A third Spare the Air alert in as many days has been issued for Friday in the Bay Area.
The alert issued by the Bay Area Air Quality Management District is a result of forecasted high levels of ozone pollution caused by a combination of high temperatures, light winds and vehicle exhaust.
The alert will be the eighth of the summer season, according to the air district.
Ozone can cause throat irritation, chest pain and other medical problems. On Spare the Air days, air district officials advise people to limit outdoor exercise to the early morning hours when ozone levels are lower.
Residents are also encouraged to take public transit, carpool, or find another way to commute rather than driving in a car alone. People can visit www.stacommutetips.org to find a list of commute programs and incentives available in the Bay Area.
The forecasts for Saturday, Sunday and Monday indicate it's unlikely a Spare the Air alert will be issued for those days, air district officials said.