Stagnating air could lead to high ozone levels

High pressure and atmospheric recirculation have prompted Valley air officials to declare a new Air Alert episode for Thursday, Sept. 29.
Although conditions are anticipated to change by Friday, the episode may be extended if required.
The Air Alert includes the counties of San Joaquin, Stanislaus, Merced, Madera, Fresno, Kings, Tulare and portions of Kern.
Air Alert episodes are called when conditions may lead to ozone formation that results in exceeding health-based ozone standards of 125 parts per billion (ppb) and triggering substantial federal monetary penalties.
This would be the fourth episode of the season and may be the last of the year, as ozone season is ending.
Despite a violation of the 1-hour ozone standard this month – which exceeded the limit by just one hour -- the past two summers have been the cleanest on record for the air basin for both the 1-hour and the more stringent 8-hour federal ozone standards. Exceedances of the 1-hour standard have declined from 56 in 1996 to just five hours this year.  The Valley has also seen a sharp decline in the number of exceedances for the tougher 8-hour ozone standard.  In fact, the number of exceedances has declined from 633 in 1997, when the standard was established by the federal EPA, to 284 this year. 2010 and 2011 are on track to be the cleanest years for both the 1-hour and 8-hour ozone standards throughout the San Joaquin Valley.
“Despite significant improvements, we continue to have significant air quality challenges that require vigilance and active participation by Valley residents and businesses. However, it’s also important to recognize the huge monetary and personal investments and sacrifices that Valley businesses and residents have made to date to achieve these unprecedented improvements,” said Seyed Sadredin, the District’s executive director and air pollution control officer.
About 80 percent of the Valley’s ozone-forming emissions are produced by vehicle use. Residents can reduce smog-forming emissions by refraining from idling when dropping off or picking up students, carpooling or vanpooling, and refraining from using drive-through services.
Businesses and municipalities can reduce emissions by shifting operations to early morning or late evening, as in lawn care; offering flexible work schedules, and encouraging carpools and
vanpools for employees. Businesses can also enroll at no cost in the Healthy Air Living Partner program.
For more information about Air Alerts, please visit To sign up for a free subscription to the Air Alert email notification system please visit
To receive information about becoming a Healthy Air Living Partner, please visit