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Risk Assessment

Step 4 - Risk Characterization

Step 4 - Risk Characterization: To summarize and integrate information from the proceeding steps of the risk assessment to synthesize an overall conclusion about risk.

This is a diagram of 4 -step Human Health Risk Assessment Process, highlighting the Risk Characterization (step 4) which is to summarize and integrate information from the proceeding steps of the risk assessment to synthesize an overall conclusion about risk.

A risk characterization conveys the risk assessor's judgment as to the nature and presence or absence of risks, along with information about how the risk was assessed, where assumptions and uncertainties still exist, and where policy choices will need to be made. Risk characterization takes place in both human health risk assessments and ecological risk assessments.

In practice, each component of the risk assessment (e.g. hazard assessment, dose-response assessment, exposure assessment) has an individual risk characterization written to carry forward the key findings, assumptions, limitations, and uncertainties. The set of these individual risk characterizations provide the information basis to write an integrative risk characterization analysis.

The final, overall risk characterization thus consists of the individual risk characterizations plus an integrative analysis. The overall risk characterization informs the risk manager and others about the rationale behind EPA's approach to conducting the risk assessment - why EPA did what it did to assess the risk.

Principles of Conducting Risk Characterizations

A good risk characterization will restate the scope of the assessment, express results clearly, articulate major assumptions and uncertainties, identify reasonable alternative interpretations, and separate scientific conclusions from policy judgments. EPA's Risk Characterization Policy calls for conducting risk characterizations in a manner that is consistent with the following principles:

  • Transparency - The characterization should fully and explicitly disclose the risk assessment methods, default assumptions, logic, rationale, extrapolations, uncertainties, and overall strength of each step in the assessment.

  • Clarity - The products from the risk assessment should be readily understood by readers inside and outside of the risk assessment process. Documents should be concise, free of jargon, and should use understandable tables, graphs, and equations as needed.

  • Consistent - The risk assessment should be conducted and presented in a manner which is consistent with EPA policy, and consistent with other risk characterizations of similar scope prepared across programs within the EPA.

  • Reasonable - The risk assessment should be based on sound judgment, with methods and assumptions consistent with the current state-of-the-science and conveyed in a manner that is complete and balanced, informative.

These four principles - Transparency, Clarity, Consistency, and Reasonableness - are referred to collectively as TCCR. In order to achieve TCCR in a risk characterization, the same principles need to have been applied in all of the prior steps in the risk assessment which lead up to the risk characterization.

For more information about Risk Characterization refer to EPA's Risk Characterization Handbook (PDF). (189 pp, 8.9 MB, About PDF)

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