Fact Sheet on Framework for Metals Risk Assessment
March 8, 2007
The Metals Framework: Establishing a Process for the Consistent Application of Scientific Principles to Metals Risk Assessment
Introduction and Purpose
EPA recognizes that metals present unique risk assessment issues, and sees the need to develop a framework document that puts forth key scientific principles for metals risk assessments to help ensure consistency in metals assessments across EPA programs and regional offices. This newly developed framework, called the “Framework for Metals Risk Assessment,” is a science-based document that describes basic principles that address the special attributes and behaviors of metals and metal compounds to be considered when assessing their human health and ecological risks.
The Framework for Metals Risk Assessment is intended to serve as a guide for all EPA programs and regional offices to supplement or update the policies, practices and guidance they currently use in their respective metals assessments. This Framework document is not a prescriptive manual on how any particular type of assessment should be conducted within an EPA program office. Rather, it outlines key metal principles and describes how they should be considered in conducting human health and ecological risk assessments to advance our understanding of metals impact and foster consistency across EPA programs and regions.
This Framework primarily addresses Agency risk assessors; however, it also communicates principles and recommendations for metals risk assessment to stakeholders and the public. It will be used in conjunction with guidance developed by the programs and regions for use in site-specific risk assessments, criteria derivation, ranking or categorization and other similar Agency activities related to metals. EPA assessments can vary in level of detail from simple screening analyses to complex, definitive assessments. More complex scientific tools and metal specific methods should be applied as the complexity of the hazard assessment or risk assessment increases.
Principles Presented in the Metals Framework
The purpose of this document is to present key guiding principles based on the unique attributes of metals (as differentiated from organic and organometallic compounds) and to describe how these metals-specific attributes and principles may then be applied in the context of existing EPA risk assessment guidance and practices. While organic compounds, for example, undergo bioaccumulation, there are unique properties, issues, and processes within these principles that assessors need to consider when evaluating metal compounds. Furthermore, the latest scientific data on bioaccumulation do not currently support the use of bioconcentration factors and bioaccumulation factors when applied as generic threshold criteria for the hazard potential of metals.
The principles pertain to general, fundamental aspects of metals that should be addressed and incorporated into inorganic metals risk assessments:
- Metals are naturally occurring constituents in the environment and vary in concentrations across geographic regions
- All environmental media have naturally occurring mixtures of metals, and metals are often introduced into the environment as mixtures
- Some metals are essential for maintaining proper health of humans, animals, plants, and microorganisms
- Metals, as chemical elements, and unlike organic chemicals, are neither created nor destroyed by biological or chemical processes, although, these processes can transform metals from one species to another (valence states) and can convert them between inorganic and organic forms
- The absorption, distribution, transformation, and excretion of a metal within an organism depend on the metal, the form of the metal or metal compound, and the organism’s ability to regulate and/or store the metal.
For More Information
The Risk Assessment Forum oversaw the development of this document, including input from stakeholders and experts throughout the Agency, obtained through several expert workshops, followed by peer review by the EPA Science Advisory Board (SAB). The published report and articles on this study are available on the Web at: http://www.epa.gov/osa/metalsframework.
For more information, contact Dr. Randall S. Wentsel, EPA, phone (202) 564-3214 or by email at email@example.com.