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Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses

EPA currently uses a series of guidelines established in 1985 to derive ambient water quality criteria (AWQC) for aquatic life. The guidelines address acute risk (short-term effects such as survival and growth) and chronic risk (longer term effects such as reproduction) for traditional pollutants.

EPA's 1985 Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses describe an objective, internally consistent, appropriate, and feasible way of deriving national criteria for the protection of aquatic ecosystems. The derivation of numerical national water quality criteria for the protection of aquatic organism and their uses is a complex process that uses information from many areas of aquatic toxicology.

After a decision is made that a national criterion is needed for a particular material, all available information concerning toxicity to, and bioaccumulation by, aquatic organisms is collected, reviewed for acceptability, and sorted. If a thorough review of the pertinent information indicates that enough acceptable data are available, numerical national water quality criteria are derived for fresh water or salt water or both to protect aquatic organisms and their uses from unacceptable effects due to exposures to high concentrations for short periods of time, lower concentrations for longer periods of time, and combinations of the two.

In 2013, EPA published a revision to one of its recommended procedures for deriving site-specific water quality criteria for the protection of aquatic life. The Revised Deletion Process for the Site-Specific Recalculation Procedure for Aquatic Life Criteria is intended to provide flexibility to States to tailor criteria development to reflect the aquatic community at a given site.

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