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| Module 8: Environmental Issues and Public Health - Air Pollution Chapter 1: Introduction |
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Economic development in the form of industrialisation has usually resulted in increasing concentrations of people in towns and cities (urban areas), and the increasing industrial, commercial and domestic activities associated with this historical process of industrial development. Industrial development may have undesirable environmental consequences, particularly an increase in air pollution in these growing urban areas. An increase in air pollution, and more generally environmental degradation, is frequently considered to be an undesirable but unavoidable result of "development". Therefore the strict control and minimisation of environmental impacts is seen as being in conflict with "development" and "progress". But an understanding of the activities and factors that generate air pollution, the human health and environmental consequences of exposure to air pollutants and the available alternative approaches for the reduction or elimination of air pollution enables a different development scenario. Namely the management and avoidance of air pollution impacts within the development process by using concepts and approaches such as "Cleaner Production", waste minimisation, recycling and reuse of "waste materials" and the development of clean renewable energy sources.
Air pollution cannot be confined. So the general public, including those who do not in any way benefit from the activity causing the pollution (such as a passing bus or a factory) may suffer the discomfort or disease burden of the air pollution. Section 24 of the South African Constitution says that we have the right to an environment that is not detrimental to our health and well-being. But the protection or enforcement of environmental rights in relation to air quality requires an insight into the relationship between the pollution source and the exposure of people or the environment to air pollutants, and the legal and regulatory framework that enables the enforcement of those environmental rights.
The link between poor air quality and ill-health has been suspected for more than 2000 years. The ancient Greeks attempted to control sources of odour such as rubbish; civil suits over smoke pollution were brought before the Roman courts. Air pollution and disease were linked in the (ancient) Islamic world a. Urbanisation and the increased use of coal (rather than wood) for domestic heating and cooking during the 18th and 19th centuries, coupled with the development of highly polluting industrial processes such as sulphuric acid manufacture resulted in a rapid deterioration of air quality in towns and cities centres.
Two of the main air pollutants arising out of coal combustion are smoke (particulate matter) and sulphur dioxide (SO2). The SO2 reacts with atmospheric water vapour and oxygen to form sulphuric acid droplets. The smoke and sulphuric acid droplets provide excellent nuclei for fog formation under weather conditions that tend to coincide with poor pollutant dispersion conditions. The link between air pollution, fog and ill health, observed since ancient times, may be ascribed to these factors.
The industrial revolution in 19th century England resulted in increased energy consumption and use of highly polluting coal. During the 19th century and through to the mid-20th century, the increased use of coal in English cities coincided with increased urban population densities. These factors, and winter weather (low level inversions, high humidity), combined to increase the number of pollution induced foggy days during this period resulted in elevated smoke (particulate matter) and sulphur dioxide (SO2) concentrations in cities and towns.
Figure 1 uses coal usage rates (imports) into the city of London as a predictor of smoke concentration. The frequency of fog occurrences appears to correlate with the predicted smoke concentration. Between the late 19th century and 1950 coal usage and measured concentrations of sulphates (formed via the oxidation of SO2 in the atmosphere) and smoke decreased.
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Figure 1: Air pollution in London since the 17th Century comparing predicted values with fog frequency, and later measurements |
The increase in the total population, and the population density, of London during the 19th to mid 20th century are illustrated in Figures 2 and 3 b.
