vvEPA
    United States
    Environmental Protection
    Agency
            EPA Protocol for the
  Second Review of Existing National Primary
     Drinking Water Regulations (Updated)

-------
Office of Water (4607M)
EPA815-B-09-002
October 2009
www.epa.gov/safewater

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing    EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

                              Table of Contents
Executive Summary	ES-1
1    Introduction	1-1
   1.1    Basic Principles	1-1
   1.2    Scope of Review	1-2
   1.3    Organization and Contents of this Document	1-5
2    Overview of Six-Year Review Protocol	2-1
   2.1    Protocol Refinements for Six-Year Review 2	2-1
   2.2    Elements of the Six-Year Review 2 Decision Tree	2-2
3    Detailed Discussion of Decision Tree Implementing the Protocol	3-1
   3.1    Initial Review Branch	3-1
     3.1.1    Inputs to the Initial Review	3-1
     3.1.2    Output of Initial Review	3-3
   3.2    Health Effects and MCLG Branch	3-3
     3.2.1    Inputs to Health Effects and MCLG Review	3-4
     3.2.2    Outputs from  Health Effects and MCLG Review	3-6
   3.3    Maximum Contaminant Level (MCL) Branches	3-6
     3.3.1    Inputs to Maximum Contaminant Level (MCL) Review	3-8
     3.3.2    Outputs from  Maximum Contaminant Level (MCL) Review	3-9
   3.4    Treatment Technique Branch	3-9
     3.4.1    Inputs to Treatment Technique Review	3-10
     3.4.2    Outputs from  Treatment Technique Review	3-10
   3.5    Treatment Technique Analysis Branch	3-10
     3.5.1    Inputs to Treatment Technique Analysis Review	3-10
     3.5.2    Outputs from  Treatment Technique Analysis Review	3-11
   3.6    Methods Branch	3-11
     3.6.1    Inputs to Methods Review	3-13
     3.6.2    Output from Methods Review	3-14
   3.7    Occurrence Branch	3-14
     3.7.1    Inputs to Occurrence Review	3-15
     3.7.2    Output from Occurrence Review	3-17
   3.8    Treatment Branch	3-17
     3.8.1    Inputs to Treatment Technology Review	3-18
     3.8.2    Output of Treatment Technology Review	3-19
   3.9    Implementation Branch	3-19
     3.9.1    Inputs to Implementation Review	3-19
     3.9.2    Outputs from  Implementation Review	3-20
4    References	4-1

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

                               Table of Exhibits
Exhibit 1-1. NPDWR Contaminants Included in Six-Year Review 2	1-3
Exhibit 1-2. NPDWR Contaminants with Recent or Ongoing Actions	1-5
Exhibit 2-1. Overview of Six-Year Review Decision Tree	2-3
Exhibit 3-1. Initial Review Branch	3-2
Exhibit 3-2. Health Effects and MCLG Branch	3-4
Exhibit 3-3. Maximum Contaminant Level Branch 1 (Potential for MCLG Revision)	3-7
Exhibit 3-4. Maximum Contaminant Level Branch 2 (No Potential for MCLG Revision)	3-8
Exhibit 3-5. Treatment Technique Branch	3-9
Exhibit 3-6. Treatment Technique Analysis Branch	3-11
Exhibit 3-7. Analytical Methods Branch	3-12
Exhibit 3-8. Occurrence Branch	3-15
Exhibit 3-9. Treatment Branch	3-18
Exhibit 3-10. Implementation Branch	3-19

-------
EPA-OGWDW
 EPA Protocol for the Second Review of Existing
  National Primary Drinking Water Regulations
EPA815-B-09-002
    October 2009
                      Abbreviations and Acronyms
2,4-D
ATSDR
BAT
CalEPA
CCRIS
CICADS

DART
DBCP
DBPR
DEHA
DEHP
EDB
EPA
EQL
FAO
GWR
HAAS
HSDB
IARC
ICR
IPCS/EHC

IRIS
JECFA
JMPR
LCR
LT2
MCL
MCLG
MDL
mg/L
MRL
N
NAS
NAWQA
NCOD
NDWAC
NELAC
NIEHS
NPDWR
NTP
2,4-dichlorophenoxyacetic acid
Agency for Toxic Substances and Disease Registry
best available technology
California Environmental Protection Agency
Chemical Carcinogenesis Research Information System
European Commission Concise International Chemical Assessment
Documents
Developmental and Reproductive Toxicology
l,2-dibromo-3-chloropropane
Disinfectants and Disinfection Byproducts Rule
di(2-ethylhexyl)adipate
di(2-ethylhexyl)phthalate
ethylene dibromide
U.S. Environmental Protection Agency
estimated quantitation level
Food and Agriculture Organization of the United Nations
Ground Water Rule
haloacetic acids
Hazardous Substances Data Bank
International Agency for Research on Cancer
Information Collection Request
International Programme on Chemical Safety/Environmental Health
Criteria
Integrated Risk Information System
Health Canada, Joint Expert Committee on Food Additives
Joint FAO/WHO Meeting on Pesticide Residues
Lead and Copper Rule
Long-Term 2 Enhanced Surface Water Treatment Rule
maximum contaminant level
maximum contaminant level goal
method detection limit
milligrams per liter
minimum reporting level
nitrogen
National Academy of Sciences
National Water Quality Assessment
National Drinking Water Contaminant Occurrence Database
National Drinking Water Advisory Council
National Environmental Laboratory Accreditation Conference
National Institute of Environmental Health Sciences
National Primary Drinking Water Regulation
National Toxicology Program

-------
EPA-OGWDW
 EPA Protocol for the Second Review of Existing
  National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
OGWDW
OPP
OW
OST
PCBs
PQL
PE
PT
PWS
R2S2
RfD
SDWA
SSCT
TT
TTHM
WHO
WS
Office of Ground Water and Drinking Water
Office of Pesticide Programs
Office of Water
Office of Science and Technology
polychlorinated biphenyls
practical quantitation level
performance evaluation
proficiency testing
public water system
Regulatory Review Support Spreadsheet
reference dose
Safe Drinking Water Act
small system compliance technology
treatment technique
total trihalomethanes
World Health Organization
water supply
                                          IV

-------
EPA-OGWDW         EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009


Executive Summary

The 1996 Safe Drinking Water Act (SDWA) Amendments require the U.S. Environmental
Protection Agency (EPA or the Agency) to review and revise National Primary Drinking Water
Regulations (NPDWRs) at least once every six years as appropriate to maintain or improve
human health protection. EPA completed and published the results of its first Six-Year Review
(Six-Year Review 1) July 18, 2003 (68 FR 42908) after developing a systematic approach, or
protocol, for the review of NPDWRs. As described in this document, EPA has applied the same
protocol with minor refinements (revised protocol) to its second Six-Year Review of NPDWRs
(Six-Year Review 2).

In Six-Year Review 2, EPA addressed the following:

•   Maximum Contaminant Level Goals (MCLGs; the health goal) - for some contaminants
    new health effects assessments completed since the MCLG was promulgated or last revised
    include revised reference doses (RfD) and/or cancer classification.
•   Maximum Contaminant Levels (MCLs; the enforceable standard) - for some contaminants,
    the MCL is  equal to the MCLG, and the health effects assessment indicates potential to
    revise the MCLG. Improvements in analytical or treatment feasibility may also indicate
    feasibility to set the MCL closer to the MCLG.
•   Treatment  Technique (TT; sometimes established in lieu of an MCL) - new information on
    health effects, analytical feasibility, or treatment feasibility may  suggests a possibility to
    revise TT.
•   Other Treatment Technology (NPDWRs contain Best Available Technologies, or BATs,
    capable of achieving MCLs) - Changes to BAT recommendations may be appropriate for
    revised MCLs.
•   Other Regulatory Requirements (Monitoring) -Other regulatory revisions may be
    appropriate  if information suggest that changes in monitoring standards (e.g., frequency)
    could reduce health risks or costs while maintaining or improving the level of public health
    protection.

This comprehensive review comprised 85 NPDWRs. To facilitate the process, EPA developed a
Six-Year Review 2 decision tree that structures a series of questions about whether there is new
information suggesting that it is possible to revise one or more NPDWR elements in a  logical
order. The order of the questions within the tree reflects the sequential relationships between the
different NPDWR elements and thus avoids unnecessary analyses.

For example, EPA must generally set the MCL as close to the MCLG as feasible. Consequently,
if the MCL is equal to the MCLG, EPA must make decisions regarding the availability and
adequacy of new information relevant to the potential to  revise the MCLG before decisions
regarding the potential to revise the MCL. Also, if there is no potential to revise the MCLG and
the MCL is already equal to the MCLG, then there is no basis for revising the MCL. In this
instance, the "branch" of the decision tree containing questions about revising the MCL is not
reached, and it is not necessary to review information related to analytical feasibility.
                                         ES-1

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

The first branch of the decision tree is an Initial Review Branch, with the purpose of identifying
contaminants for which further review of detailed technical data is premature (the contaminant is
the subject of recent or ongoing rulemaking, or there is an ongoing health effects assessment).
Excluding such contaminants from subsequent review prevents duplicative Agency efforts. For
contaminants for which there is an ongoing health effects assessment and the MCL is above the
MCLG, the review proceeds to branches that evaluate whether there is potential to lower the
MCL. The Agency's review of new information that may affect the MCL for these contaminants
is one of several refinements of the protocol. During Six-Year Review 1, EPA took no further
action on any contaminants with ongoing health effects assessments. This refinement addresses
the SDWA requirement that EPA set each MCL as close to the MCLG as feasible.

The additional branches of the decision tree are:

•   Health effects and MCLG
.   MCL
•   Treatment technique
•   Analytical methods
•   Occurrence and exposure
•   Treatment feasibility.

A series of technical support documents (U.S. EPA, 2009a-g) provide data  and analysis to
support EPA's decisions in each branch. EPA also developed an automated tool called the
Regulatory Review Support Spreadsheet (R2S2) to track the review results. This tool enhances
transparency, automates the decision process, and facilitates the Agency's reporting of its
recommendations. The Agency will continue to refine the Six-Year Review protocol during
subsequent reviews to address changing circumstances.

As  for Six-Year Review 1, Six-Year Review 2 results consist of recommendations to revise some
NPDWRs, and to take no action at this time for the remaining NPDWRs. A recommendation to
revise an NPDWR starts a regulatory process 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 not appropriate and may discontinue regulatory revision efforts. Review of that
NPDWR would, however, continue  in future Six-Year Reviews.

Similarly, a recommendation to "take no action at this time" means only that EPA does not
believe that regulatory changes to a  particular NPDWR are appropriate based on health effects,
analytical methods, treatment data, ongoing scientific reviews, priority,  or other reasons.
Reviews of these contaminants in future Six-Year Reviews may lead to  a recommendation that
regulatory changes are appropriate.
                                          ES-2

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing    EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

1    Introduction

The 1996 Safe Drinking Water Act (SDWA) Amendments require the U.S. Environmental
Protection Agency (EPA or the Agency) to periodically review existing National Primary
Drinking Water Regulations (NPDWRs). Section 1412(b)(9) of SDWA reads:

        ...[t]he Administrator shall, not less than every 6 years, review and revise, as
       appropriate, each 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.

Pursuant to the 1996 SDWA Amendments, EPA completed and published the results of its first
Six-Year Review (Six-Year Review 1) July 18, 2003 (68 FR 42908) after developing a
systematic approach, or protocol, for the review of NPDWRs. EPA has applied the same
protocol with minor refinements (revised protocol) to the second Six-Year Review of NPDWRs
(Six-Year Review 2). Section 2 provides an overview of the protocol and Section 3 describes the
protocol and the minor refinements used for the Six-Year Review 2. The Agency will continue to
refine the protocol  during subsequent six-year reviews to address changing circumstances.

1.1  Basic Principles

The primary goal of the Six-Year Review process is to identify NPDWRs for possible regulatory
revision. Although the statute does not define when a revision is "appropriate," as a general
benchmark, EPA considered a possible revision to be "appropriate" if,  at a minimum, it presents
a meaningful opportunity to:

•   improve the level of public health protection, and/or
•   achieve cost savings while maintaining or improving the  level of public health protection.

Toward this end, EPA applied a number of basic principles in reviewing NPDWRs. First, the
Agency sought to avoid redundant review efforts. Therefore, EPA classified NPDWRs that were
the subject of other rulemaking actions either ongoing or completed during this review period as
having "ongoing actions" or "recent actions" and not subject to further technical review under
Six-Year Review 2.

Second, EPA evaluated the potential  for new information to affect NPDWRs in a manner
consistent with its existing policies and procedures for developing NPDWRs. For example, in
determining whether a possible change in analytical feasibility existed, the Agency applied the
current policy and procedures  for calculating the practical quantitation level for drinking  water
contaminants.

Third, the Agency does not believe it is appropriate to consider revisions to NPDWRs for
contaminants with  an ongoing health effect assessment for which the maximum contaminant
level (MCL) is set equal to the maximum contaminant level goal (MCLG) or based on benefit-
cost analysis. This  principle stems from the fact that any new health effects information could
affect the MCL via a change in the MCLG or the assessment of the benefits associated with the
                                          1-1

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

MCL. Therefore, EPA made a "take no action" recommendation if the health effect assessment
would not be completed during the review period for each contaminant that has either an MCL
that is equal to its MCLG or an MCL that is based on the 1996 SDWA Amendments' cost-
benefit provision.

Fourth, EPA will address new information from health effect assessments completed after the
information cutoff date (March 1, 2009) for the Six-Year Review 2 and any new conclusions or
additional information associated with the contaminant during the next review cycle. The
Agency may consider accelerating a review and possible revision for a particular NPDWR
before the next review cycle when justified by new public health risk information.

Fifth, EPA identified areas of inadequate or unavailable data (data gaps) or emerging data that is
needed to determine whether revision to an NPDWR is appropriate. If EPA is able to fill such
gaps or fully evaluate the emerging information after completing Six-Year Review 2, the Agency
will consider the information as part of the next review cycle. EPA may consider accelerating a
review and possible revision for a particular NPDWR if a review and possible revision is
justified by new public health risk information.

Finally, EPA applied the Agency's peer review policy (USEPA, 2000), where appropriate, to
any new analyses.

1.2  Scope of Review

As for Six-Year Review 1, Six-Year Review 2 encompassed the individual elements of
NPDWRs, as follows:

•   MCLG changes - EPA generally considered changes to the MCLG (the health goal) only in
    instances of a new health effects assessment completed since the MCLG was promulgated or
    last revised, which resulted in a revised reference dose (RfD) and/or cancer classification
    justifying a revised MCLG.
•   MCL changes - EPA generally considered changes to the MCL (the enforceable standard)
    whenever: (1) the health effects assessment justifies a possible change to the MCLG and the
    existing MCL is set at the MCLG, or (2) the current MCL was limited by analytical or
    treatment feasibility and the review of these capabilities indicates that it may now be feasible
    to set the MCL closer to the MCLG.*
•   Treatment Technique (TT)2 changes - Treatment techniques can improve to the point where
    more protective drinking water standards may be considered. EPA generally considered
    revisions to TT requirements whenever there was new information on health effects,
    analytical feasibility, or treatment feasibility that suggests a possibility to revise the TT.
•   Changes to Other Treatment Technology - When EPA sets an MCL, the NPDWR also
    contains Best Available Technology (BAT) recommendations that address drinking water
1 Although the 1996 SDWA Amendments allow EPA in certain circumstances to set the MCL at a level 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.
2 A TT specifies a type of treatment (e.g., filtration, disinfection, or other methods of control to limit contamination
in drinking water) and means for ensuring adequate treatment performance (e.g., monitoring of water quality to
ensure treatment performance).
                                           1-2

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
   treatment processes. Although not required for compliance purposes, EPA sets BATs that
   have the capability to meet MCLs. EPA generally limited review of BAT recommendations
   for those NPDWRs with possible MCL revisions.
•  Changes to Other Regulatory Requirements - EPA generally considered other regulatory
   revisions, such as changes to monitoring requirements, if other possible NPDWR revisions or
   health effects information suggest that changes in monitoring standards (e.g., increased
   frequency in monitoring) could reduce health risks or costs while maintaining or improving
   the level of public health protection. This part of the review focused on implementation-
   related issues that are not being addressed, or have not been addressed, through alternative
   mechanisms (e.g., as part of a recent or ongoing rulemaking). Where appropriate alternative
   mechanisms do not exist, EPA generally considered implementation-related concerns if the
   possible revision met the following criteria:

   •   The possible revision indicates a possible change to an NPDWR, as defined under section
       1401 of SOW A.
   •   The possible revision was "ready" for rulemaking - that is, the problem to be resolved
       has been clearly identified and specific option(s) formulated to address the problem.
   •   The possible revision could improve the level of public health protection or represent a
       cost savings while maintaining or improving public health protection.

For Six-Year Review 2, EPA reviewed the chemical, microbiological, and radiological
NPDWRs for the 85 contaminants shown in Exhibit 1-1. Of the 85 NPDWRs, EPA is reviewing
or has revised 14 through recent or ongoing rulemakings (see Exhibit 1-2).

         Exhibit 1-1. NPDWR Contaminants Included in Six-Year Review 2
Contaminants
Acrylamide
Alachlor
Alpha particles
Antimony
Arsenic
Asbestos
Atrazine
Barium
Benzene
Benzo[a]pyrene
Beryllium
Beta particles
Bromate
Cadmium
Carbofuran
Carbon tetrachloride
Chloramines
Chlordane
MCLG
(mq/L)i
0
0
0 (pCi/L)
0.006
0
7 (million
fibers/L)
0.003
2
0
0
0.004
0 (millirems/yr)
0
0.005
0.04
0
4
0
MCL
(mq/L)i
TT
0.002
15 (pCi/L)
0.006
0.01
7 (million
fibers/L)
0.003
2
0.005
0.0002
0.004
4 (millirems/yr)
0.01
0.005
0.04
0.005
4
0.002
Contaminants
Epichlorohydrin
Ethylbenzene
Ethylene dibromide (EDB)
Fluoride
Giardia lamblia
Glyphosate
Haloacetic acids (HAA5)
Heptachlor
Heptachlor epoxide
Hexachlorobenzene
Hexachlorocyclopentadiene
Lead
Leqionella
Lindane
Mercury (inorganic)
Methoxychlor
Monochlorobenzene
(Chlorobenzene)
Nitrate (as N)
MCLG
(mq/L)i
0
0.7
0
4
0
0.7
n/a3
0
0
0
0.05
0
0
0.0002
0.002
0.04
0.1
10
MCL
(mq/L)i
TT
0.7
0.00005
4
TT
0.7
0.06
0.0004
0.0002
0.001
0.05
TT
TT
0.0002
0.002
0.04
0.1
10
                                          1-3

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
    October 2009
        Exhibit 1-1. NPDWR Contaminants Included in Six-Year Review 2
Contaminants
Chlorine
Chlorine dioxide
Chlorite
Chromium (total)
Coliform
Copper
Cryptosporidium
Cyanide
2,4-D
Dalapon
Di(2-ethylhexyl)adipate
(DEHA)
Di(2-
ethylhexyl)phthalate
(DEHP)
1,2-Dibromo-3-
chloropropane (DBCP)
1,2-Dichlorobenzene
(o-Dichlorobenzene)
1,4-Dichlorobenzene
(p-Dichlorobenzene)
1,2-Dichloroethane
(Ethylene dichloride)
1,1-Dichloroethylene
cis-1,2-
Dichloroethylene
trans-1,2-
Dichloroethylene
Dichloromethane
(Methylene chloride)
1,2-Dichloropropane
Dinoseb
Diquat
Endothall
Endrin
MCLG
(mg/L)1
4
0.8
0.8
0.1
0%2
1.3
0
0.2
0.07
0.2
0.4
0
0
0.6
0.075
0
0.007
0.07
0.1
0
0
0.007
0.02
0.1
0.002
MCL
(mg/L)1
4
0.8
1
0.1
5%2
TT
TT
0.2
0.07
0.2
0.4
0.006
0.0002
0.6
0.075
0.005
0.007
0.07
0.1
0.005
0.005
0.007
0.02
0.1
0.002
Contaminants
Nitrite (as N)
Oxamyl (Vydate)
Pentachlorophenol
Picloram
Polychlorinated biphenyls
(PCBs)
Radium
Selenium
Simazine
Styrene
2,3,7,8-TCDD (Dioxin)
Tetrachloroethylene
Thallium
Toluene
Total Trihalomethanes
(TTHMs)
Toxaphene
2,4,5-TP (Silvex)
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethylene
Uranium
Vinyl Chloride
Viruses
Xylenes (total)
MCLG
(mg/L)1
1
0.2
0
0.5
0
0 (pCi/L)
0.05
0.004
0.1
0
0
0.0005
1
n/a4
0
0.05
0.07
0.2
0.003
0
0 (Mg/L)
0
0
10
MCL
(mg/L)1
1
0.2
0.001
0.5
0.0005
5 (pCi/L)
0.05
0.004
0.1
3.00E-08
0.005
0.002
1
0.08
0.003
0.05
0.07
0.2
0.005
0.005
30 (Mg/L)
0.002
TT
10
1 . Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million.
2. No more than 5.0% samples total coliform-positive in a month.
3. There is no MCLG for all five haloacetic acids. MCLGs for some of the individual contaminants are: dichloroacetic acid (zero),
trichloroacetic acid (0.02 mg/L), and monochloroacetic acid (0.07 mg/L). Bromoacetic acid and dibromoacetic acid are regulated
with this group, but have no MCLGs.
4. There is no MCLG for total trihalomethanes. MCLGs for some of the individual contaminants are: bromodichloromethane
(zero), bromoform (zero), dibromochloromethane (0.06 mg/L), and chloroform (0.07mg/L).
                                      1-4

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
        Exhibit 1-2. NPDWR Contaminants with Recent or Ongoing Actions
Contaminant/Indicator
Recent or Ongoing Action
Disinfection Byproducts
Bromate
Chlorite
TTHMs: chloroform, bromodichloromethane,
dibromochloromethane, bromoform
HAA5: monochloroacetic acid, dichloroacetic
acid trichloroacetic acid, monobromoacetic
acid dibromoacetic acid
Stage 2 DBPR (January 4, 2006)
Stage 2 DBPR (January 4, 2006)
Stage 2 DBPR (January 4, 2006)
Stage 2 DBPR (January 4, 2006)
Disinfectant Residuals
Chlorine
Chloramines
Chlorine dioxide
GWR (November 8, 2006)
GWR (November 8, 2006)
Stage 2 DBPR (January 4, 2006)
Inorganics
Lead
Copper
Short-Term Revisions (October 10, 2007)
Long-Term Revisions currently underway
Long-Term Revisions currently underway
Microorganisms
Cryptosporidium
Giardia lamblia
Leqionella
Viruses (enteric)
Coliform
LT2 (January 5, 2006)
LT2 (January 5, 2006)
GWR (November 8, 2006)
LT2 (January 5, 2006)
GWR (November 8, 2006)
Total Coliform Rule-making currently underway
 Dates of promulgation are as follows:
 Stage 2 DBPR: 71 FR388 (January 4, 2006)
 LT2 Rule: 71 F/?654 (Januarys, 2006)
 GWR: 71 FR65574 (Novembers, 2006)
 LCR Short-Term Regulatory Revisions: 72 FR57782 (October 10, 2007)

1.3 Organization and  Contents of this Document

This document describes the review process for Six-Year Review 2:

•   Section 2 provides an overview of the Six-Year Review protocol and the decision tree EPA
    developed to implement it for Six-Year Review 2.
•   Section 3 provides detailed description of the individual branches of the decision tree
    implementing the Six-Year Review 2 protocol.

EPA has developed additional technical support documents, noted in the text, to provide detailed
discussion of each element of the review.
                                         1-5

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

2  Overview of Six-Year Review Protocol

During Six-Year Review 1, the Agency developed a systematic approach or protocol to review
existing NPDWRs (USEPA, 2003c). The Agency based this protocol on the recommendations of
the National Drinking Water Advisory Council (NDWAC), through internal Agency
deliberations, and discussions with a diverse group of stakeholders involved in drinking water
and its protection.

For Six-Year Review 2, EPA assessed this protocol and determined that it remained appropriate
and suitable for the second review. Thus, the information requirements and decision-making
process of the Six-Year Review 2 protocol are essentially the same as those implemented during
Six-Year Review 1, with some minor refinements to enhance the Agency's effectiveness in
applying the protocol to the review of NPDWRs.

The Six-Year Review 2 protocol addresses critical aspects of health protection and the setting of
standards under the SDWA. Similar to the Six-Year Review 1, the results of the Six-Year
Review 2 protocol are recommendations to revise some NPDWRs, and to take no action at this
time for the remaining NPDWRs.

The publication of a recommendation to revise pursuant to a Six-Year Review under Section
1412(b)(9) is not the end of the regulatory process, but is the beginning of one. A
recommendation to revise starts a regulatory process 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 not appropriate and may discontinue regulatory revision efforts. Review
of that NPDWR would, however, continue in future Six-Year Reviews.

Similarly, a recommendation to  "take no action 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
health effects, analytical methods, or treatment data; ongoing scientific reviews; low priority; or
other reasons. Reviews of these  contaminants in future Six-Year Reviews may lead to a
recommendation that regulatory changes are appropriate.

The Agency will continue to refine the Six-Year Review protocol during subsequent reviews to
address changing circumstances.

2.1   Protocol Refinements  for Six-Year Review 2

During Six-Year Review 2, EPA refined the protocol to implement a more detailed "decision
tree" than it used during Six-Year Review 1. The revised protocol can be broken down into a
series of questions about whether there is new information for a contaminant that suggests it is
possible to revise one or more of the NPDWR elements. These questions can be logically
ordered into a decision tree that  incorporates the sequential relationships between the different
NPDWR elements. For example, EPA must generally set the MCL as close to the MCLG as
feasible. Consequently, if the MCL is equal to the MCLG, EPA must make decisions regarding
the availability and adequacy of new information relevant to the potential to revise the MCLG
                                          2-1

-------
EPA-OGWDW         EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

before decisions regarding the potential to revise the MCL. Also, if there is no potential to revise
the MCLG and the MCL is already equal to the MCLG, then there is no basis for revising the
MCL. In this instance, the MCL branch of the decision tree is not reached, and it is not necessary
to make related  decisions such as whether the practical quantitation level (PQL) can be revised.
EPA developed an automated tool called the Regulatory Review Support Spreadsheet (R2S2) to
track the review process for each contaminant that leads to the revise/take no action
recommendations. This tool enhances transparency of the review results. The automation also
streamlines the decision process and facilitates the Agency's reporting of its recommendations.
Exhibit 2-1 shows the decision tree structure for the revised protocol.

2.2  Elements of the Six-Year Review 2 Decision  Tree

The Six-Year Review decision tree contains a "branch" with multiple questions for each review
topic. Information flows between these branches as shown in Exhibit 2-1. Each branch
corresponds to a specific technical review of an NPDWR element that EPA conducted during
Six-Year Review 2. These branches include:

•   Initial review
•   Health effects and MCLG
.   MCL
•   Treatment technique
•   Analytical methods
•   Occurrence  and exposure
•   Treatment feasibility
•   Implementation.

The following sections describe each branch and provide detailed descriptions of EPA's data
requirements, analyses, and decision-making process.
                                          2-2

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

             Exhibit 2-1. Overview of Six-Year Review Decision Tree
 INITIAL REVIEW BRANCH
   WEALTH EFFECTS &
     MCLG BRANCH —
                              MCLBRANCH 1
                                                             METHODS BRANCH
                                                           OC
                                          CE BRANCH
                       TE(

HNIOUt
NT-:,
 RANCH
                                                            TREATMENT BRAKCH
InfREATMENT
    HNtOUES
    SIS BRAN
                                                          IMPLEMENTATION BRANCH
                                       2-3

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

3  Detailed Discussion of Decision Tree Implementing the
    Protocol

This section describes the individual branches of the decision tree in detail, including the
purpose, inputs, and outputs of each branch.

3.1   Initial Review  Branch

The first branch of the decision tree is an Initial Review Branch (Exhibit 3-1), with the purpose
of identifying contaminants meeting one of three conditions for which there is a recent or
ongoing action or for which further review of detailed technical data is premature. The three
conditions are:

•  EPA has recently reviewed and revised the NPDWR (i.e., since August 2002)
•  EPA is conducting an ongoing regulatory revision
•  EPA is performing a formal health effects assessment of the regulated contaminant, the
   results are due after the cutoff data for the review, or EPA completed a health effects
   assessment, but then identified new information with potential to affect the MCLG and the
   MCL is set equal to the MCLG.

Excluding such contaminants from subsequent steps in the NPDWR review decision tree
improves the efficiency and effectiveness of the review process. It prevents duplicative Agency
data collection and  analysis efforts for recent or ongoing actions to review and revise NPDWRs.
It also avoids recommendations based on inadequate information for contaminants with ongoing
or pending health effects assessments that already have MCLs set equal to their respective
MCLGs. For a contaminant that has an ongoing health effects assessment and an MCL above its
MCLG, EPA's review continues to branches that evaluate whether there is potential to lower the
MCL. The Agency's review of new information that may affect the MCL for these contaminants
is one of several refinements of the protocol. During Six-Year Review 1, EPA took no further
action on any contaminants with ongoing health effects assessments. The refinement addresses
the SDWA requirement that EPA set each MCL as close to the MCLG as feasible; a common
limitation is the analytical capability at the time the NPDWR is promulgated, especially for a
contaminant with an MCLG equal to zero.

3.1.1  Inputs to the Initial Review
The questions in the Initial Review Branch are screening-level questions. For Six-Year Review
2, EPA answered these questions for each contaminant covered by a NPDWR. The first two
questions in the branch require information regarding whether a contaminant is the subject of
recent or ongoing rules. For Six-Year Review 2, the regulatory schedule for the Office of Ground
Water and Drinking Water (OGWDW) provided the inputs to these two decisions. Exhibit 1-2
lists the contaminants that are subject to recent or ongoing rules.
                                         3-1

-------
EPA-OGWDW
        EPA Protocol for the Second Review of Existing
         National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
                           Exhibit 3-1. Initial Review Branch
          Was a regulatory action
          undertaken since August
                2002?
          Is a regulatory review or
           revision in progress or
          planned through 2009?
          Is a new HEA [including
             reproductive and
          developmental effects] in
          progress and expected
          after March 2009, or is
         there new information* after
         completion of a new HEA?
                      Is MCLG < MCL, or
                       does MCLG=0?
                                                                                 GOTO
                                                                             Health Effects and
                                                                               MCLG Branch
 Key:
         No
         Yes
HEA = health effects assessment
*New information that could affect the MCLG. May need to re-
nominate for IRIS/OPP/OW review based on this new information.
The third question requires information regarding whether a formal Agency health effects
assessment is in progress, and if results will be available by the cutoff date for the review (March
1, 2009). Health effects assessments used to develop NPDWRs are usually performed under the
following EPA programs: Integrated Risk Information System (IRIS), Office of Pesticide
Programs (OPP), the Office of Water (OW), and the National Academy of Sciences (NAS) when
commissioned by EPA. The question expands this "No Action" category to include any
contaminant for which a health effects assessment was completed during the current review
round, but subsequent new information has the potential to affect its MCLG.

Health effects assessments are conducted outside the scope of the Six-Year Review process and
follow EPA guidelines established to assess risks for different health effects, different exposure
routes, and in different sensitive population groups and life stages including children. EPA's
Office of Science and Technology (OST) tracks the status of health effects assessments and
provides summaries to OGWDW that identify the contaminants with ongoing health effects
assessments and their expected completion dates.

For Six-Year Review 2, OST collected health effects information for contaminants that were not
part of an ongoing or recent rule.  These contaminants were in one of two lists for the purpose of
tracking health effects information:
                                            3-2

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

•   Contaminants with ongoing formal EPA health effects assessments
•   All other regulated drinking water contaminants that reached this decision tree point.

OGWDW established a cutoff date (March 1, 2009) after which it would not be feasible to fully
review and evaluate the potential to revise a contaminant's MCLG during Six-Year Review 2.

3.1.2   Output of Initial Review
The outputs of the initial  review branch are: (1) a list of regulated contaminants excluded from
further review branches during the current cycle3, (2) a list of contaminants that proceed to the
Health Effects and MCLG branch for questions about the potential to revise the MCLG, and (3)
a list of contaminants that proceed to the MCL Branch 2 despite ongoing health effects
assessments because they have MCLs that are greater than their respective MCLGs.

3.2  Health Effects and  MCLG Branch

The primary purpose of the Health Effects and MCLG Branch (Exhibit 3-2) is to identify the
NPDWRs for which there is potential to revise the MCLG. To do this, the protocol requires that:

•   A revised or new health effects assessment be completed during the current cycle before
    March 1, 2009
•   The assessment results in a change to the RfD or cancer risk.

Another refinement to the protocol for the second cycle provides an option to revisit Agency
decisions to take no action for contaminants that had a new health effects assessment that
indicated potential for an MCLG revision during the prior cycle.

The Health Effects and MCLG Branch also identifies whether there is new health effects
information identified during a review of peer-reviewed literature that leads to a nomination for a
new health effects assessment for those contaminants for which there are no recent or ongoing
assessments.
3 Contaminants that have a "Take no action" result on the Initial Review may still be affected by a cross-cutting
issue affecting multiple contaminants that qualifies for consideration under the conditions described for other
regulatory revisions.
                                           3-3

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
                     Exhibit 3-2. Health Effects and MCLG Branch
    HEA since Round 1 cutoff of
    August 2002 (July 18, 2003
         FR 42907]?
       Is the MCLG > 0?
     Is there new information*
   indicating a nonlinear mode of
       action or potential
     reproductive/dev. effects?
                  Any change in the current
                  health effects assessment
                 (i.e., RfD change or nonlinear
                 mode of action) that suggests
                    MCLG change?
  Perform full toxicological search or
  update Round 1 information. New
        information*?
                           Did a previous round suggest
                         MCLG revision but reject it because
                           of constraints on the MCL?
                 I Nominate for IRIS/OPP/OW review
               HEA = health effects assessment
               *New information that could affect the MCLG
3.2.1  Inputs to Health Effects and MCLG Review
The first question in the Health Effects and MCLG Branch identifies the contaminants having a
formal health effects and toxicological assessment completed during the current review cycle
and by the cutoff date (March 1, 2009). For Six-Year Review 2, OGWDW used the status
summaries provided by OST to answer this question.

For contaminants that have a new health effects assessment, this branch asks whether there was a
change in toxicological parameters that affect the MCLG. For Six-Year Review 2, OST provided
this information in a summary report that indicated:

•   Whether the assessment resulted in changes to the RfD or cancer classification
•   Whether these changes would potentially affect the MCLG.

OST obtained RfD and cancer classification information from the formal health effects
assessment documents developed by sources such as IRIS, OPP, and OW. OST took the
following steps to derive a possible MCLG:

•   Classified the contaminant in one of three OW Categories based on cancer risk
    classifications
                                             3-4

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

•   Derived a possible MCLG value (or range of values) using the method associated with each
    OW Category.

The document, "Six-Year Review 2 - Health Effects Assessment - Summary Report" (USEPA,
2009e) describes how OST assigned the OW Categories to contaminants and derived MCLG
values.

The next question in this branch divides contaminants that did not have a recent health effects
assessment into two categories for the purpose of a literature search: (1) those with nonzero
MCLGs, and (2) those with MCLGs of zero. Subsequent questions address whether literature
searches indicate a need for a new formal health effects assessment. For Six-Year Review 2,
OST conducted a review of the peer-reviewed literature on relevant health effects (i.e., general
toxicity, reproductive and developmental toxicity, and cancer risk via an oral route for the
general population and sensitive subpopulation groups including children) to search for new
health effects information that indicates potential that the current RfD values or cancer risk
categories are not adequately representing health risks.

OST's review for each chemical began  with the authoritative reviews or assessments by IRIS,
OPP, the National Academy of Sciences (NAS), the Agency for Toxic Substances and Disease
Registry (ATSDR), the National Toxicology Program (NTP), National Institute of
Environmental Health Sciences (NIEHS), California EPA (CalEPA), World Health Organization
(WHO), European Commission Concise International  Chemical Assessment Documents
(CICADS), International Programme on Chemical Safety/Environmental Health Criteria
(IPCS/EHC), International Agency for Research on Cancer (IARC), Health Canada, Joint Expert
Committee on Food Additives (JECFA), and Joint FAO/WHO Meeting on Pesticide Residues
(JMPR). OST obtained each organization's most recent assessment available. OST also
conducted literature searches to identify primary literature to supplement the information in the
authoritative reviews. The searches utilized the following databases: TOXLINE, MEDLINE®,
Developmental and Reproductive Toxicology (DART®), Chemical Carcinogenesis Research
Information System (CCRIS), and Hazardous Substances Data Bank (HSDB).

For contaminants for which health effects assessments were completed during Six-Year Review
2, OST also conducted supplemental literature searches covering the period from either the two
years preceding the publication date of a final IRIS, OPP, or NAS assessment or the three years
prior to the publication of an ATSDR Toxicological Profile.

The purpose of the literature search was to identify:

•   Whether there was new health effects information  indicating a nonlinear mode of action or
    potential reproductive/developmental or other toxicological effects for contaminants at
    concentrations at or below the MCL when the MCLG is zero
•   Whether there was new cancer data or toxicological information in the literature that
    potentially affects the RfDs for contaminants without a recent health effects assessment and a
    nonzero MCLG.
                                          3-5

-------
EPA-OGWDW         EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

OST provided OGWDW with summary information from the literature review, including a
recommendation about whether new information might lead OW to nominate the contaminant
for a formal health effects assessment.

The final question in this branch identifies contaminants for which there was not a new health
effects assessment in the current review cycle, but there was one during the previous review
cycle that included a change in the RfD. During Six-Year Review 1, EPA took no action to
revise the NPDWR for some of these contaminants for one of the following reasons:

•   The possible revision would not have provided a meaningful opportunity to reduce health
    risks
•   The possible revision would not have provided a meaningful opportunity to reduce costs
    while maintaining the same or greater level of health protection
•   The possible revision would have been a low priority because of 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.

During the Six-Year Review 2, EPA revisited these decisions to consider whether new
information (e.g., changes in analytical feasibility or new  occurrence and exposure analyses)
may affect that decision.

3.2.2  Outputs from  Health Effects and  MCLG Review
The Health Effects and MCLG Branch sorts the contaminants into  the following categories based
on health effects information:

•   Contaminants for which there is potential to revise the MCLG based on the availability of
    new Agency health effects information, or contaminants for which there was a potential to
    revise the MCLG during the first Six-Year Review,  but for which EPA took no action
•   Contaminants for which a literature review indicates a potential change in health effects
    information and  that should, therefore, be nominated for a formal heath effects assessment
    through OW, IRIS, or OPP
•   Contaminants for which there is no potential to revise the MCLG during Six-Year Review 2.

The decision tree directs the first category of contaminants to the MCL branch that reflects
potential for MCLG revision (MCL Branch  1). It directs the second and third categories of
contaminants to a second MCL branch that reflects no action will be taken regarding MCLG
revision (MCL Branch 2).

3.3  Maximum  Contaminant Level (MCL)  Branches

The purpose of each MCL Branch is to identify NPDWRs for which new information indicates
potential to revise the MCL. The SDWA requires that EPA generally set the MCL as close to the
MCLG as feasible [Section 1412(b)(4)(B)]. Feasibility refers to both the ability to treat water to
meet the MCL, as well as monitor water quality at the MCL. For most contaminants for which
the MCLG is greater than zero, the MCL equals the MCLG, which indicates that neither
analytical method quantitation nor treatment capabilities limit the ability to achieve the MCLG.
Conversely, when the MCLG equals zero, the MCL is usually set equal to the practical
                                          3-6

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
quantitation limit (PQL), which is based on the detection capability that most laboratories can
reliably and consistently achieve using approved analytical methods within specified limits of
precision and accuracy. Thus, the PQL is the most common limiting factor with respect to
feasibility. Consequently, the MCL branches address analytical feasibility before treatment
feasibility.

The decision tree includes two MCL Branches: one for contaminants with a possible MCLG
revision (MCL Branch 1; Exhibit 3-3),  and the other for contaminants with no action regarding
the MCLG (MCL Branch 2; Exhibit 3-4).

 Exhibit 3-3. Maximum Contaminant  Level Branch 1 (Potential for MCLG Revision)
                                 Is higher MCLG indicated?
                                     GO TO Methods
                                    Branch and return
                                         here
                                     Is PQKMCL or
                                    change indicated?
                                 GO TO Occurrence
                                  Branch and return
                                      here.
                                 Would MCL revision
                                 provide a meaningful
                                 opportunity for health
                                 risk or cost reduction?
           Is MCL based on
          treatment feasibility?
       Does new information
       indicate lower MCL is
           feasible?
           Is MCL based on
          benefit-cost analysis?
  GO TO Treatment
  Technique Branch
       Is there new benefits
       or cost information?
  GO TO Treatment
  Branch and return
       here.
   Is there sufficient
    information to
    identify BATs?
                                     Take no
                                     action on
                                     MCL or
                                      MCLG
Key:
I
*• No
Yes/ has potential
Issue health
advisory if needed.


GOTO
Implementation
Branch
                                             3-7

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
    October 2009
    Exhibit 3-4. Maximum Contaminant Level Branch 2 (No Potential for MCLG
                                     Revision)

Is stan(
MC

GO TO I
Techniqu

GO TO Meth

Jaidan Is MCL based on
L? ~* POL? "I |opnhL!.rfer

ods
sturn
nr
change indicated?




' '
,,,_,, . Does new information
Is MCL based on indicate lower MCL is
treatment feasibility? ffiqqihle?


, ,
Is MCL based on Is there new benefit or
benefit-cost analysis? cost information?


e Branch

Key:
Yes/ has potential






GO TOO
Branch a
he
— >• Would MC
provide a r
opportunity
risk or cost


/Tak
N. M(
xurrence „
nd return D
or
•e.
... Is
neanmgful
for health
reduction''


3 no N. ./
n on y <(
:L / N
GOTO

Branch

D TO Treatment
anch and return
here.
there sufficient
nformation to
dentify BATs?


/Consider N.
MCL ^>
\ revision /
i •«-!


3.3.1   Inputs to Maximum Contaminant Level (MCL) Review
The two MCL branches have similar questions and differ in that one poses the questions for
contaminants with a possible MCLG revision (MCL Branch 1), and the other poses the questions
for contaminants with no action regarding the MCLG (MCL Branch 2). For example, MCL
Branch 1 has an additional question to identify and address circumstances where the health
effects information indicates potential to revise the MCLG upward, which would affect the MCL
if the MCL is equal to the MCLG.

The initial questions on the MCL branches pertain to following:

•  Whether the standard is an MCL or a TT
•  Whether a higher or lower MCLG is indicated, if applicable
•  The basis for the current MCL.

For Six-Year Review 2, OGWDW used the NPDWRs and supporting rule documents to answer
the first and third questions. OGWDW used health effects information provided by OST to
determine whether there is potential for a higher or lower MCLG.
                                        3-8

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
Subsequent questions on the MCL branches involve subordinate branches for analytical
methods, occurrence, and treatment analysis that explore the availability of new information that
could affect OGWDW's recommendation regarding an MCL revision. Later sections of this
document address the specific data requirements of these subordinate branches and describe the
analyses that EPA conducted as part of these branches. The MCL branches combine the findings
from these subordinate branches into an overall MCL recommendation.

3.3.2  Outputs from  Maximum Contaminant Level (MCL) Review
The MCL branches identify contaminants for which the review did not identify any new
information indicating potential for MCL revision and those for which new information indicates
EPA should consider revising the MCL. After completing an MCL branch, the decision tree
directs the review to the Implementation Branch.

3.4   Treatment Technique Branch

When a contaminant has a TT standard instead of an MCL,  the protocol uses the Treatment
Technique Branch of the decision tree (Exhibit 3-5), instead of either of the MCL Branches. The
purpose of the Treatment Technique Branch is to identify whether there is potential to revise a
TT standard.

                      Exhibit 3-5. Treatment Technique Branch
       Does new health
        risk, analytical
         methods, or
      treatment technique
        information by
      March 2009 indicate
         possible TT
          revision?
                 GO TO TT Analysis
                 Branch and return
                 here. Does the new
                 information indicate
                 that a meaningful
                opportunity exists for
                 health risk or cost
                    reduction?
                                                              GOTO
                                                            Implementation
                                                              Branch
Key:

No
Yes
                                          3-9

-------
EPA-OGWDW         EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

3.4.1  Inputs to Treatment Technique Review
The TT Branch includes the following questions:

•   Does new information in the following areas indicate potential for TT revision: health risk,
    analytical methods, or treatment technique?
•   Based on the decisions on the Treatment Technique Analysis Branch, does a meaningful
    opportunity exist for health risk or cost reduction?

The following contaminants have a TT in lieu of an MCL: acrylamide, copper, Cryptosporidium,
epichlorohydrin, Giardia lamblia, lead, Legionella, and viruses. Of these contaminants, all
except acrylamide and epichlorohydrin were affected by recent or ongoing rule revisions during
Six-Year Review 2. USEPA (2009f) describes the information that the Agency obtained during
its review of the TT for acrylamide and epichlorohydrin.

3.4.2  Outputs from Treatment Technique Review
The Treatment Technique Branch identifies contaminants for which EPA should consider
revisions to a TT standard because all of the following apply:
    New health, methods, or treatment information are available that suggest revision
    There is a meaningful opportunity to lower health risks or costs.
The decision tree then directs the review to the Implementation branch.

3.5  Treatment Technique Analysis Branch

The purpose of the Treatment Technique Analysis Branch (Exhibit 3-6) is to determine whether
the new information that could affect the TT standard has the potential to constitute a meaningful
opportunity to revise the TT standard.

3.5.1  Inputs to Treatment Technique Analysis Review
The Treatment Technique Analysis Branch includes the following questions:

•   Is there a significant increase in health risk estimated from exposure to the contaminant?
•   Is there a significant improvement in analytical feasibility or treatment technique?

The first question identifies whether new health effects information indicates health risks that are
significantly different from those considered at the time EPA promulgated the NPDWR. The
second question addresses whether there are significant changes in analytical feasibility
constraints that might have originally led to a contaminant having a TT standard in lieu of an
MCL. It also addresses whether significant changes in treatment feasibility indicate potential for
revision to the TT standard.
                                         3-10

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
                 Exhibit 3-6. Treatment Technique Analysis Branch
      Is there a significant
     increase in health risk
        estimated from
        exposure to the
        contaminant?
                    Is there a significant
                     improvement in
                   analytical feasibility or
                       treatment
                      techniques?
                                 Meaningful
                                 opportunity
                                exists for TT
                                                          No
                                                       meaningful
                                                       opportunity
                                                       exists for TT
                                                        revision.
 Key:
         No
         Yes
3.5.2  Outputs from Treatment Technique Analysis Review
The Treatment Technique Analysis Branch identifies contaminants for which new information
has the potential to constitute a meaningful opportunity to lower health risks or costs through a
TT revision. The decision tree then directs the review back to the main Treatment Technique
Branch.

3.6   Methods Branch

The purpose of the Methods Branch (Exhibit 3-7) is to determine whether there is potential to
revise the PQL for a regulated contaminant. The PQL is the level at which laboratories can
reliably and consistently measure a chemical contaminant in drinking water. This is usually
interpreted as the analyte concentration at which 75% of laboratories can measure concentration
within the promulgated acceptance criteria.
                                          3-11

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
                       Exhibit 3-7. Analytical Methods Branch
               Are new analysis
               data available by
                March 2009?
                     Do PT data available
                       by March 2009
                     support quantitation
                       levels below the
                          PQL?
                                           Do MDL and/or MRL
                                             data suggest
                                            quantitation levels
                                             below the PQL?
              Did analysis in prior
                round indicate
               potential to revise
                   PQL?
                                                      There is
                                                     potential to
                                                     revise PQL.
The branch considers two categories of contaminants:

•  Contaminants for which the MCL is limited by analytical feasibility (i.e., the MCL is set at
   the PQL), and the MCLG is still appropriate.
•  Contaminants for which the health effects review indicated potential to change the MCLG
   and the current PQL is above possible MCLG values.

EPA reviews and approves analytical methods under a separate regulatory process. Therefore,
Six-Year Review 2 did not include a review to determine whether the approved analytical
methods, themselves, can be revised. Historically, EPA has used two main approaches to
determine a PQL for SDWA analytes: (1) Performance Evaluation (PE) data from Water Supply
(WS) studies is the preferred alternative when sufficient data are available; or (2) a multiplier
method, in which the PQL is calculated by multiplying the EPA-derived method detection limit
(MDL) by a factor of 5 or  10 [50 FR 46880 (November 13, 1985); 52 FR 25690 (July 8, 1987);
54 FR 22062 (May 22, 1989)]. Using PE data to derive the PQL for chemical NPDWRs involves
determining the concentration of an analyte at which 75% of EPA Regional and State
laboratories achieve results within a specified acceptance window [see 54 FR 22062 (May 22,
1989)].
                                          3-12

-------
EPA-OGWDW         EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

3.6.1  Inputs to Methods Review
The Methods Branch includes the following questions:

•   Are new data available by the cutoff date (March 1, 2009) that EPA selected for Six-Year
    Review 2?
•   Do the new analytical methods data indicate potential to revise the PQL?
•   Do other new data such as method detection limit (MDL) and/or minimum reporting level
    (MRL) information indicate potential to revise the PQL?
•   Do previous data or analyses (i.e., Six-Year Review 1) indicate potential to revise the PQL?

The document, "Analytical Feasibility Support Document for the Second Six-Year Review of
Existing National Primary Drinking Water Regulations"  (USEPA, 2009b), describes the process
EPA used to evaluate the potential to revise PQL values and provides the results for each
contaminant. The protocol developed for Six-Year Review 1 primarily utilized PE data from WS
studies. These were laboratory accreditation studies conducted under EPA oversight until  1999,
when the program was privatized. Now, the National Environmental Laboratory Accreditation
Conference (NELAC) conducts the accreditation program via Proficiency Testing (PT) studies.
EPA could not obtain actual PT study data from NELAC or any PT providers. One PT provider,
however, made pass/fail rates from its PT studies available to EPA. This provider accounts for
approximately 50% of the PT results nationwide (USEPA, 2009b). Because current PE data or
comparable PT data were not available for this review, EPA modified the  review process.

The PQL reassessments for Six-Year Review 2 use a variety of data. The primary data sources
are:

•   PE data available through late 1999, for which EPA derived passing rates during Six-Year
    Review 1
•   Laboratory passing rates based PT data (i.e., the percent of laboratories passing a proficiency
    test for a given study) from late 1999 through 2004 for a single PT provider.

EPA relied primarily on the PT passing rate results at and below the current PQL to indicate
potential for PQL revision. Passing rates for the older PE data provided supplemental
information, especially when there were no PT studies with true values below the current PQL.
EPA placed contaminants into one of three categories based on whether the PT and PE data
supported, may support, or did not support a lower PQL.  For example, EPA placed contaminants
with passing rates above 75% for PT studies with true values below the PQL in the "PQL
reassessment supports reduction of the current PQL"  category. USEPA (2009b) provides a
complete summary of the data and results by contaminant.

When the analysis of PT and PE data did not provide conclusive indications regarding whether
there was potential to revise a PQL, EPA reviewed two other sources of information. The  first
source was the minimum reporting levels in the Information Collection Request (ICR) database
(USEPA, 2009c). An MRL is the lowest level or contaminant concentration that a laboratory can
reliably achieve within specified limits of precision and accuracy under routine laboratory
operating conditions using a given method (USEPA, 2009c). EPA received voluntary
submissions of compliance monitoring data for public water systems from 51 States and entities.
                                         3-13

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

The data contain a large number of analytical non-detection records with accompanying MRLs
for regulated contaminants (see Section 3.7.1). EPA evaluated the distribution of MRL values for
each contaminant to identify the mode or value occurring most frequently for that contaminant
("modal MRL"). The use of modal MRLs to provide additional insight into whether there is
potential to revise a PQL is another refinement of the protocol, necessitated by limited
availability of PT and PE data below the current PQL and made possible by the extensive
amount of information included in the ICR database.

The second type of information that EPA reviewed to evaluate potential to change the PQL was
the MDLs for analytical methods approved by EPA for drinking water. In using MDLs, EPA
followed the multiplier approach used to derive some PQLs. This approach was also used to
identify possible analytical feasibility levels for Six-Year Review 1 (USEPA, 2003a).  USEPA
(2009b) provides the MDLs reviewed during Six-Year Review 2. Based on these MDL values,
EPA used an MDL multiplier to estimate where the possible lower limit of quantitation may
currently lie. The multiplier is 10 for most contaminants; the exception is contaminants for
which EPA developed a PQL using a multiplier of 5 (e.g., dioxin).

EPA also used the modal MRL and MDL-based estimates when it derived estimated quantitation
levels (EQLs) for the occurrence analysis to help the Agency determine if there is a meaningful
opportunity for health risk reduction. The report "Development of Estimated Quantitation Levels
for the Second Six-Year Review of National Primary Drinking Water Regulations" (USEPA,
2009c) describes the method that EPA used to develop EQLs. The EQL does not, however,
represent the Agency's intent to calculate new PQL at this time. Because of lack of data, EPA
did not recalculate PQLs during Six-Year Review 2.

3.6.2  Output from  Methods Review
The output of the Methods Branch is a decision regarding whether new information or
information from an earlier cycle indicates a potential to lower the PQL for a contaminant. The
decision tree then returns the review to the MCL Branch for subsequent questions.

3.7  Occurrence  Branch

The purpose of the Occurrence Branch (Exhibit 3-8) is to determine whether the potential to
revise an MCL presents a meaningful opportunity to:

•   Improve the level of public health protection
•   Achieve cost savings while maintaining or improving the level of public health protection.
                                         3-14

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
 EPA815-B-09-002
     October 2009
                            Exhibit 3-8. Occurrence Branch
              Are new monitoring
               data available by
                 March 2009?
               Can the data provide
               occurrence estimates
               at alternative MCLs?
               Are there Round 1
              occurrence data for
               alternative MCLs?
                                 Use
                               Round 1
                              occurrence
                                data.
     Estimate
     affected
     systems
     and pop.
Would MCL revision
provide a meaningful
opportunity for health
    risk or cost
    reduction?
                                          Data gap
                                          prevents
                                          analysis.
Key:



No
Yes
EPA's goal in evaluating contaminant occurrence is to:

•  Estimate the number of public water systems (PWSs) in which contaminants occur at levels
   of interest based on health effects or analytical methods information
•  Evaluate the number of people potentially exposed to these levels.

This occurrence and exposure information indicates how changing an MCL may affect health
risks and compliance costs.

3.7.1  Inputs to Occurrence Review
The initial questions elicit information regarding the availability of monitoring data for
estimating occurrence at alternate thresholds (e.g., MCLs and EQLs). For Six-Year Review 2,
the responses to these questions reflected new data that OGWDW received. EPA issued an ICR
as a one-time request for States to submit historical monitoring data (covering the years 1998
through 2005) for regulated contaminants voluntarily to EPA. A total of 51 States and entities
provided compliance monitoring data that included all analytical detection and non-detection
records. These data represent the national occurrence of regulated contaminants in public
drinking water systems. USEPA (2009a) provides a detailed description of the extensive data
                                           3-15

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

management efforts, quality assurance evaluations, and communications with State data
management staff.

The ICR contaminant occurrence dataset comprises more than 17 million analytical records from
approximately 136,000 PWSs in 45 States. Approximately 265 million people are served by
these PWSs nationally. The number of States and PWSs represented in the dataset varies across
contaminants because of variability in voluntary State data submissions and contaminant
monitoring schedules. This is the largest, most comprehensive set of drinking water compliance
monitoring data ever compiled and analyzed by EPA.

EPA used a two-stage analytical approach to analyze these data and characterize the national
occurrence of contaminants. The "stage 1" analysis is a simple, non-parametric count of
occurrence or regulated contaminants in public water systems. A typical stage 1 analysis
generates a count of the number (or percentage) of systems with at least one analytical detection
of a specific contaminant, or with at least one analytical detection with a concentration greater
than a concentration threshold of interest, i.e., a possible MCLG or EQL. This approach provides
information on peak occurrence levels, which are relevant for contaminants with acute health
effects. It generates conservative (i.e., potentially upwardly biased) occurrence estimates,
however, for contaminants with chronic health effects.

For the contaminants with chronic health effects, EPA developed "stage 2" analysis estimates by
generating estimated long-term mean concentrations at each system in the ICR dataset. A
complete description of the two-stage analytical approach and a detailed presentation of
occurrence estimates are in USEPA (2009a). EPA calculated the system means for the stage 2
analysis using a simple arithmetic average of all detection and non-detection data for each public
water system. Because the contaminant concentrations associated with the non-detection data are
unknown, EPA assigned three different values to the non-detect results to estimate a range of
system-level means, which then allowed EPA to estimate the number and percent of systems
with estimated means exceeding selected threshold values. Two of the three values are based on
the MRL values that accompany the non-detect results in the ICR dataset. The MRL is the
lowest level that can be reliably achieved within specified limits of precision and accuracy under
routine laboratory operating conditions using a given method. The three values that EPA
substituted for non-detect results were MRL, one-half of the MRL, and zero.

The most conservative approach was to assume that all non-detect results were equal to the
MRL. This approach yields an upper-bound estimate  of each system's level of exposure.  EPA
also explored the less conservative assumption that concentrations for the non-detected results
were uniformly distributed between the MRL and zero, thereby substituting one-half of the MRL
for all non-detected results. Finally, EPA considered the assumption that the actual concentration
for each non-detected result was typically much smaller than the MRL, supporting the use of
zero to represent each non-detect. This method yielded a lower-bound estimate of the system's
mean and also reflects the approach that may be used to calculate annual averages for
compliance. This simplified review method differs  from the stage 2 approach in the Six-Year
Review 1, which used more sophisticated modeling methods to address the non-detected results.
That analysis, however, was based on a substantially  smaller dataset (i.e., data from 16 States
instead of 45 States). EPA used the three non-detection replacement assumptions in the stage 2
                                          3-16

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

analyses to obtain reasonable bounds on the actual system mean concentrations. After EPA
calculated system means for each of the three substitution methods, it compared the results to the
various thresholds of interest to estimate the number and percent of systems with a mean
concentration above a health threshold of concern and corresponding populations.

Another refinement for Six-Year Review 2 was to include information on potential source water
quality for the contaminants with possible MCLG increases. Because the ICR data represent
water quality at entry points to the distribution system, the stage 1 and stage 2 occurrence
analysis results are not adequate to evaluate the cost savings potential for contaminants with the
potential for higher MCLG values. Therefore, for Six-Year Review 2, OGWDW also evaluated
source water quality information for these contaminants. This information came from two
national data sources: the National Water Quality Assessment (NAWQA) program conducted by
the U.S. Geological Survey (USGS), and EPA's STORET (short for STOrage and RETrieval)
data system, which are part of OGWDWs National Contaminant Occurrence Database (NCOD).
The document, "Occurrence Analysis for Data in Potential  Source Waters for the Second  Six-
Year Review of NPDWRs" (USEPA 2009d), provides additional details on this review.

Regardless of the occurrence data source and analysis method, EPA must determine whether the
extent of occurrence represents a meaningful opportunity to reduce health risks or costs. There is
no single quantitative threshold that applies to all contaminants. The EPA Administrator has the
discretion to determine which revisions are appropriate, and may consider a variety of factors
including but not limited to the type of health effects for the general population and sensitive
populations and lifestages including children, the geographical distribution of the affected
systems and populations, the size of the affected populations, and competing Agency priorities
and resource constraints.

3.7.2  Output from Occurrence Review
The output of the Occurrence Review Branch is the identification of contaminants for which
MCL revision  would provide a meaningful opportunity for health risk reduction or cost savings
while maintaining or improving the level of public health protection. An additional result is the
identification of contaminants for which data gaps prevent an occurrence review. The decision
tree then returns the review to the MCL Branch for subsequent questions.

3.8  Treatment Branch

When EPA promulgates an MCL, the NPDWR also contains BAT recommendations for
drinking water treatment processes.  To be a BAT, the treatment technology must meet several
criteria such as having demonstrated consistent removal of the target contaminant under field
conditions. Although treatment feasibility and analytical feasibility together address the technical
feasibility requirement for an MCL, historically treatment feasibility has not been a limiting
factor for MCLs. Thus, the purpose of the Treatment Review Branch (Exhibit 3-9) is to ascertain
that there are technologies that meet BAT criteria when an MCL can be lowered and doing so
presents a meaningful opportunity to reduce health risks.
                                          3-17

-------
EPA-OGWDW
         EPA Protocol for the Second Review of Existing
          National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
                            Exhibit 3-9. Treatment Branch
               Can BATs and
                SSCTs meet
              alternative MCLs?
 Key:
         No
         Yes
                                                                          Return to source
                                                                          MCL 1 or MCL 2)
                                              Cannot
                                              achieve
                                              revised
                                              MCL
    Can new
   technologies
 identified by March
2009 meet alternative
     MCLs?
3.8.1  Inputs to Treatment Technology Review
The Treatment Technology Branch includes the following questions:

•  Can the BATs and small system compliance technologies (SSCTs) meet alternative MCLs?
•  Can new technologies identified by the cutoff date (March 1, 2009) meet alternative MCLs?

For Six-Year Review 2, EPA limited its review of BATs to those NPDWRs for which it was
considering possible revisions to the MCL based on the health effects or analytical feasibility
reviews. To address both questions, OGWDW conducted a review of treatment performance
studies for all technologies that are applicable for the contaminant in question. OGWDW used
the same sources that it has relied on in the past to develop regulations and guidance, including
published EPA treatment reports, peer-reviewed journals, and other sources of technology
performance (e.g., pilot and demonstration project reports), as well as information received from
EPA stakeholders. OGWDW evaluated whether these treatment studies indicate that current
BATs are capable of achieving possibly lower MCLs and whether newer treatment technologies
potentially meet BAT criteria. The  document, "Water Treatment Technology Feasibility Support
Document for Chemical Contaminants for the Second Six-Year Review of National Primary
Drinking Water Regulations" (USEPA, 2009f), provides additional data and analysis details.
                                         3-18

-------
EPA-OGWDW
EPA Protocol for the Second Review of Existing
 National Primary Drinking Water Regulations
EPA815-B-09-002
     October 2009
3.8.2  Output of Treatment Technology Review
The output of the Treatment Technology Branch is a determination of whether treatment
feasibility would pose a limitation to revising an MCL. The decision tree then returns the review
to one of the MCL Branches for subsequent questions.

3.9  Implementation Branch

The purpose of the Implementation Branch (Exhibit 3-10) is to evaluate potential revisions
pertaining to "other" regulatory requirements, such as monitoring and system reporting.
Regulatory revisions to MCLs or TTs may affect the monitoring requirements for a contaminant
and new health risk information may also warrant revisions.

                        Exhibit 3-10. Implementation Branch
           Did MCL or TT
             change?
                      Will the change affect
                       monitoring/reporting
                         requirements?
        Is there new health risk
           information on
           reproductive or
        developmental toxicity?
             Will it affect
          monitoring/reporting
            requirements?
                                                 Take no
                                                 action on
                                                  other
                                               implements
                                               tion issues.
Key:

No
Yes
3.9.1  Inputs to Implementation Review
The Implementation Branch requires information regarding whether a change in a contaminant's
MCL or TT, or new health effects information will affect the monitoring requirements for a
particular contaminant. For Six-Year Review 2, EPA focused this review on issues that were not
already being addressed through alternative mechanisms, such as a part of a recent or ongoing
rulemaking. EPA also reviewed implementation-related NPDWR concerns that were "ready" for
rulemaking - that is, the problem to be resolved had been clearly identified, along with specific
options to address the problem, and shown to either clearly improve the level of public health
                                          3-19

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

protection, or represent a meaningful opportunity for cost savings while maintaining the same
level of public health protection. The report "Consideration of Other Regulatory Revisions in
Support of the Second  Six-Year Review of the National Primary Drinking Water Regulations"
(USEPA, 2009g) provides a description of the stakeholder process that EPA used to identify
inputs for the implementation review.

3.9.2  Outputs from Implementation Review
The output of the Implementation Branch is a determination regarding whether EPA should
consider revisions to the monitoring requirements of an NPDWR. It is the final branch of the
decision tree.
                                         3-20

-------
EPA-OGWDW        EPA Protocol for the Second Review of Existing     EPA 815-B-09-002
	National Primary Drinking Water Regulations	October 2009

4  References

USEPA. 2000. Science Policy Council Handbook: Peer Review, 2nd Edition. EPA Report 100-
B-00-001. Washington, DC: Office of Science Policy, Office of Research and Development.
December 2000. Available on the Internet at: http://www.epa.gov/OSA/spc/pdfs/prhandbk.pdf.

USEPA. 2003a. 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. March 2003.

USEPA. 2003b. Occurrence Estimation Methodology and Occurrence Findings Report for the
Six-Year Review of Existing National Primary Drinking Water Regulations. EPA 815-R-03-006.
June 2003.

USEPA. 2003c. EPA Protocol for Review of Existing National Primary Drinking Water
Regulations. EPA Report 815-R-03-002. Washington, DC: Office of Ground Water and Drinking
Water. June 2003. Available on the Internet at:
http://www.epa.gov/safewater/standard/revi ew/pdfs/support_6yr_protocal_final.pdf

USEPA. 2009a. Analysis of Occurrence Data from the Second Six-Year Review of Existing
National Primary Drinking Water Regulations. EPA 815-B-09-006.

USEPA. 2009b. Analytical Feasibility Support Document for the Second Six-Year Review of
Existing National Primary Drinking Water Regulations. EPA 815-B-09-003.

USEPA. 2009c. Development of Estimated Quantitation Levels for the Second Six-Year Review
of National Primary Drinking Water Regulations. EPA 815-B-09-005.

USEPA. 2009d. Occurrence Analysis for Potential Source Waters for the Second Six-Year
Review of National Primary Drinking Water Regulations. EPA 815-B-09-004.

USEPA. 2009e. Six-Year Review 2 - Health Effects Assessment - Summary Report. EPA 822-
R-09-006.

USEPA. 2009f Water Treatment Technology Feasibility Support Document for Chemical
Contaminants for the Second Six-Year Review of National Primary Drinking Water Regulations.
EPA815-B-09-007.

USEPA. 2009g. Consideration of Other Regulatory Revisions in Support of the Second Six-Year
Review of the National Primary Drinking Water Regulations. EPA 815-B-09-008.
                                         4-1

-------