Wednesday,

April 17, 2002

Part III

Environmental

Protection Agency

40 CFR Part 141

National Primary Drinking Water

Regulations; Announcement of the Results

of EPA’s Review of Existing Drinking

Water Standards and Request for Public

Comment; Proposed Rule

19030 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

ENVIRONMENTAL PROTECTION

AGENCY

40 CFR Part 141

[FRL–7167–9]

RIN 2040–AD67

National Primary Drinking Water

Regulations; Announcement of the

Results of EPA’s Review of Existing

Drinking Water Standards and Request

for Public Comment

AGENCY: Environmental Protection

Agency (EPA).

ACTION: Review of regulations; request

for comments.

SUMMARY: The Safe Drinking Water Act

(SDWA) requires the United States

Environmental Protection Agency (EPA)

to conduct a periodic review of existing

National Primary Drinking Water

Regulations (NPDWRs). EPA is

requesting public comment on the

results of its review of 69 NPDWRs that

were established prior to 1997,

including 68 chemical NPDWRs and the

Total Coliform Rule (TCR). The

intended purpose of the review is to

identify those NPDWRs for which

current health risk assessments, changes

in technology, and/or other factors,

provide a health or technical basis to

support a regulatory revision that will

improve or strengthen public health

protection. Based on its review, and

pending an evaluation of public

comments, the Agency preliminarily

believes that the 68 chemical NPDWRs

remain appropriate at this time, and that

the TCR should be revised.

DATES: EPA must receive public

comments on this action by June 17,

2002.

ADDRESSES: Please send your comments

to the W–01–14 Comments Clerk.

Submit electronic comments to: owdocket@epa.gov. Written comments

should be mailed to: Water Docket (MC–

4101), U.S. Environmental Protection

Agency, 1200 Pennsylvania Avenue,

NW., Washington, DC, 20460. Hand

deliveries should be delivered to EPA’s

Water Docket at East Tower Basement

(EB Room 57), Waterside Mall, 401 M

Street, SW., Washington, DC, 20460.

You may contact the docket at (202)

260–3027 between 9 a.m. and 3:30 p.m.

Eastern Time, Monday through Friday.

Comments may be submitted

electronically. See SUPPLEMENTARY

INFORMATION for file formats and other

information about electronic filing and

docket review.

FOR FURTHER INFORMATION CONTACT: For

technical inquiries contact: Judy

Lebowich, (202) 564–4884, e-mail:

lebowich.judy@epa.gov, or Wynne

Miller, (202) 564–4887, e-mail:

miller.wynne@epa.gov. 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.

SUPPLEMENTARY INFORMATION:

How Should I Submit Comments on

This Action?

EPA will accept written or electronic

comments (please do not send both).

EPA prefers electronic comments.

Commenters should use a separate

paragraph for each issue discussed. No

facsimiles (faxes) will be accepted.

Commenters who want EPA to

acknowledge receipt of their comments

should also send a self-addressed,

stamped envelope. If you submit written

comments, please submit an original

and three copies of your comments and

enclosures (including references).

Electronic comments must be

submitted in WordPerfect 8 (or an older

version) or ASCII file format.

Compressed or zipped files will not be

accepted. You may file electronic

comments on this action online at many

Federal Depository Libraries.

The Agency’s response-to-comments

document for the final decision will

address the comments received on this

action, and the response-to-comments

document will be made available in the

docket.

How Can I Obtain Materials in the

Docket?

The docket is available for inspection

from 9:00 a.m. to 4:00 p.m., Monday

through Friday, excluding legal

holidays, at the Water Docket, East

Tower Basement (EB Room 57),

Waterside Mall, USEPA, 401 M Street,

SW; Washington, DC. For access to

docket (Docket Number W–01–14)

materials, please call (202) 260–3027

between 9:00 a.m. and 3:30 p.m.,

Eastern Time, Monday through Friday,

to schedule an appointment.

Does This Action Apply to My Public

Water System?

This action itself does not impose any

requirements on anyone. Instead, it

notifies interested parties of EPA’s

preliminary revise/not revise decisions

for 69 NPDWRs.

Abbreviations and Acronyms Used in

This Action

>—greater than

2,4-D—2,4-dichlorophenoxyacetic acid

AA—activated alumina

AI—adequate intake

ASDWA—Association of State Drinking

Water Administrators

ATSDR—Agency for Toxic Substances

and Disease Registry

AWWA—American Water Works

Association

BAT—best available technology

BMD—benchmark dose

bw—body weight

CCL—Contaminant Candidate List

CFR—Code of Federal Regulations

CMR—Chemical Monitoring Reform

CWS—community water system

DBCP—1,2-dibromo-3-chloropropane

DBPR—Disinfectants and Disinfection

Byproducts Rule

DEHA—di(2-ethylhexyl)adipate

DEHP—di(2-ethylhexyl)phthalate

DRI—dietary reference intake

DWEL—drinking water equivalent level

EDB—ethylene dibromide

EPA—U.S. Environmental Protection

Agency

EPTDS—entry points to a distribution

system

FR—Federal Register

GAC—granular activated carbon

GC/MS—gas chromatography/mass

spectrometry

HHS—Department of Health and

Human Services

HPC—heterotrophic plate count

I—daily drinking water intake

IESWTR—Interim Enhanced Surface

Water Treatment Rule

IRIS—Integrated Risk Information

System

LCR—Lead and Copper Rule

LOAEL—lowest-observed-adverse-effect

level

LT1ESWTR—Long-Term 1 Enhanced

Surface Water Treatment Rule

LT2ESWTR—Long-Term 2 Enhanced

Surface Water Treatment Rule

MCL—maximum contaminant level

MCLG—maximum contaminant level

goal

M/DBP—Microbial/Disinfection

Byproducts

MDL—method detection limit

MF—modifying factor

MFL—million fibers per liter

mg/kg/day—milligrams per kilogram of

body weight per day

mg/L—milligrams per liter

MSRC—Mercury Study Report to

Congress

MTD—maximum tolerated dose

N—nitrogen

NAS—National Academy of Sciences

NCOD—National Drinking Water

Contaminant Occurrence Database

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19031

NDWAC—National Drinking Water

Advisory Council

NIPDWR—National Interim Primary

Drinking Water Regulation

NOAEL—no-observed-adverse-effect

level

NPDWR—National Primary Drinking

Water Regulation

NRC—National Research Council

NTNCWS—non-transient, noncommunity water system

NTP—National Toxicology Program

NWIS—National Water Information

System

OGWDW—Office of Ground Water and

Drinking Water

OPP—Office of Pesticide Programs

OW—Office of Water

PAC—powdered activated carbon

PCBs—polychlorinated biphenyls

POU—point-of-use

ppm—part per million

PQL—practical quantitation level

PTA—packed tower aeration

PWS—public water system

RDA—recommended dietary allowance

RfD—reference dose

RO—reverse osmosis

RSC—relative source contribution

SAB—Science Advisory Board

SDWA—Safe Drinking Water Act

SDWIS—Safe Drinking Water

Information System

SMCL—secondary maximum

contaminant level

SOC—synthetic organic chemical

SWTR—Surface Water Treatment Rule

TCR—Total Coliform Rule

TNCWS—transient, non-community

water system

TT—treatment technique

TTHM—total trihalomethanes

UF—uncertainty factor

UL—tolerable upper intake level

URCIS—Unregulated Contaminant

Information System

VOC—volatile organic chemical

WS—water supply

Table of Contents

I. Background and Summary of Today’s

Action

A. What are the Statutory Requirements for

the Six-Year Review?

B. What is the Schedule for Reviewing

Existing NPDWRs?

II. Stakeholder Involvement in the Six-Year

Review Process

A. How Have Stakeholders Been Involved

in the Review Process?

B. How Does EPA Plan to Involve the

Science Advisory Board (SAB)?

III. Regulations Included in the Six-Year

Review

IV. EPA’s Protocol for Reviewing the

NPDWRs Included in Today’s Action

A. What was EPA’s Review Process?

1. Initial Technical Review

2. In-Depth Technical Review

B. How Did EPA Review the Chemical

NPDWRs?

1. Health Effects

2. Analytical Feasibility

3. Treatment Feasibility

4. Other Regulatory Revisions

5. Occurrence and Exposure Analysis

6. Economic Considerations

C. How Is EPA Reviewing the Total

Coliform Rule?

D. How Did EPA Factor Children’s Health

Concerns into the Review?

V. EPA’s Preliminary Decisions Based on

its Review of NPDWRs Included in

Today’s Action

A. What Preliminary Decisions Has EPA

Made Regarding the Chemical NPDWRs?

1. Acrylamide

2. Alachlor

3. Antimony

4. Asbestos

5. Atrazine

6. Barium

7. Benzene

8. Benzo[a]pyrene

9. Beryllium

10. Cadmium

11. Carbofuran

12. Carbon Tetrachloride

13. Chlordane

14. Chromium

15. Copper

16. Cyanide

17. 2,4-D (2,4-Dichlorophenoxyacetic Acid)

18. Dalapon (2,2-Dichloropropionic Acid)

19. 1,2-Dibromo-3-chloropropane (DBCP)

20. 1,2-Dichlorobenzene (oDichlorobenzene)

21. 1,4-Dichlorobenzene (pDichlorobenzene)

22. 1,2-Dichloroethane (Ethylene

Dichloride)

23. 1,1-Dichloroethylene

24. cis-1,2-Dichloroethylene

25. trans-1,2-Dichloroethylene

26. Dichloromethane (Methylene Chloride)

27. 1,2-Dichloropropane

28. Di(2-ethylhexyl)adipate (DEHA)

29. Di(2-ethylhexyl)phthalate (DEHP)

30. Dinoseb

31. Diquat

32. Endothall

33. Endrin

34. Epichlorohydrin

35. Ethylbenzene

36. Ethylene Dibromide (EDB; 1,2-

Dibromoethane)

37. Fluoride

38. Glyphosate

39. Heptachlor

40. Heptachlor Epoxide

41. Hexachlorobenzene

42. Hexachlorocyclopentadiene

43. Lead

44. Lindane (-Hexachlorocyclohexane)

45. Mercury (Inorganic)

46. Methoxychlor

47. Monochlorobenzene (Chlorobenzene)

48. Nitrate (as N)

49. Nitrite (as N)

50. Oxamyl (Vydate)

51. Pentachlorophenol

52. Picloram

53. Polychlorinated Biphenyls (PCBs)

54. Selenium

55. Simazine

56. Styrene

57. 2,3,7,8-TCDD (Dioxin)

58. Tetrachloroethylene

59. Thallium

60. Toluene

61. Toxaphene

62. 2,4,5-TP (Silvex; 2,4,5-

Trichlorophenoxypropionic Acid)

63. 1,2,4-Trichlorobenzene

64. 1,1,1-Trichloroethane

65. 1,1,2-Trichloroethane

66. Trichloroethylene

67. Vinyl Chloride

68. Xylenes (Total)

B. What Preliminary Decision Has EPA

Made Regarding the Total Coliform Rule?

1. Background

2. Technical Reviews

3. Preliminary Decision

VI. Request for Comments

A. On Which Issues is EPA Soliciting

Public Comment?

B. Request for Comments on Use of Plain

Language

VII. EPA’s Next Steps

VIII. References

Appendix A: Background on the Calculation

of MCLG and Cancer Classification

System

List of Tables

Table III–1: Pre-1997 NPDWRs Included in

Today’s Action

Table III–2: NPDWRs Not Included in

Today’s Action

Table IV–1: Summary of the Outcome of the

Six-Year Health Effects Review

Table IV–2: Chemical NPDWRs Included in

the Analytical Feasibility Reassessment

and the Result of that Assessment

Table IV–3: Chemical NPDWRs Included in

the Treatment Feasibility Analysis

Table V–1: Preliminary Revise/Not Revise

Decisions for the 68 Chemical NPDWRs

and TCR

Table V–2: Benzene Occurrence

Table V–3: Beryllium Occurrence

Table V–4: Chlordane Occurrence

Table V–5: Chromium Occurrence

Table V–6: 1,2-Dibromo-3-chloropropane

Occurrence

Table V–7: Dichloromethane Occurrence

Table V–8: 1,2-Dichloropropane Occurrence

Table V–9: Heptachlor Occurrence

Table V–10: Heptachlor Epoxide Occurrence

Table V–11: Hexachlorobenzene Occurrence

Table V–12: Oxamyl Occurrence

Table V–13: Picloram Occurrence

Table V–14: Toxaphene Occurrence

Table V–15: 1,1,2-Trichloroethane

Occurrence

Table VI–1: Issues on Which EPA is

Requesting Public Comment or Data

Table A–1: Cancer Classification Systems

Used by EPA

List of Figures

Figure 1: Overview of the Protocol for the

Revise/Not Revise Decision

Figure 2: Distribution of State Rankings:

Manufacturing Establishments per

Square Mile vs. Total Farm Agricultural

Chemical Expenses

Figure 3: Geographic Distribution of the 16-

State Cross-Section Used for Occurrence

Analysis

19032 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

I. Background and Summary of Today’s

Action

A. What Are the Statutory Requirements

for the Six-Year Review?

Under the SDWA, as amended in

1996, EPA must periodically review

existing national primary drinking water

regulations (NPDWRs) and, if

appropriate, revise them. Section

1412(b)(9) of SDWA states:

The Administrator shall, not less often

than every 6 years, review and revise, as

appropriate, each national primary drinking

water regulation promulgated under this title.

Any revision of a national primary drinking

water regulation shall be promulgated in

accordance with this section, except that

each revision shall maintain, or provide for

greater, protection of the health of persons.

Pursuant to the SDWA 1996

Amendments, EPA developed a

systematic approach, or protocol, for the

review of NPDWRs discussed in today’s

action. EPA has applied the protocol

discussed in section IV of today’s action

to the Agency’s initial Six-Year Review

of NPDWRs for total coliforms and 68

inorganic and organic chemicals,

published prior to the SDWA 1996

Amendments (i.e., pre-1997 NPDWRs).

Section III of today’s action identifies

these NPDWRs and section V of today’s

action contains a summary of the review

findings for each of these 69 NPDWRs

(see Table III–1).

While the Agency expects that

modifications to the protocol will be

made in subsequent six-year reviews to

address changing circumstances, the

Agency expects to use the framework

developed for the current review as the

starting point. EPA, therefore, is seeking

public comment on the protocol that has

been applied to the current review.

B. What Is the Schedule for Reviewing

Existing NPDWRs?

EPA plans to publish its final findings

with respect to the initial review of

these 69 NPDWRs in the Federal

Register (FR) in the August 2002 time

frame.

In addition to these 69 NPDWRs,

there are additional pre-1997 NPDWRs,

which are being or have been reviewed

separately from today’s action. Section

III explains how the Agency plans to

satisfy the Six-Year Review requirement

for those regulations. In most cases, EPA

has performed or is performing the

review in conjunction with recent or

ongoing rulemakings. NPDWRs

published after the 1996 SDWA

Amendments will be reviewed as a part

of the 2002–2008 review cycle.

II. Stakeholder Involvement in the SixYear Review Process

A. How Have Stakeholders Been

Involved in the Review Process?

Stakeholders include:

• The general public;

• Congress;

• Other Federal agencies;

• State, Tribal, and local officials;

• Public health/health care providers;

• Public interest groups;

• Public water suppliers;

• National trade associations;

• Environmental groups;

• Manufacturers; and

• Agricultural producers.

EPA involved stakeholders by:

holding a stakeholder meeting;

participating in national meetings,

workshops, and technical forums;

meeting informally with associations

and technical experts; posting

information on the Office of Ground

Water and Drinking Water’s (OGWDW’s)

web page ( www.epa.gov/safewater/);

and publishing this FR notice on the

Six-Year Review.

EPA invited representatives from

State and Tribal communities, public

water systems (PWSs), public health

organizations, academia, environmental

and public interest groups, engineering

firms, and other stakeholders to a

stakeholder meeting in Washington, DC,

in November 1999 (64 FR 55711,

October 14, 1999 (USEPA, 1999c)).

Approximately 50 participants attended,

including representatives from the

invited groups. EPA discussed its

preliminary strategy for the Six-Year

Review and invited stakeholder

comment. Stakeholders generally agreed

that EPA had identified the appropriate

key elements for the review; however, in

some cases, stakeholders suggested that

EPA needed to be more proactive in

seeking out new information that might

affect the regulatory decision (USEPA,

1999e). For more detailed information

about this stakeholder meeting, the

docket for this action (Docket Number

W–01–14) contains the stakeholder

meeting discussion papers, the agenda,

the participant list, presentation

materials, and an executive meeting

summary which includes the specific

comments and questions posed by

stakeholders. The executive meeting

summary is also available on EPA’s

drinking water web page, http://

www.epa.gov/safewater/ccl/

novmtg.html.

In the Spring of 2000, the National

Drinking Water Advisory Council

(NDWAC) formed a working group to

develop recommendations regarding the

process the Agency should apply to

conduct a periodic and systematic

review of existing NPDWRs. The

Working Group held two meetings and

a conference call during June through

September 2000 (USEPA, 2000b;

USEPA, 2000c; USEPA, 2000d). The

NDWAC approved the Working Group’s

recommendations in November 2000

and formally provided them to EPA in

December 2000 (NDWAC, 2000). The

NDWAC recommended that EPA’s

review include consideration of five key

elements, as appropriate: health effects,

analytical and treatment feasibility,

implementation-related issues,

occurrence and exposure, and economic

impacts. The NDWAC suggested that the

Agency conduct an initial screening

review of each NPDWR to identify

potential candidates for an in-depth

analysis. As discussed in more detail in

section IV of today’s action, EPA has

followed the general protocol

recommended by the NDWAC.

In addition to the November 1999

stakeholder meeting and consultation

with the NDWAC, EPA representatives

have delivered presentations at a variety

of meetings held by other organizations,

including: two American Water Works

Association (AWWA) Technical

Advisory Workgroup meetings, one held

in February 2001 in Washington, DC,

and one held in February 2002 in San

Diego, CA; a meeting held by the

Association of State Drinking Water

Administrators (ASDWA) in March

2001 in Alexandria, VA; and the annual

AWWA meeting held in Washington,

DC in June 2001. At each of these

meetings, stakeholders were given the

opportunity to comment on the protocol

by which EPA was planning to perform

the review of existing NPDWRs. EPA

received valuable input from

stakeholders on the planned protocol.

B. How Does EPA Plan To Involve the

Science Advisory Board (SAB)?

EPA plans to consult with the SAB

Drinking Water Committee on today’s

action. The Agency will request their

review and comment on whether the

protocol EPA developed based on the

NDWAC recommendations was

consistently applied and appropriately

documented.

III. Regulations Included in the SixYear Review

Table III–1 lists the pre-1997 NPDWRs

covered by today’s action and the

rulemaking by which they were

originally promulgated. Table III–2 lists

the NPDWRs not covered by today’s

action. These include the remaining pre1997 NPDWRs which are being or have

already been reviewed in separate

actions and the NPDWRs promulgated

after the 1996 SDWA Amendments. The

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NPDWRs listed in Table III–2 will be

included in the 2002–2008 review

round. Section V of today’s action

summarizes the results of the review of

68 pre-1997 chemical NPDWRs and the

NPDWR for total coliforms.

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1See: 50 FR 46880, November 13, 1985 (USEPA,

1985); 52 FR 25690, July 8, 1987 (USEPA, 1987); 54

FR 22062, May 22, 1989 (USEPA, 1989a).

BILLING CODE 6560–50–C

IV. EPA’s Protocol for Reviewing the

NPDWRs Included in Today’s Action

A. What Was EPA’s Review Process?

The document, ‘‘EPA Protocol for the

Review of Existing National Primary

Drinking Water Regulations’’ (USEPA,

2002f), contains a detailed description

of the process the Agency used to

review the 69 NPDWRs discussed in

today’s action. EPA’s primary goal was

to identify and prioritize candidates for

regulatory revision in order to target

those revisions that are most likely to

result in an increased level of public

health protection and/or result in

substantial cost savings while

maintaining the level of public health

protection. This section provides an

overview of the review process. Sections

IV.B and IV.C of today’s action provide

a more detailed description of how EPA

applied the process to the review of 68

chemical NPDWRs and the TCR,

respectively.

EPA applied the following basic

principles to the review process:

• Health effects, analytical feasibility,

treatment data, and analyses underlying

existing regulations remain adequate

and relevant, except in those instances

where reliable, peer-reviewed, new data

are available that indicate a need to reevaluate an NPDWR (e.g., where a

change in health risk assessment has

occurred).

• If new data were available, EPA

determined whether changes in existing

standards were warranted. For example,

in determining whether there was a

change in analytical feasibility, the

Agency applied the current policy and

procedures for calculating the practical

quantitation level for drinking water

contaminants.1

• EPA was unable to complete

evaluation of certain new data within

the time available for the review. For

example, if a new health risk assessment

for a contaminant was not completed

during the review cycle, EPA generally

made a ‘‘not revise’’ decision on the

rationale that it was not appropriate to

revise the regulation while the

assessment was ongoing. When an

updated assessment is completed, EPA

will review the update and any new

conclusions or additional information

associated with the contaminant during

the next review cycle. The Agency may

make a determination to revise a

particular NPDWR before August 2008

where justified by new public health

risk information.

• During the review, EPA identified

areas where information is inadequate

or unavailable (data gaps) and is needed

before an NPDWR may be considered as

a candidate for revision. Where the

Agency has been unable to fill such gaps

during the review process, today’s

action provides information about the

data gaps so that further research and

data collection can be considered as part

of the second review cycle. For

example, the review may identify a need

to better understand new treatment

technologies. Such an information gap

will need to be considered in the

context of EPA’s overall OGWDW

research strategy.

• During the review process, the

Agency did not consider potential

regulatory revisions that were already

the subject of other rulemaking

activities.

• EPA applied the Agency’s peer

review policy (USEPA, 2000i), where

appropriate, to any new analyses.

Figure 1 provides an overview of the

review process. To most efficiently

utilize limited resources and assure

19038 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

continued public health protection, the

Agency conducted the review in two

phases: (1) an initial technical review of

all 69 NPDWRs discussed in today’s

action; and (2) an in-depth technical

evaluation of those NPDWRs identified

during the initial review as potential

candidates for revision.

1. Initial Technical Review

The initial review phase included

these three screening and general

evaluation steps:

• Health effects review. Identify

NPDWRs for which the Agency has

revised health risk assessments that

indicate possible changes to the

maximum contaminant level goal

(MCLG) and perhaps to the maximum

contaminant level (MCL);

• Current technology review. Identify

NPDWRs where improvements in

analytical measurement or treatment

feasibility might allow the MCL to be

established closer to the MCLG, or

where adjustments in treatment

technique (TT) requirements might be

appropriate; and/or

• Other regulatory revisions review.

Identify NPDWRs where adjustments to

system monitoring and reporting

requirements might be appropriate and

where such changes are not already

being considered as a part of another

activity.

EPA generally determined that an

NPDWR was not a candidate for

revision after the initial review if a

health risk assessment was in process or

was initiated as a result of the review,

since the Agency does not believe it is

appropriate to revise the NPDWR while

a health risk assessment is underway.

The Agency also determined that an

NPDWR was not a candidate for

revision after the initial screening if

none of the initial screening analyses

identified a health or technological basis

for a regulatory revision.

2. In-Depth Technical Review

The Agency subjected the remaining

NPDWRs to more in-depth technical

analyses. If the initial review indicated

a possible revision to the MCLG/MCL,

EPA further considered health and

technology factors that might affect the

development of a revised MCLG/MCL or

revised MCLG/TT requirements. The

Agency also estimated potential

occurrence and exposure at PWSs at

concentrations of regulatory interest for

the chemical NPDWRs and conducted a

qualitative evaluation of economic

impacts. EPA based the qualitative

economic evaluation primarily on

available occurrence and exposure data,

to determine whether the possible

revision was likely to present an

opportunity for significant gains in

public health protection and/or

significant cost savings that could be

realized without lessening the level of

public health protection.

In the case of three contaminants,

EPA identified data gaps that could not

be filled during the current review

cycle. Figure 1 shows the identification

of data gaps as the final step in the

review; however, in some instances,

data gaps were identified during earlier

steps in the process. Where this

occurred, EPA did not conduct some or

all of the remaining analyses. If the

Agency identified data gaps, EPA

determined not to revise the NPDWR.

After completing these

comprehensive analyses, EPA identified

those NPDWRs that remain appropriate

at this time, and those NPDWRs that

may be appropriate for revision.

Today’s action discusses the Agency’s

preliminary determinations and seeks

public comment on them. After

considering the public comments

received and any new peer-reviewed

data that may become available to the

Agency, EPA will publish its final

decision in the FR.

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BILLING CODE 6560–50–C

B. How Did EPA Review the Chemical

NPDWRs?

This section describes the specific

technical reviews that EPA conducted

for the chemical NPDWRs.

1. Health Effects

The document, ‘‘Six-Year Review—

Chemical Contaminants—Health Effects

Technical Support Document’’ (USEPA,

2002i), describes how EPA reviewed the

chemical contaminants discussed in

today’s action and provides the results

of the health effects technical review.

The principal objective of the health

effects review was to identify each

contaminant for which a new health risk

assessment indicated that a change in

MCLG might be appropriate. For most of

19040 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

2A zero MCLG is already considered protective

of public health and new information on

developmental and reproductive effects would not

affect the MCLG. However, for those NPDWRs with

a zero MCLG, EPA reviewed available information

to inquire whether data show a nonlinearity of the

dose-response; EPA did not find any data to support

such a mode of action (USEPA, 2002i).

the chemical NPDWRs discussed in

today’s action, the MCLG is derived

from the cancer classification and/or the

reference dose (RfD), as described in

Appendix A. Therefore, the health

effects technical review focused on

whether there has been a change to

these values. The Agency reviewed the

results of health risk assessments

completed under the following

programs to determine if there had been

a change in critical effect or doseresponse pattern that indicates the

possible need for an MCLG revision.

• EPA Integrated Risk Information

System (IRIS);

• EPA Office of Pesticide Programs

(OPP);

• Agency for Toxic Substances and

Disease Registry (ATSDR); and

• National Academy of Sciences

(NAS).

Table IV–1 reflects the outcome of the

health effects review for the 68 chemical

NPDWRs discussed in today’s action.

EPA placed each contaminant into one

of the following categories.

• New risk assessment 1997 or later.

An IRIS, OPP, ATSDR, and/or NAS

assessment has been completed in 1997

or later. These assessments have

considered developmental and

reproductive toxicity as a part of the

assessment. The Agency considers these

assessments to be recent enough that it

is not necessary to conduct a literature

search to identify any additional

relevant studies that have become

available on the toxicological effects of

these contaminants. In cases where the

health risk assessment resulted in a

change in the critical effect, or the doseresponse pattern for a regulated

contaminant, and where that change

could result in a change in the MCLG,

EPA subjected the NPDWR to more indepth analysis as a part of the review

process. Where recent assessments were

conducted by an agency other than EPA

and new developmental and

reproductive data were identified, EPA

initiated an update of its assessment.

• New risk assessment since

promulgation, but prior to 1997. An

IRIS, OPP, ATSDR, and/or NAS

assessment has been completed since

the NPDWR was promulgated but prior

to 1997. None of these assessments

reflected a change in RfD or cancer

classification. However, since these

assessments may not have specifically

considered developmental and

reproductive health effects, EPA

conducted a full literature search,

including developmental and

reproductive toxicity, for those

NPDWRs with non-zero MCLGs to

identify any relevant studies that might

affect the MCLGs of these contaminants.

EPA did not identify any chemicals for

which developmental or reproductive

effects might now be the critical effect.2

• Agency risk assessment in process

and not completed as of February 2002.

The Agency currently is conducting a

health risk assessment for the

contaminant. That assessment will

consider all relevant studies that have

become available on the toxicology of

the contaminant, including

developmental and reproductive

toxicity. EPA does not believe it is

appropriate to revise the MCLG for these

contaminants at this time.

• Original NPDWR risk assessment.

No health risk assessment has been

conducted since promulgation of the

NPDWR. The Agency conducted a full

toxicological literature search, including

developmental and reproductive

toxicity, for each of these contaminants

with non-zero MCLGs (see footnote 2) to

identify new toxicological studies that

might have an impact on the MCLGs. In

a few instances, the results of the

literature search indicate that it might

be appropriate to revise the RfD and/or

cancer classification. EPA initiated

updates to the risk assessments for these

chemicals, and established a schedule

for their completion. EPA does not

believe it is appropriate to revise the

MCLG at this time.

Thus, only contaminants in the first

category might be potential candidates

for an MCLG revision at this time.

The initial health effects review

identified beryllium, oxamyl, and

picloram as potential candidates for an

MCLG revision, depending on the

outcome of the more in-depth health

effects review and on the other technical

analyses (e.g., analytical feasibility,

treatment, occurrence, etc.). The initial

health effects review also identified

changes in the RfD for chromium as

well as data gaps with respect to its

potential carcinogenicity via oral

ingestion. EPA also identified health

effects-related data gaps for fluoride.

Contaminants in any of the categories

except the third (risk assessment in

process) may be candidates for a new

assessment if the initial health effects

review identified new studies that may

affect the contaminant’s RfD or cancer

classification. EPA has initiated a new

assessment for cyanide, di(2-

ethylhexyl)adipate, and thallium as a

result of the health effects technical

review.

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2. Analytical Feasibility

Since EPA has a process in place to

approve new analytical methods for

drinking water contaminants, the actual

review and approval of potential new

methods are outside the scope of the

Six-Year Review protocol. EPA

recognizes 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 quantify contaminants at

lower levels. For this reason, EPA

evaluated whether there have been

changes in analytical feasibility for a

subset of the 68 chemical NPDWRs

discussed in today’s action. The

document, ‘‘Analytical Feasibility

Support Document for the Six-Year

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3Although they have a zero MCLG, EPA excluded

lead and epichlorohydrin from the analytical

feasibility review since they are TT rules and do not

have an MCL.

4Using WS data to derive the PQL for chemical

NPDWRs involves determining the concentration of

an analyte at which 75 percent of EPA Regional and

State laboratories achieve results within a specified

acceptance window (see 54 FR 22062 at 22100, May

22, 1989 (USEPA, 1989a)). In re-evaluating more

recent WS data for the Six-Year Review, sufficient

data were not available around the 75 percent

critierion to actually recalculate the PQL. However,

if the passing rates for the EPA Regional and State

laboratories exceeded 80 to 85 percent at spike

concentrations close to the current PQL, this

information was considered to be indicative of a

possible change in the PQL. If data indicated a

possible change in the PQL, EPA then evaluated the

distribution of the analytical methods used to

analyze the spike samples in the WS studies.

Evaluation of the method usage over time allowed

EPA to determine the analytical methods that

appear to be the most widely used for the analysis

of a particular contaminants. Knowledge of which

analytical methods are the most widely used, along

with the MDL for these methods, and a 10 times

MDL multiplier allowed EPA to estimate where the

potential lower limit of quantitation may lie today.

This estimated PQL was used as a value in the

occurrence analysis to help the Agency determine

if there may be a significant gain in public health

protection if EPA were to consider gathering the

information needed to recalculate the PQL.

Review of Existing National Primary

Drinking Water Regulations

(Reassessment of Feasibility for

Chemical Contaminants)’’ (USEPA,

2002d), describes the process EPA used

to evaluate possible changes in

analytical feasibility and provides the

results of the analytical feasibility

analyses. The purpose of these analyses

is to determine whether changes in the

practical quantitation level (PQL) are

possible in those instances where the

MCL is limited, or might be limited, by

analytical feasibility. EPA uses the PQL

to estimate the level at which

laboratories can routinely measure a

chemical contaminant in drinking

water. Historically, EPA has used two

main approaches to determine a PQL for

SDWA analytes: (1) data from water

supply (WS) studies, the preferred

alternative when sufficient WS data are

available; or (2) a multiplier method, in

which the PQL is calculated by

multiplying the EPA-derived method

detection limit (MDL) by a factor of 5 or

10 (50 FR 46880, November 13, 1985

(USEPA, 1985); 52 FR 25690, July 8,

1987 (USEPA, 1987); 54 FR 22062, May

22, 1989 (USEPA, 1989a)).

EPA performed the analytical

feasibility analyses under two

circumstances. First, for those

contaminants where the MCL is

currently limited by analytical

feasibility (i.e., the MCL is set at the

PQL) and the MCLG is still appropriate,

EPA evaluated the currently approved

methods for those contaminants and

available WS data to determine whether

it might be possible to lower the PQL

and hence set an MCL that is closer to

the MCLG. Section V of today’s action

provides the results of the analytical

feasibility review of 11 contaminants

that are not currently undergoing a

health risk assessment and for which

the MCL was limited by analytical

feasibility. These 11 contaminants

include 10 with zero MCLGs 3 and 1

with a non-zero MCLG. Of these 11,

EPA identified 10 where the data

indicate it might be possible to set a

lower PQL (see Table IV–2). Although

the data are indicative of a lower PQL

for these 10, they are not definitive and

considered to be insufficient to support

an actual recalculation at this time. To

determine whether it was worthwhile to

gather more definitive data for PQL

recalculation, EPA estimated what the

potentially lower PQL could be for these

10 analytes and used these values in the

occurrence and exposure analyses.4 As

discussed for specific contaminants in

section V of today’s action, EPA believes

that a negligible gain in public health

exists at the possibly lower PQL for 9 of

these 10 NPDWRs. The results of the

occurrence and exposure analysis for

dichloromethane, using the possibly

lower PQL as a concentration value,

indicate that it may be appropriate to

consider gathering data to recalculate a

more definitive PQL for this analyte.

The second circumstance under

which EPA re-evaluated the PQL was

for three of the four contaminants

identified under the health effects

technical review as potential candidates

for revision (see Table IV–2). These

three contaminants were evaluated to

determine if any potential MCL revision

would be limited by analytical

feasibility. Based on this review, EPA

believes that analytical feasibility may

be a limiting factor for revising the MCL

for oxamyl (see section V.A.50 of

today’s action for a more detailed

discussion). The Agency believes that

analytical feasibility would not be a

limiting factor for the remaining two

contaminants identified by the health

effects review as having potential

changes in their MCLG (i.e., beryllium

and chromium).

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3. Treatment Feasibility

An NPDWR either identifies the Best

Available Technology (BAT) for meeting

an MCL, or establishes enforceable

treatment technique (TT) requirements.

Currently, for all the chemical NPDWRs

covered in today’s action that include

an MCL, the MCL is set equal to either

the MCLG or the PQL. None of these

MCLs are currently limited by treatment

feasibility. Thus, as a part of the SixYear Review process, EPA only needed

to review available information on

treatment technologies if either of the

following conditions applied:

• The health effects technical review

identified a potential change to the

MCLG/MCL (applied to 4 NPDWRs); or

• A health risk assessment is not in

process for the contaminant and one of

the following two conditions apply:

(1) the analytical feasibility review

identified a possible change to the PQL

and thus to the MCL (applied to 10

NPDWRs); or

(2) the NPDWR is a TT-type rule

(applied to 3 NPDWRs).

The draft EPA document, ‘‘Water

Treatment Technology Feasibility

Support Document for Chemical

Contaminants; In Support of EPA SixYear Review of National Primary

Drinking Water Regulations’’ (USEPA,

2002k), describes the process EPA used

to evaluate treatment feasibility, where

appropriate, for the chemical NPDWRs

discussed in today’s action and provides

the results of these analyses. As a part

of this review, EPA utilized the same

sources that have been the primary

resources in development of EPA

regulations and guidance, including

published EPA treatment reports, peerreviewed journals, and other technology

sources, as well as information received

from EPA stakeholders.

a. MCL-type Rules. EPA evaluated

existing treatment technology

information for 14 MCL-type NPDWRs

(see Table IV–3) to determine whether

treatment feasibility would be a limiting

factor if EPA were to lower the MCL. In

addition and where appropriate, EPA

evaluated the likelihood that systems

would discontinue existing treatment if

EPA were to raise the MCL.

Based upon this preliminary

evaluation, the Agency believes that

treatment capabilities would be

adequate to support a lower MCL value,

if EPA were to revise the MCL for any

of the contaminants for which a lower

MCL may be appropriate (USEPA,

2002k). Treatment technologies

specified as BAT within the current

NPDWR, and small system compliance

technologies which were specified by

EPA in 1998 (USEPA, 1998a) are

considered to be efficient and practical

for implementation at PWSs. However,

if EPA were to determine that it is

appropriate to revise any of these

NPDWRs, it would undertake a more

thorough review of treatment feasibility,

including a consideration of costs, to

19044 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

5Refer to the document, ‘‘Water Treatment

Technology Feasibility Support Document for

Chemical Contaminants; In Support of EPA SixYear Review of National Primary Drinking Water

Regulations’’ (USEPA, 2002k) for a description of

these research needs. 6As discussed in section V.A.9.b of today’s

action, the outcome of the health effects technical

review indicates it might be possible to either lower

or raise the MCLG/MCL.

determine whether treatment feasibility

would be a constraint or not. In a few

instances, the Agency identified some

potential treatment effectiveness

research needs that will be considered

in the context of the overall drinking

water research strategy.5 The revise/not

revise decisions discussed in section V

of today’s action do not depend on EPA

addressing these research needs.

In two instances (beryllium 6 and

picloram), the outcome of the health

effects technical review indicated it

might be appropriate to raise the MCLG/

MCL. For these two contaminants, BATs

specified in the NPDWR are also BATs

for several other contaminants (USEPA,

2002k). Available data are insufficient

for EPA to determine how many PWSs

are specifically treating for either of

these contaminants using the same

treatment for co-occurring contaminants

and/or for secondary benefits. The

Agency thus cannot determine whether

these water systems would discontinue

existing treatment if the MCL were to be

raised (USEPA, 2002c; USEPA, 2002k).

However, in both cases, relatively few

systems would be affected so there

would be little potential for significant

cost savings at a national level.

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b. Treatment Technique-type Rules.

EPA reviewed three of the four chemical

NPDWRs for which a TT is set in lieu

of an MCL (copper, epichlorohydrin,

and lead). A health risk assessment is in

process for the fourth TT-type NPDWR,

acrylamide.

The Agency found no new

information relating to new treatment or

other technology which would support

a revision to the TT for epichlorohydrin

at this time. EPA also reviewed issues

relating to current TT requirements for

copper and lead that were identified by

EPA and/or stakeholders. Sections

V.A.15 and V.A.43 of today’s action

summarize these issues for copper and

lead, respectively. EPA believes these

TT requirements remain appropriate at

this time; however, EPA has identified

a few potential treatment effectiveness

research needs and will consider them

in the context of the overall drinking

water research strategy (USEPA, 2002k).

4. Other Regulatory Revisions

In addition to possible revisions to

MCLGs, MCLs, and TTs, EPA

considered other regulatory revisions,

such as monitoring and system

reporting requirements, as a part of the

Six-Year Review process. EPA focused

this review on issues that are not

already being addressed, or have not

been addressed, through alternative

mechanisms (e.g., as part of a recent or

ongoing rulemaking, in conjunction

with possible chemical monitoring

reform, etc.). Where appropriate

alternative mechanisms do not exist,

EPA considered these implementationrelated concerns if the potential revision

met the following criteria:

• It indicated a potential change in

the 40 Code of Federal Regulations

(CFR) 141 requirements;

• It was ‘‘ready’’ for rulemaking—that

is, the problem to be resolved has been

clearly identified and specific option(s)

have been formulated to address the

problem; and

• It met at least one of the following

conditions:

—Clearly improved the level of public

health protection; and/or

—Represented a significant cost savings

while maintaining or improving the

public health protection.

The document, ‘‘Consideration of

Other Regulatory Revisions for

Chemical Contaminants in Support of

the Six-Year Review of National Primary

Drinking Water Regulations’’ (USEPA,

2002e) summarizes the specific issues

identified during the review process.

Some of these issues (e.g., the need to

specifically define new system/new

source monitoring requirements for

chemical contaminants) have already

been addressed in the recently

published arsenic and radionuclides

NPDWRs (66 FR 6975, January 22, 2001

(USEPA, 2001a); 65 FR 76707,

December 7, 2000 (USEPA, 2000g)).

Additional issues are contaminantspecific, and are discussed in

conjunction with the review of the

NPDWR in section V of today’s action.

5. Occurrence and Exposure Analysis

EPA’s goal in evaluating contaminant

occurrence was to estimate the number

of PWSs at which contaminants occur at

levels of regulatory interest in drinking

water, and to evaluate the number of

people exposed to these levels. For its

occurrence analysis, EPA used drinking

water compliance monitoring data from

16 States, collected in the 1993 to 1997

time frame, and statistically analyzed

the data to estimate occurrence. The

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19045

support document ‘‘Occurrence

Estimation Methodology and

Occurrence Findings Report for the SixYear Regulatory Review’’ describes in

detail the development of the data set

and the statistical methodology for

analysis (USEPA, 2002g). This section

presents a summary of the data and

analysis.

a. Development of the 16-State

Contaminant Occurrence Data Set. For

the current Six-Year Review, EPA used

PWS contaminant monitoring results,

voluntarily provided by 16 States, as the

primary source of information. EPA

selected these States based on their

geographic diversity and on their

agricultural and industrial pollution

potential. EPA also used data from a

number of additional sources for

comparative purposes. These secondary

sources include the Safe Drinking Water

Information System (SDWIS), the U.S.

Geological Survey’s National Water

Information System (NWIS), EPA’s

Unregulated Contaminant Information

System (URCIS), and other privatelyand publicly-available data sources

(USEPA, 2002g). In future reviews

rounds, EPA plans to use the National

Drinking Water Contaminant

Occurrence Database (NCOD) as the

primary data source when conducting

the occurrence and exposure analyses as

a part of the Six-Year Review process.

EPA is in the process of populating the

NCOD, however, sufficient data from

the NCOD are not yet available.

EPA developed the 16-State

contaminant occurrence data set in two

stages. In the first stage, EPA developed

an 8-State cross-section to support

occurrence analyses for its Chemical

Monitoring Reform (CMR) evaluation.

The Agency selected the eight States for

use in a national analysis because they

provided the best data quality and

completeness, and formed a balanced

national cross-section of occurrence

data based on the States’ geographic

distribution and relative rankings in

pollution potential, as described later in

this section. The methodology for

selecting the State data sets is described

in an EPA report, ‘‘A Review of

Contaminant Occurrence in Public

Water Systems’’ (USEPA, 1999d). EPA

had this report externally peer reviewed

and also received public comment from

stakeholders. In the second stage, for the

current Six-Year Review, EPA

augmented the data from the CMR 8-

State data set with data from 8

additional States. The resulting data set

includes 13 million analytical results,

from approximately 41,000 PWSs in 16

States. For the 14 contaminants that

EPA identified for detailed occurrence

analysis, i.e., those with either new

health effects information or a potential

change in the PQL (see Table IV–3 of

today’s action), the number of analytical

results per contaminant varies from

about 34,000 to greater than 200,000; the

number of PWSs with data varies from

about 8,000 to 23,000; and the number

of States providing relevant data varies

from 13 to 16.

All samples in the 16-State data set

were standard SDWA compliance

samples. Data were limited to those

with confirmed water source and

sampling type information. ‘‘Special’’

samples, ‘‘investigation’’ samples

(investigating a contaminant problem,

that would likely bias the results), or

samples of unknown type were

excluded from further analysis. EPA

conducted various quality control and

review checks of the results, including

follow-up questions to the States

providing the data to clarify potential

reporting inconsistencies, records with

invalid codes, or use of analytical units.

The Agency then compiled State data

sets into a single database with a unified

format.

In selecting a cross-section of State

data sets that is generally representative

of the U.S., EPA considered two broad

factors: geographic or spatial diversity,

and pollution potential. Geographic

diversity in the data set helps to ensure

that contaminant occurrence data come

from areas representing the range of

climatic and hydrologic conditions

across the U.S. A range of agricultural

and industrial pollution potential helps

to ensure that the data represent the

range of likely contaminant occurrence

across the United States.

As indicators of States’ pollution

potential, EPA used two primary

measures: the number of manufacturing

facilities per square mile (to reflect the

potential for VOC occurrence), and the

total expenditures on farm agricultural

chemicals (to reflect the potential for

synthetic organic chemical (SOC)

occurrence). In order to construct a

cross-section with a balance of pollution

potential, EPA divided the 50 States

into high and low pollution potential

groups based on their rank orderings

with respect to the two primary

pollution potential indicators. For each

of the two pollution potential

indicators, EPA ranked the 50 States

from 1 to 50 (1 being the highest and 50

being the lowest). The States were then

plotted on a two-dimensional scatter

plot (see Figure 2), with the x- and yaxes representing the manufacturing

and agricultural ranking, respectively, of

each State. The amount spent on

agricultural chemicals per State

increases along the y-axis from bottom

to top. The number of manufacturing

establishments per square mile per State

increases along the x-axis from left to

right. EPA then reviewed the rankings

and selected a subset of 16 States (the

‘‘cross-section States’’) in order to give

approximate balance across the range of

pollution indicators.

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The bold cross in the center of Figure

2 separates the plot into four quadrants.

The upper right-hand quadrant contains

the States with the most manufacturing

establishments per square mile and the

greatest amount of farm agricultural

chemical expenses. These States,

therefore, have the greatest amount of

pollution potential based on these

manufacturing and agricultural

indicators. The lower left-hand quadrant

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19047

contains the States with the least

amount of manufacturing

establishments per square mile and the

least amount of farm agricultural

chemical expenses. This quadrant,

therefore, contains the States with the

least amount of pollution potential,

based on these indicators. To identify

the location of each of the 16 States

within the quadrants, find the

intersection of the State name from the

x- and the y-axes. This intersection

should be represented by either a filledin circle (one of the original 8 States),

or a filled-in triangle (one of the

additional 8 States).

The Agency performed analyses to

verify the validity of this approach. The

results of these analyses support the

applicability of these indicators relative

to pollution potential. The mean

concentration values for select

contaminants were estimated for groups

of top quartile and bottom quartile

States. The cross-section development

approach presumes that the top quartile

States have a higher pollution potential

than the bottom quartile States, and,

therefore, the estimated mean

concentrations for the top quartile States

should be greater than those for the

bottom quartile States. The estimated

mean concentration values for the top

quartile States were always higher than

the mean concentration for the bottom

quartile States with the lone exception

of heptachlor (a very low occurrence

SOC).

EPA believes the distribution of the

16 selected States is representative of

the national distribution of States with

respect to these pollution indicators.

Eight of the selected States comprised

EPA’s original 8-State cross-section that

was used for the CMR analyses; EPA

solicited occurrence data from the

remaining eight. The geographic

distribution of the resulting 16-State

cross-section is shown in Figure 3.

Other, secondary pollution potential

indicators were also considered in order

to help ensure that the data were

representative of the range of pollution

potential across the U.S.

While this cross-section does not

represent a statistical random sample of

States, and thus, does not capture all

local variations in occurrence, EPA,

nonetheless, believes that the data set

provides a reliable picture of overall

distribution of contaminant occurrence

in the U.S.

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b. Analysis of Contaminant

Occurrence. Statistical analysis of

contaminant occurrence was focused at

the water system level. The goal was to

estimate the fraction of PWSs with

contaminant occurrence above levels of

regulatory interest, and the

corresponding fraction of people

exposed to those levels.

Occurrence analysis proceeded in two

stages. For the initial, or ‘‘Stage 1’’

analysis, EPA computed simple

occurrence measures which are more

straightforward and conservative than a

full probabilistic analysis. In this stage

of analysis, EPA estimated the percent

of PWSs and total population served by

PWSs with at least one analytical result

exceeding concentrations equal to

specified contaminant levels. EPA

considered three specified contaminant

levels: The lower limit of detection

reported by the States, one-half the

current MCL, and the current MCL. Of

the 68 chemicals discussed in today’s

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action, 60 were analyzed in this way.

The exceptions were:

• The two contaminants for which

not enough data were available (dioxin

and asbestos);

• The four contaminants for which

the NPDWR specifies a TT-type

requirement instead of an MCL

(acrylamide, copper, epichlorohydrin,

and lead); and

• The two contaminants for which

EPA did not request data, since the

Agency determined there was no health

or technological basis for revising, and

because these data would have required

extra effort for States to transmit (nitrate

and nitrite).

Because of the simple and conservative

nature of Stage 1 estimates, EPA used

them only as preliminary indicators of

contaminant occurrence, to guide

further analysis. The occurrence support

document (USEPA, 2002g) includes the

details of the Stage 1 analyses.

Following the initial occurrence

analysis, EPA performed a more

detailed, ‘‘Stage 2’’ statistical analysis of

occurrence for the 14 contaminants

identified as potential candidates by the

health effects and analytical feasibility

technical reviews. This analysis used a

statistical model, known as a Bayesian

hierarchical model, to estimate the

number of systems (and the

corresponding affected populations)

with mean contaminant concentrations

above the levels of regulatory interest.

Statistical modeling is usually required

in order to estimate mean contaminant

concentrations, because many sample

concentrations are non-detects, meaning

that the true concentration is unknown

and may range anywhere from zero to

the detection limit of the analytical

method. In the hierarchical model,

individual samples are assumed to be

log-normally distributed within entry

points to a distribution system (EPTDS)

(e.g., wells or treatment plants); EPTDS

means are assumed to be log-normally

distributed within each water system;

and system means are assumed to be

log-normally distributed nationwide.

This model can be applied to estimate

the number of systems with mean

concentrations above levels of interest,

and also the amount of variability

between sources within a system.

Population exposure can also be

estimated at the same time, by using

information from EPA’s SDWIS database

about the population served by each

system in the database. The hierarchical

model has important advantages:

• It provides a unified model for

estimating occurrence, both between

and within systems;

• It uses information about nondetected concentrations; and

• It provides uncertainty intervals

around each estimate, taking into

account both sampling variability over

time and across systems, and

uncertainty due to non-detected

concentrations.

Details of the hierarchical model, and

its application to estimating mean

contaminant concentrations, are

provided in the occurrence support

document (USEPA, 2002g).

The results of the Stage 2 analyses for

each of the 14 contaminants listed in

Table IV–3 are presented in section V.A

of today’s action. These results

represent only the systems in EPA’s 16-

State database. EPA considered this the

most straightforward and accurate way

to present the data that were available

for the review process. As indicated in

the preceding discussion of the

development of the analysis of

contaminant occurrence, EPA

developed the more refined Stage 2

analysis based on the preliminary

evaluation using the results of the Stage

1 analysis. A detailed explanation of

this process is provided in EPA’s

occurrence support document and is

available for review and comment

(USEPA, 2002g).

For those contaminants where

occurrence was evaluated with respect

to the revise/not revise decision, EPA

used the Stage 2 occurrence analysis for

the 16 States to determine the

percentage of PWSs that could be

impacted, and the percentage of the

exposed population served by these

systems. Section V contains a

discussion of the incremental

percentage of systems and the

incremental percentage of the

population served by these systems.

That is, EPA considered the difference

between levels of occurrence and

exposure above the current MCL and the

occurrence and exposure at the

potentially revised level(s).

6. Economic Considerations

While SDWA provides the Agency

with broad discretion to consider

economics in the context of the Six-Year

Review, the statute precludes EPA from

using economics as the sole basis for a

revision that would provide less health

protection than the current standard

(i.e., anti-backsliding). However, if new

peer-reviewed scientific health effects

research indicates that an MCLG could

be raised while maintaining public

health protection, then such a change is

permitted. For NPDWRs published after

the 1996 SDWA Amendments, Congress

added specific requirements for

economic and cost-benefit analyses in

their development. Where EPA decides

to revise an NPDWR based on health

effects or other technical reasons,

economic factors, including feasibility

and an assessment of costs and benefits

in accordance with Section 1412(b)(6) of

the SDWA, must then be taken into

consideration. EPA considered likely

economic impacts, based primarily on

available occurrence and exposure data,

to qualitatively evaluate whether the

potential revisions identified by the

health and technology reviews may

present a significant opportunity for

improved or strengthened public health

standards and/or a significant cost

savings while maintaining public health

protection (USEPA, 2002c).

C. How Is EPA Reviewing the Total

Coliform Rule?

The memorandum, ‘‘Six-Year Review

of the Total Coliform Rule—Comments

Received’’ (USEPA, 2002j), describes the

process EPA applied to the review of the

TCR. Where appropriate, EPA applied

the same approach to reviewing the TCR

as it did to the review of the chemical

NPDWRs discussed in today’s action.

However, because of the nature of the

TCR and the pathogens it controls, the

Agency focused its review on the

implementation-related requirements.

As discussed in section V.B of today’s

action, these analyses indicate that a

rulemaking to initiate possible revisions

to the TCR is appropriate at this time.

D. How Did EPA Factor Children’s

Health Concerns Into the Review?

The 1996 amendments to SDWA

require special consideration of all

sensitive populations (infants, children,

pregnant women, elderly, and

immunocompromised) in the

development of drinking water

regulations (Section 1412(b)(3)(C)(V) of

SDWA, as amended in 1996). Over the

past decade, the amount of available

data on the impact of chemical

contaminants on conception and early

developmental life stages has increased

dramatically. Accordingly, as a part of

the Six-Year Review process, EPA

completed a literature search covering

developmental and reproductive

endpoints (fertility, embryo survival,

developmental delays, birth defects,

endocrine effects, etc.) for regulated

chemicals that have a non-zero MCLG

and have not been the subject of an

updated 1997 or later risk assessment

(see section IV.B.1 of today’s action).

EPA reviewed the output from the

literature searches to identify any

studies that might have an influence on

the present MCLG. Three chemicals

were identified with potential

developmental/reproductive endpoints

of concern: cyanide, di(2-

ethylhexyl)adipate (DEHA), and

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thallium (see sections V.A.16, V.A.28,

and V.A.59 of today’s action). In each

case, where the literature search

indicated a need to consider recent

studies of developmental or

reproductive toxicity, EPA has initiated

the process to update the Agency risk

assessment. Assessments conducted by

EPA, ATSDR, and NAS in 1997 or later

thoroughly considered the potential for

reproductive and developmental

toxicity; thus, literature searches for

chemicals with such recent assessments

were not necessary.

Young children, especially infants,

are generally at greater health risk from

infections caused by waterborne

pathogens. Any revision to the TCR will

maintain or improve the control of

waterborne pathogens and, therefore,

the protection afforded to children.

V. EPA’s Preliminary Decisions Based

on its Review of NPDWRs Included in

Today’s Action

Table V–1 lists EPA’s preliminary

revise/not revise decision for each of the

69 NPDWRs discussed in today’s action

along with the principal rationale for

the decision. If EPA has decided it is not

appropriate to revise an NPDWR at this

time, that decision is based on one of

the following reasons.

• Health risk assessment is in

process: The Agency is currently

conducting, or has scheduled, a detailed

review of current health effects

information. Because the results of the

assessment are not yet available, the

Agency does not believe it is

appropriate to make a ‘‘revise decision’’

at this time. In these cases, today’s

action does not include a discussion of

the review of other key elements (e.g.,

technology, ‘‘other regulatory

revisions’’, and occurrence/exposure

analyses). EPA will consider the results

of the updated health risk assessment

during the 2002–2008 review cycle.

However, if the results of the health risk

assessment indicate a compelling need

to reconsider the MCLG, EPA may

decide to accelerate the review schedule

for that contaminant’s NPDWR.

• NPDWR remains appropriate after

data/information review: The outcome

of the review indicates that the current

regulatory requirements remain

appropriate and, therefore, no regulatory

revisions are warranted. Any new

information available to the Agency

either supports the current regulatory

requirements or does not justify a

revision.

• New information, but no revision

recommended because:

—Negligible gain in public health

protection: Any resulting changes to the

NPDWR would not significantly

improve the level of public health

protection or result in a major cost

savings.

—Information Gaps: Although results

of the review support consideration of a

possible revision, the available data are

insufficient to support a definitive

regulatory decision at this time.

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A. What Preliminary Decisions Has

EPA Made Regarding the Chemical

NPDWRs?

1. Acrylamide

a. Background. EPA published the

current NPDWR for acrylamide on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR imposes a TT

requirement that limits the allowable

monomer levels in products used during

drinking water treatment, storage, and

distribution to 0.05 percent acrylamide

in polyacrylamide coagulant aids dosed

at 1 part per million (ppm). Each water

system is required to certify, in writing,

to the State (using third-party or

manufacturer’s certification) that the

product used meets these residual

monomers and use-level specifications.

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to

acrylamide. The revised risk assessment

will consider relevant studies that have

become available on the toxicity of

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7Category 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

approaches 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; or (2) setting the

MCLG based upon a theoretical lifetime excess

cancer risk range of 10¥5 to 10¥6 using a

conservative mathematical extrapolation model.

acrylamide including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2004 or 2005 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for acrylamide is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

acrylamide is ongoing.

2. Alachlor

a. Background. EPA published the

current NPDWR for alachlor on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG of

zero based on a cancer classification of

B2, probable human carcinogen. The

NPDWR also established an MCL of

0.002 milligrams per liter (mg/L) based

on analytical feasibility.

b. Technical Reviews. The Agency

updated the health risk assessment for

alachlor in 1998 as a part of the

pesticides reregistration process

(USEPA, 2002i). However, the Agency

has initiated another update to the

alachlor health risk assessment. The

revised risk assessment will consider

relevant studies that have become

available on the toxicity of alachlor

including its potential developmental

and reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame.

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for alachlor is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

alachlor is ongoing.

3. 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 an RfD of 0.0004 milligrams

per kilogram of body weight per day

(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

antimony. The revised risk assessment

will consider relevant studies that have

become available on the toxicity of

antimony including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for antimony is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

antimony is ongoing.

4. Asbestos

a. Background. EPA published the

current NPDWR for asbestos on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG and

an MCL of 7 million fibers per liter

(MFL) for asbestos fibers exceeding 10

micrometers in length. EPA evaluated

asbestos as a Category II 7 contaminant

(equivalent to Group C, possible human

carcinogen) by the oral route of

exposure (see Appendix A of today’s

action for discussion of cancer

classifications).

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to

asbestos. The new risk assessment will

consider relevant studies that have

become available on the toxicity of

asbestos, including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2004 or 2005 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for asbestos is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

asbestos is ongoing.

5. Atrazine

a. Background. EPA published the

current NPDWR for atrazine on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG and

an MCL of 0.003 mg/L. EPA based the

MCLG on an RfD of 0.005 mg/kg/day

and a cancer classification of Group C,

possible human carcinogen, based on

limited evidence of carcinogenicity in

animals in the absence of human data.

EPA published an FR notice in February

1999, in which EPA responded to

recommendations by the Children’s

Health Advisory Committee, by

committing to re-evaluate the MCL for

atrazine after the Agency has finalized

its risk assessment (64 FR 5277,

February 3, 1999 (USEPA, 1999a)).

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to

atrazine. The revised risk assessment

will consider relevant studies that have

become available on the toxicity of

atrazine including its potential

developmental and neuroendocrine

effects. The Agency expects the new risk

assessment to be completed in the 2002

time frame. EPA is in the process of

conducting an occurrence and exposure

analysis.

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for atrazine is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

atrazine is ongoing. EPA has committed

to revisiting the NPDWR for atrazine if

a revision is appropriate once the results

of the revised risk assessment become

available. Therefore, EPA will revisit

this ‘‘not revise’’ decision once the new

risk assessment is completed.

6. Barium

a. Background. EPA published the

current NPDWR for barium on July 1,

1991 (56 FR 30266 (USEPA, 1991c)).

The NPDWR established an MCLG and

an MCL of 2 mg/L. EPA based the MCLG

on an RfD of 0.07 mg/kg/day and a

cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency

updated the health risk assessment for

barium in 1998 and retained the RfD

and cancer classification on which the

1991 MCLG is based (USEPA, 1999f). As

a part of the 1998 assessment, EPA

considered all relevant data on the

toxicity of barium including

developmental and reproductive

toxicity.

A review of analytical or treatment

feasibility is not necessary for barium

because changes to the MCLG are not

warranted at this time and the current

MCL is set at the MCLG. In addition, the

results of EPA’s review of possible

‘‘other regulatory revisions’’ did not

identify any barium-specific issues

(USEPA, 2002e). Since EPA did not

identify a health or technology basis for

revising the barium NPDWR, the

Agency did not conduct a detailed

occurrence and exposure analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for barium remains

appropriate and thus, it is not subject to

revision at this time.

19052 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

7. Benzene

a. Background. EPA published the

current NPDWR for benzene on July 8,

1987 (52 FR 25690 (USEPA, 1987)). The

NPDWR established an MCLG of zero

based on a cancer classification of A,

known human carcinogen. The NPDWR

also established an MCL of 0.005 mg/L

based on analytical feasibility.

b. Technical Reviews. The Agency

updated the health risk assessment for

benzene in 2000 and retained the cancer

classification on which the 1987 zero

MCLG is based (USEPA, 2000j; USEPA,

2002i). The revised risk assessment

considered relevant studies on the

toxicity of benzene including

developmental and reproductive

toxicity.

The current MCL for benzene is based

on a PQL of 0.005 mg/L. As a part of the

Six-Year Review, EPA analyzed more

recent WS data to determine if it might

be possible to recalculate the PQL

(USEPA, 2002d). In addition, the

Agency evaluated whether more

sensitive analytical methods have been

approved and put into use by a wide

number of laboratories. The analysis of

the WS data indicates that an

improvement in analytical feasibility

might exist. Evaluation of the WS data

shows that EPA Regional and State

laboratories exhibit greater than 95

percent laboratory passing rates at

concentrations around the current PQL

of 0.005 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for benzene. While this

information is indicative of a possibly

lower PQL, the WS data are insufficient

at this time to actually recalculate what

the lower PQL for benzene might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of benzene in

the more recent WS studies, laboratories

predominantly used EPA Method 524.2

(Gas Chromatography/Mass

Spectrometry or GC/MS), which has an

upper limit MDL of 0.00004 mg/L. A 10

times MDL multiplier predicts that the

PQL could lie around 0.0004 mg/L. The

0.0004 mg/L value is used as a threshold

in the occurrence analysis, which is

discussed in this section.

Since the analytical feasibility

analysis indicates that the PQL for

benzene (and therefore the MCL) could

possibly be lower if EPA had more

definitive data to recalculate the PQL,

EPA considered whether treatment

feasibility is likely to pose any

limitations (USEPA, 2002k). The current

BATs for benzene are packed tower

aeration (PTA) and granular activated

carbon (GAC). Small system compliance

technologies for benzene include GAC

and several aeration technologies. EPA

believes these BATs are still practical

and would not pose any limitations for

benzene at a possibly lower MCL.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any benzene-specific

issues (USEPA, 2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

benzene to determine whether changes

to the MCL might be appropriate and

likely to result in additional public

health protection if the PQL were

recalculated (USEPA, 2002g; USEPA

2002h). Table V–2 shows the results of

the detailed occurrence and exposure

analysis based on the 16-State crosssection for the current MCL (0.005 mg/

L) and the possible PQL/MCL based on

the analytical feasibility analysis

(0.0004 mg/L).

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The results of the detailed occurrence

and exposure analysis indicate that

approximately 0.3 percent of the 23,266

systems sampled in the 16 cross-section

States and approximately 0.3 percent of

the population served by those systems,

might be affected if EPA were to gather

information to recalculate the PQL (to a

lower PQL of around 0.0004 mg/L) and

revise the MCL accordingly.

c. Preliminary Decision. Although

there are new data that support

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 Agency does not have

sufficient data at this time on which to

base a PQL recalculation and hence an

MCL revision. In addition, because the

occurrence of benzene appears to be

minimal between the current MCL and

any likely PQL/MCL revision, the

Agency believes that any potential

revisions to the benzene NPDWR are

unlikely to significantly improve the

level of public health protection.

8. 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 established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR also

established an MCL of 0.0002 mg/L

based on analytical method feasibility.

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to

benzo[a]pyrene. The revised risk

assessment will consider relevant

studies that have become available on

the toxicity of benzo[a]pyrene including

its potential developmental and

reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for benzo[a]pyrene is

appropriate at this time because a

reassessment of the health risks

resulting from exposure to

benzo[a]pyrene is ongoing.

9. 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 human

carcinogen, based on clear evidence of

its carcinogenicity via inhalation or

injection in several animal species.

However, EPA also placed beryllium in

drinking water Category II for

regulation, 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

19054 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

8This is the RSC used for the current MCLG and

also the default value. EPA has no reason to believe

that the RSC for beryllium would change. See

Appendix A for a further discussion of the RSC.

to the RfD of 0.005 mg/kg/day (57 FR

31776 at 31785, July 17, 1992 (USEPA,

1992)).

b. Technical Reviews. The Agency

updated the health risk assessment of

beryllium in 1998. The 1998

reassessment established a new RfD of

0.002 mg/kg/day and also considered

relevant studies on the toxicity of

beryllium including its developmental

and reproductive toxicity. The 1998

assessment classified inhaled beryllium

as a B1, probable human carcinogen,

using the 1986 cancer guidelines (51 FR

33992, September 24, 1986 (USEPA,

1986b)). Using the 1996 Proposed

Guidelines for Carcinogen Risk

Assessment, the 1998 assessment

characterized inhaled beryllium as a

‘‘likely’’ carcinogen in humans and

concluded that the human carcinogenic

potential of ingested beryllium could

not be determined (61 FR 17960, April

23, 1996 (USEPA, 1996; USEPA,

1998d)). On this basis, EPA will reexamine the application of the

additional risk management factor of 10

to account for potential carcinogenicity

of beryllium via ingestion that was used

when deriving the current MCLG, if the

Agency determines that an MCLG

revision is appropriate.

EPA believes that any likely revision

to the MCLG for beryllium could range

from 0.01 mg/L to 0.001 mg/L, based on

the change in the RfD in the 1998

assessment, the inclusion or noninclusion of the risk management factor,

and using a 20 percent relative source

contribution (RSC).8 Whereas the 0.01

mg/L value assumes no adjustment for

potential carcinogenicity via oral

ingestion (i.e., no 10-fold risk

management factor), the 0.001 mg/L

value retains the current risk

management factor of 10.

Because of changes in the health risk

assessment for beryllium, EPA

considered whether analytical

feasibility is likely to be a limitation if

the Agency were to lower the MCLG/

MCL. The results of the analytical

feasibility analyses indicate that the

current PQL of 0.001 mg/L for beryllium

is still appropriate and is unlikely to

change. Therefore, the Agency believes

the PQL is unlikely to be a limiting

factor if EPA decides to lower the

MCLG/MCL (USEPA, 2002d).

EPA also considered whether

treatment feasibility is likely to pose any

limitations if EPA were to lower the

MCLG/MCL. The current BATs for

beryllium include activated alumina

(AA), ion exchange, lime softening,

coagulation/filtration, and reverse

osmosis (RO) with removal efficiencies

ranging from 80 to 99 percent. Small

system compliance technologies also

include point-of-use (POU) RO and POU

ion exchange. The Agency believes

these BATs are still practical and would

not pose any limitations if the Agency

were to lower the MCLG/MCL (USEPA,

2002k).

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues which are

specific to beryllium (USEPA, 2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

beryllium to determine whether

possible changes to the MCLG/MCL

would be likely to result in additional

public health protection or an

opportunity for significant cost savings

to PWSs and their customers (USEPA,

2002g; USEPA, 2002h). Table V–3

shows the results of the detailed

occurrence and exposure analysis based

on the 16-State cross-section at the

current MCL (0.004 mg/L), the possible

lower level of any MCLG/MCL value

(0.001 mg/L), and the possible upper

level of any MCLG/MCL value (0.01 mg/

L).

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The results of the detailed occurrence

and exposure analysis indicate that

approximately 0.07 percent of the

18,933 systems sampled in the 16 crosssection States, and approximately 0.02

percent of the population served by

those systems, might be affected if EPA

were to raise the MCLG/MCL. The

current BATs and small system

compliance technology for beryllium

also apply to other contaminants. In

addition to the removal of beryllium,

these treatment technologies have other

beneficial effects (e.g., reduction of

hardness or other common impurities)

(USEPA, 2002k). Therefore, if EPA were

to raise the MCLG/MCL, the Agency

does not know how many of these PWSs

currently treating to comply with the

current MCL of 0.004 mg/L would

discontinue any treatment that is

already in place. If, on the other hand,

EPA were to retain the risk management

factor and lower the MCLG/MCL, less

than 1 percent of the 18,933 systems

sampled in the 16 cross-section States

and less than 0.7 percent of the

population served by those systems

might be affected.

c. Preliminary Decision. Although

there are new data indicating that it

might be possible to revise the MCLG/

MCL for beryllium, EPA does not

19056 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

believe a revision to the NPDWR for

beryllium, either higher or lower, is

appropriate at this time. The Agency

believes that any change in the MCLG/

MCL would be unlikely to significantly

improve the level of public health

protection (if EPA were to lower the

MCLG/MCL) or provide an opportunity

for significant cost savings to PWSs (if

EPA were to raise the MCLG/MCL).

10. Cadmium

a. Background. EPA published the

current NPDWR for cadmium on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG and an MCL of 0.005 mg/L.

Because of inadequate dose-response

data to characterize the presence or lack

of a carcinogenic hazard from oral

exposure, the Agency regulated

cadmium as a Group D carcinogen, not

classifiable as to human carcinogenicity

by the oral route of exposure. Therefore,

EPA developed the MCLG for cadmium

based 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 risk assessment

will consider relevant studies that have

become available on the toxicity of

cadmium including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for cadmium is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

cadmium is ongoing.

11. Carbofuran

a. Background. EPA published the

current NPDWR for carbofuran on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG and an MCL of 0.04 mg/L. EPA

based the MCLG on an RfD of 0.005 mg/

kg/day and a cancer classification of E,

evidence of non-carcinogenicity for

humans.

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to

carbofuran. The revised risk assessment

will consider relevant studies on the

toxicity of carbofuran including recent

data on neurotoxicity and potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for carbofuran is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

carbofuran is ongoing.

12. Carbon Tetrachloride

a. Background. EPA published the

current MCLG for carbon tetrachloride

on July 8, 1987 (52 FR 25690 (USEPA,

1987)). The NPDWR established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR also

established an MCL of 0.005 mg/L based

on analytical feasibility.

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to carbon

tetrachloride. The revised risk

assessment will consider relevant

studies that have become available on

the toxicity of carbon tetrachloride

including its potential developmental

and reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

c. Preliminary Decision. 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 ongoing.

13. Chlordane

a. Background. EPA published the

current NPDWR for chlordane on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR also

established an MCL of 0.002 mg/L based

on analytical feasibility.

b. Technical Reviews. EPA updated its

risk assessment for chlordane in 1998

(USEPA, 1998e). That assessment

included an evaluation of

developmental and reproductive

endpoints. The assessment also retained

the B2 cancer classification, concluding

that chlordane is a probable human

carcinogen using the 1986 EPA

Guidelines for Carcinogen Risk

Assessment (51 FR 33992, September

24, 1986 (USEPA, 1986b)). Under the

1996 Proposed Guidelines for

Carcinogen Risk Assessment (61 FR

17960, April 23, 1996 (USEPA, 1996)),

chlordane is characterized as a likely

carcinogen by all routes of exposure

and, at the present time, would require

quantification using a linear dose

response, thus, the MCLG of zero

remains appropriate.

EPA based the current MCL for

chlordane on a PQL of 0.002 mg/L. As

a part of the Six-Year Review, EPA

analyzed more recent WS data to

determine if it might be possible to

recalculate the PQL (USEPA, 2002d). In

addition, the Agency evaluated whether

more sensitive analytical methods have

been approved and put into use by a

wide number of laboratories. The results

of these analyses indicate that only a

slight improvement in analytical

feasibility might exist. Evaluation of the

WS data shows that EPA Regional and

State laboratories exhibit greater than 85

percent laboratory passing rates at

concentrations around the current PQL

of 0.002 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for chlordane. While

this information is indicative of a

possibly lower PQL, the WS data are

insufficient at this time to actually

recalculate what the lower PQL for

chlordane might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of chlordane

in the more recent WS studies,

laboratories predominantly used EPA

Methods 505 (Gas Chromatography with

microextraction) and 508 (Gas

Chromatography with Electron Capture

Detector), which have MDLs of 0.00014

mg/L and 0.0000041 mg/L, respectively.

A 10 times MDL multiplier predicts that

the PQL could range from 0.0014 mg/L

to 0.000041 mg/L. EPA averaged these

two values, rounded up to 0.001 mg/L,

and used this value as a threshold in the

occurrence analysis discussed in this

section.

Since the analytical feasibility

analysis indicates that the PQL for

chlordane (and therefore the MCL)

could possibly be lower if EPA had

more definitive data to recalculate the

PQL, EPA considered whether treatment

feasibility is likely to pose any

limitations (USEPA, 2002k). The current

BAT for chlordane is GAC. Small

system compliance technologies for

chlordane include GAC, POU GAC, and

powdered activated carbon (PAC).

Because chlordane is a moderately

adsorbed pesticide, EPA believes that

GAC is still a practical treatment and

would not pose any limitations for

chlordane at a possibly lower MCL.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues which are

specific to chlordane (USEPA, 2002e).

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EPA evaluated the results of the

occurrence and exposure analyses for

chlordane to determine whether

changes to the MCL might be

appropriate and likely to result in

additional public health protection if

the PQL were recalculated (USEPA,

2002g; USEPA, 2002h). Table V–4

shows the results of the detailed

occurrence and exposure analysis based

on the 16-State cross-section for the

current MCL (0.002 mg/L) and the

possible PQL/MCL based on the

analytical feasibility analysis (0.001 mg/

L).

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The detailed occurrence and exposure

analysis indicates that chlordane is

unlikely to occur at the current MCL or

any potential MCL revision for the

States used in the cross-section. Since

chlordane uses were canceled in the

United States in 1988 and since it is

subject to the United Nations Prior

Informed Consent procedure (USEPA,

2002g; USEPA, 2002h), EPA expects the

occurrence of chlordane in PWSs to be

rare.

c. Preliminary Decision. Although

there are new data that support

consideration of a slightly 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 Agency does not have

sufficient data at this time on which to

base a PQL recalculation and hence an

MCL revision. Also, the Agency believes

that any change in the PQL would be

minimal and unlikely to significantly

improve the level of public health

protection because chlordane appears to

occur infrequently at concentrations at

or below the current MCL.

14. Chromium

a. Background. EPA published the

current NPDWR for total chromium on

January 31, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG and MCL of 0.1 mg/L. Although

the NPDWR regulates total chromium,

the adverse health effects associated

with hexavalent chromium (chromium

VI) are the basis of the current MCLG

since that is the more toxic species (56

FR 3526, January 31, 1991 (USEPA,

1991a)). EPA based the MCLG on an RfD

of 0.005 mg/kg/day and an assumed

RSC from water of 70 percent for total

chromium (refer to Appendix A for a

description of the RSC). EPA regulated

chromium as a Group D carcinogen, not

classifiable as to human carcinogenicity

by the oral route of exposure.

b. Technical Reviews. The Agency

updated the risk assessment for

chromium in 1998 (USEPA, 1998f). The

revised risk assessment considered

relevant studies that were available on

the toxicity of chromium including

potential developmental and

reproductive toxicity. Based on the

revised risk assessment, EPA has

identified changes in the health risk

assessment that support consideration

of whether it may be appropriate to

revise the MCLG and MCL (USEPA,

2002i). The 1998 assessment revised the

RfD for hexavalent chromium

(chromium VI) from 0.005 mg/kg/day to

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0.003 mg/kg/day based on a

modification to the original uncertainty

factor and the addition of a modifying

factor because of data on the potential

for gastrointestinal effects in humans as

a result of oral exposures. The critical

study used as the basis for the RfD did

not change.

The 1998 assessment of chromium VI

made no change to the cancer

classification of Group D for oral

exposures and determined that the

carcinogenicity of chromium VI cannot

be determined because of a lack of

sufficient epidemiological or

toxicological studies under the 1996

Proposed Guidelines for Carcinogen

Risk Assessment. Chromium VI is a

Group A known human carcinogen by

the inhalation route of exposure.

Public concern over the adverse

health effects of chromium VI has

increased in recent years. One issue is

whether chromium VI is a human

carcinogen through oral ingestion. In

2001, the State of California convened a

Blue Ribbon Panel to evaluate the

available data on this issue. The Panel

issued its report in August 2001 (Flegal

et al., 2001) and found no basis in either

the epidemiological or animal data

published in the literature for

concluding that orally ingested

chromium VI is a carcinogen. The

National Toxicology Program (NTP) has

agreed to study the chronic toxicity and

carcinogenicity of chromium VI after

oral exposure. That effort will include

shorter-term toxicity studies, two-year

rodent toxicity and carcinogenicity

studies as well as bioavailability,

distribution, and mechanistic studies.

NTP expects the results to be available

in the next three to five years (NTP,

2001).

The availability of new data on the

contribution of dietary chromium to

total chromium exposure supports a reevaluation of the RSC (NAS, 2001). The

Agency applied an RSC of 70 percent in

determining the current MCLG. Using

the new Agency RfD of 0.003 mg/kg/day

along with the application of 20 percent,

50 percent, or 70 percent as RSC values,

the Agency believes that any likely

revisions to the MCLG could range from

0.02 mg/L to 0.07 mg/L. A general

evaluation of the data indicates that a

revised RSC would likely fall within the

20 percent to 50 percent range.

Because the results of the health

effects review support consideration of

whether it may be appropriate to revise

the NPDWR for chromium based on

changes in the RfD and possible changes

in the RSC assumptions, EPA

considered whether analytical

feasibility is likely to be a limitation.

The results of the analytical feasibility

analyses indicate that the current PQL

of 0.01 mg/L for chromium is still

appropriate and is unlikely to change.

Therefore, the Agency believes the PQL

is unlikely to be a limiting factor if EPA

decides to revise the MCLG/MCL

(USEPA, 2002d).

EPA also considered whether

treatment feasibility is likely to pose any

limitations if EPA were to revise the

MCLG/MCL. The current BATs for

chromium include ion exchange, lime

softening, coagulation/filtration, and

RO. Small system compliance

technologies also include POU RO and

POU ion exchange. At the present time,

EPA believes these BATs are still

practical and would not pose any

limitations if the Agency were to revise

the MCLG/MCL (USEPA, 2002k).

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues which are

specific to chromium (USEPA, 2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

chromium to determine whether a

revised MCLG/MCL would be likely to

result in additional public health

protection (USEPA, 2002g; USEPA,

2002h). Table V–5 shows the results of

the detailed occurrence and exposure

analysis based on the 16-State crosssection for the current MCLG/MCL (0.1

mg/L), the possible MCLG/MCL value

retaining the 70 percent RSC (0.07 mg/

L), the possible MCLG/MCL value using

a 50 percent RSC (0.05 mg/L), and the

possible MCLG/MCL value using a 20

percent RSC (0.02 mg/L).

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9 In June 1994, EPA published a technical

amendment that provided additional information

on the basis of the copper MCLG (59 FR 33860, June

30, 1994 (USEPA, 1994b)).

The results of detailed occurrence and

exposure analysis indicate that less than

0.4 percent of the 19,695 systems

sampled in the 16 cross-section States

and approximately 0.1 percent of the

population served by those systems,

might be affected if EPA were to lower

the MCL to 0.02 mg/L.

c. Preliminary Decision. Although

EPA has identified a change to the RfD

on which the current MCLG for

chromium is based, the Agency believes

that a decision to revise the chromium

NPDWR at this time is premature in

light of the ongoing NTP studies on the

toxicology and carcinogenicity of

hexavalent chromium. The Agency is

aware of considerable public

controversy on the subject of the

appropriate level for chromium in

drinking water and realizes there are

differing views regarding the severity of

the health effects of chromium in water,

the relative importance of drinking

water as a source of chromium as

compared with other sources, and the

chemical form that should serve as the

basis for regulating chromium (total

versus hexavalent chromium). Because

the NTP studies will not be available in

time for the final revise/not revise

decision, EPA is placing chromium in

the ‘‘not revise—data gap’’ category.

When completed, the NTP results will

be considered either in the next review

round or sooner, if the Agency deems it

appropriate.

15. Copper

a. Background. EPA published the

current NPDWR for copper on June 7,

1991 (56 FR 26460 (USEPA, 1991b)).

The NPDWR established an MCLG of

1.3 mg/L, based on a lowest-observedadverse-effect level (LOAEL) of 5.3 mg/

day 9, and an action level of 1.3 mg/L for

first-draw samples at the 90th percentile

of taps tested. The NPDWR requires

water systems to monitor for copper at

the tap. Water systems must optimize

corrosion control. This requires water

systems serving more than 50,000

persons and those smaller size systems

that exceed the copper action level to

install corrosion control treatment and

to monitor for specified water quality

control parameters. The regulation also

requires any size system that exceeds

the copper action level to monitor for

copper in source water and, if

appropriate, to install source water

treatment. EPA published revisions to

the copper NPDWR on January 12, 2000

(65 FR 1950 (USEPA, 2000a)). These

revisions made changes to monitoring

and reporting requirements but did not

affect the copper MCLG, action level, or

basic TT requirements.

b. Technical Reviews. In 1999, EPA

requested that the National Research

Council (NRC) of the NAS examine the

available nutritional and toxicological

data for copper and provide a

recommendation regarding the levels in

drinking water that are associated with

adverse effects. The NRC concluded that

copper in drinking water could produce

adverse gastrointestinal effects in some

individuals at concentrations of about 3

mg/L or greater. In addition, the NRC

advised that individuals who carry a

recessive gene for Wilson’s disease

could accumulate excess copper in their

livers at these same concentrations.

Accordingly, the NAS recommended

that EPA retain the MCLG of 1.3 mg/L

while additional data are collected on

the risk to the carriers of the Wilson’s

Disease gene and other populations that

may accumulate copper in their livers

(NAS, 2000a).

EPA has initiated an assessment of

health risks resulting from exposure to

copper that will include the findings of

NAS as well as more recently published

data (USEPA, 2002i). This assessment

will consider relevant studies on the

toxicity of copper including its effects

on genetically and developmentally

sensitive populations. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

EPA has received comments on the

copper NPDWR suggesting that EPA

discontinue copper as a regulated

contaminant or change it to a secondary

standard (USEPA, 2002e). EPA is not

aware of any new information that

would warrant such a revision.

EPA has identified several potential

research needs which may be

considered in the context of an overall

drinking water research strategy. These

research needs are described in the

‘‘Water Treatment Technology

Feasibility Support Document for

Chemical Contaminants; In Support of

EPA Six-Year Review of National

Primary Drinking Water Regulations’’

(USEPA, 2002k).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for copper is appropriate at this

time because a reassessment of the

health risks resulting from exposure to

copper is ongoing. Several potential

research needs were identified for

copper. The NAS review of copper in

drinking water concluded that there was

a need to conduct research that would

characterize copper-sensitive

populations (both population size and

the factors leading to sensitivity) and

further define the contribution of copper

from drinking water to total copper

intake (NAS, 2000a). Treatment-related

research needs for copper are described

in the Six-Year Review treatment

feasibility support document (USEPA,

2002k).

16. 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 MCL

of 0.2 mg/L. The MCLG was developed

based on an RfD of 0.02 mg/kg/day and

a cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The results of

the health effects technical review

identified some information on

reproductive effects from the ATSDR

toxicological profile that indicate the

need to update the Agency’s risk

assessment for cyanide (USEPA, 2002i).

In light of this information, EPA has

initiated a reassessment of the health

risks resulting from exposure to cyanide

and has already solicited scientific

information from the public for

consideration (67 FR 1212, January 9,

2002 (USEPA, 2002a)). The new risk

assessment will consider relevant data

on the toxicity of cyanide including its

potential developmental and

reproductive toxicity. Because the new

assessment is not expected to be

completed until the 2004 or 2005 time

frame, EPA does not believe it is

appropriate to revise the MCLG at this

time.

A review of analytical or treatment

feasibility is not necessary for cyanide

because changes to the MCLG are not

warranted at this time and the current

MCL is set at the MCLG. EPA’s review

of ‘‘other regulatory revisions’’

identified a potential revision relating to

an error in the BAT specified for

cyanide in the CFR (USEPA, 2002e).

The CFR currently specifies ‘‘chlorine’’

as a BAT for cyanide for compliance

with the MCL and with variance and

exemption requirements (40 CFR 141.62

and 142.62, respectively); however, the

CFR should specify ‘‘alkaline

chlorination’’, as BAT. EPA plans to

correct this error through a technical

amendment to the cyanide NPDWR in

the near future. In the meantime, water

systems and States should continue to

be guided by the ‘‘Public Water System

Warning: Cyanide’’ (USEPA, 1994a) that

EPA distributed through its regional

offices. The warning includes

information on the use of chlorination

(non-alkaline) and the potential for

formation of harmful cyanogen chloride

due to reaction of chlorine with cyanide

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in water under those conditions. The

PWS Warning explains this process in

detail and outlines treatment practice,

including contact times, required

chlorine concentrations, and

compensation for temperature effects.

The July 25, 1990 proposed regulation

for cyanide discusses the effectiveness

of oxidation of cyanide at high pH levels

(55 FR 30370 at 30419 (USEPA, 1990))

and the PWS Warning discusses

mitigation of the formation of cyanogen

chloride. This information is also

summarized in the six-year review

treatment technology support document

(USEPA, 2002k).

Since the potential regulatory revision

identified by these analyses does not

affect the MCLG or the MCL, EPA does

not believe it is necessary to conduct a

detailed occurrence and exposure

analysis for cyanide.

c. Preliminary Decision. Other than

the technical amendment to correct the

BAT, EPA does not believe a revision to

the NPDWR for cyanide is appropriate

at this time. A reassessment of the

health risks has been initiated and the

Agency does not believe it is

appropriate to revise the NPDWR while

that effort is in process.

17. 2,4-D (2,4-Dichlorophenoxyacetic

Acid)

a. Background. EPA published the

NPDWR for 2,4-D on January 30, 1991

(56 FR 3526 (USEPA, 1991a)). The

NPDWR established an MCLG and an

MCL of 0.07 mg/L. EPA developed the

MCLG based on a RfD of 0.01 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 2,4-D.

The revised risk assessment will

consider relevant studies that have

become available on the toxicity of 2,4-

D including its potential developmental

and reproductive toxicity. EPA expects

the new risk assessment to be completed

in the 2003 or 2004 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for 2,4-D is appropriate at this

time because a reassessment of the

health risks resulting from exposure to

2,4-D is ongoing.

18. Dalapon (2,2-Dichloropropionic

Acid)

a. Background. EPA published the

current NPDWR 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 developed the

MCLG based on an RfD of 0.03 mg/kg/

day and a cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for dalapon since the NPDWR was

published. Therefore, as part of the SixYear Review process, EPA conducted a

literature search for relevant data on the

toxicology of dalapon, including its

potential developmental and

reproductive toxicity. The literature

search did not identify any studies that

warrant a review of the RfD or the

cancer classification (USEPA, 2002i).

A review of analytical or treatment

feasibility 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. In addition, the

results of EPA’s review of possible

‘‘other regulatory revisions’’ did not

identify any dalapon-specific issues

(USEPA, 2002e). Since EPA did not

identify a health or technology basis for

revising the dalapon NPDWR, the

Agency did not conduct a detailed

occurrence and exposure analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for dalapon remains

appropriate and thus, it is not subject to

revision at this time.

19. 1,2-Dibromo-3-chloropropane

(DBCP)

a. Background. EPA published the

current NPDWR for DBCP on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG of

zero based on a cancer classification of

B2, probable human carcinogen. The

NPDWR also established an MCL of

0.0002 mg/L based on analytical

feasibility.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for DBCP since the NPDWR was

published; however, ATSDR completed

a toxicological profile for DBCP in 1992

(ATSDR, 1992). This assessment and

other recent information do not warrant

a review of the cancer classification

because there are inadequate data to

support a nonlinear dose response

relationship (USEPA, 2002i).

Accordingly, the MCLG remains at zero

and the Agency believes that a further

review of the health effects of DBCP is

not warranted at this time.

EPA based the current MCL for DBCP

on a PQL of 0.0002 mg/L. As a part of

the Six-Year Review, EPA analyzed

more recent WS data to determine if it

might be possible to recalculate the PQL

(USEPA, 2002d). In addition, the

Agency evaluated whether more

sensitive analytical methods have been

approved and put into use by a wide

number of laboratories. The results of

these analyses indicate that a slight

improvement in analytical feasibility

might exist. Evaluation of the WS data

shows that EPA Regional and State

laboratories exhibit greater than 85

percent laboratory passing rates at

concentrations around the current PQL

of 0.0002 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for DBCP. While this

information is indicative of a possibly

lower PQL, the WS data are insufficient

at this time to actually recalculate what

the lower PQL for DBCP might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of DBCP in

the more recent WS studies, laboratories

predominantly used EPA Method 504.1

(Gas Chromatography with

microextraction), which has an MDL of

0.00001 mg/L. A 10 times MDL

multiplier predicts that the PQL may be

around 0.0001 mg/L (also one-half the

current MCL). The 0.0001 mg/L value is

used as a threshold in the occurrence

analysis, which is discussed in this

section.

Since the analytical feasibility

analysis indicates that the PQL for

DBCP (and therefore the MCL) could

possibly be lower if EPA had more

definitive data to recalculate the PQL,

EPA considered whether treatment

feasibility is likely to pose any

limitations (USEPA, 2002k). The BATs

for DBCP include aeration and GAC.

Small system compliance technologies

for DBCP include GAC, POU GAC, PAC,

and several aeration technologies. Since

the Henry’s Law coefficient for DBCP is

relatively low (i.e., DBCP is ‘‘less

strippable’’ than other contaminants),

GAC may in some cases be the preferred

treatment. Considering that only a slight

improvement in analytical feasibility

may exist, EPA believes that these BATs

are still practical and would not pose

any limitations for DBCP at a possibly

lower MCL.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues which are

specific to DBCP (USEPA, 2002e).

EPA evaluated the results of the

detailed occurrence and exposure

analyses for DBCP to determine whether

changes to the MCL might be

appropriate and likely to result in

additional public health protection if

19062 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

the PQL were recalculated (USEPA,

2002g; USEPA, 2002h). Table V–6

shows the results of the detailed

occurrence and exposure analysis based

on the 16-State cross-section at the

current MCL (0.0002 mg/L) and the

possible PQL/MCL based on the

analytical feasibility analysis (0.0001

mg/L).

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The results of detailed occurrence and

exposure analysis indicate that

approximately 0.5 percent of the 14,042

systems sampled in the 16 cross-section

States and approximately 0.6 percent of

the population served by those systems,

might be affected if EPA were to gather

the information to recalculate the PQL

(estimated to be around 0.0001 mg/L)

and to revise the MCL accordingly.

c. Preliminary Decision. Although

there are new data that support

consideration of a slightly 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 Agency does not have

sufficient data at this time on which to

base a PQL recalculation and hence an

MCL revision. In addition, because the

occurrence of DBCP appears to be

minimal between the current MCL and

any likely PQL/MCL revision, the

Agency believes that any potential

revisions to the DBCP NPDWR are

unlikely to significantly improve the

level of public health protection.

20. 1,2-Dichlorobenzene (oDichlorobenzene)

a. Background. EPA published the

current NPDWR for 1,2-dichlorobenzene

on January 30, 1991 (56 FR 3526

(USEPA, 1991a)). The NPDWR

established an MCLG and an MCL of 0.6

mg/L. EPA developed the MCLG based

on an RfD 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 risk

assessment will consider relevant

studies on the toxicity of 1,2-

dichlorobenzene including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for 1,2-dichlorobenzene is

appropriate at this time because a

reassessment of the health risks

resulting from exposure to 1,2-

dichlorobenzene is ongoing.

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21. 1,4-Dichlorobenzene (pDichlorobenzene)

a. Background. EPA published the

current NPDWR for 1,4-dichlorobenzene

on July 8, 1987 (52 FR 25690 (USEPA,

1987)). The NPDWR established an

MCLG and an MCL of 0.075 mg/L. EPA

developed the MCLG based on an RfD

of 0.1 mg/kg/day and a cancer

classification of C, possible human

carcinogen.

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to 1,4-

dichlorobenzene. The revised risk

assessment will consider relevant

studies on the toxicity of 1,4-

dichlorobenzene including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for 1,4-dichlorobenzene is

appropriate at this time because a

reassessment of the health risks

resulting from exposure to 1,4-

dichlorobenzene is ongoing.

22. 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 established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR also

established an MCL of 0.005 mg/L based

on analytical feasibility.

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to 1,2-

dichloroethane. The revised risk

assessment will consider relevant

studies that have become available on

the toxicity of 1,2-dichloroethane

including potential developmental and

reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for 1,2-dichloroethane is

appropriate at this time because a

reassessment of the health risks

resulting from exposure to 1,2-

dichloroethane is ongoing.

23. 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

established an MCLG and an MCL of

0.007 mg/L. The Agency developed the

MCLG based on an RfD of 0.009 mg/kg/

day and a cancer classification of C,

possible human carcinogen.

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to 1,1-

dichloroethylene. The revised risk

assessment will consider relevant

studies on the toxicity of 1,1-

dichloroethylene including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for 1,1-dichloroethylene is

appropriate at this time because a

reassessment of the health risks

resulting from exposure to 1,1-

dichloroethylene is ongoing.

24. cis-1,2-Dichloroethylene

a. Background. EPA published the

current NPDWR for cis-1,2-

dichloroethylene on January 30, 1991

(56 FR 3526 (USEPA, 1991a)). The

NPDWR established an MCLG and MCL

of 0.07 mg/L. The Agency developed the

MCLG based on an RfD of 0.01 mg/kg/

day and a cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for cis-1,2-dichloroethylene since the

NPDWR was published; however,

ATSDR completed a toxicological

profile for cis-1,2-dichloroethylene in

1996 (ATSDR, 1996a). This review did

not find data that would warrant a

review of the RfD or cancer

classification. As part of the Six-Year

Review process, EPA conducted a

literature search for relevant data on the

toxicology of cis-1,2-dichloroethylene,

including its potential developmental

and reproductive toxicity. The literature

search did not identify any studies that

warrant a review of the RfD or the

cancer classification (USEPA, 2002i).

A review of analytical or treatment

feasibility is not necessary for cis-1,2-

dichloroethylene because changes to the

MCLG are not warranted at this time

and the current MCL is set at the MCLG.

In addition, the results of EPA’s review

of possible ‘‘other regulatory revisions’’

did not identify any issues that were

specific to cis-1,2-dichloroethylene

(USEPA, 2002e). Since EPA did not

identify a health or technology basis for

revising the cis-1,2-dichloroethylene

NPDWR, the Agency did not conduct a

detailed occurrence and exposure

analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for cis-1,2-dichloroethylene

remains appropriate and thus, it is not

subject to revision at this time.

25. trans-1,2-Dichloroethylene

a. Background. EPA published the

current NPDWR for trans-1,2-

dichloroethylene on January 30, 1991

(56 FR 3526 (USEPA, 1991a)). The

NPDWR established an MCLG and an

MCL of 0.1 mg/L. The Agency

developed the MCLG based on an RfD

of 0.02 mg/kg/day and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for trans-1,2-dichloroethylene since the

NPDWR was published; however,

ATSDR completed a toxicological

profile for trans-1,2-dichloroethylene in

1996 (ATSDR, 1996a). This review did

not find data that would warrant a

review of the RfD or cancer

classification. As part of the Six-Year

Review process, EPA conducted a

literature search for relevant data on the

toxicology of trans-1,2-dichloroethylene,

including its potential developmental

and reproductive toxicity. The literature

search did not identify any studies that

warrant a review of the RfD or the

cancer classification (USEPA, 2002i).

A review of analytical or treatment

feasibility is not necessary for trans-1,2-

dichloroethylene because changes to the

MCLG are not warranted at this time

and the current MCL is set at the MCLG.

In addition, the results of EPA’s review

of possible ‘‘other regulatory revisions’’

did not identify any issues that were

specific to trans-1,2-dichloroethylene

(USEPA, 2002e). Since EPA did not

identify a health or technology basis for

revising the trans-1,2-dichloroethylene

NPDWR, the Agency did not conduct a

detailed occurrence and exposure

analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for trans-1,2-

dichloroethylene remains appropriate

and thus, it is not subject to revision at

this time.

26. Dichloromethane (Methylene

Chloride)

a. Background. EPA published the

NPDWR for dichloromethane on July 17,

1992 (57 FR 31776 (USEPA, 1992)). The

NPDWR established an MCLG of zero

based on a cancer classification of B2,

probable human carcinogen. The

NPDWR also established an MCL of

0.005 mg/L based on analytical

feasibility.

19064 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

b. Technical Reviews. The Agency has

not updated the health risk assessment

for dichloromethane since the NPDWR

was published; however, ATSDR

completed a toxicological profile for

dichloromethane in 2000 (USEPA,

2002i). This review did not find any

data that would warrant a change in the

cancer classification on which the 1992

zero MCLG is based. The ATSDR

toxicological profile considered relevant

studies on the toxicity of

dichloromethane including

developmental and reproductive

toxicity.

The current MCL for dichloromethane

is based on a PQL of 0.005 mg/L. As a

part of the Six-Year Review, EPA

analyzed more recent WS data to

determine if it might be possible to

recalculate the PQL (USEPA, 2002d). In

addition, the Agency evaluated whether

more sensitive analytical methods have

been approved and put into use by a

wide number of laboratories. The

analysis of the WS data indicates that a

slight improvement in analytical

feasibility might exist. Evaluation of the

WS data shows that EPA Regional and

State laboratories exhibit greater than 90

percent laboratory passing rates at

concentrations around the current PQL

of 0.005 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for dichloromethane.

While this information is indicative of

a possibly lower PQL, the WS data are

insufficient at this time to actually

recalculate what the lower PQL for

dichloromethane might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of

dichloromethane in the more recent WS

studies, laboratories predominantly

used EPA Methods 524.2 (GC/MS) and

502.2 (Purge and Trap Gas

Chromatography), which have MDLs of

0.00003 mg/L and 0.00002 mg/L,

respectively. A 10 times MDL multiplier

predicts that the PQL may be around

0.0003 to 0.0002 mg/L. The Agency

used the average of these two values

(0.00025 mg/L) as a threshold (i.e.,

possible PQL) in the occurrence analysis

discussed in this section.

Since the analytical feasibility

analysis indicates that the PQL for

dichloromethane (and therefore the

MCL) could possibly be lower if EPA

had more definitive data to recalculate

the PQL, EPA considered whether

treatment feasibility is likely to pose any

limitations (USEPA, 2002k). The current

BAT for dichloromethane is PTA. EPA

believes this BAT is still practical and

would not pose any limitations for

dichloromethane at a possibly lower

MCL.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any dichloromethanespecific issues (USEPA, 2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

dichloromethane to determine whether

changes to the MCL might be

appropriate and likely to result in

additional public health protection if

the PQL were recalculated (USEPA,

2002g; USEPA, 2002h). Table V–7

shows the results of the detailed

occurrence and exposure analysis based

on the 16-State cross-section for the

current MCL (0.005 mg/L) and the

possible PQL/MCL based on the

analytical feasibility analysis (0.00025

mg/L).

BILLING CODE 6560–50–P

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19065

BILLING CODE 6560–50–C

The results of the detailed occurrence

and exposure analysis indicate that less

than 5 percent of the 21,530 systems

sampled in the 16 cross-section States

and slightly more than 9 percent of the

population served by those systems,

might be affected if EPA were to gather

information to recalculate the PQL (to a

lower PQL of around 0.00025 mg/L) and

revise the MCL accordingly.

c. Preliminary Decision. EPA does not

believe it is appropriate to revise the

NPDWR for dichloromethane at this

time because the data indicating the

possibility of a PQL/MCL revision are

not sufficient to support a regulatory

revision at this time. However, EPA

believes there may be an opportunity for

improvement in the level of public

health protection if the Agency had

sufficient data to recalculate the PQL.

The Agency therefore solicits comment

on whether to gather better data on

which to recalculate the PQL. Any such

effort is unlikely to be completed in

time to inform the revise/not revise

decision for the final notice but may

provide new information for

consideration during the next six-year

review cycle.

27. 1,2-Dichloropropane

a. Background. EPA published the

current NPDWR for 1,2-dichloropropane

on January 30, 1991 (56 FR 3526

(USEPA, 1991a)). The NPDWR

established an MCLG of zero based on

a cancer classification of B2, probable

human carcinogen. The NPDWR also

established an MCL of 0.005 mg/L based

on analytical feasibility.

b. Technical Reviews. EPA has not

identified any new information that

indicates that it is appropriate to revise

the cancer classification for 1,2-

dichloropropane at this time (USEPA,

2002i). Because the MCLG remains at

zero, the Agency believes that a further

review of the health effects of 1,2-

dichloropropane is not warranted at this

time.

The current MCL for 1,2-

dichloropropane is based on a PQL of

0.005 mg/L. As a part of the Six-Year

Review, EPA analyzed more recent WS

data to determine if it might be possible

to recalculate the PQL (USEPA, 2002d).

In addition, the Agency evaluated

whether more sensitive analytical

methods have been approved and put

into use by a wide number of

laboratories. The results of these

analyses indicate that some

improvement in analytical feasibility

might exist. Evaluation of the WS data

shows that EPA Regional and State

laboratories exhibit greater than 95

percent laboratory passing rates at

concentrations around the current PQL

of 0.005 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for 1,2-dichloropropane.

While this information is indicative of

19066 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

a possibly lower PQL, the WS data are

insufficient at this time to actually

recalculate what the lower PQL for 1,2-

dichloropropane might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of 1,2-

dichloropropane in the more recent WS

studies, laboratories predominantly

used EPA Methods 524.2 (GC/MS) and

502.2 (Purge and Trap Gas

Chromatography), which have MDLs of

0.00004 mg/L and 0.00003 mg/L,

respectively. A 10 times MDL multiplier

predicts that the PQL may be around

0.0004 to 0.0003 mg/L. EPA used the

0.0004 mg/L value as a threshold in the

occurrence analysis discussed in this

section.

Since the analytical feasibility

analysis indicates that the PQL for 1,2-

dichloropropane (and therefore the

MCL) could possibly be lower if EPA

had more definitive data to recalculate

the PQL, EPA considered whether

treatment feasibility is likely to pose any

limitations (USEPA, 2002k). The current

BATs for 1,2-dichloropropane are GAC

and PTA. Small system compliance

technologies for 1,2-dichloropropane

include GAC, PTA, and several other

aeration technologies. EPA believes that

these BATs are still practical and would

not pose any limitations for 1,2-

dichloropropane at a possibly lower

MCL.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues that are

specific to 1,2-dichloropropane (USEPA,

2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

1,2-dichloropropane to determine

whether changes to the MCL might be

appropriate and likely to result in

additional public health protection if

the PQL were recalculated (USEPA,

2002g; USEPA, 2002h). Table V–8

shows the results of the detailed

occurrence and exposure analysis based

on the 16-State cross-section for the

current MCL (0.005 mg/L) and the

possible PQL/MCL based on the

analytical feasibility analysis (0.0004

mg/L).

BILLING CODE 6560–50–P

BILLING CODE 6560–50–C

The results of the detailed occurrence

and exposure analysis indicate that less

than 0.05 percent of the 21,988 systems

sampled in the 16 cross-section States

and approximately 0.1 percent of the

population served by those systems,

might be affected if EPA were to gather

the information to recalculate the PQL

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19067

(to a lower PQL of around 0.0004 mg/

L) and revise the MCL accordingly.

c. Preliminary Decision. Although

there are new data that support

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

appropriate at this time. The Agency

does not have sufficient data at this time

on which to base a PQL recalculation

and hence an MCL revision. In addition,

because the occurrence of 1,2-

dichloropropane appears to be minimal

between the current MCL and any likely

PQL/MCL revision, the Agency believes

that any potential revisions to the 1,2-

dichloropropane NPDWR are unlikely to

significantly improve the level of public

health protection.

28. Di(2-ethylhexyl)adipate (DEHA)

a. Background. EPA published the

NPDWR for DEHA on July 17, 1992 (57

FR 31776 (USEPA, 1992)). The NPDWR

established an MCLG and an MCL of 0.4

mg/L. The Agency developed the MCLG

based on an RfD of 0.6 mg/kg/day and

a cancer classification of C, possible

human carcinogen.

b. Technical Reviews. The Agency has

identified data that indicate it may be

appropriate to update the risk

assessment for DEHA (USEPA, 2002i).

The literature search on reproductive

and developmental toxicity identified

differences in the evaluation of the

critical study on which the MCLG is

based. Therefore, EPA believes it is

appropriate to update the risk

assessment and evaluate relevant new

studies that have become available on

the toxicity of DEHA and its metabolites

including its potential developmental

and reproductive toxicity. In light of

this information, EPA has initiated a

reassessment of the health risks

resulting from exposure to DEHA and

has already solicited scientific

information from the public for

consideration (67 FR 1212, January 9,

2002 (USEPA, 2002a)). Because the new

assessment is not expected to be

completed until the 2003 or 2004 time

frame, EPA does not believe it is

appropriate to revise the MCLG at this

time.

The current MCL is not limited by the

analytical or treatment feasibility.

Review of these capabilities is not

necessary since no changes to the MCL

are warranted at this time. The results

of EPA’s review of possible ‘‘other

regulatory revisions’’ did not identify

any issues that are specific to DEHA

(USEPA, 2002e). Because none of these

analyses indicate a change to the DEHA

regulation, it is not necessary to conduct

a detailed occurrence and exposure

analysis.

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for DEHA is appropriate at this

time. A reassessment of the health risks

has been initiated and the Agency does

not believe it is appropriate to revise the

NPDWR while that effort is in process.

29. Di(2-ethylhexyl)phthalate (DEHP)

a. Background. EPA published the

current NPDWR for DEHP on July 17,

1992 (57 FR 31776 (USEPA, 1992)). The

NPDWR established an MCLG of zero

based on a cancer classification of B2,

probable human carcinogen, and an

MCL of 0.006 based on analytical

feasibility.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to DEHP.

Many studies on DEHP and its

metabolites have become available over

the past decade and are being evaluated

as part of the Agency’s ongoing

assessment. The new assessment will

evaluate cancer and noncancer

endpoints, including potential

developmental and reproductive

endpoints. EPA expects the new risk

assessment to be completed in the 2002

or 2003 time frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for DEHP is appropriate at this

time because a reassessment of the

health risks resulting from exposure to

DEHP is ongoing.

30. Dinoseb

a. Background. EPA published the

current NPDWR for dinoseb on July 17,

1992 (57 FR 31776 (USEPA, 1992)). The

NPDWR established an MCLG and an

MCL of 0.007 mg/L. The Agency

developed the MCLG based on an RfD

of 0.001 mg/kg/day and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for dinoseb since the NPDWR was

published. Therefore, as part of the SixYear Review process, EPA conducted a

literature search for relevant data on the

toxicology of dinoseb, including its

potential developmental and

reproductive toxicity. The literature

search did not identify any studies that

warrant a review of the RfD or the

cancer classification (USEPA, 2002i).

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. In addition, the

results of EPA’s review of possible

‘‘other regulatory revisions’’ did not

identify any dinoseb-specific issues

(USEPA, 2002e). Since EPA did not

identify a health or technology basis for

revising the dinoseb NPDWR, the

Agency did not conduct a detailed

occurrence and exposure analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for dinoseb remains

appropriate and thus, it is not subject to

revision at this time.

31. 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. The Agency

developed the MCLG based on an RfD

of 0.002 mg/kg/day and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks from exposure to diquat. The

revised risk assessment will consider

relevant studies that have become

available on the toxicity of diquat,

including its potential developmental

and reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 time frame

(USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for diquat is appropriate at this

time because a reassessment of the

health risks resulting from exposure to

diquat is ongoing.

32. 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. The Agency

developed the MCLG based on an RfD

of 0.02 mg/kg/day and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to

endothall. The revised risk assessment

will consider relevant studies on the

toxicity of endothall including its

potential developmental and

reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2003 or 2004 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for endothall is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

endothall is ongoing.

19068 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

33. 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. The Agency

developed the MCLG based on an RfD

of 0.0003 mg/kg/day and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for endrin since the NPDWR was

published; however, ATSDR completed

a toxicological profile for endrin in 1996

(ATSDR, 1996b). This review did not

find data that would warrant a review

of the RfD or cancer classification. As

part of the Six-Year Review process,

EPA conducted a literature search for

relevant data on the toxicology of

endrin, including its potential

developmental and reproductive

toxicity. The literature search did not

identify any studies that warrant a

review of the RfD or the cancer

classification (USEPA, 2002i).

A review of analytical or treatment

feasibility is not necessary for endrin

because changes to the MCLG are not

warranted at this time and the current

MCL is set at the MCLG. In addition, the

results of EPA’s review of possible

‘‘other regulatory revisions’’ did not

identify any endrin-specific issues

(USEPA, 2002e). Since EPA did not

identify a health or technology basis for

revising the endrin NPDWR, the Agency

did not conduct a detailed occurrence

and exposure analysis. (Note: Endrin

uses were canceled in 1986 except for

use on bird perches, which was

canceled in 1991 (USDA, 1998)).

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for endrin remains

appropriate and thus, it is not subject to

revision at this time.

34. Epichlorohydrin

a. Background. EPA published the

current NPDWR for epichlorohydrin on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR imposes a TT

requirement that limits the allowable

level of epichlorohydrin monomer 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 ppm.

b. Technical Reviews. EPA has not

identified any new information that

indicate that it is appropriate to revise

the cancer classification for

epichlorohydrin at this time. Because

the MCLG remains at zero, the Agency

believes that a further review of the

health effects of epichlorohydrin is not

warranted at this time (USEPA, 2002i).

There are no standardized methods

available for epichlorohydrin at low

levels in drinking water (56 FR 3526 at

3558, July 1, 1991 (USEPA, 1991a)).

Therefore, no analysis of analytical

feasibility is appropriate for this

contaminant. EPA has no new

information that indicates it is

appropriate to revise the TT

requirement for epichlorohydrin at this

time (USEPA, 2002k). The results of

EPA’s review of possible ‘‘other

regulatory revisions’’ did not identify

any issues which are specific to

epichlorohydrin (USEPA, 2002e). Since

EPA did not identify a health or

technology basis for revising the

epichlorohydrin NPDWR, the Agency

did not conduct a detailed occurrence

and exposure analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for epichlorohydrin

remains appropriate and thus, it is not

subject to revision at this time.

35. Ethylbenzene

a. Background. EPA published the

current NPDWR for ethylbenzene on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG and an MCL of 0.7 mg/L. The

Agency developed the MCLG based on

an RfD of 0.1 mg/kg/day and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to

ethylbenzene. The revised risk

assessment will consider relevant

studies that have become available on

the toxicity of ethylbenzene, including

its potential developmental and

reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for ethylbenzene is appropriate

at this time because a reassessment of

the health risks resulting from exposure

to ethylbenzene is ongoing.

36. Ethylene Dibromide (EDB; 1,2-

Dibromoethane)

a. Background. EPA published the

current NPDWR for EDB on January 30,

1991 (56 FR 3526 (USEPA, 1991a)). The

NPDWR established an MCLG of zero

based on a cancer classification of B2,

probable human carcinogen. The

NPDWR also established an MCL of

0.00005 mg/L based on analytical

feasibility.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to EDB.

The revised risk assessment will

consider relevant studies that have

become available on the toxicity of EDB,

including its developmental and

reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for EDB is appropriate at this

time because a reassessment of the

health risks resulting from exposure to

EDB is ongoing.

37. Fluoride

a. Background. EPA published the

current NPDWR for fluoride on April 2,

1986 (51 FR 11396 (USEPA, 1986a)).

The NPDWR established an MCLG and

an MCL of 4.0 mg/L. The MCLG was

developed from a lowest effect level for

crippling skeletal fluorosis of 20 mg/day

with continuous exposures over a 20-

year or longer period. The LOAEL was

divided by an uncertainty factor 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 is considered to be an

adverse cosmetic effect. PWSs

exceeding the fluoride SMCL must

provide public notification to their

customers.

Fluoride is unique as a drinking water

contaminant because of its beneficial

effects at low level exposures, and

because it is voluntarily added to some

drinking water systems 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.

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19069

b. Technical Reviews. In 1997, NAS

established Dietary Reference Intakes

(DRI) for fluoride as a nutrient. As a

component of the DRI, NAS established

age and gender specific tolerable upper

intake levels (UL) to reflect the highest

average daily nutrient intake level likely

to pose no risk of adverse effects to

almost all individuals in the general

population. As intake increases above

the UL, the potential risk of adverse

effects increases. The NAS set the UL

for fluoride at 0.10 mg/kg/day for

infants, toddlers, and children through

eight years of age, to protect them from

moderate enamel fluorosis (NAS, 1997).

A UL of 10 mg/day was established for

adults and for children older than eight

years, based on protection against

skeletal fluorosis. The NAS UL

evaluation of fluoride does not have an

effect on the MCLG/MCL because a 2

liter drinking water intake of 4 mg/L

equals 8mg/day for adults, which is less

than 10 mg/day and allows for fluoride

in food and dental products.

In addition, the NAS established age

and gender specific Adequate Intake

(AI) values for fluoride. AI values are set

when the data do not permit

determination of the more precise and

better known Recommended Dietary

Allowance (RDA). The NAS (1997) AI

for infants, 0 through 6 months, is 0.01

mg/day and for infants, 7 through 12

months, is 0.5 mg/day. Values for

children range from 0.7 mg/day to 3 mg/

day increasing with age. For adults, the

NAS (1997) AI is 3 mg/day for females,

and 4 mg/day for males.

There are new studies regarding the

effects of fluoride on bone that have

been published since EPA established

the MCLG/MCL. EPA believes that it is

important to review these new data,

since effects on bone are the basis of the

present MCLG and MCL. The Agency

has conducted a literature search to

identify reports of the clinical and

epidemiological data on fluoride and

the skeletal system. The results of that

search indicate that a review of the new

data is justified as part of the regulatory

review process. EPA plans to request

NAS to conduct a review of these data.

In light of this planned assessment, EPA

does not believe it is appropriate to

revise the MCLG at this time.

As part of the continuing review of

the new toxicological data for fluoride,

EPA also intends to examine the RSC

used in the 1986 regulation. At that

time, a 100 percent RSC was applied in

setting the regulation. The increased use

of fluoride in dental products, the

tendency for children to swallow these

dental products, and the potential for

increased exposure from foods support

a re-evaluation of the RSC as a

component of the fluoride review.

As a part of the review of possible

‘‘other regulatory revisions,’’ EPA

identified one issue pertaining to the

public notification requirement

associated with exceedance of the SMCL

and the timing of the notification.

Currently, PWSs that exceed the SMCL

of 2.0 mg/L are required to notify their

customers within 12 months of the

exceedance. Concern has been

expressed that this requirement is not

sufficiently timely since dental fluorosis

occurs as a result of exposure to high

levels of fluoride while the tooth enamel

is being laid down. Waiting 12 months

to provide public notification may result

in young children being exposed to high

levels of fluoride during the time at

which they are most vulnerable. The

Agency will consider any such

revisions, if they are still appropriate,

once the results of the NAS evaluation

are available.

c. Preliminary Decision. EPA is

continuing its analyses of relevant

studies that have been published since

1986 regarding the adverse effects of

fluoride on the skeletal system to

determine if these data support

consideration of whether to revise the

current MCLG. As a part of this effort,

the Agency plans to request that NAS

update the fluoride health risk

assessment and review the RSC

assumptions. The Agency therefore

believes it is not appropriate to revise

the NPDWR for fluoride at this time.

When the results of the NAS assessment

are available, and if they support

consideration of whether a revision to

the MCLG and/or MCL may be

appropriate, EPA will revisit this ‘‘not

revise’’ decision.

38. Glyphosate

a. Background. EPA published the

current NPDWR for glyphosate on July

17, 1992 (57 FR 31776 (USEPA, 1992)).

The NPDWR established an MCLG and

an MCL of 0.7 mg/L. The Agency

developed the MCLG based on an RfD

of 0.1 mg/kg/day and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to

glyphosate. The revised risk assessment

will consider relevant studies that have

become available on the toxicity of

glyphosate including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for glyphosate is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

glyphosate is ongoing.

39. Heptachlor

a. Background. EPA published the

current NPDWR for heptachlor on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR also

established an MCL of 0.0004 mg/L

based on analytical feasibility.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for heptachlor since the NPDWR was

published; however, ATSDR completed

a toxicological profile for heptachlor in

1993 (ATSDR, 1993). This assessment

and other recent information do not

warrant a review of the cancer

classification because there are

inadequate data to support a nonlinear

dose-response relationship (USEPA,

2002i). Accordingly, the MCLG remains

at zero and 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. As a

part of the Six-Year Review, EPA

analyzed more recent WS data to

determine if it might be possible to

recalculate the PQL (USEPA, 2002d). In

addition, the Agency evaluated whether

more sensitive analytical methods have

been approved and put into use by a

wide number of laboratories. The results

of these analyses indicate that some

improvement in analytical feasibility

might exist. Evaluation of the WS data

shows that EPA Regional and State

laboratories exhibit greater than 90

percent laboratory passing rates at

concentrations around the current PQL

of 0.0004 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for heptachlor. While

this information is indicative of a

possibly lower PQL, the WS data are

insufficient at this time to actually

recalculate what the lower PQL for

heptachlor might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of heptachlor

in the more recent WS studies,

19070 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

laboratories predominantly used EPA

Methods 508 (GC/MS), 505 (GC

microextraction), and 525.2 (Purge and

Trap GC), which have MDLs of

0.0000015 mg/L, 0.000003 mg/L, and

0.00015 mg/L, respectively. A 10 times

MDL multiplier predicts PQLs of

0.000015 mg/L, 0.00003 mg/L, and

0.0015 mg/L. EPA chose the

intermediate value, rounded up to

0.0001 mg/L, and used this value as a

threshold in the occurrence analysis

discussed in this section.

Since the analytical feasibility

analysis indicates that the PQL for

heptachlor (and therefore the MCL)

could possibly be lower if EPA had

more definitive data to recalculate the

PQL, EPA considered whether treatment

feasibility is likely to pose any

limitations (USEPA, 2002k). The current

BAT for heptachlor is GAC. Compliance

technologies for small systems include

GAC, PAC, and POU GAC. Since

heptachlor is a moderately adsorbed

contaminant, EPA believes that the BAT

and compliance technologies are still

practical and would not pose any

limitations for heptachlor at a possibly

lower MCL.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any heptachlor-specific

issues (USEPA, 2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

heptachlor to determine whether

changes to the MCL might be

appropriate and likely to result in

additional public health protection if

the PQL were recalculated (USEPA,

2002g; USEPA, 2002h). Table V–9

shows the results of the detailed

occurrence and exposure analyses based

on the 16-State cross-section for the

current MCL (0.0004 mg/L) and the

possible PQL/MCL based on the

analytical feasibility analysis (0.0001

mg/L).

BILLING CODE 6560–50–P

BILLING CODE 6560–50–C

Based on the detailed occurrence and

exposure analysis, heptachlor is

unlikely to occur at the current MCL or

any potential MCL revision for the

States used in the cross-section. Since

all heptachlor uses were canceled in the

United States in 1988 (except for fire ant

use), and since it is subject to the United

Nations Prior Informed Consent

procedure (USEPA, 2002g; USEPA,

2002h), EPA expects the occurrence of

heptachlor in PWSs to be rare.

c. Preliminary Decision. Although

there are new data that support

consideration of a slightly 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 Agency does not have

sufficient data at this time on which to

base a PQL recalculation and hence an

MCL revision. Also, the Agency believes

that any change in the PQL would be

minimal and unlikely to significantly

improve the level of public health

protection because heptachlor appears

to occur very infrequently at

concentrations at or below the current

MCL.

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19071

40. Heptachlor Epoxide

a. Background. EPA published the

current NPDWR for heptachlor epoxide,

a degradate of heptachlor, on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG of

zero based on a cancer classification of

B2, probable human carcinogen. The

NPDWR also established an MCL of

0.0002 mg/L based on analytical

feasibility.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for heptachlor epoxide since the

NPDWR was published; however,

ATSDR completed a toxicological

profile for heptachlor epoxide in 1993

(ATSDR, 1993). This review did not find

data that would warrant a review of the

cancer classification because there are

inadequate data to support a nonlinear

dose response. Accordingly, the MCLG

remains at zero and the Agency believes

that a further review of the health 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. As a part of the Six-Year Review, EPA

analyzed more recent WS data to

determine if it might be possible to

recalculate the PQL (USEPA, 2002d). In

addition, the Agency evaluated whether

more sensitive analytical methods have

been approved and put into use by a

wide number of laboratories. The results

of these analyses indicate that a slight

improvement in analytical feasibility

might exist. Evaluation of the WS data

shows that EPA Regional and State

laboratories exhibit greater than 85

percent laboratory passing rates at

concentrations around the current PQL

of 0.0002 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for heptachlor epoxide.

While this information is indicative of

a possibly lower PQL, the WS data are

insufficient at this time to actually

recalculate what the lower PQL for

heptachlor epoxide might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of heptachlor

epoxide in the more recent WS studies,

laboratories predominantly used EPA

Methods 505 (GC microextraction), 508

(GC/MS), and 525.2 (Purge and Trap

GC), which have MDLs of 0.000004 mg/

L, 0.0000059 mg/L, and 0.00013 mg/L,

respectively. A 10 times MDL multiplier

predicts PQLs of 0.00004 mg/L,

0.000059 mg/L, and 0.0013 mg/L. EPA

chose the intermediate value, rounded

up to 0.0001 mg/L, and used this value

as a threshold in the occurrence analysis

discussed in this section.

Since the analytical feasibility

analysis indicates that the PQL for

heptachlor epoxide (and therefore the

MCL) could possibly be lower if EPA

had more definitive data to recalculate

the PQL, EPA considered whether

treatment feasibility is likely to pose any

limitations (USEPA, 2002k). The current

BAT for heptachlor epoxide is GAC.

Compliance technologies for small

systems include GAC, PAC, and POU

GAC. EPA believes that the BAT and

compliance technologies would not

pose any limitations for heptachlor

epoxide at a possibly lower MCL.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues that are

specific to heptachlor epoxide (USEPA,

2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

heptachlor epoxide to determine

whether changes to the MCL might be

appropriate and likely to result in

additional public health protection if

the PQL were recalculated (USEPA,

2002g; USEPA, 2002h). Table V–10

shows the results of the detailed

occurrence and exposure analyses based

on the 16-State cross-section for the

current MCL (0.0002 mg/L), and the

possible PQL/MCL based on the

analytical feasibility analysis (0.0001

mg/L).

BILLING CODE 6560–50–P

19072 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

BILLING CODE 6560–50–C

Based on detailed occurrence and

exposure analysis, it appears that

heptachlor epoxide is unlikely to occur

at the current MCL or any potential

MCL revision for the States used in the

cross-section. Since the parent of

heptachlor epoxide (i.e., heptachlor)

was canceled for use (except for fire ant

use) in the United States and since it is

subject to the United Nations Prior

Informed Consent procedure (USEPA,

2002g; USEPA, 2002h), EPA expects the

occurrence of heptachlor epoxide in

PWSs to be rare.

c. Preliminary Decision. Although

there are new data that support

consideration of a slightly lower PQL

(and therefore a possibly lower MCL),

EPA does not believe a revision to the

NPDWR for heptachlor epoxide is

appropriate at this time. The Agency

does not have sufficient data at this time

on which to base a PQL recalculation

and hence an MCL revision. Also, the

Agency believes that any change in the

PQL would be minimal and unlikely to

significantly improve the level of public

health protection because heptachlor

epoxide appears to occur infrequently at

concentrations at or below the current

MCL.

41. Hexachlorobenzene

a. Background. EPA published the

current NPDWR for hexachlorobenzene

on July 17, 1992 (57 FR 31776 (USEPA,

1992)). The NPDWR established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR also

established an MCL of 0.001 mg/L based

on analytical feasibility.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for hexachlorobenzene since the

NPDWR was published; however,

ATSDR completed a toxicological

profile for hexachlorobenzene in 1996

(ATSDR, 1996c). This assessment and

other recent information do not warrant

a review of the cancer classification

because there are inadequate data to

support a nonlinear dose-response

relationship (USEPA, 2002i).

Accordingly, the MCLG remains at zero

and the Agency believes that a further

review of the health effects of

hexachlorobenzene is not warranted at

this time.

The current MCL for

hexachlorobenzene is based on a PQL of

0.001 mg/L. As a part of the Six-Year

Review, EPA analyzed more recent WS

data to determine if it might be possible

to recalculate the PQL (USEPA, 2002d).

In addition, the Agency evaluated

whether more sensitive analytical

methods have been approved and put

into use by a wide number of

laboratories. The results of these

analyses indicate that some

improvement in analytical feasibility

might exist. Evaluation of the WS data

shows that EPA Regional and State

laboratories exhibit greater than 90

percent laboratory passing rates at

concentrations around the current PQL

of 0.001 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for hexachlorobenzene.

While this information is indicative of

a possibly lower PQL, the WS data are

insufficient at this time to actually

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19073

recalculate what the lower PQL for

hexachlorobenzene might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of

hexachlorobenzene in the more recent

WS studies, laboratories predominantly

used EPA Methods 508 (GC/MS), 505

(GC microextraction), and 525.2 (Purge

and Trap GC), which have MDLs of

0.0000077 mg/L, 0.000002 mg/L and

0.000001 mg/L, respectively. A 10 times

MDL multiplier predicts PQLs of

0.000077 mg/L, 0.00002 mg/L, and

0.00001 mg/L. EPA chose the highest

value, rounded up to 0.0001 mg/L, and

then used this value as a threshold in

the occurrence analysis discussed in

this section.

Since the analytical feasibility

analysis indicates that the PQL for

hexachlorobenzene (and therefore the

MCL) could possibly be lower if EPA

had more definitive data to recalculate

the PQL, EPA considered whether

treatment feasibility is likely to pose any

limitations (USEPA, 2002k). The current

BAT for hexachlorobenzene is GAC.

Compliance technologies for small

systems include GAC, PAC, and POU

GAC. Since hexachlorobenzene is a

moderately adsorbed contaminant, EPA

believes that the BAT and compliance

technologies are still practical and

would not pose any limitations for

hexachlorobenzene at a possibly lower

MCL.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues that are

specific to hexachlorobenzene (USEPA,

2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

hexachlorobenzene to determine

whether changes to the MCL might be

appropriate and likely to result in

additional public health protection if

the PQL were recalculated (USEPA,

2002g; USEPA, 2002h). Table V–11

shows the results of the detailed

occurrence and exposure analyses based

on the 16-State cross-section for the

current MCL (0.001 mg/L) and the

possible PQL/MCL based on the

analytical feasibility analysis (0.0001

mg/L).

BILLING CODE 6560–50–P

BILLING CODE 6560–50–C

The detailed occurrence and exposure

analysis indicates that

hexachlorobenzene is unlikely to occur

at the current MCL or any potential

MCL revision for the States used in the

cross-section. Since hexachlorobenzene

19074 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

uses were canceled in the United States

in 1984 and since it is subject to the

United Nations Prior Informed Consent

procedure (USEPA, 2002g; USEPA,

2002h), EPA expects the occurrence of

hexachlorobenzene in PWSs to be rare.

c. Preliminary Decision. Although

there are new data that support

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 Agency

does not have sufficient data at this time

on which to base a PQL recalculation

and hence an MCL revision. In addition,

because the occurrence of

hexachlorobenzene appears to be

minimal between the current MCL and

any likely PQL/MCL revision, the

Agency believes that any potential

revisions to the hexachlorobenzene

NPDWR are unlikely to significantly

improve the level of public health

protection.

42. Hexachlorocyclopentadiene

a. Background. EPA published the

current NPDWR for

hexachlorocyclopentadiene on July 17,

1992 (57 FR 31776 (USEPA, 1992)). The

NPDWR established an MCLG and an

MCL of 0.05 mg/L. The Agency based

the MCLG on an RfD of 0.007 mg/kg/day

and a cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency

updated the health risk assessment for

hexachlorocyclopentadiene in 2001

(USEPA, 2001c). The revised risk

assessment considered relevant studies

that were available to the Agency on the

toxicity of hexachlorocyclopentadiene

including its potential developmental

and reproductive toxicity. According to

the 1986 EPA Guidelines for Carcinogen

Risk Assessment (51 FR 33992,

September 24, 1986 (USEPA, 1986b)),

evaluation of the weight of evidence for

carcinogenicity to humans indicates that

hexachlorocyclopentadiene is most

appropriately categorized as Group E,

evidence of noncarcinogenicity to

humans, via inhalation exposure. In

accordance with EPA’s 1996 Proposed

Guidelines for Carcinogen Risk

Assessment (61 FR 17960, April 23,

1996 (USEPA, 1996)),

hexachlorocyclopentadiene is not likely

to be a human carcinogen by the

inhalation route. The potential for

carcinogenicity by the oral route is

unknown. The updated risk assessment

changed the RfD from 0.007 to 0.006

mg/kg/day. The change in RfD was the

result of a change in the procedure used

to model the data but not a change in

the underlying toxicology. The RfD

could result in a slight change to the

MCLG and MCL but that change would

not lead to any significant improvement

in public health protection.

A review of analytical or treatment

feasibility is not necessary for

hexachlorocyclopentadiene because

changes to the MCLG are not warranted

at this time and the current MCL is set

at the MCLG. In addition, the results of

EPA’s review of possible ‘‘other

regulatory revisions’’ did not identify

any hexachlorocyclopentadiene-specific

issues (USEPA, 2002e). Since EPA did

not identify a health or technology basis

for revising the

hexachlorocyclopentadiene NPDWR,

the Agency did not conduct a detailed

occurrence and exposure analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for

hexachlorocyclopentadiene remains

appropriate and thus, it is not subject to

revision at this time.

43. Lead

a. Background. EPA published the

current NPDWR for lead on June 7, 1991

(56 FR 26460 (USEPA, 1991b)). The

NPDWR established an MCLG of zero

and a lead action level of 0.015 mg/L at

the 90th percentile of taps tested. The

MCLG for lead is based on three factors:

(1) the occurrence of a variety of low

level health effects for which it is

currently difficult to identify clear

threshold exposure levels below which

there are no risks of adverse health

effects; (2) the Agency’s policy goal that

drinking water should contribute

minimal lead to total lead exposures

because a substantial portion of the

sensitive population already exceeds

acceptable blood lead levels; and (3) the

classification of lead as B2, probable

human carcinogen.

The NPDWR requires water systems

to monitor for lead at the tap. Water

systems must optimize corrosion

control. This requires water systems

serving more than 50,000 persons

(except those with extremely low levels

of lead in their distribution systems)

and those smaller size systems that

exceed the lead action level to install

corrosion control treatment and to

monitor for specified water quality

control parameters. The NPDWR also

includes other TT requirements for

those systems exceeding the lead action

level. These systems must: (1) Monitor

for lead in source water; (2) install

source water treatment, if appropriate;

(3) conduct public education for as long

as they continue to exceed the action

level; and (4) replace the portion of lead

service line in the distribution system

they own, if they continue to exceed the

action level after installing corrosion

control treatment and/or source water

treatment. EPA published revisions to

the lead NPDWR on January 12, 2000

(65 FR 1950 (USEPA, 2000a)). These

revisions made changes to monitoring

and reporting requirements, public

education, and the lead service line

replacement requirements but did not

affect the lead MCLG, action level, or

other TT requirements.

b. Technical Reviews. EPA has not

identified any new assessments that

indicate that it is appropriate to revise

the MCLG for lead at this time (USEPA,

2002i). Although ATSDR completed a

toxicological profile for lead in 1999

(ATSDR, 1999), the review did not find

data that would warrant a change in the

MCLG for lead. Because the MCLG

remains at zero, the Agency believes

that a further review of the health effects

of lead is not warranted at this time.

EPA identified several potential

research needs which may be

considered in the context of an overall

drinking water research strategy. These

research needs are described in the

‘‘Water Treatment Technology

Feasibility Support Document of

Chemical Contaminants in Support of

EPA Six-Year Review of National

Primary Drinking Water Regulations’’

(USEPA, 2002k).

Some stakeholders have suggested

that EPA allow alternatives to corrosion

control treatment (e.g., monitoring and

flushing at non-transient, noncommunity water systems (NTNCWSs))

(USEPA, 2002e). EPA considered these

alternatives as a part of the January 2000

revisions and determined that it was not

appropriate to make such revisions to

the TT requirements for lead and copper

(65 FR 1950, January 12, 2000 (USEPA,

2000a)). If new peer-reviewed scientific

information becomes available, it will

be considered.

EPA also considered several potential

revisions to requirements pertaining to

the monitoring requirements for lead

and copper in drinking water based on

concerns recently expressed by

stakeholders (USEPA, 2002e). As a part

of the Six-Year Review process, EPA

considered issues including: (1) Further

reduction of the monitoring

requirements; (2) monitoring for lead

and copper on the same frequency as

other inorganic and organic chemicals;

(3) expanding the monitoring waiver

program to water systems that have not

exceeded one-half the lead and copper

action levels for three monitoring

rounds, regardless of plumbing

materials used; (4) revising the protocol

by which tap water sampling sites are

identified; and (5) allowing fewer than

five tap water samples for NTNCWSs

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19075

10The DWEL was recommended by a panel of

experts on mercury, and was derived using the

weight of evidence from the entire inorganic

mercury database. The DWEL was later backcalculated to an RFD of 0.0003 mg/kg/day (USEPA,

1995).

that have fewer than five taps. The

Agency addressed all of these issues as

a part of the January 2000 revisions. If

new peer-reviewed scientific

information becomes available, it will

be considered.

The current action level and TT

requirements are not limited by

analytical feasibility, therefore review of

these capabilities is not needed. Since

none of the analyses indicate a change

to the lead regulation at this time, the

Agency did not conduct detailed

occurrence and exposure analyses.

c. Preliminary Decision. EPA does not

believe a revision to the NPDWR for

lead is appropriate because the Agency

is not aware of any new data/

information that provides sufficient

basis for revising the regulatory

requirements at this time. However, the

Agency has identified several

technology-related issues that could

benefit from further research. These

research needs will be considered as a

part of an overall drinking water

research strategy. As more research in

this area becomes available, the Agency

will consider the results as a part of the

review of the lead NPDWR during future

review cycles.

44. Lindane (γ-Hexachlorocyclohexane)

a. Background. EPA published the

current NPDWR for lindane on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG and

an MCL of 0.0002 mg/L. The Agency

based the MCLG on an RfD of 0.0003

mg/L and a cancer classification of C,

possible human carcinogen.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to lindane.

The revised risk assessment will

consider relevant studies that have

become available on the toxicity of

lindane including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2003 or 2004 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for lindane is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

lindane is ongoing.

45. Mercury (Inorganic)

a. Background. EPA published the

current NPDWR for inorganic mercury

on January 30, 1991 (56 FR 3526

(USEPA, 1991a)). The NPDWR

established an MCLG and an MCL of

0.002 mg/L. The Agency based the

MCLG on a Drinking Water Equivalent

Level (DWEL) of 0.01 mg/L 10 and a

cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. EPA updated

the risk assessment for mercury in 1997

as part of the Mercury Study Report to

Congress (MSRC) (USEPA, 1997b). The

MSRC entailed a review of all available

studies on inorganic mercury including

reproductive and developmental

studies. The MSRC concluded that the

database for inorganic mercury is

suggestive of effects in animals at doses

around 2 mg/kg/day. The data however,

are considered insufficient for risk

assessment based on any single study or

on the database as a whole. Evaluation

of data for germ cell mutagenicity led to

the conclusion that there is a moderate

weight of evidence for potential to

produce adverse effects in humans. The

MSRC reviewed and kept the 1987 RfD

of 0.0003 mg/kg/day based on immunemediated kidney damage in three

studies conducted in a sensitive strain

of rats.

The MSRC evaluated data for

carcinogenicity of inorganic mercury,

largely from studies of mercuric

chloride. Based on the absence of

human data and limited data in animals,

inorganic mercury was categorized as

Group C, possible human carcinogen;

this determination was posted on IRIS

for mercuric chloride (USEPA, 1995).

The MSRC also applied the proposed

revisions to the Cancer Guidelines (61

FR 17960, April 23, 1996 (USEPA,

1996)) to the evaluation of inorganic

mercury. The conclusion was that

inorganic mercury is not likely to be a

human carcinogen under conditions of

exposure generally encountered in the

environment. This was based in part on

the observation that all tumors were

observed at very high doses, in excess

of the maximum tolerated dose (MTD)

and that likely modes of action for these

tumors involved irritation and cytotoxic

effects not expected to occur at

environmental levels.

The revised risk assessments show

that inorganic mercury is not likely to

be a carcinogen at levels found in water

and that there are insufficient data to

categorize inorganic mercury as a

developmental toxicant. The EPA RfD

has not changed, and thus, EPA does

not believe it is appropriate to revise the

MCLG at this time.

A review of analytical or treatment

feasibility is not necessary for mercury

because, in EPA’s judgment, changes to

the MCLG are not warranted at this time

and the current MCL is set at the MCLG.

In addition, the results of EPA’s review

of possible ‘‘other regulatory revisions’’

did not identify any mercury-specific

issues (USEPA, 2002e). Since EPA did

not identify a health or technology basis

for revising the mercury NPDWR, the

Agency did not conduct a detailed

occurrence and exposure analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for inorganic mercury

remains appropriate and thus, it is not

subject to revision at this time.

46. Methoxychlor

a. Background. EPA published the

current NPDWR for methoxychlor on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG and an MCL of 0.04 mg/L. The

Agency based the MCLG on an RfD of

0.005 mg/kg/day and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to

methoxychlor. The revised risk

assessment will consider relevant

studies that have become available on

the toxicity of methoxychlor including

its potential developmental and

reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for methoxychlor is appropriate

at this time because a reassessment of

the health risks resulting from exposure

to methoxychlor is ongoing.

47. Monochlorobenzene

(Chlorobenzene)

a. Background. EPA published the

current NPDWR for monochlorobenzene

on January 30, 1991 (56 FR 3526

(USEPA, 1991a)). The NPDWR

established an MCLG and an MCL of 0.1

mg/L. The Agency based the MCLG on

an RfD of 0.02 mg/kg/day and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for monochlorobenzene since the

NPDWR was published. EPA therefore

conducted a literature search for

relevant studies on the toxicology of

monochlorobenzene including its

potential developmental and

reproductive toxicity as a part of the

Six-Year Review process. The literature

search did not identify any new studies

19076 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

11This request fulfilled the commitment EPA

made to form an inter-agency workgroup to

determine what, if any, oncogenic risks exist (56 FR

3526 at 3538, January 30th, 1991 (USEPA, 1991a)).

12Current monitoring requirements for nitrite: All

community water systems (CWSs), non-transient,

non-community water systems (NTNCWSs), and

transient non-community water systems (TNCWSs)

must monitor for nitrite at each entry point to the

distribution system. If the analytical result is less

than 1⁄2 the MCL (0.5 mg/L), then the system must

monitor at a frequency specified by the Primary

Agency. If the sample result is greater than or equal

to 1⁄2 the MCL (0.5 mg/L) then the entry point that

exceeded the trigger level must begin quarterly

monitoring. The Primary Agency may reduce the

quarterly monitoring to annual monitoring after the

system has collected four quarters of data. However,

the system must collect subsequent samples during

the quarter that yielded the highest analytical

result.

that warrant a review of the RfD or the

cancer classification (USEPA, 2002i).

A review of analytical or treatment

feasibility 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.

In addition, the results of EPA’s review

of possible ‘‘other regulatory revisions’’

did not identify any

monochlorobenzene-specific issues

(USEPA, 2002e). Since EPA did not

identify a health or technology basis for

revising the monochlorobenzene

NPDWR, the Agency did not conduct a

detailed occurrence and exposure

analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for monochlorobenzene

remains appropriate and thus, it is not

subject to revision at this time.

48. Nitrate (as N)

a. Background. EPA published the

current NPDWR for nitrate on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG and

MCL of 10 mg/L (as nitrogen (N)). The

Agency based the MCLG on an RfD of

1.6 mg/kg/day (as N) and a cancer

classification of D, not classifiable as to

human carcinogenicity.

b. Technical Reviews. The current RfD

and the MCLG were established to

protect infants, the most susceptible

segment of the population. At the

request of EPA 11, NAS completed an

assessment of nitrate in 1995 (NAS,

1995) and did not find any new data

that would warrant a review of the RfD

or cancer classification. The literature

search conducted during the Six-Year

Review also did not identify any new

studies that warrant a review of the RfD

or cancer classification (USEPA, 2002i).

The current MCL is not limited by the

analytical or treatment feasibility.

Review of these capabilities is not

necessary since no changes to the MCL

are warranted at this time.

As a part of the Six-Year Review,

several States have suggested that EPA

revise the current monitoring

requirements for nitrate to allow less

frequent monitoring in systems with

consistently low nitrate/nitrite levels.

Some have suggested that EPA place

nitrate monitoring under the same

monitoring framework used for most

other inorganic chemicals (USEPA,

2002e). EPA previously considered

these suggestions when the Agency

considered chemical monitoring reform

and decided not to change the frequency

of nitrate monitoring. However, primacy

agencies currently have the flexibility to

reduce nitrate monitoring for ground

water systems from annually to biennial

if the Primacy Agency adopts (and EPA

approves) an alternative monitoring

provision. EPA has established guidance

for such alternative monitoring in the

Alternative Monitoring Guidelines

(USEPA, 1997a). These guidelines were

issued after consultation with

stakeholders and no new information

has been identified that warrants

reconsideration of this issue.

Detailed occurrence and exposure

analysis is not necessary since none of

the analyses indicate a change to the

nitrate regulation at this time.

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for nitrate is appropriate at this

time because: (1) There are no changes

in the health risk assessment for nitrate;

and (2) no other new data were

identified that indicate the need to

revise the NPDWR at this time. (Also see

section V.A.49.c of today’s action for a

discussion of the Agency’s decision

pertaining to the joint nitrate/nitrite

standard.)

49. Nitrite (as N)

a. Background. EPA published the

current NPDWR for nitrite on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG and

an MCL of 1.0 mg/L (as N). The Agency

based the MCLG on an RfD of 0.16 mg/

kg/day (as N) and a cancer classification

of D, not classifiable as to human

carcinogenicity.

b. Technical Reviews. The current RfD

and MCLG were established to protect

infants, the most susceptible segment of

the population. At the request of EPA,

NAS completed an assessment of nitrite

in 1995 (NAS, 1995) and did not find

any new studies that warrant a review

of the RfD or cancer classification. The

literature search conducted during the

Six-Year Review did not identify any

new studies that warrant a review of the

RfD or the cancer classification (USEPA,

2002i).

The current MCL is not limited by the

analytical or treatment feasibility.

Review of these capabilities is not

necessary since no changes to the MCL

are warranted at this time.

As a part of the Six-Year Review of

‘‘other regulatory revisions,’’ EPA

received several suggestions regarding

the current monitoring requirements for

nitrite.12 Stakeholders raised several

potential issues concerning the current

monitoring requirements (USEPA,

2002e). These issues include:

• A need for flexibility for States to

require systems to collect a distribution

system sample for nitrite under certain

circumstances, such as if the entry point

sample is greater than 50 percent of the

MCL, if there is a large amount of

ammonia in the raw water, or if

chloramines are applied;

• A need for flexibility for States to

require systems to monitor for ammonia

in raw water; and

• Flexibility to eliminate nitrite

monitoring when a disinfection residual

is present.

EPA does not believe it has sufficient

data at this time on which to base

possible changes in monitoring

requirements (USEPA, 2002e).

Detailed occurrence and exposure

analysis is not necessary since none of

the technical analyses indicate a change

to the nitrite regulation at this time.

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for nitrite is appropriate at this

time because: (1) There are no changes

in the health risk assessment for nitrite;

and (2) no other new data were

identified that indicate the need to

revise the NPDWR at this time.

EPA also published an MCLG and an

MCL of 10 mg/L (as N) for the sum of

nitrate and nitrite on January 30, 1991

(56 FR 3526 (USEPA, 1991a)). The

Agency established this joint nitrate/

nitrite standard to account for the

possible additive toxicity of these two

chemicals and also to protect against the

deterioration of drinking water quality,

since the presence of nitrite in water is

indicative of water contaminated with

sewage. The Agency has not identified

any new data as a part of the Six-Year

Review process that indicates that this

joint nitrate/nitrite standard needs to be

revised.

50. Oxamyl (Vydate)

a. Background. EPA published the

current NPDWR for oxamyl on July 17,

1992 (57 FR 31776 (USEPA, 1992)). The

NPDWR established an MCLG and an

MCL of 0.2 mg/L. The Agency based the

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19077

13This is the RSC used for the current MCLG and

also the default value. EPA has no reason to believe

that the RSC for oxamyl would change. See

Appendix A for further discussion of the RSC.

MCLG on an RfD of 0.025 mg/kg/day

and a cancer classification of E,

evidence of non-carcinogenicity for

humans.

b. Technical Reviews. The Agency

identified a change in the health

assessment that supports consideration

of whether to revise the MCLG (USEPA,

2002i). EPA updated the risk assessment

in 2000. This new risk assessment

considered relevant studies that had

become available on the toxicity of

oxamyl including its potential

developmental and reproductive

toxicity. The new risk assessment

revised the RfD from 0.025 mg/kg/day to

0.001 mg/kg/day (USEPA, 2000e).

Based on the change in the RfD for

oxamyl and using a 20 percent RSC13,

EPA believes that any revision to the

MCLG is not likely to be lower than

0.007 mg/L.

In setting the MCLG/MCL in 1992, the

Agency determined the PQL for oxamyl

to be 0.02 mg/L and analytical

feasibility was not considered to be a

limitation. EPA has analyzed more

recent WS data to determine if

analytical feasibility is likely to be a

limiting factor in setting a lower MCL

(USEPA, 2002d). In addition, the

Agency evaluated whether more

sensitive methods have been approved

and are in use by a wide number of

laboratories. The results of these

analyses indicate that analytical

feasibility is likely to be a limiting factor

if EPA were to revise the MCLG and

MCL. Although not definitive, the

available WS data indicate that the PQL

could lie between 0.02 and 0.04 mg/L.

EPA used the 0.02 mg/L and the 0.04

mg/L values as thresholds in the

occurrence analysis discussed in this

section.

Since the health effects technical

review supports consideration of

whether a revision to the MCLG and

MCL may be appropriate, EPA evaluated

whether treatment feasibility is likely to

pose any limitations (USEPA, 2002k).

The current BAT for oxamyl is GAC.

Compliance technologies for small

systems include GAC, PAC, and POU

GAC. EPA believes that the BAT and

compliance technologies are still

practical and would not pose any

limitations for oxamyl at a possibly

lower level (i.e., a possibly lower MCL).

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues that are

specific to oxamyl (USEPA, 2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

oxamyl to determine whether changes to

the MCL might be appropriate and

likely to result in additional public

health protection if the PQL were

recalculated (USEPA, 2002g; USEPA,

2002h). Table V–12 shows the results of

the detailed occurrence and exposure

analyses based on the 16-State crosssection for several concentrations: the

current MCL (0.2 mg/L), the possible

upper and lower PQLs based on the

analytical feasibility analysis (0.02 and

0.04 mg/L), and the possible lower limit

of any MCLG value (0.007 mg/L). Based

on the detailed analysis of 16 crosssection States, it appears that oxamyl is

unlikely to occur at the current MCL or

any potential MCL value.

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c. Preliminary Decision. Although

there are new data indicating that it

might be possible to lower the MCLG

and the MCL, analytical feasibility

limitations would limit the extent to

which the MCL could be revised at the

present time. Because any changes in

the NPDWR based on setting the MCL

at the limitations of analytical feasibility

are unlikely to significantly improve the

level of public health protection, EPA

does not believe a revision to the

NPDWR for oxamyl is appropriate at

this time. In addition, because oxamyl

appears to occur infrequently at

concentrations at or below the current

MCL, EPA believes that efforts to

research more sensitive analytical

methods and/or to revise the MCL are

low priority and should not be pursued

at the present time. EPA requests

comment on the extent to which oxamyl

is likely to occur at levels between 0.007

and 0.2 mg/L at PWSs. Commenters

who disagree with the occurrence

evaluation should submit data to

support their rationale and evidence to

show that oxamyl is of national concern

at PWSs at the thresholds evaluated.

EPA does plan to update the Health

Advisory for oxamyl to reflect the new

RfD.

51. Pentachlorophenol

a. Background. EPA published the

current NPDWR for pentachlorophenol

on July 1, 1991 (56 FR 30266 (USEPA,

1991c)). The NPDWR established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR also

established an MCL of 0.001 mg/L,

based on analytical feasibility.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to

pentachlorophenol. The revised risk

assessment will consider relevant

studies that have become available on

the toxicity of pentachlorophenol

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19079

14This is the RSC used for the current MCLG and

also the default value. EPA has no reason to believe

that the RSC for picloram would change. See

Appendix A for further discussion of the RSC.

including its potential developmental

and reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for pentachlorophenol is

appropriate at this time because a

reassessment of the health risks

resulting from exposure to

pentachlorophenol is ongoing.

52. 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. The Agency based the

MCLG on an RfD of 0.07 mg/kg/day and

a cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency

identified a change in the health

assessment that could lead to a change

in the MCLG (USEPA, 2002i). EPA

updated the risk assessment in 1998.

This new risk assessment considered

relevant studies that had become

available on the toxicity of picloram

including its potential developmental

and reproductive toxicity. The new risk

assessment revised the RfD from 0.07

mg/kg/day to 0.20 mg/kg/day and

classified picloram as Group E, evidence

of noncarcinogenicity for humans,

according to the 1986 Cancer

Guidelines. Picloram has not been

evaluated against the Proposed 1996

Cancer Guidelines.

Based on the change in the RfD for

picloram and using a 20 percent RSC, 14

EPA believes that any revision to the

MCLG is not likely to be higher than 1

mg/L (an increase in the MCLG).

Analytical or treatment feasibility do

not pose any limitations for the current

MCL and would not be a limiting factor

if EPA were to raise the MCLG. The

Agency’s review of possible ‘‘other

regulatory revisions’’ did not identify

any issues that are specific to picloram

(USEPA, 2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

picloram to determine whether possible

changes to the MCL would be likely to

result in opportunities for significant

cost savings to PWSs and their

customers (USEPA, 2002g; USEPA,

2002h). Table V–13 shows the results of

the detailed occurrence and exposure

analysis based on the 16-State crosssection for the current MCL (0.5 mg/L),

and the concentration that would be

considered if the EPA revised the MCLG

and MCL (i.e., the possible MCLG/MCL

of 1 mg/L) based on the new RfD and

a 20 percent RSC. Based on the detailed

analysis, it appears that picloram is

unlikely to occur at concentrations

above 0.5 mg/L in the States used for the

cross-section.

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The results of the detailed occurrence

and exposure analysis indicate that few,

if any, of the 12,907 systems sampled in

the 16 cross-section States might be

affected if EPA were to raise the MCLG/

MCL.

c. Preliminary Decision. Although

there are new data that support

consideration of whether to revise the

MCLG/MCL for picloram, EPA does not

believe a revision to the NPDWR for

picloram is appropriate at this time. The

Agency believes that any change in the

MCLG/MCL would be unlikely to

provide an opportunity for significant

cost savings to PWSs.

53. Polychlorinated Biphenyls (PCBs)

a. Background. EPA published the

current NPDWR for PCBs on January 30,

1991 (56 FR 3526 (USEPA, 1991a)). The

NPDWR established an MCLG of zero

based on a cancer classification of B2,

probable human carcinogen. The

NPDWR also established an MCL of

0.0005 mg/L based on analytical

feasibility.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to PCBs.

The revised risk assessment will

consider relevant studies that have

become available on the toxicity of PCBs

including their potential developmental

and reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for PCBs is appropriate at this

time because a reassessment of the

health risks resulting from exposure to

PCBs is ongoing.

54. Selenium

a. Background. EPA published the

current NPDWR for selenium on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG and

an MCL of 0.05 mg/L. The Agency based

the MCLG on an RfD of 0.005 mg/kg/day

and a cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency has

not updated the risk assessment for

selenium since the NPDWR was

published (USEPA, 2002i). However, a

2000 NAS assessment of selenium

supports the current RfD based on

epidemiological studies of selenosis in

humans (NAS, 2000b). The NAS study

considered relevant studies that were

available on the toxicity of selenium,

including its developmental and

reproductive toxicity, and established a

tolerable upper intake level of 0.4 mg/

day for adolescents and adults, a value

which is equivalent to the RfD.

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. In addition, the

results of EPA’s review of possible

‘‘other regulatory revisions’’ did not

identify any selenium-specific issues

(USEPA, 2002e). Since EPA did not

identify a health or technology basis for

revising the selenium NPDWR, the

Agency did not conduct a detailed

occurrence and exposure analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for selenium remains

appropriate and thus, it is not subject to

revision at this time.

55. 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. The Agency based

the MCLG on an RfD of 0.005 mg/kg/day

and a cancer classification of C, possible

human carcinogen.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to

simazine. The revised risk assessment

will consider relevant studies that have

become available on the toxicity of

simazine including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2003 or 2004 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for simazine is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

simazine is ongoing. The Agency is also

re-examining all the triazines and their

degradation products as part of its CCL

in order to fill any necessary research

gaps to enable the Agency to determine

whether or not to regulate any or all of

the contaminants in this group of

compounds.

56. Styrene

a. Background. EPA published the

current NPDWR for styrene on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG and

an MCL of 0.1 mg/L. The Agency based

the MCLG on an RfD of 0.2 mg/kg/day

and a cancer classification of C, possible

human carcinogen.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to styrene.

The revised risk assessment will

consider relevant studies that have

become available on the toxicity of

styrene including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for styrene is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

styrene is ongoing.

57. 2,3,7,8-TCDD (Dioxin)

a. Background. EPA published the

current NPDWR for dioxin on July 17,

1992 (57 FR 31776 (USEPA, 1992)). The

NPDWR established an MCLG of zero

based on a cancer classification of B2,

probable human carcinogen. The

NPDWR also established an MCL of

3×10¥8 mg/L based on analytical

feasibility.

b. Technical Reviews. The Agency has

conducted a comprehensive assessment

of the exposure and potential human

health effects of dioxin including its

potential developmental and

reproductive toxicity. The draft

document has been reviewed by the

SAB (USEPA, 2001b). The Agency is

presently in the process of addressing

SAB and public comments, and expects

to complete the risk assessment in the

2002 or 2003 time frame.

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for dioxin is appropriate at this

time because a reassessment of the

health risks resulting from exposure to

dioxin is ongoing.

58. Tetrachloroethylene

a. Background. EPA published the

current NPDWR for tetrachloroethylene

on January 30, 1991 (56 FR 3526

(USEPA, 1991a)). The NPDWR

established an MCLG of zero based on

a cancer classification of B2, probable

human carcinogen. The NPDWR also

established an MCL of 0.005 mg/L based

on analytical feasibility.

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to

tetrachloroethylene. The revised risk

assessment will consider relevant

studies that have become available on

the toxicity of tetrachloroethylene

including its potential developmental

and reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for tetrachloroethylene is

appropriate at this time because a

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reassessment of the health risks

resulting from exposure to

tetrachloroethylene is ongoing.

59. Thallium

a. Background. EPA published the

current NPDWR for thallium on July 17,

1992 (57 FR 3526 (USEPA, 1991a)). The

NPDWR established an MCLG of 0.0005

mg/L based on an RfD 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. The results of

the health effects technical review

identified some information on

reproductive effects that indicate the

need to update the Agency’s risk

assessment for thallium (USEPA, 2002i).

In light of this information, EPA has

initiated a reassessment of the health

risks resulting from exposure to

thallium and has already solicited

scientific information from the public

for consideration (67 FR 1212, January

9, 2002 (USEPA, 2002a)). The new risk

assessment will consider relevant data

on the toxicity of thallium including its

potential developmental and

reproductive toxicity. Because the new

assessment is not expected to be

completed until the 2004 or 2005 time

frame, EPA does not believe it is

appropriate to revise the MCLG at this

time.

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for thallium is appropriate at

this time. A reassessment of the health

risks has been initiated and the Agency

does not believe it is appropriate to

revise the NPDWR while that effort is in

process.

60. Toluene

a. Background. EPA published the

current NPDWR for toluene on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG and

an MCL of 1 mg/L. The Agency based

the MCLG on an RfD of 0.2 mg/kg/day

and a cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to toluene.

The revised risk assessment will

consider relevant studies that have

become available on the toxicity of

toluene including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for toluene is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

toluene is ongoing.

61. Toxaphene

a. Background. EPA published the

current NPDWR for toxaphene on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR also

established an MCL of 0.003 mg/L based

on analytical feasibility.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for toxaphene since the NPDWR was

published; however, ATSDR completed

a toxicological profile for toxaphene in

1996 (ATSDR, 1996d). This assessment

and other recent information do not

warrant a review of the cancer

classification because the data indicate

that toxaphene is mutagenic and would

be evaluated using a linear doseresponse approach (USEPA, 2002i).

Accordingly, the MCLG remains at zero

and the Agency believes that a further

review of the health effects of toxaphene

is not warranted at this time.

The current MCL for toxaphene is

based on a PQL of 0.003 mg/L. As a part

of the Six-Year Review, EPA analyzed

more recent WS data to determine if it

might be possible to recalculate the PQL

(USEPA, 2002d). In addition, the

Agency evaluated whether more

sensitive analytical methods have been

approved and put into use by a wide

number of laboratories. The results of

these analyses indicate that some

improvement in analytical feasibility

might exist. Evaluation of the WS data

shows that EPA Regional and State

laboratories exhibit greater than 90

percent laboratory passing rates at

concentrations around the current PQL

of 0.003 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for toxaphene. While

this information is indicative of a

possibly lower PQL, the WS data are

insufficient at this time to actually

recalculate what the lower PQL for

toxaphene might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of toxaphene

in the more recent WS studies,

laboratories predominantly used EPA

Methods 508 (GC/MS) and 505 (Purge

and Trap GC). No MDL data are

available for EPA Method 508 and the

MDL for 505 is listed as 0.001 mg/L. A

10 times MDL multiplier based on EPA

Method 505 predicts a PQL of 0.01 mg/

L, which is higher than the current PQL.

Therefore, the 10 times multiplier could

not be used to predict a lower PQL and

EPA did not use this higher value as a

threshold in the occurrence analysis

discussed in this section. Instead, EPA

used concentration thresholds of onehalf the current MCL and the lower

limit of detection reported by the States.

EPA believes if a lower PQL does exist,

that the magnitude of the change would

be minimal.

Since the analytical feasibility

analysis indicates that the PQL for

toxaphene (and therefore the MCL)

could possibly be lower if EPA had

more definitive data to recalculate the

PQL, EPA considered whether treatment

feasibility is likely to pose any

limitations (USEPA, 2002k). The current

BAT for toxaphene is GAC. Compliance

technologies for small systems include

GAC, PAC, and POU GAC. EPA believes

that the BAT and compliance

technologies are still practical and

would not pose any limitations for

toxaphene at a possibly lower MCL.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues that are

specific to toxaphene (USEPA, 2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

toxaphene to determine whether

changes to the MCL might be

appropriate and likely to result in

additional public health protection if

EPA had sufficient data to recalculate

the PQL (USEPA, 2002g; USEPA,

2002h). Table V–14 shows the results of

the detailed occurrence and exposure

analyses based on the 16-State crosssection for the current MCL (0.003 mg/

L), one-half the current MCL (0.0015

mg/L), and the lower level of detection

reported by the States (0.001 mg/L).

BILLING CODE 6560–50–P

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BILLING CODE 6560–50–C

The detailed occurrence and exposure

analysis indicates that toxaphene is

unlikely to occur at the current MCL or

any potential MCL revision for the

States used in the cross-section. Since

toxaphene uses were canceled in the

United States in 1990 and since it is

subject to the United Nations Prior

Informed Consent (USEPA, 2002g;

USEPA, 2002h), EPA expects the

occurrence of toxaphene in PWSs to be

rare.

c. Preliminary Decision. Although

there are new data that support

consideration of a possibly lower PQL

(and therefore a possibly lower MCL),

EPA does not believe a revision to the

NPDWR for toxaphene is appropriate at

this time. The Agency does not have

sufficient data at this time on which to

base a PQL recalculation and hence an

MCL revision. Also, the Agency believes

that any change in the PQL would be

minimal and unlikely to significantly

improve the level of public health

protection because toxaphene appears to

occur infrequently at concentrations at

or below the current MCL.

62. 2,4,5-TP (Silvex; 2,4,5-

Trichlorophenoxypropionic Acid)

a. Background. EPA published the

current NPDWR for 2,4,5-TP on January

30, 1991 (56 FR 3526 (USEPA, 1991a)).

The NPDWR established an MCLG and

an MCL of 0.05 mg/L. The Agency based

the MCLG on an RfD of 0.008 mg/kg/day

and a cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for 2,4,5-TP since the NPDWR was

published. Therefore, as part of the SixYear Review process, 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 new studies

that warrant a review of the RfD or the

cancer classification (USEPA, 2002i).

A review of analytical or treatment

feasibility 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. In addition, the

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results of EPA’s review of possible

‘‘other regulatory revisions’’ did not

identify any 2,4,5-TP-specific issues

(USEPA, 2002e). 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

occurrence and exposure analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for 2,4,5-TP remains

appropriate and thus, it is not subject to

revision at this time.

63. 1,2,4-Trichlorobenzene

a. Background. EPA published the

current NPDWR for 1,2,4-

trichlorobenzene on July 17, 1992 (57

FR 31776 (USEPA, 1992)). The NPDWR

established an MCLG and an MCL of

0.07 mg/L. The Agency based the MCLG

on an RfD of 0.01 mg/kg/day and a

cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for 1,2,4-trichlorobenzene since the

NPDWR was published. Therefore, as

part of the Six-Year Review process,

EPA conducted a literature search for

relevant data on the toxicology of 1,2,4-

trichlorobenzene, including its potential

developmental and reproductive

toxicity. The literature search did not

identify any new studies that warrant a

review of the RfD or the cancer

classification (USEPA, 2002i).

A review of analytical or treatment

feasibility 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.

In addition, the results of EPA’s review

of possible ‘‘other regulatory revisions’’

did not identify any 1,2,4-

trichlorobenzene-specific issues

(USEPA, 2002e). Since EPA did not

identify a health or technology basis for

revising the 1,2,4-trichlorobenzene

NPDWR, the Agency did not conduct a

detailed occurrence and exposure

analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for 1,2,4-trichlorobenzene

remains appropriate and thus, it is not

subject to revision at this time.

64. 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

established an MCLG and an MCL of

0.20 mg/L. The Agency developed the

MCLG based on an RfD of 0.035 mg/kg/

day derived from an inhalation study

and a cancer classification of D, not

classifiable as to human carcinogenicity.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to 1,1,1-

trichloroethane. The revised risk

assessment will consider relevant

studies that have become available on

the toxicity of toluene including its

potential developmental and

reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2003 or 2004 time

frame (USEPA, 2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for 1,1,1-trichloroethane is

appropriate at this time because a

reassessment of the health risks

resulting from exposure to 1,1,1-

trichloroethane is ongoing.

65. 1,1,2-Trichloroethane

a. Background. EPA published the

current NPDWR for 1,1,2-

trichloroethane on July 17, 1992 (57 FR

31776 (USEPA, 1992)). The NPDWR

established an MCLG of 0.003 mg/L

based on an RfD of 0.004 mg/kg/day and

a cancer classification of C, possible

human carcinogen. The NPDWR also

established an MCL of 0.005 mg/L based

on analytical feasibility.

b. Technical Reviews. The Agency has

not updated the health risk assessment

for 1,1,2-trichloroethane since the

NPDWR was published. Therefore, as

part of the Six-Year Review process,

EPA conducted a literature search for

relevant data on the toxicology of 1,1,2-

trichloroethane including its potential

developmental and reproductive

toxicity. The literature search did not

identify any studies that warrant a

review of the RfD or the cancer

classification (USEPA, 2002i).

The current MCL for 1,1,2-

trichloroethane is based on a PQL of

0.005 mg/L. As a part of the Six-Year

Review, EPA analyzed more recent WS

data to determine if it might be possible

to recalculate the PQL (USEPA, 2002d).

In addition, the Agency evaluated

whether more sensitive analytical

methods have been approved and put

into use by a wide number of

laboratories. The results of these

analyses indicate that a slight

improvement in analytical feasibility

might exist. Evaluation of the WS data

shows that EPA Regional and State

laboratories exhibit greater than 90

percent laboratory passing rates at

concentrations around the current PQL

of 0.005 mg/L. Because most of the

laboratory passing rates exceeded the 75

percent criterion typically used to

derive a PQL from WS studies, this

information indicates that a lower PQL

corresponding to the 75 percent passing

rate might exist for 1,1,2-

trichloroethane. While this information

is indicative of a possibly lower PQL,

the WS data are insufficient at this time

to actually recalculate what the lower

PQL for 1,1,2-trichloroethane might be.

Using information about the

analytical methods most widely used to

report results in the WS studies, the

MDLs for these methods, and the 10

times MDL multiplier, EPA estimated

what the possibly lower PQL/MCL

might be. For the analysis of 1,1,2-

trichloroethane in the more recent WS

studies, laboratories predominantly

used EPA Methods 524.2 (GC/MS) and

502.2 (Purge and Trap GC), which both

have upper limit MDLs of 0.00003 mg/

L. A 10 times MDL multiplier predicts

a PQL of 0.0003 mg/L. Since this value

is below the current MCLG, this

supports consideration of whether the

MCL might be set at the MCLG if

sufficient data were available to

recalculate the PQL. EPA did not use

the possibly lower PQL as a threshold

in the occurrence analysis but instead

used 0.003 mg/L (the current MCLG)

since this is the lowest level to which

the MCL would possibly be revised.

Since the analytical feasibility

analysis indicates that the PQL for 1,1,2-

trichloroethane (and therefore the MCL)

could possibly be lower if EPA had

more definitive data to recalculate the

PQL, EPA considered whether treatment

feasibility is likely to pose any

limitations (USEPA, 2002k). The current

BATs for 1,1,2-trichloroethane include

both PTA and GAC. Small system

compliance technologies for 1,1,2-

trichloroethane include GAC and

several aeration technologies. EPA

believes that these BATs and

compliance technologies are still

practical and would not pose any

limitations for 1,1,2-trichloroethane at a

possibly lower level.

The results of EPA’s review of

possible ‘‘other regulatory revisions’’

did not identify any issues that are

specific to 1,1,2-trichloroethane

(USEPA, 2002e).

EPA evaluated the results of the

occurrence and exposure analyses for

1,1,2-trichloroethane to determine

whether changes to the MCL might be

appropriate and likely to result in

additional public health protection if

sufficient data were available to

recalculate the PQL and subsequently

set the MCL at the MCLG (USEPA,

2002g; USEPA, 2002h). Table V–15

shows the results of the detailed

occurrence and exposure analyses based

on the 16-State cross-section for the

current MCL (0.005 mg/L) and the

potentially revised MCL (0.003 mg/L)

19084 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

based on setting the MCL at the MCLG.

Based on the detailed analysis, it

appears that 1,1,2-trichloroethane is

unlikely to occur at the current MCL or any potential MCL revisions in the

States used for the cross-section.

BILLING CODE 6560–50–P

BILLING CODE 6560–50–C

c. Preliminary Decision. Although

there are new data that support

consideration of whether a lower PQL is

possible (and therefore a possibly set the

MCL at the MCLG), EPA does not

believe a revision to the NPDWR for

1,1,2-trichloroethane is appropriate at

this time. The Agency believes that any

potential revision to the MCL is unlikely

to significantly improve the level of

public health protection because 1,1,2-

trichloroethane appears to occur

infrequently at concentrations at or

below the current MCL.

66. Trichloroethylene

a. Background. EPA published the

current NPDWR for trichloroethylene on

July 8, 1987 (52 FR 25690 (USEPA,

1987)). The NPDWR established an

MCLG of zero based on a cancer

classification of B2, probable human

carcinogen. The NPDWR also

established an MCL of 0.005 mg/L based

on analytical feasibility.

b. Technical Reviews. EPA has

initiated a reassessment of the health

risks resulting from exposure to

trichloroethylene. The revised risk

assessment will consider relevant

studies that have become available on

the toxicity of trichloroethylene

including its potential developmental

and reproductive toxicity. The Agency

expects the new risk assessment to be

completed in the 2002 or 2003 time

frame (USEPA, 2002i). c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for trichloroethylene is

appropriate at this time because a

reassessment of the health risks

resulting from exposure to

trichloroethylene is ongoing.

67. Vinyl Chloride

a. Background. EPA published the

current NPDWR for vinyl chloride on

July 8, 1987 (52 FR 25690 (USEPA,

1987)). The NPDWR established an

MCLG of zero based on a cancer

classification of A, known human

carcinogen. The NPDWR also

established an MCL of 0.002 mg/L based

on analytical feasibility.

b. Technical Reviews. The Agency

updated the health risk assessment of

vinyl chloride in 2000 (USEPA, 2000k).

The updated risk assessment included

relevant studies that were available on

the toxicity of vinyl chloride including

its potential developmental and

reproductive toxicity. According to the

1986 EPA Guidelines for Carcinogen

Risk Assessment, vinyl chloride is

categorized as Group A, known human

carcinogen. Under the Proposed

Guidelines for Carcinogen Risk

Assessment (61 FR 17960, April 23,

1996 (USEPA, 1996)), EPA concluded

that vinyl chloride is a known human

carcinogen by the inhalation route of

exposure, based on human

epidemiological data and, by analogy,

by the oral and dermal routes.

The current MCL for vinyl chloride is

based on a PQL of 0.002 mg/L. As a part

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19085

15EPA is aware that Escherichia coli O157 may

be found in fecally contaminated drinking water. To

date, however, none of the EPA-approved methods

for E. coli and fecal coliforms in drinking water

detect E. coli O157. Nevertheless, E. coli O157, as

is true with nonpathogenic E. coli strains, is always

associated with fecal waste (outside the laboratory)

and should be as susceptible to disinfection as the

nonpathogenic strains. Therefore, the presence of E.

coli O157 should always be accompanied by other

E. coli strains that are detectable by the EPAapproved methods.

of the Six-Year Review, EPA analyzed

WS data to determine if it might be

possible to recalculate the PQL. In

addition, the Agency evaluated whether

more sensitive analytical methods have

been approved and put into use by a

wide number of laboratories. Based on

these analyses, the Agency believes the

current PQL, and therefore the MCL, is

still appropriate (USEPA, 2002d).

A review of treatment feasibility is not

necessary for vinyl chloride because no

changes to the MCLG or the MCL are

warranted at this time. In addition, the

results of EPA’s review of possible

‘‘other regulatory revisions’’ did not

identify any vinyl chloride-specific

issues (USEPA, 2002e). Since EPA did

not identify a health or technology basis

for revising the vinyl chloride NPDWR,

the Agency did not conduct a detailed

occurrence and exposure analysis.

c. Preliminary Decision. After

reviewing the results of the pertinent

technical analyses, the Agency believes

the NPDWR for vinyl chloride remains

appropriate and thus, it is not subject to

revision at this time.

68. Xylenes (Total)

a. Background. EPA published the

current NPDWR for total xylenes on

January 30, 1991 (56 FR 3526 (USEPA,

1991a)). The NPDWR established an

MCLG and an MCL of 10 mg/L. The

Agency based the MCLG on an RfD of

2 mg/kg/day and a cancer classification

of D, not classifiable as to human

carcinogenicity.

b. Technical Reviews. The Agency has

initiated a reassessment of the health

risks resulting from exposure to xylenes.

The revised risk assessment will

consider relevant studies that have

become available on the toxicity of

xylenes including its potential

developmental and reproductive

toxicity. The Agency expects the new

risk assessment to be completed in the

2002 or 2003 time frame (USEPA,

2002i).

c. Preliminary Decision. The Agency

does not believe a revision to the

NPDWR for xylenes is appropriate at

this time because a reassessment of the

health risks resulting from exposure to

xylenes is ongoing.

B. What Preliminary Decision Has EPA

Made Regarding the Total Coliform

Rule?

1. Background

EPA published the TCR on June 29,

1989 (54 FR 27544 (USEPA, 1989b)).

The TCR is one of several EPA

regulations that protect the public from

pathogens in drinking water. The TCR

requires all PWSs to monitor for the

presence of total coliforms in the

distribution system. Total coliforms are

a group of closely related bacteria that

are (with few exceptions) not harmful to

humans. They are natural and common

inhabitants of the soil and ambient

waters (e.g., lakes, rivers and estuaries),

as well as in the gastrointestinal tract of

animals. A few of these coliforms (fecal

coliforms, including Escherichia coli or

E. coli 15) only grow within the

intestinal tract of humans and other

warm-blooded animals. Total coliforms

may be injured by environmental

stresses (e.g., lack of nutrients) and

water treatment (e.g., chlorine

disinfection) in a manner similar to

most bacterial pathogens and many

virus pathogens. Therefore, EPA

considers them a useful indicator of

bacterial and many viral waterborne

enteric pathogens. More specifically, for

drinking water, total coliforms are used

to determine the adequacy of water

treatment and the integrity of the

distribution system. The absence of total

coliforms in the distribution system

minimizes the likelihood that fecal

pathogens are present. Thus, total

coliforms are used to determine the

vulnerability of a system to fecal

contamination.

The 1989 TCR set an MCLG of zero for

total coliforms because EPA was not

aware of any data in the scientific

literature supporting a particular value

for the concentration of coliforms below

which no known or anticipated adverse

health effects occur, with an adequate

margin of safety. The TCR requires

systems to monitor for total coliforms at

a frequency proportional to the number

of people served. If any sample is total

coliform-positive, the system must:

• Test the positive culture for the

presence of either fecal coliforms or E.

coli;

• Take one set of 3–4 repeat samples

at sites located within five or fewer

sampling sites adjacent to the location

of the routine positive sample within 24

hours; and

• Take at least 5 routine samples the

next month of operation.

2. Technical Reviews

Since the TCR was promulgated in

1989, few technical papers on the

occurrence of coliforms in treated water

have been published. Much of the

recent technical data on coliforms are

associated with biofilm studies,

specifically the factors that facilitate the

growth of coliforms and other microbes

within the distribution system (e.g.,

LeChevallier et al., 1991, 1996;

LeChevallier, 1999). In addition, several

studies have been published describing

the performance of new coliform

methods (e.g., Brenner et al., 1993;

Grant, 1997).

One recent study examined the

relationship between total coliforms and

waterborne disease outbreaks (Craun et

al., 1997). According to the study

results, coliforms were found in 84

percent of the 187 systems during an

outbreak investigation, but in the

months before any outbreak, they were

only detected by 26 percent of these

systems. For outbreaks caused by

Cryptosporidium or Giardia, coliforms

were only found during 38 percent of

the outbreaks. The study, as well as data

from the 1993 outbreak of waterborne

cryptosporidiosis in Milwaukee

(MacKenzie, et al., 1994), continues to

support the premise that coliforms are

an inadequate indicator for

Cryptosporidium oocysts and Giardia

cysts in treated waters, presumably

because these protozoa are appreciably

more resistant to disinfection than the

coliform indicators.

Since promulgation of the TCR, EPA

has received comments from a number

of stakeholders. Stakeholders have

suggested modifications to reduce the

burden of implementing the TCR. EPA

has determined that an opportunity for

implementation burden reduction exists

and will analyze the effect that such

changes would have on public health

protection as part of the Agency’s

regulatory development/revision

process. Only those measures which

reduce the TCR implementation burden

while still assuring public health

protection will be considered by EPA.

3. Preliminary Decision

EPA intends to undertake a

rulemaking process to initiate possible

revisions to the TCR. As part of this

process, EPA believes it may be

appropriate to include this rulemaking

in a wider effort to review and address

broader issues associated with drinking

water distribution systems. This would

be one way of addressing some of the

recommendations of the Microbial/

Disinfection Byproducts (M/DBP)

Federal Advisory Committee in the

Stage 2 M/DBP Agreement in Principle

(65 FR 83015, December 29, 2000

(USEPA, 2000h)). As part of the TCR

rulemaking, EPA plans to assess the

19086 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

effectiveness of the current TCR in

reducing public health risk, and what

technically supportable alternative/

additional monitoring strategies are

available that would decrease economic

burden while maintaining or improving

public health protection.

VI. Request for Comments

A. On Which Issues Is EPA Soliciting

Public Comment?

Today’s action solicits public

comment on the following broad issues.

(1) Is EPA’s protocol for the review of

the 69 NPDWRs discussed in today’s

action reasonable and appropriate?

(2) Based on the review, are EPA’s

revise/not revise conclusions

appropriate for each of the 69 NPDWRs?

EPA also invites commenters to

submit any new, relevant peer-reviewed

data pertaining to the NPDWRs

discussed in today’s action. Peerreviewed data are studies/analyses that

have been reviewed by qualified

individuals (or organizations) who are

independent of those who performed

the work, but who are collectively

equivalent in technical expertise (i.e.,

peers) to those who performed the

original work. A peer review is an indepth assessment of the assumptions,

calculations, extrapolations, alternate

interpretations, methodology,

acceptance criteria, and conclusions

pertaining to the specific major

scientific and/or technical work

products and of the documentation that

supports them (USEPA, 2000i). Relevant

data include studies/analyses pertaining

to health effects, analytical feasibility,

treatment feasibility, and occurrence/

exposure related to the contaminants

discussed in today’s action.

Table VI–1 summarizes the specific

comments requested in today’s action

and provides a cross reference to the

section of today’s action where the issue

is discussed.

BILLING CODE 6560–50–P

BILLING CODE 6560–50–C

EPA also invites commenters to

submit any new, relevant peer-reviewed

data pertaining to the NPDWRs

discussed in today’s action.

B. Request for Comments on Use of

Plain Language

Executive Order 12866 and the

President’s memorandum of June 1,

1998, require each agency to write all

rules in plain language. We invite your

comments on how to make this action

easier to understand. For example:

• Have we organized the material to

suit your needs?

• Are the decisions in the notice and

our rationale for those decisions clearly

stated?

• Does the notice contain technical

language or jargon that isn’t clear?

• Would a different format (grouping

and order of sections, use of headings,

paragraphing) make the notice easier to

understand?

• Would more (but shorter) sections

be better?

• Could we improve clarity by adding

tables, lists, or diagrams?

• What else could we do to make the

notice easier to understand?

VII. EPA’s Next Steps

EPA plans a 60-day comment period

following this action. For each NPDWR

for which the Agency has published its

preliminary revise/not revise decision

in today’s action, EPA will consider the

public comments received and review

any new peer-reviewed data submitted

in support of those public comments to

determine whether a different revise/not

revise decision is appropriate in light of

the submitted data. The Agency plans to

publish its final revise/not revise

decisions for these NPDWRs in the

August 2002 time frame.

The publication of a decision to revise

pursuant to SDWA Section 1412(b)(9) is

not the end of the regulatory process,

but is the beginning of one. A decision

to revise starts a regulatory process for

a contaminant that involves more

detailed analyses concerning health

effects, costs, benefits, occurrence, and

other matters relevant to deciding

whether and how an NPDWR should be

revised. At any point in this process,

EPA may find that regulatory revisions

are no longer appropriate and may

discontinue regulatory revision efforts at

that time. Review of that contaminant

would continue in future six-year

reviews.

Similarly, a decision not to revise at

this time means only that EPA does not

believe that regulatory changes to a

particular NPDWR are appropriate now,

based on lack of new data, ongoing

scientific reviews, low priority, or other

reasons discussed in this action. Review

of these contaminants continues and

future six-year reviews may lead to a

decision that regulatory changes are

appropriate.

VIII. References

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Dibromo-3-chloropropane. U.S.

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tp36.html.

ATSDR. 1993. Toxicological Profile for

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tp12.html.

ATSDR. 1996a. Toxicological Profile for 1,2-

Dichloroethene. U.S. Department of

Health and Human Services, Public

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19087

Health Service. 196 pp. Available on the

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ATSDR. 1996b. Toxicological Profile for

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228 pp. Available on the Internet at:

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tp89.pdf.

ATSDR. 1996c. Toxicological Profile for

Hexachlorobenzene. U.S. Department of

Health and Human Services, Public

Health Service. 352 pp.

ATSDR. 1996d. Toxicological Profile for

Toxaphene. U.S. Department of Health

and Human Services, Public Health

Service. 248 pp. Available on the

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ATSDR. 1999. Toxicological Profile for Lead.

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Brenner, K.P., C.C. Rankin, Y.R. Roybal, G.N.

Stelma, P.V. Scarpino, and A.P. Dufour.

1993. New medium for the simultaneous

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3534–3544.

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89, pp. 96–104.

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Nomination and Selection,

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NTP Interagency Committee for

Chemical Evaluation and Coordination.

Subject: Hexavalent chromium

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Flegal, R. et al. 2001. Scientific Review of

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Related to Development of a Public

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Grant, M.A. 1997. A New Membrane

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LeChevallier, M.W. 1999. The case for

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1991. Bacterial nutrients in drinking

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LeChevallier, M.W., N.J. Welch, and D.B.

Smith. 1996. Full-scale studies of factors

related to coliform regrowth in drinking

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MacKenzie W.R., N.J. Hoxie, M.E. Proctor,

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J.J. Kazmierczak, D.A. Addiss, K.R. Fox,

J.B. Rose, and J.P. Davis. 1994. A massive

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Cryptosporidium infection transmitted

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NAS. 1995. Nitrate and nitrite in drinking

water. National Academy Press,

Washington, D.C. Available on the

Internet at: http://www.nap.edu/books/

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NAS. 1997. Dietary reference intakes for

calcium, phosphorus, magnesium,

vitamin D, and fluoride. National

Academy Press, Washington, D.C.

Available on the Internet at: http://

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index.html.

NAS. 2000a. Copper in drinking water.

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html.

NAS. 2000b. Dietary reference intakes for

vitamin C, vitamin E, selenium, and

carotenoids. National Academy Press,

Washington, D.C. Available on the

Internet at: http://www.nap.edu/books/

0309069351/html.

NAS. 2001. Dietary reference intakes for

vitamin A, vitamin K, arsenic, boron,

chromium, copper, iodine, iron,

manganese, molybdenum, nickel,

silicon, vanadium, and zinc. National

Academy Press, Washington, D.C.

Available on the Internet at: http://

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NDWAC. 2000. Recommended Guidance for

Review of Existing National Primary

Drinking Water Regulations. November

2000. Available on the Internet at:

http://www.epa.gov/safewater/ndwac/

guidfnl.pdf.

NTP. 2001. NTP Study of the Hexavalent

Chromium Compound Sodium

Dichromate Dihydrate. Available on the

Internet at: http://ntpserver.niehs.nih.gov/htdocs/Studies/

HexChromium/hexchromiumpg.html.

United States Department of Agriculture

(USDA). 1998. National Agricultural

Impact Program—Reregistration

Notification Network. Volume 3, Number

11, September 10, 1993. Available on the

Internet at: http://ipmwww.ncsu.edu/

opmppiap/rnn/rnn3–11.htm.

USEPA. 1975. Water Programs: National

Interim Primary Drinking Water

Regulations. Federal Register. Vol. 40,

No. 248, p. 59566. December 24, 1975.

USEPA. 1976. Interim Primary Drinking

Water Regulations; Promulgation of

Regulations on Radionuclides. Federal

Register. Vol. 41, No. 133. p. 28401, July

9, 1976.

USEPA. 1979. National Interim Primary

Drinking Water Regulations; Control of

Trihalomethanes in Drinking Water.

Federal Register. Vol. 44, No. 231. p.

68624, November 29, 1979.

USEPA. 1985. National Primary Drinking

Water Regulations; Volatile Synthetic

Organic Chemicals; Final Rule and

Proposed Rule. Federal Register. Vol. 50,

No. 219. p. 46880, November 13, 1985.

USEPA. 1986a. National Primary and

Secondary Drinking Water Regulations;

Fluoride; Final Rule. Federal Register.

Vol. 51, No. 63. p. 11396, April 2, 1986.

USEPA. 1986b. EPA Guidelines for

Carcinogen Risk Assessment. Federal

Register. Vol. 51, No. 185. p. 33992,

September 24, 1986.

USEPA. 1987. National Primary Drinking

Water Regulations—Synthetic Organic

Chemicals; Monitoring for Unregulated

Contaminants; Final Rule. Federal

Register. Vol. 52, No. 130. p. 25690, July

8, 1987.

USEPA. 1989a. National Primary and

Secondary Drinking Water Regulations;

Proposed Rule. Federal Register. Vol. 54,

No. 97. p. 22062, May 22, 1989.

USEPA. 1989b. Drinking Water; National

Primary Drinking Water Regulations;

Total Coliforms (Including Fecal

Coliforms and E. coli); Final Rule.

Federal Register. Vol. 54, No. 124. p.

27544, June 29, 1989.

USEPA. 1989c. National Primary Drinking

Water Regulations; Filtration,

Disinfection; Turbidity, Giardia Lamblia,

Viruses, Legionella, and Heterotrophic

Bacteria; Final Rule. Part 2. Federal

Register. Vol. 54, No. 124. p. 27486, June

29, 1989.

USEPA. 1990. National Primary and

Secondary Drinking Water Regulations—

Synthetic Organic Chemicals and

Inorganic Chemicals; Proposed Rule.

Federal Register. Vol. 55, No. 143. p.

30370, July 25, 1990.

USEPA. 1991a. National Primary Drinking

Water Regulations—Synthetic Organic

Chemicals and Inorganic Chemicals;

Monitoring for Unregulated

Contaminants; National Primary

Drinking Water Regulations

Implementation; National Secondary

Drinking Water Regulations; Final Rule.

Federal Register. Vol. 56, No. 30. p.

3526, January 30, 1991.

USEPA. 1991b. Drinking Water Regulations—

Maximum Contaminant Level Goals and

National Primary Drinking Water

Regulations for Lead and Copper; Final

Rule. Federal Register. Vol. 56, No. 110.

p. 26460, June 7, 1991.

USEPA. 1991c. Drinking Water; National

Primary Drinking Water Regulations;

Monitoring for Volatile Organic

Chemicals; MCLGs and MCLs for

Aldicarb, Aldicarb Sulfoxide, Aldicarb

Sulfone, Pentachlorophenol, and

Barium; Final Rule. Federal Register.

Vol. 56, No. 126. p. 30266, July 1, 1991.

USEPA. 1992. Drinking Water; National

Primary Drinking Water Regulations—

Synthetic Organic Chemicals and

Inorganic Chemicals; National Primary

Drinking Water Regulations

Implementation; Final Rule. Federal

Register. Vol. 57, No. 138. p. 31776, July

17, 1992.

USEPA. 1994a. Public Water System

Warning: Cyanide. Memo from William

R. Diamond, Acting Director of Drinking

Water Standards Division, Office of

Ground Water and Drinking Water.

March 7, 1994.

USEPA. 1994b. Drinking Water; Maximum

Contaminant Level Goals and National

Primary Drinking Water Regulations for

19088 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

Lead and Copper; Final Rule; Technical

Corrections. Federal Register. Vol. 59,

No. 125. p. 33860, June 30, 1994.

USEPA. 1995. Integrated Risk Information

System (IRIS), Mercuric Chloride.

Available on the Internet at: http://

www.epa.gov/iris/subst/0692.htm.

USEPA. 1996. Proposed guidelines for

carcinogen risk assessment. Federal

Register. Vol. 61, No. 79. p. 17960, April

23, 1996.

USEPA. 1997a. Alternative Monitoring

Guidelines. EPA Report 816–R–97–011.

August 1997. Available on the Internet

at: http://www.epa.gov/safewater/regs/

pmrfin.html.

USEPA. 1997b. Mercury Study Report to

Congress; Volume V: Health Effects of

Mercury and Mercury Compounds. EPA

Report 452–R–97–009. Office of Air

Quality Planning and Standards, Office

of Research and Development. December

1997. Available on the Internet at:

http://www.epa.gov/ttn/oarpg/t3/

reports/volume5.pdf.

USEPA. 1998a. Small System Compliance

Technology List for Non-Microbial

Contaminants Regulated Before 1996.

EPA Report 815–R–98–002. September

1998.

USEPA. 1998b. National Primary Drinking

Water Regulations: Disinfectants and

Disinfection Byproducts; Final Rule.

Federal Register. Vol. 63, No. 241. p.

69389, December 16, 1998.

USEPA. 1998c. National Primary Drinking

Water Regulations: Interim Enhanced

Surface Water Treatment; Final Rule.

Federal Register. Vol. 63, No. 241. p.

69478, December 16, 1998.

USEPA. 1998d. IRIS, Beryllium and

Compounds. Available on the Internet at:

http://www.epa.gov/iris/subst/0012.htm.

USEPA. 1998e. IRIS, Chlordane (Technical).

Available on the Internet at: http://

www.epa.gov/iris/subst/0142.htm.

USEPA. 1998f. IRIS, Chromium (VI).

Available on the Internet at: http://

www.epa.gov/iris/subst/0144.htm.

USEPA. 1999a. Response to

Recommendations from the Children’s

Health Protection Advisory Committee

Regarding Evaluation of Existing

Environmental Standards; Notice.

Federal Register. Vol. 64, No. 22. p.

5277, February 3, 1999.

USEPA. 1999b. Guidelines for Carcinogen

Risk Assessment. NCEA-F–0644 Review

Draft. U.S. Environmental Protection

Agency Risk Assessment Forum.

Washington, D.C. July 1999.

USEPA. 1999c. Announcement of

Stakeholders Meeting on the Drinking

Water Contaminant Identification and

Selection Process, and the 6-Year Review

of All Existing National Primary

Drinking Water Regulations, as Required

by the Safe Drinking Water Act, as

Amended in 1996; Notice of

Stakeholders Meeting. Federal Register.

Vol. 64, No. 198. p. 55711, October 14,

1999.

USEPA. 1999d. A Review of Contaminant

Occurrence in Public Water Systems.

EPA Report 816–R–99–006. November

1999. Available on the Internet at: http:/

/www.epa.gov/safewater/occur/

nov99_lo.pdf.

USEPA. 1999e. Stakeholder Meeting on the

Contaminant Candidate List and the 6-

Year Review of Existing National

Primary Drinking Water Regulations.

November 1999. Available on the

Internet at: http://www.epa.gov/

safewater/ccl/novmtg.html.

USEPA. 1999f. IRIS, Barium and

Compounds. Available on the Internet at:

http://www.epa.gov/iris/subst/0010.htm.

USEPA. 2000a. National Primary Drinking

Water Regulations for Lead and Copper;

Final Rule. Federal Register. Vol. 65, No.

8. p. 1950, January 12, 2000.

USEPA. 2000b. Working Group Meeting on

Contaminant Candidate List Regulatory

Determinations and the 6-Year Review of

Existing Regulations. Office of Water.

June 2000. Available on the Internet at:

http://www.epa.gov/safewater/ccl/

junemtg.html.

USEPA. 2000c. Working Group Meeting on

Contaminant Candidate List Regulatory

Determinations and the 6-Year Review of

Existing Regulations. Office of Water.

July 2000. Available on the Internet at:

http://www.epa.gov/safewater/ccl/

julymtg.html.

USEPA. 2000d. NDWAC Working Group

Meeting on Contaminant Candidate List

Regulatory Determinations and the 6-

Year Review of Existing Regulations.

Office of Water. September 2000.

Available on the Internet at: http://

www.epa.gov/safewater/ccl/

25septmtg.html.

USEPA. 2000e. Interim Reregistration

Eligibility Decision (IRED)—Oxamyl.

EPA Report 738–R–00–015. Office of

Prevention, Pesticides, and Toxic

Substances. October 2000. Available on

the Internet at: http://www.epa.gov/

oppsrrd1/REDs/0253ired.pdf.

USEPA. 2000f. Methodology for Deriving

Ambient Water Quality Criteria for the

Protection of Human Health. EPA Report

882–B–00–004. Office of Water. October

2000.

USEPA. 2000g. National Primary Drinking

Water Regulations; Radionuclides; Final

Rule. Federal Register. Vol. 65, No. 236.

p. 76707, December 7, 2000.

USEPA. 2000h. Stage 2 Microbial and

Disinfection Byproducts Federal

Advisory Committee Agreement in

Principle; Notice. Federal Register. Vol.

65, No. 251. p. 83015, December 29,

2000.

USEPA. 2000i. Science Policy Council

Handbook: Peer Review, 2nd Edition.

EPA Report 100–B–00–001. Office of

Science Policy, Office of Research and

Development. December 2000.

USEPA. 2000j. IRIS, Benzene. Available on

the Internet at: http://www.epa.gov/iris/

subst/0276.htm.

USEPA. 2000k. IRIS, Vinyl Chloride.

Available on the Internet at: http://

www.epa.gov/iris/subst/1001.htm.

USEPA. 2000l. EPA Summary Report.

Characterization of data variability and

uncertainty: Health effects assessments

in the Integrated Risk Information

System (IRIS). In response to Congress,

HR 106–379. EPA Report 635–R–00–

005F. National Center for Environmental

Assessment, Office of Research and

Development.

USEPA. 2001a. National Primary Drinking

Water Regulation; Arsenic and

Clarifications to Compliance and New

Source Contaminants Monitoring; Final

Rule. Federal Register. Vol. 66, No. 14.

p. 6975, January 22, 2001.

USEPA. 2001b. Dioxin Reassessment—An

SAB Review of the Office of Research

and Development’s Reassessment of

Dioxin. EPA Report SAB–EC–01–006.

May 2001. Available on the Internet at:

http://www.epa.gov/sab/ec01006.pdf.

USEPA. 2001c. IRIS,

Hexachlorocyclopentadiene. Available

on the Internet at: http://www.epa.gov/

iris/subst/0059.htm.

USEPA. 2002a. Integrated Risk Information

System (IRIS); Announcement of 2002

Program; Request for Information;

Notice. Federal Register. Vol. 67, No. 6.

p. 1212, January 9, 2002.

USEPA. 2002b. National Primary Drinking

Water Regulations: Long-Term 1

Enhanced Surface Water Treatment Rule;

Final Rule. Federal Register. Vol. 67, No.

9. p. 1811, January 14, 2002.

USEPA. 2002c. An Evaluation of Available

Economic Information in Support of the

Six-Year Review of Existing National

Primary Drinking Water Regulations.

Memo from Marc Parrotta, Targeting and

Analysis Branch, Office of Ground Water

and Drinking Water. March 2002.

USEPA. 2002d. Analytical Feasibility

Support Document for the Six-Year

Review of Existing National Primary

Drinking Water Regulations

(Reassessment of Feasibility for

Chemical Contaminants). EPA Report

815–D–02–002. Draft. March 2002.

USEPA. 2002e. Consideration of Other

Regulatory Revisions for Chemical

Contaminants in Support of the Six-Year

Review of National Primary Drinking

Water Regulations. EPA Report 815–D–

02–003. Draft. March 2002.

USEPA. 2002f. EPA Protocol for Review of

Existing National Primary Drinking

Water Regulations. EPA Report 815–D–

02–004. Draft. March 2002.

USEPA. 2002g. Occurrence Estimation

Methodology and Occurrence Findings

Report for the Six-Year Regulatory

Review. EPA Report 815–D–02–005.

Draft. March 2002.

USEPA. 2002h. Occurrence Summary and

Use Support Document for the Six-Year

Regulatory Review. EPA Report 815–D–

02–006. Draft. March 2002.

USEPA. 2002i. Six-Year Review—Chemical

Contaminants—Health Effects Technical

Support Document. EPA Report 822–R–

02–001. Draft. February 2002.

USEPA. 2002j. Six-Year Review of the Total

Coliform Rule—Comments Received.

Memo from Kenneth H. Rotert,

Standards and Risk Reduction Branch,

Office of Ground Water and Drinking

Water. March 2002.

USEPA. 2002k. Water Treatment Technology

Feasibility Support Document for

Chemical Contaminants; In Support of

Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules 19089

16The MCLG for nitrite was based on a 4 kg body

weight and a 0.64 liter drinking water intake for

infants because they are the group most sensitive

to the critical effect.

EPA Six-Year Review of National

Primary Drinking Water Regulations.

EPA Report EPA 815–D–02–001. Draft.

February 2002.

Dated: March 28, 2002.

Christine Todd Whitman,

Administrator.

Appendix A: Background on the

Calculation of MCLG and Cancer

Classification System

Since the identification of contaminants for

potential revision may be dependent on

whether or not the maximum contaminant

level goal (MCLG) could change, a brief

explanation of the derivation of the MCLG is

warranted. The MCLG is the maximum level

of a contaminant in drinking water at which

no known or anticipated adverse health

effects occur, allowing for an adequate

margin of safety. MCLGs are non-enforceable

health goals. EPA establishes the maximum

contaminant level (MCL) based on the MCLG.

The MCL is the maximum permissible level

of a contaminant in water which is delivered

to any user of a public water system. It is

derived based on the MCLG. Prior to the 1996

Amendments to the Safe Drinking Water Act

(SDWA), the MCL was set as close to the

MCLG as is feasible, taking costs into

consideration. The 1996 Amendments to the

SDWA permit consideration of costs relative

to benefits in establishing a MCL. MCLs are

enforceable standards.

For chemicals exhibiting a threshold for

toxic effects, EPA establishes the MCLG on

the basis of an oral reference dose (RfD). A

change in the RfD could lead to a change in

the MCLG and thus in the MCL. The RfD is

an estimate (with uncertainty spanning

perhaps an order of magnitude) of a daily

oral exposure to the human population

(including sensitive subgroups) that is likely

to be without an appreciable risk of

deleterious noncancer effects during a

lifetime. The RfD is derived as follows:

RfD = NOAEL or LOAEL or BMD

UF MF ×

Where:

NOAEL = no-observed-adverse-effect level

LOAEL = lowest-observed-adverse-effect

level

BMD = benchmark dose

UF = uncertainty factor

MF = modifying factor

The benchmark dose (BMD) is the statistical

lower confidence limit on the dose estimated

to produce a predetermined level of change

(i.e., 10 percent) in the critical response

relative to the control. The uncertainty factor

(UF) is used to account for extrapolation

uncertainties (e.g., inter-individual variation,

interspecies differences, duration of

exposure, and use of a LOAEL instead of a

NOAEL) and database adequacy. The

modifying factor (MF) is used as a judgment

factor to account for the confidence in the

critical study (or studies) used in the

derivation of the RfD (USEPA, 20001).

The MCLG is then derived from the RfD as

follows:

MCLG = RfD bw RSC

I

× ×

Where:

bw = body weight (70 kg for adult 16)

RSC = relative source contribution, the

fraction of the RfD allocated to drinking

water

I = daily drinking water intake (2 liters for

adults 16)

The relative source contribution (RSC) is

one factor which will determine how much

a change in the RfD will lead to a change in

the MCLG. RSC refers to the method of

accounting for human exposure from

multiple sources when setting health-based

criteria. The purpose of the RSC is to ensure

that the level of a chemical allowed by a

criterion or multiple criteria, when combined

with other identified sources of exposure

common to the population of concern, will

not result in exposures that exceed the RfD.

The policy of considering multiple sources of

exposure when deriving health-based criteria

has become common in EPA’s risk

characterizations, as well as criteria and

standard-setting actions. The drinking water

program has applied a ceiling level of 80

percent of the RfD and a floor level of 20

percent of the RfD. That is, the MCLG cannot

account for more than 80 percent of the RfD,

nor less than 20 percent of the RfD. EPA

applies an RSC factor of 20 percent to the RfD

when adequate exposure data do not exist.

EPA has now revised its RSC method

to improve consistency when

considering non-water sources of

exposure (both ingestion exposures (e.g.,

food) and exposures other than the oral

route (e.g., inhalation). The approach is

called the Exposure Decision Tree. RSC

estimates will be made by EPA using

this approach, which allows for use of

either subtraction or percentage

methods, depending on chemicalspecific circumstances, within the 20 to

80 percent range described in the

previous paragraph. For a detailed

discussion on the revised approach,

refer to the ‘‘Methodology for Deriving

Ambient Water Quality Criteria for the

Protection of Human Health’’ (USEPA,

2000f).

It has also been the Agency policy to

apply an additional safety factor to the

RfD for chemicals with equivocal

evidence of carcinogenicity. This

practice is another factor that must be

evaluated to determine the impact of a

change in RfD on the MCLG.

For drinking water contaminants

regulated prior to the 1996 SDWA,

EPA’s Office of Water (OW) followed a

three-category regulatory cancer

classification system (Categories I, II, or

III). These categories specify decisions

as to degree of concern for an agent’s

carcinogenic potential as a contaminant

of drinking water, and define to some

extent the approach to risk management

which is taken for establishing MCLGs.

Categories I, II, and III are designations

not defined in guidelines but which

reflect OW policy.

EPA used the six alphanumeric

categories (A, B1, B2, C, D, E) of the

1986 cancer guidelines (51 FR 33992,

September 24, 1986 (USEPA, 1986b)) in

establishing the MCLG. The six-group

classification system is often equated to

the three-category system in the

National Primary Drinking Water

Regulation (NPDWR) Federal Register

announcements. Table A–1 describes

the three categories and, with few

exceptions (e.g., beryllium), their usual

equivalent alphanumeric classification.

If a chemical is a known or probable

human carcinogen (Category I, generally

Group A or B), the MCLG is generally

set at zero because it is assumed, in the

absence of other data, that there is no

known threshold for carcinogenicity. If

a chemical falls in Group C, an RfD

approach along with an additional

safety (risk management) factor is used

in deriving the MCLG. The methodology

used for establishing MCLGs for

chemicals with varying degrees of

evidence of carcinogenicity is also

briefly described in Table A–1.

Recent Agency assessments also use

the 1996 Proposed Guidelines for

Carcinogen Risk Assessment (61 FR

17960, April 23, 1996 (USEPA,1996)) or

the draft revised Guidelines for

Carcinogen Risk Assessment (USEPA,

1999b). The proposed guidelines use

standard descriptors as part of the

hazard narrative to express the weightof-evidence for carcinogenic hazard

potential. The 1996 descriptors are in

three categories: ‘‘Known/likely,’’

‘‘cannot be determined,’’ and ‘‘not

likely.’’ Subdescriptors are provided

under these categories to further

differentiate an agent’s carcinogenic

potential. The new descriptors permit

consideration of exposure route and

mode of action when making an

assessment of carcinogenicity. The

hazard descriptors of the 1996 proposed

Guidelines are given in the text to this

action whenever appropriate. None of

the chemicals discussed in this action

have been evaluated under the 1999

draft revised Guidelines for Carcinogen

Risk Assessment.

BILLING CODE 6560–50–P

19090 Federal Register / Vol. 67, No. 74 / Wednesday, April 17, 2002 / Proposed Rules

[FR Doc. 02–9154 Filed 4–16–02; 8:45 am]

BILLING CODE 6560–50–C