Air pollution

About air pollution

Pollutants in the air are caused by natural events (such as bushfires, windstorms and pollen) or human activities (including industrial processes, motor vehicle emissions, use of unpaved roads and smoke from wood heaters). Examples of pollutants include gases, chemicals and airborne particles (such as dust and pollen).

Melbourne suffers its worst air pollution on days of light winds and stable conditions. On these days, a wide area can be affected.

Most Melbourne suburbs experience a similar degree of air pollution, although suburbs receiving sea breezes before they have passed over the city have better air conditions. Low lying areas have worse air conditions than hilltop areas because pollutants tend to settle in valleys, particularly on calm nights.

People living on or within 100 metres of major roads also have reduced air quality.

Outdoor air pollution

Melbourne's air pollution levels have steadily reduced, resulting in the improvement of air quality since the Environment Protection Authority (EPA) Victoria started monitoring it in 1973. It is categorised as relatively good by international standards.

Air pollution events

Air pollution events resulting in high levels on summer days arise due to the effect of sunlight on airborne pollutants, producing 'photochemical oxidants' such as ozone. Winter air pollution event days arise when pollutants (particularly particles) build up around the city and are not blown away due to calm weather conditions.

On 'air pollution or air quality alert' days, people with respiratory conditions (such as asthma) and heart disease should avoid strenuous exercise.

Fuel combustion and air pollution

Airborne contaminants vary from country to country, depending on a range of factors, including population, industry, climate and the types of fuels burned.

In Melbourne, the main source of air pollution is motor vehicle emissions, caused by petroleum combustion. Combustion (burning) of other fuels (such as gas, wood, and coal) also contributes significantly to the levels of air pollutants and quality of our air.

The main pollutants resulting from fuel combustion include carbon monoxide (CO), nitrogen dioxide (NO₂), ozone (O₃), particulate matter (fine particles suspended in the air) and sulphur dioxide (SO₂).

The health effects associated with breathing in these contaminants include:

• carbon monoxide – reduces the ability of the blood to carry oxygen
• nitrogen dioxide – may trigger asthma attacks and other respiratory disorders
• ozone – may trigger asthma attacks and other respiratory disorders
• particulates – the effects depend on the chemical composition of the particles
• sulphur dioxide – may trigger asthma attacks and other respiratory disorders.

Lead was phased out of petrol in 2003. Victoria does not have any major lead-based industries.

Ozone depletion due to air pollution

The ozone layer sits around 10 to 50 kilometres above the surface of our planet. Its principle function is to moderate the amount of ultraviolet radiation from the sun that penetrates the earth’s atmosphere and reaches the earth's surface.

Ozone is produced by the action of sunlight and other chemical reactions on oxygen, and is naturally destroyed by a range of rising gases.

The production and destruction of ozone in nature is in balance, but human activity is depleting ozone faster than nature produces it. Gases including chlorofluorocarbons (CFCs) and halons (compounds containing bromine) are creating ‘holes’ in the ozone layer, which allow greater amounts of ultraviolet radiation to reach the earth's surface.

Health risks from depletion of the ozone layer include greater incidence of eye problems,, such as cataracts and pterygia (growths on the eye), and greater incidence of skin cancer.

Air pollution and the greenhouse effect

The earth insulates itself with greenhouse gases, which help to hold the warmth from the sun. Since the industrial revolution 2 centuries ago, human activity has increased the amount of greenhouse gases in the earth’s atmosphere (such as carbon dioxide, methane, nitrous oxide, CFCs and halons).

The generation of greenhouse gases has risen spectacularly in the last 50 years, mainly due to combustion of fossil fuels. An increase in greenhouse gases makes the earth warmer, and causes changes to weather and climate worldwide.

Climate change projections developed by CSIRO estimate that temperature over Victoria will warm on average by 2.8 to 4.3°C under a high emissions scenario or warm by 1.3 to 2.2°C under a medium emissions scenario between the 1990s and 2090s. These changes will impact health and wellbeing in many ways.

Indoor air pollution

Research indicates that Victorians spend most of their time indoors, making indoor air pollutants an important risk factor for people’s health. Significant indoor pollutants include:

• cigarette smoke
• emissions from faulty or unserviced gas heaters and fuel-burning appliances (can lead to carbon monoxide poisoning)
• emissions from stoves without extraction fans
• chemical odours from freshly applied paint, glues, cleaners or solvents
• animal fur or dander
• moulds
• dust
• outdoor air pollution penetrating indoors.

Other home environment air pollution

Apart from general indoor pollutants, the outdoor environment at home can be polluted with fumes, particulates and odours. These can be a nuisance that may or may not affect you or your neighbours. The main contributors are:

• wood heaters and open fires
• lawn mowers.

Dust storms and air pollution

Dust storms reduce air quality and visibility, and may affect people's health, particularly those who already have breathing-related problems such as asthma and emphysema.

The most common symptoms experienced during a dust storm are irritation to the eyes and upper airways.

Small coarse airborne dust particles (PM10) generally only reach as far as the inside of the nose, mouth or throat. However, some people with pre-existing breathing-related problems may experience difficulties when fine particles reach deeper into the sensitive regions of the respiratory tract and lungs. This can trigger allergic reactions and asthma attacks, and cause serious breathing-related problems.

Long-term exposure to airborne dust can lead to chronic breathing and lung problems, and possibly heart disease.

Hazardous substances and air pollution

Hazardous substances that can become airborne include:

• Arsenic – a substance that is found naturally in rock. It has been used to preserve timber and as an ingredient in chemicals such as pesticides and weed-killers. Small amounts of arsenic are normally taken into the body from low levels that are naturally present in soil, water, air and food. Swallowing a large amount of arsenic can cause severe health effects or even death.
• Asbestos – a silicate mineral made up of tiny fibres that form a dust when disturbed. Fibres breathed into the lungs can cause a range of health problems, including lung cancer and mesothelioma. Asbestos used to be a common building material because of its fire-resistant and insulating properties, but now that we are aware of the health risks, it is no longer mined in Australia and its use has been phased out.
• Cadmium – a mineral bound with elements such as oxygen, sulphur and chlorine. It is found naturally in low levels in most foods and is one of the ingredients of cigarette smoke. Smelting other metals, such as zinc and copper, produces cadmium. High exposure to cadmium by either breathing or eating it can cause a range of ill effects, including lung damage and kidney disease.
• Lead – a metal that can be found in paints in many homes and in contaminated soil. The natural concentration of lead in the air is very low (less than 0.1 microgram per cubic metre). Lead gets into the air naturally through soil erosion, volcanic eruptions, sea spray and bushfires. It can also enter the air as a by-product of lead smelting, mining operations and waste incineration. In the home, lead air pollution is a risk when renovating a house painted with lead-based paint. Children are particularly sensitive to the effects of lead exposure. Acute poisoning is rare, but it can occur if a young child breathes in high levels of airborne particulate lead, or swallows lead paint dust or lead paint chips off old houses.

Where to get help

• Your GP (doctor)
• Your local council's environmental health department – report domestic pollution causing health concerns, such as illegal use of incinerators
• Environment Protection Authority (EPA) Victoria Tel. 1300 372 842 (24 hours, 7 days) – for general enquiries relating to air quality and health, or to report pollution
• Environmental Health, Department of Health, Victorian Government Tel. 1300 761 874 – for information relating to climate change and health, or indoor air pollution that is created within the home