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Water: Cadmium

Aquatic Life Criteria for Cadmium: 2001 Update

April 2001

EPA has revised its aquatic life criteria for cadmium and announced the availability of the completed document entitled, 2001 Update of Ambient Water Quality Criteria for Cadmium. EPA revised its aquatic life criteria for cadmium to reflect the latest scientific knowledge regarding the effects of cadmium on aquatic organisms. The revised criteria are average concentrations of cadmium that can be present in a water body, but should not result in unacceptable effects on aquatic organisms and their uses.


Section 304(a)(1) of the Clean Water Act requires the EPA to develop, publish, and from time to time revise, criteria for water. Water quality criteria developed under section 304(a) are based solely on data and scientific judgments and should accurately reflect the latest scientific knowledge. They do not consider economic impacts or the technological feasibility of meeting the criteria in ambient water.

Under the Clean Water Act, States and Tribes are to establish water quality criteria to protect designated uses. EPA has promulgated regulations to implement this requirement (see 40 CFR part 141). EPA's recommended water quality criteria do not substitute for the Act or regulations, nor are they regulations themselves. Thus, EPA's recommended water quality criteria cannot impose legally binding requirements on EPA, States, Tribes or other regulated community. State and Tribal decisionmakers retain the discretion to adopt approaches on a case-by-case basis that differ from this guidance when appropriate. EPA may change this guidance in the future.

How does this new criteria for cadmium protect water quality?

The updated cadmium criteria reflects the latest scientific data and results in criteria that better protect aquatic organisms. Section 304(a) criteria provide guidance in adopting water quality standards and provide a scientific basis to develop controls of discharges or releases of pollutants. The criteria also provide a scientific basis for EPA to develop federal regulations under section 303(c).

Why is EPA notifying the public about the completed cadmium document?

EPA is notifying the public about the availability of the completed criteria document entitled, 2001 Update of Ambient Water Quality Criteria For Cadmium, according to its new process for developing criteria (63 FR68354). In following the Agency's new process for developing criteria, EPA notified the public of its intentions to revise the aquatic life criteria for cadmium in the Federal Register on October 29, 1999 (64 FR58409). At that time, EPA made available to the public all references identified by a recent literature review and solicited any additional pertinent data or scientific views that would be useful in revising the aquatic life criteria. EPA revised the aquatic life criteria for cadmium based on the new data and prepared a draft document. EPA then announced the peer review and the availability of the peer review draft on August 17, 2000 (65 FR50201). Again EPA solicited views from the public on issues of science pertaining to the information used in deriving the draft criteria. EPA considered the comments from the peer reviewers and the public and has revised the document accordingly. The completed document is now available.

Where can I find more information on EPA's Revised Process for Developing New or Revised Criteria?

The Agency published detailed information about its revised process for developing and revising criteria in the Federal Register on December 10, 1998 (63 FR68354) and in the EPA document National Recommended Water Quality—Correction (PDF) (EPA 822-Z-99-001; April 1999; 292 K).

Is the completed document different than the draft document?

In addressing the peer reviewers' comments and the scientific issues raised by the public, revisions were made to the draft document. These revisions resulted in no changes in the saltwater criterion maximum concentration (CMC or "acute criterion") or the saltwater criterion continuous concentration (CCC or "chronic criterion"), but did result in significant changes in the freshwater criterion maximum concentration and the criterion continuous concentration.

The freshwater criterion maximum concentration 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 for a few species. Two species mean acute values were recalculated based on all applicable data rather than only giving preference to flow-through measured test results, as in the draft.

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. Therefore, hardness slopes were established to normalize all freshwater acute and chronic values to the same hardness in order to derive the criteria. These hardness slopes were revised in the completed document. The revision to the acute slope was minor, but the chronic slope revision was more significant and resulted in a less stringent criterion continuous concentration compared to the draft document. The revised criterion continuous concentration, however, is still more stringent than EPA's 1995 criterion continuous concentration.

What are the revised criteria?

criterion maximum concentration µg/L e(1.0166[ln(hardness)]-3.924)
criterion continuous concentration µg/L e(.7409[ln(hardness)]-4.719)
criterion maximum concentration µg/L 40
criterion continuous concentration µg/L 8.8

Additional Information

For additional information contact the Health and Ecological Criteria Division, US EPA, Ariel Rios Building, 1200 Pennsylvania Avenue NW, Washington, D.C. 20460; (202) 566-1100.

2001 Cadmium Criteria Document (PDF) (166 pp., 322 K)

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