EPA Protocol for the Review
of Existing National Primary
Drinking Water Regulations
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Office of Water
Office of Ground Water and Drinking Water (4607M)
EPA815-R-03-002
www.epa.gov/safewater
June 2003
Printed on Recycled Paper
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EPA815-R-03-002
EPA Protocol for the Review of
Existing National Primary Drinking Water Regulations
June 2003
United States Environmental Protection Agency
Office of Water
Office of Ground Water and Drinking Water
Standards and Risk Management Division
Targeting and Analysis Branch
1200 Pennsylvania Avenue, NW (4607M)
Washington, DC 20460
Protocol for the Review ofNPD WRs 11 June 2003
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Acknowledgments
This document was prepared in support of the 1996-2002 Six-Year Review of Existing National
Primary Drinking Water Regulations (NPDWRs) for EPA's Office of Ground Water and
Drinking Water with James Taft as Targeting and Analysis Branch Chief during the course of the
review. Judy Lebowich served as EPA co-team lead for the Six-Year Review and as the Work
Assignment Manager for the development of this document. At different times throughout the
process, Marc Parrotta and Wynne Miller have also served as co-team leads for the project. The
Six-Year Review Work Group consists of representatives of the Office of Ground Water and
Drinking Water, the Office of Science and Technology, the Office of General Counsel, the
Office of Pesticide Programs, the Office of Research and Development, the Office of Policy,
Economics and Innovation, the Office of Solid Waste and Emergency Response, and EPA
Regions I, V, VII, IX, and X. Work Group members provided technical guidance throughout.
The National Drinking Water Advisory Council (NDWAC) and many stakeholders provided
valuable advice to improve the review process and this document. The Cadmus Group, Inc.,
served as the prime contractor for developing this document.
Protocol for the Review ofNPD WRs 111 June 2003
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TABLE OF CONTENTS
List of Acronyms and Abbreviations vi
EXECUTIVE SUMMARY viii
SECTION I: INTRODUCTION 1
A. What Is the Purpose of the Six-Year Review? 1
B. What Is the Purpose of This Protocol? 1
C. What Information Will I Find In This Document? 2
SECTION II: OVERVIEW OF THE
SIX-YEAR REVIEW PROCESS 5
A. What Basic Principles Did EPA Follow During this Review? 5
B. What Types of Analyses Did EPA Conduct? 6
1. Initial Technical Review 6
2. In-Depth Technical Analysis 7
C. What Types of Regulatory Revisions Did EPA Consider? 10
1. Changes toMCLGs 10
2. Changes to MCLs 11
3. Changes to Treatment Technique Requirements 11
4. Changes to Other Treatment Technology 12
5. Changes to Other Regulatory Revisions 12
SECTION III: DETAILED DISCUSSION OF
THE SIX-YEAR REVIEW PROCESS 15
A. Health risk assessments 15
1. What Were the Objectives of the Health Effects Review? 15
2. How Did EPA Review Health Effects Data for Chemical Contaminants? 15
3. How Did EPA Review Health Effects Data for Microbiological NPDWRs? 18
B. Technology Assessments 19
1. What Were the Objectives of the Technology Assessments? 19
2. How Did EPA Review Analytical Methods? 19
3. How Did EPA Review Treatment Technologies? 21
C. Other Regulatory Revisions 22
1. What Was the Objective of the Review of Other Regulatory Revisions? 22
2. How Did EPA Consider Other Regulatory Revisions? 22
D. Occurrence and Exposure Analysis 23
1. What Were the Objectives of the Occurrence and Exposure Analysis? 23
2. How Did EPA Conduct the Occurrence and Exposure Analysis? 23
E. Consideration of Economic Factors 24
1. What Were the Objectives of EPA's Evaluation of Economic Impacts? 24
2. How Did EPA Consider Economic Impacts? 25
Protocol for the Review ofNPD WRs IV June 2003
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TABLE OF CONTENTS, continued...
SECTION IV: STAKEHOLDER INVOLVEMENT 27
A. Who Were the Key Stakeholders in the Six-Year Review Process? 27
B. How Were Stakeholders Involved in the Six-Year Review Process? 27
C. How Did EPA Plan to Involve the Science Advisory Board? 28
REFERENCES 29
APPENDICES 33
Appendix A: List of Pre-1997 National Primary Drinking
Water Regulations (NPDWRs) A-l
Appendix B: Differences between the National Drinking Water Advisory Committee's
(NDWAC's) Recommendations and this Protocol B-l
Appendix C: Overview of the IRIS Assessments C-l
Appendix D: Overview of the OPP Process for Toxicity Assessments D-l
Appendix E: Overview of the Analytical Methods Review Process E-l
LIST OF FIGURES
Figure 1: Overview of the Protocol and Making the Revise/Not Revise Decision 9
Protocol for the Review ofNPD WRs V June 2003
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List of Acronyms and Abbreviations
ASTM
ATP
ASDWA
ATSDR
AWWA
BAT
BMP
CFR
CMR
EPA
FACA
FIFRA
FQPA
FR
IRED
IRIS
LOAEL
MCL
MCLG
MDL
mL
MOE
NAS
NDWAC
NERL
American Society for Testing and Materials
Alternate test procedure
Association of State Drinking Water Administrators
Agency for Toxic Substances and Disease Registry
American Water Works Association
Best available technology
Best management practice
Code of Federal Regulations
Chemical Monitoring Reform
U.S. Environmental Protection Agency
Federal Advisory Committees Act
Federal Insecticide, Fungicide, and Rodenticide Act
Food Quality Protection Act
Federal Register
Interim reregi strati on eligibility decision
Integrated Risk Information System
Lowest-observed-adverse-effect level
Maximum contaminant level
Maximum contaminant level goal
Method detection limit
milliliters
Margin of exposure
National Academy of Sciences
National Drinking Water Advisory Council
National Exposure Research Laboratory
Protocol for the Review ofNPDWRs
VI
June 2003
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List of Acronyms and Abbreviations
NIST
NOAEL
NPDWR
OGWDW
OPP
OW
PAD
PE
PQL
PT
PWS
RED
RfD
RSC
SAB
SDWA
SM
TCR
TT
WS
National Institute of Standards and Technology
No-observed-adverse-effect level
National Primary Drinking Water Regulation
Office of Ground Water and Drinking Water
Office of Pesticide Programs
Office of Water
Population adjusted dose (aPAD - acute; cPAD - chronic)
Performance evaluation
Practical quantitation level
Proficiency testing
Public water system
Reregi strati on eligibility decision
Reference dose (aRfD - acute RfD; cRfD - chronic RfD)
Relative source contribution
Science Advisory Board
Safe Drinking Water Act
Standard methods
Total Coliform Rule
Treatment technique
Water supply
Protocol for the Review ofNPDWRs
Vll
June 2003
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EPA Protocol for the
Review of Existing National Primary
Drinking Water Regulations
EXECUTIVE SUMMARY
The Safe Drinking Water Act (SDWA), as amended in 1996, requires that the U.S.
Environmental Protection Agency (EPA) review existing National Primary Drinking Water
Regulations (NPDWRs) no less often than every six years and, if appropriate, revise them. This
document describes the systematic approach that EPA used to review 68 chemical NPDWRs and
the Total Coliform Rule (TCR) which were promulgated prior to the 1996 Amendments. The
statutory deadline for completing this review was August 2002. EPA developed this document
based on recommendations of the National Drinking Water Advisory Council (NDWAC),
through internal Agency deliberations, and discussions with the diverse stakeholders involved in
drinking water and its protection.
As long as an NPDWR revision maintains or provides for the same or greater protection of
public health, the SDWA 1996 Amendments give the Administrator discretion to determine if
revision is appropriate. In order to determine that a revision is appropriate, EPA believes the
revision must continue to meet the basic statutory requirements of the SDWA and present
meaningful opportunities to improve the level of public health protection and/or to achieve cost-
savings while maintaining, or improving, the level of public health protection.
EPA applied the following basic principles to the review process:
The Agency assumed health effects, analytical feasibility, treatment data, and analyses
underlying existing regulations remain adequate and relevant, except in those instances
where reliable, peer-reviewed, new data were available that indicated a need to re-
evaluate an NPDWR (e.g., where a change in health risk assessment has occurred).
If new data were available, EPA determined whether changes in existing standards were
warranted. For example, in determining whether there was a change in analytical
feasibility, the Agency applied the current policy and procedures for calculating the
practical quantitation level for drinking water contaminants.
EPA was unable to complete evaluation of certain new data within the time available for
the review. For example, if a new health risk assessment for a contaminant was not
completed during the review cycle, EPA generally made a "not revise" decision on the
rationale that it was not appropriate to revise the regulation while the assessment was
ongoing. When an updated assessment is completed, EPA will review the update and
any new conclusions or additional information associated with the contaminant during
the next review cycle. The Agency may make a determination to review a particular
NPDWR before August 2008 where a compelling reason exists to revisit the "not revise"
decision sooner.
Protocol for the Review ofNPD WRs Vlll June 2003
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During the review, EPA identified areas where information was inadequate or
unavailable ("data gaps") and is needed before an NPDWR may be considered as a
candidate for revision. If EPA was unable to fill such gaps during the review process, the
Agency provided information about the data gaps to the appropriate Agency group(s) for
consideration and prioritization. The results of further research or data gathering, if any,
will be considered as part of a subsequent review.
During the review process, the Agency did not consider potential regulatory revisions
that were already the subject of other rulemaking activities.
EPA applied the Agency's peer review policy (USEPA, 2000e), where appropriate, to any
new analyses.
To most efficiently utilize limited resources and assure continued public health protection,
the Agency conducted the review in two phases: (1) an initial technical review of all 69
NPDWRs (see Appendix A for a list); and (2) an in-depth technical evaluation of those
NPDWRs identified during the initial review as potential candidates for revision. The key
elements of the review included: health effects, technology assessment (i.e., analytical and
treatment feasibility), and consideration of other regulatory requirements (e.g., monitoring). If
the Agency identified a potential health or technological basis for a revision during the initial
screening, EPA also conducted occurrence and exposure analyses and evaluated available
economic information as a part of the in-depth review.
Based on the results of comprehensive analyses, EPA identified those NPDWRs that
remained appropriate at the completion of the 1996-2002 review cycle, and those NPDWRs that
may be appropriate for revision. The Agency published its preliminary determinations and its
protocol for the review in the April 17, 2002, Federal Register to seek comment from the public
(67 FR 19030 (USEPA, 2002d)). EPA received comments from 44 commenters on these
preliminary determinations. These comments, along with other new information received since
April 2002, have been considered as a part of the current revise/not revise decisions.
Protocol for the Review ofNPD WRs IX June 2003
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EPA Protocol for the
Review of Existing National Primary
Drinking Water Regulations
SECTION I: INTRODUCTION
A. What Is the Purpose of the Six-Year Review?
Under the Safe Drinking Water Act (SDWA), as amended in 1996, the U.S. Environmental
Protection Agency (EPA) must periodically review existing National Primary Drinking Water
Regulations (NPDWRs) and, if appropriate, revise them. Section 1412(b)(9) of SDWA, states:
The Administrator shall, not less often than every 6 years, review and revise, as
appropriate, each national primary drinking water regulation promulgated under
this title. Any revision of a national primary drinking water regulation shall be
promulgated in accordance with this section, except that each revision shall
maintain, or provide for greater, protection of the health of persons.
Prior to the 1996 Amendments, the SDWA required EPA to review NPDWRs at least every
three years to determine whether any changes in technology, treatment techniques (TTs) or other
means might provide better health protection. EPA was required to publish its findings in the
Federal Register and provide an explanation, after opportunity for public comment, of any
finding that such new technology, TT, or other means would not be feasible. Although the
Agency did revise existing NPDWRs on occasion when new data became available, EPA did not
have a systematic process for reviewing NPDWRs on a regular basis.
B. What Is the Purpose of This Protocol?
This protocol defines the systematic process EPA used to review most of the NPDWRs1
promulgated prior to the 1996 Amendments during the 1996-2002 review cycle. Although this
document is specific to the initial review under the 1996 SDWA Amendments, the Agency plans
to adopt a similar approach, modified as appropriate and with stakeholder involvement, for
subsequent review cycles.
EPA presented its initial ideas for the regulatory review protocol at a stakeholder meeting in
November 1999. Based on the comments made at that meeting, EPA revised the draft protocol.
Among other changes, the revised draft clarified the role of research in the process and expanded
the discussion of the potential need to review/revise an NPDWR. The Agency provided its
1 Several NPDWRs promulgated prior to 1997 have been the subject of recent rulemaking or are the
subject of ongoing rulemaking activity. The review of these NPDWRs has been incorporated into those rulemaking
activities. Appendix A identifies each of the pre-1997 NPDWRs and indicates whether it is being reviewed in
accordance with this protocol or whether it has been or will be reviewed as a part of a separate rulemaking activity.
Protocol for the Review ofNPD WRs 1 June 2003
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revised draft to a National Drinking Water Advisory Council (NDWAC) Working Group2 that
met during the Summer of 2000 to develop recommendations regarding the protocol process.
The NDWAC Working Group submitted their recommendations to the full NDWAC in
November 2000, which approved the recommended guidance and presented it to the Agency
(NDWAC, 2000). EPA incorporated the majority of the NDWAC's recommendations into this
document. In a few cases, however, EPA either decided not to incorporate a NDWAC
recommendation, or to revise it, because of practical considerations and/or resource constraints.
Appendix B contains a summary of those NDWAC recommendations that were not incorporated
or that were substantially revised.
The systematic planning process used to develop this protocol satisfies the Agency's quality
assurance requirements (USEPA, 2002b). The process described in this protocol addresses
critical aspects of health protection and the setting of standards under the SDWA. In addition,
this protocol allows for the fact that numerous types of regulatory changes may be considered
and therefore, contains an element of flexibility to allow EPA the opportunity to consider a range
of possible issues. The review process described in this protocol document culminated with
decisions of whether or not to revise each of the reviewed NPDWRs.
EPA requested public comments on its protocol in the April 17, 2002, Federal Register. In
response to these protocol-related comments, the Agency has revised this document to better
explain how occurrence and exposure, and economic considerations have been factored into the
decision process.
The publication of a decision to revise pursuant to a section 1412(b)(9) review is not the end
of the regulatory process, but is the beginning of one. A decision to revise starts a regulatory
process for a contaminant that involves more detailed analyses concerning health effects, costs,
benefits, occurrence, and other matters relevant to deciding whether and how an NPDWR should
be revised. At any point in this process, EPA may find that regulatory revisions are no longer
appropriate and may discontinue regulatory revision efforts at that time. Review of that
NPDWR would continue in future Six-Year Reviews.
Similarly, a decision "not to revise at this time" means only that EPA does not believe that
regulatory changes to a particular NPDWR are appropriate due to: a lack of new data, ongoing
scientific reviews, low priority, or other reasons discussed in this document. Reviews of these
contaminants continue and future Six-Year Reviews may lead to a decision that regulatory
changes are appropriate.
C. What Information Will I Find In This Document?
This protocol is divided into three remaining sections as follows:
Section II: Overview of the Six-Year Review Process provides a summary of the
review process. It discusses how potential candidates for regulatory revision were
2 The NDWAC Working Group and the Ml NDWAC operate in accordance with the provisions of the
Federal Advisory Committees Act (FACA). All meetings are announced in the Federal Register and members of the
public are welcome to attend as observers.
Protocol for the Review ofNPD WRs 2 June 2003
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identified; how this list was refined to nominate NPDWR(s) for revision; and the
potential types of regulatory decisions that EPA considered.
Section III: Detailed Discussion of the Review Process provides an in-depth
discussion of each of the analyses that were conducted (i.e., health effects, analytical and
technology assessments, consideration of other regulatory revisions, occurrence and
exposure, and evaluation of available economic information), and how these analyses
interrelate.
Section IV: Stakeholder Involvement discusses how EPA involved the public during
the Six-Year Review process.
This protocol also contains five appendices as described below:
Appendix A: List of pre-1997 National Primary Drinking Water Regulations
(NPDWRs) identifies each of pre-1997 NPDWRs and indicates whether it was being
reviewed in accordance with this protocol or whether it has been/will be reviewed as a
part of a separate rulemaking activity.
Appendix B: Differences between the National Drinking Water Advisory Council's
(NDWAC's) Recommendations and this Protocol summarizes the NDWAC
recommendations that EPA either modified or did not include in this protocol.
Appendix C: Overview of the IRIS Assessments provides a discussion of how EPA
conducts its Integrated Risk Information System (IRIS) health assessments.
Appendix D: Overview of the OPP Process for Toxicity Assessments contains a
discussion of the Office of Pesticide Programs (OPP) process for conducting toxicity
assessments.
Appendix E: Overview of the Analytical Methods Review Process describes EPA's
process for approving new analytical methods for chemical drinking water contaminants
and how the Agency has derived practical quantitation levels in the past.
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Protocol for the Review ofNPD WRs 4 June 2003
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SECTION II: OVERVIEW OF THE
SIX-YEAR REVIEW PROCESS
This section provides an overview of the review process. It contains a discussion of the basic
principles that EPA followed during the review, the types of analyses that EPA conducted, and
the types of regulatory revisions that EPA considered. Figure 1 in this section provides a
graphical overview of the review process. A more detailed discussion of each of the analyses,
that were conducted under the review, is provided in section III.
A. What Basic Principles Did EPA Follow During this Review?
EPA's primary goal was to identify and prioritize candidates for regulatory revision in order
to target those revisions that are most likely to result in a meaningful opportunity for health risk
reduction and/or result in a meaningful opportunity for cost-savings while maintaining the level
of public health protection. In conducting the review, EPA applied the following basic
principles:
The Agency assumed that health effects, occurrence, analytical feasibility, treatment data,
and analyses underlying existing regulations remain adequate and relevant, except in
those instances where reliable, peer-reviewed3, new data were available that indicated a
need to re-evaluate an NPDWR (e.g., where a change in health risk assessment has
occurred).
If new data were available, EPA determined whether changes in existing standards were
warranted. For example, in determining whether there was a change in analytical
feasibility, the Agency applied the current policy and procedures for calculating the
practical quantitation level for drinking water contaminants.4
EPA generally made a "not revise at this time" decision for those NPDWRs whenever
evaluation of certain new data could not be completed within the time available for the
review. For example, if a new health risk assessment for a contaminant was not
completed during the review cycle, EPA made a "not revise at this time" decision on the
rationale that it was not appropriate to revise the regulation while the assessment was
ongoing. When an updated assessment is completed, EPA will review the update and
3 "Peer review" is a documented critical review of a specific major scientific and/or technical work product.
The peer review is conducted by qualified individuals (or organizations) who are independent of those who
performed the work, but who are collectively equivalent in technical expertise (i.e., peers) to those who performed
the original work. The peer review is conducted to ensure that activities are technically adequate, competently
performed, properly documented, and satisfy established quality requirements. The peer review is an in-depth
assessment of the assumptions, calculation, extrapolations, alternate interpretations, methodology, acceptance
criteria, and conclusions pertaining to the specific major scientific and/or technical work product and of the
documentation that supports them.
4 EPA establishes a practical quantitation level to estimate the level at which laboratories can routinely
measure a chemical contaminant in drinking water. See: 50 FR 46902, November 13, 1985 (USEPA, 1985); 52 FR
25690, July 8, 1987 (USEPA, 1987); 54 FR 22062, May 22, 1989 (USEPA, 1989a).
Protocol for the Review ofNPD WRs 5 June 2003
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any new conclusions or additional information associated with the contaminant during
the next review cycle. The Agency may make a determination to review a particular
NPDWR before August 2008 where a compelling reason exists to revisit the "not revise"
decision sooner.
During the review, EPA identified areas where information was inadequate or
unavailable ("data gaps") and is needed before an NPDWR may be considered as a
candidate for revision. Where EPA was unable to fill such gaps during the review
process, the Agency has provided information about the data gaps to the appropriate
Agency group(s) for consideration and prioritization so that further research and data
collection can be considered as part of a subsequent review cycle.
During the review process, the Agency did not consider potential regulatory revisions
that were already the subject of other periodic rulemaking activities.
EPA applied the Agency's peer review policy, where appropriate, to any new analyses
(USEPA, 2000e).
B. What Types of Analyses Did EPA Conduct?
To most efficiently utilize limited resources and assure continued public health protection,
the Agency conducted the review in two phases: (1) an initial technical review of all 69
NPDWRs included in this Six-Year Review (see Appendix A for a list); and (2) an in-depth
technical evaluation of those NPDWRs identified during the initial review as potential
candidates for revision. Figure 1, at the end of this section, illustrates the Six-Year Review
process.
1. Initial Technical Review
The initial review phase included these three screening and general evaluation steps:
Health effects review. The purpose of the health effects review was to identify NPDWRs
for which the Agency has revised health risk assessments that indicate possible changes
to the maximum contaminant level goal (MCLG) and perhaps to the maximum
contaminant level (MCL);
Current technology review. The purpose of the current technology review was to identify
NPDWRs where improvements in analytical or treatment feasibility might allow the
MCL to be established closer to the MCLQ or where adjustments in TT requirements
might be appropriate; and/or
Other regulatory revisions review. The purpose of the other regulatory revisions review
was to identify where adjustments to implementation aspects of NPDWRs (e.g., system
monitoring and reporting requirements) might be appropriate, and where such changes
were not already being addressed, or had not been addressed, through alternative
mechanisms such as a recent or ongoing rulemaking.
EPA primarily performed these reviews independently. Once the results of the individual
reviews were available, the Agency integrated the results to determine whether a potential health
or technological basis existed to support a regulatory revision. For the purposes of the Six-Year
Protocol for the Review ofNPD WRs 6 June 2003
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Review, EPA considered a potential health basis to exist if the results of the health effects review
indicated that a possible basis existed for revising the MCLG and, if appropriate, the MCL. EPA
considered a potential technological basis to exist if the results of the current technology review
and/or the results of the other regulatory revisions review provided a possible basis for revising
the MCL, TT, and/or other regulatory requirements.
EPA generally determined after the initial review that an NPDWR was not a candidate for
revision at that time, if a health risk assessment was in process or had been initiated as a result of
the review. The Agency made this determination because EPA does not believe it is appropriate
to revise an NPDWR while a health risk assessment is underway. EPA also determined, after the
initial review, that an NPDWR was not a candidate for revision at that time if none of the initial
screening analyses identified a basis for a potential regulatory revision.
2. In-Depth Technical Analysis
The Agency subjected the remaining NPDWRs to more in-depth technical analyses. If the
results of the initial review indicated a possible revision to the MCLG/MCL, EPA further
considered health and technology factors that might affect the development of a revised standard
(e.g., revisions to the MCLG, MCL, or TT requirements, and/or revisions to other regulatory
revisions such as system monitoring and reporting requirements).
For the chemical NPDWRs, if the outcome of these analyses indicated that a regulatory
revision might be appropriate, the Agency also estimated potential occurrence and exposure at
public water systems (PWSs). The Agency used the results of the other analyses to determine
the contaminant concentrations that would be used in the occurrence and exposure analyses (i.e.,
the levels of regulatory interest). EPA also conducted a qualitative economic evaluation, which
was primarily based on available occurrence and exposure data. The Agency used the results of
these analyses to determine whether, in the Agency's judgement, an opportunity existed for
meaningful health risk reduction and/or meaningful cost savings to PWSs and their customers
without lessening the level of public health protection.
If EPA identified data gaps that could not be filled during the current review cycle, the
Agency did not conduct some or all of the remaining analyses. Although, Figure 1, on page 8
shows the identification of data gaps as the final step in the review; in some instances, data gaps
were identified during earlier steps in the process. If the Agency identified data gaps, EPA
determined that a revision to the NPDWR was not appropriate during the current review.
Based on the results of comprehensive analyses, EPA identified those NPDWRs that
remained appropriate at the completion of the 1996-2002 review cycle, and those NPDWRs that
may be appropriate for revision. If the Agency decided that it was not appropriate to revise an
NPDWR during the 1996-2002 review cycle, that decision was based on one of the following
reasons.
Health risk assessment in process: At the time the review was completed, the Agency
was conducting, or had scheduled, a detailed review of current health effects information.
Because the results of the assessment were not available at the time the review was
completed, the Agency did not believe it was appropriate to revise the NPDWR at that
time. In these cases, EPA will consider the results of the updated health risk assessment
during the 2002-2008 review cycle. However, if the results of the health risk assessment
Protocol for the Review ofNPD WRs 7 June 2003
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indicate a compelling reason to reconsider the MCLQ EPA may decide to accelerate the
review schedule for that contaminant's NPDWR.
NPDWR remained appropriate after data/information review. The outcome of the
review indicated that the current regulatory requirements remained appropriate and,
therefore, no regulatory revisions were warranted. Any new information available to the
Agency either supported the current regulatory requirements or did not justify a revision.
New information but no revision appropriate at the completion of the review because:
Low priority: In EPA's judgment, any resulting revisions to the NPDWR would not
provide a meaningful opportunity for health risk reduction or result in meaningful
cost-savings to PWSs and their customers.5 EPA considers these revisions to be a
low priority activity for the Agency and, thus, "not appropriate" for revision "at this
time" because of one or more of the following considerations: competing workload
priorities; the administrative costs associated with rulemaking; and the burden on
States and the regulated community to implement any regulatory change that resulted.
Information gaps: Although results of the review support consideration of a possible
revision, the available data were insufficient to support a definitive regulatory
decision.
EPA published its preliminary determinations and its protocol for the review in the April 17,
2002, Federal Register in order to seek comment from the public. EPA received comments from
44 commenters on these preliminary determinations. These comments, along with other new
information received since April 2002, have been considered as a part of the current revise/not
revise decisions.
5 EPA conducted occurrence and exposure analyses to help in determining whether a revision was a
priority for the Agency. For example, the Agency estimated occurrence and exposure to a contaminant at
concentrations between the current MCL and any possible MCL to help determine whether there was likely to be a
meaningful opportunity for health risk reduction or cost-savings to PWSs and their customers, if EPA were to revise
the MCL.
Protocol for the Review ofNPD WRs 8 June 2003
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Figure 1: Overview of the Protocol and Making the Revise/Not Revise Decision
NPDWRs under review
Initial Technical Review
Health Effects, Methods and Treatment
Feasibility, and Other Regulatory
Revisions
Is a health risk assessment
in process/planned?
No
Does the review suggest possible changes
in MCLG/MCL/TT and/or other
regulatory revisions?
Yes
Yes
Pending health
risk assessment
No
NPDWR remains appropriate
after data/information review
In-depth Technical Analysis
New risk assessment, methods feasibility,
treatment effectiveness, occurrence and exposure
and economic implications.
No Revision
at this time
1
Is a meaningful opportunity for health risk
reduction or meaningful opportunity for
cost savings likely to occur?
Yes 1
Are the data sufficient to support
regulatory revision?
1
No ^
No ^
No meaningful opportunity
and/or cost savings
Data gaps - determine
research needs
k_ ^
I
^
k
1. Publish FR notice with preliminary revise/not decisions.
2. Review Public Comments and consider revising decisions
in context of new information.
3. Publish FR notice with list of NPDWRs to be revised
Protocol for the Review of NPDWRs
June 2003
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C What Types of Regulatory Revisions Did EPA Consider?
As a part of the review, EPA considered regulatory revisions, with the primary goal of
improving or maintaining public health protection. The types of revisions considered were based
on the various components of each NPDWR. Some NPDWRs set enforceable MCLs for
particular contaminants in drinking water. Others impose TTs to remove chemical contaminants
or microbiological pathogens from drinking water. Most standards also include requirements for
water systems to test for contaminants in the water to make sure standards are achieved.
NPDWRs also specify recordkeeping and reporting requirements, define what constitutes
compliance, and specify language and delivery requirements for public notification.
Some regulatory revisions that are not listed below (e.g., revisions to approved analytical
methods) are already addressed through periodic rulemaking activities of SDWA, and thus, were
not included in the Six-Year Review.
1. Changes to MCLGs
SDWA requires EPA to establish non-enforceable health-based MCLGs. As a part of the
Six-Year Review, EPA considered MCLG changes only in those instances where a new health
risk assessment had been completed since the MCLG was promulgated or last revised, and where
the most current assessment resulted in a revised reference dose (RfD) and/or cancer
classification which justified calculating a revised MCLG.
A revision to an MCLG may result in a more or less stringent standard. The legislative
history of the SDWA Amendments of 1996 makes clear that Congress envisioned the possibility
that a relaxed standard might be appropriate under circumstances that would not result in a
lessening of the level of public health protection. In its discussion of potential revisions to an
existing drinking water standard, Senate Report Number 104-169 (available electronically at
http://thomas.loc.gov/) states:
Amendments made by the bill require that any future standard issued for a
contaminant already regulated must maintain or provide for greater protection of
the health of persons. Generally, this will preclude the promulgation of a revised
standard for a contaminant that is less stringent than the standard already in
place. However, there are circumstances under which a standard may be
relaxed. The maximum contaminant level goal for a contaminant is set at a level
at which there is no adverse effect on the health of persons with an adequate
margin of safety. New scientific information may cause the MCLG to be revised
and in some cases these revisions may be to less stringent levels. This may lead
to a revision of the maximum contaminant level since it need be no more stringent
than the MCLG. New information may also allow for a smaller margin of safety
because it narrows the range of uncertainty for estimates of health risks. Finally,
some substances which have been regulated as carcinogens for ingestion in
drinking water may be reclassified (as asbestos has been in the most recent
revision) or assigned a threshold for the effect based on new scientific
information. In each of these cases, EPA may issue a revised standard for a
contaminant that is less stringent than the one it replaces.
(S. Rep. 104-169, 104th Cong., 1st Sess. (1995) at 38)
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EPA also believes it is reasonable to consider the extent of potential cost-savings for PWSs
and their customers when determining whether revisions that potentially would result in a
relaxed standard (i.e.., where a health basis exists for a less stringent standard) or streamlined
implementation are appropriate. These considerations allow the Administrator to better
prioritize efforts that are most likely to result in a meaningful opportunity for health risk
reduction or cost-savings to PWSs and their customers. Revisions that do not satisfy at least one
of these criteria are a low priority activity for the Agency, and, thus not appropriate "at this time"
because of one or more of the following considerations:
Competing workload priorities;
The administrative costs associated with rulemaking; and
The burden on States and the regulated community to implement any regulatory change
that resulted.
Further, because section 1412(b)(9) of SDWA requires that any revision to an existing
NPDWR maintain or improve the level of public health protection, EPA believes that a clear,
technically-based demonstration regarding the absence of potential risk is necessary to
deregulate a contaminant.
2. Changes to MCLs
An MCL is an enforceable standard for a contaminant. SDWA generally requires the MCL
to be set as close to the MCLG as is feasible. As a part of the Six-Year Review, EPA
considered MCL revisions under the following circumstances6:
The health effects review indicated a change to the MCLG that also indicated a change to
the MCL was appropriate7; and/or
The current MCL was limited by analytical or treatment feasibility and the review of
these capabilities indicated it might now be feasible to set the MCL closer to the MCLG.
3. Changes to Treatment Technique Requirements
When it is not economically or technically feasible to set an MCL, or when there is no
reliable or economically feasible method to detect contaminants in the water, EPA sets a TT
requirement in lieu of an MCL. A TT specifies a type of treatment (e.g., filtration, disinfection,
other methods of control to limit contamination in drinking water, etc.) and means for ensuring
adequate treatment performance (e.g., monitoring of water quality to ensure treatment
performance, etc.).
Water TTs may improve to the point where more protective drinking water standards may be
considered. Before EPA would consider a revision to TT requirements, the potential methods
6 Although the 1996 Amendments to SDWA allow EPA to set the MCL at higher than the feasible level if
the benefits do not justify the costs, SDWA also precludes the Agency from making an existing standard less
stringent solely on economic considerations. Therefore, EPA does not believe it is appropriate to revise a pre-1997
MCL unless a health or technical basis exists for the revision.
7 Potential changes to MCLs may be appropriate in circumstances where the potentially revised MCLG is
more or less stringent than the current MCL (refer back to section II.C. 1 for further discussion).
Protocol for the Review ofNPD WRs 11 June 2003
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must be generally available and must have demonstrated consistent control of the subject
contaminant in drinking water. As a part of the Six-Year Review, EPA reviewed available
information on TTs for those chemical NPDWRs for which: (1) a TT is set in lieu of an MCL;
and (2) no health risk assessment was in process to determine if changes to TT requirements
might be warranted.
4. Changes to Other Treatment Technology
When EPA sets an MCL, the NPDWR also contains Best Available Technology (BAT)
recommendations that address drinking water treatment processes. Although not required for
compliance purposes, EPA sets BATs that have the capability to meet MCLs.
As part of the Six-Year Review, the Agency limited its review of BATs to those NPDWRs
for which EPA was considering possible revisions to the MCL based on the health effects or
analytical feasibility reviews. To revise a BAT, the treatment technology must be generally
available and must have demonstrated consistent removal of the subject contaminant under field
conditions.
EPA has a separate program in place to periodically review specific treatment technology
issues, such as compliance and variance technology for small systems (i.e., systems serving up to
10,000 people) for both the MCL-type and the TT-type rules (however, for microbiological
contaminant regulations, no variances are allowed).8 As a part of its periodic review of small
system compliance and variance technology, the Agency also plans to include the identification
of: (1) BATs for larger systems for future regulations, and (2) new and emerging technologies as
potential compliance and variance technologies for all system sizes for existing and future
regulations. EPA believes that this separate review of treatment technologies is appropriate
because it maintains the focus of technology assessment within one program function (USEPA,
1998a).
5. Changes to Other Regulatory Revisions
In addition to possible revisions to MCLGs, MCLs, and TTs, EPA considered other
regulatory revisions, such as monitoring and system reporting requirements, as a part of the Six-
Year Review process. EPA focused this review on issues that were not already being addressed,
or had not been addressed, through alternative mechanisms (e.g., as part of a recent or ongoing
rulemaking). Where appropriate alternative mechanisms did not exist, EPA considered these
implementation-related concerns if the potential revision met the following criteria:
8 The 1996 SDWA Amendments identify two classes of technologies for systems serving 10,000 and fewer
persons: compliance technologies and variance technologies. A compliance technology is defined in
§ 1412(b)(4)(E)(ii) as a technology or other means that is affordable and achieves compliance with an MCL or
satisfies a TT requirement. EPA listed compliance technologies in the EPA publication entitled Small System
Compliance Technology List for the Non-Microbial Contaminants Regulated Before 1996 (USEPA, 1998a).
Variance technologies, defined in §1412(b)(15)(A), are specified for those system size category/source water quality
combinations for which there are no listed compliance technologies. Variance technologies, where they are
permitted, may not achieve compliance with a particular MCL or TT requirement; however, they must achieve the
maximum reduction or inactivation efficiency that is affordable, taking into consideration system size and source
water quality. Variance technologies must also achieve a level of contaminant reduction that is protective of public
health.
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It indicated a potential change to an NPDWR, as defined under section 1401 of SDWA;
It was "ready" for rulemaking - that is, the problem to be resolved has been clearly
identified and specific option(s) have been formulated to address the problem; and
It met at least one of the following conditions:
- clearly improved the level of public health protection; and/or
- represented a meaningful opportunity for cost savings while not lessening public
health protection.
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SECTION III: DETAILED DISCUSSION OF
THE SIX-YEAR REVIEW PROCESS
This section provides a detailed discussion of how EPA conducted its review of health risk
assessments, technology assessments, other regulatory revisions, and, where appropriate,
occurrence and exposure analyses, and economic factors.
A. Health risk assessments
1. What Were the Objectives of the Health Effects Review?
The objectives for the examination of health effects under the Six-Year Review were to:
Identify new health risk assessments for individual contaminants that could change the
MCLG for the contaminant in question and affirm or change the MCL, thus, affording
the same or greater protection of human health provided by the present MCLG;
Use existing Agency health risk assessments in accomplishing the health effects data
review;
Ensure that the health effects data for each contaminant is the subject of a detailed review
at least once in every two, Six-Year Review cycles (with the exception of pesticides that
are still in active use, because they are subject to a detailed review that is conducted on a
different schedule9); and
Accomplish the review within the limitations imposed by Agency resources.
The procedure for review of health effects data differed depending on whether the substance
to be controlled is a chemical contaminant or a microbiological pathogen/indicator, as discussed
in detail below. The health risk assessment identified a list of NPDWRs that were possible
candidates for regulatory revisions based on changes in health considerations. This list of
NPDWRs was combined with those identified by other key elements of the review to develop a
list of NPDWRs that were candidates for additional evaluation.
2. How Did EPA Review Health Effects Data for Chemical Contaminants?
EPA used a systematic approach in reviewing the health effects data for chemical
contaminants. This approach considered the risk assessment policies that link the MCLG and
MCL as well as the data that have become available since the time of regulation. The document,
Six-Year Review - Chemical Contaminants - Health Effects Technical Support Document
9 The health effects for these contaminants are reassessed no less frequently than every 15 years. Within
EPA, health risk assessments for pesticides are conducted by the OPP under authority of the Federal Insecticide,
Fungicide, and Rodenticide Act (FIFRA), and the Food Quality Protection Act (FQPA) of 1996. A goal of FIFRA is
that EPA reviews each pesticide's registration every 15 years. Under some circumstances, a pesticide's health effects
may be reassessed more frequently.
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(USEPA, 2003e), describes how EPA reviewed the chemical contaminants and provides the
results of the health effects technical review.
If there is evidence that a chemical may cause cancer, and if the cancer mode of action is
linear, there is no dose below which the chemical is considered safe, and thus the MCLG is set at
zero. In these instances, the MCL is based on feasible technology (analytical
methods/treatment). If a chemical is carcinogenic and acts by a well-documented, nonlinear
mode of action, the MCLG may be set at a level above zero. As the health risks of nonlinear
carcinogens undergo reassessment, this may provide regulatory options for MCLGs for
carcinogens that are greater than zero.
For non-carcinogenic chemicals, the MCLG is based on an oral RfD. The RfD is an estimate
(with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human
population (including sensitive subgroups) that is likely to be without an appreciable risk of
deleterious non-cancer effects during a lifetime. A change in an Agency RfD for a chemical
could accordingly lead to a change in an MCLG and MCL. In deriving the MCLG for a
non-carcinogen, the Agency applies a Relative Source Contribution (RSC) factor to allocate a
portion of the total allowable exposure to drinking water. The RSC is one factor which will
determine whether or not a change in RfD will lead to a change in the MCLG/MCL.
In the past, it was Agency policy to apply a risk management factor to the RfD for chemicals
with equivocal data on carcinogenicity. This policy is a second factor that must be evaluated to
determine the impact of a change in RfD on the MCLG/MCL for these chemicals.
For most of the 68 chemical NPDWRs included in the Six-Year Review, the MCLG is
derived from the cancer classification and/or the RfD. Therefore, the health effects technical
review focused on whether there has been a change to these values. The Agency reviewed the
results of health risk assessments completed under the following programs to determine if there
has been a change in critical effect or dose-response pattern that indicates the possible need for
an MCLG revision.
EPAs IRIS (see Appendix C)10
OPP (see Appendix D)11
Agency for Toxic Substances and Disease Registry (ATSDR)
National Academy of Sciences (NAS).
Where possible, an oral RfD or comparable value is derived and an assessment of
carcinogenicity from oral exposure is conducted under each of these programs.
10 For purposes of the Six-Year Review protocol, EPA considered a risk assessment final when an Interim
Reregistration Eligibility Decision (IRED), Reregistration Eligibility Decision (RED), and/or IRIS assessments was
complete. The IRED is an intermediate decision for an individual pesticide that does not take into account
cumulative risk issues for pesticides with a common mode of action. The RED does include cumulative risk. If an
IRIS assessment was also in process when the IRED or RED was signed, EPA made a case-by-case decision on
whether to wait for the IRIS assessment before considering possible revisions to the NPDWR.
11 See footnote 10.
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As a result of the health effects review, EPA placed each of the 68 chemical NPDWRs into
one of the following categories:
(1) New risk assessment 1997 or later. An IRIS, OPP, ATSDR, and/or NAS assessment has
been completed in 1997 or later. These assessments have considered developmental and
reproductive toxicity as a part of the assessment. The Agency considered these
assessments to be recent enough that it was not necessary to conduct a literature search to
identify any additional relevant studies that have become available on the toxicological
effects of these contaminants. In cases where the health risk assessment resulted in a
change in the critical effect, or the dose-response pattern for a regulated contaminant, and
where that change could result in a change in the MCLG, EPA subjected the NPDWR to
a more in-depth analysis as a part of the review process. Where recent assessments were
conducted by an agency other than EPA and new developmental and reproductive data
were identified, EPA initiated an update of its assessment.
(2) New risk assessment since promulgation, but prior to 1997. An IRIS, OPP, ATSDR,
and/or NAS assessment has been completed since the NPDWR was promulgated, but
prior to 1997. None of these assessments reflected a change in RfD or cancer
classification. However, since these assessments may not have specifically considered
developmental and reproductive health effects, EPA conducted a full literature search,
including developmental and reproductive toxicity, for those NPDWRs with non-zero
MCLGs to identify any relevant studies that might affect the MCLGs of these
contaminants.12 In a few instances, the results of the literature search indicated that it
might be appropriate to revise the RfD and/or cancer classification. EPA initiated
updates to risk assessments for these chemicals, and established a schedule for their
completion. EPA did not consider these NPDWRs appropriate candidates for revision
during the 1996-2002 review cycle.
(3) Agency risk assessment in progress during the Six-Year health effects review. The
Agency was conducting a health risk assessment for the contaminant but the assessment
was not completed in time for consideration during the 1996-2002 review cycle. When
completed, the assessment will consider all relevant studies that have become available
on the toxicology of the contaminant, including developmental and reproductive toxicity.
EPA generally did not consider these NPDWRs appropriate candidates for revision
during the 1996-2002 review cycle.
(4) Original NPDWR risk assessment. No health risk assessment has been conducted since
promulgation of the NPDWR. The Agency conducted a full toxicological literature
search, including developmental and reproductive toxicity, for each of these
contaminants with non-zero MCLGs to identify new toxicological studies that might
12 For the 1996-2002 review, EPA considered a zero MCLG to be protective of public health and that new
information on developmental and reproductive effects would not affect the MCLG. However, for those NPDWRs
with a zero MCLG, EPA reviewed available information to inquire whether data show a non-linearity of the dose-
response; EPA did not find any data to support such a mode of action (USEPA, 2003e). EPA recognizes that
information on potential reproductive and developmental effects for chemicals with MCLGs of zero may have an
impact on risk management strategies, such as monitoring frequency, to control peak occurrence. This aspect of the
assessment will be considered during subsequent Six-Year Review cycles, in conjunction with available occurrence
data, to determine whether changes in risk management strategies might provide for better public health protection.
Protocol for the Review of NPDWRs 17 June 2003
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have an impact on the MCLGs. In a few instances, the results of the literature search
indicated that it might be appropriate to revise the RfD and/or cancer classification. EPA
initiated updates to risk assessments for these chemicals, and established a schedule for
their completion. EPA did not consider these NPDWRs appropriate candidates for
revision during the 1996-2002 review cycle.
Thus, only contaminants in the first category were considered to be potential candidates for an
MCLG revision during the 1996-2002 review cycle. If the revised health risk assessment
indicated changes to the MCLG/MCL, the Agency conducted a detailed occurrence and
exposure assessment. See section HID for more discussion of how EPA conducted the
occurrence and exposure analyses.
The document, Six-Year Review - Chemical Contaminants - Health Effects Technical
Support Document, (USEPA, 2003e) describes the process that EPA used to address the health
effects aspect of the current review for the chemical contaminants.
3. How Did EPA Review Health Effects Data for Microbiological NPD WRs ?
The Total Coliform Rule (TCR) is one of several EPA regulations that protect the public
from pathogens in drinking water. The TCR requires all PWSs to monitor for the presence of
total coliforms in the distribution system. Total coliforms are a group of closely related bacteria
that are (with few exceptions) not harmful to humans. They are natural and common inhabitants
of the soil and ambient waters (e.g., lakes, rivers and estuaries), as well as in the gastrointestinal
tract of animals. A few of these coliforms (fecal coliforms, including Escherichia coli or E. coif)
only grow within the intestinal tract of humans and other warm-blooded animals. Total
coliforms may be injured by environmental stresses (e.g., lack of nutrients) and water treatment
(e.g., chlorine disinfection) in a manner similar to most bacterial pathogens and many virus
pathogens. Therefore, EPA considers them a useful indicator of bacterial and many viral
waterborne enteric pathogens. More specifically, for drinking water, total coliforms are used to
determine the adequacy of water treatment and the integrity of the distribution system. The
absence of total coliforms in the distribution system minimizes the likelihood that fecal
pathogens are present. Thus, total coliforms are used to determine the vulnerability of a system
to fecal contamination.
The 1989 TCR set an MCLG of zero for total coliforms because EPA was not aware of any
data in the scientific literature supporting a particular value for the concentration of coliforms
below which no known or anticipated adverse health effects occur, with an adequate margin of
safety.
The memorandum, Six-Year Review of the Total Coliform Rule - Comments Received
(USEPA, 2002c), describes the process EPA applied to the review of the TCR. Where
appropriate, EPA applied the same approach to reviewing the TCR as it did to the review of the
68 chemical NPDWRs. However, because of the nature of the TCR, the pathogens it controls,
the Agency focused its review on the implementation-related requirements.
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B. Technology Assessments
1. What Were the Objectives of the Technology Assessments?
SDWA generally requires that MCLs be set as close to the MCLG as is feasible. When
determining feasibility, the Agency considers cost and capability of the analytical and treatment
methods to respectively measure and remove/reduce drinking water contaminants, and the
availability of these technologies. In some cases, particularly when the Agency sets a zero
MCLQ EPA establishes a higher MCL based on the limitations of analytical or treatment
feasibility.
Where these constraints apply to the current MCL, the objectives of the technology
assessments were to determine whether there have been improvements in analytical methods or
treatment technologies that may allow EPA to lower the MCL.
2. How Did EPA Review A nalytical Methods ?
As described in Appendix E, EPA's Office of Ground Water and Drinking Water (OGWDW)
has a process in place to approve new and/or improved analytical methods for drinking water
contaminants. The review and approval of new methods, updates to §§141.23, 141.24, or
141.25, and the approval of methods through §141.27 (alternate analytical techniques - also
known as alternate test procedures or ATP) is generally performed through periodic method
update rules. The review and approval of new methods and/or updates to the methods is also
performed through the rulemaking process to regulate a contaminant or revise the standard for a
contaminant, when appropriate (e.g., the January 22, 2001 final rule for arsenic, (66 FR 6975
(USEPA, 200lb)). More recent methods update rules include 62 FR 10167, March 5, 1997
(USEPA, 1997a), 64 FR 67449, December 1, 1999 (USEPA, 1999d), and 66 FR 3526, a
proposed rule published January 16, 2001 (USEPA, 200la).
The Six-Year Review did not duplicate those efforts, but used the information from these
method updates in the review process. In those instances where the MCL has been established
based on the limitations of analytical method capabilities and/or where the health effects analysis
suggests that the MCLG/MCL should be lowered, EPA reviewed the existing approved methods
in the context of potential changes in analytical feasibility. The goal of this part of the review
was for EPA to determine whether the currently approved methods provide sufficient analytical
capability to reliably measure the contaminant at levels lower than the current MCL. If the
currently approved method capabilities (i.e., a method detection limit (MDL)) and the practical
quantitation level (PQL) remain limiting factors for revising an MCL, and if the occurrence and
exposure analyses suggest that a meaningful opportunity for health risk reduction could occur
with a more stringent standard, then EPA may determine that the revision may be appropriate.
Under these circumstance, EPA will consider including a request in the Federal Register for
potential new and/or improved methods that are technologically and economically feasible.
However, once a more sensitive method is approved for a contaminant, there may be a time lag
between the time of promulgation and the ability of laboratories to begin using the new method.
Any time lag in the usage of more sensitive methods may therefore result in the delay of any
noticeable change in the feasible level of quantitation.
The remainder of this section generally describes how EPA determines the feasible level of
measurement for chemical and microbiological contaminants for SDWA purposes. It also
discusses how EPA evaluated available, new data to determine if any changes in analytical
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feasibility for the chemical contaminants have occurred since promulgation of the NPDWR. The
document, Analytical Feasibility Support Document for the Six-Year Review of Existing National
Primary Drinking Water Regulations: Reassessment of Feasibility for Chemical Contaminants,
(USEPA, 2003a) describes the process that EPA used to address the analytical feasibility aspect
of the current review for specific chemical contaminants.
Chemical Contaminants
OGWDW establishes a PQL to estimate the level at which laboratories can routinely measure
a chemical contaminant in drinking water. Historically, OGWDW has typically used two main
approaches to determine a PQL for SDWA analytes. The preferred approach used data from
Water Supply (WS) studies (which were predominantly used to certify drinking water
laboratories).13 In most cases, OGWDW used the WS method when sufficient WS data were
available to calculate a PQL. In the absence of sufficient WS data, OGWDW used a multiplier
method, in which the PQL was calculated by multiplying the EPA-derived MDL by a factor of 5
or 10.
Although there are several approaches that could have been used for the reassessment or
re-evaluation of the PQLs, to be consistent with the historical process, only the "WS data
method" and the "MDL Multiplier method" were considered for this Six-Year Review process.
Of these two approaches, the Agency preferred to use the WS data approach since it relies on
actual data from a number of EPA Regional and State laboratories. In cases where the WS data
were indicative of a change in the PQL, the MDL multiplier method was only used to estimate
what the potentially new PQL could be.
EPA reviewed analytical capabilities for contaminants under two circumstances: (1) for those
NPDWRs where the current MCL is set at the PQL and there is no indication that the MCLG
would change; and (2) for those NPDWRs that have undergone a health effects review and there
was a potentially more stringent MCLG. For each of these chemical NPDWRs, EPA used the
following steps to evaluate whether changes in analytical feasibility have occurred:
(1) a methods comparison step to identify whether the ability to detect (and therefore
quantify) these contaminants at lower levels has increased;
(2) a methods usage over time step to identify the analytical methods that appear to be the
most widely used for the analysis of particular contaminants.
(3) a WS data analysis step to determine if a PQL could be recalculated (if sufficient WS
information were available) or if there was an indication that a PQL might be lower using
the available information.
The results of these three steps aided in assessing whether a PQL might change for a specific
contaminant and, if so, an estimate of what the new PQL might be. Ultimately, the purpose of
this analysis was to determine whether the analytical method capabilities would support a lower
MCL.
13 Because the WS program has been externalized, the Agency is currently deciding how it should assess
the multiple laboratory data that are used to determine the PQL for chemical contaminants. Appendix E briefly
discusses the externalization of the Performance Evaluation program.
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Microbiological Contaminants
For microbes, EPA does not have, or currently envision, a routine pathogen monitoring
requirement, but rather employs indicators of water quality (e.g., total coliforms, E. coli). PQLs
have not been used for microbial indicators because, for approval, the method must be able to
detect a single cell (i.e., MDL and PQL must both be one cell) in a 100 milliliter (mL) water
sample (40 CFR 141.21(f)). In addition, the false-positive and false-negative (i.e., recovery)
rates must be reasonable. EPA is considering whether to define "reasonable" in numerical terms.
In some cases, EPA may require systems to determine the density of a particular pathogen or
indicator in either their source waters or drinking waters. For example, under the future Long
Term 2-Enhanced Surface Water Treatment Rule (LT2-ESWTR), EPA may require surface
water systems to determine the density of Cryptosporidium in the source water to determine the
level of water treatment the system would need. In this case, the accuracy and precision of the
method at low levels of pathogen density would have to be determined using interlaboratory
studies. The method would have to be sufficiently sensitive to detect a single oocyst. Therefore,
the PQLs and MDLs are not meaningful. In addition, it may be appropriate to determine an
MDL and PQL for some required non-microbial measurements associated with microbial water
quality such as turbidity, disinfectant residual, and algal microcystins. Currently, accurate
measurement of microbiological density is problematic. Moreover, regulation of most
microbiological contaminants are currently treatment-technique based. Therefore, for the
purposes of making a revise/not revise decision, the Agency primarily focused the review on the
treatment-technique (if appropriate) and "other regulatory revisions" aspects of the NPDWRs for
microbiological contaminants. The TCR is the only microbiological NPDWR reviewed under
this protocol as a part of the 1996-2002 review cycle. The TCR is a monitoring rule. Rather
than specify TT requirements, the TCR provides PWSs with a list of recommended best
management practices (BMPs). The review of the "other regulatory revisions" for the TCR
considered whether revisions to the BMPs might be appropriate.
3. How Did EPA Review Treatment Technologies?
As discussed previously, an NPDWR either identifies the BAT for meeting the MCL (even
though BATs are not required for compliance purposes), or establishes enforceable TT
requirements. Currently, for all the pre-1997 chemical NPDWRs reviewed in accordance with
this protocol that include an MCL, the MCL is set equal to the MCLG or the PQL. None of
these MCLs are currently limited by treatment feasibility. Thus, although EPA generally
reviews treatment technologies through alternative mechanisms, there were a few scenarios for
which EPA reviewed treatment feasibility as a part of the Six-Year Review process:
The health effects technical review identified a potential change to the MCLG/MCL; or
A health risk assessment was not in process for the contaminant and one of the following
two conditions applied:
(1) the analytical feasibility review identified a possible change to the MCL; or
(2) the NPDWR is a TT-type rule.
EPA also considered revisions that clarify or modify BAT or TT requirements where existing
requirements were not clear or were incorrectly specified. In addition, and where appropriate,
EPA evaluated the likelihood that systems would discontinue existing treatment if EPA were to
raise the MCL. See section III.E for further discussion of how EPA considered economic
factors, as they relate to treatment.
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Treatment capabilities of existing BATs and TTs are well documented by EPA and other
organizations. Likewise, small system compliance and variance technologies are well
documented and periodically reviewed by the Agency. During the development of NPDWRs,
EPA provides state-of-the-science and feasibility of treatment information primarily through its
technical support documents (e.g., EPA technologies and costs reports, and guidance materials
published to assist in regulatory implementation). As part of the Six-Year Review process, EPA
used these same resources, in addition to newer treatment and cost reports, peer-reviewed data,
and other available treatment technology information including that received by EPA from
stakeholders.
The evaluation of treatment technologies supported the regulatory review process by
identifying any known water treatment limitations that might affect a revision of an MCL. In the
case of TT-type rules, this effort supported consideration of whether changes to TT requirements
were warranted. For example, consideration was given to any new treatment processes that are
available and appropriate. If the Agency identified treatment technology-related research needs
as a part of the Six-Year Review process, those research needs were forwarded to the appropriate
Agency group(s) for consideration and prioritization as a part of the overall drinking water
research strategy.
The document, Water Treatment Technology Feasibility Support Document for Chemical
Contaminants; In Support of EPA Six-Year Review of National Primary Drinking Water
Regulations, (USEPA, 2003f) describes the process that EPA used to address the treatment
feasibility aspect of the current review for specific chemical contaminants.
C. Other Regulatory Revisions
1. What Was the Objective of the Review of Other Regulatory Revisions?
In addition to possible revisions to MCLGs, MCLs, and TTs, EPA considered other
regulatory revisions, such as monitoring and system reporting requirements, as a part of the Six-
Year Review process. The objective of the review of other regulatory revisions was to identify
potential revisions related to the implementation of the rules that may result in improved public
health protection, and/or present the opportunity for meaningful cost-savings while maintaining,
or improving, the level of public health protection.
2. How Did EPA Consider Other Regulatory Revisions?
EPA focused its review on issues that were not already being addressed, or had not been
addressed, through alternative mechanisms (e.g., as part of a recent or ongoing rulemaking).
Where appropriate alternative mechanisms did not exist, EPA considered these implementation-
related concerns if the potential revision met the following criteria:
It indicated a potential change to an NPDWR, as defined under section 1401 of SDWA;
It was "ready" for rulemaking - that is, the problem to be resolved has been clearly
identified and specific option(s) have been formulated to address the problem; and
It met at least one of the following conditions:
- clearly improved the level of public health protection; and/or
- represented a meaningful opportunity for cost-savings while maintaining or
improving the public health protection.
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The document, Consideration of Other Regulatory Revisions for Chemical Contaminants in
Support of the Six-Year Review of National Primary Drinking Water Regulations (USEPA,
2003b) summarizes the specific issues identified during the review process. Some of these
issues (e.g., the need to specifically define new system/new source monitoring requirements for
chemical contaminants) have already been addressed in the recently published arsenic and
radionuclides NPDWRs (66 FR 6975, January 22, 2001 (USEPA, 200Ib); 65 FR 76707,
December 7, 2000 (USEPA, 2000d)).
D. Occurrence and Exposure Analysis
1. What Were the Objectives of the Occurrence and Exposure Analysis?
The objectives of the occurrence and exposure analysis components of the review process
were to estimate the numbers of PWSs at which contaminants occur at levels of regulatory
interest in drinking water, and to evaluate the number of people exposed to these levels. This
analysis was not necessary for the TCR, since national data were not available and were not
needed. If an organism is known to be transmitted by the fecal-oral route, and has caused at least
one waterborne disease outbreak in this country, that is sufficient reason to control the organism
nationally. The number of systems affected by an organism depends on the characteristics of the
waterborne organism and the type of water source. Therefore, the remaining discussion of the
occurrence and exposure analysis pertains only to the chemical NPDWRs under review.
Combined with results of the other technical analyses described in section III (e.g., health
effects), the results of the occurrence and exposure analysis were used to help determine which
revisions are most likely to provide the greatest public benefit. In some cases, these results may
also be used as a factor when recalculating RSCs.14 EPA plans to perform further, in-depth,
occurrence and exposure analysis prior to any proposed revision to an NPDWR.
2. How Did EPA Conduct the Occurrence and Exposure Analysis ?
During the 1996-2002 review cycle, EPA used data voluntarily provided by eight States as a
part of the Agency's occurrence analyses for its Chemical Monitoring Reform (CMR) evaluation
(USEPA, 1999b). EPA augmented this information with other data that were voluntarily
submitted by an additional eight States, based on the same geographic diversity and agricultural
and industrial pollution potential analyses utilized in the CMR analyses.
The Agency does not believe it is appropriate to revise a pre-1997 NPDWR solely on the
basis that a contaminant is low-occurring or high-occurring at PWSs. However, in assessing
whether to revise the MCL and/or other regulatory revisions, EPA considered the estimated
occurrence and exposure to a contaminant at PWSs at concentrations between the current MCL
and any possible MCL. More specifically, this assessment helped the Agency to determine
whether such revisions were likely to provide a meaningful opportunity for health risk reduction
or cost-savings to PWSs and their customers. Therefore, EPA conducted a detailed occurrence
14 While occurrence and exposure estimates factor into the derivation of an RSC, a much more important
factor is exposure information for other media (air, food, etc.) relative to that for water. Exposure information for
other media will be assessed as a part of the health risk assessment described in section III. A of this document, and
not as a part of the occurrence and exposure assessment described in this section.
Protocol for the Review ofNPD WRs 23 June 2003
-------
and exposure analysis if a regulated chemical contaminant was identified as a potential candidate
for revision by the health effects, technology, and/or other regulatory revisions reviews.
As a part of a "Stage 1" analysis, EPA estimated the percent of PWSs (and the total
population served by those PWSs) with at least one analytical result exceeding the following
thresholds: the lowest level of detection reported by the States; one-half the current MCL, and
the current MCL. Of the chemicals reviewed under this first regulatory review cycle, all were
analyzed in this way, except for contaminants for which: (1) not enough data were available; (2)
the NPDWR specifies a TT-type requirement instead of an MCL; and (3) EPA did not request
data, since the Agency determined there was no health or technological basis for revising, and
because these data would have required extra burden for States to transmit.
Based on the outcome of the health effects, technology, and other regulatory revision
reviews, EPA determined the level(s) of regulatory interest and performed a more detailed,
"Stage 2" statistical analysis. The "Stage 2" analysis estimated the numbers of systems (and the
corresponding affected populations) with mean contaminant concentrations above the levels of
regulatory interest. For example, where WS data in the analytical feasibility review indicated a
possibly lower PQL, EPA estimated a value and used this as a threshold in the occurrence and
exposure analysis. If this analysis indicated that a contaminant was unlikely to occur at
concentrations above those of regulatory interest, EPA determined that a revision was not
warranted during the 1996-2002 review cycle.
The document, Occurrence Estimation Methodology and Occurrence Findings Report for the
Six-Year Review of Existing National Primary Drinking Water Regulations, (USEPA, 2003 c)
describes the process that EPA used to address the occurrence and exposure aspect of the current
review for specific chemical contaminants
E. Consideration of Economic Factors
1. What Were the Objectives of EPA's Evaluation of Economic Impacts?
While section 1412(b)(9) of SDWA provides the Agency broad discretion to consider
economic impacts in the context of the Six-Year Review, the statute precludes EPA from using
economic impacts as the sole basis for a revision that would provide less health protection than
the current standard (anti-backsliding). However, if new peer-reviewed scientific health effects
research indicates that an MCLG could be raised while maintaining public health protection,
then such a change is permitted. For NPDWRs published prior to the 1996 SDWA
Amendments, consideration of economic factors was of limited use when determining whether
revisions were appropriate, except in those situations where a health or technical basis existed
for a potential regulatory revision. Therefore, EPA qualitatively evaluated available economic
information for those NPDWRs identified as potential candidates for revision by the health and
technology reviews. The purpose of this analysis was to determine whether a potential revision
is likely to provide a meaningful opportunity for health risk reduction and/or cost-savings that at
least maintain the current level of public health protection.
Protocol for the Review ofNPD WRs 24 June 2003
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2. How Did EPA Consider Economic Impacts?
EPA did not quantify likely costs and benefits as a part of the review, since many of the
factors that are needed for such calculations depend on specific regulatory options that will not
be definitive until EPA begins the actual rulemaking process. EPA therefore conducted a
qualitative assessment based on the extent of occurrence of a contaminant at the MCL, as well as
at alternative levels, to help determine whether possible changes to an MCL offered a
meaningful opportunity for health risk reduction and/or cost-savings to PWSs and their
customers. For example, in those instances where the health effects and/or technology reviews
indicated that a more stringent MCL might be appropriate, EPA considered the difference
between the levels of occurrence and exposure at the current MCL and the occurrence and
exposure at potentially revised regulatory level(s) indicated by those reviews. On the other
hand, if the health effects review indicated it might be appropriate to establish a less stringent
MCLG/MCL, EPA considered whether such a revision would be likely to offer a meaningful
opportunity for cost-savings. In making this assessment, EPA considered the number of PWSs
with concentrations above the current MCL that may avoid the need to install treatment.
For any NPDWR for which the Agency made a revise decision, the Agency will conduct
detailed cost and benefit analyses, as required, prior to proposing specific regulatory revisions.
Protocol for the Review ofNPD WRs 25 June 2003
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Protocol for the Review ofNPD WRs 26 June 2003
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SECTION IV: STAKEHOLDER INVOLVEMENT
Section IV discusses how the Agency involved the public during the Six-Year Review
process. More specifically, it lists those organizations with which EPA coordinated during the
Six-Year Review process (i.e.., key stakeholders), describes the mechanisms EPA used to keep
these stakeholders involved, and discusses the Science Advisory Board's (SAB's) role in the
review process.
A. Who Were the Key Stakeholders in the Six-Year Review Process?
The key stakeholders for the 1996-2002 review cycle included members of the following:
The general public Public water suppliers
Congress National trade associations
Other Federal agencies Environmental groups
State, Tribal, and local officials Manufacturers
Public health/health care providers Agricultural producers.
Public interest groups
B. How Were Stakeholders Involved in the Six-Year Review Process?
EPA involved stakeholders by: holding periodic stakeholder meetings; participating in
national meetings, workshops, and technical forums; meeting informally with associations and
technical experts; posting information on the OGWDW web page (www.epa.gov/safewater/):
and publishing Federal Register notices on the Six-Year Review.
EPA invited representatives from State and Tribal communities, PWSs, public health
organizations, academia, environmental and public interest groups, engineering firms, and other
stakeholders to a stakeholder meeting in Washington, DC, in November 1999 (64 FR 55711,
October 14, 1999 (USEPA, 1999a)). Approximately 50 participants attended, including
representatives from the invited groups. EPA discussed its preliminary strategy for the Six-Year
Review and invited stakeholder comment. Stakeholders generally agreed that EPA had
identified the appropriate key elements for the review; however, in some cases, stakeholders
suggested that EPA needed to be more proactive in seeking out new information that might
affect the regulatory decision (USEPA, 1999c). The executive meeting summary is available on
EPA's drinking water web page, http://www.epa.gov/safewater/ccl/novmtg.html.
In the Spring of 2000, the NDWAC formed a working group to develop recommendations
regarding the process the Agency should apply to conducting a periodic and systematic review of
existing NPDWRs. The Working Group held two meetings and a conference call from June
through September 2000 (USEPA, 2000a-2000c). The NDWAC approved the Working Group's
recommendations in November 2000 and formally provided them to EPA in December 2000
(NDWAC, 2000). The NDWAC recommended that EPA's review include consideration of five
key elements, as appropriate: health effects, analytical and treatment feasibility,
implementation-related issues, occurrence and exposure, and economic impacts. The NDWAC
Protocol for the Review ofNPD WRs 27 June 2003
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suggested that the Agency conduct a preliminary screening review of each NPDWR to identify
potential candidates for an in-depth analysis. Except where noted in Appendix B, EPA has
followed the protocol recommended by the NDWAC.
In addition to the November 1999 stakeholder meeting and consultation with the NDWAC,
EPA representatives delivered presentations at a variety of meetings held by other organizations,
including: American Water Works Association (AWWA) Technical Advisory Workgroup
meetings, held in February 2001 in Washington, DC and in February 2002 in San Diego, CA; a
meeting held by the Association of State Drinking Water Administrators (ASDWA) in March
2001 in Alexandria, VA; and the annual AWWA meeting held in Washington, DC in June 2001.
At each of these meetings, stakeholders were given the opportunity to comment on the protocol
by which EPA was planning to perform the review of existing NPDWRs. EPA received valuable
input from stakeholders on the proposed protocol to reviewing existing NPDWRs.
In December of 2000, EPA Headquarters circulated a memorandum to its Regional offices
requesting feedback on issues relating to the implementation of its drinking water regulations.
Although the memorandum specified a "potential set of issues" for consideration, Regions were
asked to identify any other known issues related to regulatory implementation. In addition,
ASDWA was asked to confer with the States regarding implementation issues that they felt
needed to be reviewed or addressed. In response to the memorandum and the request to
ASDWA, EPA received comments from four EPA Regions (3, 6, 7, and 8), five States (Iowa,
Michigan, Minnesota, Pennsylvania, and Texas), and ASDWA.
In the April 17, 2002, Federal Register, EPA published its protocol and its preliminary
revise/not revise decisions for the 69 NPDWRs, and requested public comment. The Agency
received and reviewed comments from 44 commenters. EPA discussed the major public
comments and the Agency's response to these comments in the document entitled, Public
Comment and Response Summary for the Six-Year Review of National Primary Drinking Water
Regulations (USEPA, 2003d). Based on these public comments, EPA revised this protocol
document to better explain how the Agency integrated the separate analyses and where it applied
judgment in the decisionmaking. EPA also revised several of its technical support documents to
clarify how the Agency conducted the specific analyses that support its revise/not revise
decisions.
C. How Did EPA Plan to Involve the Science Advisory Board?
In June 2002, EPA consulted with the SAB Drinking Water Committee and requested their
review and comment on whether the protocol EPA developed based on the NDWAC
recommendations was consistently applied and appropriately documented. The SAB provided
verbal feedback regarding the transparency and clarity of ERA s decision criteria for making its
revise/not revise decisions under the 1996-2002 review cycle. EPA revised this protocol
document to better explain how the decision criteria were applied and will also take the SAB
comments into consideration when planning for the next review cycle.
Protocol for the Review ofNPD WRs 28 June 2003
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REFERENCES
NDWAC. 2000. Recommended Guidance for Review of Existing National Primary Drinking
Water Regulations. November 2000. Available on the Internet at:
http://www.epa.gov/safewater/ndwac/guidfnl.pdf.
Senate Report. 1995. COMMITTEE OF ENVIRONMENT AND PUBLIC WORKS, SAFE DRINKING
WATER ACT AMENDMENTS OF 1995, S. Doc. No. 169, 104th Cong., 1st Sess. 38 (1995).
USEPA. 1975. Water Programs: National Interim Primary Drinking Water Regulations.
Federal Register. Vol. 40, No. 248, p. 59566. December 24, 1975.
USEPA. 1976. Interim Primary Drinking Water Regulations; Promulgation of Regulations on
Radionuclides. Federal Register. Vol. 41, No. 133. p. 28401, July 9, 1976.
USEPA. 1979. National Interim Primary Drinking Water Regulations; Control of
Trihalomethanes in Drinking Water. Federal Register. Vol. 44, No. 231. p. 68624,
November 29, 1979.
USEPA. 1985. National Primary Drinking Water Regulations; Volatile Synthetic Organic
Chemicals; Final Rule and Proposed Rule. Federal Register. Vol. 50, No. 219. p. 46902,
November 13, 1985.
USEPA. 1986. National Primary and Secondary Drinking Water Regulations; Fluoride; Final
Rule. Federal Register. Vol. 51, No. 63. p. 11396, April 2, 1986.
USEPA. 1987. National Primary Drinking Water Regulations - Synthetic Organic Chemicals;
Monitoring for Unregulated Contaminants; Final Rule. Federal Register. Vol. 52, No. 130.
p. 25690, July 8, 1987.
USEPA. 1989a. National Primary and Secondary Drinking Water Regulations; Proposed Rule.
Federal Register. Vol. 54, No. 97. p. 22062, May 22, 1989.
USEPA. 1989b. National Primary Drinking Water Regulations; Filtration, Disinfection;
Turbidity, Giardia Lamblia, Viruses, Legionella, and Heterotrophic Bacteria; Final Rule.
Part 2. Federal Register. Vol. 54, No. 124. p. 27486, June 29, 1989.
USEPA. 199la. National Primary Drinking Water Regulations - Synthetic Organic Chemicals
and Inorganic Chemicals; Monitoring for Unregulated Contaminants; National Primary
Drinking Water Regulations Implementation; National Secondary Drinking Water
Regulations; Final Rule. Federal Register. Vol. 56, No. 30. p. 3526, January 30, 1991.
USEPA. 1991b. Drinking Water Regulations - Maximum Contaminant Level Goals and
National Primary Drinking Water Regulations for Lead and Copper; Final Rule. Federal
Register. Vol. 56, No. 110. p. 26460, June 7, 1991.
USEPA. 1991c. Drinking Water; National Primary Drinking Water Regulations; Monitoring for
Volatile Organic Chemicals; MCLGs and MCLs for Aldicarb, Aldicarb Sulfoxide, Aldicarb
Protocol for the Review ofNPD WRs 29 June 2003
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Sulfone, Pentachlorophenol, and Barium; Final Rule. Federal Register. Vol. 56, No. 126.
p. 30266, July 1, 1991.
USEPA. 1992. Drinking Water; National Primary Drinking Water Regulations - Synthetic
Organic Chemicals and Inorganic Chemicals; National Primary Drinking Water Regulations
Implementation; Final Rule. Federal Register. Vol. 57, No. 138. p. 31776, July 17, 1992.
USEPA. 1996. Performance Evaluation Studies Supporting Administration of the Clean Water
Act and the Safe Drinking Water Act. Federal Register. Vol. 61, No. 139. p. 37464, July
18, 1996.
USEPA. 1997a. National Primary Drinking Water Regulations: Analytical Methods for
Radionuclides; Final Rule and Proposed Rule. Federal Register. Vol. 62, No. 43. p. 10167,
March 5, 1997.
USEPA. 1997b. National Drinking Water Advisory Council, Occurrence and Contaminant
Selection Working Group; Notice of Open Meeting. Federal Register. Vol. 62, No. 113. p.
32113, June 12, 1997.
USEPA. 1998a. Small System Compliance Technology List for the Non-Microbial
Contaminants Regulated Before 1996. EPA 815-R-98-002 (September 1998)
USEPA. 1998b. National Primary Drinking Water Regulations: Disinfectants and Disinfection
Byproducts; Final Rule. Federal Register. Vol. 63, No. 241. p. 69389, December 16, 1998.
USEPA. 1998c. National Primary Drinking Water Regulations: Interim Enhanced Surface
Water Treatment; Final Rule. Federal Register. Vol. 63, No. 241. p. 69478, December 16,
1998.
USEPA. 1999a. Announcement of Stakeholders Meeting on the Drinking Water Contaminant
Identification and Selection Process, and the 6-Year Review of All Existing National
Primary Drinking Water Regulations, as Required by the Safe Drinking Water Act, as
Amended in 1996; Notice of Stakeholders Meeting. Federal Register. Vol. 64, No. 198. p.
55711, October 14, 1999.
USEPA. 1999b. A Review of Contaminant Occurrence in Public Water Systems. EPA Report
816-R-99-006. November 1999. Available on the Internet at:
http://www.epa.gov/safewater/occur/nov99_lo.pdf.
USEPA. 1999c. Stakeholder Meeting on the Contaminant Candidate List and the 6-Year
Review of Existing National Primary Drinking Water Regulations. November 1999.
Available on the Internet at: http://www.epa.gov/safewater/ccl/novmtg.html.
USEPA. 1999d. National Primary and Secondary Drinking Water Regulations - Chemical and
Microbiological Contaminants, Analytical Methods; and Laboratory Certification
Requirements Revisions. Federal Register. Vol. 64, No. 230. p. 67449, December 1, 1999.
USEPA. 2000a. Working Group Meeting on Contaminant Candidate List Regulatory
Determinations and the 6-Year Review of Existing Regulations. Office of Water. June 2000.
Available on the Internet at: http://www.epa.gov/safewater/ccl/junemtg.html.
Protocol for the Review ofNPDWRs 30 June 2003
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USEPA. 2000b. Working Group Meeting on Contaminant Candidate List Regulatory
Determinations and the 6-Year Review of Existing Regulations. Office of Water. July 2000.
Available on the Internet at: http://www.epa.gov/safewater/ccl/julymtg.html.
USEPA. 2000c. NDWAC Working Group Meeting on Contaminant Candidate List Regulatory
Determinations and the 6-Year Review of Existing Regulations. Office of Water. September
2000. Available on the Internet at: http ://www.epa.gov/safewater/ccl/25septmtg.html.
USEPA. 2000d. National Primary Drinking Water Regulations; Radionuclides; Final Rule.
Federal Register. Vol. 65, No. 236. p. 76707, December 7, 2000.
USEPA. 2000e. Science Policy Council Handbook: Peer Review, 2nd Edition. EPA Report 100-
B-00-001. Office of Science Policy, Office of Research and Development. December 2000.
USEPA. 200la. National Primary and Secondary Drinking Water Regulations - Pollutants
Analysis; Test Procedures; Guidelines Establishment. Federal Register. Vol. 66, No. 10.
p.3526, January 16,2001.
USEPA. 200Ib. National Primary Drinking Water Regulation; Arsenic and Clarifications to
Compliance and New Source Contaminants Monitoring; Final Rule. Federal Register. Vol.
66, No. 14. p. 6975, January 22, 2001.
USEPA. 2002a. National Primary Drinking Water Regulations: Long-Term 1 Enhanced Surface
Water Treatment Rule; Final Rule. Federal Register. Vol. 67, No. 9. p. 1811, January 14,
2002.
USEPA, 2002b. Quality Assurance for the Six-Year Review of National Primary Drinking
Water Regulations. Memo from Judy Lebowich and Wynne Miller, Targeting and Analysis
Branch. Office of Ground Water and Drinking Water. March 2002.
USEPA. 2002c. Six-Year Review of 'the Total Coliform Rule - Comments Received. Memo
from Kenneth H. Rotert, Standards and Risk Reduction Branch, Office of Ground Water and
Drinking Water. March 2002.
USEPA. 2002d. National Primary Drinking Water Regulations - Announcement of the Results
of EPA's Review of Existing Drinking Water Standards and Request for Public Comment;
Proposed Rule. Federal Register. Vol. 67, No. 74. p. 19030, April 17, 2002.
USEPA. 2003 a. Analytical Feasibility Support Document for the Six-Year Review of Existing
National Primary Drinking Water Regulations (Reassessment of Feasibility for Chemical
Contaminants). EPA 815-R-03-003. Final. March 2003.
USEPA. 2003b. Consideration of Other Regulatory Revisions for Chemical Contaminants in
Support of the Six-Year Review of National Primary Drinking Water Regulations. EPA
815-R-03-005. Final. June 2003.
USEPA. 2003 c. Occurrence Estimation Methodology and Occurrence Findings Report for the
Six-Year Review of Existing National Primary Drinking Water Regulations. EPA
815-R-03-006. Final. June 2003.
Protocol for the Review ofNPD WRs 31 June 2003
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USEPA. 2003d. Public Comment and Response Summary for the Six-Year Review of National
Primary Drinking Water Regulations. EPA815-R-03-001. Final. June 2003.
USEPA. 2003e. Six-Year Review - Chemical Contaminants - Health Effects Technical Support
Document. EPA 822-R-03-008. Final. June 2003.
USEPA. 2003 f. Water Treatment Technology Feasibility Support Document for Chemical
Contaminants; In Support of EPA Six-Year Review of National Primary Drinking Water
Regulations. EPA 815-R-03-004. Final. June 2003.
Protocol for the Review ofNPDWRs 32 June 2003
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APPENDICES
Appendix A: Pre-1997 National Primary Drinking Water
Regulations (NPDWRs)
Appendix B: Differences between the National Drinking Water
Advisory Council's (NDWAC's) Recommendations
and the Protocol
Appendix C: Overview of the IRIS Assessments
Appendix D: Overview of the OPP Process for Toxicity
Assessments
Appendix E: Overview of Analytical Methods Review Process
Protocol for the Review ofNPD WRs June 2003
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Protocol for the Review ofNPDWRs 34 June 2003
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Appendix A: List of Pre-1997 National Primary Drinking
Water Regulations (NPDWRs)
Table A-l identifies the NPDWRs promulgated prior to the 1996 SDWA Amendments
(pre-1997 NPDWRs) and the rulemaking by which they were originally promulgated. EPA
reviewed these NPDWRs by 2002 in accordance with the review protocol described in this
document. Table A-2 identifies the remaining pre-1997 NPDWRs which are being or have
already been reviewed in separate actions and the NPDWRs promulgated after the 1996 SDWA
Amendments. The NPDWRs listed in Table A-2 will be reviewed as a part of the 2002-2008
review cycle.
Table A-l: Pre-1997 NPDWRs Reviewed in Accordance with this Protocol
Contaminant
Corresponding NPDWR
Chemical Contaminants
Acrylamide
Alachlor
Antimony
Asbestos
Atrazine
Barium
Benzene
Benzo[a]pyrene
Beryllium
Cadmium
Carbofuran
Carbon tetrachloride
Chlordane
Chromium (total)
Copper
Cyanide
2,4-D
Dalapon
l,2-Dibromo-3-
chloropropane (DBCP)
1 ,2-Dichlorobenzene (o-
Dichlorobenzene)
1 ,4-Dichlorobenzene (p-
Dichlorobenzene)
1 ,2-Dichloroethane
(Ethylene dichloride)
1 , 1 -Dichloroethy lene
Monochlorobenzene
(Chlorobenzene)
Phase II Rule
Phase II Rule
Phase V Rule
Phase II Rule
Phase II Rule
Phase IIB Rule
Phase I Rule
Phase V Rule
Phase V Rule
Phase II Rule
Phase II Rule
Phase I Rule
Phase II Rule
Phase II Rule
Lead and Copper Rule (LCR)
Phase V Rule
Phase II Rule
Phase V Rule
Phase II Rule
Phase II Rule
Phase I Rule
Phase I Rule
Phase I Rule
Phase II Rule
Contaminant
Corresponding NPDWR
Chemical Contaminants (continued)
cis-1 ,2-Dichloroethylene
trans- 1,2-
Dichloroethylene
Dichloromethane
(Methylene chloride)
1 ,2-Dichloropropane
Di(2-ethylhexyl)adipate
(DEHA)
Di(2-ethylhexyl)
phthalate (DEHP)
Dinoseb
Diquat
Endothall
Endrin
Epichlorohydrin
Ethylbenzene
Ethylene dibromide
(EDB)
Fluoride
Glyphosate
Heptachlor
Heptachlor epoxide
Hexachlorobenzene
Hexachlorocyclopenta-
diene
Lead
Lindane
Mercury (Inorganic)
Methoxychlor
Thallium
Phase II Rule
Phase II Rule
Phase V Rule
Phase II Rule
Phase V Rule
Phase V Rule
Phase V Rule
Phase V Rule
Phase V Rule
Phase V Rule
Phase II Rule
Phase II Rule
Phase II Rule
Fluoride Rule; Phase II Rule
revised monitoring requirements
Phase V Rule
Phase II Rule
Phase II Rule
Phase V Rule
Phase V Rule
LCR
Phase II Rule
Phase II Rule
Phase II Rule
Phase V Rule
Protocol for the Review of NPDWRs
A-l
June 2003
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Table A-l: Pre-1997 NPDWRs Reviewed in Accordance with this Protocol
Contaminant
Nitrate (as N)
Nitrite (as N)
Oxamyl (Vydate)
Pentachlorophenol
Picloram
Polychlorinated biphenyls
(PCBs)
Selenium
Simazine
Styrene
2,3,7,8-TCDD (Dioxin )
Tetrachloroethylene
Corresponding NPDWR
Phase II Rule
Phase II Rule
Phase V Rule
Phase IIB Rule
Phase V Rule
Phase II Rule
Phase II Rule
Phase V Rule
Phase II Rule
Phase V Rule
Phase II Rule
Contaminant
Toluene
Ibxaphene
2,4,5-TP (Silvex)
1 ,2,4-Trichlorobenzene
1,1,1 -Trichloroethane
1 ,1 ,2-Trichloroethane
rrichloroethylene
Vinyl chloride
Xylenes (total)
Corresponding NPDWR
Phase II Rule
Phase II Rule
Phase II Rule
Phase V Rule
Phase I Rule
Phase V Rule
Phase I Rule
Phase I Rule
Phase II Rule
Microorganisms
Total coliforms
(including fecal coliform
and£. coli)
Total Coliform Rule (TCR)
Dates of original promulgation are as follows:
- Phase II Rule: 56 FR 3526, January 30, 1991 (USEPA, 1991a) ' LCR: 56 FR 26460> June 7- 1991 (USEPA, 1991b)
- Phase V Rule: 57 FR 31776, July 17, 1992 (USEPA, 1992) - Fluoride Rule: 51 FR 11396, April 2, 1986 (USEPA, 1986)
- Phase IIB Rule: 56 FR 30266, July 1, 1991 (USEPA, 1991c) - TCR: 54 FR 27562, June 29, 1989 (USEPA, 1989b)
- Phase I Rule: 52 FR 25690, July 8, 1987 (USEPA, 1987)
Protocol for the Review of NPDWRs
A-2
June 2003
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Table A-2: NPDWRs Not Covered by this Protocol
Contaminant/Indicator
Corresponding NPDWR1
Reason Not Included
Chemical Contaminants
Arsenic
Pre-1986 National Interim Primary
Drinking Water Regulation (NIPDWR)
Reviewed/revised under January 22,
2001 Arsenic Rule23
Radionucttdes
Beta particles and photon emitters
Gross alpha particle activity
Radium-226/228 (combined)
Uranium
Pre-1 986 NIPDWR
2000 Radionuclides Rule
Reviewed/revised under December 7,
2000 Radionuclides Rule2
Promulgated after 1996. NPDWR
established in the December 7, 2000
Radionuclides Rule2
Microorganisms
Cryptosporidium
Giardia lambia
Heterotrophic plate count (HPC)
Legionella
Turbidity
Viruses
Interim Enhanced Surface Water
Treatment Rule (IESWTR)
Long-Term 1 Enhanced Surface Water
Treatment Rule (LT IESWTR)
Surface Water Treatment Rule (SWTR);
IESWTR; LT1ESWTR
SWTR
SWTR
SWTR; IESWTR; LT1ESWTR
SWTR; IESWTR; LT1ESWTR
Subject of ongoing rulemaking activity -
Long-Term 2 ESWTR (LT2ESWTR)
(November 2003 to mid 2004 )4
Disinfection Byproducts
Bromate ion
Chlorite ion
Haloacetic acids: Monobromoacetic
acid; Dibromoacetic acid;
Monochloroacetic acid;
Dichloroacetic acid; and
Trichloroacetic acid
Total Trihalomethanes (TTHMs):
Chloroform; Bromodichloro-
methane; Dibromochloromethane;
and Bromoform
Disinfectants and Disinfection
Byproducts Rule Stage 1 (DBPR)
TTHM Rule; Requirements revised
under Stage 1 DBPR
Revised rule promulgated after 1996 and
additional revisions to be considered
under Stage 2 DBPR (July 2003 to mid
2004)4
Revised rule promulgated after 1996 and
additional revisions to be considered
under Stage 2 DBPR (July 2003 to mid
2004)4
Disinfectant Residuals
Chlorine
Chloramines
Chlorine dioxide
Stage 1 DBPR
Revised rule promulgated after 1996
Protocol for the Review of NPDWRs
A-3
June 2003
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Table A-2: NPDWRs Not Covered by this Protocol
'Dates of original promulgation are as follows:
-Arsenic Rule: 40 FR 59566, December 24, 1975 (USERA, 1975)
- Radionuclides Rule: 41 FR 28402, July 9, 1976 (USEPA, 1976)
- IESWTR: 63 FR 69478, December 16, 1998 (USEPA, 1998c)
- LT1ESWTR: 67 FR 1811, January 14,2002 (USEPA, 2002a)
- SWTR: 54 FR 27486, June 29, 1989 (USEPA, 1989b)
- Stage 1 DBPR Rule: 63 FR 69389, December 16, 1998 (USEPA, 1998b)
- TTHM Rule: 44 FR 68624, November 29, 1979 (USEPA, 1979)
2 Indicates date of rule revision.
- Arsenic Rule: 66 FR 6976, January 22, 2001 (USEPA, 2001b)
- Radionuclides Rule: 65 FR 76707, December 7, 2000 (USEPA, 2000d)
3 After promulgation of the revised arsenic NPDWR on January 22, 2001, EPA initiated a review of the new MCL, and
postponed the effective date of the rule until February 22, 2002. EPA requested independent expert panel reviews of the
science, cost and benefits analyses for the January 2001 rule, and in July 2001, sought additional public comment on a range
of MCLs. Following receipt of the final expert panel reports in the Fall of 2001, EPA requested comment on the reports.
EPA will continue to evaluate the expert panel reports, the voluminous comments received during these comment periods,
and other relevant information and comments as they become available as part of the next Six-Year Review; EPA expects to
make a final decision on whether to revise the January 2001 rule as part of that Six-Year Review, which is due in August
2008. In the meantime, as announced by the Administrator on October 31, 2001, EPA will not further postpone the January
2001 rule, and EPA also does not expect to take any other additional action relative to the July 2001 proposal in the interim.
The revised arsenic MCL became effective on February 22, 2002. The date for compliance with the MCL remains January
23,2006.
4 Indicates anticipated date of promulgation.
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Appendix B: Differences between the National Drinking Water Advisory Committee's
(NDWAC's) Recommendations and this Protocol
This table indicates those NDWAC recommendations that EPA either did not incorporate or that
EPA changed substantially in this protocol document. Overall, EPA incorporated the majority of
the NDWAC's recommendations
NDWAC Recommendation
EPA Response
EPA should review the basis of all existing
NPDWRs during the first review round (/'. e., the
review round ending August 2002)
EPA does not believe that such a review is
practical in light of resource constraints and has
not incorporated it into the protocol. EPA will
review the basis of existing regulations only if
new data suggest the need for regulatory
revision(s).
Effective with review rounds starting after August
2002, EPA should complete both the review and
the revision within the Six-Year window.
This recommendation does not apply to the 1996-
2002 review round.
EPA should fully consider "other regulatory
revisions" (e.g., monitoring requirements system
data reporting requirements, etc.) as a part of the
Six-Year Review process.
EPA believes that many of these issues are best
addressed through mechanisms other than the Six-
Year Review process. Where appropriate
alternative mechanisms to consider these issues
are not available, EPA may consider them as a
part of the Six-Year Review if they meet the
following criteria:
they indicated a potential change to an
NPDWR, as defined under section 1401;
they are "ready" for rulemaking - that is, the
problem to be resolved has been clearly
identified and specific option(s) have been
formulated to address the problem; and
they represented a meaningful opportunity
for cost-savings while maintaining or
improving the level of public health
protection.
EPA should consider non-regulatory options, in
addition to regulatory changes, if the costs of
other regulatory compliance are considered to be
too high or interim measures are needed pending
promulgation of a rule.
EPA agrees that this suggestion has merit but
believes it is outside the scope of the Six-Year
Review effort and should be addressed through
alternative mechanisms. The recommendation
has not been incorporated into the protocol
document.
EPA should consider changes in State data-
reporting requirements, as well as changes to
system data-reporting requirements, as a part of
the Six-Year Review process.
EPA believes that revisions to State data-
reporting requirements are best considered
through other mechanisms outside the scope of
the Six-Year Review effort. The recommendation
has not been incorporated into the protocol
document.
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NDWAC Recommendation
EPA Response
EPA should consider multi-media mitigation
options as a part of the Six-Year Review process.
Efforts to pursue multi-media mitigation for
contaminants are outside the scope of the Six-
Year process, except in those instances where the
SDWA specifically authorizes EPA to consider a
multi-media approach as a part of the NPDWR.
Therefore, consideration of multi-media
mitigation is outside the scope of the 1996-2002
Six-Year Review.
EPA should quantify, to the maximum extent
practicable, costs and benefits associated with
possible regulatory revisions.
EPA does not believe it is practicable to quantify
costs and benefits during the review phase. This
is best done as a part of the rulemaking phase
before EPA proposes actual revisions. Instead,
EPA will conduct a qualitative assessment of
economic considerations for those NPDWRs
where a health or technical basis exists for a
possible regulatory revision.
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Appendix C: Overview of the IRIS Assessments
The Integrated Risk Information System (IRIS) is an EPA database containing Agency
consensus scientific positions on potential adverse human health effects that may result from
chronic exposure to chemical substances found in the environment.15 Assessments by IRIS
undergo internal and external peer reviews by health scientists.
The main reasons for including a chemical in the IRIS program are (1) Agency statutory,
regulatory, or program implementation needs; and (2) availability of new scientific information
or new methodology that might significantly change current IRIS assessment.
IRIS assessments are based solely on scientifically valid studies. Evaluations of original
toxicological and epidemiological studies conducted by the National Toxicology Program,
National Cancer Institute, National Institute of Environmental Health Sciences, EPA's National
Center for Environmental Assessment, industry, universities, etc., are all used in risk assessment.
These studies are individually evaluated for their soundness, methodological strength and
weaknesses, and whether or not they have been conducted according to current quality standards.
IRIS reviews are not based on secondary sources such as reviews conducted by other
national or international organizations (e.g., State of California, World Health Organization or
the International Agency for Research on Cancer), although such assessments are often
examined as part of the IRIS review.
A full list of chemicals assessed in IRIS and those for which assessments are planned can
be found on IRIS web site (http://www.epa.gov/iris). A large number of these IRIS assessments
are of direct relevance to the regulatory function of Office of Water (OW) and more specifically
to the six-year review. Some of the reviews are being conducted by OW. Others were
nominated for review by OW.
15 IRIS contains chemical specific health effects information. Information on synergistic effects of chemical
mixtures is scarce and is seldom available for inclusion in IRIS.
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Appendix D: Overview of the OPP Process for Toxicity Assessments
Under the requirements of the Federal Insecticide, Fungicide, and Rodenticide Act
(FIFRA), a registrant (manufacturer) is required to submit animal toxicity data on the potential
human health effects that may be posed by pesticide chemicals. Toxicity data are provided
during the initial registration of a pesticide as well as during the periodic re-registration review
of the pesticide as required by FIFRA. The schedule priority, for when an existing pesticide
enters a re-review is set in part by regulatory requirements which include provisions to give
priority to certain active ingredients. The Office of Pesticides Programs (OPP) will establish the
review schedule taking into account the procedures outlined in the Act. A more complete
discussion of the re-registration process can be found in section 4(a)-(f) of FIFRA.
In 1998, The Office of Water's (OW's) OGWDW and the OPP established major areas of
coordination on cross-cutting scientific issues. Included in the major efforts was the
harmonization of the human health hazard assessments and dose-response relationships for
pesticides. The two offices have agreed to share health effects data and coordinate activities on
the issues such as endpoint selection, dose-response information, and quantifying risks.
Therefore, the OW and OPP are working closely on establishing consistency in health effects
endpoints through resource and information sharing.
The OPP receives health effects data that are generated under specific scientific
guidelines established by the Agency and conducted under the requirements of Good Laboratory
Practices. These guidelines are available on the EPA's Internet site at the following location:
http://www.epa.gov/opptsfrs/OPPTS_Harmonized/870_Health_Effects_Test_Guidelines/indexx.
html.
In addition to the required guideline studies, the OPP will obtain and review open
literature data on adverse effects to test species. Although these studies are not used in
establishing health end-points (RfDs) and cancer potency or threshold values, they are used in
establishing the "weight of evidence" for an adverse effect. Data sources include, but are not
limited to, published, peer-reviewed journal articles in the open literature and toxicity data
submitted to other U.S. federal or international agencies that do not conform to the OPP's test
guidelines.
Below is a brief overview of end-point selection.
Toxicity Assessment
Non-Cancer Effects:
Reference Dose. For non-cancer effects, toxicity is represented by an RfD; it may be
calculated for acute effects (acute RfD (aRfD)) and chronic effects (chronic RfD (cRfD)). RfDs
are calculated by determining the No-Observed-Adverse-Effect Level (NOAEL) or bench-mark
dose point of departure from either acute or chronic toxicity studies (the choice of study depends
on which type of RfD is being calculated - aRfD or cRfD) and dividing it by the appropriate
uncertainty factors. Typically, an uncertainty factor is applied to account for: variation within
the human population (i.e., intraspecies); the differences between humans and animals as the
animal data are extrapolated to humans (i.e., interspecies); the duration of the study; the end
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point used in the calculation (NOAEL or Lowest-Observed-Adverse-Effect Level (LOAEL));
and the completeness of the database.
If the RfD will be used in dietary risk assessment, then it is adjusted to take into account
the Food Quality Protection Act (FQPA) Safety Factor for infants and children. Such an
adjusted RfD is called a Population Adjusted Dose (PAD). Like the RfD, it may be acute
(aPAD) or chronic (cPAD). In making the decision regarding the FQPA Safety Factor, the
Agency takes into account both information on the toxicity of the pesticide and the completeness
of the toxicity and exposure databases. For more information on how the Agency applies the
FQPA Factor, see the document "Standard Operating Procedures for use of FQPA Safety
Factor," April 26, 1999 at http://www.epa.gov/pesticides/trac/science/. However, these standard
operating procedures are currently under revision; and notification of the release of these
revisions is posted at: http://www.epa.gov/oppfeadl/trac/science.
Cancer Effects:
Linear Effect - Cancer Potency Factor (ql *). The cancer potency factor, which is
commonly known as a ql*, is the relative strength of a carcinogen. The bigger the ql*, the more
potent the carcinogen. It is calculated using a computer model that assumes linearity at doses
below which the effect occurred in the studies.
Non-Linear Effect -Margin of Exposure. For some carcinogenic pesticides, it is not
considered appropriate to calculate a potency factor. In these cases, the cancer effect is assumed
to have a threshold, as for non-cancer effects, and as such, a Margin of Exposure (MOE) is
derived. The MOE is a ratio calculated by dividing the toxicity Point of Departure (such as a
NOAEL or benchmark dose) by the estimated or calculated exposure level. EPA has not yet
established a policy on the level of risk that is of no concern for non-linear cancer risk
assessment.
During the review of the toxicity data and the dose-response assessment, the pesticide
being evaluated undergoes review by several in-house peer review committees.
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Appendix E: Overview of the Analytical Methods Review Process
A. What Section ofSDWA Requires the Agency to Specify Analytical Methods?
SDWA directs EPA to promulgate NPDWRs which specify either MCLs or TTs for
drinking water contaminants (SDWA section 1412; 42 U.S.C. § 300g-l). According to SDWA
(section 1401(1)(D)), NPDWRs include "criteria and procedures to assure a supply of drinking
water which dependably complies with such maximum contaminant levels; including accepted
methods for quality control and testing procedures to insure compliance with such levels." (42
U.S.C. § 300f(l)(D)) Moreover, EPA is to set an MCL for such NPDWRs "if, in the judgement
of the Administrator, it is economically and technologically feasible to ascertain the level of a
contaminant in water in public water systems." (SDWA section 1401(l)(C)(i); 42 U.S.C. §
300f(l)(C)(i)). Alternatively, if it is not economically or technologically feasible to so ascertain
the level of a contaminant, the Administrator may identify known TTs, which sufficiently reduce
the contaminant in drinking water, in lieu of an MCL (SDWA section 1401(l)(C)(ii)).
B. What is the Typical Process for Approving Methods for SD WA Analytes?
Methods are initially approved as a part of an MCL or monitoring requirement
rulemaking. Thereafter, as revisions to the approved methods are published or as new
technologies are developed, the Agency, from time-to-time, will group a set of methods for
proposal in a methods update rule. It generally takes 18 to 24 months to promulgate a methods
update rule. This can increase significantly if there is adverse public comment on a proposed
method.
The revised or new methods included in a methods update rule may be from EPA, other
Federal or State agencies, or standards organizations (e.g., American Society for Testing and
Materials (ASTM) or Standard Methods (SM)). These non-EPA entities have independent
review and/or collaborative testing requirements. In addition, under 40 CFR 141.27 (alternate
analytical techniques, also known as alternate test procedures or ATP) methods may also be
developed by private laboratories, vendors or groups. Independent review and collaborative
testing of these privately developed methods is accomplished by requiring submission of the
method to the Agency under the alternate test procedure (ATP) program. An alternate technique
is accepted "only if it is substantially equivalent to the prescribed test in both precision and
accuracy as it relates to the determination of compliance with the MCL." (40 CFR 141.27(a))
Initially, many ATP applications are missing data. Once a completed ATP application is
recorded by the Agency, the ATP pass/fail decision generally takes three to four months. For
successful ATPs, this period is followed by the formal rulemaking process, which was described
above as taking 18-24 months.
C. What Factors Does the Agency Consider in Approving Analytical Methods and in
Determining Feasible Limits?
In deciding whether an analytical method is economically and technologically feasible to
determine the level of a contaminant in drinking water, the Agency generally considers the
following (50 FR 46902, November 13, 1985 (USEPA, 1985); 52 FR 25690, July 8, 1987
(USEPA, 1987); 54 FR 22062, May 22, 1989a):
Is the method sensitive enough to address the level of concern (i.e., is quantitation
sufficient to meet the MCL)?
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Does the method give reliable analytical results at the MCL? What is the precision
(or reproducibility) and the bias (accuracy or recovery)?
Is the method specific? Does the method identify the contaminant of concern in the
presence of potential interferences?
Is the availability of certified laboratories, equipment and trained personnel sufficient
to conduct compliance monitoring?
Is the method rapid enough to permit routine use in compliance monitoring?
What is the cost of the analysis to Water Supply systems?
Regarding the first criteria (i.e.., sensitivity), the method detection limit (MDL) and the
practical quantitation level (PQL) are two performance measures used by EPA to estimate the
limits of performance of analytic chemistry methods for measuring contaminants in drinking
water. For SDWA analytes, EPA defines the MDL as "the minimum concentration of a
substance that can be measured and reported with 99% confidence that the analyte concentration
is greater than zero"(40 CFR Part 136 Appendix B). MDLs can be operator, method, laboratory,
and matrix specific. MDLs are not necessarily reproducible within a laboratory or between
laboratories on a daily basis due to the day-to-day analytical variability that can occur and the
difficulty of measuring an analyte at very low concentrations. In an effort to integrate this
analytical chemistry data into regulation development, the Agency uses the PQL to estimate or
evaluate the minimum, reliable quantitation level that most laboratories can be expected to meet
during day-to-day operations. EPA's Drinking Water program generally defines the PQL as "the
lowest level that can be reliably achieved within specified limits of precision and accuracy
during routine laboratory operating conditions" (50 FR 46902, November 13, 1985 (USEPA,
1985)) For several SDWA analytes, EPA has set the MCL at the PQL.
D. How Are PQLs Typically Determined for SDWA Contaminants?
Historically, EPA's OGWDW has used two main approaches to determine a PQL for
SDWA analytes. The preferred approach, the WS method, uses data from WS studies to
calculate the lower limit of quantitation. The WS method was used in most cases when
sufficient WS data are available to calculate a PQL. In the absence of WS data, the second
approach that EPA used was the MDL multiplier method. In this approach, the PQL was
calculated by multiplying the EPA-derived MDL by a factor of 5 or 10. The 5 or 10 multiplier
was used to account for the variability and uncertainty that can occur at the MDL.
1. How Were Water Supply Studies Conducted?
Water supply laboratory performance evaluation (PE) studies have been an integral part
of EPA's certification program for drinking water laboratories for over 20 years. Historically,
EPA's National Exposure Research Laboratory (NERL) in Cincinnati, Ohio conducted WS
studies for all current and proposed drinking water contaminants. Although EPA conducted the
WS studies semi-annually, for certification purposes, laboratories were only required to
demonstrate acceptable performance once a year (141.23(k)(3) and 141.24(f)(17)).
Each WS study included WS samples (or sample concentrates) that were analyzed for
both SDWA analytes and analytes being considered for regulation under the SDWA. During
these WS studies, EPA-NERL sent participating laboratories a set of the stable WS sample
concentrates in sealed glass ampules, a data reporting form, and appropriate instructions.
EPA-NERL sent WS samples to all laboratories that conducted drinking water analyses,
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including utility laboratories, commercial laboratories, and State and EPA Regional laboratories.
With appropriate dilution, the laboratory then analyzed the WS samples using the specified
procedures. Afterwards, the laboratory sent the completed reporting form to EPA for evaluation.
After evaluation, EPA returned a fully detailed report to each participating laboratory.
At this point in time, WS PE studies are no longer performed by EPA. On July 18, 1996
(61 FR 37464 (USEPA, 1996)), EPA proposed options for the externalization of the PE studies
program (now referred to as the Proficiency Testing or PT program). After evaluating public
comment, in the June 12, 1997 final notice EPA stated that the Agency has decided (62 FR
32113 (USEPA, 1997b)):
...on a program where EPA would issue standards for the operation of the program, the
National Institute of Standards and Technology (NIST) would develop standards for
private sector PE (PT) suppliers and would evaluate and accredit PE suppliers, and the
private sector would develop and manufacture PE (PT) materials and conduct PE (PT)
studies. In addition, as part of the program, the PE (PT) providers would report the
results of the studies to the study participants and to those organizations that have
responsibility for administering programs supported by the studies.
2. PQL Determinations - How Are WS Studies Evaluated and What Criteria Are
Used?
The derivation of the PQL involves determining the concentration of an analyte at which
a set percentage of the laboratories achieve results within a specified range of the spiked value.
Historically, the percentage of laboratories was set at 75 percent, while a range of acceptance
limits around the spiked value were used. In many cases, EPA derived PQLs only from the data
submitted by the EPA Regional and State laboratories that participate in the WS studies.
A PQL derived from WS data in such a manner is considered a stringent target for
routine laboratory performance because:
WS samples are prepared in reagent water and therefore do not contain the matrix
interferences that may occur in field samples.
Laboratories analyze only a small number of samples for the study and are aware that
the samples are for the purposes of PE (i.e., they are not "blind" samples).
In deriving a PQL from WS study data, the Agency typically sets a fixed percentage or 2
sigma (2 standard deviation) acceptance window around the known concentration (or spike
value) of the WS samples. Then percentage of laboratories achieving results within the specified
acceptance window (y-axis) is plotted against the known spike concentration of the WS study
samples (x-axis). While the acceptance limits for inorganics typically range from 15 to 30
percent, the acceptance limits for organics generally range from 40 to 50 percent. Several
SDWA analytes have acceptance limits of 2 sigma (2 standard deviation). Linear regression or
graphical analysis is performed on the WS data to determine the concentration at which 75
percent of EPA Regional and State laboratories achieve acceptable results.
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EPA 815-R-03-002
EPA Protocol for the Review of
Existing National Primary Drinking Water Regulations
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