Source: Stacey Semiklit

8. Air pollution

8.2 ACT trends

This section looks at trends for the following air pollution issues:

What are the main air pollution findings from the 2023 ACT State of the Environment Report? Watch the video and see the infographic below to find out.

Monitoring the ACT’s air quality

There are three air quality monitoring stations in the ACT: the Monash station in Tuggeranong, the Florey station in Belconnen, and the Civic station in the city. These stations measure the amount of carbon monoxide, nitrogen dioxide, ozone, and particulate matter (small particles) in the air. The monitoring determines whether pollutant levels meet national standards to ensure people have clean air to breathe.

Air pollution depends on weather, the amount of pollutant emissions, and whether the area is flat or has valleys and mountains. For example, wood smoke levels are greater in winter in the Tuggeranong Valley than in other areas of the ACT. This is largely because the shape of the valley tends to trap the smoke.

Florey air quality station in Belconnen. Source: ACT Directorate of Health.

Air pollution during the Black Summer bushfires

Did you know?

For many days during Black Summer, the air quality in Canberra was the worst of any major city in the whole world!

A girl and her dog watch the smoke from their rooftop.
Source: Lauren Sandeman.

The Black Summer bushfires in NSW and the ACT severely impacted Canberra’s air quality (see Bushfires in the ACT). The worst air quality occurred in December 2019 to early January 2020, with smoke from nearby NSW fires moving across the ACT. Over the 91 days of summer, air pollution monitoring at the Monash Station in Tuggeranong showed that there were periods on 56 days where the pollution levels exceeded the national standards for health, including 42 days with air pollution above the hazardous to health rating. On 1 January, PM2.5 pollution levels were at around 25 times the threshold to be considered hazardous.

This graph shows the impacts of the NSW bushfires on ACT’s air quality. The pink dotted line shows the level at which air quality is classed as hazardous to human health. The data shows that air quality exceeded the hazardous rating many times over the summer, sometimes by a very significant amount.

Data sourced from: ACT Health Directorate.

The bushfire smoke had major impacts on Canberrans’ health, everyday lives and work. Many businesses, institutions, services and attractions were forced to close, with social and financial consequences. Canberrans were advised to stay indoors whenever possible, with vulnerable people urged to take extra care. For more, see Life in the Haze.

Bushfire smoke caused an estimated 31 excess deaths in the ACT, as well as 318 hospital admissions.

Source: OCSE.

Particulate pollution

Small and smaller

Particles in air pollution include dust, dirt, soot, smoke and liquid droplets. Some of the particles in soot or smoke are large or dark enough to be seen, but others are so small that they can only be seen with a microscope.

Scientists measure the size of air pollution particles in micrometres (millionths of a metre). Particles of 10 micrometres or less in diameter are known as particulate matter 10 or PM10. Really fine particles, 2.5 micrometres or less, are called particulate matter 2.5 or PM2.5. By comparison, a human hair is about 70 micrometres wide, equivalent to seven times the diameter of the largest PM10 particles.

Because smaller particles can penetrate deep into the lungs, air pollution with high levels of PM2.5 represents the greatest problem for human health.

Particulate matter 2.5 or PM2.5. is the most serious air quality problem for the ACT. Even during non-bushfire periods, PM2.5 levels can affect people’s health. PM2.5 pollution tends to happen on calm autumn and winter days when smoke from wood heaters builds up.

Wood heater smoke billowing out a chimney. Source: OCSE.

Between 2015 and 2022, levels of PM2.5 in the ACT were higher than national standards on 67 days – not including days with bushfire smoke (see Air pollution during the Black Summer bushfires). This means that the air quality on those 67 days did not meet the requirements to protect human health. Smoke from wood heaters was responsible for most of the high levels of PM2.5, causing pollution levels higher than national standards on 48 occasions – 40 of these in Tuggeranong. Other reasons for high PM2.5 levels include controlled burns (11 days) and dust storms (8 days).

This graph shows the number of times the ACT’s PM2.5 levels were higher than national standards between 2015 and 2022. The graph also shows the causes of the high pollutant levels. This data shows that wood heater smoke is clearly the main air quality issue in the ACT. Note that this data does not include smoke from bushfires, which is excluded from the ACT’s air quality compliance assessments.

Data sourced from: ACT Health Directorate.

Levels of particulate matter 10 or PM10 in the ACT were higher than national standards on 64 occasions between 2015 and 2022. Dust storms originating outside of the ACT were responsible for nearly one third of the high PM10 levels. Dust storms are strongly linked to the hot and dry conditions associated with climate change, and will likely increase in the future (see Climate change section).

Wood heater pollution

Of all the causes of high PM2.5 levels, wood heaters are the easiest to address. Replacing wood heaters with energy efficient electric heating is critical to improving air quality in the ACT. This is particularly the case for the Tuggeranong Valley, where wood heaters were responsible for nearly 80% of the daily PM2.5 exceedances from 2015 to 2022.

During the ACT’s late autumn and winter months, when wood heaters are used the most, PM2.5 levels are the highest. We can even see the impact of wood heaters on PM2.5 levels over a 24-hour period. Air quality monitoring shows that PM2.5 levels increase significantly in the evenings when wood heaters are used, peaking at night, before decreasing until 6am. There is then a smaller increase in PM2.5 levels as wood heaters are again used to warm residences in the morning, before dropping to lower levels throughout the daylight hours.

This timing means that PM2.5 levels can be high when people are commuting to and from work, going to school in the morning, playing evening sports, and exercising or walking the dog after work. Smoke can also enter homes through cracks around doors and windows, or through air conditioners that draw air in from outside.

This graph shows hourly PM2.5 levels on 11 July 2020. There is an increase in PM2.5 levels in response to peak wood heater use at night and in the early morning. This day exceeded the air quality standard which means air quality levels did not meet requirements to protect community health.

Data sourced from: ACT Health Directorate.

Transport pollution

Motor vehicles like cars and trucks are another major source of air pollution. Vehicles can account for nearly 20% of PM2.5 emissions in the ACT.

The ACT relies a lot on cars for transport (see Human settlements – Transport). The number of vehicles and how much we use them is increasing. Most trips around Canberra involve cars. Fewer than one in four trips involve public transport, cycling or walking, although people have used public transport more in recent years. Only 5% of vehicles in the ACT are electric or hybrid.

The number of diesel-powered passenger vehicles in the ACT is increasing. In 2010, they represented 6% of all passenger vehicles. In 2023, it was 20%. This large increase is concerning, as diesel engines generally emit more nitrogen oxides and far more particles than petrol engines.

Wood heater smoke over Tuggeranong. Source OCSE.

Other air quality pollutants

The non particulate pollutants monitored in the ACT – carbon monoxide, nitrogen dioxide, and ozone – are only found to be higher than the national standards during periods of severe bushfire smoke. Despite this, it is important to reduce air pollution as much as possible for our health, even for pollutants that are already lower than the national air quality standards. This is particularly important because some people are more sensitive to pollution than others.

Climate change and air pollution

Higher temperatures and reduced rainfall associated with climate change are likely to increase the impact of smoke and dust on air quality. Higher temperatures in the future are also likely to speed up the chemical reactions that create harmful ozone gas in the lower atmosphere. More frequent and severe bushfires, as well as controlled burns to reduce the severity of bushfires, are also likely to increase the amount of smoke in the air.

It’s important that we try to limit climate change to protect our air quality into the future (see Climate change). Meanwhile, we must reduce air pollution from sources we have control over, such as wood heaters and the cars we choose to drive.

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