New Jersey Environmental Public Health Tracking Program

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Ozone in Outdoor Air

What is Ozone?

Ozone is an invisible gas.  "Good" ozone occurs naturally about 10 to 30 miles above the earth’s surface, forming a layer in the atmosphere that protects life on earth from the sun’s harmful rays.  "Bad" ozone, or ground-level ozone, forms when precursor pollutants that come from cars, power plants and other sources react with each other in heat and sunlight.  Ground-level ozone pollution is a concern primarily during the summer months.  Wind can carry precursor pollutants and ozone long distances. 

How Does Ground-Level Ozone Affect Human Health?

Ozone in Outdoor AirProlonged breathing of ozone in the air has been linked to asthma, bronchitis, heart attack and other cardiovascular problems, and premature death.  Symptoms of exposure to high concentrations of ozone are wheezing, pain when breathing deeply, shortness of breath, throat and lung irritation, headaches and nausea.  Long-term ozone exposure may result in premature aging of the lungs, a decrease in lung function, and lung inflammation.  Ozone exposure can make the symptoms of chronic lung diseases worse.

What is Being Done to Protect Human Health?

In an effort to protect human health, the Clean Air Act was enacted by Congress to direct the U.S. Environmental Protection Agency (USEPA) to set National Ambient Air Quality Standards for several pollutants, including ground-level ozone.  The current standard for ground-level ozone is 0.075 parts per million (ppm), averaged over an 8-hour period.

The USEPA has developed the Air Quality Index (AQI) to explain to the public how the level of ozone and other air pollutants may impact human health.  The color-coded AQI has the following values: "Good", "Moderate", "Unhealthy for Sensitive Groups", "Unhealthy", "Very Unhealthy", and "Hazardous". The AQI is publicized through radio, television, newspapers and the internet.  Depending on the measured or forecast AQI level, some people may be advised to limit or avoid strenuous outdoor exercise.      

The NJDEP and USEPA have established a variety of programs to meet the health-based National Ambient Air Quality Standards.  For ozone, these efforts include reduction of precursor pollutant emissions, reformulating automobile fuels and other consumer products, limiting emissions from motor vehicles, encouraging carpooling, and planting trees to reduce urban temperatures.

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