ENVIRONMENTAL PR OTECTION AGENCY [EPA-HQ-OW-2008-0747; FRL– ] RIN 2040-AE90 National Primary Drinking Water Regulation s; Announcement of the Results of EPA’s Review of Existing Drinking Water Standard s and Request for Public Comment and/or Information on Related Issues AGENCY: Environmental Protection Agency (EPA). ACTION: Notice; request for comments. SUMMARY: The Safe Drinking Water Act (SDW A) requires the United States Environmental Protection Agency (EPA) to conduct a periodic review of existing National Primary Drinking Water Regulations (NPDWRs) and determine which, if any, need to be revised. The purpose of the review, called th e Six-Year Review, is to identify those NPDWRs for which current health effects asse ssments, changes in technology, and/or other factors provide a health or technical basis to support a regulatory re vision that will improve or strengthen public health protection. EP A has completed its de tailed review of 71 NPDWRs and at this time believes that four NPDWRs are candidates fo r regulatory revision. These four NPDWRs are acrylamide, epic hlorohydrin, tetrachl oroethylene, and trichloroethylene. EPA requests public comment and/or relevant information that will assist the Agency as we move forward with regulatory action to revise thes e four NPDWRs. In addition to the 71 NPDWRs discussed in detail in today’s action, this review also includes 14 other NPDWRs that need no detailed review because of recent or ongoing revision actions. DATES: Comments must be re ceived on or before [INSERT DATE 60 DAYS AFTER THE DATE OF THE PUBLICATION IN THE FEDERAL REGISTER] , 60 days after publication in the Federal Register. ADDRESSES : Submit your comments, identifie d by Docket ID No. EPA-HQ-OWMay 2009 Draft EPA document. Do not cite or distribute. 12008-0747, by one of the following methods:

• http://www.regulations.gov : Follow the online instructions for submitting comments.

• Mail: Water Docket, Environmental Protection Agency, Mailcode: 2822T, 1200 Pennsylvania Ave., NW, Washington, DC 20460.

• Hand Delivery: EPA Docket Center Public Reading Room, EPA Headquarters West, Room 3334, 1301 Constitution Ave., NW, Wash ington, DC. Such deliveries are only accepted during the Docket's normal hours of operation, and special arrangements should be made for deliveries of boxed information.
Instructions : Direct your comments to Docket ID No. EPA-HQ-OW-2008-0747. EPA's policy is that all comments received will be in cluded in the public docket without change and may be made available online at http://www.regulations.gov , including any personal information provided, unless the comment includes informa tion claimed to be Confidential Business Information (CBI) or other information whose disclo sure is restricted by st atute. Do not submit information that you consider to be CBI or otherwise protected using http://www.regulations.gov . Please contact EPA prior to submitting CBI. The http://www.regulations.gov web site is an “anonymous access” system, which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an e-mail comment directly to EPA without going through http://www.regulations.gov your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, EPA recommends th at you include your name and other contact information in the body of your comment and withany disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification,

May 2009 Draft EPA document. Do not cite or distribute. 2EPA may not be able to consider your comment. Electronic files should a void the use of special characters, any form of encryption, and be free of any defects or viru ses. For additional instructions on submitting comments, go to section I.B of this document.
Docket : All documents in the doc ket are listed in the http://www.regulations.gov index. Although listed in the index, some information is not publicly availabl e, e.g., CBI or other information whose disclosure is re stricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in http://www.regulations.govor in hard copy at the Water Docket, EPA/ DC, EPA West, Room 3334, 1301 Constituti on Ave., NW, Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4: 30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Publ ic Reading Room is (202) 566-1744, and the telephone number for the EPA Do cket Center is (202) 566-2426. FOR FURTHER INFORMATION CONTACT: For technical inquiries contact: Rajiv Khera, (202) 564–4881, or Karen Wirth, (202) 564-5246, Office of Ground Water and Drinking Water, Environmental Protection Agency

. For general information about, and copies of, this document or information about the existing NPDWRs discussed in this action, contact the Safe Drinking Water Hotline. Callers within the United States may reach the Hotline at (800) 426- 4791. The Hotline is open Monday through Friday, excluding Federal holidays, from 9 a.m. to 5:30 p.m. Eastern Time. ABBREVIATIONS AND ACRONYMS USED IN THIS ACTION >—greater than 2,4-D—2,4-dichlorophenoxyacetic acid
μ g/L—microgram per liter

May 2009 Draft EPA document. Do not cite or distribute. 3AMG—Alternative Monitoring Guidelines ASDWA—Association of State Dr inking Water Administrators ATSDR—Agency for Toxic Substances and Disease Registry AWWA—American Water Works Association BAT—best available technology CARC—Cancer Assessment Review Committee CBI—Confidential Business Information CCL—Contaminant Candidate List
CFR— Code of Federal Regulations Cr III—trivalent chromium Cr VI—hexavalent chromium CWS—community water system DBPs—disinfection byproducts DBCP—1,2-dibromo-3-chloropropane DBPR—Disinfectants and Di sinfection Byproducts Rule DEHA—di(2-ethylhexyl)adipate DEHP—di(2-ethylhexyl)phthalate DWEL—drinking water equivalent level EDB—ethylene dibromide EPA—U.S. Environmental Protection Agency EQL—estimated quantitation level ESA—ethanesulfonic acid
FR— Federal Register

May 2009 Draft EPA document. Do not cite or distribute. 4FQPA—Food Quality Protection Act GAC—granular activated carbon GWR—Ground Water Rule HAA5—haloacetic acids IARC—International Agency for Research on Cancer ICR—Information Collection Request IRED—Interim Reregistrati on Eligibility Decision IRIS—Integrated Risk Information System LCR—Lead and Copper Rule LH—lutenizing hormone LOAEL—lowest-observed- adverse-effect level LT2ESWTR—Long-Term 2 Enhanced Surface Water Treatment Rule MCL—maximum contaminant level MCLG—maximum contaminant level goal MDL—method detection limit mg/kg-day—milligrams per kil ogram of body weight per day mg/L—milligrams per liter MOA—mode of action MRL—minimum reporting level N—nitrogen NAS—National Academy of Sciences NAWQA—National Water Quality Assessment NCFAP—National Center for Food and Agricultural Policy

May 2009 Draft EPA document. Do not cite or distribute. 5NCOD—National Drinking Water C ontaminant Occurrence Database NDWAC—National Drinking Water Advisory Council NELAC—National Environmental Labor atory Accreditation Conference NOAEL—no-observed-adverse-effect level NPDWR—National Primary Dr inking Water Regulation NRC—National Research Council NTNCWS—non-transient, non-community water system NTP—National Toxicology Program OPP—Office of Pesticide Programs ORD—Office of Research and Development OW—Office of Water PCBs—polychlorinated biphenyls PCE—tetrachloroethylene PE—Performance Evaluation pCi/L—picoCurie per liter PN—public notification ppb—part per billion (e.g., microgram per liter) ppm—part per million (e.g., milligram per liter) PQL—practical quantitation limit PT—Performance Testing PTA—packed tower aeration PWS—public water system R2S2—Regulatory Review Support Spreadsheet

May 2009 Draft EPA document. Do not cite or distribute. 6RED—Reregistration Eligibility Decision RfD—reference dose RSC—relative source contribution SAB—Science Advisory Board SSCT—Small System Compliance Technology SDWA—Safe Drinking Water Act SDWIS/FED—Safe Drinking Water Info rmation System/Federal version SMCL—secondary maximum contaminant level SOC—synthetic organic chemical STORET—STOrage and RETrieval data system SWTR—Surface Water Treatment Rule T3—triiodothyronine (thyroid hormone) T4—levothyroxine (thyroid hormone) TCDD—tetrachlorodibenzo-p-dioxin TCE—trichloroethylene TNCWS—transient, non-com munity water system TP—trichlorophenoxypropionic acid TRED—Interim Tolerance Reassessment and Risk Management Decisions TRI—Toxics Release Inventory TSC—Technical Support Center TT—treatment technique TTHM—total trihalomethanes USDA—U.S. Department of Agriculture

May 2009 Draft EPA document. Do not cite or distribute. 7UCMR 2—second Unregulated Contaminant Monitoring Rule USGS—U.S. Geological Survey VOC—volatile organic compound WS—water supply Table of Contents

I. General Information .............................................................................................................10 A. Does This Action Apply to My Public Water System? .....................................................10 B. How Should I Submit Comments on This Action? ...........................................................11 C. What Should I Consider as I Prepare My Comments for EPA?........................................11 II. Statutory Requirements for the Six-Year Review ..............................................................12 III. Stakeholder Involvement in the Six-Year Review Process ...............................................12 A. How Have Stakeholders Been I nvolved in the Review Process?......................................12 B. How Did EPA Incorporate Feedback fromthe Science Advisory Board’s 2002 Comments on the Six-Year Review Protocol? ..............................................................................13 IV. Regulations Included in the Six-Year Review ..................................................................13 V. EPA’s Protocol for Reviewing th e NPDWRs Included in This Action ..............................16 A. What Was EPA’s Review Process? ...................................................................................16 B. How Did EPA Conduct the Initial Review and Evaluate Key Technical Elements of the NPDWRs? 21

58 1. Initial Review .....................................................................................................................21 2. Health Effects .....................................................................................................................23 3. Analytical Feasibility .........................................................................................................28 4. Occurrence and Exposure Analysis ...................................................................................35 5. Treatment Feasibility .........................................................................................................41 6. Other Regulatory Revisions ...............................................................................................42 C. How Did EPA Factor Children’s Health Concerns Into the Review?...............................46 VI. Results of EPA’s Review of NPDWRs .............................................................................47 A. What are the Review Result Categories? ...........................................................................47 1. No Action at this Time and the NPDWR is Still Appropriate. ..........................................47 2. Candidate for Revision. .....................................................................................................48 B. What Are the Details of EPA’s Review of Each NPDWR? .............................................50 1. Acrylamide ...........................................................................................................................50 2. Alachlor

............................................................................................................................... .52 3. Alpha Particle Emitters ........................................................................................................56 4. Antimony

............................................................................................................................. 5. Arsenic

............................................................................................................................... ..58
May 2009 Draft EPA document. Do not cite or distribute. 86. Asbestos

............................................................................................................................... 59

84

114 115
121

126 7. Atrazine

............................................................................................................................... .60 8. Barium

............................................................................................................................... ...61 9. Benzene

............................................................................................................................... .64 10. Benzo(a)pyrene ..................................................................................................................68 11. Beryllium ...........................................................................................................................70 12. Beta Particle and Photon Emitters .....................................................................................71 13. Cadmium ............................................................................................................................73 14. Carbofuran .........................................................................................................................73 15. Carbon Tetrachloride .........................................................................................................75 16. Chlordane ...........................................................................................................................79 17. Chromium ..........................................................................................................................82 18. Cyanide

.............................................................................................................................. 19. 2,4-D (2,4-Dichlorophenoxyacetic acid) ...........................................................................85 20. Dalapon (2,2-Dichloropropionic Acid) ..............................................................................87 21. Di(2-ethylhexyl)adipate (DEHA) ......................................................................................88 22. Di(2-ethylhexyl)phthalate (DEHP)....................................................................................89 23. 1,2-Dibromo-3-chloropropane (DBCP) .............................................................................90 24. 1,2-Dichlorobenzene (o-Dichlorobenzene)........................................................................94 25. 1,4-Dichlorobenzene (p-Dichlorobenzene)........................................................................94 26. 1,2-Dichloroethane (Ethylene Dichloride) .........................................................................95 27. 1,1-Dichloroethylene .........................................................................................................99 28. cis-1,2-Dichloroethylene..................................................................................................102 29. trans-1,2-Dichloroethylene ..............................................................................................103 30. Dichloromethane (Methylene Chloride) ..........................................................................103 31. 1,2-Dichloropropane ........................................................................................................110 32. Dinoseb

............................................................................................................................ 33. Diquat

............................................................................................................................... 34. Endothall ..........................................................................................................................118 35. Endrin

............................................................................................................................... 36. Epichlorohydrin ...............................................................................................................122 37. Ethylbenzene ....................................................................................................................124 38. Ethylene Dibromide (EDB; 1,2-Dibromoethane) ............................................................125 39. Fluoride

............................................................................................................................ 40. Glyphosate .......................................................................................................................129 41. Heptachlor ........................................................................................................................131 42. Heptachlor Epoxide .........................................................................................................135 43. Hexachlorobenzene ..........................................................................................................138 44. Hexachlorocyclopentadiene .............................................................................................142 45. Lindane (gamma-Hexachlorocyclohexane) .....................................................................145 46. Mercury (Inorganic) .........................................................................................................148 47. Methoxychlor ...................................................................................................................149 48. Monochlorobenzene (Chlorobenzene) .............................................................................150 49. Nitrate (as N)....................................................................................................................150 50. Nitrite (as N) ....................................................................................................................152 51. Oxamyl (Vydate) .............................................................................................................154

May 2009 Draft EPA document. Do not cite or distribute. 952. Pentachlorophenol ............................................................................................................158 53. Picloram ...........................................................................................................................160 54. Polychlorinated Biphenyls (PCBs) ..................................................................................163 55. Combined Radiums (226 and 228) ..................................................................................164 56. Selenium ..........................................................................................................................166 57. Simazine ...........................................................................................................................167 58. Styrene

............................................................................................................................. 168

176 59. 2,3,7,8-TCDD (Dioxin) ....................................................................................................169 60. Tetrachloroethylene .........................................................................................................170 61. Thallium ...........................................................................................................................174 62. Toluene

............................................................................................................................ 63. Toxaphene ........................................................................................................................179 64. 2,4,5-TP (Silvex; 2,4,5-Tric hlorophenoxypropionic Acid) .............................................182 65. 1,2,4-Trichlorobenzene....................................................................................................183 66. 1,1,1-Trichloroethane.......................................................................................................184 67. 1,1,2-Trichloroethane.......................................................................................................186 68. Trichloroethylene.............................................................................................................190 69. Uranium ...........................................................................................................................194 70. Vinyl chloride ..................................................................................................................195 71. Xylenes (Total) ................................................................................................................199 VII. EPA’s Request for Comments .......................................................................................201 A. Request for Comment and/or Inform ation on the Candidates for Revision ....................201 B. Request for Information/Data on Other Review Topics ..................................................202 C. Requests for Information on the Impacts of Climate Change on Water Quality .............203 VIII. EPA’s Next Steps .........................................................................................................203 IX. References .......................................................................................................................204

SUPPLEMENTARY INFORMATION:

I. General Information A. Does This Action Apply to My Public Water System? This action itself does not impose any requireme nts on anyone. Instead, it notifies interested parties of EPA’s review of ex isting NPDWRs and its conclusions about which of these warrants new regulatory action at this time. EPA requests public comment on the four NPDWRs identified as candidates for revision, with a specific focus on comments and/or relevant information that will inform the regulatory revisions.

May 2009 Draft EPA document. Do not cite or distribute. 10B. How Should I Submit Comments on This Action? Please see Section VII for the i ssues related to this notice for which EPA requests comment and/or information. EPA will accept written or electronic comments (please do not send both). Instructions for submitting comments are in th e preceding section. EPA prefers electronic comments. No facsimiles (faxes) will be accep ted. Commenters who want EPA to acknowledge receipt of their comments should also send a self-addressed, stamped envelope. The Agency intends to address the comments received on the four NPDWRs identified as candidates for revision in subsequent Federal Register notices propos ing and finalizing the regulatory revisions, and in docum ents that will be made available in the docket for those notices.

C. What Should I Consider as I Prepare My Comments for EPA? You may find the following suggestions helpful for preparing your comments:

• Explain your views as clearly as possible.

• Describe any assumptions that you used.

• Provide any technical information and/or data you used that support your views.

• If you estimate potential burden or costs, explain how you arrived at your estimate.

• Provide specific examples to illustrate your concerns.

• Offer alternatives.

• Make sure to submit your comments by the comment period deadline.

• To ensure proper receipt by EPA, identify the appropriate docket identification number in the subject line on the first page of your response. It would also be helpful if you provided the name, date, and Federal Register citation related to your comments.

May 2009 Draft EPA document. Do not cite or distribute. 11II. Statutory Requirements fo r the Six-Year Review Under the SDWA, as amended in 1996, EPA mu st periodically revi ew existing national primary drinking water regulati ons (NPDWRs) and, if appropriate, revise them. Section 1412(b)(9) of SDWA states: The Administrator shall, not less often than every 6 years, review and revise, as appropriate, each national primary drinking water regulation promulgated under this title. Any revision of a national primary drinking water regulation shall be promulgated in accordance with this section, except that each revision shall maintain, or provide for greater, protecti on of the health of persons. Pursuant to the 1996 SDWA Amendments, EPA completed and published the results of its first Six-Year Review (Six-Year Review 1) July 18, 2003 (68 FR 42908, USEPA, 2003e) after developing a systematic approach, or protocol, for the review of NPDWRs. EPA has applied the same protocol with minor refinements (revised protocol) to the second Six-Year Review of NPDWRs (Six-Year Review 2). Section V of today’s action describes the protocol and the minor refinements used for the Six-Year Review 2 and section VI describes the review findings for each of the NPDWRs covered by the current effort (see Table IV-1 ).

III. Stakeholder Involvement in the Six-Year Review Process A. How Have Stakeholders Been Involved in the Review Process? The Agency developed a Six-Year Review pr otocol during the first review cycle with extensive stakeholder inputs, incl uding a stakeholder meeting, Agency presentations at a variety of meetings, and consultation with the Nationa l Drinking Water Advisory Council (NDWAC). NDWAC formed a working group to develop recommendations regarding the process the Agency should apply to conduct a periodic and sy stematic review of existing NPDWRs. The Working Group held two meetings and a conf erence call during June through September 2000 (67 FR 19030, April 17, 2002, USEPA, 2002c). The NDWAC approved the Working Group’s recommendations in November 2000, and forma lly provided them to EPA in December 2000 May 2009 Draft EPA document. Do not cite or distribute. 12(NDWAC, 2000). The NDWAC recommended that EP A’s review include c onsideration of five key elements, as appropriate: health effects, an alytical and treatment feasibility, implementationrelated issues, occurrence and exposure, and econo mic impacts. As discussed in more detail in section V of today’s action, EPA continues to follow the genera l protocol recommended by the
NDWAC.

B. How Did EPA Incorporate Feedback from the Science Advisory Board’s 2002 Comments on the Six-Year Review Protocol? In June 2002 and during the Six-Year Review 1, EPA consulted with the Science Advisory Board (SAB) Drinking Water Committee and reque sted their review and comment on whether the protocol that EPA developed based on th e NDWAC’s recommendations was consistently applied and appropriately documented. The SA B provided verbal feed back regarding the transparency and clarity of EPA's criteria for maki ng its Six-Year Review 1 decisions. At that time, EPA revised the protocol to better explain how the decision criteria were applied. For the Six-Year Review 2 and to increase transparency and clarity, EPA also developed a more detailed decision tree and an automated tool, called the Regulatory Review Support Spreadsheet (R2S2). The more detailed decision tree incorporates the sequential rela tionships between the various NPDWR review elements and R2S2 tracks each contaminant through the decision making process. The Agency has documented the decisiontree and the automated tool in the document, “EPA Protocol for the Second Review of Exis ting National Primary Drinking Water Regulations (Updated)” (USEPA, 2009a).

IV. Regulations Included in the Six-Year Review Table IV-1 lists all the NPDWRs established to da te. The table also reports the maximum contaminant level goal (MCLG), which is “set at the level at which no known or anticipated

May 2009 Draft EPA document. Do not cite or distribute. 13adverse effects on the health of persons occur and which allows an adequate margin of safety” (SDWA section 1412(b)(4)), and the maximum contaminant level (MCL), which is the maximum permissible level of a contaminant in water delivered to any user of a public water system and “is as close to the maximum contamin ant level goal as is feasible” (SDWA section 1412(b)(4)(B)), except for contaminan ts that have a treatment technique (TT) in lieu of an MCL because it is not “economically or technicallyfeasible” to set an MCL (SDWA section 1412(b)(7)(A)). Of these 85 NPDWRs, EPA has reviewed 14 as part of recent or ongoing regulatory actions and, as a result, they are not subject to a detailed review in today’s notice. The review for the remaining 71 is disc ussed in detail in today’s action.

Table IV-1. Contaminants with NPDW Rs Included in Six-Year Review 2 Contaminants MCLG (mg/L) 1 MCL (mg/L) 1 Contaminants MCLG (mg/L) 1 MCL (mg/L) 1 Acrylamide 0 TT Epichlorohydrin 0 TT

Alachlor 0 0.002 Ethylbenzene 0.7 0.7 Alpha particles 0 (pCi/L) 15 (pCi/L) Ethylene dibromide (EDB) 0 0.00005 Antimony 0.006 0.006 Fluoride 4 4 Arsenic 0 0.01 Giardia lamblia 0 TT Asbestos 7 (million fibers/L) 7 (million fibers/L) Glyphosate 0.7 0.7 Atrazine 0.003 0.003 Haloacetic acids (HAA5) n/a 2 0.06 Barium 2 2 Heptachlor 0 0.0004 Benzene 0 0.005 Heptachlor Epoxide 0 0.0002 Benzo(a)pyrene 0 0.0002 Hexachlorobenzene 0 0.001 Beryllium 0.004 0.004 Hexachlo rocyclopentadiene 0.05 0.05 Beta particles 0 (millirems/yr) 4 (millirems/yr) Lead 0 TT Bromate 0 0.01 Legionella 0 TT Cadmium 0.005 0.005 Lindane 0.0002 0.0002 Carbofuran 0.04 0.04 Mercury (Inorganic) 0.002 0.002 Carbon tetrachloride 0 0.005 Methoxychlor 0.04 0.04 Chloramines 4 4 Monochlorobenzene (Chlorobenzene) 0.1 0.1 Chlordane 0 0.002 Nitrate (as nitrogen, N) 10 10

Chlorine 4 4 Nitrite (as N) 1 1 Chlorine dioxide 0.8 0.8 Oxamyl (Vydate) 0.2 0.2 Chlorite 0.8 1 Pentachlorophenol 0 0.001 Chromium (total) 0.1 0.1 Picloram 0.5 0.5 Coliform 0% 3 5% 3 Polychlorinated biphenyls (PCBs) 0 0.0005

May 2009 Draft EPA document. Do not cite or distribute. 14Table IV-1. Contaminants with NPDW Rs Included in Six-Year Review 2 Contaminants MCLG (mg/L) 1 MCL (mg/L) 1 Contaminants MCLG MCL (mg/L) 1 (mg/L) 1 Copper 1.3 TT Radium 0 (pCi/L) 5 (pCi/L) Cryptosporidium 0 TT Selenium 0.05 0.05 Cyanide 0.2 0.2 Simazine 0.004 0.004

2,4- Dichlorophenoxyacetic acid (2,4-D) 0.07 0.07 Styrene 0.1 0.1

Dalapon 0.2 0.2 2,3,7,8-Tetrachlorodibenzop-dioxin (2,3,7,8-TCDD or dioxin) 0 3.00E-08 Di(2-ethylhexyl)adipate (DEHA) 0.4 0.4 Tetrachloroethylene (PCE) 0 0.005 Di(2-ethylhexyl)phthalate (DEHP) 0 0.006 Thallium 0.0005 0.002 1,2-Dibromo-3- chloropropane (DBCP) 0 0.0002 Toluene 1 11,2-Dichlorobenzene (oDichlorobenzene) 0.6 0.6 Total trihalomethanes (TTHM) n/a 4 0.081,4-Dichlorobenzene (pDichlorobenzene) 0.075 0.075 Toxaphene 0 0.003 1,2-Dichloroethane (Ethylene dichloride) 0 0.005 2,4,5-Trichlorophenoxypropionic acid (2,4,5-TP or Silvex) 0.05 0.05 1,1-Dichloroethylene 0.007 0.007 1, 2,4-Trichlorobenzene 0.07 0.07 cis-1,2-Dichloroethylene 0.07 0. 07 1,1,1-Trichloroethane 0.2 0.2 trans-1,2- Dichloroethylene 0.1 0.1 1,1,2-Trichloroethane 0.003 0.005 Dichloromethane (Methylene chloride) 0 0.005 Trichloroethylene (TCE) 0 0.005 1,2-Dichloropropane 0 0.005 Uranium 0 ( μ g/L) 30 ( μ g/L) Dinoseb 0.007 0.007 Vinyl chloride 0 0.002 Diquat 0.02 0.02 Viruses 0 TT Endothall 0.1 0.1

Endrin 0.002 0.002 Xylenes (total) 10 10 1. Units are in milligrams per liter (mg/L) unle ss otherwise noted, e.g., micrograms per liter ( μ g/L) and picoCuries per liter (pCi/L). Milligrams per liter are equivalent to par ts per million (ppm) and micrograms per liter are equivalent to parts per billion (pp b). 2. There is no MCLG for all five haloacetic acids. MCLGs for so me of the individual contaminants are: dichloroacetic acid (zer o), trichloroacetic acid (0.02 mg/L), and monochloroacetic acid (0.07 mg/L). Bromoacetic acid and dibromoacetic acid are regulated with this group but have no MCLGs. 3. No more than 5.0% samples total coliform-positive in a month. 4. There is no MCLG for total trihalomethanes. MCLGs for some of the individual contaminants are: bromodichloromethane (zero), bromoform (zero), dibromochloromethane (0.06 mg/L), and chloroform (0.07mg/L).

May 2009 Draft EPA document. Do not cite or distribute. 15V. EPA’s Protocol for Reviewing the NPDWRs Included in This Action A. What Was EPA’s Review Process? The protocol document, “EPA Protocol for the Review of Existing National Primary Drinking Water Regulations (Updated)” (USEPA, 2009a ), contains a detailed description of the process the Agency used to review the NPDWRs discussed in today’s action. EPA’s primary goal was to identify and prioritize candidates for regulatory revision to target those revisions that are most likely to result in an increased leve l of public health protec tion and/or result in substantial cost savings for systems and their customers while maintaining the level of public health protection. This section provides an overview of the review process and section V.B provides a more detailed descri ption of how EPA applied the pr ocess to the review of the NPDWRs discussed intoday’s action. EPA applied the following basic prin ciples to the review process:

• The Agency sought to avoid redundant review efforts. Because EPA has reviewed information for 14 contaminants as part of re cent or ongoing regulatory actions, they are not subject to the detailed re view in today’s notice.

• EPA evaluated the potential for new information to affect NPDWRs in a manner consistent with existing policies and proce dures for developing NPDWRs. For example, in determining whether a possible change in analytical feasibil ity existed, the Agency considered the current policy and procedures for calculating the pr actical quantitation level for drinking water contaminants. 1

1 The following Federal Register notices describe the process the Agen cy has used to determine analytical feasibility for drinking water contaminants: 50 FR 46880, November 13, 1985 (USEPA, 1985); 52 FR 25690, July 8, 1987 (USEPA, 1987); 54 FR 22062, May 22, 1989 (USEPA, 1989b). For this Six Year Review effort and to supplement the analytical feasibility evaluation, the Agency also reviewed extensive minimum reporting level (MRL) data obtained from States and primacy entities as part of the Six-Year Review information collection request (ICR) for SDWA compliance monitoring data. May 2009 Draft EPA document. Do not cite or distribute. 16• Because any possible change in an MCLG affects other NPDWR elements, EPA will not generally consider potential revisions to any contaminant with a health effects assessment in process that would not be completed duri ng the review period, where either the contaminant’s MCL is equal to its MCLG or the MCL is based on the 1996 SDWA Amendments’ cost-benefit provision. The rati onale for this outcome is that any new information from the health effects assessment could affect the MCL or the assessment of the benefits associated with the MCL for these c ontaminants. Therefore, the Agency does not believe it is appropriate to c onsider revisions to these NP DWRs while a health effects assessment is ongoing.

• For this review, EPA considered new informati on from health effects assessments that were completed by a March 1, 2009 cutoff date. If an updated assessment is completed after the March 1, 2009 information cutoff date, then EPA will review the update and any new conclusions or additional inform ation associated with the cont aminant during the next review cycle or during the revision of an NPDWR (e .g., acrylamide, PCE and TCE). The Agency may consider accelerating a review and potential revision for a particul ar NPDWR before the next review cycle when justified by new public health risk information.

• During the review, EPA identified areas where in formation is inadequate or unavailable (data gaps) or emerging and is needed to determine whether revision to an NPDWR is appropriate. When the Agency is able to fill such gaps or fully evaluate the emerging information, the Agency will consider it as pa rt of the next review cycle. The Agency may consider accelerating a review and potenti al revision for a particular NPDWR if the information becomes available before the next review cycl e and if review and a potential revision are justified by new public hea lth risk information.

May 2009 Draft EPA document. Do not cite or distribute. 17• EPA applied the Agency’s peer review polic y (USEPA, 2000d), where appropriate, to any new analyses. During Six-Year Review 1, the Agency develo ped a systematic approach or protocol (USEPA, 2003b). The Agency based this prot ocol on the recommendations of the NDWAC, through internal Agency deliberations, and discus sions with the diverse group of stakeholders involved in drinking water a nd its protection. The overview of the protocol in Figure V-1 shows the sequence of key decisions that led to EP A assigning each NPDWR to one of two major categories of outcomes in the Six-Year Review 2. The two major outcomes of the review are either: 1) the NPDWR is still appropriate and no action is necessary at this time, or 2) the NPDWR is a candidate for revision. The reasons for a Six-Year Review outcome of no further action at this time include:

• The NPDWR has been reviewed or is being reviewed in a recent or ongoing action;

• The NPDWR has an ongoing health effects asse ssment (i.e., especially for those NPDWRs with an MCL set at the MCLG or the MCL is based on the SDWA cost benefit provision);

• EPA is considering whether a new he alth effects assessment is needed;

• EPA did not identify any new, relevant inform ation that indicate changes to the NPDWR;

• New information indicate a po ssible change to the MCLG and/or MCL but changes to the NPDWR are a low priority activity due to neglig ible gains in public he alth protection and/or cost savings; or

• There are data gaps or emerging info rmation that needs to be evaluated.

May 2009 Draft EPA document. Do not cite or distribute. 18Figure V-1. Six-Year Review Protocol Overview and Major Categories of Revise/Take No Action Outcomes

Yes

No New information to suggest possible changes (i.e., to an MCLG, MCL, Treatment Technique and/or other regulatory revisions)?

Meaningful opportunity for health risk reduction for persons served by PWS and/or cost savings while maintaining/improving public health protection? Outcome: No action at this time

Outcome: Candidate for Revision Data sufficient to support

regulatory revision? No new information

Low priority - No meaningful opportunity Data gaps/emerging information

Yes No Ongoing or planned HEA Health effects assessment (HEA) in process or planned? * NPDWRs Under Review

Yes No Yes

No NPDWR reviewed in recent or ongoing action?

No Yes Regulatory action ongoing or recently completed

* Contaminants with an HEA in process that have an MCL based on practical quantitation limit and are greater than MCLG are passed to the next question to evaluate potential to revise the MCL. Uncertain – emerging information

During the current Six-Year Review, the Agen cy assessed the protocol and determined it remained appropriate and suitable for the sec ond review. The research requirements and decision-making process of the Si x-Year Review 2 protocol are essentially the same as those implemented during Six-Year Review 1. The Agen cy made some minor refinements to enhance the Agency’s effectiveness in applying the protoc ol to the review of NPDWRs. The refinements that address SAB’s comments aboutthe clarity and the transparency of the protocol’s decision making process are described in the next two paragraphs. Section V.B describes the key technical elements and any refinements in the da ta and/or the analysis methods used during SixYear Review 2. May 2009 Draft EPA document. Do not cite or distribute. 19The primary refinement to the protocol during Six-Year Review 2 is the implementation of a more detailed “decision tree” than either the one used during Six-Y ear Review 1 (USEPA, 2003b) or the overview shown in Figure V-1 . The protocol is broken down into a series of questions about whether there is new informati on for a contaminant that suggests potential to revise each of the NPDWR elements . These questions are logicallyordered into a decision tree that incorporates the sequential relationships between the different NPDWR elements. For example, when EPA establishes an MCL, it must generally set the MCL as close to the MCLG as feasible. Consequently, for a c ontaminant that has an MCL equa l to its MCLG, EPA must make decisions about the availability and adequacy of new information regarding the possibility to revise the MCLG before decisions regarding the possibility to re vise the MCL. It also means that if there is no possibility to revise a cont aminant’s MCLG and the MCL is already equal to the MCLG, then there is no basis for revising the MC L. In this instance, the MCL branch of the decision tree is not reached, and it is not necessary to make related decisions such as whether the practical quantitation limit (PQL) can be revised. This approach results in a more efficient review process. EPA also developed an auto mated tool called the R2S2 that tracks each contaminant’s movement through the decision tree, including the revise/take no action outcomes. This tool enhances transparency throughout the decision process. The automation also streamlines the decision process and facilitates th e Agency’s reporting of its review results. The Agency has documented the decision tree and the automated tool in the document entitled, “EPA Protocol for the Second Review of Existing National Primary Drinking Water Regulations (Updated)” (USEPA, 2009a).

May 2009 Draft EPA document. Do not cite or distribute. 20B. How Did EPA Conduct the Initial Review and Evaluate Key Technical Elements of the NPDWRs? This section describes the speci fic technical reviews that EPA conducted, including the initial review, health effects, analytical methods, o ccurrence and exposure, treatment feasibility, and economic analysis.

1. Initial Review EPA’s initial review of all the contaminants included in the Six-Year Review 2 involved a simple identification of the NPDWRs that were being reviewed under concurrent EPA actions or had been reviewed and revised in EPA actions completed since 2002. Table V-1 provides a list of the 14 contaminants that met one of these crit eria and identifies the re cent or ongoing action in which the contaminant has been reviewed or is undergoing review. While these 14 contaminants are part of the Six-Year Review 2, they were not subject to any de tailed analysis given that new information on these contaminants has been recently reviewed under separate actions. However, EPA requests comments on these contaminants al ong with the other contaminants discussed in detail in this notice. The remaining 71 contaminants pass through this step to the review of the technical NPDWR elements, which are described in the following sections.

May 2009 Draft EPA document. Do not cite or distribute. 21Table V-1. NPDWRs That Have Been Reviewed or Are Being Re viewed Under Recent or Ongoing Actions Contaminant/Indicator Recent or Ongoing Action Disinfection Byproducts Bromate Stage 2 DBPR Chlorite 1 Stage 2 DBPR HAA5: monochloroacetic acid, dichloroacetic acid trichloroacetic acid, monobromoacetic acid dibromoacetic acid Stage 2 DBPR TTHMs: chloroform, bromodichloromethane, dibromochloromethane, bromoform Stage 2 DBPR Disinfectant Residuals Chloramines 1 Stage 2 DBPR Chlorine 1 Stage 2 DBPR Chlorine dioxide Stage 2 DBPR Inorganics Copper Under consideration for long-term revisions Lead LCR Short-Term Revisions Under consideration for long-term revisions Microorganisms Coliform Total Coliform Rule-making currently underway Cryptosporidium LT2ESWTR Giardia lamblia LT2ESWTR Legionella 2 LT2ESWTR CCL3 3

V iruses 2 LT2ESWTR GWR CCL3 3 DBPR – Disinfectants and Disinfection Byproducts Rule LT2ESWTR – Long-Term 2 Enhanced Surface Water Treatment Rule LCR – Lead and Copper Rule GWR – Ground Water Rule Dates of promulgation are as follows: Stage 2 DBPR: 71 FR 388, January 4, 2006 (USEPA, 2006h) LT2ESWTR: 71 FR 654, January 5, 2006 (USEPA, 2006g) LCR Short-Term Regulatory Revisions: 72 FR 57782, October 10, 2007 (USEPA, 2007f) GWR: 71 FR 65574, November 8, 2006 (USEPA, 2006f) 1. Although the standard for this disinfectant was not revised as part of the Stage 2 DBPR, regulatory revisions need to be considered in conjunction with other disinfectant residuals and disinfection byproducts. 2. LT2ESWTR and GWR promulgated treatment techniques th at built upon and enhanced the existing regulations (Surface Water Treatment Rule, Interim Enhanced Surface Water Treatment Rule, and Long-Term 1 Enhanced Surface Water Treatment Rule) that address broad categories of microorganisms in treated water. 3. Listed on the draft third Drinking Water Contaminant Candidate List or CCL3 (73 FR 9628, February 21, 2008 (USEPA, 2008b) in order to capture health and treatment informati on that may not be addressed by the current regulations.

May 2009 Draft EPA document. Do not cite or distribute. 222. Health Effects The document, “Six-Year Review 2 —Health Effects Assessment - Summary Report” (USEPA, 2009b), describes how EPA reviewed the contaminants discussed in today’s action and provides the results of the health effects technical review. The prin cipal objectives of the health effects review are to identify: 1) contaminan ts for which a new health effects assessment indicates that a change in MC LG might be appropriate (e.g., because of a change in cancer classification or a reference dose (RfD)), and 2) contaminants for which the Agency identifies new health effects information suggesting a need to initiate a new hea lth effects assessment. To meet the first objective, the Agency review ed the results of hea lth effects assessments completed under the following programs and identif ied, where feasible, possible MCLG values.

• EPA Integrated Risk Information System (IRIS)

• EPA Office of Pesticide Programs (OPP)

• National Academy of Sciences (NAS; when commissioned by EPA). To meet the second objective, the Agency first conducted an extensive literature review to identify peer-reviewed studies. Then the Agen cy reviewed the studies to determine whether there was new health effects information such as reproductive and developmental toxicity that potentially affects the MCLG of any of the remaining contaminants that do not have an ongoing health effects assessment, including those with re cently completed health effects assessments. Table V-2 reflects the outcome of the health eff ects review for the NPDWRs discussed in today’s action. EPA placed each contaminant into one of the following categories.

• Agency health effects assessment in process and not completed as of March 1, 2009. The Agency currently is conducting a health eff ects assessment for the contaminant. That assessment will consider all available, relevant studies on the toxicology of the contaminant,

May 2009 Draft EPA document. Do not cite or distribute. 23including developmental and re productive toxicity. This cat egory has three subsets of contaminants.

• The first subset contains 14 contaminants with MCLGs equal to zero and either MCLs that are limited by analytical feasibili ty or TT standards. For this subset, EPA conducted further review of the potential fo r revisions to the MCL due to possible changes in analytical feasibility. The Agen cy’s review of new information that might affect the MCL for the first subset is a re finement of the protoc ol. During Six-Year Review 1, EPA took no further action on any c ontaminants with ongoing health effects assessments. EPA generally sets each MCL as close to the MCLG as is feasible, and a common limitation is the availability of an alytical methods to reliably measure the contaminant.

• The second subset contains two contaminan ts, arsenic and uranium. The MCLG for each of these contaminants is equal to zero and the MCL was established based on the costs and benefits balancing provision in SDWA 1412(b)(6)(A). Any changes in the ongoing health effects assessment could impact the evaluation of benefits for these contaminants. Therefore, EPA has decided to take no further action to evaluate these two contaminants until completion of the health effects assessment.

• The third subset contains 14 contamin ants with non-zero MCLGs and MCLs generally equal to their re spective MCLGs. Because EPA cannot determine whether there is potential to revise either the MCLG or the MCL until after the health effects assessment is completed, EPA plans to take no further action on these contaminants at this time. The exception is thallium, which has an MCL limited by analytical feasibility.

May 2009 Draft EPA document. Do not cite or distribute. 24Consequently, EPA conducted further review of the potential for revisions to the MCL for thallium in the event of possible changes in analytical feasibility.

• New health effects assessment comp leted since Six-Year Review 1. An IRIS or OPP assessment has been completed since 2002. EPA also conducted a follow-up literature search to confirm that no new information became available following the completion of the new health effects assessment. Table V-2 shows four subcategorie s of contaminants with new health effects assessments: four with re sults indicating potentia l for lower MCLG, five with results indicating potential for higher MCLG, two with results indicating the MCLG remains appropriate, and three contaminants for which emerging information following the completion of a health effects assessment or a pending pesticide can cellation decision may affect EPA’s review.

• Literature review only conducted during Six-Year Review 2. For the contaminants that did not have a new or ongoing health effects asse ssment completed during the current review period, EPA conducted a review of the health eff ects literature to identify whether there was new information with potential to revise the MC LG. This category has four major subsets of contaminants.

• The first subset contains contaminants that had a health effects assessment completed during Six-Year Review 1, including two w ith possible lower MCLGs, three with possible higher MCLGs, and three with no poten tial to revise their MCLGs. During SixYear Review 1, the Agency determined that possible changes to these contaminants’ NPDWRs were a low priority activity for the Agency because of: competing workload priorities, the administrative costs associated with rulemaking, and the burden on States and the regulated community to implement any regulatory changes. As part of Six-Year

May 2009 Draft EPA document. Do not cite or distribute. 25Review 2, EPA is assessing whether there is new information that affects this determination.

• The second subset contains five contamin ants for which the Agency identified new information, described in section VI, that could impact the MCLG and, therefore, these contaminants are considered potential nominees for a new assessment.

• The third subset of seven contaminants c ontains carcinogens, for which the literature review sought new information on whether th ere might be a nonlinear mode of action or other reproductive and developmental health effects.

• The fourth subset contains seven cont aminants with non-zero MCLGs, for which EPA conducted a full literature search, in cluding developmental and reproductive toxicity.

May 2009 Draft EPA document. Do not cite or distribute. 26Table V-2. Summary of the Outcome of the Six-Year Health Effects Review Health Effects Review Category Contaminants MCLG = 0 and MCL based on Analytical Feasibility or standard is a TT 14 Total - acrylamide; alpha particles; benzo(a)pyrene; beta particles; carbon tetrachloride; DEHP; 1,2-dichloroethane; dichloromethane;

pentachlorophenol; PCBs; radium; dioxin;

tetrachloroethylene; trichloroethylene MCLG = 0 and MCL based on cost-benefit 2 Total – arsenic and uranium Health Effects Assessment

in Process

During Information

Review Period for the Notice MCLG > 0 14 Total – antimony; asbestos; beryllium; cadmium; cyanide; DEHA; 1,2-dichlorobenzene; 1,4- dichlorobenzene; cis-1,2-dichloroethylene; trans-1,2-

dichloroethylene; ethylbenzene; fluoride; styrene; thallium 1 New health risk info rmation could lower MCLG/MCL 4 Total – 2,4-D (2005, new data); endothall (2005, new data); toluene (2005, uncertainty factor adjustment); total xylenes (2003, uncertainty factor adjustment) New health risk information could raise MCLG/MCL 5 Total – alachlor (2006 2 ); barium (2005); diquat (2002 3 ); glyphosate (2002 4 ); 1,1,1-trichloroethane (2007, new data) No new health risk information 2 Total – benzene (2003); EDB (2004) Health Effects Assessment CompletedSince SixYear Review 1 Awaiting the outcome of emerging health studies or cancellation decision 3 Total - atrazine 5 ; simazine 5 ; carbofuran 6 New health risk information

could lower MCLG/MCL 2 Total – hexachlorocyclopentadiene (2001); oxamyl (2000) New health risk information could raise MCLG/MCL 3 Total – 1,1-dichloroethylene (2002); lindane (2002); picloram (1995) Health Effects Assessment CompletedDuring SixYear Review 1 No new health risk information 3 Total – chlordane (1998), inorganic mercury (1997), vinyl chloride (2000) New Information Identified; Potential

Nominee for a New Assessment 5 Total – total chromium (hexavalent); nitrate; nitrite; selenium; 1,2,4-trichlorobenzene MCLG = 0 No new health risk information 7 Total –- DBCP; 1,2-dichloropropane; epichlorohydrin; heptachlor; heptachlor epoxide; hexachlorobenzene; toxaphene Literature

Review

Only

MCLG > 0 No new health risk information 7 Total – dalapon; dinoseb; endrin; methoxychlor; monochlorobenzene; 2,4,5-TP; 1,1,2-trichloroethane 1. Thallium is in this category because it has a non-zero MC LG. Its MCL, however, is limited by analytical feasibility. Therefore, EPA followed the protocol of revi ewing new information that might affect MCL for all contaminants with MCLs greater than their MCLGs, most of which have MCLGs of zero. 2. The 2006 cumulative risk document (USEPA, 2006a) does not pres ent a new assessment; it uses the cancer assessment in the 1998 Reregistration Eligibility Decision (RED; USEPA, 1998a). 3. The 2002 Interim Tolerance Reassessment and Risk Management Decisions (TRED; USEPA, 2002d) does not include a change in risk values, which are those reported in the 1995 RED (USEPA, 1995a). 4. The 2002 TRED (USEPA, 2002a) uses risk values consistentwith those reported in the 1993 RED (USEPA, 1993b), with differences only in RfD rounding. 5. Although atrazine and simazine had new health effects assessm ents completed during the Six-Year Review 2 information period, there are emerging health effects studies that the Agency is reviewing. 6. Although carbofuran had a new health effects assessment comple ted during the Six-Year Review 2 information period, a recent pesticide cancellation decision could affect the MCLG.

May 2009 Draft EPA document. Do not cite or distribute. 273. Analytical Feasibility EPA has a process in place to approve ne w analytical methods for drinking water contaminants; therefore, the review and approva l of potential new methods are outside the scope of the Six-Year Review protocol. EPA recogni zes, however, that the approval and addition of new and/or improved analytical methods (since the promulgation of the NPDWRs under this review) may enhance the ability of laboratories to quan tify contaminants at lower levels. This ability of laboratories to measur e a contaminant at lower levels could affect its PQL, the value at which an MCL is set when it is limited by analyti cal feasibility. Therefore, the Six-Year Review process includes a review of whether there have been changes in analytical feasibility for the subset of the NPDWRs that reached this stage of the decision tree. These include carcinogens with or without ongoing health effects assessments that have MCLs limited by analytical feasibility and contaminants with possible MC LGs that are lower than their current PQLs. The document, “Analytical Feasibility Support Do cument for the Second Six-Year Review of Existing National Primary Drinking Water Regulations” (USEPA, 2009c), describes the process EPA used to evaluate possible changes in analy tical feasibility and provides the results of the analytical feasibility analyses. The purpose of th ese analyses is to determine whether changes in PQL are possible in those instances where the MC L is limited, or might be limited, by analytical feasibility. EPA uses the PQL to estimate the le vel at which laboratories can routinely measure a chemical contaminant in drinking water. Histor ically, EPA has used two main approaches to determine a PQL for SDWA analyt es: (1) Performance Evaluation (P E) data from Water Supply (WS) studies, which is the preferred alternative when sufficient data are available; or (2) a multiplier method, in which the PQL is calc ulated by multiplying the EPA-derived method detection limit (MDL) by a factor of 5 or 10 (50 FR 46880, November 13,1985 (USEPA, 1985); 52 FR 25690 July 8, 1987 (USEPA, 1987); 54 FR 22062 May 22, 1989 (USEPA, 1989b)). May 2009 Draft EPA document. Do not cite or distribute. 28The review protocol for Six-Y ear Review 1 utilized data from WS studies, which were laboratory accreditation studies conducted under EPA oversight until 1999, when the program was privatized. Now, the National Environm ental Laboratory Accreditation Conference (NELAC) conducts the accreditation program via Performance Testing (PT) studies. PQL reassessments discussed in this notice are based on the Six-Year 1 PE data through late 1999 and laboratory passing rate PT data from late 1999 through 2004. One PT provider made pass/fail rates from PT studies available to EPA. This major provider accounts fo r a large portion of the PT results nationwide (USEPA, 2009c). Using PE or PT data to derive the PQL fo r chemical NPDWRs involves determining the concentration of an analyte at which 75 percent of EPA Regional and Stat e laboratories achieve results within a specified acceptance window (see 54 FR 22062 at 22100, May 22, 1989 (USEPA, 1989b)). For Six-Year Review 2, EPA di d not have sufficient PT data to actually recalculate any PQL. Instead, EPA used the PT passing rate results (i.e., the percent of laboratories passing a performance test for a gi ven study) at and below the current PQL to indicate potential for PQL revision. When PT results were not available below th e PQL or when the results did not provide conclusive indications regarding a potential to revise a PQL, EPA relied on two alternate approaches to estimate possible PQLs: an a pproach based on the minimum reporting levels (MRLs) obtained as part of the Six-Year Re view Information Collection Request (ICR) (see section V.B.4), and an approach based on method detection limits (MDL). While EPA prefers to use laboratory performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL.

May 2009 Draft EPA document. Do not cite or distribute. 29An MRL is the lowest level of a contaminant concentration that a laboratory can reliably achieve within specified limits of precision a nd accuracy under routin e laboratory operating conditions using a given method (USEPA, 2009c). EPA evaluated the distribution of MRL values for each contaminant to identify the m ode or value occurring most frequently for that contaminant (modal MRL). The use of modal MRLs is a refinement of the protocol, necessitated by limited availability of PT (formerly PE) data below the current PQL and made possible by the extensive amount of information included in th e Six-Year Review ICR dataset (see section V.B.4). The second source of information that EPA re viewed to evaluate possible changes in analytical feasibility (or the PQL) was the MDL approach. As noted previously, this approach has been used in the past to derive PQLs for regulated contaminants. In addition, this same approach was used to identify possible analytical feasibility levels for Six-Year Review 1 (USEPA, 2003a). In deriving these levels, the Agency used the MDLs associated with the analytical methods approved by EPA for drinki ng water analysis. EPA obtained MDL values and/or ranges from individual analytical me thods developed and approved by EPA for use on drinking water. Based on these MDL values, EPA used an MDL multiplier to estimate where the possible lower limit of quantitation may currently lie. The multiplier is 10 for most contaminants except dioxin, which has a multiplier of 5 in its original PQL. EPA also considered both the modal MRL and MDL-based estimates when it derived estimated quantitation levels (E QLs) (USEPA, 2009e) for the occurrence analysis (see section V.B.4) to help the Agency determine if there may be a meaningful opportunity to improve public health protection. The possible lower bound PQ L value was derived us ing the alternative sources of information (MRL and MDL) is referred to as EQL. It should be noted, however, that

May 2009 Draft EPA document. Do not cite or distribute. 30the EQL does not represent the Agency’s intent to promulgate new PQLs with this notice. Any revisions to PQLs will be part of future rule making efforts. EPA performed analytical feasibility anal yses for three cate gories of NPDWRs. Table V-3 shows the three categories and the outcomes of the Agency’s review.

• A health effects assessment indicates potential for lower MCLG . This category includes the six contaminants identified in the health eff ects review as having in formation indicating the potential for a lower MCLG – four with new health effects assessments completed during Six-Year Review 2 and two with health e ffects assessments completed during Six-Year Review 1. Although their currentMCLs are not limited by a PQ L, EPA reviewed analytical feasibility to determine if analytical feasibili ty might limit the potential for MCL revisions. For two contaminants (endothall and oxamyl), the current PQL is higher than the possible MCLG identified in the health e ffects review. For these contam inants, the potential to lower their PQLs is inconclusive. C onsequently, analytical feasibility might be a limiting factor for setting the MCL equal to the possible MCLG (see sections VI.B.34 and VI.B.51 of today’s action for a more detailed discussion). The current PQL is not a limiting factor for the remaining four contaminants identified by th e health effects review as having possible changes in their MCLG (i.e., 2,4-D, hexach lorocyclopentadiene, to luene, and xylenes).

• Contaminants with ongoing heal th effects assessments and existing MCLs are based on analytical feasibility . This category includes 14 contaminants with ongoing health assessments with existing MCLs that are great er than their MCLGs because they are limited by analytical feasibility. One contaminan t has a non-zero MCLG (thallium) and the remaining 13 contaminants have MCLGs equal to zero. Although a risk assessment is in process for these contaminants, because SDWA requires the Agency to set the MCL as close

May 2009 Draft EPA document. Do not cite or distribute. 31to the MCLG as feasible, EPA evaluated whether the PQL is likely to be lower for these contaminants. For four of these contamin ants (carbon tetrachloride, 1,2-dichloroethane, tetrachloroethylene, and trichloroethylene), EP A concluded that new information from PT studies, along with MRL and MDL data, indicate the potential to revise the PQL. For one contaminant (dichloromethane), data from PT studies are inconclusive, but MRL and MDL data indicate the potential to revise the PQL. For the remaining nine contaminants, either EPA did not have sufficient new information to evaluate analytical feasibility or EPA concluded that new information does not indicate the potential for a PQL revision.

• Contaminants with no ongoing health effects assessment and existing MCLs are based on analytical feasibility and greater than thei r MCLGs. For the 11 contaminants in this category, EPA evaluated available PT and WS data as well as MRL and MDL data to determine whether there is potential to lower th e PQL and thereby set the MCL closer to the MCLG. For five of these contaminants (benzene 2 , chlordane, 1,2-dichloropropane, hexachlorobenzene, and 1,1,2-trichloroethane) EP A concluded that new information from PT studies, along with MRL and MD L data, indicates that while it might be possible to set a lower PQL, the data are insufficient to support an actual PQL recalculatio n at this time. For five additional contaminants (DBCP, heptach lor, heptachlor epoxide, toxaphene, and vinyl chloride), the data from PT studies are in conclusive, but MRL and/or MDL data indicate potential for a lower PQL, as indicated in Table V-3 . For the final contaminant, ethylene dibromide (EDB) 3 , none of the data sources indicate potential to revise the PQL.

2 Although the new health effects assessment completed for benzene during Six-Year Review 2 indicated no potential to revise its MCLG, its MCL is still limited by its PQL and, therefore, it is included in this group of contaminants. 3 Although the new health effect s assessment completed for EDB during Six-Year Review 2 indicated no potential to revise its MCLG, its MCL is still limited by its PQL and, therefore, it is included in this group of contaminants. May 2009 Draft EPA document. Do not cite or distribute. 32Table V-3 lists the type of data th at indicate potential for a PQ L reduction. The list includes “PT” when the PQL reassessment based on PT da ta (USEPA, 2009c) report s that a reduction is supported. The list also includes “MRL” and “MDL” when either of these approaches indicates potential for PQL reduction. A result of “PQL re duction supported” without a “PT” in the list indicate that the PQL reassessmen t outcome is uncertain, but othe r data (i.e., MRL and/or MDL) indicate potential for PQL reductio n. When the PQL reassessment outcome is that the current PQL remains appropriate, Table V-3 shows the result “Data do not support PQL reduction.” The contaminant specific discussions in section VI of today’s action provide the results of the analytical feasibility review for all the contaminants in Table V-3

.

May 2009 Draft EPA document. Do not cite or distribute. 33Table V-3. NPDWRs Included in the Analytical Feasibility Reassessment and the Result of that Assessment Contaminant Current PQL Analytical Feasibility Reassessment Result 1 6 Contaminants Identified Under the Health Eff ects Review as Having Potential for Lower MCLG 2,4-D (possible MCLG: 0.04 mg/L) 0.005 mg/L PQL not limiting Endothall (possible MCLG: 0.05 mg/L) 0.09 mg/L PQL reduction supported (MRL, MDL) Hexachlorocyclopentad iene (possible MCLG: 0.04 mg/L) 0.001 mg/L PQL not limiting Oxamyl (possible MCLG: 0.002 mg/L) 0.02 mg/L PQL reduction supported (MRL, MDL) Toluene (possible MCLG: 0.6 mg/L) 0.005 mg/L PQL not limiting Total xylenes (possible MCLG: 1 mg/L) 0.005 mg/L PQL not limiting 14 Contaminants with Ongoing Health Effects Assessments and MCLs Are Based on Analytical Feasibility and Higher than MCLGs Alpha particles No PQL and n o new information Benzo(a)pyrene 0.0002 mg/L Data do not support PQL reduction Beta particles No PQL and n o new information Carbon Tetrachloride 0.005 mg/L PQL reduction supported (PT, MRL, MDL) DEHP 0.006 mg/L Data do not support PQL reduction 1,2-dichloroethane 0.005 mg/L PQL reduction supported (PT, MRL, MDL) Dichloromethane 0.005 mg/L PQL reduction supported (MRL, MDL) Pentachlorophenol 0.001 mg/L Data do not support PQL reduction PCBs 0.0005 mg/L Data do not support PQL reduction Radium No PQL and n o new information Dioxin 3E-08 mg/L Data do not support PQL reduction Tetrachloroethylene 0.005 mg/L PQL reduction supported (PT, MRL, MDL) Thallium 0.002 mg/L Data do not support PQL reduction Trichloroethylene 0.005 mg/L PQL reduction supported (PT, MRL, MDL) 11 Contaminants without Ongoing Health Effects Assessments and MCLs Ar e Based on Analytical Feasibility and Higher than MCLGs Benzene 0.005 mg/L PQL reduction supported (PT, MRL, MDL) Chlordane 0.002 mg/L PQL reduction supported (PT, MRL, MDL) DBCP 0.0002 mg/L PQL reduction supported (MDL) 1,2-dichloropropane 0.005 mg/L PQL reduction supported (PT, MRL, MDL) EDB 0.0005 mg/L Data do not support PQL reduction Heptachlor 0.0004 mg/L PQL reduction supported (MRL, MDL) Heptachlor epoxide 0.0002 mg/L PQL reduction supported (MRL, MDL) Hexachlorobenzene 0.001 mg/L PQL reduction supported (PT, MRL, MDL) Toxaphene 0.003 mg/L PQL reduction supported (MRL, MDL) 1,1,2-trichloroethane 0.005 mg/L PQL r eduction supported (PT, MRL, MDL) Vinyl chloride 0.002 mg/L PQL reduction supported (MRL) mg/L – milligrams per liter

May 2009 Draft EPA document. Do not cite or distribute. 344. Occurrence and Exposure Analysis To support the national contaminant occurrence asse ssments under Six-Year Review 2, EPA conducted voluntarily submit their SDWA compliance monitori ng data. This request was for the submission o

compliance monitoring data collected between Ja nuary 1998 and December 2005 for 79 regulated contaminants. A total of 51 States and entities prov ided compliance monitoring data that included all analytical detection and non-detecti on records. These data represent th e national occurrence of regulate contaminants in public drinking water systems. Through extensive da ta management efforts, quality assurance evaluations, and communications with Stat e data management staff, EPA established a high an Information Collection Request. Through this process EPA requested that all St ates and primacy entities f

d
quality dependable contaminant occurre nce database consisting of data from 45 States (see map in

Figure V-2 ). Details of the data management and data quality assurance evaluations are available in the support document entitled, “Analy sis of Occurrence Data from the Second SixYear Review of Existing National Primar y Drinking Water Regulations” (USEPA, 2009f).

May 2009 Draft EPA document. Do not cite or distribute. 35Figure V-2. States with Compliance Monitori ng Data Included in the Six-Year Review 2

The contaminant occurrence data from the 47 States and entities comprise more than 15 million analytical records from approximately132,000 public water systems. Approximately 254 million people are served by these public wate r systems nationally. Records were submitted for 16 inorganic chemicals, 32 synthetic organi c chemicals, 21 volatile organic chemicals, 7 radiological contaminants, and 3 microbiological 4 contaminants. The number of States and public water systems represented in the dataset va ries across contaminants because of variability in voluntary State data submissions and contaminant monitoring sche dules. This is the largest, most comprehensive set of drinking water co mpliance monitoring data ever compiled and analyzed by EPA.

4 The compliance monitoring data for the microbiological contaminants were collected to support ongoing rule development so these data have not been analyzed separately in this action. May 2009 Draft EPA document. Do not cite or distribute. 36EPA used a two-stage analytical approach to analyze these data and characterize the national occurrence of contaminants. 5 The first stage of analysis prov ides a straightforward evaluation of contaminant occurrence. This st age 1 occurrence analysis is a simple, non-parametric count of occurrence of regulated contamin ants in public water systems. 6 A typical stage 1 occurrence analysis generates a count of the number (or per centage) of systems with at least one analytical detection of a specific contaminant, or with at least one analytical detection with a concentration greater than a concentration thres hold of interest, i.e., a possible MCLG or EQL. This approach generates a conservative (i.e., upwardly biased) estimate of th e number of potential systems having contaminant occurrence at levels of interest. The stage 2 occurrence analysis estimates national contaminant o ccurrence by generating estimated long-term mean concentrations of a sp ecific contaminant at systems nationally. This provides occurrence analyses that are less cons ervative than the stage 1 occurrence analysis (because the stage 2 occurrence analysis is based on estimated mean concen trations rather than on single maximum concentrations), and also provides occurrence analyses that may be more reflective of potential chronic exposure. Genera lly, the stage 1 occurren ce analysis reflects a rough approximation of peak occurrence while the stage 2 occurrence analysis is based on estimated average occurrence. A complete descri ption of the two-stage an alytical approach and a detailed presentation of occurrence estimates are available in the support document entitled, “Analysis of Occurrence Data from the Second Six-Year Review of Ex isting National Primary Drinking Water Regulations” (USEPA, 2009f).

5 The use of the stage 1 and stage 2 terminology should not be confused with the Stage 1 and Stage 2 Disinfectants and Disinfection By Products Rulemakings. Instead, this terminology has been used to describe the two stages of the occurrence analyses performed for Si x-Year Review 2, as well as Six-Year Review 1. 6 These analyses are conservative in the sense that th ey are protective of human health (i.e., they are more likely to overestimate risks to human health than underestimate them).

May 2009 Draft EPA document. Do not cite or distribute. 37EPA calculated the system means for the st age 2 occurrence analysis using a simple arithmetic average of all detection and non-detect ion data for each public water system. Because the contaminant concentrati ons associated with the non- detection data are unknown, EPA assigned three different values to the non-detection results to es timate a range of system-level means, which then allowed EPA to estimate number and percent of sy stems with estimated means exceeding selected threshold values. Tw o of the three values are based on the MRL values that accompany the non-detection results inthe Six-Year Review ICR dataset. The MRL is the lowest level that can be reliably achieved within specif ied limits of precision and accuracy under routine laboratory operating conditions using a given method. The three values that EPA substituted for non-detection results were MRL, 1/2 MRL, and zero. The most conservative approach was to assume that all non-detection results were equal to the MRL. This approach yields an upper-bound estimate of each system's level of exposure. EPA also explored the less conservative assump tion that concentrations of the non-detection results were uniformly distributed between the MRL and zero, thereby substituting one-half the MRL for all non-detection results. Finally, EP A considered the assump tion that the actual concentration for each non-detection result was typically much smaller than the MRL, supporting the use of zero to represent each non -detection. This method yielded a lower-bound estimate of the system’s mean. This simplifie d approach differs from the stage 2 occurrence analysis approach in the Six- Year Review 1, which used more sophisticated modeling methods to address the non-detection resu lts. That analysis, however, was based on a substantially smaller dataset (i.e., data from 16 States instead of 45 States). (Note that many States substitute zero for all non-detections when determining comp liance with the NPDWRs.) EPA uses each of the assumptions in the stage 2 occurrence analys es in order to obtain reasonable bounds on the

May 2009 Draft EPA document. Do not cite or distribute. 38actual system mean concentrations . Once the system means were calculated for each of the three substitution methods, the results means were then co mpared to the various thresholds of interest (e.g., the number and percent of sy stems with a mean concentrati on above a health threshold of concern). The two-stage analytical approach was previo usly developed for Six-Year Review 1. The data management and general occurrence analyti cal approach were peer-reviewed for use under the Six-Year Review 1. EPA conducted the stage 2 occurrence an alysis for 5 of the 14 NPDWRs in Table V-3 with ongoing health effects assessment and MCLs that are limited by PQLs for which EPA identified analytical feasibility data supporting po ssible PQL revision: carbon tetrachloride; dichloromethane; 1,2-dichloroethane; tetrachloroe thylene; and trichloroe thylene. EPA also conducted the stage 2 occurrence an alysis for the 6 contaminants with health effects assessment changes that indicate potential to reduce the MC LG, and the 11 contaminants that do not have ongoing health effects assessments, but do have MCLs limited by PQLs and new data indicate potential to reduce the PQLs (see Table V-3). EPA used the results of the stage 2 occurrence analyses to identify which possible NPDWR re visions present a meaningful opportunity to improve the level of health protection or a meaningful opportunity for co st savings to drinking water systems and their customers while maintaining the same level of health protection. Section VI contains occurrence results and EPA’s review results for the contaminants in Table
V-3 that have potential for MCL revisions. Because the Six-Year Review ICR data reflect water quality at entry points to the distribution system, the occurrence analysis method described is not adequate to evaluate the cost savings potential for the nine contaminants that have health effects assessment changes that indicate

May 2009 Draft EPA document. Do not cite or distribute. 39potential for higher MCLG values (see Table V-2 ). EPA lacks the comprehensive information on source water quality and existi ng treatment needed to determ ine how many systems would be able to alter treatment practices were an MCLG to increase. To review the potential for cost savings, EPA obtained publicly available source water quality data and conducted a qualitative assessment of treatment cost savings for systems that might be treating these contaminants with best available technologies (BATs) or small sy stem compliance technologies (SSCTs) listed in the NPDWR for each contaminant (USEPA, 2009g). Source water quality data were needed to determine cost savings potential for the contam inants for which a health effects assessment indicates the potential for highe r MCLG values. There is no co mprehensive database of water quality in drinking water sources. Therefore, EPA used source water quality information from two national data sources, the National Water Quality Assessment (NAWQA) program conducted by the U.S. Geological Survey (USG S), and EPA’s STORET (short for STOrage and RETrieval) data system, which are part of EP A’s Office of Ground Water and Drinking Water’s National Contaminant Occurrence Database (NC OD). The STORET data come from a variety of monitoring programs and the NAWQA data come from watershed or “study units” that USGS selected to reflect important hydrologic a nd ecological resources; critical sources of contaminants, including agricultural, urban, and natural sources; and a high percentage of population served by municipal water supply and ir rigated agriculture. The original 51 study units account for more than 70 percent of total water use (excluding thermoelectric and hydropower) and more than 50 percent of the pop ulation’s supply of drinking water (Gilliom et al., 2006). For each dataset, EPA estimated the number of monitoring locations with maximum contaminant levels above each contaminant’s current MCL and a possible MCLG based on the

May 2009 Draft EPA document. Do not cite or distribute. 40new information from the contaminant’s health eff ects assessment. Section VI reports the results by contaminant.

5. Treatment Feasibility An NPDWR either identifies the BATs for m eeting an MCL, or establishes enforceable treatment technique requirements. For the NPDW Rs addressed in section VI of today’s action, two have TT requirements and the rest have an MCL. All of the MCLs are set equal to the MCLG or the PQL or by benefit-cost analys is; none are currently limited by treatment feasibility. As a refinement for Six-Year Revi ew 2, EPA considered treatment feasibility after identifying contaminants with potential to lower an MCL or change a TT that constituted a meaningful opportunity to improve the level of health protection. The EPA document, ‘‘Water Treatment Technology Feasibility Support Document for Chemical Contaminants for the Second Six-Year Review of National Primary Drinki ng Water Regulations’’ (USEPA, 2009g), describes the process EPA used to evaluate treatment feasibility, where appropriate, and provides the results of these analyses. As a part of this re view, EPA utilized the same sources that have been the primary resources in development of EPA regulations and guidan ce, including published EPA treatment reports, peer-r eviewed journals, and other technology sources, as well as information received from EPA stakeholders.

a. MCL-Type Rules. EPA evaluated existing treatment technology information for two MCL-type NPDWRs to determine whether treatment feasibility would be a limiting factor if EPA were to lower the MCL for tetrachloroethylene and trichloroethylene. Based on this evaluation, the Agency believes th at treatment capabilities would be adequate to support a lower MCL value fo r any of these contaminants for which a lower MCL may be

May 2009 Draft EPA document. Do not cite or distribute. 41appropriate (USEPA, 2009g). Tr eatment technologies specified as BAT within the current NPDWR, and small system compliance techno logies, which were specified by EPA in 1998 (USEPA, 1998b) for these contaminants are cons idered to be efficient and practical for implementation at a public water sy stem (PWS). If EPA were to determine that it is appropriate to revise these NPDWRs, it woul d undertake a more thorough revi ew of treatment feasibility, including a consideratio n of costs, to determine whether treatment feasibility would be a constraint or not.

b. Treatment Technique-Type Rules. EPA reviewed two chemical NPDWRs – acrylam ide and epichlorohydrin (both classified B2 carcinogens) – for which a TT is set in lieu of an MCL. The TT requirement limits the allowable acrylamide and epichlorohydrin monomer levels in polymeric coagulant aids and their dosages for drinking water treatment, stor age, and distribution. Although a health effects assessment for acrylamide is ongoing, it is a carcinogen with an MCLG of zero and the draft health effects assessment indicates that the cancer classificati on remains the same. As a refinement in SixYear Review 2, EPA considered new information to determine if the TTs for these contaminants may need to be revised. This information indicates that improvements in manufacturing capabilities have reduced the residual monomer c ontent in acrylamide and epichlorohydrin-based polymeric coagulants aids and these changes w ould support revisions to the TTs for acrylamide and epichlorohydrin. Sections VI.B.1 and VI.B.36 of today’s action summarize these issues for acrylamide and epichlorohydrin, respectively.

6. Other Regulatory Revisions In addition to possible revisions to MCLGs, MCLs, and TTs, EPA considered whether other regulatory revisions are needed, such as monitori ng and system reporting requirements, as a part

May 2009 Draft EPA document. Do not cite or distribute. 42of the Six-Year Review 2. EPA utilized the prot ocol established during the Six-Year Review 1 to evaluate which implementation issues to c onsider (USEPA, 2003b). EPA’s protocol focused on items that were not already being addressed, or had not beenaddressed, through alternative mechanisms (e.g., as a part of a recent or ongoing rulemaking). EPA considered potential implementation-related revisions in these cases if the revisions:

• Represented a change to an NPDWR, as defined under section 1401 of SDWA 7 ;

• Were "ready" for rulemaking – that is, the prob lem to be resolved had been clearly defined, and specific options to address the problem had been formulated; and

• Would clearly improve the leve l of public health protection and/or provide a meaningful opportunity for cost savings (either monetary or burden reduction) while not lessening public health protection.

a. Issues Identified by the EPA/State Workgroup To gather input regarding implementation-relate d concerns and help the Agency identify the top one or two issues for Six-Year Review 2 (USEPA, 2009h), EPA requested that the Association of State Drinking Water Administrators (ASDWA) form a workgroup of member States and primacy agencies. In the fall of 2007, ten member States agreed to participate and confer with EPA on a joint EPA/State workgroup. The State/EPA workgroup initially identified 22 issues, but narrowed the list to 4 items. Of th ese four items, three app eared to be within the scope of an NPDWR review, and EPA agreed that an information or fact sheet might be appropriate for the fourth item regarding public notification (PN) re quirements for fluoride 8

.

7 The subject of the Six-Year-Review, as specified in section 1412(b)(9) of th e SDWA, is "each national primary drinking water regulation," as defined under section 1401 of the SDWA. 8 Currently, PWSs that exceed the fluoride MCL of 4.0 mg/L are required to notify their customers within 30 days of the exceedance. If a PWS exceeds the fluoride SMCL of 2.0 mg/L, they are required to notify their customers within 12 months of the ex ceedance. The States voiced concerns about (1) the confus ion that occurs between the different PN requirements for the MCL and th e SMCL, and (2) the timeliness of the PN requirement for May 2009 Draft EPA document. Do not cite or distribute. 43The EPA/State workgroup agreed that public input via the Federal Register would provide additional insight on the national scop e of these three issues (i.e., Are the issues isolated to a few States or more widespread?), the importance of these issues to other States as well as water systems, and ideas on po tential resolutions. Table V-4 provides a brief description of the remaining three issues and some of the potential solutions discu ssed in the workgr oup meetings. EPA is requesting public input and further info rmation on these three implementation issues to better inform future State/ EPA workgroup discussions. More specifically, EPA would like to gauge how many States and/or pub lic water utilities may be affected by these issues, and which one or two issues are most important to States. EPA also requests input and suggestions from commenters regarding any other pote ntial solutions to th e issues. As part of the public comment process, EPA also welcomes any data on the oc currence of nitrates and/or nitrites in the distribution system, especially as it may relate to nitrification associated with the use of chloramines for disinfection.

the SMCL. The workgroup indicated th at waiting 12 months to notify custom ers of an exceedance of the SMCL does not adequately protect young children from dental fluorosis during a critical stage of tooth enamel development. The participating States requested that EPA consider regulatory re visions to clarify the PN requirements and better reflect the heal th and aesthetic implications of each. EPA noted that PN requirements are not within the scope of an NPDWR review. However the Ag ency agreed that a fact or information sheet may be useful to clarify any confusion. May 2009 Draft EPA document. Do not cite or distribute. 44Table V-4. Issues Identified by the EPA/State Workgr oup That Fall within the Scope of an NPDWR Review Implementation Issue Examples of Potential Solutions discussed by the Workgroup Change the location of nitrate-nitrite monitoring to address possible nitrification within the distribution system for water systems using chloramines 1 • Location of Monitoring



### - Move sampling location from the entry point to the distribution to the distribution

system



### - Or, maintain entry point sampling and also sample in the distribution system

• Frequency of Monitoring



### - Consider sampling in conjunction with DBPs, TCR or some other scheme.

• EPA notes that 40 Code of Federal Regulations (CFR) 141.23(a)(2) may allow surface water systems discretion to locate the sampling point in the distribution system if that is more representative of the source after treatment. 2 Reduce the monitoring for ground water systems with historically low levels of nitrate-nitrite • Consider revisions to change the frequency of monitoring, the trigger level and the duration of time for systems to qualify for reduced monitoring. Examples included:



### - A monitoring frequency of 3, 6, or 9 years (consistent with the existing

standardized monitoring framework) or some other frequency.



### - A new trigger level set at either 1/2 the MCL (or some other fraction), the

PQL/MDL (or some other level of detection), or another appropriate level.



### - As for the duration of how long a system wo uld need to meet the trigger level in

order to be allowed to begin reduced monitoring, some options included a 3-, 6-, or 9-year period (consistent with the standardized monitoring framework) or a 5-, 10-, or 15-year period.

• Or consider providing a waiver option to give States discretion to reduce monitoring.

• Or consider a non-regulatory option such as the Alternative Monitoring Guidelines (which some considered too burdensome). Revise the monitoring requirements for Non Community Water Systems (NCWS) to better target the potential health risks associated with chronic contaminants. In light of the probability and magnitude of health threats, some monitoring requirements for these systems may be insufficient, and others may be excessive. • Revise all contaminant rules to include additional monitoring requirements for Transient Non Community Water Systems (TNCWS), as well as radionuclide monitoring requirements for Non Transient Non Community Water Systems (NTNCWS)

• Or review existing regulated contaminants and include TNCWS monitoring requirements based on the relative health risk from chronic exposure.

• Or develop general language that would apply to all contaminant rules, giving States the discretion to require additional monitoring for contaminants that pose chronic exposure risks and can have acute health effe cts at elevated levels potentially found at TNCWSs (the preferred option from States).

• Note: For some of these options, EPA would need to evaluate whether sufficient occurrence and exposure information is available for TNCWS and NTNCWS to assess the need for revised monitoring strategies.

1. The health effects technical review identified new informat ion on developmental effects of nitrate and nitrite, as well as data regarding its carcinogenicity, that may indicate the need to update the Agency’s risk assessment (see section VI.B.49 and VI.B.50 of today’s action). In light of this information, EPA is considering nitrate and nitrit e as potential candidates for n ew health effects assessments. If new assessments are initiated and comp leted, EPA will be able to determine the potential impacts on the MCLG, MCL, and/or monitoring requirements, and w hat future actions may or may not be appropriate. 2. 40 CFR 141.23(a)(2) states: Surface water systems shall ta ke a minimum of one sample at every entry point to the distribution system after any application of treatment or in t he distribution system at a point which is representative of each source after treatment (hereafter called a sampling point) beginning in the initial compliance period. The system shall take e ach sample at the same sampling point unless conditions make another sampling point more representative of each source or treatment plant.

May 2009 Draft EPA document. Do not cite or distribute. 45b. Other Issues (Synthetic Organic Chemicals Trigger Levels) 40 CFR 141.24(h)18 of the national primary drinki ng water regulations lists detection limits for the synthetic organic chemicals (SOCs), includi ng pesticides. These detection limits serve as triggers for determining whether the compliance monitoring frequency for SOCs may be reduced; public water systems det ecting SOCs at or below trigge r concentration can qualify for reduced monitoring. Several Regions and States have requested guidance and clarification on the use of detection limits in monitoring of drinking water samples for SOCs. The primary concern is that some laboratories have reported difficulty in achieving the detection limits for some SOCs on a regular basis a nd, in those cases, the water systems that they support are not able to qualify for reduced monitoring. EPA is seeking information about the extentand magnitude of any issues related to the ability of laboratories to achieve the SOC tri gger levels specified in section 141.24(h)(18). EPA wishes to determine if this issue is widespread or limited to specific SOCs and/or specific laboratories. EPA is requesti ng that stakeholders provide in formation/data to support their concerns related to SOC triggers.

C. How Did EPA Factor Children’s Health Concerns Into the Review? The 1996 amendments to SDWA require specia l consideration of all sensitive populations (e.g., infants, children, pregnant women, elderly, and individuals with a history of serious illness) in the development of drinking water regulat ions (section 1412(b)(3 )(C)(V) of SDWA, as amended in 1996). As a part of the Six-Year Review 2, EPA completed a literature search covering developmental and reproductive endpoints (e.g., fertility, embryo survival, developmental delays, birth defects, and endocrine effects) for regulated ch emicals that have not been the subject of a health effects assessment during this review peri od (see section V.B.1 of

May 2009 Draft EPA document. Do not cite or distribute. 46today’s action). EPA reviewed the output from the literature searches to identify any studies that might have an influence on the present MCLG. Three chemicals were identified with potential developmental/reproductive endpoi nts of concern that might not be addressed by the current NPDWR: nitrate, nitrite, and selenium. In each cas e, where the literature search indicated a need to consider recent studies of developmental or reproductive toxicity, EPA is considering whether to nominate the contaminant for a new health effects assessment.

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

A. What are the Review Result Categories? For each of the 71 NPDWRs discussed in detail in the following sections of today’s action, the review results in one of the following outcomes:

1. No Action at this Time and the NPDWR is Still Appropriate. The NPDWR is appropriate and no action is n ecessary at this time due to one of the following reasons:

a. A health effects assessment is in process or the Agency is considering whether to initiate an assessment . For those contaminants with a health effects assessment in process that will not be completed in time for the current review, the MCL remains appropriate because either, (1) it is equal to the MCLG, (2) the MCL is based on SDWA’s cost-benefit pr ovision, (3) there is no potential to change the MCL base d on changes in analytical feas ibility, or (4) there may be a potential change to the MCL based on analytical feasibility, but a ny such change is unlikely to provide a meaningful opportunity to improve public health protection. For several contaminants, EPA identified new health information that may wa rrant a new health effects assessment.

May 2009 Draft EPA document. Do not cite or distribute. 47b. NPDWR remains appropriate afte r data/information review. The outcome of the review indicates that the current re gulatory requirements remain appropriate and, therefore, no regulatory revisions are warranted at this time. Any new information available to the Agency either supports the current regulatory requirements or does not justify a revision.

c. New information is available, bu t no revision recommended because:

• Negligible gain in public health protection and/or cost savings: Any resulting changes to the NPDWR would not significantly improve the level of public health protection or result in a major cost savings for p ublic water systems and their customers.

• Information Gaps or Emerging Information: Either new information is emerging that could affect EPA’s evaluation of the NPDWR or the available data are insufficient to support a definitive regulatory recommendation at this time. 2. Candidate for Revision. The NPDWR is a candidate for revision based on the review of new information.

May 2009 Draft EPA document. Do not cite or distribute. 48Table VI-1. Summary of Six-Year Review 2 Results

Recent or Ongoing Action (14 NPDWRs) Bromate Chloramines Chlorine Chlorine dioxide Chlorite Coliform Copper Cryptosporidium Giardia lamblia HAA5 Lead Legionella TTHMs Viruses

Risk assessment in process or potential nominee for an assessment (32 NPDWRs) Alpha particles (or emitters) Antimony Arsenic Asbestos Benzo(a)pyrene Beryllium Beta particles and photon emitters Cadmium Carbon tetrachloride Chromium Cyanide 1,2-Dichlorobenzene 1,4-Dichlorobenzene 1,2-Dichloroethane cis-1,2-Dichloroethylene trans-1,2-Dichloroethylene Dichloromethane Di(2-ethylhexyl)adipate Di(2-ethylhexyl)phthalate Ethylbenzene Fluoride Nitrate Nitrite Pentachlorophenol Polychlorinated biphenyls (PCBs) Radiums Selenium Styrene 2,3,7,8-TCDD (dioxin) Thallium 1,2,4-Trichlorobenzene Uranium NPDWR remains appropriate after data/information review (8 NPDWRs) Dalapon Dinoseb Endrin Ethylene Dibromide (EDB) Mercury (inorganic) Methoxychlor Monochlorobenzene (chlorobenzene) 2,4,5-Trichorophenoxy-propionic acid (2,4,5-TP)

Low priority (24 NPDWRs) Alachlor Barium Benzene Chlordane 1,2-Dibromo-3-chloropropane (DBCP) 1,1-Dichloroethylene 1,2-Dichloropropane 2,4-Dichlorophenoxyacetic acid (2,4-D) Diquat Endothall Glyphosate Heptachlor Heptachlor epoxide Hexachlorobenzene Hexachlorocyclopentadiene Lindane Oxamyl Picloram Toluene Toxaphene 1,1,1-Trichloroethane 1,1,2-Trichloroethane Xylenes Vinyl chloride Not A ppropriate for Revision at this Time

New information, but no revisionrecommended because:

Information gaps (3 NPDWRs) Atrazine Carbofuran Simazine Candidate for Revision Based on new information (4 NPDWRs) Acrylamide Epichlorohydrin Tetrachloroethylene (PCE) Trichloroethylene (TCE)

May 2009 Draft EPA document. Do not cite or distribute. 49B. What Are the Details of EPA’s Review of Each NPDWR? 1. Acrylamide

a. Background . EPA published the current NPDWR for acrylamide on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establis hed an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR imposes a TT requirement that limits the allowable monomer levels in products used during drinking water treatment, storage, and distribution to 0.05 percent acrylamide in pol yacrylamide coagulant aids dosed (maximum) at 1 mg/L (ppm). Each water system is require d to certify, in writing, to the State (using thirdparty or manufacturer’s certificat ion) that the product used m eets these residual monomers and use-level specifications. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to acrylamide. The revised health eff ects assessment is considering relevant studies on the toxicity of acrylamide, incl uding its potential developmental and reproductive toxicity. The draft assessment was published in the Federal Register on December 28, 2007 (72 FR 73813 (USEPA, 2007b)). The Science Advisory Bo ard (SAB) conducted a pe er review of the document, which also included a re view of public comments received on the draft assessment. The SAB panel concurred with the Agency’s rati onale and justification for acrylamide being a “likely human carcinogen” via mutagenic mechanism. At the present time, acrylamide is still under evaluation by the Agency, and the IRIS Su bstance Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment. However, as the present draft reassessment does not change the cancer classification for acrylamide, its MCLG will continue to be zero. EPA therefore considered whether there was potential to revise the TT for acr ylamide. EPA has identified in formation that suggests that the

May 2009 Draft EPA document. Do not cite or distribute. 50residual acrylamide content in water treatment polymers has decreased significantly, likely due to improvements in manufacturing proce sses and technologies (USEPA, 2009g). NSF International analyses co nducted between January 2005 and June 2007 found that, in 66 polyacrylamide products submitted for certification under NSF Standard 60, the median residual acrylamide content was 0.006%, and the 90th percen tile acrylamide content was 0.025%, half of the limit set in the treatment technique. Acrylamide standards in Europe and Australia are also stricter than the NPDWR. Based on the maximum allowable dosage and monomer level in the NPDWR, finished water could contain up to 0.5 μ g/L (ppb) of acrylamide. By contrast, the Eu ropean Union requires that finished water contain less than 0.1 μ g/L (parts per billion or ppb) acrylam ide, and Australia requires that the concentration in finished water be less than 0.2 μ g/L (ppb). The United Kingdom requires that polyacrylamides used in drinki ng water contain less than 0.02% re sidual acrylamide, and that the polyacrylamide dose be less than 0.5 mg/L (parts per million or ppm) at all times, for a maximum finished water concentration of 0.1 μ g/L (ppb) . To assess the occurrence of acrylamide in dri nking water, EPA sought data on current usage practices for polyacrylamide coagulant aids. The Agency is not presently aware of any recent, large-scale studies of polymer usage in drinki ng water facilities, and therefore cannot fully characterize the occurrence of acrylamide in drinking water. However, the 1996 WATER:\STATS database (descr ibed in Levine et al., 2004), based on an American Water Works Association (AWWA) surve y, indicates that 13% of gr ound water systems and 66% of surface water systems surveyed use a polymer for water treatment. Many of these are anionic and nonionic polymers, particularly for ground water systems; anionic and nonionic polymers used to treat drinking water ar e most likely polyacrylamides.

May 2009 Draft EPA document. Do not cite or distribute. 51Additional information on the extent of use of polyacrylamide in drinking water and the impending health effects assessment will further a ssist the Agency in determining the potential public health benefits associated with a revisi on to the treatment technique for acrylamide. Because most polyacrylamides available today ha ve a lower residual monomer content than that specified in the treatment technique, EPA believes that the costs of a revision would be minimal (USEPA, 2009g).

c. Review Result. The Agency believes it is appropriate to revise the NPDWR for acrylamide although a health effects assessment is currently in progress. The existing MCLG is still zero (based on the current B2 cancer classification) and NSF International data indicate that polyacrylamides are widely available with lowe r monomer levels than required by the existing NPDWR. Hence, revisions to the acrylamide NPDWR will provide a meaningful opportunity for health risk reduction. EPA expects that the final health effects assessment will further support the public health benefits associated with any revision. As discussed in Section VII, the Agency solicits information from public on the ex tent of use of polyacrylamide in drinking water facilities (since this may provide additional information on the occurrence of acrylamide in drinking water) to help inform the regulatory revision. EPA notes that any changes to the NPDWR for acrylamide may also include revi sions to the closely related NPDWR for epichlorohydrin. 2. Alachlor

a. Background . EPA published the current NPDWR fo r alachlor on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establishe d an MCLG of zer o based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.002 mg/L, based on anal ytical feasibility.

May 2009 Draft EPA document. Do not cite or distribute. 52b. Technical Reviews. In 2006, the Agency updated its heal th effects assessment of alachlor (USEPA, 2006a). The Agency identified a change in this assessment that could lead to a change in the MCLG. This assessment considered releva nt studies on the toxici ty of alachlor including developmental and reproductive toxicity. For no ncancer effects, the assessment confirmed the RfD of 0.01 mg/kg-day (milligrams per kilogram of body weight per day). The assessment also concluded that alachlor is likely to be a human carcinogen at hi gh doses; not likely to be a human carcinogen at low doses, and that a linear dose-re sponse extrapolation is no longer appropriate. It established a health refe rence value of 0.005 mg/kg-day for the nonlinear cancer assessment (USEPA, 2006a). Since the hea lth reference value of 0.005 mg/kg- day is lower than the RfD of 0.01 mg/kg-day, the Agency used this value to ca lculate a possible MCLG. Based on the health reference value of 0.005 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters water intake per day, the drinking water equivalent le vel (DWEL) could be 0.2 mg/L. A relative source contribution (RSC) of 20% results in a possible MCLG of 0.04 mg/L (USEPA, 2009b). Since the health review for al achlor indicates that the MCLG could possibly increase to 0.04 mg/L (from its current MCLG of zero) and because the current MCL is based on a PQL of 0.002 mg/L, neither analytical nor treatment feasibility would be a limiting fact or for a possible higher level of 0.04 mg/L. EPA evaluated the results of the occurrence and exposure anal yses for alachlor to determine whether a revised MCLG/MCL woul d be likely to result in a m eaningful opportunity for cost savings to PWSs and their customers while main taining or improving the level of public health protection (USEPA, 2009f). Reviewof health information for alachlor indicated that the MCLG could be increased to 0.04 mg/L from its current MCLG of ze ro. Consequently, the MCL of alachlor possibly can also increase to 0.04 mg/L . Although the Agency obtained and evaluated the finished water occurrence data for alachlor, its usefulness is limited for determining potential

May 2009 Draft EPA document. Do not cite or distribute. 53cost savings to PWSs and their customers because the Agency does not know which systems are treating for this contaminant. As an alternativ e, the Agency evaluated available data on source water quality and conducted a qualitative asse ssment of treatment cost savings. Table VI-2 provides summary data for contam inant occurrence based on maximum sample values for the locations included in the ST ORET and NAWQA data. Although the degree to which these occurrence rates represent national drinking water source occurrence is uncertain, the information shows no to low occurrence at thre shold levels of interest. This information indicates that any resulting NP DWR change would affect system s that rely on source water at less than 0.4% of the NAWQA locations and less than 0.3% of the STORET locations.

Table VI-2. Ambient Water Quality M onitoring Occurrence Summary for Alachlor Number of Locations (% of locations) Maximum Concentration STORET 1 NAWQA 2 Total 2,691 (100.0%) 9,236 (100.0%) Nondetect 2,017 (75%) 8,571 (92.8%) Detected 674 (25%) 665 (7.2%) Exceeds current MCL of 0.002 mg/L 7 (0.26%) 35 (0.38%) Exceeds alternative value of 0.04 mg/L 1 (0.04%) 1 (0.01%) 1. STORET database 1992-2008. 2. NAWQA database 1992-2006. Source: USEPA, 2004c
The BATs and small system compliance technolo gies for alachlor have other beneficial effects, e.g., reduction of other co-occurring cont aminants, precursors for disinfection byproducts (DBPs) or other common impurities. Therefore, if EPA were to consider a higher level, the Agency does not know how many PWSs that are currently treating to comp ly with the existing MCL of 0.002 mg/L would be likely to discontinue treatment that is already in place (USEPA, 2009d). Also, the Agency does not know to what extent affected systems might be able to reduce costs given that capital costs are not reco verable. However, the Agency recognizes that

May 2009 Draft EPA document. Do not cite or distribute. 54there may be opportunities to achieve operational co st savings if these systems are able to reoptimize current treatment. Given these challenges, the Agency believes th at any resulting revi sion is not likely to provide a meaningful opportunity for cost savings. In view of this, any revision would be a low priority activity and not appropriate at this time. The Agency notes that alachlor and two of its unregulated acid degradates (alachlor ethanesulfonic acid or ESA a nd alachlor oxanilic acid or OA 9 ) are currently listed on the second Unregulated Contaminants Monitoring Rule (UCMR 2) (72 FR 367, January 4, 2007 (USEPA, 2007e)). The Agency also listed alachlor ESA and OA on the draft CCL3 (73 FR 9628, February 21, 2008 (USEPA, 2008b)). Once the UC MR 2 monitoring results are available for alachlor and its degradates, the Agency will be able to more fully evaluate alachlor along with its degradates in determining how this information might impact the current regulation for alachlor and/or the need for any revised or new regulat ion to capture the impact from the ESA and OA degradates. Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for alachl or, EPA does not believe a revi sion to the NPDWR for alachlor is appropriate at this time. In making this de cision, the Agency considered whether any possible

9 Between 2004 and 2006, the United States Department Agriculture’s Pesticide Data Program (USDA PDP) collected data for alachlor and its ESA and OA degradates from finished and untreated water samples for a limited number of water systems (USDA, 2004, 2005, and 2006). While alachlor was rarely detected (i.e., 0% to 0.8% of the samples by year), the alachlor ESA and OA degradates were commonly detected (i.e., 19% to 51% of the samples by year for the ESA degradate and 7% to 40% of th e samples by year for the OA degradate). The detected values for the ESA and OA degradates ranged from 0.0028 to 0.357 μ g/L and 0.001 to 0.102 μ g/L, respectively. The detected values for alachlor ranged from 0.0163 to 0.043 μ g/L. May 2009 Draft EPA document. Do not cite or distribute. 55revision to the NPDWR for alachlor is likely to provide a meaningful opportunity for cost savings to public water systems and their cu stomers. Taking into consideration the low occurrence of this contaminant in source wate rs, EPA has decided that any revision to the NPDWR would be a low priority activity for the Ag ency, and, thus, is not a ppropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. In addition, the Agency considers it premature to make any decision to revise the alachlor NPDWR pending the final UCMR 2 monitoring results. 3. Alpha Particle Emitters

a. Background . EPA published an interim NPDWR a nd set an MCL of 15 pCi/L for gross alpha particle activity on July 9, 1976 (41 FR 28402 (USEPA, 1976)). As noted in the August 14, 1975 proposal (40 FR 34324 (USEPA, 1975)) a nd a subsequent September 30, 1986 FR notice (51 FR 34836 (USEPA, 1986a), EPA consideredthe feasibility of treatment techniques, analytical methods and monitoring when es tablishing the MCL of 15 pCi/L. EPA also considered the risks associated with other al pha emitting particles relative to radium-226, which generally fell within the Agency ’s acceptable risk range of 10 -4 to 10 -6 at the MCL of 15 pCi/L. On December 7, 2000 (65 FR 76708 (USEPA, 2000c)), EPA established an MCLG of zero based on a cancer classification of A (known huma n carcinogen) and fi nalized the NPDWR by retaining the MCL of 15 pCi/L. EPA noted in the December 7, 2000, FR notice that new risk estimates from Federal Guidance Report 13 reaffirmed that the 15 pC i/L gross alpha particle MCL (including radium 226 but ex cluding uranium and radon) was appropriate and protective.
May 2009 Draft EPA document. Do not cite or distribute. 56b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to alpha particle emitters. The revised health effects assessment will consider relevant studies on the toxicity of alpha particle em itters, including its potential developmental and reproductive toxicity. The new health effect s assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA , 2009b). However, EPA does not expect the health effects assessment to change the cancer classification for alpha particles, and the MCLG would remain at zero. As a part of the Six-Year Review, the Agen cy considered whether new information was available regarding analytical and treatment feasibility for gross alpha particles. EPA promulgated a detection limit of 3 pCi/L in 1976 (41 FR 28402 (USEPA, 1976)) and retained the use of a detection limit as the required measure of sensitivity for radiochemical analysis in lieu of an MDL or PQL in the final rule (65 FR 76708 (USEPA, 2000c)). EPA did not identify new analytical methods during the current review that would feasibly lower the detection limit. In addition, since the December 7, 2000, regulation, there is no new information regarding treatment feasibility. Since there is no new in formation regarding analytical or treatment feasibility that suggests changes to the MCL, EP A does not believe it is necessary to conduct an occurrence analysis at this time.

c. Review Result. The Agency does not believe a re vision to the NPDWR for gross alpha particles is appropriate at this time because a reassessment of the health risks resulting from exposure to alpha particles is in progress (USEPA, 2009b). Furthermore, there is no new information regarding analytical or treatment f easibility that would warra nt reconsideration of the MCL.

May 2009 Draft EPA document. Do not cite or distribute. 574. Antimony

a. Background . EPA published the current NPDWR for antimony on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.006 mg/L. EPA based the MCLG on a reference dose of 0.0004 mg/kg-day and a cancer cla ssification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to antimony. The revised health effect s assessment will consider relevant studies on the toxicity of antimony, includ ing its potential developmental and reproductive toxicity. The Agency does not expect the new health effects as sessment to be completed in the time frame of the current Six-Year Review cycle (USE PA, 2009b). On December 21, 2007 (72 FR 72715 (USEPA, 2007c)), the Agency noted that the health effects assessment for antimony is in
process.

c. Review Result. Since the MCL for antimony is set at its MCLG and a reassessment of the health risks resulting from exposure to antimony is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time.

5. Arsenic

a. Background . EPA published the current NPDWR for arsenic on January 22, 2001 (66 FR 6976 (USEPA, 2001c)). The NPDWR establishe d an MCLG of zer o based on a cancer classification of A, known hu man carcinogen. The NPDWR also established an MCL of 0.010 mg/L, which is higher than the feasible analyt ical level of 0.003 mg/L . EPA exercised its discretionary authority to set an MCL at a level higher than feasible (SDWA Section 1412(b)(6)), based on the finding that a final MCL of 0.010 mg/L represents the level that best maximizes health risk reduction bene fits at a cost that is justif ied by the benefits (66 FR 6976 at 7020 (USEPA, 2001c)).

May 2009 Draft EPA document. Do not cite or distribute. 58b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to arsenic. In June 2007, EPA’s Scienc e Advisory Board (SAB) issued its evaluation of the Agency’s 2005 draft toxico logical review for inorganic ar senic (USEPA, 2007a). In its 2007 report, SAB supports the continued use of a lin ear cancer risk model for inorganic arsenic, noting that the available data do not describe the shape of the dos e-response curve at low doses. The new health effects assessment (both cancer and noncancer) were not completed by March 1, 2009, the review cutoff date for this notice. The revised health effects assessments will consider relevant studies on the toxicity of arsenic, including its poten tial developmental and reproductive toxicity. The IRIS Substance A ssessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessments.

c. Review Result. The Agency does not believe a re vision to the NPDWR for arsenic is appropriate at this time because a reassessment of the health risks resulting from exposure to arsenic is ongoing (USEPA, 2009b). As noted pr eviously, the arsenic MCL is based on the SDWA cost benefit provision (Section 1412(b)(6)) and the health effects assessment is important for reviewing the benefits associat ed with the basis of the MCL.

6. Asbestos

a. Background . EPA published the current NPDWR fo r asbestos on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an MCLG and an MCL of 7 million fibers/L. EPA evaluated asbestos as a Category II 10 contaminant (equivalent to Group C, possible human carcinogen) by the oral route of exposure.

10 Category II contaminants include those contaminants for which EPA has determined there is limited evidence of carcinogenicity from drinking water considering weight of evidence, pharmacokinetics, potency, and exposure. For Category II contaminants, EPA has used two approach es to set the MCLG: Either (1) setting the MCLG based upon noncarcinogenic endpoints of toxicity (the RfD) then applying an additional risk management factor of 1 to 10; May 2009 Draft EPA document. Do not cite or distribute. 59b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to asbestos. The revised health effect s assessment will consider relevant studies on the toxicity of asbestos, includi ng its potential developmental an d reproductive toxicity. The Agency does not expect the new health effects as sessment to be completed in the time frame of the current Six-Year Review cycle (USEPA, 2009 b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/iristrac/inde x.cfm) has the most up-to-date information on the status of the hea lth effects assessment.

c. Review Result. Since the MCL for asbestos is set at its MCLG and a reassessment of the health risks resulting from expos ure to asbestos is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time.

7. Atrazine

a. Background . EPA published the current NPDWR fo r atrazine on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an MCLG and an MCL of 0.003 mg/L. EPA based the MCLG on a reference dose of 0.005 mg /kg-day and a cancer classification of C, possible human carcinogen. b. Technical Reviews. In 2006, the Agency finalized a he alth effects assessment for the reregistration of atrazine as a pesticide (USEPA, 2006c). This assessment examined an extensive toxicology database and included investigati on of atrazine’s neur oendocrine mode of action and related reproductive and developmenta l effects. The assessment established a new RfD of 0.018 mg/kg-day, based on attenuation of pre-ovulatory lute inizing hormone (LH) surge, a key event indicative of hypothalamic func tion disruption. In accordance with the 1999 Interim Guidelines for Carcinogen Risk Assessment , EPA’s Cancer Assessment Review Committee

or (2) setting the MCLG based upon a theoreti cal lifetime excess cancer risk range of 10 -5 to 10 -6 using a conservative mathematical extrapolation model.
May 2009 Draft EPA document. Do not cite or distribute. 60(CARC) classified atrazine as “not likely to be carcinogeni c to humans” because the tumor response in the Sprague-Dawley rats was determined to be a strain specific mechanism which is not relevant to humans.

c. Review Result. The Agency believes it is not appr opriate to consider revisions to the NPDWR for atrazine at this time because there ar e some forthcoming studies on atrazine and its metabolites from the Agency’s Office of Resear ch and Development (ORD). While the LH effect remains a biologically plausible and se nsitive endpoint for the atrazine human health effects assessment, EPA will continue to analyze any relevant information regarding the adverse health effects of atrazine. The Agency doe s not anticipate that the ORD research will significantly change the atrazi ne health effects assessment conclusions supporting the Food Quality Protection Act (FQPA) reregistrati on decision published in 2006 (USEPA, 2006c). However, it is unclear whether the new data would impact the Agency’s determination on whether any revisions to the current MCLG/N PDWR for atrazine ar e appropriate (USEPA, 2009b). The Agency expects to publish the ORD studies in 2009.

8. Barium

a. Background . EPA published the current NPDWR for barium on July 1, 1991 (56 FR 30266 (USEPA, 1991b)). The NPDWR established an MCLG and an MCL of 2 mg/L. EPA based the MCLG on a reference dose of 0.07 mg/ kg-day and a cancer classification of D, not classifiable as to human carci nogenicity via the oral route. b. Technical Reviews. In 2005, the Agency updated the hea lth effects assessment of barium and revised the RfD from 0.07 mg/kg-day to 0.2 mg/kg-day (USEPA, 2005a). The change in the RfD could lead to a change in the MCLG. This assessment cons idered relevant studies on the toxicity of barium including developmenta l and reproductive toxicity. The assessment concluded that barium is not lik ely to be carcinogenic to humans (USEPA, 2005a). Based on the

May 2009 Draft EPA document. Do not cite or distribute. 61new IRIS assessment and RfD of 0.2 mg/kg- day, and assuming 70 kg body weight and 2 liters water intake per day, the DWEL c ould be 7.0 mg/L. An RSC of 80% 11 results in a possible MCLG of 6.0 mg/L. Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor if EPA were to raise the MCLG. EPA evaluated the results of the occurrence and exposure analyses for barium to determine whet her a revised MCLG/MCL would be likely to result in a meaningful opportunity to achieve cost savings for PWSs and their customers while maintaining, or improving, the level of public health protection (USE PA, 2009f). Although the Agency obtained and evaluated the finished water occurrence data for barium, its usefulness is limited for determining potential cost savings to PWSs and their customers because the Agency does not know which systems are treating for this contaminant. As an alternative, the Agency evaluated available data on s ource water quality and conducted a qualitative assessment of treatment cost savings. Table VI-3 provides summary data for contam inant occurrence based on maximum sample values for the locations included in the ST ORET and NAWQA data. Although the degree to which these occurrence rates represent national drinking water source occurrence is uncertain, the information shows no to low occurrence at thre shold levels of interest. This information indicates that any resulting NP DWR change would affect system s that rely on source water at less than 0.1% of the NAWQA locations and less than 0.3% of the STORET locations.

11 The present MCLG for barium does not include an RSC because the dose used in the calculation applied to only the dose from the drinking water. If a new MCLG were to be developed from the animal data that support the 2005 IRIS RfD, an RSC would be required. Regulations or guidelines pertaining to barium from media other than water were not identified. Barium meta borate is a registered pesticide but it does not have any food uses and does not have a human health ambient water quality guideline value. EPA used the subtraction calculation method to determine the possible RSC of 80% for drinking water (the ceiling on RSC specified by the methodology).

May 2009 Draft EPA document. Do not cite or distribute. 62Table VI-3. Ambient Water Quality M onitoring Occurrence Summary for Barium Number of Locations (% of locations) Maximum Concentration STORET 1 NAWQA 2 Total 16,595 (100.0%) 4,864 (100.0%) Nondetect 2,294 (13.8 %) 43 (0.9%) Detected 14,301 (86.2%) 4,821 (99.1%) Exceeds current MCL/MCLG of 2.0 mg/L 60 (0.36%) 3 (0.1%) Exceeds alternative value of 6.0 mg/L 21 (0.13%) 0 (0.0%) 1. STORET database 2002-2007. 2. NAWQA database 1992-2005. Source: USEPA, 2004c
The BATs and small system compliance techno logies for barium have other beneficial effects, e.g., reduction of other co-occurring contaminants or other common impurities. Therefore, if EPA were to consider a higher level, the Agency does not know how many PWSs that are currently treating to comply with the existing MCL of 2 mg/L would be likely to discontinue treatment that is already in place (USEPA, 2009d). Also, the Agency does not know to what extent affected systems might be able to reduce costs given thatcapital costs are not recoverable. However, the Agency recognize s that there may be opportunities to achieve operational cost savings if these systems ar e able to re-optimize current treatment. Given these challenges, the Agency believes th at any resulting revi sion is not likely to provide a meaningful opportunity for cost savings. In view of this, any revision would be a low priority activity and not appropriate at this time.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for barium, EPA does not believe a revision to the NPDWR for barium is appropriate at this time. In making this de cision, the Agency considered whether any possible revision to the NPDWR for barium is likely to pr ovide a meaningful opportunity for cost savings to public water systems and their customers. Taking into consideration the low occurrence of this contaminant in source waters, EPA has deci ded that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:
May 2009 Draft EPA document. Do not cite or distribute. 63• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted.

9. Benzene

a. Background . EPA published the current NPDWR for benzene on July 8, 1987 (52 FR 25690 (USEPA, 1987)). The NPDWR establishe d an MCLG of zer o based on a cancer classification of A, known hu man carcinogen. The NPDWR also established an MCL of 0.005 mg/L, based on analytical feasibility. b. Technical Reviews. In 2000 and 2003, the Agency updated the IRIS assessment of benzene. The cancer assessment was complete d first and characteri zed benzene as a known human carcinogen by all routes of exposure; the one-in-a million risk estimates for cancer by the oral route of exposure ranged from 1 μ g/L to 10 μ g/L (USEPA, 2000b). This cancer assessment was also noted in the first Six-Year Review(67 FR 19030, April 17, 2002 (USEPA, 2002c)). As part of the Six-Year Review process, the Agen cy’s Office of Water (O W) conducted a literature search through June 2007 for relevant data on th e carcinogenicity of benzene as well as its potential developmental and repr oductive toxicity (USEPA, 2009b). While the literature search did identify several new studies that evaluated the cancer and nonc ancer effects of benzene, none of the new studies would affect the cancer classification, which serv es as the basis for the MCLG of zero. A recent occupational study (Lan et al., 2004) of the noncancer effects of benzene identified hematological effects in workers at levels below those previously reported. The Agency for Toxic Substances and Disease Registry (ATSDR) (2007) chronic MRL based on the Lan et al. (2004) data of 0.0005 mg /kg/day is lower than the IR IS RfD of 0.004 mg/kg/day. If the ATSDR MRL were used as the basis for a noncancer health reference level, the value would

May 2009 Draft EPA document. Do not cite or distribute. 64be 0.004 mg/l, a value that is s lightly below the current MCL. Because the MCLG remains at zero, the Agency believes that a further review of the health effects of benzene is not warranted at this time. The current MCL for benzene is based on a PQ L of 0.005 mg/L. For the Six-Year Review, the Agency considered whether changes in the anal ytical feasibility of benzene might lead to a lower MCL. EPA reviewed WS data from the fi rst Six-Year Review cycle and then analyzed more recent PT data to determine if the PQL can be revised (i.e., analytical feasibility). Passing rates for WS data available through late 1999 for benzene are above 95 percent around the current PQL of 0.005 mg/L, includin g two studies with true values below the current PQL. All passing rates in the WS data exc eeded 75 percent. More recentPT data from late 1999 through 2004, supplied by a PT provider, al so show greater than 90 percent passing rates for studies around the PQL, including eight with true values below the current PQL. Because most of the laboratory passing rates from WS and PT studies exceeded the 75 percent criterion typically used to derive a PQL, a lowering of the PQL for benzene might be possible. These results, however, are insufficient to recalculate a revised PQL for benzene because not enough data points are available below the current PQL to derive a value at the 75 percent passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of be nzene (Methods 502.2 and 524.2). While EPA prefers to use laboratory perfo rmance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Re view ICR dataset contains MRL values for 139,190 samples. Of these, 120,308 (86%) equal the modal MRL of 0.0005 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 65An additional 17,964 (13%) are lower than 0.0005 mg/L. The MDLs of approved methods range from 0.00001 to 0.0004 mg/L. Applying a multiplie r of 10 would give a possible PQL range from 0.0001 to 0.004 mg/L

. Because of the preponderance of MRL values of 0.0005 mg/L, EPA selected that value as the minimum threshold fo r the occurrence and expo sure analysis (USEPA, 2009e). Based on these varied and unrelated approach es/sources of information, EPA believes that there is potential to lower the PQL for benzene. To determine whether any MCL revision is likely to provide a meaningful opportunity to improve public health protection, EPA evaluated the occurrence of benzene at thresholds of 0.0005, 0.001, and 0.0025 mg/L (USEPA, 2009f). Table VI-4 shows the results of the occurrence and exposure anal ysis for the current MCL and EQLs set equal to 0.0025 mg/L, 0.001 mg/L, and 0.0005 mg/L. The Six-Year Review ICR occurrence data have a modal MR L of 0.0005 mg/L, which limits reliable contaminant detection to 0.0005 mg/L. As indicated, average concentr ations exceed the current MCL for 10 of 50,435 systems (0.020%) serving 14,000 people (or 0.006% of 227 million people). Note that these results do not necessarily reflect MCL viol ations, which are based on annual average concentrations at entry points; Safe Drinki ng Water Information System/Federal version (SDWIS/FED) indicates 41 MCL violations for benzene between 1998 and 2005, with annual violations ranging from 1 to 12 (USEPA, 2007g). The occurrence and exposure analysis shows that average concentrations at 95 to 123 of 50,435 systems (0.188% to 0.244%), serving 304,000 to 485,000 people (or 0.134% to 0.214% of 227 million people), exceed the EQL of 0.0005 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 66Table VI-4. Number and Percent of Systems with Mean Concentrations Exceeding Benzene Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold(Percentages based on 50,435 systems with benzene data in the SixYear Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 10 (0.020%) 10 (0.020%) 10 (0.020%) 1/2 MCL (0.0025 mg/L) 16 (0.032%) 14 (0.028%) 14 (0.028%) 2xEQL (0.001 mg/L) 70 (0.139%) 58 (0.115%) 52 (0.103%) EQL (0.0005 mg/L) not applicable 123 (0.244%) 95 (0.188%) Corresponding Population Served (Percentages based on 226,947,000 people served by the systems with benzene data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 14,000 (0.006%) 14,000 (0.006%) 14,000 (0.006%) 1/2 MCL (0.0025 mg/L) 111,000 (0.049%) 110,000 (0.048%) 110,000 (0.048%) 2xEQL (0.001 mg/L) 180,000 (0.079%) 159,000 (0.070%) 158,000 (0.070%) EQL (0.0005 mg/L) not applicable 485,000(0.214%) 304,000 (0.134%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.0005 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for benzene is appropriate at this time. The o ccurrence and exposure analysis based on possible changes in analytical feasibility indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration the low

May 2009 Draft EPA document. Do not cite or distribute. 67occurrence of this contaminant, EPA has decide d that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 10. Benzo(a)pyrene

a. Background . EPA published the current NPDWR for benzo(a)pyrene on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR establis hed an MCLG of ze ro based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.0002 mg/L, based on analytical feasibility. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to benzo(a)pyrene. The revised health effects assessmentwill consider relevant studies on the toxicity of benzo(a)pyrene, including its potential developmental and reproductive toxicity. The new health e ffects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). Th e IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/iristr ac/index.cfm) has the most up-to-date information on the status of the health effects assessment. Although a risk assessment is in process for be nzo(a)pyrene, the existi ng MCLG is zero and the current MCL of 0.0002 mg/L is based on the PQL. For the Six-Year Review, the Agency evaluated several sources of information to dete rmine whether changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determ ine if the PQL can be re vised (i.e., analytical feasibility). Passing ra tes for WS data available through late 1999 for benzo(a)pyrene are all

May 2009 Draft EPA document. Do not cite or distribute. 68above 75 percent. However, the true concentrat ions were all higher than the current PQL of 0.0002 mg/L. More recent PT data from late 1999 through 2004, supplied by a PT provider, show several true concentrations with passing rates less than the 75 pe rcent criterion typically used to derive a PQL. All of the true concentrations in the PT data were higher than the current PQL. Given the variability in passing rates and the lack of data points below the current PQL, a lowering of the PQL for benzo(a)pyrene is not appropriate at this time (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of benzo(a)pyrene (Methods 550, 550.1, and 525.2). While EPA prefers to use laborato ry performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Review I CR dataset contains MRL values for 55,487 samples. Of these, 29,769 ( 54%) equal the modal MRL of 0.00002 mg/L. An additional 970 (2%) are lower than 0.00002 mg/L, and 21,198 (38%) are between 0.00002 mg/L and 0.0001 mg/L. The MDLs of approve d methods are 0.000016, 0.000029, and 0.00023 mg/L. Because the MDL values fall across a wide range, EP A selected the intermediate value, applied a multiplier of 10, and rounded up. The resulting 10×MDL value is 0.0003 mg/L. Since the MRL values are widely dispersed, and the intermediate 10×MDL value is higher than the current PQL, these data do not support a PQL reduction. Based on these varied and unrelated approaches/sources of information, EPA believes th at there is no potential to lower the PQL for benzo(a)pyrene. Since the MCL is constraine d by the PQL, and the PQL is unchanged, EPA does not believe it is necessary to conduct an occurrence analysis at this time.

c. Review Result. The Agency does not believe a revi sion to the NPDWR for benzo(a)pyrene is appropriate at this time because a reassessmen t of the health risks resulting from exposure to

May 2009 Draft EPA document. Do not cite or distribute. 69benzo(a)pyrene is in progress (USEPA, 2009b). Furt hermore, a review of analytical feasibility did not identify a potential to revise the MCL, which is limited by feasibility. 11. Beryllium

a. Background . EPA published the current NPDWR for beryllium on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.004 mg/L. EPA classified beryllium in Group B2, probable hum an carcinogen, based on cl ear evidence of its carcinogenicity via inhalation or in jection in several animal species. However, EPA also placed beryllium in drinking water Category II for regu lation, based on the weight of evidence for carcinogenicity via ingestion, and the potency, exposure and pharmacokinetics of this chemical. EPA derived the MCLG by applying an additional risk management factor of 10 to the RfD of 0.005 mg/kg-day (57 FR 31776 at 31 785, July 17, 1992 (USEPA, 1992)). b. Technical Reviews. As noted in Six Year Review 1 (68 FR 42908, USEPA, 2003e), EPA updated its assessment of the health risks resu lting from exposure to beryllium in 1998 (USEPA, 1998c). The 1998 IRIS assessment uses the 1986 EPA cancer guidelines (USEPA, 1986b) and classifies beryllium as Group B1, probable humancarcinogen, via inhalation route. However, the 1998 IRIS assessment states that the database is inadequate for assess ing the carcinogenicity of ingested beryllium and concluded that the human carcinogenic potential of ingested beryllium cannot be determined. The Agency considered the 1998 assessessment in Six Year Review 1 and decided that it was not appropriate to revise the NPDWR at that time. EPA has initiated a reassessment of the health risks resulting from ex posure to beryllium. The new assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa .gov/iristrac/index.cfm) has the most up-to-date information on the st atus of the health effects assessment.

May 2009 Draft EPA document. Do not cite or distribute. 70c. Review Result. Since the MCL for beryllium is set at its MCLG and a reassessment of the health risks resulting from exposure to beryllium is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time.

12. Beta Particle and Photon Emitters

a. Background . EPA published an interim NPDWR and set an MCL of 4 millirems/yr (mrem/yr) for beta particle and photon emitters on July 9, 1976 (41 FR 28402 (USEPA, 1976)). As noted in the August 14, 1975 proposal ( 40 FR 34324 (USEPA, 1975)) and a subsequent September 30, 1986 FR (51 FR 34836 (USEPA , 1986a) advanced notice of proposed rulemaking, EPA considered the feasibility of treatment techniques, analytical methods and monitoring when establishing the MCL of 4 mrem/yr. EPA also considered the risks associated with beta particle and photon emitters, which generally fell within the Agency’s acceptable risk range of 10 -4 to 10 -6 at the MCL of 4 mrem/yr. OnDecember 7, 2000 (65 FR 76708 (USEPA, 2000c)), EPA established an MCLG of zero based on a cancer clas sification of A (known human carcinogen) and finalized the NP DWR by retaining the MCL of 4 mrem/yr. EPA noted in the December 7, 2000, FR notice that new risk es timates from Federal Guidance Report 13 reaffirmed that the 4 mrem/yr MC L was appropriate and protective 12

. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to beta particles. The revised health effects assessment will consider relevant studies on the toxicity of beta particles, including its potential developmental an d reproductive toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date

12 After the December 7, 2000, final regulation, two tr ade associations and severa l municipal water systems challenged EPA’s standard for the beta photon emitters by claiming that the Agency did not use the best available science when finalizing the standard. In February of 2003 , the District of Columbia (DC) Circuit Court of Appeals upheld EPA’s regulation for beta and photon emitters (as well as radium 226 and 228 and uranium). In July, 2004, the DC Circuit Court of Appeals also upheld the policy and scientific basis of EPA’s application of the beta particle and photon (man-made) drinking water standards to the ground water protection standards used for Yucca Mountain under 40 CFR part 197 (66 FR 32073, June 13, 2001 (USEPA, 2001d)). May 2009 Draft EPA document. Do not cite or distribute. 71for this notice (USEPA, 2009b). However, EPA does not expect the health effects assessment to change the cancer classification for beta part icles, and the MCLG would remain at zero. As a part of the Six-Year Review, the Agen cy considered whether new information was available regarding the analytical and treatment feasibility for beta particle and photon emitters. EPA promulgated the MCL of 4 mrem/yr for man-made beta particle and photon emitters (present in any combination) in 1976 (41 FR 28402 (USEPA, 1976)) and reta ined the use of the detection limit as the required measure of sensit ivity in the December 2000 final rule (65 FR 76708 (USEPA, 2000c)). The original rule estimated a risk ceiling of 5.6×10 -5 for whole body doses. Limits were set in picoCurie units for each nuclide equivalent to a 4 mrem dose. The newer dosimetry found in Federal Guidance13 and reported in the December 2000 final rule reveals more exact risks that are still within the Agency’s acceptable li mits. While individual dose estimates changed over time, the overall lim it of 4 mrem was retained along with a twotiered screening level to avoid analyzing each possible nuclide below the screen, and still be protective. EPA did not identify new analytical methods during the curre nt review that would feasibly lower the detection limits for beta particle and photon emitters. In addition, since the December 7, 2000 regulation, there is no new inform ation regarding treatment feasibility. Since there is no new information regard ing analytical or treatment feas ibility that suggests changes to the MCL, EPA does not believe it is necessary to conduct an occurren ce analysis at this time.

c. Review Result. The Agency does not believe a revisi on to the NPDWR for beta particles is appropriate at this time because a reassessment of the health risks resulting from exposure to beta particles is in progress (USEPA , 2009b). Furthermore, there is no new information regarding analytical or treatment feasibility that would warrant reconsid eration of the MCL.

May 2009 Draft EPA document. Do not cite or distribute. 7213. Cadmium

a. Background . EPA published the current NPDW R for cadmium on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establis hed an MCLG and an MCL of 0.005 mg/L. Because of inadequate dose-response data to char acterize the presence or lack of a carcinogenic hazard from oral exposure, the Agency clas sified cadmium as a Group D carcinogen, not classifiable as to human carcinogenicity by th e oral route of exposure. Therefore, EPA developed the MCLG for cadmium ba sed on the RfD of 0.0005 mg/kg-day. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to cadmium. The revised health effect s assessment will consider relevant studies on the toxicity of cadmium, includ ing its potential developmental and reproductive toxicity. The new health effects assessment was not comple ted by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). The IRIS Subs tance Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment.

c. Review Result. Since the MCL for cadmium is set at its MCLG and a reassessment of the health risks resulting from expos ure to cadmium is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time.

14. Carbofuran

a. Background . EPA published the current NPDWR for carbofuran on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establis hed an MCLG and an MCL of 0.04 mg/L. EPA based the MCLG on a reference dose of 0.005 mg/kg-day and a cancer classification of E, evidence of non-carcinoge nicity for humans. b. Technical Reviews. In 2006, the Agency updated health effects assessment of carbofuran. The Agency identified a change in this assessmen t that could lead to a change in the MCLG (73

May 2009 Draft EPA document. Do not cite or distribute. 73FR 44864, July 31, 2008 (USEPA, 2008a)). This asse ssment considered relevant studies on the toxicity of carbofuran including developmenta l and reproductive toxicity. The assessment revised the RfD from 0.005 mg/kg-day to an acute RfD of 0.00006 mg/kg-day and concluded that carbofuran is not likely to be carcinoge nic to humans (USEPA, 2006d). Based on the revised acute RfD of 0.00006 mg/kg-day, and as suming 10 kg body weight and 1 liter water intake per day for a child, the resulting DWEL would be 0.0006 mg/L. Using an RSC of 20%, a possible new MCLG would be 0.00012 mg/L. The default RSC value of 20% was selected because of the significant exposures resulti ng from actual food dietary exposure for children from 1 to 6 years old, which approach es 100% of the updated RfD (USEPA, 2006d). Two recent Agency actions may affect carbofuran presence in food and water sources. In May 2009, EPA revoked all toleran ces (maximum residue limits) for carbofuran, which could prohibit all carbofuran residues on food, e ffective December 31, 2009 (74 FR 23046, May 15, 2009 (USEPA, 2009i)). The registrant and intere sted parties had until July 14, 2009, to raise objections and/or request a hearing on the tolerance revocations. Revoking carbofuran tolerances is part of a broader series of Agency actions to cancel all uses of carbofuran in the United States due to dietary, occupational, and ec ological risks of concer n. Following resolution of the current on-going administra tive process for resolving the safety of the tolerances, EPA will proceed to cancel the remaining uses of carbofuran. In addition, prior to the tole rance revocation, the registrant , FMC Corporation, voluntarily cancelled 22 uses of carbofuran (74 FR 11551, March 18, 2009 (USEPA, 2009j)). Existing stocks of carbofuran can be applied to food crops until December 31, 2009, and to non-food crops according to the label until supplies are depl eted. These decisions are expected to reduce exposure to carbofuran and its metabolite (3-hyd roxycarbofuran) in food products and in water, which would affect the RSC used to derive a possible MCLG. Therefore, EPA believes that it

May 2009 Draft EPA document. Do not cite or distribute. 74should factor in the effect of these actions, on ce completed, before the Agency determines the potential for an NPDWR revision. The occurrence of carbofuran in drinking water is an additional source of uncertainty in the review process that is compounded by the re cent voluntary cancellations and tolerance revocations. The Six-Year Review ICR occurrence data are based on the Standardized Monitoring Framework for synthe tic organic compounds, which is designed to evaluate longterm exposure to contaminants with chronic exposure health endpoints. As a result, short-term seasonal peaks, which correspond with carbofuran a pplication as a pesticid e, cannot be readily detected in this dataset. The cancellation will reduce carbofuran application and the potential for seasonal peaks to occur. Reductions in overall car bofuran use is expected to reduce the potential occurrence of carbofuran in drinking water sources.

c. Review Result. Although there are new health data that support consideration of whether to revise the MCLG/MCL for carbofuran, the on-going regulatory acti ons could affect the possible MCLG. Therefore, EPA is placing carbofuran in the information gap category due to the uncertainty of the cancella tion impacts the MCLG. In additi on, EPA notes that the decision to cancel the reregistration of carbofuran w ould reduce the presence of this compound in the environment and the likelihood of exposure to car bofuran in food and drinking water sources. Consequently, EPA believes it is not appropriate to consider a ny revisions to the NPDWR for carbofuran at this time.

15. Carbon Tetrachloride

a. Background . EPA published the current NPDWR for carbon tetrachloride on July 8, 1987 (52 FR 25690 (USEPA, 1987)). The NPDWR establis hed an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.005 mg/L, based on anal ytical feasibility.

May 2009 Draft EPA document. Do not cite or distribute. 75b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to carbon tetrachloride. The revised h ealth effects assessment will consider relevant studies on the toxicity of car bon tetrachloride, including its potential developmental and reproductive toxicity. The new health effect s assessment was not completed by March 1, 2009, the review cutoff date for this notice (USE PA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/ir istrac/index.cfm) has the most up-to-date information on the status of the health effects assessment. Although a risk assessment is in process for car bon tetrachloride, the ex isting MCLG is zero and the current MCL of 0.005 mg/L is based on the PQL. For the Six-Year Review, the Agency evaluated several sources of information to dete rmine whether changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determ ine if the PQL can be re vised (i.e., analytical feasibility). Passing ra tes for WS data available through late 1999 for carbon tetrachloride are at or above 95 percent around the current PQL of 0.005 mg/L, includi ng one study with a true value below the current PQL. More recent PT data from late 1999 through 2004, supplied by a PT provider, also show greater than 90 percent pass ing rates for studies ar ound the PQL, except for one study with a passing rate of 85 percent. Nine PT studies had true va lues below the current PQL. Because most of the la boratory passing rates from WS and PT studies exceeded the 75 percent criterion typically used to derive a PQL, a lowering of the PQL for carbon tetrachloride might be possible. These results, however, ar e insufficient to recalculate a revised PQL for carbon tetrachloride because not enough data poi nts are available below the current PQL to derive a value at the 75 percen t passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR

May 2009 Draft EPA document. Do not cite or distribute. 76dataset, and the MDLs for approved methods for the detection of carbon tetrachloride (Methods 502.2, 524.2, and 551.1). While EPA prefers to use labor atory performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the cu rrent PQL. The Six-Year Review ICR dataset contains MRL values for 139,221 samples. Of these, 119,849 (86%) equal the modal MRL of 0.0005 mg/L. An additional 16,195 (12%) are lower than 0.0005 mg/L. The MDLs of approved methods range from 0.000002 to 0.00021 mg/L. A pplying a multiplier of 10 would give a possible PQL range from 0.00002 to 0.0021 mg/L. Because of the preponderance of MRL values of 0.0005 mg/L, EPA selected that value as the minimum threshold for the occurrence and exposure analysis (USEPA, 2009e). Based on these varied and unrelated approach es/sources of information, EPA believes that there is potential to lower th e PQL for carbon tetrachloride. To determine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of carbon tetrachloride at thres holds of 0.0005, 0.001, and 0.0025 mg/L (USEPA, 2009f). Table VI-5 show s the results of the occurrence and exposure analysis for the current MCL and EQLs set equal to 0.0025 mg/L, 0.001 mg/L, and 0.0005 mg/L. The occurrence and exposure analysis shows that aver age concentrations exceed the current MCL for five of 50,446 systems (0.010%), serving fewer than 2,000 people (or 0.001% of 227 million people). Note that these results do not necessa rily reflect MCL violations, which are based on annual average concentrations at entry points; SDWIS/FED indicates 19 MCL violations for carbon tetrachloride between 1998 and 2005 with annua l violations ranging from 1 to 4 (USEPA, 2007g). Average concentrations for 84 to 118 of 50,446 systems (0.167% to 0.234%), serving 368,000 to 750,000 people (or 0.162% to 0.330% of 227 million people), exceed the EQL of 0.0005 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 77Table VI-5. Number and Percent of Systems with Mean Concentrations Exceeding Carbon Tetrachloride Thresholds and Correspondi ng Estimates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 50,446 systems with carbon tetrachloride data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 5 (0.010%) 5 (0.010%) 5 (0.010%) 1/2 MCL (0.0025 mg/L) 13 (0.026%) 12 (0.024%) 12 (0.024%) 2xEQL (0.001 mg/L) 59 (0.117%) 50 (0.099%) 40 (0.079%) EQL (0.0005 mg/L) not applicable 118 (0.234%) 84 (0.167%) Corresponding Population Served (Percentages based on 226,935,000 people served by the systems with carbon tetrachloride data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 1,800 (0.001%) 1,700 (0.001%) 1,700 (0.001%) 1/2 MCL (0.0025 mg/L) 5,800 (0.003%) 5,500 (0.002%) 5,500 (0.002%) 2xEQL (0.001 mg/L) 265,000 (0.117%) 212,000 (0.093%) 190,000 (0.084%) EQL (0.0005 mg/L) not applicable 750,000 (0.330%) 368,000(0.162%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.0005 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. The Agency does not believe a revision to the NPDWR for carbon tetrachloride is appropriate at this time because a reassessment of the health risks resulting from exposure to carbon tetrachloride is in progress (USEPA, 2009b). Furthermore, the occurrence and exposure analysis based on po ssible changes in anal ytical feasibility indicates that any revision to the MCL is unlikely to provide a m eaningful opportunity to improve public health
May 2009 Draft EPA document. Do not cite or distribute. 78protection. After consideration of the low occurrence of this contaminant, EPA has decided that any revision to the NPDWR would be a low prio rity activity for the Ag ency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted.

16. Chlordane

a. Background . EPA published the current NPDWR for chlordane on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establis hed an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.002 mg/L, based on anal ytical feasibility. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the carcinogenicity of chlordane as well as its potential developmental and reproductive toxicity. EPA ha s not identified any new information that indicates that it is appropriate to consider revisions to the cancer classification for chlordane at this time (USEPA, 2009b). Because the MCLG remains at zero, the Ag ency believes that a further review of the health effects of chlordane is not warranted at this time. The current MCL for chlordane is based on a PQL of 0.002 mg/L. For the Six-Year Review, the Agency considered whether changes in the anal ytical feasibility of chlordane might lead to a lower MCL. EPA reviewed WS data from the fi rst Six-Year Review cycle and then analyzed more recent PT data to determine if the PQL can be revised (i.e., analytical feasibility). Passing rates for WS data available through late 1999 for chlordane are above 80 percent around the current PQL of 0.002 mg/L, includin g three studies with true valu es below the current PQL.

May 2009 Draft EPA document. Do not cite or distribute. 79More recent PT data from late 1999 through 2004, supplied by a PT provider, also show greater than 80 percent passing rates, except for two studies with pass ing rates equal to or below 75 percent. There are no PT studies with true values below the PQL. Because most of the laboratory passing rates from WS and PT studies – including three below the PQL – exceeded the 75 percent criterion typically used to derive a PQL, a lowering of the PQL for chlordane might be possible. These results, however, ar e insufficient to recalculate a revised PQL for chlordane because not enough data points are availa ble below the current PQL to derive a value at the 75 percent passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of ch lordane (Methods 505 and 508). While EPA prefers to use laboratory perfor mance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Review ICR dataset contains MRL values for 57,506 samples. Of these, 26,893 (47%) equal th e modal MRL of 0.0002 mg/L. An additional 9,764 (17%) are lower than 0.0002 mg/L, and 20, 844 (36%) are between 0.0002 mg/L and the MCL of 0.002 mg/L. The MDLs of approved methods range from 0.0000041 to 0.00014 mg/L. Applying a multiplier of 10 would give a po ssible PQL range from 0.000041 to 0.0014 mg/L. Because of the broad dispersion in MRL values , EPA averaged the 10×MDL values, rounded up to 0.001 mg/L, and used that value as the mini mum threshold in the occurrence and exposure analysis. Based on these varied and unrelated approach es/sources of information, EPA believes that there is potential to lower the PQL for chlordan e. To determine whether any MCL revision is likely to provide a meaningful opportunity to improve public health protection, EPA evaluated

May 2009 Draft EPA document. Do not cite or distribute. 80the occurrence of chlord ane at an estimated quantitation level of 0.001 mg/L (USEPA, 2009f). Table VI-6 shows the results of the occurrence and exposure analys is for the current MCL and an EQL set equal to 0.001 mg/L. The occurrence and exposure analysis shows that average concentrations exceed the current MCL for one of 31,841 systems (0.003%) serving 80 people (or 0.00004% of 182 million people). Note that th ese results do not necessarily reflect MCL violations, which are based on annual average concentrations at entry points; SDWIS/FED indicates no MCL violations for chlordan e between 1998 and 2005 (USEPA, 2007g). Average concentrations at one to two of 31,841 systems (0.003% to 0.006%), still serving approximately 80 to 120 people (or 0.00004 to 0.00007% of 182 million people), exceed the EQL of 0.001 mg/L. Table VI-6. Number and Percent of Systems wi th Mean Concentrations Exceeding Chlordane Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold(Percentages based on 31,841 systems with chlordane data in the SixYear Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.002 mg/L) 1 (0.003%) 1 (0.003%) 1 (0.003%) EQL (0.001 mg/L) 2 (0.006%) 2 (0.006%) 1 (0.003%) Corresponding Population Served (Percentages based on 182,037,000 people served by the systems with chlordane data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.002 mg/L) 80 (0.00004%) 80 (0.00004%) 80 (0.00004%) EQL (0.001 mg/L) 120 (0.00007%) 120 (0.00007%) 80 (0.00004%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations. May 2009 Draft EPA document. Do not cite or distribute. 81c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for chlordane is appropriate at this time. The occurrence and exposure analysis based on possible changes in analytical feasibility indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration the low occurrence of this contaminant, EPA has decide d that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted.

17. Chromium

a. Background . EPA published the current NPDWR fo r total chromium on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establ ished an MCLG and an MCL of 0.1 mg/L. Although the NPDWR regulates tota l chromium, the adverse health effects associated with hexavalent chromium (Cr VI) are the basis of th e current MCLG because th at is the more toxic species (56 FR 3526, January 31, 1991 (USEPA, 1991a)). EPA base d the MCLG on an RfD of 0.005 mg/kg-day and an assumed RSC from wate r of 70 percent for total chromium. EPA regulated chromium as a Group D carcinogen, not cl assifiable as to human carcinogenicity by the oral route of exposure. b. Technical Reviews. The health effects technical re view identified some information regarding the carcinogenicity of ch romium that may indicate the need to update the Agency’s health effects assessment (USEPA, 2009b). In 1998, the Agency (USEPA, 1998d) updated the IRIS assessment for Cr VI, which revised the RfD from 0.0048 mg/kg-day (rounded to 0.005) to

May 2009 Draft EPA document. Do not cite or distribute. 820.003 mg/kg-day. While both RfDs are based on the same one-year drinking water rat study (MacKenzie et al., 1958), the change in the RfD in 1998 was due to the following factors: (a) a slight change in the no-observed-adverse-e ffect level (NOAEL), (b) a modification to the original uncertainty factor, and (c ) the addition of a modifying factor of three because of data on the potential for gastrointestinal effects in human s as a result of oral exposure. There is no current RfD for soluble trivalent chromium (sol uble Cr III); the Cr III RfD of 1.5 mg/kg-day on IRIS (USEPA, 1998e) is for insoluble Cr III salts. In 2002 and as part of the first Six Year Review (67 FR 19030 (USEPA, 2002c)), EPA noted that the National Toxicology Pr ogram (NTP) had agreed to st udy the chronic toxicity and carcinogenicity of oral exposure to Cr VI. The NTP study, conducted with sodium dichromate dehydrate (i.e., Cr VI) in rats and mice, is now available (NTP, 2008), as is a pre-peer review draft of a similar study with chromium picolinate (Cr III) (N TP, 2007). The Cr VI study found clear evidence of carcinogenic ac tivity of sodium dichromate dihydrate in male and female F344 rats based on increased incidences of squamous cell neoplasms of the oral cavity, specifically the squamous epithelium that lines the oral muco sa and tongue (NTP, 2008). NTP also concluded that there was clear evidence of carcinogenic activity of sodiumdichromate dihydrate in male and female B6C3F1 mice based on increased inci dences of neoplasms in the small intestine (adenomas and/or carcinomas of the duodenum, jejunum, or ileum). The observed noncancer effects in the Cr VI study included histiocytic cellular infiltration in the liver, small intestine, and pancreatic and mesenteric lymph nodes of rats a nd mice, and diffuse epith elial hyperplasia in the small intestine of male and female mice. A peer-reviewed report for the study of chromium picolinate (Cr III) is not yet av ailable. Zhang and Li (1987) evaluated the effects of human exposure to Cr VI in drinking water in Chinese v illages. In a recent analysis of the human data originally reported in these Chin ese villages, Sedman et al. (2006) further support a statistically

May 2009 Draft EPA document. Do not cite or distribute. 83significant increase in stomach cancer in the populat ion exposed to Cr VI in their drinking water, thus suggesting a potential for carcinogenicity of Cr VI in drinking water. On December 21, 2007 (72 FR 72715 (USEPA, 2007c )), the Agency nominated and included Cr VI on its 2008 IRIS agenda. The Agency is currently conducting additional literature searches for Cr VI along with 19 other chemicals. Based on the results of the literature searches and as resources allow, the Agency may begi n assessments on these chemicals to support the development of toxicity values or re-evaluate cancer designations. A review of analytical or treatment feasibility is not necessary for total chromium because changes to the MCLG are not warranted at this time and the current MCL is set at the MCLG. Since EPA did not identify a health or tec hnology basis for revisi ng the total chromium NPDWR, the Agency did not conduct a deta iled occurrence and exposure analysis.

c. Review Result. The Agency does not believe a revision to the NPDWR for total chromium is appropriate at this time. A reassessment of the health risks asso ciated with chromium exposure may be initiated and the Agency does not believe it is appropriate to revise the NPDWR while that effort is in process. 18. Cyanide

a. Background . EPA published the current NPDWR for cyanide on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.2 mg/L. EPA based the MCLG on a reference dose of 0.02 mg/ kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. During the first Six-Year Review cycle, EPA recommended a revision to the BATs for cyanide to clarify that “chlorine” should be “alkaline chlorine” to avoid potential for the formation of harmful cyanogen chloride. EPA promulgated that revision in 69 FR 38850, June 29, 2004 (USEPA, 2004b).

May 2009 Draft EPA document. Do not cite or distribute. 84b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to cyanide. The revised health effect s assessment will consider relevant studies on the toxicity of cyanide, including its potential developmen tal and reproductive toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). The IRIS Substan ce Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment 13

.

c. Review Result. Since the MCL for cyanide is set at its MCLG and a re assessment of the health risks resulting from expos ure to cyanide is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time. 19. 2,4-D (2,4-Dichlorophenoxyacetic acid)

a. Background . EPA published the current NPDW R for 2,4-D on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an MCLG and an MCL of 0.07 mg/L. EPA based the MCLG on a reference dose of 0.01 mg/ kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. In 2005, the Agency updated its heal th effects assessment of 2,4-D (USEPA, 2005c). The Agency identified a change in this assessment that could lead to a change in the MCLG. This assessment considered rele vant studies on the toxicity of 2,4-D including developmental and reproductive toxicity. The assessment revised the RfD from 0.01 mg/kg-day to 0.005 mg/kg-day and concluded that 2,4-D is not classifiable as to its carcinogenicity (USEPA, 2005c). Based on the new Office of Pe sticide Programs (OPP) assessment and RfD of 0.005 mg/kg-day, and assuming a 70-kg adult body we ight and 2 liters water intake per day, the

13 Note that cyanide is listed as hydrogen cyanide in the IRIS tracking system. May 2009 Draft EPA document. Do not cite or distribute. 85DWEL could be 0.2 mg/L. An RSC of 20% resu lts in a possible MCLG of 0.04 mg/L (USEPA, 2009b). Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor for the possible MCLG decrease under considerati on. EPA evaluated the results of the occurrence and exposure analyses for 2,4- D to determine whether a revised MCLG/MCL would be likely to result in a meaningful oppor tunity to improve the level of public health protection (USEPA, 2009f). Table VI-7 shows the results of the occurrence and exposure analysis for the current MCL and the possible MCLG set equal to 0.04 mg/L based on the new health effects information. The occurrence and exposure analysis shows that average concentrations do not exceed the current MCL for any system in the analysis. Note that these results are consistent with the MCL violations, which are based on annual average concentrations at entry points; SDWIS/FED indicates no MCL violations for 2,4-D between 1998 and 2005 (USEPA, 2007g). The occurrence and exposure anal ysis shows that average concentrations do not exceed the possible MCLG based on new health effects information (0.04 mg/L). Table VI-7. Number and Percent of Systems with Mean Concentrations Exceeding 2,4-D Thresholds and Corresponding Estimates of Population Served Systems with Mean Concentrati ons that are Greater than the Regulatory or Health-based Threshold (Percentages based on 33,187 systems wi th 2,4-D data in the Six-Year Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.07 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Possible MCLG (0.04 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Corresponding Population Served (Percentages based on 187,451,200 people served by the systems with 2,4-D data in the Six-Year Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.07 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Possible MCLG (0.04 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) 1. Results are based on setting all nondetect results eq ual to MRL values in the Si x-Year Review ICR dataset 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset.

May 2009 Draft EPA document. Do not cite or distribute. 863. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for 2,4-D, EPA does not believe a revision to the NPDWR for 2,4-D is appropriate at this time. In making this deci sion, the Agency considered whether any possible revision to the NPDWR for 2,4-D is likely to prov ide a meaningful opportunity for health risk reductions. Taking into consideration the low oc currence of this contaminant, EPA has decided that any revision to the NPDWR would be a low priority activ ity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 20. Dalapon (2,2-Dichloropropionic Acid)

a. Background . EPA published the current NPDW R for dalapon on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.2 mg/L. EPA based the MCLG on a reference dose of 0.03 mg/ kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the toxicology of dalapon, including its pot ential developmental and

May 2009 Draft EPA document. Do not cite or distribute. 87reproductive toxicity. The literature search did not identify any studies that warran t a review of the RfD or the cancer cla ssification (USEPA, 2009b). A review of analytical or treatment feasibil ity is not necessary for dalapon because changes to the MCLG are not warranted at this time and the current MCL is set at the MCLG. Since EPA did not identify a health or technology basi s for revising the dalapon NPDWR, the Agency did not conduct a detailed occurren ce and exposure analysis.

c. Review Result. EPA’s review shows that there ar e no data supporting a change to the dalapon NPDWR. As a result, a revision to the NPDWR would not be appr opriate at this time. 21. Di(2-ethylhexyl)adipate (DEHA)

a. Background . EPA published the current NP DWR for DEHA on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.4 mg/L. EPA based the MCLG on a reference dose of 0.6 mg/kg- day and a cancer classifi cation of C, possible human carcinogen. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to DEHA. The revised health effects assessment will consider relevant studies on the toxicity of DEHA, including its potential developmental and re productive toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). The IRIS Substan ce Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment.

c. Review Result. Since the MCL for DEHA is set at its MCLG and a reassessment of the health risks resulting from exposure to DEHA is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time.

May 2009 Draft EPA document. Do not cite or distribute. 8822. Di(2-ethylhexyl)phthalate (DEHP)

a. Background . EPA published the current NPDW R for DEHP on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR establishe d an MCLG of zer o based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.006 mg/L, based on anal ytical feasibility. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to DEHP. The revised health effects assessment will consider relevant studies on the toxicity of DEHP, including its potential developmental and re productive toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). The IRIS Substan ce Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment. Although a risk assessment is in process fo r DEHP, the existing MC LG is zero and the current MCL of 0.006 mg/L is based on the PQL. For the Six-Year Review, the Agency evaluated several sources of information to dete rmine whether changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determ ine if the PQL can be re vised (i.e., analytical feasibility). Passing rates for WS data available thr ough late 1999 for DEHP are below 75 percent for several concentrations around the current PQL, including two studies with true values below the current PQL. More recent PT data from late 1999 through 2004, supplied by a PT provider, show passing rates below the 75 percent criterion for three studies, and all of the true concentrations in the PT data were higher thanthe current PQL. Gi ven the passing rates around the current PQL, a lowering of the PQL for DE HP is not appropriate at this time (USEPA, 2009c).

May 2009 Draft EPA document. Do not cite or distribute. 89EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods for the detection of DEHP (Methods 525.2 and 506). While EPA prefers to use laboratory perfor mance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Review ICR dataset contains MRL values for 50,490 samples. Of these, 22,980 (45%) equal th e modal MRL of 0.001 mg/L. An additional 15,842 (31%) are lower than 0.001 mg/L, and 11,659 (23%) are between 0.001 mg/L and the MCL of 0.006 mg/L. The MDLs of approved methods range from 0.0013 to 0.00225 mg/L. Applying a multiplier of 10 would give a possi ble PQL range from 0.013 to 0.0225 mg/L. Since nearly a quarter of samples do not achieve the modal MRL, and the 10×MDL values are higher than the current PQL, these data do not support a PQL reduction. Based on these varied and unrelated approaches/sources of information, EPA believes that there is no potential to lower the PQL for DEHP. Since the MCL is constrained by the PQL, and the PQL is unchanged, EPA does not believe it is necessary to conduct an occurrence analysis at this time.

c. Review Result. The Agency does not believe a re vision to the NPDWR for DEHP is appropriate at this time because a reassessment of the health risks resulting from exposure to DEHP is in progress (USEPA, 2009b) . Furthermore, a review of analytical feasibility did not identify a potential to revise the MCL, which is limited by feasibility. 23. 1,2-Dibromo-3-chloropropane (DBCP)

a. Background . EPA published the current NPDW R for DBCP on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establishe d an MCLG of zer o based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.0002 mg/L, based on analytical feasibility.

May 2009 Draft EPA document. Do not cite or distribute. 90b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the carcinogenicity of DBCP as well as its potential developmental and reproductive toxicity. EPA ha s not identified any new information that indicates that it is appropriate to consider revisions to the cancer classification fo r DBCP at this time (USEPA, 2009b). Because the MCLG remains at zero, the Ag ency believes that a further review of the health effects of DBCP is not warranted at this time. The current MCL for DBCP is based on a PQ L of 0.0002 mg/L. For the Six-Year Review, the Agency considered whether changes in the an alytical feasibility of DBCP might lead to a lower MCL. EPA reviewed WS data from the fi rst Six-Year Review cycle and then analyzed more recent PT data to determine if the PQL can be revised (i.e., analytical feasibility). Passing rates for WS data available through late 1999 for DBCP are above 85 percent, including one study with a true value below the current PQL. More recent PT data from late 1999 through 2004, supplied by a PT provider, also show greater than 75 percent passing rates, including three with a true value below the current PQL. B ecause all of the laboratory passing rates from WS and PT studies, including four with true values slightly below the PQL, exceeded the 75 percent criterion typically used to derive a PQL, a lo wering of the PQL for DBCP might be possible. These results, however, are insufficient to r ecalculate a revised PQL for DBCP because not enough data points are available below the current PQL to deri ve a value at the 75 percent passing rate (USEPA, 2009c). EPA examined two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods for the detection of DBCP (Methods 504.1 and 551.1). While EPA prefers to use laboratory perfo rmance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to

May 2009 Draft EPA document. Do not cite or distribute. 91quantitate at levels below the current PQL. However, there are substantial uncertainties in interpreting the MRLs (USEPA, 20 09e). For example, some Stat es have reported modal MRLs that are higher than the MCL. EPA therefore considered only MDL data to verify the potential to revise the PQL, and to establish a threshol d for the occurrence and exposure analysis. The MDLs of approved methods are 0.000009 and 0.00001 mg/L. Applying a multiplier of 10 would give a possible PQL range from 0.00009 to 0.0001 mg/L. Because of the number of reported MRLs above the MCL, EPA averaged the 10×MDL values, rounded up to 0.0001 mg/L, and used that value as the minimum threshol d for the occurrence and exposure analysis. Based on the PT data and the MDLs for appr oved methods, EPA believe s that there may be potential to lower the PQL for DBCP. To dete rmine whether any MCL revision is likely to provide a meaningful opportunity to improve public health protection, EPA evaluated the occurrence of DBCP at an estimated quantitatio n level of 0.0001 mg/L (U SEPA, 2009f). Table VI-8 shows the results of the occurrence and expo sure analysis for the current MCL and an EQL set equal to 0.0001 mg/L. The occurrence and exposure analysis shows that average concentrations exceed the current MCL for 42 of 37,618 systems (0.112%) serving 25,000 people (or 0.013% of 194 million people). Note that these results do not ne cessarily reflect MCL violations, which are based on annual average concentrations at entry points; SDWIS/FED indicates only nine MCL violations fo r DBCP between 1998 and 2005 (USEPA, 2007g). Average concentrations at 92 to 97 of 37,618 systems (0.245% to 0.258%), serving approximately 1.2 to 1.4 million people (0.610% to 0.713% of 194 million people), exceed the EQL of 0.0001 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 92Table VI-8. Number and Percent of Systems with Mean Concentrations Exceeding DBCP Thresholds and Corresponding Estimates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 37,618 systems with DBCP data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.0002 mg/L) 42 (0.112%) 42 (0.112%) 42 (0.112%) EQL (0.0001 mg/L) 97 (0.258%) 93 (0.247%) 92 (0.245%) Corresponding Population Served (Percentages based on 193,749,000 people served by the systems with DBCP data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.0002 mg/L) 25,000 (0.013%) 25,000 (0.013%) 25,000 (0.013%) EQL (0.0001 mg/L) 1,382,000 (0.713%) 1,371,000 (0.707%) 1,181,000 (0.610%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for DBCP is appropriate at this time. The occurrence and exposure analysis based on possible changes in analytical feasibility indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration the low occurrence of this contaminant, EPA has decide d that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

May 2009 Draft EPA document. Do not cite or distribute. 93• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 24. 1,2-Dichlorobenzene (o-Dichlorobenzene)

a. Background . EPA published the current NPDWR for 1,2-dichlorobenzene on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR es tablished an MCLG and an MCL of 0.6 mg/L. EPA based the MCLG on a reference dos e of 0.09 mg/kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to 1,2-dichlorobenzene. The revised h ealth effects assessment will consider relevant studies on the toxicity of 1,2- dichlorobenzene, including its potential developmental and reproductive toxicity. The new health effect s assessment was not completed by March 1, 2009, the review cutoff date for this notice (USE PA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/ir istrac/index.cfm) has the most up-to-date information on the status of the health effects assessment.

c. Review Result. Since the MCL for 1,2-dichlorobe nzene is set at its MCLG and a reassessment of the health risks resulting from ex posure to 1,2-dichlorobenzene is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time. 25. 1,4-Dichlorobenzene (p-Dichlorobenzene)

a. Background . EPA published the current NPDWR for 1,4-dichlorobenzene on July 8, 1987 (52 FR 25690 (USEPA, 1987)). The NPDWR es tablished an MCLG and an MCL of 0.075 mg/L. EPA based the MCLG on a reference dose of 0.1 mg/kg-day and a can cer classification of C, possible human carcinogen.

May 2009 Draft EPA document. Do not cite or distribute. 94b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to 1,4-dichlorobenzene. The revised h ealth effects assessment will consider relevant studies on the toxicity of 1,4- dichlorobenzene, including its potential developmental and reproductive toxicity. The new health effect s assessment was not completed by March 1, 2009, the review cutoff date for this notice (USE PA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/ir istrac/index.cfm) has the most up-to-date information on the status of the health effects assessment.

c. Review Result. Since the MCL for 1,4-dichlorobe nzene is set at its MCLG and a reassessment of the health risks resulting from ex posure to 1,4-dichlorobenzene is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time. 26. 1,2-Dichloroethane (Ethylene Dichloride)

a. Background . EPA published the current NPDWR for 1,2-dichloroethane on July 8, 1987 (52 FR 25690 (USEPA, 1987)). The NPDWR establ ished an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.005 mg/L, based on anal ytical feasibility. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to 1,2-dichloroethane. The revised heal th effects assessment will consider relevant studies on the toxicity of 1,2- dichloroethane, including its potential developmental and reproductive toxicity. The new health effect s assessment was not completed by March 1, 2009, the review cutoff date for this notice (USE PA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/ir istrac/index.cfm) has the most up-to-date information on the status of the health effects assessment 14

.

14 Note that 1,2-dichloroethane is listed as ethylene dichloride in the IRIS tracking system. May 2009 Draft EPA document. Do not cite or distribute. 95Although a risk assessment is in process for 1,2- dichloroethane, the existing MCLG is zero and the current MCL of 0.005 mg/L is based on the PQL. For the Six-Year Review, the Agency evaluated several sources of information to dete rmine whether changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determ ine if the PQL can be re vised (i.e., analytical feasibility). Passing ra tes for WS data available through late 1999 for 1,2-dichloroethane are above 95 percent around the curr ent PQL of 0.005 mg/L, including one study with a true value below the current PQL. More recent PT data from late 1999 through 2004, supplied by a PT provider, also show greater than 90 percent pa ssing rates for studies around the current PQL, including seven with true values below the curr ent PQL. Because all of the laboratory passing rates from WS and PT studies – including several with true c oncentrations below the PQL – exceeded the 75 percent criterion typically used to derive a PQL, a lowering of the PQL for 1,2- dichloroethane might be possible. These resu lts, however, are insufficient to recalculate a revised PQL for 1,2-dichloroethane because no t enough data points are available below the current PQL to derive a value at the 75 percent passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of 1,2-di chloroethane (Methods 502.2 and 524.2). While EPA prefers to use laborato ry performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Review I CR dataset contains MRL values for 139,085 samples. Of these, 116,533 (84%) equal the modal MRL of 0.0005 mg/L. An additional 18,160 (13%) are lower than 0.0005 mg/L. The MDLs of approved methods range from 0.00003 to 0.00006 mg/L. Applying a multiplie r of 10 would give a possible PQL range

May 2009 Draft EPA document. Do not cite or distribute. 96from 0.0003 to 0.0006 mg/L. Because of the preponderance of MRL values of 0.0005 mg/L, EPA selected that value as the minimum thre shold for the occurrence and exposure analysis (USEPA, 2009e). Based on these varied and unrelated approach es/sources of information, EPA believes that there is potential to lower th e PQL for 1,2-dichloroethane. To determine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of 1,2-dichloroethane at thresholds of 0.0005, 0.001, and 0.0025 mg/L (USEPA, 2009f). Table VI-9 show s the results of the occurrence and exposure analysis for the current MCL and EQLs set equal to 0.0025 mg/L, 0.001 mg/L, and 0.0005 mg/L. The occurrence and exposure analysis shows that aver age concentrations exceed the current MCL for three of 50,442 systems (0..006%) serving 150 people (or 0.00007% of 227 million people). Note that these results do not necessarily re flect MCL violations, wh ich are based on annual average concentrations at entry points; SD WIS/FED indicates 27 MC L violations for 1,2- dichloroethane between 1998 and 2005 (USEPA, 2007g). Average concentrations at 63 to 82 of 50,442 systems (0.125% to 0.163%), serving 210,000 to 277,000 people (or 0.092% to 0.122% of 227 million people), exceed the EQL of 0.0005 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 97Table VI-9. Number and Percent of Systems with Mean Concentrations Exceeding 1,2-Dichloroethane Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 50,442 systems wi th 1,2-dichloroethane data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 3 (0.006%) 3 (0.006%) 3 (0.006%) 1/2 MCL (0.0025 mg/L) 9 (0.018%) 9 (0.018%) 8 (0.016%) 2xEQL (0.001 mg/L) 46 (0.091%) 37 (0.073%) 30 (0.059%) EQL (0.0005 mg/L) not applicable 82 (0.163%) 63 (0.125%) Corresponding Population Served (Percentages based on 226,934,000 people served by the systems with 1,2-dichloroethane data in the Six- Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 150 (0.00007%) 150 (0.00007%) 150 (0.00007%) 1/2 MCL (0.0025 mg/L) 870 (0.0004%) 870 (0.0004%) 830 (0.0004%) 2xEQL (0.001 mg/L) 190,000 (0.084%) 145,200 (0.064%) 87,150 (0.038%) EQL (0.0005 mg/L) not applicable 277,000 (0.122%) 210,000 (0.092%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.0005 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. The Agency does not believe a revision to the NPDWR for 1,2- dichloroethane is appropriate at this time b ecause a reassessment of the health risks resulting from exposure to 1,2-dichloroethane is in progress (USEPA, 2009b). Furthermore, the occurrence and exposure analysis based on possible changes in analytical feasibility indicates that any revision to the MCL is unlikely to pr ovide a meaningful opportunity to improve public

May 2009 Draft EPA document. Do not cite or distribute. 98health protection. After consid eration of the low o ccurrence of this contaminant, EPA has decided that any revision to the NPDWR would be a low prior ity activity for the Agency, and, thus, is not appropriate to re vise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 27. 1,1-Dichloroethylene

a. Background . EPA published the current NPDWR for 1,1-dichloroethylene on July 8, 1987 (52 FR 25690 (USEPA, 1987)). The NPDWR es tablished an MCLG and an MCL of 0.007 mg/L. EPA based the MCLG on a reference dos e of 0.01 mg/kg-day and a cancer classification of C, possible human carcinogen. b. Technical Reviews. In the first Six-Year Review cy cle, EPA evaluated new information from a health effects assessment completed in 2002 (USEPA, 2002b). At that time, the Agency could not determine that a revision to the NP DWR would provide a meaningful opportunity for cost savings to public water system s or their customers, and decide d that any revision would be a low priority activity for the Agency because of co mpeting workload priorities, the administrative costs associated with rulemaking, and the burde n on States and the regulated community to implement any regulatory change (68 FR 42908 (USEPA, 2003e)). The 2002 assessment considered relevant studies on the toxicity of 1,1-dichloroethylene including developmental and reproductive toxicity. The assessment revised the RfD from 0.01 mg/kg-day to 0.05 mg/kg-day and concluded that there is inadequate informati on to assess carcinogenic potential via the oral route (USEPA, 2002b). In the current review cy cle, EPA conducted a literature search through June 2007 for relevant data on the toxicology of 1,1-dichloroethylene, including its potential

May 2009 Draft EPA document. Do not cite or distribute. 99developmental and reproductive toxicity. The lit erature search did not identify any additional new data that would affect the RfD or cancer classification (USEPA, 2009b). Based on the 2002 IRIS assessment and RfD of 0.05 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters water intake per day, the DWEL coul d be 1.75 mg/L. The 2002 cancer assessment indicates that the risk manageme nt factor of 10, applied to th e current MCLG, may no longer be needed. An RSC of 20% results in a possible MCLG of 0.35 mg/L (USEPA, 2009b). Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor if EPA were to raise the MCLG. EPA evaluated the results of the occurrence and exposure analyses for 1,1-dichloroethylene to determine whether a re vised MCLG/MCL would be likely to result in a meani ngful opportunity to achieve co st savings for PWSs and their customers while maintaining, or improving, the level of public health protection (USEPA, 2009f). Although the Agency obtained and evaluated the finished water occurrence data for 1,1- dichloroethylene, its usefulness is limited for pot ential cost savings to PW Ss and their customers because the Agency does not know which systems are treating for this contaminant. As an alternative, the Agency evaluated available data on source water quality and conducted a qualitative assessment of tr eatment cost savings. Table VI-10 provides summary data for contam inant occurrence based on maximum sample values for the locations included in the ST ORET and NAWQA data. Although the degree to which these occurrence rates represent national drinking water source occurrence is uncertain, the information shows no to low occurrence at thre shold levels of interest. This information indicates that any resulting NP DWR change would affect system s that rely on source water at less than 0.02% of the NAWQA locations and less than 5% of the STORET locations.

May 2009 Draft EPA document. Do not cite or distribute. 100Table VI-10. Ambient Water Quality Monitori ng Occurrence Summary for 1,1-Dichloroethylene Number of Locations (% of locations) Maximum Concentration STORET 1 NAWQA 2 Total 2,448 (100.0%) 5,788 (100.0%) Nondetect 1,498 (61.2%) 5,636 (97.37%) Detected 950 (38.8%) 152 (2.63%) Exceeds current MCLG of 0.007 mg/L 165 (6.7%) 1 (0.02%) Exceeds alternative value of 0.35 mg/L 58 (2.4%) 0 (0.0%) 1. STORET database 2002-2007. 2. NAWQA database 1992-2006. Source: USEPA, 2004c
The BATs and small system compliance techno logies for 1,1-dichloro ethylene have other beneficial effects, e.g., reduction of other co-o ccurring contaminants, precursors for DBPs, or other common impurities. Therefore, if EPA were to consider a higher level, the Agency does not know how many PWSs that are currently treating to comply with the existing MCL of 0.007 mg/L would be likely to discontinue treatment th at is already in plac e (USEPA, 2009d). Also, the Agency does not know to what extent affectedsystems might be able to reduce costs given that capital costs are not rec overable. However, the Agencyrecognizes that there may be opportunities to achieve operational co st savings if these systems ar e able to re-optimize current

treatment. Given these challenges, the Agency believes th at any resulting revi sion is not likely to provide a meaningful opportunity for cost savings. In view of this, any revision would be a low priority activity and not appropriate at this time.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for 1,1- dichloroethylene, EPA does notbelieve a revision to the NPDWR for 1,1-dichloroethylene is appropriate at this time. In making this decision, the Agency considered whether any possible revisi on to the NPDWR for 1,1- dichloroethylene is

May 2009 Draft EPA document. Do not cite or distribute. 101likely to provide a meaningful opportunity for co st savings to public water systems and their customers. Taking into consideration the low oc currence of this contaminant in source waters, EPA has decided that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 28. cis-1,2-Dichloroethylene

a. Background . EPA published the current NPDWR for cis-1,2-dichloro ethylene on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDW R established an MCLG and an MCL of 0.07 mg/L. EPA based the MCLG on a refe rence dose of 0.01 mg/kg-day and a cancer classification of D, not classifi able as to human carcinogenicity. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to cis-1,2-dichloroethylene. The re vised health effects assessment will consider relevant studies on the toxicity of cis-1,2-dichloroethylene, incl uding its potential developmental and reproductive toxicity. The new health e ffects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). Th e IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/ir istrac/index.cfm) has the most up-to-date information on the status of the health effects assessment.

c. Review Result. Since the MCL for cis-1,2-dichloroe thylene is set at its MCLG and a reassessment of the health risks resulting from exposure to cis-1,2-di chloroethylene is in progress, the Agency does not be lieve a revision to the NPDWR is appropriate at this time.

May 2009 Draft EPA document. Do not cite or distribute. 10229. trans-1,2-Dichloroethylene

a. Background . EPA published the current NPDWR for trans-1,2-dichloroethylene on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). Th e NPDWR established an MCLG and an MCL of 0.1 mg/L. EPA based the MCLG on a reference dose of 0.02 mg/kg-day and a cancer classification of D, not classifi able as to human carcinogenicity. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to trans-1,2-dichloroethylene. The revi sed health effects assessment will consider relevant studies on the toxicity of trans- 1,2-dichloroethylene, including its potential developmental and reproductive toxicity. The ne w health effects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/iristrac/index.cfm) has the most upto-date information on the status of the health effects assessment.

c. Review Result. Since the MCL for trans-1,2-dichloro ethylene is set at its MCLG and a reassessment of the health risks resulting from exposure to trans-1,2-dich loroethylene is in progress, the Agency does not be lieve a revision to the NPDWR is appropriate at this time. 30. Dichloromethane (Methylene Chloride)

a. Background . EPA published the current NPDW R for dichloromethane on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR establis hed an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.005 mg/L, based on anal ytical feasibility. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to dichloromethane. The revised heal th effects assessment will consider relevant studies on the toxicity of di chloromethane, including its potential developmental and reproductive toxicity. The new health effect s assessment was not completed by March 1, 2009,

May 2009 Draft EPA document. Do not cite or distribute. 103the review cutoff date for this notice (USE PA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/ir istrac/index.cfm) has the most up-to-date information on the status of the health effects assessment 15

. Although a risk assessment is in process for dichloromethane, the existing MCLG is zero and the current MCL of 0.005 mg/L is based on the PQL. For the Six-Year Review, the Agency evaluated several sources of information to dete rmine whether changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determ ine if the PQL can be re vised (i.e., analytical feasibility). Passing ra tes for WS data available through late 1999 for dichloromethane are all above 90 percent for studies near the PQL. More recent PT data from late 1999 through 2004, supplied by a PT provider, also show greater than 85 percent pa ssing rates for studies around the PQL, except for one study with a passing rate of 76 percent. However, all of the true concentrations in the WS and PT data were hi gher than the current PQL of 0.005 mg/L. Given the lack of WS and PT study resu lts below the current PQL to derive a value at the 75 percent passing rate, WS and PT data are insufficient to support a PQL reduction (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of di chloromethane (Methods 502.2 and 524.2). While EPA prefers to use laborato ry performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Review I CR dataset contains MRL values for 138,445 samples. Of these, 121,532 (88%) equal the modal MRL of 0.0005 mg/L. An additional 11,294 (8%) are lower than 0.0005 mg /L. The MDLs of approved methods range

15 Note that dichloromethane is listed as methylene chloride in the IRIS tracking system. May 2009 Draft EPA document. Do not cite or distribute. 104from 0.00002 to 0.00009 mg/L. Applying a multiplie r of 10 would give a possible PQL range from 0.0002 to 0.0009 mg/L. Because of the preponderance of MRL values of 0.0005 mg/L, EPA selected that value as the minimum thre shold for the occurrence and exposure analysis (USEPA, 2009e). Based on these varied and unrelated approaches/s ources of information, there is evidence of a potential to lower the PQL for dichloromethane even though the WS and PT data are insufficient to support a PQL reduction.. To determine whethe r any MCL revision is likely to provide a meaningful opportunity to improve public healthprotection, EPA evaluated the occurrence of dichloromethane at thresholds of 0.0005, 0.001, and 0.0025 mg/L (USEPA, 2009f). Table VI-11 shows the results of the occurr ence and exposure analysis for the current MCL and EQLs set equal to 0.0025 mg/L, 0.001 mg/L, and 0.0005 mg/L. The occurrence and exposure analysis shows that average concentrations exceed the current MCL for 13 to 17 of 50,169 systems (0.026% to 0.034%) serving 11,000 to 12,000 people (or 0.005% of 227 million people). Note that these results do not necessarily reflect MCL violations, wh ich are based on annual average concentrations at entry points; SDWIS/FED i ndicates 67 MCL violations for dichloromethane between 1998 and 2005 with annual violations ranging from 4 to 14 (USEPA, 2007g). Average concentrations at 383 to 579 of 50,169 systems (0.763% to 1.154%), serving approximately 1.8 to 3.5 million people (or 0.813% to 1.542% of 227 million people), exceed the EQL of 0.0005 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 105Table VI-11. Number and Percent of Systems with Mean Concentrations Exceeding Dichloromethane Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 50,169 systems with dichloromethane data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 17 (0.034%) 16 (0.032%) 13 (0.026%) EQL (0.0025 mg/L) 53 (0.106%) 51 (0.102%) 46 (0.092%) EQL (0.001 mg/L) 276 (0.550%) 208 (0.415%) 169 (0.337%) EQL (0.0005 mg/L) not applicable 579 (1.154%) 383 (0.763%) Corresponding Population Served (Percentages based on 226,844,000pe ople served by the systems with dichloromethane data in the Six-Y ear Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 12,000 (0.005%) 12,000 (0.005%) 11,000 (0.005%) EQL (0.0025 mg/L) 44,000 (0.019%) 40,000 (0.018%) 39,000 (0.017%) EQL (0.001 mg/L) 1,517,000 (0.669%) 1,386,000 (0.611%) 946,000 (0.417%) EQL (0.0005 mg/L) not applicable 3,497,000 (1.542%) 1,844,000 (0.813%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.0005 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
During Six-Year Review 1, a stakeholder questi oned the feasibility of lowering the PQL for dichloromethane below 0.001 mg/L because its use in EPA analytical methods makes it a common laboratory contaminant (68 FR 42908 (USE PA, 2003e)). EPA responded that the high passing rates among WS studies at concentrations close to the current PQL of 0.005 mg/L would not be expected if this were the case and that EPA had no data to suggest that the occurrence estimates reflected monitoring sample contam ination (68 FR 42908 (USEPA, 2003e)). For SixYear Review 2, EPA notes that itdoes not have WS or PT study results at either 0.001 mg/L or 0.0005 mg/L and, therefore, cannot assess the po tential for laboratory contamination of

May 2009 Draft EPA document. Do not cite or distribute. 106dichloromethane to affect passing rates at th is level. A USGS study of volatile organic compound (VOC) occurrence (Moran, 2006) indicates this potential exis ts at low concentrations. The study presented dichloromethane laboratory re porting levels for newer low-level analytical methods (i.e., defined as the level that limits the frequency of false positiv es and false negatives to 1% of test results) that ranged from 0.00006 mg/L to 0.00757 mg/L, with a median value of 0.00038 mg/L. The report noted thatthe laboratory reporting levels for dichloromethane tend to be higher than levels for other VOCs such as PCE (levels ranging from 0.000027 mg/L to 0.0005 mg/L with a median of 0.0001 mg/L) and TCE (ranging from 0.000038 mg/L to 0.0005 mg/L with a median of 0.000038 mg/L) because it was a frequent laboratory contaminant. A USGS study of ground water, source wate r, and drinking wate r quality indicated consistently lower dichloromethane (methylene chloride) occurrence frequencies compared to either PCE or TCE, which are among the most frequently occurring VOCs included in the study (Moran, 2006). Table VI-12 provides a summary of the occurrence results reported in the USGS study. This study also determined that popula tion density was the st rongest predictor of dichloromethane occurrence.

Table VI-12. Summary of USGS VOC Occurrence Study Findings for Dichloromethane (Methylene Chloride) Ground Water Samples Source Water Samples Drinking Water Samples Number 5,054 577 1,680

Type 3,877 NAWQA 1,177 Other sources Ground water sources for community water systems Ground water community water systems Location National National New England and Mid-Atlantic States

Dichloro methane Results • 3% exceed 0.00002 mg/L

• <1% exceed 0.0002 mg/L

• Ranked 30th of 55 VOCs based on median concentration (0.00005 mg/L) • 0.2% (1 sample) exceed 0.0002 mg/L

• Ranked 8th of 52 VOCs based on median concentration (0.0017 mg/L – 1 sample) • 3% exceed 0.0002 mg/L

• Ranked 11th of 51 VOCs in detection frequency

• Ranked 31st of 55 solvents in median concentration (0.001 mg/L)
May 2009 Draft EPA document. Do not cite or distribute. 107PCE • 11% exceed 0.00002 mg/L

• 4% exceed 0.0002 mg/L

• Ranked 12th of 55 VOCs based on median concentration (0.00007 mg/L) • 4% exceed 0.0002 mg/L

• Ranked 16th of 52 VOCs based on median concentration (0.0009 mg/L) • 4% exceed 0.0002 mg/L

• Ranked 7th of 51 VOCs in detection frequency

• Ranked 11th of 55 solvents in median concentration (0.0014 mg/L)

TCE • 5% exceed 0.00002 mg/L

• 2.5% exceed 0.0002 mg/L

• Ranked 20th of 55 VOCs based on median concentration (0.00012 mg/L) • 3% exceed 0.0002 mg/L

• Ranked 10th of 52 VOCs based on median concentration (0.0015 mg/L) • 4% exceed 0.0002 mg/L

• Ranked 8th of 51 VOCs in detection frequency

• Ranked 8th of 55 solvents in median concentration (0.0015 mg/L) Source: Moran, 2006

EPA compared Six-Year Review ICR occurrence patterns for dichloromethane with contaminant release information to determine if drinking water occurr ence corresponds with potential contaminant sources reported in the To xics Release Inventory (TRI) and found that the states with the majority of systems with mean concentratio ns that exceed 0.0005 mg/L did not tend to be the States with th e highest dichloromethane releas es (Moran, 2006). Table VI-13 provides summary information from that compar ison. In particular, the numbers of system means exceeding 0.0005 mg/L in Montana and Alaska seem inconsistent with TRI release information and the USGS study finding that popul ation density is the strongest predictor of dichloromethane occurrence. Because of data gaps regardi ng the feasibility of PQL reducti on and potential occurrence data accuracy at the lowest EQL, EPA concluded that revising the MCL may not constitute a meaningful opportunity to improve th e level of public health protection.

May 2009 Draft EPA document. Do not cite or distribute. 108Table VI-13. Stage 2 Occurrence Summary for Dichloromethane Systems with Mean > 0.0005 mg/L Nondetect = 1/2 MRL 1 Total Reported TRI On-Site or Off-Site Disposal or Release of Dichloromethane – All Industries, 2006 2 Total Reported TRI On-Site or Off-Site Disposal or Release

of Dichloromethane – All Industries, 2004 2

State Number Percent of 579 Total Systems Pounds Percent of 6.8 Million Total Pounds Pounds Percent of 7.9 Million Total Pounds MT 67 12% 22,700 0% 30,600 0% TX 45 8% 314,120 5% 410,103 5% FL 40 7% 31,451 0% 246,775 3% AK 37 6% No data 0% No data 0% IN 29 5% 509,303 7% 699,783 9% WI 28 5% 111,403 2% 98,113 1% MO 27 5% 51,002 1% 32,860 0% CA 26 4% 149,423 2% 86,554 1% OH 24 4% 192,237 3% 203,269 3% NM 21 4% No data 0% No data 0% IL 19 3% 279,024 4% 285,101 4% AL 18 3% 319,529 5% 375,650 5% MN 17 3% 39,851 1% 81,309 1% CO 15 3% 18,475 0% 17,003 0% MI 13 2% 75,141 1% 129,959 2% WY 13 2% No data 0% No data 0% IA 12 2% 2,348 0% 1,657 0% MD 12 2% 36,990 1% 31,347 0% NC 12 2% 49,800 1% 600,032 8% NY 11 2% 322,382 5% 712,197 9% 1. Source: USEPA, 2009f 2. Source: TRI Explorer Chemical Report Summa ry on-line state summaries for 2006 and 2004.

c. Review Result. The Agency does not believe a revision to the NPDWR for dichloromethane is appropriate at this time because a reassessment of the health risks resulting from exposure to dichloromethane is in progre ss (USEPA, 2009b). In view of the fact that dichloromethane is a common laboratory contaminan t, there is uncertainty regarding the extent

May 2009 Draft EPA document. Do not cite or distribute. 109to which a PQL revision is feasible or whether the Six-Year Review ICR data are reliable at concentrations well below the current PQL. Furthermore, the occurrence and exposure analysis based on possible changes in anal ytical feasibility indicates th at any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. After consideration of these factors, EPA has decided that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is no t appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 31. 1,2-Dichloropropane

a. Background . EPA published the current NPDWR for 1,2-dichloropropane on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR es tablished an MCLG of zero based on a cancer classification of B2, pr obable human carcinogen. The NPDW R also established an MCL of 0.005 mg/L, based on an alytical feasibility. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the carcinogenicity of 1,2-dichloropropane as well as its potential developmental and reproductive toxicity. EPA has not identified any new information that indicates that it is appropriat e to consider revisions to the cancer classification for 1,2- dichloropropane at this time (USEPA, 2009b). Because the MCLG remains at zero, the Agency believes that a further review of the health effects of 1,2-dichloropr opane is not warranted at this time. The current MCL for 1,2-dichloropropane is based on a PQL of 0.005 mg/L. For the SixYear Review, the Agency considered whether changes in the analytic al feasibility of 1,2-

May 2009 Draft EPA document. Do not cite or distribute. 110dichloropropane might lead to a lower MCL. EP A reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determine if the PQL can be revised (i.e., analytical feasibility). Passing rates for WS data available through late 1999 for 1,2- dichloropropane are above 90 percent near th e current PQL of 0.005 mg/L, but there were no results for WS studies with true values below the current PQL. More recent PT data from late 1999 through 2004, supplied by a PT provider, also show greater than 90 percent passing rates around the PQL, including nine studies with true values below the current PQL. Because most of the laboratory passing rates from WS and PT studies – includi ng several with true concentrations below the PQL – exceeded the 75 percent criterion typicall y used to derive a PQL, a lowering of the PQL for 1,2-dichloropropane might be possible. These results, however, are insufficient to recalculate a revised PQL for 1,2-dichloropr opane because not enough data points are available below the current PQL to de rive a value at the 75 percent passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of 1,2-di chloropropane (Methods 502.2 and 524.2). While EPA prefers to use laborato ry performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Review I CR dataset contains MRL values for 139,237 samples. Of these, 119,831 (86%) equal the modal MRL of 0.0005 mg/L. An additional 18,311 (13%) are lower than 0.0005 mg/L. The MDLs of approved methods range from 0.00003 to 0.00004 mg/L. Applying a multiplie r of 10 would give a possible PQL range from 0.0003 to 0.0004 mg/L. Because of the preponderance of MRL values of 0.0005 mg/L,

May 2009 Draft EPA document. Do not cite or distribute. 111EPA selected that value as the minimum thre shold for the occurrence and exposure analysis (USEPA, 2009e). Based on these varied and unrelated approach es/sources of information, EPA believes that there is potential to lower th e PQL for 1,2-dichloropropane. To determine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of 1,2-dichloropropane at thresholds of 0.0005, 0.001, and 0.0025 mg/L (USEPA, 2009f). Table VI-14 s hows the results of the occurren ce and exposure analysis for the current MCL and EQLs set equal to 0.0025 mg/L, 0.001 mg/L, and 0.0005 mg/L. The occurrence and exposure analysis shows that aver age concentrations do no t exceed the current MCL for any system in the analysis. Note that these results do not necessarily reflect MCL violations, which are based on annual average concentrations at entry points; SDWIS/FED indicates three MCL violati ons for 1,2-dichloropropane between 1998 and 2005 (USEPA, 2007g). Average concentrations at 47 to 61 of 50,437 systems (0.093% to 0.121%), serving 296,000 to 494,000 people (0.130% to 0.218% of 227 million people), exceed the EQL of 0.0005 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 112Table VI-14. Number and Percent of System s with Mean Concentrations Exceeding 1,2- Dichloropropane Thresholds and Corres ponding Estimates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 50,437 systems w ith 1,2-dichloropropane data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) 1/2 MCL (0.0025 mg/L) 2 (0.004%) 2 (0.004%) 2 (0.004%) 2xEQL (0.001 mg/L) 27 (0.054%) 24 (0.048%) 21 (0.042%) EQL (0.0005 mg/L) not applicable 61 (0.121%) 47 (0.093%) Corresponding Population Served (Percentages based on 226,912,000 people served by the systems with 1,2-dichloropropane data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) 1/2 MCL (0.0025 mg/L) 120 (0.00005%) 120 (0.00005%) 120 (0.00005%) 2xEQL (0.001 mg/L) 286,000 (0.126%) 286,000 (0.126%) 284,000 (0.125%) EQL (0.0005 mg/L) not applicable 494,000 (0.218%) 296,000 (0.130%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.0005 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for 1,2-dichloropropane is appr opriate at this time. The occurrence and exposure analysis based on possible changes in analytical feasibility indica tes that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration
May 2009 Draft EPA document. Do not cite or distribute. 113the low occurrence of this contaminant, EPA has decided that any revisi on to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted.

32. Dinoseb

a. Background . EPA published the current NPDW R for dinoseb on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.007 mg/L. EPA based the MCLG on a reference dose of 0.001 mg/kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the toxicology of dinoseb, including its pot ential developmental and reproductive toxicity. The literature search did not identify any studies that warran t a review of the RfD or the cancer cla ssification (USEPA, 2009b). A review of analytical or treatment feasibility is not necessary for dinoseb because changes to the MCLG are not warranted at this time and the current MCL is set at the MCLG. Since EPA did not identify a health or technology basis for revising the dinoseb NPDWR, the Agency did not conduct a detailed occurren ce and exposure analysis.

c. Review Result. EPA’s review shows that there ar e no data supporting a change to the dinoseb NPDWR. As a result, a revision to the NPDWR would not be appr opriate at this time.

May 2009 Draft EPA document. Do not cite or distribute. 11433. Diquat

a. Background . EPA published the current NPDWR for diquat on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.02 mg/L. EPA based the MCLG on a reference dose of 0.0022 mg/kg-day and a cancer cla ssification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. In 2001, the Agency updated its heal th effects assessment of diquat (USEPA, 2001a). A subsequent r eassessment of tolerances for re sidues in or on raw agricultural products (USEPA, 2002d) did not identify any new health effects information and based the updated tolerances on health e ffects information in the 2002 assessment (USEPA, 2001a). The Agency identified a change in this assessment that could lead to a change in the MCLG. This assessment considered relevant studies on the toxicity of diquat including developmental and reproductive toxicity. The assessment revise d the RfD from 0.002 mg/kg-day to 0.005 mg/kgday and developed a cancer clas sification of E, evidence of n oncarcinogenicity (USEPA, 2001a). Based on the new OPP assessment and RfD of 0.005 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters water intake per day, the DWEL could be 0.175 mg/L. An RSC of 20% results in a possible MCLG of 0.035 mg/L, rounded to 0.04 mg/L. Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor if EPA were to raise the MCLG . EPA evaluated the available occurrence and exposure information for diquat to determine wh ether a revised MCLG/MCL would be likely to result in a meaningful opportunity to achieve cost savings for PWSs and their customers while maintaining, or improving, the level of public health protection (USE PA, 2009f). Although the Agency obtained and evaluated the finished wate r occurrence data for diquat, its usefulness is limited for determining potential cost savings to PWS and their customers because the Agency does not know which systems are treating for this contaminant. As an alternative, the Agency

May 2009 Draft EPA document. Do not cite or distribute. 115evaluated available data on s ource water quality and conducted a qualitative assessment of treatment cost savings. Because the primary in formations sources used to evaluate potential
source water occurrence—STORE T and NAWQA—do not report mon itoring results for diquat, the Agency obtained available informati on on diquat use and fate and transport. Diquat’s primary uses are as an algaecide, defoliant, desiccant, and herbicide (USEPA, 1995a). The most recent pesticide application esti mates in the Pesticide Use Database developed by the National Center for Food and Agricultur al Policy (NCFAP) indicate overall cropland application of almost 270,000 pounds in 1997, prim arily on potato and alfalfa crops (NCFAP, 2000). The NCFAP based these estimates on State- level pesticide usage patterns for the period 1994-1998 and State-level crop acreage for 1997. Th ese estimates reflect several limitations: they do not include noncropland ap plications, the data sources vary in quality, and State-level pesticide use data gaps are fill ed using data for nearby states. The USGS estimated county-level pesticide usage for 2002 based on crop acreage estimates in the 2002 Census of Agriculture and State-level application rate s for the period 1999-2004 developed by the CropLife Foundation (USGS, no date), which implemented the NC FAP method for estimating pesticide usage (Gianessi and Regner, 2006) and, th erefore, has similar limitations . The USGS estimates total diquat application to crops of approximately200,000 pounds per year, with potatoes accounting for almost 90% of these applicatio ns (USGS, no date). Diquat us e on crops occurred primarily in regions of New England, the Great Lakes, North Dakota, the Pacific Northwest, California, and Florida. In comparison to other commonly us ed pesticides, diquat has the lowest national estimate for use on crops (Gianessi and Regner, 2006). The Reregistration Eligibility Deci sion (RED) for Diquat Dibromide (USEPA, 1995a) notes that although diquat is persistent(i.e., it does not hydrolyze and is resistant to degradation), it becomes immobile when it adsorbs to soil particles and, therefore, is not expected to contaminant

May 2009 Draft EPA document. Do not cite or distribute. 116ground water. Furthermore, diquat dissipates qu ickly from surface water because it adsorbs to soil sediments, vegetation, and organic matter; the estimated half-lif e is 1 to 2 days for diquat in surface water based on a study of two ponds in Florida (USEPA, 1995a). These factors indicate the possibility of low occurren ce in drinking water sources. The BAT and small system compliance technologies for diquat have othe r beneficial effects, e.g., removing other co-occurring contaminants. Th erefore, if EPA were to consider a higher level, the Agency does not know how many PWSs th at are currently treati ng to comply with the existing MCL of 0.02 mg/L would be likely to disc ontinue treatment that is already in place (USEPA, 2009d). Also, the Agencydoes not know to what extentaffected systems might be able to reduce costs given that capital costs are not recoverable. However, the Agency recognizes that there may be opportunities to ac hieve operational cost sa vings if these systems are able to re-optimize current treatment. Given these challenges, the Agency believes th at any resulting revi sion is not likely to provide a meaningful opportunity for cost savings. In view of this, any revision would be a low priority activity and not appropriate at this time.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for diquat, EPA does not believe a revision to th e NPDWR for diquat is appropriate at this time. In making this deci sion, the Agency considered whether any possible revision to the NPDWR for diquat is likely to provide a meaningful opportunity for cost savings to public water systems and their customers. After consideration of this factor, EPA has decided that any revision to the NPDWR would be a low priority activ ity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

May 2009 Draft EPA document. Do not cite or distribute. 117• The burden on States and the regu lated community to implement any regulatory change that resulted.

34. Endothall

a. Background . EPA published the current NPDWR for endothall on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.1 mg/L. EPA based the MCLG on a reference dose of 0.02 mg/ kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. In 2005, the Agency updated its healtheffects assessme nt of endothall (USEPA, 2005d). The Agency identified a change in this assessment that could lead to a change in the MCLG. This assessment considered releva nt studies on the toxicityof endothall including developmental and reproductive toxicity. The assessment revised the RfD from 0.02 mg/kg-day to 0.007 mg/kg-day and concluded that endothall is unlikely to be carcinogenic to humans (USEPA, 2005d). Based on the new OPP a ssessment and RfD of 0.007 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters water intake per day, the DWEL could be 0.245 mg/L. An RSC of 20% results in a possible MCLG of 0.05 mg/L. Because of a possible change inthe MCLG for endothall, EPA c onsidered whether analytical feasibility is likely to be a lim itation if the Agency were to consider lowering the MCL to 0.05 mg/L (the possible MCLG). EPA reviewed WS da ta from the first Six-Year Review cycle and then analyzed more recent PT data to determ ine if the PQL can be re vised (i.e., analytical feasibility). Passing ra tes for WS data available through late 1999 for endothall are generally above 80 percent, but there were no results for WS studies with true values below the current PQL of 0.09 mg/L. More recent PT data from late 1999 through 2004, supplied by a PT provider, show passing rates above 75 percent for most studies, but there are four studies with passing rates equal to or less th an the 75 percent criterion, incl uding two close to the current

May 2009 Draft EPA document. Do not cite or distribute. 118PQL. No PT studies had true values below the cu rrent PQL. Given the variable results from the PT studies and the lack of WS and PT study resu lts below the current PQL, WS and PT data are insufficient to support a PQL reduction.(USEPA, 2009c). While the PT data are not sufficient to support a lowering of the PQL for endothall at this time, the current PQL of 0.09 mg/L is greater than the possible MC LG. It would therefore limit a possible revision to the MCL. EPA evaluate d two alternative sources of information to determine whether they indicate any potential to revise the PQL: labor atory minimum reporting levels in the Six-Year ReviewICR dataset, and the MDLs fo r the approved method for the detection of endothall (Method 548.1). While EPA prefers to use laboratory performance data to calculate the PQL, the MRL and MDL information canbe valuable for this review to indicate whether it is possible to quantit ate at levels below the current PQL. The Six-Year Review ICR dataset contains MRL values for 21,792 samples. Of these, 21,445 (98%) have an MRL value of 0.05 mg/L or lower. The MDL of the appr oved method is 0.00179 mg/L. Applying a multiplier of 10 would give a pos sible PQL of 0.0179 mg/L

. Because most MRL values are at or below the possible MCLG of 0.05 mg/L, EPA selected that value as the minimum threshold for the occurrence and exposure analysis. Based on these varied and unrelated approaches/s ources of information, there is evidence of a potential to lower the PQL for endothall even th ough the WS and PT data are insufficient to support a PQL reduction. To determine whether any MCL revision is likely to provide a meaningful opportunity to improve public healthprotection, EPA evaluated the occurrence of endothall at the possible MCLG of 0.05 mg/L (USEPA, 2009f). Table VI-15 shows the results of the occurrence and exposure analysis for the current MCL and the possible MCLG set equal to 0.05 mg/L based on the new health effects info rmation and the laboratory minimum reporting levels in the Six-Year Review ICR dataset. The occurrence an d exposure analysis shows that

May 2009 Draft EPA document. Do not cite or distribute. 119average concentrations do not exceed the current MC L for any system in the analysis. Note that these results do not necessarily reflect MCL violations, which are based on running annual average concentrations at entry points; nevert heless, SDWIS/FED indicates no MCL violations for endothall between 1998 and 2005 (USEPA, 2007g). The average concentr ation at one of the 14,156 systems (0.007%), serving 10,000 people (o r 0.008% of 119 million people), exceeds the possible MCLG based on new health effects information (0.05 mg/L).

Table VI-15. Number and Per cent of Systems with Mean Con centrations Exceeding Endothall Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrati ons that are Greater than the Regulatory or Health-based Threshold (Percentages based on 14,156 systems with endothall data in the SixYear Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.1 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Possible MCLG (0.05 mg/L) 1 (0.007%) 1 (0.007%) 1 (0.007%) Corresponding Population Served (Percentages based on 118,536,800 people served by the systems with endothall data in the Six-Year Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.1 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Possible MCLG (0.05 mg/L) 10,000 (0.008%) 10,000 (0.008%) 10,000 (0.008%) 1. Results are based on setting all nondetect results eq ual to MRL values in the Si x-Year Review ICR dataset 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for endothall, EPA doe s not believe a revision to the NPDWR for endothall is appropriate at this time. In making this decision, the Agency considered whether May 2009 Draft EPA document. Do not cite or distribute. 120any possible revision to the NPDWR for endothall is likely to pr ovide a meaningful opportunity for health risk reductions. Taking into consider ation the low occurrence of this contaminant, EPA has decided that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted.

35. Endrin

a. Background . EPA published the current NPDWR for endrin on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.002 mg/L. EPA based the MCLG on a reference dose of 0.0003 mg/kg-day and a cancer cla ssification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the toxicology of endrin, including its poten tial developmental and reproductive toxicity. The literature search did not identify any studies that warran t a review of the RfD or the cancer cla ssification (USEPA, 2009b). A review of analytical or treatment feasibility is not necessary for endrin because changes to the MCLG are not warranted at th is time and the current MCL is set at the MCLG. Since EPA did not identify a health or t echnology basis for revising the e ndrin NPDWR, the Agency did not conduct a detailed occurrence and exposure analysis.

c. Review Result. EPA’s review shows that there ar e no data supporting a change to the endrin NPDWR. As a result, a revision to the NPDWR would not be appropriate at this time.

May 2009 Draft EPA document. Do not cite or distribute. 12136. Epichlorohydrin

a. Background . EPA published the current NPDWR for epichlorohydrin on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establ ished an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR imposes a TT requirement that limits the allowable level of epichlorohydrin monom er in the polymer that is added to drinking water as a flocculent to remove particulates. Each water system is required to certify, in writing, to the State (using third-party or manufacturer’s certification) that the combination (or product) of dose and monomer level does not exceed the following level: 0.01 percent residual epichlorohydrin monomer in polymer products used during water treatment and dosed at 20 mg/L (ppm). b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the carcinogenicity of epichlorohydrin as well as its potential developmental and reproductive toxicity. EPA has not identified any new information that indicates that it is appropriate to consider revisions to the cancer classification for epichlorohydrin at this time (USEPA, 2009b). Because the MCLG remains at zero, the Agency believes that a further review of the health effects of epichlor ohydrin is not warranted at this time. EPA has identified information that suggests th at the residual epichl orohydrin content in water treatment polymers has decreased significantly, likely due to improvements in manufacturing processes and technologies (USEPA, 2009g). NSF International analyses conducted between January 2005 and June 2007 found that, in 84 epichlorohydrin-based polymers/co-polymers submitted for certificat ion under NSF Standard 60, the residual epichlorohydrin content was always below the detection limit of 0.002%.

May 2009 Draft EPA document. Do not cite or distribute. 122Epichlorohydrin standards in Europe and Australi a are also stricter th an the NPDWR. Based on the concentration of dose and monomer level in the NPDWR, finished water could contain up
to 2 μ g/L (ppb) of epichlorohydrin. By contrast, the European Union requires that finished water contain less than 0.1 μ g/L (ppb) epichlorohydrin, and Australia requires that the concentration in finished water be less than 0.5 μ g/L (ppb). The United Kingdom re quires that polymers used in drinking water contain less than 0.002% resi dual epichlorohydrin, and the dose of these polymers be less than 5 mg/L (ppm) at all times, for a maximum finished water concentration of
0.1 μ g/L (ppb). To assess the occurrence of epichlorohydrin in drinking water, EPA sought data on current usage practices for polymers containing it. The Agency is not presently aware of any recent, large-scale studies of polymer usage in drinki ng water facilities, and therefore cannot fully characterize the occurren ce of epichlorohydrin in drinking wa ter. However, cationic polymers used in water treatment often contain epic hlorohydrin. The 1996 WATER:\STATS database (described in Levine et al ., 2004), based on an AWWA surve y, indicates that 13% of ground water systems and 66% of surface water systems surveyed use a polymer for water treatment. Many of these are cationic polymers, particular ly for surface water systems; cationic polymers used to treat drinking water ofte n use epichlorohydrin monomer. Additional information on the extent of use of epichlorohydrin based polymers/co-polymers in drinking water would further assist the Agen cy in evaluating the potential public health benefits associated with a revision to the tr eatment technique for epcichlorohydrin. Because most epichlorohydrin-based polymers available today have a significantly lower residual monomer content than that specif ied in the treatment technique, EPA believes that the costs of a revision would be minimal (USEPA, 2009g).

May 2009 Draft EPA document. Do not cite or distribute. 123c. Review Result. The Agency believes it is ap propriate to revise the NPDWR for epichlorohydrin. The existing MCLG is zero (based on the current B2 cancer classification) and NSF International data indicate that polyacrylamides are widelyavailable with lower monomer levels than required by the existing NPDWR. Hence, revisions to the epichlorohydrin NPDWR will provide a meaningful opportunity for health risk reduction. As discussed in Section VII, the Agency solicits public comment on the use of epichlorohydrin-based polymers/co-polymers in drinking water facilities (since this may provi de additional information on the occurrence of epichlorohydrin in drinking water) to help inform the regulatory revisions. EPA notes that any changes to the NPDWR for epichlorohydin may also include revisions to the closely related NPDWR for acrylamide. 37. Ethylbenzene

a. Background . EPA published the current NPDW R for ethylbenzene on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establ ished an MCLG and an MCL of 0.7 mg/L. EPA based the MCLG on a reference dose of 0.1 mg /kg-day and a cancer clas sification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to ethylbenzene. The re vised health effects assessment wi ll consider relevant studies on the toxicity of ethylbenzene, including its po tential developmental an d reproductive toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment.

May 2009 Draft EPA document. Do not cite or distribute. 124c. Review Result. Since the MCL for ethylbenzene is se t at its MCLG and a reassessment of the health risks resulting from exposure to ethyl benzene is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time. 38. Ethylene Dibromide (EDB; 1,2-Dibromoethane)

a. Background . EPA published the current NPDW R for EDB on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establishe d an MCLG of zer o based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.00005 mg/L, based on analytical feasibility. b. Technical Reviews. The Agency updated the health effects assessment for EDB in 2004 and retained the cancer classification on which the 1991 MCLG is based (USEPA, 2004a). As a part of the 2004 assessment, EPA considered rele vant studies on the toxicity of EDB, including its potential developmental and reproductive toxicity. The current MCL for EDB is based on a PQL of 0.00005 mg/L. For the Six-Year Review, the Agency considered whether changes in the an alytical feasibility of EDB might lead to a lower MCL. EPA reviewed WS data from the fi rst Six-Year Review cycle and then analyzed more recent PT data to determine if the PQL can be revised (i.e., analytical feasibility). Passing rates for WS data available through late 1999 for ED B are all 75 percent or higher. However, the true concentrations were all hi gher than the current PQL of 0.00005 mg/L. More recent PT data from late 1999 through 2004, supplied by a PT provider, likewise show passing rates of 75 percent or higher, but again, all of the true concentrations in th e PT data were higher than the current PQL. Because of the lack of data belo w the PQL, a lowering of the PQL for EDB is not appropriate at this time (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR

May 2009 Draft EPA document. Do not cite or distribute. 125dataset, and the MDLs for approved methods for the detection of EDB (Methods 504.1 and 551.1). While EPA prefers to use laboratory perfo rmance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Re view ICR dataset contains MRL values for 83,063 samples. Of these, 26,926 ( 32%) equal the modal MRL of 0.00001 mg/L. An additional 454 (0.5%) are lowe r than 0.00001 mg/L, and 8,416 ( 10%) are between 0.00001 mg/L and the MCL of 0.00005 mg/L. The MDLs of approved methods are 0.00001 and 0.000032 mg/L. Applying a multiplier of 5, which was used to establish the PQL, would give a possible PQL range from 0.00005 to 0.00016 mg/L. Since most MRLs do not achieve the modal value, and the current PQL is at the low end of the ra nge of 5×MDL values, EPA believes that there is no potential to lower the PQL for EDB. Since the MCL is constrained by the PQL, and the PQL is unchanged, EPA does not believe it is necessary to conduct an occurrence analysis at this time.

c. Review Result. EPA did not identify new data thatsupport consideration of a possibly lower PQL (and therefore a possibly lower MCL). Therefore, EPA does not believe a revision to the NPDWR for EDB is appropriate at this time.

39. Fluoride

a. Background . EPA published the current NPDWR for fluoride on April 2, 1986 (51 FR 11396 (USEPA, 1986c)). The NPDWR established an MCLG and an MCL of 4.0 mg/L. The MCLG was developed from a lowest effect level for crippling sk eletal fluorosis of 20 mg/day with continuous exposures over a 20-year or long er period. The lowest- observed-adverse-effect level (LOAEL) was divided by an uncertainty fact or of 2.5 and a drinking water intake of 2 liters/day (L/day) to obtain the MCLG. Drinking water was considered to be the only source of exposure for the calculation. At the same time, EPA published a secondary maximum contaminant level (SMCL) for fluoride of 2.0 mg/L to protect against dental fluorosis, which was

May 2009 Draft EPA document. Do not cite or distribute. 126considered to be an adverse cosmetic effect. PWSs exceeding the fluoride SMCL must provide public notification to their customers. Fluoride is unique because of its beneficial e ffects at low level exposures, and because it is voluntarily added to some drinking water system s as a public health measure for reducing the incidence of cavities among the treated population. The amount of fluoride added to drinking water for fluoridation ranges from 0.7 to 1.2 mg/L , depending on ambient air temperatures. The decision to fluoridate a water supply is made by the State or local municipality, and is not mandated by EPA or any other Federal entity. b. Technical Reviews. As a result of the first Six-Year Review of the fluoride NPDWR (67 FR 19030 (USEPA, 2002c) (preliminary); 68 FR 42908 (USEPA, 2003e) (final)), EPA requested that the National Research Council (NRC) of th e National Academies of Science (NAS) conduct a review of the recent health and exposure data on orally ingested fluoride. In 2006, the NRC published the results of their ev aluation in a report entitled, Fluoride in Drinking Water: A Scientific Review of EPA’s Standards . Based on its review, NRC c oncluded that severe dental fluorosis is an adverse health effect when it causes confluent thinning and pitting of the enamel, a situation that compromises the function of the enamel in protecting the dentin and eventually the pulp from decay and infection. There was c onsensus among the committee that severe dental fluorosis is an effect that should be avoided and that “expos ure at the MCLG clearly puts children at risk of developing severe enamel fl uorosis.” In addition, the committee examined the scientific data on the impact of fluoride on the strength and structure of bone and the majority concluded that the MCLG “is not likely to be protective against bone fractures.” NRC recommended that EPA use the av ailable dose-response data for th e effects of fluoride on severe dental fluorosis and skeletal fractures in comb ination with data on the relative contribution of

May 2009 Draft EPA document. Do not cite or distribute. 127drinking water to total fluoride e xposure to identify an MCLG th at would be protective against these effects. The NRC also evaluated the impact of fluoride on reproduction and development, neurotoxicity and behavior, the endocrine system , genotoxicity, cancer and other effects. They concluded that the available data were inadequate to determine if a risk for effects on these endpoints exists at an MCLG of 4 mg/L and ma de recommendations for additional research. After considering the ge notoxicity data, cancer studies in humans and animals, and studies of mode of action in cell systems, NRC determined that the evidence on the potential of fluoride to initiate or promote cancers, par ticularly of the bone, is tentative and mixed. They recommended that EPA await the results and publication of an in-process hosp ital-based, case- control study of osteosarcoma and fluoride exposure from the Harvard School of Dent al Medicine before determining if an Agency update of the cance r risk assessment for fluoride is necessary 16

.

c. Review Result. The Agency does not believe a revi sion to the NPDWR for fluoride is appropriate at this time because the Agency’s Office of Water (OW) is in the process of developing its dose-response assessment of the noncancer impacts of fluoride on severe dental fluorosis and the skeletal system. In addition, the OW is updating its ev aluation of the relative contribution of drinking water to total fluoride exposure consid ering the contributions from dental products, foods, pesticide residues, and other sources such as ambient air and medications. Once the Agency completes and publishes peer reviewed versions of these in-process assessments, it will be able to determine the potential impacts on the MCLG, MCL, and/or the SMCL and whether any revisions to these would be appropriate.

16 At this time, the results of the osteosarcoma cancer study recommended by NAS have not been published. May 2009 Draft EPA document. Do not cite or distribute. 12840. Glyphosate

a. Background . EPA published the current NPDW R for glyphosate on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.7 mg/L. EPA based the MCLG on a reference dose of 0.1 mg/k g-day and a cancer clas sification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. In 2002, the Agency updated its health effects assessment of glyphosate (USEPA, 2002a). The Agency identified a change in this assessment that could lead to a change in the MCLG. This assessment c onsidered relevant studies on the toxicity of glyphosate including developmental and reproductive toxicity. The assessment revised the RfD from 0.1 mg/kg-day to 2 mg/kg-day and conc luded that glyphosate has evidence of noncarcinogenicity in humans (USEPA, 2002a). Ba sed on the new OPP assessment and RfD of 2 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters water intake per day, the DWEL could be 70 mg/L. An RSC of 20% results in a possible MCLG of 14 mg/L, (USEPA, 2009b). Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor if EPA were to raise the MCLG. EPA evaluated the results of the occurrence and exposure analyses for glyphosate to determine wh ether a revised MCLG/MCL would be likely to result in a meaningful opportunity to achieve cost savings for PWSs and their customers while maintaining, or improving, the level of public health protection (USE PA, 2009f). Although the Agency obtained and evaluated the finished wate r occurrence data for glyphosate, its usefulness is limited for determining potential cost savings to PWSs and their customers because the Agency does not know which systems are treating for this contaminant. As an alternative, the Agency evaluated available data on source wate r quality and conducted a qualitative assessment of treatment cost savings.

May 2009 Draft EPA document. Do not cite or distribute. 129Table VI-16 provides summary data for contam inant occurrence based on maximum sample values for the locations included in the ST ORET and NAWQA data. Although the degree to which these occurrence rates represent national drinking water source occurrence is uncertain, the information shows no to low occurrence at thre sholds levels of interest. This information indicates that any resulting NP DWR change would not affect sy stems that rely on source water at any of the NAWQA or STORET locations.

Table VI-16. Ambient Water Quality M onitoring Occurrence Summary for Glyphosate Number of Locations (% of locations) Maximum Concentration STORET 1 NAWQA 2 Total 241 (100.0%) 41 (100.0%) Nondetect 180 (74.7%) 37 (90.2%) Detected 61 (25.3%) 4 (9.8%) Exceeds current MCLG of 0.7 mg/L 0 (0.0%) 0 (0.0%) Exceeds alternative value of 14.0 mg/L 0 (0.0%) 0 (0.0%) 1. STORET database 2002-2007. 2. NAWQA database 1992-2005. Source: USEPA, 2004c
The BAT and small system compliance technolo gies for glyphosate ha ve other beneficial effects, e.g., pretreatment for other co-occurring c ontaminants or disinfection. Therefore, if EPA were to consider a higher level, the Agency does not know how many PWSs that are currently treating to comply with the ex isting MCL of 0.7 mg/L would be likely to discontinue treatment that is already in place (USE PA, 2009d). Also, the Agency does not know to what extent affected systems might be able to reduce costs given that capital costs are not recoverable. However, the Agency recognizes that there ma y be opportunities to ach ieve operational cost savings if these systems are able to re-optimize current treatment.

May 2009 Draft EPA document. Do not cite or distribute. 130Given these challenges, the Agency believes th at any resulting revi sion is not likely to provide a meaningful opportunity for cost savings. In view of this, any revision would be a low priority activity and not appropriate at this time.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for glyphosate, EPA doe s not believe a revision to the NPDWR for glyphosate is appropriate at this time. In making this decision, the Agency considered whether any possible revision to the NPDW R for glyphosate is likely to pr ovide a meaningful opportunity for cost savings to public water systems and thei r customers. Taking into consideration the low occurrence of this contaminant in source wate rs, EPA has decided that any revision to the NPDWR would be a low priority activity for the Ag ency, and, thus, is not a ppropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 41. Heptachlor

a. Background . EPA published the current NPDWR for heptachlor on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establis hed an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.0004 mg/L, based on analytical feasibility. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the carcinogeni city of heptachlor as well as its potential developmental and reproductive toxicity. EPA has not identified any new information that indicates that it is appropriate to consider revisi ons to the cancer classifi cation for heptachlor at

May 2009 Draft EPA document. Do not cite or distribute. 131this time (USEPA, 2009b). Because the MCLG re mains at zero, the Agency believes that a further review of the health effects of heptachlor is not warranted at this time. The current MCL for heptachlor is based on a PQL of 0.0004 mg/L. For the Six-Year Review, the Agency considered whether changes in the analytical feasibilit y of heptachlor might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determine if the PQ L can be revised (i.e., an alytical feasibility). Passing rates for WS data available through late 1999 for heptachlor are above 90 percent around the current PQL of 0.0004 mg/L, including three studies with true values below the current PQL. All passing rates in the WS data exceeded 80 pe rcent. More recent PT data from late 1999 through 2004, supplied by a PT provider, show greater than 75 percen t passing rates for a majority of studies, but there are no studies with true values below the current PQL. There are three PT studies with passing rates below 75 percent. Despite this variability, most of the laboratory passing rates from WS and PT studies, including three with true values below the PQL, exceeded the 75 percent criteri on typically used to derive a PQ L. Therefore, a lowering of the PQL for heptachlor might be po ssible. These results, however, are insufficient to recalculate a revised PQL for heptachlor because not enough data points are available below the current PQL to derive a value at the 75 pe rcent passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods for the detection of heptachlor (Methods 505, 508, 508.1, 525.2, and 551.1). While EPA prefers to use labor atory performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the cu rrent PQL. The Six-Year Review ICR dataset contains MRL values for 58,758 samples. Of these, 24,918 (42%) equal the modal MRL of

May 2009 Draft EPA document. Do not cite or distribute. 1320.00004 mg/L. An additional 7,966 (14%) are lo wer than 0.00004 mg/L, and 24,752 (42%) are between 0.00004 mg/L and 0.0001 mg/L. The MDLs of approved methods are 0.000003, 0.0000015, 0.000005, 0.00015, and 0.000081 mg/L. Applying a multiplier of 10 would give a possible PQL range from 0.000015 to 0.0015 mg/L. Because of the broad dispersion in MRL values, EPA used the 10×MDL values to develo p thresholds in the occurrence and exposure analysis. EPA took the median 10×MDL va lue of 0.00005 mg/L and rounded up to 0.0001 mg/L to establish a minimum threshold for the occurrence and exposure analysis. Based on these varied and unrelated approach es/sources of information, EPA believes that there may be potential to lower the PQL for heptachlor. To determine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of heptachlor at thresholds of 0.0001 and 0.0002 mg/L (USEPA, 2009f). Table VI-17 shows the re sults of the occurrenc e and exposure analysis for the current MCL and EQLs set equal to 0.0002 mg/L and 0.0001 mg/L. The occurrence and exposure analysis shows that average concentrations exceed the current MCL for one of 33,020 systems (0.003%) serving 325 people (or 0.0002% of 184 million people). Note that these results do not necessarily reflect MCL violati ons, which are based on annual av erage concentrations at entry points; SDWIS/FED indicates no MCL violations for heptachlor between 1998 and 2005 (USEPA, 2007g). Average concentrations at 42 of 33,020 systems (0.127%), serving 31,500 people (or 0.017% of 184 million peopl e), exceed the EQL of 0.0001 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 133Table VI-17. Number and Percent of Systems wi th Mean Concentrations Exceeding Heptachlor Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 33,020 systems with heptachlor data in the SixYear Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.0004 mg/L) 1 (0.003%) 1 (0.003%) 1 (0.003%) 1/2 MCL (0.0002 mg/L) 1 (0.003%) 1 (0.003%) 1 (0.003%) EQL (0.0001 mg/L) 42 (0.127%) 42 (0.127%) 42 (0.127%) Corresponding Population Served (Percentages based on 184,444,000 people served by the systems with heptachlor data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.0004 mg/L) 325 (0.0002%) 325 (0.0002%) 325 (0.0002%) 1/2 MCL (0.0002 mg/L) 325 (0.0002%) 325 (0.0002%) 325 (0.0002%) EQL (0.0001 mg/L) 31,500 (0.017%) 31,500 (0.017%) 31,500 (0.019%) 1. Results are based on setting all nondetect results eq ual to MRL values in the Si x-Year Review ICR dataset. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for heptachlor is appropriate at this time. The occurrence and exposure analysis based on possible changes in analytical feasibility indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration the low occurrence of this contaminant, EPA has decide d that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

May 2009 Draft EPA document. Do not cite or distribute. 134• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 42. Heptachlor Epoxide

a. Background . EPA published the current NPDWR for heptachlor epoxide on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR es tablished an MCLG of zero based on a cancer classification of B2, pr obable human carcinogen. The NPDW R also established an MCL of 0.0002 mg/L, based on analytical feasibility. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the carcinogenicity of heptachlor epoxide as well as its potential developmental and reproductive toxicity. EPA has not identified any new information that indicates that it is appropriate to consider revi sions to the cancer classi fication for heptachlor epoxide at this time (USEPA, 2009b). Because th e MCLG remains at zero, the Agency believes that a further review of the heal th effects of heptachlor epoxide is not warranted at this time. The current MCL for heptachlor epoxide is based on a PQL of 0.0002 mg/L. For the SixYear Review, the Agency considered whether changes in the analytical feasibility of heptachlor epoxide might lead to a lower MCL. EPA review ed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determine if the PQL can be revised (i.e., analytical feasibility). Passing rates for WS data available through late 1999 for heptachlor epoxide are above 85 percent around the curr ent PQL of 0.0002 mg/L, including two studies with true values below the current PQL. All pa ssing rates in the WS dataexceeded 80 percent. More recent PT data from late 1999 through 2004, supplied by a PT provider, show greater than 75 percent passing rates for a majority of studies, but there are no studies with true values below

May 2009 Draft EPA document. Do not cite or distribute. 135the PQL. There are two PT studies with passing rates below 75 percent. Despite this variability, most of the laboratory passing rates from WS and PT studies exceeded the 75 percent criterion typically used to derive a PQL. Therefore, a lowering of the PQL for heptachlor epoxide might be possible. These results, how ever, are insufficient to recalcul ate a revised PQL for heptachlor epoxide because not enough data points are availabl e below the current PQL to derive a value at the 75 percent passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of hept achlor epoxide (Methods 505, 508, 508.1, 525.2, and 551.1). While EPA prefers to use laboratory performance data to calculate the PQL, the MRL and MDL information canbe valuable for this review to indicate whether it is possible to quantit ate at levels below the current PQL. The Six-Year Review ICR dataset contains MRL values for 58,731 samples. Of these, 26,424 (45%) equal the modal MRL of 0.00002 mg/L. An additional 5,969 (10%) are lower than 0.00002 mg/L, and 25,888 (44%) are between 0.00002 mg/L and 0.0001 mg/L. Th e MDLs of approved methods are 0.000004, 0.0000059, 0.000001, 0.00013, and 0.000202 mg/L. Applying a multiplier of 10 would give a possible PQL range from 0.00001 to 0.00202 mg/L. Because of the broad dispersion in MRL values, EPA used the 10×MDL values to develo p thresholds in the occurrence and exposure analysis. EPA took the median 10×MDL value of 0.000059 mg/L and rounded up to 0.0001 mg/L to establish a minimum threshold for the occurrence and exposure analysis. Based on these varied and unrelated approach es/sources of information, EPA believes that there may be potential to lower the PQL for he ptachlor epoxide. To determine whether any MCL revision is likely to provide a meaningful opportunity to im prove public health protection, EPA evaluated the occurrence of heptachlor epox ide at an estimated quantitation level of 0.0001

May 2009 Draft EPA document. Do not cite or distribute. 136mg/L (USEPA, 2009f). Table VI-1 8 shows the results of the occurrence and exposure analysis for the current MCL and an EQL set equal to 0.0001 mg/L. The occurrence and exposure analysis shows that average concentrations exceed the current MCL for one of 33,015 systems (0.003%) serving 325 people (or 0.0002% of 184 million people). Note that these results do not necessarily reflect MCL violati ons, which are based on annual av erage concentrations at entry points; SDWIS/FED indicates two MCL violations for hept achlor epoxide between 1998 and 2005 (USEPA, 2007g). Average concentrations at three of 33,015 systems (0.009%), serving 14,400 people (or 0.008% of 184 million peopl e), exceed the EQL of 0.0001 mg/L.

Table VI-18. Number and Percent of Systems wi th Mean Concentrations Exceeding Heptachlor Epoxide Thresholds and Corresponding Estimates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 33,015 systems with heptachlor epoxide data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.0002 mg/L) 1 (0.003%) 1 (0.003%) 1 (0.003%) EQL (0.0001 mg/L) 3 (0.009%) 3 (0.009%) 3 (0.009%) Corresponding Population Served (Percentages based on 184,478,000 people served by the systems with heptachlor epoxide data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.0002 mg/L) 325 (0.0002%) 325 (0.0002%) 325 (0.002%) EQL (0.0001 mg/L) 14,400 (0.008%) 14,400 (0.008%) 14,400 (0.008%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

May 2009 Draft EPA document. Do not cite or distribute. 137c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for heptachlor epoxide is appr opriate at this time. The occurr ence and exposure analysis based on possible changes in analytical feasibility indica tes that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration the low occurrence of this contaminant, EPA has decided that any revisi on to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted.

43. Hexachlorobenzene

a. Background . EPA published the current NPDWR for hexachlorobenzene on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR establ ished an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.001 mg/L, based on anal ytical feasibility. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the carcinogenicity of hexachlorobenzene as well as its potential developmental and reproductive toxicity. EPA has not identified any new information that indicates that it is appropriate to consider revisions to the cancer classification for hexachlorobenzene at this time (USEPA, 2009b) . Because the MCLG remains at zero, the Agency believes that a further review of the hea lth effects of hexachlorobenzene is not warranted at this time.

May 2009 Draft EPA document. Do not cite or distribute. 138The current MCL for hexachlorobenzene is ba sed on a PQL of 0.001 mg/L . For the Six-Year Review, the Agency considered whether changes in the analytical feasibility of hexachlorobenzene might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determine if the PQL can be revised (i.e., analytical feasibility). Passing rates fo r WS data available through late 1999 for hexachlorobenzene are above 80 percent around th e current PQL of 0.001 mg/L, including eight studies with true values below the current PQ L. More recent PT data from late 1999 through 2004, supplied by a PT provider, also show greater than 75 percent passing rates for a majority of studies, including eight out of ni ne studies with true values be low the current PQL. There are two PT studies with passing rates equal to or less than 75 percent, including one with a true value below the PQL. Despite this variability, most of the laboratory passing rates from WS and PT studies – including several with true concentr ations below the PQL – exceeded the 75 percent criterion typically used to derive a PQL. Therefore, a lowering of the PQL for hexachlorobenzene might be possible. These re sults, however, are insufficient to recalculate a revised PQL for hexachlorobenzene because no t enough data points are available below the current PQL to derive a value at the 75 percent passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of hex achlorobenzene (Methods 505, 508, 508.1, 525.2, and 551.1). While EPA prefers to use laboratory performance data to calculate the PQL, the MRL and MDL information canbe valuable for this review to indicate whether it is possible to quantit ate at levels below the current PQL. The Six-Year Review ICR dataset contains MRL values for 58,713 samples. Of these, 40,791 (69%) equal the modal MRL of 0.0001 mg/L. An additional 7,380 (13%) ar e lower than 0.0001 mg/L. The MDLs of

May 2009 Draft EPA document. Do not cite or distribute. 139approved methods are 0.000002, 0.0000077, 0.000001, 0.00013, and 0.000003 mg/L. Applying a multiplier of 10 would give a possible PQL range from 0.00001 to 0.0013 mg/L; however, the median 10×MDL value is 0.00003 mg/L, which is less than the modal MRL. Because of the preponderance of MRL values of 0.0001 mg/L, EPA selected that value as the minimum threshold for the occurrence and exposure analysis. Based on these varied and unrelated approach es/sources of information, EPA believes that there is potential to lower the PQL for hexach lorobenzene. To determine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of hexachlorobenzene at thresholds of 0.0001 and 0.0005 mg/L (USEPA, 2009f). Table VI-19 s hows the results of the occurren ce and exposure analysis for the current MCL and EQLs set equal to 0.0005 mg /L and 0.0001 mg/L. The occurrence and exposure analysis shows that average concentr ations exceed the curren t MCL for three of 32,826 systems (0.009%) serving 2,000 people (or 0.001% of 184 million people). Note that these results do not necessarily reflect MCL viol ations, which are based on annual average concentrations at entry points; SDWIS/ FED indicates two MC L violations for hexachlorobenzene between 1998 an d 2005 (USEPA, 2007g). Average c oncentrations at 9 to 16 of 32,826 systems (0.027% to 0.049%), servi ng approximately 9,000 to 94,000 people (or 0.005% to 0.051% of 184 million peopl e), exceed the EQL of 0.0001 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 140Table VI-19. Number and Percent of Syst ems with Mean Concentrations Exceeding Hexachlorobenzene Thresholds and Corresponding Estimates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 32,826 systems with hexachlorobenzene data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.001 mg/L) 3 (0.009%) 3 (0.009%) 3 (0.009%) 1/2 MCL (0.0005 mg/L) 4 (0.012%) 4 (0.012%) 4 (0.012%) EQL (0.0001 mg/L) not applicable 16 (0.049%) 9 (0.027%) Corresponding Population Served (Percentages based on 184,124,800 people served by the systems with hexachlorobenzene data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.001 mg/L) 2,000 (0.001%) 2,000 (0.001%) 2,000 (0.001%) 1/2 MCL (0.0005 mg/L) 5,000 (0.003%) 5,000 (0.003%) 5,000 (0.003%) EQL (0.0001 mg/L) not applicable 94,000(0.051%) 9,000 (0.005%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.001 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for hexachlorobenzene is appropriate at this time. The occurrence and exposure analysis based on possible changes in analytical feasibility indica tes that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration the low occurrence of this contaminant, EPA has decided that any revisi on to the NPDWR would

May 2009 Draft EPA document. Do not cite or distribute. 141be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 44. Hexachlorocyclopentadiene

a. Background . EPA published the current NPDWR fo r hexachlorocyclopentadiene on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDW R established an MCLG and an MCL of 0.05 mg/L. EPA based the MCLG on a refe rence dose of 0.007 mg/kg-day and a cancer classification of D, not classifi able as to human carcinogenicity. b. Technical Reviews. In the first Six-Year Review cy cle, EPA evaluated new information from a health effects assessment completed in 2001 (USEPA, 2001b). At that time, the Agency could not determine that a revision to the NP DWR would provide a meaningful opportunity for public health protection (67 FR 19030 (USEPA , 2002c)). The 2001 assessment considered relevant studies on the toxicity of hexachlo rocyclopentadiene includ ing developmental and reproductive toxicity. The assessment revise d the RfD from 0.007 mg/kg-day to 0.006 mg/kgday (USEPA, 2001b). In the current review cy cle, EPA conducted a literature search through June 2007 for relevant data on the toxicology of hexachlorocyclopent adiene, including its potential developmental and reprodu ctive toxicity. The literature se arch did not identify any new data that would affect the RfD or cancer cl assification (USEPA, 2009b). Based on the 2001 IRIS assessment and RfD of 0.006 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters water intake per day, the DWEL could be 0.21 mg /L. An RSC of 20% results in a possible MCLG of 0.04 mg/L (USEPA, 2009b).

May 2009 Draft EPA document. Do not cite or distribute. 142Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor for the possible MC LG decrease under consideration. EPA evaluated the results of the occurrence and exposure analyses for hexachlorocyclopentadiene to determine whether a revised MCLG/MCL would be likely to result in a meaningful opportunity to improve the level of public health protection (USEPA, 2009f). Table VI-20 shows the re sults of the occurrenc e and exposure analysis for the current MCL and the possible MCLG. The occurrence and exposure analysis shows that average concentrations do not exceed the current MCL for any systems in the analysis. Note that these results do not necessarily reflect MCL violations, which are based on running annual average concentrations at entry points; SDWI S/FED indicates no MCL violations for hexachlorocyclopentadiene between 1998 a nd 2005 (USEPA, 2007g). The occurrence and exposure analysis shows that average concentr ation do not exceed the possible MCLG based on health effects information (0.04 mg/L).

May 2009 Draft EPA document. Do not cite or distribute. 143Table VI-20. Number and Percent of Syst ems with Mean Concentrations Exceeding Hexachlorocyclopentadiene Thresholds and Corresponding Estimates of Population Served Systems with Mean Concentrati ons that are Greater than the Regulatory or Health-based Threshold (Percentages based on 32,801 systems with hexachlorocyclopentadiene data in the Six-Year Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.05 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Possible MCLG (0.04 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Corresponding Population Served (Percentages based on 184,738,000 people served by the systems with hexachlorocyclopentadiene data in the Six-Year Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.05 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Possible MCLG (0.04 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) 1. Results are based on setting all nondetect results eq ual to MRL values in the Si x-Year Review ICR dataset 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for hexachlorocyclopentad iene, EPA does not believe a revision to the NPDWR for hexachlorocyclopentadiene is appropriate at this time. In making this decision, the Agency considered whether any possible revision to the NPDWR for hexachlorocyclopentadiene is likely to provide a meani ngful opportunity for health risk reductions. Taking into consideration the low occurrence of this contamin ant, EPA has decided that any revision to the NPDWR would be a low priority activity for the Ag ency, and, thus, is not a ppropriate to revise at this time because of: May 2009 Draft EPA document. Do not cite or distribute. 144• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 45. Lindane (gamma-Hexachlorocyclohexane)

a. Background . EPA published the current NPDWR for lindane on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an MCLG and an MCL of 0.0002 mg/L. EPA based the MCLG on a reference dose of 0.0003 mg /kg-day and a cancer cl assification of C, possible human carcinogen. b. Technical Reviews. In the first Six-Year Review cy cle, EPA evaluated new information from a health effects assessment completed in 2002 (USEPA, 2006b). At that time, the Agency could not determine that a revision to the NP DWR would provide a meaningful opportunity for cost savings to public water system s or their customers, and decide d that any revision would be a low priority activity for the Agency because of co mpeting workload priorities, the administrative costs associated with rulemaking, and the burde n on States and the regulated community to implement any regulatory change (68 FR 42908, July 18, 2003 (USEPA, 2003e)). The 2002 assessment considered relevant studies on the to xicity of lindane including developmental and reproductive toxicity. The assessment revise d the RfD from 0.0003 mg/kg-day to 0.0047 mg/kgday and classified it as “Suggestive evidence of carcinogenicity, but not sufficient to assess human carcinogenic potential” (USEPA, 2006b). Duri ng the current review cycle, all uses of lindane were cancelled voluntarily (71 FR 74905, December 13, 2006 (USEPA, 2006e)), effective July 1, 2007. However, lindane is a persistent and bioaccumulative pesticide. Accordingly, EPA conducted a lit erature search for relevant da ta on the toxicology of lindane, including its potential developmental and reprodu ctive toxicity. The lit erature search did not

May 2009 Draft EPA document. Do not cite or distribute. 145identify any additional new data that would affect the RfD or cancer classification (USEPA, 2009b).The possible revised MCLG is base d on the 2002 OPP assessment and RfD of 0.0047 mg/kg-day, a body weight of 70 kg, water intake of 2 L/day, and an RSC of 20%. Uncertainty factors related to reproductive and developmenta l effects, and/or a possible risk management factor based on the suggested ev idence of carcinogenicity, coul d be used in developing a possible revised MCLG. Depending on the choice of uncertainty factors, the MCLG could range between 0.001 mg/L and 0.03 mg/L. Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor if EPA were to raise the MCLG. EPA evaluated the results of the occurrence and exposure analyses for lindane to determine whet her a revised MCLG/MCL would be likely to result in a meaningful opportunity to achieve cost savings for PWSs and their customers while maintaining, or improving, the level of public health protection (USE PA, 2009f). Although the Agency obtained and evaluated the finished water occurrence data for lindane, its usefulness is limited for determining potential cost savings to PWSs and their customers because the Agency does not know which systems are treating for this contaminant. As an alternative, the Agency evaluated available data on s ource water quality and conducted a qualitative assessment of treatment cost savings. Table VI-21 provides summary data for contam inant occurrence based on maximum sample values for the locations included in the STOR ET and NAWQA. Although the degree to which these occurrence rates re present national drinking water source occurrence is uncertain, the information shows no to low occurrence at thre shold levels of intere st. In the upper bound analysis, an NPDWR change woul d affect systems that rely on source water at less than 0.01% of the NAWQA locations and less than 0.3% of the STORET locations. Any MCLG/MCL

May 2009 Draft EPA document. Do not cite or distribute. 146revision to a potentially highe r level of 0.001 mg/L (the lowe r bound) or 0.03 mg/L (the upper bound) would likely affect fewer systems.

Table VI-21. Ambient Water Quality M onitoring Occurrence Summary for Lindane Number of Locations (% of locations) Maximum Concentration STORET 1 NAWQA 2 Total 2,691 (100.0%) 8,195 (100.0%) Nondetect 2,017 (75%) 8,058 (98.3%) Detected 674 (25%) 137 (1.7%) Exceeds current MCLG of 0.0002 mg/L 7 (0.26%) 1 (0.01%) Exceeds upper bound alternative value of 0.03 mg/L 1 (0.04%) 0 (0.0%) 1. STORET database 2002-2007. 2. NAWQA database 1992-2005. Source: USEPA, 2004c
The BATs and small system compliance techno logies for lindane have other beneficial effects, e.g., reduction of other co-occurring contaminants, precursors for DBPs, or other common impurities. Therefore, if EPA were to consider a higher level, the Agency does not know how many PWSs that are cu rrently treating to comply with the existing MCL of 0.0002 mg/L would be likely to discontinue treatment th at is already in plac e (USEPA, 2009d). Also, the Agency does not know to what extent affectedsystems might be able to reduce costs given that capital costs are not rec overable. However, the Agencyrecognizes that there may be opportunities to achieve operational co st savings if these systems ar e able to re-optimize current

treatment. Given these challenges, the Agency believes th at any resulting revi sion is not likely to provide a meaningful opportunity for cost savings. In view of this, any revision would be a low priority activity and not appropriate at this time.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for lindane, EPA does not believe a revision to the NPDWR for lindane

May 2009 Draft EPA document. Do not cite or distribute. 147is appropriate at this time. In making this de cision, the Agency considered whether any possible revision to the NPDWR for lindane is likely to provide a meaningf ul opportunity for cost savings to public water systems and their customers. Taking into consideration the low occurrence of this contaminant in source waters, EPA has deci ded that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 46. Mercury (Inorganic)

a. Background . EPA published the current NPDWR for inorganic mercury on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR es tablished an MCLG and an MCL of 0.002 mg/L. The Agency based the MCLG on a DWEL of 0.01 mg/L 17 and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the toxicology of inorganic mercury, in cluding its potential developmental and reproductive toxi city. The literature search di d not identify any studies that warrant a review of the RfD or th e cancer classification (USEPA, 2009b). A review of analytical or treatment feasibility is not necessary for inorganic mercury because changes to the MCLG are not warranted at this time and the current MCL is set at the MCLG. Since EPA did not identify a health or techno logy basis for revising the inorganic mercury NPDWR, the Agency did not conduct a deta iled occurrence and exposure analysis.

17 The DWEL was recommended by a panel of experts on mercury, and was derived using the weight of evidence from the entire inorganic mercury database. Th e DWEL was later back-calculated to an RfD of 0.0003 mg/kg-day (USEPA, 1995). May 2009 Draft EPA document. Do not cite or distribute. 148c. Review Result. EPA’s review shows that there ar e no data supporting a change to the inorganic mercury NPDWR. As a result, a revision to the NPDW R would not be appropriate at this time. 47. Methoxychlor

a. Background . EPA published the current NPDWR for methoxychlor on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establ ished an MCLG and an MCL of 0.04 mg/L. EPA based the MCLG on a reference dose of 0.005 mg/kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the toxicology of methoxychlor, including its potential developmental and reproductive toxicity. The liter ature search did not identify any studies that warrant a review of the RfD or the cancer classi fication (USEPA, 2009b). The Six-Y ear Review 1 stated that the Agency had initiated a reassessment of the hea lth risks posed by exposure to methoxychlor (67 FR 19030 (USEPA, 2002c)). Since 2002, the Agen cy has cancelled all product uses and concluded that the database to complete the health effects assessment for methoxychlor was inadequate (USEPA, 2004c). In its Reregistra tion Eligibility Decision, OPP noted substantive data gaps for methoxychlor, including lack of Guideline studies for chronic systemic toxicity as well as reproductive and developm ental toxicity (USEPA, 2004c). A review of analytical or treatment feasibil ity is not necessary for methoxychlor because changes to the MCLG are not warranted at this time and the current MCL is set at the MCLG. Since EPA did not identify a health or techno logy basis for revising the methoxychlor NPDWR, the Agency did not conduct a detailed occurrence and exposure analysis.

May 2009 Draft EPA document. Do not cite or distribute. 149c. Review Result. EPA’s review shows that there ar e no data supporting a change to the methoxychlor NPDWR. As a resu lt, a revision to the NPDWR woul d not be appropriate at this time. 48. Monochlorobenzene (Chlorobenzene)

a. Background . EPA published the current NPDWR for monochlorobenzene on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR es tablished an MCLG and an MCL of 0.1 mg/L. EPA based the MCLG on a reference dos e of 0.02 mg/kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the toxicology of monochlorobenzene, including its potential developmental and reproductive toxi city. The literature search di d not identify any studies that warrant a review of the RfD or th e cancer classification (USEPA, 2009b). A review of analytical or treatment feasib ility is not necessary for monochlorobenzene because changes to the MCLG are not warranted at this time and the current MCL is set at the MCLG. Since EPA did not identify a heal th or technology basis for revising the monochlorobenzene NPDWR, the Agency did no t conduct a detailed occurrence and exposure analysis.

c. Review Result. EPA’s review shows that there ar e no data supporting a change to the monochlorobenzene NPDWR. As a result, a revi sion to the NPDWR woul d not be appropriate at this time. 49. Nitrate (as N)

a. Background . EPA published the current NPDWR for nitrate on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an MCLG and an MCL of 10 mg/L (as N). EPA based the MCLG on a survey of epidemio logic studies of infant methemoglobinemia in

May 2009 Draft EPA document. Do not cite or distribute. 150populations exposed to nitrate contaminated wa ter. No cancer classification is currently available for nitrate (USEPA, 2009b). b. Technical Reviews. The health effects technical re view identified new information on developmental effects of nitrate, as well as data regarding its carcinogen icity, that may indicate the need to update the Agency’s health eff ects assessment (USEPA, 2009 b). Several studies suggest that nitrate in drinki ng water can have adverse effect s on the thyroid (Mukhopadhyay et al., 2005; Tajtakova et al., 2006; Zaki et al., 2004). Nitrate has long been known as a competitive inhibitor of iodide uptake in the thyroid (Wolff and Maury, 1963). Inhibition of iodide uptake can lead to a lteration in thyroid hormone le vels including decreases in levothyroxine (T4) levels. NAS ( 1995) stated that it is likely that the motor changes reported by Markel et al. (1989) when the an imals were young were not a direct effect of nitrate, but were secondary to effects on learning behavior. Based on these considerations, a new assessment of the noncancer effects of nitrate may be warranted, including consid eration of whether methemoglobinemia in infants, which is an acute effect, is still the most appropriate basis for the chronic exposure limit for nitrate. In additi on, recent information may suggest the consideration of separate acute and chr onic values for nitrate. The health effects review iden tified a number of relevant ne w studies that may warrant a review of the cancer classification for nitrat e. These studies include a number of new epidemiology studies (Cocco et al., 2003; Coss et al., 2004; de Roos et al., 2003; Mueller et al., 2004; Volkmer et al., 2005; Ward et al., 2003; Ward et al., 2005a; Ward et al., 2005b; Ward et al., 2006; Yang et al., 2007; Zeegers et al., 2006), as well as a recent report from an International Agency for Research on Cancer (IARC) Working group (Grosse et al., 2006). This latter report concluded that, under conditions that result in e ndogenous nitrosation, ingested nitrate or nitrite is probably carcinogenic to humans.

May 2009 Draft EPA document. Do not cite or distribute. 151In light of this information, EPA considers nitrate as a potential candidate for a new health effects assessment. The Agency solicits feedback on its plans to reassess health risks resulting from exposure to nitrate. The Agency also welcom es any scientific information related to nitrate health risks from the public. Because EPA consid ers nitrate as a candidate for a new assessment, EPA does not believe it is approp riate to consider any possible revisions to the MCLG (as well as the MCL) at this time. A review of analytical or treatment feasibility is not necessary for nitrate because changes to the MCLG are not warranted at th is time and the current MCL is set at the MCLG. Since EPA did not identify a health or t echnology basis for revising the n itrate NPDWR, the Agency did not conduct a detailed occurrence and exposure analysis.

c. Review Result. The Agency is considering whether to initiate a new health assessment for nitrate and therefore does not be lieve a revision to the NPDWR is appropriate at this time. As discussed in Section VII, the Agency is asking for input and information about several implementation issues related to nitrate (see section V.B.6). 50. Nitrite (as N)

a. Background . EPA published the current NPDWR for nitrite on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an MCLG and an MCL of 1 mg/L (as N).EPA based the MCLG on extrapolation from nitrate, assuming the conversion of 10% of nitratenitrogen to nitrite-nitr ogen. No cancer classification is curr ently available fo r nitrite (USEPA, 2009b). b. Technical Reviews. The health effects technical re view identified new information on developmental effects of nitrite, as well as data regarding its carcinogenic ity, that may indicate the need to update the Agency’s health eff ects assessment (USEPA, 2009 b). Several studies suggest that nitrate in drinki ng water can have adverse effect s on the thyroid (Mukhopadhyay et

May 2009 Draft EPA document. Do not cite or distribute. 152al., 2005; Tajtakova et al., 2006; Zaki et al., 2004). Since nitrite is formed from nitrate, and the current nitrite RfD is based on nitrate data, the impact of these new data on a nitrite noncancer assessment should be evaluated. Nitrite has long b een known as a competitive inhibitor of iodide uptake in the thyroid; although it is a weaker inhibitor than nitrate (Wolff and Maury, 1963). Inhibition of iodide uptake can le ad to alteration in thyroid hormone levels including decreases in T4. A developmental toxicity study in rats (Vorhees et al ., 1984) observed statistically significant delays in swimming development inaddition to pup mortality and body weight changes. Based on these considerations, a new assessment of the noncancer effects of nitrite may be warranted, including cons ideration of whether methemoglobi nemia in infants, which is an acute effect, is still the mostappropriate basis for the chronic exposure limit for nitrite. In addition, recent information may suggest the consid eration of separate ac ute and chronic values for nitrite. The health effects review iden tified a number of relevant ne w studies that may warrant a review of the cancer classification for nitrat e. These studies include a number of new epidemiology studies (Cocco et al., 2003; Coss et al., 2004; de Roos et al., 2003; Mueller et al., 2004; Volkmer et al., 2005; Ward et al., 2003; Ward et al., 2005a; Ward et al., 2005b; Ward et al., 2006; Yang et al., 2007; Zeegers et al., 2006). In addition, a recent report from an International Agency for Research on Cancer (IARC) Working group (Grosse et al., 2006) concluded that, under conditions that result in e ndogenous nitrosation, ingested nitrate or nitrite is probably carcinogenic to humans. In light of this information, EPA considers nitr ite as a potential candidate for a new health effects assessment. The Agency solicits feedback on its plans to reassess health risks resulting from exposure to nitrite. The Agency also welcom es any scientific information related to nitrite health risks from the public. Because EPA consid ers nitrite as a candidate for a new assessment,

May 2009 Draft EPA document. Do not cite or distribute. 153EPA does not believe it is approp riate to consider any possible revisions to the MCLG (as well as the MCL) at this time. A review of analytical or treatment feasibility is not necessary for nitrite because changes to the MCLG are not warranted at th is time and the current MCL is set at the MCLG. Since EPA did not identify a health or t echnology basis for revising the n itrite NPDWR, the Agency did not conduct a detailed occurrence and exposure analysis.

c. Review Result. The Agency is considering whether to initiate a new health assessment for nitrite and therefore does not be lieve a revision to the NPDWR is appropriate at this time. As discussed in Section VII, the Agency is requesting input and informationon about several implementation issues related to nitrite (see section V.B.6). 51. Oxamyl (Vydate)

a. Background . EPA published the current NPDW R for oxamyl on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.2 mg/L. EPA based the MCLG on a reference dose of 0.025 mg /kg-day and a cancer classification of E, evidence of non-carcinoge nicity for humans. b. Technical Reviews. In 2000, the Agency updated its heal th effects assessment of oxamyl (USEPA, 2000a). The Agency identified a change in this assessment that could lead to a change in the MCLG. This assessment considered releva nt studies on the toxici ty of oxamyl including developmental and reproductive toxicity. Th e assessment revised the RfD from 0.025 mg/kgday to 0.001 mg/kg-day and conclu ded that there is evidence thatoxamyl is noncarcinogenic to humans (USEPA, 2000a). Based on the new O PP assessment and RfD of 0.001 mg/kg-day, and assuming a 10-kg child body weight and 1 liter wa ter intake per day, the DWEL could be 0.01 mg/L. An RSC of 20% was selected based on the actual food dietary exposure (81%) for

May 2009 Draft EPA document. Do not cite or distribute. 154children who are 1 to 6 years old (USEPA, 2000a); this RSC re sults in a possible MCLG of 0.002 mg/L (USEPA, 2009b). Because of a possible change in the MCLG fo r oxamyl, EPA considered whether analytical feasibility is likely to be a lim itation if the Agency were to consider lowering the MCL to 0.002 mg/L (the possible MCLG). EPA reviewed WS da ta from the first Six-Year Review cycle and then analyzed more recent PT data to determin e if it might be possible to recalculate the PQL, which is 0.02 mg/L and might be a limit to a possible MCLG of 0.002 mg/L (i.e., analytical feasibility). Passing rates for WS data available thr ough late 1999 for oxamyl are below 75 percent for most studies with true concentrations below the current PQL of 0.02 mg/L. More recent PT data from late 1999 through 2004, supplied by a PT provider, show no results below the current PQL but had most passing rates above 75 percent with true values at or above the current PQL. Given the variable results from th e WS and PT studies, and the lack of PT data below the current PQL, WS and PT data are insufficient to support a PQL reduction (USEPA, 2009c). While the PT data are not sufficient to support a lowering of the PQL for oxamyl at this time, the present PQL of 0.02 mg/L is greater than the possible MCLG . It would therefore limit a possible revision to the MCL. EPA evaluated two alternative sources of information to determine whether they indicate any potential to revise the PQL: labor atory minimum reporting levels in the Six-Year Revi ew ICR dataset, and the MDLs for approved methods for the detection of oxamyl (Methods 531.1 and 531.2). While EPA prefers to use laboratory performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The SixYear Review ICR dataset contains MRL valu es for 52,201 samples. Of these, 45,290 (87%) have an MRL value of 0.002 mg/L or lower. Method 531.1 has an MDL of 0.00086 mg/L, and

May 2009 Draft EPA document. Do not cite or distribute. 155Method 532.2 has a detection limit (DL) of 0.00 0065 mg/L. Applying a multiplier of 10 would give a possible PQL range from 0.00065 to 0.0086 mg/L

. Because most MRL values are at or below the possible MCLG of 0.002 mg/L, EPA selected that value as the minimum threshold for the occurrence and exposure analysis. Based on these varied and unrelated approaches/s ources of information, there is evidence of a potential to lower the PQL for oxamyl even though the WS and PT data are insufficient to support a PQL reduction. To determine whether any MCL revision is likely to provide a meaningful opportunity to improve public healthprotection, EPA evaluated the occurrence of oxamyl at the possible MCLG of 0.002 mg/L (U SEPA, 2009f). Table VI-22 shows the results of the occurrence and exposure analysis for the current MCL and the possible MCLG. The analysis uses single sample or peak results inst ead of system average re sults because the health endpoint is associated with acute exposure. The occurrence and exposur e analysis shows that individual sample concentrations exceed the current MCL of 0.2 mg/L for one of 30,876 systems (0.003%) serving 200 people (or 0.000% of 167 million people). Note that these results do not necessarily reflect MCL violati ons, which are based on running annua l average concentrations at entry points; SDWIS/FED indi cates no MCL violations for oxamyl between 1998 and 2005 (USEPA, 2007g). Individual sample concentrat ions at 18 of 30,876 systems (0.058%), serving fewer than 0.3 million people (0.177%), exceeded the possible MCLG of 0.002 mg/L at least one time between 1998 and 2005.

May 2009 Draft EPA document. Do not cite or distribute. 156Table VI-22. Number and Percent of Systems with Mean Concentrations Exceeding Oxamyl Thresholds and Corresponding Esti mates of Population Served

Regulatory or Health-based Threshold Systems with Any Sample that is Greater than the Regulatory or Health-based Threshold (Percentages based on 30,876 systems with oxamyl data in the Six-Year Review ICR occurrence dataset) MCL (0.2 mg/L) 1 (0.003%) Possible MCLG (0.002 mg/L) 18 (0.058%)

Regulatory or Health-based Threshold Corresponding Population Served (Percentages based on 167,378,400 people served by the

systems with oxamyl data in the Six-Year Review ICR occurrence dataset) MCL (0.2 mg/L) 200 (0.0001%) Possible MCLG (0.002 mg/L) 297,000 (0.177%) Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for oxamyl, EPA does not believe a revision to the NPDWR for oxamyl is appropriate at this time. In making this de cision, the Agency considered whether any possible revision to the NPDWR for oxamyl is likely to pr ovide a meaningful opportunity for health risk reductions. Taking into consideration the low oc currence of this contaminant, EPA has decided that any revision to the NPDWR would be a low priority activ ity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

May 2009 Draft EPA document. Do not cite or distribute. 157• The burden on States and the regu lated community to implement any regulatory change that resulted. 52. Pentachlorophenol

a. Background . EPA published the current NPDWR for pentachlorophenol on July 1, 1991 (56 FR 30266 (USEPA, 1991b)). The NPDWR establ ished an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.001 mg/L, based on anal ytical feasibility. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to pentachlorophenol. The revised heal th effects assessment will consider relevant studies on the toxicity of pentachlorophenol, including its potential developmental and reproductive toxicity. The new health effect s assessment was not completed by March 1, 2009, the review cutoff date for this notice (USE PA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/ir istrac/index.cfm) has the most up-to-date information on the status of the health effects assessment. Although a risk assessment is in process for pe ntachlorophenol, the existing MCLG is zero and the current MCL of 0.001 mg/L is based on the PQL. For the Six-Year Review, the Agency evaluated several sources of information to dete rmine whether changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determ ine if the PQL can be re vised (i.e., analytical feasibility). Several passing ra tes in the WS data for pentach lorophenol available through late 1999 are below 75 percent, and none of the true concentrations were below the current PQL. There are six WS studies with pa ssing rates equal to or less than the 75 percent criterion, and only one of 16 true values in the WS data is belo w the current PQL. More recent PT data from late 1999 through 2004, supplied by a PT provider, show passing rates below the 75 percent

May 2009 Draft EPA document. Do not cite or distribute. 158criterion for eight studies, and all of the true concentra tions in the PT data were higher than the current PQL. Because of the variability in passi ng rates and the lack of data points below the current PQL, a lowering of the PQL for pentac hlorophenol is not appropr iate at this time (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of pe ntachlorophenol (Methods 515.1, 515.2, and 525.2). While EPA prefers to use labor atory performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the cu rrent PQL. The Six-Year Review ICR dataset contains MRL values for 59,594 samples. Of these, 26,666 (45%) equal the modal MRL of 0.00004 mg/L. An additional 2,399 (4%) are lower than 0.00004 mg/L. Above the modal MRL, 13,419 (23%) are between 0.00004 and 0.0001 mg/L, and 17,095 (29%) are between 0.0002 mg/L and the MCL of 0.001 mg/L. The MDLs of approved methods are 0.000032, 0.00016, and 0.001 mg/L. Because the MDL values fall across a wide range, EPA selected the intermediate value, applied a multiplier of 10, and rounded up. The resulting 10×MDL value is 0.002 mg/L. Since the MRL values are widely dispersed, and the intermediate 10×MDL value is higher than the current PQL, these data do not support a PQL reduction. Based on these varied and unrelated approaches/sources of information, EPA believes th at there is no potential to lower the PQL for pentachlorophenol. Since the MC L is constrained by the PQL, and the PQL is unchanged, EPA does not believe it is necessary to conduct an occurrence analysis at this time.

c. Review Result. The Agency does not believe a revision to the NPDWR for pentachlorophenol is appropr iate at this time because a reassessment of the health risks resulting from exposure to pentachloropheno l is in progress (USEPA, 2009b). Furthermore, a review of

May 2009 Draft EPA document. Do not cite or distribute. 159analytical feasibility did not identify a potenti al to revise the MCL, which is limited by feasibility.

53. Picloram

a. Background . EPA published the current NPDWR for picloram on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.5 mg/L. EPA based the MCLG on a reference dose of 0.07 mg/ kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. In the first Six-Year Review cy cle, EPA evaluated new information from a health effects assessment completed in 1995 (USEPA, 1995b). At that time, the Agency could not determine that a revision to the NP DWR would provide a meaningful opportunity for cost savings to public water system s or their customers, and decide d that any revision would be a low priority activity for the Agency because of co mpeting workload priorities, the administrative costs associated with rulemaking, and the burde n on States and the regulated community to implement any regulatory change (67 FR 19030 (USEPA, 2002c); 68 FR 42908 (USEPA, 2003e)). The 1995 assessment considered relevant st udies on the toxicity of picloram including developmental and reproductive toxicity. The assessment revised the RfD from 0.07 mg/kg-day to 0.2 mg/kg-day and classified picloram as Gr oup E, evidence of noncarcinogenicity (USEPA, 1995b). In the current review cycle, EPA conduc ted a literature sear ch through June 2007 for relevant data on the toxicology of piclor am, including its potentia l developmental and reproductive toxicity. The literature search did not identify any new data that would affect the RfD or cancer classification (USEPA, 2009b). Based on the 1995 OPP assessment and RfD of 0.2 mg/kg-day, and assuming a 70-kg adult body wei ght and 2 liters water intake per day, the DWEL could be 7 mg/L. An RSC of 20% resu lts in a possible MCLG of 1 mg/L (USEPA, 2009b).

May 2009 Draft EPA document. Do not cite or distribute. 160Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor if EPA were to raise the MCLG. EPA evaluated the results of the occurrence and exposure analyses for picloram to determine wh ether a revised MCLG/MCL would be likely to result in a meaningful opportunity to achieve cost savings for PWSs and their customers while maintaining, or improving, the level of public health protection (USE PA, 2009f). Although the Agency obtained and evaluated the finished water occurrence data for picloram, its usefulness is limited for determining potential cost savings to PWSs and their customers because the Agency does not know which systems are treating for this contaminant. As an alternative, the Agency evaluated available data on s ource water quality and conducted a qualitative assessment of treatment cost savings. Table VI-23 provides summary data for contam inant occurrence based on maximum sample values for the locations included in the ST ORET and NAWQA data. Although the degree to which these occurrence rates represent national drinking water source occurrence is uncertain, the information shows no to low occurrence at thre shold levels of interest. This information indicates that any resulting NP DWR change would not affect sy stems that rely on source water at any of the NAWQA or STORET locations.

Table VI-23. Ambient Water Quality M onitoring Occurrence Summary for Picloram Number of Locations (% of locations) Maximum Concentration STORET 1 NAWQA 2 Total 870 (100%) 5,772 (100.0%) Nondetect 745 (85.6%) 5,733 (99.3%) Detected 125 (14.4%) 39 (0.7%) Exceeds current MCLG of 0.5 mg/L 0 (0%) 0 (0.0%) Exceeds alternative value of 1.0 mg/L 0 (0%) 0 (0.0%) 1. STORET database 2002-2007. 2. NAWQA database 1992-2005. Source: USEPA, 2004c

May 2009 Draft EPA document. Do not cite or distribute. 161The BATs and small system compliance technolo gies for picloram have other beneficial effects, e.g., reduction of other co-occurring contaminants, precursors for DBPs, or other common impurities. Therefore, if EPA were to consider a higher level, the Agency does not know how many PWSs that are currently trea ting to comply with the existing MCL of 0.5 mg/L would be likely to discontinue treatment that is already in place (USEPA, 2009d). Also, the Agency does not know to what extent affected sy stems might be able to reduce costs given that capital costs are not recoverable. However, the Agency recognizes that there may be opportunities to achieve operational co st savings if these systems ar e able to re-optimize current

treatment. Given these challenges, the Agency believes th at any resulting revi sion is not likely to provide a meaningful opportunity for cost savings. In view of this, any revision would be a low priority activity and not appropriate at this time.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for picloram, EPA doe s not believe a revision to the NPDWR for picloram is appropriate at this time. In making this decision, th e Agency considered whether any possible revision to the NPDWR fo r picloram is likely to provide a meaningful opportunity for cost savings to public water systems and their customers. Taking into consideration the low occurrence of this contaminant in source wate rs, EPA has decided that any revision to the NPDWR would be a low priority activity for the Ag ency, and, thus, is not a ppropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted.

May 2009 Draft EPA document. Do not cite or distribute. 16254. Polychlorinated Biphenyls (PCBs)

a. Background . EPA published the current NPDW R for PCBs on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establishe d an MCLG of zer o based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.0005 mg/L, based on analytical feasibility. b. Technical Reviews. EPA has initiated a reassessment of the cancer health risks resulting from exposure to PCBs. The revised health eff ects assessment will consider relevant studies on the toxicity of PCBs, including its potential de velopmental and reproducti ve toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). On December 21, 2007 (72 FR 72715 (USEPA, 2007c)), the Agency noted that the health effects assessment for PCBs is in process. Although a risk assessment is in process for PCBs , the existing MCLG is zero and the current MCL of 0.0005 mg/L is based on the PQL. For the Six-Year Review, the Agency evaluated several sources of information to determine whethe r changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determine if the PQ L can be revised (i.e., an alytical feasibility). The WS data for PCBs available through late 199 9 includes only one true concentration below the current PQL, and the passing rate for that concentration is below 75 percent. The passing rates for studies above the PQL are above 75 percent. More recent PT data from late 1999 through 2004, supplied by a PT provider, show passi ng rates above 75 percent for all studies, but includes no studies below the current PQL. Because of the lack of data points below the current PQL, a lowering of the PQL for PCBs is notappropriate at this time (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR

May 2009 Draft EPA document. Do not cite or distribute. 163dataset, and the MDL for the approved method fo r the detection of PCBs (Method 508A). While EPA prefers to use laboratory performance da ta to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is pos sible to quantitate at levels below the current PQL. The Six-Year Review ICR dataset contains MRL values for 35,178 samples. Of these, 23,785 (68%) equal th e modal MRL of 0.0001 mg/L. An additional 2,355 (7%) are lower than 0.0001 mg/L, and 7,489 (21%) are between 0.0001 mg/L and the MCL of 0.0005 mg/L. The MDL of approved me thod is 0.00008 mg/L. Applying a multiplier of 10 would give a possible PQ L of 0.0008 mg/L. Since more than 20% of samples do not achieve the modal MRL, and the 10×MDL value is higher than the current PQL, these data do not support a PQL reduction. Based on these varied and unrelated approaches/sources of information, EPA believes that there is no potenti al to lower the PQL for PCBs. Since the MCL is constrained by the PQL, and the PQL is unchanged, EPA does not believe it is necessary to conduct an occurrence anal ysis at this time.

c. Review Result. The Agency does not believe a re vision to the NPDWR for PCBs is appropriate at this time because a reassessment of the health risks resulting from exposure to PCBs is in progress (USEPA, 2009b). Furthermore, a review of analyti cal feasibility did not identify a potential to revise the MCL, which is limited by feasibility. 55. Combined Radiums (226 and 228)

a. Background . EPA published an interim NPDWR and set an MCL of 5 pCi/L for combined radium 226 and 228 on July 9, 1976 (41 FR 28402 (U SEPA, 1976)). As noted in the August 14, 1975 proposal (40 FR 34324 (USEPA, 1975)) and a subsequent September 30, 1986 FR notice, EPA considered the feasibility of treatment techniques, analytical methods and monitoring when establishing the MCL of 5 pCi/L. EPA also cons idered the risks associated with exposure to radium 226 and 228, which generally fell within the Agency’s acceptabl e risk range of 10 -4 to 10 -

May 2009 Draft EPA document. Do not cite or distribute. 1646 at the MCL of 5 pCi/L. On Decemb er 7, 2000 (65 FR 76708 (USEPA, 2000c)), EPA established an MCLG of zero ba sed on a cancer classification of A (known human carcinogen) and finalized the NPDWR by retaining the MCL of 5 pCi/L. EPA noted in the December 7, 2000 FR notice that new risk estimates from Fe deral Guidance Report 13 reaffirmed that the 5 pCi/L MCL was appropr iate and protective 18 . EPA also tightened the monitoring requirements for combined radiums by requiring that system s monitor for radium 226 and 228 separately. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to radiums. The revised health effect s assessment will consider relevant studies on the toxicity of radiums, including its potential deve lopmental and reproductive toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). However, EPA does not exp ect the health effects assessment to change the cancer classification for radiums, and the MCLG would remain at zero. As a part of the Six-Year Review, the Agen cy considered whether new information was available regarding analytical and treatment feas ibility for radiums. EPA promulgated detection limits of 1 pCi/L for both radium 226 and radium 228 in 1976 (41 FR 28402 (USEPA, 1976)) and retained the use of a detection limit as the required measure of sensit ivity for radiochemical analysis in lieu of an MDL or PQL in the final rule (65 FR 76708, December 7, 2000 (USEPA, 2000c)). EPA did not identify new analytical me thods during the current review that would feasibly lower the detection limits. In additi on, since the December 7, 2000, regulation, there is no new information regarding treatment feasibility. Since there is no new information regarding analytical or treatment feasibility that suggest s changes to the MCL, EP A does not believe it is necessary to conduct an occurren ce analysis at this time.

18 After the December 7, 2000 final regulation, two tr ade associations and severa l municipal water systems challenged EPA’s standard fo r combined radiums by claiming that the Agen cy did not use the best available science when finalizing the standard. In February of 2003, the DC Circuit Court of Appeals upheld EPA’s regulation for combined radiums (as well as beta and photon emitters and uranium). May 2009 Draft EPA document. Do not cite or distribute. 165c. Review Result. The Agency does not believe a re vision to the NPDWR for combined radiums is appropriate at this time because a reassessment of the health risks resulting from exposure to radium is in progr ess (USEPA, 2009b). Furthermore, there is no new information regarding analytical or treatment feasibility th at would warrant recons ideration of the MCL.

56. Selenium

a. Background . EPA published the current NPDWR for selenium on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establis hed an MCLG and an MCL of 0.05 mg/L. EPA based the MCLG on a maximum safe intake 19 of 0.4 mg/person/day and a cancer classification of D, not classifi able as to human carcinogenicity. b. Technical Reviews. The health effects technical review identified new data that relate to the biological properties of selenium in mammalian species, as well as data regarding its cancer and anticancer properties, that may indicate the need to update the Agency’s health effects assessment (USEPA, 2009b). Hawkes and Keim (2003) reported thyroi d hormone and related metabolism changes in subjects treat ed with deficient, sufficient, and excess dietary selenium. The excess selenium dose was associated with a sli ght decrease in triiodothyronine (T3) levels, a thyrotropin increase, and an increase in body we ight compared to the selenium-sufficient subjects. The opposite responses occurred in the selenium-deficie nt subjects. Several studies identified changes in sperm parameters and fert ility in mice fed either selenium-deficient or excess-selenium diets compared to diets with ad equate selenium. In addition, new information about the metabolism of selenium since the IR IS review (USEPA, 1991a, 1993a) suggests that it may be appropriate to differentiate between inorganic selenium and organic selenium in the form

19 The 0.4 mg/day safe level was based on data (Yang et al., 1989a, 1989b) that extrapolated from blood selenium levels to estimated dietary intake in the studied population. As described in the January 30, 1991 FR (56 FR 3526 (USEPA, 1991c)), the Agency partially considered selenium’s status as a nutrient and did not use the typical procedure for deriving the MCLG. Hence, there is no specific reference to an RfD for selenium in the 1991 FR notice. After the publication of the regulation, IRIS (USEPA, 1991a) posted an RfD of 0.005 mg/kg-day for selenium using the same data that are the basis of the regulation. May 2009 Draft EPA document. Do not cite or distribute. 166of selenoproteins and selenoaminoacids for an assessment that applies to drinking water. Although selenium is not a candidate for an MCLG of zero because of its status as a micronutrient, new data releva nt to the cancer assessment are now available (e.g., DuffieldLillico et al., 2003; Su et al., 2005) and may need further evaluation. In light of this information, EPA considers sele nium as a potential candidate for a new health effects assessment. The Agency solicits genera l feedback on its plans to reassess health risks resulting from exposure to selenium. The Agency also welcomes any scientific information related to selenium health risks from the public. Because EPA considers selenium as a candidate for a new assessment, EPA does not believe it is appropriate to consider any revisions to the MCLG (as well as the MCL) at this time. A review of analytical or treatment feasibility is not necessary for selenium because changes to the MCLG are not warranted at this time and the current MCL is set at the MCLG. Since EPA did not identify a health or technology basis for revising the selenium NPDWR, the Agency did not conduct a detailed occurren ce and exposure analysis.

c. Review Result. The Agency is considering whether to initiate a new health assessment for selenium and therefore does not believe a revisi on to the NPDWR is appropriate at this time.

57. Simazine

a. Background . EPA published the current NPDWR for simazine on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG and an MCL of 0.004 mg/L. EPA based the MCLG on a reference dose of 0.005 mg /kg-day and a cancer classification of C, possible human carcinogen. b. Technical Reviews. In 2006, the Agency finalized a he alth effects assessment for the reregistration of simazine as a pesticide (USE PA, 2006i). Because the database for simazine’s potential neuroendocrine effects is less robust than the atrazine database, and because simazine

May 2009 Draft EPA document. Do not cite or distribute. 167and atrazine share a common neuroendocrine mechanis m of toxicity, the atra zine data were used as bridging data for simazine. Thus, the 2006 assessment established a new RfD of 0.018 mg/kg-day for simazine, based on the attenuation of pre-ovulat ory LH surge from atrazine exposure. Similarly, simazine was reclassified in 2006 as “not likely to be carcinogenic to humans” based on weight-of-evidence that it is no t genotoxic and because the tumor response in the Sprague-Dawley rats was determined to be a strain specific mechanism which is not relevant to humans.

c. Review Result. The Agency believes it is not appr opriate to consider revisions to the NPDWR for simazine at this time because there ar e some forthcoming studies of atrazine and its metabolites from the Agency’s ORD. The Agen cy does not anticipate that the ORD research will significantly change the atrazine health effects assessm ent conclusions supporting the FQPA reregistration decision published in 2006 (USEPA , 2006c). However, it is unclear whether the new data would impact the Agency’s determin ation on whether any revisions to the current MCLG/NPDWR for simazine are appropriate (USEPA, 2009b). Th e Agency expects to publish the ORD studies in 2009. 58. Styrene

a. Background . EPA published the current NPDWR for styrene on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an MCLG and an MCL of 0.1 mg/L. EPA based the MCLG on a reference dose of 0.2 mg/kg- day and a cancer classifi cation of C, possible human carcinogen. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to styrene. The revised health effect s assessment will consider relevant studies on the toxicity of styrene, includi ng its potential developmental an d reproductive toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date for this

May 2009 Draft EPA document. Do not cite or distribute. 168notice (USEPA, 2009b). The IRIS Substan ce Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment.

c. Review Result. Since the MCL for styrene is set at its MCLG and a re assessment of the health risks resulting from expos ure to styrene is in progress, the Agency does not believe a revision to the NPDWR is appropriate at this time. 59. 2,3,7,8-TCDD (Dioxin)

a. Background . EPA published the current NPDW R for dioxin on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR establishe d an MCLG of zer o based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of
3×10 -8 mg/L, based on analytical feasibility. b. Technical Reviews. In 2003, the Agency prepared a dr aft human health reassessment for dioxin and its related compounds (USEPA, 2003c) that underwent external review by the National Academy of Science. In their peer review report ( NAS, 2006), NAS recommended that EPA reevaluate its conclusions regarding the ca rcinogenicity of dioxin based on the criteria set out in the 2005 cancer guidelines ; that EPA should consider developing more information on the noncancer effects of dioxin; and th at EPA evaluate new dose-response data released by the NTP. The Agency is currently considering the NAS recommendations. The Agency does not expect any new health effects assessment to be completed in the time frame of the current Six-Year Review cycle (USEPA, 2009b). The IRIS Subs tance Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment. Although a health effects assessmen t is in process for dioxin, the existing MCLG is still zero and the current MCL is based on a PQL of 3×10 -8 mg/L. Therefore, as a part of the Six-Year

May 2009 Draft EPA document. Do not cite or distribute. 169Review, the Agency considered whether changes in analytical feasibility might lead to a lower MCL. The PT data currently available for dioxin are not sufficient to ev aluate the potential for PQL revision (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDL for the approved method fo r the detection of dioxin (Method 1613). While EPA prefers to use laboratory performance da ta to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is pos sible to quantitate at levels below the current PQL. The Six-Year Review ICR dataset contains MRL values for 1,278 samples. Of these, 964 (75%) equal the modal MRL of 5×10 -9 mg/L. An additional 191 (15%) are lower than 5×10 -9 mg/L. The MDL of the approved method is 1×10 -8 mg/L. Applying a multiplier of 5 would give a possible PQL of 5×10 -8 mg/L, which is only s lightly higher than the current PQL. There are too few samples in the MRL data to provide a definitive result, but the samples that are available do suggest that the PQL might be lowered. Taken together, these approaches are inconclusive. EPA therefore be lieves that a PQL reduction for dioxin is not appropriate at present. Since the MCL is c onstrained by the PQL, and the PQL is unchanged, EPA does not believe it is necessary to conduc t an occurrence analysis at this time.

c. Review Result. The Agency does not believe a re vision to the NPDWR for dioxin is appropriate at this time because a reassessment of the health risks resulting from exposure to dioxin is in progress (USEPA, 2009b) . Furthermore, a review of analytical feasibility did not identify a potential to revise the MCL, which is limited by feasibility. 60. Tetrachloroethylene

a. Background . EPA published the current NPDWR for tetrachloroethylene on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR es tablished an MCLG of zero based on a

May 2009 Draft EPA document. Do not cite or distribute. 170cancer classification of B2, pr obable human carcinogen. The NPDW R also established an MCL of 0.005 mg/L, based on an alytical feasibility. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to tetrachloroethylene. The revised h ealth effects assessment will consider relevant studies on the toxicity of te trachloroethylene, including its potential developmental and reproductive toxicity. The new health effect s assessment was not completed by March 1, 2009, the review cutoff date for this notice (USE PA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/ir istrac/index.cfm) has the most up-to-date information on the status of the health effects assessment. Although a risk assessment is in process for tetr achloroethylene, the ex isting MCLG is zero and the current MCL of 0.005 mg/L is based on the PQL. For the Six-Year Review, the Agency evaluated several sources of information to dete rmine whether changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determin e if the PQL could be revised (i.e., analytical feasibility). Passing ra tes for WS data available through late 1999 for tetrach loroethylene are above 95 percent at the lowest concentrations. Ho wever, the true concentrations were all higher than the current PQL of 0.005 mg /L. More recent PT data fr om late 1999 through 2004, supplied by a PT provider, also show greater than 90 pe rcent passing rates for studies around the current PQL, including 13 with true values below the PQL. Because most of the laboratory passing rates from WS and PT studies exceeded the 75 percent criterion typically used to derive a PQL, including several with true values below the PQ L, a lowering of the PQL for tetrachloroethylene might be possible. These results, however, ar e insufficient to recalculate a revised PQL for tetrachloroethylene because not enough data points are available below the current PQL to derive a value at the 75 percent passing rate (USEPA, 2009c).

May 2009 Draft EPA document. Do not cite or distribute. 171EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods for the detection of tetrach loroethylene (Methods 502.2, 524.2, and 551.1). While EPA prefers to use labor atory performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the curren t PQL. EPA also noted that the State of New Jersey uses a PQL of 0.001 mg/L, based on a 1987 study of laboratory performance at low concentrations that used criteriasimilar to those in the PT da ta (NJDWQI, 1987). The Six-Year Review ICR dataset contains MRL values fo r 138,348 samples. Of these, 117,033 (85%) equal the modal MRL of 0.0005 mg/L. An additiona l 15,848 (11%) are lower than 0.0005 mg/L. The MDLs of approved methods range are 0.00005, 0.00014, and 0.000008 mg/L. Applying a multiplier of 10 would give a possible PQL range from 0.00008 to 0.0014 mg/L. Because of the preponderance of MRL values of 0.0005 mg/L, EPA selected that value as the minimum threshold for the occurrence and exposure analysis (USEPA, 2009e). Based on these varied and unrelated approach es/sources of information, EPA believes that there is potential to lower the PQL for tetrach loroethylene. To determine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of tetrachloroethylene at thres holds of 0.0005, 0.001, and 0.0025 mg/L. Table VI-24 shows the results of the occurrence and e xposure analysis for the current MCL and EQLs set equal to 0.0025 mg/L, 0.001 mg/L, a nd 0.0005 mg/L. The occurrence and exposure analysis shows that average concentrations exceed the current MCL for 23 to 25 out of 50,436 systems (0.046% to 0.050%) serving approxima tely 630, 000 to 1.1 million people (or 0.277% to 0.473% of 227 million people). Note that thes e results do not necessarily reflect MCL violations, which are based on annual average concentrations at entry points; SDWIS/FED

May 2009 Draft EPA document. Do not cite or distribute. 172indicates 174 MCL violations for tetrachlo roethylene between 1998 and 2005, with annual violations ranging from 10 to 33 (USEPA, 2007g). Average concentrations at 412 to 519 of 50,436 systems (0.817% to 1.029%), serving 12.4 to 14.6 million people (or 5.466% to 6.419% of 227 million people), exceed th e lowest EQL of 0.0005 mg/L.

Table VI-24. Number and Percent of Syst ems with Mean Concentrations Exceeding Tetrachloroethylene Thresholds and Corr esponding Estimates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 50,436 systems with tetrachloroethylene data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 25 (0.050%) 23 (0.046%) 23 (0.046%) 1/2 MCL (0.0025 mg/L) 75 (0.149%) 71 (0.141%) 68 (0.135%) 2xEQL (0.001 mg/L) 286 (0.568%) 251 (0.498%) 220 (0.437%) EQL (0.0005 mg/L) not applicable 519 (1.030%) 412 (0.818%) Corresponding Population Served (Percentages based on 227,009,000 people served by the systems with tetrachloroethylene data in the Six- Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 1,074,000 (0.473%) 628,000 (0.277%) 628,000 (0.277%) 1/2 MCL (0.0025 mg/L) 1,706,000 (0.752%) 1,692,000 (0.745%) 1,647,000 (0.726%) 2xEQL (0.001 mg/L) 10,706,000 (4.716%) 10,177,000 (4.483%) 9,625,000 (4.240%) EQL (0.0005 mg/L) not applicable 14,572,000 (6.419%) 12,408,000 (5.466%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.0005 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that a revision to the MCL may provide a meaningful opportunity to improve the level of public health protection, EPA considered whether treatment feasibility is likely to pose any limitations if the MCL were lowered (USEPA, 2009g). The current BATs for tetrachloroethylene are packed tower aeration (PTA) and granular activated

May 2009 Draft EPA document. Do not cite or distribute. 173carbon (GAC). Small system compliance technol ogies (SSCTs) for tetrachloroethylene include GAC and several aeration technolog ies. EPA believes these BATs and SSCTs are still practical and would not pose any limitations if EPA were to revise the MCL. EPA is not currently able to assess the poten tial health benefits from a revised MCL for tetrachloroethylene, because the revised health eff ects assessment is not yet available. However, based on its B2 cancer classification (MCLG of zero) and the o ccurrence and exposure analysis at possible MCL values, the Agency believes that a revision to the MCL may provide a meaningful opportunity to re duce public health risks.

c. Review Result. The Agency believes it is appr opriate to revise to the NPDWR for tetrachloroethylene although a heal th effects assessment is current ly in progress. The existing MCLG is zero (based on the current B2 cancer cl assification) and the current MCL is based on a PQL (i.e., analytical feasibility) of 0.005 mg/L. The Agency’s revi ew indicates that analytical feasibility could be as much as 10 times lo wer (~ 0.0005 mg/L) and occu rrence at this level appears to be relatively widespread. Hence, revisions to the tetrachloroethylene NPDWR will provide a meaningful opportunity for health risk reduction. EPA expects that the final health effects assessment for tetrachloroethylene will further support the public health benefits associated with any revision. As discussed in Section VII, the Agency solicits public comment and/or relevant information that may inform the regulatory revision for tetrachloroethylene. EPA is also requesting that stakeholders provid e information/data aboutthe lowest level of quantitation (including the analytic al method used) that laboratories can reliably and consistently achieve.

61. Thallium

a. Background . EPA published the current NPDWR for thallium on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR established an MCLG of 0.0005 mg/L. EPA based the

May 2009 Draft EPA document. Do not cite or distribute. 174MCLG on a reference dose of 0.00007 mg/kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. The NPDWR also established an MCL of 0.002 mg/L, based on analytical feasibility. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to thallium. The revised health effect s assessment will consider relevant studies on the toxicity of thallium, including its potential deve lopmental and reproductive toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). The IRIS Substan ce Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment. Although a health effects assessment is in pro cess for thallium, the current MCL is based on a PQL of 0.002 mg/L. Therefore, as a part of the Six-Year Review, the Agency evaluated several sources of information to determine whether changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determine if the PQ L can be revised (i.e., an alytical feasibility). Passing rates for WS data available through late 1999 for thallium are above 80 percent around the current PQL of 0.002 mg/L, including one st udy with a true concen tration less than the current PQL. More recent PT data from la te 1999 through 2004, supplied by a PT provider, show passing rates at or above 75 percent, but tending to fall below 80% as the true concentration approaches the current PQL. No studies had true concentrations below the current PQL. Given the lack of data points below the current PQL and the low PT passing rates close to the PQL, a lowering of the PQL for thallium is not appropriate at th is time (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR

May 2009 Draft EPA document. Do not cite or distribute. 175dataset, and the MDLs for approved methods for the detection of thallium (Methods 200.8 and 200.9). While EPA prefers to use laboratory perfo rmance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Re view ICR dataset contains MRL values for 73,409 samples. Of these, 46,273 ( 63%) equal the modal MRL of 0.001 mg/L. An additional 11,032 (15%) are lower than 0.001 mg /L. Finally, 15,953 (22%) equal the MCL of 0.002 mg/L, and 151 samples exceed the MCL. Th e MDLs of approved methods range from 0.0003 to 0.0007 mg/L. Applying a multiplier of 10 would give a possible PQL range from 0.003 to 0.007 mg/L. Although the majority of MR L values are below the current PQL, the 10×MDL values are higher than the current PQ L, and do not support a PQL reduction. Based on these varied and unrelated approaches/sources of information, EPA believes that there is no potential to lower the PQL for thallium. Since the MCL is constrained by the PQL, and the PQL is unchanged, EPA does not believe it is necessary to conduct an occurrence analysis at this time.

c. Review Result. The Agency does not believe a revi sion to the NPDWR for thallium is appropriate at this time because a reassessment of the health risks resulting from exposure to thallium is in progress (USEPA, 2009b). Furthermor e, a review of analytic al feasibility did not identify a potential to revise the MCL, which is limited by feasibility.

62. Toluene

a. Background . EPA published the current NPDWR for toluene on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR established an MCLG and an MC L of 1 mg/L. EPA based the MCLG on a reference dose of 0.2 mg/k g-day and a cancer clas sification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. In 2005, the Agency updated its heal th effects assessment of toluene (USEPA, 2005b). The change in this assessment could lead to a change in the MCLG. This

May 2009 Draft EPA document. Do not cite or distribute. 176assessment considered relevant studies on the to xicity of toluene including developmental and reproductive toxicity. The assessment revised the RfD from 0.2 mg/kg-day to 0.08 mg/kg-day and concluded that there is inadequate informa tion to assess the carcinogenic potential of toluene (USEPA, 2005b). Although there were no changes in the critical study or effect, there were changes in the toxicity database that increase concern for immunotoxicity and neurotoxicity via the oral exposure route and justified the higher uncertainty factor for the revised RfD (USEPA, 2005b). Based on the new IRIS assessment a nd RfD of 0.08 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters water intake per day, the DWEL could be 2.8 mg/L. An RSC of 20% results in a possible MCLG of 0.6 mg/L. Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor for the possible MCLG decrease under considerati on. EPA evaluated the results of the occurrence and exposure analyses for tolu ene to determine whether a revised MCLG/MCL would be likely to result in a meaningful oppor tunity to improve the level of public health protection (USEPA, 2009f). Table VI-25 shows the results of the occurrence and exposure analysis for the current MCL and the possible MCLG set equal to 0.6 mg/L based on the new health effects information. The occurrence and exposure analysis shows that average concentrations exceed the current MCL fo r one system out of 50,451 (0.002%) serving approximately 500 people (0.0002% of 227 million pe ople). Note that these results do not necessarily reflect MCL violati ons, which are based on annual av erage concentrations at entry points; SDWIS/FED indicates MC L violations for toluene at only one system in one year between 1998 and 2005 (USEPA, 2007g). Averag e concentrations at two of 50,451 systems (0.004%), serving 800 people (or 0.0004% of 227 million people), exceed the possible MCLG based on new health effects information (0.06 mg/L).

May 2009 Draft EPA document. Do not cite or distribute. 177Table VI-25. Number and Percent of Systems with Mean Concentrations Exceeding Toluene Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrati ons that are Greater than the Regulatory or Health-based Threshold (Percentages based on 50,451 systems with toluene da ta in the SixYear Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (1 mg/L) 1 (0.002%) 1 (0.002%) 1 (0.002%) Possible MCLG (0.6 mg/L) 2 (0.004%) 2 (0.004%) 2 (0.004%) Corresponding Population Served (Percentages based on 226,955,000 people served by the systems with toluene data in the Six-Year Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (1 mg/L) 500 (0.0002%) 500 (0.0002%) 500 (0.0002%) Possible MCLG (0.6 mg/L) 800 (0.0004%) 800 (0.0004%) 800 (0.0004%) 1. Results are based on setting all nondetect results eq ual to MRL values in the Si x-Year Review ICR dataset 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for toluene, EPA does not believe a revision to the NPDWR for toluene is appropriate at this time. In making this de cision, the Agency considered whether any possible revision to the NPDWR for toluene is likely to pr ovide a meaningful opportunity for health risk reductions. Taking into consideration the low oc currence of this contaminant, EPA has decided that any revision to the NPDWR would be a low priority activ ity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

May 2009 Draft EPA document. Do not cite or distribute. 178• The burden on States and the regu lated community to implement any regulatory change that resulted. 63. Toxaphene

a. Background . EPA published the current NPDWR for toxaphene on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establis hed an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.003 mg/L, based on anal ytical feasibility. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the carcinogeni city of toxaphene as well as its potential developmental and reproductive toxicity. EPA has not identified any new information that indicates that it is appropriate to consider revi sions to the cancer classi fication for toxaphene at this time (USEPA, 2009b). Because the MCLG re mains at zero, the Agency believes that a further review of the health effects of toxaphene is not warra nted at this time. The current MCL for toxaphene is based on a PQL of 0.003 mg/L. For the Six-Year Review, the Agency considered whether changes in the anal ytical feasibility of toxaphene might lead to a lower MCL. EPA reviewed WS data from the fi rst Six-Year Review cycle and then analyzed more recent PT data to determine if the PQL can be revised (i.e., analytical feasibility). Passing rates for WS data available through late 1999 for toxaphene are generally above 90 percent around the current PQL of 0.003 mg/L, including three studies with tr ue values below the current PQL. All passing rates in the WS data exceeded 80 percent. More recent PT data from late 1999 through 2004, supplied by a PT provider, show greater than 80 percen t passing rates for a majority of studies, but there are no studies with true values below the current PQL. There are two PT studies with passing rate s equal to or below 75 percent, at true values well above the current PQL. Despite this variability, most of the laboratory passing rates from WS and PT

May 2009 Draft EPA document. Do not cite or distribute. 179studies exceeded the 75 percent cr iterion typically used to derive a PQL, including three with true values below the PQL. Therefore, a loweri ng of the PQL for toxaphene might be possible. These results, however, are insu fficient to recalculate a revise d PQL for toxaphene because not enough data points are available below the current PQL to deri ve a value at the 75 percent passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods for the detection of toxaphene (Methods 505, 508.1, and 525.2). While EPA prefers to use laborato ry performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Review I CR dataset contains MRL values for 54,529 samples. Of these, 36,763 ( 67%) equal the modal MRL of 0.001 mg/L. An additional 8,525 (16%) are lower than 0.001 mg/L . The MDLs of approved methods are 0.0017, 0.001, and 0.00013 mg/L. Applying a multiplier of 10 would give a possible PQL range from 0.0013 to 0.017 mg/L. Because of the preponde rance of MRL values of 0.001 mg/L, EPA selected that value as the minimum threshol d for the occurrence and exposure analysis. Based on these varied and unrelated approach es/sources of information, EPA believes that there may be potential to lower the PQL fo r toxaphene. To determine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of toxaphene at thresholds of 0.0015 and 0.001 mg/L (USEPA, 2009f). Table VI-26 shows the results of the occurrence and e xposure analysis for the current MCL and EQLs set equal to 0.0015 mg/L and 0.001 mg/L. The occurrence and exposure analysis shows that average concentrations exceed the curren t MCL for three to four of 30,387 systems (0.010% to 0.013%) serving 23,000 people (or 0.014% of 160 m illion people). Note that these results do

May 2009 Draft EPA document. Do not cite or distribute. 180not necessarily reflect MCL violations, which are based on annual average concentrations at entry points; SDWIS/FED indicates three MCL violations for toxaphene between 1998 and 2005 (USEPA, 2007g). Average concentrations atfive of 30,387 systems (0.016%), serving 23,000 people (or 0.015% of 160 million peopl e), exceed the EQL of 0.001 mg/L.

Table VI-26. Number and Percent of Systems with Mean Concentrations Exceeding Toxaphene Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold(Percentages based on 30,387 systems with toxaphene data in the SixYear Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.003 mg/L) 4 (0.013%) 3 (0.010%) 3 (0.010%) 1/2 MCL (0.0015 mg/L) 5 (0.016%) 5 (0.016%) 5 (0.016%) EQL (0.001 mg/L) not applicable 5 (0.016%) 5 (0.016%) Corresponding Population Served (Percentages based on 160,012,000 people served by the systems with toxaphene data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.003 mg/L) 23,000 (0.014%) 23,000 (0.014%) 23,000 (0.014%) 1/2 MCL (0.0015 mg/L) 23,000 (0.014%) 23,000 (0.014%) 23,000(0.014%) EQL (0.001 mg/L) not applicable 23,000 (0.014%) 23,000(0.014%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.001 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for

May 2009 Draft EPA document. Do not cite or distribute. 181toxaphene is appropriate at this time. The occurrence and exposure analysis based on possible changes in analytical feasibility indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration the low occurrence of this contaminant, EPA has decide d that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 64. 2,4,5-TP (Silvex; 2,4,5-Tric hlorophenoxypropionic Acid)

a. Background . EPA published the current NPDW R for 2,4,5-TP on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establis hed an MCLG and an MCL of 0.05 mg/L. EPA based the MCLG on a reference dose of 0.008 mg/kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the toxicology of 2,4,5-TP, including its potential developmental and reproductive toxicity. The literature search did not identify any studies that warran t a review of the RfD or the cancer cla ssification (USEPA, 2009b). A review of analytical or treatment feasibil ity is not necessary for 2,4,5-TP because changes to the MCLG are not warranted at this time and the current MCL is set at the MCLG. Since EPA did not identify a health or technology basis for revising the 2,4,5-TP NPDWR, the Agency did not conduct a detailed occurren ce and exposure analysis.

c. Review Result. EPA’s review shows that there ar e no data supporting a change to the 2,4,5-TP NPDWR. As a result, a revision to the NPDWR would not be appr opriate at this time.

May 2009 Draft EPA document. Do not cite or distribute. 18265. 1,2,4-Trichlorobenzene

a. Background . EPA published the current NPDW R for 1,2,4-trichlorobenzene on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR es tablished an MCLG and an MCL of 0.07 mg/L. EPA based the MCLG on a reference dos e of 0.01 mg/kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. The health effects technical revi ew identified information regarding the carcinogenicity of 1,2,4-trichlorobenzene, as we ll as its noncancer effect s, that may indicate the need to update the Agency’s health effects assessment (USEPA, 2009b). Two chronic carcinogenicity studies of 1,2,4-trichlorobenzene, one in mice (Moore et al., 2004a) and one in rats (Moore et al., 2004b), reported liver effects in both mice and rats , as well as kidney effects in rats. Mice appeared more sensitive than rats fo r noncancer effects, and mi ce also demonstrated a significant treatment-related increase in the in cidence of hepatocellu lar carcinomas. No increased incidence of any tumor type was observed in rats. These health effect data could have implications for the 1,2,4-trichlorobenzene MCLG because they identify effect levels for noncancer effects in the liver and kidney, as well as evidence of car cinogenicity in mice. In light of this information, EPA considers 1,2,4 -trichlorobenzene as a potential candidate for a new health effects assessment. The Agency so licits general feedback on its plans to reassess health risks resulting from e xposure to 1,2,4-trichlorobenzene. The Agency also welcomes any scientific information related to 1,2,4-trichlorobenzene health risks from the public. Because EPA considers 1,2,4-trichlorobenzene as a candidate for a new assessment, EPA does not believe it is appropriate to consider revisions to the MCLG (as well as the MCL) at this time. A review of analytical or treatment feasib ility is not necessary for 1,2,4-trichlorobenzene because changes to the MCLG are not warranted at this time and the current MCL is set at the MCLG. Since EPA did not identify a healthor technology basis for revising the 1,2,4-

May 2009 Draft EPA document. Do not cite or distribute. 183trichlorobenzene NPDWR, the Agency did not conduct a detailed occurrence and exposure analysis.

c. Review Result. The Agency is considering whether to initiate a new health assessment for 1,2,4-trichlorobenzene and therefore does not believe a revision to the NPDWR is appropriate at this time. 66. 1,1,1-Trichloroethane

a. Background . EPA published the current NPDWR for 1,1,1-trichloroethane on July 8, 1987 (52 FR 25690 (USEPA, 1987)). The NPDWR establ ished an MCLG and anMCL of 0.20 mg/L. EPA based the MCLG on a reference dose of 0.035 mg/kg-day and a cancer classification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. In 2007, the Agency updated its h ealth effects assessment of 1,1,1- trichloroethane (USEPA, 2007d). The Agency identif ied a change in this assessment that could lead to a change in the MCLG. This assessment considered rele vant studies on the toxicity of 1,1,1-trichloroethane including developmental and re productive toxicity. The assessment revised the RfD from 0.035 mg/kg-day to 2 mg/kg-day and concluded that th ere is inadequate information to assess the carcinogenic potenti al of 1,1,1-trichloroethane (USEPA, 2007d). Based on the new IRIS assessment and RfD of 2 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters water intake per day, the DW EL could be 70 mg/L. AnRSC of 20% results in a possible MCLG of 14 mg/L (USEPA, 2009b). Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor if EPA were to raise the MCLG. EPA evaluated the results of the occurrence and exposure analyses for 1,1,1-trichloroethane to determine whether a revised MCLG/MCL would be likely to result in a meani ngful opportunity to achieve co st savings for PWSs and their customers while maintaining, or improving, the level of public health protection (USEPA,

May 2009 Draft EPA document. Do not cite or distribute. 1842009f). Although the Agency obtained and evalua ted the finished wate r occurrence data for 1,1,1-trichloroethane, its usefulness is limited for determining potential cost savings to PWSs and their customers because the Agency does not know which systems are treating for this contaminant. As an alternative, the Agency ev aluated available data on source water quality and conducted a qualitative assessment of treatment cost savings. Table VI-27 provides summary data for contam inant occurrence based on maximum sample values for the locations included in the ST ORET and NAWQA data. Although the degree to which these occurrence rates represent national drinking water source occurrence is uncertain, the information shows no to low occurrence at thre shold levels of interest. This information indicates that any resulting NP DWR change would affect system s that rely on source water at none of the NAWQA locations and at less than 0.4% of the STORET locations.

Table VI-27. Ambient Water Quality Monitori ng Occurrence Summary for 1,1,1-Trichloroethane Number of Locations (% of locations) Maximum Concentration STORET 1 NAWQA 2 Total 3,429 (100.0%) 5,788 (100.0%) Nondetect 2,825 (82.84%) 5,290 (91.4%) Detected 604 (17.16%) 498 (8.6%) Exceeds current MCLG of 0.2 mg/L 11 (0.32%) 0 (0.0%) Exceeds alternative value of 14 mg/L 0 (0.0%) 0 (0.0%) 1. STORET database 1992-2008. 2. NAWQA database 1992-2006. Source: USEPA, 2004c
The BATs and small system compliance techno logies for 1,1,1-trichloroethane have other beneficial effects, e.g., reduction of other co-o ccurring contaminants, precursors for DBPs, or other common impurities. Therefore, if EPA were to consider a higher level, the Agency does not know how many PWSs that are currently treating to comply with the existing MCL of 0.2 mg/L would be likely to discontinue treatment th at is already in plac e (USEPA, 2009d). Also,

May 2009 Draft EPA document. Do not cite or distribute. 185the Agency does not know to what extent affectedsystems might be able to reduce costs given that capital costs are not rec overable. However, the Agencyrecognizes that there may be opportunities to achieve operational co st savings if these systems ar e able to re-optimize current

treatment. Given these challenges, the Agency believes th at any resulting revi sion is not likely to provide a meaningful opportunity for cost savings. In view of this, any revision would be a low priority activity and not appropriate at this time.

c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for 1,1,1-trichloroethan e, EPA does not believe a revision to the NPDWR for 1,1,1-trichloroethane is appropriate at this time. In making this decision, the Agency considered whether any possible revisi on to the NPDWR for 1,1,1-trichloroethane is likely to provide a meaningful opportunity for co st savings to public water systems and their customers. Taking into consideration the low oc currence of this contaminant in source waters, EPA has decided that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 67. 1,1,2-Trichloroethane

a. Background . EPA published the current NPDW R for 1,1,2-trichloroethane on July 17, 1992 (57 FR 31776 (USEPA, 1992)). The NPDWR es tablished an MCLG of 0.003 mg/L. EPA based the MCLG on a reference dose of 0.004 mg /kg-day and a cancer classification of C,

May 2009 Draft EPA document. Do not cite or distribute. 186possible human carcinogen. The NPDWR also established an MCL of 0.005 mg/L, based on analytical feasibility. b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the toxicology of 1,1,2-trichloroethane, including its potential developmental and reproductive toxi city. The literature search di d not identify any studies that warrant a review of the RfD or th e cancer classification (USEPA, 2009b). The current MCL for 1,1,2-trichloroethane is based on a PQL of 0.005 mg/L. For the SixYear Review, the Agency considered whether changes in the analytic al feasibility of 1,1,2- trichloroethane might lead to a lower MCL. EP A reviewed WS data fr om the first Six-Year Review cycle and then analyzed more recent PT data to determine if the PQL can be revised (i.e., analytical feasibility). Passing rates for WS data available through late 1999 for 1,1,2- trichloroethane are above 95 per cent near the current PQL of 0.005 mg/L, but there were no WS studies with true values below the current PQ L. More recent PT data from late 1999 through 2004, supplied by a PT provider, show greater th an 90 percent passing rates around the current PQL, including twelve studies withtrue values below the PQL. Because most of the laboratory passing rates from PT studies – including severa l with true concentrations below the PQL – exceeded the 75 percent criterion typically used to derive a PQL, a lowering of the PQL for 1,1,2-trichloroethane might be possible. These re sults, however, are insuffi cient to recalculate a revised PQL for 1,1,2-trichloroethane because no t enough data points are available below the current PQL to derive a value at the 75 percent passing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of 1,1,2-tr ichloroethane (Methods 502.2 and 524.2). While EPA prefers to use laborato ry performance data to calculate the PQL,

May 2009 Draft EPA document. Do not cite or distribute. 187the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the current PQL. The Six-Year Review I CR dataset contains MRL values for 139,672 samples. Of these, 117,788 (84%) equal the modal MRL of 0.0005 mg/L. An additional 17,142 (12%) are lower than 0.0005 mg/L. The MDLs of approved methods range from 0.00004 to 0.0001 mg/L. Applying a multiplie r of 10 would give a possible PQL range from 0.0004 to 0.001 mg/L

. Because the preponderance of MRLs are at 0.0005 mg/L, below the MCLG for 1,1,2-trichloroethane, EPA believes that th ere is potential to revi se the PQL to a level that would not limit the MCL. Based on these varied and unrelated approach es/sources of information, EPA believes that there is potential to lower the PQL for 1,1,2-trichloroethane. To determine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of 1,1,2-trichloroethane at the curr ent MCLG of 0.003 mg/L (USEPA, 2009f). Table VI-28 shows the re sults of the occurrenc e and exposure analysis for the current MCL and the current MCLG of 0.003 mg/L. The occurrence and exposure analysis shows that average concentrations do not exceed the current MC L for any system in the analysis. Note that these results do not necessarily reflect MCL violations, which are based on annual average concentrations at entry points; SDWIS/ FED indicates six MC L violations for 1,1,2- trichloroethane between 1998 and 2005 (USEPA, 2007g) . The average concentration at one out of 50,195 systems (0.002%), serving approxi mately 700 people (or 0.0003% of 227 million people), exceeds the curr ent MCLG of 0.003 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 188Table VI-28. Number and Percent of System s with Mean Concentrations Exceeding 1,1,2- Trichloroethane Thresholds and Corresponding Estimates of Population Served Systems with Mean Concentrati ons that are Greater than the Regulatory or Health-based Threshold (Percentages based on 50,195 systems w ith 1,1,2-trichloroethane data in the Six-Year Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Current MCLG (0.003 mg/L) 1 (0.002%) 1 (0.002%) 1 (0.002%) Corresponding Population Served (Percentages based on 226,852,000 people served by the systems with 1,1,2-trichloroethane data in th e Six-Year Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Current MCLG (0.003 mg/L) 700 (0.0003%) 700 (0.0003%) 700 (0.0003%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for 1,1,2-trichloroethane is appropriate at this time. The occurrence and exposure analysis based on possible changes in analytical feasibility indica tes that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration the low occurrence of this contaminant, EPA has decided that any revisi on to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

May 2009 Draft EPA document. Do not cite or distribute. 189• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 68. Trichloroethylene

a. Background . EPA published the current NPDWR for trichloroethylene on July 8, 1987 (52 FR 25690 (USEPA, 1987)). The NPDWR establ ished an MCLG of zero based on a cancer classification of B2, probable human carcinoge n. The NPDWR also established an MCL of 0.005 mg/L, based on anal ytical feasibility. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to trichloroethylene. The revised health effects asse ssment will consider relevant studies on the toxicity of tr ichloroethylene, including its potential developmental and reproductive toxicity. The new health effect s assessment was not completed by March 1, 2009, the review cutoff date for this notice (USE PA, 2009b). The IRIS Substance Assessment Tracking System website (http://cfpub.epa.gov/ir istrac/index.cfm) has the most up-to-date information on the status of the health effects assessment. Although a risk assessment is in process for tric hloroethylene, the existing MCLG is zero and the current MCL of 0.005 mg/L is based on the PQL. For the Six-Year Review, the Agency evaluated several sources of information to dete rmine whether changes in analytical feasibility might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determ ine if the PQL can be re vised (i.e., analytical feasibility). Passing ra tes for WS data available through late 1999 for trichl oroethylene are above 95 percent at the lowest concentrations. Ho wever, the true concentrations were all higher than the current PQL of 0.005 mg /L. More recent PT data from 1999 to 2004, supplied by a PT provider, also show greater than 95 percent pa ssing rates for studies around the current PQL,

May 2009 Draft EPA document. Do not cite or distribute. 190including 6 with true values below the PQL. Be cause most of the labora tory passing rates from WS and PT studies exceeded the 75 percent criterion typi cally used to derive a PQL, including several with true values below the PQL, a lowe ring of the PQL for tric hloroethylene might be possible. These results, however, are insu fficient to recalculate a revised PQL for trichloroethylene because not enoug h data points are available belo w the current PQL to derive a value at the 75 percent pa ssing rate (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods fo r the detection of tric hloroethylene (Methods 502.2, 524.2, and 551.1). While EPA prefers to use labor atory performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate whether it is possible to quantitate at levels below the curren t PQL. EPA also noted that the State of New Jersey uses a PQL of 0.001 mg/L, based on a 1987 study of laboratory performance at low concentrations that used criteriasimilar to those in the PT da ta (NJDWQI, 1987). The Six-Year Review ICR dataset contains MRLs for 138,439 sa mples. Of these, 118,193 (85%) equal the modal MRL of 0.0005 mg/L. An additional 17,057 (12%) are lower than 0.0005 mg/L. The MDLs of approved methods range are 0.00006, 0.00019, and 0.000042 mg/L. Applying a multiplier of 10 would give a possible PQL range from 0.00042 to 0.0019 mg/L. Because of the preponderance of MRL values of 0.0005 mg/L, EPA selected that value as the minimum threshold for the occurrence and exposure analysis (USEPA, 2009e). Based on these varied and unrelated approach es/sources of information, EPA believes that there is potential to lower the PQL for trichl oroethylene. To determine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of trichloroet hylene at thresholds of 0.0005, 0.0010, and 0.0025 mg/L

May 2009 Draft EPA document. Do not cite or distribute. 191(USEPA, 2009f). Table VI-29 s hows the results of the occurren ce and exposure analysis for the current MCL and EQLs set equal to 0.0025 mg/L, 0.001 mg/L, and 0.0005 mg/L. The occurrence and exposure analysis shows that aver age concentrations exceed the current MCL for 25 out of 50,432 systems (0.050%) serving a pproximately 410,000 people (or 0.181% of 227 million people). Note that these results do not necessarily reflect MCL violations, which are based on annual average concentrations at entry points; SDWIS/ FED indicates 191 MCL violations for trichloroethyl ene between 1998 and 2005 (USEPA, 2007g ), with annual violations ranging from 12 to 31. Average concentratio ns at 310 to 388 of 50,432 systems (0.615% to 0.769%), serving approximately 12.0 to 13.0 million people (or 5.237% to 5.670% of 227 million people), exceed the EQL of 0.0005 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 192Table VI-29. Number and Percent of Systems with Mean Concentrations Exceeding Trichloroethylene Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 50,432 systems w ith trichloroethylene data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 25 (0.050%) 25 (0.050%) 25 (0.050%) 1/2 MCL (0.0025 mg/L) 70 (0.139%) 68 (0.135%) 64 (0.127%) 2xEQL (0.001 mg/L) 239 (0.474%) 208 (0.412%) 182 (0.361%) EQL (0.0005 mg/L) not applicable 388 (0.769%) 310 (0.615%) Corresponding Population Served (Percentages based on 226,908,000 people served by the systems with trichloroethylene data in the Six- Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.005 mg/L) 410,000 (0.181%) 410,000 (0.181%) 410,000 (0.181%) 1/2 MCL (0.0025 mg/L) 4,765,000 (2.100%) 4,691,000 (2.067%) 4,598,000 (2.026%) 2xEQL (0.001 mg/L) 10,367,000 (4.569%) 8,282,000 (3.650%) 7,399,000 (3.261%) EQL (0.0005 mg/L) not applicable 12,866,000 (5.670%) 11,884,000 (5.237%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.0005 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that a revision to the MCL may provide a meaningful opportunity to improve the level of public health protection, EPA considered whether treatment feasibility is likely to pose any limitations if the MCL were lowered (USEPA, 2009g). The current BATs for trichloroethylene are packed tower aeration (PTA) and granular activated carbon (GAC). Small system compliance technol ogies for trichloroeth ylene include GAC and several aeration technologies. EPA believes thes e BATs and SSCTs are s till practical and would not pose any limitations if EPA were to revise the MCL. EPA is not currently able to assess the poten tial health benefits from a revised MCL for trichloroethylene, because the re vised health effects assessment is not yet available. However,

May 2009 Draft EPA document. Do not cite or distribute. 193based on its B2 cancer classification (MCLG of zero) and the o ccurrence and exposure analysis at possible MCL values, the Agency believes that a revision to the MCL may provide a meaningful opportunity to re duce public health risks.

c. Review Result. The Agency believes it is ap propriate to revise the NPDWR for trichloroethylene although a health effects assessment is curren tly in progress. The existing MCLG is zero (based on the current B2 cancer cl assification) and the current MCL is based on a PQL (i.e., analytical feasibility) of 0.005 mg/L. The Agency’s revi ew indicates that analytical feasibility could be as much as 10 times lo wer (~ 0.0005 mg/L) and occu rrence at this level appears to be relatively widespread. Hence, revisions to the trichloroethylene NPDWR may provide a meaningful opportunity for health risk reduction. EPA expects that the final health effects assessment for trichloroethylene will furt her support the public health benefits associated with any revision. As discussed in Section VI I, the Agency solicits public comment and/or relevant information that may inform the regulato ry revision for trichloroethylene. EPA is also requesting that stakeholders provide informati on/data about the lowestlevel of quantitation (including the analytical method us ed) that laboratories can reliably and consistently achieve.

69. Uranium

a. Background . EPA published the current NPDW R for uranium on December 7, 2000 (65 FR 76708 (USEPA, 2000c)). The NPDWR establis hed an MCLG of zero based on a cancer classification of A, known human carcinogen. As noted in the December 2000 FR, uranium has also been identified as a nephr otoxic metal (kidney toxicant) and EPA derived a drinking water equivalent level of 20 μ g/L as a noncancer health endpoint for kidney toxicity. The NPDWR also established an MCL of 30 μ g/L, which is higher than the feasible level of 20 μ g/L and the level associated with kidney toxicity. InDecember 2000, EPA exercised its discretionary authority to set an MCL at a level higher thanfeasible (SDWA Secti on 1412(b)(6)), based on the

May 2009 Draft EPA document. Do not cite or distribute. 194finding that “benefits do not justify th e costs at the feasible level (20 μ g/L) and that the net benefits are maximized at a level (30 μ g/L) that is still protective of health with an adequate margin of safety” (65 FR 76708 (USEPA, 2000c)) 20

. b. Technical Reviews. EPA has initiated a reassessment of the health risks resulting from exposure to uranium. The revised health effect s assessment will consider relevant studies on the toxicity of uranium, including its potential developmen tal and reproductive toxicity. The new health effects assessment was not completed by March 1, 2009, the review cutoff date for this notice (USEPA, 2009b). The IRIS Substan ce Assessment Tracking System website (http://cfpub.epa.gov/iristrac /index.cfm) has the most up-to-date information on the status of the health effects assessment.

c. Review Result. The Agency does not believe a revision to the NPDWR for uranium is appropriate at this time because a reassessment of the health risks resulting from exposure to uranium is ongoing (USEPA, 2009b). As noted pr eviously, the uranium MCL is based on the SDWA cost benefit provision (Section 1412(b)(6)) and the health effects assessment is important for reviewing the benefits associat ed with the basis of the MCL. 70. Vinyl chloride

a. Background . EPA published the current NPDWR fo r vinyl chloride on July 8, 1987 (52 FR 25690 (USEPA, 1987)). The NPDWR establis hed an MCLG of ze ro based on a cancer classification of A, known hu man carcinogen. The NPDWR also established an MCL of 0.002 mg/L, based on analytical feasibility.

20 After the December 7, 2000 final regulation, two tr ade associations and severa l municipal water systems challenged EPA’s standard fo r uranium by claiming that the Agency did not use the best available science when finalizing the standard. In February of 2003, the DC Circuit Court of Appeals upheld EPA's regulation for uranium (as well as combined radiums, and beta particle and photon emitters) May 2009 Draft EPA document. Do not cite or distribute. 195b. Technical Reviews. As part of the Six-Year Reviewprocess, EPA conducted a literature search for relevant data on the carcinogenicity of vinyl chloride as well as its potential developmental and reproductive toxicity. EPA has not identified any new information that indicates that it is appropriate to consider revisi ons to the cancer classification for vinyl chloride at this time (USEPA, 2009b). Because the MCLG remains at zero, the Agency believes that a further review of the health effects of vinyl chloride is not warra nted at this time. The current MCL for vinyl chloride is base d on a PQL of 0.002 mg/L. For the Six-Year Review, the Agency considered whether changes in the analytical feasibility of vinyl chloride might lead to a lower MCL. EPA reviewed WS data from the first Six-Year Review cycle and then analyzed more recent PT data to determ ine if the PQL can be re vised (i.e., analytical feasibility). Passing ra tes for WS data available through late 1999 for vinyl chloride are generally in the 75 to 80 percen t range near the current PQL of 0.002 mg/L, but there were no results for WS studies with true values below the current PQL. More recent PT data from late 1999 through 2004, supplied by a PT provider, also show greater than 80 percent passing rates for studies around the current PQL, including two studies with true values below the PQL. Despite the limited data below the PQL, most of the laboratory passing rates from WS and PT studies – including two with true concentra tions below the PQL – exceeded the 75 percent criterion usually used to derive a PQL. Therefore, a lowering of the PQL for vinyl chloride might be possible (USEPA, 2009c). EPA evaluated two alternative sources of inform ation to determine whether they indicate any potential to revise the PQL: laboratory minimum reporting levels in the Six-Year Review ICR dataset, and the MDLs for approved methods for the detection of vinyl chloride (Methods 502.2 and 524.2). While EPA prefers to use laboratory performance data to calculate the PQL, the MRL and MDL information can be valuable for this review to indicate wh ether it is possible to

May 2009 Draft EPA document. Do not cite or distribute. 196quantitate at levels below the current PQL. The Six-Year Re view ICR dataset contains MRL values for 139,494 samples. Of these, 105,410 (76%) equal the modal MRL of 0.0005 mg/L. An additional 25,723 (18%) are lower than 0.0005 mg/L. The MDLs of approved methods range from 0.00017 to 0.00018 mg/L. Applying a multiplie r of 10 would give a possible PQL range from 0.0017 to 0.0018 mg/L. Because of the preponderance of MRL values of 0.0005 mg/L, EPA selected that value as the minimum thre shold for the occurrence and exposure analysis (USEPA, 2009e). Based on these varied and unrelated approach es/sources of information, EPA believes that there may be potential to lower the PQL for vi nyl chloride. To dete rmine whether any MCL revision is likely to provide a meaningful oppor tunity to improve public health protection, EPA evaluated the occurrence of vinyl chloride at thresholds of 0.001 and 0.0005 mg/L (USEPA, 2009f). Table VI-30 shows the re sults of the occurrenc e and exposure analysis for the current MCL and EQLs set equal to 0.001 mg/L and 0.0005 mg/L. The occurrence and exposure analysis shows that average concentrations exceed the current MCL for 8 to 11 of 50,411 systems (0.016% to 0.022%) serving fewer than 14,000 people (or 0.003% to 0.006% of 226 million people). Note that these results do not necessarily reflect MCL violations, which are based on annual average concentrations at entry points; SDWIS/ FED indicates 25 MCL violations for vinyl chloride between 1998 and 2005 (USEPA, 2007g). Average concentrations at 32 to 49 of 50,411 systems (0.063% to 0.097%), serving 483,000 to 766,000 people (or 0.213% to 0.338% of 226 million peopl e), exceed the EQL of 0.0005 mg/L.

May 2009 Draft EPA document. Do not cite or distribute. 197Table VI-30. Number and Percent of Systems with Mean Concentrations Exceeding Vinyl Chloride Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrations th at are Greater than the Regulatory or Feasibility-based Threshold (Percentages based on 50,411 systems with vinyl chloride data in the Six-Year Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.002 mg/L) 11 (0.022%) 10 (0.020%) 8 (0.016%) 1/2 MCL (0.001 mg/L) 21 (0.042%) 18 (0.037%) 15 (0.030%) EQL (0.0005 mg/L) not applicable 49 (0.097%) 32 (0.063%) Corresponding Population Served (Percentages based on 226,464,000 people served by the systems with

vinyl chloride data in the Six-Y ear Review ICR occurrence dataset) Regulatory or Feasibility-based Threshold Nondetect Values = MRL 1 Nondetect Values = 1/2 MRL 2 Nondetect Values= 0

3 MCL (0.002 mg/L) 14,000 (0.006%) 12,000 (0.005%) 6,000 (0.003%) 1/2 MCL (0.001 mg/L) 56,000 (0.025%) 23,000 (0.010%) 18,000 (0.008%) EQL (0.0005 mg/L) not applicable 766,000 (0.338%) 483,000 (0.213%) 1. Results are based on setting all nondetect results equa l to MRL values in the Six-Year Review ICR dataset. Results are not reported at the EQL of 0.0005 mg/L because this is the modal MRL and setting a majority of the results equal to this value result s in an upwardly biased estimate of the number of systems with mean concentrations that exceed this value. 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

c. Review Result. Although there are new data that s upport consideration of a possibly lower PQL (and therefore a possibly lower MCL), EPA does not believe a revision to the NPDWR for vinyl chloride is appropriate at this time. The occurrence and exposure analysis based on possible changes in analytical feasibility indica tes that any revision to the MCL is unlikely to provide a meaningful opportunity to improve public health protection. Taking into consideration the low occurrence of this contaminant, EPA has decided that any revisi on to the NPDWR would

May 2009 Draft EPA document. Do not cite or distribute. 198be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted. 71. Xylenes (Total)

a. Background . EPA published the current NPDW R for total xylenes on January 30, 1991 (56 FR 3526 (USEPA, 1991c)). The NPDWR establ ished an MCLG and an MCL of 10 mg/L. EPA based the MCLG on a reference dose of 2 mg /kg-day and a cancer clas sification of D, not classifiable as to human carcinogenicity. b. Technical Reviews. In 2003, the Agency updated its heal th effects assessment of xylenes (USEPA, 2003d). The change in this assessment could lead to a change in the MCLG. This assessment considered relevant studies on the to xicity of xylenes including developmental and reproductive toxicity. The assessment revised th e RfD from 2 mg/kg-day to 0.2 mg/kg-day and concluded that there is inadequa te information to assess the carc inogenic potential of xylenes (USEPA, 2003d). Based on the new IRIS assess ment and RfD of 0.2 mg/kg-day, and assuming a 70-kg adult body weight and 2 liters water intake per day, the DWEL could be 7 mg/L. An RSC of 20% results in a pos sible MCLG of 1 mg/L. Analytical feasibility does notpose any limitations for the cu rrent MCL and would not be a limiting factor for the possible MCLG decrease under considerati on. EPA evaluated the results of the occurrence and exposure analyses for to tal xylenes to determine whether a revised MCLG/MCL would be likely to re sult in a meaningful opportunity to improve the level of public health protection (USEPA, 2009f). Table VI-3 1 shows the results of the occurrence and

May 2009 Draft EPA document. Do not cite or distribute. 199exposure analysis for the curren t MCL and the possible MCLG set equal to 1 mg/L based on the new health effects information. The occurren ce and exposure analysis shows that average concentrations do not exceed the current MCL for any system in the analysis. Note that these results do not necessarily reflect MCL viol ations, which are based on annual average concentrations at entry points; SDWIS/FED i ndicates two MCL violati ons for xylene between 1998 and 2005 (USEPA, 2007g). The occurrence and exposure analysis shows that average concentrations do not exceed the possible MCLG based on new health effects information (1 mg/L).

Table VI-31. Number and Percent of Systems with Mean Concentrations Exceeding Xylene Thresholds and Corresponding Esti mates of Population Served Systems with Mean Concentrati ons that are Greater than the Regulatory or Health-based Threshold (Percentages based on 47,698 systems with xylene data in the SixYear Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (10 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Possible MCLG (1 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Corresponding Population Served (Percentages based on 218,072,000 people served by the systems with xylene data in the Six-Year Review ICR occurrence dataset)Regulatory or Healthbased Threshold Nondetect Values = MRL 1 Nondetect Values= 1/2 MRL 2 Nondetect Values= 0

3 MCL (10 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) Possible MCLG (1 mg/L) 0 (0.000%) 0 (0.000%) 0 (0.000%) 1. Results are based on setting all nondetect results eq ual to MRL values in the Si x-Year Review ICR dataset 2. Results are based on setting all nondetect results equal to 1/2 MRL values in the Six-Year Review ICR dataset. 3. Results are based on setting all nondetect results equal to zero. Source: USEPA, 2009f.
Since the occurrence analysis indicates that any revision to the MCL is unlikely to provide a meaningful opportunity to improve the level of public health prot ection, it was not necessary to perform any additional reviews on treatment feasibility or economic considerations.

May 2009 Draft EPA document. Do not cite or distribute. 200c. Review Result. Although there are new data that support consideratio n of whether to revise the MCLG/MCL for total xylenes, EPA does not believe a revision to the NPDWR for total xylenes is appropriate at th is time. In making this decision, the Agency considered whether any possible revision to the NPDWR for total xylenes is likely to provide a meaningful opportunity for health risk reduc tions. Taking into considerati on the low occurrence of this contaminant, EPA has decided that any revision to the NPDWR would be a low priority activity for the Agency, and, thus, is not appropriate to revise at this time because of:

• Competing workload priorities;

• The administrative costs associated with rulemaking; and

• The burden on States and the regu lated community to implement any regulatory change that resulted.

VII. EPA’s Request for Comments A. Request for Comment and/or Informa tion on the Candidates for Revision EPA invites commenters to submit any new, re levant peer-reviewed data or information pertaining to the four NPDWRs identified in today’s action as candidates for revision (i.e. acrylamide, epichlorohydrin, tetrechloroethylene and trichloroethylene). This information will inform EPA’s evaluation as the Agency moves fo rward with the regulato ry revisions for these four NPDWRs. Peer reviewed da ta are studies/analyses that have been reviewed by qualified individuals (or organizations) w ho are independent of those w ho performed the work, but who are collectively equivalent in tec hnical expertise (i.e., peers) to those who performed the original work. A peer review is an in-depth assessment of the assumptions, calculations, extrapolations, alternate interpretations, methodology, acceptance criteria, and c onclusions pertaining to the specific major scientific and/or technical work products and of the documentation that supports

May 2009 Draft EPA document. Do not cite or distribute. 201them (USEPA, 2000d). Relevant data include studies/analyses pert aining to analytical feasibility, treatment feasibility, and occurr ence/exposure related to the four NPDWRs candidates for revision list ed as in today’s action 21

. Table VII- provides a list of the specific items for which EPA is requesting comment and/ or information for the four candidates for revision. It also provides a cross-refere nce to the section a ddressing the issue.

Table VII-1. Items for Which EPA is Re questing Comment and/or Information for the Four Candidates for Revision

Issue Notice Section Any new, relevant peer-reviewed data or information that would inform the revision of the NP DWR for acrylamide, including information pertaining to extent of use of polyacrylamide in drinking water facilities Section VI.B.1

Any new, relevant peer-reviewed data or information that would inform the revision of the NPDW R for epichlorohydrin, including information pertaining to extent of use of epichlorohydrin-based polymers/co-polymers in drinking water facilities Section VI.B.36

Any new, relevant peer-reviewed data or information that would inform the revision of the NPDWR for tetrachloroethylene, including information/data about the lowest le vel of quantitation (and analytical method used) that laboratories can reliably and cons istently achieve Section VI.B.60

Any new, relevant peer-reviewed data or information that would inform the revision of the NPDWR for trichloroethylene, including information/data about the lowest level of quantitation (and the analytical method used) that laborat ories can reliably and consistently achieve Sections VI.B.65

B. Request for Information/Data on Other Review Topics EPA also invites commenters to submit new, relevant information on several other review topics referenced in this noti ce and listed in Table VII-2. Table VII-2. Issues for Which EPA is Reque sting Public Input and/or Information Issue Notice Section Location for nitrate and nitrite monitoring Section V.B.6 Monitoring frequency for ground wate r systems with low nitrate and nitrite concentrations Section V.B.6

21 Note that new health effects studies /information for acrylamide, PCE and TCE are being considered as part of the IRIS update to these health assessments.
May 2009 Draft EPA document. Do not cite or distribute. 202Monitoring requirements for non-commun ity water systems Section V.B.6 Detection limits that serve as triggers to determine compliance monitoring frequency for SOCs Section V.B.6 New, relevant health effects info rmation that will help the Agency decide whether to initiate a ne w health effects assessment for chromium Section VI.B.17

New, relevant health effects info rmation that will help the Agency decide whether to initiate or nom inate nitrate and nitrite for a new health effects assessment Sections VI.B.49 and VI.B.50 New, relevant health effects info rmation that will help the Agency decide whether to initiate or nominate selenium for a new health effects assessment Sections VI.B.56

New, relevant health effects info rmation that will help the Agency decide whether to initiate or nominate 1,2,4-trichlorobenzene for a new health effects assessment Sections VI.B.65

C. Requests for Information on the Impacts of Climate Change on Water Quality The Agency recognizes that changes in global climate can impact temperature, rainfall patterns, and snow and ice cover. Changes in these climate indicators can impact water quantity and water quality. In an effort to assess the impacts of climate change on water quality, EPA is asking if public water systems and/or States have any information or data that illustrates the impact of climate change (e.g., changes in rain fall, drought, temperature, and snow/ice cover) on the occurrence of contaminants indrinking water, both in source water and in finished water. EPA also requests data on changes in the variab ility of occurrence and impacts on drinking water treatment to address occurrenc e or variability changes.

VIII. EPA’s Next Steps EPA will consider the public comments and/or any new, relevant, peer-reviewed data submitted for the four NPDWRs listed as candida tes for revision as the Agency proceeds with the regulatory revisions for these regulations. The announcement that the Agency intends to revise an NPDWR (pursuant to SDWA section 1412( b)(9)) is not a regulato ry decision. Instead, it initiates a regulatory process that will involve more detailed analyses of health effects,

May 2009 Draft EPA document. Do not cite or distribute. 203analytical and treatment feasibility, occurrence, benefits, costs, and other regulatory matters relevant to deciding whether anNPDWR should be revised. The Six-Year Review results do not obligate the Agency to revise an NPDWR in the event that EPA determin es during the regulatory process that revisions are no l onger appropriate and discontinues further efforts to revise an NPDWR. Similarly, the fact thatan NPDWR has not been select ed for revision means only that EPA believes that regulatory change s to a particular NPDWR are notappropriate at this time for the reasons given in today’s actio n; future reviews may identify information that leads to an initiation of the revision process.

IX. References ATSDR (Agency for Toxic Substances and Diseas e Registry). 2007. Toxicological profile for benzene. Atlanta, GA: Agency for Toxic Subs tances and Disease Registry, Public Health Service, U.S. Department of Health and Hu man Services. Available on the Internet at: http://www.atsdr.cdc.go v/toxprofiles/tp3.html. Cocco, P, G. Broccia, et al. 2003. Nitrate in community wate r supplies and incidence of nonHodgkin's lymphoma in Sardinia, Italy. Journa l of Epidemiology and Community Health. v. 57, pp. 510-511. Coss, A., K.P. Cantor, et al. 2004. Pancreatic cancer and drinking water and dietary sources of nitrate and nitrite. American J ournal of Epidemiology. v. 159, pp. 693-701. de Roos, A.J., M.H. Ward, et al. 2003. Nitrate in public water supplies and the risk of colon and rectum cancers. Epidemiology. v. 14, pp. 640-649. Duffield-Lillico, A.J., E.H. Slate, et al. 2003. Selenium supplementation and secondary prevention of nonmelanoma skin cancer in a ra ndomized trial. J ournal of the National Cancer Institute. v. 95, pp. 1477-1481.

May 2009 Draft EPA document. Do not cite or distribute. 204Gianessi, L. and N. Reigner. 2006. Pes ticide Use in U.S. Crop Production: 2002 With Comparison to 1992 and 1997 – Fungicides & He rbicides. Washington, D.C.: CropLife Foundation. Gilliom, R.J., J.E. Barbash, C.G. Crawford, P. A. Hamilton, J.D. Martin, N. Nakagaki, L.H. Nowell, J.C. Scott, P.E. Stackelberg, G.P. Thelin, and David M. Wolock. 2006. The Quality of Our Nation's Waters: Pesticides in th e Nation's Streams and Ground Water, 1992-2001. U.S. Geological Surv ey Circular 1291. Grosse, Y., R. Baan, et al. 2006. Carcinogenicit y of nitrate, nitrite, and cyanobacterial peptide toxins. The Lancet Oncology. v. 7, pp. 628-629. Hawkes, W.C., and N.L. Keim. 2003. Dietary selenium intake modulates thyroid hormone and energy metabolism in men. Journal of Nutrition. v. 133, pp. 3443-3448. Lan, Q., L. Zhang, et al. 2004. Hematotoxicity inworkers exposed to low levels of benzene. Science. v. 306, pp. 1774-1776. Levine, Audrey D., Brian A. Bolto, and David R. Dixon. 2004. Reactions of Polyelectrolytes With Other Water Treatment Chemicals . AwwaRF Report #2509. MacKenzie, R.D., R.U. Byerrum, C.F. Decker, et al. 1958. Chronic to xicity studies. II. Hexavalent and trivalent chromium administer ed in drinking water to rats. American Medical Association Archives of Industrial Health. v. 18, pp. 232-234. Markel, E, C. Nyakas, and S. Ormai. 1989. Nitrate induced changes in sensorimotor development and learning behavior in rats. Acta Physiologica Hungarica. v. 74, pp. 69-75. Moore, M. 1994a. 104-week dietary carcinogenicity study with 1,2,4-trichlorobenzene in mic e. Hazleton Washington, Inc. Rockville, Maryland. HWA 2603-102. EPA/OTS Doc #88-
930000429.

May 2009 Draft EPA document. Do not cite or distribute. 205Moore, M. 1994b. Final report- 104-week dietary carcinogenicity study with 1,2,4- trichlorobenzene in rats . Hazleton Washington, Inc. Roc kville, Maryland. HWA 2603-103.
OTS0558832. OPPTS-44612. Moran, M.J. 2006. Occurrence And Implications Of Selected Chlorinated Solvents In Ground Water And Source Water In The United States And In Drinking Water In 12 Northeast And Mid-Atlantic States, 1993–2002. U. S. Geological Survey Scient ific Investigations Report 2005–5268. Reston, VA: U.S. Geological Survey. Mueller, B.A., S.S. Nielsen, et al. 2004. Hous ehold water source and th e risk of childhood brain tumours: results of the SEARCH International Brain Tumor Study. International Journal of Epidemiology. v. 33, pp. 1209-1216. Mukhopadhyay, S., D. Ghosh, et al. 2005. Evaluati on of possible goitroge nic and anti-thyroidal effect of nitrate, a potential environmenta l pollutant. Indian J ournal of Physiology & Pharmacology. v. 49, pp. 284-288. NAS (National Academy of Sciences). 1995. Nitr ate and nitrite in drinking water. Committee on Toxicology, Subcommittee on Nitrate and Nitrite in Drinking Water. National Academy Press, Washington, DC. NAS. 2006. Health Risks from Dioxin and Related Compounds: Evaluation of the EPA Reassessment. Committee on EPA's Exposure and Human Health Reassessment of TCDD and Related Compounds, National Research Council. NCFAP (National Center for Food and Agricultural Policy). 2000. Pesticide Use in U.S. Crop Production: 1997. National Summary Repor t. Washington, D.C.: NCFAP. NDWAC (National Drinking Water Advisory C ouncil). 2000. Recommended Guidance for Review of Existing National Primary Dri nking Water Regulations. November 2000. Available on the Internet at: http:/ /www.epa.gov/safewater/ndwac/guidfnl.pdf.

May 2009 Draft EPA document. Do not cite or distribute. 206NTP (National Toxicology Program). 2007. Draft Report. Toxicology and carcinogenesis studies of chromium picolinate monohydrate (C AS # 27882-76-4) in F344 rats and B6C3F1 mice (feed studies). TR-556. NTP. 2008. Technical report on the toxico logy and carcinogenesis studies of sodium dichromate dihydrate (CAS # 7789-12-0) in F 344 rats and B6C3F1 mice (drinking water studies). TR-546. July 2008. Sedman, R.M., J. Beaumont, et al. 2006. Review of the eviden ce regarding the carcinogenicity of hexavalent chromium in drinking water. Journal of Environmental Science and Health, Part C, Environmental Carcinogenesis and Ecotoxicology Reviews. v. 24, pp. 155-182. Su, Y.P., J.M. Tang, et al. 2005. Histological and ultrastructura l changes induced by selenium in early experimental gastric carcinogenesis . World Journal of Gastroenterology. v. 11, pp.
4457-4460. Tajtakova, M., Z. Semanova, et al. 2006. Increa sed thyroid volume and frequency of thyroid disorders signs in schoolchildren from nitr ate polluted area. Chemosphere. v. 62, pp. 559-
564. USDA (U.S. Department of Agriculture). 2004. Pesticide Data Program Annual Summary Calendar Year 2004. Available on the Internet at: http://www.ams.usda.gov/AMSv1.0/ge tfile?dDocName=PDP2004Summary. USDA. 2005. Pesticide Data Program Annual Summary Calendar Year 2005. Available on the Internet at: http://www.ams.usda.gov /AMSv1.0/getfile?dDocName=STELPRDC5049946. USDA. 2006. Pesticide Data Program Annual Summary Calendar Year 2006. Available on the Internet at: http://www.ams.usda.gov /AMSv1.0/getfile?dDocName=STELPRDC5064786.

May 2009 Draft EPA document. Do not cite or distribute. 207USEPA (U.S. Environmental Protection Agency ). 1975. Interim Primary Drinking water Regulations; Radionuclides; Proposed Rule. Federal Register . Vol. 40. No. 158. p. 34324, August 14, 1975. USEPA. 1976. Interim Primary Drinking Wa ter Regulations; Radionuclides; Final Rule. Federal Register . Vol. 41. No. 133. p. 28402, July 9, 1976. USEPA. 1985. National Primary Drinking Water Regulations: Volatile Synthetic Organic Chemicals; Final Rule and Proposed Rule. Federal Register . Vol. 50, No. 219. p. 46880, November 13, 1985. USEPA. 1986a. National Primary Dri nking Water Regulations; Radionuclides. Federal Register . Vol. 51, No. 189. p. 34836, September 30, 1986. USEPA 1986b. Guidelines for carcinogen risk assessment. Federal Register Vol. 51, No.185. p. 33992, September 24, 1986. USEPA. 1986c. National Primary and Secondary Drinking Water Regulations; Fluoride; Final Rule. Federal Register . Vol. 51, No. 63. p. 11396, April 2, 1986. USEPA. 1987. National Primary Drinking Water Regulations—Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants; Final Rule. Federal Register . Vol. 52, No. 130. p. 25690, July 8, 1987. USEPA. 1989a. National Primary Water Re gulations, Filtration, Di sinfection, Turbidity, Giardia Lamblia, Viruses, Legionella, Helterotrophic Bacteria Final Rule. Federal Register

. Vol. 54, No.124. p. 27485, June 29, 1989 USEPA. 1989b. National Primary and Secondary Drinking Water Regulations: Proposed Rule. Federal Register . Vol. 54, No. 97. p. 22062, May 22, 1989. USEPA. 1991a. IRIS, Selenium. Oral RfD. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0472.htm#reforal.

May 2009 Draft EPA document. Do not cite or distribute. 208USEPA. 1991b. Drinking Water; National Primar y Drinking Water Regulations; Monitoring for Volatile Organic Chemicals; MCLGs and MCLs for Aldicarb, Aldicar b Sulfoxide, Aldicarb Sulfone, Pentachlorophenol, and Barium; Final Rule. Federal Register . Vol. 56, No. 126. p. 30266, July 1, 1991. USEPA. 1991c. National Primary Drinking Wa ter Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for Unregulated Contaminants; National Primary Drinking Water Regulations Implementati on; National Secondary Drinking Water Regulations; Final Rule. Federal Register . Vol. 56, No. 30. p. 3526, January 30, 1991. USEPA. 1992. Drinking Wate r; National Primary Drinking Water Regulations—Synthetic Organic Chemicals and Inorganic Chemicals; National Primary Drinking Water Regulations Implementation; Final Rule. Federal Register . Vol. 57, No. 138. p. 31776, July 17, 1992. USEPA. 1993a. IRIS, Selenium. Cancer assessment. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0472.htm#carc. USEPA. 1993b. Reregistrati on Eligibility Decision (RED ): Glyphosate. EPA 738-R-93-014. September.
USEPA. 1995a. Reregistration Eligibility Deci sion (RED)--Diquat Dibromide . EPA Report 738-R-95-016. Washington, D.C.: Office of Prev ention, Pesticides and Toxic Substances. July 1995. Available on the Internet at: http://www.epa.gov/oppsrrd1/REDs/0288.pdf. USEPA. 1995b. Reregistration Eligibility Decision (RED)--Picloram . EPA Report 738-R95- 019. Washington, DC: Office of Prevention, Pe sticides, and Toxic Substances. August 1995. Available on the Internet at: http://www.epa.gov/oppsrrd1/REDs/0096.pdf.
USEPA. 1998a. Reregistration Eligibil ity Decision: Alachlor . Office of Prevention, Pesticides, and Toxic Substances. EPA 738-R-98-020. December.

May 2009 Draft EPA document. Do not cite or distribute. 209USEPA. 1998b. Small System Complian ce Technology List for the Non-Microbial Contaminants Regulated before 1996. Office of Water. EPA 815-R-98-002. September. USEPA 1998c. IRIS: Beryllium and Com pounds. Available on the Internet at: http://www.epa.gov/iris/subst/0012.htm. USEPA. 1998d. Toxicological review of He xavalent Chromium in support of summary information on the Integrated Risk Informati on System (IRIS). Washington, DC: Office of Research and Development, National Center for Environmental Assessment. August 1998. Available on the Internetat: http://www.epa.gov/ncea/ iris/toxreviews/0144-tr.pdf. USEPA. 1998e. Toxicological review of Trivalent Chromium in support of summary information on the Integrated Risk Informati on System (IRIS). Washington, DC: Office of Research and Development, National Center for Environmental Assessment. August 1998. Available on the Internetat: http://www.epa.gov/ncea/ iris/toxreviews/0028-tr.pdf.
USEPA. 2000a. Interim reregistration eligib ility decision (IRED)--Oxamyl . EPA Report 738- R-00-015. Washington, DC: Office of Prevention, Pesticides and Toxic Substances. October 2000. Available on the Internet at: http://www.epa.gov/pesticides/rer egistration/REDs/0253ired.pdf. USEPA. 2000b. IRIS, Benzene. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0276.htm. USEPA. 2000c. National Primary Drinking Wa ter Regulations; Radionuclides; Final Rule. Federal Register . Vol. 65, No. 236. p. 76707, December 7, 2000. USEPA. 2000d. Science Policy Council Handbook: Peer Review, 2nd Edition . EPA Report 100-B-00-001. Washington, DC: Office of Sc ience Policy, Office of Research and Development. December 2000. Available on the Internet at: http://www.epa.gov/OSA/spc/pdfs/prhandbk.pdf.

May 2009 Draft EPA document. Do not cite or distribute. 210USEPA. 2001a. HED Toxicology Chapter for Diquat Dibromide. Wa shington, DC: Office of Prevention, Pesticides and Toxic Substances. USEPA. 2001b. IRIS, Hexachlorocyclopent adiene. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0059.htm. USEPA. 2001c. National Primary Drinking Wate r Regulation; Arsenic a nd Clarifications to Compliance and New Source Contamin ants Monitoring; Final Rule. Federal Register . Vol. 66, No. 14. p. 6975, January 22, 2001. USEPA. 2001d. Public Health and Environm ental Radiation Protection Standards for Yucca Mountain, NV; Final Rule. Federal Register . Volume 66, Number 114. p. 32073, June 13,
2001. USEPA. 2002a. Glyphosate in/ on pasture and rangeland grasse s, Roundup Ready® wheat, and non-grass animal feeds. H ealth Effects Division (HED) Risk Assessment. PP#s 0F06130, 0F06195, and 0F06273. Barcode D280831. PC Codes 103601 & 417300. Case 292955. Submission S579658. Washington, DC: Office of Prevention, Pesticides, and Toxic Substances. USEPA. 2002b. IRIS, 1,1-Dichloroethylen e. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0039.htm. USEPA. 2002c. National Primary Drinking Water Regulations—Announcement of the Results of EPA’s Review of Existing Drinking Wate r Standards and Request for Public Comment; Proposed Rule. Federal Register . Vol. 67, No. 74. p. 19030, April 17, 2002. USEPA. 2002d. Report of the Food Quality Protection Act (FQPA) Tolerance Reassessment Progress and Risk Management Decision (TRE D): Diquat Dibromide. Washington, D.C.: Office of Prevention, Pesticides and Toxic Substances. April 2002. Available on the Internet at: http://www.epa.gov/ oppsrrd1/REDs/di quat_tred.pdf.

May 2009 Draft EPA document. Do not cite or distribute. 211USEPA. 2003a. Analytical Fe asibility Support Document for th e Six-Year Review of Existing National Primary Drinking Water Regulations (Reassessment of Feasibility for Chemical Contaminants). EPA 815-R-03-003. March 2003. USEPA. 2003b. EPA Protocol for Review of Existi ng National Primary Drinking Water Regulations . EPA Report 815-R-03-002. Washingt on, DC: Office of Ground Water and Drinking Water. June 2003. Available on the Internet at: http://www.epa.gov/safewater/standard/rev iew/pdfs/support_6yr_protocal_final.pdf. USEPA. 2003c. Exposure and Human HealthReassessment of 2,3,7,8-Tetrachlorodibenzo-pDioxin (TCDD) and Related Compounds. Prelim inary Review Draft. National Center for Environmental Assessment, Research and Development. USEPA. 2003d. IRIS, Xylenes. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0270.htm. USEPA. 2003e. National Primary Drinking Wa ter Regulations; Announ cement of Completion of EPA’s Review of Existing Drin king Water Standards; Notice. Federal Register . Vol. 68, No. 138. p. 42908, July 18, 2003. USEPA. 2004a. IRIS, 1,2-Dibromoethan e. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0361.htm. USEPA. 2004b. National Primary Drinking Water Regulations: Mi nor Corrections and Clarification to Drinking Water Regulations ; National Primary Drinking Water Regulations for Lead and Copper. Federal Register . Volume 69, Number 124. p. 38850, June 29, 2004.
USEPA. 2004c. Reregistration Eligibility Decision (RED)--Methoxychlor . EPA Report 738-R04-010. Washington, DC: Office of Prevention, Pe sticides, and Toxic Substances. June 2004. Available on the Internet at: http://www.epa.gov/oppsrrd1/ REDs/methoxychlor_red.htm.

May 2009 Draft EPA document. Do not cite or distribute. 212USEPA. 2005a. IRIS, Barium. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0010.htm. USEPA. 2005b. IRIS, Toluene. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0118.htm. USEPA. 2005c. Reregistrati on Eligibility Decision (RED)-- 2,4-D. EPA Report 738-R-05-002. Office of Prevention, Pesticides, and Toxic Subs tances. June 2005. Available on the Internet at: http://www.epa.gov/opps rrd1/REDs/24d_red.pdf. USEPA. 2005d. Reregistration Eligibility De cision (RED) for Endothall. EPA Report 738-R05-008. Office of Prevention, Pesticides and To xic Substances. September 2005. Available on the Internet at: http:// www.epa.gov/oppsrrd1/reregistratio n/REDs/endothall_red.pdf. USEPA. 2006a. Acetochlor/Alach lor: Cumulative Risk Assessment for the Chloroacetanilides. Washington, DC: Office of Pesticide Programs. March 8, 2006. Available on the Internet at: http://www.epa.gov/oppsrrd1/cumula tive/chloro_cumulative_risk.pdf. USEPA. 2006b. Addendum to the 2002 Lindane Reregist ration Eligibility Decision (RED)

. EPA Report 738-R-06-028. Washington, DC: Offi ce of Prevention, Pesticides, and Toxic Substances. July 2006. Ava ilable on the Internet at: http://www.epa.gov/oppsrrd1/RE Ds/lindane_red_addendum.pdf. USEPA. 2006c. Finalization of Atrazine IRED, and Completion of Tolerance Reassessment and Reregistration Eligibility Process. Washingt on, DC: Office of Prev ention, Pesticides, and Toxic Substances. April 2006. Available on the Internet at: http://www.epa.gov/oppsrrd1/REDs/atrazine_combined_docs.pdf. USEPA. 2006d. Interim Reregistration Eligibility Decision (IRED)--Carbofuran . EPA Report 738-R-06-031. Office of Prevention, Pestic ides, and Toxic Substances. August 2006.

May 2009 Draft EPA document. Do not cite or distribute. 213Available on the Internet at: http://www.epa.gov/oppsrrd1/reregi stration/REDs/carbofuran_ired.pdf. USEPA. 2006e. Lindane; Cancellation Order. Federal Register . Vol. 71, No. 239. p. 74905, December 13, 2006. USEPA. 2006f. National Primary Drinking Wate r Regulations: Ground Water Rule; Final Rule. Federal Register . Vol. 71, No. 216. p. 65574, November 8, 2006. USEPA. 2006g. National Primary Drinking Wate r Regulations: Long Term 2 Enhanced Surface Water Treatment Rule; Final Rule. Federal Register . Vol. 71, No. 3. p. 654, January 5,
2006. USEPA. 2006h. National Primary Drinking Wa ter Regulations: Stage 2 Disinfectants and Disinfection Byproducts Rule; Final Rule. Federal Register . Vol. 71, No. 2. p. 388, January 4, 2006. USEPA. 2006i. Reregistration Eligibility Decision (RED)--Simazine . EPA Report 738-R-06- 008. Washington, DC: Office of Prevention, Pes ticides, and Toxic Substances. April 2006. Available on the Internet at: http:/ /www.epa.gov/oppsrrd1/REDs/simazine_red.pdf. USEPA. 2007a. Advisory on EPA’s Assessmen ts of Carcinogenic Effects of Organic and Inorganic Arsenic: A Report of the US EPA Science Advisory Board (SAB). EPA-SAB-07- 008. June 2007. Available on the Internet at: http://yosemite.epa.gov/sab/sabprodu ct.nsf/EADABBF40DED2A0885257308006741EF/$Fil e/sab-07-008.pdf. USEPA. 2007b. Draft Toxicological Review of Acrylamide: In Support of Summary Information on the Integrated Risk Information System (IRIS). Federal Register . Vol. 72, No. 248. p. 73813, December 28, 2007.

May 2009 Draft EPA document. Do not cite or distribute. 214USEPA. 2007c. Integrated Risk Informati on System (IRIS); Announcement of 2008 Program; Notice. Federal Register . Vol. 72, No. 245. p. 72715, December 21, 2007. USEPA. 2007d. IRIS, 1,1,1-Trichloroethan e. Available on the Internet at: http://www.epa.gov/ncea/iris/subst/0197.htm. USEPA. 2007e. Unregulated Contaminant M onitoring Regulation (UCMR) for Public Water Systems; Revisions; Final Rule. Federal Register . Vol. 72, No, 2. p. 367, January 4, 2007. USEPA. 2007f. National Primary Drinking Wa ter Regulations for Lead and Copper: ShortTerm Regulatory Revisions and Clarifications; Final Rule. Federal Register . Vol. 72, No. 195. p. 57782, October 10, 2007. USEPA. 2007g. Safe Drinking Water Inform ation System/Federal version (SDWIS/FED) FY2006 Inventory Data. Available online at http://www.epa.gov/ogwdw000/da tabases/pivottables.html. USEPA. 2008a. Carbofuran; Proposed Tolerance Revocations; Proposed Rule. Federal Register . Vol. 73, No. 87. p. 44864, July 31, 2008. USEPA. 2008b. Drinking Water Contamin ant Candidate List 3—Draft; Notice. Federal Register . Vol. 73, No. 35. p. 9628, February 21, 2008. USEPA. 2009a. EPA Protocol for the Second Review of Existing National Primary Drinking Water Regulations (Updated). EPA Report 815-B-09-002. July 2009. USEPA. 2009b. Six-Year Review 2– Health Effects Assessment - Summary Report. EPA Report 822-R-09-006. July 2009. USEPA. 2009c. Analytical Fe asibility Support Document for th e Second Six-Year Review of Existing National Primary Drinking Water Regulations. EPA Report 815-B-09-003. July
2009.

May 2009 Draft EPA document. Do not cite or distribute. 215USEPA. 2009d. Occurrence Analysis for Pote ntial Source Waters for the Second Six-Year Review of National Primary Drinking Wate r Regulations. EPA Report 815-B-09-004. July
2009. USEPA. 2009e. Development of Estimated Quantitation Levels for the Second Six-Year Review of National Primary Drinking Wate r Regulations. EPA Report 815-B-09-005. July
2009. USEPA. 2009f. Analysis of Occurrence Data from the Second Six-Year Review of Existing National Primary Drinking Water Regulat ions. EPA Report 815-B-09-006. July 2009. USEPA. 2009g. Water Treatment Technology F easibility Support Document for Chemical Contaminants for the Second Six-Year Re view of National Primary Drinking Water Regulations. EPA Report 815-B-09-007. July 2009. USEPA. 2009h. Consideration of Other Regul atory Revisions in Support of the Second SixYear Review of the National Primary Dr inking Water Regulations. EPA Report 815-B-09- 008. July 2009. USEPA. 2009i. Carbofuran; Final Tolerance Revocations; Final Rule. Federal Register. Vol.74, No. 93. p. 23046, May 15, 2009.
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May 2009 Draft EPA document. Do not cite or distribute. 217Zaki, A., A. Ait Chaoui, et al. 2004. Impact of nitrate intake in drin king water on the thyroid gland activity in male rat. Toxicology Letters. v. 147, pp. 27-33. Zeegers, M.P., R.F. Selen, et al. 2006. Nitrate intake does not influence bladder cancer risk: the Netherlands cohort study. Environmenta l Health Perspectives. v. 114, pp. 1527-1531. Zhang, J. and X. Li. 1987. Chromium pollution of soil and water in Jinzhou. Journal of Chinese Preventive Medicine. v. 21, pp. 262-264.

Dated: [INSERT SIGNATURE DATE]

Lisa P. Jackson Administrator.

May 2009 Draft EPA document. Do not cite or distribute. 218