Federal Register/Vol. 82, No. 7/Wednesday, January 11, 2017

3518 Federal Register / Vol. 82, No. 7 / Wednesday, January 11, 2017 / Proposed Rules

ENVIRONMENTAL PROTECTION ADDRESSES: Submit your comments, AWWA—American Water Works Association AGENCY identified by Docket ID No. EPA–HQ– BAT—Best Available Technology OW–2016–0627, to the Federal CBI—Confidential Business Information [EPA–HQ–OW–2016–0627; FRL–9957–49– eRulemaking Portal: http:// CDC—Centers for Disease Control and OW] Prevention www.regulations.gov. Follow the online CFR—Code of Federal Regulations 40 CFR Part 141 instructions for submitting comments. CT—Concentration × Contact Time Once submitted, comments cannot be cVOCs—Carcinogenic Volatile Organic RIN 2040–ZA26 edited or withdrawn. EPA may publish Compounds any comment received to its public CWS—Community Water System National Primary Drinking Water docket. Do not submit electronically any DBCP—1,2-Dibromo-3-Chloropropane Regulations; Announcement of the information you consider to be DBP—Disinfection Byproducts Results of EPA’s Review of Existing Confidential Business Information (CBI) D/DBP—Disinfectants/Disinfection Drinking Water Standards and Request Byproducts or other information whose disclosure is for Public Comment and/or Information D/DBPR—Disinfectants/Disinfection restricted by statute. Multimedia on Related Issues Byproducts Rule submissions (audio, video, etc.) must be DEHA—Di(2-ethylhexyl)adipate AGENCY: Environmental Protection accompanied by a written comment. DEHP—Di(2-ethylhexyl)phthalate Agency (EPA). The written comment is considered the DOC—Dissolved Organic Carbon DPD—N,N-diethyl-p-phenylenediamine ACTION: Request for public comments. official comment and should include discussion of all points you wish to EDB—Ethylene Dibromide EJ—Environmental Justice SUMMARY: The Safe Drinking Water Act make. EPA will generally not consider EO—Executive Order (SDWA) requires the U.S. comments or comment contents located EPA—U.S. Environmental Protection Agency Environmental Protection Agency (EPA) outside of the primary submission (i.e. EQL—Estimated Quantitation Level to conduct a review every six years of on the web, cloud, or other file sharing FAC—Federal Advisory Committee existing national primary drinking water system). For additional submission FBRR—Filter Backwash Recycling Rule regulations (NPDWRs) and determine methods, the full EPA public comment FDA—U.S. Food and Drug Administration which, if any, need to be revised. The policy, information about CBI or FRN—Federal Register Notice purpose of the review, called the Six- multimedia submissions, and general GAC—Granulated Activated Carbon Year Review, is to evaluate current guidance on making effective GWR—Ground Water Rule information for regulated contaminants comments, please visit http:// GWUDI—Ground Water Under the Direct Influence of Surface Water to determine if there is new information www2.epa.gov/dockets/commenting- HAA5—Haloacetic Acids (five) (sum of on health effects, treatment epa-dockets. monochloroacetic acid, dichloroacetic technologies, analytical methods, Mail: Water Docket, Environmental acid, trichloroacetic acid, occurrence and exposure, Protection Agency, Mail code: 2822T, monobromoacetic acid and dibromoacetic implementation and/or other factors 1200 Pennsylvania Ave. NW., acid) that provides a health or technical basis Washington, DC 20460. HAAs—Haloacetic Acids to support a regulatory revision that will Hand Delivery: EPA Docket Center HAV—Hepatitis A Virus improve or strengthen public health Public Reading Room, EPA HPC—Heterotrophic Plate Count protection. EPA has completed a Headquarters West, Room 3334, 1301 IARC—International Agency for Research on Cancer detailed review of 76 NPDWRs and at Constitution Ave. NW., Washington, DC. Hand deliveries are only accepted ICR—Information Collection Request this time has determined that eight IESWTR—Interim Enhanced Surface Water NPDWRs are candidates for regulatory during the Docket’s normal hours of Treatment Rule revision. The eight NPDWRs are operation, and special arrangements IRIS—Integrated Risk Information System included in the Stage 1 and the Stage 2 should be made for deliveries of boxed LT1—Long-Term 1 Enhanced Surface Water Disinfectants and Disinfection information. Treatment Rule Byproducts Rules, the Surface Water FOR FURTHER INFORMATION CONTACT: For LT2—Long-Term 2 Enhanced Surface Water Treatment Rule, the Interim Enhanced technical inquiries contact: Richard Treatment Rule Surface Water Treatment Rule and the Weisman, (202) 564–2822, or Kesha MCL—Maximum Contaminant Level Forrest, (202) 564–3632, Office of MCLG—Maximum Contaminant Level Goal Long Term 1 Enhanced Surface Water MDBP—Microbial and Disinfection Treatment Rule. EPA requests Ground Water and Drinking Water, Byproducts comments on the eight NPDWRs Environmental Protection Agency. For MDL—Method Detection Limit identified as candidates for revision and general information about the existing MRDL—Maximum Residual Disinfectant will consider comments and data as it NPDWRs discussed in this action, Level proceeds with determining whether contact the Safe Drinking Water Hotline. MRDLG—Maximum Residual Disinfectant further action is needed. In addition, as Callers within the United States may Level Goal part of this Six-Year Review, EPA reach the Hotline at (800) 426–4791. MRL—Minimum Reporting Level identified 12 other NPDWRs that were The Hotline is open Monday through NAS—National Academy of Sciences Friday, excluding Federal holidays, NCWS—Non-Community Water System or continue to be addressed in recently NDMA—N-Nitrosodimethylamine completed, ongoing or pending from 10 a.m. to 5:30 p.m. Eastern Time. NDWAC—National Drinking Water Advisory regulatory actions. EPA thus excluded SUPPLEMENTARY INFORMATION: Council those 12 NPDWRs from detailed review. Abbreviations and Acronyms Used in NIH—National Institutes of Health This document is not a final regulatory NPDWR—National Primary Drinking Water This Action decision, but rather the initiation of a Regulation process that will involve more detailed ADWR—Aircraft Drinking Water Rule NRC—National Research Council analyses of factors relevant to deciding AGI—Acute Gastrointestinal Illness NTNCWS—Non-Transient Non-Community whether a rulemaking to revise an AOC—Assimilable Organic Carbon Water System NTP—National Toxicology Program NPDWR should be initiated. ASDWA—Association of State Drinking Water Administrators PCBs—Polychlorinated Biphenyls DATES: Comments must be received on ATSDR—Agency for Toxic Substances and PCE—Tetrachloroethylene or before March 13, 2017. Disease Registry PHS—U.S. Public Health Service

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PT—Proficiency Testing 2. Fluoride II. Six-Year Review—Statutory PQL—Practical Quantitation Limit 3. Disinfectants/Disinfection Byproducts Requirements and Next Steps PWS—Public Water System Rules (D/DBPRs) qPCR—Quantitative Polymerase Chain 4. Microbial Contaminants Regulations Under the Safe Drinking Water Act Reaction VII. EPA’s Request for Comments (SDWA), as amended in 1996, EPA must RfD—Reference Dose References periodically review existing NPDWRs RICP—Research and Information Collection I. General Information and, if appropriate, revise them. Section Partnership 1412(b)(9) of the SDWA states: ‘‘The RSC—Relative Source Contribution A. Does this action apply to me? RTCR—Revised Total Coliform Rule Administrator shall, not less often than SDWA—Safe Drinking Water Act This action itself does not impose any every six years, review and revise, as SMCL—Secondary Maximum Contaminant requirements on individual people or appropriate, each national primary Level entities. Instead, it notifies interested drinking water regulation promulgated SOC—Synthetic Organic Chemical parties of EPA’s review of existing under this title. Any revision of a SWTR—Surface Water Treatment Rule national primary drinking water national primary drinking water SWTRs—Surface Water Treatment Rules regulation shall be promulgated in (including SWTR, IESWTR and LT1) regulations (NPDWRs) and its SYR—Six-Year Review conclusions about which of these accordance with this section, except TCE—Trichloroethylene NPDWRs may warrant new regulatory that each revision shall maintain, or TC/EC—Total Coliforms/E. coli action at this time. EPA requests public provide for greater, protection of the TCR—Total Coliform Rule comment on the eight NPDWRs health of persons.’’ THM—Trihalomethanes identified as candidates for revision. Pursuant to the 1996 SDWA TTHM—Total Trihalomethanes (sum of four EPA will consider comments received Amendments, EPA completed and THMs: chloroform, published the results of its first Six-Year bromodichloromethane, as the Agency moves forward with dibromochloromethane and bromoform) determining whether regulatory actions Review (Six-Year Review 1) on July 18, TNCWS—Transient Non-Community Water are necessary for the eight NPDWRs. 2003 (68 FR 42908, USEPA, 2003b) and the second Six-Year Review (Six-Year System B. What should I consider as I prepare TOC—Total Organic Carbon Review 2) on March 29, 2010 (75 FR TT—Treatment Technique my comments for EPA? 15500, USEPA, 2010h), after developing UCFWR—Uncovered Finished Water Please see Section VII for the topic a systematic approach, or protocol, for Reservoirs areas related to this document for which the review of NPDWRs. UCMR—Unregulated Contaminant EPA requests comment and/or Monitoring Rule In this document EPA is announcing USGS—U.S. Geological Survey information. EPA will accept written or the results of the third Six-Year Review UV—Ultraviolet electronic comments (please do not (Six-Year Review 3). Consistent with the WBDOSS—Waterborne Disease Outbreak send both). Instructions for submitting process applied in the Six-Year Review Surveillance System comments can be found in the 2, EPA is requesting comments on this WHO—World Health Organization ADDRESSES section of this document. document and will consider the public Table of Contents EPA prefers electronic comments. No comments and/or any new, relevant facsimiles (faxes) will be accepted. data submitted for the eight NPDWRs I. General Information Commenters who want EPA to listed as candidates for revision as the A. Does this action apply to me? acknowledge receipt of their written Agency proceeds with determining B. What should I consider as I prepare my comments should also send a self- comments for EPA? whether revisions of these regulations II. Statutory Requirements for the Six-Year addressed, stamped envelope. are necessary. The announcement Review You may find the following whether or not the Agency intends to III. Stakeholder Involvement in the Six-Year suggestions helpful when preparing revise an NPDWR (pursuant to SDWA Review Process your comments: § 1412(b)(9)) is not a regulatory IV. Regulations Included in the Six-Year • Explain your views as clearly as decision. Instead, it initiates a process Review 3 possible. that will involve more detailed analyses V. EPA’s Protocol for Reviewing the NPDWRs • Describe any assumptions that you of health effects, analytical and Included in This Action used. treatment feasibility, occurrence, A. What was EPA’s review process? • B. How did EPA conduct the review of the Provide any technical information benefits, costs and other regulatory NPDWRs? and/or data you used that support your matters relevant to deciding whether a 1. Initial Review views. rulemaking to revise an NPDWR should 2. Health Effects • If you estimate potential burden or be initiated. The Six-Year Review 3. Analytical Feasibility costs, explain how you arrived at your results do not obligate the Agency to 4. Occurrence and Exposure Analysis estimate. revise an NPDWR in the event that EPA 5. Treatment Feasibility • Provide specific examples to determines during the regulatory 6. Risk-Balancing illustrate your concerns. process that revisions are no longer 7. Other Regulatory Revisions • C. How did EPA factor children’s health Offer alternatives. appropriate and discontinues further concerns into the review? • Make sure to submit your efforts to revise the NPDWR. Similarly, D. How did EPA factor environmental comments by the comment period the fact that an NPDWR has not been justice concerns into the review? deadline. selected for revision means only that VI. Results of EPA’s Review of NPDWRs To ensure proper receipt by EPA, EPA believes that regulatory changes to A. What are the review result categories? identify the appropriate docket a particular NPDWR are not appropriate 1. The NPDWR is Not Appropriate for identification number in the subject line at this time for the reasons given in this Revision at This Time on the first page of your response. It action; future reviews may identify 2. The NPDWR is a Candidate for Revision information that leads to an initiation of B. What are the detailed results of EPA’s would also be helpful if you provide the third six-year review cycle? name, date, and volume/page numbers the revision process. 1. Chemical Phase Rules/Radionuclides of the Federal Register document you The reasons that EPA has identified Rules are commenting on. an NPDWR as a ‘‘candidate for revision’’

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is that, at a minimum, the revision Periodic Retrospective Review of Existing dioxide), the values reported in the table presents a meaningful opportunity to: Regulations’’ (USEPA, 2011). EPA agreed to are not MCLGs and MCLs, but • Improve the level of public health ‘‘assess and analyze new data/information maximum residual disinfectant level protection, and/or regarding occurrence, treatment, analytical goals (MRDLGs) and maximum residual • Achieve cost savings while methods, health effects, and risk from all relevant waterborne pathogens to evaluate disinfectant levels (MRDLs). maintaining or improving the level of whether there are new or additional ways to Table IV–1 also includes NPDWRs public health protection. manage risk while assuring equivalent or that EPA identified as candidates for III. Stakeholder Involvement in the Six- improved protection, including with respect revision in past Six-Year Reviews. Year Review Process to the covering of finished water reservoirs’’ During the Six-Year Review 1, EPA (USEPA, 2011). EPA hosted three public identified the Total Coliform Rule (TCR) The Agency has involved interested meetings in Washington, DC, on December 7, as a candidate for revision.4 EPA stakeholders in the Six-Year Review 3 2011, April 24, 2012 and November 15, 2012. published the Revised Total Coliform process. Below are examples of such EPA presented information about: The LT2 Rule (RTCR) in 2013 (78 FR 10270, involvement: requirements, monitoring data collected under the LT2, analytical methods, forecasts USEPA, 2013a). Four additional • In November 2014, EPA briefed the about the second round of monitoring and NPDWRs for acrylamide, National Drinking Water Advisory Council the treatment technique requirements. In epichlorohydrin, tetrachloroethylene (NDWAC) on the Six-Year Review protocol addition to presentations to educate the (PCE) and trichloroethylene (TCE) were and the key elements of that protocol as they public, the meetings included public identified as candidates for revision relate to the microbial and disinfection statements, panel discussions, question and during the Six-Year Review 2. Of the 88 byproducts (MDBP) rules. The briefing answer sessions and requests by EPA to included information on how EPA is NPDWRs, EPA identified 12 as part of provide data and information about the recently completed, ongoing or pending implementing NDWAC’s previous implementation of the LT2 to inform the recommendations (NDWAC, 2000) on the regulatory review. regulatory actions; as a result, these 12 Six-Year Review process in review of the are not subject to a detailed review for MDBP rules; IV. Regulations Included in the Six- the Six-Year Review 3. This action • In January 2015, states provided input Year Review 3 involves the remaining 76 NPDWRs. (through the Association of State Drinking Table IV–1 lists all 88 NPDWRs EPA applied the same protocol used for Water Administrators (ASDWA)) on rule previous Six-Year Reviews, with minor implementation issues related to the established to date. The table also NPDWRs being reviewed as part of the Six- reports the maximum contaminant level clarifications (USEPA, 2016f), to the Year Review 3 (ASDWA, 2016); goal (MCLG) and the maximum Six-Year Review 3 process. Section V of • EPA initiated a series of public contaminant level (MCL). The MCLG is this action describes the revised stakeholder meetings about the review of the ‘‘set at the level at which no known or protocol used for the Six-Year Review 3 Long Term 2 Enhanced Surface Water anticipated adverse effects on the health and Section VI describes the results of Treatment Rule (LT2). These meetings were of persons occur and which allows an the review of the NPDWRs. held in accordance with the recommendation adequate margin of safety’’ (SDWA In addition to the regulated of the MDBP Federal Advisory Committee (FAC) 1 to have public meetings following the § 1412(b)(4)). The MCL is the maximum chemicals, radiological and first round of monitoring under the LT2, and permissible level of a contaminant in microbiological contaminants included as a result of the Executive Order (E.O.) water delivered to any user of a public in the previous reviews, this document 13563 ‘‘Improving Regulation and Regulatory water system (PWS) and generally ‘‘is as also includes the review of the MDBP Review.’’ 2 E.O. 13563 states that regulations close to the maximum contaminant regulations that were promulgated shall be based ‘‘on the open exchange of level goal as is feasible’’ (SDWA under the following actions: The information and perspectives among state, § 1412(b)(4)(B)).3 Where it is not Ground Water Rule (GWR); the Surface local, and tribal officials, experts in relevant ‘‘economically or technically feasible’’ Water Treatment Rules (SWTRs); the disciplines, affected stakeholders in the to set an MCL, EPA can establish a Disinfectants and Disinfection private sector, and the public as a whole.’’ Some affected stakeholders recommended treatment technique (TT), which must Byproducts (D/DBP) Rules; and the that EPA include the LT2 among the prevent adverse health effects ‘‘to the Filter Backwash Recycling Rule (FBRR). Agency’s top priorities for review under E.O. extent feasible’’ (SDWA § 1412(b)(7)(A)). EPA reviewed the LT2 in response to 13563. EPA included the LT2 in its In the case of disinfectants (e.g., EO 13563 (USEPA, 2011) and as part of ‘‘Improving our Regulations: Final Plan for chlorine, chloramines and chlorine the Six-Year Review 3 process.

TABLE IV–1—NPDWRS INCLUDED IN SIX-YEAR REVIEW 3

Contaminants/parameters MCLG MCL or TT Contaminants/parameters MCLG MCL or TT (mg/L) 13 (mg/L) 123 (mg/L) 13 (mg/L) 23

Acrylamide ...... 0 ...... TT ...... Ethylbenzene ...... 0.7 ...... 0.7 Alachlor ...... 0 ...... 0.002 ...... Ethylene dibromide (EDB) 0 ...... 0.00005 Alpha/photon emitters ...... 0 (pCi/L) ...... 15 (pCi/L) ...... Fluoride ...... 4.0 ...... 4.0 Antimony ...... 0.006 ...... 0.006 ...... Giardia lamblia 4 ...... 0 ...... TT Arsenic ...... 0 ...... 0.010 ...... Glyphosate ...... 0.7 ...... 0.7

1 https://www.epa.gov/sites/production/files/ regulatory priorities.’’ https://www.gpo.gov/fdsys/ when issuing new or revised standards for these 2015-11/documents/stage_2_m-dbp_agreement_in_ pkg/FR-2011-01-21/pdf/2011-1385.pdf. contaminants/parameters, EPA has often grouped principle.pdf. 3 Under limited circumstances, SDWA the standards together in more general regulations, 2 E.O. 13563 requires federal agencies to § 1412(b)(6)(A) also gives the Administrator the such as the Total Coliform Rule, the Surface Water ‘‘consider how best to promote retrospective discretion to promulgate an MCL that is less Treatment Rule or the Phase V rules. In this action, analysis of rules that may be outmoded, ineffective, stringent than the feasible level and that however, for clarity, EPA discusses the drinking insufficient, or excessively burdensome, and to modify, streamline, expand, or repeal them in ‘‘maximizes health risk reduction benefits at a cost water standards as they apply to each specific accordance with what has been learned.’’ The order that is justified by the benefits.’’ regulated contaminant/parameter (or group of required each federal agency to develop a plan 4 The NPDWRs apply to specific contaminants/ contaminants), not the more general regulation in ‘‘consistent with law and its resources and parameters or groups of contaminants. Historically, which the contaminant/parameter was regulated.

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TABLE IV–1—NPDWRS INCLUDED IN SIX-YEAR REVIEW 3—Continued

MCL or TT Contaminants/parameters MCLG MCL or TT Contaminants/parameters MCLG (mg/L) 13 (mg/L) 123 (mg/L) 13 (mg/L) 23

Asbestos ...... 7 (million fibers/L) ...... 7 (million fibers/L) ...... Haloacetic acids (HAA5) ... n/a 5 ...... 0.060 Atrazine ...... 0.003 ...... 0.003 ...... Heptachlor ...... 0 ...... 0.0004 Barium ...... 2 ...... 2 ...... Heptachlor epoxide ...... 0 ...... 0.0002 Benzene ...... 0 ...... 0.005 ...... Heterotrophic bacteria 6 ..... n/a ...... TT Benzo[a]pyrene ...... 0 ...... 0.0002 ...... Hexachlorobenzene ...... 0 ...... 0.001 Beryllium ...... 0.004 ...... 0.004 ...... Hexachlorocyclopentadiene 0.05 ...... 0.05 Beta/photon emitters ...... 0 (millirems/yr) ...... 4 (millirems/yr) ...... Lead ...... 0 ...... TT Bromate ...... 0 ...... 0.010 ...... Legionella ...... 0 ...... TT Cadmium ...... 0.005 ...... 0.005 ...... Lindane ...... 0.0002 ...... 0.0002 Carbofuran ...... 0.04 ...... 0.04 ...... Mercury (inorganic) ...... 0.002 ...... 0.002 Carbon tetrachloride ...... 0 ...... 0.005 ...... Methoxychlor ...... 0.04 ...... 0.04 Chloramines ...... 4 ...... 4.0 ...... Monochlorobenzene (Chlo- 0.1 ...... 0.1 robenzene). Chlordane ...... 0 ...... 0.002 ...... Nitrate (as N) ...... 10 ...... 10 Chlorine ...... 4 ...... 4.0 ...... Nitrite (as N) ...... 1 ...... 1 Chlorine dioxide ...... 0.8 ...... 0.8 ...... Oxamyl (Vydate) ...... 0.2 ...... 0.2 Chlorite ...... 0.8 ...... 1.0 ...... Pentachlorophenol ...... 0 ...... 0.001 Chromium (total) ...... 0.1 ...... 0.1 ...... Picloram ...... 0.5 ...... 0.5 Copper ...... 1.3 ...... TT ...... Polychlorinated biphenyls 0 ...... 0.0005 (PCBs). Cryptosporidium ...... 0 ...... TT ...... Radium ...... 0 (pCi/L) ...... 5 (pCi/L) Cyanide ...... 0.2 ...... 0.2 ...... Selenium ...... 0.05 ...... 0.05 2,4-Dichlorophenoxyacetic 0.07 ...... 0.07 ...... Simazine ...... 0.004 ...... 0.004 acid (2,4-D). Dalapon ...... 0.2 ...... 0.2 ...... Styrene ...... 0.1 ...... 0.1 Di(2-ethylhexyl)adipate 0.4 ...... 0.4 ...... 2,3,7,8-TCDD (Dioxin) ...... 0 ...... 3.00E–08 (DEHA). Di(2-ethylhexyl)phthalate 0 ...... 0.006 ...... Tetrachloroethylene ...... 0 ...... 0.005 (DEHP). 1,2-Dibromo-3- 0 ...... 0.0002 ...... Thallium ...... 0.0005 ...... 0.002 chloropropane (DBCP). 1,2-Dichlorobenzene (o- 0.6 ...... 0.6 ...... Toluene ...... 1 ...... 1 Dichlorobenzene). 1,4-Dichlorobenzene (p- 0.075 ...... 0.075 ...... Total coliforms (under n/a ...... TT Dichlorobenzene). ADWR 7 and RTCR 8). 1,2-Dichloroethane (Ethyl- 0 ...... 0.005 ...... Total Trihalomethanes n/a 9 ...... 0.080 ene dichloride). (TTHM). 1,1-Dichloroethylene ...... 0.007 ...... 0.007 ...... Toxaphene ...... 0 ...... 0.003 cis-1,2-Dichloroethylene .... 0.07 ...... 0.07 ...... 2,4,5-TP (Silvex) ...... 0.05 ...... 0.05 trans-1,2-Dichloroethylene 0.1 ...... 0.1 ...... 1,2,4-Trichlorobenzene ...... 0.07 ...... 0.07 Dichloromethane (Meth- 0 ...... 0.005 ...... 1,1,1-Trichloroethane ...... 0.20 ...... 0.2 ylene chloride). 1,2-Dichloropropane ...... 0 ...... 0.005 ...... 1,1,2-Trichloroethane ...... 0.003 ...... 0.005 Dinoseb ...... 0.007 ...... 0.007 ...... Trichloroethylene ...... 0 ...... 0.005 Diquat ...... 0.02 ...... 0.02 ...... Turbidity 6 ...... n/a ...... TT E. coli ...... 0 ...... MCL 10 and TT 8 ...... Uranium ...... 0 ...... 0.030 Endothall ...... 0.1 ...... 0.1 ...... Vinyl Chloride ...... 0 ...... 0.002 Endrin ...... 0.002 ...... 0.002 ...... Viruses ...... 0 ...... TT Epichlorohydrin ...... 0 ...... TT ...... Xylenes (total) ...... 10 ...... 10 1. MCLG: The maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, allowing an adequate margin of safety. 2. MCL: The maximum level allowed of a contaminant in water which is delivered to any user of a public water system. TT: An enforceable procedure or level of technological performance which public water systems must follow to ensure control of a contaminant. 3. Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million. For chlorine, chloramines and chlorine dioxide, values presented are MRDLG and MRDL. 4. The current preferred taxonomic name is Giardia duodenalis, with Giardia lamblia and Giardia intestinalis as synonymous names. However, Giardia lamblia was the name used to establish the MCLG in 1989. Elsewhere in this document, this pathogen will be referred to as Giardia spp. or simply Giardia unless discussing information on an individual species. 5. 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. 6. Includes indicators that are used in lieu of direct measurements (e.g., of heterotrophic bacteria, turbidity). 7. The Aircraft Drinking Water Rule (ADWR) 40 CFR part 141 Subpart X, promulgated October 19, 2009, covers total coliforms. 8. Under the RTCR, a PWS is required to conduct an assessment if it exceeded any of the TT triggers identified in 40 CFR 141.859(a). It is also required to correct any sanitary defects found through the assessment. 9. There is no MCLG for total trihalomethanes (TTHM). MCLGs for some of the individual contaminants are: Bromodichloromethane (zero), bromoform (zero), dibromochloromethane (0.06 mg/L), and chloroform (0.07 mg/L). 10. A PWS is in compliance with the E. coli MCL unless any of the conditions identified under 40 CFR 141.63(c) occur.

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V. EPA’s Protocol for Reviewing the present negligible gains in public health these NPDWRs are not subject to the NPDWRs Included in This Action protection; (2) possible changes present detailed review in this document. limited opportunity for cost savings • The Agency does not believe it is A. What was EPA’s review process? while maintaining the same or greater appropriate to consider revisions to Overview level of health protection; and (3) NPDWRs for contaminants with an This section provides an overview of possible changes are a low priority ongoing or planned health effect the process the Agency used to review because of competing workload assessment and for which the MCL is set the NPDWRs discussed in this action. priorities, limited return on the equal to the MCLG or based on benefit- The protocol document, ‘‘EPA Protocol administrative costs associated with cost analysis. This principle stems from for the Third Review of Existing rulemaking and the burden on states the fact that any new health effects National Primary Drinking Water and the regulated community associated information could affect the MCL via a Regulations,’’ contains a detailed with implementing any regulatory change in the MCLG or the assessment description of the process the Agency change that would result. of the benefits associated with the MCL. used to review the NPDWRs (USEPA, Alternatively, the reasons for a Six- Therefore, EPA noted that these 2016f). The foundation of this protocol Year Review outcome that an NPDWR is NPDWRs are not appropriate for was developed for the Six-Year Review a ‘‘candidate for revision’’ are that, at a revision and no action is necessary at 1 based on the recommendations of the minimum, the revision presents a this time if the health effects assessment NDWAC (2000). The Six-Year Review 3 meaningful opportunity to: would not be completed during the • process is very similar to the process Improve the level of public health review period for each contaminant that implemented during the Six-Year protection, and/or has either an MCL that is equal to its • Review 1 and the Six-Year Review 2, Achieve cost savings while MCLG or an MCL that is based on the with some clarifications to the elements maintaining or improving the level of 1996 SDWA Amendments’ cost-benefit related to the review of NPDWRs public health protection. provision. If the health effects included in the MDBP rules. Figure V– Individual regulatory provisions of assessment is completed before the next 1 presents an overview of the Six-Year NPDWRs that are evaluated as part of Six-Year Review, EPA will consider the Six-Year Review are: MCLG, MCL, these NPDWRs at that time. review protocol and review outcomes. • The primary goal of the Six-Year MRDLG, MRDL, TT, other treatment In evaluating the potential for new Review process is to identify and technologies such as best available information to affect NPDWRs, EPA prioritize NPDWRs for possible technology (BAT), and regulatory assumed no change to existing policies regulatory revision. The two major requirements, such as monitoring and procedures for developing outcomes of the detailed review are requirements. NPDWRs. For example, in determining either: For example, the microbial whether new information affected the 1. The NPDWR is not appropriate for regulations include TT requirements feasibility of analytical methods for a revision and no action is necessary at because there is no reliable method that contaminant, the Agency assumed no this time. is economically and technically feasible change to current policies and 2. The NPDWR is a candidate for to measure the microbial contaminants procedures for calculating practical revision. covered by those regulations. These TT quantitation levels. The reasons for a Six-Year Review requirements rely on the use of • EPA considered new information outcome of ‘‘not appropriate for revision indicators that can be measured in from health effects assessments that at this time’’ can include: drinking water, such as the were completed by the information • Regulatory action—recently concentration of a disinfectant, to cutoff date. Assessments completed completed, ongoing or pending. The provide public health protection. As after this cutoff date will be reviewed by NPDWR was recently completed, is part of the Six-Year Review 3, EPA EPA during the next review cycle or (if being reviewed in an ongoing action, or evaluated new information related to applicable) during the revision of an is subject to a pending action. the use of those indicators to determine NPDWR. The information cutoff date for • Ongoing or planned health effects if there is a meaningful opportunity to the Six-Year Review 3 was December assessment. The NPDWR has an improve the level of public health 2015. ongoing health effects assessment (i.e., protection. Results of EPA’s review of • During the review, EPA identified especially for those NPDWRs with an the MDBP regulations are presented in areas where information is inadequate MCL set at the MCLG or where the MCL Sections VI.B.3 and VI.B.4. or unavailable (data gaps) or emerging is based on the SDWA cost benefit For the purpose of this document and is needed to determine whether provision), or EPA is considering (except where noted for clarity), revision to an NPDWR is appropriate. whether a new health effects assessment discussions of the review of MCLGs and To the extent EPA is able to fill data is needed. MCLs should be assumed to also apply gaps or fully evaluate the emerging • No new information. EPA did not to the review of MRDLGs and MRDLs information, the Agency will consider identify any new, relevant information for disinfectants. the information as part of the next that indicates changes to the NPDWR. review cycle. Basic Principles • Data gaps/emerging information. • EPA may consider accelerating There are data gaps or emerging EPA applied a number of basic review and potential revision for a information that need to be evaluated. principles to the Six-Year Review particular NPDWR before the next • Low priority and/or no meaningful process: review cycle when justified by new opportunity. New information indicates • The Agency sought to avoid public health risk information. a possible change to the MCLG and/or redundant review efforts. Because EPA • Finally, EPA assured scientific MCL but changes to the NPDWR are not has reviewed information for certain analyses supporting the review were warranted due to one or more of the NPDWRs as part of recently completed, consistent with the Agency’s peer following reasons: (1) Possible changes ongoing or pending regulatory actions, review policy (USEPA, 2015a).

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B. How did EPA conduct the review of Review (cutoff date was August 2008). toxicity data, that could potentially the NPDWRs? In addition, the initial review also affect the MCLG, or otherwise change The protocol for the Six-Year Review identified contaminants with ongoing the Agency’s understanding of the 3 is broken down into a series of health effects assessments that have an health effects of contaminants under questions that can inform a decision MCL equal to the MCLG. Excluding consideration. EPA then evaluated the about the appropriateness of revising an such contaminants from the Six-Year need to plan the initiation of a new NPDWR. These questions are logically Review 3 prevents duplicative agency health effects assessment. efforts. ordered into a decision tree. This 3. Analytical Feasibility section provides an overview of each of 2. Health Effects the review elements that EPA When establishing an NPDWR, EPA considered for each NPDWR during the The principal objectives of the health identifies a practical quantitation limit Six-Year Review 3, including the effects review are to identify: (1) (PQL), which is ‘‘the lowest achievable following: Initial review, health effects, Contaminants for which a new health level of analytical quantitation during analytical feasibility, occurrence and effects assessment indicates that a routine laboratory operating conditions exposure, treatment feasibility, risk change in the MCLG might be within specified limits of precision and balancing and other regulatory appropriate (e.g., because of a change in accuracy’’, as noted in the November 13, revisions. The final review combines the cancer classification or a change in 1985, Federal Register proposed rule findings from all of these review reference dose (RfD)), and (2) (50 FR 46880, USEPA, 1985). EPA has elements to recommend whether an contaminants for which new health a separate process in place to approve NPDWR is a candidate for revision. effects information indicates a need to new analytical methods for drinking Further information about the review initiate a new health effects assessment. water contaminants; therefore, review elements is described in the protocol To meet the first objective, EPA and approval of potential new methods document (USEPA, 2016f). Results from reviewed the results of health effects is outside the scope of the Six-Year the review of these elements are assessments completed before December Review protocol. EPA recognizes, presented in Section VI. 2015, the information cutoff date for the however, that the approval and Six-Year Review 3. adoption in recent years of new and/or 1. Initial Review To meet the second objective, the improved analytical methods may EPA’s initial review of all the Agency conducted an extensive enable laboratories to quantify contaminants included in the Six-Year literature review to identify peer- contaminants at lower levels than was Review 3 involved a simple reviewed studies published before possible when NPDWRs were originally identification of the NPDWRs that have December 2015. The Agency reviewed promulgated. This ability of laboratories either been recently completed, or are the studies to determine whether there to measure a contaminant at lower being reviewed in an ongoing or was new health effects information, levels could affect its PQL, the value at pending action since the last Six-Year such as reproductive and developmental which an MCL is set when it is limited

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by analytical feasibility. Therefore, the USEPA, 2010a). EPA requested that all provide an opportunity to revise the TT Six-Year Review process includes an states and primacy entities (tribes and requirement. examination of whether there have been territories) voluntarily submit their 6. Risk-Balancing changes in analytical feasibility that compliance monitoring data for could possibly change the PQL for the regulated contaminants in public EPA reviews risk-balancing to subset of the NPDWRs that reached this drinking water systems. Specifically, examine how the Six-Year Review can stage of the review. EPA requested the submission of address tradeoffs in risks among To determine if changes in analytical compliance monitoring data and related different NPDWRs and take into account feasibility could possibly support information collected between January unregulated contaminants as well. changes to PQLs, EPA relied primarily 2006 and December 2011 for regulated Under this review, EPA considers on two alternate approaches to develop contaminants and related parameters whether a change to an MCL and/or TT an estimated quantitation limit (EQL): (e.g., water quality indicators). Forty-six will increase the public health risk an approach based on the minimum states plus eight primacy agencies posed by one or more contaminants, reporting levels (MRLs) obtained as part provided data. The assembled data and, if so, the Agency considers of the Six-Year Review 3 Information constitute the largest, most revisions that will balance overall risks. Collection Request (ICR), and an comprehensive set of drinking water This review element is relevant only to approach based on method detection compliance monitoring data ever the NPDWRs included in the MDBP limits (MDLs). compiled and analyzed by EPA to rules, which were promulgated to An MRL is the lowest level or inform decision making, containing address risk-balancing between contaminant concentration that a almost 47 million records from microbial and DBP requirements, and laboratory can reliably achieve within approximately 167,000 PWSs, serving among differing types of DBPs. The risk- specified limits of precision and approximately 290 million people balancing approach was based on the accuracy under routine laboratory nationally. Through extensive data SDWA requirements that EPA operating conditions using a given management efforts, quality assurance ‘‘minimize the overall risk of adverse method. The MRL values provide direct evaluations, and communications with health effects by balancing the risk from evidence from actual monitoring results state data management staff, EPA the contaminant and the risk from other about whether quantitation below the established the SYR3 ICR database contaminants the concentrations of PQL using current analytical methods is (USEPA, 2016i). The number of states which may be affected by the use of a feasible. An MDL is a measure of and PWSs represented in the dataset TT or process that would be employed analytical method sensitivity. MDLs varies across contaminants because of to attain the maximum contaminant have been used in the past to derive variability in state data submissions and level or levels’’ (SDWA PQLs for regulated contaminants. contaminant monitoring schedules. § 1412(b)(5)(B)(i)). EPA used the EQL as a threshold for Except as noted in Section VI, EPA EPA reviewed risk-balancing between occurrence analysis to help the Agency believes that these data are of sufficient microbial and DBP contaminants. For determine if there may be a meaningful quality to inform an understanding of example, EPA considered the potential opportunity to improve public health the national occurrence of regulated impact on DBP concentrations should protection. It should be noted, however, contaminants and related parameters. there be a consideration to increase the that the use of an EQL does not Details of the data management and data stringency of microbial NPDWRs. This necessarily indicate the Agency’s quality assurance evaluations are approach also was used during the intention to promulgate a new PQL. Any available in the supporting document development of more recent MDBP rules revision to PQLs will be part of future (USEPA, 2016q). The resulting database such as the LT2 rule and the Stage 2 rulemaking efforts if EPA has is available online on the Six-Year Disinfectants/Disinfection Byproducts determined that an NPDWR is a Review Web site (https://www.epa.gov/ Rule (D/DBPR) rule. In addition, EPA candidate for revision. dwsixyearreview). reviewed risk-balancing between different types of DBP contaminants. 4. Occurrence and Exposure Analysis 5. Treatment Feasibility Depending on the stringency of The occurrence and exposure analysis An NPDWR either identifies the BAT potential DBP regulations, compliance is conducted in conjunction with other for meeting an MCL, or establishes strategies used by the regulated review elements to determine if there is enforceable TT requirements. EPA community might have the effect of a meaningful opportunity to revise an reviews treatment feasibility to ascertain increasing the concentrations of other NPDWR by: if there are technologies that meet BAT types of contaminants, both regulated • Estimating the extent of criteria for a hypothetical more stringent and unregulated. EPA considered these contaminant occurrence, i.e., the MCL, or if there is new information that potential compliance strategies when number of PWSs in which contaminants demonstrates an opportunity to improve conducting its Six-Year Review 3 with occur at levels of interest (health-effects- public health protection through a goal to balance the overall health risks. revision of an NPDWR TT requirement. based thresholds or analytical method 7. Other Regulatory Revisions limits), and To be a BAT, the treatment • Evaluating the number of people technology must meet several criteria In addition to possible revisions to potentially exposed to contaminants at such as having demonstrated consistent MCLGs, MCLs and TTs, EPA evaluated these levels. removal of the target contaminant under whether other revisions are needed to To evaluate national contaminant field conditions. Although treatment regulatory provisions, such as occurrence under the Six-Year Review feasibility and analytical feasibility monitoring and system reporting 3, EPA reviewed data from the Six-Year together address the technical feasibility requirements. EPA focused this review Review 3 ICR database (SYR3 ICR requirement for an MCL, historically, element on issues that were not already database), the UCMR datasets (USEPA, treatment feasibility has not been a being addressed through alternative 2016j) and other relevant sources. limiting factor for MCLs. The result of mechanisms, such as a recently For the Six-Year Review 3, EPA this review element is a determination completed, ongoing or pending collected SDWA compliance monitoring of whether treatment feasibility would regulatory action. EPA also reviewed data through use of an ICR (75 FR 6023, pose a limitation to revising an MCL or implementation-related NPDWR

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concerns that were ‘‘ready’’ for Year Review 3, EPA completed a by directing agencies to identify and rulemaking—that is, the problem to be literature search covering address disproportionately high and resolved had been clearly identified, developmental and reproductive adverse human health or environmental along with specific options to address endpoints (e.g., fertility, embryo effects of its programs, policies and the problem that could be shown to survival, developmental delays, birth activities on minority and low-income either clearly improve the level of defects and endocrine effects) for populations. EPA evaluates potential EJ public health protection, or represent a information published as of December concerns when developing regulations. meaningful opportunity for achieving 2015 for regulated chemicals that had This Six-Year Review was developed in cost savings while maintaining the same not been the subject of a health effects compliance with E.O. 12898. Should the level of public health protection. The assessment during this review period. Six-Year Review lead to a decision to result of this review element is a EPA reviewed the results of the revise an NPDWR, any subsequent determination regarding whether EPA literature searches to identify any should consider revisions to the studies that might suggest a need to rulemakings will include an EJ monitoring and/or reporting revise MCLGs. These studies were component and an opportunity for requirements of an NPDWR. considered in EPA’s review of NPDWRs, public comment. which is discussed in Section VI. C. How did EPA factor children’s health VI. Results of EPA’s Review of NPDWRs concerns into the review? D. How did EPA factor environmental Table VI–1 lists the results of EPA’s justice concerns into the review? The 1996 amendments to SDWA review for each of the 76 NPDWRs require special consideration of Executive Order (E.O.) 12898, discussed in this section of this action, sensitive life stages and populations ‘‘Federal Actions to Address along with the principal rationale for (e.g., infants, children, pregnant women, Environmental Justice in Minority the review outcomes. Table VI–1 also elderly and individuals with a history of Populations or Low-Income includes a list of the 12 NPDWRs that serious illness) in the development of Populations,’’ establishes a federal have been recently completed, or have drinking water regulations (SDWA policy for incorporating environmental ongoing or pending regulatory actions. § 1412(b)(3)(C)(V)). As a part of the Six- justice (EJ) into federal agency missions

TABLE VI–1—SUMMARY OF SIX-YEAR REVIEW 3 RESULTS

Not Appropriate for Re- Recently completed, 1,2-Dichloroethane (Ethylene dichloride) ...... E. coli. vision at this Time. ongoing or pending 1,2-Dichloropropane ...... Lead. regulatory action. Benzene ...... Tetrachloroethylene (PCE). Carbon Tetrachloride ...... Total coliforms (under ADWR and RTCR). Copper Trichloroethylene (TCE) Dichloromethane (Methylene chloride) ...... Vinyl chloride. Not Appropriate for Re- Health effects assess- Alpha/photon emitters ...... Mercury 1 vision at this Time 2. ment in process (as Arsenic ...... Nitrate 1 of December 2015) Atrazine ...... Nitrite 1 or contaminant nom- Benzo(a)pyrene (PAHs) ...... o-Dichlorobenzene 1 inated for health as- Beta/photon emitters ...... p-Dichlorobenzene 1 sessment. Cadmium 1 ...... Polychlorinated biphenyls (PCBs). Chromium ...... Radium. Di(2-ethylhexyl) phthalate (DEHP) 1 ...... Simazine. Ethylbenzene ...... Uranium 1 Glyphosate No new information, 1,2-Dibromo-3-chloropropane (DBCP) ...... Dalapon. NPDWR remains 2,4,5-TP (Silvex) ...... Di(2-ethylhexyl)adipate (DEHA). appropriate after re- Antimony ...... Dinoseb. view. Asbestos ...... Endrin. Bromate ...... Ethylene dibromide. Chloramines (under D/DBPR) ...... Pentachlorophenol. Chlorine (under D/DBPR) ...... Thallium. Chlorine dioxide ...... trans-1,2-Dichloroethylene. Chlorobenzene (monochlorobenzene) ...... Turbidity. Low priority and/or no 1,1,1-Trichloroethane ...... Epichlorohydrin. meaningful oppor- 1,1,2-Trichloroethane ...... Fluoride. tunity. 1,1-Dichloroethylene ...... Heptachlor. 1,2,4-Trichlorobenzene ...... Heptachlor epoxide. 2,3,7,8-TCDD (Dioxin) ...... Hexachlorobenzene. 2,4-D ...... Hexachlorocyclopentadiene. Acrylamide ...... Lindane. Alachlor ...... Methoxychlor. Barium Oxamyl (Vydate). Beryllium ...... Picloram. Carbofuran ...... Selenium. Chlordane ...... Styrene. cis-1,2-Dichloroethylene ...... Toluene. Cyanide ...... Toxaphene. Diquat ...... Xylenes. Endothall

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TABLE VI–1—SUMMARY OF SIX-YEAR REVIEW 3 RESULTS—Continued Candidate for Revision New information ...... Chlorite ...... Heterotrophic Bacteria. Cryptosporidium (under SWTR, IESWTR, LT1) Legionella. Giardia lamblia ...... TTHM. Haloacetic Acids (HAA5) ...... Viruses (under SWTR). 1 Contaminants nominated for Integrated Risk Information System (IRIS) assessments per SYR Protocol. 2 LT2, FBRR, and GWR also identified as not appropriate for revision at this time. See Section VI.B.4 for additional information on the results of EPA’s review of these regulations.

A. What are the review result categories? new information to suggest possible available today for water treatment have For each of the 76 NPDWRs discussed changes in MCLG/MCL; new lower residual monomer content than in detail in the following sections of this information did not present a when EPA promulgated residual content action, the review outcomes fall in one meaningful opportunity for health risk as a TT (USEPA, 2016s). For example, of the following categories: reduction or cost savings while the 90th percentile concentration of maintaining/improving public health acrylamide residual monomer levels 1. The NPDWR is Not Appropriate for protection; or there was an ongoing or was approximately one-half the residual Revision at This Time pending regulatory action. Details level listed in the current TT and no The current NPDWR remains related to the review of all Phase Rules residual epichlorohydrin was detected. appropriate and no action is necessary and Radionuclide Rules contaminants The health benefits associated with the at this time. In this category, NPDWRs can be found in the ‘‘Chemical lower impurity levels are already being are grouped under the following Contaminant Summaries for the Third realized by communities throughout the subcategories: Six-Year Review of National Primary country; therefore, a regulatory revision • Health effects assessment in process Drinking Water Regulations’’ (USEPA, will minimally affect health risk. Given (as of December 2015) or contaminant 2016b). resource limitations, competing nominated for health assessment, Initial Review workload priorities, and administrative • No new information and NPDWR costs and burden to states to adopt any remains appropriate after review, The initial review identified 12 regulatory changes associated with the • Data gaps/emerging information, chemical contaminants with NPDWRs rulemaking, as well as limited potential and under the Chemical Phase Rules that health benefits, these NPDWRs are • No meaningful opportunity. were being considered as part of considered a low priority and no longer ongoing or pending regulatory actions, candidates for revision at this time. 2. The NPDWR Is a Candidate for and 61 chemical or radionuclide EPA is also currently considering Revision NPDWRs were identified as appropriate Long-Term Revisions to the Lead and for review. The NPDWRs with ongoing The NPDWR is a candidate for Copper Rule; and therefore, evaluation or pending regulatory actions included revision based on the review of new of that NPDWR under the Six-Year eight carcinogenic volatile organic information. Review process would be redundant. compounds (cVOCs), lead, copper, B. What are the detailed results of EPA’s acrylamide and epichlorohydrin. Health Effects third six-year review cycle? In 2011, EPA announced its plans to address a group of regulated and The principal objectives of the health 1. Chemical Phase Rules/Radionuclides effects review are to identify: (1) Rules unregulated cVOCs in a single regulatory effort. The eight regulated Contaminants for which a new health Background VOCs being currently evaluated for a effects assessment indicates that a The NPDWRs for chemical potential cVOCs group regulation change in MCLG might be appropriate contaminants, collectively called the include: Benzene; carbon tetrachloride; (e.g., because of a change in cancer Phase Rules, were promulgated between 1,2-dichloroethane; 1,2- classification or an RfD), and (2) 1987 and 1992 (after the 1986 SDWA dichloropropane; dichloromethane; contaminants for which the Agency has amendments). In December 2000, EPA PCE; TCE; and vinyl chloride. The identified new health effects promulgated final radionuclide regulatory revisions to TCE and PCE, information suggesting a need to initiate regulations, which were issued as initiated as an outcome of the Six-Year a new health effects assessment. interim rules in July 1976. Information Review 2, are also being considered as Before identifying chemical NPDWR related to the review for fluoride is part of the group regulatory effort. Since contaminants for which an updated discussed separately in Section VI.B.2. a regulatory effort is ongoing for these MCLG may be appropriate, EPA first eight contaminants, they were excluded identified chemicals with ongoing or Summary of Review Results from a detailed review as part of the planned EPA health effects assessments. EPA has decided that it is not third Six-Year Review. As of December 31, 2015, 19 chemical/ appropriate at this time to revise any of The NPDWRs for acrylamide and radiological contaminants reviewed had the NPDWRs covered under the Phase epichlorohydrin were also previously ongoing or planned formal EPA health Rules or Radionuclide Rules. These identified as candidates for regulatory effects assessments. Table VI–2 below NPDWRs were determined not to be revision and were pending regulatory lists the 19 contaminants with ongoing candidates for revision for one or more action. The polyacrylamides and or planned EPA assessments and the of the following reasons: There was no epichlorohydrin-based polymers status of those reviews.

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TABLE VI–2—SIX-YEAR REVIEW CHEMICAL/RADIOLOGICAL CONTAMINANTS WITH ONGOING OR PLANNED EPA HEALTH ASSESSMENTS

Chemical/radionuclide Status

Alpha/photon emitters ...... EPA is conducting a review of alpha and beta photo emitters. Arsenic, inorganic ...... Inorganic arsenic is being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). Atrazine ...... Atrazine and simazine are being assessed under EPA’s pesticide registration review process. Benzo(a)pyrene ...... Benzo(a)pyrene is being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). Beta/photon emitters ...... EPA is conducting a review of alpha and beta photo emitters. Cadmium ...... Cadmium is included in the EPA IRIS Multi-Year Agenda. Chromium (VI) as part of total Cr) ...... Chromium VI is being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). DEHP ...... DEHP is included in the EPA IRIS Multi-Year Agenda. Ethylbenzene ...... Ethylbenzene is being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). Glyphosate ...... GlyphosateGlyphosate is being assessed under EPA’s pesticide registration review process. Mercury ...... Mercury is included in the EPA IRIS Multi-Year Agenda. Nitrate ...... Nitrate is included in the EPA IRIS Multi-Year Agenda. Nitrite ...... Nitrite is included in the EPA IRIS Multi-Year Agenda. o-Dichlorobenzene ...... o-Dichlorobenzene is included in the EPA IRIS Multi-Year Agenda. p-Dichlorobenzene ...... p-Dichlorobenzene is included in the EPA IRIS Multi-Year Agenda. PCBs ...... PCBs are being assessed by the EPA IRIS Program. The assessment status can be found at: (https://cfpub.epa.gov/ncea/iris2/atoz.cfm). Radium (226, 228) ...... EPA is conducting a review of radium. Simazine ...... Atrazine and simazine are being assessed under EPA’s pesticide registration review process. Uranium ...... Uranium is included in the EPA IRIS Multi-Year Agenda.

For chemicals that were not excluded changes in the RfD and/or in the cancer available new health effects information due to an ongoing or planned health risk assessment from oral exposure or and the sources of the relevant new effects assessment by EPA, or by the new relevant non-EPA assessments that information. As shown in this table, 11 National Academy of Sciences (NAS), might support a change to the MCLG. chemical contaminants have commissioned by EPA, a more detailed These 21 chemicals were further information that could support a lower review was undertaken. Of the evaluated as part of the Six-Year Review MCLG and 10 contaminants have new chemicals that underwent a more 3 to determine whether they were information that could support a higher detailed review, EPA identified 21 for candidates for regulatory revision. Table MCLG. which there have been official Agency VI–3 lists the 21 chemicals with

TABLE VI–3—CHEMICALS WITH AVAILABLE NEW HEALTH ASSESSMENT THAT COULD SUPPORT A CHANGE IN MCLG

Chemical Relevant new assessment

Potential Decrease in MCLG

Carbofuran ...... USEPA, 2008a (OPP). Cyanide ...... USEPA, 2010e (IRIS). cis-1,2-Dichloroethyelene ...... USEPA, 2010d (IRIS). Endothal ...... USEPA, 2005f (OPP). Hexachloropentadiene ...... USEPA, 2001a (IRIS). Methoxychlor ...... CalEPA 2010a. Oxamyl ...... USEPA, 2010f (OPP). Selenium ...... Health Canada 2014. Styrene ...... CalEPA 2010b. Toluene ...... USEPA, 2005c (IRIS). Xylenes ...... USEPA, 2003a (IRIS).

Potential Increase in MCLG

Alachlor ...... USEPA, 2006a (OPP). Barium ...... USEPA, 2005b (IRIS). Beryllium ...... USEPA, 1998a (IRIS). 1,1-Dichloroethylene ...... USEPA, 2002b (IRIS). 2,4 Dichlorophenoxy-acetic Acid ...... USEPA, 2013b (OPP). Diquat ...... USEPA, 2002a (OPP). Lindane ...... USEPA, 2002d (OPP). Picloram ...... USEPA, 1995 (OPP). 1,1,1-Trichloroethane ...... USEPA, 2007a (IRIS). 1,2,4-Trichlorobenzene ...... ATSDR, 2010.

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Details of the health effects review of health effects assessments indicate carcinogenic and have a non-zero MCLG the chemical and radiological potential for lower MCLGs; and and the remaining 12 contaminants are contaminants are documented in the contaminants where existing MCLs are carcinogens with MCLGs equal to zero. ‘‘Six-Year Review 3—Health Effects based on analytical feasibility. EPA evaluated whether the PQL could Assessment for Existing Chemical and • A health effects assessment be lowered for each of these Radionuclides National Primary indicates potential for lower MCLG. This contaminants. For one contaminant, Drinking Water Regulations—Summary category includes the 11 contaminants 1,1,2-trichloroethane, EPA concluded Report’’ (USEPA, 2016h). identified in the health effects review as that new information from Proficiency having information indicating the Analytical Feasibility Testing (PT) studies, along with MRL potential for a lower MCLG. EPA and MDL data, indicate the potential to EPA performed analytical feasibility reviewed analytical feasibility to revise the PQL. For two contaminants analyses for the contaminants that determine if analytical feasibility could (dioxin and PCBs), data from PT studies reached this portion of the review. limit the potential for MCL revisions. were inconclusive, but MRL and MDL These contaminants included the 11 For six contaminants (carbofuran, data indicated the potential to revise the chemical contaminants identified under cyanide, endothall, methoxychlor, PQL. For five contaminants (chlordane, the health effects review as having oxamyl and styrene), the current PQL is heptachlor, heptachlor epoxide, potential for a lower MCLG and an higher than the potential new MCLG hexachlorobenzene and toxaphene) data additional 14 contaminants with MCLs identified in the health effects review. from PT and MRL studies were based on analytical feasibility and MCLs For these contaminants, the PQL inconclusive, but MDL data indicate the higher than the current MCLGs. The assessment did not support reduction of potential to revise the PQL. For the document ‘‘Analytical Feasibility the current PQL, or data were remaining five contaminants, either EPA Support Document for the Third Six- inconclusive or insufficient to reach a did not have sufficient new information Year Review of National Primary conclusion. Consequently, analytical to evaluate analytical feasibility or EPA Drinking Water Regulations: Chemical feasibility could be a limiting factor for concluded that new information does Phase Rules and Radionuclides Rules’’ setting the MCL equal to the potential not indicate the potential for a PQL (USEPA, 2016a) describes the first step new MCLG. The current PQL is not a revision. in the process EPA used to evaluate limiting factor for the remaining five whether changes in PQL are possible in contaminants identified by the health Where these evaluations indicated the those instances where the MCL is effects review for possible changes in potential for a PQL reduction, Table VI– limited, or may be limited, by analytical their MCLG (i.e., cis-1,2- 4 lists the type of data that support this feasibility. The EQL analysis is dichloroethylene, conclusion. The notation ‘‘PT’’ indicates documented in the ’’ Development of hexachlorocyclopentadiene, selenium, that the PQL reassessment based on PT Estimated Quantitation Levels for the toluene and xylene). data (USEPA, 2016a) supports the Third Six-Year Review of National • Contaminants for which existing reduction. The notations ‘‘MRL’’ and Primary Drinking Water Regulations MCLs are based on analytical feasibility. ‘‘MDL’’ indicates that these two (Chemical Phase Rules)’’ (USEPA, This category includes 14 contaminants approaches support PQL reduction. The 2016d). with existing MCLs that are greater than findings based on PT offer more Table VI–4 shows the outcomes of their MCLGs because they are limited by certainty. When the PQL reassessment EPA’s analytical feasibility review for analytical feasibility. Two of the outcome is that the current PQL remains two general categories of drinking water contaminants (thallium and 1,1,2- appropriate, Table VI–4 shows the result contaminants: Contaminants where trichloroethanetrichloroethane) are non- ‘‘Data do not support PQL reduction.’’

TABLE VI–4—NPDWRS INCLUDED IN ANALYTICAL FEASIBILITY REASSESSMENT AND RESULT OF THAT ASSESSMENT

Current PQL Analytical feasibility reassessment Contaminant (μg/L) result

11 Contaminants Identified Under the Health Effects Review as Having Potential for Lower MCLG

Carbofuran ...... 7 Data do not support PQL reduction. Cyanide ...... 100 Data do not support PQL reduction. cis-1,2-Dichloroethylene ...... 5 PQL not limiting. Endothall ...... 90 PQL reduction supported (MRL, MDL). Hexachlorocyclopentadiene ...... 1 PQL not limiting. Methoxychlor ...... 10 PQL reduction supported (PT, MRL). Oxamyl ...... 20 PQL reduction supported (MRL, MDL). Selenium ...... 10 PQL not limiting. Styrene ...... 5 PQL reduction supported (PT, MRL, MDL). Toluene ...... 5 PQL not limiting. Xylene ...... 5 PQL not limiting.

14 Contaminants With MCLs Based on Analytical Feasibility and Higher Than MCLGs

Benzo(a)pyrene ...... 0.2 Data do not support PQL reduction. Chlordane ...... 2 PQL reduction supported (MRL, MDL). 1,2-Dibromo-3-chloropropane (DBCP) ...... 0.2 Data do not support PQL reduction. Di(2-ethylhexyl)phthalate (DEHP) ...... 6 Data do not support PQL reduction. Ethylene dibromide (EDB) ...... 0.05 Data do not support PQL reduction. Heptachlor ...... 0.4 PQL reduction supported (MDL). Heptachlor Epoxide ...... 0.2 PQL reduction supported (MDL). Hexachlorobenzene ...... 1 PQL reduction supported (PT, MDL). Pentachlorophenol ...... 1 Data do not support PQL reduction.

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TABLE VI–4—NPDWRS INCLUDED IN ANALYTICAL FEASIBILITY REASSESSMENT AND RESULT OF THAT ASSESSMENT— Continued

Current PQL Analytical feasibility reassessment Contaminant (μg/L) result

PCBs ...... 0.5 Data do not support PQL reduction. Dioxin ...... 3.0 × 10¥5 PQL reduction supported (MRL, MDL). Thallium ...... 2 Data do not support PQL reduction. Toxaphene ...... 3 PQL reduction supported (MDL). 1,1,2-Trichloroethane ...... 5 PQL reduction supported (PT, MRL, MDL).

Occurrence and Exposure National Primary Drinking Water indicating that revisions to NPDWRs are Regulations: Chemical Phase Rules and unlikely to provide a meaningful Using the SYR3 ICR database, EPA Radionuclides Rules’’ (USEPA, 2016p). opportunity to improve public health conducted an assessment to evaluate Based on benchmarks identified in the protection across the nation. Therefore, national occurrence of regulated health effects and analytical feasibility these contaminants were not identified contaminants and estimate the potential analyses, EPA conducted the occurrence as candidates for regulatory revision. population exposed to these and exposure analysis for 18 Table VI–5 lists the benchmarks used to contaminants. The details of the current contaminants. conduct the occurrence analysis, the chemical occurrence analysis are This analysis shows that these 18 total number of systems with mean documented in ‘‘The Analysis of contaminants occur at levels above the concentrations exceeding a benchmark Regulated Contaminant Occurrence Data identified benchmark in a very small from Public Water Systems in Support percentage of systems, which serve a and the estimated population served by of the Third Six-Year Review of very small percentage of the population, those systems.

TABLE VI–5—OCCURRENCE AND POTENTIAL EXPOSURE ANALYSIS FOR CHEMICAL NPDWRS

Population served by Number (and percent- systems with a mean Benchmark 1 age) of systems with a concentration higher Contaminant (ug/L) mean concentration than benchmarks (and higher than benchmarks percentage of total population)

Contaminants Identified Under the Health Effects Review as Having Potential for Lower MCLG

Carbofuran ...... >5 1 (0.00%) 993 (0.0004%) Cyanide ...... >50 98 (0.27%) 574,038 (0.27%) cis-1,2-Dichloroethylene ...... >10 4 (0.01%) 5,569 (0.00%) Endothall ...... >50 1 (0.01%) 993 (0.001%) Hexachlorocyclopentadiene ...... >40 0 (0.00%) 0 (0.00%) Methoxychlor ...... >1 1 (0.003%) 993 (0.000%) Oxamyl ...... >9 2 (0.01%) 9,742 (0.004%) Selenium ...... >40 49 (0.10%) 135,685 (0.05%) Styrene ...... >0.5 117 (0.210%) 571,425 (0.217%) Toluene ...... >600 0 (0.00%) 0 (0.00%) Xylene ...... >1,000 2 (0.004%) 825 (0.0003%)

Contaminants With MCLs Based on Analytical Feasibility and Higher Than MCLGs

Chlordane ...... >1 3 (0.01%) 1,353 (0.001%) Heptachlor ...... >0.1 3 (0.01%) 1,643 (0.00%) Heptachlor Epoxide ...... >0.04 14 (0.04%) 11,659 (0.005%) Hexachlorobenzene ...... >0.1 6 (0.016%) 8,703 (0.004%) 2,3,7,8-TCDD (Dioxin) ...... >0.000005 2 (0.06%) 1,450 (0.002%) Toxaphene ...... >1 6 (0.02%) 715,106 (0.32%) 1,1,2-Trichloroethane ...... >3 0 (0.00%) 0 (0.00%)

In addition, EPA performed a source data available to characterize occurrence in source water. The water occurrence analysis for the 10 contaminant occurrence was limited analysis of the available contaminant chemical contaminants in which because there is no comprehensive occurrence data for potential drinking updated health effects assessments dataset that characterizes source water water sources indicated relatively low indicated the possibility to increase (i.e., quality for drinking water systems. Data contaminant occurrence in the render less stringent) the MCLG values. from the U.S. Geological Survey (USGS) concentration ranges of interest. As a EPA conducted this analysis to National Water Quality Assessment consequence, EPA could not conclude determine if there was a meaningful program and the U.S. Department of that there is a meaningful opportunity opportunity to achieve cost savings Agriculture Pesticide Data Program for system cost savings by increasing the while maintaining or improving the water monitoring survey provide useful MCLG and/or MCL for these 10 level of public health protection. The insights into potential contaminant contaminants. The results of this

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analysis were documented in issues, such as revisions to monitoring significance and relevance of the issues ‘‘Occurrence Analysis for Potential and system reporting requirements, as a (ASDWA, 2016). The complete list of Source Waters for the Third Six-Year part of the Six-Year Review 3. EPA used implementation issues related to the Review of National Primary Drinking the protocol to evaluate which Phase Rules and Radionuclide Rules is Water Regulations’’ (USEPA, 2016e). implementation issues to consider presented in ‘‘Consideration of Other Treatment Feasibility (USEPA, 2016f). EPA’s protocol focused Regulatory Revisions in Support of the on items that were not already being Third Six-Year Review of the National Currently, all of the MCLs for addressed, or had not been addressed, Primary Drinking Water Regulations: chemical and radiological contaminants through alternative mechanisms (e.g., as Chemical Phase Rules and Radionuclide are set equal to the MCLGs or PQLs or a part of a recent or ongoing Rules’’ (USEPA, 2016c). are based on benefit-cost analysis; none rulemaking). The Agency determined that the are currently limited by treatment following three issues, identified by feasibility. EPA considers treatment Implementation Issues Identified for the state stakeholders, were within the feasibility after identifying Six-Year Review 3 scope of NPDWR review and were the contaminants with the potential to most substantive: lower the MCLG/MCL that constitute a EPA compiled information on a. Nitrogen monitoring in consecutive meaningful opportunity to improve implementation related issues systems and the distribution system, public health. No such contaminants associated with the Chemical Phase were identified in the occurrence and Rules. EPA also identified unresolved b. Alternative nitrate-nitrogen MCL of exposure analysis described above. implementation issues/concerns from 20 mg/L for non-community water previous Six-Year Reviews. EPA shared systems (NCWSs), and Other Regulatory Revisions the list of identified potential c. Synthetic organic chemical (SOC) In addition to possible revisions to implementation issues with a group of detection limits. MCLGs, MCLs and TTs, EPA considered state representatives convened by Table VI–6 provides a brief whether other regulatory revisions are ASDWA to obtain input from state description of the three issues and the needed to address implementation drinking water agencies concerning the Agency’s findings to date.

TABLE VI–6—CHEMICAL RULE IMPLEMENTATION ISSUES IDENTIFIED THAT FALL WITHIN THE SCOPE OF AN NPDWR REVIEW

Implementation issue Description and findings

Nitrogen Monitoring in Consecutive Current nitrite and nitrate standards are measured at the point of entry to the distribution system. Under Systems and the Distribution some conditions, nitrification of ammonia in water system distribution networks could potentially result in System. increased total nitrite or nitrate concentrations at the point of use. To address the concern, certain water systems could develop and implement a nitrification monitoring program, which would include changing or adding additional monitoring locations. Research is needed to further evaluate the extent of this potential issue, including development of criteria to identify the specific systems where distribution system monitoring could be targeted. If the outcome of the research suggests that the magnitude of the problem represents a meaningful opportunity to improve public health protection, the regulation could be considered for revision. Alternative Nitrate-Nitrogen MCL of EPA evaluated the possibility of removing or further restricting the option for some NCWSs to use an alter- 20 mg/L for NCWS. native nitrate-nitrogen MCL of up to 20 mg/L. The nitrate-nitrogen MCL in PWSs is 10 mg/L. However, § 141.11 of the Code of Federal Regulations (CFR) provides that states have the discretion to allow some NCWSs to use an alternative nitrate-nitrogen MCL of up to 20 mg/L if certain conditions are met, including conditions where water will not be available to children under six months of age. Other provisions related to this issue are included in § 141.23 of the CFR, which pertains to monitoring. This section states: ‘‘Transient, non-community water systems shall conduct monitoring to determine compliance with the nitrate and nitrite MCL in §§ 141.11 and 141.62 (as appropriate) in accordance with this section.’’ The monitoring section does not address non-transient non-community water systems (NTNCWSs) eligibility to use an alternative nitrate MCL. Two potential concerns identified with the current rule provisions are: • Potential health concerns other than methemoglobinemia associated with the ingestion of nitrate-nitrogen, such as possible effects on fetal development. • The fact that the alternative MCL was initially intended to be used by entities such as industrial plants that do not provide drinking water to children under six months of age (44 FR 42254, USEPA, 1979). Industrial plants are generally considered to be NTNCWSs. Therefore, it is possible the alternative MCL was intended to apply specifically to NTNCWSs and not transient non-community water systems (TNCWSs). The Agency has nominated nitrate and nitrite for an IRIS assessment as a result of the Six-Year Review process, and both of these contaminants are listed in the IRIS multi-year plan. An updated assessment is needed that evaluates health effects other than methemoglobinemia. Specifically, an assessment is needed that evaluates potential health effects of nitrate-nitrogen at levels between 10 and 20 mg/L on adult populations. When completed, the IRIS assessment may support initiation of a rule revision if potential adverse health effects were identified at drinking water concentrations below the alternative nitrate MCL of 20 mg/L for populations other than infants less than six-months of age.

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TABLE VI–6—CHEMICAL RULE IMPLEMENTATION ISSUES IDENTIFIED THAT FALL WITHIN THE SCOPE OF AN NPDWR REVIEW—Continued

Implementation issue Description and findings

Synthetic Organic Chemical (SOC) According to states, some laboratories have reported difficulty in achieving the detection limits for some Detection Limits. SOCs on a regular basis. Section 40 CFR 141.24(h)18 provides detection limits for the SOCs, including some pesticides. PWSs that do not detect a SOC contaminant above these concentrations may qualify for reduced monitoring frequency for individual contaminants. It was reported that some SOCs may have detection limits that are lower than levels that can be economically and efficiently achieved by laboratories using approved methods. Thus, some water systems may not be able to qualify for reduced monitoring if the laboratories cannot achieve the listed detection limits. This issue was also identified as a concern by the states during the Six-Year Review 2. To address the SOC method detection limits, the Agency investigated the MRL values for SOCs from the SYR 3 ICR and found there was an existing approved analytical method for each SOC that laboratories can use to achieve the appropriate detection limits in order to reduce monitoring requirements. Using the MRL values, the Agency evaluated the percentage of records in the ICR database at or below the detection limit. EPA considered this percentage as an indication of laboratories’ collective ability to detect contaminant concentrations at or below these levels. The Agency found that for most of the SOCs, nearly half of the records were at or below the detection limit listed in the regulation while other SOCs had a sufficient number of records below the detection limit to determine that there was an approved analytical method that could be used.

2. Fluoride provided under the statute, the SMCL is Effects’’ (USEPA, 2010b) identified an not enforceable in the same manner as oral RfD for fluoride of 0.08 milligrams Background the MCL. Public notification is required per kilograms per day (mg/kg/day) Fluoride can occur naturally in when PWSs exceed the MCL or SMCL. based on studies of severe dental drinking water as a result of the EPA has reviewed the NPDWR for fluorosis among children in the six geological composition of soils and fluoride in previous Six-Year Review months to 14 year age group (USEPA, bedrock. Some areas of the country have cycles. As a result of the first Six-Year 2010b). The ‘‘Exposure and Relative high levels of naturally occurring Review (68 FR 42908, USEPA, 2003b), Source Contribution Analysis’’ (USEPA, fluoride. EPA established the current EPA requested that the National 2010c) concluded that the RSC values NPDWR to reduce the public health risk Research Council (NRC) of the National for drinking water range from 40 to 70 associated with exposure to high levels Academies of Sciences (NAS) conduct a percent, with the higher values of naturally occurring fluoride in review of the health and exposure data associated with infants fed with drinking water sources. on orally ingested fluoride. In 2006, the powdered formula or concentrate Low levels of fluoride are frequently NRC published the results of its review reconstituted with residential tap water added to drinking water systems as a and concluded that severe dental (70%) and with adults (60%). The major public health protection measure for fluorosis is an adverse health effect contributors to total daily fluoride reducing the incidence of cavities. The when it causes both a thinning and intakes for these age groups are drinking decision to fluoridate a community pitting of the enamel, a situation that water, commercial beverages, solid water supply is made by the state or compromises the function of the enamel foods and swallowed fluoride- local municipality, and is not mandated in protecting against decay and containing toothpaste (USEPA, 2010c). by EPA or any other federal entity. The infection (NRC, 2006a). The NRC Summary of Review Results U.S. Public Health Service (PHS) recommended that EPA develop a dose- recommendation for community water response assessment for severe dental The Agency has determined that a fluoridation is 0.7 mg/L (U.S. fluorosis as the critical effect and update revision to the NPDWR for fluoride is Department of Health and Human an assessment of fluoride exposure from not appropriate at this time. EPA Services, 2015). Fluoride is also added all sources. acknowledges information regarding the to various consumer products (such as During the Six-Year Review 2, the exposure and health effects of fluoride toothpaste and mouthwash) because of Agency was in the process of (as discussed later in the ‘‘Health its beneficial effects at low level developing a dose-response assessment Effects’’ and ‘‘Occurrence and exposures. of the non-cancer impacts of fluoride on Exposure’’ sections). However, with EPA published the current NPDWR severe dental fluorosis and the skeletal EPA’s identification of several other on April 2, 1986 (51 FR 11396, USEPA, system. In addition, EPA was in the significant NPDWRs as candidates for 1986) to reduce the public health risk process of updating its evaluation of the near-term revision (see Sections VI.B.3 associated with exposure to high levels relative source contribution (RSC) of and VI.B.4), potential revision of the of naturally occurring fluoride in drinking water to total fluoride exposure fluoride NPDWR is a lower priority that drinking water sources. The current considering the contributions from would divert significant resources from NPDWR established an MCLG and MCL dental products, foods, pesticide the higher priority candidates for of 4.0 mg/L to protect against the most residues, and other sources such as revision that the Agency has identified, severe stage of skeletal fluorosis ambient air and medications. These as well as other high priority work (referred to as the ‘‘crippling’’ stage) assessments were not completed at the within the drinking water office. These (NRC, 2006a). EPA also established a time of the Six-Year Review 2; thus, no other candidates for revision include the secondary maximum contaminant level action was taken under the Six-Year Stage 1 and Stage 2 Disinfectants and (SMCL) for fluoride of 2.0 mg/L to Review 2 (75 FR 15500, USEPA, 2010h). Disinfection Byproducts Rules (D/ protect against moderate and severe In 2010, EPA published fluoride DBPRs) that apply to approximately dental fluorosis, which was considered health assessments. The ‘‘Dose 42,000 PWSs, and for which EPA has at the time to be a cosmetic effect. As Response Analysis for Non-Cancer identified the potential to further reduce

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bladder cancer risks attributed to that would exclude fluoride from the Health Effects Assessment Summary exposure to DBPs; the Surface Water Six-Year Review 3. Report’’ (USEPA, 2016h). Treatment Rules, for which the Agency Health Effects Analytical Feasibility has identified the potential to further reduce risks from a myriad of serious The NRC (2006a) evaluated the The current PQL for fluoride is 0.5 waterborne diseases (e.g., giardiasis, impact of fluoride on reproduction and mg/L (USEPA, 2009a). EPA has not cryptosporidiosis, legionellosis, development, neurotoxicity and identified any changes in analytical hepatitis, meningitis and encephalitis) behavior, the endocrine system, feasibility that could limit its ability to for approximately 12,000 surface water genotoxicity, cancer and other effects, in revise the MCL/MCLG for fluoride. addition to the tooth and bone effects. systems; and the pending revisions to Occurrence and Exposure the lead and copper NPDWR which At fluoride levels below 4.0 mg/L, the apply to approximately 68,000 PWSs. NRC found no evidence substantial EPA analyzed fluoride occurrence While EPA has evaluated the enough to support adverse effects other using the SYR3 ICR database, which available health effects and exposure than severe dental fluorosis and skeletal contains fluoride analytical results from information related to fluoride (as fractures. The NRC concluded that the approximately 47,000 PWSs in 49 discussed later in the ‘‘Health Effects’’ available data were inadequate to states/entities from 2006 to 2011. and ‘‘Occurrence and Exposure’’ determine if a risk of effects on other Sample records for fluoridated water sections), the Agency also recognizes endpoints exists at an MCLG of 4.0 mg/ (i.e., in which a system adds fluoride to that new studies on fluoride are L and made recommendations for maintain a concentration in the 0.7 to currently being performed. These additional research. 1.2 mg/L range) were omitted from the include new studies that address health EPA assessments (USEPA, 2010b; analysis because the fluoridated systems endpoints of concern other than dental 2010c) found that the RSC values are would not be impacted by revisions to fluorosis. Based on the NRC lower than the RSC of 100 percent used the fluoride NPDWR. EPA estimated the recommendations, EPA evaluated dental to derive the original MCLG of 4.0 mg/ number and percent of systems that fluorosis for the purposes of this action. L, where EPA assumed that drinking have mean fluoride concentrations EPA will continue to monitor the water was the sole source of exposure to exceeding various benchmarks and the evolving science, and, when fluoride. EPA has concluded that corresponding estimates of population appropriate, will reconsider the fluoride information on the dose-response and served by those systems. The data NPDWR’s relative priority for revision exposure assessment may support indicated that about 130 systems (0.3 and take any other available and lowering the MCLG to reflect levels that percent), serving approximately 60,000 appropriate action to address fluoride would protect against risk of severe people (0.03 percent), had an estimated risks under SDWA. dental fluorosis and skeletal fractures. system mean concentration exceeding Finally, most community water As part of this Six-Year Review, EPA the current MCL of 4.0 mg/L, whereas systems (CWSs) that provide reviewed health effects data on the more than 900 systems (2 percent), fluoridation of their drinking water have impact of fluoride on reproduction and serving approximately 1.5 million already lowered their fluoridation level development, neurotoxicity and people (0.8 percent), had an estimated to a single level of 0.7 mg/L from a behavior, the endocrine system, system mean concentration greater than previous range of 0.7 to 1.2 mg/L to genotoxicity, cancer and other effects the SMCL of 2.0 mg/L. Among these accommodate the updated PHS that were identified by the NRC as systems, many are small systems recommendation (U.S. Department of requiring additional research (NRC, (serving fewer than 10,000 people) and Health and Human Services, 2015). The 2006a). EPA noted limitations in some very small systems (serving fewer than U.S. Food and Drug Administration of these studies such as lack of details 500 people). Evaluations based on mean (FDA) also issued a letter to bottled and confounding factors. Overall, the (or average) fluoride concentrations water manufacturers recommending that new data were insufficient to alter the generally reflect an approximation of they not add fluoride to bottled water in NRC conclusion that severe dental chronic (long-term) exposure. It is excess of the revised PHS fluorosis is the critical health effects important to note that these average recommendations (FDA, 2015). In endpoint for the MCLG. concentration-based evaluations help to addition, the FDA stated it intends to Based upon the recommendations of inform Six-Year Review results, but do revise the quality standard regulation the NRC, EPA has evaluated dental not assess compliance with regulatory for fluoride added to bottled water to be fluorosis as a critical endpoint of standards nor should be viewed as consistent with the updated PHS concern for this Six-Year Review compliance forecasts for PWSs. recommendation. Therefore, EPA (USEPA, 2010b; 2010c). However new anticipates that a significant portion of studies are underway to examine other Treatment Feasibility the population’s exposure to fluoride in health endpoints (i.e., developmental A BAT or small system compliance drinking water, as well as some neurobehavior effects, endocrine technology for fluoride was not commercial beverages that use disruption and genotoxicity). One established in the Code of Federal fluoridated water from CWSs and example is an ongoing National Regulations (40 CFR 141.62). However, certain bottled water, has already been Toxicology Program (NTP) systematic EPA (1998d) identified activated or will be reduced. Notwithstanding this review of animal studies that examined alumina and reverse osmosis as BATs action’s decision, EPA will continue to the impact of fluoride on learning and for fluoride. address risk associated with fluoride in memory (NTP, 2016). For more Activated alumina is the most drinking water, with a specific focus on information about fluoride commonly used treatment technology the small systems with naturally developmental neurotoxicity visit the for fluoride removal. It is capable of occurring fluoride in their source National Toxicology Program Web site removing fluoride to concentrations waters. at https://ntp.niehs.nih.gov/pubhealth/ well below the MCL of 4.0 mg/L, but hat/noms/fluoride/neuro-index.html. with a shortened media life at lower Initial Review Additional information related to the target concentrations. Membrane EPA did not identify any recent, review of the fluoride NPDWR is technologies, such as reverse osmosis, ongoing or pending action on fluoride provided in the ‘‘Six-Year Review 3 nanofiltration, and electrodialysis, are

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also capable of removing fluoride to the overall risks from DBP mixtures Compliance monitoring data very low levels (<0.3 mg/L). They are while continuing to provide public evaluated for the Six-Year Review 3 often used to remove fluoride along health protection from microbial risks. show widespread occurrence of DBPs with other contaminants such as total and their organic precursors (as Summary of Review Results dissolved solids, arsenic, and uranium. measured as TOC) in drinking water. In general, these technologies are costly EPA has identified the following Research that has been published since and complex to operate—and thus NPDWRs within the D/DBPRs as the development of the Stage 2 D/DBPR likewise present potential challenges for candidates for revision under this Six- has improved EPA’s understanding of small water systems (USEPA, 2014a). Year Review cycle because of the the effectiveness of and limitations opportunity to further reduce public associated with various treatment 3. Disinfectants/Disinfection Byproducts health risk from exposure to DBPs: approaches, such as those for removal of Rules (D/DBPRs) Chlorite, HAA5 and TTHM. This result precursors, use of disinfectants other Background is based on a scientific review of than chlorine and localized treatment. Given that this is the first time EPA The D/DBPRs were promulgated in publicly available information. EPA’s is conducting a Six-Year Review of the two stages—Stage 1 in 1998 (63 FR review process follows the protocol D/DBPRs, extensive information about 69390, USEPA, 1998b) and Stage 2 in described in Section V of this review findings is provided below, with 2006 (71 FR 388, USEPA, 2006d). document. New information has further information provided in EPA’s Disinfection byproducts (DBPs) are strengthened the weight of evidence ‘‘Six-Year Review 3 Technical Support formed when the disinfectants supporting an association between Document for Disinfectants/Disinfection commonly used in PWSs to kill chlorination DBPs and bladder cancer risk compared to the information Byproducts Rules’’ (USEPA, 2016l). microorganisms react with organic and Additional information related to the inorganic matter in source water. DBPs available during development of the existing D/DBPRs. New information also review of D/DBPRs is provided in the have been associated with potential ‘‘Six-Year Review 3 Technical Support adverse health effects, including cancer is available related to the reproductive/ developmental effects discussed in the Document for Chlorate’’ (USEPA, 2016k) and developmental and reproductive and the ‘‘Six-Year Review 3 Technical effects. Monitoring parameters within Stage 2 D/DBPR. In addition, new toxicological data are available to Support Document for Nitrosamines’’ the D/DBPRs consist of the following: (USEPA, 2016o). DBPs—TTHM, HAA5, bromate and support the development of MCLGs for chlorite; disinfectants—chlorine, some individual DBPs currently lacking Initial Review MCLGs (for example, dibromoacetic chloramines and chlorine dioxide; and There are no recently completed, water quality indicators—total organic acid). ongoing or pending regulatory actions carbon (TOC) and alkalinity. The rules This result will also provide for on the D/DBPRs that would exclude include MCLGs/MRDLGs, as well as additional opportunity to address them from the Six-Year Review 3. MCLs/MRDLs and TT requirements, concerns with unregulated DBPs: For which were developed for individual example, nitrosamines and chlorate. In Health Effects parameters considering their health the Federal Register document for Under the Stage 1 and 2 D/DBPRs, risks. Preliminary Regulatory Determination 3 toxicology studies for specific DBPs and For organic DBPs, the concern is (79 FR 62715, USEPA, 2014b), the disinfectant residuals were used to potential increased risk of cancer and Agency stated that ‘‘because chlorate inform MCLGs (and cancer potency short-term adverse reproductive and and nitrosamines are DBPs that can be factors where MCLGs are zero) and developmental effects. For bromate, the introduced or formed in PWSs partly MRDLGs. Epidemiology studies were concern is potential increased risk of because of disinfection practices, the used to estimate potential risks from cancer. Chlorite (a regulated DBP) and Agency believes it is important to DBP mixtures (due to cancer and chlorine dioxide (a disinfectant) are evaluate these unregulated DBPs in the developmental/reproductive effects) and associated with methemoglobinemia, context of the review of the existing support the benefits analysis. and for infants, young children and DBP regulations. DBPs need to be Epidemiology studies supported a pregnant women, effects on the thyroid evaluated collectively, because the potential association between exposures are also of concern. For chlorine and potential exists that the strategy used to to elevated THM4 levels in chlorinated chloramines, health effects include eye/ control a specific DBP could increase drinking water and cancer, but the nose irritation and stomach discomfort the concentrations of other DBPs. evidence was insufficient to establish a (for chloramines, also anemia). Therefore, the Agency is not making a causal relationship. The most consistent The D/DBPRs apply to all sizes of regulatory determination for chlorate evidence was for bladder cancer. For the CWSs and non-transient non- and nitrosamines at this time.’’ development of the benefits analysis for community water systems (NTNCWSs) Chlorate and chlorite are two different both the Stage 1 and the Stage 2 D/ that chemically disinfect their water or oxidation states of chlorine and are DBPRs, EPA used five bladder cancer receive chemically disinfected water chemically inter-convertible. They case-control epidemiology studies that (that is, involving any disinfectants occur, and can co-occur, when were conducted in the 1980s and 1990s other than ultraviolet (UV) light), as hypochlorite solution and/or chlorine (Cantor et al., 1985; 1987; McGeehin et well as transient non-community water dioxide are applied during the drinking al., 1993; King and Marrett, 1996; systems (TNCWSs) that add chlorine water treatment process. Chlorite is a Freedman et al., 1997; Cantor et al., dioxide. The rules require that these regulated DBP. New information has 1998). In addition, EPA used one meta- systems comply with established MCLs, shown that the relative source analysis (Villanueva et al., 2003) and TTs, operational evaluation levels for contribution for chlorite could be lower one pooled analysis (Villanueva et al., DBPs and MRDLs for disinfectants. than previously estimated in the 2004). The five case-control studies A major challenge for water suppliers existing D/DBPRs, which could lead to used similar (though not identical) is balancing the risks from microbial a lower MCLG, and that there are exposure metrics based on years of pathogens and DBPs. The risk-balancing common health endpoints associated exposure to chlorinated drinking water tradeoff approach was intended to lower with exposure to chlorite and chlorate. (primarily chlorinated surface water) to

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estimate odds ratios. All five studies 2007; Stayner et al., 2014; Kenyon et al., halomethanes that did not contain showed an increase in the odds ratio for 2015), in conjunction with nitrogen. bladder cancer incidence with an epidemiology studies (Villanueva et al., Approximately 40 new studies about increased duration of exposure. Using 2007; Kogevinas et al., 2010; Cantor et developmental/reproductive effects the published odds ratio results from al., 2010), indicate that non-ingestion have become available since the these five studies, EPA calculated an routes of exposure (dermal and development of the Stage 2 D/DBPR. estimate for the lifetime cancer risk inhalation) from some brominated DBPs These studies address endpoints such as (population attributable risk) that may play a significant role in fetal growth (low birth weight, small for ranged from 2 to 17 percent; between 2 influencing increased bladder cancer gestational age and pre-term delivery), and 17 percent of bladder cancers risk, and that there may be greater congenital anomalies and male occurring in the U.S. could be attributed concern about sub-populations with reproductive outcomes. These studies to long-term exposure to chlorinated certain genetic characteristics continue to support a potential health drinking water at the time of the Stage (polymorphisms). EPA’s ‘‘Six-Year concern, though, as discussed above, the 1 D/DBPR. Detailed explanations of Review 3 Technical Support Document relationship of DBP exposure to these these calculations can be found in the for Disinfectants/Disinfection types of adverse outcomes may not be benefits analysis for the Stage 2 D/DBPR Byproducts Rules’’ (USEPA, 2016l) well enough understood to permit (USEPA, 2005a). The evidence from the characterizes the research that informs quantification of risks or benefits. A studies in 1985 to 1998, the meta- the mode of action by which brominated recent ‘‘four-lab study’’ on the effects of analysis in 2003 and the pooled analysis DBPs may be contributing to bladder DBP mixtures on animals, conducted by in 2004 was strong enough to support cancer. EPA researchers (Narotsky et al., 2011; the benefit analysis with several While uncertainties remain regarding 2013; 2015), suggests diminished thousand potential bladder cancer cases the degree to which specific DBPs concern for many developmental/ per year estimated as being avoided contributed to the bladder cancer reproductive endpoints. from the combined effects of the Stage incidence observed in epidemiology EPA also examined data about health 1 and Stage 2 D/DBPRs (USEPA, 2005a). studies, the collective data suggest a effects for inorganic DBPs, including Studies from the 1970s to 2005 also stronger case for causality than when information showing that the RSC for suggested a possible association the Stage 2 D/DBPR was promulgated chlorite could be lower than 80 percent between adverse developmental/ (Regli et al., 2015; USEPA, 2016l). (which could potentially support reproductive health effects and However, the Agency recognizes there lowering the MCLG) because there is exposure to chlorinated drinking water. are also different perspectives on this more dietary exposure than previously Effects were observed in all areas but issue, including suggestions about areas assumed due to the increased use of lacked consistency across studies and for additional research (Hrudey et al., chlorine dioxide and acidified sodium did not provide enough of a basis to 2015). chlorite as disinfectants in the quantify risks or benefits. The adverse processing of foods (U.S. EPA, 2006e; Further, the Agency has identified developmental/reproductive effects WHO, 2008). In addition, chlorate, new information about health effects consisted of effects on fetal growth chlorite and chlorine dioxide may share from unregulated DBPs. This includes (small for gestational age, low birth common health endpoints, namely health effects information on chlorate weight and pre-term delivery), effects on hematological and thyroid effects (Couri and nitrosamines that, along with viability (spontaneous abortion, and Abdel-Rahman, 1980; Bercz et al., occurrence/exposure information, was stillbirth) and malformations (neural 1982; Moore and Calabrese, 1982; previously noted in the Preliminary tube, oral cleft, cardiac or urinary Abdel-Rahman et al., 1984; Khan et al., Regulatory Determination 3 (79 FR defects). 2005; Orme et al., 1985; NTP, 2005; 62715, USEPA, 2014b). The Agency is Since the development of the Stage 2 USEPA, 2006e; WHO, 2008; Lee et al, considering the health effects of chlorate D/DBPR, EPA has identified additional 2013; Nguyen et al, 2014). and nitrosamines within the broader sources of information related to health The Agency did not identify any context of the health effects of regulated effects of DBPs. New toxicological relevant data that suggest an DBPs (USEPA, 2016k; 2016o). information could be used to develop opportunity to revise the MCLG for MCLGs for the following regulated DBPs EPA also identified information about bromate, or the MRDLG for chlorine or (within HAA5): Dibromoacetic acid the relative cytotoxicity and chloramines. (NTP, 2007), other brominated genotoxicity of many other unregulated haloacetic acids not currently regulated, DBPs (Richardson et al., 2007; Analytical Feasibility including bromochloroacetic acid (NTP, Richardson et al., 2008; Plewa and The Agency has not identified any 2009) and bromodichloroacetic acid Wagner 2009; Plewa et al., 2010; improvements to analytical feasibility (NTP, 2014), plus additional Ferna´ndez et al., 2010; Richardson and that could lead to improvements to the unregulated DBPs such as nitrosamines Postigo, 2011; Yang et al., 2014). Data NPDWRs included in the D/DBPRs. and chlorate (USEPA, 2016k; 2016o). from in vitro mammalian cell testing, Development of these rules was not EPA has identified new which compared the cytotoxicity and constrained by the availability of epidemiological, pharmacokinetic and genotoxicity of iodinated, brominated, analytical methods, and new EPA- pharmacodynamic studies that, and chlorinated DBPs, showed that the approved methods that would revise considered together with studies iodinated DBPs (those containing this finding have not been identified. available during the development of the iodine) were generally more toxic than Should new, EPA-approved methods for Stage 2 D/DBPR, add to the weight of the brominated DBPs (those containing one or more D/DBPRs be identified, that evidence for bladder cancer being bromine), which were in turn more information might be able to help associated with exposure to chlorination toxic than the chlorinated DBPs (those inform potential future regulatory DBPs (notably those containing containing chlorine). Nitrogen- development efforts. bromine) in drinking water. containing DBPs, including Pharmacokinetic and haloacetonitriles, haloacetamides and Occurrence and Exposure pharmacodynamic studies (Ross and halonitromethanes, were more cytotoxic In this Six-Year Review evaluation of Pegram, 2003; 2004; Leavens et al., and genotoxic than the haloacids and D/DBP occurrence and exposure, EPA

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evaluated compliance monitoring Approximately 32 percent of surface That proposal includes provisions for information collected under the SYR3 water systems and five percent of collection of data about unregulated ICR, which was previously discussed in ground water systems reported at least haloacetic acids and related precursors. Section V.B.4. EPA also evaluated one instance of TTHM occurrence at a Such data would help EPA to develop information from the DBP ICR database concentration greater than or equal to a better understanding of patterns of (USEPA, 2000a) that had been used to the MCL of 80 mg/L. For HAA5, occurrence for those contaminants. prepare the original D/DBPRs. approximately 19 percent of surface Overview of Water Quality Indicator Additionally, EPA used data from the water systems and two percent of Occurrence third monitoring cycle of the ground water systems reported at least Unregulated Contaminant Monitoring one instance of occurrence at a The Stage 1 D/DBPR requires that Rule (UCMR3) to evaluate chlorate concentration greater than or equal to DBP precursors (measured as TOC) be occurrence in 2013–2015, and data from the MCL of 60 mg/L. EPA anticipates monitored in source and treated the UCMR2 to evaluate nitrosamine that many of these peak concentrations drinking water. EPA evaluated occurrence in 2008–2010. This will have been significantly lowered compliance monitoring data from information is briefly described below, based on implementation of the 2006 surface water systems for TOC in source with additional information in EPA’s Stage 2 D/DBPR, which was designed, and treated water, using the SYR3 ICR ‘‘Six-Year Review 3 Technical Support in part, to lower such occurrences. database. Data from 2011 showed that Document for Disinfectants/Disinfection Approximately nine percent of approximately 70 percent of all plants Byproducts Rules’’ (USEPA, 2016l). systems had one or more samples that had average TOC concentrations greater It is important to note that the were greater than or equal to the than 2 mg/L in their source water and information collected through the SYR3 bromate MCL of 10 mg/L. Approximately that approximately 29 percent of plants ICR spans the years 2006–2011. As four percent of systems had one or more had average TOC concentrations greater such, it primarily reflects occurrence samples that were greater than or equal than 2 mg/L in their treated water. following the effective date for the Stage to the chlorite MCL of 1,000 mg/L. Under the Stage 1 D/DBPR, a system is 1 D/DBPR, but prior to the effective date The occurrence of six nitrosamine not required to further remove TOC for the Stage 2 D/DBPR. These species was evaluated by EPA using when its treated water TOC level, prior evaluations help to inform Six-Year data from the UCMR2. These data to the point of continuous chlorination, Review results but do not assess showed elevated concentrations of is less than 2 mg/L. The reader is compliance with regulatory standards. nitrosamines (relative to their health referred to later portions of this New information since the reference levels) in multiple drinking document under ‘‘DBP Precursor promulgation of the Stage 2 D/DBPR has water systems, especially N- Removal’’ for information about EPA’s improved our understanding on DBP nitrosodimethylamine (NDMA) in evaluation of TOC data relative to the formation and occurrence. As part of systems that use chloramines (USEPA, Stage 1 D/DBPR TOC removal this Six-Year Review, EPA has 2016o). The Agency is seeking public requirement. identified literature describing more comment regarding potential As discussed in the background than 600 specific DBPs that have been approaches that provide enhanced portion of this section, the D/DBPRs found in drinking water (e.g., protection from health risks posed by require systems to maintain disinfectant Richardson et al., 2007); these include nitrosamines in drinking water systems. residual levels (reported as free and/or chlorinated, brominated and iodinated The occurrence of chlorate was total chlorine) in accordance with the DBPs, as well as nitrogenous evaluated by EPA using data from the MRDL requirements. EPA evaluated free compounds. Additionally, EPA UCMR3 (USEPA, 2016j). These data and total chlorine measurements identified literature on the sources of showed that chlorate levels above the (collected during coliform sampling) precursors (both organic and inorganic), health reference level of 210 mg/L from the SYR3 ICR database and found as well as the influence that different occurred frequently in systems that use that very few records exceeded 4.0 mg/ precursors have on DBP formation. For hypochlorite, chlorine dioxide or L (the MRDL for chlorine and example, some of this literature chloramines. In addition, EPA evaluated chloramine residuals). Additional discusses the extent to which the co-occurrence of chlorite and information is provided in ‘‘Six-Year brominated or iodinated DBPs might chlorate and noted that these Review 3 Technical Support Document form as a result of source water bromide contaminants often co-occur (USEPA, for Disinfectants/Disinfection or iodide concentrations (Nguyen et al., 2016k). The Agency is seeking public Byproducts Rules’’ (USEPA, 2016l). 2005; Duirk et al, 2011; Lui et al., 2012; comment regarding potential Treatment Feasibility Zhang et al., 2012; Callinan et al., 2013; approaches that provide enhanced Emelko et al., 2013; Mikkelson et al., protection from health risks posed by During the development of the Stage 2013; Rice et al., 2013; Samson et al., chlorite, chlorate and chlorine dioxide. 1 and Stage 2 D/DBPRs, a variety of 2013; Rice and Westerhoff, 2014). See Section VII for more information. technologies were evaluated for their The American Water Works effectiveness, applicability, unintended Overview of DBP Occurrence Association (AWWA), through the consequences and overall feasibility for EPA collected occurrence information Water Industry Technical Action Fund achieving compliance with the TT for THMs (includes TTHM along with #266, conducted its own survey of post- requirements and MCLs, as well as information on four individual species), Stage 2 D/DBPR occurrence for systems providing a basis for the BATs (63 FR HAAs (includes HAA5 along with that serve more than 100,000 people. 69390; 71 FR 388; USEPA, 1998b; information on five individual species), Results from the AWWA survey 2005a; 2005g; 2006d; 2007b). bromate and chlorite as part of the SYR3 (Samson, 2015) provide an overview of Since the Stage 2 D/DBPR, the Agency ICR. DBP occurrence for 395 systems across has identified information that improves Data from the SYR3 ICR show that 44 states, covering a time period from our understanding of technologies concentrations at or above the MCLs for 1980 to 2015. available for lowering occurrence of and TTHM and HAA5 were found in many In December 2015, EPA issued a exposure to regulated and unregulated surface water systems and, to a lesser proposal for the fourth cycle of the DBPs. The information addresses the degree, in ground water systems. UCMR (80 FR 76897, USEPA, 2015b). full spectrum of drinking water system

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operations, including removal of organic Krasner et al., 2015). As noted by recognized that the extent to which precursors to DBPs (measured as TOC), McGuire et al. (2014), if the removal of occurrence and associated health effects disinfection practices, source water precursors for DBPs other than TTHM/ data may be lacking for one group of management and localized treatment. HAA5 becomes part of the treatment DBP contaminants versus another, as The information is briefly discussed goals, then performance parameters in well as for DBP mixtures, may make below, with additional information in addition to TOC may also be needed treatment decisions challenging when EPA’s ‘‘Six-Year Review 3 Technical (e.g., parameters indicating both trying to evaluate DBP risk tradeoffs. Support Document for Disinfectants/ vulnerability and nitrosamine formation Source Water Management Disinfection Byproducts Rules’’ potential). (USEPA, 2016l). Overall, the As was known during development of New information shows that source information collectively indicates that: the Stage 1 and the Stage 2 D/DBPRs, waters with relatively elevated sewage (1) Greater removals of DBP precursors granular activated carbon (GAC) and contributions have been associated with can and are being achieved compared to membranes can be added to existing increased nitrosamine formation the TT requirement under the Stage 1 D/ treatment trains to achieve additional (Westerhoff et al., 2015; Krasner et al., DBPR; and (2) occurrence of DBPs can reductions of DBP formation potential. 2013) and that source waters with be further controlled. One longstanding issue has been the elevated bromide levels from industrial extent to which organic precursor discharges have been associated with DBP Precursor Removal removal may cause a shift of chlorinated increased brominated THMs (McTigue The SYR3 ICR database (USEPA, species to more brominated species (as et al., 2014; States et al., 2013). Such 2016i) includes paired source and described earlier in this Section under factors as these impacts can increase the treated water TOC data. This the ‘‘Health Effects’’) when the bromide challenge of controlling DBPs during information was used to evaluate the level is relatively high in source water treatment and distribution. Weiss et al. extent to which TOC was removed from (Summers et al., 1993; Symons et al., (2013) developed a model for making source waters (i.e., percent removal) 1993). The ICR Treatment Study source water selection decisions based relative to the Stage 1 D/DBPR TOC database (USEPA, 2000b) provides on real-time DBP precursor removal requirement (i.e., requirement extensive bench- and pilot-scale data by concentrations. per the 3x3 matrix, which was which to evaluate the effects of GAC Information shows that bank filtration established based on three different and membrane removal of TOC and can reduce dissolved organic carbon ranges of raw water TOC and alkalinity resulting shifts in brominated THMs. (DOC) and nitrogenous DBP precursors levels, respectively). This TT EPA’s recent analysis of these data (Brown et al., 2015; Krasner et al., 2015), requirement is applicable to surface generally shows increased percent as well as removing pathogens (USEPA, water systems that have conventional reduction of brominated THMs as TOC 2016m). treatment plants, unless such systems removal by GAC increases (e.g., from a Localized Treatment meet the alternative criteria (63 FR target effluent level of two mg/L to one 69390, USEPA, 1998b). The analytical mg/L), especially for source waters with Localized treatment in distribution results of TOC removal (i.e., comparing high bromide concentrations (USEPA, systems, such as aeration in storage TOC levels from source water to treated 2016l). It also shows that bromoform tanks, sometimes with the addition of water) can help to characterize national formation increases as bromide GAC, has also been shown to reduce treatment baselines among these concentrations increase and that elevated levels of THMs (Walfoort et al., treatment plants. bromoform becomes the dominating 2008; Fiske et al., 2011; Brooke and The data show a wide range of species when source water bromide Collins, 2011; Johnson et al., 2009; percent TOC removal for each concentrations exceed 200 mg/L. Duranceau, 2015). Aeration approaches combination of raw water TOC and have been most successful in reducing alkalinity levels provided in the Stage 1 Disinfection Practices concentrations of chloroform and the D/DBPR TT requirement. The data also Various combinations of disinfectants more volatile brominated species but indicate that the mean removal for each and precursor removal processes have may have little impact on less volatile element of the 3x3 matrix was six to 19 been used to achieve DBP MCLs, while species (Johnson et al., 2009; percent greater than the requirement. also meeting the requirements of the Duranceau, 2015). These observations are consistent with microbial standards. Data from the notion that ‘‘since the Stage 1 D/ successive national drinking water Risk-Balancing DBPR does not require that all datasets (including the DBP ICR, The Agency has considered the risk- coagulable dissolved organic matter be UCMR2 and UCMR3 datasets) show that balancing aspects of the MDBP rules removed, there is a potential for the percentage of systems using and has determined that potential additional removal of organic matter disinfectants other than chlorine has revisions to the D/DBPRs could provide beyond that required by the 3x3 matrix’’ increased during the past two decades, greater protection of public health while (McGuire et al., 2014). as had been forecasted in the ‘‘Economic still being protective of microbial risks. Some of the TOC removal greater than Analysis of Stage 2 D/DBPR’’ (USEPA, The risk-balancing activities considered the Stage 1 D/DBPR requirement may 2005a). For example, data from the by the Agency include those between reflect operational optimization of UCMR3 (2013–2015) and the DBP ICR the microbial and disinfection conventional treatment, including use of (1998) have shown a relative increase in byproduct rules, as well as those innovative coagulants/coagulant aids use of chloramines, which is associated between different groups of DBPs. This and/or use of biofiltration (Yan et al., with the formation of nitrosamines, as a includes risk-balancing for the THMs 2008; Hasan et al., 2010; McKie et al., disinfection practice. and HAAs included in the D/DBPRs, 2015; Azzeh et al., 2015; Delatolla et al., EPA reviewed information related to additional brominated HAAs, 2015; Pharand et al., 2015). Studies have the extent to which different types of nitrosamines identified in the Federal shown that biological filtration can also DBPs may form when disinfectants are Register document for the Preliminary reduce precursors of the DBPs other applied at different points in the Regulatory Determination 3 (79 FR than TTHM/HAA5 (Sacher et al., 2008; treatment train and/or in combination 62715, USEPA, 2014b) and other DBP Farre´ et al., 2011; Liao et al., 2014; with other disinfectants. EPA groups such as iodinated DBPs. It also

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includes risk-balancing for inorganic Stage 2 D/DBPR Consecutive System In this document, the SWTR, the DBPs such as chlorite and chlorate (79 Monitoring IESWTR and the LT1 are collectively FR 62715, USEPA, 2014b). Monitoring in some combined referred to as the SWTRs because of the Potential revisions could offer distribution systems may be insufficient close association among the three rules enhanced protection from both to adequately characterize DBP (IESWTR and LT1 were amendments to regulated and unregulated DBPs. exposure. Some large, hydraulically the SWTR—additional information Potential revisions that consider areas complex combined water distribution provided in Section VI.B.4.a). The LT2 such as further constraints on systems may be conducting monitoring is discussed separately in this document precursors, and/or more targeted that is not adequate to characterize because EPA reviewed the LT2 in constraints on precursors (e.g., based on exposure throughout the distribution accordance with the Six-Year Review watershed vulnerabilities), could system. requirements and the Executive Order minimize the formation of harmful 13563 ‘‘Improving Regulation and Stage 2 D/DBPR Compliance DBPs without compromising protection Regulatory Review’’ (also known as Monitoring—Chlorine Burn against microbial risks. These potential Retrospective Review). Background revisions were identified based on a Compliance monitoring for DBPs in information on each of the microbial preliminary, qualitative assessment; it is some systems may not fully capture contaminants regulations is presented in important to note that further DBP levels to which customers may be the subsequent sections. assessment would be an important exposed during certain portions of the The microbial contaminants component of any further rulemaking year. Systems that use chloramines as a regulations establish treatment activities. For example, a watershed residual disinfectant (generally as part technique (TT) requirements in lieu of vulnerability characterization that of a compliance strategy to meet DBP MCLs. The review elements of the includes information about wastewater MCLs) often temporarily switch to free microbial contaminants regulations are: (i.e., sewage) contributions, land use chlorine as the residual disinfectant for initial review, health effects, analytical (point/non-point sources of pollution), a period (from two to eight weeks) in feasibility, occurrence and exposure, and streamflow variations over time (for order to control nitrification in the treatment feasibility, risk-balancing and example, sewage contributions during distribution system. This practice is other regulatory revisions. low flow conditions), could help to commonly called a ‘‘chlorine burn.’’ At this time, the SWTRs are being inform considerations about DBP During the chlorine burn, higher levels identified as a candidate for regulatory formation potentials and possible of DBPs are expected to be formed. revision, but the LT2, the FBRR and the control strategies. Systems often conduct their compliance GWR are not. A summary of review findings of each rule is described in the The Agency is seeking public monitoring outside of the chlorine burn period; and therefore, potentially higher subsequent sections. Additional comment regarding potential revisions information is provided in the ‘‘Six-Year to D/DBPR. See Section VII for more TTHM and HAA5 levels may not be included in compliance calculations. Review 3 Technical Support Document information. Further discussion about for Microbial Contaminant Regulations’’ potential revisions to existing D/DBPRs 4. Microbial Contaminants Regulations (USEPA, 2016n) and the ‘‘Six-Year will occur as part of a separate Background Review 3 Technical Support Document regulatory development process. for Long-Term 2 Enhanced Surface Except for the 1989 Total Coliform Water Treatment Rule’’ (USEPA, Other Regulatory Revisions Rule, which was reviewed under the 2016m). In addition to evaluating information Six-Year Review 1, this is the first time about health effects, analytical EPA is conducting a Six-Year Review of a. SWTRs feasibility, occurrence and exposure, the following microbial contaminant Background treatment feasibility and risk-balancing regulations: • Surface Water Treatment Rule EPA promulgated the SWTR in June related to the NPDWRs included in the 1989. It requires all water systems using D/DBPRs, EPA considered whether (SWTR), • Interim Enhanced Surface Water surface water sources or ground water other regulatory revisions are needed, Treatment Rule (IESWTR), under the direct influence of surface such as revisions to monitoring and • Long Term 1 Enhanced Surface water (GWUDI) sources (also known as system reporting requirements, as a part Water Treatment Rule (LT1), Subpart H systems) to remove (via of the Six-Year Review 3. EPA used the • Long Term 2 Enhanced Surface filtration) and/or inactivate (via protocol to evaluate which of these Water Treatment Rule (LT2), disinfection) microbial contaminants implementation issues to consider • Filter Backwash Recycling Rule (54 FR 27486, USEPA, 1989). Under the (USEPA, 2016f). As with the Chemical (FBRR), and SWTR, EPA established NPDWRs for Phase Rules/Radionuclides Rules, EPA • Ground Water Rule (GWR). Giardia, viruses, Legionella, turbidity shared the list of identified potential As discussed in Section V, the Initial and heterotrophic bacteria and set implementation issues with the ASDWA Review branch of the protocol identifies MCLGs of zero for Giardia lamblia, to obtain input from state drinking NPDWRs with recent or ongoing actions viruses and Legionella. Under the water agencies concerning the and excludes them from the review IESWTR (63 FR 69477, USEPA, 1998c) significance and relevance of the issues process to prevent duplicative agency and the LT1 (67 FR 1812, USEPA, (ASDWA, 2016). Implementation issues efforts. The cutoff date for the NPDWRs 2002c), EPA established an NPDWR for will be considered as part of the reviewed under the Six-Year Review 3 Cryptosporidium and set an MCLG of activities associated with potential was August 2008. Based on the Initial zero. future rulemaking efforts; some of these Review, EPA excluded the Aircraft The SWTRs established TT might be addressed through regulatory Drinking Water Rule, which was requirements in lieu of MCLs in these revision or clarification, while others promulgated in 2009, and the Revised NPDWRs. The 1989 SWTR established might be handled through guidance. Total Coliform Rule (RTCR) (the TT requirements for systems to control Examples of implementation-related revision of the 1989 TCR), which was G. lamblia by achieving at least 99.9 considerations include the following: promulgated in 2013. percent (3-log) removal/inactivation by

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filtration and/or disinfection, and to (2) significant and relatively rapid shifts • Cryptosporidium (also under control viruses by achieving at least in water characteristics such as IESWTR and LT1). 99.99 percent (4-log) removal/ turbidity, temperature, conductivity or This result is based on a scientific inactivation (54 FR 27486, USEPA, pH that closely correlate to review of available information, 1989). For a few systems able to meet climatological or surface water following the protocol described in source water criteria and site-specific conditions. The final SWTR defined Section V. Based on the availability of conditions (e.g., protective watershed GWUDI as being regulated as surface new information, the review focused on control program and other conditions), waters because Giardia contamination the following major provisions of the they were permitted to achieve the TT of infiltration galleries, springs and SWTRs: requirements by using disinfection only. wells have been found (Hoffbuhr et al., • Requirements to maintain a The SWTR also established TT 1986; Hibler et al., 1987). Some minimum disinfectant residual in the requirements for disinfectant residuals contamination of springs and wells have distribution system, (54 FR 27486, USEPA, 1989). The resulted in giardiasis outbreaks (Craun • GWUDI classification, and • residual disinfectant concentration at and Jakubowski, 1986). Direct influence CT criteria for virus disinfection. the entry point to the distribution was to be determined for individual Collectively, the new information system may not be less than 0.2 mg/L sources in accordance with criteria suggests an opportunity to revise the TT for more than four hours. The residual established by the state (54 FR 27486, provisions of the SWTRs to provide disinfectant concentration in the USEPA, 1989). The GWUDI designation greater protection of public health. More distribution system ‘‘cannot be identifies PWSs using ground water that detailed information about the review undetectable in more than 5 percent of must be regulated as if they are surface results related to the major provisions of the samples each month, for any two water systems. All other PWSs using the SWTRs is provided in the following consecutive months that the system ground water are regulated by the GWR. subsections. serves water to the public.’’ (40 CFR Surface water and GWUDI systems Requirements To Maintain a Minimum 141.72). A detectable residual may be use concentration x time (CT) tables Disinfectant Residual in the Distribution established by: (1) an analytical published by EPA to determine log- System measurement or (2) having a inactivation credits for the use of a EPA evaluated information related to heterotrophic bacteria concentration disinfectant to meet the disinfection TT the maintenance of a minimum less than or equal to 500 per mL requirements. The ‘‘SWTR Guidance disinfectant level in the distribution measured as heterotrophic plate count Manual’’ provides CT tables for Giardia system and determined that there is an (HPC). The purpose of these disinfectant and virus inactivation by free chlorine, opportunity to reduce residual risk from residual requirements was to: chloramines, ozone and chlorine • pathogens (includes opportunistic Ensure that the distribution system dioxide (USEPA, 1991). EPA obtained pathogens such as Legionella) beyond is properly maintained and identify and these CT values from bench-scale the risk addressed by the SWTRs. The limit contamination from outside the experiments with hepatitis A virus detectable concentration of disinfectant distribution system when it might (HAV). occur, The IESWTR applies to all PWSs residual in the distribution system may • Limit growth of heterotrophic using surface water, or GWUDI, which not be adequately protective of bacteria and Legionella within the serve 10,000 or more people. The microbial pathogens because of distribution system, and concerns about analytical methods and • IESWTR established TT requirements Provide a quantitative limit, which for Cryptosporidium by requiring the potential for false positives if exceeded would trigger remedial filtered systems to achieve at least a 99 (Wahman and Pressman, 2015; action. percent (two-log) removal, revising the Westerhoff et al., 2010). Maintaining a The SWTR also established sanitary definition of GWUDI and watershed disinfectant residual above a set survey requirements. The purpose of the control program under the SWTR to numerical value in the distribution sanitary survey requirements, which include Cryptosporidium, requiring system may improve public health include consideration of distribution sanitary surveys for all surface water protection from a variety of pathogens. system vulnerabilities, is to identify and GWUDI systems, and setting Such a change could have benefits for water system deficiencies that could disinfection profiling and benchmarking controlling occurrence of all types of pose a threat to public health and to requirements to prevent increases in pathogens in distribution systems, permit correction of such deficiencies. microbial risk while systems complied except for those most resistant to As part of the development of the with the Stage 1 D/DBPR. The LT1 (67 disinfection, such as Cryptosporidium. SWTR, EPA needed to clarify which Given our understanding of the FR 1812, USEPA, 2002c) extended the systems would be regulated under distribution system vulnerabilities (e.g., requirements from the IESWTR to Subpart H. In particular, EPA needed to NRC, 2006b), there may be systems serving fewer than 10,000 clarify when systems that could be opportunities to enhance the criteria for people. considered as ground water systems indicating distribution system integrity, were more appropriate to regulate as Summary of Review Results as well as the potential health risk that surface water systems (for example, EPA identified the following NPDWRs may be associated with pathogens systems where the drinking water intake under the SWTR as candidates for potentially growing and released from was in a riverbed, not in the river). revision under the Six-Year Review 3 biofilms. These opportunities include Thus, to identify a system as either because of the opportunity to further revisiting the distribution system ground or surface water, the SWTR reduce residual risk from pathogens disinfectant residual criteria and defined ‘‘ground water under the direct (including opportunistic pathogens such revisiting the existing alternative HPC influence of surface water (GWUDI).’’ as Legionella) beyond the risk addressed criteria. The NRC report (2006b) GWUDI is any water beneath the surface by the current SWTR: describes that water quality integrity is of the ground with: (1) significant • Giardia lamblia, an important factor that water occurrence of insects or other • heterotrophic bacteria, professionals must take into account for macroorganisms, algae or large-diameter • Legionella, the protection of public health, and that pathogens such as Giardia lamblia, or • viruses, and the sudden loss of disinfectant residuals

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can indicate a change in water quality tables published in the ‘‘1991 SWTR Surveillance System about the or system characteristics. However, the Guidance Manual’’ (USEPA, 1991). Over occurrences and causes of drinking report was inconclusive on the level of the years, many studies have indicated water-associated outbreaks. This disinfectant residual that should be that HAV is less chlorine-resistant than surveillance system is the primary provided in distribution systems. some enteroviruses, such as Coxsackie source of data concerning such virus B5 (Black et al., 2009; Cromeans outbreaks in the U.S. (Beer et al., 2015). GWUDI Classification et al., 2010; Keegan et al., 2012), and The drinking water-associated outbreak EPA reviewed information on disease also less chloramine-resistant than data from 1971–2012 illustrate that outbreaks, a randomized controlled adenovirus (Sirikanchana et al., 2008; there is an observable reduction of intervention study, pathogenic Hill and Cromeans, 2010). Based on this reported outbreaks over that time frame, protozoan occurrence data and studies review, EPA identified a potential need which may be, at least in part, due to evaluating parasitic protozoan removal to update CT values for virus the implementation of the TCR and the surrogates and hydrogeologic studies, inactivation by free chlorine or SWTR beginning in 1991. all of which were completed since the chloramines, particularly for water with Although the historic number of SWTR was published. The information a relatively high pH. This assessment is drinking water-associated outbreaks is suggests that there is an opportunity to also relevant to the LT2 and the GWR, declining, CDC notes that the level of provide greater public health protection which refer to the same CT tables in the surveillance and reporting activity, as by improved identification of original ‘‘1991 SWTR Guidance well as reporting requirements, varies unrecognized GWUDI PWSs. The data Manual.’’ across states and localities. For these suggest that the SWTR regulation and reasons, outbreak surveillance data guidance has performed well in Health Effects likely underestimate actual values, and identifying GWUDI for the PWS systems This section summarizes EPA’s should not be used to estimate the total most at risk from Giardia and review of the information related to number of outbreaks or cases of Cryptosporidium presence in ground human health risks from exposure to waterborne disease (Beer et al., 2015). water. However, the information (e.g., microbial contaminants in drinking Deficiencies at private wells and Colford et al., 2009) suggests that a water. EPA evaluated whether any new premise plumbing systems are subset of GWUDI systems are also at risk toxicological data, or waterborne increasingly responsible for disease but are potentially misclassified as endemic infection or infectious disease outbreaks associated with drinking ground water systems, and therefore, information, would justify modifying water (Beer et al., 2015). Premise not subject to requirements that provide the MCLGs. EPA reviewed information plumbing is the portion of the protection against parasitic protozoans. that included data from the Waterborne distribution system from the water Improved public health protection may Disease and Outbreak Surveillance meter to the consumer tap in homes, result if there is improved recognition of System (WBDOSS) collected by the schools, and other buildings (NRC, GWUDI systems, including those that Centers for Disease Control and 2006b). In 2011–2012, the two most may disinfect but do not provide Prevention (CDC) (http://www.cdc.gov/ frequent deficiencies related to engineered filtration or have not healthywater/surveillance/drinking- drinking-water-associated outbreaks conducted a demonstration of surveillance-reports.html) and other were Legionella in premise plumbing performance to document the necessary available data that documents drinking systems (66 percent) and untreated Cryptosporidium alternative treatment water-associated outbreaks. ground water (13 percent) (Beer et al., and removal required under the LT2. 2015). The potential public health MCLGs In addition to epidemic illness, improvement is most relevant to those The SWTRs set MCLGs of zero for sporadic illness (i.e., isolated cases not systems that have a large surface water Giardia lamblia, viruses, associated with an outbreak) accounts component and poor subsurface Cryptosporidium, and Legionella since for an unknown but probably significant removal capabilities but are not yet any exposure to these microbial portion of waterborne disease and is recognized as GWUDI and warrants pathogens presents a potential health more difficult to recognize (71 FR further examination in any rulemaking risk. In the Six Year Review 3, EPA did 65573, USEPA, 2006b). activities. not identify new information related to Collectively, the data indicate that EPA suggests that the number of potentially revising these MCLGs. New outbreaks associated with drinking potentially misclassified GWUDI PWSs dose-response data from some water may have been reduced as a result may be estimated by: (1) waterborne waterborne pathogens are available from of drinking water regulations. However, disease outbreak compilations, (2) the both human and animal exposure opportunities remain to address disease UCMR3 occurrence data (aerobic spore studies (Teunis et al., 2002a; 2002b; outbreaks associated with distribution detections and concentrations), and (3) Armstrong and Haas, 2007; 2008; Buse systems and untreated ground water the SYR2 ICR and the SYR3 ICR (total et al., 2012). Concurrently, new models and, at the same time, to potentially coliform detections). EPA’s preliminary seek to use the new data to provide address some of the waterborne disease characterization of the number of the improved infectivity, morbidity and outbreaks associated with little to no potentially misclassified GWUDI PWSs mortality predictions (Messner et al., disinfectant residual in the distribution is described in the ‘‘Six-Year Review 3 2014; USEPA, 2016m). The newer system (Geldreich et al., 1992; Bartrand Technical Support Document for models are specifically designed to et al., 2014). Microbial Contaminant Regulations’’ address low dose exposure typical of The precise burden of disease is not (USEPA, 2016n). drinking water rather than high dose well quantified. Five primarily exposure typical of food ingestion or waterborne diseases (giardiasis, CT Criteria for Virus Disinfection vaccine studies. cryptosporidiosis, Legionnaires’ disease, EPA evaluated whether the current otitis externa, and non-tuberculous CT criteria based on hepatitis A virus Waterborne Disease Outbreaks mycobacterial infection) were (HAV) are sufficiently protective against Associated With Drinking Water responsible for over 40,000 other types of viruses. EPA reviewed EPA reviewed information from the hospitalizations per year at a cost of disinfection studies relevant to the CT Waterborne Disease and Outbreaks nearly $1 billion per year (Collier et al.,

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2012). Given this information, there are County obtained water from five number of constituents can interfere opportunities for substantial cost horizontal collector wells along the with measurements of disinfectant savings if such incidence can be Russian River, four regulated as ground residuals. In general, most strong reduced through better risk water and one regulated as GWUDI (part oxidants will interfere with management. Most of these costs are of the year). Colford et al. (2009) found measurement of chlorine. In addition, attributed to Legionella and non- that highly credible AGI in the color, turbidity and particles will also tuberculous mycobacteria. These population aged 55 and over was interfere with colorimetric techniques bacteria can proliferate under favorable attributable to drinking water exposure. such as DPD. conditions at locations in the premise Illness occurred even though the water For some systems using chloramines plumbing and in some parts of the utility met all federal, state and local (a mixture of biocidal inorganic distribution system that are further from drinking water regulations. chloramines, of which monochloramine the central parts of the system, where is the most effective), the presence of water has aged the longest and where Pathogenic Protozoa Occurrence in organic chloramines can be problematic there may be very little to no Ground Water since these related compounds have disinfectant residual. Further, the In a karst aquifer in France, 18 ground minimal biocidal properties, they can quality of the water delivered to water samples were taken from the interfere with residual monitoring, and building systems and households can Norville (Haute-Normandie) public they can give the false impression that affect these pathogens’ ability for growth water supply well (5,000 customers, the finished water contains more active and disease transmission. There are chlorine treatment) and tested for disinfectant than is actually present opportunities to enhance the current Cryptosporidium oocysts. Thirteen of (Wahman and Pressman, 2015; disinfectant residual requirements to the 18 samples were found to be Westerhoff et al., 2010). Organic more effectively kill pathogens or Cryptosporidium positive by solid- chloramines will continue to form in the contain their growth, and to better phase cytometry; the maximum distribution system while inorganic indicate, through a stronger signal of the concentration was four oocyst per 100 L chloramines decay, and thus areas of the absence of a residual, when targeted (Khaldi et al., 2011). These data show distribution system with relatively high improvements to treatment practices or that Cryptosporidium in karst ground water ages may have residuals distribution conditions may provide water includes, for some highly containing a significant amount of greater public health protection. vulnerable systems, Cryptosporidium organic chloramines (Wahman and Pressman, 2015). GWUDI-Related Disease Outbreaks occurrence resulting from poor Cryptosporidium removal during In addition, EPA reviewed research Wallender et al. (2014) summarized infiltration from the surface rather than published regarding potential CDC outbreak data for the years 1971– poor removal during induced improvements to methods or 2008 and determined that GWUDI was infiltration from nearby surface water. technologies used in the determination a ‘‘contributing factor’’ in 11 percent Because the SWTR definition assumes of free or total chlorine (Dong et al., (six percent with Giardia etiology) of all that all Cryptosporidium in PWS wells 2012; Tang et al., 2014; Saad et al., outbreaks using untreated ground water. is transported from adjacent surface 2005). Analytical methods that can The total number of untreated ground water, it is silent on the issue of measure inorganic chloramines without water outbreaks during this time period Cryptosporidium transport directly from the organic chloramine interferences are was 248. Three quarters of the outbreaks the surface, as apparently was the case available, but not approved for involved PWSs. These findings indicate in Norville, France. Karst aquifers are a determining compliance with NPDWRs. that some of the ground water systems vital ground water resource in the U.S. Field test kits based on the indophenol examined by CDC that are not currently method are available that can According to the USGS, about 40 required to disinfect are contaminated specifically measure monochloramine percent of the ground water used for with pathogens. Reclassifying these without inclusion of mass from drinking water comes from karst potentially ‘‘unrecognized’’ GWUDI dichloramine or organic chloramines aquifers (USGS, 2004). PWSs may provide greater public health (Lee et al., 2007). protection against microbial Analytical Feasibility Use of Aerobic Spores as Pathogenic contamination because these PWSs Analytical Methods for Chlorine Protozoa Surrogates would be subject to stricter Residuals requirements. As an example, a 2007 EPA’s existing microbial outbreak of giardiasis occurred in a New Because of concerns about analytical contaminants regulations require Hampshire community (205 homes) methods and the potential for false monitoring of pathogenic protozoa in using untreated ground water (Daly et positives, the detectable concentration source water (e.g., Cryptosporidium) al., 2010). This GWUDI of disinfectant residuals in the and microorganisms that indicate a misclassification-related outbreak was distribution system may not be possible pathway for contamination the largest giardiasis drinking water- adequately protective of microbial (e.g., total coliform, E. coli). In this Six- associated outbreak in the preceding 10 pathogens. To further inform these Year Review, EPA evaluated additional years. concerns, EPA reviewed analytical microorganisms that could be used to methods that have been approved for identify PWSs most at risk from Randomized Controlled Intervention free chlorine, total chlorine and chlorine Cryptosporidium in ground water. New Study dioxide under the SWTR and the data suggest that aerobic spores are A randomized, controlled, triple- D/DBPRs. Nearly all utilities use either useful surrogates for Cryptosporidium blinded drinking water intervention the DPD (N,N-diethyl-p- occurrence and removal. Aerobic spores study was conducted in Sonoma phenylenediamine) or amperometric originate in shallow soil. The spore County, California (Colford et al., 2009). titration methods to measure presence in a sample from a PWS well The purpose of the study was to distribution system disinfectant indicates that there is a pathway for determine the proportion of acute residual, and these measurements are water infiltration into the well, either gastrointestinal illnesses (AGI) generally performed in the field vertically from the surface or attributable to drinking water. Sonoma (Wahman and Pressman, 2015). A horizontally from nearby surface water.

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EPA previously used aerobic spores as supporting bacterial growth or an • State implementation of surrogate measures of Cryptosporidium intrusion event into the distribution disinfection residual requirements, removal by alternative treatment in a system. On the other hand, the absence • Disinfectant residuals for control of demonstration of field performance of coliforms and/or E. coli does not Legionella in premise plumbing (USEPA, 2010f). Field demonstrations necessarily mean the absence of systems, showed that the spores performed well pathogens that are more resistant to the • in demonstrating two-log removal of disinfectant residual. Detection of HPC alternative to detectable Cryptosporidium at Casper, Wyoming, coliform bacteria is commonly residual measurement, and and Kennewick, Washington (USEPA, associated with low distribution system • CT criteria for viruses. 2010f). Spores also performed well in disinfectant residuals. According to In addition, EPA reviewed key demonstrating that a Nebraska PWS was LeChevallier et al. (1996), disinfectant findings by the Research and unable to achieve better than two-log residuals of 0.2 mg/L or more of free Information Collection Partnership removal of Cryptosporidium, and that chlorine, or 0.5 mg/L or more of total (RICP) on drinking water distribution UV or other engineered treatment would chlorine, are associated with reduced system issues and research and be required (State of Nebraska, 2013). levels of coliform bacteria. information needs. The RICP is a To assess the relationship between Headd and Bradford (2015) summarized working group formed on the disinfectant residual and occurrence of the relevant scientific literature, recommendation of the Total Coliform indicators for pathogens in distribution conducted spore and Cryptosporidium Rule Distribution System Advisory laboratory experiments, and performed systems, EPA evaluated information Committee to identify specific high- porous media transport modeling. They about chlorine residuals and total priority research and information found that spores are suitable coliforms and E. coli (TC/EC) using collection activities and to stimulate Cryptosporidium surrogates in ground compliance monitoring data from the water distribution system research and water. These new data suggest that SYR3 ICR database. EPA paired TC/EC information collection (USEPA, 2008b; aerobic spores are useful as surrogates results with field chlorine residual data USEPA and Water Research Foundation, for Cryptosporidium removal estimates collected at the same time and location. 2016). via subsurface passage (USEPA, 2010f) It is important to note that these and may be useful as supplemental evaluations help to inform the SYR3 Detectable Residual for Systems Using surrogates to improve recognition of results, but do not assess compliance Chloramine Disinfection GWUDI systems. with regulatory standards. Locas et al. (2008) found that aerobic EPA found that there was a lower rate As discussed in the background spores were present in six of nine wells of occurrence of both TC and EC as the portion of this section, for surface water sampled in Quebec, Canada, and in 45 free or total chlorine residual increased systems or GWUDI systems, the SWTR of 109 samples taken. The authors to higher levels (note: total chlorine is requires that a disinfectant residual conclude that aerobic spore presence is often used as a measure for systems that cannot be undetectable in more than an indicator of a change in water quality use chloramines). For example, the TC five percent of samples each month for and warrants further investigation to positive rate was less than one percent any two consecutive months. determine the source of potential when chlorine residuals were equal to EPA identified two issues that have contamination. or greater than 0.2 mg/L of free chlorine implications for the protectiveness of In EPA’s investigation of virus or 0.5 mg/L of total chlorine. This allowing a detectable residual as a occurrence in untreated PWS wells relationship between chlorine residuals surrogate for bacteriological quality: under the UCMR3, 252 of 793 wells (317 and occurrence of TC and EC was Organic chloramines and nitrification. of 1,047 samples) were positive for similar to that reported by the Colorado Organic chloramines affect the aerobic spores (USEPA, 2016j). Department of Public Health and effectiveness of disinfectant residuals Measured concentrations spanned three Environment (Ingels, 2015). because they: (1) Form during the use of orders of magnitude, with about three A disinfectant residual also serves as free chlorine or chloramines, (2) percent having over 100 spore-forming an indicator of the effectiveness of interfere with commonly used analytical units per 100 ml). Because aerobic distribution system best management methods for free and total chlorine spores originating in soil are found in practices. Best management practices measurements, and (3) are poor GWUDI and ground water PWS wells, include flushing, storage tank disinfectants compared to free chlorine the UCMR3 data suggest that aerobic maintenance, cross-connection control, and monochloramine (Wahman and spores could be used as an indicator of leak detection and effective pipe Pressman, 2015). the susceptibility of PWS wells to replacement and repair practices. The surface water infiltration. Together with effective implementation of best Because chloramination involves other indicators and/or parasitic management practices helps water introduction of ammonia into drinking protozoa data from PWS wells, newer suppliers to lower chlorine demand and water, and decomposition of methods including spores (occurrence, maintain an adequate disinfectant chloramines can further release concentration, and/or removal residual throughout the distribution ammonia in the distribution system, estimates) might be useful in identifying system. These same practices can also chloramine use comes with the risk of unrecognized GWUDI PWS wells. The help control DBP formation. distribution system nitrification (i.e., the LT2 Toolbox Guidance Manual biological oxidation of ammonia to identified aerobic spores as the Treatment Feasibility nitrite and eventually nitrate). Drinking indicator to determine Cryptosporidium EPA reviewed new information water distribution system nitrification is removal for systems using bank related to the TT requirements in the undesirable and can result in water filtration for LT2 additional treatment SWTR and identified the following quality degradation. Information shows requirements (USEPA, 2010f). treatment-related topics that support that maintaining a high enough level of potential revisions to the SWTRs to total chlorine or monochloramine Occurrence and Exposure improve public health protection: residuals in the distribution system can Coliform and/or E. coli occurrence • Detectable residual for systems help prevent both nitrification and can be an indication of conditions using chloramine disinfection, residual depletion (Stanford et al, 2014).

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State Implementation of Disinfectant warm temperature) tend to support risk management decisions regarding Residual Requirements growth and persistence of opportunistic treatment and control of Legionella in States may adopt federal drinking pathogens. buildings. Studies indicate that distribution EPA also reviewed the scientific water regulations or promulgate more systems can play a role in influencing literature on the effectiveness of stringent drinking water requirements, the transmission and contamination of disinfectant residuals at controlling including those for disinfectant Legionella in premise plumbing systems biofilm growth. Many factors influence residuals. Preliminary information (Lin et al., 1998; States et al., 2013). the concentration of the disinfectant shows that 26 states require a detectable Hospitals served by PWSs using residual in the distribution system; and disinfectant residual in the distribution chloramines reported fewer outbreaks of therefore, the ability of the residual to system. Twenty of these 26 states legionellosis than those using free control microbial growth and biofilm require a minimum free chlorine chlorine (Kool et al., 1999; Heffelginger formation. These factors include the residual of 0.2 mg/L or more (Ingels, et al., 2003). Some building systems level of assimilable organic carbon 2015; Wahman and Pressman, 2015). supplied by PWSs which have switched (AOC), the type and concentration of Five of the 20 states set standards even to chloramines have seen marked disinfectant, water temperature, pipe more stringent than 0.2 mg/L: Louisiana reduction in the colonization of materials, and system hydraulics. requires at least 0.5 mg/L free chlorine Legionella (Flannery et al., 2006; Moore Problems associated with biofilms in in its emergency rule, while Florida, et al., 2006). One implication of these distribution systems include enhanced Illinois, Iowa, and Delaware require 0.3 studies is the importance of being able corrosion of pipes and deterioration of mg/L. For minimum total chlorine to reliably measure and sustain water quality. Biofilms can provide residual, state requirements vary from chloramine residuals to increase the ecological niches that are suited to the 0.05 mg/L (New Jersey) to 1.00 mg/L or likelihood of its effectiveness at potential survival of pathogens (Walker higher (Kansas, Oklahoma, Iowa, Ohio, controlling Legionella in premise and Morales, 1997; Baribeau et al., 2005; and North Carolina). North Carolina has plumbing systems. On the other hand, Behnke et al., 2011; Wang et al., 2012; a numeric requirement for total chlorine some studies have indicated that the Biyela et al., 2012; Revetta et al., 2013; residual but not for free chlorine occurrence of another pathogen, non- Ashbolt, 2015). The biofilm can protect residual. tubercular Mycobacterium, may increase microorganisms from disinfectants and Colorado has amended its minimum under chloramination conditions (Pryor can enhance nutrient accumulation and disinfectant residual requirements in et al., 2004; Moore et al., 2006; Duda et transport (Baribeau et al., 2005). the distribution system to be greater al., 2014). HPC Alternative to Detectable Residual than or equal to 0.2 mg/L, effective Legionella species can multiply in Measurement April 1, 2016 (Ingels, 2015). warm, stagnant water environments, Pennsylvania recently proposed to such as in community water storage Under the SWTR, a system may strengthen its disinfectant residual tanks with low disinfectant residuals demonstrate that its HPC levels are less requirements by increasing the during warm months. Cohn et al. (2014) than 500 per mL, at any sampling minimum disinfectant residual in the observed increased incidence of locations, in lieu of demonstrating the distribution system to 0.2 mg/L free or legionellosis among institutions and presence of a detectable disinfectant total chlorine (Pennsylvania Bulletin, private homes near a community water residual at that location, per primacy 2016). Louisiana’s Emergency storage tank when the disinfectant agency approval. EPA reviewed new Distribution Disinfectant Residual Rule residual in the storage tank dropped information that suggests development was established in 2013 to control (from greater than 0.2 mg/L to less than of criteria which may be more protective Naegleria fowleri, an amoeba found in 0.2 mg/L) during hot summer months. than the HPC criterion. For example, several PWSs. That rule requires a Based on these findings, the authors criteria used in the Netherlands for minimum free or total chlorine recommended that, regardless of total systems operating without a distribution disinfectant level of 0.5 mg/L to be coliform occurrence, remedial actions system disinfectant residual provides an maintained at all times in finished water be taken (e.g., flushing of mains, example of an alternative criteria than storage tanks and the entire distribution checking for closed valves that can the HPC criterion. In the Netherlands, system (Louisiana Department of Health result in hydraulic dead-ends, and chlorine is not used routinely for and Hospitals, 2013). The state agency possibly installing re-chlorination primary or secondary disinfection. intends to continue to renew the stations) when low chlorine residuals Dutch water systems use the following Emergency Rule until a final rule can be are observed during hot summer general approach to control microbial promulgated (Louisiana Department of months. They also noted that this activity in the distribution system Health and Hospitals, 2014). storage tank had been cleaned without a disinfectant residual (Smeets subsequent to the outbreak (Cohn et al., Disinfectant Residuals for Control of et al., 2009): Produce a biologically 2014; Ashbolt, 2015). Legionella in Premise Plumbing Systems stable drinking water; use distribution To help address concerns about system materials that are non-reactive Since the reporting of disease Legionella, EPA developed a document and biologically stable; and optimize outbreaks due to Legionella began in entitled ‘‘Technology for Legionella distribution system operations and 2001, Legionella has been shown to Control in Premise Plumbing Systems: maintenance practices to prevent cause more drinking-water-related Scientific Literature Review’’ (USEPA, stagnation and sediment accumulation. outbreaks than any other 2016r). The document summarizes For the determination of a biologically microorganism. Addressing premise information about the effectiveness of stable water they use AOC as an plumbing issues is particularly different approaches to control indicator. challenging. Premise plumbing may be Legionella in a building’s premise largely outside of water utilities’ plumbing system. EPA expects that use CT Criteria for Virus Disinfection operations and management control. of this document will further improve EPA reviewed new disinfection Also, the characteristic features of public health by helping primacy studies published since the release of premise plumbing (e.g., low agencies, facility maintenance operators, the original CT tables. Collectively, the disinfectants residuals, stagnation, and and facility owners make science-based data in the recent literature indicate that

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EPA CT values for free chlorine rules, as well as those between different lead to significant water quality disinfection are sufficient to inactivate groups of DBPs. This includes balancing degradation and health risks to most enteric viruses in drinking water, the reduction in risks from microbial consumers (USEPA, 1999). Examples of except for Coxsackie virus B5 at a pH pathogens should there be additional such water quality degradation include higher than 7.5 (Black et al., 2009; requirements to maintain a disinfectant increases in algal cells, coliform Cromeans et al., 2010; Keegan et al., residual with the increased risk from D/ bacteria, heterotrophic bacteria, 2012). DBPs resulting from such requirements. particulates, disinfection byproducts, EPA’s CT values for chlorine EPA also considered the potential metals, taste and odor, insect larvae, incorporate a safety factor of three to impact of further constraints on DBP Giardia, Cryptosporidium and nitrate account for differences between precursors on the reduction of demand (USEPA, 1999). Contamination of dispersed and aggregated hepatitis A for disinfectant residual. The risk- reservoirs occurs through surface water virus and between buffered, demand- balancing review was based on a runoff, bird and animal wastes, human free water and environmental water. In preliminary, qualitative assessment of activity, algal growth, airborne light of new information about the unintended consequences; it is deposition and insects and fish. hepatitis A virus and the effects of important to note that further The LT2 requires PWSs using source water quality on chlorine assessment of such consequences would uncovered finished water storage disinfection, EPA concludes that the be an important component of any facilities to either cover the storage safety factor of three should be re- further rulemaking activities. facility or treat the storage facility evaluated to ensure its adequacy. A discharge (i.e., prior to entering the b. LT2 larger safety factor (thus higher EPA CT distribution system) to achieve values) is expected to enhance Background inactivation and/or removal of 4-log waterborne pathogen control but could EPA promulgated the LT2 on January virus, 3-log G. lamblia, and 2-log lead to higher DBP formation and 5, 2006 (71 FR 654, USEPA, 2006c). The Cryptosporidium spp. on a state- warrants further examination in any LT2 applies to all PWSs that use surface approved schedule. rulemaking activity. water or ground water under the direct Under the LT2, PWSs were required Adenovirus is the virus that is most influence of surface water as drinking to notify their state/primacy agency by resistant to chloramines, through it is water. The LT2 builds upon the April 1, 2008, if they used UCFWRs. very susceptible to free chlorine IESWTR and the LT1 by improving Additionally, the LT2 required all PWSs disinfection. Several studies revealed control of microbial pathogens, to either meet the requirement to cover that monochloramine disinfection might specifically the contaminant the UCFWR, or treat the UCFWR not provide adequate control of Cryptosporidium. The purpose of the discharge to the distribution system or adenovirus in drinking water, LT2 is to reduce illness linked with the be in compliance with a state-approved particularly in waters with relatively contaminant Cryptosporidium and other schedule for meeting these requirements high pH and at low temperature disease-causing microorganisms in no later than April 1, 2009. Under this (Sirikanchana et al., 2008; Hill and drinking water. The LT2 supplements review, EPA evaluated published Cromeans, 2010). the IESWTR and the LT1 regulations by information to assess whether allowing Research and Information Collection establishing additional Cryptosporidium a state-approved risk management plan Partnership Findings treatment requirements for higher-risk would justify revisions to the LT2. systems. The LT2 requires source water Summary of Review Results The RICP partners are EPA and Water occurrence monitoring which is used to Research Foundation. EPA examined determine additional treatment Information available since information from the 10 high priority requirements. The LT2 rule provides for promulgation of the LT2 either supports RICP areas in the context of the Six-Year additional CT credits for the current regulatory requirements or Review, particularly information related Cryptosporidium inactivation by ozone does not justify a revision. EPA to the effectiveness of sanitary survey and chlorine dioxide. The LT2 also determined that no regulatory revisions and corrective action requirements provides UV treatment credits for to the UCFWR requirements of the LT2 under the IESWTR. However, EPA Cryptosporidium, Giardia and virus are warranted at this time based on the found limited information that would inactivation. EPA recognized that review of available information. shed light on the frequency and research in the field of Cryptosporidium Health Effects magnitude of distribution system inactivation is ongoing and included a vulnerability events (e.g., backflow provision in the rule that allows EPA reassessed the health risks events, storage tank breeches), unfiltered systems using a disinfectant resulting from exposure to associated risk implication, and costs other than chlorine to demonstrate the Cryptosporidium spp., Giardia lamblia for preventing such events from log inactivation that can be achieved. and viruses, as well as other potential occurring. The RICP report identifies The LT2 also contains provisions to microbiological risks to human health. potential follow-up research areas that reduce risks from uncovered finished The Agency also reviewed new could help to address these gaps water reservoirs (UCFWRs).5 The rule information on other pathogens of (USEPA and Water Research ensures that systems maintain microbial potential concern to determine whether Foundation, 2016). protection when they take steps to additional measures are warranted to provide greater public health protection Risk-Balancing decrease the formation of disinfection byproducts in systems that add a from these pathogens, particularly in the The Agency has considered the risk- chemical disinfectant (i.e., other than context of the UCFWR provisions of the balancing aspects of the MDBP rules UV light) or receive a chemically LT2. and has determined that potential The principal objectives of this health disinfected water. Storage of treated revisions to the SWTRs could provide effects review were to: (1) Evaluate drinking water in open reservoirs can improved health protection. The risk- whether there are new or additional balancing activities considered by the 5 LT2 uses the term ‘facilities’’ instead of ways to estimate risks from Agency include those between the ‘reservoirs’. The term reservoirs is used in this Cryptosporidium and other pathogenic microbial and disinfection by-product document. microorganisms in drinking water and

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(2) evaluate surveillance and outbreak their source waters for Cryptosporidium variability. The difference observed data on Cryptosporidium and other spp. (and/or E. coli) to identify between occurrence at the time of the contaminants of potential concern. additional treatment requirements. ICR Supplemental Surveys (USEPA, Based on the review, the new PWSs must monitor their source water 2000c) and the LT2 Round 1 monitoring information does not justify a revision (i.e., the influent water entering the indicates year-to-year variability. Round to the health basis for the LT2 at this treatment plant) over two different 2 monitoring began in 2015. Under this time. For more information regarding timeframes (Round 1 and Round 2) to review, EPA considered whether a third EPA’s review of health effects, see the determine the Cryptosporidium level. round of monitoring would be justified ‘‘Six-Year Review 3 Technical Support Monitoring results determine the extent at this time, in particular, requiring the Document for Long-Term 2 Enhanced of Cryptosporidium treatment use of Method 1623.1. EPA also Surface Water Treatment Rule’’ (USEPA, requirements under the LT2. considered whether a modification to 2016m). Under the LT2, the date for PWSs to the action bin boundaries should be begin monitoring is staggered by PWS made based on requiring Method Analytical Feasibility size, with smaller PWSs starting at a 1623.1. The LT2 specifies approved analytical later time than larger systems. Because of the relatively modest gains methods to determine the levels of According to the LT2 rule requirements, in public health protection predicted by Cryptosporidium in source waters for all PWSs were expected to complete the Round 2 monitoring EPA does not the identification of additional Round 1 in 2012. believe a third round of monitoring is treatment needs. The LT2 requires To reduce monitoring costs, small justified at this time, even if the Agency systems and/or laboratories to use either filtered PWSs (serving fewer than were to require the use of Method ‘‘Method 1622: Cryptosporidium in 10,000 people) initially monitor for E. 1623.1 for this monitoring. Round 1 Water by Filtration/IMS/FA’’ (EPA 815– coli for one year as a screening analysis Cryptosporidium occurrence was lower R–05–001, USEPA, 2005d) or ‘‘Method and are required to monitor for than expected (3.3–5.3 percent of Bin 1 1623: Cryptosporidium and Giardia in Cryptosporidium only if their E. coli systems from Round 1 would be moved Water by Filtration/IMS/FA’’ (EPA 815– levels exceed specified trigger values. to a higher bin). As mentioned earlier, R–05–002, USEPA, 2005e). EPA Small filtered PWSs that exceed the E. EPA will not require the use of Method Methods 1622 or 1623 is used in coli trigger, as well as small unfiltered 1623.1 for Cryptosporidium monitoring. monitoring programs to characterize PWSs, must monitor for Therefore, EPA will not make changes Cryptosporidium levels in the source Cryptosporidium for one or two years, to the action bin boundaries at this time. water of PWSs for the purposes of risk- depending on the sampling frequency. targeted treatment requirements under Based on the source water monitoring Treatment Feasibility the LT2. Method recoveries of more results, filtered systems were classified LT2 includes a variety of treatment than 3,000 matrix spiked samples from in one of four risk categories to and control options, collectively termed the first round of monitoring for the LT2 determine additional treatment needed the ‘‘microbial toolbox,’’ that PWSs can indicated an average recovery of oocysts (Bins 1–4). Systems in Bin 1 are implement to comply with the LT2’s with Methods 1622 and 1623 to be 40 required to provide no additional additional Cryptosporidium treatment percent. In addition to evaluating the Cryptosporidium treatment. Filtered requirements. Most options in the results from the first round of systems in Bins 2–4 must achieve 1.0– microbial toolbox carry prescribed monitoring, EPA gathered new 2.5 log of treatment (i.e., 90 to 99.7 credits toward Cryptosporidium information on Cryptosporidium percent reduction) for Cryptosporidium treatment and control requirements. The analytical methods by investigating over and above that provided by LT2 Toolbox Guidance Manual (USEPA, improvements to Methods 1622 and conventional treatment, depending on 2010f) provides guidance on how to 1623. EPA evaluated whether the the Cryptosporidium concentrations. apply the toolbox options. required use of a revised method Filtered PWSs must meet the additional The LT2 also requires all unfiltered (Method 1623.1) would be justified for Cryptosporidium treatment PWSs to provide at least 2 to 3-log (i.e., Round 2 monitoring under the LT2. requirements in Bins 2, 3, or 4 by 99 to 99.9 percent) inactivation of Though new information is available selecting one or more technologies from Cryptosporidium. Further, under the that indicates the potential for a the microbial toolbox of options for LT2, unfiltered PWSs must achieve their regulatory revision, the Agency does not ensuring source water protection and overall inactivation requirements believe it is appropriate to revise the management, and/or Cryptosporidium (including Giardia and virus rule to require the use of Method removal or inactivation. All unfiltered inactivation as established by earlier 1623.1, since the Agency believes such water systems must provide at least 99 regulations) using a minimum of two a change would not provide or 99.9 percent (2 or 3-log) inactivation disinfectants. substantially greater protection of public of Cryptosporidium, depending on the EPA reviewed information available health at the national level. The use of results of their monitoring. since the promulgation of the LT2 on Method 1623.1 during the LT2 Round 2 Additionally, all filtered systems that the use of the microbial toolbox to monitoring is optional, and not provide, or will provide, 5.5 log determine if the information would required. Since EPA is not planning treatment for Cryptosporidium are support a potential change to the changes to the methods required under exempt from monitoring and subsequent prescribed credits or the associated the LT2, the schedule for the LT2 Round bin classification. Systems providing 5.5 design and operational criteria. In 2 monitoring remains the same as log Cryptosporidium treatment must addition, EPA searched for information described in the final LT2, which is notify the state no later than the date by on new and emerging tools that would scheduled to be completed no later than which the system must submit a support their potential addition to the 2021 for all PWSs. sampling plan. toolbox. The Agency also received input Six years after the initial bin on the use and effectiveness of the Occurrence and Exposure classification, filtered systems must microbial toolbox tools through public The LT2 requires PWSs using surface conduct a second round of monitoring. meetings, research of publicly available water or ground water under the direct Round 2 monitoring is in place to information and by actively influence of surface water to monitor understand year-to-year occurrence communicating with some systems. EPA

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also considered benefits and/or either supports the current regulatory determining if there is an opportunity to difficulties observed by the PWSs when requirements or does not justify a improve public health protection. using the available tools. revision. For more information Implementation of the GWR was not yet EPA also examined information from regarding EPA’s review of treatment completed for the period of time some PWSs with UCFWRs to evaluate feasibility see the ‘‘Six-Year Review 3 covered by the SYR3 ICR. The RTCR the potential effectiveness of risk Technical Support Document for Long- was promulgated in 2013 and became management measures taken by those Term 2 Enhanced Surface Water effective on April 1, 2016. EPA expects PWSs for protecting the finished water Treatment Rule’’ (USEPA, 2016m). that implementation on the RTCR may in the UCFWRs from contamination. impact the percent of ground water The New York City Department of c. FBRR systems that will be triggered into Environmental Protection (NYC DEP) Background source water monitoring and taking any has undertaken more activities than any EPA promulgated the FBRR in 2001 corrective actions under the GWR. other PWS to protect their Hillview (66 FR 31086, USEPA, 2001b). It Therefore, the effects of the GWR and Reservoir from contamination. These requires PWSs to review their backwash the RTCR implementation in addressing activities include wildlife management water recycling practices to ensure vulnerable ground water systems are not (e.g., bird harassment and deterrents, microbial control is not compromised, yet known. EPA notes that the GWR was mammal relocation), security measures, and it requires PWSs to recycle filter also recently reviewed under Section runoff control, public health backwash water. 610 of the Regulatory Flexibility Act, surveillance, microbial monitoring (e.g., which required federal agencies to Cryptosporidium, E. coli) and a Summary of Review Results review regulations that have significant Cryptosporidium and Giardia action EPA reviewed this rule as part of the economic impact on a substantial plan.6 EPA reviewed information Six-Year Review 3, and the result is to number of small entities within 10 years pertaining to these activities and take no action on the basis that EPA did after their adoption as final rules. The concluded that the information is not identify any relevant information 610 Review of the GWR was recently inadequate to support regulatory that indicate changes to the NPDWR. completed; three comments were changes at the national level. The data received. A report is available is also insufficient to demonstrate that d. GWR discussing the 610 Review, comments risk management activities provide Background received, and EPA’s response to major equivalent public health protection comments (USEPA, 2016g). EPA promulgated the GWR in 2006 compared to covering the reservoir or (71 FR 65573, USEPA, 2006b) to provide Health Effects treating the outflow from the reservoir. The LT2 includes disinfection profile protection against microbial pathogens Borchardt et al. (2012) studied the and benchmark requirements to ensure in PWSs using ground water sources. health effects associated with enteric that any significant change in The rule establishes a risk-based virus occurrence in undisinfected PWS disinfection, whether for disinfection approach to target undisinfected ground wells in 14 communities in Wisconsin. byproducts control under the Stage 2 water systems that are vulnerable to Drinking water samples were assayed D/DBPR, improved Cryptosporidium fecal contamination. If a system has an for a suite of viral pathogens using control under the LT2, or both, does not initial total coliform positive in the quantitative polymerase chain reaction significantly compromise existing distribution system (based on routine (qPCR). Community members kept daily Giardia and virus protection. The coliform monitoring under the RTCR), diaries to self-report AGI. The study profiling and benchmarking followed by a fecal indicator positive found a statistically significant requirements under the LT2 are similar (E. coli, enterococci or coliphage) in a association between enteric virus to those promulgated under the IESWTR follow-up source water sample, it is occurrence in the drinking water and and the LT1 (USEPA, 2002c) and are considered to be at risk of fecal AGI incidences in the communities. applicable to systems that make a contamination. Systems at risk of fecal Using the 2005 data, EPA estimated a significant change to their disinfection contamination must take corrective national average TC detection rate of 2.4 practices. action to reduce potential illness from percent for routine samples from EPA did not identify information that exposure to microbial pathogens. undisinfected CWSs with populations would support a potential change to the Disinfecting systems that can less than 4,100 people (USEPA, 2012). methodology and calculations for demonstrate 4-log virus inactivation are The 14 communities (with developing the disinfection profile and not subject to the monitoring undisinfected PWS wells) studied by benchmark under the LT2. However, requirements. Borchardt et al. (2012) had TC EPA identified information that would In addition to the protection provided detections of 2.3 percent. These data support a potential change to the CT by the Revised Total Coliform Rule suggest that the 14 communities studied values required for virus disinfection (as (RTCR) and GWR monitoring by Borchardt et al. (2012) had TC discussed in the Section VI.B.4.a. requirements, systems that do not detection rates no different from an ‘‘SWTRs’’). EPA is considering this disinfect are also protected by the average undisinfected community PWS information in the review of the overall sanitary survey provisions of the GWR in the U.S. and the Level 1 assessment provisions filtration and disinfection requirements Analytical Methods in the SWTR. of the RTCR. Since the promulgation of the GWR in Based on the outcome of this review, Summary of Review Results 2006, EPA has approved several new EPA determined that no regulatory EPA has not identified the GWR as a methods for the analysis of TC samples revisions to the microbial toolbox candidate for revision under the Six- used as a trigger for GWR source water options are warranted at this time. Any Year Review 3 because EPA needs to monitoring, or for source water fecal new information available to the Agency evaluate emerging information from full indicators used under the GWR. These methods can be found on the EPA Web 6 http://www.nyc.gov/html/dep/pdf/reports/fad_ implementation of the GWR (71 FR 4.1_waterfowl_managementprogram_annual_ 65573, USEPA, 2006b) and the RTCR site (https://www.epa.gov/ report.07-12.pdf. (78 FR 10270, USEPA, 2013a) before dwanalyticalmethods/approved-

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drinking-water-analytical-methods). softening or other treatment. The targeted constraints on precursors (e.g., However, PWSs are not required to use UCMR3 monitoring results are available based on watershed vulnerabilities) that these new methods. Additionally, EPA online at: https://www.epa.gov/dwucmr/ could provide for an improvement in did eliminate the use of fecal coliforms data-summary-third-unregulated- health protection from mixtures of DBPs from the RTCR as an indicator of fecal contaminant-monitoring-rule. while considering risk-balancing. For contamination. VII. EPA’s Request for Comments and example, commenters are requested to Occurrence and Exposure Next Steps provide information about an approach that provides for an option to either New information suggests that total EPA invites commenters to submit control source water vulnerabilities coliform occurrence varies among small any relevant data or information (e.g., de facto reuse) or to further undisinfected ground water systems, pertaining to the NPDWRs identified in constrain precursors associated with depending upon whether the system is this action as candidates for revision, as unregulated DBPs. In addition, a community, non-transient non- well as other relevant comments. EPA commenters are requested to provide community or transient non-community will consider the public comments and/ information that considers a PWS (USEPA, 2016n). Statistical or any new, relevant data submitted for comprehensive analysis of source modeling of 2011 data (about 60,000 the eight NPDWRs listed as candidates waters for the formation of a wide systems based on occurrence data for revision as the Agency moves variety of byproducts (e.g., TTHM, collected from undisinfected ground forward in determining whether HAA5, and unregulated DBPs such as water systems) shows that undisinfected regulatory revisions for these NPDWRs nitrosamines, brominated and iodinated transient non-community ground water are necessary. The announcement compounds). systems have the highest occurrence, at whether or not the Agency intends to • Potential approaches that could approximately four percent median revise an NPDWR (pursuant to SDWA enhance protection from chlorite, routine TC positive occurrence as § 1412(b)(9)) is not a regulatory chlorate, and chlorine dioxide. compared with three percent for decision. Specifically, commenters are requested undisinfected non-transient non- Relevant data include studies/ to provide information about community ground water systems and analyses pertaining to health effects, approaches that could involve, for two percent for undisinfected analytical feasibility, treatment example: Setting standards for systems community ground water systems feasibility and occurrence/exposure. using hypochlorite that address (USEPA, 2016n). These occurrence This information will inform EPA’s combined exposure to chlorite and levels are similar to those estimated evaluation as the Agency moves forward chlorate; and setting standards for during the development of the RTCR determining whether regulatory systems using chlorine dioxide (alone or using 2005 data (USEPA, 2012). revisions for these NPDWRs are in combination with other disinfectants) Additionally, according to the 2005 and necessary. The data and information 2011 datasets, the smaller systems had requested by EPA include peer- that address combined exposure from reviewed science and supporting chlorite, chlorate, and chlorine dioxide. higher median TC occurrence than the • larger systems. All positive total studies conducted in accordance with Potential approaches that could coliform samples were assayed for E. sound and objective scientific practices, provide increased protection from coli; about one in 20 were E. coli and data collected by accepted methods microbial pathogens and that take into positive. or best available methods (if the consideration the issues noted about A small percentage of undisinfected reliability of the method and the nature disinfection residual requirements, ground water systems have higher TC of the review justifies use of the data). while considering the risk-balancing detection rates. For example, of the Peer-reviewed data are studies/ aspects of the MDBP rules. In addition, 52,000 undisinfected transient, non- analyses that have been reviewed by commenters are requested to provide community ground water systems qualified individuals (or organizations) information about approaches that serving populations less than 101 who are independent of those who could offer enhanced protection without people (the total count is from USEPA, performed the work, but who are the use of a chlorine-based disinfectant 2006b), EPA (2012) estimated that about collectively equivalent in technical residual in the distribution system, 2,600 (five percent) of those systems (4.6 expertise (i.e., peers) to those who including technology and management percent for the 2005 data set) had TC performed the original work. A peer systems associated with those detection rates of 20 percent or more. review is an in-depth assessment of the approaches. Under the third monitoring cycle of assumptions, calculations, • Information about how frequently the Unregulated Contaminant extrapolations, alternate interpretations, PWS monitor for DBPs during chlorine Monitoring Rule (UCMR3), EPA methodology, acceptance criteria and burn periods, including revised sampled about 800 randomly selected conclusions pertaining to the specific monitoring schedules for DBPs, taking undisinfected ground water systems major scientific and/or technical work into account occurrence and exposure to serving fewer than 100 people for virus products and the documentation that DBPs during chlorine burn periods, and and virus indicators. These data show supports them (USEPA, 2015a). related short-term health effects on that only a small number of samples Specifically, EPA is requesting sensitive populations. were virus positive by qPCR (16 out of comment and/or information related to References 1,044 or two percent) (USEPA, 2016j). the following aspects of potential This result contrasts significantly with revisions to the MDBP NPDWRs: Abdel-Rahman, M.S., D. Couri, and R.J. Bull. the virus positive sample rate from • Potential approaches that could 1984. Toxicity of chlorine dioxide in Borchardt et al. (2012) (287 out of 1,204 enhance protection from DBPs, drinking water. International Journal of or 24 percent). One difference is that including both those that are regulated Toxicology. 3(4): 277–284. Agency for Toxic Substances and Disease Borchardt et al. (2012) sampled prior to and those currently unregulated (e.g., Registry (ATSDR). 2010. Toxicological any treatment in the undisinfected wells nitrosamines). Specifically, commenters Profile for Trichlorobenzenes. U.S. (e.g., softening, iron/manganese are requested to provide information Department of Health and Human removal). In contrast, many wells in the about requiring greater removal of Services: Atlanta, GA. http:// UCMR3 virus study were sampled after precursors (e.g., TOC), and/or more www.atsdr.cdc.gov/toxprofiles/tp199.pdf

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Prevention, Pesticides, and Toxic Relative Source Contribution Analysis. USEPA. 2015b. Revisions to the Unregulated Substances: Washington, DC. http:// EPA 820–R–10–015. December 2010. Contaminant Monitoring Rule (UCMR4) for archive.epa.gov/pesticides/reregistration/ USEPA. 2010d. Integrated Risk Information Public Water Systems and Announcement web/pdf/endothall_red.pdf System (IRIS): Toxicological Review of cis- of a Public Meeting. 70 FR 76897. December 11, 2015. Available online at: USEPA. 2005g. Technologies and Costs for 1,2-Dichloroethylene and trans-1,2- https://www.epa.gov/sites/production/ the Final Long Term 2 Enhanced Surface Dichloroethylene in Support of Summary files/2015–11/documents/ucmr4_proposal_ Water Treatment Rule and Final Stage 2 Information. National Center for 151130.pdf. Disinfectants and Disinfection Byproducts Environmental Assessment, Office of USEPA. 2016a. Analytical Feasibility Rule. EPA 815–R–05–012. December 2005. 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National Primary Drinking Washington, DC. http://cfpub.epa.gov/ _ Regulatory Revisions in Support of the Water Regulations: Long Term 2 Enhanced ncea/iris/iris documents/documents/ Third Six-Year Review of the National Surface Water Treatment Rule; Final Rule. toxreviews/0060tr.pdf Primary Drinking Water Regulations: 71 FR 654. January 5, 2006. USEPA. 2010f. Long Term 2 Enhanced Chemical Phase Rules and Radionuclides USEPA. 2006d. National Primary Drinking Surface Water Treatment Rule Toolbox Rules. EPA–810–R–16–003. Water Regulations: Stage 2 Disinfectants Guidance Manual. EPA 815–R–09–016. USEPA. 2016d. Development of Estimated and Disinfection Byproducts Rule; Final April 2010. Quantitation Levels for the Third Six-Year Rule. 71 FR 388. January 4, 2006. USEPA. 2010g. Memorandum: Updated Review of National Primary Drinking USEPA. 2006e. Reregistration Eligibility toxicity endpoints for oxamyl. Office of Water Regulations (Chemical Phase Rules). 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