Cover Image
close this bookConducting Environmental Impact Assessment in Developing Countries (United Nations University, 1999, 375 p.)
close this folder9. Emerging developments in EIA
close this folder9.4 Environmental risk assessments
View the document9.4.1 What is environmental risk assessment?
Open this folder and view contents9.4.2 Terminology associated with ERA
View the document9.4.3 ERA and the project cycle
View the document9.4.4 ERA builds upon EIA
View the document9.4.5 Basic approach to ERA
View the document9.4.6 Characterization of risk
View the document9.4.7 Risk comparison
View the document9.4.8 Quantitative risk assessments
View the document9.4.9 Risk communication
View the document9.4.10 Risk management
Open this folder and view contents9.4.11 Guidelines for disaster management planning

9.4.5 Basic approach to ERA

The process by which an ERA proceeds involves several successive interactive stages. The first and probably the most important activity is "problem identification'' in which the resources that may be affected and the possible consequences of the proposed action are described. Key issues and concerns, such as the possible impact on human health and environmental resources, are provided. The concerns identified during this stage become the focus of the next step which involves parallel evaluation of risks to human health and to the ecosystem through the use of HHRA and EcoRA.

In order for the assessments to be efficient, the processes of EcoRA and HHRA should proceed in a stepwise iterative fashion, as shown in Figure 9.5.

As seen in the figure, scoping forms the first tier and the output of this activity, as in the case of EIA, and identifies issues and concerns that have potential risks. In the event of indications of there being unacceptable risks, more detailed studies need to be done. The scoping activity proceeds by choosing from various options for levels of analysis, system boundaries, and types of risk expression.

Levels of analysis. Micro, systems, or national?

System boundaries. Routine releases 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 into 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?

Scoping is essentially a process of choosing system boundaries, units of measurement, and the level of analysis that are relevant to the management questions of concern. Consequently, the process requires the input of all those groups that will be using the results.


Figure 9.5 The interactive nature of environmental risk assessment

Source: Environmental Risk Assessment for Sustainable Cities, Technical Publication Series [3], International Environmental Technology Centre, Osaka. 1996.

There is a direct linkage between the hazard identification/accounting stages and risk assessment. During this stage the questions of concern are used to set the boundaries of the risk assessment steps to follow. Since the design of the risk assessment will depend on the type of questions being asked, there is no universal risk assessment method independent of the use for which it will be put. This means that in practice project officers will engage in an ERA scoping process with the project proponents, the risk consultants, and other affected and concerned parties, preferably together, to establish a mutually agreed upon and practical set of system boundaries, units of measurement, and level of analysis. Guidance may also be available from the EIA that led to the ERA.

These decisions make up the accounting step and establish priorities as to which hazards need to be evaluated first and to identify linkages leading to mitigation measures. In some cases, failure to think carefully through the scoping decisions can lead to quite misleading conclusions and suboptimizations (i.e., a focus on relatively unimportant risks or even promoting actions that increase overall risk).

In order to evaluate hazards at this stage, a number of methods exist, summarized in Table 9.9.

The screening tier is an intermediate level ERA that incorporates greater rigour than the scoping tier in describing hazards and exposure. In this tier, the greatest effort is placed on analysis of data describing the dose-response relationships of exposure scenarios. In cases where the estimates of risk are unusually or inexplicably high a more rigorous estimation of likely exposure and a review of existing hazard information is warranted. The methodology for hazard evaluation is as used in scoping, relying on conservative estimates and deterministic approaches to estimating risk. The main objective at this stage is to identify major outstanding risk issues and, if possible, eliminate some of the lesser issues before proceeding with detailed investigations.

The final tier involves more sophisticated modelling of exposure and direct measure of effect where possible. Exposures may be quantified in a probabilistic manner. Hazards are reviewed in-depth for more accurate estimations appropriate to the exposure or species in question. Rather than relying on conservative assumptions of exposure and hazard, this tier of risk characterization provides a more realistic quantification of potential risks associated with the relevant exposures.