which area in the united states has the most serious urban smog problem
Air pollution in the United States Los Angeles has the most contaminated air in the country. With a population of roughly over 10 million, the Los Angeles area is a large basin with the Pacific Ocean to the west, and several mountain ranges with 11,000-foot peaks to the east and south. Diesel engines, ports, motor vehicles, and industries are main sources of air pollution in Los Angeles. Frequent sunny days and low rainfall contribute to ozone formation, as well as high levels of fine particles and dust.[72] The strong relationship between AQI and ozone levels may be found on air pollution maps.[73]