Aquatic Life Criteria

An EPA recommended ambient water quality criterion for aquatic life or National Recommended Water Quality Criterion is the level of a pollutant or other measurable parameter that allows for protection of aquatic life in our nation's water.  These aquatic life criteria are developed under Section 304(a) of the Clean Water Act of 1972.

Water quality criteria are developed by assessing the relationship between pollutants and their effect on aquatic life. These criteria are used by states and tribes to establish water quality standards and ultimately provide a basis for controlling discharges or releases of pollutants.

An aquatic life criterion is the highest concentration of a pollutant or parameter in water that is not expected to pose a significant risk to the majority of species in a given environment.

National water quality criteria for the protection of aquatic organisms and their uses:

• Current Criteria
• Guidelines for deriving numeric criteria
• EPA Science Advisory Board activities related to Guidelines revisions
• Criteria Development Training
• Other information

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Current Criteria

• Current Criteria Table containing 304(a) aquatic life criteria for pollutants.

Guidelines for deriving numeric criteria

• Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses (1985 Guidelines) (PDF) (59 pp, 556K)
• Supporting information regarding the review of toxicity tests for evaluating the appropriateness of studies with aquatic organisms can be found in the Toxicity Test Acceptability (PDF) (13 pp, 197K)
• Revised Deletion Process for the Site-Specific Recalculation Procedure (PDF) (15 pp, 200K)
• Fact Sheet (PDF) (1 pg, 147K)

EPA Science Advisory Board activities related to Guidelines revisions

• Common Effects Methodology for Pesticides in Water and Other Environmental Media
• Contaminants of Emerging Concern, including pharmaceuticals and personal care products
• Draft Strategy: Proposed Revisions (PDF) (5 pp, 74K) (February 6, 2003)
  We established a guidelines revision workgroup to identify, evaluate, and revise the existing guidelines.

Criteria Development Training

Standards Development training page covers the purpose and basis of water quality criteria, how criteria are expressed, what different criteria types are, and how criteria is protective.

Other information

• Letter on Marine pH Criteria: EPA to Center for Biological Diversity (PDF) (4 pp, 246K) (April 15, 2010)
• Fact Sheet: Ocean Acidification and Marine pH Water Quality Criteria (April 2009)
• Federal Register Notice: Notice of Data Availability on Ocean Acidification and Marine pH Water Quality Criteria (April 15, 2009)
• Order criteria documents from National Service Center for Environmental Publications online at www.epa.gov/nscep/.

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