While there is no evidence that air pollution causes asthma, it can trigger attacks in people who have asthma. Some air pollutants can also worsen asthma symptoms.

People with asthma have sensitive airways that are easily affected by air pollutants such as particles, sulphur dioxide, nitrogen oxides and ozone.

Airborne particles

The sources of particles in air can be natural (pollens, bacteria, fungi) or man-made (motor vehicle emissions, tobacco smoke, wood heaters). Smoke from bushfires is also a source of airborne particles. Fine particles are the worst offenders as they can get deep into the lungs. These particles irritate airways and can trigger asthma attacks.

Sulphur dioxide

Sulphur dioxide is formed when coal and oil are burned. People with asthma who are exposed to sulphur dioxide can experience wheezing, chest tightness and shortness of breath. Sulphur dioxide is not a major air pollutant in Australia outside areas near power stations and smelters.

Nitrogen oxides

The major sources of nitrogen oxides are the burning of coal and oil in power stations and motor vehicle emissions. Exposure to nitrogen oxides may cause infection in airways – especially in children – and the worsening of asthma symptoms.

Ozone

The ozone layer in the upper atmosphere protects us from harmful ultraviolet rays, but if present in the air we breathe ozone can irritate the lungs and make breathing difficult. Studies show that hospital admissions for asthma increase when there is more ozone in the air.

Ozone and nitrogen oxides are the major pollutants in smog (smoke and fog) that occurs in some busy cities.

Air Quality Index

The Air Quality Index, which is presented as part of weather forecasts in the media, will help you in monitoring information on air pollution. The lower the index is, the better the quality of our air. There are five categories in the index:

What you can do

The following measures may help reduce exposure to outdoor air pollutants:

Smog

• Remain indoors and close external doors and windows on smoggy days.
• If outdoors, avoid heavy physical activity.

Bushfires

• Remain indoors and close external doors and windows, unless advised to evacuate.
• If travelling in a vehicle through smoke, close windows and vents and use recirculated air to stop smoke entering the vehicle.
• Wear a dust mask if exposure to smoke cannot be avoided. The mask will need to firmly cover the nose and mouth to stop smoke entering from around the mask.
• Water down any dry dusty areas before trying to clean up after a fire.

Content Updated March 2005