[Federal Register: March 29, 2010 (Volume 75, Number 59)]
[Notices]
[Page 15499-15572]
[DOCID:fr29mr10-135]

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Part II

Environmental Protection Agency

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National Primary Drinking Water Regulations; Announcement of the
Results of EPA's Review of Existing Drinking Water Standards and
Request for Public Comment and/or Information on Related Issues; Notice

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OW-2008-0747; FRL-9130-3]
RIN 2040-AE90

National Primary Drinking Water Regulations; Announcement of the
Results of EPA's Review of Existing Drinking Water Standards and
Request for Public Comment and/or Information on Related Issues

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice; request for comments.

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SUMMARY: The Safe Drinking Water Act (SDWA) requires the United States
Environmental Protection Agency (EPA) to conduct a periodic review of
existing National Primary Drinking Water Regulations (NPDWRs) and
determine which, if any, need to be revised. The purpose of the review,
called the Six-Year Review, is to identify those NPDWRs for which
current health effects assessments, changes in technology, and/or other
factors provide a health or technical basis to support a regulatory
revision that will improve or strengthen public health protection. EPA
has completed its detailed review of 71 NPDWRs and at this time
believes that four NPDWRs are candidates for regulatory revision. These
four NPDWRs are acrylamide, epichlorohydrin, tetrachloroethylene, and
trichloroethylene. EPA requests public comment and/or relevant
information that will assist the Agency as we move forward with
regulatory action to revise these four NPDWRs. In addition to the 71
NPDWRs discussed in detail in today's action, this review also includes
14 other NPDWRs that need no detailed review because of recent or
ongoing revision actions.

DATES: Comments must be received on or before May 28, 2010, 60 days
after publication in the Federal Register.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2008-0747, by one of the following methods:
     http://www.regulations.gov: Follow the online instructions
for submitting comments.
     Mail: Water Docket, Environmental Protection Agency,
Mailcode: 2822T, 1200 Pennsylvania Ave., NW., Washington, DC 20460.
     Hand Delivery: EPA Docket Center Public Reading Room, EPA
Headquarters West, Room 3334, 1301 Constitution Ave., NW., Washington,
DC. Such deliveries are only accepted during the Docket's normal hours
of operation, and special arrangements should be made for deliveries of
boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OW-2008-
0747. EPA's policy is that all comments received will be included in
the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information
provided, unless the comment includes information claimed to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Do not submit information that you
consider to be CBI or otherwise protected using http://
www.regulations.gov. Please contact EPA prior to submitting CBI.
    The http://www.regulations.gov Web site is an ``anonymous access''
system, which means EPA will not know your identity or contact
information unless you provide it in the body of your comment. If you
send an e-mail comment directly to EPA without going through http://
www.regulations.gov your e-mail address will be automatically captured
and included as part of the comment that is placed in the public docket
and made available on the Internet. If you submit an electronic
comment, EPA recommends that you include your name and other contact
information in the body of your comment and with any disk or CD-ROM you
submit. If EPA cannot read your comment due to technical difficulties
and cannot contact you for clarification, EPA may not be able to
consider your comment. Electronic files should avoid the use of special
characters, any form of encryption, and be free of any defects or
viruses. For additional instructions on submitting comments, go to
section I.B of this document.
    Docket: All documents in the docket are listed in the http://
www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the Water Docket, EPA/
DC, EPA West, Room 3334, 1301 Constitution Ave., NW., Washington, DC.
The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday
through Friday, excluding legal holidays. The telephone number for the
Public Reading Room is<PHONE_NUMBER>, and the telephone number for the
EPA Docket Center is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: For technical inquiries contact: Rajiv
Khera,<PHONE_NUMBER>, or Karen Wirth,<PHONE_NUMBER>, Office of Ground
Water and Drinking Water, Environmental Protection Agency. For general
information about, and copies of, this document or information about
the existing NPDWRs discussed in this action, contact the Safe Drinking
Water Hotline. Callers within the United States may reach the Hotline
at<PHONE_NUMBER>. The Hotline is open Monday through Friday, excluding
Federal holidays, from 9 a.m. to 5:30 p.m. Eastern Time.

Abbreviations and Acronyms Used in This Action

>--greater than
2,4-D--2,4-dichlorophenoxyacetic acid
[mu]g/L--microgram per liter
AMG--Alternative Monitoring Guidelines
ASDWA--Association of State Drinking Water Administrators
ATSDR--Agency for Toxic Substances and Disease Registry
AWWA--American Water Works Association
BAT--best available technology
CARC--Cancer Assessment Review Committee
CBI--Confidential Business Information
CCL--Contaminant Candidate List
CFR--Code of Federal Regulations
Cr III--trivalent chromium
Cr VI--hexavalent chromium
CWS--community water system
DBPs--disinfection byproducts
DBCP--1,2-dibromo-3-chloropropane
DBPR--Disinfectants and Disinfection Byproducts Rule
DEHA--di(2-ethylhexyl)adipate
DEHP--di(2-ethylhexyl)phthalate
DWEL--drinking water equivalent level
EDB--ethylene dibromide
EPA--U.S. Environmental Protection Agency
EQL--estimated quantitation level
ESA--ethanesulfonic acid
FR--Federal Register
FQPA--Food Quality Protection Act
GAC--granular activated carbon
GWR--Ground Water Rule
HAA5--haloacetic acids
IARC--International Agency for Research on Cancer
ICR--Information Collection Request
IRED--Interim Reregistration Eligibility Decision
IRIS--Integrated Risk Information System
LCR--Lead and Copper Rule
LH--lutenizing hormone
LOAEL--lowest-observed-adverse-effect level
LT2ESWTR--Long-Term 2 Enhanced Surface Water Treatment Rule
MCL--maximum contaminant level
MCLG--maximum contaminant level goal
MDL--method detection limit
mg/kg-day--milligrams per kilogram of body weight per day
mg/L--milligrams per liter
MOA--mode of action
MRL--minimum reporting level
N--nitrogen
NAS--National Academy of Sciences

NAWQA--National Water Quality Assessment
NCFAP--National Center for Food and Agricultural Policy
NCOD--National Drinking Water Contaminant Occurrence Database
NDWAC--National Drinking Water Advisory Council
NELAC--National Environmental Laboratory Accreditation Conference
NOAEL--no-observed-adverse-effect level
NPDWR--National Primary Drinking Water Regulation
NRC--National Research Council
NTNCWS--non-transient, non-community water system
NTP--National Toxicology Program
OPP--Office of Pesticide Programs
ORD--Office of Research and Development
OW--Office of Water
PCBs--polychlorinated biphenyls
PCE--tetrachloroethylene
PE--Performance Evaluation
pCi/L--picoCurie per liter
PN--public notification
ppb--part per billion (e.g., microgram per liter)
ppm--part per million (e.g., milligram per liter)
PQL--practical quantitation limit
PT--Performance Testing
PTA--packed tower aeration
PWS--public water system
R2S2--Regulatory Review Support Spreadsheet
RED--Reregistration Eligibility Decision
RfD--reference dose
RSC--relative source contribution
SAB--Science Advisory Board
SSCT--Small System Compliance Technology
SDWA--Safe Drinking Water Act
SDWIS/FED--Safe Drinking Water Information System/Federal version
SMCL--secondary maximum contaminant level
SOC--synthetic organic chemical
STORET--STOrage and RETrieval data system
SWTR--Surface Water Treatment Rule
T3--triiodothyronine (thyroid hormone)
T4--levothyroxine (thyroid hormone)
TCDD--tetrachlorodibenzo-p-dioxin
TCE--trichloroethylene
TNCWS--transient, non-community water system
TP--trichlorophenoxypropionic acid
TRED--Interim Tolerance Reassessment and Risk Management Decisions
TRI--Toxics Release Inventory
TSC--Technical Support Center
TT--treatment technique
TTHM--total trihalomethanes
USDA--U.S. Department of Agriculture
UCMR 2--second Unregulated Contaminant Monitoring Rule
USGS--U.S. Geological Survey
VOC--volatile organic compound
WS--water supply

Table of Contents

I. General Information
    A. Does This Action Apply to My Public Water System?
    B. How Should I Submit Comments on This Action?
    C. What Should I Consider as I Prepare My Comments for EPA?
II. Statutory Requirements for the Six-Year Review
III. Stakeholder Involvement in the Six-Year Review Process
    A. How Have Stakeholders Been Involved in the Review Process?
    B. How Did EPA Incorporate Feedback from the Science Advisory
Board's 2002 Comments on the Six-Year Review Protocol?
IV. Regulations Included in the Six-Year Review
V. EPA's Protocol for Reviewing the NPDWRs Included in This Action
    A. What Was EPA's Review Process?
    B. How Did EPA Conduct the Initial Review and Evaluate Key
Technical Elements of the NPDWRs?
    1. Initial Review
    2. Health Effects
    3. Analytical Feasibility
    4. Occurrence and Exposure Analysis
    5. Treatment Feasibility
    6. Other Regulatory Revisions
    C. How Did EPA Factor Children's Health Concerns Into the
Review?
VI. Results of EPA's Review of NPDWRs
    A. What Are the Review Result Categories?
    1. No Action at This Time and the NPDWR is Still Appropriate
    2. Candidate for Revision
    B. What Are the Details of EPA's Review of Each NPDWR?
    1. Acrylamide
    2. Alachlor
    3. Alpha Particle Emitters
    4. Antimony
    5. Arsenic
    6. Asbestos
    7. Atrazine
    8. Barium
    9. Benzene
    10. Benzo(a)pyrene
    11. Beryllium
    12. Beta Particle and Photon Emitters
    13. Cadmium
    14. Carbofuran
    15. Carbon Tetrachloride
    16. Chlordane
    17. Chromium
    18. Cyanide
    19. 2,4-D (2,4-Dichlorophenoxyacetic acid)
    20. Dalapon (2,2-Dichloropropionic Acid)
    21. Di(2-ethylhexyl)adipate (DEHA)
    22. Di(2-ethylhexyl)phthalate (DEHP)
    23. 1,2-Dibromo-3-chloropropane (DBCP)
    24. 1,2-Dichlorobenzene (o-Dichlorobenzene)
    25. 1,4-Dichlorobenzene (p-Dichlorobenzene)
    26. 1,2-Dichloroethane (Ethylene Dichloride)
    27. 1,1-Dichloroethylene
    28. cis-1,2-Dichloroethylene
    29. trans-1,2-Dichloroethylene
    30. Dichloromethane (Methylene Chloride)
    31. 1,2-Dichloropropane
    32. Dinoseb
    33. Diquat
    34. Endothall
    35. Endrin
    36. Epichlorohydrin
    37. Ethylbenzene
    38. Ethylene Dibromide (EDB; 1,2-Dibromoethane)
    39. Fluoride
    40. Glyphosate
    41. Heptachlor
    42. Heptachlor Epoxide
    43. Hexachlorobenzene
    44. Hexachlorocyclopentadiene
    45. Lindane (gamma-Hexachlorocyclohexane)
    46. Mercury (Inorganic)
    47. Methoxychlor
    48. Monochlorobenzene (Chlorobenzene)
    49. Nitrate (as N)
    50. Nitrite (as N)
    51. Oxamyl (Vydate)
    52. Pentachlorophenol
    53. Picloram
    54. Polychlorinated Biphenyls (PCBs)
    55. Combined Radiums (226 and 228)
    56. Selenium
    57. Simazine
    58. Styrene
    59. 2,3,7,8-TCDD (Dioxin)
    60. Tetrachloroethylene
    61. Thallium
    62. Toluene
    63. Toxaphene
    64. 2,4,5-TP (Silvex; 2,4,5-Trichlorophenoxypropionic Acid)
    65. 1,2,4-Trichlorobenzene
    66. 1,1,1-Trichloroethane
    67. 1,1,2-Trichloroethane
    68. Trichloroethylene
    69. Uranium
    70. Vinyl chloride
    71. Xylenes (Total)
VII. EPA's Request for Comments
    A. Request for Comment and/or Information on the Candidates for
Revision
    B. Request for Information/Data on Other Review Topics
    C. Requests for Information on the Impacts of Climate Change on
Water Quality
VIII. EPA's Next Steps
IX. References

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does This Action Apply to My Public Water System?

    This action itself does not impose any requirements on anyone.
Instead, it notifies interested parties of EPA's review of existing
NPDWRs and its conclusions about which of these warrants new regulatory
action at this time. EPA requests public comment on the four NPDWRs
identified as candidates for revision, with a specific focus on
comments and/or relevant information that will inform the regulatory
revisions.

B. How Should I Submit Comments on This Action?

    Please see Section VII for the issues related to this notice for
which EPA requests comment and/or information. EPA will accept written
or electronic comments (please do not send both). Instructions for
submitting comments are in the preceding section. EPA prefers
electronic comments. No

facsimiles (faxes) will be accepted. Commenters who want EPA to
acknowledge receipt of their comments should also send a self-
addressed, stamped envelope.
    The Agency intends to address the comments received on the four
NPDWRs identified as candidates for revision in subsequent Federal
Register notices proposing and finalizing the regulatory revisions, and
in documents that will be made available in the docket for those
notices.

C. What Should I Consider as I Prepare My Comments for EPA?

    You may find the following suggestions helpful for preparing your
comments:
     Explain your views as clearly as possible.
     Describe any assumptions that you used.
     Provide any technical information and/or data you used
that support your views.
     If you estimate potential burden or costs, explain how you
arrived at your estimate.
     Provide specific examples to illustrate your concerns.
     Offer alternatives.
     Make sure to submit your comments by the comment period
deadline.
     To ensure proper receipt by EPA, identify the appropriate
docket identification number in the subject line on the first page of
your response. It would also be helpful if you provided the name, date,
and Federal Register citation related to your comments.

II. Statutory Requirements for the Six-Year Review

    Under the SDWA, as amended in 1996, 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.

    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, USEPA, 2003e) 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 V of today's
action describes the protocol and the minor refinements used for the
Six-Year Review 2 and section VI describes the review findings for each
of the NPDWRs covered by the current effort (see Table IV-1).

III. Stakeholder Involvement in the Six-Year Review Process

A. How Have Stakeholders Been Involved in the Review Process?

    The Agency developed a Six-Year Review protocol during the first
review cycle with extensive stakeholder inputs, including a stakeholder
meeting, Agency presentations at a variety of meetings, and
consultation with the National Drinking Water Advisory Council (NDWAC).
NDWAC formed a working group to develop recommendations regarding the
process the Agency should apply to conduct a periodic and systematic
review of existing NPDWRs. The Working Group held two meetings and a
conference call during June through September 2000 (67 FR 19030, April
17, 2002, USEPA, 2002c). 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. As discussed in
more detail in section V of today's action, EPA continues to follow the
general protocol recommended by the NDWAC.

B. How Did EPA Incorporate Feedback From the Science Advisory Board's
2002 Comments on the Six-Year Review Protocol?

    In June 2002 and during the Six-Year Review 1, EPA consulted with
the Science Advisory Board (SAB) Drinking Water Committee and requested
their review and comment on whether the protocol that EPA developed
based on the NDWAC's recommendations was consistently applied and
appropriately documented. The SAB provided verbal feedback regarding
the transparency and clarity of EPA's criteria for making its Six-Year
Review 1 decisions. At that time, EPA revised the protocol to better
explain how the decision criteria were applied. For the Six-Year Review
2 and to increase transparency and clarity, EPA also developed a more
detailed decision tree and an automated tool, called the Regulatory
Review Support Spreadsheet (R2S2). The more detailed decision tree
incorporates the sequential relationships between the various NPDWR
review elements and R2S2 tracks each contaminant through the decision
making process. The Agency has documented the decision tree and the
automated tool in the document, ``EPA Protocol for the Second Review of
Existing National Primary Drinking Water Regulations (Updated)''
(USEPA, 2009a).

IV. Regulations Included in the Six-Year Review

    Table IV-1 lists all the NPDWRs established to date. The table also
reports the maximum contaminant level goal (MCLG), which is ``set at
the level at which no known or anticipated adverse effects on the
health of persons occur and which allows an adequate margin of safety''
(SDWA section 1412(b)(4)), and the maximum contaminant level (MCL),
which is the maximum permissible level of a contaminant in water
delivered to any user of a public water system and ``is as close to the
maximum contaminant level goal as is feasible'' (SDWA section
1412(b)(4)(B)), except for contaminants that have a treatment technique
(TT) in lieu of an MCL because it is not ``economically or technically
feasible'' to set an MCL (SDWA section 1412(b)(7)(A)).\1\ Of these 85
NPDWRs, EPA has reviewed 14 as part of recent or ongoing regulatory
actions and, as a result, they are not subject to a detailed review in
today's notice. The review for the remaining 71 is discussed in detail
in today's action.
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    \1\ Under limited circumstances, SDWA Section 1412(b)(6)(A) also
gives the Administrator the discretion to promulgate an MCL that is
less stringent than the feasible level and that ``maximizes health
risk reduction benefits at a cost that is justified by the
benefits.''

                                           Table IV-1--Contaminants With NPDWRs Included in Six-Year Review 2
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         Contaminants                  MCLG  (mg/L) \1\                 MCL  (mg/L) \1\            Contaminants     MCLG  (mg/L) \1\     MCL (mg/L) \1\
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Acrylamide....................  0.............................  TT............................  Epichlorohydrin..  0.................  TT
Alachlor......................  0.............................  0.002.........................  Ethylbenzene.....  0.7...............  0.7
Alpha particles...............  0 (pCi/L).....................  15 (pCi/L)....................  Ethylene           0.................  0.00005
                                                                                dibromide (EDB).
Antimony......................  0.006.........................  0.006.........................  Fluoride.........  4.................  4
Arsenic.......................  0.............................  0.01..........................  Giardia lamblia..  0.................  TT
Asbestos......................  7 (million fibers/L)..........  7 (million fibers/L)..........  Glyphosate.......  0.7...............  0.7
Atrazine......................  0.003.........................  0.003.........................  Haloacetic acids   n/a \2\...........  0.06
                                                                                (HAA5).
Barium........................  2.............................  2.............................  Heptachlor.......  0.................  0.0004
Benzene.......................  0.............................  0.005.........................  Heptachlor         0.................  0.0002
                                                                                Epoxide.
Benzo(a)pyrene................  0.............................  0.0002........................  Hexachlorobenzene  0.................  0.001
Beryllium.....................  0.004.........................  0.004.........................  Hexachlorocyclope  0.05..............  0.05
                                                                                ntadiene.
Beta particles................  0 (millirems/yr)..............  4 (millirems/yr)..............  Lead.............  0.................  TT
Bromate.......................  0.............................  0.01..........................  Legionella.......  0.................  TT
Cadmium.......................  0.005.........................  0.005.........................  Lindane..........  0.0002............  0.0002
Carbofuran....................  0.04..........................  0.04..........................  Mercury            0.002.............  0.002
                                                                                (Inorganic).
Carbon tetrachloride..........  0.............................  0.005.........................  Methoxychlor.....  0.04..............  0.04
Chloramines...................  4.............................  4.............................  Monochlorobenzene  0.1...............  0.1
                                                                                (Chlorobenzene).
Chlordane.....................  0.............................  0.002.........................  Nitrate (as        10................  10
                                                                                nitrogen, N).
Chlorine......................  4.............................  4.............................  Nitrite (as N)...  1.................  1
Chlorine dioxide..............  0.8...........................  0.8...........................  Oxamyl (Vydate)..  0.2...............  0.2
Chlorite......................  0.8...........................  1.............................  Pentachlorophenol  0.................  0.001
Chromium (total)..............  0.1...........................  0.1...........................  Picloram.........  0.5...............  0.5
Coliform......................  0% \3\........................  5% \3\........................  Polychlorinated    0.................  0.0005
                                                                                biphenyls (PCBs).
Copper........................  1.3...........................  TT............................  Radium...........  0 (pCi/L).........  5 (pCi/L)
Cryptosporidium...............  0.............................  TT............................  Selenium.........  0.05..............  0.05
Cyanide.......................  0.2...........................  0.2...........................  Simazine.........  0.004.............  0.004
2,4-Dichlorophenoxyacetic acid  0.07..........................  0.07..........................  Styrene..........  0.1...............  0.1
 (2,4-D).
Dalapon.......................  0.2...........................  0.2...........................  2,3,7,8-           0.................  3.00E-08
                                                                                Tetrachlorodiben
                                                                                zo-p-dioxin
                                                                                (2,3,7,8-TCDD or
                                                                                dioxin).
Di(2-ethylhexyl)adipate (DEHA)  0.4...........................  0.4...........................  Tetrachloroethyle  0.................  0.005
                                                                                ne (PCE).
Di(2-ethylhexyl)phthalate       0.............................  0.006.........................  Thallium.........  0.0005............  0.002
 (DEHP).
1,2-Dibromo-3-chloropropane     0.............................  0.0002........................  Toluene..........  1.................  1
 (DBCP).
1,2-Dichlorobenzene (o-         0.6...........................  0.6...........................  Total              n/a \4\...........  0.08
 Dichlorobenzene).                                                                               trihalomethanes
                                                                                (TTHM).
1,4-Dichlorobenzene (p-         0.075.........................  0.075.........................  Toxaphene........  0.................  0.003
 Dichlorobenzene).
1,2-Dichloroethane (Ethylene    0.............................  0.005.........................  2,4,5-             0.05..............  0.05
 dichloride).                                                                                Trichlorophenoxy
                                                                                pro-pionic acid
                                                                                (2,4,5-TP or
                                                                                Silvex).
1,1-Dichloroethylene..........  0.007.........................  0.007.........................  1,2,4-             0.07..............  0.07
                                                                                Trichlorobenzene.
cis-1,2-Dichloroethylene......  0.07..........................  0.07..........................  1,1,1-             0.2...............  0.2
                                                                                Trichloroethane.
trans-1,2-Dichloroethylene....  0.1...........................  0.1...........................  1,1,2-             0.003.............  0.005
                                                                                Trichloroethane.
Dichloromethane (Methylene      0.............................  0.005.........................  Trichloroethylene  0.................  0.005
 chloride).                                                                                (TCE).
1,2-Dichloropropane...........  0.............................  0.005.........................  Uranium..........  0 ([mu]g/L).......  30 ([mu]g/L)
Dinoseb.......................  0.007.........................  0.007.........................  Vinyl chloride...  0.................  0.002
Diquat........................  0.02..........................  0.02..........................  Viruses..........  0.................  TT
Endothall.....................  0.1...........................  0.1...........................  Xylenes (total)..  10................  10
Endrin........................  0.002.........................  0.002.........................
--------------------------------------------------------------------------------------------------------------------------------------------------------
1. Units are in milligrams per liter (mg/L) unless otherwise noted, e.g., micrograms per liter ([mu]g/L) and picoCuries per liter (pCi/L). Milligrams
  per liter are equivalent to parts per million (ppm) and micrograms per liter are equivalent to parts per billion (ppb).
2. 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.
3. No more than 5.0% samples total coliform-positive in a month.
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).

V. EPA's Protocol for Reviewing the NPDWRs Included in This Action

A. What Was EPA's Review Process?

    The protocol document, ``EPA Protocol for the Review of Existing
National Primary Drinking Water Regulations (Updated)'' (USEPA, 2009a),
contains a detailed description of the process the Agency used to
review the NPDWRs discussed in today's action. EPA's primary goal was
to identify and prioritize candidates for regulatory revision to target
those revisions that are most likely to result in an increased level of
public health protection and/or result in substantial cost savings for
systems and their customers while maintaining the level of public
health protection.\2\ This section provides an overview of the review
process and section V.B provides a more detailed description of how EPA
applied the process to the review of the NPDWRs discussed in today's
action.
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    \2\ Note that the legislative history of the 1996 SDWA
Amendments indicate 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
(see Senate Report Number 104-169, 104th Congress, 1st Session, 1995
at 38). In other words, an MCL could be relaxed (i.e., increased) in
cases where a revised health risk assessment leads to a less
stringent (higher) MCLG than the existing MCL so that the level of
health protection is maintained. There have been several instances
in which revised health assessments have suggested higher MCLGs and
the Agency could have considered relaxing the MCLs. In these
instances and because SDWA allows EPA to determine when revisions
are appropriate, the Agency decided that there would be a negligible
gain in public health protection and/or cost savings and any
revision would be a low priority activity because of competing
workload priorities, the administrative costs associated with
rulemaking, and the burden on States and the regulated community to
implement any regulatory changes.
---------------------------------------------------------------------------

    EPA applied the following basic principles to the review process:
     The Agency sought to avoid redundant review efforts.
Because EPA has reviewed information for 14 contaminants as part of
recent or ongoing regulatory actions, they are not subject to the
detailed review in today's notice.
     EPA evaluated the potential for new information to affect
NPDWRs in a manner consistent with existing policies and procedures for
developing NPDWRs. For example, in determining whether a possible
change in analytical feasibility existed, the Agency considered the
current policy and procedures for calculating the practical
quantitation level for drinking water contaminants.\3\
---------------------------------------------------------------------------

    \3\ The following Federal Register notices describe the process
the Agency has used to determine analytical feasibility for drinking
water contaminants: 50 FR 46880, November 13, 1985 (USEPA, 1985); 52
FR 25690, July 8, 1987 (USEPA, 1987); 54 FR 22062, May 22, 1989
(USEPA, 1989b). For this Six Year Review effort and to supplement
the analytical feasibility evaluation, the Agency also reviewed
extensive minimum reporting level (MRL) data obtained from States
and primacy entities as part of the Six-Year Review information
collection request (ICR) for SDWA compliance monitoring data.
---------------------------------------------------------------------------

     Because any possible change in an MCLG affects other NPDWR
elements, EPA will not generally consider potential revisions to any
contaminant with a health effects assessment in process that would not
be completed during the review period, where either the contaminant's
MCL is equal to its MCLG or the MCL is based on the 1996 SDWA
Amendments' cost-benefit provision. The rationale for this outcome is
that any new information from the health effects assessment could
affect the MCL or the assessment of the benefits associated with the
MCL for these contaminants. Therefore, the Agency does not believe it
is appropriate to consider revisions to these NPDWRs while a health
effects assessment is ongoing.
     For those contaminants with ongoing health assessments
that have MCLGs equal to or greater than zero and MCLs limited by
analytical feasibility or the standard is based on a Treatment
Technique, EPA conducted a further review of the potential to revise
the MCL or TT. The rationale for this approach is that the MCL or TT is
based on technology limitations and therefore, EPA should consider
whether there have been improvements in technology and whether any
revision might provide a meaningful opportunity to improve or at least
maintain public health protection. If EPA found that there were no
changes in technology (i.e., analytical feasibility or a TT) or if
changes were possible but there was no meaningful opportunity to
improve public health protection or reduce costs (while maintaining
public health protection), these contaminants remained in the ongoing
health effects assessment category.
     For this review, EPA considered new information from
health effects assessments that were completed by a March 1, 2009
cutoff date. If an updated assessment is completed after the March 1,
2009 information cutoff date, then EPA will review the update and any
new conclusions or additional information associated with the
contaminant during the next review cycle or during the revision of an
NPDWR (e.g., acrylamide, PCE and TCE). If the health effects
assessments are not completed in time for the regulatory revisions for
acrylamide, PCE and TCE, EPA does not plan to change the existing MCLG
of zero. EPA is currently considering how best to evaluate the benefits
for these regulatory revisions if the EPA health effects assessments
are not complete. One option would be to use the same health effects
information that was used for promulgating the original regulation.
Another option is to consider using other best available, peer-reviewed
health risk assessments that are complete as the Agency is proceeding
with the regulatory revisions. EPA requests comment on these options
and any other options that the public considers appropriate to evaluate
the benefits.
     The Agency may consider accelerating a review and
potential revision for a particular NPDWR before the next review cycle
when justified by new public health risk information.
     During the review, EPA identified areas where information
is inadequate or unavailable (data gaps) or emerging and is needed to
determine whether revision to an NPDWR is appropriate. When the Agency
is able to fill such gaps or fully evaluate the emerging information,
the Agency will consider it as part of the next review cycle. The
Agency may consider accelerating a review and potential revision for a
particular NPDWR if the information becomes available before the next
review cycle and if review and a potential revision are justified by
new public health risk information.
     EPA applied the Agency's peer review policy (USEPA,
2000d), where appropriate, to any new analyses.
    During Six-Year Review 1, the Agency developed a systematic
approach or protocol (USEPA, 2003b). The Agency based this protocol on
the recommendations of the NDWAC, through internal Agency
deliberations, and discussions with the diverse group of stakeholders
involved in drinking water and its protection. The overview of the
protocol in Figure V-1 shows the sequence of key decisions that led to
EPA assigning each NPDWR to one of two major categories of outcomes in
the Six-Year Review 2. The two major outcomes of the review are either:
1) The NPDWR is still appropriate and no action is necessary at this
time, or 2) the NPDWR is a candidate for revision. The reasons for a
Six-Year Review outcome of no further action at this time include at
least one or more of the following reasons:
     The NPDWR has been reviewed or is being reviewed in a
recent or ongoing action;
     The NPDWR has an ongoing health effects assessment (i.e.,
for those

NPDWRs with an MCL set at the MCLG or the MCL is based on the SDWA cost
benefit provision);
     EPA is considering whether a new health effects assessment
is needed;
     EPA did not identify any new, relevant information that
indicate changes to the NPDWR;
     New information indicate a possible change to the MCLG
and/or MCL but changes to the NPDWR are a low priority activity due to
negligible gains in public health protection and/or cost savings; or
     There are data gaps or emerging information that needs to
be evaluated.
[GRAPHIC] [TIFF OMITTED] TN29MR10.000

    During the current Six-Year Review, the Agency assessed the
protocol and determined it remained appropriate and suitable for the
second review. The research requirements and decision-making process of
the Six-Year Review 2 protocol are essentially the same as those
implemented during Six-Year Review 1. The Agency made some minor
refinements to enhance the Agency's effectiveness in applying the
protocol to the review of NPDWRs. The

refinements that address SAB's comments about the clarity and the
transparency of the protocol's decision making process are described in
the next two paragraphs. Section V.B describes the key technical
elements and any refinements in the data and/or the analysis methods
used during Six-Year Review 2.
    The primary refinement to the protocol during Six-Year Review 2 is
the implementation of a more detailed ``decision tree'' than either the
one used during Six-Year Review 1 (USEPA, 2003b) or the overview shown
in Figure V-1. The protocol is broken down into a series of questions
about whether there is new information for a contaminant that suggests
potential to revise each of the NPDWR elements. These questions are
logically ordered into a decision tree that incorporates the sequential
relationships between the different NPDWR elements. For example, when
EPA establishes an MCL, it must generally set the MCL as close to the
MCLG as feasible. Consequently, for a contaminant that has an MCL equal
to its MCLG, EPA must make decisions about the availability and
adequacy of new information regarding the possibility to revise the
MCLG before decisions regarding the possibility to revise the MCL. It
also means that if there is no possibility to revise a contaminant's
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 limit (PQL) can be revised.
This approach results in a more efficient review process. EPA also
developed an automated tool called the R2S2 that tracks each
contaminant's movement through the decision tree, including the revise/
take no action outcomes. This tool enhances transparency throughout the
decision process. The automation also streamlines the decision process
and facilitates the Agency's reporting of its review results. The
Agency has documented the decision tree and the automated tool in the
document entitled, ``EPA Protocol for the Second Review of Existing
National Primary Drinking Water Regulations (Updated)'' (USEPA, 2009a).

B. How Did EPA Conduct the Initial Review and Evaluate Key Technical
Elements of the NPDWRs?

    This section describes the specific technical reviews that EPA
conducted, including the initial review, health effects, analytical
methods, occurrence and exposure, treatment feasibility, and economic
analysis.
1. Initial Review
    EPA's initial review of all the contaminants included in the Six-
Year Review 2 involved a simple identification of the NPDWRs that were
being reviewed under concurrent EPA actions or had been reviewed and
revised in EPA actions completed since 2002. Table V-1 provides a list
of the 14 contaminants that met one of these criteria and identifies
the recent or ongoing action in which the contaminant has been reviewed
or is undergoing review. While these 14 contaminants are part of the
Six-Year Review 2, they were not subject to any detailed analysis given
that new information on these contaminants has been recently reviewed
under separate actions. However, EPA requests comments on these
contaminants along with the other contaminants discussed in detail in
this notice.
    The remaining 71 contaminants pass through this step to the review
of the technical NPDWR elements, which are described in the following
sections.

  Table V-1--NPDWRs That Have Been Reviewed or Are Being Reviewed Under
                        Recent or Ongoing Actions
------------------------------------------------------------------------
         Contaminant/indicator               Recent or ongoing action
------------------------------------------------------------------------
                         Disinfection Byproducts
------------------------------------------------------------------------
Bromate................................  Stage 2 DBPR.
Chlorite\1\............................  Stage 2 DBPR.
HAA5: monochloroacetic acid,             Stage 2 DBPR.
 dichloroacetic acid, trichloroacetic
 acid, monobromoacetic acid,
 dibromoacetic acid.
TTHMs: chloroform,                       Stage 2 DBPR.
 bromodichloromethane,.
dibromochloromethane, bromoform........
------------------------------------------------------------------------
                         Disinfectant Residuals
------------------------------------------------------------------------
Chloramines\1\.........................  Stage 2 DBPR.
Chlorine\1\............................  Stage 2 DBPR.
Chlorine dioxide.......................  Stage 2 DBPR.
------------------------------------------------------------------------
                               Inorganics
------------------------------------------------------------------------
Copper.................................  Under consideration for long-
                                          term revisions.
Lead...................................  LCR Short-Term Revisions
                                         Under consideration for long-
                                          term revisions.
------------------------------------------------------------------------
                             Microorganisms
------------------------------------------------------------------------
Coliform...............................  Total Coliform Rule-making
                                          currently underway.
Cryptosporidium........................  LT2ESWTR.
Giardia lamblia........................  LT2ESWTR.
Legionella \2\.........................  LT2ESWTR,
                                         CCL3 \3\.
Viruses \2\............................  LT2ESWTR, GWR, CCL3 \3\.
------------------------------------------------------------------------
DBPR--Disinfectants and Disinfection Byproducts Rule.
LT2ESWTR--Long-Term 2 Enhanced Surface Water Treatment Rule.
LCR--Lead and Copper Rule.
GWR--Ground Water Rule.

Dates of promulgation are as follows:
Stage 2 DBPR: 71 FR 388, January 4, 2006 (USEPA, 2006h).
LT2ESWTR: 71 FR 654, January 5, 2006 (USEPA, 2006g).
LCR Short-Term Regulatory Revisions: 72 FR 57782, October 10, 2007
  (USEPA, 2007f).
GWR: 71 FR 65574, November 8, 2006 (USEPA, 2006f).
\1\ Although the standard for this disinfectant was not revised as part
  of the Stage 2 DBPR, regulatory revisions need to be considered in
  conjunction with other disinfectant residuals and disinfection
  byproducts.
\2\ LT2ESWTR and GWR promulgated treatment techniques that built upon
  and enhanced the existing regulations (Surface Water Treatment Rule,
  Interim Enhanced Surface Water Treatment Rule, and Long-Term 1
  Enhanced Surface Water Treatment Rule) that address broad categories
  of microorganisms in treated water.
\3\ Listed on the third Drinking Water Contaminant Candidate List or
  CCL3 (74 FR 51850, October 8, 2009 (USEPA, 2009l) in order to capture
  health and treatment information that may not be addressed by the
  current regulations.

    2. Health Effects
    The document, ``Six-Year Review 2 --Health Effects Assessment--
Summary Report'' (USEPA, 2009b), describes how EPA reviewed the
contaminants discussed in today's action and provides the results of
the health effects technical review. The principal objectives of the
health effects review are to identify: (1) Contaminants for which a new
health effects assessment indicates that a change in MCLG might be
appropriate (e.g., because of a change in cancer classification or a
reference dose (RfD)), and (2) contaminants for which the Agency
identifies new health effects information suggesting a need to initiate
a new health effects assessment.
    To meet the first objective, the Agency reviewed the results of
health effects assessments completed under the following programs and
identified, where feasible, possible MCLG values.
     EPA Integrated Risk Information System (IRIS).
     EPA Office of Pesticide Programs (OPP).
     National Academy of Sciences (NAS; when commissioned by
EPA).
    To meet the second objective, the Agency first conducted an
extensive literature review to identify peer-reviewed studies. Then the
Agency reviewed the studies to determine whether there was new health
effects information such as reproductive and developmental toxicity
that potentially affects the MCLG of any of the remaining contaminants
that do not have an ongoing health effects assessment, including those
with recently completed health effects assessments.
    Table V-2 reflects the outcome of the health effects review for the
NPDWRs discussed in today's action. EPA placed each contaminant into
one of the following 13 categories.
     Agency health effects assessment in process and not
completed as of March 1, 2009. The Agency currently is conducting a
health effects assessment for the contaminant. That assessment will
consider all available, relevant studies on the toxicology of the
contaminant, including developmental and reproductive toxicity. This
outcome contains three categories of contaminants.
     Category 1 contains 15 contaminants with MCLGs equal to or
greater than zero and either MCLs that are limited by analytical
feasibility or TT standards. For this category, EPA conducted further
review of the potential for revisions to the MCL due to possible
changes in analytical feasibility. The Agency's review of new
information that might affect the MCL for one of these contaminants is
a refinement of the protocol. During Six-Year Review 1, EPA took no
further action on any contaminants with ongoing health effects
assessments. EPA generally sets each MCL as close to the MCLG as is
feasible, and a common limitation is the availability of analytical
methods to reliably measure the contaminant.
     Category 2 contains two contaminants (arsenic and uranium)
that have MCLGs equal to zero and MCLs that are based on the costs and
benefits balancing provision in SDWA 1412(b)(6)(A). Any changes in the
ongoing health effects assessment could impact the evaluation of
benefits for these contaminants. Therefore, EPA has decided to take no
further action to evaluate these two contaminants until completion of
the health effects assessment.
     Category 3 contains 13 contaminants with non-zero MCLGs
and MCLs generally equal to their respective MCLGs. Because EPA cannot
determine whether there is potential to revise either the MCLG or the
MCL until after the health effects assessment is completed, EPA plans
to take no further action on these contaminants at this time.
     New health effects assessment completed since Six-Year
Review 1. An IRIS or OPP assessment has been completed since 2002. EPA
also conducted a follow-up literature search to confirm that no new
information became available following the completion of the new health
effects assessment. Table V-2 shows four categories of contaminants
with new health effects assessments: four with results indicating
potential for lower MCLG (Category 4), five with results indicating
potential for higher MCLG (Category 5), two with results indicating the
MCLG remains appropriate (Category 6), and three contaminants for which
emerging information following the completion of a health effects
assessment or a pending pesticide cancellation decision may affect
EPA's review (Category 7).
     Literature review only conducted during Six-Year Review 2.
For the contaminants that did not have an ongoing health effects
assessment or a new one completed during the current review period, EPA
conducted a review of the health effects literature to identify whether
there was new information with potential to revise the MCLG. There are
six categories of contaminants.
     Three categories pertain to contaminants that had a health
effects assessment completed during Six-Year Review 1, including two
with possible lower MCLGs (Category 8), three with possible higher
MCLGs (Category 9), and three with no potential to revise their MCLGs
(Category 10). During Six-Year Review 1, the Agency determined that
possible changes to these contaminants' NPDWRs were a low priority
activity for the Agency because of: competing workload priorities, the
administrative costs associated with rulemaking, and the burden on
States and the regulated community to implement any regulatory changes.
As part of Six-Year Review 2, EPA is assessing whether there is new
information that affects this determination.
     Category 11 contains five contaminants for which the
Agency identified new information, described in section VI, that could
impact the MCLG and, therefore, these contaminants are considered
potential nominees for a new health assessment.
     Category 12 contains seven carcinogens for which the
literature review sought new information on whether there might be a
nonlinear mode of action or other reproductive and developmental health
effects.

     Category 13 contains seven contaminants with non-zero
MCLGs, for which EPA conducted a full literature search, including
developmental and reproductive toxicity.

[GRAPHIC] [TIFF OMITTED] TN29MR10.001

    In addition to identifying for which contaminants there is
information that potentially affects the MCLG, the health effects
review indicates which contaminants proceed to other review steps under
the protocol. Several

contaminants proceed to the analytical methods review to determine
whether improvements in analytical methods indicate potential to revise
the practical quantitation limit (PQL) in the NPDWRs. As Table V-3
shows, 14 contaminants from Category 1 proceed to the analytical
methods review--despite an ongoing health effects assessment--because
their MCLs are limited by their respective PQLs. These 14 include alpha
particles; benzo(a)pyrene; beta particles; carbon tetrachloride; DEHP;
1,2-dichloroethane; dichloromethane; pentachlorophenol; PCBs; radium;
dioxin; tetrachloroethylene; thallium; trichloroethylene. In addition,
two contaminants in Category 6 (benzene and EDB) and two in Category 10
(chlordane and vinyl chloride) have MCLs that are limited by PQLs and,
therefore, these contaminants proceed to the analytical methods review
even though their health effects assessments indicated no change to
their respective MCLG values. Similarly, six contaminants in Category
12 (DBCP; 1,2-dichloropropane; heptachlor; heptachlor epoxide;
hexachlorobenzene; toxaphene) and one in Category 13 (1,1,2-
trichloroethane) have MCLs that are limited by their respective PQL
and, therefore, proceed to the analytical methods review despite there
being no new information on health effects.
    Among the contaminants having new health effects information during
either Six-Year Review 2 or the previous review that potentially
affects their respective MCLG values (i.e., potentially lower MCLGs),
four in Category 4 (2,4-D; endothall; toluene; total xylenes) and two
in Category 8 (hexachlorocyclopentadiene and oxamyl) proceed to the
analytical methods review. For each of these contaminants, EPA
evaluated whether analytical feasibility might become a limiting factor
if EPA were to consider a lower MCLG and whether new information
indicates there is a potential to revise the PQL.
    Two contaminants (acrylamide from Category 1 and epichlorohydrin
from Category 12) bypass the analytical methods review because they
have TT standards and PQLs are not a limiting factor for the standards.
Five contaminants from Category 5 (alachlor; barium; diquat;
glyphosate; 1,1,1-trichloroethane) and three from Category 9 (1,1-
dichloroethylene; lindane; picloram) bypass the analytical methods
review because the new health effects information identified either
during Six-Year Review 2 or Six-Year Review 1 indicated possible
increases in their respective MCLGs. Each of these contaminants has a
PQL that is lower than its MCLG and, therefore, a review of whether the
PQL could be lower is inconsequential.

Table V-3--Contaminants Proceeding to Analytical Feasibility Review From
                          Health Effects Review
------------------------------------------------------------------------
                                             Contaminants proceeding to
     Health effects review category\1\         analytical feasibility
                                                       review
------------------------------------------------------------------------
Health Effects Assessment in Process
 During Information Review Period for the
 Notice (and not available by the March 1,
 2009 cutoff date):
    Category 1............................  14 of 15 proceeding because
                                             PQL limits MCL: alpha
                                             particles; benzo(a)pyrene;
                                             beta particles; carbon
                                             tetrachloride; DEHP; 1,2-
                                             dichloroethane;
                                             dichloromethane;
                                             pentachlorophenol; PCBs;
                                             radium; dioxin;
                                             tetrachloroethylene;
                                             thallium;
                                             trichloroethylene.
                                             Acrylamide bypasses the
                                             analytical review because
                                             it does not have a PQL.
    Category 2............................  0 of 2 proceeding because
                                             there is no potential to
                                             revise MCL unless completed
                                             health effects assessment
                                             indicates change to
                                             benefits analysis (arsenic
                                             and uranium).
    Category 3............................  0 of 13 did not proceed
                                             because MCL set at MCLG and
                                             health assessment still in
                                             process.
Health Effects Assessment Completed Since
 Six-Year Review 1:
    Category 4............................  4 of 4 proceeding to
                                             evaluate whether PQL is or
                                             could be below possible
                                             MCLG: 2,4-D; endothall;
                                             toluene; total xylenes.
    Category 5............................  0 of 5 proceeding; all 5
                                             bypass analytical review
                                             because PQL not a factor in
                                             review.
    Category 6............................  2 of 2 proceeding because
                                             PQL limits MCL: benzene and
                                             EDB.
    Category 7............................  0 of 3 proceeding because
                                             there is no potential to
                                             revise an MCL that is based
                                             on the MCLG under review.
Literature Review Only:
    Category 8............................  2 of 2 proceeding to
                                             evaluate whether PQL is or
                                             could be below possible
                                             MCLG:
                                             hexachlorocyclopentadiene;
                                             oxamyl.
    Category 9............................  0 of 3 proceeding; all 3
                                             bypass analytical review
                                             because PQL not a factor in
                                             review.
    Category 10...........................  2 of 3 proceeding because
                                             PQL limits MCL: chlordane
                                             and vinyl chloride.
    Category 11...........................  0 of 3 proceeding because
                                             there is no potential to
                                             revise an MCL that is based
                                             on the MCLG that may be
                                             further reviewed.
    Category 12...........................  6 of 7 proceeding because
                                             PQL limits MCL: DBCP; 1,2-
                                             dichloropropane;
                                             heptachlor; heptachlor
                                             epoxide; hexachlorobenzene;
                                             toxaphene epichlorohydrin
                                             bypasses the analytical
                                             review because it does not
                                             have a PQL.
    Category 13...........................  1 of 7 proceeding because
                                             PQL limits MCL: 1,1,2-
                                             trichloroethane.
------------------------------------------------------------------------
\1\ These categories correspond to the categories in Table V-2.

3. Analytical Feasibility
    EPA has a process in place to approve new analytical methods for
drinking water contaminants; therefore, the review and approval of
potential new methods are outside the scope of the Six-Year Review
protocol. EPA recognizes, however, that the approval and addition of
new and/or improved analytical methods (since the promulgation of the
NPDWRs considered under this section of the review) may enhance the
ability of laboratories to quantify contaminants at lower levels. This
ability of laboratories to measure a contaminant at lower levels could
affect its PQL, the value at which an MCL is set when it is limited by
analytical feasibility. Therefore, the Six-Year Review process includes
a

review of whether there have been changes in analytical feasibility for
the subset of the NPDWRs that reached this stage of the decision tree.
These include contaminants with or without ongoing health effects
assessments that have MCLs limited by analytical feasibility and
contaminants with possible MCLGs that are lower than their current
PQLs.
    The document, ``Analytical Feasibility Support Document for the
Second Six-Year Review of Existing National Primary Drinking Water
Regulations'' (USEPA, 2009c), describes the process EPA used to
evaluate whether changes in PQL are possible in those instances where
the MCL is limited, or might be limited, by analytical feasibility. EPA
uses the PQL to estimate the level at which laboratories can routinely
measure a chemical contaminant in drinking water. Historically, EPA has
used two main approaches to determine a PQL for SDWA analytes: (1)
Performance Evaluation (PE) data from Water Supply (WS) studies, which
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 (USEPA, 1985); 52 FR 25690 July 8, 1987
(USEPA, 1987); 54 FR 22062 May 22, 1989 (USEPA, 1989b)).
    The review protocol for Six-Year Review 1 utilized data from PE
studies, which 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 Performance Testing (PT)
studies. PQL reassessments discussed in this notice are based on the
Six-Year 1 PE data collected through late 1999 and laboratory passing
rate PT data collected from late 1999 through 2004. One PT provider
made pass/fail rates from PT studies available to EPA. This major
provider accounts for a large portion of the PT results nationwide
(USEPA, 2009c).
    Using PE or PT data to derive the PQL for chemical NPDWRs involves
determining the concentration of an analyte at which 75 percent of EPA
Regional and State laboratories achieve results within a specified
acceptance range (see 54 FR 22062 at 22100, May 22, 1989 (USEPA,
1989b)). For Six-Year Review 2, EPA did not have sufficient PT and PE
data to recalculate any PQL values, in part because the spiked
concentrations were rarely far enough below current PQLs. Instead, EPA
used the PT and PE passing rate results (i.e., the percent of
laboratories passing a performance test for a given study) at and below
the current PQL to determine whether data may support a lower PQL.
    When PT results were not available below the PQL or when the
results did not provide conclusive indications regarding a potential to
revise a PQL, EPA used two alternate approaches to estimate possible
PQLs: an approach based on the minimum reporting levels (MRLs) obtained
as part of the Six-Year Review Information Collection Request (ICR)
(see section V.B.4), and an approach based on method detection limits
(MDL). While EPA prefers to use laboratory performance data to
calculate a PQL, the MRL and MDL information can be valuable for this
review to indicate whether it is possible to quantitate at levels below
the current PQL.
    A laboratory reports an MRL when it does not detect a particular
contaminant in a sample of water. The MRL is the lowest concentration
level of a contaminant that a laboratory can reliably measure or
quantitate within specified limits of precision and accuracy under
routine laboratory operating conditions using a given method (USEPA,
2009c). MRL values were included with the data provided by the States
in response to the Six-Year Review ICR. EPA evaluated the distribution
of MRL values for each contaminant to identify the mode or value
occurring most frequently for that contaminant (i.e., the modal MRL)
and estimated the percentage of MRL values that are equal to or less
than the modal MRL. When this percentage was at least 80 percent and
the modal MRL was below the PQL, EPA chose to use this modal MRL value
as an estimated quantitation limit (also referred to as an EQL
throughout this document). The use of modal MRLs is a 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 Six-Year Review ICR dataset (see section
V.B.4).
    When the MRL data did not meet the 80 percent threshold used for
deriving an EQL via this approach, EPA used an MDL approach to derive
an EQL. As noted previously, this approach has been used in the past to
derive PQLs for regulated contaminants. In addition, this same approach
was used to identify possible analytical feasibility levels for Six-
Year Review 1 (USEPA, 2003a). In deriving these levels, the Agency used
the MDLs associated with the analytical methods approved by EPA for
drinking water analysis. EPA obtained MDL values from individual
analytical methods developed and approved by EPA for use on drinking
water. EPA applied a multiplier to these MDL values and based the EQL
on the midpoint of the resulting range (i.e., the mean if there are two
MDLs or a median if there are more than two MDLs). The multiplier is 10
for most contaminants except dioxin and EDB, which have PQLs that were
historically based on an MDL multiplier of 5.\4\ EPA also used the MDL
multiplier approach to confirm whether EQLs based on MRL data are
consistent with the range of values based on an MDL multiplier
approach.
---------------------------------------------------------------------------

    \4\ As noted in Table V-4 and sections VI.38 and VI.59, EPA
found that there was no potential to lower the PQL for dioxin and
EDB. Even if EPA had used a 10 x MDL multiplier for these two
contaminant instead of the 5 x MDL multiplier, this would not have
changed the outcome of the analytical feasibility assessments.
---------------------------------------------------------------------------

    EPA used the EQL thresholds derived via the modal MRL or MDL-
multiplier approaches for the occurrence analysis (see section V.B.4)
to help the Agency determine if there may be a meaningful opportunity
to improve public health protection. It should be noted, however, that
the EQL does not represent the Agency's intent to promulgate new PQLs
with this notice. Any revisions to PQLs will be part of future rule
making efforts.
    EPA performed analytical feasibility analyses for the contaminants
identified in Table V-3 as proceeding to this portion of the review.
Table V-4 shows the contaminants gathered into three more general
categories and the outcomes of the Agency's review.
     A health effects assessment indicates potential for lower
MCLG. This category includes the six contaminants identified in the
health effects review as having information indicating the potential
for a lower MCLG--four with new health effects assessments completed
during Six-Year Review 2 and two with health effects assessments
completed during Six-Year Review 1. Although their current MCLs are not
limited by a PQL, EPA reviewed analytical feasibility to determine if
analytical feasibility might limit the potential for MCL revisions. For
two contaminants (endothall and oxamyl), the current PQL is higher than
the possible MCLG identified in the health effects review. For these
contaminants, the potential to lower their PQLs based on PE and PT data
is inconclusive, but MRL and MDL data indicate the potential to revise
the PQL. EPA thus proceeded to evaluate occurrence data to determine
whether a lower PQL, and thus the MCL, may provide a meaningful
opportunity to improve public health protection. The current PQL is not
a limiting factor for the

remaining four contaminants identified by the health effects review as
having possible changes in their MCLG (i.e., 2,4-D,
hexachlorocyclopentadiene, toluene, and xylenes).
     Contaminants with ongoing health effects assessments and
existing MCLs are based on analytical feasibility. This category
includes 14 contaminants with ongoing health assessments with existing
MCLs that are greater than their MCLGs because they are limited by
analytical feasibility. One contaminant has a non-zero MCLG (thallium)
and the remaining 13 contaminants have MCLGs equal to zero. Although a
risk assessment is in process for these contaminants, because SDWA
requires the Agency to set the MCL as close to the MCLG as feasible,
EPA evaluated whether the PQL is likely to be lower for these
contaminants. For four of these contaminants (carbon tetrachloride,
1,2-dichloroethane, tetrachloroethylene, and trichloroethylene), EPA
concluded that new information from PT studies, along with MRL and MDL
data, indicate the potential to revise the PQL. For one contaminant
(dichloromethane), data from PT studies are inconclusive, but MRL and
MDL data indicate the potential to revise the PQL. For these five
contaminants, EPA proceeded to evaluate occurrence data to determine
whether lowering the PQL, and thus the MCL, may provide a meaningful
opportunity to improve public health protection.\5\ For the remaining
nine contaminants, either EPA did not have sufficient new information
to evaluate analytical feasibility or EPA concluded that new
information does not indicate the potential for a PQL revision.
Consequently, the outcome of the review for these nine contaminants is
to take no action at this time.
---------------------------------------------------------------------------

    \5\ If EPA found that there was no meaningful opportunity to
revise the MCL (i.e., carbon tetrachloride, 1,2-dichloroethane and
dichloromethane), these contaminants remained in the health effects
assessment in process category.
---------------------------------------------------------------------------

     Contaminants without ongoing health effects assessments or
for which no new health risk information was identified and for which
existing MCLs are based on analytical feasibility and greater than
their MCLGs. For the 11 contaminants in this category, EPA evaluated
available PT and PE data as well as MRL and MDL data to determine
whether there is potential to lower the PQL and thereby set the MCL
closer to the MCLG. For five of these contaminants (benzene chlordane,
1,2-dichloropropane, hexachlorobenzene, and 1,1,2-trichloroethane) EPA
concluded that new information from PT studies, along with MRL and MDL
data, indicates that while it might be possible to set a lower PQL, the
data are insufficient to support an actual PQL recalculation at this
time. Consequently, the outcome of the review for these contaminants is
to take no action at this time. For five additional contaminants (DBCP,
heptachlor, heptachlor epoxide, toxaphene, and vinyl chloride), the
data from PT studies are inconclusive, but MRL and/or MDL data indicate
potential for a lower PQL, as indicated in Table V-4. For these five
contaminants, EPA proceeded to evaluate occurrence data to determine
whether lowering the PQL, and thus the MCL, may provide a meaningful
opportunity to improve public health protection. For the final
contaminant, ethylene dibromide (EDB), none of the data sources
indicate potential to revise and the outcome of the review for this
contaminant is to take no action at this time.
    Table V-4 lists the type of data that indicate potential for a PQL
reduction. The list includes ``PT'' when the PQL reassessment based on
PT and PE data (USEPA, 2009c) reports that a reduction is supported.
The list also includes ``MRL'' and ``MDL'' when either of these
approaches indicates potential for PQL reduction. A result of ``PQL
reduction supported'' without a ``PT'' in the list indicate that the
PQL reassessment outcome is uncertain, but other data (i.e., MRL and/or
MDL) indicate potential for PQL reduction. When the PQL reassessment
outcome is that the current PQL remains appropriate, Table V-4 shows
the result ``Data do not support PQL reduction.'' The contaminant
specific discussions in section VI of today's action provide the
results of the analytical feasibility review for all the contaminants
in Table V-4.

     Table V-4--NPDWRs Included in the Analytical Feasibility Reassessment and the Result of That Assessment
----------------------------------------------------------------------------------------------------------------
           Contaminant                 Current PQL             Analytical feasibility reassessment result
----------------------------------------------------------------------------------------------------------------
          6 Contaminants Identified Under the Health Effects Review as Having Potential for Lower MCLG
----------------------------------------------------------------------------------------------------------------
2,4-D (possible MCLG: 0.04 mg/L).  0.005 mg/L........  PQL not limiting.
Endothall (possible MCLG: 0.05 mg/ 0.09 mg/L.........  PQL reduction supported (MRL, MDL).
 L).
Hexachlorocyclopentadiene          0.001 mg/L........  PQL not limiting.
 (possible MCLG: 0.04 mg/L).
Oxamyl (possible MCLG: 0.002 mg/   0.02 mg/L.........  PQL reduction supported (MRL, MDL).
 L).
Toluene (possible MCLG: 0.6 mg/L)  0.005 mg/L........  PQL not limiting.
Total xylenes (possible MCLG: 1    0.005 mg/L........  PQL not limiting.
 mg/L).
----------------------------------------------------------------------------------------------------------------
 14 Contaminants with Ongoing Health Effects Assessments (as of March 1, 2009) and MCLs Are Based on Analytical
                                        Feasibility and Higher than MCLGs
----------------------------------------------------------------------------------------------------------------
Alpha particles..................                          No PQL and no new information.
Benzo(a)pyrene...................  0.0002 mg/L.......  Data do not support PQL reduction.
                                  ------------------------------------------------------------------------------
Beta particles...................                          No PQL and no new information.
                                  ------------------------------------------------------------------------------
Carbon Tetrachloride.............  0.005 mg/L........  PQL reduction supported (PT, MRL, MDL).
DEHP.............................  0.006 mg/L........  Data do not support PQL reduction.
1,2-dichloroethane...............  0.005 mg/L........  PQL reduction supported (PT, MRL, MDL).
Dichloromethane..................  0.005 mg/L........  PQL reduction supported (MRL, MDL).
Pentachlorophenol................  0.001 mg/L........  Data do not support PQL reduction.
PCBs.............................  0.0005 mg/L.......  Data do not support PQL reduction.
                                  ------------------------------------------------------------------------------
Radium...........................                          No PQL and no new information.
                                  ------------------------------------------------------------------------------

Dioxin...........................  3E-08 mg/L........  Data do not support PQL reduction.
Tetrachloroethylene..............  0.005 mg/L........  PQL reduction supported (PT, MRL, MDL).
Thallium.........................  0.002 mg/L........  Data do not support PQL reduction.
Trichloroethylene................  0.005 mg/L........  PQL reduction supported (PT, MRL, MDL).
----------------------------------------------------------------------------------------------------------------
   11 Contaminants without Ongoing Health Effects Assessments and MCLs Are Based on Analytical Feasibility and
                                                Higher than MCLGs
----------------------------------------------------------------------------------------------------------------
Benzene..........................  0.005 mg/L........  PQL reduction supported (PT, MRL, MDL).
Chlordane........................  0.002 mg/L........  PQL reduction supported (PT, MRL, MDL).
DBCP.............................  0.0002 mg/L.......  PQL reduction supported (MDL).
1,2-dichloropropane..............  0.005 mg/L........  PQL reduction supported (PT, MRL, MDL).
EDB..............................  0.0005 mg/L.......  Data do not support PQL reduction.
Heptachlor.......................  0.0004 mg/L.......  PQL reduction supported (MRL, MDL).
Heptachlor epoxide...............  0.0002 mg/L.......  PQL reduction supported (MRL, MDL).
Hexachlorobenzene................  0.001 mg/L........  PQL reduction supported (PT, MRL, MDL).
Toxaphene........................  0.003 mg/L........  PQL reduction supported (MRL, MDL).
1,1,2-trichloroethane............  0.005 mg/L........  PQL reduction supported (PT, MRL, MDL).
Vinyl chloride...................  0.002 mg/L........  PQL reduction supported (MRL).
----------------------------------------------------------------------------------------------------------------
mg/L--milligrams per liter......................................................................................
----------------------------------------------------------------------------------------------------------------

    EPA conducted occurrence and exposure analyses for the contaminants
in Table V-4 for which a PQL reduction is supported or the PQL is not
limiting. This includes the 6 contaminants with new health effects
assessments that indicate potentially lower MCLGs, 5 of the 14
contaminants with ongoing health effects assessments and MCLs limited
by PQLs, and 10 of the 11 contaminants without ongoing health effects
assessments and MCLs limited by PQLs.
4. Occurrence and Exposure Analysis
    To support the national contaminant occurrence assessments under
Six-Year Review 2, EPA conducted an Information Collection Request.
Through this process EPA requested that all States and primacy entities
voluntarily submit their SDWA compliance monitoring data. This request
was for the submission of compliance monitoring data collected between
January 1998 and December 2005 for 79 regulated contaminants. 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. Through extensive data management efforts,
quality assurance evaluations, and communications with State data
management staff, EPA established a high quality dependable contaminant
occurrence database consisting of data from 45 States and two Indian
Tribes (see map in Figure V-2). Details of the data management and data
quality assurance evaluations are available in the support document
entitled, ``Analysis of Occurrence Data from the Second Six-Year Review
of Existing National Primary Drinking Water Regulations'' (USEPA,
2009f).

[GRAPHIC] [TIFF OMITTED] TN29MR10.002

    The contaminant occurrence data from the 45 States and two Indian
Tribes comprise more than 15 million analytical records from
approximately 132,000 public water systems. Approximately 254 million
people are served by these public water systems nationally. Records
were submitted for 16 inorganic chemicals, 32 synthetic organic
chemicals, 21 volatile organic chemicals, 7 radiological contaminants,
and 3 microbiological \6\ contaminants. The number of States and public
water systems 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.
---------------------------------------------------------------------------

    \6\ The compliance monitoring data for the microbiological
contaminants were collected to support ongoing rule development so
these data have not been analyzed separately in this action.
---------------------------------------------------------------------------

    EPA used a two-stage analytical approach to analyze these data and
characterize the national occurrence of contaminants.\7\ The first
stage of analysis provides a straightforward evaluation of contaminant
occurrence. This stage 1 occurrence analysis is a simple, non-
parametric count of occurrence of regulated contaminants in public
water systems.\8\ A typical stage 1 occurrence analysis generates a
count of the number (or percentage) of systems with at least one
analytical detection having a concentration greater than a
concentration threshold of interest, i.e., a possible MCLG or EQL. It
provides a health protective approach that may be more appropriate for
contaminants that produce health effects after shorter than lifetime
exposure periods (e.g., several months or less). This approach also
generates a conservative (i.e., upwardly biased) estimate of the number
of potential systems having contaminant occurrence at levels of
interest for contaminants having health risks that are only related to
chronic or long-term exposure over many years.
---------------------------------------------------------------------------

    \7\ The use of the stage 1 and stage 2 terminology should not be
confused with the Stage 1 and Stage 2 Disinfectants and Disinfection
By Products Rulemakings. Instead, this terminology has been used to
describe the two stages of the occurrence analyses performed for
Six-Year Review 2, as well as Six-Year Review 1.
    \8\ These analyses are conservative in the sense that they are
protective of human health (i.e., they are more likely to
overestimate risks to human health than underestimate them).
---------------------------------------------------------------------------

    The stage 2 occurrence analysis estimates national contaminant
occurrence by generating estimated long-term mean concentrations of a
specific contaminant at systems nationally. This provides occurrence
analyses that are less conservative than the stage 1 occurrence
analysis (because the stage 2 occurrence analysis is based on estimated
mean concentrations rather than on single maximum concentrations), and
also provides occurrence analyses that may be more reflective of
potential chronic exposure. Generally, the stage 1 occurrence analysis
reflects a rough approximation of peak occurrence while the stage 2
occurrence analysis is based on estimated average occurrence. A
complete description of the two-stage analytical approach and a
detailed presentation of occurrence estimates are available in the
support document entitled, ``Analysis of Occurrence Data from the
Second Six-Year Review of Existing National Primary Drinking Water
Regulations'' (USEPA, 2009f).
    EPA calculated the system means for the stage 2 occurrence 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-detection results to
estimate a range of system-level means, which then allowed EPA to
estimate 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-detection results in the Six-Year Review
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-detection results were MRL, \1/2\ MRL, and
zero.
    The most conservative approach was to assume that all non-detection
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 of the non-detection
results were uniformly distributed between the MRL and zero, thereby
substituting one-half the MRL for all non-detection results. Finally,
EPA considered the assumption that the actual concentration for each
non-detection result was typically much smaller than the MRL,
supporting the use of zero to represent each non-detection. This method
yielded a lower-bound estimate of the system's mean. This simplified
approach differs from the stage 2 occurrence analysis approach in the
Six-Year Review 1, which used more sophisticated modeling methods to
address the non-detection results. That analysis, however, was based on
a substantially smaller dataset (i.e., data from 16 States instead of
45 States). (Note that many States substitute zero for all non-
detections when determining compliance with the NPDWRs.) EPA uses each
of the assumptions in the stage 2 occurrence analyses in order to
obtain reasonable bounds on the actual system mean concentrations. Once
the system means were calculated for each of the three substitution
methods, the results means were then compared to the various thresholds
of interest (e.g., the number and percent of systems with a mean
concentration above a health threshold of concern).
    The two-stage analytical approach was previously developed for Six-
Year Review 1. The data management and general occurrence analytical
approach were peer-reviewed for use under the Six-Year Review 1.
    EPA conducted the stage 2 occurrence analysis for 5 of the 14
NPDWRs in Table V-4 with ongoing health effects assessment and MCLs
that are limited by PQLs for which EPA identified analytical
feasibility data supporting possible PQL revision: carbon
tetrachloride; dichloromethane; 1,2-dichloroethane;
tetrachloroethylene; and trichloroethylene. EPA also conducted the
stage 2 occurrence analysis for the five contaminants with health
effects assessment changes that indicate potential to reduce the MCLG
and the ten contaminants that do not have ongoing health effects
assessments, but do have MCLs limited by PQLs and new data indicate
potential to reduce the PQLs (see Table V-4). Note that EPA conducted
the Stage 1 analysis for one contaminant with health effects assessment
changes that indicate a potential to reduce the MCLG (i.e., oxamyl)
because the health endpoint is associated with acute exposure. EPA used
the results of these analyses to identify which possible NPDWR
revisions present a meaningful opportunity to improve the level of
health protection. Section VI contains the occurrence estimates for
each of the 21 contaminants (shown in Table V-4) having either new
information suggesting potentially lower MCLGs or MCLs based on PQLs
that might be lower based on new information.
    Because the Six-Year Review ICR data reflect water quality at entry
points to the distribution system, the occurrence analysis method
described above is not adequate to evaluate the cost savings potential
for the nine contaminants that have health effects assessment changes
that indicate potential for higher MCLG values (see Table V-2). EPA
lacks the comprehensive information on source water quality and
existing treatment needed to determine how many systems would be able
to alter treatment practices were an MCLG to increase. To review the
potential for cost savings, EPA conducted a qualitative assessment of
the potential for treatment cost savings based on three factors: the
magnitude of the difference between the current MCLG and the possible
MCLG; available source water occurrence information; and the potential
for systems having best available technologies (BATs) or small system
compliance technologies (SSCTs) to realize operational cost savings
(USEPA, 2009g).
    There is no comprehensive database of water quality in drinking
water sources. Therefore, EPA used source water quality information
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 EPA's Office of Ground Water and Drinking Water's National
Contaminant Occurrence Database (NCOD). The STORET data come from a
variety of monitoring programs and the NAWQA data come from watershed
or ``study units'' that USGS selected to reflect important hydrologic
and ecological resources; critical sources of contaminants, including
agricultural, urban, and natural sources; and a high percentage of
population served by municipal water supply and irrigated agriculture.
The original 51 study units account for more than 70 percent of total
water use (excluding thermoelectric and hydropower) and more than 50
percent of the population's supply of drinking water (Gilliom et al.,
2006). For each dataset, EPA estimated the number and percent of
monitoring locations with at least one sample result above each
contaminant's current MCL, and above a possible MCLG based on the new
information from the contaminant's health effects assessment. Although
these results do not indicate how many systems may be treating for each
contaminant, they provide the best available information regarding the
frequency of contaminant occurrence at levels of interest. Section VI
reports the results by contaminant.
5. Treatment Feasibility
    An NPDWR either identifies the BATs for meeting an MCL, or
establishes enforceable treatment technique requirements. For the
NPDWRs addressed in section VI of today's action, two have TT
requirements and the rest have an MCL. All of the MCLs are set equal to
the MCLG or the PQL or by benefit-cost analysis; none are currently
limited by treatment feasibility. As a refinement for Six-Year Review
2, EPA considered treatment feasibility after identifying contaminants
with potential to lower an MCL or change a TT that constituted a
meaningful opportunity to improve the level of health protection. The
EPA document, ``Water Treatment Technology Feasibility Support Document
for Chemical Contaminants for the Second Six-Year Review of National
Primary Drinking Water Regulations'' (USEPA, 2009g), describes the
process EPA used to evaluate treatment feasibility, where appropriate,
and provides the results of these analyses. As a part of this review,
EPA utilized the same sources that have been the primary resources in
development of EPA regulations and guidance, including published EPA
treatment reports, peer-reviewed journals, and other technology
sources, as well as information received from EPA stakeholders.
a. MCL-Type Rules
    EPA evaluated existing treatment technology information for two
MCL-type NPDWRs (tetrachloroethylene and trichloroethylene) where EPA
determined that lowering the PQL and thus the MCL could lead to a
meaningful opportunity to improve public health protection, to
determine whether treatment feasibility would be a limiting factor.
    Based on this evaluation, the Agency believes that treatment
capabilities would be adequate to support a lower MCL value for these
contaminants for which a lower MCL may be appropriate (USEPA, 2009g).
EPA's assessment of the treatment technologies for these

contaminants that are specified as BAT in the current NPDWR and some of
the small system compliance technologies specified by EPA in 1998
(USEPA, 1998b), shows that they are effective enough to achieve
concentrations as low as the EQL. If EPA were to determine that it is
appropriate to revise these NPDWRs, it would undertake a more thorough
review of treatment feasibility, including a consideration of costs, to
determine whether treatment feasibility would be a constraint or not.
b. Treatment Technique-Type Rules
    EPA reviewed two chemical NPDWRs--acrylamide and epichlorohydrin
(both classified B2 carcinogens)--for which a TT is set in lieu of an
MCL. The TT requirement limits the allowable acrylamide and
epichlorohydrin monomer levels in polymeric coagulant aids and their
dosages for drinking water treatment, storage, and distribution.
Although a health effects assessment for acrylamide is ongoing, it is a
carcinogen with an MCLG of zero and the draft health effects assessment
indicates that the cancer classification remains the same. As a
refinement in Six-Year Review 2, EPA considered new information to
determine if the TTs for these contaminants may need to be revised.
This information indicates that improvements in manufacturing
capabilities have reduced the residual monomer content in acrylamide
and epichlorohydrin-based polymeric coagulants aids and these changes
would support revisions to the TTs for acrylamide and epichlorohydrin.
Sections VI.B.1 and VI.B.36 of today's action summarize these issues
for acrylamide and epichlorohydrin, respectively.
6. Other Regulatory Revisions
    In addition to possible revisions to MCLGs, MCLs, and TTs, EPA
considered whether other regulatory revisions are needed, such as
monitoring and system reporting requirements, as a part of the Six-Year
Review 2. EPA utilized the protocol established during the Six-Year
Review 1 to evaluate which implementation issues to consider (USEPA,
2003b). EPA's protocol focused on items that were not already being
addressed, or had not been addressed, through alternative mechanisms
(e.g., as a part of a recent or ongoing rulemaking). EPA considered
potential implementation-related revisions in these cases if the
revisions:
     Represented a change to an NPDWR, as defined under section
1401 of SDWA; \9\
---------------------------------------------------------------------------

    \9\ The subject of the Six-Year-Review, as specified in section
1412(b)(9) of the SDWA, is ``each national primary drinking water
regulation,'' as defined under section 1401 of the SDWA.
---------------------------------------------------------------------------

     Were ``ready'' for rulemaking--that is, the problem to be
resolved had been clearly defined, and specific options to address the
problem had been formulated; and
     Would clearly improve the level of public health
protection and/or provide a meaningful opportunity for cost savings
(either monetary or burden reduction) while not lessening public health
protection.
a. Issues Identified by the EPA/State Workgroup
    To gather input regarding implementation-related concerns and help
the Agency identify the top one or two issues for Six-Year Review 2
(USEPA, 2009h), EPA requested that the Association of State Drinking
Water Administrators (ASDWA) form a workgroup of member States and
primacy agencies. In the fall of 2007, ten member States agreed to
participate and confer with EPA on a joint EPA/State workgroup. The
State/EPA workgroup initially identified 22 issues, but narrowed the
list to 4 items. Of these four items, three appeared to be within the
scope of this NPDWR review, and EPA agreed that an information or fact
sheet might be appropriate for the fourth item regarding public
notification (PN) requirements for fluoride.\10\ The EPA/State
workgroup agreed that public input via the Federal Register would
provide additional insight on the national scope of these three issues
(i.e., Are the issues isolated to a few States or more widespread?),
the importance of these issues to other States as well as water
systems, and ideas on potential resolutions. Table V-5 provides a brief
description of the remaining three issues and some of the potential
solutions discussed in the workgroup meetings.
---------------------------------------------------------------------------

    \10\ Currently, PWSs that exceed the fluoride MCL of 4.0 mg/L
are required to notify their customers within 30 days of the
exceedance. If a PWS exceeds the fluoride SMCL of 2.0 mg/L, they are
required to notify their customers within 12 months of the
exceedance. The States voiced concerns about (1) the confusion that
occurs between the different PN requirements for the MCL and the
SMCL, and (2) the timeliness of the PN requirement for the SMCL. The
workgroup indicated that waiting 12 months to notify customers of an
exceedance of the SMCL does not adequately protect young children
from dental fluorosis during a critical stage of tooth enamel
development. The participating States requested that EPA consider
regulatory revisions to clarify the PN requirements and better
reflect the health and aesthetic implications of each. EPA noted
that PN requirements are not within the scope of this NPDWR review.
However the Agency agreed that a fact or information sheet may be
useful to clarify any confusion.
---------------------------------------------------------------------------

    EPA is requesting public input and further information on these
three implementation issues to better inform future State/EPA workgroup
discussions. More specifically, EPA would like to gauge how many States
and/or public water utilities may be affected by these issues, and
which one or two issues are most important to States. EPA also requests
input and suggestions from commenters regarding any other potential
solutions to the issues. As part of the public comment process, EPA
also welcomes any data on the occurrence of nitrates and/or nitrites in
the distribution system, especially as it may relate to nitrification
associated with the use of chloramines for disinfection.

Table V-5--Issues Identified by the EPA/State Workgroup That Fall Within
                     the Scope of This NPDWR Review
------------------------------------------------------------------------
                               Examples of potential solutions discussed
     Implementation issue                   by the workgroup
------------------------------------------------------------------------
Change the location of          Location of Monitoring
 nitrate-nitrite monitoring    --Move sampling location from the entry
 to address possible            point to the distribution to within the
 nitrification within the       distribution system.
 distribution system for       --Or, maintain entry point sampling and
 water systems using            also sample in the distribution system.
 chloramines\1\

                                Frequency of Monitoring
                               --Consider sampling in conjunction with
                                DBPs, TCR or some other scheme.
                                EPA notes that 40 Code of
                                Federal Regulations (CFR) 141.23(a)(2)
                                may allow surface water systems
                                discretion to locate the sampling point
                                in the distribution system if that is
                                more representative of the source after
                                treatment.\2\
Reduce the monitoring for       Consider revisions to change the
 ground water systems with      frequency of monitoring, the trigger
 historically low levels of     level and the duration of time for
 nitrate-nitrite.               systems to qualify for reduced
                                monitoring. Examples included:
                               --A monitoring frequency of 3, 6, or 9
                                years (consistent with the existing
                                standardized monitoring framework) or
                                some other frequency.
                               --A new trigger level set at either \1/2\
                                the MCL (or some other fraction), the
                                PQL/MDL (or some other level of
                                detection), or another appropriate
                                level.
                               --As for the duration of how long a
                                system would need to meet the trigger
                                level in order to be allowed to begin
                                reduced monitoring, some options
                                included a 3-, 6-, or 9-year period
                                (consistent with the standardized
                                monitoring framework) or a 5-, 10-, or
                                15-year period.
                                Or consider providing a waiver
                                option to give States discretion to
                                reduce monitoring.
                                Or consider a non-regulatory
                                option such as the Alternative
                                Monitoring Guidelines (which some
                                considered too burdensome).
Revise the monitoring           Revise all contaminant rules to
 requirements for Non           include additional monitoring
 Community Water Systems        requirements for Transient Non Community
 (NCWS) to better target the    Water Systems (TNCWS), as well as
 potential health risks         radionuclide monitoring requirements for
 associated with chronic        Non Transient Non Community Water
 contaminants. In light of      Systems (NTNCWS).
 the probability and            Or review existing regulated
 magnitude of health threats,   contaminants and include TNCWS
 some monitoring requirements   monitoring requirements based on the
 for these systems may be       relative health risk from chronic
 insufficient, and others may   exposure.
 be excessive.                  Or develop general language that
                                would apply to all contaminant rules,
                                giving States the discretion to require
                                additional monitoring for contaminants
                                that pose chronic exposure risks and can
                                have acute health effects at elevated
                                levels potentially found at TNCWSs (the
                                preferred option from States).
                                Note: For some of these options,
                                EPA would need to evaluate whether
                                sufficient occurrence and exposure
                                information is available for TNCWS and
                                NTNCWS to assess the need for revised
                                monitoring strategies.
------------------------------------------------------------------------
\1\ The health effects technical review identified new information on
  developmental effects of nitrate and nitrite, as well as data
  regarding its carcinogenicity, that may indicate the need to update
  the Agency's risk assessment (see section VI.B.49 and VI.B.50 of
  today's action). In light of this information, EPA is considering
  nitrate and nitrite as potential candidates for new health effects
  assessments. If new assessments are initiated and completed, EPA will
  be able to determine the potential impacts on the MCLG, MCL, and/or
  monitoring requirements, and what future actions may or may not be
  appropriate.
\2\ 40 CFR 141.23(a)(2) states: Surface water systems shall take a
  minimum of one sample at every entry point to the distribution system
  after any application of treatment or in the distribution system at a
  point which is representative of each source after treatment
  (hereafter called a sampling point) beginning in the initial
  compliance period. The system shall take each sample at the same
  sampling point unless conditions make another sampling point more
  representative of each source or treatment plant.

b. Other Issues (Synthetic Organic Chemicals Trigger Levels)
    40 CFR 141.24(h)18 of the national primary drinking water
regulations lists detection limits for the synthetic organic chemicals
(SOCs), including pesticides. These detection limits serve as triggers
for determining whether the compliance monitoring frequency for SOCs
may be reduced; public water systems detecting SOCs at or below trigger
concentration can qualify for reduced monitoring. Several Regions and
States have requested guidance and clarification on the use of
detection limits in monitoring of drinking water samples for SOCs. The
primary concern is that some laboratories have reported difficulty in
achieving the detection limits for some SOCs on a regular basis and, in
those cases, the water systems that they support are not able to
qualify for reduced monitoring.
    EPA is seeking information about the extent and magnitude of any
issues related to the ability of laboratories to achieve the SOC
trigger levels specified in section 141.24(h)(18). EPA wishes to
determine if this issue is widespread or limited to specific SOCs and/
or specific laboratories. EPA is requesting that stakeholders provide
information/data to support their concerns related to SOC triggers.

C. How Did EPA Factor Children's Health Concerns Into the Review?

    The 1996 amendments to SDWA require special consideration of all
sensitive populations (e.g., infants, children, pregnant women,
elderly, and individuals with a history of serious illness) in the
development of drinking water regulations (section 1412(b)(3)(C)(V) of
SDWA, as amended in 1996). As a part of the Six-Year Review 2, EPA
completed a literature search covering developmental and reproductive
endpoints (e.g., fertility, embryo survival, developmental delays,
birth defects, and endocrine effects) for regulated chemicals that have
not been the subject of a health effects assessment during this review
period (see section V.B.1 of today's action). EPA reviewed the output
from the literature searches to identify any studies that might have an
influence on the present MCLG. Three chemicals were identified with
potential developmental/reproductive endpoints of concern that might
not be addressed by the current NPDWR: Nitrate, nitrite, and selenium.
In each case, where the literature search indicated a need to consider
recent studies of developmental or reproductive toxicity, EPA is
considering whether to nominate the contaminant for a new health
effects assessment.

VI. Results of EPA's Review of NPDWRs

    Table VI-1 lists EPA's review results for each of the 71 NPDWRs
discussed in this section of today's action along with the principal
rationale for the review outcomes. Table VI-1 also includes a list of
the 14 NPDWRs that have been or are being reviewed/revised by recent or
ongoing regulatory actions.

A. What Are the Review Result Categories?

    For each of the 71 NPDWRs discussed in detail in the following
sections of today's action, the review results in one of the following
outcomes:
1. No Action at This Time and the NPDWR Is Still Appropriate
    The NPDWR is appropriate and no action is necessary at this time
for one of the following reasons:

    a. A health effects assessment is in process or the Agency is
considering whether to initiate an assessment. The MCL remains
appropriate because either, (1) it is equal to the MCLG, (2) the MCL
is based on SDWA's cost-benefit provision, (3) there is no potential
to change the MCL based on changes in analytical feasibility, or (4)
there may be a potential change to the MCL based on analytical
feasibility, but any such change is unlikely to provide a meaningful
opportunity to improve public health protection. This group includes
both contaminants where an assessment is in process, and
contaminants where EPA identified new health information that may
warrant a new health effects assessment.
    b. NPDWR remains appropriate after data/information review.
There is no ongoing health assessment and the outcome of the review
indicates that the current regulatory requirements remain
appropriate and, therefore, no regulatory revisions are warranted at
this time. Any new information available to the Agency either
supports the current regulatory requirements or does not justify a
revision.
    c. New information is available that indicates potential for a
regulatory revision, but no revision recommended because:
     Negligible gain in public health protection and/or cost
savings: Any resulting changes to the NPDWR would not significantly
improve the level of public health protection or result in a major
cost savings for public water systems and their customers.
     Information Gaps or Emerging Information: Either new
information is emerging that could affect EPA's evaluation of the
NPDWR or the available data are insufficient to support a definitive
regulatory recommendation at this time.
2. Candidate for Revision
    The NPDWR is a candidate for revision based on the review of new
information.

[GRAPHIC] [TIFF OMITTED] TN29MR10.003

B. What Are the Details of EPA's Review of Each NPDWR?

1. Acrylamide
    a. Background. EPA published the current NPDWR for acrylamide on
January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an
MCLG of zero based on a cancer classification of B2, probable human
carcinogen. The NPDWR imposes a TT requirement that limits the
allowable monomer levels in products used during drinking water
treatment, storage, and distribution to 0.05 percent acrylamide in
polyacrylamide coagulant aids, and limits the dosage of such products
to a maximum of 1 mg/L (ppm). Each water system is required to certify,
in writing, to the State (using third-party or manufacturer's
certification) that the product used meets these residual monomers and
use-level specifications.
    b. Technical Reviews. EPA has initiated a reassessment of the
health risks resulting from exposure to acrylamide. The revised health
effects assessment is considering relevant studies on the toxicity of
acrylamide, including its potential developmental and reproductive
toxicity. The draft assessment was published in the Federal Register on
December 28, 2007 (72 FR 73813 (USEPA, 2007b)). The Science Advisory
Board (SAB) conducted a peer review of the document, which also
included a review of public comments received on the draft assessment.
The SAB panel concurred with the Agency's rationale and justification
for acrylamide being a ``likely human carcinogen'' via mutagenic
mechanism. At the present time, acrylamide is still under evaluation by
the Agency, and the IRIS Substance Assessment Tracking System Web site
(http://cfpub.epa.gov/iristrac/index.cfm) has the most up-to-date
information on the status of the health effects assessment.
    Although there is an ongoing health effects assessment, the MCLG is
zero and the current TT standard allows exposure at levels above the
MCLG. Therefore, EPA reviewed whether there is potential to revise the
TT for acrylamide. EPA has identified information that suggests that
the residual acrylamide content in water treatment polymers has
decreased significantly, likely due to improvements in manufacturing
processes and technologies (USEPA, 2009g). NSF International analyses
conducted between January 2005 and June 2007 found that, in 66
polyacrylamide products submitted for certification under NSF Standard
60, the median residual acrylamide content was 0.006 percent, and the
90th percentile acrylamide content was 0.025 percent, half of the limit
set in the treatment technique.
    Acrylamide standards in Europe and Australia are also stricter than
the NPDWR. Based on the maximum allowable dosage and monomer level in
the NPDWR, finished water could contain up to 0.5 [mu]g/L (ppb) of
acrylamide. By contrast, the European Union requires that finished
water contain less than 0.1 [mu]g/L (parts per billion or ppb)
acrylamide, and Australia requires that the concentration in finished
water be less than 0.2 [mu]g/L (ppb). The United Kingdom requires that
polyacrylamides used in drinking water contain less than 0.02 percent
residual acrylamide, and that the polyacrylamide dose be less than 0.5
mg/L (parts per million or ppm) at all times, for a maximum finished
water concentration of 0.1 [mu]g/L (ppb).
    To assess the occurrence of acrylamide in drinking water, EPA
sought data on current usage practices for polyacrylamide coagulant
aids. The Agency is not presently aware of any recent, large-scale
studies of polymer usage in drinking water facilities, and therefore
cannot fully characterize the occurrence of acrylamide in drinking
water. However, the 1996 WATER:\STATS database (described in Levine et
al., 2004), based on an American Water Works Association (AWWA) survey,
indicates that 13 percent of ground water systems and 66 percent of
surface water systems surveyed use a polymer for water treatment. Many
of these are anionic and nonionic polymers, particularly for ground
water systems; anionic and nonionic polymers used to treat drinking
water are most likely polyacrylamides.
    Additional information on the extent of use of polyacrylamide in
drinking water and the impending health effects assessment will further
assist the Agency in determining the potential public health benefits
associated with a revision to the treatment technique for acrylamide.
Because most polyacrylamides available today have a lower residual
monomer content than that specified in the current treatment technique
(USEPA, 2009g), EPA believes that the costs of a revision would be
minimal and recognizes that the benefits may also be small.
    c. Review Result. The Agency believes it is appropriate to revise
the NPDWR for acrylamide although a health effects assessment is
currently in progress. The existing MCLG is still zero (based on the
current B2 cancer classification) and NSF International data indicate
that polyacrylamides are widely available with lower residual monomer
levels than required by the existing NPDWR. Hence, revisions to the
acrylamide NPDWR will provide a meaningful opportunity to maintain the
health risk reductions achieved by technological advances in
manufacturing. If the updated health effects assessment is completed in
time to consider for the regulatory revision of acrylamide, the Agency
will consider this final assessment in its evaluation of health
benefits. As discussed in Section VII, the Agency solicits information
from the public on the extent of use of polyacrylamide in drinking
water facilities (since this may provide additional information on the
occurrence of acrylamide in drinking water) to help inform the
regulatory revision. EPA notes that any changes to the NPDWR for
acrylamide may also include revisions to the closely related NPDWR for
epichlorohydrin.
2. Alachlor
    a. Background. EPA published the current NPDWR for alachlor on
January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an
MCLG of zero based on a cancer classification of B2, probable human
carcinogen. The NPDWR also established an MCL of 0.002 mg/L, based on
analytical feasibility.
    b. Technical Reviews. In 2006, the Agency updated its health
effects assessment of alachlor (USEPA, 2006a). The Agency identified a
change in this assessment that could lead to a change in the MCLG. This
assessment considered relevant studies on the toxicity of alachlor
including developmental and reproductive toxicity. For noncancer
effects, the assessment confirmed the RfD of 0.01 mg/kg-day (milligrams
per kilogram of body weight per day). The assessment also concluded
that alachlor is likely to be a human carcinogen at high doses; not
likely to be a human carcinogen at low doses, and that a linear dose-
response extrapolation is no longer appropriate. It established a
health reference value of 0.005 mg/kg-day for the nonlinear cancer
assessment (USEPA, 2006a). Since the health reference value of 0.005
mg/kg-day is lower than the RfD of 0.01 mg/kg-day, the Agency used this
value to calculate a possible MCLG. Based on the health reference value
of 0.005 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters
water intake per day, the drinking water equivalent level (DWEL) could
be 0.2 mg/L. A relative source contribution (RSC) of 20 percent results

in a possible MCLG of 0.04 mg/L (USEPA, 2009b).
    Since the health review for alachlor indicates that the MCLG could
possibly increase to 0.04 mg/L (from its current MCLG of zero) and
because the current MCL is based on a PQL of 0.002 mg/L, neither
analytical nor treatment feasibility would be a limiting factor for a
possible higher level of 0.04 mg/L.
    EPA evaluated the results of the occurrence and exposure analyses
for alachlor to determine whether a revised MCLG/MCL would be likely to
result in a meaningful opportunity for cost savings to PWSs and their
customers while maintaining or improving the level of public health
protection (USEPA, 2009f). Review of health information for alachlor
indicated that the MCLG could be increased to 0.04 mg/L from its
current MCLG of zero. Consequently, the MCL of alachlor possibly can
also increase to 0.04 mg/L. Although the Agency obtained and evaluated
the finished water occurrence data for alachlor, its usefulness is
limited for determining potential cost savings to PWSs and their
customers because the Agency does not know which systems are treating
for this contaminant. As an alternative, the Agency evaluated available
data on source water quality and conducted a qualitative assessment of
treatment cost savings.
    Table VI-2 provides summary data for contaminant occurrence based
on maximum sample values for the locations included in the STORET and
NAWQA data. Although the degree to which these occurrence rates
represent national drinking water source occurrence is uncertain, the
information shows no to low occurrence at threshold levels of interest.
This information indicates that any resulting NPDWR change would affect
systems that rely on source water at less than 0.4 percent of the NAWQA
locations and less than 1.8 percent of the STORET locations.

   Table VI-2--Ambient Water Quality Monitoring Occurrence Summary for
                                Alachlor
------------------------------------------------------------------------
                                   Number of locations (% of locations)
     Maximum concentration      ----------------------------------------
                                    STORET \1\           NAWQA \2\
------------------------------------------------------------------------
Total..........................  2,252 (100.0%)..  9,236 (100.0%)
Nondetect......................  1,669 (74.1%)...  8,571 (92.8%)
Detected.......................  583 (25.9%).....  665 (7.2%)
Exceeds current MCL of 0.002 mg/ 40 (1.8%).......  35 (0.38%)
 L.
Exceeds alternative value of     0 (0.0%)........  1 (0.01%)
 0.04 mg/L.
------------------------------------------------------------------------
\1\ STORET database 2002-2006.
\2\ NAWQA database 1992-2008.
Source: USEPA, 2009d.

    The BATs and small system compliance technologies for alachlor have
other beneficial effects, e.g., reduction of other co-occurring
contaminants, precursors for disinfection byproducts (DBPs) or other
common impurities. Therefore, if EPA were to consider a higher level,
the Agency does not know how many PWSs that are currently treating to
comply with the existing MCL of 0.002 mg/L would be likely to
discontinue treatment that is already in place (USEPA, 2009d). Also,
the Agency does not know to what extent affected systems might be able
to reduce costs given that capital costs are not recoverable. However,
the Agency recognizes that there may be opportunities to achieve
operational cost savings if these systems are able to re-optimize
current treatment.
    Given these considerations, the Agency believes that any resulting
revision is not likely to provide a meaningful opportunity for cost
savings. In view of this, any revision would be a low priority activity
and not appropriate at this time.
    The Agency notes that alachlor and two of its unregulated acid
degradates (alachlor ethanesulfonic acid or ESA and alachlor oxanilic
acid or OA\11\) are currently listed on the second Unregulated
Contaminants Monitoring Rule (UCMR 2) (72 FR 367, January 4, 2007
(USEPA, 2007e)). The Agency also listed alachlor ESA and OA on the CCL3
(74 FR 51850, October 8, 2009 (USEPA, 2009l)). Once the UCMR 2
monitoring results are available for alachlor and its degradates, the
Agency will be able to more fully evaluate alachlor along with its
degradates in determining how this information might impact the current
regulation for alachlor and/or the need for any revised or new
regulation to capture the impact from the ESA and OA degradates.
---------------------------------------------------------------------------

    \11\ Between 2004 and 2006, the United States Department
Agriculture's Pesticide Data Program (USDA PDP) collected data for
alachlor and its ESA and OA degradates from finished and untreated
water samples for a limited number of water systems (USDA, 2004,
2005, and 2006). While alachlor was rarely detected (i.e., 0 to 0.8
percent of the samples by year), the alachlor ESA and OA degradates
were commonly detected (i.e., 19 to 51 percent of the samples by
year for the ESA degradate and 7 to 40 percent of the samples by
year for the OA degradate). The detected values for the ESA and OA
degradates ranged from 0.0028 to 0.357 [mu]g/L and 0.001 to 0.102
[mu]g/L, respectively. The detected values for alachlor ranged from
0.0163 to 0.043 [mu]g/L.
---------------------------------------------------------------------------

    Since the occurrence analysis indicates that any revision to the
MCL is unlikely to provide a meaningful opportunity to improve the
level of public health protection, it was not necessary to perform any
additional reviews on treatment feasibility or economic considerations.
    c. Review Result. Although there are new data that support
consideration of whether to revise the MCLG/MCL for alachlor, EPA does
not believe a revision to the NPDWR for alachlor is appropriate at this
time. In making this decision, the Agency considered whether any
possible revision to the NPDWR for alachlor is likely to provide a
meaningful opportunity for cost savings to public water systems and
their customers. Taking into consideration the low occurrence of this
contaminant in source waters, EPA has decided that any revision to the
NPDWR would be a low priority activity for the Agency, and, thus, is
not appropriate to revise at this time 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.
    In addition, the Agency considers it premature to make any decision
to revise the alachlor NPDWR pending the final UCMR 2 monitoring
results.
3. Alpha Particle Emitters
    a. Background. EPA published an interim NPDWR and set an MCL of 15
pCi/L for gross alpha particle activity on July 9, 1976 (41 FR 28402
(USEPA, 1976)). As noted in the August 14, 1975 proposal (40 FR 34324
(USEPA, 1975))

and a subsequent September 30, 1986 FR notice (51 FR 34836 (USEPA,
1986a), EPA considered the feasibility of treatment techniques,
analytical methods and monitoring when establishing the MCL of 15 pCi/
L. EPA also considered the risks associated with other alpha particle
emitters relative to radium-226, which generally fell within the
Agency's acceptable risk range of 10-4 to 10-6 at
the MCL of 15 pCi/L. On December 7, 2000 (65 FR 76708 (USEPA, 2000c)),
EPA established an MCLG of zero based on a cancer classification of A
(known human carcinogen) and finalized the NPDWR by retaining the MCL
of 15 pCi/L. EPA noted in the December 7, 2000, FR notice that new risk
estimates from Federal Guidance Report 13 reaffirmed that the 15 pCi/L
gross alpha particle MCL (including radium 226 but excluding uranium
and radon) was appropriate and protective.
    b. Technical Reviews. EPA has initiated a reassessment of the
health risks resulting from exposure to alpha particle emitters. The
revised health effects assessment will consider relevant studies on the
toxicity of alpha particle emitters, including its potential
developmental and reproductive toxicity. The new health effects
assessment was not completed by March 1, 2009, the review cutoff date
for this notice (USEPA, 2009b).
    Although there is an ongoing health effects assessment, the MCLG is
zero and the current MCL is higher than the MCLG. Therefore, EPA
reviewed whether there is potential to revise the MCL based on new
information regarding analytical and treatment feasibility for gross
alpha particles. EPA promulgated a detection limit of 3 pCi/L in 1976
(41 FR 28402 (USEPA, 1976)) and retained the use of a detection limit
as the required measure of sensitivity for radiochemical analysis in
lieu of an MDL or PQL in the final rule (65 FR 76708 (USEPA, 2000c)).
EPA did not identify new analytical methods during the current review
that would feasibly lower the detection limit. In addition, since the
December 7, 2000, regulation, there is no new information regarding