Saturday has been declared the first Spare the Air day of the summer season, according to the Bay Area Air Quality Management District.
Air quality is expected to be poor Saturday due to high temperatures and tailpipe exhaust, according to district officials.
"To help avoid unhealthy air quality this summer, we are asking residents to leave their car at home at least twice a week -- take transit, work from home, carpool or bike to work instead of driving alone," said Jack Broadbent, the district's executive officer.
Spare the Air alerts are issued when ozone pollution, also known as smog, is expected to reach unhealthy levels. Ozone can cause throat irritation, congestion and chest pain, trigger asthma, inflame the lungs and worsen bronchitis and emphysema. It is especially harmful to young children, the elderly and those with respiratory and heart conditions.
There is no free transit available Saturday, and wood-burning bans are in place. Residents are advised to avoid outdoor activity during the hottest part of the day, and reduce ozone emissions by carpooling, taking transit, biking or walking.