Environmental Modeling and Health Risk Analysis (ACTS/RISK) The purpose of this book is to provide the reader with an integrated perspective on several fields. First, it discusses the fields of environmental modeling in general and multimedia (the term “multimedia” is used throughout the text to indicate that environmental transformation and transport processes are discussed in association with three environmental media: air, groundwater and surface water pathways) environmental transformation and transport processes in particular; it also provides a detailed description of numerous mechanistic models that are used in these fields. Second, this book presents a review of the topics of exposure and health risk analysis. The Analytical Contaminant Transport Analysis System (ACTS) and Health RISK Analysis (RISK) software tools are an integral part of the book and provide computational platforms for all the models discussed herein. The most recent versions of these two software tools can be downloaded from the publisher’s web site. The author recommends registering the software on the web download page so that users can receive updates about newer versions of the software.