The two regions in the most populous US state routinely rank among the nation's dirtiest in terms of air pollution. The results are a variety of costs associated with poorer health ranging from missed work days, to increased respiratory troubles to premature deaths.

Emissions from fossil fuels are the main problem, said Jane Hall, an economics professor at California State University, Fullerton who worked on the report.

"We need to find ways to clean up diesel, find ways to make transportation more efficient," Hall said, adding, "A lot of it is just reducing combustion of fossil fuels in these two basins."

In the Los Angeles area the cost of air pollution tops $1,250 per person per year and in the San Joaquin Valley, part of California's central valley and agricultural center, it is more than $1,600 per person annually, according to the report.

One reason air pollution's health costs are less in the more populous Los Angeles area is because winds off the Pacific Ocean push the pollution east, researchers said.

The San Joaquin Valley's air pollution is trapped by mountains, creating a "soup bowl" effect where harmful emissions keep mixing, Hall said.