At a glance
Global observations of atmospheric levels of the major ozone depleting substances (ODSs)—principally chlorofluorocarbons and halons (used as refrigerants, industrial solvents, flame retardants and propellants in aerosol spray cans)—show them reaching a peak in the mid-1990s and declining since then. As a result, stratospheric levels of the breakdown products of ODSs (such as chlorine and bromine), which react with and destroy ozone, have also begun to decline. This drop is expected to continue with the ongoing phase-out of these ODSs under the Montreal Protocol. However, the stability of these substances will result in the continued depletion of stratospheric ozone for many decades.
Ambient air quality in Australia’s major urban centres is generally good. National health-based standards are rarely exceeded for prolonged periods, and very high levels of pollution are usually associated with short-lived extreme events, such as bushfires and dust storms, that generate very high levels of particulate pollution. Despite substantial population growth, industry expansion and greatly increased motor vehicle use, levels of carbon monoxide, nitrogen dioxide, sulfur dioxide and lead have declined in urban areas over the past two decades.
However, this overall favourable situation should not be taken to imply that air quality in our major cities does not impact on human health. Levels of particles and of the secondary pollutant ozone have not decreased. Both these pollutants are known to impact on cardiovascular and respiratory health. Research into the health effects of particles and ozone, along with pollutants such as sulfur dioxide, indicates that there is no threshold level below which they have no health effect. This means that sensitive individuals—such as asthmatics and people with respiratory or cardiovascular disease—may be affected even when air quality standards are met. By one estimate, there were close to 3000 deaths due to urban air pollution in 2003—nearly twice the national road toll.
Most Australians spend more than 90% of their time indoors, leading to concern over the possible impacts of indoor air quality on our health. Symptoms associated with poor indoor air quality can range from acute to chronic, and from mild and generally nonspecific (eyes, nose and throat irritation, and headaches and dizziness) to severe (asthma, allergic responses and increased cancer risk). Despite the potentially significant health effects of indoor air, data on indoor air quality in Australia are limited, and Australia has no specific guidelines for indoor air quality to provide a firm basis for forming assessments of overall status and trend.
This section describes aspects of the atmosphere other than the effects of atmospheric composition on climate.
Assessing the state of Australia's atmosphere in essence involves assessing the impact of a number of contaminants on three main areas: the stratospheric ozone layer, ambient (outdoor) air and indoor air.