Atmosphere

Urban air pollution in Australia

Australian Academy of Technological Sciences and Engineering, 1997
ISBN 1 8756 1837 6

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About this report

The prime objective of the Inquiry is to determine the need for and to propose actions that will maintain or improve air quality. This Inquiry Report and the supporting reports are therefore written from this standpoint.

The Inquiry Terms of reference specify six major pollutants for examination; airborne lead, oxides of sulfur (SOx), oxides of nitrogen (NOx), carbon monoxide (CO), particles and photochemical oxidants (as ozone) including ozone precursors (hydrocarbons, VOCs). Of these, lead and SOx no longer appear to be major issues within coastal capital city airsheds and receive lesser attention. CO emissions to the total airshed have generally reduced and are mainly a local problem in heavily trafficked corridors. Some other issues, such as indoor air, not in the terms of reference, are covered in supporting reports.

Australia's population is concentrated in our coastal cities with the result that our major urban airsheds are located on coastal strips with mountain ranges nearby. Each capital city airshed suffers conditions which frequently trap or circulate the air mass over urban areas during periods of high sunlight intensity, or winter inversions. Levels of photochemical smog or airborne particulates can then approach or exceed air quality standards. These conditions can be considerably exacerbated by the occurrence of bushfires or hazard reduction burning in the vicinity of the airshed or even at some distance from it.

The Inquiry has examined past and present levels of air pollutants in the major airsheds and summarises the identified sources of emissions. Analysis by the Inquiry shows that, on days conducive to smog formation, underlying day-long concentrations of ozone and other components of photochemical smog can be substantial even when exceedence of current standards does not actually occur.

However, Australian cities have generally managed to maintain air quality over the past decade, especially compared to similar sized cities around the world.

Despite Australia's vehicle fleet being the single greatest source of atmospheric pollutants, the introduction of unleaded petrol and of catalytic converters to minimise vehicle tailpipe emissions has had a marked effect on lead loading into airsheds as well as helping to contain the level of other pollutants. Initiatives such as the banning of back yard burning and location of major pollutant sources, such as power stations, away from capital city airsheds have also contributed significantly.

Notwithstanding efforts to date, the continued growth of our cities will place increasing pressure on their urban air quality. This is particularly the case for the three pollutants (NOx, hydrocarbons and particulates) of most concern to this Inquiry. On a 'business as usual' basis, pollution episodes would be expected to increase in number with increases in vehicle kilometres travelled by private and, increasingly, commercial vehicles.

An accompanying feature of city size is traffic congestion. Already, a number of densely trafficked corridors in major cities produce high local levels of congestion and a corresponding increase in pollutants both for travellers and local residents. Excessive slowing of vehicles within our cities also increases fuel use and reduces the efficiency of personal and commercial movement.

Taken together, a range of stationary or area sources such as power stations in or near airsheds, co-generation plants, seasonal use of domestic wood burners of lower standard, paint and solvent use and a variety of lesser activities contribute significantly to both airshed and local pollution levels.

Provided a range of initiatives, both long and short term, are pursued, air quality can still be maintained at levels close to or within the band of required standards into the longer term of 15–20 years or more. Many initiatives, such as new emission standards for vehicles, will take seven or more years to have major effect. The decisions to implement them need to be taken now. A number, such as in-service maintenance of vehicles ensuring compliance with pertinent emission standards can have a much more immediate effect.

There are two major considerations to be taken into account by all jurisdictions, Commonwealth, State and local, and by producers and consumers.

Firstly, acceptable air quality will only be assured by the pursuit of a wide range of actions and measures, not all of which will be universally popular. These measures will only succeed through co-ordination of transport planning, infrastructure development and environmental management. Appropriate investment decisions will need to be predicated on this base. A concerted effort to inform and educate the whole community about the importance and amenity of, and their responsibilities in relation to, clean air and well managed cities – 'you and a million others can make a difference' – will also play a key role.

Secondly, even with emissions minimised to the extent economically and behaviourally practicable, typical coastal conditions coupled with Australia's high sunlight flux, will continue to give a finite number of occasions each year when adverse meteorological conditions will lead to photochemical smog formation or particulate loads evidenced by 'brown haze' and reduced visibility. The nation's aim should be to keep air quality for all citizens at adequate health and amenity levels and to ensure that exceedences of the appropriate standards occur only when conditions are strongly adverse.

This Report proposes, in Section 4, a range of technical, management and economic measures and options which, if implemented, would produce this result over both the intermediate and the longer term. They are evaluated in cost effectiveness terms to provide policy makers with a relative framework within which measures may be considered.

Cover of Urban air pollution in Australia

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