Clean Air Reports

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Executive Summary

Despite years of progress in cleaning up California’s air, millions of Californians continue to breathe the dirtiest air in the nation.  In fact, the Golden State is home to eight of the 10 most ozone-polluted counties in the United States.  Unfortunately, scientists predict that rising temperatures from global warming will increase conditions conducive to ozone formation (often called “smog”).  This report examines the correlation between higher temperatures and ozone pollution at eight locations in California, and concludes that, in order to protect the health of Californians, policy-makers must take aggressive steps to reduce pollution that leads to smog, while also continuing to lead national and international efforts to tackle global warming.

Ground-level ozone, the primary component of smog, is a severe respiratory irritant that can aggravate asthma and cause other respiratory problems, including permanent lung damage.  Using temperature and air quality data from the California Air Resources Board, this report found that the warmer the weather the more likely that Californians are breathing dirty air. 

Key findings include the following:

• In Bakersfield, ozone levels exceeded the state 8-hr health standard 91 percent of the days that the daily maximum temperature was 100°F or more.  Ozone levels exceeded the state 1-hr health standard 58 percent of those days.
• In Burbank, ozone levels exceeded the state 8-hr health standard 42 percent of the days that the daily maximum temperature was 100°F or more.  Ozone levels exceeded the state 1-hr health standard 41 percent of those days.
• In Folsom, ozone levels exceeded the state 8-hr health standard 83 percent of the days that the daily maximum temperature was 100°F or more.  Ozone levels exceeded the state 1-hr health standard 58 percent of those days.
• In Fresno, ozone levels exceeded the state 8-hr health standard 84 percent of the days that the daily maximum temperature was 100°F or more.  Ozone levels exceeded the state 1-hr health standard 75 percent of those days.
• In Riverside, ozone levels exceeded the state 8-hr health standard 79 percent of the days that the daily maximum temperature was 100°F or more.  Ozone levels exceeded the state 1-hr health standard 69 percent of those days.
• In San Bernardino, ozone levels exceeded the state 8-hr health standard 75 percent of the days that the daily maximum temperature was 100°F or more.  Ozone levels exceeded the state 1-hr health standard 67 percent of those days.
• In San Diego, ozone levels exceeded the state 8-hr health standard 16 percent of the days that the daily maximum temperature was 90°F or more.  Ozone levels exceeded the state 1-hr health standard 15 percent of those days.
• In Sequoia National Park, ozone levels exceeded the state 8-hr health standard 75 percent of the days that the daily maximum temperature was 80°F or more.  Ozone levels exceeded the state 1-hr health standard 59 percent of those days.

Unfortunately, with worldwide emissions of global warming pollution increasing each year, temperatures are expected to rise in the coming decades.  Scientists predict that higher temperatures from global warming will lead to higher levels of ozone pollution in California by increasing emissions of ozone-forming pollutants and accelerating chemical processes that generate ozone. 

Given California’s existing air pollution problems and the expectation that global warming will increase ozone formation that leads to smog, state policy-makers and environmental agencies should work to significantly reduce ozone-forming pollutants while simultaneously reducing global warming emissions to levels that scientists have concluded are necessary to prevent a dramatic increase in temperature.

To reduce smog pollution state policy-makers and agencies should prioritize a variety of policy measures, including measures outlined in California’s State Implementation Plan for federal ambient air quality standards.  Measures to prioritize include:

Passenger vehicles – Increase the sale and use of zero-emission and low-polluting passenger cars and light-duty trucks, accelerate vehicle retirement, and strengthen the state smog check program; trucks and off-road equipment – Reduce emissions from medium- and heavy-duty diesel trucks and off-road equipment by strengthening emissions standards, increasing Ports & goods movement – Require cleaner marine engines and fuels, increase the number of ships with the ability to use shore-side power (“cold ironing”), increase retrofits, and accelerate the introduction of cleaner port trucks, harbor craft and locomotives;
Agriculture – Accelerate the replacement of agricultural equipment through regulation and incentives; and
Strong enforcement of existing pollution control rules– Enforce tough standards for cleaner construction equipment, airport ground support, and other off-road vehicles.

To reduce global warming emissions state policy-makers and agencies should prioritize successful implementation of the Global Warming Solutions Act of 2006 (Assembly Bill 32), which commits California to reducing global warming emissions to 1990 levels by 2020.