More than just a prelude to summer, the beginning of May is also the start of the Bay Area Air Quality Management District’s summer Spare the Air season, which begins today.

The air alerts are issued when weather conditions and pollution levels combine to 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.

Ozone is formed when volatile organic compounds and nitrogen oxides from motor vehicle exhaust, gasoline vapors, industrial emissions and household chemicals combine with oxygen in the presence of heat and sunlight.

According to the air district, tailpipe exhaust from millions of cars on Bay Area roads is the largest contributor to smog.

“Reducing the number of cars on our roads remains the biggest air quality challenge we face in the Bay Area,” air district executive office Jack Broadbent said in a statement Tuesday.

On Spare the Air days, people are encouraged to take public transportation, work from home, or bike or carpool to work. Outdoor exercise should be performed in the morning on those days, when ozone concentrations are lower.

Using electric-powered lawn and garden tools and linking errands to reduce driving can also help reduce pollution.

The air district encourages people to drive less year-round, but particularly on Spare the Air days.

“We are urging residents to re-think their commute and leave their car at home at least twice a week,” Broadbent said.

More information about the air alerts can be found at or

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