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                      Water Qualty

           Lakes, streams, rivers, wetlands--our nation's
   waters are a national treasure. Clean water supports an  '
   incredible diversity of plant and animal life, and it is a
   source of drinking water and food that sustains human life.
   It is a valuable resource that is used for many other
   activities, such as boating and swimming.  It is also used by
   industry and for agricultural purposes. For these, and
   many more reasons, the U. S. Environmental Protection
  Agency (EPA), states*, and Indian tribes*, carry out
  programs to protect the quality of the nation's waters.
              Water Quality Standards

         Water quality standards are the foundation of
.the nation's ;surfae~e water qualify protection prpgfSni'T
 States set water quality standards for all surface waters
 within their boundaries.  Water quality standards form
; %;legal:basis foj-cpnfrojs on thsjimourit of poilutSitsJ
 entering these waters from sources such as industrial""
 facilities, wastewater treatment plants, and storm
 sewers.  They are also the technical basis for reducing
 runoff from rural and urban areas. Water quality
 standards comprise three components, each of which
 are specific to a defined body of water:

 B       The Use (such as swimming and boating)
         designated for the water body
    H       Water quality criteria, or limits on chemical
            concentrations that may be present in the wa

   H       Antidegradation Policy to protect existing w;

           This brochure focuses on the second
   component: water quality criteria.

                 Water Quality Criteria

           Many types of microscopic plants and anima
   such as plankton, water beetles, and insects that live ir
   or on the water, serve as food for small fish. Small fis
   are eaten by larger fish which, in turn, are consumed b
   even larger fish. These large fish may ultimately be
   consumed by humans.  All life along this food chain is
   dependent on the water environment and it is for this
  reason that the quality of the nation's surface waters
  must be protected.

          The Clean Water Act directs EPA to develop
  criteria for water quality that accurately reflect the late:
 . scientific knowledge about the effects of pollutants on
  aquatic life and human  health.  In developing these
  criteria, EPA examines the effects of specific pollutant;
. .on plankton, fish, shellfish, wildlife, plant life,
 ,,fesjheticj,_and,rec|eationin any body of water,. This
 includes specific information on the concentration and *
 dispersal of pollutants through biological, physical, and
-.chemical processes as well as the effects of pollutants p
 Biological communities as a wholes1"'•-'-"'•—~-~--i-^x'^-=-^&
 'The terms state and Indian tribe, as used in this brochure,
refer to the 50 states, U. S. Territories, the District of    '' '
Columbia and Indian tribes that are authorized to administer
the water quality standards program.
Criteria f"°
Aquatic f^->
Life V — -
Criteria _|

            States may use the criteria that are developed
    by EPA to help'-set water quality standards that protect
    the uses of their waters or they may develop their own
    water quality criteria.  EPA publishes human health and
    aquatic life criteria and is currently developing sediment
   1 and biological criteria. These criteria are complemen-
    tary: each is designed  to protect specific types of living
    organisms or ecological systems from the adverse
    effects of pollution.

                 Human Health Criteria
          People can potentially be exposed to water
  pollutants when they drink untreated surface water or
  eat fish, shellfish, or wildlif e that have been  ™
_.  Contaminated by pollutants in surface .waters,, To reduce-
7  'the risk to humans from these sources,""EPA; scientists  "
  research information to determine the levels at which
-.  ^^jfitphsmicals are not likely to adversely affect	
•  human3fejrth.  EPA publishes thesele%^fisrhilmair ""'
  health criteria that the states use, along with other
  information, to set allowable concentrations of
  pollutants in their water quality standards.  In this way,
  EPA and the states work together to protect people from
  exposure to harmful pollutants in surface waters.

                 Aquatic Life Criteria

         Aquatic life criteria provide protection for
 plants and animals that are found in surface waters.
 EPA develops these criteria as numeric limits on the
 amounts of chemicals that can be present in river, lake,
 or stream water without harm to aquatic life. Aquatic '

  life criteria are designed to provide protection for both
  freshwater and saltwater aquatic organisms from the
  effects of acute (short term) and chronic (long term)
  exposure to potentially harmful chemicals. Aquatic life
  criteria are based on toxicity information and are
  developed to protect aquatic organisms from death,
  slower growth, reduced reproduction, and the
  accumulation of harmful levels of toxic chemicals in
  their tissues that may adversely affect consumers of
  such organisms.

          Sediment Quality Criteria Guidance
         In a healthy aquatic community, sediments
 provide a habitat for many living organisms. Worms,
 plants, and tiny micro-organisms living in or on the  '
: sediment sustain the fish;and shellfish that, in turn,   "
 nourish larger fish, wildlife, and man.	

        .^Gontrolling fee concentration of pollutants in
 the sediment helps'to pfotecFbottom dwelling species
 and prevents harmful toxins from moving up the food
 chain and accumulating in the tissue of animals at
 progressively higher levels. This is particularly
 important at the lower levels of the food chain because
 the concentration of many pollutants may increase at
 each link in the food chain. A pollutant level in the
 sediment that does not harm snails or small fish may
bioaccumulate in the food chain and become very
harmful to larger fish, birds, mammals,  wildlife,  and

        EPA develops sediment quality criteria
  guidance on the concentrations or amounts of indrvidual
  chemicals that can be present in river, lake, or stream
  sediments and still protect sediment-dwelling organisms
  -and ultimately animals higher in the food chain-from
  the harmful effects of toxic pollutants.

                   Biological Criteria
         The water body depicted inside this brochure is
 shown in its natural condition.  It is free from the
 harmful effects of pollution, habitat loss, and other
 negative stressors.  It is characterized by a particular
, biological diversity and abundance of organisms.  This
 biological integrity-or natural structure and function of
 aquatic life-can be dramatically different in various
 types of jwater bodies in different parts of the country.
 Because of this, EPA is developing methodologies that
Jtetest&ri use to as|e?s'the biological3ntegrity of their"""
 waters  and, in so doing, set protective water quality
 standards.  These methodologies will describe scientific
 methodsJpr determining spartidxilafaquatic      ,. ":l~;f'.'
 community's health and for maintaining optimal
 conditions in various bodies of water.

               For More Information

        For information about your state's water quality
standards contact the state or Indian tribal agency
responsible for water quality. You may also contact the
U. S. Environmental Protection Agency, Office of Water,
Office of Science, and Technology, (Mail Code 4301),
Washington, D. C. 20460. Information related to water
quality standards and criteria may also be obtained by
visiting the Office of Water, Office of Science and
Technology's Home Page at: http://www.epa.gov/OST.