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Water: Water Quality Standards Academy

Getting Started: Prioritizing Chemicals for Criteria Development

Aquatic Life Criteria

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Basic Course: Supplemental Topics


EPA follows an established, risk-based process for determining which chemicals should be given priority for developing aquatic life criteria. The process involves identifying candidate chemicals, assessing the availability of data, and then ranking the chemicals based on risk. Essentially the same process is used for selecting chemicals with criteria that are due for reevaluation.

To identify candidate chemicals, the Agency solicits and reviews suggestions from EPA Regions, States, Tribes, and stakeholders. EPA then compiles a list of chemicals that have been proposed by two or more of these submitters.

Next, EPA narrows down the list based on the availability of toxicity data. At a minimum, the 1985 Guidelines call for acute data on eight families and chronic data on three species (i.e., for chronic, at least need acute-chronic studies from which the chronic criterion can be derived as a ratio of the final acute value).

The chemicals with the necessary data are then scored and ranked according to risk based on:

  • Occurrence. Frequency at which a chemical is found in ambient water and/or fish tissue.
  • Toxicity. Relative potential to have an adverse effect on aquatic life.

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

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