Hazard identification for contaminants.

In recent years, the recognition of generation of large quantities of toxicants and their by-products due to the industrial and/or cultural activities and transport and their persistence in the environment and biological activities brings out the necessity and importance of their assessment of risk they pose to the ecosystems (e.g. aquatic environment-coastal waters, rivers, lakes and ground water). Indeed, understanding the impacts of contaminants on the environment, including the organisms which live in it, is rather complicated. Nevertheless, the need for protection of the scarce natural resources in the environment and wiser use of them brings the necessity and importance of focusing more attention to the issue. Accordingly the process of ecological risk assessment (ERA) has evolved rapidly since the Environmental Protection Agency (EPA) issued a framework for ecological risk assessment in 1992. The ecological risk assessment involves three stages in a continuous process: (1) problem formulation (problem identification-hazard identification), (2) the analysis of exposure and effects and (3) risk characterisation. Risk management follows the risk characterisation. Of these stages, problem identification is the most critical one which establishes the direction and scope of the ecological risk assessment. The stage involves identifying the actual environmental value(s) to be protected (assessment endpoints) and selecting ways in which these can be measured and evaluated (measurement endpoints). The accuracy of the risk estimation is largely based on the availability of the key information about the contaminant characteristics, ecosystem at risk and ecological effects and the less uncertainty associated with them. The key information required during this phase of the risk assessment process are as follows: (a) potential/actual contaminant of concern, (b) source of contaminant; current and historic use, (c) mode of action of the contaminant, (d) contaminant characteristics (e.g. physical/chemical properties and environmental behaviour, persistence in the ecosystem, transformation products and bioaccumulation), (e) ecosystem potentially at risk and (f) areas of uncertainty. Finally based on these information a conceptual model has to be developed to define the possible exposure and assessment scenarios. Herein, the aforementioned key issues concerning the problem-hazard identification stage of ecological risk assessment for contaminants have been briefly reviewed.