30. Major Accidents

CHAPTER 30: MAJOR ACCIDENTS - THE PROBLEM

Technology-related accidents are of major concern as sources of impacts on human health and the environment (Chapter 18). This concern arises from three interrelated characteristics: unpredictability of when and exactly how they will occur (and hence perceived lack of control), uncertainty over environmental pathways and impacts, and unforeseen interactions (human and technical) in the source facility. There is already substantial evidence of the short- and long-term level of human catastrophe which can result, for example, following the nuclear accident at Chernobyl and explosions such as at Los Alfaques and the release of dioxins at Seveso. The complex and possibly long-term damage to environmental resources (particularly soils and water) and dependent ecosystems is cause of increasing concern.

The causes of impacts from major accidents are distinguished by the fact that, although the source activities (eg, power generation, chemical processes and transportation) are planned and generally continuous, the hazards and environmental pressures associated with accidents are neither routine nor planned. Although statistics of past accidents provide an indication of what can be expected in the future, it is not possible to predict with absolute confidence either where or when an accident will happen. Combined with the significant uncertainty attached to the nature and magnitude of the resulting impacts, this justifies treating accidents as a significant source of societal 'risk' for the purpose of assessment and management. Risk, in this sense, can be characterised as the nature and magnitude of an undesired effect in relation to the probability of its occurring.

The industrial activities which give rise to these risks (primarily production and transport of chemicals) are increasing in intensity (see Chapter 20). In addition, interactions between human society and the natural environment are showing increasing signs of vulnerability to hazardous events (eg, the effects of Chernobyl and Seveso on agricultural activity, and the effects of hurricanes on the international insurance business). The prevention and control of such accidents to minimise the risks to within 'acceptable' limits can therefore be considered a priority. This chapter focuses on how appropriate goals can be set for a problem with such diverse elements, and how the risk can be managed by the parties concerned ­ industrial operators, regulatory and planning authorities and the public. Nuclear accidents are dealt with separately at the end of the chapter.

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Contents:

30.1 - The problem

30.2 - Goals: setting acceptable risk levels

30.2.1 - Human health risk

30.2.2 - The importance of risk perception

30.2.3 - Risk to the environment

30.3 - Managing the risks

30.3.1 - Basic elements

30.3.2 - Source safety

30.3.3 - Emergency response planning

30.3.4 - Landuse and transport planning

30.3.5 - Integrated risk assessment and management

30.4 - Nuclear accidents

30.4.1 - Causes

30.4.2 - Objectives

30.4.3 - Strategies