Water: Water Quality Standards Academy
Deriving the CMC: Step 1—Calculate the Genus Mean Acute Values
- Listing Impaired Waters and Developing TMDLs
- Monitoring & Assessment
- NPDES Permit Program
- Human Health Ambient Water Quality Criteria
- Aquatic Life Criteria
- EPA's Role
- Two Concentration-Related Criteria
- Steps in Deriving the Criteria
- Prioritizing Chemicals
- Collecting Effects Data
- Assessing Acute Effects Data
- Calculate the GMAVs
- Rank the GMAVs
- Calculate the FAV
- From FAV to CMC
- Factoring in Water Characteristics
- CCC Approach Based on Available Data
- Assessing Chronic Effects Data
- CCC Calculation of the FCV
- FCV to CCC
- Criteria Review Process
- Site-Specific Criteria
Basic Course: Supplemental Topics
Often, available verified data include multiple toxicity tests for a species. In such cases, the species data are pooled and averaged to provide a geometric mean of the species toxic concentration, or Species Mean Acute Value (SMAV).
Similarly, if data from several species in a single genus are available, the SMAVs are pooled to calculate a geometric mean of the genus toxic concentration, or Genus Mean Acute Value (GMAV).
Key Point. If data exist for only one species, the SMAV for that species becomes the GMAV.
Sample calculations of a SMAV (using short-term toxicity data) and GMAV are presented below.
|Species Mean Acute Value (SMAV)|
|Daphnia magna EC50||25 µg/L|
|Daphnia magna EC50||30 µg/L|
|Daphnia magna EC50||35 µg/L|
|Daphnia magna EC50||28 µg/L|
|SMAV =||29 µg/L|
|Genus Mean Acute Value (GMAV)|
|Daphnia magna||29 µg/L|
|Daphnia pulex||38 µg/L|
|Daphnia ambigua||42 µg/L|
|GMAV =||36 µg/L|
Note: Totals for both are rounded down.