Ozone

Health effects

The main constituent of oxidant (sometimes called photochemical smog) is ozone. It affects the linings of the throat and lungs, restricting the air passages and makes breathing difficult. It also increases the risk of respiratory infections. Other substances in the oxidant mix increase the effect of ozone and produce eye irritation.

Sources

Oxidants are produced photochemically in air by reactions between hydrocarbons and nitrogen oxides. Some hours of strong sunlight are required to allow high levels of oxidant to form. Light wind conditions are also required to minimise the oxidant dispersion. Sources of the emissions from which oxidants are formed are widespread and include:

• automobiles
• industry
• power stations
• commercial and domestic activities.

Current standards

The current one-hour and four-hour standard levels for oxidant are 0.10 parts per million (ppm) and 0.08ppm respectively.

Goal

Maximum allowable exceedences should be one day a year for both one-hour and four-hour standard levels.

Consequences

In recent years levels have remained below the standards except when bushfire emissions have caused ozone peaks.

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