Background

Fact Sheet on Ozone Pollution in the San Joaquin Valley

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What is ozone?

• Ozone (O3) is a gas consisting of three oxygen atoms.
• In our atmosphere, there are two types of ozone – "good" ozone and "bad" ozone.
• "Good" ozone forms the "ozone layer," miles above the earth that protects humans and all other living things from the sun's harmful ultraviolet rays.
• "Bad" ozone accumulates at ground level and causes the air pollution known as smog.

How does smog form?

• "Bad" ozone (smog) is formed at ground level when pollutants, known as "ozone precursors," mix in the sun's heat and light.
• Levels of smog are highest during the summer months due to increased sunlight and heat.
• VOCs (volatile organic compounds) come primarily from cars and other gasoline-burning engines. Other major industrial sources of VOCs include gas stations, dry cleaners, paints, insecticides, and solvents used in degreasing operations.
• NOx (oxides of nitrogen) are produced mainly by burning fossil fuels. Motor vehicles, heavy industry, and power plants are the major sources of these chemicals.

Smog pollution in the Valley

• The Central Valley of California has the fastest growing air pollution in California. Federal 1 hour ozone standards were exceeded on 39 days in the San Joaquin Valley in 1998. That compares with only 9 days in San Diego County and 8 days in the San Francisco Bay Area. The tougher 8-hour ozone standards were exceeded 92 times in the South Coast Air Basin, 82 times in the San Joaquin Valley, and 16 times in the SF Bay Area.
• To date in 2001, preliminary data indicate that there have already been 12 exceedance days of the federal 1-hour standard and 43 exceedance days of the 8-hour standard. This is a significant increase over levels in the past several years.
• According to the recently released American Lung Association report "State of the Air 2001," the top five most smog polluted counties in the country are in California, and three of those are in the San Joaquin Valley -- Kern, Fresno, and Tulare.
• The San Joaquin Valley region has the second highest level of smog in the country after Los Angeles.(1)
• For more than half of the summer months in the Valley, the air is too polluted for children to safely play outside.
• Throughout the 1990s, smog levels in Los Angeles have steadily decreased, while the San Joaquin Valley's levels have not improved(2), and this year the Valley is getting worse.
• The Great Valley Center reported that while smog trends nationwide have declined, in the San Joaquin Valley smog violations have persisted at dangerous levels(3).
• If these trends persist, smog levels in the San Joaquin Valley could become the worst in the country(4).
• The San Joaquin Valley is home to 9 percent of California's population but accounts for 14 percent of the state's pollution(5).
• Since the passage of the Clean Air Act in 1977, residents have never had a safe summer. Current smog levels mandate that the region should be designated by the EPA as a "severe" non-attainment area – which would require the region to adopt stricter rules for new pollution sources.
• The responsible air district has never come up with a plan that will reduce ozone pollution by the deadlines. After failing to reduce smog levels by the 1999 deadline, the district still lacks a plan to bring healthy air and blue skies back to the Valley.

Footnotes:

1. State of the Air 2001

2. Data are from California Air Resources Board

3. Indications based on days of exceedance of national 1-hour ozone standard from 1990-2000

4. April 2001, Assessment of Air Quality and Air Pollutant Impacts in Class I National Parks in California, published by the US Department of the Interior.

Sources:

"The Ozone Problem" Published by the New England EPA

"Smog – who does it hurt?" Published by the EPA in July, 1999

"State of the Air: 2001," published by the American Lung Association