PARENT SESSION
SP2 - Fate & Effect of metals: Regulation and Risk
Chair: Gorsuch, Joe1, 1 Kodak, Webster, NY
Co-chair: Reiley, Mary2, 2 U.S. EPA, Washington, DC
2:10 PM to 5:30 PM - Sunday, 17 November 2002
Room Ballroom J
(103) Developing a Framework For Assessing Hazard Of Metals And Metal Compounds.
Adams, William*,1, Brix, Kevin2, Green, Andrew3, 1 Rio Tinto, Salt Lake City, UT, USA2 EcoTox, Newport, OR, USA3 International Lead Zinc Research Organization, Research Triangle Park, NC, USA
ABSTRACT- Procedures for aquatic hazard identification of organic and inorganic substances are currently being harmonized by the OECD for the purpose of classifying market-place substances. Such a system already exists in Europe where it is recognized that special attention must be given to sparingly soluble metal-containing compounds. A challenge has arisen because standard hazard testing procedures designed for soluble organic and inorganic chemicals do not accommodate the characteristics of sparingly soluble metals and metal compounds (SSMMCs). Aquatic hazard identification procedures currently used in many countries are based upon toxicity, persistence and bioaccumulation (PBT) measurements. A PBT list of substances was developed in the U.S., but never finalized. A key issue is how to assess the hazard of metals. Toxicity of a metal is due predominately to the free metal ion in solution. In order to assess the aquatic toxicity of SSMMCs the rate and extent of transformation of a metal element or insoluble metal compound to a soluble form must be measured. Transformation of insoluble metal substances to soluble forms is a function of several key factors including particle size, surface area, and the pH of the test solution. A standard protocol for measuring transformation is currently being developed by the OECD. Persistence measurements typically used for organic substances (biodegradation) do not apply to metals. Alternative measurements such as complexation, precipitation, and mineral formation are more appropriate. Bioaccumulation of metals by aquatic organisms is important in terms of nutritional sufficiency and potential food chain transfer and toxicity. Unlike organic substances, bioaccumulation potential cannot be estimated using log octanol-water partition coefficients (Kow). Additionally, bioaccumulation and bioconcentration factors (BAFs/BCFs) are inversely related to exposure concentration and are not reliable predictors of concern for chronic toxicity or food chain accumulation. An alternate framework for assessing metal hazard will be presented.
Key words: PBT, metals, hazard, framework