FRESNO, Calif. (AP) — California's vast San Joaquin Valley farming region has some of the nation's dirtiest air, with a persistent problem from fine particulate matter, or harmful pollution from soot, smoke, dust and chemicals.

Listed below are the portions of that pollution detected in the valley from various sources in 2016:

MOBILE - 16 PERCENT
Cars, big trucks and trains
STATIONARY - 14 PERCENT
Oil and gas production, landfills, agriculture and food processing
AREAWIDE - 70 PERCENT
Restaurant grills, home fireplaces, dry cleaners, gas stations, dust from unpaved roads, lawn and garden equipment, and recreational boats

Source: California Air Resources Control Board