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APPLICATION AND SCOPE OF EnRA
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.,
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.
Questions/Issues for EnRA Scoping
|Level of Analysis
||Macro, systems, national or regional?
- 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?
- 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
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.
The human health risk assessment component of environmental risk assessment
The ecological risk component of environmental risk assessment