Six of the top 8 polluted metropolitan areas are in California. Everyone blames industry, vehicles and chemicals as the main causes. California has very low industrial pollution compared to Pittsburgh? Just about everyone owns a car or truck in El Paso, as in California and CA has stricter vehicle emissions laws?
Maybe we need to look at density of population? With a maximum population of 500 humans per square mile, mother nature will clean the air for us.
Sounds like 8,000,000 people need to leave LA.
#1: Fresno-Madera, CA
#2: Visalia-Porterville-Hanford, CA
#3: Bakersfield, CA
#3: Los Angeles-Long Beach, CA
#5: Modesto-Merced, CA
#6: Pittsburgh-New Castle-Weirton, PA-OH-WV
#7: El Centro, CA
#8: El Paso-Las Cruces, TX-NM