EPA Identifies 243 Most Polluted Counties
"The two worst areas in the country were in California: the San Joaquin Valley and the greater Los Angeles area. Except for California, a corner of northwestern Montana and the St. Louis area, all the most polluted counties are east of the Mississippi River... All states with counties on the list will have to show that plans for new roads and public transit systems conform to the air quality goals, and new industrial polluters in the violating areas will be required to use pollution controls. Beyond that, states have leeway to craft solutions to their fine-particle problems."
Thanks to Laura Kranz