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An ozone molecule is made up of three oxygen atoms. Chemical formula and description

The chemical formula for ozone is O3.

Ozone is a very reactive gas that can absorb Ultra Violet (UV) radiation.


Ozone is present in two different areas of the atmosphere and plays two different roles. Ozone is produced naturally in the outer layers of the atmosphere (the stratosphere) very high above earth. This stratospheric ozone helps protect the planet from the Sun's ultraviolet rays that can damage our skin and health. This ozone is typically known as the ozone layer.

Although ozone is vital in the stratosphere, here at the Earth’s surface, it is a pollutant that can damage our health and the environment.

Ozone is formed by other compounds reacting together in the air rather than being discharged from a source itself – it is called a secondary pollutant. Ozone is formed by reactions of primary pollutants in the sunlight such as nitrogen oxides and volatile organic compounds (VOCs) (known as a photochemical reaction) and often produces photochemical smog.

Primary pollutants are produced mainly from motor-vehicle emissions, other combustion sources, and industrial and domestic use of solvents and coatings.

Effects on health

Studies show a wide variety of effects caused from exposure to ozone including increased daily mortality, respiratory and cardiovascular disease. In the short term, health effects can include irritation to your eyes, nose and throat, coughing and headaches. It also contributes to asthma. Ozone can affect how your lungs perform.

Groups most sensitive to ozone

People with asthma and lung disease, healthy adults exercising for long periods of time outdoors, and older people, particularly those with heart disease.

Standards and Guideline values to protect health

The national environmental standard for ozone is 150 µg/m3 as a 1-hour average.
The national ambient air quality guideline for ozone is 100 µg/m3 as an 8-hour average.

Effects on ecosystems

Ozone and other chemicals formed by photochemical reactions are toxic to plants in high concentrations. They can affect photosynthesis and plant respiration, reduce growth rates, and affect reproduction.

Effects on buildings

Ozone is corrosive to most materials at high concentrations, including plastics and metals.

Effects on visibility

Photochemical reactions in the atmosphere produce fine particles, such as sulphates, nitrates and organic aerosols in the air. These contaminants scatter light and can affect visibility.

Usual levels in New Zealand

In New Zealand, Auckland, Hamilton and Christchurch have been identified as having the highest potential for ozone pollution.  Monitoring around these centres has indicated no exceedences of the ambient standard.  However, the Musick Point monitoring site in Auckland did exceed the ambient guideline twice in 2002. 

For more information see the state of the environment report 2007.

Areas where ozone may affect health and the environment

Because ozone forms over time, the highest concentrations are usually found in rural areas away from areas such as major cities where most contaminants are released.


Last updated: 17 July 2009