The report underscores what's been known for a while: Central Valley air is very polluted. The report goes on to cite motor vehicle emissions as a key reason for the dirty air.

Andy Weisser of the American Lung Association of California says automobile manufacturers could help reduce pollution by keeping up with the demand for environmentally friendly vehicles. 

"There continue to be very long waiting lists for cleaner cars, including hybrid-electrics, natural gas, and pure electric."

But Sean Comey of the Northern California Chapter of Triple-A says a lack of affordable housing is really to blame for air pollution problems.

"The cost of housing is so high in California that people are forced to endure incredibly long commutes to find a place to live. This ultimately contributes to the amount of air pollution that they create."

Meanwhile, car makers say it's a challenge to market a product that's only popular in one state. But they plan to increase the volume of hybrids as well as the variety of models over the next few years.

(Photo KXJZ)