The U.S. Environmental Protection Agency is approving California's air quality plans for fine particles -- known as PM2.5 -- in the South Coast and San Joaquin Valley. These plans will reduce pollution to the level required by the health based 1997 PM2.5 standard by 2015.

“These air quality plans rely on first-of-their kind requirements for the engines in trucks, ships and construction equipment, impacting almost a million vehicles in California,” said Jared Blumenfeld, EPA’s Regional Administrator for the Pacific Southwest. “Clean air is critical to everyone’s health, especially our children and seniors.”

Over the past 10 years, at the worst monitors, particulate matter has improved by 14 percent in the San Joaquin Valley and by 43 percent in the South Coast.  “Worst monitors” are those that have the highest annual average PM2.5 concentration for a three year period in the air basin.

PM2.5 is made up of small particulate matter — 1/30th the diameter of a human hair. Fine particle pollution can be emitted directly or formed secondarily in the atmosphere and can penetrate deep into the lungs and worsen conditions such as asthma and heart disease. Reducing exposure helps reduce asthma, cardiovascular disease, emergency room visits, cancer and premature death. According to a 2010 California Air Resources Board study, PM2.5 exposure leads to 9,200 premature deaths annually in CA.

Mobile sources of diesel, such as trucks, construction equipment and marine vessels, are the largest source of PM2.5 in California. Trucks and buses account for 40 percent of the total diesel emissions. The state has adopted aggressive rules to target diesel emissions including the In-Use Diesel Truck and Bus rules, the Drayage Truck Rules and the Ocean Going Vessels Clean Fuels rule. The truck and bus rules are the first of their kind throughout the nation and will prevent an estimated 3,500 deaths.

EPA is disapproving the plans’ contingency measures because they do not provide sufficient emissions reductions.  EPA will continue to work with the state to resolve these remaining issues.