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U.S. EPA proposes San Joaquin Valley, South Coast, Southeast Desert as failing to meet one hour ozone air standard

Release Date: 09/02/2011
Contact Information: Francisco Arcaute, (213) 244-1815, Cell (213) 798-1404,

SAN FRANCISCO – With the continuing goal of improving air quality for millions of Californians, the U.S. Environmental Protection Agency announced today that it is proposing to find that the San Joaquin Valley, and California’s South Coast and the Southeast Desert have failed to meet the 1-hour ozone standard by their required deadlines. Children and the elderly are most impacted by ozone pollution.
The 1-hour ozone standard was superseded in 2005 by the health-based 8-hour ozone standard. However, EPA is required to continue to implement federal Clean Air Act requirements for the 1-hour ozone standard to prevent deterioration in air quality.

In 1997, the EPA first established the 8-hour ozone standard (0.08 ppm), which replaced the older 1-hour ozone standard (0.12 ppm). The 8-hour standard is more protective of human health because it addresses the impacts of exposure over longer periods of time. EPA will soon propose actions on the South Coast and San Joaquin Valley air quality plans for 8-hour ozone.

Ground-level ozone is formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the atmosphere in the presence of sunlight. NOx and VOCs are called ozone precursors. Motor vehicle exhaust, industrial emissions, and chemical solvents are the major sources of these chemicals. Ozone pollution is a concern especially when the weather conditions needed to form it, lots of sun and hot temperatures occur. Ozone pollution can irritate airways, worsen asthma symptoms and increase hospitalizations for respiratory cases.

EPA is providing a 30-day public comment period on the 1-hour ozone proposed actions. For more information, please visit: