Perth air quality: Is there a problem and what’s causing it?

By global standards, Perth experiences good air quality most of the time, much like the rest of Australia.

But that doesn’t mean air pollution isn’t an issue in Australia. At times, air quality in some parts of the country has reached 23 times the ‘hazardous’ level.

These bad air quality days—called exceedance days—happen when air quality exceeds safe pollutant levels. And they happen in Perth throughout the year.

The health impacts of air pollution are varied, from mild and temporary discomfort to more serious and lasting issues, sometimes even death.

The latest figures from the Australian Institute of Health and Welfare revealed air pollution contributed to an estimated 3,236 deaths in 2018. That same year, the number of deaths attributable to air pollution was more than 26 per cent higher than in 2015.

To better understand Perth’s air quality, whether we have a problem and how it impacts you, first we need to talk air pollution.

What is air pollution?

Air pollution occurs when there are chemical, biological, and physical pollutants in the air, such as dust and fumes, that can affect human health. These pollutants come from natural and human-made sources.

Dust storms, smoke and ash from wildfires, and sulfur and chlorine gases released during volcano eruptions are examples of natural air pollution sources. Even pollen is considered a natural air pollutant.

Significant human-influenced air pollution sources include fossil fuel, emissions from road traffic, industrial processes, power generation, controlled burn-offs, and domestic woodfire heaters.

What are the impacts of air pollution?

According to the World Health Organisation (WHO), almost 99 per cent of the global population breathe polluted air. WHO now considers air pollution the biggest environmental threat to human health.

Stroke, heart disease, lung cancer and pneumonia are just some of the ways air pollution can impact health. There is also evidence that suggests air pollution increases the risk of other cancers, diabetes, and neurological diseases.

To encourage global action on air pollution, the WHO introduced Air Quality Guidelines that provide thresholds and limits for key air pollutants that pose risks to human health.

Particulate matter (PM_2.5 and PM₁₀) is one of the key measures—these are liquid droplets or solid particles suspended in air.

You can sometimes see particulate matter in the form of dust, dirt, soot, or smoke. At other times particles are so small they’re invisible.

PM₁₀—particles less than 10 microns in diameter—can penetrate and lodge deep inside the lungs. PM_2.5—particles less than 2.5 microns in diameter—are of particular concern because they’re small enough to enter your bloodstream through your lungs and cause serious health issues.

The guidelines also measure carbon monoxide (CO), ozone (O₃), nitrogen dioxide (NO₂), and sulphur dioxide (SO₂) gases.

How good is Perth’s air quality?

Perth’s air quality is generally considered good by global standards. But there are a few days each year when air quality exceeds safe levels.

Exceedance days in Perth are usually the result of severe weather events, wildfires, and controlled burn-offs.

Poor air quality days can also be brought about by thermal inversions.

A thermal inversion is a weather phenomenon where a blanket of hot air traps pollutants closer to the earth’s surface—including vehicle emissions and wood fire smoke that would normally disperse into the upper atmosphere—making air quality particularly bad while the inversion lasts.

What causes air pollution in Perth?

Cars and traffic

In major cities across Australia, one of the main sources of air pollution is tailpipe emissions from motor vehicles.

Carbon monoxide, particulate matter, and sulfur dioxide are just some of the air pollutants produced during fuel combustion.

Cars also produce hydrocarbons and nitrogen oxides. These exhaust fumes react with sunlight to form ground-level ozone—commonly known as smog—a visible form of air pollution.

In 2020/21, Western Australians travelled 19.5 billion kilometres by car. On average, every person aged 17 and older travelled 9,300km by car.

For perspective, while the rest of the country experienced a drop in average vehicle emissions per person between 1990 and 2020, WA saw an increase. Over that period, the average emissions per person from road transport increased by almost 11 per cent in WA, while the national average declined by almost 1 per cent.

But it’s not all bad news. Low emission and zero emission vehicles, such as electric vehicles, produce significantly less or no tail pipe emissions. And their uptake in WA is on the rise.

According to a recent survey, 1 in 2 RAC members would consider an electric car as their next vehicle. Continued adoption of electric vehicles is one of the ways we can help keep our air clean and healthy.

Dirty fuel

Fuel quality affects the level of emissions emitted by combustion engine vehicles.

Despite improvements in the past few decades, of all OECD countries, Australia currently allows the lowest quality fuel.

Diesel fuel has met maximum allowable 10ppm (parts per million) sulfur specifications since January 2009, but the allowable sulfur content in unleaded petrol is up to 150ppm—15 times the international standard.

Fortunately, Australia’s dirty fuel is getting cleaner. From the end of 2024, all petrol sold in Australia will have a maximum sulfur level of 10ppm.

Vehicle emissions standards

Australia is the only developed country that does not have a mandatory carbon dioxide (CO₂) standard for new light vehicles, and our noxious emissions standards are less strict than elsewhere.

RAC has called on government to introduce impactful CO₂ and Euro 6d (or equivalent) emissions standards for new light vehicles, to speed up the transition to cleaner vehicles and reduce harmful vehicle emissions and the impacts on human health and the environment.

Other factors

Smoke and ash from bushfires and controlled burn-offs, as well as windborne dust and marine aerosols (like salt spray) also contribute to air pollution in Perth. As does smoke from domestic woodfire heaters.

What should you do when air quality is bad?

It doesn’t take constant exposure for air pollution to affect you.

When air quality is bad, try to limit your exposure to outdoor air. Stay indoors with the doors and windows shut and avoid exercising outside.

If you feel the air in your home is uncomfortable, consider going to a place with cleaner air (such as an air-conditioned building like a library or shopping centre) if it’s safe to do so.

Anyone can feel the effects of air pollution, though children, pregnant women, and elderly people are particularly vulnerable. As are those with heart or respiratory conditions, such as asthma.

For more information on what to do on bad air quality days, visit the Department of Water and Environmental Regulation.

Last updated: November 2022