April 17, 2001—The U. S. Environmental Protection Agency (EPA) announced the availability of its 2001 Update to the Aquatic Life Criteria Document for Cadmium in an April 12 Federal Register notice.
Section 304(a)(1) of the Clean Water Act requires (EPA) to develop and publish, and from time to time revise, criteria for water accurately reflecting the latest scientific knowledge. EPA has revised its aquatic life criteria for cadmium.
Water quality criteria are used to develop state water quality standards. The criteria are established at levels designed to protect both aquatic life and human health. EPA has been revising the current aquatic life criteria for copper, silver, lead, cadmium, iron and selenium and has been developing new aquatic life criteria for atrazine, diazinon, nonylphenol, methyl tertiary-butyl ether (MtBE), manganese and saltwater dissolved oxygen
There are no changes in the saltwater criterion maximum concentration (CMC or ``acute criterion'') or the saltwater criterion continuous concentration (CCC or ``chronic criterion''). There are, however, significant changes in the freshwater CMC and CCC.
The freshwater CMC changed due to several factors including the addition of data for bull trout and rainbow trout, the elimination of some data and the recalculation of species mean acute values (SMAVs) for a few species. Two SMAVs were recalculated based on all applicable data rather than only giving preference to flow-through measured test results, as in the draft.
The new freshwater criterion expressed as functions of the water hardness are a maximum concentration of e(1.0166[ln(hardness)]-3.924) ug/L and a continuous concentration of e(.7409[ln(hardness)]-4.719) ug/L. The newly established saltwater criterion concentrations established are 40 ug/L maximum and 8.8 ug/L continuous.
EPA's freshwater metals criteria are expressed as hardness dependent values because water quality characteristics such as hardness (and other parameters that covary with hardness) influence the toxicity of metals on aquatic organisms. This revision resulted in less stringent CCC compared to the draft document, but still more stringent than EPA's 1995 value.
EPA revised the document to address the peer reviewers' comments and the scientific issues raised by the public after publishing its draft on August 17, 2000.
In spite of comments that EPA should not proceed with the cadmium update until the biotic ligand model (BLM) is available for cadmium, EPA revised the criteria. When and if it changes the BLM is changed, The cadmium criteria may be revised in the future based on the BLM, the cadmium criteria again may be revised in the future.
The BLM, estimates the bio-available portion of dissolved metals in the water column based on site-specific water quality parameters such as alkalinity, pH and dissolved organic carbon. Future development of the BLM is contingent upon resources and availability of sufficient data.
For additional information, contact Cindy Roberts, Health and Ecological Criteria Division, (4304),US EPA, Ariel Rios Building, 1200 Pennsylvania Avenue NW, Washington, D.C. 2060; (202) 260-2787; [email protected]. The Federal Register notice and the new 166-page aquatic life criteria document for cadmium are available at: http://www.epa.gov/waterscience/criteria/ on the Internet.
