A third consecutive Spare the Air smog alert has been issued for Saturday.
An unhealthy amount of ozone accumulation is expected in the Bay Area for the third day this week because of forecasted hot weather with low winds, according to the Bay Area Air Quality Management District.
On a Spare the Air day, Bay Area residents are asked to avoid driving alone and instead take public transit, carpool, walk or bike to get around, according to the air district.
Smog can cause throat irritation, congestion, chest pain, asthma and can worsen bronchitis and emphysema.
The summer Spare the Air season started on April 28. The three this week are the first three of the season, air district officials said.