Lay views on uncertainty in environmental health risk assessment

It has been argued that presenting uncertainty in environmental health risk estimates may increase citizens' risk knowledge and trust in the honesty and competence of the institutions providing such estimates; on the other hand, careless communication could have undesirable results. Reported here is a study of how American laypeople think about uncertainty in risk assessment, and its implications for risk management, extending earlier experimental research (Johnson and Slovic, 1995). A long closedended questionnaire (based in part on qualitative research) was given to 280 Eugene, Oregon, residents (largely college students). Uncertainty was presented in the form of a range of risk estimates, primarily in a hypothetical case of a chemical in drinking water. The findings suggest that it will be a challenge to present uncertainty in environmental health risk estimates to the public in ways that inform, rather than confuse or outrage, this important audience.