United States Office of Water
Environmental Protection Agency 4304
EPA-822-F-00-005
October 2000
Revised Methodology for Deriving Health-Based
Ambient Water Quality Criteria (2000)
Abstract
The U.S. Environmental Protection Agency is publishing revisions to the 1980 Ambient
Water Quality Criteria National Guidelines to better protect human health. The 1980
Ambient Water Quality Criteria National Guidelines outline the methodology used by states
and tribes to develop human health water quality criteria. Revisions to the 1980 guidelines
incorporate significant scientific advances in key areas such as cancer and non-cancer risk
assessments, exposure assessments, and bioaccumulation in fish. The revised
methodology will provide more flexibility for decision-making at the state, tribal and EPA
regional levels. It is most likely that the methodology will result in more stringent criteria for
bioaccumulatives and generally similar values of nonbioaccumulatives.
Human Health Water Quality Criteria
Human health ambient water quality criteria
(AWQC) are numeric values limiting the amount
of chemicals present in our nation's waters.
Human health cntena are developed under
Section 304(a) of the Clean Water Act of 1972
and are designed to protect human health. Water
quality criteria are developed by assessing the
relationship between pollutants and their effect
on human health and the environment. These
criteria are used by states and Indian tribes to
establish water quality standards and ultimately
provide a basis for controlling discharges or
releases of pollutants.
The Clean Water Act (CWA) requires EPA to
develop, publish and revise ambient water quality
criteria (AWQC). In 1980, EPA published
AWQC for 64 pollutants/pollutant classes and
provided a methodology for deriving the criteria.
These national guidelines addressed three types
of endpoints: noncancer, cancer and organoleptic
(taste and odor) effects.
The states and tribes use these cntena to develop
water quality standards for each water body. EPA
is required to review periodically cntena adopted
by states and tnbes. The revisions to the EPA's
1980 methodology will help states and tnbes
establish water quality cntena and standards that
protect human health.. They provide detailed
means for developing water quality cntena,
including systematic procedures for evaluating
cancer risk, noncancer health effects, human
exposure, and bioaccumulation potential in fish.
EPA Methodology for Deriving Criteria
States and tribes must develop water quality
standards that include designated uses and water
quality critena necessary to support those uses.
The Methodology is the guidance for states and
tnbes to help them establish water quality critena
and standards to protect human health. It
provides detailed means for developing the water
quality cntena, including systematic procedures
for evaluating cancer nsk, noncancer health
effects, human exposure, and bioaccumulation
potential in fish.
Risk assessment practices have evolved
significantly since 1980, particularly in the areas
of cancer and noncancer nsk assessments (with
new information, procedures, and numerous
published Agency guidelines), exposure
assessments (with new studies on human intake
and exposure patterns, and new science policy
guidelines) and methodologies on accounting for
bioaccumulation in fish.
General Background of the Revision Process
Revisions began with a national workshop in
1992, where participants discussed critical issues.
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Based on individual expertise, attendees were
assigned to technical workgroups including
cancer risk, noncancer risk, exposure, and
bioaccumulation m fish.
EPA submitted recommendations from the
workshop for review and comment by the EPA
Science Advisory Board. EPA created a
workgroup in 1994, including program office and
regional participants, to revise the methodology.
Numerous stakeholder participation activities
were conducted between 1995 and 1998,
including presentations to the Federal-State
Toxicology and Risk Analysis Committee and
several multi-regional water quality coordmators
meetings in 1996 and 1997, which included
participants from EPA regions, states, tribes and
some industry.
Following publication of the draft Methodology
revisions, written public comments were
accepted. Further presentations included the
1998 Annual Meeting of the Society For Risk
Analysis and the 1999 Annual Meeting of the
Society of Toxicology. In May 1999, a peer
review workshop was held. A public stakeholders
meeting was also held then. EPA received
extensive input on the Methodology from each of
these groups. EPA considered all comments and
incorporated a substantial portion of them into
the final AWQC Methodology Revisions.
Major Methodology Revisions
Publication of final revisions satisfies the
requirements of the CWA that EPA periodically
revise criteria for water quality to reflect
accurately the latest scientific knowledge on the
kind and extent of all identifiable effects on
health and welfare that may be expected from the
presence of pollutants in any body of water.
These Final AWQC Methodology Revisions to
the 1980 AWQC National Guidelines are
necessitated by the many significant scientific
advances made during the past 20 years in the
key areas of cancer and noncancer assessments,
exposure assessments, and bioaccumulation in
fish.
The major revisions are in four assessment areas:
cancer, non-cancer, exposure, and
bioaccumulation.
Recommend more sophisticated methods to
comprehensively determine the likely
mechanism of human carcinogenic ity.
Recommend a mode of action (MOA)
approach to determine the most appropriate
low-dose extrapolation for carcinogenic
agents.
For noncarcinogens:
Use EPA guidance on assessing
noncarcinogenic effects of chemicals and for
the Reference Dose (RfD) derivation.
Recommend consideration of other issues
related to the RID process including:
integrating reproductive/ developmental,
unmunotoxicity, and neurotoxicity data into
the calculation.
Recommend the use of quantitative dose-
response modelling for the derivation of
RiDs. -
Provide guidance for states and tribes on the
use of an alternative value from the RID
point estimate, within a limited range, to
reflect the inherent imprecision of the RID.
For exposure assessment:
Encourage states and tribes to use local
studies on fish consumption that better
reflect local intake patterns and choices.
Recommend default fish consumption
values for the general population,
recreational fishers and subsistence fishers.
Account for other sources of exposure, such
as food and air, when deriving AWQC for
noncarcinogens and nonlinear carcinogens.
For bioaccumulation:
Focus on the use of bioaccumulation factors
(BAFs), instead of bioconcentration factors
(BCFs) for estimating potential human
exposure to contaminants via the
consumption of contaminated fish and
shellfish.
Use high quality field data over laboratory
or model-derived estimates for deriving
BAFs, since field data best reflect factors
which can affect the extent of
For carcinogen (cancer) risk assessment:
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bioaccumlation (e.g., chemical metabolism,
food web structure).
EPA does not plan to completely revise all of the
criteria developed in 1980 or those updated as
part of the 1992 National Toxics Rule. Partial
updates of all cntena may be necessary. EPA
will continue to develop and update toxicology
and exposure data needed in the derivation of
AWQC that may be impractical for the states and
regions to obtain.
Methodology Revisions Implementation by
EPA/States
EPAs future role in developing AWQC for the
protection of human health will include:
The development of revised cntena for
chemicals of high priority and national
importance (including, but not limited to,
chemicals that bioaccumulate, such as
PCBs, dioxin, and mercury).
The development or revision of AWQC for
some additional priority chemicals.
Techmcal assistance to states and tribes on
the toxicology, exposure and
bioaccumulation methods, and review of
state/tribal water quality standards.
EPA encourages states and tribes to use the
revised methodology to develop or revise AWQC
to reflect local conditions appropnately. EPA
believes that AWQC inherently require several
risk management decisions that are, in many
cases, better made at the state and regional level
(e.g., fish consumption rates, target risk levels).
Effect on State and EPA Regional Offices
The revised methodology will provide more
flexibility for decision-making at state, tribal and
EPA regional levels. EPA believes the AWQC
require several risk management decisions that
are often better made at the state, tribal and
regional level. The methodology will probably
result in more stringent criteria for
bioaccumulatives (due to the use of BAFs instead
of BCFs) and generally similar, or less stringent,
values of nonbioaccumulatives.
Information
For additional information concerning these
recommended methodology revisions, contact
Denis R. Borum, Health and Ecological Cntena
Division (4304), Office of Science and
Technology, U.S. Environmental Protection
Agency, 1200 Pennsylvania Ave., N.W.,
Washington, D.C., 20460 (telephone: 202- 260-
8996).
You may view the Federal Register (FR) Notice
and the AWQC Methodology revisions on the
Internet at:
http ://www.epa.gov/waterscience/humanhealth.
The FR Notice explains how to obtain additional
information and how to review the complete
administrative record for these Methodology
revisions.
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