down the valley from NorCal. There are mountains on the southern end of the valley between Kern County and LA that stop the dirty air from leaving. Think of a 3 sided bowl. That’s the Central Valley with Bakersfield at the Southern end.
Once the air gets pushed down it doesn’t have anywhere else to go.