Relationship between Water Quality Criteria and Water Quality Standards
Water Quality Standards
Water quality standards are regulations that include designated uses and water quality criteria to protect those uses. The criteria adopted and incorporated into the standards are the allowable concentrations of pollutants in State, Territory and authorized Tribal waters. These standards, which include water quality criteria, are adopted by the State, Territory or authorized Tribe and reviewed and approved or disapproved by EPA. For more information, visit EPA’s page describing water quality standards and the four components that make up water quality standards.
Water Quality Criteria
The Clean Water Act requires the U.S. Environmental Protection Agency to develop criteria for surface water quality that accurately reflect the latest scientific knowledge on the impacts of pollutants on human health and the environment. Criteria represent the conditions (e.g., concentrations of particular chemicals, levels of certain parameters) sufficient to restore and maintain the chemical, physical, and biological integrity of waterbodies and protect applicable designated uses. Water quality criteria may be expressed as numeric values (e.g., pollutant concentrations, biological metrics) or as narrative statements (e.g., descriptions of desired biological condition) depending on the pollutant, designated use, and available data. Water quality criteria fall into several categories—aquatic life, biological, human health, and recreational—each tailored to protect specific uses of surface waters. These criteria are complementary: each is designed to protect specific types of living organisms or ecological systems from the adverse effects of pollution. EPA has developed national recommended criteria for many pollutants; states, territories, and authorized Tribes may adopt EPA’s values or establish their own scientifically supported criteria in their water quality standards.