Nature of uncertainty sources

Uncertainty is the lack of knowledge of vital parts that are needed to perform an exposure assessment. Uncertainty can, at least in principle, be reduced by research to obtain necessary or applicable information or data. 

Uncertainty pertains to different steps and approaches in the assessment. It can be classified into three broad categories  

1) Scenario uncertainty Uncertainty in specifying the exposure scenario that is consistent with the scope and purpose of the assessment. 

2) Model uncertainty Uncertainty due to gaps in scientific knowledge that hamper an adequate capture of the correct causal relations between exposure factors. 

3) Parameter uncertainty Uncertainty involved in the specification of numerical values (be they point values or distributions of values) for the factors that determine the exposure. 

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