Ozone (O3) is a highly reactive gas that is a form of oxygen. It results primarily from the action of sunlight on hydrocarbons and nitrogen oxides emitted in fuel combustion. Ozone reacts chemically ("oxidizes") with internal body tissues that it comes in contact with, such as those in the lung. It also reacts with other materials such as rubber compounds, breaking them down.
- For almost two decades prior to 1997, the federal air quality standard for ozone had been 0.12 parts per million (ppm) averaged over one hour, but tests carried out on healthy adults and children undergoing moderate exercise while exposed to this and even lower levels of ozone show a decrease in subjects' breathing ability.
- In response to a lawsuit filed by the American Lung Association, the U.S. Environmental Protection Agency in July 1997 set a new stricter ozone standard of 0.08 ppm averaged over an eight-hour period. Compliance is based on the fourth highest reading per year averaged over three years.
- The EPA is expected to designate ozone nonattainment areas for the new 8-hour standard in early 2001. However, based on 1994-96 monitoring data, the EPA has determined that a total of 270 counties in 33 states will violate the new standard. An estimated 117 million people living in those counties are at risk from the health effects of elevated ozone levels.
- In response to an industry lawsuit, the Court of Appeals for the D.C. Circuit in 1999 ruled that the 1997 national ozone standard could not be implemented. That decision is currently being appealed to the U.S. Supreme Court by the U.S. Department of Justice and the American Lung Association.
- Ozone levels typically rise between May and October when higher temperatures and the increased amount of sunlight combine with the stagnant atmospheric conditions that are associated with ozone air pollution episodes.
- To reduce ozone air pollution, the American Lung Association supports the use of stringent controls on motor vehicle and pollution emissions produced by the commercial and industrial sources of the hydrocarbon compounds and oxides of nitrogen that form ozone. These controls include:
- stronger pollution control requirements for new motor vehicles
- cleaner fuel standards, including diesel
- cleaner diesel vehicles
- improved in-use performance of existing pollution control equipment
- stricter pollution control requirements for power plants, including those that will bring older power plants up to current emissions control standards
- Ozone acts as a powerful respiratory irritant at the levels frequently found in most of the nation's urban areas during summer months. Ozone exposure may lead to:
- shortness of breath
- chest pain when inhaling deeply
- wheezing and coughing
- Long-term, repeated exposure to high levels of ozone may lead to large reductions in lung function, inflammation of the lung lining and increased respiratory discomfort. The EPA estimates that 5 to 20 percent of the total U.S. population is especially susceptible to the harmful effects of ozone air pollution.
- The EPA has identified three groups of people who are at particular risk from high ozone levels:
- people with pre-existing respiratory disease;those already afflicted with lung disease such as asthma, chronic bronchitis and emphysema
- individuals who exercise outdoors
- "responders"who are more susceptible to ozone exposure
- The harmful man-made ground-level ozone in the lower atmosphere (troposphere) should not be confused with the natural protective layer of ozone in the upper atmosphere (stratosphere), which protects us from the sun's harmful ultraviolet rays.
This article was published by the American Lung Association, copyright 2013. It can be accessed online at the following link: link.Air Pollution in Los Angeles County
Air Quality in Large Buildings
Determining the Quality of Indoor Air
Air Pollution by AFFA
Outdoor Air Pollution Fact Sheet
The Air Quality Index
Particle Pollution Fact Sheet