The Bay Area Air Quality Management District's summer "Spare the Air" season has started.
For the past 20 years, the air district has been declaring "Spare the Air" days when weather conditions and pollution levels combine to create high levels of ground-level ozone or smog, which can cause throat irritation, congestion and chest pain.
The smog can also trigger asthma, inflame the lining of the lungs and worsen bronchitis and emphysema, according to the air district.
On Spare the Air days, people are encouraged to take public transportation, work from home, or bike to carpool to work. Using electric-powered lawn and garden tools and linking errands to reduce driving can also help reduce pollution.
Last year, air quality reached unhealthy levels twice in April and the air district launched its Spare the Air season on May 11, air district spokeswoman Kristine Roselius said.
This year, the district decided to kick off the season more than a week earlier, in part to have the beginning of the smog season coincide with the start of national Air Quality Awareness week, Roselius said.
The air district encourages people to drive less year-round, but particularly on Spare the Air days.
"Tailpipe exhaust from the 3 to 4 million vehicles on our roads each day remains the largest source of smog in the Bay Area," said Jack Broadbent, executive director of the air district. "To reduce the health impacts from smog, we all need to think differently about how we use our cars as part of our daily routine."
Roselius said surveys have shown that Bay Area residents have been making efforts to drive less on Spare the Air days.
There will be no free transit on Spare the Air days this year, she said.