is an increasingly important and inseparable component of risk communication. Until recently, there has been little discussion of uncertainty communication by risk communication professionals because they assumed that the public was unable to conceptualize uncertainty (Wynne, 1992) or that admitting uncertainty could be seen as a sign of incompetence (Johnson and Slovic, 1995). The historic lack of communication about uncertainties has increased public distrust in the motives of regulators and scientists (Frewer, 2004).

All risk assessments are based to a certain extent on unproven assumptions and incomplete knowledge that limit the precision of risk estimates. This is certainly the case for assessments of cancer risks in populations near nuclear facilities, because data on exposures and disease occurrence may not be complete (see Chapter 3 and 4). Although uncertainties can be reduced by obtaining additional data, such acquisition can require great effort and can result only in marginal gains in precision.

Describing the uncertainties in a risk analysis can enhance the understanding of risk estimates. In describing uncertainties, it is important to separate known and speculative uncertainties and to identify areas of disagreement among experts. This helps others to make informed independent judgments about the meaning of the risk estimates.

In cases where scientific findings are ambiguous, communication may take place in an environment marked by disagreements, misunderstanding, and suspicion. Communicators must diagnose these difficulties, find ways to create trust and credibility to overcome them, and deepen understanding (Rowan, 1994). Creating trust, based on the expectations that the communicator is competent and well meaning, is probably the priority of a risk communication plan. People are generally uninterested in understanding a subject or taking any sort of action if they do not trust those who are communicating with them.


Although this Phase 1 study did not involve a formal assessment of cancer risk, the committee understood the importance of engaging with the public to understand their views and concerns. The project sponsor (USNRC) also encouraged the committee to engage with the public during this Phase 1 study and provided funding to make this possible.

The committee judged that public engagement would improve the outcome of this Phase 1 study, particularly in helping the committee to identify Phase 2 study designs that could help to address public concerns. The committee membership includes experts in risk communication and public health (see Appendix B); these experts helped the committee to engage with the public during this Phase 1 study.

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