What is air pollution?

The invisible dangers you could be breathing

Air pollution isn’t static.  It’s a complex and constantly changing mixture of chemicals, particles, smoke, dusts, vapours, and pollens.

Air pollution can contain particles (known as particulate matter or PM for short) and gases such as nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3) and carbon monoxide (CO). Pollen is measured separately.

Particulate matter is classified according to the particle size.  For example, PM2.5 is the name for particles smaller than 2.5 micrometres in diameter. PM10 includes particles smaller than 10 micrometres in diameter. Fine particulate matter (PM2.5) is particularly harmful as it can get deep into our lungs and enter our bloodstream. Exposure to PM2.5 increases the risk of suffering from chronic lung diseases including asthma, heart diseases, stroke, and cancer.

For us in Australia, bushfire smoke, woodfire heater smoke and vehicle exhausts are usual sources of fine particulate matter (PM2.5). Vehicle emissions, as well as some gas appliances, are a major contributor to nitrogen dioxide (NO2) in our air, which is linked to a higher risk of breathing problems and asthma attacks.

Common indoor pollution sources include:

  • Cigarette and tobacco smoke
  • Wood fire heaters
  • Gas heaters and gas cook tops
  • Household products such as solvents, paints and adhesives

Common outdoor sources of air pollution are:

  • Woodfire heaters
  • Bushfires
  • Hazard reduction burns
  • Motor vehicle exhausts
  • Industry including mining and coal-fired power generation
  • Wind-blown dust

Pollen from trees and grasses can also flare-up asthma and hay fever symptoms.

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By telling you what’s in the air, AirSmart helps you plan daily activities
and better protect your health.

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How is air quality measured?

Air Quality Categories (AQC) provide at-a-glance information so that you can change your plans if pollution levels are high.

AirSmart utilises the Air Quality Categories and colour indicators provided by the New South Wales Department of Planning, Industry and Environment to summarise air quality measurements.

Five colour indicators classify air quality as either:

Air Quality Categories are measurements of key air pollutants monitored over relevant periods of time (from 1 to 8 hours depending on the pollutant) including:

What do the Air Quality Categories mean?

Air Quality Categories (AQC) provide at-a-glance information to help you plan your day. By checking the AQC and following the general health advice, you can take steps to reduce your exposure to air pollution. For example, if the AQC for your local area is ‘Very Poor’ (red), the health advice in the activity guide can assist you in understanding how this might affect your health and recommend actions to take.

While there is no safe level of exposure to air pollution for anyone, some people are more sensitive to air pollution than others.

Sensitive groups include:

  • People living with asthma or other lung conditions
  • People with heart disease
  • People living with diabetes
  • People with a history of stroke
  • Young children
  • Elderly people
  • Pregnant people, unborn and newborn babies.

There are different recommendations for sensitive groups for each AQC.

What are the key pollutants I should know about?

PM 2.5 (fine particles)


Smoke from fires including woodfire heaters, bushfires, hazard reduction burns; car and truck exhaust; industry.


These particles are less than 2.5 micrometres in diameter.  The most common impacts are irritation to eyes, nose and throat. Because they’re so tiny, they can be inhaled into the lungs causing breathing problems and asthma flareups.   From the lungs, the smaller particles can enter the bloodstream and trigger inflammatory responses throughout the body that, over time, can increase the risk of many conditions including heart disease, stroke, and diabetes. Exposure to PM2.5 has also been linked with very small increases in the risk of earlier than expected births, slightly lower birth weight, and some complications of pregnancy like gestational diabetes.

PM 10


PM10 is generated from smoke from fires including woodfire heaters, bushfires, hazard reduction burns; car and truck exhaust and industry, sea salt and dust.  PM10 levels can increase with wind-blown dust because these particles tend to be larger (such as dust from unsealed roads).


PM10 particles are less than 10 micrometres in diameter, so PM10 includes those fine particles grouped as PM2.5 as well as coarser particles.   The most common impacts of PM10 are irritation to the eyes, nose and throat.   PM10 can cause and worsen symptoms of asthma (cough, difficulty breathing, wheeze and chest tightness) and heart conditions.

Nitrogen Dioxide (NO2)


The most common source of NO2 is the exhaust from trucks and cars, but it is also produced by other kinds of combustion including gas heaters and cookers, coal-fired power stations, ships, and industry.


Exposure to NO2 can irritate the airways and lungs. It is linked to the development of asthma in children and asthma symptoms. In people with asthma, exposure to NO2 can increase the risk of developing lung infections, increase the risk of reacting to triggers like pollen or exercise, and worsen asthma potentially causing more frequent asthma attacks. NO2 may also be associated with reduced lung function.

Ozone (O3)


Ground level O3 is created by a chemical reaction between other gaseous pollutants (like NO2) and volatile organic compounds.  This happens when pollutants emitted by car and truck exhaust, industry, coal fired power stations, or bushfire smoke react with sunlight.  O3 is most likely to reach unhealthy levels on hot and sunny days in urban and rural environments.


O3 irritates the upper airways and gets into the lung. Exposure to O3 can cause irritation of eyes, nose, throat and lower airways triggering breathing problems and asthma. Long-term exposure to ozone can be a cause of reduced lung function and chronic lung disease. Sensitive groups include children, the elderly and those with lung conditions.

Download the AirSmart App

You can start being AirSmart right now by downloading the free AirSmart app (Android and IOS). Asthma Australia’s AirSmart app gives you the information you need to be more in control of the air you breathe when you’re out and about, in the palm of your hand.

Learn more

Get in touch

We’d love to hear what you think of this campaign, your feedback on the AirSmart app and your experiences of air pollution in Australia.

This campaign is part of a broader program which includes working with government and other stakeholders to reduce exposure to air pollution and improve air quality. Your experience will assist us in this goal.

Call us at     1800 278 462
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