Bay Area residents have been asked to avoid driving alone again on Wednesday during the second consecutive Spare the Air Day.
It is the second Spare the Air alert issued for the season. High temperatures and light winds forecasted throughout the week are expected to lead to unhealthy smog.
During Spare the Air days, the Bay Area Air Quality Management District asks that residents take public transit, carpool, walk or bike rather than driving alone.
In addition, residents are advised not to exercise outdoors during the hottest times of day, when smog levels are at their highest.
Smog can lead to throat irritation, congestion, chest pain, asthma attacks and can worsen bronchitis or emphysema, according to the air district.
"Tailpipe exhaust is the biggest contributor to smog so we're asking Bay Area residents to leave their cars at home and find a better way to work rather than driving alone," air district executive officer Jack Broadbent said in a statement.
More information about Spare the Air alerts is available at sparetheair.org.