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What is Ozone

Ozone is an air pollutant at ground level that can be harmful to breathe and damages crops, trees and vegetation.  It is the result of urban smog generated from the emissions of other pollutants, mostly from motor vehicles.

Ground-level or "bad" ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOC.

This ozone differs from ozone high above the earth in the stratosphere which filters out Ultraviolet (UV) light that causes skin cancer. Hence the former ozone is sometimes called “bad” ozone and the latter, “good” ozone.

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Ozone’s Health Impacts

Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma. "Bad" ozone also can reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue.

Healthy people also experience difficulty breathing when exposed to ozone pollution. Because ozone forms in hot weather, anyone who spends time outdoors in the summer may be affected, particularly children, outdoor workers and people exercising. Millions of Americans live in areas where the national ozone health standards are exceeded.

Depending on the meteorological conditions of a given year, 60 to 80 million Americans live in areas not in compliance with EPA’s National Ambient Air Quality Standard (NAAQS) for ozone. The American Lung Association estimates that nearly 50 percent of United States inhabitants live in counties that are not in ozone compliance (State of the Air, 2006). Perhaps of greater significance is that of those who might be considered susceptible due to age and/or preexistent cardiopulmonary impairments, 80 to 90 percent live in these areas that fail to comply with the present ozone standards.

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Contributions in Ozone Research

The potential health effects of ozone have been extensively studied by EPA’s Office of Research and Development over the last 30 years.  The research has provided the scientific foundation for the Agency’s ozone standards.

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Current Ozone Research Activities

EPA's Air, Climate, and Energy Research continues to support the scientific needs for review of the ozone standards which are required about every five years. Research on ozone is also a part of a new multipollutant research approach to understand the effects of mixtures of pollutants, including ozone, in the air.

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