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Water: Aquatic Life

Aquatic Life Criteria

Office of Science and Technology is hosting an invited expert meeting to gather information regarding the state of the science for ecological risk assessment as it pertains to revising the 1985 Guidelines (Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses, Stephan et al. 1985) used to derive National Ambient Water Quality Criteria for the protection of aquatic life. EPA will consider information presented regarding new and alternative methods for deriving aquatic life criteria to inform revision of EPA’s existing guidance using the newest, most appropriate science available. Abstracts are being accepted from experts wishing to present.

For more information see the 2015 Invited Expert Meeting on Guidelines Revisions webpage.

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:


You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Current Criteria

Guidelines for deriving numeric criteria

EPA activities related to Aquatic Life Guidelines revision

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

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