dents are events that are perceived by some segments of society as producing unacceptable impacts or as indicating the danger that such impacts might occur in the future. These incidents do not necessarily produce large numbers of casualties or damage, but they can result in a societal response disproportionate to the risks involved, relative to that posed by natural disasters, such as earthquakes and hurricanes.

There are many apparent contradictions in the societal management of risk that can be explained (although far from perfectly) by recent models of disaster impacts² and the social amplification or attenuation of risk.³ One model, the Disasters Impact Model (DIM) shown in Figure 5.1, describes the determinants of disaster consequences. The effects of hazardous incidents are determined in part by three pre-impact conditions: (a) hazard exposure, (b) physical vulnerability, and (c) social vulnerability. When a hazardous incident occurs, it is subject to event-specific (d) hazardous incident characteristics that combine with the pre-impact conditions to produce (e) physical impacts. In turn, these physical impacts cause (f) social impacts. However, the physical impacts can be reduced by (g) improvised emergency response, and the social impacts can be reduced by (h) improvised disaster recovery activities. In addition, the impacts of the incident can be further reduced by means of pre-impact hazard planning and management actions such as (i) hazard mitigation practices and (j) emergency preparedness practices that reduce the physical impacts and (k) recovery preparedness practices that reduce the social impacts.

Some shortcomings must be kept in mind when applying the DIM to the chemical sector: