The Los Angeles basin that also includes Long Beach again registered the highest level of air pollution among the largest urban areas in the U.S., according to the American Lung Association's (ALA) 2014 ranking.
The Los Angeles area ranked at the top of the list of ozone-polluted metropolitan areas, according to the ALA. It was followed by four other California areas, including Visalia/Porterville/Hanford; Bakersfield; Fresno/Madera; and Sacramento/Roseville.
The ALA also released its list of the highest concentration of particulate matter (PM 2.5) during a 24-hour period, and the highest concentration of particulate matter year round. Fresno/Madera ranked at the top of the 24-hour list, followed by Visalia/Porterville/Hanford, and Los Angeles/Long Beach.
Fresno/Madera came in at the top of the annual list. No areas outside of California appeared among the top five of any of the three lists.
In past years, the ALA has cited tailpipe emissions from passenger cars and light-duty trucks as a major contributor to air pollution. In its 2013 report, the ALA called on the EPA to finalize its Tier 3 emission and fuel standards, which happened in March.
Read the full report at the ALA website here.