Water: Water Quality Standards Academy
Preparation for Deriving the CCC: Assessing Chronic Effects Data
- 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
Chronic tests are performed at sub-lethal toxin concentrations and measure effects on, for instance, growth of individuals or their reproductive capability. Assessing the quality and completeness of collected data includes screening for validity based on the same criteria used on data compiled for deriving the CMC. Regarding chronic values, for example, concentrations of the test chemical should have been measured at appropriate times during the test to verify consistency of exposure.
Two effect levels are identified in chronic effects testing:
- No observed adverse effect concentration (NOAEC). The concentration at which no observable effect occurs (e.g., no statistically significant reduction in growth).
- Lowest observed adverse effect concentration (LOAEC). The lowest concentration at which effects occur (e.g., statistically significant reduction in growth).
In general, the chronic criterion is derived from the geometric mean of these two effect levels. In some cases (e.g., for ammonia), the EC20 from chronic tests—based on concentration-effect regression analyses—is used.
Illustration. View graphic showing overview of ALC derivation. Proceed to the Illustration. » (Note: This link launches a pop-up window.)