Monday, October 03, 2005

Uncertainty in Risk Management and Risk Communication

© 2004-2005 William Charteris

Decision model uncertainty, also called decision-rule uncertainty, is another type of ‘knowledge uncertainty’. It is of greatest concern to the risk manager. It arises, for example, out of the need to balance different societal concerns when choosing between alternative courses of action (incl. no action) to reduce risk to a ‘politically acceptable’ level.

Decision model uncertainty may necessitate recourse to the Precautionary Principle when a scientific evaluation of the risk, which because of data imprecision, incompleteness, uncertainty or disagreement, makes it impossible to determine with sufficient certainty the risk in question. Although the Precautionary Principle is intuitively straightforward to understand, there is no agreed way of applying it to real decision-making. In this regard, a combination of ignorance auditing and plotting methods has proven useful in its application by the Commission to contentious issues, such as GMOs and hormone treated beef.

In the past decade or so, the paradigm shift away from the use of point estimates towards the use of probabilistic distributions to quantitatively address variability and uncertainty in risk assessment has created new challenges for risk managers and risk communicators. Instead of comparing single point estimates to “bright lines” of risk, risk managers must now struggle with decisions about how to use distributions (or parts thereof) in the decision-making process. In recognizing variability in a population, they must address questions about who to protect and by how much, questions that are significantly different in nature to those that have been replaced, i.e. “Is this risk above the bright line or not?” While appreciation of the artificial nature of the “bright line” criterion and the dramatic oversimplification of the risk assessment required to derive a point estimate might provide some reassurance of the importance of using a probabilistic analysis to characterize the variability and uncertainty in the risks, it does not make the risk manager’s job of picking criteria to determine the ‘acceptability’ of risk any easier.

While risk managers are now beginning to grapple with the challenge of dealing with probabilistic risk assessment results, the challenges for risk communication have only been minimally appreciated or explored. In December 2000, the Commission identified that its scientific committees did not share a common approach for the presentation of the findings of risk assessments. Indeed, major differences were identified in the opinions of different committees with regard to scope, format, degree of detail, size, and use of terminology. In addition, uncertainty in the assessment of risk was often not expressed clearly and committees varied in the way in which they addressed these uncertainties. The Commission addressed this situation by proposing a format to be used in the expression of scientific opinions. This initiative has been adopted by EFSA’s scientific committee. Clearly, further work is required involving a range of stakeholders in order to progress this aspect of risk communication. In this regard, we must arm risk communicators with better information about variability and uncertainty in the risks that they use for risk comparisons, and encourage them to test different strategies for communicating variability and uncertainty in risk using both qualitative and quantitative information.

This abstract is taken from a paper entitled 'Uncertainty and risk', which was published on December 6, 2004. The paper comprises 3,900 words and 25 references. Individual copies of the paper may be requested by e-mail from the author.