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NRMRL-CIN-1351 Hofstetter**, P., and Hammitt, J. K. Human Health Metrics for Environmental Decision Support Tools: Lessons from Health Economics and Decision Analysis. Risk Analysis 600/R/01/104, Available: on internet, www.epa.gov/ORD/NRMRL/Pubs/600R01104, [NET]. 03/07/2001 Decision makers using environmental decision support tools are often confronted with information that predicts a multitude of different human health effects due to environmental stressors. If these health effects need to be contrasted with costs or compared with alternative scenarios, then decision makers may find it useful to have a common metric. Similar needs led researchers in medical decision making and health economics to develop a multitude of metrics and a rich body of research literature. This paper provides a review of this literature with special attention to aspects relevant in the environmental context. Further, three metrics (quality adjusted life years (QALYs), disability adjusted life years (DALYs) and willingness-to-pay (WTP), have been used to compare a wide range of diffferent environmental risk factors like, e.g., particulate matter, ozone depletion or noise. Based on a characterization of medical and environmental applications, recommendations for the use of human health metrics in different environmental decision support tools have been derived. Some of the findings include that WRP tends - if typical values of statistical life are used - to reflect mortality outcomes only. QALYs and DALYs are very similar metrics that are sensitive to mild illnesses that affect large number of people. Since the typically applied methods to derive quality weights show flaws when applied to mild illnesses, biased assessmens are likely. Further, both DALYs and QALYs do not include costs of illnesses, which may be needed to provide a full account of health costs or benefits. Since health metrics tend to follow the paradigm of utility maximization, it is suggested to supplement these metrics with a semi-quantitative discussion of distributional and ethical aspects. Finally, we found that different environmental decision support tools may require different metrics. However, if the same metric can be used, its characteristics like discounting, life tables, elicitation methods and judges may differ. The magnitude of age-dependent disutility due to mortality for both monetary and non-monetary metrics may bear the largest practical relevance out of a series of suggested research questions.

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