The Environmental Protection Agency (EPA) earlier this month released its final Framework for Metals Risk Assessment (Metals Framework), a science-based document that identifies the basic principles regarding the attributes and behaviors of metals and metal compounds that should be considered when assessing human health and environmental risks. EPA's Risk Assessment Forum oversaw the development of this document, including input from stakeholders, experts from both inside and outside of EPA, several expert workshops, and peer review by EPA’s Science Advisory Board.

Under its past practices, EPA tended to classify metals as higher risk based primarily on overly conservative assumptions that metals were persistent bioaccumulative toxins. This analysis was not appropriate for metals generally because metals are, by their nature, "infinitely persistent" and do not pose the same potential bioaccumulation hazards as organic compounds. The new Metals Framework supports the argument that the toxic properties of metals and the associated risks depend on the metal, the form of the metal or metal compound, and the ability of the target organism to regulate, process and/or store the metal.

EPA indicates that the new Metals Framework is intended to be a guide for all EPA programs and regional offices to supplement and update existing policies, practices and guidance that are being used to assess metals risks for regulatory purposes. The Framework outlines the key metals principles and describes how they should be considered in conducting human health and environmental risk assessments.

The following principles are general, fundamental attributes of metals that should be addressed and incorporated into all EPA metals risk assessment guidance and practices:

• 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.

More information about the Framework for Metals Risk Assessment and supporting documents is available on EPA's website at www.epa.gov/osa/metalsframework.