Establishing Causation and the Weight of Evidence Approach

The determination of causality is critical to the risk assessment process. Risk assessments require the construction of mechanistic linkages operating at spatial and temporal scales appropriate to the scale of the risk assessment. 

risk assessments must construct a conceptual model that embeds a series of potential cause-and-effect relationships. In many cases these relationships, such as the concentration-response, are based upon laboratory 

Second, risk assessment is a process of hypothesis generation. The uncertainty of a risk assessment can be reduced if at least a part of the hypothesis can be tested and found to be confirmed. A method of accomplishing this is to perform further field research designed to test the causality hypotheses. 

In order to support the processes described above, methods for assigning causality are required that are compatible and consistent with current understandings of the workings of ecological systems. Incorporating scale and dynamics with the inherently open nature of ecological systems is a tremendous challenge. 

There have been two parallel approaches to establishing causality. First is the establishment of specific criteria for the identification of mechanisms for observed effects. The second is the WoE approach. 

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