of an animal species as an analog for human health impacts is outside the expertise of this committee. Another NRC report describes issues related to the use of animal analog models (NRC 2001b). However, computational models, particularly statistical dose-response models, that are used to extrapolate laboratory animal data to humans are included.
Additionally, the committee’s focus is on models used in the development, assessment, and implementation of environmental regulatory actions. EPA also uses models in a variety of other applications including planning, project scheduling, data collection, research, prediction, and forecasting. In so far as these models are computational, the committee’s recommendations may be useful for these models and their applications. But the committee in no way focused on some of the unique attributes of model selection and use at EPA in these other activities. Because of the wide array of environmental modeling at the agency, there is sometimes not a clear distinction between models used for regulatory purposes that are within the scope of this study and models considered to be used for nonregulatory purposes. For example, the same model may be used for both a regulatory application and a research application. In this way there is sometimes a continuum from models clearly in the regulatory domain under the purview of this study and other applications clearly outside the scope of work. However, not all model applications at EPA directly lead to regulation and there are clearly some model applications that fall outside the committee’s scope.
This report documents the committee’s response to the charge described above. The report consists of six chapters and a summary. Chapter 2 describes the diversity of model use at EPA, how the agency currently integrates models into its policies, and some of the challenges to model use. Chapter 3 discusses the major steps in environmental regulatory model development, focusing on the main lessons learned from previous efforts in EPA. Chapter 4 discusses the evaluation of these models. Chapter 5 describes issues that arise in selecting models for their application in environmental regulatory activities. The report closes by discussing future environmental regulatory model activities in Chapter 6.