As sunburn victims and Al Gore fans well know, we're short on stratospheric ozone these days. But ozone created near the ground—the primary component of urban smog—is one of the country's most widespread and most damaging air pollutants, and few are complaining about its gradual depletion.
Many metropolitan areas have successfully cracked down on their ground-level ozone pollution problems since the Environmental Protection Agency passed the Clean Air Act in 1990. Between 1990 and 2005, ground-level ozone concentration dropped 9.2% on average in the metro areas in which the EPA monitored these data.
Aggressive Reduction of Ozone
Orange County, Calif., reduced its "bad" ozone levels by more than 50% during this time period, rising from the fifth-worst metro area for air quality to the 39th best, out of 197 metro areas. Seattle cut ozone pollution by 43% and San Diego saw a 42.5% decrease. On the East Coast, Atlantic City, N.J., decreased ozone levels by 37% between 1990 and 2005, and ozone pollution in the New London (Conn.) area dropped more than 35%. These measurements are based on the second-highest reading in each area for each year (researchers disregard the highest reading, which is often a fluke that could skew the data).
Unlike "good" ozone, which is produced naturally in the stratosphere (the part of the atmosphere 6–30 miles above the earth's surface), ground-level ozone is created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) under the influence of sunlight. The chemicals involved come from emissions from industrial factories and electric utilities, motor vehicle exhaust, and vapors from oil wells and gasoline, paint, and other solvents.
Many cities and suburbs in the U.S. suffer from high levels of bad ozone due to the high concentration of motor vehicle traffic and industry in those areas, but even rural areas can be subject to high ozone levels as winds carry emissions hundreds of miles away from their original source, according to the EPA. The metro areas with the highest ozone pollution levels (based on second-highest annual readings) are Danbury, Conn.; New Haven, Conn.; Riverside, Calif.; and Wilmington, Del. Ozone levels are lowest in Honolulu; Santa Cruz, Calif.; Santa Rosa, Calif.; and Bellingham, Wash.
Evidence from Atlanta Olympics
While stratospheric ozone protects people from the sun's harmful ultraviolet rays, ground-level ozone triggers and aggravates all kinds of respiratory problems. It can cause coughing, chest pain, and throat irritation, and worsen conditions like asthma, emphysema, and bronchitis. "It's like getting a sunburn on your lungs when you inhale," says Janice Nolen, assistant vice-president for the American Lung Assn.
The 1996 Summer Olympic Games in Atlanta allowed researchers at the Centers for Disease Control & Prevention a rare opportunity to observe the impact of ozone on respiratory health. During the Olympics, Atlanta implemented a number of measures to reduce traffic, including providing 24-hour public transportation, adding an additional 1,000 city buses to its existing fleet, and closing downtown streets to all but public transportation vehicles. In the two-week period, the study found that peak ozone levels dropped by more than 25% and Medicaid expenses for asthma were cut by 40% as hospitalizations for asthma attacks decreased.
Under the 1990 Clean Air Act, the EPA now monitors air quality across the country and sets and reviews national air-quality standards for ozone to protect public health. Ozone concentration is measured in parts per million (ppm), the number of molecules of ozone (O3) per every 1 million molecules of other gases that make up the air. The peak levels for each hour are averaged for the day. The EPA's standard for the second-highest daily average in a given year was 0.125 ppm until 1997, when the standard was tightened to 0.08 ppm for the fourth-highest daily average. Only the seven worst metro areas in the U.S. exceeded the original "second-max" ozone standard in 2005.
The Carrot and the Stick
According to the EPA, cleaner air will save billions of dollars in health care and welfare costs. Using computer models and emission and cost data, the EPA has estimated that in 2010 the benefits of Clean Air Act programs due to decreased illness and fewer premature deaths will total roughly $110 billion, while the costs of achieving these benefits will be only about $27 billion. In addition, the EPA says by 2010 the amendments of 1990 will have prevented 23,000 premature deaths, 1.7 million incidences of asthma attacks, and 4.1 million lost workdays.
Though it is a federal law, individual states do much of the work to carry out the Clean Air Act. States need to develop state implementation plans (SIPs) that explain how they will meet the standards set by the EPA, and the EPA must in turn approve each state's SIP. If a state fails to submit a plan, they could lose federal highway money, according to the EPA.
States and cities have consequently instituted many programs to meet health-based standards, including programs to cut emissions from vehicles and industrial facilities; programs to reduce pollution by reformulating fuels, paints, and solvents that contain VOCs; and voluntary programs that encourage communities to carpool.
"They're doing it because the Clean Air Act requires it," Nolen says. "We simply have to have air that doesn't make people sick."
California Leads in Reduction Rates
Out of necessity, California has been spearheading the effort to decrease ozone and other air pollution. Due to traffic and a warm and sunny climate that breeds ozone, California cities aren't known for their clean air, but they now lead the nation in smog-reduction rates, thanks largely to regulations on tailpipe emissions. In addition to Orange County and San Diego, the Riverside, Los Angeles, Chico, Santa Barbara, and Ventura metro areas have all seen ozone concentration levels drop more than 25% since 1990. At 0.07 ppm (per eight-hour-period average), the state's ozone standards are tighter than the 0.08 ppm required by the EPA.
"Nine out of 10 Californians breathe polluted air," says Jerry Martin, a spokesperson for the California Environmental Protection Agency's Air Resources Board. "We don't have the luxury of being light on pollution."
By 2024, the CalEPA projects that all of the state will be in compliance with federal ozone standards. But they are working on environmental problems across the board, Martin says. Next up is that "other" ozone problem—global warming.
To see a roundup of America's most cleaned-up metros, click here for the slide show.