California, which has some of the toughest clean air laws after decades of fighting some of the worst smog in the nation, is in the final phase of building a cap-and-trade market to provide incentives to reduce greenhouse emissions.
The U.S. Environmental Protection Agency is approving California's air quality plans for reducing microscopic pollution caused by diesel trucks, ship traffic and other sources in Central and Southern California.
Southern California and the San Joaquin Valley suffer from some of the worst pollution in the nation. The plans, approved Monday, are required to reduce pollution to a certain level by 2015.
The particles, which measure 1/30th the diameter of a human hair, can penetrate deep into the lungs and aggravate asthma and heart disease. According to a 2010 California Air Resources Board
study, exposure to such pollution leads to 9,200 premature deaths annually across the state.
The largest sources of such pollution are diesel trucks, construction equipment and marine vessels. The state has adopted aggressive rules to target diesel emissions.