The Sacramento Metropolitan Air Quality Management District said the region's air quality is forecast to be unhealthy for sensitive groups Thursday.
"People who are already susceptible to ozone air pollution like those with asthma, upper-respiratory diseases, children, pregnant women, outdoor athletes, need to be aware of what air quality is doing during the day," said Kobza.
Kobza said the ozone reaches its worst level during the afternoon and early evening hours. She said high levels happen most often during the summer. The primary source of ground-level ozone is cars, trucks, buses, construction equipment and agricultural equipment.