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Ozone is a colorless gas composed of three atoms of oxygen. Ozone forms both in the Earth's upper atmosphere and at the surface. Where ozone forms determines whether it is helpful or harmful to your well-being.
Good ozone naturally forms in a layer about 10 - 30 miles (16 - 48 km) above Earth's surface. This protective layer shields us from the sun's harmful ultraviolet rays. Without this layer, we would all be blinded and sunburned. Unfortunately, human-created chemicals are destroying this beneficial layer of ozone. Over the South Pole in springtime, the ozone loss is so severe that an "Ozone Hole" forms, letting significant amounts of harmful ultraviolet light reach the surface. A smaller Ozone Hole sometimes occurs over the northern polar regions.
Bad ozone forms near Earth's surface when the ultraviolet light in sunlight triggers a chemical reaction with "precursor pollutants" emitted by cars, power plants, and industrial sources. These precursor pollutants consist of nitrogen oxides (NOx) and volatile organic hydrocarbons (VOC). Ozone near ground level is a harmful pollutant. Ozone levels are carefully monitored during the summer months when the weather conditions are perfect for it to form. Sunshine, hot temperatures, and high emissions of NOx and VOC pollutants lead to high levels of ozone.
An Ozone Action Day
is declared when weather conditions are likely to combine
with pollution emissions to form high concentrations of ground-level ozone that
may cause harmful health effects. People and businesses should take action
to reduce emissions of ozone-causing pollutants.
In 1997, the Environmental Protection Agency (EPA) proposed a new standard for ozone and particulate matter levels in the atmosphere. The ozone levels were not to exceed 0.080 ppm during an 8-hour period. However, a coalition of business and industry interests sued to have those standards blocked, claiming they were too expensive and ill-conceived. In 1999 a federal court agreed, issuing a ruling blocking implementation of the tougher standards.
Changes were made again in February 2001, when the U.S. Supreme Court unanimously upheld the constitutionality of the Clean Air Act as EPA had interpreted it in setting health-protective air quality standards for ground-level ozone and particles. The Supreme Court also reaffirmed EPA's long-standing interpretation that it must set these standards based solely on public health considerations without consideration of costs.
However, the Supreme Court did find that the EPA's plans for implementing the rules were unreasonable, and it ordered the agency to develop new implementation policies. Industry opponents immediately promised to use this aspect of the ruling as the basis for new legal challenges to weaken implementation of the new standards. It remains to be seen if the new standards will truly take effect as legislated.
According to the EPA, the new ozone and particulate matter standards will have the following effects:
Reduced risk of moderate to severe respiratory symptoms in children. The new standards should result in hundreds of thousands of fewer incidences each year of symptoms such as aggravated coughing and difficult or painful breathing.
Reduced risk of hospital admissions and emergency room visits for respiratory causes. The new standards should result in thousands fewer admissions and visits for individuals with asthma.
Reduced risks of more frequent childhood illnesses and more subtle effects such as repeated inflammation of the lung, impairment of the lung's natural defense mechanisms, increased susceptibility to respiratory infection, and irreversible changes in lung structure. Such risks can lead to chronic respiratory illnesses such emphysema and chronic bronchitis later in life and/or premature aging of the lungs.
Reduced yield losses of major agricultural crops, such as soybeans and wheat, and commercial forests by almost $500,000,000.
High ozone levels have been linked to increases in the severity of asthma attacks and other respiratory health problems, especially for children and the elderly.
Even healthy people will experience irritation of the respiratory system. Ozone causes constriction of the bronchial airways such as coughing, sore throat, ear aches, wheezing, chest discomfort, uncomfortable breathing. People who exercise or work outdoors may experience reduced exercise capacity. Those individuals with heart and lung disease react more severely to air pollution. People with asthma have more asthma attacks when ozone levels are high. Ozone makes individuals become more sensitive to allergens and can also be involved in the development of asthma. Ozone weakens the immune system and facilitates the development of lung infections. Thus ozone can inflame and damage the lung tissue.
Children are most at risk from exposure to ozone:
Asthmatics and Asthmatic Children:
For detailed information about real-time pollution levels in the U.S., visit the Environmental Protection Agency's Website.
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