The US Environmental Protection Agency ruled earlier this month that the region's air did not have excessive levels of tiny pollution particles linked to asthma.
But environmental groups say the EPA's own data shows that federal pollution standards were exceeded nine times from 2003 to 2006.
Erin Tobin is an associate attorney with Earthjustice. She says they filed the suit for a couple of reasons.
"The first and most important reason is that particulate matter continues to be a very serious public health program in the Central Valley. Children in the valley still have the highest asthma rates in the state. And the second big problem is that air quality monitors in the Central Valley continue to report exceedances of the air quality standard."
But EPA officials attribute the higher levels to wind events….and improperly installed air monitors during construction activity.
Deborah Jordan with EPA’s Pacific Southwest region says the Central Valley “continues to move toward cleaner air.”