Dealing with Uncertainty: From Health-Risk Assessment to Environmental Decision Making

There is growing overlap between environmental matters, driven by quantitative needs and whenever causes and effects are in issue, and matters that confront health-risk management. Risk assessors have generated methods that can be usefully adopted by those concerned with environmental decision making. The discussions currently taking place at the Intergovernmental Negotiating Committee for a Framework Convention on Climate Change, in Geneva, Switzerland, and in other environmental forums involve costly outcomes, about which scientific knowledge is uncertain and information is imperfect. It is appropriate to review the methods used in those discussions and to attempt to provide reasoned means to deal with uncertainty through a common frame of reference. This paper characterizes types of uncertainty, discusses approaches to deal with them, and provides statistical and mathematical examples from human-health-risk assessment on how to deal with them. The main conclusion is that the methods from applied risk assessment provide some of the means to deal coherently with decision making under uncertainty. Nevertheless, each method has advantages and disadvantages. Heuristics such as scenarios are therefore still useful, provided that their use is combined with modern techniques available to deal with not only probabilistic thinking, but also with situations in which probabilistic methods fail for technical and practical reasons.