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Water: Water Quality Standards Academy

Preparation for Deriving the CCC: Approach Based on Available Data

Aquatic Life Criteria

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Basic Course: Supplemental Topics

For deriving the Criterion Continuous Concentration (or Chronic Criterion), the 1985 Guidelines call for using the same procedure as the one described above to derive the CMC (or acute criterion) when sufficient data are available. That is, if chronic values are available for at least eight families with the required taxonomic diversity, the CCC is set to the fifth percentile of the Genus Mean Chronic Values (GMCVs) in the same way the FAV for the CMC is calculated from GMAVs.

Often, however, available chronic toxicity test data are insufficient to meet the guidelines’ minimum requirements—because chronic toxicity tests take longer to carry out and thus are more expensive than acute effects testing. For such situations, the 1985 Guidelines provide an alternate way to derive a chronic criterion by using ratios derived from studies in which both acute and chronic tests have been conducted simultaneously for the same species.

For informational purposes only–Not official statements of EPA policy.

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