Scientific issues in the U.S. EPA Framework for Metals Risk Assessment.

This article on the U.S. Environmental Protection Agency document, "Framework for Metals Risk Assessment" (U.S. EPA, 2007a) was presented at the "Health Risk Assessment of Essential Metals" Workshop held at the University of Ottawa in May 2008. This article discusses the basic principles included in the Framework for Metals Risk Assessment and outlines how these principles need to be considered in human health and ecological risk assessment practices. Recognizing that metals present unique risk assessment issues, the article includes discussion of the various scientific issues related to metals assessments, such as environmental chemistry, bioavailability, bioaccumulation, and essentiality.