9.4.1 What is environmental risk assessment?

Environmental risk assessment (ERA) is a qualitative and quantitative evaluation of environmental status performed in an effort to define the risk posed to human health and the environment by the presence, potential presence, or use of specific pollutants. ERA should be conducted when it is determined that a management action may have consequences to either humans or the environment. Effective conducting of ERA entails adopting a systematic approach, as shown in Figures 9.2 and 9.3.

ERA is comprised of two related disciplines; that is, human health risk assessment (HHRA) and ecological risk assessment (EcoRA).

The process for HHRA often involves the following steps:

• hazard identification - the determination of whether a particular chemical is or is not causally linked to a particular health effect on human beings;

• dose-response assessment - the determination of the relationship between the magnitude of the exposure and the probability of occurrence of the health effects in question;

• exposure assessment - determination of the extent of exposure;

• risk characterization - description of the nature and often the magnitude of risk including attendant uncertainty.

Figure 9.2 Systematic approach to risk assessment

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

EcoRA is conceptually similar to the approach used for HHRA. During this assessment, the likelihood of the occurrence/non-occurrence of adverse ecological effects as a result of exposure to stressors is determined. The term "stressor'' here may be defined as any chemical, physical, or biological entity that can induce adverse effects on individuals, populations, communities, or ecosystems. The various components are schematically represented in Figure 9.4 for both HHRA and EcoRA.