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Risk assessment, in general, forms the basis of the insurance industry. EnRA is amply applied by the chemical and pharmaceutical industry to study risks from production, consumption and disposal of synthetic chemicals. Thus, most of its concepts, methodological framework and terminologies are derived from risk assessment of chemical release to the environment. However, the virtues of EnRA are now being applied to other effects caused by "non-chemical" risks such as physical disturbances and biological agents as depicted earlier in Figure 3.

The use of formal risk assessment process in urban environmental management is advantageous for the following reasons (Suter, 1993):

  • EnRA quantifies the comparison and prioritization of risks;
  • EnRA provides an informed, scientific basis for cost-benefit analyses;
  • EnRA considers uncertainties, thus making the assessment more credible;
  • EnRA distinguishes the scientific process of risk assessment from the value-laden selection of risk management measures

In its expanded form, EnRA may be conducted for any activity or condition that will likely cause a harmful consequence. Several EnRA conceptual and methodological frameworks arose from the wider practice of EnRA, including a proposal for an ENRA for developing countries (Claudio, 1988; Smith et al., 1988)

EnRA may take several forms depending on the questions asked or the issues raised by the risk managers, the stakeholders and the risk assessors (see Table 1) (ADB, 1990). Three broad applications of EnRA are chemical evaluations, site assessments and natural resource assessments.

Table 1
Questions/Issues for EnRA Scoping

Level of Analysis Macro, systems, national or regional?
System Boundaries
  • Routine release and/or accidents?
  • Which population?
  • Which parts of the flow cycle?
  • Which geographic boundaries for each?
  • Which phases of the project?
  • Effects for how long in the future?
  • Which health endpoints?
  • Which ecosystem risk endpoints?
  • Which parts of the causal chain?
  • Interaction with other projects, existing or planned?
Risk Expressions


  • Which risk indicators?
  • Which methods of exposure determination?
  • Which environmental concentrations will be used?
  • Which final risk measures?
  • Which confidence levels?


An example of a chemical evaluation is to estimate the risk of release of toxic chemicals such as dioxim and furans from an incinerator to the atmosphere, agricultural farms and the local population, or in comparing land filling versus incineration as waste management options. EnRA can also be used in selecting a disinfection method for drinking water as against the risk of generating and ingesting chlorinated organic chemicals. EnRA can facilitate site assessments, such as site selection for a petrochemical industrial park or a nuclear power plant.

EnRA can be used also in natural resource assessment. Two EnRA approaches were used recently to assess a regional marine resource system (GEF/UNDP/IMO, 1997): the Retrospective Approach and the Prospective Approach. This case is further described in a later section of this paper. The Retrospective Approach provides the factual basis for the Prospective Approach and in turn the Prospective Approach explains findings established by the Retrospective Approach. The Retrospective Approach is also compared to Forensic Ecology and not considered by some as true risk assessment.

As may be inferred from these examples, geographic and thematic scopes of EnRa can range from micro-EnRA (wherein a single pollutant is the agent and the workers as well as local residents are receptors) and to a macro-EnRA involving many risk sources spanning national and international scales which can be called cumulative risk assessment (USEPA, 1997). Two illustrative cases of this range of EnRA applications are also described in a later section.


The SCP-EnRA Framework

In this paper, preference was given to the unified framework of the sustainable Cities Program (SCP) here referred to as the SCP-EnRA framework, details of which can be found in the UNEP International Environmental Technology Centre Technical Publication Series 3: Environmental Risk Assessment of Sustainable Cities, Osaka/Shiga, 1996.

The SCP-EnRA Framework depicted in Figure 2 incorporates two interrelated disciplines that developed separately, namely, Human Health Risk Assessment and Ecological Risk Assessment. Human Health Risk Assessment is used for predicting the probability of effects on health of humans (Figure 7); and Ecological Risk Assessment is applied to predicting the probability of effects on environmental resources (Figure 8).

In both cases, risk is broadly understood as the likelihood that a harmful consequence will occur as the result of an action or condition. Risk is the combined evaluation of hazard and exposure. Hazard is defined as the potential of an agent, stress or source (physical, chemical or biological) to cause harm or adverse effect to a receptor (which can be the environment or humans). The pathway leading to the exposure of the receptor to the hazard forms the third element in risk. Ascribing the probability of exposure to the hazard by a receptor characterizes the risk. All of the three elements must be evaluated to form an effective and useful EnRA for specific scenarios.

Figure 7
The human health risk assessment component of environmental risk assessment


Figure 8
The ecological risk component of environmental risk assessment

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