The Los Angeles and Long Beach ports–which handle 40 percent of U.S. imports and are the single largest source of air pollution in Southern California–approved the Clean Air Action Plan last week, which will phase out the use of diesel trucks for natural gas-fueled and zero-emissions vehicles through 2035. Supporters say reducing the ports’ diesel emissions will slash pollution and carbon emissions and reduce pollution-related illnesses like asthma as well as set the ports apart as environmental leaders.