In the seventh year of the reign of the Emperor Nero, the philosopher Seneca commented on the quality of the air in Rome:
As soon as I had gotten out of the heavy air of Rome and from the stink of the smoky chimneys thereof, which, being stirred, poured forth whatever pestilential vapours and soot they have enclosed in them, I felt an alteration of my disposition. Lucius Annaeus Seneca1
Seneca was probably not the first, and certainly not the last, to comment adversely on the quality of urban air. Until quite recently, the histories of major cities such as London have been punctuated by complaints from kings and commoners alike about pollution of the air and its effects on amenity and health. Throughout the 19th and much of the 20th centuries, uncontrolled industrial emissions, lack of effective collection and treatment of sewage, and widespread burning of fossil fuels combined to make most large cities unattractive and unhealthy places to live. The great London smog of December 1952, which is now reckoned to have claimed as many as 8000 lives, was but one of a number of instances of killer smogs.2-3
Historically, Australian cities too have suffered from poor air quality—Melbourne was known as ‘Smellbourne’ in the 1880s, due largely to the lack of an effective system for treating and disposing of sewage well away from the city.4 By the mid–1960s, air pollution in some of Australia’s largest cities had reached levels prompting broad public and political concern.
Evidence received by the Committee indicates that an air pollution problem already exists in some parts of Australia and while not yet a problem of the magnitude existing in well known centres of pollution such as London, New York, Los Angeles and Tokyo, [it is] a problem which nevertheless warrants urgent planning and action. Parliament of Australia,5p. 4
Fortunately, the quality of the air in Australian cities has improved significantly during the past 20–30 years in response to a mix of regulatory and nonregulatory approaches to controlling both point and diffuse sources of pollution, applied at national, state and local levels. Such improvements have occurred despite growing populations, expansion of industry and greatly increased use of motor vehicles. Monitoring of the air in our cities against national health-based standards shows that episodes of poor and very poor air quality are limited, often being associated with extreme events such as bushfires and dust storms.6 Despite this, each year, urban air pollution is estimated to account for more deaths than the nation’s road toll.7
Clearly there is still a need to press for further improvements in our urban air quality, particularly as new scientific knowledge emerges about the impacts of pollutants such as fine particles. Nevertheless, the focus of scientific, political and community concern has shifted to another essential issue for the atmosphere—the effects on the world’s climate of changes in the atmosphere caused by human activities. Here, over the relatively short span of 250 years and for the first time in human history, we have changed and are continuing to change the composition of the atmosphere on a global scale. This has led to a clearly defined trend of increasing average global temperatures (Figure 3.1), and there is increasing evidence of consequent changes in the complex set of interlinked atmospheric, oceanic and terrestrial processes that shape climate at the global, continental and regional scales.8-11
Australians, on a per capita basis, contribute disproportionately to the emissions of carbon dioxide (CO2) and other greenhouse gases (GHGs) that are driving these changes. As inhabitants of the driest of the world’s inhabitable continents—much of which is unsuitable or only marginally suitable for agriculture—Australians have more at risk than most in a warming world.12-13
This chapter is divided into two sections: climate, and ambient air quality and other atmospheric issues. The climate section discusses the influence of GHGs, particularly those generated by human activities, on Earth’s climate and some of the likely impacts of global climate change on human health and the environment. The second part of the chapter discusses other aspects of the atmosphere, including stratospheric ozone, ambient air quality and indoor air quality.