National Recommended Wafer Quality Criteria


Under the United States Clean Water Act (CWA)
(33 U.S.C. Sections 125 I-I 387), EPA is required to take
a number of actions to protect and restore the ecological
integrity of the Nation’s water bodies. One particular
action required under Section 304(a) of the CWA is the
development and publication of water quality criteria.
Water quality criteria are levels of individual pollutants,
water quality characteristics or descriptions of condi-
tions of a water body that, if met, should protect the des-
ignated use(s) of the water. Designated uses of a water
body are such things as: swimming, drinking water
source, fishing, fish spawning, navigation and others.
States and authorized tribes establish designated uses
for their water bodies. Water quality criteria are recom-
mended guidance that states and tribes use as part of
their water quality standards.
There are three principle categories of water quali-
ty criteria: criteria to protect human health, criteria to
protect aquatic life and criteria to protect wildlife.
Within these broad categories, there are different types
of criteria. For example, within the human health cate-
gory there are chemical-specific, microbiological and
physical criteria. Within the aquatic life category, there
are chemical-specific, toxicity, biological, sediment and
physical criteria.
Water quality criteria developed under Section
304(a) are based on data and scientific determinations
on the relationship between pollutant concentrations
and environmental and human health effects. Section
304(a) criteria do not consider social and economic
impacts nor the technological feasibility of meeting the
chemical concentration values in ambient water.
Economic and technical feasibility factors are consid-
ered by states and tribes when they adopt water quality
criteria into their water quality standards under CWA
Section 303(c) and when states, tribes, and EPA consid-
er requests for relaxing specific permit limits for regula-
tory controls. Moreover, states and tribes may consider
other scientifically-defensible approaches when they
adopt criteria into their water quality standards. These
approaches and criteria may be different from the ones
that EPA publishes under Section 304(a).

Water quality criteria are expressed in either narrative
or numeric form. Criteria may also be developed to app’y
generally within a State, or to site-specific situations.
Numeric criteria are values expressed as the amount of a
pollutant per liter of water (or levels for physical charac-
teristics). Narrative criteria are written descriptions of how
a water body and its aquatic life or habitat should be.
Narrative criteria are often expressed as “free from” and
are usually used as the basis for controlling nuisance con-
ditions such as objectionable floating debris or deposits.
States and tribes establish narrative criteria where numer-
ic criteria cannot he established or to supplement numeric
Numeric criteria are important because they provide a
proven effective tool for programs that implement the
CWA. For example, numeric criteria are often the basis for
setting National Pollutant Discharge Elimination System
(NPDES) water quality-based permit limits for point
source dischargers and for establishing a Total Maximum
Daily Load (TMDL) for a water body as a whole. Numeric
criteria are also useful non-point source pollution assess-
ment and management tools.
“The Administrator thai! develop and publish,
(and from time to time thereafter revise) criteria
for water quality accurately reflecting the latest sd-
entjfic knowledge (A) on the kind and extent of all
identUlahie effects on health and welfare including,
but not limited to, plankton, fish, shellfish, wilt/lift,
plant life, shorelines, beaches, esthetics! and recre-
ation which may he expected from the presence of
pollutants in any body qf water; including ground
water; (B) on the concentration and dispersal of
pollutants, or their byproducts, through biological,
physical, and chemical processes; and (C) on the
effects of pollutants on the biological community
divercity, productivity, and stability, including in for-
mation on the factors affecting rates of eutrophica-
tion and rates of organic and inorganic sedimenta-
tion for varying types of receiving waterc.”

Numeric criteria to protect aquatic life from toxic
chemicals are expressed as short-term and long-term
concentrations in order to reflect toxicological and real
world conditions as accurately as possible. The combi-
nation of a Criterion Maximum Concentration (CMC),
over a one-hour acute duration (a short-term average
acute limit), and a Criterion Continuous Concentration
(CCC), over a four-day chronic duration (a long-term
average chronic limit) provide protection of aquatic life
against both short and long-term effects. Recommended
averaging periods are relatively short because events
higher than the average can kill or cause substantial
damage in short periods of time.
Frequency limitations are specified in both acute
and chronic criteria. The recommended chronic criteria
or Criterion Continuous Concentration (CCC) is based
on a once in a three year period chemical concentration,
coupled with a four-day chronic averaging period, that
approximately corresponds to a once-in-ten year, seven-
day-average low flow (7Q10). The acute criteria or
Criterion Maximum Concentration (CMC) is also based
on a once in a three year period chemical concentration,
coupled with a one hour averaging period, that approxi-
mately corresponds to the historically used criterion
concentration that is expected to occur in a once-in-ten
year one-day-average low flow (1 QI 0).
Numeric criteria to protect human health are
expressed as daily concentrations that, if not exceeded,
will protect against noncancer health effects over the
course of a lifetime or against exceeding an acceptable
incremental increase in the rate incidence of cancer.
Noncancer effects that the criteria protected against may
be acute, chronic or subchronic, or health effects
depending on the basis of the Reference Dose (RID)
value. The RID is always derived to protect against the
most sensitive health endpoint measured.
This brochure contains EPA ’s most recent numeric
or narrative chemical-specific water quality criteria
designed to protect aquatic life and human health from
pollutants and physical stressors that are, or may be,
harmful when introduced into or imposed on water bod-
ies. The criteria listed in the table cover approximately
1 50 pollutants.

Office of Water
Office of Science and Technology
Health and Ecological Criteria Division (4304T)
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/tpp/ving •Scit,ut’ ( 1 1 1 ( 1 J()( I:noli’çv
to Protect Wa ler Qua! liv
Heidi Bell (202) 566-1089
Denis Borum (202) 566-1090
Luis Cruz (202) 566-1095
Charles Delos (202) 566-1097
Frank Gostomski (202) 566-1105
Tala Henry (202) 566-1323
Mary Reiley (202) 566- 1123
Treda Smith (202) 566-1128
William Swietlik (202) 566-1129
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U.S. Environmental Protection Agency
Office of Water
Office of Science and Technology
Health and Ecological Criteria Division (4303T)
1200 Pennsylvania Avenue, NW
Washington, D.C. 20460