High temperatures, low winds and an inversion layer have caused ozone levels to rise in the Sacramento region. Air quality agencies have issued "Spare the Air" alerts for Sacramento, Yolo, Solano, El Dorado and Placer counties.
"That inversion layer clamps down on the Sacramento region like a bull," says Jamie Arno, with the Sacramento Metropolitan Air Quality Management District. "So all the air pollution that is produced from cars and trucks just sits around and doesn't go anywhere."
She says 70 percent of the ground level ozone problem in the region is caused from car and truck emissions.
Arno says Wednesday and Thursday are Spare the Air days, because ozone levels are considered "unhealthy for sensitive groups" - children, the elderly, and anyone with respiratory disease, such as asthma.
"Going outside and doing your exercise in the morning is OK, our ozone levels are very good in the morning," says Arno. "It's probably between 2 p.m. and 6 p.m. that you want to avoid outdoor exertion."
Arno says reducing one car trip, by carpooling or taking public transit can help reduce ozone and improve air quality.
In Yolo County, rides on YOLOBUS and Unitrans fixed route services are free Wednesday and Thursday because of the "Spare the Air Day" designation.
Arno says smoke from fires in Nevada, Placer and Solano counties does not appear to be "making a big impact on the ozone levels, but it's possible they could be a contributing factor in the future."