[Federal Register Volume 59, Number 145 (Friday, July 29, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-17651]


[[Page Unknown]]

[Federal Register: July 29, 1994]


_______________________________________________________________________

Part II





Environmental Protection Agency





_______________________________________________________________________



40 CFR Parts 141 and 142



National Primary Drinking Water Regulations; Disinfectants and 
Disinfection Byproducts; Proposed Rule
ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 141 and 142

[WH-FRL-4998-2]

 

Drinking Water; National Primary Drinking Water Regulations: 
Disinfectants and Disinfection Byproducts

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

-----------------------------------------------------------------------

SUMMARY: In this document, EPA is proposing maximum residual 
disinfectant level goals (MRDLGs) for chlorine, chloramines, and 
chlorine dioxide; maximum contaminant level goals (MCLGs) for four 
trihalomethanes (chloroform, bromodichloromethane, 
dibromochloromethane, and bromoform), two haloacetic acids 
(dichloroacetic acid and trichloroacetic acid), chloral hydrate, 
bromate, and chlorite; and National Primary Drinking Water Regulations 
(NPDWRs) for three disinfectants (chlorine, chloramines, and chlorine 
dioxide), two groups of organic disinfection byproducts (total 
trihalomethanes (TTHMs)--a sum of the four listed above, and haloacetic 
acids (HAA5)--a sum of the two listed above plus monochloroacetic acid 
and mono- and dibromoacetic acids), and two inorganic disinfection 
byproducts (chlorite and bromate). The NPDWRs consist of maximum 
residual disinfectant levels or maximum contaminant levels or treatment 
techniques for these disinfectants and their byproducts. The NPDWRs 
also include proposed monitoring, reporting, and public notification 
requirements for these compounds. This notice proposes the best 
available technology (BAT) upon which the MRDLs and MCLs are based and 
the BAT for purposes of issuing variances.

DATES: Written comments must be postmarked or hand-delivered by 
December 29, 1994. Comments received after this date may not be 
considered. Public hearings will be held at the addresses indicated 
below under ``ADDRESSES'' on August 29 (and 30, if necessary) in 
Denver, CO and on September 12 (and 13, if necessary) in Washington, 
DC.

ADDRESSES: Send written comments on the proposed rule to Disinfectant/
Disinfection By-Products Comment Clerk, Drinking Water Docket (MC 
4101), Environmental Protection Agency, 401 M Street, S.W., Washington, 
D.C. 20460. Commenters are requested to submit three copies of their 
comments and at least one copy of any references cited in their written 
or oral comments. A copy of the comments and supporting documents are 
available for review at the EPA, Drinking Water Docket (4101), 401 M 
Street, S.W., Washington, DC 20460. For access to the docket materials, 
call (202) 260-3027 between 9:00 a.m. and 3:30 p.m.
    The Agency will hold public hearings on the proposal at two 
different locations indicated below:

1. Denver Federal Center, 6th and Kipling Streets, Building 25, Lecture 
Halls A and B (3d Street), Denver, CO 80225 on August 29 (and 30, if 
necessary), 1994.
2. EPA Education Center Auditorium, 401 M Street SW., Washington, D.C. 
20460, on September 12 (and 13, if necessary), 1994.

    The hearings will begin at 9:30 a.m., with registration at 9:00 
a.m. The Hearings will end at 4:00 p.m., unless concluded earlier. 
Anyone planning to attend the public hearings (especially those who 
plan to make statements) may register in advance by writing the D/DBPR 
Public Hearing Officer, Office of Ground Water and Drinking Water 
(4603), USEPA, 401 M Street, S.W., Washington, D.C. 20460; or by 
calling Tina Mazzocchetti, (703) 931-4600. Meeting dates are tentative 
and should be confirmed by calling the Safe Drinking Water Hotline 
prior to making travel plans. Oral and written comments may be 
submitted at the public hearing. Persons who wish to make oral 
presentations are encouraged to have written copies (preferably three) 
of their complete comments for inclusion in the official record.
    Copies of draft health criteria, analytical methods, and regulatory 
impact analysis documents are available at some Regional Offices listed 
below and for a fee from the National Technical Information Service 
(NTIS), U.S. Department of Commerce, 5285 Port Royal Road, Springfield, 
Virginia 22161. The toll-free number is (800) 336-4700 or local at 
(703) 487-4650.

FOR FURTHER INFORMATION CONTACT: General information may be obtained 
from the Safe Drinking Water Hotline, telephone (800) 426-4791; Stig 
Regli, Office of Ground Water and Drinking Water (4603), U.S. 
Environmental Protection Agency, 401 M Street, SW., Washington, DC 
20460, telephone (202) 260-7379; Tom Grubbs, Office of Ground Water and 
Drinking Water (4603), U.S. Environmental Protection Agency, 401 M 
Street, SW., Washington, DC 20460, telephone (202) 260-7270; or one of 
the EPA Regional Office contacts listed below.

SUPPLEMENTARY INFORMATION:

EPA Regional Offices

I. Robert Mendoza, Chief, Water Supply Section, JFK Federal Bldg., 
Room 203, Boston, MA 02203, (617) 565-3610
II. Robert Williams, Chief, Water Supply Section, 26 Federal Plaza, 
Room 824, New York, NY 10278, (212) 264-1800
III. Jeffrey Hass, Chief, Drinking Water Section (3WM41), 841 
Chestnut Building, Philadelphia, PA 19107, (215) 597-9873
IV. Phillip Vorsatz, Chief, Water Supply Section, 345 Courtland 
Street, Atlanta, GA 30365, (404) 347-2913
V. Charlene Denys, Chief, Water Supply Section, 77 W. Jackson Blvd., 
Chicago, IL 60604, (312) 353-2650
VI. F. Warren Norris, Chief, Water Supply Section, 1445 Ross Avenue, 
Dallas, TX 75202, (214) 655-7155
VII. Ralph Flournoy, Chief, Water Supply Section, 726 Minnesota 
Ave., Kansas City, KS 66101, (913) 234-2815
VIII. Doris Sanders, Chief, Water Supply Section, One Denver Place, 
999 18th Street, Suite 500, Denver, CO 80202-2405, (303) 293-1424
IX. Bill Thurston, Chief, Water Supply Section, 75 Hawthorne Street, 
San Francisco, CA 94105, (415) 744-1851
X. William Mullen, Chief, Water Supply Section, 1200 Sixth Avenue, 
Seattle, WA 98101, (206) 442-1225.
    Abbreviations used in this document.

AECL: Alternate enhanced coagulant level
AOC: Assimilable organic carbon
ASDWA: Association of State Drinking Water Administrators
AWWA: American Water Works Association
AWWARF: AWWA Research Foundation
BAC: Biologically active carbon
BAF: Biologically active filtration
BAT: Best Available Technology
BCAA: Bromochloroacetic acid
BDOC: Biodegradable organic carbon
BTGA: Best Technology Generally Available
CI: Confidence interval
CWS: Community Water System
DBP: Disinfection byproducts
D/DBP: Disinfectants and disinfection byproducts
D/DBPR: Disinfectants and disinfection byproducts rule
DBPP: Disinfection byproduct precursors
DBPRAM: DBP Regulatory Assessment model
DPD: N,N-diethyl-p-phenylenediamine
DWEL: Drinking Water Equivalent Level
EBCT: Empty bed contact time
EMSL: EPA Environmental Monitoring and Support Laboratory 
(Cincinnati)
EPA: United States Environmental Protection Agency
ESWTR: Enhanced Surface Water Treatment Rule
FY: Fiscal year
GAC: Granular Activated Carbon
GWDR: Ground Water Disinfection Rule
GWSS: Ground Water Supply Survey
HAA5: Haloacetic acids (five)
HOBr: Hypobromous acid
IC: Ion chromotography
ICR: Information Collection Rule
IOC: Inorganic chemical
LOAEL: Lowest observed adverse effect level
LOQ: Limit of Quantitation
MCL: Maximum Contaminant Level (expressed as mg/l, 1,000 micrograms 
(g) = 1 milligram (mg))
MCLG: Maximum Contaminant Level Goal
MDL: Method Detection Limit
MF: Modifying factor
mg/dl: Milligrams per deciliter
mg/l: Milligrams per liter
MGD: Million Gallons per Day
MRDL: Maximum Residual Disinfectant Level (as mg/l)
MRL: Minimum reporting level
MRDLG: Maximum Residual Disinfectant Level Goal
NCI: National Cancer Institute
ND: Not detected
NIPDWR: National Interim Primary Drinking Water Regulation
NOAEL: No observed adverse effect level
NOMS: National Organic Monitoring Survey
NORS: National Organics Reconnaissance Survey for Halogenated 
Organics
NPDWR: National Primary Drinking Water Regulation
NTNCWS: Nontransient noncommunity water system
OBr: Hypobromite ion
OR: Odds ratio
PE: Performance evaluation
POE: Point-of-Entry Technologies
POU: Point-of-Use Technologies
ppb: Parts per billion
PQL: Practical Quantitation Level
PTA: Packed Tower Aeration
PWS: Public Water System
RIA: Regulatory Impact Analysis
RMCL: Recommended Maximum Contaminant Level
RNDB: Regulations Negotiation Data Base
RSC: Relative Source Contribution
SDWA: Safe Drinking Water Act, or the ``Act,'' as amended in 1986
SM: Standard Method
SMCL: Secondary Maximum Contaminant Level
SMR: Standardized mortality ratios
SOC: Synthetic Organic Chemical
SWTR: Surface Water Treatment Rule
THMFP: Trihalomethane formation potential
TOC: Total organic carbon
TTHM: Total trihalomethanes
TWG: Technologies Working Group
VOC: Volatile Synthetic Organic Chemical
WIDB: Water Industry Data Base
WS: Water Supply

Table of Contents

I. Summary of Today's Action
    A. Applicability.
    B. Proposed MRDLGs and MRDLs for disinfectants
    C. Proposed MCLGs and MCLs for organic byproducts
    D. Treatment technique for DBP precursors
    E. Proposed Stage 1 MCLGs and MCLs for inorganic byproducts
    F. Proposed BAT for disinfectants
    G. Proposed BAT for organic byproducts
    H. Proposed BAT for inorganic byproducts
    I. Proposed Compliance Monitoring Requirements
    J. Analytical Methods
    K. Laboratory Certification Criteria
    L. Variances and Exemptions
    M. State Primacy, Recordkeeping, Reporting Requirements
    N. System Reporting Requirements
    O. D/DBP Stage 2 Rule requirements
    P. Guidance
    Q. Triennial Regulation Review
II. Statutory Authority
    A. MCLGs, MCLs, and BAT
    B. Variances and Exemptions
    C. Primacy
    D. Monitoring, Quality Control, and Records
    E. Public Water Systems
    F. Public Notification
III. Overview of Existing Interim Standard for TTHMs
IV. Overview of Preproposal Regulatory Development
    A. October 1989 Strawman Rule
    B. June 1991 Status Report on D/DBP rule development
    C. Initiation of Regulatory Negotiation Process
V. Establishing MCLGs
    A. Background
    B. Proposed MRDLGs and MCLGs
    1. Chlorine, hypochloriteion and hypochlorous acid
    2. Chloramines
    3. Epidemiology Studies of Chlorinated and Chloraminanted Water
    4. Chlorine dioxide, chlorite, and chlorate
    5. Chloroform
    6. Bromodichloromethane
    7. Dibromochloromethane
    8. Bromoform
    9. Dichloroacetic acid
    10. Trichloroacetic acid
    11. Chloral hydrate
    12. Bromate
VI. Occurrence of TTHMs, HAA5, and other DBPs
    A. Relationship of TTHMs, HAA5 to disinfection and source water 
quality
    B. Chlorination Byproducts
    C. Other Disinfection Byproducts
    1. Ozonation Byproducts
    2. Chlorine Dioxide Byproducts
    3. Chloramination Byproducts
VII. General Basis for Criteria of Proposed rule
    A. Goals of regulatory negotiation
    B. Concern for downside microbial risks and unknown risks from 
DBPs of different technologies
    C. Ecological concerns
    D. Watershed protection
    E. Narrowing of regulatory options through reg-neg process
VIII. Summary of the Proposed National Primary Drinking Water 
Regulation for Disinfectants and Disinfection Byproducts
    A. Schedule and coverage
    B. Summary of DBP MCLs, BATs, and monitoring and compliance 
requirments
    C. Summary of disinfectant MRDLs, BATs, and Monitoring and 
compliance requirements
    D. Enhanced coagulation and enhanced softening requirements
    E. Requirement for systems to use qualified operators
    F. Basis for analytical method requirements
    G. Public Notice Requirements
    H. Variances and Exemptions
    I. Reporting and Record Keeping requirements for PWSs
    J. State Implementation Requirements
IX. Basis for Key Specific Criteria of Proposed Rule
    A. 80/60 TTHM/HAA5 MCLs, enhanced coagulation requirements, and 
BAT
    1. basis for umbrella concept vs. individual MCLs
    2. basis for level of stringency in MCLs, BAT, and concurrent 
enhanced coagulation requirements
    3. basis for enhanced coagulation and softening criteria
    4. basis for GAC definitions
    5. basis for monitoring requirements
    B. Bromate MCL and BAT
    C. Chlorite MCL and BAT
    D. Chlorine MRDL and BAT
    E. Chloramine MRDL and BAT
    F. Chlorine dioxide MRDL and BAT
    G. Basis for analytical method requirements
    H. Basis for compliance schedule and applicability to different 
groups of systems, timing with other regulations
    I. Basis for qualified operator requirements and monitoring 
plans
    J. Basis for Stage 2 proposed MCLs
X. Laboratory Certification and Approval
    A. PE-Sample Acceptance Limits for Laboratory Certification
    B. Approval Criteria for Disinfectants and Other Parameters
    C. Other Laboratory Performance Criteria
XI. Variances and Exemptions
    A. Variances
    B. Exemptions
XII. State Implementation
    A. Special primacy requirements
    B. State recordkeeping
    C. State reporting
XIII. System Reporting and Recordkeeping Requirements
XIV. Public Notice Requirements
XV. Economic Analysis
    A. Executive Order 12866
    B. Predicted cost impacts on public water systems
    1. Compliance treatment cost forecasts
    2. Compliance treatment forecasts
    3. DBP exposure estimates
    4. System level cost estimates
    5. Effect on household costs
    6. Monitoring and State implementation costs, labor burden 
estimates
    C. Concepts of cost analysis
    D. Benefits
XVI. Other Requirements
    A. Consultation with State, Local, and Tribal Governments
    B. Regulatory Flexibility Act
    C. Paperwork Reduction Act
    D. National Drinking Water Advisory Council and Science Advisory 
Board
XVII. Request for Public Comment
XVIII. References and Public Docket

I. Summary of Today's Action

    In 1992 EPA initiated a negotiated rulemaking to develop a 
disinfectant/disinfection byproduct rule. The Agency decided to use the 
negotiated rulemaking process because it believed that the available 
occurrence, treatment, and health effects data were inadequate to 
address EPA's concerns about the tradeoff between risks from 
disinfectants and disinfection byproducts and microbial pathogen risk, 
and wanted all stakeholders to participate in the decision-making on 
setting proposed standards. The negotiators included State and local 
health and regulatory agency staff and elected officials, consumer 
groups, environmental groups, and representatives of public water 
systems. The group met from November 1992 through June 1993.
    Early in the process, the negotiators agreed that large amounts of 
information necessary to understand how to optimize the use of 
disinfectants to concurrently minimize microbial and disinfectant/
disinfection byproduct risk were unavailable.
    Therefore, the group agreed to propose a disinfectant/disinfection 
byproduct rule to extend coverage to all community water systems that 
use disinfectants, reduce the current total trihalomethane (TTHM) 
maximum contaminant level (MCL), regulate additional disinfection 
byproducts, set limits for the use of disinfectants, and reduce the 
level of compounds that may react with disinfectants to form 
byproducts. These requirements were based on available information. The 
group further agreed that revisions to the current Surface Water 
Treatment Rule might be required at the same time to ensure that 
microbial risk is not increased as byproduct rules go into effect. 
Finally, the group agreed that additional information on health risk, 
occurrence, treatment technologies, and analytical methods needed to be 
developed in order to better understand the risk-risk tradeoff, whether 
further control was needed, and how to accomplish this overall risk 
reduction.
    The outcome of the negotiation was three rules: a Disinfectant/
Disinfection Byproduct rule (this notice), an Enhanced Surface Water 
Treatment Rule (also proposed today and appearing separately in today's 
Federal Register), and an Information Collection Rule (proposed 
February 10, 1994, 59 FR 6332). The Information Collection Rule will 
provide information necessary to determine whether the Enhanced Surface 
Water Treatment Rule needs to be promulgated and, if so, what 
requirements it should set. The Information Collection Rule will also 
provide information on the need for, and content of, long-term rules. 
The schedule to produce these rules has also been negotiated and is 
provided elsewhere in this document. A summary of today's rule follows.
    A. Applicability. This action applies to all community water 
systems and nontransient noncommunity water systems that add a 
disinfectant during any part of the treatment process including 
addition of a residual disinfectant. In addition, certain provisions 
apply to transient noncommunity water systems that use chlorine 
dioxide.
    B. Proposed MRDLGs and MRDLs for disinfectants. EPA is proposing 
the following maximum disinfectant residual level goals and maximum 
residual disinfectant levels. 

------------------------------------------------------------------------
    Disinfectant Residual         MRDLG (mg/l)           MRDL (mg/l)    
------------------------------------------------------------------------
(1) Chlorine................  4 (as Cl2)..........  4.0 (as Cl2).       
(2) Chloramines.............  4 (as Cl2)..........  4.0 (as Cl2).       
(3) Chlorine dioxide........  0.3 (as ClO2).......  0.8 (as ClO2).      
------------------------------------------------------------------------

    C. Proposed MCLGs and MCLs for organic byproducts. EPA is proposing 
the following maximum contaminant level goals and maximum contaminant 
levels.

------------------------------------------------------------------------
                                                      MCLG(mg/   MCL(mg/
                                                        l)         l)   
------------------------------------------------------------------------
Total trihalomethanes (TTHM).......................  \1\N/A        0.080
Haloacetic acids (five) (HAA5).....................  \2\N/A         .060
Chloroform.........................................       0       \1\N/A
Bromodichloromethane...............................       0       \1\N/A
Dibromochloromethane...............................       0.06    \1\N/A
Bromoform..........................................       0       \1\N/A
Dichloroacetic acid................................       0       \2\N/A
Trichloroacetic acid...............................       0.3     \2\N/A
Chloral hydrate....................................       0.04   \3\N/A 
------------------------------------------------------------------------
\1\Total trihalomethanes are the sum of the concentrations of           
  bromodichloromethane, dibromochloromethane, bromoform, and chloroform.
                                                                        
\2\Haloacetic acids (five) are the sum of the concentrations of mono-,  
  di-, and trichloroacetic acids and mono- and dibromoacetic acids.     
\3\EPA did not set an MCL for chloral hydrate because the TTHM and HAA5 
  MCLs and the treatment technique (i.e., enhanced coagulation) for     
  disinfection byproduct precursor removal will control for chloral     
  hydrate. (See Section IX.)                                            

    D. Treatment Technique for DBP Precursors. EPA is proposing that 
water systems that use surface water or ground water under the direct 
influence of surface water and use conventional filtration treatment be 
required to remove specified amounts of organic materials (measured as 
total organic carbon) that may react with disinfectants to form 
disinfection byproducts. Removal would be achieved through a treatment 
technique (enhanced coagulation or enhanced softening) unless the 
system met certain criteria.
    E. Proposed Stage 1 MCLGs and MCLs for inorganic by-products. EPA 
is proposing the following maximum contaminant level goals and maximum 
contaminant levels. 

------------------------------------------------------------------------
                                                     MCLG(mg/           
                                                        l)     MCL(mg/l)
------------------------------------------------------------------------
Chlorite..........................................       0.08      1.0  
Bromate...........................................       0         0.010
------------------------------------------------------------------------

    F. Proposed BAT for disinfectants. EPA is proposing the following 
best available technologies for limiting residual disinfectant 
concentrations in the distribution system.

Chlorine residual--control of treatment processes to reduce 
disinfectant demand and control of disinfection treatment processes to 
reduce disinfectant levels
Chloramine residual--control of treatment processes to reduce 
disinfectant demand and control of disinfection treatment processes to 
reduce disinfectant levels
Chlorine dioxide residual--control of treatment processes to reduce 
disinfectant demand and control of disinfection treatment processes to 
reduce disinfectant levels.

    G. Proposed BAT for organic byproducts. EPA is proposing the 
following best available technologies for control of organic 
disinfection byproducts in each stage of the rule.
    1. Proposed Stage 1 BAT for organic by-products. Total 
trihalomethanes--enhanced coagulation or GAC10, with chlorine as the 
primary and residual disinfectant. Total haloacetic acids--enhanced 
coagulation or GAC10, with chlorine as the primary and residual 
disinfectant.
    2. Proposed Stage 2 BAT for organic byproducts. Total 
trihalomethanes--enhanced coagulation and GAC10, or GAC20; with 
chlorine as the primary and residual disinfectant. Total haloacetic 
acids--enhanced coagulation and GAC10, or GAC20; with chlorine as the 
primary and residual disinfectant.
    H. Proposed BAT for inorganic by-products. EPA is proposing the 
following best available technologies for control of inorganic 
disinfection byproducts.

Chlorite--control of treatment processes to reduce disinfectant demand 
and control of disinfection treatment processes to reduce disinfectant 
levels.
Bromate--control of ozone treatment process to reduce production of 
bromate.

    I. Proposed Compliance Monitoring Requirements. Compliance 
monitoring requirements are explained in Section IX of the preamble and 
were developed during the negotiated rulemaking. EPA has developed 
routine and reduced monitoring schemes that address the health effects 
of each disinfectant or contaminant in an individually appropriate 
manner.
    J. Analytical Methods. EPA is proposing to withdraw one method for 
measurement of chlorine residual and to approve three new methods for 
measurement of chlorine residuals. EPA is proposing to approve one new 
method for measurement of trihalomethanes; two new methods for 
measurement of haloacetic acids; one new method for measurement of 
bromate, chlorite, and bromide; and two new methods for measurement of 
total organic carbon.
    K. Laboratory Certification Criteria. Consistent with other 
drinking water regulations, EPA is proposing that only certified 
laboratories be allowed to analyze samples for compliance with the 
proposed MCLs and treatment technique requirements. For disinfectants 
and other specified parameters in today's rule that the Agency believes 
can be adequately measured by other than certified laboratories and for 
which there is a good reason to allow analysis at other locations 
(e.g., for samples which normally deteriorate before reaching a 
certified laboratory, especially when taken at remote locations), EPA 
is requiring that such analyses be conducted by a party acceptable to 
EPA or the State.
    L. Variances and Exemptions. Variances and exemptions will be 
permitted.
    M. State Primacy, Recordkeeping, Reporting Requirements. 
Requirements for States to maintain primacy are listed in Section XII 
of the preamble. In addition to routine requirements, EPA has included 
special primacy requirements.
    N. System Reporting Requirements. System reporting requirements 
remain consistent with requirements in previous rules.
    O. D/DBP Stage 2 Rule requirements. EPA is proposing a total 
trihalomethane MCL of 0.040 mg/l and a haloacetic acid (five) MCL of 
0.030 mg/l, to apply only to systems using surface water or ground 
water under the direct influence of surface water and serving at least 
10,000 persons, as part of a plan to develop new standards which 
incorporates the results of additional research conducted under the 
Information Collection Rule (59 FR 6332).
    P. Guidance. EPA is in the process of developing guidance for both 
systems and States for implementation of this rule.
    Q. Triennial Regulation Review. Under the provisions of the Safe 
Drinking Water Act (SDWA or the Act) (Section 1412(b)(9)), the Agency 
is required to review national primary drinking water regulations at 
least once every three years. As mentioned previously, today's proposed 
rule revises, updates, and (when promulgated) supersedes the 
regulations for total trihalomethanes, initially published in 1979. 
Since that time, there have been significant changes in technology, 
treatment techniques, and other regulatory controls that provide for 
greater protection for health of persons. As such, in proposing today's 
rule, EPA has analyzed innovations and changes in technology and 
treatment techniques that have occurred since promulgation of the 
initial TTHM regulations. This analysis, contained primarily in the 
cost and technology document supporting this proposal, supports 
amendment of the TTHM regulation for the greater protection of persons. 
EPA believes that the innovations and changes in technology and 
treatment techniques will result in amendments to the TTHM regulations 
that are feasible within the meaning of SDWA Section 1412(b)(9).

II. Statutory Authority

    Section 1412 of the Safe Drinking Water Act, as amended in 1986 
(``SDWA'' or ``the Act''), requires EPA to publish Maximum Contaminant 
Level Goals (MCLGs) and promulgate National Primary Drinking Water 
Regulations (NPDWRs) for contaminants in drinking water which may cause 
any adverse effect on the health of persons and which are known or 
anticipated to occur in public water systems. Under Section 1401, the 
NPDWRs are to include Maximum Contaminant Levels (MCLs) and ``criteria 
and procedures to assure a supply of drinking water which dependably 
complies'' with such MCLs. Under Section 1412(b)(7)(A), if it is not 
economically or technically feasible to ascertain the level of a 
contaminant in drinking water, EPA may require the use of a treatment 
technique instead of an MCL.
    Under Section 1412(b), EPA was to establish MCLGs and promulgate 
NPDWRs for 83 contaminants by June 19, 1989. An additional 25 
contaminants are to be regulated every 3 years. To meet this latter 
requirement, EPA has developed a list of contaminants (National 
Drinking Water Priority List; 53 FR 1892) including pesticides, organic 
and inorganic elements or compounds, and disinfectants and disinfection 
by-products (D/DBP), plus the protozoan Cryptosporidium. From this 
list, EPA is to choose at least 25 contaminants for regulation every 
three years. Today's regulatory proposal represents part of the first 
group of 25 chemicals to be regulated. Both the general contaminants 
(organics, inorganics, and pesticides), and the D/DBPs were considered 
for regulation. In today's notice, EPA is proposing to regulate certain 
disinfectants and disinfection byproducts; Cryptosporidium is proposed 
to be regulated in a separate Notice today.
    In October of 1990, EPA entered into a consent order with Citizens 
Concerned about Bull Run Inc. regarding a timeframe for proposing the 
first group of 25. The consent decree stipulated a June 1993 date for 
proposal. That decree was subsequently amended to establish a proposal 
date of May 30, 1994, for the Disinfectants/Disinfection Byproducts 
Rule and a proposal date of February 28, 1995, for the other 
contaminants that comprise the required group of 25.

A. MCLGs, MCLs, and BAT

    Under Section 1412 of the Act, EPA is to establish MCLGs at the 
level at which no known or anticipated adverse effects on the health of 
persons occur and which allow an adequate margin of safety. MCLGs are 
nonenforceable health goals based only on health effects and exposure 
information.
    MCLs are enforceable standards which the Act directs EPA to set as 
close to the MCLGs as feasible. ``Feasible'' means feasible with the 
use of the best technology, treatment techniques, and other means which 
the Administrator finds available (taking cost into consideration) 
after examination for efficacy under field conditions and not solely 
under laboratory conditions (SDWA, section 1412(b)(5)). Also, the SDWA 
requires the Agency to identify the best available technology (BAT) 
which is feasible for meeting the MCL for each contaminant.
    Also, in this proposal, EPA is introducing several new terms--
``maximum residual disinfectant level goals (MRDLGs)'' and ``maximum 
residual disinfectant levels (MRDLs)''--to reflect the fact that these 
substances have beneficial disinfection properties. As with MCLGs, EPA 
has established MRDLGs at the level at which no known or anticipated 
adverse effects on the health of persons occur and which allow an 
adequate margin of safety. MRDLGs are nonenforceable health goals based 
only on health effects and exposure information and do not reflect the 
benefit of the addition of the chemical for control of waterborne 
microbial contaminants.
    MRDLs are enforceable standards, analogous to MCLs, which recognize 
the benefits of adding a disinfectant to water on a continuous basis 
and in addressing emergency situations such as distribution system pipe 
breaks. As with MCLs, EPA has set the MRDLs as close to the MRDLGs as 
feasible. The Agency has also identified the best available technology 
(BAT) which is feasible for meeting the MRDL for each disinfectant.

B. Variances and Exemptions

    Section 1415 authorizes the State to issue variances from NPDWRs 
(the term ``State'' is used in this preamble to mean the State agency 
with primary enforcement responsibility for the public water supply 
system program or EPA if the State does not have primacy). The State 
may issue a variance if it determines that a system cannot comply with 
an MCL despite application of the best available technology (BAT). 
Under Section 1415, EPA must propose and promulgate its finding of the 
best available technology, treatment techniques, or other means 
available for each contaminant, for purposes of section 1415 variances, 
at the same time that it proposes and promulgates a maximum contaminant 
level for such contaminant. EPA's finding of BAT, treatment techniques, 
or other means for purposes of issuing variances may vary among 
systems, depending upon the number of persons served by the system or 
for other physical conditions related to engineering feasibility and 
costs of complying with MCLs, as considered appropriate by EPA. The 
State may not issue a variance to a system until it determines that an 
unreasonable risk to health (URTH) does not exist. When a State grants 
a variance, it must at the same time prescribe a schedule for (1) 
compliance with the NPDWR and (2) implementation of any additional 
control measures.
    Under Section 1416(a), the State may exempt a public water system 
from any MCL or treatment technique requirement if it finds that (1) 
due to compelling factors (which may include economic factors), the 
system is unable to comply, (2) the system was in operation on the 
effective date of the MCL or treatment technique, or, for a newer 
system, that no reasonable alternative source of drinking water is 
available to that system, and (3) the exemption will not result in an 
unreasonable risk to health. Under section 1416(b), at the same time it 
grants an exemption, the State is to prescribe a compliance schedule 
and a schedule for implementation of any required interim control 
measures. The final date for compliance may not exceed three years 
after the initial date of issuance unless the public water system 
establishes that: (1) the system cannot meet the standard without 
capital improvements which cannot be completed within the period of 
such exemption; (2) the system has entered into an agreement to obtain 
financial assistance for necessary improvements; or (3) the system has 
entered into an enforceable agreement to become part of a regional 
public water system. For systems which serve 500 or fewer service 
connections and which need financial assistance to come into 
compliance, the State may renew the exemption for additional two-year 
periods if the system is taking all practicable steps to meet the above 
requirements.
    For exemptions resulting from a NPDWR promulgated after June 19, 
1986, the system's final compliance date must be within 12 months of 
issuance of the exemption. However, the State may extend the final 
compliance date for up to three years if the public water system shows 
that capital improvements to meet the MCL or treatment technique 
requirement cannot be completed within the exemption period and, if the 
system needs financial assistance for the improvements, it has an 
agreement to obtain this assistance or the system has an enforceable 
agreement to become part of a regional public water system. For systems 
that have 500 or fewer service connections that need financial 
assistance to comply with the MCLs, the State may renew the exemption 
for additional two-year periods if the system is taking all practicable 
steps to comply.

C. Primacy

    As indicated above, States, territories, and Indian Tribes may 
assume primary enforcement responsibility (primacy) for public water 
systems under Section 1413 of the SDWA. To date, 55 States and 
territories have primacy. To assume or retain primacy, States, 
territories, or Indian Tribes need not adopt the MCLGs but must adopt, 
among other things, NPDWRs (i.e., MCLs, monitoring, analytical, and 
reporting requirements) that are no less stringent than those EPA 
promulgates.

D. Monitoring, Quality Control, and Records

    Under Section 1401(1)(D) of the Act, NPDWRs are to contain 
``criteria and procedures to assure a supply of drinking water which 
dependably complies with such maximum contaminant levels; including 
quality control and testing procedures to insure compliance with such 
levels * * *.''

E. Public Water Systems

    Public water systems are defined in section 1401 of the Act as 
those systems which provide piped water for human consumption and have 
at least 15 connections or regularly serve at least 25 people. By 
regulation EPA has divided public water systems into community, 
nontransient noncommunity, and (transient) noncommunity water systems. 
Community water systems (CWSs) serve at least 15 service connections 
used by year-round residents or regularly serve at least 25 year-round 
residents (40 CFR 141.2). Nontransient noncommunity water systems 
(NTNCWSs) regularly serve at least 25 of the same people over six 
months of the year. Schools and factories which serve water to 25 or 
more of the same people for six or more months of the year are examples 
of NTNCWSs. Transient noncommunity systems, by definition, are all 
other public water systems. Transient noncommunity systems may include, 
for example, restaurants, gas stations, campgrounds, and churches.
    This rule would apply to all CWSs, all NTNCWSs, and any transient 
noncommunity water systems that use chlorine dioxide as a disinfectant 
or oxidant.

F. Public Notification

    Section 1414(c) of the Act requires the owner or operator of a 
public water system which does not comply with an applicable maximum 
contaminant level or treatment technique, testing procedure, or Section 
1445(a) (unregulated contaminant) monitoring requirement to give notice 
to the persons served by the system. Notice must also be given if a 
variance or exemption is in effect or the system fails to comply with a 
compliance schedule resulting from a variance or exemption. EPA's 
public notification regulations are codified at 40 CFR Section 141.32. 
Those regulations were amended by EPA on October 28, 1987 (52 FR 
41534).

III. Overview of Existing Interim Standard for TTHMS

    In 1974, researchers in The Netherlands and the United States 
clearly demonstrated that total trihalomethanes (TTHMs) are formed as a 
result of drinking water chlorination (Rook, 1974; Bellar et al, 1974). 
EPA subsequently conducted surveys confirming widespread occurrence of 
TTHMs in chlorinated water supplies (Symons, 1975; USEPA, 1978). During 
this time toxicological studies became available which supported the 
contention that chloroform, one of the four trihalomethanes, is 
carcinogenic in at least one strain of rat and one strain of mouse 
(National Academy of Sciences, 1977).
    EPA then set an interim maximum contaminant level (MCL) for the 
TTHMs of 100 g/l as an annual average in November 1979 (USEPA, 
1979). This standard was based on the need to balance the requirement 
for continued disinfection of water to reduce exposure to pathogenic 
microorganisms while simultaneously lowering exposure to animal 
carcinogens like chloroform.
    The interim TTHM standard only applies to systems serving at least 
10,000 people that add a disinfectant (oxidant) to the drinking water 
during any part of the treatment process. At their discretion, States 
are allowed to extend coverage to smaller size systems. About 80 
percent of the smallest systems are served by groundwater systems that 
are mostly low in THM precursor content (USEPA, 1979).
    The proportion of these small groundwater systems that use chlorine 
is less than that of large systems; currently, less than half of these 
systems disinfect. Also, the shorter hydraulic detention and chlorine 
contact times in the small system distribution systems results in lower 
TTHM concentrations. Therefore, drinking water systems serving less 
than ten thousand people are less likely to have high concentrations of 
TTHMs.
    Moreover, these small systems are most likely to have greater risks 
of significant microbiological contamination, especially if they reduce 
or eliminate chlorination. In 1979, the majority of outbreaks 
attributable to inadequate disinfection occurred in small systems. 
Further, small systems have limited or no access to the financial 
resources and technical expertise needed for TTHM control. Therefore, 
EPA concluded that small system resources would best be spent on 
maintaining and improving microbiological quality and safety. The 
revised drinking water regulations now under consideration will extend 
to these small systems as required by the Safe Drinking Water Act 
Amendments of 1986 (P.L. 99-339, 1986). EPA will also be considering 
disinfection as a treatment technique requirement and maximum 
contaminant levels (MCLs) for the residual disinfectants. The impacts 
these requirements will have on small systems is an important component 
of the regulation development process.

Technology Basis for the Interim TTHM Standard

    When an MCL is established for TTHMs or any other contaminant that 
can be measured, EPA is not required to specify any particular method 
for achieving that standard. Instead, the requirement for the interim 
regulations was to set an MCL which could be achieved using technology 
generally available in 1974. Three general control alternatives were 
available:

(1) use of a disinfectant (oxidant) that does not generate (or produces 
less) THMs in water;
(2) treatment to lower precursor concentrations prior to chlorination; 
and
(3) treatment to remove THMs after their formation.

    There are many possible choices among these broad options and in 
some cases a combination of approaches might be necessary. The ultimate 
choice was left up to the water supplier based on its individual 
circumstances.
    EPA's evaluation led to the following conclusions concerning 
generally available technologies for setting the TTHM MCL:

(1) alternate oxidants like ozone, chloramines, and chlorine dioxide 
are available;
(2) precursor removal strategies like changing the point of 
disinfection, off-line raw water storage, and improved coagulation are 
available; and,
(3) precursor removal using granular activated carbon (GAC) as a 
replacement for existing filter media with a regeneration frequency of 
one year is feasible as well as biologically activated carbon (ozone 
plus GAC) with a regeneration frequency of every two years.

    Three conditions concerning modifications of disinfection processes 
were also proposed by EPA:

(1) the total quantity of chlorine dioxide added during the treatment 
process should not exceed 1 mg/l;
(2) chloramines should not be utilized as a primary disinfectant; and
(3) monitoring for heterotrophic plate count bacteria (HPC) should be 
conducted as determined by the State, but at least every day for a 
minimum of one month prior to and six months subsequent to the 
modifications.

    These recommendations concerning disinfection, although useful, 
were deleted from the final regulation to allow States greater 
discretion. The basis for the MCL became alternate oxidants and 
precursor removal.

Technology Basis for Variances

    Later, in 1983, EPA promulgated regulations specifying best 
technology generally available for obtaining variances (USEPA, 1983). A 
variance is granted by the State when a system has installed the best 
technology generally available as specified in the regulation and still 
cannot meet the MCL. The best technologies generally available for 
variances to the TTHM MCL are:

(1) Use chloramines as an alternate or supplemental disinfectant or 
oxidant.
(2) Use chlorine dioxide as an alternate or supplemental disinfectant 
or oxidant.
(3) Improve existing clarification for THM precursor reduction.
(4) Move the point of chlorination to reduce TTHM formation and, where 
necessary, substituting for the use of chlorine as a pre-oxidant 
chloramines, chlorine dioxide, or potassium permanganate.
(5) Use of powdered activated carbon for THM precursor or TTHM 
reduction seasonally or intermittently at dosages not to exceed 10 mg/l 
on an annual average basis.

    EPA also identified Group II technologies, which are not 
``generally available,'' but may be available to some systems:

(1) Introduction of off-line water storage for THM precursor reduction.
(2) Aeration for TTHM reduction, where geographically and 
environmentally appropriate.
(3) Introduction of clarification where not currently practiced.
(4) Consideration of alternative sources of raw water.
(5) Use of ozone as an alternate or supplemental disinfectant or 
oxidant.

    Note that GAC and BAC are not mentioned as either Group I or Group 
II technologies even though they were discussed as technologies for 
standard setting purposes (USEPA, 1979). EPA concluded in its cost and 
technologies document for the removal of trihalomethanes from drinking 
water that (USEPA, 1981):

(1) GAC in the sand replacement mode of operation is often 
inappropriate due to the short performance life and high frequency of 
regeneration required to achieve substantial TTHM or THM-formation 
potential reduction;
(2) the finding took into consideration costs, but primarily was made 
due to the complexities of the modifications to prior unit operations, 
i.e., disinfection, and in the logistics of the carbon replacement;
(3) greater operating, maintenance, and monitoring than for other 
treatments; and
(4) on-site regeneration had only been demonstrated at one U.S. site.

    Thus, EPA decided to defer the decision to include GAC and BAC as 
best generally available technology for granting variances under the 
Safe Drinking Water Act Amendments of 1974.
    EPA also did not list ozonation as being ``generally available'' 
because:

(1) lack of experience in the U.S.;
(2) mixed results in experimental studies; and
(3) most States require a residual in the distribution system which is 
not obtainable with ozone.

    Thus, EPA decided to defer the decision to include ozone as best 
generally available technology for granting variances under the Safe 
Drinking Water Act Amendments of 1974.

Economic Impacts of the Interim Standard

    Currently, there are 2,700 community water supply systems serving 
at least 10,000 people required to comply with the interim TTHM 
regulation. In 1988, a survey of large systems found that, on average, 
the MCL of 0.10 mg/l had reduced the concentration of TTHMs by 40 to 50 
percent (McGuire and Meadows, 1988). Of these, 33 were in violation of 
the standard in FY88 (average=115 g/l, range=108-180 
g/l). However, by FY92, only nine systems (a decrease of 73 
percent) violated the requirements, for a total of 14 violations. Seven 
of the nine violating systems and 12 of the 14 violations occurred in 
systems serving 10,000 to 50,000 people. This indicates that even when 
systems violate, they are able to return to compliance after one or two 
violations of the running annual average.
    In 1979, approximately 500 systems were estimated to exceed 100 
g/l TTHMs. Most of these were able to come into compliance 
with minor modifications of chlorination practices. A smaller portion 
used alternate oxidants like chlorine dioxide and chloramines. No 
system installed ozone or GAC to meet the interim TTHM regulations. 
Compliance with the interim TTHM standard involved estimated capital 
expenditures of between $31 million and $102 million and yearly 
operating and maintenance costs of between $8 million and $29 million 
for systems required to comply with the TTHM MCL (i.e., community water 
systems serving a population of at least 10,000 people) (McGuire and 
Meadows, 1988).

IV. Overview of Preproposal Regulatory Development

A. October 1989 Strawman Rule

    1. Purpose. EPA was required to develop rules for additional 
contaminants under the 1986 Amendments to the Act. In order to solicit 
public comment in developing a rule, EPA released a strawman rule 
(preproposal draft) in October 1989. A strawman was used because of the 
complexity of the problem, the large amount of (occasionally 
contradictory) information, and the ability to reorient the rule 
approach based on public comment or new data. In this strawman, EPA 
included a lead option of setting MCLGs and MCLs for TTHMs, haloacetic 
acids, chlorine, chloramines, chlorine dioxide, chlorite, and chlorate. 
The Agency also identified potential add-on compounds: chloropicrin, 
cyanogen chloride, hydrogen peroxide, bromate, iodate, and 
formaldehyde. Some of these compounds could also conceivably be used as 
surrogate monitoring compounds for the compounds identified in Table 
IV-1 below. 

                Additional Candidate Byproduct Compounds                
------------------------------------------------------------------------
       Chlorination byproducts                Ozonation byproducts      
------------------------------------------------------------------------
--Individual THMs: chloroform,         --Aldehydes: acetaldehyde,       
 bromodichloromethane,                  hexanal, heptanal.              
 dibromochloromethane, bromoform.                                       
--Individual haloacetic acids: mono-,  --Organic acids.                 
 di-, and trichloroacetic acids; mono- --Ketones.                       
  and dibromoacetic acids.             --Epoxides.                      
--Individual haloacetonitriles: di-    --Peroxides.                     
 and trichloroacetonitrile;            --Nitrosamines.                  
 bromochloroacetonitrile,                                               
 dibromoacetonitrile.                                                   
--Haloketones: 1,1 di- and 1,1,1-                                       
 trichloropropanone.                                                    
--Chlorophenols: 2-; 2,4-di; and       --N-oxy compounds.               
 2,4,6-trichlorophenol.                --Quinones.                      
--Others: chloral hydrate, N-          --Bromine substituted compounds. 
 organochloroamines.                                                    
------------------------------------------------------------------------

    In addition, the strawman provided that EPA would set treatment 
technique requirements or provide guidance for control of the 
following: MX, as a surrogate for mutagenicity; total oxidizing 
substances, as a surrogate for organic peroxides and epoxides; and 
assimilable organic carbon, as a surrogate for microbiological quality 
of oxidized waters. Monitoring parameters based on the particular 
disinfection process were also identified.
    As BAT, EPA included precursor removal (conventional treatment 
modifications, GAC of up to 30 minute duration and three months 
regeneration), alternate oxidants (ozone plus chloramines, chlorine 
dioxide with chlorite removal plus chloramines), and byproduct removal 
(aeration, GAC adsorption, reducing agents, AOC removal). Each of the 
options had problems. GAC was not universally applicable to all waters 
for either precursor removal or DBP removal. Membranes were not 
included as BAT because of lack of full-scale experience.
    As lead options, EPA included a TTHM MCL of 25 or 50 g/l 
and other MCLs based on feasibility analyses similar to those that 
would be used to develop the TTHM MCL.
    2. Summary of Public Comments. Several commentors expressed a 
desire for EPA to look at coordination of requirements with those for 
other regulations, including issues such as requirements for 
maintenance of distribution system disinfectant residuals and system 
optimization for multiple contaminants. Many commentors were concerned 
about the lack of health data and the interpretation of existing data. 
Many system operators were also concerned about the effects of 
modifying their treatment processes to meet DBP MCLs. These concerns 
included lowered microbiological protection, creation of conditions 
that favored distribution system microbiological growth (e.g., use of 
ozone would create biodegradable organics and use of chloramines would 
create a nitrogen source), and creation of other environmental problems 
when changing treatment (e.g., residual handling with precursor removal 
and GAC regeneration). While commentors expressed concern about use of 
alternate disinfectants, several offered to provide data and others 
recommended epidemiological studies in systems with long histories of 
alternative disinfectant use.

B. June 1991 Status Report on D/DBP Rule Development

    1. Purpose and transition from Strawman Rule. EPA published a 
status report on the development of D/DBPR in June 1991 that was 
designed to indicate the Agency's thinking on rule criteria. The status 
report indicated that EPA was considering extending coverage under the 
rule to all nontransient systems (instead of just those serving at 
least 10,000 people, as under the 1979 TTHM rule) and proposing a 
shorter list of compounds for regulation than were included in the 1989 
strawman. The 1991 list included disinfectants (chlorine, chloramines, 
and chlorine dioxide), THMs, haloacetic acids, chloral hydrate, 
bromate, chlorite, and chlorate). For both THMs and haloacetic acids, 
three options were included: MCLs for individual compounds, a single 
MCL for the total, and a combination of the two. Individual MCLs were 
considered because health risks for compounds differed, in some cases 
significantly. The total MCL was considered because of the precedent 
established in the 1979 TTHM rule and to act as a surrogate to limit 
other DBPs for which the Agency lacked adequate health effects and/or 
occurrence data.
    The list of compounds was shorter than that in the 1989 strawman 
for several reasons. Several compounds were deleted because they did 
not appear to pose significant health effects at levels present in 
drinking water (e.g., haloacetonitriles, chloropicrin). Others were 
deleted because the health risks were not expected to be adequately 
characterized in time for rule proposal (e.g., certain aldehydes and 
organic peroxides), although it was noted that these compounds might be 
regulated in the future when more data became available.
    2. Major issues. In the status report, EPA identified several major 
issues that needed to be considered as the D/DBP rule was developed. 
The first was that of trade-offs with microbial and DBP risks. The goal 
was to ensure that the water remained microbiologically safe at the 
level that disinfectant and DBP MCLs were set. The discussion raised 
questions regarding uncertainties in defining microbial and DBP risks, 
levels of risks that would be considered acceptable and at what cost, 
and defining practical (implementable) criteria to demonstrate that an 
achievable risk had been reached.
    The second issue was the use of alternate disinfectants to limit 
chlorination byproducts. The Agency recognized that while alternate 
disinfection schemes (e.g., ozone and chloramines) could greatly reduce 
byproducts typical of chlorination, little was known about the 
byproducts of the alternate disinfectants and their associated health 
risks. EPA did not want to promulgate a standard that encouraged the 
shift to alternate disinfectants unless the associated risks (including 
both those from byproducts and differential microbial risks from a 
change in disinfectants) were adequately understood.
    The third issue was integration with the Surface Water Treatment 
Rule. Although the rule only mandated 3-log removal or inactivation of 
Giardia and 4-log of viruses, EPA guidance recommended higher levels 
for poorer quality source waters. EPA was concerned that systems would 
reduce microbial protection to levels nearer to the regulatory 
requirements by reducing disinfection and possibly greatly increase 
microbial risks in an effort to meet DBP MCLs. The Agency wanted to 
ensure adequate microbial protection while reducing risk from DBPs.
    The last issue was the best available technology. The BAT defined 
would determine the levels at which MCLs were set. For example, 
allowing alternate disinfectants as BAT would drive the chlorination 
byproduct MCLs down, but could result in increased exposure to (not 
well characterized) alternate byproducts. EPA believed that it 
therefore might be appropriate to define chlorine and a precursor 
removal technology as BAT.
    To address these issues, EPA suggested two possible regulatory 
strategies. One was to define the MCL(s) based on what was possible to 
achieve using the most effective DBP precursor removal strategy as BAT 
(e.g., GAC or membrane filtration). While installing such precursor 
removal technology might minimize health concerns, the costs would be 
substantial (without finding out if other less costly technologies, 
such as use of alternative disinfectants, provided similar benefits). 
Also, since systems are not required to install BAT to meet MCLs, EPA 
believed that many systems would attempt to meet the MCLs by lower-cost 
alternative disinfectants (ozone, chloramines, chlorine dioxide). Since 
health effects for alternative disinfectant byproducts are not 
adequately characterized, risks may not be reduced.
    The second strategy was a two-phase regulation, with the first 
phase designed to address risks using lower cost options during 
concurrent efforts to obtain more data on treatment alternatives and 
health effects of compounds not currently adequately characterized. 
This strategy would prevent major shifts into use of new treatment 
technology until the full consequences of such shifts (both costs and 
benefits) are better understood.
    3. Suggested monitoring scenario. In its fact sheet accompanying 
the status report, EPA recommended that routine TTHM and haloacetic 
acid monitoring for systems serving at least 10,000 people have the 
same monitoring requirements as were in the 1979 TTHM rule. Smaller 
systems would have less frequent monitoring requirements, but would 
have compliance based on worst-case samples. EPA included provisions 
for reduced monitoring (compliance based on worst-case samples or 
surrogate monitoring), waiver criteria, and requirements for 
disinfectant and other DBP monitoring.
    4. Summary of public comments. EPA received comments on the status 
report from numerous parties. Many commentors agreed with EPA's 
concerns with issues such as alternative disinfectant DBPs and 
balancing microbial and DBP risks. Several commentors supported the 
two-phase regulatory approach, but expressed concern about timing. 
Others recommended that DBP MCLs not be set so low as to force many 
systems to install expensive technology or decrease microbial 
protection. Several commentors were concerned with the availability of 
both analytical methods and certified laboratories for the low levels 
that were being considered. One commentor recommended that EPA make it 
clear that MCLs set for disinfectants should allow temporary high 
levels to address distribution system microbiological problems. 
Finally, many commentors supported allowing reduced monitoring wherever 
possible.

C. Initiation of the Regulatory Negotiation Process

    EPA became interested in pursuing a negotiated rulemaking process 
for the development of the D/DBP rule, in large part, because no clear 
path for addressing all the major issues identified in the June 1991 
Status Report on D/DBP rule was apparent. EPA's most significant 
concern was developing regulations for DBPs while also ensuring that 
adequate treatment be maintained for controlling microbiological 
concerns. A negotiated rule process would help people understand the 
complexities of the risk-risk tradeoff issue and, hopefully, reach a 
consensus on the most appropriate regulation to address concerns from 
both DBPs and microorganisms.
    It also appeared to EPA that the criteria for initiating a 
negotiated rule under the Negotiated Rulemaking Act of 1990 for 
establishing a negotiated rulemaking could be met. These include:
    (1) there is a need for a rule,
    (2) there are a limited number of identifiable interests that will 
be significantly affected by the rule,
    (3) there is a reasonable likelihood that a committee can be 
convened with a balanced representation of persons who--
    (A) can adequately represent the interests identified under 
paragraph (2); and
    (B) are willing to negotiate in good faith to reach a consensus on 
the proposed rule,
    (4) there is a reasonable likelihood that a committee will reach a 
consensus on the proposed rule within a fixed period of time,
    (5) the negotiated rulemaking procedure will not unreasonably delay 
the notice of proposed rulemaking and the issuance of a final rule,
    (6) the Agency has adequate resources and is willing to commit such 
resources, including technical assistance, to the committee, and
    (7) the Agency, to the maximum extent possible consistent with the 
legal obligations of the Agency, will use the consensus of the 
committee with respect to the proposed rule as the basis for the rule 
proposed by the Agency for notice and comment.
    In 1992 EPA hired a contractor, Resolve, which added a 
subcontractor, Endispute, to assess the feasibility and usefulness of 
convening a negotiated rulemaking. Resolve and Endispute conducted more 
than forty interviews during the summer of 1992 with representatives of 
State and local health and regulatory agencies, water suppliers, 
manufacturers of equipment and supplies used in drinking water 
treatment, and consumer and environmental organizations. These 
interviews revealed that:
    (1) The entities interested in or affected by the rulemaking were 
readily identifiable and relatively few in number.
    (2) The rulemaking required resolution of a limited number of 
interdependent issues, about which there appeared to be a sufficiently 
well-developed factual base to permit meaningful discussion. Further, 
there appeared to be several ways to resolve these issues, providing a 
potential basis for productive joint problem-solving.
    (3) The parties expressed some common goals, along with an 
unusually strong degree of good faith interest in resolving the issue 
through negotiation.
    (4) The Agency had adequate staff and technical resources and was 
willing to commit such resources to the negotiated rulemaking.
    Resolve and Endispute recommended to EPA that the negotiated 
rulemaking proceed. EPA concurred with this recommendation.
    However, it was also noted that reaching consensus on the proposed 
rule would be a challenge. The interviews revealed that parties 
differed in their perceptions about the nature and magnitude of the 
risks associated with DBPs, and many expressed strong doubts about the 
adequacy of available scientific and technical information. Moreover, 
some parties stated that marginal improvements in disinfection 
technology were all that should be done until the relative risks are 
better understood, while others said that a fundamentally new approach 
focusing on precursor reduction should be considered.
    EPA published a notice of intent to proceed with a negotiated 
rulemaking on September 15, 1992 (57 FRN 42533), proposing 17 parties 
to be Negotiating Committee members. In general, comments indicated 
very positive support for the negotiated rulemaking.
    As part of the convening process, an organizational meeting was 
held September 29-30, 1993. Participants discussed Negotiating 
Committee composition and organizational protocols. Between comments 
expressed at the meeting and submitted in writing, eleven additional 
parties--including water suppliers not substantially represented by the 
Committee's original proposed membership, and chemical and equipment 
suppliers--asked to be added to the Committee. In addition, 
participants discussed the need to develop accurate scientific and 
technical information.
    On November 13, 1992, EPA published a notice of establishment for 
the Negotiating Committee (57 FRN 53866), and an 18th member was added 
to the Negotiating Committee.
    Based on comments received at the organizational meeting, a 
Technical Workshop was organized and conducted on November 4-5, 1992. 
Composed of presentations and panel discussion by 23 of the Nation's 
leading experts on drinking water treatment, the workshop provided 
participants with opportunities to familiarize themselves with the 
technical elements in this rulemaking and to explore the range of 
scientific opinions about: (1) The nature and magnitude of potential 
health effects from exposure to DBPs and microbial contaminants in 
drinking water, (2) available information on the cost and efficacy of 
precursor removal and drinking water disinfection technologies, and (3) 
EPA's efforts to model and compare chemical and microbial risks in 
drinking water.
    Additional presentations were given throughout the rulemaking 
process, as new information became available and more questions were 
raised by participants.
    At the first formal negotiating session, on November 23-24, 1992, 
participants formed a technologies working group (TWG) to develop 
reliable and consistent information about the cost and efficacy of 
drinking water treatment technologies. This approach provided a forum 
for participants to arrive at a shared understanding of complex issues 
in the rulemaking, setting a cooperative tone for the rest of their 
discussions. The working group, which continued to meet throughout the 
rulemaking, also provided a formal opportunity for input from the 
chemical and equipment suppliers who had not been named to the 
Committee.
    In addition, three experts were hired through EPA's contract with 
Resolve to provide ongoing scientific advice and technical support to 
participants in the Committee and on the technologies working group, 
principally for members without access to similar resources within 
their own organizations.
    Based on scientific data presented and discussed through the 
November 23-24 meeting, participants agreed that some type of DBP Rule 
was warranted.
    The Committee developed and reached agreement on criteria for a 
``good'' DBP Rule at the September 29-30 and November 23-24 meetings. A 
good rule is one which would be flexible and affordable and would 
protect public health from chemical and microbial risks. It was noted 
that limiting some DBPs could encourage changes in treatment that might 
increase the formation of other DBPs, or compromise protections against 
microbial contaminants.
    Next, Committee members and other participants were invited to 
present regulatory options as a starting point for further discussion. 
Sixteen options were introduced at the December 17-18 meeting, and 
discussed at the meeting on January 13-14, 1993. These were merged into 
three consolidated options at the January 13-14 meeting, and discussion 
continued at the meeting on February 9-10. At this point, areas of 
disagreement included:
    (1) Whether to regulate DBPs through Maximum Contaminant Levels 
(MCLs) or through a treatment technique (i.e., by exceeding DBP 
``action levels,'' systems would trigger additional steps to minimize 
chemical and microbial risks).
    (2) Whether to minimize formation of the DBPs about which 
relatively little is known by establishing a regulatory limit for their 
naturally occurring organic precursors (e.g., Total Organic Carbon, or 
TOC) in the water prior to the point of disinfection.
    (3) Whether to provide greater protection against microbial 
contaminants in drinking water, in conjunction with new DBP limits, by 
developing an enhanced Surface Water Treatment Rule (ESWTR).
    (4) Whether to develop a second round of DBP controls along with 
the first (assuring broad improvements in drinking water quality), or 
to wait until better scientific information becomes available.
    Concurrently, the TWG modelled systems' potential compliance 
choices under several regulatory scenarios, and presented revised 
household and national compliance cost estimates at several meetings.
    Using a ``strawman'' developed from the consolidated options by EPA 
staff as the starting point for negotiation, the Committee worked out 
an ``agreement in principle'' on the first round of DBP controls at its 
February 24-25 meeting. The ``Stage 1'' agreement set MCLs for 
trihalomethanes and haloacetic acids--two principal classes of 
chlorination by-products--at levels the Committee deemed protective of 
public health, based on current information: 80 and 60 micrograms per 
liter, respectively. To limit DBP precursors, the Committee agreed to 
develop a series of ``enhanced coagulation'' requirements, to vary 
according to systems' influent water quality and treatment plant 
configurations. Members also agreed to reconvene in several years to 
develop a second stage of DBP regulations, when the results of more 
health effects research and water quality monitoring are available. In 
addition, members agreed that more expeditious changes to the rules may 
be necessary if additional information becomes available on short- term 
or acute health effects of DBPs. Members also agreed that, if data on 
short-term or acute health effects warrant earlier action, a meeting 
shall be convened to review the results and to develop recommendations.
    A drafting group was named at the February 24-25 meeting. Assisted 
by the TWG, these members drafted an ``agreement in principle'' for 
presentation and discussion at the March 18-19 meeting. Using ``straw'' 
provisions from the facilitators, the Committee devised a regulatory 
``backstop'' (i.e., Stage 2 MCLs of 0.040 mg/l for TTHMs and 0.030 mg/l 
for HAA5 for surface water systems serving at least 10,000 people) at 
this meeting to assure participants favoring further DBP controls that 
other members would return for the ``Stage 2'' negotiation. The 
Committee also agreed to recommend that EPA propose several ESWTR 
options for comment, developed a collaborative process to guide the 
health effects research program, and agreed to formulate short-term 
water quality and technical data collection provisions within an 
Information Collection Rule.
    Based on the discussion to this point, one member withdrew from the 
Committee at the March 18-19 meeting.
    The drafting group presented regulatory language for the DBP Rule, 
ESWTR, and ICR at each of the Committee's last two meetings, held May 
12-13 and June 22-23, 1993. These texts provided a framework for 
further discussion and resolution of remaining issues, including: 
limits for residual disinfectants and individual by-products; public 
notification and affordability provisions; and timing, applicability, 
and conditions under which systems might qualify for exceptions from 
various requirements. Committee members agreed to reserve their rights 
to comment on the draft preambles.
    The drafting group continued working through the summer of 1993, 
and revisions to each of the rules and their preambles were mailed to 
the Committee for comment on July 8, 1993, September 8, 1993, February 
8, 1994, and May 12, 1994. Each member had signed the agreement by June 
7, 1994.
    Unless otherwise noted, EPA has adopted the recommendations of the 
Negotiating Committee and its Technologies Working Group and reflects 
those recommendations in the following preamble and proposed 
regulations.

V. Establishing MCLGs

A. Background

1. MCLGs and MCLs Must Be Proposed and Promulgated Simultaneously
    Congress revised the Safe Drinking Water Act in 1986 to require 
that MCLGs and National Primary Drinking Water Regulations (NPDWRs) be 
proposed simultaneously and promulgated simultaneously [SDWA section 
1412 (a)(3)]. Simultaneous promulgation was intended to streamline the 
development of drinking water regulations.
2. How MCLGs Are Developed
    MCLGs are set at concentration levels at which no known or 
anticipated adverse health effects occur, allowing for an adequate 
margin of safety. Establishment of an MCLG for each specific 
contaminant depends on the evidence of carcinogenicity from drinking 
water exposure or an assessment for adverse noncarcinogenic health 
effects.
    a. MCLG Three Category Approach. EPA currently follows a three-
category approach in developing MCLGs for drinking water contaminants 
(Table V-1). 

    Table V-1.--EPA'S Three-Category Approach for Establishing MCLGs    
------------------------------------------------------------------------
                               Evidence of                              
       Category            carcinogenicity via         MCLG approach    
                            drinking water\1\                           
------------------------------------------------------------------------
I......................  Strong evidence          Zero.                 
                          considering weight of                         
                          evidence,                                     
                          pharmacokinetics,                             
                          potency and exposure.                         
II.....................  Limited evidence         RfD approach with     
                          considering weight of    added safety margin  
                          evidence,                of 1 to 10 or 10-5 to
                          pharmacokinetics,        10-6 cancer risk     
                          potency and exposure.    range.               
III....................  Inadequate or no animal  RfD approach.         
                          evidence.                                     
------------------------------------------------------------------------
\1\Considering oral exposure data such as drinking water, dietary and   
  gavage studies.                                                       

    Each chemical is evaluated for evidence of carcinogenicity from 
drinking water. For volatile contaminants, inhalation data are also 
considered. EPA takes into consideration the overall weight of evidence 
for carcinogenicity, pharmacokinetics, potency and exposure.
    EPA's policy is to set MCLGs for Category I contaminants at zero. 
The MCLG for Category II contaminants is calculated by using the 
Reference dose (RfD) approach (described below) with an added margin of 
safety to account for possible cancer effects. If adequate data are not 
available to calculate an RfD, then the MCLG is based on a cancer risk 
level of 10-5 to 10-6. MCLGs for Category III contaminants 
are calculated using the RfD approach.
    Category I contaminants are those for which EPA has determined that 
there is strong evidence of carcinogenicity from drinking water. The 
MCLG for Category I contaminants is set at zero because it is assumed, 
in the absence of other data, that there is no threshold dose for 
carcinogenicity. In the absence of route specific (e.g., oral) data on 
the potential cancer risk from drinking water, chemicals classified as 
Group A or B carcinogens (see section c below) are generally placed in 
Category I.
    Category II contaminants include those contaminants for which EPA 
has determined that there is limited evidence of carcinogenicity from 
drinking water, considering weight of evidence, pharmacokinetics, 
potency, and exposure. In the absence of route specific data, chemicals 
classified in Group C (see section c below) are generally placed in 
Category II.
    For Category II contaminants, one of two options have traditionally 
been used to set the MCLG. The first option sets the MCLG based upon 
noncarcinogenic endpoints of toxicity (the RfD), then applies an 
additional safety factor of 1 to 10 to the MCLG to account for possible 
carcinogenicity. An MCLG set by the option 1 approach is compared with 
the cancer risk, if quantified. The second option is to set the MCLG 
based upon a theoretical lifetime excess cancer risk level of 10-5 
to 10-6 using a conservative mathematical extrapolation model. EPA 
generally uses the first option; however, the second approach is used 
when valid noncarcinogenic data are not available to calculate an RfD 
and adequate experimental data are available to quantify the cancer 
risk.
    Category III contaminants include those contaminants for which 
there is inadequate or no evidence of carcinogenicity from drinking 
water. If there is no additional information to consider, contaminants 
classified in Group D or E (see section c below) are generally placed 
in Category III. For these contaminants, the MCLG is established using 
the RfD approach.
    b. Assessment of Noncancer Health Effects. The risk assessment for 
noncancer health effects can be characterized by a Reference Dose 
(RfD). The oral RfD (expressed in mg/kg/day) is an estimate, with 
uncertainty spanning perhaps an order of magnitude, of a daily exposure 
to the human population (including sensitive subgroups) that is likely 
to be without an appreciable risk of deleterious health effects during 
a lifetime. The RfD is derived from a no- or lowest-observed-adverse-
effect level (called a NOAEL or LOAEL, respectively) that has been 
identified from a subchronic or chronic study of humans or animals. The 
NOAEL or LOAEL is then divided by an uncertainty factor(s) to derive 
the RfD. Although the RfD is represented as a point estimate, it is 
actually a range since the RfD is a number with an inherent uncertainty 
of an order of magnitude.
    Uncertainty factors are used to estimate the comparable ``no-
effect'' level for a large heterogeneous human population. The use of 
uncertainty factors accounts for several data gaps including intra- and 
inter-species differences in response to toxicity, the small number of 
animals tested compared to the size of the population, sensitive 
subpopulations and the possibility of synergistic action between 
chemicals (see 52 FR 25690 for further discussion on the use of 
uncertainty factors).
    EPA has established certain guidelines (shown below) to determine 
how to apply uncertainty factors when establishing an RfD (USEPA, 
1986).
     Use a 1- to 10-fold factor when extrapolating from valid 
experimental results from studies in average healthy humans. This 
factor is intended to account for the variation in sensitivity among 
the members of the human population.
     Use an additional 10-fold factor when extrapolating from 
valid results of long-term studies on experimental animals when results 
of studies of human exposure are not available or are inadequate. This 
factor is intended to account for the uncertainty in extrapolating 
animal data to the case of humans.
     Use an additional 10-fold factor when extrapolating from 
less than chronic results on experimental animals when there are no 
useful long-term human data. This factor is intended to account for the 
uncertainty in extrapolating from less than chronic NOAELs to chronic 
NOAELs.
     Use an additional 10-fold factor when deriving an RfD from 
a LOAEL instead of a NOAEL. This factor is intended to account for the 
uncertainty in extrapolating from LOAELs to NOAELs.
     An additional uncertainty factor may be used according to 
scientific judgment when justified.
     Use professional judgment to determine another uncertainty 
factor (also called a modifying factor, MF) that is greater than zero 
and less than or equal to 10. The magnitude of the MF depends upon the 
professional assessment of scientific uncertainties of the study and 
data base not explicitly treated above, e.g., the completeness of the 
overall data base and the number of species tested. The default value 
for the MF is 1.
    To determine the MCLG, the RfD is adjusted by the body weight of 
the protected (or most sensitive) individual (usually a 70 kg adult), 
average volume of water consumed daily over a lifetime (2 L/day for an 
adult) and exposure to the contaminant from a drinking water source 
(relative source contribution or RSC).
    Generally, EPA assumes that the RSC from drinking water is 20 
percent of the total exposure, unless other exposure data for the 
chemical are available [see 54 FR 22069 and 56 FR 3535]. When adequate 
data are available and the data indicate that drinking water exposure 
contributes between 20 and 80 percent of total exposure, EPA uses the 
actual percentage to determine the MCLG, as is indicated by equation 
(3), below. When data indicate that contributions from drinking water 
are between zero and 20 percent, or between 80 and 100 percent, EPA 
utilizes a 20 percent floor and an 80 percent ceiling, respectively.
    The calculations below express the derivation of the MCLG based on 
noncancer health effects:

TP29JY94.000

    c. Assessment of Carcinogenic Health Effects. For chemicals 
suspected of being carcinogenic to humans, the assessment for non-
threshold toxicants consists of the weight of evidence of 
carcinogenicity in humans, using bioassays in animals and human 
epidemiological studies as well as information that provides indirect 
evidence (i.e., mutagenicity and other short-term test results). The 
objectives of the assessment are to determine the level or strength of 
evidence that the substance is a carcinogen and to provide an 
upperbound estimate of the possible risk of human exposure to the 
substance in drinking water. A summary of EPA's general carcinogen 
classification scheme is (USEPA, 1986):
    Group A--Human carcinogen based on sufficient evidence from 
epidemiological or other human studies.
    Group B--Probable human carcinogen based on limited evidence of 
carcinogenicity in humans (Group B1) or based on sufficient evidence in 
animals with inadequate or no data in humans (Group B2).
    Group C--Possible human carcinogen based on limited evidence of 
carcinogenicity in animals in the absence of human data.
    Group D--Not classifiable based on lack of data or inadequate 
evidence of carcinogenicity from animal data.
    Group E--No evidence of carcinogenicity for humans (no evidence for 
carcinogenicity in at least two adequate animal tests in different 
species or in both epidemiological and animal studies).
    d. MRDLGs--appropriateness of a new concept? As stated in section 
II.A of this preamble, EPA is proposing a new term, ``maximum residual 
disinfectant level goal'' (MRDLG), in lieu of MCLGs for all 
disinfectants because disinfectants are intentionally added to drinking 
water as a treatment technique to kill disease-causing microorganisms. 
The proposal of this concept was agreed to through the negotiated 
rulemaking process.
    Certain members of the Negotiating Committee were concerned that if 
``MCLGs,'' which included the term ``contaminant,'' were set for 
disinfectants, water treatment plant operators might be reluctant to 
apply disinfectant dosages above the MCLG during short periods of time 
to control for microbial risk, even though such exposure to elevated 
disinfectant concentration levels would pose little or no risk. For 
example, NOAELs for chlorine and chloramines are based upon animal 
studies following long term exposure to high levels of the 
disinfectants in drinking water. Short-term exposures at elevated 
levels would not be a concern (see the following discussion on health 
effects for chlorine and chloramines). During emergency situations such 
as distribution system pipe breaks or significant fluctuations in 
source water quality, systems will on occasion need to apply short term 
disinfectant residual concentrations of chlorine or chloramines, well 
above the regulatory goal, to protect from waterborne disease.
    The MRDLGs are developed in the same way as MCLGs. EPA solicits 
comment on the appropriateness of adopting the term ``MRDLG'' in lieu 
of MCLGs for disinfectants in the final rule.

B. Proposed MRDLGs and MCLGs

    The following includes a summary of the health effects information 
available for each disinfectant or by-product. These summaries are 
taken from more complete and comprehensive descriptions of the data 
given in the cited Health Criteria Documents that have been developed 
for each of these chemicals. These documents are available in the water 
docket.
1. Chlorine, hypochlorite ion and hypochlorous acid
    The following assessment for both chlorine and chloramines includes 
a consideration of available animal data, as well as epidemiology 
studies which have been conducted on chlorinated or chloraminated 
drinking water. The epidemiology data are discussed in section C of 
this preamble.
    Chlorine (CAS # 7782-50-5) hydrolyses in water to form hypochlorite 
(CAS # as sodium salt 7790-92-3) and hypochlorous acid (CAS # 7681-52-
9). Because of their oxidizing characteristic and solubility, chlorine 
and hypochlorites are used in water treatment to disinfect drinking 
water, sewage and wastewater, swimming pools, and other types of water 
reservoirs. They are also used for general sanitation and control of 
bacterial odors in the food industry.
    Chlorine is a highly reactive and water soluble species. The fate, 
transport, and distribution of chlorine in natural waters is not well 
understood. Much of the available information comes from the addition 
and oxidation reactions with inorganic and organic compounds known to 
occur in aqueous solutions. Factors such as reactant concentrations, 
pH, temperature, salinity and sunlight influence these reactions.
    Occurrence and Human Exposure. For the purpose of setting an MRDLG, 
consideration is given to chlorine levels resulting from disinfection 
of drinking water. Chlorine exposures from swimming pools and hot tubs 
are not evaluated in determining the MRDLG. Persons who swim frequently 
or use a hot tub may have greater dermal and possibly inhalation 
exposure to chlorine.
    Chlorine is added to drinking water as chlorine gas (Cl2) or 
as calcium or sodium hypochlorite. In drinking water, the chlorine gas 
hydrolyses to hypochlorous acid and hypochlorite ion and can be 
measured as the free chlorine residual. Maintenance of a chlorine 
residual throughout the distribution system is important for minimizing 
bacterial growth and for indicating (by the absence of a residual) 
water quality problems in the distribution system. Currently, maximum 
chlorine dosage is limited by taste and odor constraints and for 
systems needing to comply with the total trihalomethane (TTHM) standard 
regularly. Additionally, for systems using chlorination, the surface 
water treatment rule (SWTR) requires a minimum residual of 0.2 mg/L 
prior to the entry point to the distribution system, and the presence 
of a detectable residual throughout the distribution system.
    Table V-2 presents occurrence information available for chlorine in 
drinking water. Descriptions of these surveys and other data are 
detailed in ``Occurrence Assessment for Disinfectants and Disinfection 
By-Products (Phase 6a) in Public Drinking Water,'' USEPA 1992a. The 
table lists five surveys conducted by Federal, as well as private 
agencies. Median concentrations of chlorine in drinking water appear to 
range from <1 to 2 mg/L.

                                                   Table V-2.--Summary of Occurrence Data for Chlorine                                                  
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        Occurrence of chlorine in drinking water                                                        
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                               Concentration (mg/L)                     
     Survey (year)\1\                Location              Sample information (No. of   ----------------------------------------------------------------
                                                                    samples)                Range        Mean        Median              Other          
--------------------------------------------------------------------------------------------------------------------------------------------------------
EPA, 1992b\2\ (1987-1991).  Disinfection By-Products    Finished Water:                                                                                 
                             Field Studies.             At the Plant (71)..............      0.1-5.0          1.7          1.4                          
                                                        Distribution System (45).......      0.0-3.2          0.7          0.5                          
AWWARF (1987) McGuire &     National Survey...........  Finished Water From:                                                    (Typical doses).        
 Meadow, 1988.                                          Lakes..........................                                         2.2\3\                  
                                                        Flowing Streams................                                         2.3\3\                  
                                                        Ground Waters..................                                         1.2\3\                  
                                                        Mixed-supplies.................                                         1.0\3\                  
EPA/AMWA/CDHS\2\ (1988-     35 Water Utilities          Samples from Clearwell               0.3-5.2          1.5          1.0  ........................
 1989) Krasner et al.,       Nationwide.                 Effluent, 4 Quarters (17).                                                                     
 1989b.                                                                                                                                                 
WIDB (1989-1990)..........  228 SW Plants.............  Residual Chlorine Provided to          0-3.5        0.937          0.8  ........................
                            215 GW Plants.............   the Average Customer (systems           0-5        0.872        0.325                          
                                                         >50,000 people).                                                                               
AWWA Disinfection Survey    283 Utilities in the U.S..  Finished Water Entering          ...........     0.07-5.0          1.1  ........................
 (1991).                                                 Distribution System.                                                                           
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                                                          
\2\May not be representative of national occurrence.                                                                                                    
\3\Typical dosage used by treatment plants.                                                                                                             
                                                                                                                                                        
SW: Surface Water.                                                                                                                                      
GW: Ground Water.                                                                                                                                       
AMWA: Association of Metropolitan Water Agencies.                                                                                                       
AWWA: American Water Works Association.                                                                                                                 
AWWARF: American Water Works Association Research Foundation.                                                                                           
CDHS: California Department of Health Services.                                                                                                         
EPA: Environmental Protection Agency.                                                                                                                   
WIDB: Water Industry Data Base.                                                                                                                         

    Exposure to chlorine residual varies both between systems and 
within systems. Chlorine residual within systems will vary based on 
where customers are located within the distribution system and changes 
in the system's disinfection needs over time. Using residual 
concentrations from the 1989-1991 AWWA Disinfection Survey and WIDB, 
exposure to chlorine due to drinking water can be estimated using a 
consumption rate of 2 liters per day. Based on the estimated 25th 
percentile and 75th percentile chlorine residuals in the 1991 AWWA 
Disinfection Survey, exposure was determined to range from 1.5 to 3.8 
mg/day and the median would be 2.2 mg/day. Using the WIDB data, 
exposures to the average customer from surface and ground water sources 
using chlorination, respectively, were determined to be 1.9 mg/day and 
1.7 mg/day.
    Little information is available concerning the occurrence of 
chlorine in food and indoor air in the United States. The Food and Drug 
Administration (FDA) does not analyze for chlorine in foods. However, 
there are several uses of chlorine in food production, such as the 
disinfection of chicken in poultry plants and the superchlorination of 
water at soda and beer bottling plants (Borum, 1991). Therefore, the 
possibility exists for dietary exposure to chlorine from its use in 
food production. However, monitoring data are not available to 
characterize adequately the extent of such potential exposures. 
Additionally, preliminary discussions with FDA suggest that there are 
no approved uses for chlorine in most foods consumed in the typical 
diet. Similarly, EPA's Office of Air and Radiation is not currently 
conducting any sampling studies for chlorine in indoor air. Data on 
levels of chlorine in ambient air are forthcoming.
    Considering the limited number of food groups that are believed to 
contain chlorine and that no significant levels of chlorine are 
expected in ambient or indoor air, it is anticipated that drinking 
water is the predominant source of exposure to chlorine. Air and food 
are believed to provide only small contributions, although the 
magnitude and frequency of these potential exposures are issues 
currently under review. EPA, therefore, is considering setting an MRDLG 
for chlorine in drinking water using an RSC value of 80%, the current 
exposure assessment policy ceiling. EPA requests any additional data on 
known concentrations of chlorine in drinking water, food and air.
    Health Effects. The health effects information for chlorine is 
summarized from the draft Drinking Water Health Criteria Document for 
Chlorine, Hypochlorous Acid and Hyperchlorite Ion (USEPA, 1994a). The 
studies cited within this section are summarized in the draft criteria 
document.
    Chlorine and the hypochlorites are very reactive and thus can react 
with the constituents of saliva and possibly food and gastric fluid to 
yield a variety of reaction by-products (e.g., trihalomethanes). Thus, 
the health effects associated with the administration of high levels of 
chlorine and/or the hypochlorites in various animal studies may be due 
to these reaction by-products and not the disinfectant itself. 
Oxidizing species such as chlorine and the hypochlorites are probably 
short-lived in biological systems due to both their reactivity and the 
large number of organic compounds found in vivo. Scully and White 
(1991) noted that reactions of aqueous chlorine with sulfur-containing 
amino acids appear to be so fast in saliva that all free available 
chlorine is dissipated before the water is swallowed.
    Oral studies with radiolabeled (i.e., 36Cl) hypochlorite and 
hypochlorous acid indicate that, as measured by the radiolabel, these 
compounds may be well absorbed and distributed throughout the body with 
the highest levels measured in plasma and bone marrow. However, 
considering the reactivity of the hypochlorites, these results may only 
reflect the presence of reaction by-products (e.g., chloride). The 
major route of excretion appears to be urine and then the feces.
    Acute oral LD50 values for calcium and sodium hypochlorite 
have been reported at 850 mg/kg in rats and 880 mg/kg in mice, 
respectively. Humans have consumed hyperchlorinated water for short 
periods of time at levels as high as 50 mg/L (1.4 mg/kg) with no 
apparent adverse effects.
    Short-term oral studies in animals have indicated decreases in 
blood-glutathione levels, hemolysis and biochemical changes in liver in 
rodents following a gavage dose of hypochlorite in water. No adverse 
effects on reproduction (Druckery, 1968) or development were observed 
in rats administered chlorine in drinking water at concentrations of 
100 mg/L or less. However, Meier et al. (1985) observed an increase in 
sperm-head abnormalities in mice receiving hypochlorite at 200 mg/L, 
but not at 100 mg/L or less.
    No systemic effects were observed in rodents following oral 
exposure to chlorine as hypochlorite in distilled water at levels up to 
275 mg/L over a 2 year period (NTP, 1990).
    Chlorinated water has been shown to be mutagenic to bacterial 
strains and mammalian cells. Investigations with rodents to determine 
the potential carcinogenicity of chlorine, or chlorinated water have 
been negative. In the most recent study, no apparent carcinogenic 
potential was demonstrated following oral exposure to chlorine in 
distilled drinking water as hypochlorite, at levels up to 275 mg/L over 
a 2 year period (NTP, 1990). However, NTP observed a marginal increase 
in the incidence of mononuclear cell leukemia in mid-dose female F344 
rats but not in male rats or male and female mice (NTP, 1990). 
Mononuclear cell leukemia has a high spontaneous rate of occurrence in 
female F344 rats. The levels reported in the NTP study are within the 
historical control range of incidence for the sex and strain of rat. 
EPA believes that mononuclear cell leukemia can not be solely 
attributed to exposures to chlorine in drinking water but rather may 
reflect the high background rate of mononuclear cell leukemia in the 
test species.
    EPA has classified chlorine in Group D, not classifiable as to 
human carcinogenicity (IRIS, 1993). This classification stems from the 
findings of the NTP (1990) study indicating equivocal evidence in 
female rats (increased mononuclear cell leukemia) and no evidence in 
male rats or male and female mice. The International Agency for 
Research on Cancer (IARC, 1991) also evaluated chlorinated drinking 
water and hypochlorite for potential human carcinogenicity. IARC 
determined that there was inadequate evidence for carcinogenicity of 
chlorinated drinking water and hypochlorite salts in humans and 
animals. (See section C for a description of these studies.) IARC 
concluded that chlorinated drinking water and hypochlorite salts were 
not classifiable as to their carcinogenicity to humans and thus 
assigned these chemicals to IARC Group 3. This category is similar to 
EPA cancer classification Group D.
    Based on the previous discussion, EPA is proposing that chlorine, 
hypochlorite and hypochlorous acid be placed in Category III for the 
purpose of setting an MRDLG. The study selected for determining an RfD 
is the previously mentioned 2 year rodent study that was conducted by 
the National Toxicology Program (NTP, 1990). In this study, male and 
female F344 rats and B6C3F1 mice were given chlorine in distilled 
drinking water at levels of 0, 70, 140 and 275 mg/L for 2 years. Based 
on body weight and water consumption values, these concentrations 
correspond to doses of approximately 0, 4, 7 and 14 mg/kg/day for male 
rats; 0, 4, 8, and 14 mg/kg/day for female rats; 0, 7, 14, and 24 mg/
kg/day for male mice and 0, 8, 14 and 24 mg/kg/day for female mice. 
There was a dose related decrease in water consumption for both rats 
and mice, presumably due to taste aversion. No effect on body weight or 
survival were observed for any of the treated animals. Using a NOAEL of 
14 mg/kg/d identified from female rats in the NTP (1990) study an MRDLG 
of 4 mg/L, based on lack of toxicity in a chronic study is derived as 
follows.

TP29JY94.001

    Where 14 mg/kg/d is the NOAEL for female rats in the NTP study, and 
100 is the uncertainty factor applied to account for inter and intra-
species differences in accordance with EPA guidelines when a NOAEL from 
a chronic animal study is the basis for the RfD. The MRDLG is based on 
a 70 kg adult consuming an average of 2 liters water per day over their 
lifetime. In addition, an 80% RSC is assumed in the absence of data to 
the contrary.
    Public comments are requested on the following issues: 1) placing 
chlorine in Category III for developing an MRDLG, 2) selection of the 
study and NOAEL as the basis for the MRDLG, 3) the 80% RSC, 4) the 
appropriateness of the UF of 100, 6) the cancer classification for 
chlorine.
2. Chloramines
    Inorganic chloramines (CAS Nos. 10599-90-3 and 10025-85-1 for mono- 
and trichloramine, respectively) are formed in waters undergoing 
chlorination which contain ammonia. Monochloramines, dichloramines and 
trichloramines may be formed. Monochloramine is the principal 
chloramine formed in chlorinated natural and wastewater at a neutral pH 
and is much more persistent in the environment.
    Chloramine is used as a disinfectant in drinking water to control 
taste and odor problems, limit the formation of chlorinated 
disinfection by-products, and maintain a residual in the distribution 
system for controlling biofilm growth. At typical pHs of most drinking 
waters, the predominant chloramine specie is monochloramine. For 
purposes of this regulation, only monochloramine will be considered 
since the other chloramines occur at much lower concentrations in 
almost all drinking waters. Monochloramine has also been much more 
extensively studied.
    Monochloramine, the principal chloramine formed in chlorinated 
natural and wastewaters at neutral pH, is relatively stable when 
discharged to the environment. First-order decay rate constants of 0.03 
to 0.075 hr-1 for monochloramine in the laboratory, and higher 
rate constants of 0.28 to 0.31 hr-1 outdoors using chlorinated 
effluents, have been reported. If discharged into receiving waters 
containing bromide, monochloramine will decompose faster, probably 
through the formation of NHBrCl and decomposition of the dihalamine. 
The rate of monochloramine disappearance is primarily a function of pH 
and salinity. For example, at pH 7 and 25 deg.C, the half-life of 
monochloramine is 6 hr at 5 parts per thousand (ppt) salinity and 0.75 
hr at 35 ppt salinity; at pH 8.5 and 25 deg.C, the half-life is 188 hr 
at 5 ppt salinity and 25 hr at 35 ppt salinity. Monochloramine is 
expected to decompose in wastewater discharges receiving waters via 
chlorine transfer to organic nitrogen-containing compounds.
    Occurrence and Human Exposure. Chloramine occurs in drinking water 
both as a by-product and intentionally for disinfection. Chloramine is 
formed during chlorination when source waters contain ammonia. It is 
also used as a primary or secondary disinfectant, usually with 
chloramine being generated on site by the addition of ammonia to water 
following treatment by chlorination. The use of chloramines has been 
shown to reduce the formation of certain by-products, notably 
trihalomethanes, relative to the by-products formed with chlorination 
alone. Chlorination by-product formation can be minimized when the 
ammonia is added prior to or in combination with chlorine by reducing 
the chlorine residual of the water being treated. In most plants, 
however, ammonia is added some time after the addition of chlorine, to 
allow for more effective disinfection since chlorine is a much stronger 
disinfectant than chloramines.
    Table V-3 presents occurrence information available for chloramine 
in drinking water. Descriptions of these surveys and other data are 
detailed in ``Occurrence Assessment for Disinfectants and Disinfection 
By-Products (Phase 6a) in Public Drinking Water,'' USEPA, 1992a. 
Typical dosages of chloramine used as a disinfectant in drinking water 
treatment facilities range from 1.5 to 2.7 mg/L. Median concentrations 
of chloramine in drinking water were found to range from 1.1 to 1.8 mg/
L.

                                                 Table V-3.--Summary of Occurrence Data for Chloramines                                                 
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Occurrence of chloramine in drinking water                                                       
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                               Concentration (mg/L)                     
     Survey (year)\1\                Location              Sample information (No. of   ----------------------------------------------------------------
                                                                    samples)                Range         Mean        Median              Other         
--------------------------------------------------------------------------------------------------------------------------------------------------------
AWWARF (1987) McGuire &     National Survey...........  Finished Water From:             ...........  ...........  ...........  Typical dosages:        
 Meadow, 1988.                                          Lakes..........................                                         1.5 mg/L                
                                                        Flowing Streams................                                         2.7 mg/L                
EPA/AMWA/CDHS\2\ (1988-     35 Water Utilities          Samples from Clearwell               0.9-5.5          2.3          1.8  ........................
 1989) Krasner et al.,       Nationwide.                 Effluent, 4 Quarters (13).                                                                     
 1989b.                                                                                                                                                 
EPA, 1992b\2\ (1987-1991).  Disinfection By-Products    At the Plant (11)..............      1.2-3.6          2.1          1.5  ........................
                             Field Studies.             Distribution System (8)........      0.1-3.3          1.4          1.1                          
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                                                          
\2\May not be representative of national occurrence.                                                                                                    
                                                                                                                                                        
AMWA: Association of Metropolitan Water Agencies.                                                                                                       
AWWARF: American Water Works Association Research Foundation.                                                                                           
CDHS: California Department of Health Services.                                                                                                         
EPA: Environmental Protection Agency.                                                                                                                   

    Based on the residual concentrations given above, a high and low 
estimate for exposure to chloramine from drinking water can be 
calculated using an assumed consumption of 2 liters per day. Using the 
target range of 1.5 to 2 mg/L, the exposure may range from 3 to 4 mg/
day. Some systems may deviate significantly from this range.
    No information is available on the occurrence of chloramine in food 
or air. Currently, the Food and Drug Administration (FDA) does not 
measure for chloramine in foods since the analytical methods have not 
been developed. Preliminary discussions with FDA suggest that there are 
not approved uses for chloramine in foods consumed in the typical diet. 
Similarly, EPA's Office of Air and Radiation is not sampling 
chloramines in air (Borum, 1991).
    Based on the previous discussion, EPA assumes that drinking water 
is the predominant source of exposure to chloramine. Air and food 
intakes are believed to provide only small contributions, although the 
magnitude and frequency of these potential exposures are issues 
currently under review. EPA, therefore, is proposing to establish an 
MRDLG for chloramine in drinking water with an RSC value of 80%, the 
current exposure assessment policy ceiling. EPA requests any additional 
data on known concentrations of chloramine in drinking water, food and 
air.
    Health Effects. The health effects information in this section is 
summarized from the draft Drinking Water Health Criteria Document for 
Chloramines (USEPA, 1994b). Studies mentioned in this section are 
summarized in the Criteria Document.
    Short-term inhalation exposures to high levels (500 ml of 5% 
household ammonia mixed with 5% hypochlorite bleach) of chloramines in 
humans result in burning in the eyes and throat, dyspnea, coughing, 
nausea and vomiting. Inhalation of the chloramine fumes resulted in 
pneumonitis but did not result in permanent pulmonary damage.
    Short-term exposures to chloramines in drinking water, in which 
human subjects were administered single concentrations ranging between 
1 and 24 mg/L (1, 8, 18 or 24 mg/L), have not resulted in any adverse 
effects in human subjects. Following human exposure, the subject's 
physical condition, urinalysis, hematology, and clinical chemistry were 
evaluated. No adverse clinical effects were noted in any of the 
studies.
    In another study, acute hemolytic anemia, characterized by 
oxidation of hemoglobin to methemoglobin and denaturation of 
hemoglobin, was reported in hemodialysis patients when tap water 
disinfected with chloramines was used for dialysis baths. Chloramines 
were reported to produce oxidant damage to red blood cells and inhibit 
the metabolic pathway used by red blood cells to prevent and repair 
such damage. Many dialysis centers have installed reverse osmosis units 
coupled with charcoal filtration or the addition of ascorbic acid to 
prevent hemolytic anemia.
    Animal studies indicate varying sensitivity and conflicting results 
among different animal species. Toxic effects noted among rats are 
changes in blood glutathione and methemoglobin. Both monkeys and mice 
were unaffected during short-term assays with doses up to 200 mg/L 
chloramines. Based on studies up to 6 weeks in length, rats appear to 
be more sensitive to monochloramine than mice and monkeys.
    Toxicokinetic studies of chloramines indicate that the absorption 
of chloramines is rapid, peaking within 8 hours of administration. In 
the rat, chloramines are metabolized to chloride ion and excreted 
mostly through the urine with a small portion excreted through the 
feces.
    Longer-term oral studies (90 days or longer) showed decreased body 
and organ weights in rodents. Some effects to the liver (weight 
changes, hypertrophy, and chromatid pattern changes) appear to be 
related to overall body weight changes caused by decreased water 
consumption due to the unpalatibility of chloramines to the test 
animals.
    In addition, chloramine may induce immunotoxicity in rats in the 
form of increased prostaglandin E2 synthesis, reduced antibody 
synthesis, and spleen weight at levels as low as 9 to 19 mg/L 
chloramines for 90 days. The significance of these findings for risk 
use in risk assessment is compromised by the design flaws of the study 
(i.e., animals were exposed to two antigens) and the lack of 
corroboration of these findings by a follow-up study.
    Two lifetime rodent studies involving oral exposures to rats and 
mice via drinking water have been considered by EPA for the derivation 
of the MRDLG for monochloramine. Both studies were performed by the 
National Toxicology Program (NTP, 1990) and involved 70 animals/sex/
dose exposed to distilled drinking water containing 0, 50, 100 or 200 
ppm chloramines.
    The first NTP (1990) study was a 2-year study in mice to determine 
the potential chronic toxicity or carcinogenic activity of 
chloraminated drinking water. B6C3F1 mice were administered 
chloramine at doses of 0, 50, 100 and 200 ppm in distilled drinking 
water. These doses were calculated based on a time-weighted average to 
be 0, 5.0, 8.9 and 15.9 mg/kg/day for male mice and 0, 4.9, 9.0 and 
17.2 mg/kg/day for female mice. There was a dose-related decrease in 
the amount of water consumed by both sexes; this decrease was noted 
during the first week and continued throughout the study. Dosed male 
and female mice had similar food consumption as controls except for 
females in the 200 ppm dose group that exhibited slightly lower 
consumption than controls.
    Study results indicated that there was a dose-related decrease in 
mean body weights of dosed male and female mice throughout the study. 
Mean body weights of high-dose male mice were 10-22% lower than their 
control group after week 37 and the body weights of high-dose female 
mice were 10-35% lower after week 8. However, the survival of mice 
receiving monochloramine in drinking water was not significantly 
different than controls. Clinical findings observed were not attributed 
to the consumption of chloraminated drinking water. Body weight loss 
and systemic toxicity were not considered related to the toxicity of 
chloramine, but rather due to decreased water consumption resulting 
from the unpalatability of chloramines in drinking water to the test 
animals. Therefore, the highest dose tested, 17.2 mg/kg/day, is 
considered a NOAEL in mice.
    In the second study F344/N rats were administered monochloramine 
for 2 years at doses of 0, 50, 100 and 200 ppm in distilled drinking 
water. These doses were calculated on the basis of a time-weighted 
average to be 0, 2.1, 4.8 and 8.7 mg/kg/day for male rats and 0, 2.8, 
5.3 and 9.5 mg/kg/day for female rats. There was a dose-related 
decrease in the amount of water consumed by both sexes; this decrease 
was noted during the first week and continued throughout the study. 
Food consumption of treated rats was the same as the controls with 
males consuming more. In addition, mean body weights of 200 ppm dosed 
rats (both sexes) were lower than their control groups. However, mean 
body weights of rats receiving monochloramine in drinking water (at all 
levels) were within 10% of controls until week 97 for females and week 
101 for males. Though several clinical changes were noted, no clinical 
changes were attributable to chloraminated drinking water. The survival 
of rats receiving chloraminated drinking water was not significantly 
different than controls except that, for the 50 ppm dose groups, 
survival was greater than that of controls. Therefore, EPA considers 
the highest dose tested, 9.5 mg/kg/day, as the NOAEL.
    Based on two bacterial assays, monochloramine appears to be weakly 
mutagenic. One study examining the reproductive effects and another 
which examined developmental effects of chloramines concluded that 
there are no chemical-related effects due to chloramines.
    The NTP evaluation, using the results of the two lifetime NTP 
bioassays, concluded that chloramines exhibited equivocal evidence of 
carcinogenic activity of chloraminated drinking water in female F344/N 
rats. This conclusion results from an increase in mononuclear cell 
leukemia. There was no evidence of carcinogenic activity in male rats 
or mice of either sex. The findings do not establish a link between 
chloramine exposure and carcinogenicity because of the high historical 
background occurrence of this type of cancer in test animals. The 
incidence of mononuclear cell leukemia in the female control groups 
(16%) was substantially less than the incidence reported in untreated 
historical controls (25%). Incidence of mononuclear cell leukemia in 
test animals reached a high of 32% in the high dose female rats. This 
study also discovered incidence of renal tubular cell neoplasms in two 
high-dose male mice receiving chloraminated water. Since this type of 
tumor is rarely seen in historical controls, there is some concern that 
these may be treatment related. However, the overall evidence regarding 
the potential carcinogenicity of chloramines in drinking water can be 
described as inconclusive since no long-term study has linked any tumor 
development to actual chloramination exposure. On this basis, as well 
as consideration of those studies described in section C, EPA placed 
chloramine in Group D: not classifiable based on inadequate evidence of 
carcinogenicity.
    EPA selected the lifetime study in rats (NTP, 1990) as the basis 
for calculating the MRDLG for chloramines. The NOAEL for the rat (9.5 
mg/kg/d) is proposed because the rat was not tested at the higher doses 
where mice were tested (17.2 mg/kg/d). Rats appear to be more sensitive 
considering observed changes in biochemistry. Following a Category III 
approach and using the rat NOAEL of 9.5 mg/L from the NTP study, an 
MRDLG of 4 mg/L (measured as total chlorine), based on lack of toxic 
effects in a chronic study can be derived for the 70-kg adult consuming 
2 liters of water per day applying an uncertainty factor of 100, which 
is appropriate for use of a NOAEL derived from an animal study and 
assuming an RSC drinking water contribution of 80 percent. 
---------------------------------------------------------------------------

    *Since chloramines, on a practical basis, will be measured as 
total chlorine, it is necessary to present the MRDLG in terms of a 
chlorine equivalent concentration. Three mg/L chloramine is 
equivalent to 4 mg Cl2/liter, based on the molecular weights of 
Cl2 and NH2Cl.

TP29JY94.002

    EPA requests comments on the proposed MRDLG for chloramines and the 
RSC of 80%, the significance of the findings of immunotoxicity for 
setting the RfD instead of the NTP study, the significance of the 
finding of mononuclear cell leukemia in female F344 rats, the 
significance of the finding of tubular cell neoplasms in high-dose 
exposed mice, and whether the adjusted MRDLG, which takes into account 
the measurement of monochloramine as total chlorine, is appropriate.

TP29JY94.003

3. Epidemiology Studies of Chlorinated and Chloraminated Water
    Several studies have been conducted to evaluate the association of 
chlorination or chloramination with the risk of cancer, cardiovascular 
disease or adverse reproductive effects in humans. A summary of some of 
these studies is given below. This discussion reflects EPA's assessment 
of these data and is summarized from the draft Drinking Water Criteria 
Documents for Chlorine (USEPA, 1994a) and Chloramines (USEPA, 1994b), 
respectively.
     Introduction to Epidemiology Studies. Two distinct types of 
epidemiology studies have been conducted: ecologic and analytical. 
These types of studies differ markedly in what they reveal about the 
association between water quality and disease. In an ecological 
epidemiology study, information is available on exposure and disease 
for groups of people rather than for individuals, and therefore, the 
results are difficult to interpret. What is considered to be an 
important or relevant group variable may not be important for or may 
not pertain to individuals within that group. Theoretical and empirical 
analyses have offered no consistent guidelines for the interpretation 
of ecological associations, and results from these studies are 
appropriate only to suggest hypotheses for further study by analytical 
epidemiological methods (Piantiadosi et al., 1988; Connor and Gillings, 
1974).
    Analytical epidemiology studies provide an estimate of the 
magnitude of risk and information which can be used to evaluate 
causality. For each individual in the study, information is obtained 
about disease status and exposure to various contaminants and other 
characteristics. In several of the studies reported here, individual 
exposures to disinfected water or specific disinfection by-products 
were estimated using group exposure information. All reported 
epidemiological associations from analytical studies require an 
evaluation of random error (statistical significance) and potential 
sources of systematic bias (misclassification, selection, observation, 
and confounding biases) so that results can be interpreted properly. It 
must be noted that random error or chance can never be completely ruled 
out as the explanation for an observed association and that statistical 
significance does not necessarily imply biological significance. 
Regardless of statistical significance, it is important to consider 
potential biological mechanisms. Random error does not address the 
possibility of systematic error or bias. Misclassification of exposure 
and disease, selection bias, and observation bias must be avoided; 
confounding bias, on the other hand, can be prevented both in study 
design and during analysis if information is obtained about possible 
confounders. It is important to determine for each specific 
epidemiology study the validity of the association observed between 
exposure and disease before considering possible causality between 
exposure and disease or inferring that the results apply to a larger or 
target population. Systematic bias can lead to spurious associations; 
in some but not all instances, the direction of the bias can be 
determined. For example, a random misclassification of exposure usually 
biases a study toward not observing an effect or observing a smaller 
risk than may actually be present, but nonrandom misclassification can 
result in either higher or lower estimates of risk depending upon the 
distribution of misclassification.
    In addition, because of the observational nature of epidemiology, 
the interpretation of epidemiology studies requires a sufficient number 
of well designed and well conducted epidemiology studies, and must 
include appropriate toxicological and biological information. Judging 
causality from epidemiology studies is based largely on guidelines 
developed over the years, including sequence of events, strength of 
association (relative risk or odds ratio), consistency of results under 
different conditions of study, biological plausibility, dose or 
exposure response relationship, and specificity of effect. The relative 
risk represents a basic measure of an association between exposure and 
disease. It is defined as the rate of disease in the exposed population 
divided by the rate of disease in an unexposed population.
    a. Cancer Studies. Since the early 1970's, numerous epidemiologic 
studies have attempted to assess the association between cancer and the 
long term consumption of water from various sources with and without 
disinfection and of various chemical quality, especially chlorinated 
surface waters which supply the majority of the U.S. population. 
Ecological, case control, and cohort studies have been conducted. Case 
control studies have included incident and decedent cases; in some 
studies information about various risk factors has been collected 
through interviews, but in others information was obtained primarily 
from death certificates.
    i. Ecological Studies. The earliest studies were analyses of group 
or aggregate data available on drinking water exposures and cancer. 
Usually the variables selected for analyses were readily available in 
published census, vital statistics, or public records and easily 
abstracted and assembled. These analyses, referred to as ecological but 
also called aggregate, geographical, or correlational, were designed to 
investigate cancer mortality rates, usually on a county or State level. 
Areas of different water quality, source, and chlorination status were 
compared to identify possible statistical associations for further 
study. Drinking water exposures were most often characterized as simple 
dichotomous variables which served as indicators of exposure to 
differing source water quality, e.g., the drinking water source for the 
county or geographic area was categorized as a surface or groundwater 
source. In some instances exposure variables included estimates of the 
proportion of the area's or county's population that received surface 
or groundwater and whether it was chlorinated. Surface water was 
assumed to be more contaminated with synthetic organics than 
groundwater, but no attempt was made to estimate levels of 
contaminants.
    In 1974 it was discovered that when surface waters were disinfected 
with chlorine, the chlorine reacted with pre-existing organic materials 
in the water to create a great number of chemical by-products (Craun, 
1988). The major group of disinfection by-products (by weight) was the 
trihalomethanes (THMs) which included an animal carcinogen, chloroform. 
Chlorinated surface water was evaluated as an exposure variable in 
several of the ecological studies, and since almost all surface waters 
are chlorinated, the analyses usually compared cancer mortality among 
populations receiving chlorinated surface water with those receiving 
unchlorinated groundwater. Chlorinated water was assumed to contain 
disinfection by-products, and at higher levels than chlorinated 
groundwaters. However, the quality of surface and groundwater may also 
differ for other contaminants, and this was not considered. Any 
observed association might be due to other water quality differences 
among surface and groundwaters (e.g., organic contaminants from 
nonpoint and point source discharges to surface waters from industrial, 
urban, and agricultural sources before pollution control regulations).
    In some ecological analyses, the investigators attempted to study 
the association between cancer mortality and an estimate of group 
exposure to levels of chlorinated by-products based on THM or 
chloroform levels was determined from a limited number of water 
samples. The exposure information used in ecological studies was 
available in only broad geographic units such as census tracts or 
counties (Crump and Guess, 1982; Shy, 1985). Although these exposure 
variables were statistically associated with mortality rates for all 
cancers combined and several site-specific cancers, the interpretation 
must necessarily be cautious due to limitations of ecological studies. 
In several of these studies, aggregate or group information on several 
covariates, e.g., occupation, income, or population density, also was 
included in the statistical analysis in an attempt to adjust for 
potential confounding factors. In one study the statistical 
significance of the observed associations between stomach and rectal 
cancer mortality and group exposures to current THM levels disappeared 
when migration patterns and ethnic data were included in the regression 
model (Tuthill and Moore, 1980). A wide range of cancer sites was found 
to be statistically associated with estimates of population group 
exposures based on current levels of THM or chloroform including gall 
bladder, esophagus, kidney, breast, liver, pancreas, prostate, stomach, 
bladder, colon, and rectum. The most frequent associations observed 
were for the last four sites; however, these associations were not 
consistent when viewed by gender, race, and geographic region.
    The ecologic design coupled with the lack of specific exposure 
indicators in these studies precludes the inference of a causal 
relationship (Morgenstern, 1982). A subcommittee of the National 
Academy of Sciences (NAS, 1980) reviewed 12 of the ecological studies 
and noted ``Results of these studies demonstrate the problems of 
establishing relationships between health statistics and environmental 
variables, and lend emphasis to the caution with which they should be 
interpreted.'' The NAS further commented that the ecological studies in 
which the current THM exposures were estimated were deemed to be more 
informative than others and ``suggest that higher concentrations of THM 
in drinking water may be associated with an increased frequency of 
cancer of the bladder. The results do not establish causality, and the 
quantitative estimates of increased or decreased risk are extremely 
crude. The effects of certain potentially important confounding 
factors, such as cigarette smoking, have not been determined.'' The 
studies are useful, however, as an initial step for identification of 
potential hazards and they indicated the need for further epidemiologic 
studies or analytic studies of individuals with a specific etiologic 
hypothesis.
    ii. Cohort Studies. A cohort study (or follow-up) study (the study 
can be called either retrospective or prospective) is one in which two 
or more groups (referred to as `cohorts') of people that differ 
according to the extent of exposure to a potential cause of disease are 
compared with respect to incidence of the disease of interest in each 
of the groups. The essential element of this study type is that 
incidence rates are calculable directly for each study group (Rothman, 
1986). One advantage of this study type is the ability to study 
multiple disease endpoints. One disadvantage of this study type is that 
a large study population is needed to detect a relatively small risk. 
In addition, because of the latency period for carcinogenicity, a long 
follow-up time may be required for the study.
    There exists one cancer drinking water cohort study where 
individual data were available for a well-defined, fairly homogeneous 
area that allowed disease rates to be computed by presumed degree of 
exposure to by-products of chlorination, although the population was 
relatively small. Wilkins and Comstock (1981) studied the residents of 
Washington County, Maryland and ascertained the source of drinking 
water at home for each county resident in a private census conducted in 
1963. In addition to water source, information was collected on age, 
marital status, education, smoking history, number of years lived in 
the household, and frequency of church attendance. Death certificates 
and cancer registry information was sought for county residents whose 
date of death or diagnosis occurred in the 12 year period following the 
census. Sex and site-specific cancer rates were constructed for 
malignant neoplasms of biliary passages and liver, kidney, and bladder. 
Several additional causes of death were analyzed as well for comparison 
purposes. The population was stratified into three separate exposure 
subgroups: chlorinated surface water, unchlorinated deep wells, and 
small municipal systems with a mixture of chlorinated and unchlorinated 
water, each reflecting a different history of exposure to by-products 
of chlorination. The study group which included individuals who 
obtained drinking water from small municipal systems were not included 
as a comparison with the other drinking water cohorts because of their 
exposure to both chlorinated and unchlorinated water.
    Both crude and adjusted incidence rates for liver cancer in males 
and females and for cancer of the liver among males were essentially 
the same for persons supplied with chlorinated surface water at home 
(high THM exposure) and for persons with deep wells (low THM exposure). 
The adjusted rates for bladder cancer (RR=1.6; 95% CI=0.54,6.32) and 
cancer of the liver (RR=1.8; 95% CI=0.64,6.79) among females were 
highest among persons using chlorinated surface water. Given the low 
relative risk and broad confidence intervals, the authors indicated 
that this finding could be attributed to chance (Wilkins and Comstock, 
1981). Confounding bias may also influence the interpretation of a 
small relative risk. EPA considers that the results of this study are 
inconclusive because the results are based on small numbers of cases, 
hence, the reported rates are statistically unstable and subject to 
random variation.
    iii. Case Control Studies. In a case control study, persons with a 
given disease (the cases) and persons without the given disease (the 
controls) are selected for study. The proportions of cases and controls 
who have certain background characteristics or who have been exposed to 
possible risk factors are then determined and compared. Exposure odds 
ratios (ORs) are determined. The odds of exposure among cases is 
compared with that of controls. For rare diseases, the ORs are 
considered good estimates of relative risk. These studies are sometimes 
called case-referent or retrospective studies. Because there are many 
variations of this study design (e.g., how cases and controls are 
selected, how information on exposures, risk factors, and confounding 
factors are obtained, and who is interviewed), each case control study 
should be evaluated individually to determine if the specific study 
design parameters introduce systematic bias (Kelsy et al., 1986). As 
previously noted, all epidemiology studies require careful evaluation 
of systematic bias. For those studies with major bias, the results are 
generally considered inconclusive. Those studies with minor bias may 
still provide useful information.
    Two types of studies were conducted: (1) Decedent cases without 
interviewing survivors for information about residential histories and 
risk factors and (2) incident cases with interviews.
    Decedent Case-Control Studies. Several case-control studies were 
conducted to continue to investigate the possibility that there was a 
causal relationship between chlorinated drinking water, including 
byproducts such as THMs, and gastrointestinal or urinary tract cancers. 
Most of these case-control studies used deceased cases of the specific 
cancers of interest, although some continued their investigations in a 
relatively nonspecific way by using both total cancer mortality as well 
as several of the site- specific cancers studied in the ecologic 
studies (Crump and Guess, 1982; Shy, 1985). Controls were noncancer 
deaths from the same geographic area and in all but one study matched 
for several potentially confounding variables including age, race, sex, 
and year of death. As in all studies of this design (i.e., death 
certificate studies with no available interviews), control of 
confounding factors was restricted to information that is routinely 
recorded on death certificates and no information was obtained from 
next-of-kin interviews. The exposure variables of interest at this time 
included a comparison of surface v ground water sources, or chlorinated 
v nonchlorinated ground water sources. The place of residence listed on 
the death certificate was linked to public records of water source and 
treatment practices in order to classify the drinking water exposure 
variable for a particular case or control (Shy, 1985).
    Similar to the earlier ecologic studies, the Agency considers the 
results from these studies to be inconsistent in their findings. The 
calculated ORs, varied by cancer site and sex, as well as in their 
magnitude and statistical significance. This variability was found for 
all the cancer endpoints studied including those of specific interest, 
i.e., bladder, colo-rectal, and/or colon. These endpoints were found to 
vary by geographic region. For example, a statistically significant 
increased bladder cancer risk was observed in North Carolina for males 
and females combined (OR=1.54) and New York for males (OR=2.02), but 
not for females; no statistically significant risk was seen in 
Louisiana, Wisconsin or Illinois. Increased colon cancer risk was 
observed in Wisconsin (OR=1.35) and North Carolina (OR=1.30) for males, 
but not females; no increased risk was seen in Louisiana or Illinois. 
Increased rectal cancer risk was observed in North Carolina (OR=1.54) 
and Louisiana (OR=1.68) for males and females combined, in Illinois for 
females (OR=1.35) but not males, and in New York for males (OR=2.33) 
but not females; no increased risk was seen in Wisconsin. Although 
increased risk was observed for cancer of the liver and kidney 
(OR=2.76), esophagus (OR=2.39), and pancreas (OR=2.23) among males in 
New York, no increased risk for these cancers was seen among females in 
New York, Illinois, Wisconsin or Louisiana.
    Although many of the ORs were statistically significant, these 
decedent case control studies with extremely limited information on 
confounding factors and potential exposures to chlorinated water are of 
limited usefulness in assessing whether cancer is associated with 
chlorinated drinking water, or judging the causality of such as 
association. Although some of the ORs were large enough to cause 
concern about an exposure association, the magnitude of the OR was such 
that the association could be attributed to incomplete control of 
confounding factors and the ORs might represent spurious elevations 
(Crump and Guess, 1982).
    Although not subject to all the same limitations as ecologic 
studies, decedent case-control studies are considered more limited by 
some epidemiologists than others as a tool for causal inference because 
of a high probability of systematic bias associated with the use of 
information obtained only from the death certificate (e.g., inadequate 
or no information on residential history, water exposures, and major 
potential confounders). The variability seen in these five studies is 
likely a combination of several factors, including available sample 
size, choice of causes of death included as controls, regional 
variability in true composition of the raw and treated drinking waters, 
definition of exposure variables, a high probability of exposure 
misclassification from imputing a lifetime exposure to a certain water 
source or treatment from residence listed on the death certificate, and 
uncontrolled confounding (e.g., diet and smoking).
    Given the limitations of decedent case control studies without 
interviews, the evidence from these studies are considered insufficient 
to determine a causal association between any or all the components 
which exist in the complex mixture created during the chlorination of 
surface waters and any site-specific cancer. The findings provided a 
stimulus for a further refined epidemiologic study using incident cases 
of bladder and colon cancer and appropriate controls who could be 
interviewed for residential history and numerous other covariates.
    Case-Control Studies with Interviews. At the time when these more 
recent studies were planned, it was still believed that THMs were the 
major by-products of chlorinated drinking water that should be 
investigated and studies were designed and conducted in areas where a 
THM difference might be expected and somehow measurable. Exposure 
assessment for individuals remained problematic in the study design. 
The best available means of exposure measurement, however, was at best 
a surrogate for the true exposure of interest which is the actual level 
of THMs or other by-products ingested over a person's lifetime through 
consumption of surface water disinfected with chlorine. Only two 
studies attempted to estimate long-term exposure to THMs. Most studies 
used residence at a location served by chlorinated drinking water. In 
all except one of the studies, comparisons of exposure were between 
chlorinated surface water and unchlorinated groundwater. As previously 
discussed in the section on ecological studies, the water quality for 
surface and ground water differ for many other consituents.
    Because it was known that disinfection of surface water using 
chloramine produced very low levels of THMs and other by-products 
compared to the same water disinfected with chlorine, a study was 
conducted in Massachusetts to compare the patterns of mortality in 
communities which used these different disinfectants (Zierler et al., 
1986). Statewide mortality records for 1969-1983 were analyzed using 
standardized mortality ratios (SMRs) and showed little variation by 
community. However, mortality odds ratios (MORs) comparing bladder 
cancer deaths to all other deaths were considered by the authors to 
indicate a slight elevation for last residence in a chlorinated 
community compared to a chloraminated community (MOR=1.7; 95% CI=1.3, 
2.2). The authors noted that the results were preliminary and ``crude 
descriptions of the relationship under study'' (Zierler et al., 1986). 
The authors further indicated that the results may have been caused by 
unidentified or uncontrolled confounding factors.
    Bladder cancer deaths were investigated further using a case-
control design with proxy interviews to determine residential and 
smoking histories (Zierler et al., 1988). The association of bladder 
cancer was assessed for individuals with lifetime and usual exposure to 
chlorinated and chloraminated water depending on the number of years of 
residence at a particular water source. Residence in a community using 
chlorinated drinking water was used as an index for exposure to 
chlorinated by-products, while residence in a community using 
chloramine for disinfection was considered an index for no exposure to 
chlorinated by-products. An association was observed between bladder 
cancer and both lifetime (MOR=1.6; 95% CI=1.2-2.1) and usual (MOR=1.4; 
95% CI=1.1-1.8) exposure to chlorinated water. A subgroup of study 
participants was noted to have lived their entire lives in an area 
served with water supplied by the Massachusetts Water Resources 
Authority, disinfected with either chlorine or chloramine (same water 
source, different disinfectant, lifetime exposure). Within this group 
the bladder cancer mortality risk was 1.6 times higher (MOR=1.6; 95% 
CI=1.1, 2.4) when the water had been disinfected with chlorine compared 
to chloramine (Zierler et al., 1988).
    In addition to analyses using a control group which consisted of 
deaths from cardiovascular disease, cerebrovascular disease, chronic 
obstructive lung disease, lung cancer, and lymphatic cancer, a separate 
analysis was done using only the lymphatic cancer controls. This was 
considered necessary by the authors because of the possibility that 
some of the other deaths among controls may also be related to the 
exposure of interest. If true, then the MOR estimate would be biased 
toward the hypothesis of no increased risk. When the analysis 
considered only lymphatic cancer controls, the magnitude of the 
association with chlorinated water increased for lifetime exposure 
(MOR=2.7; 95% CI=1.7-4.3), usual exposure (MOR=2.0; 95% CI=1.4-3.0), 
and lifetime exposure in the previously mentioned subgroup (MOR=3.5; 
95% CI=1.8-6.7). Sources of misclassification bias that may have been 
present were considered to be randomly distributed among the cases and 
controls which implies that the observed MOR would be an underestimate 
of risk (Zierler et al., 1988). It is also possible that 
nondifferential misclassification of the variables used to control 
confounding, leading to residual confounding of the summary estimates, 
could have caused a systematic spurious elevation in the MORs.
    The largest study to date investigating the relationship of 
chlorinated water and bladder cancer incidence involved an ancillary 
study to the National Cancer Institute's (NCI) 10 area study of bladder 
cancer and artificial sweeteners (Cantor et al., 1985, 1987, 1990). The 
original study conducted interviews with 2,982 newly diagnosed bladder 
cancer cases and 5,782 population controls; lifetime information on 
source and treatment of drinking water was collected and analyzed for 
only a subset of the original study population (1,244 cases and 2,550 
controls). Subgroup analyses of nonsmokers among participants and those 
reporting beverage intake necessarily involved even smaller numbers. 
Duration of exposure, measured by years of residence at a chlorinated 
surface or nonchlorinated ground water source was presumed to be a 
surrogate for dose of disinfectant by-products. Overall, there was no 
association of duration of exposure with bladder cancer risk (Cantor et 
al., 1985, 1987). In nonsmokers who never smoked, a 2-fold increased 
risk was reported for those exposed for 60 or more years to chlorinated 
surface water (n=46 cases, 77 controls) compared to unchlorinated 
ground water (n=61 cases, 268 controls) users (OR=2.3; 95% CI=1.3, 
4.2). These data were further analyzed according to beverage intake 
level, type of water source and treatment (Cantor et al., 1987, 1990). 
It was observed that people who reported drinking the most tap water-
based beverages from any source (>1.96 liters/day) had a bladder cancer 
risk about 40% higher (OR=1.43; 95% CI=1.23-1.67, males and females 
combined) than people who drank the least. The association between 
water ingestion and bladder cancer risk for males was an OR=1.47; 95% 
CI=1.2-1.8, and for females an OR=1.29; 95% CI=0.9-1.8.
    Evaluation of bladder cancer risk by both duration of exposure and 
amount of water consumed showed that the risk increased with higher 
water consumption only among those who drank chlorinated surface water 
for 40 or more years. Evaluation of risk by smoking status revealed 
that most of the duration effect was observed in nonsmokers. Among 
nonsmokers who consumed tap water in amounts above the population 
median (>1.4 L/day), a risk gradient was apparent only for males. 
However, a higher risk was also seen for nonsmoking females who 
consumed less than the median level. The increasingly smaller numbers 
of cases and controls available for these subgroup analyses produce 
statistically unstable OR estimates making it difficult to evaluate the 
trend results.
    This is the first study of incident bladder cancer cases that 
obtained and analyzed fluid consumption patterns in this way. The noted 
inconsistencies in the reported data must be more thoroughly explored 
and indicate a need for replication before any causal relationship can 
be assumed (Devesa et al., 1990). An additional consideration is a more 
refined exposure measurement; many of the disinfection by-products are 
volatile. Thus exposure may occur through inhalation as well as 
ingestion.
    Two conflicting studies of colon cancer and presumed THM exposure 
have been reported. The first one (Cragle et al., 1985) was a hospital 
based case control study that included 200 incident colon cancer cases 
from seven hospitals and 407 hospital controls with no history of 
cancer who were diagnosed with diseases unrelated to colon cancer. It 
should be noted that both colon and rectal cancer cases were included 
as cases in the study. Controls were matched to cases on hospital and 
admission date, as well as age, race, sex and vital status. Residential 
histories were linked with water source and disinfectant information 
for the 25 years prior to diagnosis. Logistic regression analysis using 
qualitative data groupings for the variables of interest showed a 
strong interaction of age and chlorination status (Table V-4). THM 
levels were not estimated. Odds ratios computed from the regression 
coefficients increased with age, and within age groups. The ORs are 
higher for a longer duration of exposure.

       Table V-4.--Comparison of OR's By Exposure Duration and Age      
------------------------------------------------------------------------
                                     OR (95% CI) 1-15   OR (95% CI) > 15
            Age (years)               years exposure     years exposure 
------------------------------------------------------------------------
20-29.............................               0.23                   
                                         (0.11, 0.49)               0.48
                                                            (0.23, 1.01)
30-39.............................               0.36                   
                                          (0.2, 0.66)                0.6
                                                            (0.33, 1.09)
40-49.............................               0.57                   
                                         (0.36, 0.88)               0.75
                                                            (0.48, 1.18)
50-59.............................               0.89                   
                                         (0.83, 1.12)               0.94
                                                            (0.69, 1.29)
60-69.............................               1.18                   
                                         (0.94, 1.47)               1.38
                                                             (1.1, 1.72)
70-79.............................               1.47                   
                                         (1.16, 1.84)               2.15
                                                             (1.7, 2.69)
80-89.............................               1.83                   
                                         (1.32, 2.53)               3.36
                                                            (2.41, 4.61)
------------------------------------------------------------------------

    From these data, it appears that risk is increased only in those 
persons 60 years old and older with greater than 15 years of exposure 
to chlorinated water and in those greater than 70 years of age, 
regardless of exposure duration.
    A second colon cancer study (Young et al., 1987) conducted in 
Wisconsin involved 366 incident colon cancer cases, 785 controls 
diagnosed with other cancers, and 654 population controls. Extensive 
interviews were conducted with all participants to obtain information 
on past drinking water sources, drinking water habits and a number of 
potentially confounding covariates. This information was combined with 
data provided by water companies to construct models to predict 
historical levels of THMs to be used as both cross-sectional and 
cumulative exposure variables. Simpler methods of defining exposure 
were also used, (e.g., surface vs. ground, chlorinated v. 
nonchlorinated), and all methods looked at the data by period specific 
exposure levels. The results did not indicate any association between 
THMs in Wisconsin drinking water and colon cancer risk. Odds ratios for 
all exposure variables were uniformly close to 1.0 with few exceptions. 
It should be noted, however, that in this study the majority of the 
water supplies contained less than 20 g/l of THMs. No excess 
risk was observed at these levels, given the limitations of this study 
design in detecting a small risk.
    The association of THM and colo-rectal cancer was studied in New 
York where the THM levels were higher than those in the above Wisconsin 
study (Lawrence et al., 1984). A total of 395 colon and rectal cancer 
deaths among white female teachers in New York State (excluding New 
York City) was compared with an equal number of deaths of teachers from 
causes of death other than cancer. All deaths were ascertained using 
the defined cohort of the New York State Teachers Retirement System. 
Cumulative chloroform exposure was estimated by the application of a 
statistical model to operational records from water systems that served 
the home and work addresses of the study participants during the 20 
years prior to death. The distribution of chloroform exposure was not 
significantly different between cases and controls. No effect of 
cumulative chloroform exposure was observed in a logistic analysis 
controlling for type, population density, marital status, age, and year 
of death. No excess risk was associated with exposure to a surface 
water source containing THMs (OR=1.07; 90% CI=0.79, 1.43). Although the 
data were not presented in the article, the authors reported that no 
appreciable differences were seen when the colon and rectal cases were 
analyzed separately, compared to the combined analyses reported above.
    Although most all the studies reviewed here have looked at colon, 
colo-rectal or bladder cancer risk, one recently published work 
investigated the risk of pancreatic cancer in relation to presumed 
exposure to chlorinated drinking water. Ijsselmuiden et al. (1992) 
conducted a population-based case-control study in Washington County, 
Maryland, using the same population data that were originally 
ascertained during a private population census for an earlier cohort 
study (Wilkins and Comstock, 1981). The original cohort study did not 
find any association between pancreatic cancer and chlorinated drinking 
water (OR=0.80, 95% CI=0.44-1.52).
    This case-control study was conducted to reexamine chlorinated 
drinking water as a possible independent risk factor for pancreatic 
cancer in this population. It is not reported of any of the other 
endpoints from the original study also were reexamined, e.g., bladder, 
kidney, or liver cancer. Cases were those residents who were reported 
to the County cancer registry with a first time pancreatic cancer 
diagnosis during the period July, 1975 through December 1989, and who 
had been included in the 1975 census (n=101). Controls were randomly 
selected by computer from the 1975 census population (n=206). Drinking 
water source, as obtained during the 1975 census, was the exposure 
variable used. In univariate analyses, municipal water as a source of 
drinking water, increasing age, and unemployment were significantly 
associated with increased risk of pancreatic cancer. Multivariable 
analyses that controlled for confounding variables indicated that the 
use of municipal chlorinated water at home was associated with a 
significant OR of 2.23 (95% CI=1.24-4.10). The OR adjusted is 2.18 (95% 
CI=1.20-3.95); only age and smoking were assessed as potential 
confounders.
    Interpretation of these findings is hampered by several problems 
regarding the assessment of exposure, including the fact that 
information obtained in 1975 on type of water and other variables is an 
exposure collected at one point in time and may not reflect actual 
exposure patterns prior to 1975. In addition, there is no information 
on the actual amounts of water consumed. Additionally, different 
residential criteria were used for the cases and controls. The cases 
had to still be residing in the County at the time of their cancer 
diagnosis to be included in the study, but the controls may not have 
been current residents. If controls emigrated out of the county 
differentially on the basis of exposure, the ORs may be an over- or 
underestimate of the risk depending on emigration patterns. Finally, it 
can not be ruled out that the exposure variable used for this and other 
studies--residence served by a particular water source--is simply a 
surrogate for some other unidentified factor associated with nonrural 
living. The nonspecific relationship of several different causes of 
death and water source at home observed in the earlier cohort study 
(Wilkins and Comstock, 1981) lends some support to this possibility. 
More valid individual exposure information over a long period of time 
for both specific contaminants and the use of chlorinated/unchlorinated 
water are needed to assess the results of this and other analytical 
epidemiology studies.
    Morris et al. (1992) conducted a meta-analysis, evaluating 12 
studies and pooling the relative risks from 10 epidemiological studies 
of cancer and a presumed exposure to chlorinated water and its 
byproducts. Meta-analysis refers to the application of quantitative 
methods to combine the published results of a related body of 
literature (Dickerson and Berlin, 1992). Morris et al. (1992) reported 
a pooled relative risk estimate of 1.21 (95% CI, 1.09-1.34) for bladder 
cancer and 1.38 (95% CI, 1.01-1.87) for rectal cancer (i.e., 9% of 
bladder cancer cases and 15% of the rectal cancer cases in the U.S. or 
approximately 10,000 additional cases of cancer per year could be 
attributed to chlorinated water and its by-products). Pooled relative 
risk estimates for ten other site specific cancers including colon, 
colo-rectal and pancreas were not felt to be significantly elevated nor 
were they statistically significant.
    If the indications from this analysis are true such that water 
chlorination could result in as many as 10,000 cases of cancer a year, 
then chlorination could represent a significant cause of rectal and 
bladder cancer in the U.S. However, there was disagreement among the 
negotiating parties over the appropriateness of this meta-analysis. 
Some believed that the use of the meta-analysis may not be appropriate 
for these data. Others disagreed, expressing their view that the 
analysis was statistically probative and otherwise valuable. Meta-
analysis has been used successfully to combine the results of small 
clinical trials and of some epidemiology studies that have similar 
experimental design and exposure conditions. Application of meta-
analysis to the water chlorination data requires careful consideration 
of exposure variables and systematic bias in each of the studies. 
Chlorinated drinking water is a complex mixture of many substances that 
vary geographically and seasonally. There is even variability within a 
geographic region. In addition, the information on exposure and 
potential confounding is much more limited for the four decedent case 
control studies used in the meta-analysis. Their study design is 
dissimilar to the other studies included, resulting in concerns about 
their inclusion in the meta-analysis. Study-specific methodological 
problems, systematic bias, and problems of exposure definition and 
assessment could not be corrected by this analysis (Murphy, 1993). 
Thus, the overall results of the Morris et al. analysis may over- or 
underestimate the risk. However, the estimate of risk in regard to 
rectal cancer might be particularly affected by the inclusion of these 
case control studies. It should also be noted that the results of the 
Morris et al. analysis does not provide additional information to 
establish causality.
    The chlorinated drinking water epidemiology studies have been 
reviewed extensively by EPA, the National Academy of Sciences, the 
International Agency for Research on Cancer (IARC), and the 
International Society for Environmental Epidemiology (ISEE). In 1987, 
the National Academy of Sciences Subcommittee on Disinfectants and 
Disinfectant By-Products concluded that there was a major health 
concern with the chronic ingestion of low levels of disinfection 
byproducts (NRC, 1987). The Subcommittee commented that some of the 
epidemiology studies reported ``increased rates of bladder cancer 
associated with trends of levels of certain contaminants in water 
supplies. Interpretation of these studies is hampered by a lack of 
control for confounding variables (e.g., age, sex, individual health, 
smoking history, other exposures).'' The Subcommittee recommended that 
epidemiologists continue to improve protocols and conduct studies on 
drinking water and bladder cancer where exposure data can be obtained 
from individuals, rather than through estimation from exposure models.
    EPA and IARC, along with other individual scientists, have 
interpreted the epidemiologic evidence as inadequate. IARC concluded 
that ``there is inadequate evidence for carcinogenicity of chlorinated 
drinking water in humans.''
    The ISEE presented a full spectrum of opinion regarding the 
epidemiology data (Neutra and Ostro, 1992). The ISEE reported a 
``general consensus that the results of the recent EPA-sponsored 
studies of cancer endpoints have strengthened the evidence for linking 
bladder cancer with long term exposure to chlorinated drinking water. 
The evidence for links with colon cancer are not convincing. * * * Any 
risks, if real, are low when compared to the risk of infection from not 
disinfecting water.''
    In 1992, the International Life Sciences Institute sponsored a 
conference with the Pan American Health Organization, EPA, Food and 
Drug Administration, World Health Organization, and the American Water 
Works Association on the safety of water disinfection. Although they do 
not necessarily reflect the views of the sponsoring organizations, 
conclusions prepared by the conference's editor and editorial board 
(Craun et al., 1993) noted that ``Adverse human health effects may be 
associated with the chemical disinfection of drinking water. However, 
current scientific evidence is inadequate to conclude that water 
chlorination poses a significant risk to humans. Uncertainties about 
the available toxicologic evidence limit assessment of human health 
risks associated with chlorine, chloramine, chlorine dioxide, and ozone 
disinfection. The epidemiologic evidence for increased cancer risks of 
chlorinated drinking water is equivocal.''
    Some members of the reg-neg committee felt that the epidemiology 
data, taken in conjunction with the results from toxicological studies, 
provide an ample and sufficient basis to conclude that the usual 
exposure to disinfection by-products in drinking water could result in 
an increased cancer risk at levels encountered in some public water 
supplies.
    Because of the spectrum of conclusions concerning these data, the 
Agency is pursuing additional research to reduce the uncertainties 
associated with these data and better characterize the potential of 
cancer risks associated with the consumption of chlorinated drinking 
water.
    b. Serum Lipids/Cardiovascular Disease. Laboratory studies on 
animals, conducted in the early 1980's indicated a possible link 
between consumption of chlorinated drinking water and elevated serum 
lipid profiles which are indicators of cardiovascular disease (USEPA 
1994a). The animal work was followed by a cross-sectional study in 
humans (Zeighami et al., 1990) that included 1,520 adult residents, 
aged 40 to 70 years, in 46 Wisconsin communities supplied with either 
chlorinated or unchlorinated drinking water of varying hardness. The 
study was designed to determine whether differences in calcium or 
magnesium intake from water and food and chlorination of drinking water 
affect serum lipids.
    The communities selected for study had the following 
characteristics: (1) They were small in population size (300-4,000) and 
not suburbs of larger communities; (2) they had not undergone more than 
20% change in population between 1970 and 1980; (3) they had been in 
existence for at least 50 years; and (4) all obtained water from 
groundwater sources with no major changes in water supply 
characteristics since 1980 and did not artificially soften water. The 
water for the communities contained total hardness of either 
 80 mg/l CaCO3 (soft water) or  200 mg/l 
CaCO3 (hard water); 24 communities used chlorine for disinfection and 
22 communities did not disinfect. Eligible residents were identified 
through state driver's license tapes and contacted by telephone; an 
age-sex stratified sampling technique was used to choose a single 
participant from each eligible household. Only persons residing in the 
community for at least the previous 10 years were included. A 
questionnaire was administered to each participant to obtain data on 
occupation, health history, medications, dietary history water use, 
water supply and other basic demographic information. Water samples 
were collected from a selected subset of homes and analyzed for 
chlorine residual, pH, calcium, magnesium, lead, cadmium, and sodium. 
Fasting blood specimens were collected from each participant and 
analyzed for total cholesterol, triglycerides and high- and low-density 
lipoprotein (HDL and LDL, respectively) subfractions.
    Among females, adjusted mean total serum cholesterol levels were 
statistically significantly higher in the chlorinated communities 
compared to the nonchlorinated communities (249 mg/dl and 238 mg/dl, 
respectively). These changes are not considered biologically 
significant as they reflect background variation. Total serum 
cholesterol levels were also higher for males in chlorinated 
communities, on the average, but the difference was smaller and not 
statistically significant (236 mg/dl vs. 232 mg/dl). LDL mean values 
followed a similar pattern to that for total cholesterol, higher in 
chlorinated communities for females, but not different for males. 
However, for both sexes, HDL cholesterol levels are nearly identical in 
chlorinated and nonchlorinated communities and there were no 
significant differences found in the HDL/LDL ratios. The implications 
of these findings for cardiovascular disease risk are unclear at this 
time given the inconsistencies in the data. The possibility exists that 
the observed association in females may have resulted from some unknown 
or undetermined variable in the chlorinated communities.
    The results from a second study, designed to further explore the 
findings among female participants in the Wisconsin study (Zieghami et 
al., 1990), were presented in 1992 (Riley et al., 1992, manuscript 
submitted for publication). Participants were 2,070 white females, aged 
65 to 93 years who were enrolled in the Study of Osteoporotic Fractures 
(University of Pittsburgh Center) and had completed baseline 
questionnaires on various demographic and lifestyle factors. Total 
serum cholesterol was determined for all participants. Full lipid 
profiles (total cholesterol, triglycerides, LDL, total HDL, HDL-2, HDL-
3, Apo-A-I, and Apo-B) were available from fasting blood samples for a 
subset of 821 women. Interviews conducted in 1990 ascertained 
residential histories and type of water source used back to 1950 and 
all reported public water sources were contacted for verification of 
disinfectant practices. Private water sources were presumed to be 
nonchlorinated. A total of 1,896 women reported current use of public, 
chlorinated water, 201 reported current use of nonchlorinated springs, 
cisterns, or wells and 35 reported having mixed sources of water. Most 
of the women had been living in the same home with the same water 
service for at least 30 years.
    Overall, there were no meaningful differences detected in any of 
the measured serum lipid levels between women currently exposed to 
nonchlorinated water and those exposed to chlorinated water (246 mg/dl 
vs. 247 mg/dl, respectively, for total cholesterol). The data were also 
stratified by age and person-years of exposure to chlorinated water at 
home. There was some suggestion that women with no exposure to chlorine 
had lower total cholesterol levels but this finding was inconsistent 
and may represent random fluctuation since there was no trend noted 
with LDL cholesterol or Apo-B, both of which are known to correlate 
with total cholesterol. There was also no association between 
increasing duration of exposure to chlorine and HDL cholesterol, Apo-A-
I, or triglycerides.
    The only notable differences were that women with chlorinated water 
reported significantly more cigarette and alcohol consumption than the 
women with nonchlorinated drinking water (Riley et al., 1992). This was 
evident in all age groups and across strata of duration of exposure. 
This finding lends support to the possibility that the previously 
reported association of chlorinated drinking water and elevated total 
serum cholesterol (Zeighami et al., 1990) may have arisen due to 
incomplete control of lifestyle factors which were differentially 
distributed across chlorination exposure groups.
    c. Reproductive/Developmental Outcomes. Several recently conducted 
epidemiologic studies have examined the relationship between different 
reproductive or developmental endpoints and various components of 
drinking water. Kramer et al. (1992) conducted a population-based case-
control study to determine whether water supplies containing relatively 
high levels of chloroform and other THMs within the state of Iowa are 
associated with low birthweight, prematurity, or intrauterine growth 
retardation (IUGR). Iowa birth certificate data from January, 1989 
through June, 1990 served as the source of both cases and controls. 
Definitions for cases and controls were as follows: the low birthweight 
group included 159 live singleton infants weighing <2,500 grams and 795 
randomly selected control infants weighing 2,500 grams from 
the same population; the prematurity group included 342 live singleton 
infants with gestational ages of <37 weeks as determined from the 
mother's reported last menstrual period, and 1,710 randomly selected 
control infants with gestational ages 37 weeks; IUGR 
analyses included 187 IUGR infants (defined as weighing less than the 
5th percentile for a particular gestational age based on California 
standards for non-Hispanic whites) and 935 randomly selected controls. 
Exposure status was assigned to infants according to reported maternal 
residence in a given municipality at the time of birth. The assigned 
THM levels came from a water survey conducted in 1987 in the state of 
Iowa so the exposure information came from aggregate data. Odds ratios 
were computed using multiple logistic regression to control for 
measured confounders (including smoking, but not alcohol consumption). 
The authors reported an increased risk for IUGR associated with 
residence in communities where chloroform levels exceeded 10 ug/l 
(OR=1.8; 95% CI=1.1-2.9). Prematurity was not associated with 
chloroform exposure and the risk for low birthweight was only slightly 
increased (OR=1.3; 95% CI=0.8-2.2).
    The authors considered the results of this study to be preliminary. 
Accordingly, they should be interpreted with caution. They considered 
the major limitations of the study to involve assessment and 
classification of individual exposure, the potential misclassification 
due to residential mobility and the fluctuation of THM levels.
    Aschengrau et al. (1993) conducted a case-control study in 
Massachusetts to determine the relationship between community drinking 
water quality and a wide range of adverse pregnancy outcomes, including 
congenital anomalies, stillbirths, and neonatal deaths. The data were 
obtained during a previous study of 14,130 pregnant women who delivered 
infants at Brigham and Women's Hospital in Boston between 1977 and 
1980. Drinking water quality information came from routine analyses of 
the metal and chemical content of Massachusetts public water. An 
attempt was made to link each woman in the study to the result of the 
water analyses conducted in her town at the time of her pregnancy. 
Information was also obtained on drinking water source and chlorination 
of surface water. Drinking water samples from 155 towns were linked to 
2,348 pregnant women to estimate exposure for the case-control study.
    A large number of exploratory analyses were conducted with this 
data set, which demonstrated both increases and decreases in risk 
associated with various water quality parameters. A higher frequency of 
stillbirths was correlated with chlorination and detectable lead 
levels, cardiovascular defects were associated with lead levels, CNS 
defects with potassium levels, and face, ear, and neck anomalies with 
detectable silver levels. A decrease in neonatal deaths was associated 
with detectable fluoride levels.
    The authors indicated that the findings from this study, being non-
specific, must be considered as preliminary given the problems and 
limitations of the exposure assessment and the lack of an a priori 
study hypothesis. They indicated a need for further research 
(Aschengrau et. al. 1993).
    The New Jersey Department of Health recently reported the results 
of a cross-sectional study and a case-control study evaluating the 
association of drinking water contaminants with birth weight and 
selected birth defects (Bove et al. 1992a and b). Four counties 
selected for the study were included because they had the highest 
levels of monitored drinking water and they were served by well defined 
public water systems which used ground and surface water, or a mixture 
of these sources. The exposures evaluated total volatile organic 
contaminants (VOCs) as well as individual VOCs such as 
trichloroethylene, tetrachloroethylene, carbon tetrachloride, benzene 
and THMs. The cross sectional study base included 81,055 live single 
births and 599 single fetal deaths between January, 1985 and December, 
1988; 593 mothers were interviewed in the case control study. Exposure 
scenarios to THMs were stratified as follows: >20-40 g/L, >40-
60 g/L, >60-80 g/L, and >80 g/L.
    In the cross sectional study, ORs with exposure to THMs >80 
g/L were elevated for low term birth weight (OR=1.34; 95% 
CI=1.13-1.6; adjusted OR=1.29; 95% CI=1.08-1.5), small for gestational 
age (OR=1.22; 95% CI=1.12-1.3; adjusted OR=1.14; 95% CI=1.04-1.3), and 
prematurity (OR=1.09; 95% CI=0.99-1.2; adjusted OR=1.04; 95% CI=0.94-
1.1). Among birth defects, the ORs were elevated for all surveillance 
malformations: OR=1.53; 95% CI=1.14-2.1; central nervous system defects 
OR=2.6; 95% CI=1.48-4.6; neural tube defects: OR=2.98; 95% CI=1.25-7.1; 
and cardiac defects: OR= 1.44; 95% CI=0.97-2.1. In the case control 
study, associations were found between THMs >80 g/L and neural 
tube defects (OR=4.25; 95% CI=1.02-17.7) and between THM levels >15 
g/L and cardiac defects (OR=2.0; 95% CI= 0.94-4.5). The 
authors note their findings should be interpreted with caution because 
of possible exposure misclassification, unmeasured confounding, and 
associations which could be due to chance occurrences. Although the 
case control study included interviews of mothers for information about 
residence and various risk factors, the authors reported a number of 
limitations in the interpretation of the results from the case control 
study, especially as a result of selection bias. Evaluation of 
selection bias indicated that the bias led to an overestimate of the 
associations with THM levels.
    Some members of the Reg Neg committee viewed that these studies 
indicate the possibility of a reproductive risk related to exposure to 
disinfectant by-products. As a result of this concern, EPA convened a 
panel of experts to review the epidemiology studies described above 
(USEPA, 1993a). The panel concluded that the studies by Bove et al. 
(1992a and b) were useful for hypothesis generation and identification 
of a number of areas for further research. The panel further concluded 
that the findings were limited by a number of issues surrounding study 
design and data analysis. Some of the limitations included untested 
assumptions of maternal exposure to chlorinated water, limitations in 
the exposure assessment for THMs and other disinfection by-products, 
possibility for exposure misclassification, confounding risk factors 
and that some of these findings may have been due to chance.
    d. Request for Public Comments. EPA requests comments on the 
significance of the epidemiological studies with chlorine and 
chloramines as indicators of risk. EPA recognizes that there are 
different interpretations of these epidemiological studies and 
specifically solicits comment on the rationale for EPA's 
interpretations. EPA further requests comments on the studies 
suggesting a reproductive risk related to disinfectant by-product 
exposure.
4. Chlorine Dioxide, Chlorite and Chlorate
    Chlorine dioxide is used as a disinfectant in drinking water 
treatment as well as an additive with chlorine to control tastes and 
odors in water treatment. It has also been used for bleaching pulp and 
paper, flour and oils and for cleaning and tanning of leather. Chlorine 
dioxide is a strong oxidizer that does not react with organics in the 
water, as does chlorine, to produce by-products such as the 
trihalomethanes. Chlorine dioxide is fairly unstable and rapidly 
dissociates into chlorite, and chloride in water. Chlorate may also be 
formed as a result of inefficient generation or generation of chlorine 
dioxide under very high or low pH conditions. The dissociation of 
chlorine dioxide into chlorite and chloride may be reversible with some 
chlorite converting back to chlorine dioxide if free chlorine is 
available. Chlorite ion is generally the primary product of chlorine 
dioxide reduction. The distribution of chlorite, chloride and chlorate 
is influenced by pH and sunlight. Chlorite, (as the sodium salt), is 
used in the onsite production of chlorine dioxide and as a bleaching 
agent by itself, for pulp and paper, textiles and straw. Chlorite is 
also used to manufacture waxes, shellacs and varnishes. Chlorate, as 
the sodium salt, was once a registered herbicide to defoliate cotton 
plants during harvest, to tan leather and in the manufacture of dyes, 
matches, explosives as well as chlorite.
    Occurrence and Human Exposure. Based on information from the Water 
Industry Data Base (WIDB), it has been estimated that for large systems 
(serving greater than 10,000 people), approximately 10% of community 
surface water systems serving 12.4 million people and 1% of community 
ground water systems, serving 0.2 million people currently use chlorine 
dioxide for disinfection in the United States. It was assumed that none 
of the smaller community systems (fewer than 10,000 people) use 
chlorine dioxide (WIDB, 1990).
    Table V-5 presents occurrence information available for chlorine 
dioxide, chlorate, and chlorite in drinking water. Descriptions of 
these surveys and other data are detailed in ``Occurrence Assessment 
for Disinfectants and Disinfection By- Products (Phase 6a) in Public 
Drinking Water,'' (USEPA, 1992a). Typical dosages of chlorine dioxide 
used as a disinfectant in drinking water treatment facilities appear to 
range from 0.6 to 1.0 mg/L. For plants using chlorine dioxide, median 
concentrations of chlorite and chlorate were found to be 240 and 200 
g/L, respectively. However, the data base upon which these 
numbers are based is very limited. A more extensive discussion of 
chlorine dioxide and chlorite occurrence is described in section VI. of 
this preamble.

                    Table V-5:--Summary of Occurrence Data For Chlorine Dioxide and Chlorite                    
                    Occurrence of Chlorine Dioxide, Chlorate, and Chlorite in Drinking Water                    
----------------------------------------------------------------------------------------------------------------
                                                                        Concentration (g/L)            
Survey (year)\1\       Location        Sample information  -----------------------------------------------------
                                       (No. of samples)        Range        Mean        Median         Other    
----------------------------------------------------------------------------------------------------------------
AWWARF (1987)                        Finished Water From:                                                       
 McGuire &                                                                                                      
 Meadow, 1988.                                                                                                  
                                     Lakes................               1.0 mg/L\3\                            
                                     Flowing Streams......               0.6 mg/L\3\                            
                                     Plants Using CIO2:                                            Positive     
                                                                                                    Detections  
                                     Chlorite at the Plant       15-740          240          110  100%         
                                      (4).                                                                      
EPA, 1992b\2\      Disinfection By-  Chlorate at the Plant       21-330          200          220  100%         
 (1987-1991).       Products Field    (4).                                                                      
                    Studies                                                                                     
                                     Plants Not Using                                                           
                                      CIO2:                                                                     
                                     Chlorate at the Plant      <10-660           87           16  60%          
                                      (30).                                                                     
                                     Chlorate, Distr.            <10-47           18           13  75%          
                                      System (4).                                                               
----------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                  
\2\May not be representative of national occurrence.                                                            
\3\Typical dosage used by treatment plants.                                                                     
AWWARF American Water Works Association Research Foundation.                                                    
EPA Environmental Protection Agency.                                                                            

    No information is available on the occurrence of chlorine dioxide, 
chlorate, and chlorite in food or ambient air. Currently, the Food and 
Drug Administration (FDA) does not analyze for these compounds in 
foods. Preliminary discussions with FDA suggest that there are not 
approved uses for chlorine dioxide in foods consumed in the typical 
diet. In addition, the EPA Office of Air and Radiation does not require 
monitoring for these compounds in air. However, chlorine dioxide is 
used as a sanitizer for air ducts (Borum, 1991).
    EPA believes that drinking water is the predominant source of 
exposure for these compounds. Air and food exposures are considered to 
provide only small contributions to the total chlorine dioxide, 
chlorate, and chlorite exposures, although the magnitude and frequency 
of these potential exposures are issues currently under review. 
Therefore, EPA is considering proposing to regulate these compounds in 
drinking water with an RSC value of 80 percent, the current exposure 
assessment policy ceiling. EPA requests any additional data on known 
concentrations of chlorine dioxide, chlorate and chlorite in drinking 
water, food and air.
    Health Effects. The following health effects information is 
summarized from the draft Drinking Water Health Criteria Document for 
Chlorine Dioxide, Chlorite and Chlorate (USEPA, 1994c). Studies cited 
in this section are summarized in the draft criteria document.
    As noted above, chlorine dioxide is fairly unstable and rapidly 
dissociates predominantly into chlorite and chloride, and to a lesser 
extent, chlorate. There is a ready interconversion among chemical 
species in water (before administration to animals) and in the gut 
(after ingestion). Therefore, what exists in water or the stomach is a 
mixture of these chemical species and possibly their reaction products 
with the gastrointestinal contents. Thus, the toxicity information on 
chlorite, the predominant degradation product of chlorine dioxide, may 
also be relevant to characterizing chlorine dioxide toxicity. In 
addition, studies conducted with chlorine dioxide may be relevant to 
characterizing the toxicity of chlorite. As a result, the toxicity data 
for one compound are considered applicable for addressing toxicity data 
gaps for the other.
    The main health effects associated with chlorine dioxide and its 
anionic by-products include oxidative damage to red blood cells, 
delayed neurodevelopment and decreased thyroxine hormone levels. 
Chlorine dioxide, chlorite and chlorate are well absorbed by the 
gastrointestinal tract and excreted primarily in urine. Once absorbed, 
36Cl-radiolabeled chlorine dioxide, chlorite and chlorate are 
distributed throughout the body. Lethality data for ingested chlorine 
dioxide have not been located in the available literature. A lethal 
concentration for guinea pigs by inhalation was reported at 150 ppm. 
Oral LD50 values for chlorite have been reported at 100 to 140 mg/
kg in rats. A more recent study indicates that the oral LD50 may 
be closer to 200 mg/L. Limited data suggest an oral LD50 value 
between 500 to 1500 mg/kg for chlorate in dogs.
    In subchronic and chronic studies, animals given chlorine dioxide 
treated water exhibited osmotic fragility of red blood cells (1 mg/kg/
d), decreased thyroxine hormone levels (14 mg/kg/d), possibly due to 
altered iodine metabolism and hyperplasia of goblet cells and 
inflammation of nasal tissues. The nasal lesions are not considered 
related to ingested chlorine dioxide. However, it is not clear if the 
nasal effects are due to off-gassing of chlorine dioxide from the 
sipper tube of the animal water bottles, or from dermal contact while 
the animal drinks from the sipper tube. In addition, the chlorine 
dioxide treated group drank water at a pH of 4.7 which may also have 
contributed to the nasal tissue inflammation. The concentration 
associated with this effect (25 mg/L) is considerably greater than what 
would be found in drinking water.
    Studies evaluating developmental or reproductive effects have 
described decreases in the number of implants and live fetuses per dam 
in female rats given chlorine dioxide in drinking water before mating 
and during pregnancy. Delayed neurodevelopment has been reported in rat 
pups exposed perinatally to chlorine dioxide (14 mg/kg/d) or chlorite 
(3 mg/kg/d) treated water. Delayed neurodevelopment was assessed by 
decreased locomotor activity and decreased brain development.
    Subchronic studies with chlorite administered to rats via drinking 
water resulted in transient anemia, decreased red blood cell 
glutathione levels and increased hydrogen peroxide formation at doses 
greater than 5 mg/kg/d. Chlorite administration orally to cats at a 
dose of 7 mg/kg/d produced 10 to 40 percent methemoglobin formation 
within a couple of hours following dosing. Exposure to chlorite in 
drinking water resulted in an increased turnover of red blood cells in 
cats rather than oxidation of hemoglobin.
    Oral studies with chlorate also demonstrate effects on 
hematological parameters and formation of methemoglobin, but at much 
higher doses than chlorite (157-256 mg/kg/d).
    No clear tumorigenic activity has been observed in animals given 
oral doses of chlorine dioxide, chlorite or chlorate. Chlorine dioxide 
concentrates did not increase the incidence of lung tumors in mice nor 
was any initiating activity observed in mouse skin or rat liver 
bioassays. Lung and liver tumors were increased in mice given sodium 
chlorite; however, the incidence was within the historical range for 
these tumor types. Carcinogenic studies on chlorate were not located in 
the available literature. Chlorate has been reported to be mutagenic in 
bacterial and Drosophila tests. EPA has classified chlorine dioxide and 
chlorite in Group D: not classifiable as to human carcinogenicity. This 
classification is for chemicals with inadequate evidence or no data 
concerning carcinogenicity in animals in the absence of human data. EPA 
has not classified chlorate with respect to carcinogenicity.
    There are a number of cases of poisoning in humans who used 
chlorate as an herbicide. Effects observed following exposures to 11 to 
3,400 mg/kg include cyanosis, renal failure, convulsions and death. The 
lowest lethal dose reported in adults is approximately 200 mg/kg. It is 
not clear if this is the actual dose received or if other components in 
the formulation were contributors to the toxicity. In an epidemiology 
study of a community where chlorine dioxide was used as the primary 
drinking water disinfectant for 12 weeks, no consistent changes were 
observed in the clinical parameters measured.
    Three studies have been selected as the basis for the RfD and MRDLG 
for chlorine dioxide. These studies identify a NOAEL of 3 mg/kg/d and a 
LOAEL of approximately 10 mg/kg/d. A NOAEL of 3 mg/kg/d has been 
identified in an 8 week rat study by Orme et al. (1985). In this study, 
chlorine dioxide was administered to female rats via drinking water at 
concentrations of 0, 2, 20 and 100 mg/L before mating, during gestation 
and lactation until the pups were 21 days old. Based on body weight and 
water consumption data, these concentrations correspond to doses of 1, 
3 and 14 mg/kg/d. No effects were noted in dams. Pups in the high dose 
group (14 mg/kg/d) exhibited decreased exploratory and locomotor 
activity and a significant depression of thyroxine. These effects were 
not observed at the 3 mg/kg/d dose level. In a second experiment, pups 
were given 14 mg/kg/d chlorine dioxide directly by gavage during 
postnatal days 5 through 20. A greater and more consistent delay in 
neurobehavioral activity was observed along with a greater depression 
in thyroxine. Analysis of the DNA content of cells in the cerebellum 
from animals in the high dose drinking water group (14 mg/kg/day) at 
postnatal day 21 and the gavage group at day 11 indicated a significant 
depression (Taylor and Pfohl, 1985). Another study confirmed 14 mg/kg/d 
as a LOAEL based on decreased brain cell proliferation in rats exposed 
postnatally by gavage (Toth et al., 1990).
    The no-effect level of 3 mg/kg/day is also supported by a monkey 
study (Bercz et al., 1982), where animals were given chlorine dioxide 
at concentrations of 0, 30, 100 or 200 mg/L in drinking water following 
a rising dose protocol. These concentrations correspond to doses of 0, 
3.5, 9.5 and 11 mg/kg/d based on animal body weight and water 
consumption. Animals showed signs of dehydration at the high dose; 
exposure was discontinued at that dose (11 mg/kg/d). A slight 
depression of thyroxine was observed following exposure to 9.5 mg/kg/d. 
No effects were seen with 3.5 mg/kg/d, which is considered the NOAEL.
    MRDLG for Chlorine Dioxide. EPA is proposing an MRDLG for chlorine 
dioxide based on developmental neurotoxicity following a Category III 
approach. Using a NOAEL of 3 mg/kg/d and an uncertainty factor of 300, 
an RfD of 0.01 mg/kg/d for chlorine dioxide is calculated. An 
uncertainty factor of 300 is used to account for differences in 
response to toxicity within the human population and between humans and 
animals. This factor also accounts for lack of a two-generation 
reproductive study. Availability of an acceptable two-generation 
reproduction study would likely reduce the total uncertainty factor to 
100. The Chlorine Dioxide panel of the Chemical Manufacturers 
Association is conducting a two-generation reproductive study with 
chlorite to address this data gap. EPA will review the results of this 
study and determine if any changes to the RfD for chlorine dioxide are 
warranted.
    After adjusting for an adult consuming 2 L water per day, an RSC of 
80 percent is applied to calculate an MRDLG of 0.3 mg/L. An RSC of 80% 
is used since most chlorine dioxide exposure is likely to come from a 
drinking water source.

TP29JY94.004

    The Drinking Water Committee of the Science Advisory Board (SAB) 
agreed with the use of the Orme et al. (1985) study as the basis for 
the MRDLG and suggested that an uncertainty factor of 100 be applied 
(USEPA, 1992c). They also suggested that a child's body weight of 10 kg 
and water consumption of 1 L/d may be more appropriate for setting the 
MRDLG than the adult parameters, given the acute nature of the toxic 
effect. EPA requests comments on the SAB's suggestion.
    EPA also requests comment on the appropriateness of the 300-fold 
uncertainty factor, the studies selected as the basis for the RfD, and 
the 80% relative source contribution.
    MCLG for Chlorite. The developmental rat study by Mobley et al. 
(1990) has been selected to serve as the basis for the RfD and MCLG for 
chlorite. Other studies reported effects at doses higher than the 
Mobley et al. study. In this study, female Sprague-Dawley rats (12/
group) were given drinking water containing 0, 20, or 40 mg/L chlorite 
(0, 3, or 6 mg chlorite ion/kg/day) as the sodium salt beginning 10 
days prior to breeding with untreated males until the pups were 
sacrificed at 35 to 42 days postconception (a total exposure of 9 
weeks). Exploratory activity was depressed in the pups treated with 3 
mg/kg/day chlorite on postconception days 36-37 but not on days 38-40. 
Pups from the high exposure group also exhibited depressed exploratory 
behavior during days 36-39 postconception (p<0.05). Exploratory 
activity was comparable among the treated and control groups on 
postconception days 39-41. No significant differences in serum total 
thyroxine or triiodothyronine were observed between treated and control 
pups. Free thyroxine was significantly elevated in the 6 mg/kg/day 
pups. A LOAEL of 3 mg/kg/day was determined in this study based on the 
neurobehavioral effect (depressed exploratory behavior) in rats. This 
endpoint is similar to that reported for chlorine dioxide.
    EPA had considered using a study by Heffernan et al. (1979) which 
described dose-related decreases in red blood cell glutathione levels 
from rats orally exposed to chlorite in drinking water for up to 90 
days. The decreases in glutathione were accompanied by decreases in red 
blood cell concentration, hemaglobin concentration and packed red cell 
volume. Taken together, these effects were considered reflective of 
oxidative stress resulting from the ingested chlorite. In this study, a 
NOAEL of 1 mg/kg/d and LOAEL og 5 mg/kg/d were identified.
    The EPA Science Advisory Board had cautiously agreed with the 
selection of the Heffernan et al. (1979) study as the basis for the 
RfD, but noted that the endpoint would likely be controversial since 
normal fluctuations occur with glutatione levels. Thus this effect, 
alone, may not necessarily be the result of chlorite exposure. The EPA 
RfD workgroup was unable to reach consensus on decreased glutathione 
levels as an appropriate endpoint to base an RfD. They agreed with the 
selection of the Mobley et al. (1990) study since the endpoint, 
developmental neurotoxicity, represented the next critical effect and 
was consistent with the toxicity observed with chlorine dioxide.
    Following a Category III approach, EPA is proposing an MCLG of 0.08 
for chlorite. The MCLG is based on an RfD of 0.003 determined from the 
LOAEL of 3 mg/kg/day from the Mobley et al. study. This endpoint was 
selected since it is similar to that reported for chlorine dioxide. An 
uncertainty factor of 1,000 is used in the derivation of the RfD and 
MCLG to account for use of a LOAEL from an animal study.
    After adjusting for an adult consuming 2 L water per day, an RSC of 
80% is applied to calculate an MCLG of 0.08 mg/L. An RSC of 80% was 
used since most exposure to chlorite is likely to come from drinking 
water.

TP29JY94.005

    The Drinking Water Committee of the EPA Science Advisory Board 
suggested that EPA consider basing the MCLG on the child body weight of 
10 kg and water consumption of 1 L/day instead of the adult default 
values. EPA requests comments on the SAB's suggestion along with the 
study selected as the basis for the MCLG, the uncertainty factor and 
the RSC of 80%.
    MCLG for Chlorate. Data are considered inadequate to develop an 
MCLG for chlorate at this time. A NOAEL of 0.036 mg/kg/d (the only dose 
tested) was identified in the Lubbers et al. (1982) human clinical 
study following a 12-week exposure to chlorate in drinking water. 
NOAELs identified from animal studies are considerably higher 
(approximately 78 mg/kg/d). However, doses that are lethal to humans 
(200 mg/kg/d) are only 2-fold greater than this animal no-effect level. 
No information is available to characterize the potential human 
toxicity between the doses of 0.036, the only human NOAEL and 200 mg/
kg/d, the apparent human lethal dose. Thus, EPA considers the data base 
too weak to derive a separate MCLG for chlorate at this time. The 
Agency will continue to evaluate the animal data and any new 
information that become available for future consideration of an MCLG 
for chlorate.
    EPA requests comments on the decision not to propose an MCLG for 
chlorate at this time.
5. Chloroform
    Chloroform [trichloromethane, CAS No. 67-66-3] is a nonflammable, 
colorless liquid with a sweet odor and high vapor pressure (200 mm Hg 
at 25  deg.C). It is moderately soluble in water (8 gm/L at 20  deg.C) 
and soluble in organic solvents (log octanol/water partition 
coefficient of 1.97). Chloroform is used primarily to manufacture 
fluorocarbon-22 (chlorodifluoromethane) which in turn is used for 
refrigerants and fluoropolymer synthesis. A small percentage of the 
manufactured chloroform is used as an extraction solvent for various 
products (e.g. resins, gums). In the past, chloroform was used in 
anesthesia and medicinal preparations and as a grain fumigant 
ingredient. Chloroform can be released to the environment from direct 
(manufacturing) and indirect (processing/use) sources and chloroform is 
a prevalent chlorination disinfection by-product. Volatilization is the 
principle mechanism for removal of chloroform from lakes and rivers. 
Chloroform bioconcentrates slightly in aquatic organisms and adsorbs 
poorly to sediments and soil. Chloroform can be biodegraded in water 
and soil (half-life of weeks to months) and ground water (half-life of 
months to years), and photo-oxidized in air (half-life of months).
    Occurrence and Human Exposure. The principle source of chloroform 
in drinking water is the chemical interaction of chlorine with commonly 
present natural humic and fulvic substances and other precursors 
produced by either normal organic decomposition or by the metabolism of 
aquatic biota. Because humic and fulvic material are generally found at 
much higher concentrations in surface water sources than in ground 
water sources, surface water systems have higher frequencies of 
occurrence and higher concentrations of chloroform than ground water 
systems. Several water quality factors affect the formation of 
chloroform including Total Organic Carbon (TOC), pH, and temperature. 
Different treatment practices can reduce the formation of chloroform. 
These include the use of precursor removal technologies such as 
coagulation/filtration, granular activated carbon (GAC), and membrane 
filtration and the use of chlorine dioxide, chloramination, and 
ozonation.
    Table V-6 presents occurrence information available for chloroform 
in drinking water. Descriptions of these surveys and other data are 
detailed in ``Occurrence Assessment for Disinfectants and Disinfection 
By-Products (Phase 6a) in Public Drinking Water,'' (USEPA, 1992a). The 
table lists six surveys conducted by Federal and private agencies. 
Median concentrations of chloroform in drinking water appear to range 
from 14 to 57 g/L for surface water supplies and 
0.5 g/L for ground-water supplies (many of which do 
not disinfect). The lower bound median concentration for chloroform in 
surface water supplies is biased to the low side because concentrations 
in this survey were measured in the plant effluent; the formation of 
chloroform would be expected to increase in the distribution in systems 
using chlorine as their residual disinfectant.

                              Table V6.--Summary of Occurrence Data For Chloroform                              
                                  [Occurrence of Chloroform in Drinking Water]                                  
----------------------------------------------------------------------------------------------------------------
                                                                        Concentration (g/L             
  Survey (year)        Location        Sample information  -----------------------------------------------------
                                       (No. of samples)        Rage         Mean        Median         Other    
----------------------------------------------------------------------------------------------------------------
CWSS (1978) Brass  450 Water Supply  Finished Water         ...........  ...........  ...........  Positive     
 et al., 1981.      Systems           (1,100):.                                                     Detections: 
                   ................  Surface Water........  ...........        \3\60  ...........  \4\97%       
                   ................  Ground Water.........  ...........      \3\<0.5  ...........  \4\34%       
RWS (1978-1980)    >600 Rural        Drinking Water from:.  ...........  ...........  ...........  Postive      
 Brass, 1981.       Systems (>2,000                                                                 Detection:  
                    Households)                                                                                 
                   ................  Surface Water........  ...........        \3\84           57  \4\82%       
                   ................  Ground Water.........  ...........       \3\8.9         <0.5  \4\17%       
GWSS (1980-1981)   945 GW Systems:   .....................  ...........  ...........  ...........  90th         
 Westrick et al.                                                                                    percentile: 
 1983.                                                                                                          
                   (466 Random and   Serving >10,000 (327)     Max. 300  ...........          0.5  17           
                   479 Nonrandom)    Serving <10,000 (618)     Max. 430  ...........            0  7.8          
EPA, 1991a\2\      Unregulated       Sampled at the Plant   ...........           17            5  .............
 (1984-1991).       Contaminant       (5,806).                                                                  
                    Data Base--                                                                                 
                    Treatment                                                                                   
                    Facilities from                                                                             
                    19 States                                                                                   
EPA, 1992b\2\      Disinfection By-  Finished Water:......  ...........  ...........  ...........  Positive     
 (1987-1991).       Products Field                                                                  Detections: 
                    Studies                                                                                     
                   ................  At the Plant (73)....     <0.2-240           36           28  96%          
                   ................  Distribution System       <0.2-340           57           42  98%          
                                      (56).                                                                     
EPA/AMWA/CDHS\2\   35 Water          Samples from              Max. 130  ...........    \5\9.6-15  75% of Data  
 (1988-1989).       Utilities         Clearwell.                                                    was Below 33
                    Nationwide                                                                      gL.
Krasner et al.,    ................  Effluent for 4         ...........  ...........           14  .............
 1989b.                               Quarters.                                                                 
----------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                  
\2\May not be representative of national occurrence.                                                            
\3\Mean of the positives.                                                                                       
\4\Of systems sampled.                                                                                          
\5\Range of medians for individual quarters.                                                                    
AMWA Association of Metropolitan Agencies.                                                                      
CDHS California Department of Health Services.                                                                  
CWSS Community Water Supply Survey.                                                                             
GWSS Ground Water Supply Survey.                                                                                
RWS Rural Water Survey.                                                                                         
EPA Environmental Protection Agency.                                                                            

    Several studies have assessed inhalation exposure to chloroform. 
The major source of these data is from the USEPA's Total Exposure 
Assessment Methodology (TEAM) studies, which measured chloroform 
exposure to approximately 750 persons in eight geographic areas from 
1980 to 1987. Personal exposure to chloroform from air was measured 
over a 12-hour period (excluding showers) for individuals in three 
areas. The average exposures were reported to range from 4 to 9 
g/m3 in New Jersey and Baltimore, and about 0.5 to 4 
g/m3 in California cities (Wallace, 1992). In the 1987 
Los Angeles TEAM study, chloroform in indoor air was measured in the 
living room and kitchen of private residences. Observed mean indoor 
concentrations ranged from 0.9 to 1.5 g/m3 (Pellizzari et 
al., 1989 and Wallace et al., 1990 in Wallace, 1992). For outdoor 
levels, the 12-hour average outdoor concentrations measured in the 
California and New Jersey TEAM studies ranged from 0.2 to 0.6 
g/m3 and 0.1 to 1.5 g/m3, respectively 
(Pellizzari et al., 1989, Wallace et al., 1990 and PEI et al., 1989 in 
Wallace, 1992).
    Given the limited exposure data in air, inhalation exposure can be 
estimated using an inhalation rate of 20 m3/day. Resulting 
estimates for average ambient air exposures range from 2 to 30 
g/d and 18-30 g/d for average indoor air exposures. 
However, based on the personal air monitoring data, a potentially 
higher average inhalation exposure is indicated with a range of 10 to 
180 g/d.
    Two studies analyzed some foods for chloroform. In a pilot market 
basket survey of four food groups at five sites, measured chloroform 
levels were as follows: dairy composite, 17 ppb (1 of 5 sites); meat 
composite, not detected; oil and fat composite, trace amounts (1 of 5 
sites); beverage composite, 6 to 32 ppb (4 of 5 sites) (Entz et al., 
1982). In a study of 15 table-ready food items, chloroform was detected 
in 53% of the foods tested: butter, 670 ppb; cheddar cheese, 80 ppb; 
plain granola, 57 ppb; peanut butter, 29 ppb; chocolate chip cookies, 
22 ppb; frozen fried chicken dinner, 29 ppb; and high meat dinner, 17 
ppb (Heikes, 1987).
    Limited data are available to characterize dietary exposure to 
chloroform. Although some uses of chlorine have been identified in the 
food production/food processing area, monitoring data are not adequate 
to characterize the magnitude or frequency of exposure to chloroform. 
Based on the limited number of food groups that are believed to contain 
chloroform and low levels expected in ambient and indoor air, EPA 
assumes that drinking water is the predominant source of chloroform 
intake. The characterization of potential food and air exposures are 
issues currently under review. EPA requests any additional data on 
known concentrations of chloroform in drinking water, food, and air.
    Health Effects. The health effects information is summarized from 
the draft Drinking Water Criteria Document for Trihalomethanes (USEPA, 
1994d). Studies cited in this section are summarized in the criteria 
document.
    Chloroform has been shown to be rapidly absorbed upon oral, 
inhalation and peritoneal administration and subsequently metabolized. 
The reported mean human lethal dose, from clinical observations of 
overdoses, was around 630 mg/kg. The LD50 values in mice and rats 
have been reported in the range of 908-1,400 mg/kg. Several reactive 
metabolic intermediates (e.g. phosgene, carbene, dichloromethyl 
radicals) can be produced via oxidation (major pathway) or reduction 
(minor pathway) by microsomal preparations. Experimental studies 
suggested that these active metabolic intermediates are responsible for 
the hepatic and renal toxicity and possibly, carcinogenicity, of the 
parent compound. Animal studies suggest that the extent of chloroform 
metabolism varies with species and sex. The retention of chloroform in 
organs after dosing was small. Due to the lipophilic nature of the 
compound, the residual concentration is in tissues with higher fatty 
content. In humans, the majority of the tested oral intake doses (0.1 
to 1 gm) were excreted through the lungs in the form of a metabolite 
CO2 or as the unchanged compound. Urinary excretion levels were 
below 1%.
    Mammalian bioeffects following exposure to chloroform include 
effects on the central nervous system (CNS), hepatotoxicity, 
nephrotoxicity, reproductive toxicity and carcinogenicity. Chloroform 
caused CNS depression and affected liver and kidney function in humans 
in both accidental and long term occupational exposure situations. In 
experimental animals, chloroform caused changes in kidney, thyroid, 
liver, and serum enzyme levels. These responses are discernible in 
mammals from exposure to levels of chloroform ranging from 15 to 290 
mg/kg; the intensity of response was dependent upon the dose and the 
duration of the exposure. Ataxia and sedation were noted in mice 
receiving a single dose of 500 mg/kg chloroform. Short-term exposure to 
the low levels of chloroform typically found in air, food, and water 
are not known to manifest acute toxic effects. The potential for human 
effects from chronic lifetime exposure is the basis for this 
regulation.
    Developmental toxicity and reproductive toxicity have been 
investigated in animals. One developmental study reported maternal 
toxicity in rabbits administered chloroform by the oral route. 
Decreased weight gain and mild fatty changes in liver were observed in 
dams receiving 50 mg/kg/day (LOAEL); the maternal NOAEL was noted to be 
35 mg/kg/day. There was no evidence of developmental effects.
    The data from a 7.5-year oral study in dogs conducted by Heywood et 
al. (1979) were used to calculate the RfD. EPA considers this study 
suitable for the RfD derivation since it is a chronic study and 
sensitive indices of hepatotoxicity (serum enzyme levels, liver 
histology) of sufficient numbers of experimental animals were 
monitored. In this study, chloroform was administered to beagle dogs 
(16 per dose group) in toothpaste base gelatin capsules at dose levels 
of 15 or 30 mg/kg/day 6 days/week for 7.5 years. A LOAEL of 15 mg/kg/
day was established based on the observation of hepatic fatty cysts in 
treated animals at both doses. An RfD of 0.01 mg/kg/day has been 
derived from this LOAEL by the application of an uncertainty factor of 
1,000, in accordance with EPA guidelines.
    The results of a number of assays to determine the mutagenicity 
potential of chloroform are inconclusive. Studies on the in vitro 
genotoxicity of chloroform reported negative results in bacteria (Ames 
assays), negative results for gene mutations and chromosomal 
aberrations in mammalian cells, and mixed results in yeasts. In vivo 
and in vitro DNA damage tests indicate that chloroform will bind to 
DNA. Gene mutation tests in Drosophila were marginal, whereas tests for 
chromosomal aberrations and sperm abnormalities were mixed.
    Several chronic animal studies confirmed the carcinogenicity of 
chloroform. Chloroform induced hepatocellular carcinomas in mice when 
administered by gavage in corn oil (NCI, 1976). Chloroform also induced 
renal adenomas and adenocarcinomas in male rats regardless of the 
carrier vehicle (oil or drinking water) employed (NCI, 1976; Roe et 
al., 1979; Jorgenson et al., 1985).
    In the study by Jorgenson et al. (1985), chloroform was 
administered in drinking water to male Osborne-Mendel rats and female 
B6C3F1 mice at doses of 0, 200, 400, 900 or 1,800 ppm (0, 19, 38, 
81 or 160 mg/kg/day in rats and 0, 34, 65, 130 or 263 mg/kg/day in 
mice) for 2 years. Chloroform increased the incidence of kidney tumors 
in male rats in a dose-related manner. The combined incidence of renal 
tubular cell adenomas, renal tubular cell adenocarcinomas, and 
nephroblastomas in control, 200, 400, 900 and 1,800 ppm groups were 5/
301, 6/313, 7/148, 3/48, and 7/50, respectively. Jorgenson's study 
reported no statistically significant increase in the incidence of 
hepatocellular carcinomas in the female mice exposed to similar doses 
of chloroform as reported in the 1976 NCI study.
    Since hepatic changes appeared to be related to the corn oil 
vehicle, the interaction of corn oil and chloroform could account for 
the enhanced hepatic toxicity and thus for the difference in the NCI 
and Jorgenson studies. Because the drinking water study did not 
replicate hepatic tumors in female mice and the potential role of corn 
oil in enhancing toxicity, the National Academy of Science Subcommittee 
on the Health Effects of Disinfectants and Disinfection By-Products 
(NAS, 1987) recommended that male rat kidney tumor data obtained from 
Jorgenson's study be used to estimate the carcinogenic potency of 
chloroform. EPA agreed with the NAS Subcommittee recommendation for 
estimating risks of chloroform from drinking water exposures.
    Based on all kidney tumor data in male Osborne-Mendel rats reported 
by Jorgenson et al. (1985), EPA used a linearized multistage model and 
derived a carcinogenic potency factor for chloroform of 6.1  x  
10-3 (mg/kg/day)-1. Assuming a daily consumption of two 
liters of drinking water and an average human body weight of 70 kg, the 
95% upper bound limit lifetime cancer risk levels of 10-6, 
10-5, and 10-4 are associated with concentrations of 
chloroform in drinking water of 6, 60 and 600 g/L, 
respectively.
    In 1987 the Commission on Life Sciences of the National Research 
Council published Drinking Water and Health (NAS, 1987). Volume 7, 
Disinfectants and Disinfectant By-Products, prepared by the Subcomittee 
on Disinfectants and Disinfection By-Products, discussed the available 
data on chloroform, which are the same data summarized above. The 
Subcommittee concluded that ``[n]oting that chloroform is the principal 
THM produced by chlorination, the subcommittee found [the 100 THM] 
level to be unsupportable on the basis of the risk values for 
chloroform developed in this review,'' and that the level should be 
reduced.
    EPA has classified chloroform in Group B2, probable human 
carcinogen, based on sufficient evidence of carcinogenicity in animals 
and inadequate evidence in humans (IRIS, 1985). The International 
Agency for Research on Cancer (IARC) has classified chloroform as a 
Group 2B carcinogen, agent possibly carcinogenic to humans. (IARC, 
1982).
    According to EPA's three-category approach for establishing MCLGs, 
chloroform is placed in Category I since there is sufficient evidence 
of carcinogenicity via ingestion considering weight of evidence, 
potency, pharmacokinetics, and exposure. Thus, EPA is proposing an MCLG 
of zero for this contaminant. EPA requests comment on the basis for the 
proposed MCLG for chloroform.
6. Bromodichloromethane
    Bromodichloromethane (BDCM; CAS No. 75-27-4) is a nonflammable, 
colorless liquid with a relatively high vapor pressure (50 mmHg at 
20 deg.C). BDCM is moderately soluble in water (3.3 gm/L at 30 deg.C) 
and soluble in organic solvents (log octanol/water partition 
coefficient of 1.88). Only a small amount of BDCM is currently produced 
commercially in the United States. The chemical is used as an 
intermediate for organic synthesis and as a laboratory reagent. The 
principle source of BDCM in drinking water is the chemical interaction 
of chlorine with the commonly present organic matter and bromide ions. 
Degradation of BDCM is not well studied, but probably involves 
photooxidation. The estimated atmospheric half-life of BDCM is two to 
three months. Volatilization is the principal mechanism for removal of 
BDCM from rivers and streams (half-life of hours to weeks). Limited 
studies reported that BDCM adsorbed poorly to sediments and soils. No 
study of bioaccumulation of BDCM was located. Based on the data of a 
few structurally similar chemicals such as chloroform, the 
bioconcentration potential of BDCM in aquatic organisms is low. 
Biodegradation of BDCM is limited under aerobic conditions and 
extensive (completion within days) under anaerobic conditions.
    Occurrence and Human Exposure. BDCM, occurs in public water systems 
that chlorinate water containing humic and fulvic acids and bromine 
that can enter source waters through natural and anthropogenic means. 
Several water quality factors affect the formation of BDCM including 
Total Organic Carbon (TOC), pH, bromide, and temperature. Different 
treatment practices can reduce the formation of BDCM. These include the 
use of chlorine dioxide, chloramination, and ozonation prior to 
chloramination, as well as the use of precursor removal technologies 
such as coagulation/filtration, granular activated carbon (GAC), and 
membrane filtration.
    Table V-7 presents occurrence information available for BDCM in 
drinking water. Descriptions of these surveys and other data are 
detailed in ``Occurrence Assessment for Disinfectants and Disinfection 
By-Products (Phase 6a) in Public Drinking Water,'' (USEPA, 1992a). The 
table lists six surveys conducted by Federal and private agencies. 
Median concentrations of BDCM in drinking water appear to range from 
6.6 to 15 g/L for surface water supplies and <0.5 g/L 
for ground-water supplies. The lower bound median concentration for 
BDCM in surface water supplies is biased to the low side because 
concentrations in this survey were measured in the plant effluent; the 
formation of BDCM would be expected to increase in the distribution 
system when chlorine is used as the residual disinfectant.

                                             Table V-7: Summary of Occurrence Data for Bromodichloromethane                                             
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Occurrence of Bromodichloromethane                                                           
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                        Concentration (g/L)                    
    Survey (Year)\1\              Location            Sample Information(No. of   ----------------------------------------------------------------------
                                                               Samples)                Range          Mean         Median                Other          
--------------------------------------------------------------------------------------------------------------------------------------------------------
CWSS (1978, Brass et      450 Systems.............  Finished Water (1,100):                                                   Positive Detections:      
 al., 1981.                                         Surface Water................                       \3\12  6.8            94%\4\                    
                                                    Ground Water.................                      \3\5.8  <0.5           33%\4\                    
RWS (1978-1980) Brass,    >600 Rural Systems        Drinking Water from:                                                      Positive Detections:      
 1981.                     (>2,000 households).     Surface Water................  .............  ...........  11             76%\4\                    
                                                    Ground water.................  .............  ...........  <0.5           13%\4\                    
GWSS (1980-1981)          945 GW Systems:                                                                      .............  90Percentile              
 Westrick et al. 1983.    (466 Random and 479       Serving >10,000 (327)........  Max. 110.....  ...........  0.4            9.2                       
                           Nonrandom)..             Serving <10,000 (618)........  Max. 79......  ...........  0              6.1                       
EPA, 1991a\2\ (1984-      Unregulated Contaminant   Finished Water at Treatment    .............          5.6  3                                        
 1991).                    Data Base--Treatment      Plants (4,439).                                                                                    
                           Facilities from 19                                                                                                           
                           States.                                                                                                                      
EPA, 1992b\2\ (1987-      Disinfection By-Products  Finished Water:                                                           Positive Detections:      
 1989).                    Field Studies.           At the Plant (73)............  <0.2-90......           13  11             96%                       
                                                    Distribution System (56).....  <0.2-100.....           17  15             98%                       
EPA/AMWA/CDHS\2\ (1988-   35 Water Utilities        Samples from Clearwell         Max. 82......    4.1-10\5\  6.6            75% of Data was Below 14  
 1989) Krasner et al.,     Nationwide.               Effluent for 4 Quarters.                                                  g/L.            
 1989b.                                                                                                                                                 
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                                                          
\2\May not be representative of national occurrence.                                                                                                    
\3\Mean of the positives.                                                                                                                               
\4\Of systems sampled.                                                                                                                                  
\5\Range of medians for individual quarters.                                                                                                            
                                                                                                                                                        
AMWA: Association of Metropolitan Water Agencies.                                                                                                       
CDHS: California Department of Health Services.                                                                                                         
CWSS: Community Water Supply Survey.                                                                                                                    
GWSS: Ground Water Supply Survey.                                                                                                                       
RWS: Rural Water Survey.                                                                                                                                
EPA: Environmental Protection Agency.                                                                                                                   

    BDCM is usually found in air at low concentrations. Based on 
information obtained through a literature review, Howard (1990) 
estimated the average daily intake of BDCM from air using an inhalation 
rate of 20 m\3\/day. Assuming a range of 6.7 to 670 ng/m\3\, the 
average exposure may be as low as 0.134 g/day or as high as 
13.4 g/day.
    BDCM is not a common contaminant in food. In one market study of 39 
different food items, BDCM was detected in one dairy composite (1.2 
ppb), butter (7 ppb), and two beverages (0.3 and 0.6 ppb). Analysis of 
cola soft drinks found BDCM in three samples with reported 
concentrations of 2.3 ppb, 3.4 ppb, and 3.8 ppb (Entz et al., 1982 in 
Howard, 1990).
    Limited data are available to characterize food and air exposures 
to BDCM. Although some uses of chlorine have been identified in the 
food production/food processing area, monitoring data are inadequate to 
characterize the magnitude and frequency of potential BDCM exposures. 
Based on the limited number of food groups that are believed to contain 
BDCM and that there are not significant levels expected in ambient or 
indoor air, EPA assumes that drinking water is the predominant source 
of BDCM intake. EPA requests any additional data on known 
concentrations of BDCM in drinking water, food, and air.
    Health Effects. The health effects information in this section is 
summarized from the draft Drinking Water Criteria Document for 
Trihalomethanes (USEPA, 1994d). Studies mentioned below are summarized 
in the criteria document.
    Studies indicated that gastrointestinal absorption of BDCM is high 
in animals. No studies were located regarding BDCM in humans or animals 
following inhalation or dermal exposure. By analogy with the 
experimental data of a structurally-related halomethane chloroform, 
inhalation and dermal absorption may be high for BDCM. The reported 
LD50 values in mice and rats ranged from 450 to 969 mg/kg. Under 
both in vivo and in vitro conditions, several active metabolic 
intermediates (e.g. dichlorocarbonyl, dichloromethyl radicals) were 
produced via oxidation or reduction by microsomal preparations. 
Experimental studies suggested that these active metabolic 
intermediates may be responsible for hepatic and renal toxicity and 
possibly, carcinogenicity of the parent compound. Animal studies 
suggest that the extent of BDCM metabolism varies with species and sex. 
The retention of BDCM in organs after dosing was small, even after 
repeated doses. Urinary excretion levels were below 3 percent.
    Mammalian bioeffects following exposure to BDCM include effects on 
the central nervous system (decreased operant response), 
hepatotoxicity, nephrotoxicity, reproductive toxicity, and 
carcinogenicity. In experimental mice and rats, BDCM caused changes in 
kidney, liver, serum enzyme levels, and decreased body weight. These 
responses were discernible in rodents from exposure to levels of BDCM 
that ranged from 6 to 300 mg/kg; the intensity of response was 
dependent upon the dose and the duration of the exposure. Ataxia and 
sedation were observed in mice receiving a single dose of 500 mg/kg 
BDCM.
    One study investigated developmental and reproductive toxicity of 
BDCM in rodents. Ruddick et al. (1983) administered BDCM in corn oil to 
groups of pregnant rats by gavage at doses of 0, 50, 100 or 200 mg/kg/
day on days 6 to 15 of gestation. At 200 mg/kg/day, BDCM significantly 
(p <0.05) decreased maternal weight (25%) and increased relative kidney 
weights. There were no increases in the incidence of fetotoxicity or 
external/visceral malformations, but sternebral anomalies were more 
prevalent at 100 and 200 mg/kg than at 50 mg/kg. The sternebral 
anomalies were not considered by the authors to be evidence of a 
teratogenic effect, but rather evidence of maternal toxicity.
    Data from a National Toxicology Program (NTP) chronic oral study in 
B6C3F1 mice (NTP, 1987) was used to calculate the RfD. BDCM in 
corn oil was given to mice by gavage 5 days/week for 102 weeks. Male 
mice (50/dose) were administered doses of 0, 25 or 50 mg/kg/day while 
female mice (50/dose) received doses of 0, 75 or 150 mg/kg/day. 
Following treatment, mortality, body weight and histopathology were 
observed. Renal cytomegaly and fatty metamorphosis of the liver was 
observed in male mice 25 mg/kg/day). Compound-related 
follicular cell hyperplasia of the thyroid gland was observed in both 
males and females. The survival rate decreased in females and decreases 
in mean body weights were observed in both males and females at high 
doses. Based on the observed renal, liver and thyroid effects in male 
mice, a LOAEL of 25 mg/kg/day was identified. A RfD of 0.02 mg/kg/day 
has been derived from the LOAEL of 25 mg/kg/day in mice by the 
application of an uncertainty factor of 1,000, in accordance with EPA 
guidelines for use of a LOAEL derived from a chronic animal study.
    In vitro genotoxicity studies reported mixed results in bacterial 
Salmonella strains and yeasts. BDCM was not mutagenic in mouse lymphoma 
cells without metabolic activation, but induced mutation with 
activation. An increase in frequency of sister chromatid exchange was 
reported in cultured human lymphocytes, rat liver cells, and mouse bone 
marrow cells (in vivo), but not in Chinese hamster ovary cells. 
Overall, more studies yielded positive results and evidence of 
mutagenicity for BDCM is considered adequate.
    Evidence of the carcinogenicity of BDCM has been confirmed by a NTP 
(1987) chronic animal study. In this study BDCM in corn oil was 
administered via gavage to groups of 50 rats (Fischer 344/N) of each 
sex at doses of 0, 50 or 100 mg/kg, 5 days/week, for 102 weeks (NTP, 
1987). Male B6C3F1 mice (50/dose) were administered 0, 25 or 50 
mg/kg by the same route while females received 0, 75 or 150 mg/kg/day. 
BDCM caused statistically significant increases in kidney tumors in 
male mice, the liver in female mice, and the kidney and large intestine 
in male and female rats. In male mice, the combined incidence of 
tubular cell adenomas or adenocarcinomas of the kidneys increased 
significantly in the high-dose group (vehicle control, 1/46; low-dose, 
2/49; high-dose 9/50). The combined incidences of hepatocellular 
adenomas or carcinomas in vehicle control, low-dose and high-dose 
female mice groups were 3/50, 18/48 and 29/50, respectively.
    In rats from the NTP study, the combined incidences of tubular cell 
adenomas or adenocarcinomas in vehicle control, low-dose and high-dose 
groups were 0/50, 1/49 and 13/50 for males and 0/50, 1/50 and 15/50 for 
females, respectively. Tumors of large intestines were significantly 
increased in a dose-dependent manner in male rats, and only observed in 
high-dose female rats. The combined incidences of adenocarcinomas or 
adenomatous polyps were 0/50, 13/49, 45/50 for males and 0/46, 0/50, 
12/47 for females, respectively. The combined tumor incidences of large 
intestine and kidney were 0/50, 13/49, 46/50 for male rats and 0/46, 1/
50, 24/48 for female rats, respectively.
    Using the linearized multistage model, several cancer potency 
factors for BDCM were derived based on the observed cancer incidence of 
various tumor types (large intestine, kidney, or combined) in mice or 
rats reported in the NTP bioassay. The resulting cancer potency factors 
are in the range of 4.9 x 10-3 to 6.2 x 10-2 (mg/kg/
day)-1. A potency factor of 1.3 x 10-1 (mg/kg/day)-1 was 
derived from the incidence of hepatic tumors in female mice (IRIS, 
1990). However, hepatic tumor data should be interpreted with caution 
because studies of an analog chloroform indicated a possible role of 
the corn oil vehicle in induction of these tumors. Until future studies 
can provide a better understanding of the corn oil effect on hepatic 
carcinogenicity, EPA considers carcinogenic risk quantification for 
BDCM based on kidney or large intestine tumor data to be more 
appropriate. EPA is presently conducting a cancer bioassay with BDCM in 
drinking water for comparison with the NTP study. EPA will evaluate the 
results of this study when available to determine if changes to the 
risk assessment are warranted.
    Following the Agency's Cancer Risk Assessment Guidelines (USEPA, 
1986), when two or more significantly elevated tumor sites or types are 
observed in the same study, the slope factor of the greatest 
sensitivity preferably should be used for carcinogenic risk estimation. 
Based on the potency factor of 6.2 x 10-2 (mg/kg/day)-1 
derived from the kidney tumor incidence in male mice, the estimated 
concentrations of BDCM in drinking water associated with excess cancer 
risks of 10-4, 10-5 and 10-6 are 60, 6 and 0.6 
g/L, respectively.
    EPA has classified BDCM in Group B2, probable human carcinogen, 
based on sufficient evidence of carcinogenicity in animals and 
inadequate evidence in humans. The International Agency for Research on 
Cancer (IARC) has recently classified BDCM as a Group 2B carcinogen, 
agent probably carcinogenic to humans (IARC, 1991).
    Following EPA's three-category approach for establishing MCLGs, 
BDCM is placed in Category I since there is sufficient evidence for 
carcinogenicity via ingestion considering weight of evidence, potency, 
pharmacokinetics, and exposure. Thus, EPA is proposing an MCLG of zero 
for this contaminant. EPA requests comments on the basis of the 
proposed MCLG for BDCM and the use of tumor data of large intestine and 
kidney, but not liver, in quantitative estimation of carcinogenic risk 
of BDCM from oral exposure.
7. Dibromochloromethane
    Dibromochloromethane (DBCM; CAS No. 124-48-1) is a nonflammable, 
colorless liquid with a relatively high vapor pressure (76 mmHg at 20 
deg.C). DBCM is moderately soluble in water (4 gm/l at 20  deg.C) and 
soluble in organic solvents (log octanol/water partition coefficient of 
2.09). Currently DBCM is not produced commercially in the United 
States. The chemical has only limited uses as a laboratory agent. The 
principal source of DBCM in drinking water is the chemical interaction 
of chlorine with commonly present organic matter and bromide ions. 
Degradation of DBCM has not been well studied, but probably involves 
photooxidation. The estimated atmospheric half-life of DBCM is one to 
two months. Volatilization is the principle mechanism for removal of 
DBCM from rivers and streams (half-life of hours to weeks). Several 
studies reported that DBCM adsorbs poorly to soil and sediments. No 
experimental study was found regarding the bioconcentration of DBCM. 
Based on the data of a few structurally similar chemicals, the 
bioconcentration potential of DBCM in aquatic organisms is assumed to 
be low. Biodegradation of DBCM is limited under aerobic conditions and 
more extensive under anaerobic conditions.
    Occurrence and Human Exposure. DBCM occurs in public water systems 
that chlorinate water containing humic and fulvic acids and bromine 
that can enter source waters through natural and anthropogenic means. 
Several water quality factors can affect the formation of DBCM, 
including Total Organic Carbon (TOC), pH, bromide, and temperature. 
Different treatment practices can reduce the formation of DBCM in 
drinking water. These include the use of precursor removal technologies 
such as coagulation/filtration, granular activated carbon (GAC), 
membrane filtration, and the use of chlorine dioxide, chloramination, 
and ozonation.
    Table V-8 presents occurrence information available for DBCM in 
drinking water. Descriptions of these surveys and other data are 
detailed in ``Occurrence Assessment for Disinfectants and Disinfection 
By-Products (Phase 6a) in Public Drinking Water,'' (USEPA, 1992a). The 
table lists six surveys conducted by Federal and private agencies. 
Median concentrations of DBCM in drinking water appear to range from 
0.6 to 3.6 g/L for surface water supplies and <0.5 g/
L for ground-water supplies. The lower bound median concentration for 
DBCM in surface water supplies is biased to the low side because 
concentrations in this survey were measured in the plant effluent; the 
formation of DBCM would be expected to increase in the distribution in 
systems using chlorine as their residual disinfectant.

                                             Table V-8.--Summary of Occurrence Data for Dibromochloromethane                                            
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  Occurrence of dibromochloromethane in drinking water                                                  
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                     Concentration (g/L)                       
     Survey (year)\1\             Location          Sample information(No. of --------------------------------------------------------------------------
                                                            samples)               Range          Mean         Median                  Other            
--------------------------------------------------------------------------------------------------------------------------------------------------------
CWSS (1978) Brass et al.,   450 Systems..........  Finished Water (1,100):                                                Positive Detections:          
 1981.                                             Surface Water.............  .............       \3\5.0  1.5            67%\4\                        
                                                   Ground Water..............  .............       \3\6.6  <0.5           34%\4\                        
RWS (1978-1980) Brass,      >600 Rural Systems     Drinking Water from:                                                   Positive Detections:          
 1981.                       (>2,000 households).  Surface Water.............  .............       \3\8.5  0.8            \4\56%                        
                                                   Ground Water..............  .............       \3\9.9  <0.5           \4\13%                        
GWSS (1980-1981) Westrick   945 GW Systems: (466                                                                          90th Percentile:              
 et al. 1983.                Random and 479        Serving >10,000 (327).....  Max. 59......  ...........  0.7            9.2                           
                             Nonran.               Serving <10,000 (618).....  Max. 63......  ...........  0              5.6                           
                            dom).................                                                                                                       
EPA, 1991a2 (1984-1991)...  Unregulated            Sampled at the Plant        .............          3.0  1.7            ..............................
                             Contaminant Data       (4,439).                                                                                            
                             Base--Treatment                                                                                                            
                             Facilities from 19                                                                                                         
                             States.                                                                                                                    
EPA, 1992b2 (1987-1989)...  Disinfection By-       Finished Water:                                                        Positive Detections:          
                             Products Field        At the Plant (73).........  <0.2-41......          4.9  2.0            92%                           
                             Studies.              In Distribution System      <0.2-41......          6.6  3.4            93%                           
                                                    (56).                                                                                               
EPA/AMWA/CDHS\2\ (1988-     35 Water Utilities     Samples from Clearwell      Max. 63......  ...........  3.6            75% of Data was Below 9.1     
 1989) Krasner et al.,       Nationwide.            Effluent for 4 Quarters.                               2.6-4.5\5\      g/L                 
 1989b.                                                                                                                                                 
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                                                          
\2\May not be representative of national occurrence.                                                                                                    
\3\Mean of the positives.                                                                                                                               
\4\Of systems sampled.                                                                                                                                  
\5\Range of medians for individual quarters.                                                                                                            
                                                                                                                                                        
AMWA: Association of Metropolitan Water Agencies.                                                                                                       
CDHS: California Department of Health Services.                                                                                                         
CWSS: Community Water Supply Survey.                                                                                                                    
GWSS: Ground Water Supply Survey.                                                                                                                       
RWS: Rural Water Survey.                                                                                                                                
EPA: Environmental Protection Agency.                                                                                                                   

    No information is available concerning the occurrence of DBCM in 
food in the United States. The Food and Drug Administration (FDA) does 
not analyze for DBCM in foods. However, there are several uses of 
chlorine in food production, such as disinfection of chicken in poultry 
plants and the superchlorination of water at soda and beer bottling 
plants (Borum, 1991). Therefore, the possibility exists for dietary 
exposure from the by-products of chlorination in food products.
    Based on information obtained through a literature review, Howard 
(1990) estimated the average daily intake of DBCM from air using an 
inhalation rate of 20m\3\/day. Assuming a range of 8.25 to 425 ng/m\3\ 
the exposure may be as low as 0.17 g/day or as high as 
8.5g/day.
    Although some uses of chlorine have been identified in the food 
production/food processing area, monitoring data are not available to 
adequately characterize the magnitude or frequency of potential 
exposure to DBCM. Additionally, preliminary discussions with FDA 
suggest that there are not approved uses for chlorine in most foods 
consumed in the typical diet. Based on the limited number of food 
groups that are believed to contain chlorinated chemicals and that 
there are not significant levels expected in ambient or indoor air, EPA 
assumes that drinking water is the predominant source of DBCM intake. 
Characterization of food and air exposure are issues currently under 
review. EPA, therefore, is proposing to regulate DBCM in drinking water 
with an RSC value at the ceiling level of 80 percent. EPA requests any 
additional data on known concentration of DBCM in drinking water, food, 
and air.
    Health Effects. The health effects information in this section is 
summarized from the Drinking Water Health Criteria Document for 
Trihalomethanes (USEPA, 1994d). Studies mentioned in this section are 
summarized in the criteria document.
    Studies indicated that gastrointestinal absorption of DBCM is high 
in animals. No studies were located regarding DBCM in humans or animals 
following inhalation or dermal exposure. Based on the physical-chemical 
properties of DBCM, and by analogy with the structurally-related 
halomethanes such as chloroform, it is expected that the inhalation and 
dermal absorption could be significant for DBCM.
    The LD50 values in mice and rats range from 800 to 1,200 mg/
kg. Under both in vivo and in vitro conditions, several active 
metabolic intermediates (e.g. dihalocarbonyl, bromochloromethyl 
radicals) can be produced via oxidation or reduction by microsomal 
preparations. Environmental studies suggest that these active metabolic 
intermediates are responsible for the hepatic and renal toxicity, and 
possibly carcinogenicity, of the parent compound. Animal studies 
suggest that the extent of DBCM metabolism varies with species and sex. 
The retention of DBCM in organs after dosing was small and relatively 
higher concentrations were found in stomach, liver and kidneys. Urinary 
excretion levels were below 2 percent.
    Mammalian bioeffects following oral exposure to DBCM include 
effects on the central nervous system (decreased operant response), 
hepatotoxicity, nephrotoxicity, reproductive toxicity and possible 
carcinogenicity. In experimental mice and rats, DBCM caused changes in 
kidney, liver, and serum enzyme levels, and decreased body weight. 
These responses are discernible in mammals from exposure to levels of 
DBCM ranging from 39 to 250 mg/kg; the intensity of response was 
dependent upon the dose and the duration of the exposure. Ataxia and 
sedation were observed in mice receiving a single dose of 500 mg/kg 
DBCM.
    Developmental and reproductive toxicity of DBCM was investigated in 
rodents. A multi-generation reproductive study of mice treated with )in 
drinking water showed maternal toxicity (weight loss, liver 
pathological changes) and fetal toxicity (decreased pup weight & 
viability). The study identified a NOAEL of 17 mg/kg/day and a LOAEL of 
171 mg/kg/day.
    The National Toxicology Program (NTP, 1985) evaluated the 
subchronic and chronic toxicity of DBCM in F344/N rats and B6C3F1 
mice. In this study corn oil is used as the gavage vehicle. The chronic 
data indicated that doses of 40 and 50 mg/kg/day produced 
histopathological lesions in the liver of rats and mice, respectively. 
However, the chronic studies did not identify a reliable NOAEL. The 
subchronic study identified both a LOAEL and a NOAEL for 
hepatotoxicity, and was used to calculate the RfD of 0.02 mg/kg/d.
    In the NTP subchronic study, DBCM in corn oil was administered to 
Fischer 344/N rats and B6C3F1 mice via gavage at dose levels of 0, 
15, 30, 60, 125 or 250 mg/kg/day, 5 days a week for 13 weeks. Following 
treatment, survival, body weight, clinical signs, histopathology and 
gross pathology were evaluated. Final body weights of rats that 
received 250 mg/kg/day were depressed 47% for males and 25% for 
females. Kidney and liver toxicity was observed in male and female rats 
and male mice at 250 mg/kg/day. A dose-dependent increase in hepatic 
vacuolation was observed in male rats. Based on this hepatic effect, 
the NOAEL and LOAEL in rats were 30 and 60 mg/kg/day, respectively.
    Several studies on the mutagenicity potential of DBCM have reported 
inconclusive results. Studies on the in vitro genotoxicity of DBCM 
reported mixed results in bacteria Salmonella typhimurium strains and 
yeasts. DBCM produced sister chromatid exchange uncultured human 
lymphocytes and Chinese hamster ovary cells (without activation). An 
increased frequency of sister chromatid exchange was observed in mouse 
bone marrow cells from mice dosed orally, but not via the 
intraperitoneal route.
    The carcinogenicity of DBCM was reported in a NTP (1985) chronic 
animal study. In this study DBCM in corn oil was administered via 
gavage to groups of male and female F344/N rats at doses of 0, 40 or 80 
mg/kg/day, 5 days/week for 104 weeks; and groups of male and female 
mice at 0, 50 or 100 mg/kg/day, 5 days/week for 105 weeks. 
Administration of DBCM showed a significant increase in the incidence 
of hepatocellular adenomas in high-dose female mice (vehicle control, 
2/50; low dose, 4/49; high dose, 11/50) and combined incidence of 
hepatocellular adenomas or carcinomas (6/50, 10/49, 19/50). In high-
dose male mice, administration of DBCM showed a significant increase in 
the incidence of hepatocellular carcinomas (10/50, -, 19/50); however, 
the combined incidence of hepatocellular adenomas or carcinomas was 
only marginally increased (23/50, -, 27/50). Administration of DBCM did 
not result in increased incidence of tumors in treated rats.
    Using the linearized multistage model, EPA derived a cancer potency 
factor of 8.4 x 10-2 (mg/kg/day)-1 (IRIS, 1990). The 
derivation was based on the tumor incidence of the hepatocellular 
adenomas or carcinomas in the female mice reported in the 1985 NTP 
study. Due to the possible role of the corn oil vehicle in induction of 
hepatic tumors as reported in studies on chloroform, some uncertainty 
exists regarding the relevance of this derived cancer potency factor to 
exposure via drinking water. However, the only tumor data currently 
available on DBCM are for liver tumors in mice. Until future studies 
can provide additional data, EPA considers this cancer potency factor 
valid for potential carcinogenic risk quantification for DBCM.
    EPA has classified DBCM in Group C, possible human carcinogen, 
based on the limited evidence of carcinogenicity in animals (only in 
one species) and inadequate evidence of carcinogenicity in humans. The 
International Agency for Research on Cancer (IARC) has classified DBCM 
as a Group 3 carcinogen: agent not classifiable as to its 
carcinogenicity to humans.
    Using EPA's three-category approach for establishing MCLG, DBCM is 
placed in Category II since there is limited evidence for 
carcinogenicity via drinking water considering weight of evidence, 
potency, pharmacokinetics, and exposure. As a Category II chemical, EPA 
proposes to follow the first option and set the MCLG for DBCM on 
noncarcinogenic endpoints (the RfD) with the application of an 
additional safety factor to account for possible carcinogenicity. An 
RfD of 0.02 mg/kg/day has been derived from the NOAEL of 30 mg/kg/d, 
adjusted for dosing 5 days per week and divided by an uncertainty 
factor of 1,000. This factor is appropriate for use of a NOAEL derived 
from a subchronic animal study. EPA is proposing an MCLG of 0.06   mg/L 
for DBCM based on liver toxicity and possible carcinogenicity. An 
additional safety factor of 10 for possible carcinogenicity is used to 
calculate the MCLG along with an assumed drinking water contribution of 
80 percent of total exposure.

TP29JY94.006

    EPA requests comments on the basis for the proposed MCLG for DBCM, 
the RSC of 80%, and the cancer classification for DBCM.
8. Bromoform
    Bromoform (tribromomethane, CAS No. 75-25-2) is a nonflammable, 
colorless liquid with a sweet odor and a relatively high vapor pressure 
(5.6 mmHg at 25  deg.C). Bromoform is moderately soluble in water (3.2 
gm/L at 30  deg.C) and soluble in organic solvents (log octanol/water 
partition coefficient of 2.38). Bromoform is not currently produced 
commercially in the United States. The chemical has only limited uses 
as a laboratory agent and as a fluid for mineral ore separation. The 
principle source of bromoform in drinking water is the chemical 
interaction of chlorine with commonly present organic matter and 
bromide ion. Degradation of bromoform is not well studied, but probably 
involves photooxidation. The estimated atmospheric half-life of 
bromoform is one to two months. Volatilization is the principle 
mechanism for removal of bromoform from rivers and streams (half-life 
of hours to weeks). Studies reported that bromoform adsorbs poorly to 
sediments and soils. No experimental studies were located regarding the 
bioconcentration of bromoform. Based on the data from a few 
structurally similar chemicals, the potential for bromoform to be 
bioconcentrated by aquatic organisms is low. Biodegradation of 
bromoform is limited under aerobic conditions but more extensive under 
anaerobic conditions.
    Occurrence and Human Exposure. Bromoform occurs in public water 
systems that chlorinate water containing humic and fulvic acids and 
bromine that can enter source waters through natural and anthropogenic 
means. Several water quality factors affect the formation of bromoform 
including Total Organic Carbon (TOC), pH, and temperature. Different 
treatment practices can reduce the level of bromoform. These include 
the use of chloride dioxide, chloramination, and ozonation prior to 
chloramination.
    Table V-9 presents occurrence information available for bromoform 
in drinking water. Descriptions of these surveys and other data are 
detailed in ``Occurrence Assessment for Disinfectants and Disinfection 
By-Products (Phase 6a) in Public Drinking Water,'' (USEPA, 1992a). The 
table lists six surveys conducted by Federal and private agencies. 
Median concentrations of bromoform in drinking water appear to range 
from <0.2 to 0.57 g/L for surface water supplies and <0.5 
g/L for ground- water supplies. The lower bound median 
concentration for bromoform in surface water supplies is biased to the 
low side because concentrations in this survey were measured in the 
plant effluent; the formation of bromoform would be expected to 
increase in the distribution in systems using chlorine as their 
residual disinfectant.

                                                  Table V-9.--Summary of Occurrence Data for Bromoform                                                  
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        Occurrence of bromoform in drinking water                                                       
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                      Concentration (g/L)                      
     Survey (year)\1\             Location         Sample information (No. of --------------------------------------------------------------------------
                                                            samples)               Range          Mean         Median                  Other            
--------------------------------------------------------------------------------------------------------------------------------------------------------
CWSS (1978) Brass et al.,   450 Systems..........  Finished Water (1,100):                                 .............  Positive Detections:          
 1981.                                             Surface Water.............                      \3\2.1  <1.0           13%\4\                        
                                                   Ground Water..............                       \3\11  <0.5           26%\4\                        
RWS (1978-1980) Brass,      >600 Rural Systems     Drinking Water from:                                    .............  Positive Detections:          
 1981.                       (>2,000 Households).  Surface Water.............                      \3\8.7  <0.5           18%\4\                        
                                                   Ground Water..............                       \3\12  <0.5           12%\4\                        
GWSS (1980-1981) Westrick   945 GW Systems: (466   ..........................  .............  ...........  .............  90th Percentile:              
 et al. 1983.                Random and 479        Serving >10,000 (327).....  Max. 68......               0              8.3                           
                             Nonran-dom).          Serving <10,000 (618).....  Max. 110.....               0              4.1                           
EPA, 1991a\2\ (1984-1991).  Unregulated            Sampled at the Plants       .............          2.5  1              ..............................
                             Contaminant Data       (1,409).                                                                                            
                             Base--Treatment                                                                                                            
                             Facilities from 19                                                                                                         
                             States.                                                                                                                    
EPA, 1992b\2\ (1987-1989).  Disinfection By-       Finished Water:                                                        Positive Detections:          
                             Products Field        At the Plant (73).........  <0.2-6.7.....          0.7  <0.2           45%                           
                             Studies.              In Distr. System (56).....  <0.2-10......          1.0  <0.2           48%                           
EPA/AMWA/CDHS\2\ (1988-     35 Water Utilities     Samples from Clearwell      Max. 72......  ...........  .............  75% of Data was Below 2.8     
 1989) Krasner et. al.,      Nationwide.            Effluent for 4 Quarters.                               0.33-0.88\5\                                 
 1989b.                                                                                                    0.57                                         
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                                                          
\2\May not be representative of national occurrence.                                                                                                    
\3\Mean of the positives.                                                                                                                               
\4\Of systems sampled.                                                                                                                                  
\5\Range of medians for individual quarters.                                                                                                            
                                                                                                                                                        
AMWA: Association of Metropolitan Water Agencies.                                                                                                       
CDHS: California Department of Health Services.                                                                                                         
CWSS: Community Water Supply Survey.                                                                                                                    
GWSS: Ground Water Supply Survey.                                                                                                                       
RWS: Rural Water Survey.                                                                                                                                
EPA: Environmental Protection Agency.                                                                                                                   

    No information is available concerning the occurrence of bromoform 
in food in the United States. The Food and Drug Administration (FDA) 
does not analyze for bromoform in foods. However, there are several 
uses of chlorine in food production, such as disinfection of chicken in 
poultry plants and the superchlorination of water at soda and beer 
bottling plants (Borum, 1991). Therefore, the possibility exists for 
dietary exposure from the by-products of chlorination in food products.
    Bromoform is usually found in ambient air at low concentrations. 
One study reported ambient air concentrations from several urban 
locations across the U.S. The overall mean concentration of positive 
samples was found to be 4.15 ng/m\3\ and the maximum level was 71 ng/
m\3\ (Brodzinsky and Singh, 1983 in USEPA, 1991b). Although the data 
are limited for bromoform, an inhalation intake could be estimated 
using the mean and maximum values from the Brodzinsky and Singh (1983) 
study, indicating a possible range of 0.08 to 1.4 g/d.
    Based on the limited number of food groups that are believed to 
contain bromoform and that significant levels are not expected in 
ambient or indoor air, EPA is assuming that drinking water is the 
predominant source of bromoform intake. Characterization of food and 
air exposures are issues currently under review. The EPA requests any 
additional data on known concentrations of bromoform in drinking water, 
food, and air.
    Health Effects. The health effects information in this section is 
summarized from the draft Drinking Water Health Criteria Document for 
Trihalomethanes (USEPA, 1994d) and the draft Drinking Water Health 
Advisory for Brominated Trihalomethanes (USEPA, 1991b). Studies 
mentioned in this section are summarized in the criteria document or 
health advisory.
    Studies have indicated that gastrointestinal absorption of 
bromoform is high in humans and animals. No studies were located 
regarding bromoform in humans or animals following inhalation or dermal 
exposure. Based on the physical-chemical properties of bromoform, and 
by analogy with the structurally-related halomethanes such as 
chloroform, it is expected that both inhalation and dermal absorption 
could be significant for bromoform.
    Bromoform was used as a sedative for children with whooping cough. 
Based on clinical observations of accidental overdose cases, the 
estimated lethal dose for a 10- to 20-kg child is about 300 mg/kg. The 
clinical signs in fatal cases were central nervous system (CNS) 
depression followed by respiratory failure.
    The LD50 values in mice and rats have been reported in the 
range of 1,147-1550 mg/kg. Under both in vivo and in vitro conditions, 
several active metabolic intermediates (e.g., dibromocarbonyl, 
dibromomethyl radicals) are produced via oxidation or reduction by 
microsomal preparations. Experimental studies suggested that these 
active metabolic intermediates are responsible for hepatic and renal 
toxicity and possibly, carcinogenicity, of the parent compound. Animal 
studies suggest that the extent of bromoform metabolism varies with 
species and sex. The retention of bromoform in organs after dosing was 
small; relatively higher concentrations were found in tissues with 
higher lipophilic content. Urinary excretion levels were below 5 
percent.
    Mammalian bioeffects following exposure to bromoform include 
effects on the central nervous system (CNS), hepatotoxicity, 
nephrotoxicity, and carcinogenicity. Bromoform causes CNS depression in 
humans. The reported LOAEL which results in mild sedation in humans is 
54 mg/kg. In experimental mice and rats, bromoform caused changes in 
kidney, liver, serum enzyme levels, decrease of body weight, and 
decreased operant response. These responses are discernible in mammals 
from exposure to levels of bromoform ranging from 50 to 250 mg/kg; the 
intensity of response was dependent upon the dose and the duration of 
the exposure. Ataxia and sedation were noted in mice receiving a single 
dose of 1,000 mg/kg bromoform or 600 mg/kg for 14 days.
    Few studies have investigated developmental and reproductive 
toxicity of bromoform in rodents. A developmental study in rats showed 
no fetal variations in a group fed with 50 mg/kg/day. An increased 
incidence of minor anomalies was noted at doses of 100 and 200 mg/kg/
day. No maternal toxicity in rats was observed. One detailed 
reproductive toxicity study reported no apparent effects on fertility 
and reproduction when male and female rats were administered bromoform 
via gavage in corn oil at doses up to 200 mg/kg/day.
    EPA used subchronic data from an oral study (NTP, 1989) to 
calculate the RfD. In this study, bromoform was administered to rats in 
corn oil via gavage at dose levels of 0, 12, 25, 50, 100 or 200 mg/kg/
day 5 days a week for 13 weeks. Based on the observation of 
hepatocellular vacuolization in treated male rats, a NOAEL of 25 mg/kg/
day was established. An RfD of 0.02 mg/kg/day has been derived from 
this NOAEL by the application of an uncertainty factor of 1,000, in 
accordance with EPA guidelines for use of a NOAEL from a subchronic 
study.
    A number of studies investigated the mutagenicity potential of 
bromoform. Studies on the in vitro genotoxicity of bromoform reported 
mixed results in bacterial Salmonella typhimurium strains. Bromoform 
produced mutations in cultured mouse lymphoma cells and sister 
chromatid exchange in human lymphocytes. Under in vivo condition 
bromoform induced sister chromatid exchange, and chromosomal aberration 
and micronucleus in mouse bone marrow cells. Overall, most studies 
yielded positive results and evidence of mutagenicity for bromoform is 
considered adequate.
    The National Toxicology Program (NTP, 1989) conducted a chronic 
animal study to investigate the carcinogenicity of bromoform. In this 
study bromoform was administered in corn oil via gavage to F344/N rats 
(50/sex/group) at doses of 0, 100 or 200 mg/kg/day, 5 days/week for 105 
weeks. An evaluation of the study results showed that adenomatous 
polyps or adenocarcinoma (combined) of the large intestine (colon or 
rectum) were induced in three male rats (vehicle control, 0/50; low 
dose, 0/50; high dose, 3/50) and in nine female rats (0/50, 1/50, 8/
50). The increase was considered to be significant since these tumors 
are rare in control animals. Neoplastic lesions in the large intestine 
in female rats reported in the NTP study were used to estimate the 
carcinogenic potency of bromoform. EPA derived a cancer potency factor 
of 7.9 x 10-3 (mg/kg/day)-1 using the linearized multistage 
model (IRIS, 1990). Assuming a daily consumption of two liters of 
drinking water and an average human body weight of 70 kg, the 95% upper 
bound limit lifetime cancer risks of 10-6, 10-5 and 10-4 
are associated with concentrations of bromoform in drinking water of 4, 
40 and 400 g/L, respectively.
    EPA classified bromoform in Group B2, probable human carcinogen, 
based on the sufficient evidence of carcinogenicity in animals and 
inadequate evidence of carcinogenicity in humans. The International 
Agency for Research on Cancer (IARC) has recently classified bromoform 
in Group 3: agent not classifiable as to its carcinogenicity to humans 
(IARC, 1991). IARC determined that there was limited evidence of 
carcinogenicity in animals, in contrast to EPA's judgment that there is 
sufficient evidence in laboratory animals. EPA requests comments on the 
different viewpoints between IARC and EPA regarding bromoform's 
carcinogenic potential.
    Using EPA's three-category approach for establishing MCLG, 
bromoform is placed in Category I since there is sufficient evidence 
for carcinogenicity from drinking water considering weight of evidence, 
potency, pharmacokinetics, and exposure. Thus, EPA is proposing an MCLG 
of zero for this contaminant. EPA requests comments on the basis for 
the proposed MCLG for bromoform.
9. Dichloroacetic Acid
    Chlorination of water containing organic material (humic, fulvic 
acids) results in the generation of many organic compounds, including 
dichloroacetic acid (DCA) (CAS. No. 79-43-6), a nonvolatile compound.
    Though DCA is generally a concern due to its occurrence in 
chlorinated drinking water, it is also used as a chemical intermediate, 
and an ingredient in pharmaceuticals and medicine. Previously, DCA was 
used experimentally to treat diabetes and hypercholesterolemia in human 
patients. In addition, DCA was used as an agricultural fungicide and 
topical astringent. It has also been extensively investigated for 
potential therapeutic use as a hypoglycemic, hypolactemic and 
hypolipidemic agent.
    Occurrence and Human Exposure. DCA has been found to occur as a 
disinfection by-product in public water systems that chlorinate water 
containing humic and fulvic acids.
    Table V-10 presents occurrence information available for DCA in 
drinking water. Descriptions of these surveys and other data are 
detailed in ``Occurrence Assessment for Disinfectants and Disinfection 
By-Products (Phase 6a) in Public Drinking Water,'' (USEPA, 1992a). 
Median concentrations of DCA in drinking water were found to range from 
6.4 to 17 g/L. The lower bound median concentration for DCA in 
surface water supplies is biased to the low side because concentrations 
in this survey were measured in the plant effluent; the formation of 
DCA would be expected to increase in the distribution system in systems 
using chlorine as their residual disinfectant.

                                             Table V-10.--Summary of Occurrence Data for Dichloroacetic Acid                                            
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   Occurence of dichloroacetic acid in drinking water                                                   
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                         Concentration (g/L)                   
     Survey (year)\1\               Location            Sample information (No. of   -------------------------------------------------------------------
                                                                 samples)                 Range          Mean        Median              Other          
--------------------------------------------------------------------------------------------------------------------------------------------------------
EPA, 1992b\2\ (1987-1989)  Disinfection By-Products   Finished Water:                 .............           18           16  Positive Detections:     
                            Field Studies.            At the Plant (72)               <0.4-61                 21           17  93%                      
                                                      In the Distr. System (56)       <0.4-75                                  96%                      
EPA/AMWA/CDHS\2\ (1988-    35 Water Utilities         Samples from Clearwell          <0.6-46        ...........   \3\5.0-7.3  75% of Data was Below 12 
 1989) Krasner et al.,      Nationwide.                Effluent for 4 Quarters.                                           6.4   g/L DL = 0.6   
 1989b.                                                                                                                         g/L            
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                                                          
\2\May not be representative of national occurrence.                                                                                                    
\3\Range of medians for individual quarters.                                                                                                            
                                                                                                                                                        
AMWA: Association of Metropolitan Water Agencies.                                                                                                       
CDHS: California Department of Health Services.                                                                                                         
EPA: Environmental Protection Agency.                                                                                                                   

    Based on the above data, a range of exposure to DCA from drinking 
water can be calculated using a consumption rate of 2 liters per day. 
The expected median exposure from drinking water would range from 13 to 
34 g/day, using these data sets.
    No information is available concerning the occurrence of DCA in 
food and ambient or indoor air in the United States. The Food and Drug 
Administration (FDA) does not analyze for DCA in foods. However, there 
are several uses of chlorine in food production, such as the 
disinfection of chicken in poultry plants and the superchlorination of 
water at soda and beer bottling plants. Therefore, the possibility 
exists for dietary exposure from the by-products of chlorination in 
food products. However, monitoring data are not available to 
characterize adequately the magnitude or frequency of potential DCA 
exposure from diet. Additionally, preliminary discussions with FDA 
suggest that there are not approved uses for chlorine in most foods 
consumed in the typical diet. Similarly, EPA's Office of Air and 
Radiation is not currently sampling for DCA in air (Borum, 1991). 
Little exposure to DCA from air is expected since DCA is nonvolatile.
    Since only a limited number of food groups are expected to contain 
chlorinated chemicals and no significant DCA levels are expected in 
ambient or indoor air, EPA believes that drinking water is the 
predominant source of DCA intake. Characterization of the potential 
exposures from food and air are issues currently under review. EPA 
requests any additional data on known concentrations of DCA in drinking 
water, food, and air.
    Health Effects. The health effects information in this section is 
summarized from the draft Drinking Water Health Criteria Document for 
Chlorinated Acetic Acids, Alcohols, Aldehydes and Ketones (USEPA, 
1994e). Studies mentioned in this section are summarized in the 
criteria document.
    Humans treated with DCA for 6 to 7 days at 43 to 57 mg/kg/day have 
experienced mild sedation, reduced blood glucose, reduced plasma 
lactate, reduced plasma cholesterol levels, and reduced triglyceride 
levels. At the same time, the DCA treatment depressed uric acid 
excretion, resulting in elevated serum uric acid levels.
    A longer term study in two young men receiving 50 mg/kg for 5 weeks 
up to 16 weeks, indicated that DCA significantly reduces serum 
cholesterol levels and blood glucose, and causes peripheral neuropathy 
in the facial, finger, leg and foot muscles.
    Estimates of acute oral LD50 values range from 2,800 to 4,500 
mg/kg in rats and up to 5,500 mg/kg in mice. Short-term studies in dogs 
and rats indicate an effect on intermediary metabolism, as demonstrated 
by decreases in blood lactate and pyruvate. Exposures to DCA up to 3 
months in dogs and rats result in a variety of adverse effects 
including effects to the neurological and reproductive systems. These 
effects are seen above 100 mg/kg/day in dogs and rats.
    Studies on the toxicokinetics of DCA indicate that absorption is 
rapid and that DCA is quickly distributed to the liver and muscles in 
the rat. DCA is metabolized to glyoxylate which in turn is metabolized 
to oxalate. Although there are few studies regarding the excretion of 
DCA, studies in which rats, dogs and humans received intravenous 
injections of DCA indicated that the half-life of DCA in human blood 
plasma is much shorter than in rats or dogs. Urinary excretion of DCA 
was negligible after 8 hours. Total excretion of DCA was less than 1% 
of total dose.
    A drinking water study by Bull et al. (1990) reported a dose-
related increase in hepatic effects in mice that received DCA at 270 
mg/kg/day for 37 weeks and at 300 mg/kg/day for 52 weeks. Adverse 
effects included enlarged livers, marked cytomegaly with massive 
accumulation of glycogen in hepatocyte and focal necrosis. The NOAEL 
for this study was 137 mg/kg/day for 52 weeks.
    DeAngelo et al. (1991) conducted a drinking water study in which 
mice received DCA at levels of 7.6, 77, 410, and 486 mg/kg/day for 60 
or 75 weeks. While this study was intended as an assessment of 
carcinogenicity, other systemic effects were measured. This study 
concluded that levels at 77 mg/kg/day and above caused an extreme 
increase of relative liver weights and a significant increase in 
neoplasia at levels of 410 mg/kg/day and above. This study indicates a 
NOAEL of 7.6 mg/kg/day for noncancer liver effects.
    Based on the available data, DCA does not appear to be a potent 
mutagen. Studies in bacteria have indicated that DCA did not induce 
mutation or activate repair activity. Two studies have shown some 
potential for mutagenicity but these results have not been 
reproducible.
    DCA appears to induce both reproductive and developmental toxicity. 
Damage and atrophy to sexual organs has been reported in male rats and 
dogs exposed to levels from 50 mg/kg/day to 2000 mg/kg/day for up 3 
months. Malformation of the cardiovascular system has been observed in 
rats exposed to 140 mg/kg/day DCA from day 6 to 16 of pregnancy.
    A 90-day dog study was selected to determine the RfD for DCA 
(Cicmanec et al., 1991). In this study, four month old beagle dogs (5/
sex/group) were administered gelatin capsules containing 0, 12.5, 39.5, 
or 72 mg/kg DCA/day for 90 days. Dogs were observed for clinical signs 
of toxicity; blood samples were collected for hematology and serum 
chemistry analysis. Clinical signs included diarrhea and dyspnea in the 
mid and high dose groups. Dyspnea was evident at 45 days and became 
more severe with continued exposure leading to general depression and 
decreased activity by day 90. Hindlimb paralysis was observed in 3 dogs 
in the high dose group. Other effects included conjunctivitis, weight 
loss, reduced food and water consumption, pneumonia, decreased liver 
weights, and elevated kidney weights in the dosed animals. 
Histopathology revealed toxic effects in liver, testis, and brain of 
the treated dogs. A NOAEL was not identified in this study. The lowest 
dose tested, 12.5 mg/kg/d, was considered a LOAEL. An uncertainty 
factor of 3,000 was applied in accordance with EPA guidelines to 
account for use of a LOAEL from a less-than-lifetime animal study in 
which frank effects were noted as the critical effect. The resulting 
RfD is 0.004 mg/kg/d.
    Several studies indicate that DCA is a carcinogen in both mice and 
rats exposed via drinking water lifetime studies. These studies 
indicate that DCA induces liver tumors. In one study with male 
B6F3F1 mice, exposure to DCA at 0.5 g/L and 3.5 g/L for 104 weeks 
resulted in tumor formation in exposed animals at 75% (18/24) and 100% 
(24/24) respectively. In female mice exposed for 104 weeks to DCA at 
the same levels, tumor prevalence was 20% and 100%, respectively. In 
male rats exposed to 0.05, 0.5 or 5 g/L DCA for 104 weeks, tumor 
prevalence increased to 22% in the highest dose. No tumors were seen at 
the lower doses. However, at 0.5 g/L, there was an increase in the 
prevalence of proliferation of liver lesions. Some of these lesions are 
likely to progress into malignant tumors.
    EPA has classified DCA in Group B2: probable human carcinogen, 
based on positive carcinogenic findings in two animal species exposed 
to DCA in drinking water. A quantitative risk estimate has not yet been 
determined for DCA.
    Following a Category I approach, EPA is proposing an MCLG for DCA 
of zero based on the strong evidence of carcinogenicity via drinking 
water. EPA requests comments on the basis for the proposed MCLG for DCA 
in drinking water and the cancer classification of Group B2.
10. Trichloroacetic Acid.
    Trichloroacetic acid (TCA; CAS No. 76-03-9) is also a major by-
product of chlorinated drinking water. Chlorination of source waters 
containing organic materials (humic, fulvic acids) results in the 
generation of organic compounds such as TCA.
    TCA is also sold as a pre-emergence herbicide. It is used in the 
laboratory to precipitate proteins and as a reagent for synthetic 
medicinal products. It is applied medically as a peeling agent for 
damaged skin, cervical dysplasia and removal of tatoos.
    Occurrence and Human Exposure. TCA occurs in public water systems 
that chlorinate water containing humic and fulvic acids.
    Table V-11 presents the most recent and comprehensive occurrence 
information available for TCA in drinking water. Descriptions of these 
surveys and other data are detailed in ``Occurrence Assessment for 
Disinfectants and Disinfection By-Products (Phase 6a) in Public 
Drinking Water,'' (USEPA, 1992a). Median concentrations of TCA acid in 
drinking water were found to range from 5.5 to 15 g/L. The 
lower bound median concentration for TCA in surface water supplies is 
biased to the low side because concentrations in this survey were 
measured in the plant effluent; the formation of TCA would be expected 
to increase in the distribution system in systems using chlorine as 
their residual disinfectant. Based on the available data sets, and 
assuming a drinking water consumption rate of 2 L/day, median exposures 
from drinking water would range from 11 to 30 g/day.

                                            Table V-11.--Summary of Occurrence Data for Trichloroacetic Acid                                            
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  Occurrence of trichloroacetic acid in drinking water                                                  
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                       Concentration (g/L)                     
     Survey (year)\1\               Location           Sample information (No.  ------------------------------------------------------------------------
                                                             of samples)             Range          Mean        Median                 Other            
--------------------------------------------------------------------------------------------------------------------------------------------------------
EPA, 1992b\2\ (1987-1989)  Disinfection By-Products   Finished Water:            .............  ...........  ...........  Positive Detections:          
                            Field Studies.            At the Plant (72)          <0.4-54                 13           11  90%                           
                                                      Distribution System        <0.4-77                 15           15  91%                           
                                                      (56).....................                                                                         
EPA/AMWA/CDHS\2\ (1988-    35 Water Utilities         Samples from Clearwell     .............  ...........      4.0-5.8  75% of Data was Below 15.3    
 1989) Krasner et al.,      Nationwide.                Effluent for 4 Quarters.                                      5.5   g/L DL = 0.6        
 1989b.                                                                                                                                                 
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                                                          
\2\May not be representative of national occurrence.                                                                                                    
\3\Range of medians for individual quarters.                                                                                                            
                                                                                                                                                        
AMWA: Association of Metropolitan Water Agencies.                                                                                                       
CDHS: California Department of Health Services.                                                                                                         
EPA: Environmental Protection Agency.                                                                                                                   

    No information is available concerning the occurrence of TCA in 
food and ambient or indoor air in the United States. The Food and Drug 
Administration (FDA) does not analyze for TCA in foods. However, there 
are several uses of chlorine in food production, such as the 
disinfection of chicken in poultry plants and the superchlorination of 
water at soda and beer bottling plants. Therefore, the possibility 
exists for dietary exposure from the by-products of chlorination in 
food products. Also, TCA has limited use as a herbicide. However, 
monitoring data are not available to characterize adequately the 
magnitude or frequency of potential TCA exposure from diet. Similarly, 
EPA's Office of Air and Radiation is not currently measuring for TCA in 
air (Borum, 1991). The exposure from air for TCA is probably not a 
large source since TCA is nonvolatile.
    Since only a limited number of food groups are expected to contain 
chlorinated chemicals and no significant TCA levels are expected in 
ambient or indoor air, EPA assumes that drinking water is the 
predominant source of TCA intake. Characterization of potential 
exposures from food and air are issues currently under review. EPA is, 
therefore, proposing to regulate TCA in drinking water with a relative 
source contribution (RSC) value at the ceiling level of 80 percent. EPA 
requests any additional data on known concentrations of TCA in drinking 
water, food, and air.
    Health Effects. The health effects information in this section is 
summarized from the Drinking Water Health Criteria Document for 
Chlorinated Acetic Acids, Alcohols, Aldehydes and Ketones (USEPA, 
1994e). Studies mentioned in this section are summarized in the 
criteria document.
    Estimates of acute and LD50 values for TCA range from 3.3 to 5 
g/kg in rats to 4.97 g/kg in mice. Short-term studies, up to 30 days, 
in rats demonstrate few effects other than decreased weight gain after 
administration of 240-312 mg/kg/day.
    Few studies on toxicokinetics of TCA were located; however, a human 
study and a dog study show TCA to respond pharmacokinetically similarly 
to DCA. The response indicates a rapid absorption, distribution to the 
liver and excretion primarily through the urine. The two studies 
indicate that TCA is readily absorbed from all sections of the 
intestine and that the urinary bladder may be significant in the 
absorption of TCA. TCA is also a major metabolite of trichloroethylene.
    Longer-term studies in animals indicate that TCA affects the liver, 
kidney and spleen by altering weights, focal hepatocellular 
enlargement, intracellular swelling, glycogen accumulation, focal 
necrosis, an accumulation of lipofuscin, and ultimately tumor 
generation in mice.
    In a study by Mather et al. (1990), male rats received TCA in their 
drinking water at 0, 4.1, 36.5 or 355 mg/kg/day. The high dose resulted 
in spleen weight reduction and increased relative liver and kidney 
weights. Hepatic peroxisomal -oxidation activity was 
increased. Liver effects at the high dose included focal hepatocellular 
enlargement, intracellular swelling and glycogen accumulation. The 
NOAEL for this study was 36.5 mg/kg/day.
    Parnell et al. (1988) exposed male rats to TCA in their drinking 
water at 2.89, 29.6 or 277 mg/kg/day for up to one year. No significant 
changes were detected in body weight, organ weight or histopathology 
over the study duration. This study identified a NOAEL as the highest 
dose tested, 277 mg/kg/day.
    Bull et al. (1990) investigated the effects of TCA on liver lesions 
and tumor induction in male and female B6C3F1 mice. Mice received 
TCA in their drinking water at 0, 1 or 2 g/L (164 or 329 mg/kg/day) for 
37 or 52 weeks. Dose-related increases in relative and absolute liver 
weights were seen in females and males exposed to 1 and 2 g/L for 52 
weeks. Small increases in liver cell size, accumulation of lipofuscin 
and focal necrosis were also seen. A LOAEL of 164 mg/kg/day (1 g/L) was 
identified.
    Several studies show that TCA can produce developmental 
malformations in fetal Long Evans rats, particularly in the 
cardiovascular system. Teratogenic effects were observed at the lowest 
dose tested, 330 mg/kg/day.
    With regard to mutagenicity tests, TCA was negative in Ames 
mutagenicity tests using Salmonella strain TA100, but was positive for 
bone marrow chromosomal aberrations and sperm abnormalities in mice. It 
also induced single-strand DNA breaks in rats and mice exposed by 
gavage.
    TCA has induced hepatocellular carcinomas in two tests with 
B6C3F1 mice, one of 52 weeks and another of 104 weeks. In the Bull 
et al. (1990) study, a dose-related increase in the incidence of 
hepatoproliferative lesions was observed in male B6C3F1 mice 
exposed to 1 or 2 g/L for 52 weeks. An increase in hepatocellular 
carcinomas was observed in males at both dose levels. Carcinomas were 
not found in females.
    DeAngelo et al. (1991) administered mice and rats with TCA over 
their lifetime. Male and female B6C3F1 mice were exposed to 4.5 g/
L TCA for 104 weeks. Male mice at 4.5 g/L TCA had a tumor prevalence of 
86.7%. Female mice appeared to be less sensitive to TCA than males: 60% 
prevalence over a 104-week exposure to 4.5 g/L. At 104 weeks, 0.5 g/L 
TCA did not result in a significant increase in tumors. In a 
preliminary study of 60 weeks exposure to 0.05, 0.5 and 5 g/L, no 
significant additional increase in tumors was seen at 0.05 g/L, but 
tumor prevalence was 37.9% and 55.2% at 0.5 and 5 g/L, respectively.
    F344 male rats administered TCA over a lifetime at 0.05 to 5 g/L 
did not produce a significant increase in carcinogenicity.
    EPA has placed TCA in Group C: possible human carcinogen. Group C 
is for those chemicals which show limited evidence of carcinogenicity 
in animals in the absence of human data.
    EPA is following a Category II approach for setting an MCLG for 
TCA. The developmental toxicity study by Smith et al. (1989) has been 
selected to serve as the basis for the RfD and MCLG. In this 
developmental study, pregnant Long-Evans rats (20/dose) were 
administered TCA at doses of 0, 330, 800, 1,200, or 1,800 mg/kg/d by 
gavage during gestation days 6-15. Maternal body weight was 
significantly reduced at doses of 800 mg/kg/d and above. Maternal 
spleen and kidney weights were increased significantly in a dose-
dependent manner. Postimplantation loss was noted in the three highest 
dose groups with a significant decrease in the number of live fetuses 
per litter observed in the two highest dose groups. Other fetal effects 
included decreased fetal weight and crown-rump length, and 
malformations of the cardiovascular system, particularly the heart. The 
lowest dose tested, 330 mg/kg/d, was identified as a LOAEL. A NOAEL was 
not identified from this study.
    An RfD of 0.1 mg/kg/day was derived using the LOAEL of 330 mg/kg/d 
and an uncertainty factor of 3,000 to account for use of a LOAEL and 
lack of a 2 generation reproductive study. Adjusting the RfD for a 70 
kg adult drinking 2 L water per day, possible carcinogenicity and an 
RSC of 80%, an MCLG of 0.3 mg/L can be determined.

TP29JY94.007

    EPA requests comments on the basis for the MCLG and the cancer 
classification for TCA.
11. Chloral Hydrate
    Chlorination of water containing organic materials (humic, fulvic 
acids) results in the generation of organic compounds such as 
trichloroacetaldehyde monohydrate or chloral hydrate (CH) (CAS No. 302-
17-0).
    CH is used as a hypnotic or sedative drug (i.e., knockout drops) in 
humans, including neonates. CH is also used in the manufacture of DDT.
    Occurrence and Human Exposure. CH has been found to occur as a 
disinfection by-product in public water systems that chlorinate water 
containing humic and fulvic acids.
    Table V-12 presents occurrence information available for chloral 
hydrate in drinking water. Descriptions of these surveys and other data 
are detailed in ``Occurrence Assessment for Disinfectants and 
Disinfection By-Products (Phase 6a) in Public Drinking Water,'' (USEPA, 
1992a). Median concentrations of chloral hydrate in drinking water were 
found to range from 2.1 to 4.4 g/L.

                                               TABLE V-12.--Summary of Occurrence Data for Chloral Hydrate                                              
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Occurrence of chloral hydrate in drinking water                                                    
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                       Concentration (g/L)                     
     Survey (Year)\1\               Location           Sample information (No.  ------------------------------------------------------------------------
                                                             of samples)             Range         Mean        Median                 Other             
--------------------------------------------------------------------------------------------------------------------------------------------------------
EPA, 1992b\2\ (1987-1989)  Disinfection By-Products   Finished Water:..........  <0.2-25                5.0          2.5  Positive Detections:          
                            Field Studies.            At the Plant (67)........  <0.2-30                7.8          4.4  90%                           
                                                      Distribution System......                                           91%                           
                                                      (53).....................                                                                         
EPA/AMWA/CDHS\2\ (1988-    35 Water Utilities         Samples from Clearwell     Max. 22        ...........   \3\1.7-3.0  75% of Data was below 4.1     
 1989) Krasner et al.,      Nationwide.                Effluent for 4 Quarters.                                      2.1   g/L\4\              
 1989b.                                                                                                                                                 
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                                                          
\2\May not be representative of national occurrence.                                                                                                    
\3\Range of medians for individual quarters.                                                                                                            
\4\Detection limit was 0.02 g/L in the first quarter and 0.1 g/L thereafter.                                                          
                                                                                                                                                        
AMWA: Association of Metropolitan Water Agencies.                                                                                                       
CDHS: California Department of Health Services.                                                                                                         
EPA: Environmental Protection Agency.                                                                                                                   

    Based on the available data sets, median exposures from CH due to 
drinking water would range from 3.4 to 8.8 g/day, based on the 
consumption of 2 liters per day.
    No information is available concerning the occurrence of CH in food 
and ambient or indoor air in the United States. The Food and Drug 
Administration (FDA) does not analyze for CH in foods since the 
analytical methods for such an evaluation have not been developed 
(Borum, 1991).
    CH has been used as a sedative of hypnotic drug (see Health Effects 
Section). There are several uses of chlorine in food production, such 
as the disinfection of chicken in poultry plants and the 
superchlorination of water at soda and beer bottling plants. Therefore, 
the possibility exists for dietary exposure from the by-products of 
chlorination in food products. However, monitoring data are not 
available to adequately characterize the magnitude or frequency of 
potential CH exposure from the diet. Similarly, EPA's Office of Air and 
Radiation is not currently measuring for CH in air (Borum, 1991). 
However, CH from indoor air may contribute to exposure due to the 
volatilization from tap water.
    Since only a limited number of food groups are expected to contain 
chlorinated chemicals and no significant levels are expected in ambient 
or indoor air, EPA believes that drinking water is the predominant 
source of CH intake. Characterization of potential food and air 
exposures are issues currently under review. EPA is therefore, 
proposing to regulate CH in drinking water with an RSC value at the 
ceiling level of 80 percent. EPA requests any additional data on known 
concentrations of CH in drinking water, food, and air.
    Health Effects. The health effects information in this section is 
summarized from the draft Drinking Water Health Criteria Document for 
Chlorinated Acetic Acids, Alcohols, Aldehydes and Ketones (USEPA, 
1994e). Studies mentioned in this section are summarized in the 
criteria document.
    In its use as a sedative or hypnotic drug in humans, a history of 
adverse effects related to CH exposure have been recorded. The acute 
and toxic dose to humans is about 10 g (or 140 mg/kg), causing severe 
respiratory depression and hypertension. Adverse reactions such as 
central nervous system depression and gastrointestinal disturbances are 
seen between 0.5 and 1.0 g CH. Cardiac arrhythmias are seen when 
patients receive levels between 10 and 20 g (167-333 mg/kg). Chronic 
use of CH may result in development of tolerance, physical dependence, 
and addiction.
    Estimates of acute oral LD50s in mice range from 1,265 to 
1,400 mg/kg with central nervous system depression and inhibition of 
respiration being the cause of death. Rats may be more sensitive than 
mice with acute oral LD50 values ranging from 285 mg/kg in newborn 
to 500 mg/kg in adults.
    Short-term studies in mice indicate that the liver is the target of 
CH toxicity with changes in liver weight as the primary effect. NOAELs 
vary between 14 and 144 mg/kg/day.
    Toxicokinetic studies of CH indicate that absorption is rapid and 
complete in dogs and humans. CH is metabolized to trichloroacetic acid 
(TCA) and trichloroethanol. CH is rapidly excreted primarily through 
the urine as trichloroethanol glucuronide and more slowly as TCA.
    Three 90-day studies in mice were considered by EPA to derive the 
MCLG for CH. Each used the same dose levels (16 or 160 mg/kg/day) in 
mice. The first study (Kallman et al., 1984) exposed groups of 12 male 
mice to drinking water containing CH at concentrations of 70 and 700 
mg/L for 90 days. These concentrations correspond to doses of 15.7 and 
160 mg/kg/day. No treatment-related effects were observed for 
mortality, body weight, physical appearance, behavior, locomotor 
activity, learning in repetitive tests of coordination, response to 
painful stimuli, strength, endurance or passive avoidance learning. 
Both doses resulted in a decrease of about 1 deg. in mean body 
temperature (p <0.05). The biological significance of this hypothermic 
effect is uncertain.
    In the second study, Sanders et al. (1982) supplied groups of 32 
male and female CD-1 mice with CH in deionized drinking water (70 or 
700 mg/L, corresponding to time-weighted average doses of approximately 
16 mg/kg/day or 160 mg/kg/day, respectively). After 90 days, the liver 
appeared to be the tissue most affected. Males appeared to be more 
sensitive than females. In males, there was a dose-related hepatomegaly 
and microsome proliferation, accompanied by small changes in serum 
chemistry values for potassium, cholesterol, and glutathione. Females 
did not show hepatomegaly, but did display changed hepatic microsomal 
parameters. Based on hepatomegaly, this study identifies a LOAEL of 16 
mg/kg/day for CH (the lowest dose tested).
    In the third study, Kauffman et al. (1982) studied the effect of CH 
on the immune system. Groups of 13 to 18 male and female CD-1 mice were 
supplied with water containing 70 or 700 mg/L (corresponding to time-
weighted average doses of approximately 16 or 160 mg/kg/day, 
respectively) for 90 days. In males, no effects were detected in either 
humoral or cell-mediated immunity at either dose level. In females, 
exposure to the high dose (160 mg/kg/day) resulted in decreased humoral 
immune function (p <0.05), but no effects on cell-mediated immunity 
were noted. Based on this study, a NOAEL of 16 mg/kg/day and a LOAEL of 
160 mg/kg/day were identified.
    CH is weakly mutagenic in Salmonella, yeast and molds. It has also 
caused chromosomal aberration in yeast and nondisjunction of 
chromosomes during spermatogenesis.
    One study has observed neurobehavioral effects on mice pups from 
female mice receiving CH at 205 mg/kg/day for three weeks prior to 
breeding. Exposure of females continued until pups were weaned at 21 
days of age. Pups from the high dose group (205 mg/kg/day) showed 
impaired retention in passive avoidance learning tasks. This result can 
be construed as a developmental effect of CH.
    Two studies on the carcinogenicity of CH indicate that CH produces 
mouse liver tumors. In the earlier study, Rijhsinghani et al. (1986), 
B6C3F1 mice given a single oral dose of CH at 5 or 10 mg/kg 
developed a significant increase in liver tumors after 92 weeks.
    In a later study, Daniel et al. (1992), reported that male mice, 
receiving 166 mg/kg/day CH for 104 weeks, showed a total liver tumor 
prevalence of 71 percent (17/24). Proliferative liver lesions 
recognized and tabulated in this study included hyperplastic nodules, 
hepatocellular adenomas and hepatocellular carcinomas. No other studies 
were located on the carcinogenicity of CH in other test species.
    Based on the limited evidence of carcinogenicity in these two 
studies and the extensive mutagenicity of CH, EPA has classified CH in 
Group C: possible human carcinogen. The concentrations associated with 
a 10-4, 10-5, and 10-6 excess cancer risk are 40 
g/L, 4 g/L and 0.4 g/L, respectively.
    EPA is placing CH in Category II for setting an MCLG based on liver 
toxicity and limited evidence of carcinogenicity from drinking water. 
EPA believes the 90-day study by Sanders et al. (1982) is most 
appropriate to calculate the RfD and MCLG for CH because the liver 
effects observed in this study (i.e., change to hepatic microsomal 
parameters and hepatomegaly) appear to be more severe than the other 
studies have indicated at similar dose levels. From the mouse LOAEL of 
16 mg/kg/day and an uncertainty factor of 10,000 for use of a LOAEL 
from a less than lifetime animal study, an MCLG of 0.04 mg/L is 
derived.

TP29JY94.008

    EPA is proposing to use an extra safety factor of 1 instead of 10 
to account for possible carcinogenicity since an uncertainty factor of 
10,000 has already been applied to the RfD. In addition, the proposed 
MCLG equals the 10-4 excess cancer risk. EPA requests comment on 
the Category II approach for setting an MCLG, the extra safety factor 
of 1 instead of 10 for a Category II contaminant, and whether the 
endpoint of liver weight increase and hepatomegaly is a LOAEL or NOAEL 
given the lack of histopathology.
12. Bromate
    Bromate (CAS #7789-38-0 as sodium salt) is a white crystal that is 
very soluble in water. Bromate may be formed by the reaction of bromine 
with sodium carbonate. Sodium bromate can be used with sodium bromide 
to extract gold from gold ores. Bromate is also used to clean boilers 
and in the oxidation of sulfur and vat dyes. It is formed in water 
following disinfection via ozonation of water containing bromide ion. 
In laboratory studies, the rate and extent of bromate formation depends 
on the ozone concentration used in disinfection, pH and contact time.
    Occurrence and Human Exposure. Bromide and organobromine compounds 
occur in raw waters from both natural and anthropogenic sources. 
Bromide can be oxidized to bromate or hypobromous acid; however, in the 
presence of excess ozone, bromate is the principal product.
    Table V-13 presents occurrence information available for bromate in 
drinking water. Descriptions of this data are detailed in ``Occurrence 
Assessment for Disinfectants and Disinfection By-Products (Phase 6a) in 
Public Drinking Water,'' (USEPA, 1992a__). Significant bromate 
concentrations may occur in ozonated water with bromide. More recent 
occurrence data on bromate and the influence of bromide concentration 
and ozone on bromate formation is discussed in Section VI of this 
preamble.

                                                   Table V-13.--Summary of Occurrence Data for Bromate                                                  
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Occurrence of bromate in drinking water                                                        
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                       Concentration (g/L)                     
     Survey (year)\1\               Location           Sample information (No.  ------------------------------------------------------------------------
                                                             of samples)             Range          Mean        Median                 Other            
--------------------------------------------------------------------------------------------------------------------------------------------------------
McGuire et al., 1990\2\..  MWD Pilot Plant Studies..  Ozonation: Hydrogen        Max. 60                                                                
                                                       Peroxide/Ozone.           Max. 90                                                                
EPA, 1992b\2\ (1987-1991)  Disinfection By-Products   Finished Water, Plants     <10            ...........  ...........  Detection                     
                            Field Studies.             Not Using Ozone (33).                                              Limit of 5 g/L       
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dates indicate period of sample collection.                                                                                                          
\2\May not be representative of national occurrence.                                                                                                    
                                                                                                                                                        
EPA: Environmental Protection Agency.                                                                                                                   

    Although bromate is used as a maturing agent in malted beverages, 
as a dough conditioner, and in confectionery products (Borum, 1991), 
monitoring data are not available to adequately characterize the 
magnitude or frequency of potential bromate exposure from the diet. 
Currently, the Food and Drug Administration does not have available 
data for bromate in foods, as bromate is not a part of their Total Diet 
Study program. Similarly, EPA's Office of Air and Radiation is not 
currently measuring for bromate in air (Borum 1991).
    Since only a limited number of food groups are expected to contain 
bromate and no significant bromate levels are expected in ambient or 
indoor air, EPA believes that drinking water is the predominant source 
of intake for bromate, and contributions from air and food would be 
small. Characterization of potential exposures from food and air are 
issues currently under review. EPA requests any additional data on 
known concentrations of bromate in drinking water, food, and air.
    Health Effects. The health effects information in this section is 
summarized from the Drinking Water Health Quantification of 
Toxicological Effects Document for Bromate (USEPA, 1993b). Studies 
mentioned in this section are summarized in the criteria document.
    The noncancer effects of ingested bromate have not been well 
studied. Bromate is rapidly absorbed, in part unchanged, from the 
gastrointestinal tract following ingestion. It is distributed 
throughout the body, appearing in plasma and urine as bromate and in 
other tissues as bromide. Following exposure to bromate, bromide 
concentrations were significantly increased in kidney, pancreas, 
stomach, small intestine, red blood cells and plasma. Bromate is 
reduced in tissues probably by glutathione or by other sulfhydryl-
containing compounds. Excretion occurs via urine and to a lesser extent 
feces.
    Acute oral LD50 values range from 222 to 360 mg bromate/kg for 
mice and 500 mg/kg for rats. Acute symptoms of toxicity include 
decreased locomotion and ataxia, tachypnea, hypothermia, hyperemia of 
the stomach mucosa, kidney damage and lung congestion. In subchronic 
drinking water studies, decreased body weight gain and marked kidney 
damage were observed in treated rodents. These effects were observed at 
the lowest doses tested (30 mg/kg/d).
    Bromate was positive in a rat bone marrow assay to determine 
chromosomal aberrations. Positive findings for bromate were also 
reported in a mouse micronucleus assay. Bromate has also been found to 
be carcinogenic to rodents following long-term oral administration. In 
these studies, an increased incidence in kidney tumors was reported for 
male and female rats. Other tumors observed include thyroid follicular 
cell tumor and peritoneal mesothelioma. No carcinogenic effects have 
been seen in mice. Dose and time studies indicate that the minimum 
exposure time to produce tumors in rats is 13 weeks.
    The available data are considered insufficient to calculate an RfD. 
Only one noncarcinogenic toxicity study (Nakano et al., 1989) was 
located in the literature. The study failed to provide dose response 
data and did not identify a NOAEL. Histopathological lesions in kidney 
tubules that coincided with decreased renal function were noted in rats 
exposed to 30 mg bromate/kg/d for 15 months. The available 
carcinogenicity studies also do not provide sufficient information on 
non-cancer related effects to determine an RfD.
    In a cancer bioassay, Kurokawa et al. (1986a) supplied groups of 50 
male and 50 female F344 rats (4-6 weeks old) with drinking water 
containing 0, 250 or 500 mg/L (the maximum tolerated dose) of potassium 
bromate (KBrO3). The high dose (500 mg/L) caused a marked 
inhibition of weight gain in males, and so at week 60 this dose was 
reduced to 400 mg/L. Exposure was continued through week 110. The 
authors stated the average doses for low dose and high dose groups were 
12.5 or 27.5 mg KBrO3/kg/day in males (equivalent to 9.6 and 21.3 
mg BrO3/kg/day) and 12.5 or 25.5 mg KBrO3 in females 
(equivalent to 9.6 and 21.3 mg BrO3). The incidence of renal 
tumors in the three groups (control, low dose, high dose) was 6%, 60% 
and 88% in males and 0%, 56% and 80% in females. The effects were 
statistically significant (p <0.001) in all exposed groups. The 
incidence of peritoneal mesotheliomas in males at three doses was 11% 
(control), 33% (250 mg/L, p <0.05) AND 59% (500 mg/L, p <0.001). The 
authors concluded that KBrO3 was carcinogenic in rats of both 
sexes.
    In a subsequent study, Kurokawa et al. (1986b) supplied F344 rats 
with water containing KBrO3 at 0, 154, 30, 60, 125, 250 or 500 mg/
L for 104 weeks. The authors reported that these exposures resulted in 
average doses of 0, 0.9, 1.7, 3.3, 7.3, 16.0 or 43.4 mg/kg/day of 
KBrO3, equivalent to doses of 0, 0.7, 1.3, 2.5, 5.6, 12 or 33.4 
mg/kg/day of BrO3. The incidence of renal cell tumors in these 
dose groups was 0%, 0%, 4%, 21% (p <0.05), 50% (p <0.001), 95% (p 
<0.001) and 95% (p <0.001). Using the linearized multistage model, 
estimates of cancer risks were derived. Combining incidence of renal 
adenomas and adenocarcinomas in rats, and a daily water consumption for 
an adult, lifetime risks of 10-4, 105 and 106 are 
associated with bromate concentrations in water at 5, 0.5 and 0.05 
g/L, respectively. Equivalent concentrations in terms of 
KBrO3, lifetime risks would be 7, 0.7 and 0.07 g/L, 
respectively.
    The International Agency for Research on Cancer placed bromate in 
Group 2B, for agents that are probably carcinogenic to humans. EPA has 
performed a cancer weight of evidence evaluation, and has placed 
bromate in Group B2: probable human carcinogen since bromate has been 
shown to produce several types of tumors in both sexes of rats 
following drinking water exposures. In addition, positive mutagenicity 
studies which have been reported include indications of DNA 
interactions with bromate. As a result of bromate formation following 
disinfection, particularly with ozone, there is a potential for 
considerable exposure in drinking water. Thus, EPA is proposing an MCLG 
based on carcinogenicity and a Category I approach. The resulting MCLG 
is zero.
    EPA is also interested in examining the mechanism of toxicity of 
bromate in rats in terms of whether renal tumor formation is due to 
direct action of bromate or indirectly through formation of specific 
adduct in kidney DNA of rats treated with bromate.
    EPA requests comment on the MCLG of zero based on carcinogenic 
weight of evidence and the mechanism of action for carcinogenicity 
related to DNA adduct.

VI. Occurrence of TTHMs, HAA5, and other DBPs

A. Relationship of TTHMs, HAA5 to Disinfection and Source Water Quality

1. Primary and Residual Disinfectant Use Patterns in U.S. and 
Relationship to Formation of DBPs
    A survey of 727 utilities nationwide was conducted for the American 
Water Works Association Research Foundation (AWWARF) in 1987 to 
determine the extent and cost of compliance with the 1979 maximum 
contaminant level (MCL) for trihalomethanes (THMs) (McGuire et al., 
1988). The AWWARF survey reflected more than 67 percent of the 
population represented by water utilities serving more than 10,000 
customers. The survey found that chlorine remained the most common 
disinfectant among water utilities. At the time of the survey, chlorine 
was used by 85 percent of the flowing stream and lake surface water 
systems and by 80 percent of the ground water systems. The median 
chlorine dose for flowing stream and lake systems was 2.2-2.3 mg/L and 
for ground water systems it was 1.2 mg/L. The range of chlorine doses 
was 0.1 to >20 mg/L.
    Chloramines were used by 25 percent of the flowing stream systems 
and larger lake systems, but by only 13 percent of the smaller lake 
systems. Chloramines were rarely used by ground water systems reporting 
in the AWWARF THM survey. Typical chloramine doses for flowing stream 
systems was 2.7 mg/L, compared with 1.5 mg/L for lake systems. In 
addition, 10 percent of the flowing stream systems and 5 percent of the 
lake systems reported using chlorine dioxide. The latter systems 
typically served more than 25,000 customers. The typical chlorine 
dioxide doses ranged from 0.6 mg/L for the flowing stream systems to 
1.0 mg/L for the lake systems. No ground water systems reported using 
this disinfectant. At the time of this survey, three utilities reported 
using ozone.
    The AWWA Disinfection Committee also performed nationwide surveys 
on disinfectant use in 1978 (AWWA Disinfection Committee, 1983) and 
1990 (AWWA Water Quality Division Disinfection Committee, 1992), 
principally among systems serving >10,000 persons (<3 percent of the 
surveyed systems served 10,000 persons or fewer). Chlorine has 
historically been applied early in the water treatment process 
(precoagulation) in order to utilize the benefit of chlorine as a 
disinfectant and an oxidant and to control biological growths in 
basins. In the 1978 survey, the vast majority (>85 percent) of those 
who relied on surface waters prechlorinated (AWWA Disinfection 
Committee, 1983). The 1990 survey found a significant reduction in the 
frequency of chlorine addition prior to coagulation, along with an 
increase in chlorine application after sedimentation (AWWA Water 
Quality Division Disinfection Committee, 1992). The AWWARF THM survey 
had found that 150 systems surveyed had changed the point of 
disinfection to comply with the 0.10-mg/L THM MCL (McGuire et al., 
1988). However, the 1990 AWWA survey (AWWA Water Quality Division 
Disinfection Committee, 1992) still found that 35 percent of the 
utilities reported chlorination before coagulation or sedimentation. 
The range and median chlorine doses in the 1990 AWWA survey were 
similar to the AWWARF THM survey.
    In the 1990 AWWA survey, disinfection modifications to reduce THMs 
included (1) changes in prechlorination practices (24 percent of 
respondents moved the first point of chlorination, 23 percent ceased 
prechlorination, while 20 percent decreased the prechlorination dose), 
(2) implementation of ammonia addition (19 percent added ammonia after 
some free chlorine time, while nine percent added ammonia before 
chlorination), (3) or changed preoxidant (10 percent switched to 
potassium permanganate, five percent to chlorine dioxide, and 0.5 
percent to ozone). A surprisingly large percentage of utilities 
reported operational problems with disinfection modifications used for 
THM reduction (e.g., 56 percent of utilities that implemented 
postammoniation reported such problems; as well as 44, 36, and 28 
percent of those who moved the first point of chlorination downstream, 
ceased prechlorination, and decreased the prechlorination dose, 
respectively). Neither the exact nature of the problems noted, nor 
their duration, were defined in the survey. However, the Disinfection 
Committee believed that many of the reported problems were probably 
transitional and were alleviated after further experience.
    The 1990 AWWA survey (Haas et al., 1990) found that disinfection 
modifications for THM minimization differed between ground and surface 
water utilities. For example, 13 percent of surface water systems 
changed their preoxidation practices, while this option was rarely used 
by ground water systems (which rarely preoxidize). Sixteen and 25 
percent of surface and ground water utilities, respectively, reported 
adding ammonia after some free chlorine contact as their modification 
strategy to reduce THMs. Because 65 percent of the surveyed ground 
waters had a THM formation potential (THMFP) (a worst-case measure of 
the possible THM production rather than the amount actually produced in 
the distribution system) of <100 g/l, most ground water 
systems probably did not require modifications to meet the 1979 TTHM 
rule.
    AWWA established a Water Industry Data Base (WIDB) in 1990-91 (AWWA 
Water Industry Data Base, 1991). The WIDB contains information from 
about 500 utilities supplying water to more than 50,000 people and over 
800 utilities supplying between 10,000 and 50,000 people. The utilities 
in the WIDB represent a combined population of 209 million people. In 
addition, a database for the Disinfectants/Disinfection By-Products (D/
DBP) negotiated regulation (``reg neg'' data base, RNDB) (JAMES M. 
MONTGOMERY, CONSULTING ENGINEERS, INC., 1992) was developed for AWWA. 
The RNDB comprises data on nationwide and regional DBP studies, 
including data on individual THMs and haloacetic acids (HAAs), chloral 
hydrate, and bromate, performed by EPA, water utilities, universities, 
and engineering consultants, as well as total THM (TTHM) data from the 
WIDB. The non-WIDB part of the RNDB (i.e., those studies on individual 
DBP occurrence and control) includes 166 utilities serving a combined 
population of about 72 million people. The majority of systems in the 
non-WIDB data occurrence part of the RNDB are also in the WIDB. Thus, 
the former data base represents a subset of the latter data base, in 
which specialized DBP studies were conducted. In addition, many of 
these studies attempted to select utilities that were representative of 
source water quality, treatment plant operations, disinfectant use, 
population served, and geographical locations throughout the United 
States (Krasner et al., 1989). Furthermore, the RNDB includes data on 
48 utilities (serving a combined population of 37 million people) which 
have evaluated alternative treatments to comply with future DBP 
regulations.
    Figure VI-1 shows a comparison of disinfectant/oxidant uses 
reported in the WIDB and the non-WIDB part of the RNDB. In general, the 
current usage of disinfectants/oxidants in both data bases are 
comparable, which indicates that the non-WIDB part of the RNDB is 
representative of nationwide disinfectant usage. Figure VI-2 shows 
disinfectants evaluated under alternative treatments in the RNDB. While 
ozone is the most prevalent alternative disinfectant under 
investigation in the RNDB, this data base is somewhat biased, as it 
does include two AWWARF studies involving ozonation. However, Figure 
VI-2 does demonstrate that ozone is an alternate disinfectant that is 
being widely evaluated. While most systems currently use chlorine only, 
the percentage drops when the data are population based. Figure VI-1 
shows that chloramine use is higher on a population basis, probably due 
to its usage by some of the larger utilities.

BILLING CODE 6560-50-P

TP29JY94.011


TP29JY94.012

BILLING CODE 6560-50-C
2. National Occurrence of TOC
    The total organic carbon (TOC) level of a water is generally a good 
indication of the amount of THM and other DBP precursors present in a 
water (Singer et al., 1989). In the WIDB, 157 utilities provided TOC 
data. For the 100 surface waters with TOC data, the range was ``not 
detected'' (ND) to 30 mg/L. For these waters, the 25th, 50th, and 75th 
percentiles were 2.6, 4.0, and 6.0 mg/L, respectively. For the 57 
ground waters with TOC data, the range was ND to 15 mg/L. For these 
waters, the 25th, 50th, and 75th percentiles were ND, 0.8, and 1.9 mg/
L, respectively. Typically, most ground waters are low in TOC. However, 
there are some high-TOC ground waters, especially in the southeastern 
part of the United States (EPA Region IV; see Figure VI-3 and Table VI-
1). For surface waters, the high-TOC waters also tend to be in the 
southeastern part of the United States, although there are some 
relatively high-TOC waters in the south central (EPA Region VI) and the 
mountain (EPA Region VIII) states (see Figure VI-3 and Table VI-2).

BILLING CODE 6560-50-P

TP29JY94.013


BILLING CODE 6560-50-C

 Table VI-1.--Statistics on Average Raw Groundwater Total Organic Carbon (mg/L) for Utilities in the AWWA Water 
                                               Industry Database                                                
----------------------------------------------------------------------------------------------------------------
                                Number of                                              Percentile               
                 Number of      utilities                              -----------------------------------------
 EPA region      utilities    with missing   Min value     Max value                                            
                 with data        data                                      25th          50th          75th    
----------------------------------------------------------------------------------------------------------------
1............             2             48            ND          1.38  ............  ............  ............
2............             3             72            ND          1.91  ............  ............  ............
3............             3             96  ............  ............  ............          2.74  ............
4............            13            163            ND         15.00            ND          2.19          8.50
5............            11            182            ND          4.00          0.63          1.45          1.92
6............             4             82            ND          1.87  ............  ............  ............
7............             5             53            ND          1.40  ............  ............  ............
8............             4             46          0.71          2.00  ............  ............  ............
9............            11            118            ND          1.00            ND            ND          0.30
10...........             1             37          0.80          0.80  ............  ............  ............
ALL..........            57            897            ND         15.00            ND          0.84          1.88
----------------------------------------------------------------------------------------------------------------


Table VI-2.--Statistics on Average Raw Surface Water Total Organic Carbon (mg/L) for Utilities in the AWWA Water
                                               Industry Database                                                
----------------------------------------------------------------------------------------------------------------
                                Number of                                              Percentile               
                 Number of      utilities                              -----------------------------------------
 EPA region      utilities    with missing   Min value     Max value                                            
                 with data        data                                      25th          50th          75th    
----------------------------------------------------------------------------------------------------------------
1............             6             44          3.00          9.00          3.48          3.50          4.50
2............            10             65          2.10         20.00          2.50          4.55          5.00
3............            20             79            ND         25.00          2.15          2.87          4.80
4............            11            165          1.60         30.00          5.27          7.40         12.60
5............            14            179            ND          9.17          2.70          4.50          5.90
6............            10             76          2.00         10.00          3.90          5.50          6.90
7............             2             56          7.00         10.00  ............  ............  ............
8............             7             43          1.00         14.00          1.75          3.30          8.50
9............            16            113            ND          5.90          1.95          3.25          3.88
10...........             4             34          1.25          3.30  ............  ............  ............
ALL..........           100            854            ND         30.00          2.55          4.00          5.95
----------------------------------------------------------------------------------------------------------------

    For surface waters that filter but do not soften, the median and 
90th percentile TOC levels are 3.7 and 7.5 mg/L, respectively (see 
Figure VI-4). However, when the data are flow-weighted (which would 
represent more closely the distribution by population), the median and 
90th percentile values drop to 2.7 and 5.1 mg/L, respectively (see 
Figure VI-4). This is due, in part, to a number of large facilities 
treating water with TOC levels <4 mg/L. When this same category of 
surface waters is examined for choice of disinfectants between chlorine 
and chloramines, the latter group has a higher TOC cumulative 
probability than the former (see Figure VI-5). Switching from free 
chlorine only to chloramination was one of the options utilized by 
utilities with high-TOC waters to comply with the 0.10 mg/L TTHM MCL.

BILLING CODE 6560-50-P

TP29JY94.014


TP29JY94.015


BILLING CODE 6560-50-C
    As part of a ground water supply survey (GWSS), TOC was measured at 
the point of entry into the distribution system (see Figure VI-6). 
Because most groundwater systems do not have precursor-removal 
technology as part of their treatment, these treated-water TOC levels 
provide a good indication of the range of raw-water TOC levels in 
ground waters. The median and 90th percentile TOC levels of systems 
without softening who chlorinate were 0.7 and 2.9 mg/L, respectively. 
However, the median and 90th percentile TOC levels of systems with 
softening who chlorinate were 1.7 and 6.8 mg/L, respectively.

BILLING CODE 6560-50-P

TP29JY94.016

    In addition, the breakdown of treated-water TOC levels of ground 
waters was examined geographically (see Table VI-3). As indicated above 
(see Table VI-1), the southeastern part of the United States (i.e., EPA 
Region 4) has groundwaters with a relatively higher level of TOC (see 
Tables VI-3A and VI-3C). In addition, the mountain states (i.e., EPA 
Region 8) also tended to have a higher distribution of TOCs in the 
ground waters tested (see Tables VI-3A and VI-3C). Furthermore, these 
data are also broken down into those that chlorinate and those that do 
not (see Table VI-3). Typically, ground waters that are currently 
undisinfected tend to be ones with lower TOC levels. Thus, promulgation 
of the Ground Water Disinfection Rule will probably tend to have an 
impact on waters with a lower precursor level than are currently 
disinfecting. 

                            Table VI-3A.--TOC Values for GWSS Systems That Chlorinate                           
----------------------------------------------------------------------------------------------------------------
                                Number of                                       Percentile                      
         EPA region             utilities    Max value   -------------------------------------------------------
                                with data                     25th          60th          75th          90th    
----------------------------------------------------------------------------------------------------------------
1............................           19        4.3           0.4           0.5           0.95          2.3   
2............................           59        4.6           0.3           0.5           0.9           1.5   
3............................           62        4.2           0.3           0.5           0.7           1.2   
4............................          185       14             0.8           0.7           2.1           5.3   
5............................           90        8.9           0.7           1.1           1.8           2.6   
6............................           46        8             0.6           1             1.7           2.4   
7............................          103        7.8           0.8           0.8           1.8           3.7   
8............................           26       11             0.6           1.9           3.1           6.6   
9............................           39       11            <2             0.2           0.5           1.2   
10...........................           25        3.3           0.3           0.9           1.4           2.2   
                                                                                                                
ALL..........................          654       14             0.3           0.7           1.7           3.3   
----------------------------------------------------------------------------------------------------------------


                        Table VI-3B.--TOC Values for GWSS Systems That Do Not Chlorinate                        
----------------------------------------------------------------------------------------------------------------
                                Number of                                       Percentile                      
         EPA region             utilities    Max value   -------------------------------------------------------
                                with data                     25th          50th          75th          90th    
----------------------------------------------------------------------------------------------------------------
1............................           27        3.6           0.3           0.5           0.8           1.3   
2............................           14        0.8          <2             0.3           0.5           0.6   
3............................           28        5.3          <2             0.3           0.6           1.5   
4............................           34        3.2           0.3           0.5           0.8           1.7   
5............................           41       18             0.7           1.3           2.2           3.4   
6............................           26        5.6           0.2           0.6           1.5           2.9   
7............................           18        2.9           0.6           0.9           1.1           2.2   
8............................           14        5.9           0.3           0.4           1.8           2.7   
9............................           49        3.4          <2             0.3           0.4           0.9   
10...........................           40        5             0.2           0.4           0.8           2     
                                                                                                                
ALL..........................          291       18             0.3           0.5           1.1           2.2   
----------------------------------------------------------------------------------------------------------------


                                  Table VI-3C.--TOC Values for all GWSS Systems                                 
----------------------------------------------------------------------------------------------------------------
                                Number of                                       Percentile                      
         EPA region             utilities    Max value   -------------------------------------------------------
                                with data                     25th          50th          75th          90th    
----------------------------------------------------------------------------------------------------------------
1............................           46        4.3           0.3           0.5           0.8           1.6   
2............................           73        4.6           0.3           0.5           0.8           1.3   
3............................           90        5.3           0.3           0.4           0.7           1.2   
4............................          219       14             0.3           0.7           1.9           4.8   
5............................          131       18             0.7           1.2           1.9           3.2   
6............................           72        8             0.4           0.9           1.7           2.4   
7............................          121        7.8           0.4           0.9           1.7           3.2   
8............................           40       11             0.3           1.8           2.7           5.9   
9............................           88       11            <2             0.2           0.5           1     
10...........................           65        5             0.2           0.5           1.2           2.2   
                              ----------------------------------------------------------------------------------
ALL..........................          945       18             0.3           0.6           1.4           2.9   
----------------------------------------------------------------------------------------------------------------

3. National Occurrence of Bromide
    Bromide is a concern in both chlorinated and ozonated supplies. In 
chlorinated supplies, while the organic precursor level of a source 
water has an impact on the amount of DBPs formed, the bromide 
concentration has an impact on the speciation as well as the overall 
yield (Symons et al., 1993). Typically, regardless of the organic 
content in water, bromate can be formed when waters containing 
sufficient levels of bromide are ozonated (Krasner et al., Jan. 1993).
    In a 35-utility nationwide DBP study, bromide ranged from <0.01 to 
3.0 mg/L and the median bromide level was 0.1 mg/L (Krasner et al., 
1989). Some utilities have bromide in their source water due to 
saltwater intrusion (one utility had as much as 0.4 to 0.8 mg/L bromide 
due to this phenomenon) (Krasner et al., 1989). However, some non-
coastal communities can have moderate-to-high levels of bromide due to 
connate waters (ancient seawater that was trapped in sedimentary 
deposits at the time of geological formation) or industrial and oil-
field brine discharges. The highest bromide detected in the latter 
study (2.8-3.0 mg/L) (Krasner et al., 1989) was from a water in the 
midsouthern part of the U.S.
    Currently, a nationwide bromide survey of 70 utilities has found 
bromide levels ranging from <0.005 to >3.0 mg/L (Amy et al., 1992-3). 
Some waters have been sampled more than once (up to three seasonal 
samples to date) in order to determine the variability in bromide 
occurrence. The average raw-water bromide level per water, though, 
provides an indication of the typical occurrence of bromide in each 
water. Table VI-4 provides some preliminary insight into the 
geographical occurrence of bromide. Ideally, more data per region are 
needed; however, sufficient data are available for general trends. 
Regions 6 (which includes Texas) and 9 (which includes California) have 
the highest occurrence of bromide. While some California communities 
have problems with saltwater intrusion, some Texas communities may have 
bromide from connate waters or oil-field brines. However, most 
geographical regions have at least one high-bromide water in their 
area, except for the systems surveyed in the Pacific Northwest (EPA 
Region 10) and the northeast (EPA Regions 1 and 2).

   Table VI-4.--Statistics on Average Raw-Water Bromide (mg/L) for Utilities in the Nationwide Bromide Survey   
----------------------------------------------------------------------------------------------------------------
                           Number of                                              Percentile                    
       EPA region          utilities  Min value   Max value  ---------------------------------------------------
                          with data                               25th         50th         75th        90th    
----------------------------------------------------------------------------------------------------------------
1.......................           8       0.005       0.089        0.02         0.03         0.05         0.05 
2.......................           4       0.023       0.093        0.03         0.05         0.08        NA    
3.......................           8       0.005       0.276        0.03         0.06         0.07         0.08 
4.......................           7       0.010       0.190        0.02         0.04         0.05         0.05 
5.......................           6       0.012       0.322        0.05         0.09         0.12         0.14 
6.......................           7       0.014       >3.00        0.02         0.03         0.25         0.37 
7.......................           6       0.042       0.206        0.06         0.08         0.09         0.10 
8.......................           7       0.006       0.368        0.02         0.02         0.06         0.09 
9.......................          11       0.008       0.429        0.05         0.08         0.33         0.36 
10......................           6      <0.005       0.015       <0.005        0.006        0.009        0.012 
----------------------------------------------------------------------------------------------------------------
NA=Not applicable; insufficient number of utilities to determine.                                               

    Figures VI-7 and VI-8 show the cumulative probability distribution 
of average raw-water bromide levels in surface and ground waters, 
respectively, in the nationwide bromide survey. In surface waters in 
this survey, the median, 75th, 90th, and 95th percentile bromide level 
were 0.04, 0.08, 0.2, and 0.35 mg/L, respectively. In ground waters in 
this survey, the median, 75th, 90th, and 95th percentile bromide level 
were 0.06, 0.1, 0.25, and 0.35 mg/L, respectively. Overall, ground 
waters appear to have a somewhat higher probability of bromide 
occurrence than in surface waters. In the 35-utility DBP study, one 
midwest utility pumped ground water into a lake to augment a low-lake 
level during a drought period. Bromide rose from 0.19 to 0.68 mg/L 
during this period of time.

BILLING CODE 6560-50-P

TP29JY94.017


TP29JY94.018


BILLING CODE 6560-50-C

B. Chlorination Byproducts

1. TTHMs--Occurrence Studies
    Prior to the promulgation of an MCL of 0.10 mg/L TTHMs in 1979, EPA 
performed two surveys to obtain information on the occurrence of THMs 
and other organic compounds: the National Organics Reconnaissance 
Survey (NORS) in 1975 (Symons et al., 1975) and the National Organic 
Monitoring Survey (NOMS) in 1976-77 (Brass et al., 1977 and The 
National Organics Monitoring Survey, unpubl.). NORS and NOMS were 
conducted primarily to determine the extent of THM occurrence in the 
United States. These data were used, in part, in determining the 1979 
THM regulation. Surveys in the 1980s were performed to provide data for 
assessing a new MCL for THMs, as well as to develop regulations for 
other DBPs.
    The AWWARF THM survey used data from 1984-86, and these THM values 
reflected the result of compliance with the 1979 THM regulation. Mean 
TTHM values were computed for each of the utilities in the AWWARF THM 
survey; these means, as well as data from the NORS and NOMS surveys, 
are plotted (see Figure VI-9) on a frequency distribution curve. The 
AWWARF survey's overall TTHM average was 42 g/L, which was a 
40-50 percent reduction in national THM concentrations as compared to 
the averages of the NORS and NOMS (all phases) results. It is important 
to note that the disinfection practices of some of the utilities in the 
AWWARF survey (such as the use of chloramines as a primary 
disinfectant) were employed to meet the 1979 TTHM MCL, and not to meet 
the requirements of the recently promulgated Surface Water Treatment 
Rule (SWTR). Thus, THM and DBP levels at some utilities would most 
likely be different if their current treatment practices required 
modification in order to meet the new disinfection requirements of the 
SWTR.

BILLING CODE 6560-50-P

TP29JY94.019


BILLING CODE 6560-50-C
    Median TTHM concentrations in the AWWARF survey for the spring, 
summer, fall, and winter seasons were 40, 44, 36, and 30 g/L, 
respectively. THM levels were highest in the summer and lowest in the 
winter, due primarily to the faster formation rates in warmer water 
temperatures. In the 35-utility DBP study, the second highest THM 
levels were in the fall (Krasner et al., 1989). For many utilities in 
California and the southern United States, fall can be almost as warm 
as summer. However, seasonal impacts may be due to changes in the 
nature of naturally occurring organics or bromide levels as well. 
Compliance with the THM regulation is based on a running annual average 
to reflect these types of seasonal variations.
    Because the 1979 regulation did not apply to systems that serve 
<10,000 people, the running annual average TTHM distribution for small 
systems is expected to be different. In the AWWARF THM survey, TTHM 
data for small systems from 12 states were obtained (McGuire et al., 
1988). While the number of utilities (677) for which TTHM data were 
received represents only a small percentage of the total number serving 
fewer than 10,000 customers (55,449), some important observations can 
be made. The range of TTHMs was from ND to 313 g/L, with a 
mean of 36 g/L and a median of 18 g/L (McGuire et 
al., 1988). The cumulative probability distribution differs 
significantly from the NORS and NOMS data (see Figure VI-10). This lack 
of agreement is probably due to many of the small systems using ground 
water sources, which are generally much lower in THM precursors than 
surface water sources. In addition, the overall statistics of the 
AWWARF survey (for 677 cities) were markedly affected by the low TTHM 
results (range of ND to 42 g/L with a mean of 2 g/L) 
of the 204 systems sampled in Wisconsin. Although McGuire does not 
identify a reason for low TTHMs in Wisconsin, EPA data indicate that 
over 90 percent of Wisconsin systems use ground water (probably with 
low precursor levels) as a primary source. Since 30 percent of the 
systems in the survey were from Wisconsin, this would bias the results.

BILLING CODE 6560-50-P

TP29JY94.020


BILLING CODE 6560-50-C
    Since the AWWARF THM survey, EPA measured DBP data in a number of 
small systems. These data represent part of the non-WIDB data in the 
RNDB. Figure VI-11 compares the TTHM frequency distribution for the 
WIDB (large systems only) with that of the non-WIDB data on both large 
and small systems. For the small systems, there is essentially a 
biomodal distribution of TTHM levels: 50 percent of the small systems 
have 10 g/L TTHMs, while the remaining utilities 
have TTHM levels of 20 to 430 g/L. Most likely, many of the 
very low THM levels are associated with treatment of low-TOC, low-
bromide ground waters. For community water, non-purchased systems 
serving <10,000 people, 4562 systems treat surface water, while 17941 
disinfect ground water. For systems serving >10,000 people, 1395 treat 
surface water and 1117 disinfect ground water. Thus, small systems are 
utilizing ground water more than surface water.

BILLING CODE 6560-50-P

TP29JY94.021


BILLING CODE 6560-50-C
    In the WIDB (which only includes large systems), 482 utilities that 
treat surface water or a mix of surface and ground waters had TTHM 
median, 75th, and 90th percentile values of 43, 59, and 74 g/
L, respectively. In the WIDB, 277 utilities that treat ground water 
only had TTHM median, 75th, and 90th percentile values of 13, 34, and 
60 g/L, respectively. However, systems using both types of 
source waters had TTHM levels in the neighborhood of 100 g/L. 
Thus, while ground waters in general tend to form less THMs than 
surface waters, there are some ground waters with sufficient precursor 
levels to form significant amounts of THMs.
2. HAAs and Other Chlorination DBPs--Occurrence Studies
    a. Discovery of Additional Chlorination By-Products. In 1985, EPA 
determined chlorination DBPs at 10 operating utilities, using both 
target-compound and broad-screen analyses (Stevens et al., 1989). A 
total of 196 compounds that can be attributed to the chlorination 
process were found in one or more of the 10 utilities' finished waters. 
Approximately half of the compounds contained chlorine and many were 
structurally identified; however, 128 compounds were of unknown 
chemical structure. The compounds which were quantifiable represented 
from 30 to 60 percent of the total organic halide (TOX) of those 
supplies. That study served to significantly reduce the list of 
compounds that EPA considered most significant for further work.
    b. Available Data on Chlorination By-Products. Taken as an example 
of subsequent survey results where quantifiable target-compound 
analyses were used, Figure VI-12 shows the occurrence of DBPs in the 
35-utility study (Metropolitan Water District of So. Calif et al., 
1989). The figure presents an overview of the results of four seasonal 
sampling quarters combined. In addition, all sampling was performed at 
treatment-plant clearwell effluents. It is important to note that these 
survey results do not reflect any impacts of the SWTR under which a 
substantial number of systems could be expected to modify disinfection 
practice to achieve compliance. On a weight basis, THMs were the 
largest class of DBPs detected in this study; the second largest 
fraction was haloacetic acids (HAAs). At the time of this study, 
commercial standards were only available for five of the nine 
theoretical species: monochloro-, dichloro-, trichloro-, monobromo-, 
and dibromoacetic acid. The data indicate that the median level of THMs 
(i.e., 36 g/L) was approximately twice that of HAAs (i.e., 17 
g/L). The third largest fraction was the aldehydes (i.e., 
formaldehyde and acetaldehyde). These two low-molecular-weight 
aldehydes were initially discovered as by-products of ozonation, but 
they also appear to be by-products of chlorination. Every target-
compound DBP was detected at some time in some utility's water during 
the study; however, 2,4,6-trichlorophenol was only detected at low 
levels at a few utilities during the first sampling quarter and was not 
detected in subsequent samplings.

BILLING CODE 6560-50-P

TP29JY94.022


BILLING CODE 6560-50-C
    The 35-utility DBP study assessed systems using a range of 
disinfectants, a number of which used chloramines as a residual 
disinfectant. In a study (in 1987-89) by EPA, primarily chlorine-only 
systems were evaluated at the plant and in the distribution system 
(typically a terminal location). The range of total HAAs (THAAs) (a sum 
of the five aforementioned species) at the plant effluent was <1 to 86 
g/L (representing 73 samples), with a median value of 28 
g/L (Fair, 1992). In the distribution system (56 samples 
collected), the range and median THAAs were <1-136 and 35 g/L, 
respectively.
    In a six-utility DBP survey in North Carolina (Grenier et al., 
1992), the sum of four measured HAAs--dibromoacetic acid was not 
included in this study, as these waters are all low in bromide--ranged 
from 14 to 141 g/L in the distributed waters (with utility 
annual averages of 51 to 97 g/l). In this survey, HAA 
concentrations consistently exceeded the concentration of TTHMs (which 
ranged from 13 to 114 g/l, with utility annual averages of 34 
to 72     g/l). The prevalence of the HAAs may be due, in 
part, to chlorination of settled and finished waters with pH levels of 
5.9 to 7.8. Chlorination at lower pH levels results in lower THM 
formation but higher HAA concentrations (Stevens et al., 1989).
    Recently, a commercial standard for bromochloroacetic acid (BCAA) 
has become available. Studies to date suggest that the other mixed 
bromochloroacetic acids may be unstable (Pourmoghaddas et al., 1992). 
The RNDB includes the occurrence of BCAA for 25 utilities. The median, 
75th and 90th percentile occurrence were 3, 5, and 8 g/L, 
respectively. In the chlorinated distribution system of a water 
containing from 0.04 to 0.31 mg/L bromide (i.e., an average- and a 
high-bromide source water were being treated), BCAA was present from 6 
to 17 g/L and accounted for 25 percent of the concentration of 
the sum of the six measured HAA species (D/DBP Regulations Negotiation 
Data Base (RNDB), 1992). Thus, most DBP studies which measured only 
five of the HAA species will have some level of underestimation of 
total HAAs present, although that should be a small error in low 
bromide waters.
    The RNDB includes HAA data, including from the 35-utility, EPA, and 
North Carolina DBP studies. When a utility was sampled more than once 
in time and space, a ``quasi'' running annual average value was 
determined (RNDB). Figure VI-13 shows the cumulative probability 
occurrence of THAAs (the four- to six-species sums) for large and small 
systems. The median THAA for either population group is 30 g/
L, although the small systems have 30 percent of the utilities with 
7 g/L THAAs. The difference at the low THAA levels 
was probably due to treatment of low-precursor source waters in small 
systems. The high end of the THAA occurrence was not significantly 
different, most likely due to a lack of a HAA regulation and the fact 
that pH of chlorination impacts THM and HAA formation in opposite ways. 
In the RNDB, 121 of the utilities treated surface water or a ground 
water/surface water mix. For those systems treating some percentage of 
surface water, the median, 75th, 90th percentile, and maximum values 
were 28, 50, 73, and 155 g/L, respectively. In the RNDB, 13 of 
the utilities treated ground water only. For this limited ground water 
data set, the median, 90th percentile, and maximum values were 4, 13, 
and 37 g/L, respectively.

BILLING CODE 6560-50-P

TP29JY94.023


BILLING CODE 6560-50-C
3. Modeling (DBPRAM) Formation TTHMs, HAA5 and Extrapolation to 
National Occurrence and Effects of SWTR
    As part of the D/DBP rulemaking process, EPA developed regulatory 
impact assessments of technologies that will allow utilities to comply 
with possible new disinfection and DBP standards (Gelderloos et al., 
1992). As part of this process, a DBP Regulatory Assessment Model 
(DBPRAM) was developed. The DBPRAM included predictive equations to 
estimate DBP concentrations during water treatment (Harringon et al., 
1992). However, because reliable equations for predicting individual 
DBP formation in a wide range of waters (e.g., those containing high 
levels of bromide) were not available, the regulatory impact 
assessments emphasized TTHM (Amy et al., 1987) and total HAA5 
formation. Because BCAA was not commercially available when HAAs were 
measured during the development of the HAA predictive equations, those 
equations only included the formation of five HAA species (Mallon et 
al., 1992). However, for a low-bromide water, the error from not 
including mixed bromochloro HAA species was probably low.
    The DBPRAM predicted the removal of TOC during alum coagulation, 
granular activated carbon (GAC) adsorption, and nanofiltration 
(Harrington et al., 1992 and Harrington et al., 1991). These equations 
were developed based upon a number of bench-, pilot-, and full-scale 
studies. The removal of TOC during precipitative softening, though, has 
not been modeled to date. However, systems that soften represent a 
small percentage of the surface-water treatment plants (about 10 
percent). The DBPRAM also predicted the alkalinity and pH changes 
resulting from chemical addition (Harrington et al., 1992), as well as 
the decay of residual chlorine and chloramines in the plant and 
distribution system (Dharmarajah et al., 1991).
    In developing regulatory impact assessments, the first step was to 
estimate the occurrence of relevant source-water parameters (Letkiewicz 
et al., 1992). TOC data from the WIDB and bromide data from the 
nationwide bromide survey formed the basis for determining the DBP 
precursor levels (Wade Miller Associates, 1992). Actual water quality 
data were used to simulate predicted occurrence values based upon a 
statistical function such as a log-normal distribution (Letkiewicz et 
al., 1992 and Wade Miller Associates, 1992). In running the DBPRAM, the 
production of DBPs was restricted to surface-water plants that filtered 
but did not soften. Surface waters typically have higher disinfection 
criteria--and thus a greater likelihood to produce more DBPs--than 
ground waters (i.e., Giardia in surface waters is more difficult to 
inactivate than viruses in ground waters). As mentioned before, an 
equation to predict TOC removal during softening was not available. 
However, the surface water systems which were modeled represented water 
treated and distributed to approximately 103 million people (Letkiewicz 
et al., 1992). Another mechanism was developed for accounting for DBP 
occurrence in other water systems (see below).
    The second step in the regulatory impact assessment was to prepare 
a probability distribution of nationwide THM and HAA occurrence if all 
surface water plants that filter but do not soften used a particular 
technology for DBP control (i.e., enhanced coagulation, GAC, 
nanofiltration, or alternative disinfectants). Even though individual 
utilities will consider a range of technologies to meet disinfection 
and D/DBP rules, the DBPRAM can only predict the performance of one 
technology at a time. Subsequently, a decision-making process was 
employed to examine the predicted compliance choices that systems will 
make (Gelderloos et al., 1992). As part of the DBPRAM, compliance with 
the SWTR, a potential enhanced SWTR, the total coliform rule, and the 
lead-corrosion rule were modeled. Thus, while nationwide DBP studies 
typically measured DBP occurrence prior to implementation of these new 
microbial and corrosion rules, the DBPRAM allowed one to assess the 
impacts of meeting a multitude of rules simultaneously.
    During the D/DBP negotiated rulemaking, a Technology Workgroup 
(TWG) of engineers and scientists was formed. The TWG reviewed the 
DBPRAM and regulatory impact assessments, and provided input to ensure 
that the predicted output was consistent with real-world data. Prior 
validation of the model in Southern California (where bromide 
occurrence was relatively high) indicated that the central tendency was 
to underpredict TTHMs by 20-30 percent (Harrington et al., 1992). In 
addition, evaluation of the model in low-bromide North Carolina waters 
also found that the model tended to underpredict both THM and HAA 
concentrations and resulted in absolute median deviations of 
approximately 25-30 percent (Grenier et al., 1992). Neither Harrington 
nor Grenier were able to identify reasons for the underpredictions. 
Therefore, the TWG adjusted the DBPRAM output to correct for the 
underpredictions; the resultant data were confirmed against full-scale 
data from throughout the United States.
    Prior validation of the alum coagulation part of the model was 
performed in several eastern states, as well as in Southern California. 
The overall central tendency was to overpredict TOC removal by 5-10 
percent. The TWG believed that utilities would implement an overdesign 
factor to ensure that precursor removal technologies could consistently 
meet water quality objectives. A 15 percent overdesign factor for TOC 
removal compensated for a typical overprediction in TOC removal by 
alum. For plants that do not filter or filter with softening, case 
studies on a number of systems through the nation were used to assess 
compliance choices and predicted water qualities. For ground waters, 
data from the WIDB and GWSS on TOC and THM levels were used in 
developing regulatory impact analyses (RIAs) for those systems.
    With the revised DBPRAM output, the proposed stage 1 D/DBP rule--
i.e., MCLs of 80 g/L TTHMs and 60 g/L THAAs, as well 
as a performance criteria for DBP precursor removal--would affect large 
systems that filter but do not soften as follows: TTHMs would drop on a 
median basis from 45 to 32 g/L, while the 95th percentile 
would drop from 104 to 58 g/L; THAAs would drop on a median 
basis from 27 to 20 g/L, and the 95th percentile would drop 
from 86 to 43 g/L.

C. Other Disinfection Byproducts

1. Ozonation Byproducts
    a. Identification of Ozonation Byproducts. Ozone can convert 
organic matter in water to aldehydes (e.g., formaldehyde) (Glaze et 
al., 1989) and assimilable organic carbon (AOC) (Van der Kooij et al., 
1982). Recent research optimized the aldehyde method in order to 
quantitatively recover additional carbonyls of interest (e.g., 
dialdehydes such as glyoxal and aldo-ketones such as methyl-glyoxal 
(Sclimenti et al., 1990)). AOC is the fraction of organic carbon that 
can be metabolized by microorganisms; it also represents a potential 
for biological regrowth in distribution systems. Polyfunctional ozone 
DBPs such as ketoacids have been detected at higher levels than the 
low-molecular-weight aldehydes and have been shown to correlate well 
with AOC (Xie et al., 1992). Using resin columns to accumulate organics 
from ozonated waters, Glaze and co-workers detected aldehydes, 
carboxylic acids, aliphatic and alicyclic ketones, and hydrocarbons 
(Glaze et al., August 1989). Ozone is known to produce other organic 
oxygenated DBPs, such as peroxides and epoxides (Glaze et al., 1989). 
Analytical methods for low-level detection are currently not available 
for epoxides, but progress in detecting peroxides (inorganic and 
organic) has recently been made (Weinberg et al., 1991). As with 
chlorine, occurrence data for ozone DBPs are limited to compounds that 
can be detected by current methods.
    Although most ozone by-products are oxygenated species, the 
presence of bromide will result in the formation of brominated DBPs 
(Haag et al., 1983 and Dore et al., 1988). When bromide is present in a 
source water, it may be oxidized by ozone to hypobromous acid (HOBr). 
At common drinking-water pH levels, HOBr is in equilibrium with the 
hypobromite ion, OBr-. Once produced, HOBr can react with organic 
THM/DBP precursors to form bromoform and other brominated organic by-
products (Dore et al., 1988 and Glaze et al., Jan. 1993). OBr- 
(but not HOBr) can be oxidized by ozone to bromate (BrO3-) 
(Krasner et al., Jan 1993 and Haag et al., 1983). Krasner and 
colleagues found that ozonation of bromide-containing waters can form a 
number of brominated organic DBPs that are analogous to chlorinated 
DBPs (e.g., bromoform, dibromoacetic acid, tribromonitromethane 
[bromopicrin], and cyanogen bromide) (Krasner et al., 1990 and Krasner 
et al., 1991). Similarly, Glaze and co-workers studied the formation of 
bromo-organic DBPs formed during ozone (e.g., bromoform; 
dibromoacetonitrile; mono-, di-, and tribromoacetic acid; and 
monobromoacetone) (Glaze et al., Jan. 1993). However, only a fraction 
of the dissolved organic bromide was found as targeted brominated 
organic DBPs (Glaze et al., Jan. 1993). As with chlorination, not all 
of the halogenated DBPs can be accounted for with existing analytical 
methodologies. However, researchers are continuing to try to uncover 
new DBPs all the time, such as the bromine-substituted analogues of 
chloral hydrate (trichloroacetaldehyde) formed during chlorination and/
or ozonation (Xie et al., 1993, in press).
    b. National Occurrence--Trends--i. Ozone use in U.S., pre vs. post 
SWTR. While ozone technology in drinking-water treatment has been in 
use for more than 80 years in Europe, applications in the United States 
(U.S.) have been much more limited. However, the use of this 
disinfectant/oxidant is growing rapidly in the U.S. as utilities are 
working to meet the requirements of the SWTR, anticipation of a D/DBP 
Rule, regulations for volatile and synthetic organic chemicals, and for 
taste-and-odor control (Ferguson et al., 1991 and Tate, 1991). 
Virtually every surface water system use of ozone was intended to 
accomplish multiple water quality objectives, such as disinfection, DBP 
control, taste and odor, or any combination of these (Tate, 1991). 
Ground water plants in Florida have used ozone for controlling DBPs, 
color, and odor (Tate, 1991).
    The first U.S. ozone plant was on-line in 1978. The number 
increased to 18 by June 1990 (Tate, 1991). A recent survey has 
identified an additional 11 facilities under construction, as well as 
at least 37 U.S. ozone pilot-plant studies underway (Rice, Aug.-Sept. 
1992). As part of the D/DBP negotiated regulation, the TWG has 
evaluated compliance choices for meeting stage 1 and possible stage 2 
criteria. For example, the TWG predicted that six percent of surface 
water systems will use ozone/chloramines in addition to enhanced 
coagulation to achieve compliance with Stage 1 requirements. Depending 
on the role of precursor-removal criteria in a stage 2 Rule, it is 
predicted that from 8 to 27 percent of large surface-water systems 
would use ozone/chloramines as part of the treatment process. The 
current and projected ozone usage is based on an existing SWTR and the 
anticipation of a DBP Rule, both of which have led to the choice of 
ozone, a powerful disinfectant that typically produces limited DBPs.
    ii. AWWARF bromide/bromate survey and studies. In order to comply 
with new and more stringent regulations, alternative treatments are 
being studied. A 2-year study of ozone treatment at 10 North American 
utilities was conducted at pilot and full scale (Glaze et al., 1993 in 
press). For four of the six surveyed utilities where the bromide level 
was 0.06 mg/L, bromate was not detected with minimum 
reporting level (MRL) values of 5-10 g/L at the ozone dosages 
investigated (Krasner et al., Jan. 1993). For the other two low-bromide 
utilities, bromate at 5-8 g/L was detected inconsistently over 
time and space. For three of the four tested waters in which the 
ambient bromide level was 0.18-0.33 mg/L, bromate was typically 
detected at levels of 9-18 g/L. No bromate was detected at one 
utility where the very high level of TOC (i.e., 26 mg/L) may have 
produced an ozone demand that overwhelmed the production of bromate. In 
another study, using a special, labor-intensive concentration method at 
an EPA research facility, bromate was detected in seven of the nine 
ozonated waters tested at an MRL of 0.4 g/L or higher (Sorrell 
et al., 1992). In one instance, bromate was detected in the source 
water at this MRL value.
    Utilizing these data, as well as that of other EPA and AWWARF 
investigators (Krasner et al., Jan 1993, Amy et al., 1992-93, Sorrell 
et al., 1992, Hautman, 1992, and Miltner, Jan. 1993). The nationwide 
distribution of bromate occurrence if all surface water plants switched 
to ozone for predisinfection was estimated (Krasner et al., 1993). It 
was estimated that the 20th, median, and 80th percentile for bromate 
occurrence in surface waters using ozone for predisinfection might be 
0.5-0.8, 1-2, and 3-5 g/L, respectively.
    The 90th to 95th percentile occurrence of bromate could be in the 
range of 5 to 20 g/L (Krasner et al., 1993). However, the 
proposed regulation for bromate would result in either (1) some 
utilities choosing not to employ ozonation or (2) other utilities 
operating the ozonation process in a manner which would reduce bromate 
formation. For example, demonstration-scale tests of the ozonation of a 
surface water containing bromide at approximately the 90th to 95th 
percentile level of occurrence (i.e., 0.17 to 0.49 mg/L) at an ambient 
pH of 8 produced from <3 to 25 g/L bromate, depending on the 
amount of ozone added (Gramith et al., 1993). In the latter tests, 
Giardia inactivations from ozonation of from 0.5 to 3 logs were 
achieved. When the pH of ozonation was reduced to about 6, bromate 
formation in this water was consistently below 10 g/L and 
often below 5 g/L. In addition, Giardia inactivations of up to 
4 logs were achieved at this pH.
    c. Potential DBPs not regulated at this time.--i. Aldehydes, 
ketones, peroxides, and formation of precursors for other DBPs--
national occurrence. Miltner and co-workers ozonated a surface water 
with 1.4 mg/L TOC at various ozone doses up to an ozone-to-TOC ratio of 
2.8:1 mg/mg (Miltner et al., Nov. 1992). They found that the formation 
of the three most-prevalent aldehydes (formaldehyde, glyoxal, and 
methyl-glyoxal) continued to increase as the ozone dose increased, and 
that these three aldehydes had not reached maximum yields before the 
highest ozone-to-TOC ratio was tested. Weinberg and colleagues studied 
the formation of aldehydes at 10 North American utilities at pilot- and 
full-scale plants (Weinberg et al., 1993) . The interquartile range 
(i.e., 25th to 75th percentile occurrence) of formaldehyde was 11 to 20 
g/L, while the sum of aldehydes tested had an interquartile 
range of 23 to 47 g/L. The utility with the highest TOC in the 
10-utility study (8.1 mg/L in the ozonator influent) represented a 
maximum outlier in aldehyde production (i.e., about 70 g/L 
formaldehyde and up to 150 g/L of summed aldehydes). The 
minimum outlier was the summer testing of a low-TOC water (1.0 mg/L) 
which received an applied ozone dose of 1.0 mg/L. When the occurrence 
data were normalized to TOC level, the interquartile ranges were 3.9 to 
8.4 g formaldehyde per mg TOC and 9 to 20 g of summed 
aldehydes per mg TOC. This normalization brought the water with the 
highest TOC into the interquartile range. When the aldehyde formation 
was further normalized for the ozone dose, the interquartile ranges per 
unit TOC and per ozone dose were 1.2 to 4.2 g formaldehyde/(mg 
* mg/L) and 2.9 to 11 g summed aldehydes/(mg * mg/L). With 
this latter normalization, the high-TOC water dropped to almost the 
minimum outlier. Because the ozone demand of the latter water exceeded 
the dose, it is possible that more aldehydes could have been produced 
with a higher dose. These limited data suggest that either TOC or ozone 
dose can be the limiting factor in aldehyde production (i.e., for the 
low-TOC water in the summer testing and the high-TOC water, 
respectively).
    While ozonation can produce significant levels of aldehydes, the 
presence of these ozone by-products in the distribution system are 
highly dependent on whether the filters downstream of ozone are 
operated biologically (i.e., no secondary disinfectant is applied 
before the filters), as well as the choice of filter media and 
filtration rate (or more exactly, the empty bed contact time [EBCT] in 
the filter media) (Miltner et al., Nov. 1992, Weinberg et al., 1993, 
and Krasner et al., May 1993).
    Using a bioreactor, many aldehydes can be quantitatively removed 
(Miltner et al., Nov. 1992). In pilot- and full-scale studies, 
formaldehyde tended to be the most biodegradable of the aldehydes 
tested, while the glyoxals, in some instances, were somewhat 
recalcitrant (Weinberg et al., 1993, and Krasner et al., May 1993). 
These aldehydes (including the glyoxals) were typically best removed at 
utilities in which granular activated carbon (GAC) contactors or 
filters were employed, even when the GAC was removing little or no TOC 
(Weinberg et al., 1993, and Krasner et al., May 1993). When anthracite 
coal/sand filters were used without a secondary disinfectant before 
filtration, these aldehydes could be removed to varying degrees with 
the best results at low filtration rates (or high EBCTs) (Weinberg et 
al., 1993, and Krasner et al., May 1993). Because part of the proposed 
D/DBP Rule sets criteria for biological filtration following ozonation 
of raw water, it is anticipated that the occurrence of aldehydes, while 
not directly regulated, can be minimized in the finished water.
    Other oxygenated organic ozone by-products (e.g., ketoacids (Xie et 
al., 1992) and organic peroxides (Weinberg et al., 1991) can also be 
reduced during biological filtration. The use of biological treatment 
for drinking water treatment in the United States is currently very 
limited, while in Europe such processes are more common. However, 
research into the incorporation of biological filtration in the United 
States is now being extensively studied and its implementation is 
becoming more common (Weinberg et al., 1993). In addition, some ozone 
by-products are relatively unstable (e.g., peroxides and epoxides) and 
may not persist in the finished water. Furthermore, because hydrogen 
peroxide can reduce chlorine to chloride ions (Connick, 1947), the 
addition of free chlorine should destroy a peroxide residual (Weinberg 
et al., 1991). Finally, because GAC can reduce oxidant residuals, GAC 
downstream of ozone should be able to destroy hydrogen peroxide.
    While ozone can partially destroy the precursors of some THMs and 
HAAs (Miltner et al., 1992), it can increase the formation potential of 
other DBPs (e.g., chloropicrin (Miltner et al., Nov. 1992 and Hoigne et 
al., 1988) and chloral hydrate (Mcknight et al., 1992)). However, 
Miltner and co-workers found that ozonation followed by biotreatment 
reduced chloropicrin formation potential (Miltner et al., 1992). 
McKnight and Reckhow found that if acetaldehyde--an ozone by-product--
undergoes an initial chlorine substitution, then the reaction should 
rapidly proceed to form the trichlorinated product chloral hydrate 
(Mcknight et al., 1992). Because acetaldehyde can be reduced during 
biological filtration (Miltner et al., Nov. 1992 and Weinberg et al., 
May 1993), this should minimize subsequent formation during 
postchlorination. Jacangelo and colleagues found that when biological 
filtration was not practiced, preozonation increased chloral hydrate 
formation in postchlorinated waters (Jacangelo et al., 1989). However, 
these researchers also observed that chloral hydrate production for 
systems using preozonation/postchloramination was lower than that for 
systems using chlorination only (Jacangelo et al., 1989). To avoid by-
products of secondary disinfection, more research into the relative 
merits of biological filtration and/or postchloramination for systems 
using preozonation must be pursued.
    d. Concerns with AOC in high TOC source waters. Typically a high-
TOC water will have a high oxidant demand. Thus, ozonating a high-TOC 
water has the potential to form a higher level of ozone by-products, 
such as aldehydes (see Section VI.C.1.c. above). In addition, there are 
concerns that more AOC can be formed in such a water.
    Amy and colleagues found that biodegradable organic carbon (BDOC) 
correlated well (r\2\=0.92) with the TOC level of ozonated waters (Amy 
et al., 1992). On the average, 28 percent of the TOC was present as 
BDOC after ozonation (typical ozone dose of 1:1 mg ozone/mg TOC). 
However, the correlation between BDOC and AOC for the six waters 
studied was poor, suggesting that individual source waters may have a 
unique relationship between these constituents.
    While there is a concern over forming AOC, BDOC, aldehydes, etc., 
during ozonation, current research is examining the ability of the 
treatment plant to remove significant portions of the biodegradable 
organic matter (e.g., through biological filtration). A question 
remains as to what level AOC needs to be reduced to minimize biological 
regrowth.
    e. Removal of by-products. Ozonated waters may require GAC 
treatment or other biological processes for removal of aldehydes, AOC, 
other DBPs. There are concerns that switching to ozone may increase the 
availability of AOC and potentially increase bacterial populations in 
distribution systems. In addition, some ozone by-products (e.g., 
certain aldehydes and organic peroxides) may be regulated at a future 
date when more data become available (USEPA, 1991).
    During the 35-utility DBP study performed in 1988-1989, two 
utilities switched to ozonation as the primary disinfectant 
(Metropolitan Water District of So. Calif et al., 1989 and Jacangelo et 
al., 1989). Both utilities applied a secondary disinfectant (chlorine 
or chloramines) before the filtration step. At both plants, ozonation 
produced formaldehyde and acetaldehyde (aldehydes for which analytical 
methodology was being used), the levels of which were undiminished in 
passing through the filters and distribution system. Subsequently, a 
North American study of 10 utilities that used ozonation at a pilot- 
and/or full-scale in 1990-1991 (Glaze et al., 1993, in press; and 
Weinberg et al., 1993) indicated the following:
     Aldehydes and aldo-ketones--especially formaldehyde, 
glyoxal, and methyl-glyoxal--were ubiquitous ozone DBPs, formed in all 
the surveyed utilities.
     These compounds were removed to varying extents by filters 
which were allowed to operate in a biological mode (i.e., secondary 
disinfection was postponed until after filtration).
     In studies where formaldehyde and acetaldehyde were 
efficiently removed, glyoxals were sometimes removed to a lesser 
extent.
     These aldehydes were typically best removed at utilities 
in which GAC contactors or filters were employed, even when the GAC was 
removing little or no TOC.
     However, GAC filters in this survey were almost always 
operated at lower filtration rates (1.0 to 5.0 gpm/sf), whereas 
anthracite coal filters were typically operated at higher filtration 
rates (3.8 to 13.5 gpm/sf).
     In addition, secondary disinfection, which was sometimes 
applied before the anthracite filters, was never applied before the GAC 
filters in this survey.
    Because surveys provide a ``snapshot'' of treatment practices in 
use, other investigators have performed studies to better assess 
individual parameters that impact the efficacy of biological 
filtration. Merlet and co-workers (Merlet et al., 1991) evaluated 
biological activated carbon (BAC) for the reduction in BDOC produced by 
ozonation. As the EBCT of the BAC was varied up to 25 min, BDOC removal 
increased up to a point, at which its efficacy plateaued out. 
LeChevallier and colleagues (LeChevallier et al., 1992) also observed 
that increased EBCTs increased AOC removal; however, AOC levels of <100 
g/L could be achieved with a 5- to 10-min EBCT. In addition, 
the latter researchers found that the application of free chlorine to 
GAC filters did not inhibit AOC removal, whereas the application of 
chloramines showed a slight inhibitory effect. Furthermore, 
LeChevallier and colleagues found that GAC filter media supported 
larger bacterial populations and provided better removal of AOC than 
conventional filter media (LeChevallier et al., 1992).
    Miltner and co-workers (Miltner et al., 1992) found that biological 
activity was established within approximately one week, as evidenced by 
90-percent removal of certain aldehydes. However, approximately 80 days 
of filter use were required before half of the AOC could be removed. 
Price and colleagues (Price et al., 1992) found that dual-media filters 
(anthracite coal/sand) performed as well as GAC after time, especially 
as the water temperature went up. The latter researchers also observed 
that GAC/sand filters operating at 1, 3, and 5 gpm/sf provided similar 
removals of AOC. Reckhow and co-workers (Reckhow et al., 1992) found 
that GAC/sand filters removed less AOC and aldehydes when backwashed 
with chlorinated water. As the filtration rate increased, filters 
backwashed with chlorinated water achieved lower removals, whereas 
filters backwashed with non-chlorinated waters were less impacted by 
filtration rate.
    Clearly, many researchers are investigating means of optimizing the 
removal of AOC, BDOC, and aldehydes produced by ozonation through 
biologically active filtration. Because many plants that are switching 
to ozonation are retrofitting existing treatment plants, it is 
desirable to achieve biological filtration with the same filters used 
for turbidity removal. In pilot-plant testing of ozonation at 
Metropolitan Water District of Southern California (Metropolitan Water 
District of So. Calif. et al., 1991), dual-media (anthracite/sand) 
filters operating at 3 gpm/sf were evaluated, as these were 
representative of the operation at some of Metropolitan's full-scale 
facilities. When secondary disinfection was delayed until after 
filtration, these filters were able to remove AOC, formaldehyde, and 
acetaldehyde (Paszko-Kolva et al., 1992 and Metropolitan Water District 
of So. Calif. et al., 1991). However, when the aldehyde analysis was 
expanded to include glyoxals at the end of the project, limited testing 
indicated that glyoxals were not well removed by these filters 
(Metropolitan Water District of So. Calif. et al., 1991). In addition, 
there were concerns that because some of Metropolitan's facilities 
operate with higher filtration rates (up to 9 gpm/sf), this could 
impact the biological filtration process.
    A new pilot-plant study was initiated to evaluate biological 
filtration for the removal of AOC and aldehydes, including the glyoxals 
. Analyzing for a wide range of aldehydes (i.e., monoaldehydes, such as 
formaldehyde; the dialdehyde glyoxal; and the aldo-ketone methyl-
glyoxal) allowed for a more thorough investigation into the efficacy of 
biological filtration. Not only may these individual carbonyls pose 
different health concerns (USEPA, June 1991), but they also have the 
potential to represent organic matter which is relatively biodegradable 
(i.e., formaldehyde) and which is potentially somewhat recalcitrant to 
biological filtration (i.e., the glyoxals).
    The latter pilot testing indicated that biological activity was 
established sooner on slow-filtration-rate filters with a 4.2-min EBCT, 
but the high-filtration-rate filters with 2.1- and 1.4-min EBCTs 
eventually were able to achieve comparable capabilities for the removal 
of AOC and most aldehydes (Krasner et al., May 1993 and Paszko-Kolva et 
al., 1992). However, even 111 days of operation did not allow the 
anthracite coal filter operating with a 1.4-min EBCT an opportunity to 
demonstrate consistently high removal (80 percent) of the glyoxals. The 
latter filter, though, did remove significant amounts of AOC and 
formaldehyde. Glyoxals were well removed on the anthracite filter 
operated at a low filtration rate (with a 4.2-min EBCT) or the GAC 
filters operated at either low or high filtration rates (with 4.2- and 
1.4-min EBCTs, respectively). Note that these filters were able to 
remove aldehydes and AOC efficiently at relatively short EBCTs and that 
the higher EBCTs associated with GAC contactors were not required.
    Use of a biological filter can produce a more biologically stable 
water and can minimize the presence of aldehydes and other ozone by-
products (e.g., ketoacids (Xie et al., 1992) and peroxides (Weinberg et 
al., 1991)) of potential health and regulatory concern. As the studies 
to date demonstrate, the appropriate choice of media and filtration 
rate can ensure that AOC and specific organic ozone by-products can be 
significantly reduced in concentration.
2. Chlorine Dioxide Byproducts
    Chlorine dioxide is used as an alternative disinfectant to chlorine 
to treat drinking water for THM control, taste-and-odor control, 
oxidation of iron and manganese, and oxidant-enhanced coagulation-
sedimentation (Aieta et al., 1986). In 1977, 103 facilities in the U.S. 
were using or had used chlorine dioxide (Symons et al., 1979). 
Currently, 500 to 900 municipalities in the U.S. use chlorine dioxide, 
although some use was only seasonal (Private communication with 
Chemical Manufacturers' Association, 1993). In Europe, several thousand 
utilities have used chlorine dioxide, mostly to maintain a disinfectant 
residual in the distribution system (Aieta et al., 1986).
    Chlorine-free chlorine dioxide does not react with natural organic 
matter such as humic and fulvic acids to form THMs (Symons et al., 
1981). Studies show that the TOX formed with chlorine dioxide is from 1 
to 25 percent of the TOX formed with chlorine under the same reaction 
conditions (Aieta et al., 1986 and Symons et al., 1981). Before the 
introduction of high-yield chlorine dioxide systems that were capable 
of producing nearly chlorine-free chlorine dioxide solutions, 
significant amounts of chlorine could be present in the chlorine 
dioxide solutions used in water treatment. Chlorine dioxide has been 
used effectively by many utilities in order to comply with the 1979 THM 
Rule (Aieta et al., 1986 and Lykins et al., 1986).
    However, when chlorine dioxide is used, the inorganic by-products 
chlorite and chlorate are produced. During water treatment, 
approximately 50-70 percent of the chlorine dioxide reacted will 
immediately appear as chlorite and the remainder as chlorate (Aieta et 
al., 1984). The residual chlorite continues to degrade in the water 
distribution system in reactions with oxidizable material in the 
finished water or in the distribution system. In a study of five U.S. 
utilities employing chlorine dioxide, median chlorite and chlorate 
concentrations in the distribution systems tested typically ranged from 
0.4 to 0.8 mg/L and between 0.1 to 0.2 mg/L, respectively (Gallagher et 
al., 1993, in press). For the latter systems, the 75th percentiles for 
chlorite concentrations ranged from 0.4 to 1.4 mg/L.
    Data for up to 17 utilities in EPA Region 6 who employ chlorine 
dioxide were obtained (Personal communication, Novatek 1993). In many 
instances, data for chlorite occurrence on a monthly basis were 
available. As an example, for June 1992 chlorite ranged from 0.4 to 1.2 
mg/L, while in January 1993 chlorite was at values of 0.2 to 0.8 mg/L. 
The higher values in June may have been due, in part, to the need for 
more chlorine dioxide in warmer months to meet the oxidant demand of 
the water. When the data are examined quarterly (e.g., quarter 1 is 
January through March), Figure VI-14 shows that the highest occurrence 
for chlorite in the systems sampled in EPA Region 6 was during the 
spring and summer seasons.

BILLING CODE 6560-50-P

TP29JY94.024


BILLING CODE 6560-50-C
    a. Potential chlorine dioxide DBPs not regulated at this time. This 
proposed regulation will not include an MCLG or MCL for chlorate. 
Insufficient data exist at this time to develop an MCLG for chlorate 
(Orme-Zavaleta, 1992). If chlorate is regulated in the future, systems 
which use hypochlorination will also need to monitor for this by-
product (Bolyard et al., August 1992). Limited testing shows that 
chlorine dioxide can form low concentrations of aldehydes (Weinberg et 
al., 1993). However, studies also demonstrate that chlorine can produce 
aldehydes (Krasner et al., August 1989 and Jacangelo et al., 1989).
3. Chloramination Byproducts
    a. Cyanogen chloride. Typically, chloramines do not react to form 
significant levels of THMs and other chlorinated DBPs. Because 
monochloramine (the predominant form of chloramines in most drinking-
water applications) is a much less potent oxidant or chlorinating agent 
than chlorine, the by-products of monochloramine reactions with organic 
substances are much less extensively oxidized or chlorinated (Scully, 
1990). Nevertheless, chloramines appear to chlorinate natural organic 
matter sufficient to produce low levels of TOX.
    During the 35-utility DBP study, 14 of the 35 utilities surveyed 
were utilizing chloramines (Krasner et al., 1989). Ten of these had 
free-chlorine contact time prior to ammonia addition, and the remaining 
four added chlorine and ammonia concurrently. The median value of 
cyanogen chloride in utilities that used only free chlorine was 0.4 
g/L. Utilities that pre-chlorinated and postammoniated had a 
cyanogen chloride median of 2.2 g/L. The 95-percent confidence 
intervals around the medians indicated that these two disinfection 
schemes were statistically different with regard to the cyanogen 
chloride levels detected in the clearwell effluents. Krasner and co-
workers found that a number of parameters affect the formation of 
cyanogen chloride during chloramination (Krasner et al., 1991).
    b. Potential other chloramination DBPs not regulated at this time. 
Studies have demonstrated the formation of organochloramines by the use 
of inorganic chloramines in the disinfection of water (Scully, 1982). 
Recently, an analytical method has been developed to distinguish 
organic chloramines from the inorganic species (Jersy et al., 1991). 
Monochloramine has been shown to react with aldehydes to yield nitriles 
(Le Cloirec et al., 1985). The presence of cyanogen chloride and low 
concentrations of TOX in chloraminated waters indicate a need to 
further identify chloramine by-products.

VII. General Basis for Criteria of Proposed Rule

A. Goals of Regulatory Negotiation

    In the Federal Register ``Notice of Intent to Form an Advisory 
Commitee to Negotiate the Disinfection Byproducts Rule and Announcement 
of Public Meeting'' (USEPA, 1992), EPA identified key issues to be 
addressed and resolved during the conduct of the negotiation. They 
were:

--What disinfectants and disinfection byproducts present the greatest 
risks, and how should they be grouped for regulation?
--Which categories of public water suppliers should be regulated?
--Should the regulation establish Maximum Contaminant Levels or be 
technology driven?
--How effective are advanced technologies and alternative disinfectants 
in the removal of disinfectants, disinfection byproducts, and microbial 
risks?
--How should disinfectants, disinfection byproducts, and microbial 
risks be compared, given differences in the type and certainty of their 
effects?
--What levels of disinfectant, disinfection byproduct, and microbial 
risks are acceptable, and at what cost?
--How should the achievement of acceptable levels of risks be defined?
--How might risk-risk models be used, if at all, in the development of 
Maximum Contaminant levels within the current regulatory schedule?
--How should the needs of sensitive populations be taken into account 
in the rule?
--How should Best Available Technology be defined for the removal of 
disinfectants and disinfection byproducts?
--Should a comprehensive disinfectant/disinfection byproduct regulation 
be issued in 1995, or should the control of certain disinfectants/
disinfection byproducts be deferred until research confirms the safety 
of alternative treatment methods?
--How should affordability be factored into judgements regarding 
feasibility of treatment techniques?
--How should monitoring requirements be defined?
--How can the rule be drafted to be most easily understood by both 
State regulators and small system operators?

    In addition to the issues identified in the Federal Register that 
needed to be resolved, potential negotiating committee members 
identified the following additional issues (RESOLVE, 1992a):

--How can the rule be drafted to be most easily accepted and 
understandable by the general public?
--Is there a need for further regulation of DBPs?
--How should the rule account for differences in size of a system 
(i.e., number of people served) or a system's water source?
--How should the rule account for differences in type of disinfection 
technology and quality of source water?
--How should the rule account for the particular characteristics of 
some water distribution systems that complicate efforts to minimize DBP 
formation?
--How should the rule account for the cross-media environmental impacts 
and ecological risks associated with DBP control technologies?
--Will the DBP rule be compatible with other EPA regulations (e.g., 
groundwater, lead, surface water)? Will current exposure and occurrence 
data change with implementation of other rules? Are EPA's models good 
enough to predict the effects of other regulations on the occurrence of 
various DBPs in drinking water?
--To what extent are watershed protection and maintenance of source 
water quality useful strategies to achieve risk reduction?
--How should analytic methods be defined? Should DBP content be 
monitored at the treatment plant, within the distribution system, or at 
the tap?
--How much has already been achieved by the THM rule? How can this be 
taken into account in the assumptions for this rule?
--What types of research on DBP effects and controls are presently 
being or should be conducted in the future?
--What are the assumptions that underlie EPA's description of 
acceptable risk from exposure to microbes and DBPs in drinking water? 
Is there a safe level for human exposure to DBPs? How certain are EPA's 
models? Should EPA's cancer risk assessment policies be reopened in 
this forum?
--How can the rule be most easily implemented?

B. Concerns for Downside Microbial Risks and Unknown Risks From DBPs of 
Different Technologies

    This rule is intended to limit concentrations of disinfectants and 
their byproducts in public water systems. However, there is the 
possibility that reducing the level of disinfection without adequately 
addressing microbial risk may result in increasing microbial exposure. 
The Negotiating Committee wanted to ensure that drinking water 
utilities can effectively provide treatment that controls both 
disinfectants and their byproducts and microbial contaminants. The 
Negotiating Committee believes it accomplished this goal by developing 
an additional proposed rule (Enhanced Surface Water Treatment Rule, 
proposed elsewhere in today's Federal Register) to control the level of 
microbial risk.
    If disinfection is decreased to reduce byproduct formation, there 
is the possibility that risk from pathogenic organisms could increase. 
This relationship is not well understood, particularly as it applies to 
the many different source waters and the various disinfectants that may 
be used. To better understand and characterize this risk-risk 
relationship, EPA proposed an Information Collection Rule [59 FR 6332] 
to gather needed information.
    In addition to concerns about increasing microbial risk, the 
Negotiating Committee had concerns about large numbers of systems 
switching from chlorine to an alternative disinfectant (e.g., ozone, 
chlorine dioxide, chloramines) whose disinfection efficacy and 
byproducts (both occurrence and health effects) are not as well 
understood as those of chlorine. Chlorine has been studied far more 
than the alternative disinfectants; this additional study may account 
for some or all of the differences in known health risks. Chlorine has 
proved to be an effective disinfectant under a wide range of 
conditions. For conditions where chlorine was not adequate as a 
disinfectant (e.g., high TTHM formation potential or high pH), systems 
have changed to other disinfectants. However, the Committee does not 
want to force large numbers of additional systems to switch 
disinfectants before more information is available, since research has 
indicated that health risks from alternative disinfectants may be 
significant (e.g., bromate formation from ozonation).

C. Ecological Concerns

    In addition to concerns about risk-risk tradeoffs and risks from 
alternative disinfectants, the Technologies Working Group (TWG) 
identified ecological risks that could result from a change in 
technology. These concerns included:

--Moving the point of chlorination may result in problems with zebra 
mussel infestation in the intake pipe.
--Increasing addition of coagulants may result in increased sludge 
production and attendent disposal problems.
--Changing to ozone may require large amounts of additional energy 
(electricity) for ozone generation.
--Adding GAC makes construction of on- or off-site GAC regeneration 
facilities necessary.
--Adding membranes may require large amounts of additional energy 
(electricity) for pressure, may cause problems in disposing of brine in 
some areas, and may not be feasible in water-short areas.

D. Watershed Protection

    One issue that the Negotiating Committee considered throughout the 
negotiation process was the relationship and role of watershed 
protection to these proposed regulations. The Committee desired to 
promote watershed protection and to provide incentives to establish new 
watershed protection programs and to improve existing ones. These 
desires were prompted by the benefits that watershed protection 
provides not only for disinfectant byproduct control, but for a wide 
range of potential drinking water contaminants and related water supply 
and environmental issues.
    Watershed protection reduces microbial contamination in water 
sources, and hence the amount of disinfectant needed to reduce 
microbial risk to a specified level in a finished water supply. It also 
reduces the level of turbidity, pesticides, volatile organic compounds, 
and other synthetic organic drinking water contaminants found in some 
water sources. Precursor (material that reacts with disinfectants to 
form disinfection byproducts) levels can be lowered, which may lower 
the levels of DBPs formed. Watershed protection results in economic 
benefits for water supply systems by minimizing reservoir sedimentation 
and eutrophication and reducing water treatment operation and 
maintenance costs. Moreover, adequate watershed protection in many 
cases will reduce overall organic matter (TOC) in source water and 
therefore reduce DBP formation. Watershed protection also provides 
other environmental benefits through improvements in fisheries and 
ecosystem protection.
    The types of watershed programs that the Committee wished to 
encourage are those that consider agricultural controls, silvicultural 
controls, urban non-point controls, point discharge controls, and land 
use protections which are tailored to the environmental and human 
characteristics of the individual watershed. These characteristics 
include the hydrology and geology of the watershed, the nature of human 
sources of contaminants, and the legal, financial and political 
constraints surrounding entities which have control of aspects of the 
watershed.
    The Committee considered options for providing incentives for 
watershed protection programs directly within these proposed 
regulations through such things as reduced monitoring or reduced 
requirements based on the existence of a watershed program. However, 
unlike other potential contaminants whose introduction can be directly 
prevented by watershed protection, disinfectant byproducts do not 
directly enter the water source, but are formed in the water treatment 
process.
    Because of general agreement that watershed protection had 
qualitative benefits, the Committee agreed that watershed protection 
was desirable and included several indirect incentives for watershed 
protection within these proposed regulations. The TOC levels which 
trigger enhanced coagulation requirements under the proposed 
Disinfectant Byproducts Rule and which trigger pilot studies under the 
proposed Information Collection Rule are those that are typically 
achieved in water supplies with protected watersheds. Systems which 
meet the source water criteria for unfiltered systems under the Surface 
Water Treatment Rule do not have to conduct virus monitoring under the 
proposed Information Collection Rule [59 FR 6332], whether the system 
is filtered or unfiltered. These systems are likely to have watershed 
protection programs. The proposed Enhanced Surface Water Treatment Rule 
(proposed elsewhere in today's FR) contains proposed options which 
require less water treatment for water sources with lower levels of 
microbial contamination. Such sources can achieve those levels through 
watershed protection programs. The Negotiating Committee believes that 
these indirect incentives will result in enhancements to watershed 
protection efforts in many systems.

E. Narrowing of Regulatory Options Through Reg-Neg Process

    The Negotiating Committee considered a wide range of regulatory 
options during the development process. The initial approach was to 
come up with several straw regulation outlines. These could generally 
be classified as being either (1) MCL regulations (in which compliance 
would be determined by meeting MCLs for specified disinfectants and 
DBPs) or (2) treatment technique regulations (in which compliance would 
be determined by meeting specified treatment parameters or surrogate 
compound maximum levels).
    The Negotiating Committee considered two categories of MCL options. 
The first was MCLs for groups of related DBPs, such as TTHMs and HAA5. 
Advantages of this approach included regulatory simplicity, avoidance 
of tinkering with disinfection operations to address minor exceedances 
of MCLs of individual DBPs, and the complex, not-well-understood 
production relationships among related DBPs. MCLs for individual 
compounds were also considered. Some members of the Negotiating 
Committee felt that individual MCLs approach best met the intent of the 
SDWA by regulating specific, measurable chemicals.
    The Negotiating Committee also considered treatment technique 
options. The first would have required systems to reduce the levels of 
DBP precursors (DBPP)--compounds that react with disinfectants to form 
DBPs, such as total organic carbon--to less than some specified level 
before adding any disinfectant. This approach may be inappropriate for 
two reasons. First, systems have different levels and types of 
precursors; using a surrogate such as TOC as a trigger may result in 
tremendous variation in DBP levels from system to system due to the 
disinfectant used, composition and reactivity of the DBPP, and presence 
of other DBPPs such as bromide. Also, many systems must add a 
disinfectant as an oxidant immediately at the source water intake to 
control water quality problems (e.g., zebra mussels, iron).
    The second treatment technique option was enhanced coagulation, 
which is the addition of higher levels of coagulant than required to 
meet turbidity limits for the purpose of removing higher levels of 
DBPPs. However, enhanced coagulation is practical only in systems that 
operate conventional filtration treatment. Systems using other 
filtration technologies (e.g., direct filtration, slow sand filtration) 
or that do not filter (such as most ground water systems) cannot 
operate enhanced coagulation without addition of conventional 
filtration treatment. Also, some systems have water that cannot be 
effectively treated by enhanced coagulation.
    A final option considered was a ``risk bubble''. Under this option, 
systems would be required to keep the sum of estimated risks from 
levels of specified DBPs under a certain risk level. However, this 
option was quickly dropped because of many problems, including failure 
to account for potential synergisms and antagonisms between DBPs, data 
gaps, and the evolving nature of risk assessment.

VIII. Summary of the Proposed National Primary Drinking Water 
Regulation for Disinfectants and Disinfection Byproducts

    The Disinfectants and Disinfection Byproducts Rule (D/DBPR) 
proposal addresses a number of complex and interrelated drinking water 
issues. EPA must balance the health risks from microbial organisms 
(such as Giardia, Cryptosporydium, bacteria, and viruses) against risks 
from compounds formed during water disinfection. Most of the DBPs that 
have been measured in drinking water are byproducts from the use of 
chlorine. While there is some occurrence information on even these 
DBPs, the extent of exposure for systems that have not reported DBP 
levels can only be estimated using available information on TOC levels 
and the available models. A subset of DBPs has been studied to 
determine whether long-term exposure to them presents a risk to public 
health. The current lack of data on certain relatively unstudied DBPs 
and on the effectiveness of certain treatment techniques has made 
regulatory decisions more difficult. Water treatment facilities and 
their customers potentially face significant changes to treatment 
operations in response to the proposed regulations and will have to pay 
more for water treatment. For these reasons, EPA is proposing the D/
DBPR in two stages. The two-stage process allows the best use of 
information available during the regulatory development.
    The Stage 1 D/DBPR, which will be proposed, promulgated, and 
implemented concurrently with the Interim Enhanced Surface Water 
Treatment Rule, will:

--Lower the maximum contaminant level (MCL) for total trihalomethanes 
(the only DBPs currently regulated);
--Add new disinfectants and DBPs for regulation; and
--Extend regulations to include all system sizes.

    For the Stage 2 D/DBPR, EPA will collect data on parameters that 
influence DBP formation and occurrence of DBPs in drinking water 
through an Information Collection Rule for large community water 
systems (59 FR 6332). Based on this information and new data generated 
through research, EPA will reevaluate the Stage 2 regulations and 
repropose, as appropriate, depending on criteria agreed on in a second 
regulatory negotiation (or similar rule development process). In 
addition, Stage 2 D/DBPR MCLs for TTHMs and HAA5 are being proposed in 
this Federal Register notice.

A. Schedule and Coverage

    The requirements of this rule will apply to community water systems 
(CWSs) and nontransient noncommunity water systems (NTNCWSs) that treat 
their water with a chemical disinfectant for either primary or residual 
treatment. In addition, MRDL and monitoring requirements for chlorine 
dioxide will also apply to transient noncommunity water systems because 
of the short-term health effects from high levels of chlorine dioxide 
(see section V. for a detailed discussion of health effects).
    The effective dates for compliance with these requirements will be 
staggered based on system size and raw water source. The schedule is 
summarized in Table VIII-1. Members of the Negotiating Commitee 
reserved the right to comment on the timetable for promulgation of the 
final rule and on the compliance dates of the rule.

--Subpart H systems (systems that use surface water or ground water 
under the direct influence of surface water, in whole or in part) 
serving 10,000 or more persons must comply with the Stage 1 
requirements beginning 18 months from promulgation.
--Subpart H systems serving fewer than 10,000 persons must comply with 
the Stage 1 requirements beginning 42 months from promulgation.
--A CWS or NTNCWS using only ground water not under the direct 
influence of surface water serving 10,000 or more persons must comply 
with the Stage 1 requirements beginning 42 months from promulgation.
--A CWS or NTNCWS using only ground water not under the direct 
influence of surface water serving fewer than 10,000 persons must 
comply with the Stage 1 requirements beginning 60 months from 
promulgation.

    Table VIII-1.--Compliance Date of Stage 1 Regulations for CWSs or   
                                NTNCWSs                                 
------------------------------------------------------------------------
                                                           Following    
                                           Number of     promulgation,  
            Raw water source                 people       regulations   
                                             served     become effective
                                                             after      
------------------------------------------------------------------------
Surface.................................                     
                                               10,000         18 Months.
Surface.................................      <10,000         42 Months.
Ground..................................                     
                                               10,000         42 Months.
Ground..................................      <10,000         60 Months.
------------------------------------------------------------------------

    In this proposal, EPA has not specified how monitoring and 
compliance requirements should be split among wholesalers and retailers 
of water. The Agency believes that Sec. 141.29 (consecutive systems) 
provides the State adequate flexibility and authority to address 
individual situations. EPA solicits comment on whether any specific 
federal regulatory requirements are necessary to handle such 
situations. If so, what are they?

B. Summary of DBP MCLs, BATs, and Monitoring and Compliance 
Requirements

    EPA is proposing to amend Subpart G, Maximum Contaminant Levels, by 
adding Sec. 141.64, Maximum Contaminant Levels for Disinfection 
Byproducts. Section 141.64 lists the proposed MCLs for total 
trihalomethanes (TTHMs--i.e., the sum of the concentrations of 
chloroform, bromodichloromethane, dibromochloromethane, and bromoform), 
haloacetic acids (five) (HAA5--i.e., the sum of the concentrations of 
mono-, di-, and trichloroacetic acids and mono- and dibromoacetic 
acids), bromate, and chlorite. Routine monitoring requirements for all 
DBPs and residual disinfectants are summarized in Table VIII-2. Reduced 
monitoring requirements for all DBPs and residual disinfectants are 
summarized in Table VIII-3. Members of the Negotiating Committee 
reserved the right to comment on the question of whether compliance 
monitoring is defined as an average of several samples across the 
distribution system and over time or whether it will be based upon 
monitoring at points of maximum residence time. See Section IX of this 
notice for further discussion and EPA's solicitation of comments on 
this issue.

                                Table VIII-2.--Routine Monitoring Requirements\7\                               
----------------------------------------------------------------------------------------------------------------
   Requirement        Location for      Large surface      Small surface       Large ground       Small ground  
   (reference)          sampling          systems\1\         systems\1\      water systems\2\   water systems\2\
----------------------------------------------------------------------------------------------------------------
TOC                Paired             1 paired sample/   1 paired sample/   NA...............  NA.              
 (141.133(b)(3)).   samples\3\--Only   month/ plant\3\.   month/plant\3\.                                       
                    required for                                                                                
                    plants with                                                                                 
                    conventional                                                                                
                    filtration                                                                                  
                    treatment.                                                                                  
TTHMs              25% in dist sys    4/plant/ quarter.  1/plant/quarter\6  1/plant/quarter\6  1/plant/year6,8  
 (141.133(b)(1)(i   at max res time,                      \ at maximum       \ at maximum       at maximum      
 )).                75% at dist sys                       residence time     residence time.    residence time  
                    representative                        if pop. <500,                         during warmest  
                    locations.                            then 1/plant/                         month.          
                                                          yr\8\.                                                
THAAs              25% in dist sys    4/plant/ quarter.  1/plant/quarter\6  1/plant/quarter\6  1/plant/year6,8  
 (141.133(b)(1)(i   at max res time,                      \ at maximum       \ at maximum       at maximum      
 )).                75% at dist sys                       residence time     residence time.    residence time  
                    representative                        if pop. <500,                         during warmest  
                    locations.                            then 1/plant/                         month.          
                                                          yr\8\.                                                
Bromate\4\         Dist sys entrance  1/month/trt plant  1/month/trt plant  1/month/trt plant  1/month/trt plant
 (141.133(b)(1)(i   point.             using O3.          using O3.          using O3.          using O3.       
 ii)).                                                                                                          
Chlorite\5\        1 near first       3/month..........  3/month..........  3/month..........  3/month.         
 (141.133(b)(1)(i   cust, 1 in dist                                                                             
 i)).               sys middle, 1 at                                                                            
                    max res time.                                                                               
Chlorine           Same points as     Same times as      Same times as      Same times as      Same times as    
 (141.133(b)(2)(i   coliform in TCR.   coliform in TCR.   coliform in TCR.   coliform in TCR.   coliform in TCR.
 )).                                                                                                            
Chlorine           Entrance to dist   Daily/trt plant    Daily/trt plant    Daily/trt plant    Daily/trt plant  
 dioxide\5\         sys.               using ClO2.        using ClO2.        using ClO2.        using ClO2.     
 (141.133(b)(2)(i                                                                                               
 i)).                                                                                                           
Chloramines        Same points as     Same times as      Same times as      Same times as      Same times as    
 (141.133(b)(2)(i   coliform in TCR.   coliform in TCR.   coliform in TCR.   coliform in TCR.   coliform in TCR.
 )).                                                                                                            
----------------------------------------------------------------------------------------------------------------
\1\Large surface (Subpart H) systems serve 10,000 or more persons. Small surface (Subpart H) systems serving    
  fewer than 10,000 persons.                                                                                    
\2\Large systems using ground water not under the direct influence of surface water serve 10,000 or more        
  persons. Small systems using ground water not under the direct influence of surface water serve fewer than    
  10,000 persons.                                                                                               
\3\Subpart H systems which use conventional filtration treatment (defined in Section 141.2) must monitor 1)     
  source water TOC prior to any treatment and 2) treated TOC before continuous disinfection (except that systems
  using ozone followed by biological filtration may sample after biological filtration) at the same time; these 
  two samples are called paired samples.                                                                        
\4\Only required for systems using ozone for oxidation or disinfection.                                         
\5\Only required for systems using chlorine dioxide for oxidation or disinfection. Additional chlorine dioxide  
  monitoring requirements apply if any chlorine dioxide sample exceeds the MRDL.                                
\6\Multiple wells drawing water from a single aquifer may, with State approval, be considered one treatment     
  plant for determining the minimum number of samples.                                                          
\7\Samples must be taken during representative operating conditions. Provisions for reduced monitoring shown    
  elsewhere.                                                                                                    
\8\If the annual monitoring result exceeds the MCL, the system must increase monitoring frequency to 1/plant/   
  quarter. Compliance determinations will be based on the running annual average of quarterly monitoring        
  results.                                                                                                      


                               Table VIII-3.--Reduced Monitoring Requirements\2\                                
----------------------------------------------------------------------------------------------------------------
                                Location for reduced sampling                                                   
   Requirement (reference)                                     Reduced monitoring frequency and prerequisites\1\
----------------------------------------------------------------------------------------------------------------
TOC (141.133(c)(3))...........  Paired samples\3\............  Subpart H systems-reduced to 1 paired sample/    
                                                                plant/quarter if 1) avg TOC <2.0mg/l for 2 years
                                                                or 2) avg TOC <1.0mg/l for 1 year.              
TTHMs and THAAs                 In dist sys at point with max  Monitoring cannot be reduced if source water TOC 
 (141.133(c)(1)).                res time.                      >4.0mg/l.                                       
                                                               Subpart H systems serving 10,000 or more-reduced 
                                                                to 1/plant/qtr if 1) system has completed at    
                                                                least 1 yr of routine monitoring and 2) both    
                                                                TTHM and THAA running annual averages are no    
                                                                more than 40 g/l and 30 g/l,  
                                                                respectively.                                   
                                                               Subpart H systems serving <10,000 and ground     
                                                                water systems\6\ serving 10,000 or more-reduced 
                                                                to 1/plant/yr if 1) system has completed at     
                                                                least 1 yr of routine monitoring and 2) both    
                                                                TTHM and THAA running annual averages are no    
                                                                more than 40 g/l and 30 g/l,  
                                                                respectively. Samples must be taken during month
                                                                of warmest water temperature. Subpart H systems 
                                                                serving <500 may not reduce monitoring to less  
                                                                than 1/plant/yr.                                
                                                               Groundwater systems\6\ serving <10,000-reduced to
                                                                1/plant/3yr if 1) system has completed at least 
                                                                2 yr of routine monitoring and both TTHM and    
                                                                THAA running annual averages are no more than 40
                                                                g/l and 30 g/l, respectively  
                                                                or 2) system has completed at least 1 yr of     
                                                                routine monitoring and both TTHM and THAA annual
                                                                samples are no more than 20 g/l and 15 
                                                                g/l, respectively. Samples must be     
                                                                taken during month of warmest water temperature.
Bromate\4\ (141.133(c)(1))....  Dist sys entrance point......  1/qtr/trt plant using O3, if system demonstrates 
                                                                1) avg raw water bromide <0.05 mg/l (based on   
                                                                annual avg of monthly samples).                 
Chlorite\5\ (141.133(c)(1))...  NA...........................  Monitoring may not be reduced.                   
Chlorine, chlorine dioxide\5\,  NA...........................  Monitoring may not be reduced.                   
 chloramines (141.133(c)(2)).                                                                                   
----------------------------------------------------------------------------------------------------------------
\1\Requirements for cancellation of reduced monitoring are found in the regulation.                             
\2\Samples must be taken during representative operating conditions. Provisions for routine monitoring shown    
  elsewhere.                                                                                                    
\3\Subpart H systems which use conventional filtration treatment (defined in Section 141.2) must monitor 1)     
  source water TOC prior to any treatment and 2) treated TOC before continuous disinfection (except that systems
  using ozone followed by biological filtration may sample after biological filtration) at the same time; these 
  two samples are called paired samples.                                                                        
\4\Only required for systems using ozone for oxidation or disinfection.                                         
\5\Only required for systems using chlorine dioxide for oxidation or disinfection.                              
\6\Multiple wells drawing water from a single aquifer may, with State approval, be considered one treatment     
  plant for determining the minimum number of samples.                                                          

1. Maximum Contaminant Levels for Total Trihalomethanes and Total 
Haloacetic Acids
    The formation rate of DBPs is affected by type and amount of 
disinfectant used, water temperature, pH, amount and type of precursor 
material in the water, and the length of time that water remains in the 
treatment and distribution systems. For this reason, the proposed rule 
specifies the point in the distribution system (and in some cases, the 
time) where samples must be taken.
    In this action today, EPA proposes to lower the MCL for TTHMs from 
0.10 mg/l to 0.080 mg/l. In addition, EPA proposes to set the Stage 1 
MCL for HAA5 at 0.060 mg/l. EPA believes that by meeting MCLs for TTHMs 
and HAA5, water suppliers will also control the formation of other DBPs 
not currently regulated that may also adversely affect human health.
    a. Subpart H Systems Serving 10,000 or More People.
    Routine Monitoring: CWSs and NTNCWSs using surface water (or ground 
water under direct influence of surface water) (Subpart H systems) that 
treat their water with a chemical disinfectant and serve 10,000 or more 
people must routinely take four water samples each quarter for both 
TTHMs and HAA5 for each treatment plant in the system. At least 25 
percent of the samples must be taken at the point of maximum residence 
time in the distribution system. The remaining samples must be taken at 
representative points in the distribution system. This monitoring 
frequency is the same as the frequency required under the current TTHM 
rule (Sec. 141.30).
    Reduced Monitoring: To qualify for reduced monitoring, systems must 
meet certain prerequisites (see Figure VIII-1). Systems eligible for 
reduced monitoring may reduce the monitoring frequency for TTHMs and 
HAA5 to one sample per quarter. Systems on a reduced monitoring 
schedule may remain on that reduced schedule as long as the average of 
all samples taken in the year is no more than 75 percent of each MCL. 
Systems that do not meet these levels revert to routine monitoring.
    Compliance Determination: A public water system (PWS) is in 
compliance with the MCL when the running annual average of quarterly 
averages of all samples, computed quarterly, is less than or equal to 
the MCL. If the running annual average computed for any quarter exceeds 
the MCL, the system is out of compliance.

 Figure VIII-1.--Eligibility for Reduced Monitoring: All Systems Serving
   10,000 or More People and Surface Water Systems Serving 500 or More  
                                 People                                 
                                                                        
                                                                        
All systems serving                                                     
 10,000 or more                                                         
 people, and                                                            
 surface water                                                          
 systems serving                                                        
 500 or more                                                            
 people, may reduce                                                     
 monitoring of                                                          
 TTHMs and HAA5 if                                                      
 they meet all of                                                       
 the following                                                          
 conditions:                                                            
  --The annual                                                          
   average for                                                          
   TTHMs is no more                                                     
   than 0.040 mg/l.                                                     
  --The annual                                                          
   average for HAA5                                                     
   is no more than                                                      
   0.030 mg/l.                                                          
  --At least one                                                        
   year of routine                                                      
   monitoring has                                                       
   been completed.                                                      
  --Annual average                                                      
   source water                                                         
   Total Organic                                                        
   Carbon (TOC)                                                         
   level is no more                                                     
   than 4.0 mg/l                                                        
   prior to                                                             
   treatment.                                                           

    b. Ground Water Systems Serving 10,000 or More People.
    Routine Monitoring: CWSs and NTNCWSs using only ground water 
sources not under the direct influence of surface water that treat 
their water with a chemical disinfectant and serve 10,000 or more 
people are required to take one water sample each quarter for each 
treatment plant in the system. Samples must be taken at points that 
represent the maximum residence time in the distribution system. For 
purposes of this regulation, multiple wells drawing raw water from a 
single aquifer may, with State approval, be considered one plant for 
determining the minimum number of samples. Systems may take additional 
samples if they desire. If additional samples are taken, at least 25 
percent of the total number of samples must be taken at the point of 
maximum residence time in the distribution system. The remaining 
samples must be taken at representative points in the distribution 
system.
    Reduced Monitoring: To qualify for reduced monitoring, systems must 
meet certain prerequisites (see Figure VIII-1). Systems eligible for 
reduced monitoring may reduce the monitoring frequency to one sample 
per treatment plant per year. Systems that are on a reduced monitoring 
schedule may remain on that reduced schedule as long as the average of 
all samples taken in the year is no more than 75 percent of the MCLs. 
Systems that do not meet these levels must revert to routine 
monitoring.
    Compliance Determination: A PWS is in compliance with the MCL when 
the running annual average of quarterly averages of all samples, 
computed quarterly, is less than or equal to the MCL. If the running 
annual average for any quarter exceeds the MCL, the system is out of 
compliance.
    c. Subpart H Systems Serving 500 to 9,999 People.
    Routine Monitoring: Systems are required to take one water sample 
each quarter for each treatment plant in the system. All samples must 
be taken at the point of maximum residence time in the distribution 
system.
    Reduced Monitoring: To qualify for reduced monitoring, systems must 
meet certain prerequisites (see Figure VIII-1). Systems eligible for 
reduced monitoring may reduce the monitoring frequency for TTHMs and 
HAA5 to one sample per year per treatment plant. Systems that are on a 
reduced monitoring schedule may remain on that reduced schedule as long 
as the average of all samples taken in the year is no more than 75 
percent of the MCLs. Systems that do not meet these levels must revert 
to routine monitoring.
    Compliance Determination: A PWS is in compliance with the MCL when 
the running annual average of quarterly averages of all samples, 
computed quarterly, is less than or equal to the MCL. If the average 
for any quarter exceeds the MCL, the system is out of compliance.
    d. Subpart H Systems Serving Fewer than 500 People.
    Routine Monitoring: Subpart H systems serving fewer than 500 people 
are required to take one sample per year for each treatment plant in 
the system. The sample must be taken at the point of maximum residence 
time in the distribution system during the month of warmest water 
temperature. If the annual sample exceeds the MCL, the system must 
increase monitoring to one sample per treatment plant per quarter, 
taken at the point of maximum residence time in the distribution 
system.
    Reduced Monitoring: These systems may not reduce monitoring. 
Systems on increased monitoring may return to routine monitoring if the 
annual average of quarterly samples is no more than 75 percent of the 
TTHM and HAA5 MCLs.
    Compliance Determination: A PWS is in compliance when the annual 
sample (or average of annual samples, if additional sampling is 
conducted) is less than or equal to the MCL. If the annual sample 
exceeds the MCL, the system must increase monitoring to one sample per 
treatment plant per quarter. If the running annual average of the 
quarterly samples then exceeds the MCL, the system is out of 
compliance.
    e. Ground Water Systems Serving Fewer than 10,000 People.
    Routine Monitoring: CWSs and NTNCWSs using only ground water 
sources not under the direct influence of surface water that treat 
their water with a chemical disinfectant and serve fewer than 10,000 
people are required to sample once per year for each treatment plant in 
the system. The sample must be taken at the point of maximum residence 
time in the distribution system during the month of warmest water 
temperature. If the sample (or the average of all annual samples, when 
more than the one required sample is taken) exceeds the MCL, the system 
must increase monitoring to one sample per treatment plant per quarter.
    Reduced Monitoring: To qualify for reduced monitoring, systems must 
meet certain prerequisites (see Figure VIII-2). Systems eligible for 
reduced monitoring may reduce the monitoring frequency for TTHMs and 
HAA5 to one sample per three-year monitoring cycle. Systems on a 
reduced monitoring schedule may remain on that reduced schedule as long 
as the average of all samples taken in the year is no more than 75 
percent of the MCLs. Systems that do not meet these levels must resume 
routine monitoring. Systems on increased monitoring may return to 
routine monitoring if the annual average of quarterly samples is no 
more than 75 percent of the TTHM and HAA5 MCLs. 

Figure VIII-2.--Eligibility for Reduced Monitoring: Ground Water Systems
                    Serving Fewer than 10,000 People                    
                                                                        
                                                                        
Systems using                                                           
 ground water not                                                       
 under the direct                                                       
 influence of                                                           
 surface water that                                                     
 serve fewer than                                                       
 10,000 people may                                                      
 reduce monitoring                                                      
 for TTHMs and HAA5                                                     
 if they meet                                                           
 either of the                                                          
 following                                                              
 conditions:                                                            
  1. The average of                                                     
   two consecutive                                                      
   annual samples                                                       
   for TTHMs is no                                                      
   more than 0.040                                                      
   mg/l, the                                                            
   average of two                                                       
   consecutive                                                          
   annual samples                                                       
   for HAA5 is no                                                       
   more than 0.030                                                      
   mg/l, at least                                                       
   two years of                                                         
   routine                                                              
   monitoring has                                                       
   been completed,                                                      
   and the annual                                                       
   average source                                                       
   water Total                                                          
   Organic Carbon                                                       
   (TOC) level is                                                       
   no more than 4.0                                                     
   mg/l prior to                                                        
   treatment.                                                           
  2. The annual                                                         
   sample for TTHMs                                                     
   is no more than                                                      
   0.020 mg/l, the                                                      
   annual sample                                                        
   for HAA5 is no                                                       
   more than 0.015                                                      
   mg/l, at least                                                       
   one year of                                                          
   routine                                                              
   monitoring has                                                       
   been completed,                                                      
   and the annual                                                       
   average source                                                       
   water Total                                                          
   Organic Carbon                                                       
   (TOC) level is                                                       
   no more than 4.0                                                     
   mg/l prior to                                                        
   treatment.                                                           

    Compliance Determination: A PWS is in compliance when the annual 
sample (or average of annual samples) is less than or equal to the MCL.
    f. Best Available Technology.
    EPA has identified the best technology available for achieving 
compliance with the MCLs for both TTHMs and HAA5 as enhanced 
coagulation or treatment with granular activated carbon with a ten 
minute empty bed contact time and 180 day reactivation frequency 
(GAC10), with chlorine as the primary and residual disinfectant. 
Enhanced coagulation means the addition of excess coagulant for 
improved removal of disinfection byproduct precursors by conventional 
filtration treatment.
2. Maximum Contaminant Level for Bromate
    Bromate is one of the principal byproducts of ozonation in bromide-
containing source waters. The proposed MCL for bromate is 0.010 mg/l.
    Routine Monitoring: CWSs and NTNCWSs using ozone, for disinfection 
or oxidation, are required to take at least one sample per month for 
each treatment plant in the system using ozone. The sample must be 
taken at the entrance to the distribution system when the ozonation 
system is operating under normal conditions.
    Reduced Monitoring: If a system's monthly measurements for one year 
indicate that the average raw water bromide concentration is less than 
0.05 mg/l, the system may reduce the monitoring frequency to once per 
quarter.
    Compliance Determination: A PWS is in compliance if the running 
annual average of samples, computed quarterly, is less than or equal to 
the MCL.
    Best Available Technology: EPA has identified the best technology 
available for achieving compliance with the MCL for bromate as control 
of ozone treatment process to reduce production of bromate.
3. Maximum Contaminant Level for Chlorite
    Chlorite is an inorganic DBP formed when drinking water is treated 
with chlorine dioxide. The proposed MCL for chlorite is 1.0 mg/l.
    Routine Monitoring: CWSs and NTNCWSs using chlorine dioxide for 
disinfection or oxidation are required to take three samples each month 
in the distribution system. One sample must be taken at each of the 
following locations: as close as possible to the first customer, in a 
location representative of average residence time, and as close as 
possible to the end of the distribution system (reflecting maximum 
residence time in the distribution system).
    Reduced monitoring: Systems required to monitor for chlorite may 
not reduce monitoring.
    Compliance Determination: A PWS is in compliance if the monthly 
average of samples is less than or equal to the MCL.
    Best Available Technology: EPA has identified as the best means 
available for achieving compliance with the chlorite MCL as control of 
treatment processes to reduce disinfectant demand, and control of 
disinfection treatment processes to reduce disinfectant levels.

C. Summary of Disinfectant MRDLs, BATs, and Monitoring and Compliance 
Requirements

    Disinfectants are added during water treatment to control 
waterborne microbial contaminants. Some residual disinfectants will 
remain in water after treatment. MRDLs protect public health by setting 
limits on the level of residual disinfectants in drinking water. MRDLs 
are similar in concept to MCLs--MCLs set limits on contaminants and 
MRDLs set limits on residual disinfectants. MRDLs, like MCLs, are 
enforceable.
1. MRDL for Chlorine
    Chlorine is a widely used and highly effective water disinfectant. 
The proposed MRDL   for   chlorine   is   4.0 mg/l.
    Routine Monitoring: As a minimum, CWSs and NTNCWSs must measure the 
residual disinfectant level at the same points in the distribution 
system and at the same time as total coliforms, as specified in 
Sec. 141.21. Subpart H systems may use the results of residual 
disinfectant concentration sampling done under the SWTR 
(Sec. 141.74(b)(6) for unfiltered systems, Sec. 141.74(c)(3) for 
systems that filter) in lieu of taking separate samples.
    Reduced monitoring: Monitoring for chlorine may not be reduced.
    Compliance Determination: A PWS is in compliance with the MRDL when 
the running annual average of monthly averages of all samples, computed 
quarterly, is less than or equal to the MRDL. Notwithstanding the MRDL, 
operators may increase residual chlorine levels in the distribution 
system to a level and for a time necessary to protect public health to 
address specific microbiological contamination problems (e.g., 
including distribution line breaks, storm runoff events, source water 
contamination, or cross-connections).
    Best Available Technology: EPA has identified the best means 
available for achieving compliance with the MRDL for chlorine as 
control of treatment processes to reduce disinfectant demand, and 
control of disinfection treatment processes to reduce disinfectant 
levels.
2. MRDL for Chloramines
    Chloramines are formed when ammonia is added during chlorination. 
The proposed MRDL for chloramines is 4.0 mg/l (as total chlorine).
    Routine Monitoring: As a minimum, CWSs and NTNCWSs must measure the 
residual disinfectant level at the same points in the distribution 
system and at the same time as total coliforms, as specified in 
Sec. 141.21. Subpart H systems may use the results of residual 
disinfectant concentration sampling done under the SWTR 
(Sec. 141.74(b)(6) for unfiltered systems, Sec. 141.74(c)(3) for 
systems that filter) in lieu of taking separate samples.
    Reduced monitoring: Monitoring for chloramines may not be reduced.
    Compliance Determination: A PWS is in compliance with the MRDL when 
the running annual average of monthly averages of all samples, computed 
quarterly, is less than or equal to the MRDL. Notwithstanding the MRDL, 
operators may increase residual chloramine levels in the distribution 
system to a level and for a time necessary to protect public health to 
address specific microbiological contamination problems (e.g., 
including distribution line breaks, storm runoff events, source water 
contamination, or cross-connections).
    Compliance Determination: A PWS is in compliance with the MRDL when 
the running annual average of samples, computed quarterly, is less than 
or equal to the MRDL. EPA recognizes that it may be appropriate to 
increase residual disinfectant levels in the distribution system of 
chloramines significantly above the MRDL for short periods of time to 
address specific microbiological contamination problems (e.g., 
distribution line breaks, storm runoff events, source water 
contamination, or cross-connections).
    Best Available Technology: EPA identifies the best means available 
for achieving compliance with the MRDL for chloramines as control of 
treatment processes to reduce disinfectant demand, and control of 
disinfection treatment processes to reduce disinfectant levels.
3. MRDL for Chlorine Dioxide
    Chlorine dioxide is used primarily for the oxidation of taste and 
odor-causing organic compounds in water. It can also be used for the 
oxidation of reduced iron and manganese and color, and is also a 
powerful disinfectant and algicide. Chlorine dioxide reacts with 
impurities in water very rapidly, and is dissipated very quickly. EPA 
is proposing an MRDL of 0.80 mg/l for chlorine dioxide.
    Routine Monitoring: CWSs and noncommunity systems must monitor for 
chlorine dioxide only if chlorine dioxide is used by the system for 
disinfection or oxidation. If monitoring is required, systems must take 
daily samples at the entrance to the distribution system. If the MRDL 
is exceeded, the system must go to increased monitoring.
    Increased Monitoring: If any daily sample taken at the entrance to 
the distribution system exceeds the MRDL, the system is required to 
take three additional samples in the distribution system on the next 
day. Samples must be taken at the following locations.
     Systems using chlorine as a residual disinfectant and 
operating booster chlorination stations after the first customer. These 
systems must take three samples in the distribution system: One as 
close as possible to the first customer, one in a location 
representative of average residence time, and one as close as possible 
to the end of the distribution system (reflecting maximum residence 
time in the distribution system).
     Systems using chlorine dioxide or chloramines as a 
residual disinfectant or chlorine as a residual disinfectant and not 
operating booster chlorination stations after the first customer. These 
systems must take three samples in the distribution system as close as 
possible to the first customer at intervals of not less than six hours.
    Reduced monitoring: Monitoring for chlorine dioxide may not be 
reduced.
    Compliance Determination: Acute violations. If any daily sample 
taken at the entrance to the distribution system exceeds the MRDL and 
if, on the following day, any sample taken in the distribution system 
exceeds the MRDL, the system will be in acute violation of the MRDL and 
must take immediate corrective action to lower the occurrence of 
chlorine dioxide below the MRDL and issue the required acute public 
notification. Failure to monitor in the distribution system on the day 
following an exceedance of the chlorine dioxide MRDL shall also be 
considered an acute MRDL violation.
    Nonacute violations. If any two consecutive daily samples taken at 
the entrance to the distribution system exceed the MRDL, but none of 
the samples taken in the distribution system exceed the MRDL, the 
system will be in nonacute violation of the MRDL and must take 
immediate corrective action to lower the occurrence of chlorine dioxide 
below the MRDL. Failure to monitor at the entrance to the distribution 
system on the day following an exceedance of the chlorine dioxide MRDL 
shall also be considered a nonacute MRDL violation.
    Important note. Unlike chlorine and chloramines, the MRDL for 
chlorine dioxide may not be exceeded for short periods of time to 
address specific microbiological contamination problems.
    Monitoring for CT credit: Subpart H systems required to operate 
enhanced coagulation or enhanced softening may receive credit for 
compliance with CT requirements in Subpart H if the following 
monitoring is completed and the required operational standards are met.

--For each chlorine dioxide generator, the system must demonstrate that 
the generator is achieving at least 95 percent yield and producing no 
more than five percent free chlorine by testing a minimum of once per 
week.
--On any day that a generator fails to achieve at least 95 percent 
yield, and on subsequent days until at least 95 percent yield is 
achieved, and/or any day that the generator produces more than five 
percent free chlorine and on subsequent days until no more than five 
percent free chlorine is produced, the system may not receive credit 
for compliance with CT requirements.
--On any day that a generator achieves at least 90 percent, but less 
than 95 percent, yield, and/or any day that a generator produces more 
than five percent, but less than 10 percent, free chlorine, the system 
may take immediate corrective action to achieve a minimum of 95 percent 
yield and no more than five percent free chlorine. If subsequent 
testing conducted on the same day demonstrates at least 95 percent 
yield and no more than five percent free chlorine, the system may 
receive credit for compliance with CT requirements on that day. If the 
generator continues to fail to demonstrate at least 95 percent yield 
and/or continues to produce more than five percent free chlorine, the 
system may not receive credit for compliance with CT requirements on 
that day.
--Measurements must be made at least every seven days. If, in the 
interim, the system changes generator conditions (e.g., change in 
chlorine dose, change conditions to match changing plant flow rate), it 
shall remeasure for chlorine dioxide yield and free chlorine.

    To calculate compliance with Sec. 141.133(b)(2)(ii)(C) in order to 
receive credit for CT compliance, Method 4500-ClO2 E (Standard 
Methods for the Examination of Water and Wastewater, 18th Ed. 1992) 
must be used to determine concentrations of chlorine dioxide, chlorine, 
and related species in the generator effluent. Calculations are 
performed as demonstrated below.
    1. Perform titration on generator sample aliquots as required by 
Method 4500-ClO2 E. Record the titration readings for A through E 
below, the normality (N) of the titrant used, and the sample dilution.

--A (ml titrant/ml sample) for titration of chlorine and one-fifth of 
ClO2.
--B (ml titrant/ml sample) for titration of four-fifths of ClO2 
and of chlorite.
--C (ml titrant/ml sample) for titration of nonvolatilized chlorine.
--D (ml titrant/ml sample) for titration of chlorite.
--E (ml titrant/ml sample) for titration of chlorine, ClO2, 
chlorate, and chlorite.
--N (normality of the titrant used in equivalents per liter).

    2. Determine chlorine dioxide generator performance (yield). The 
calculations in a. through c. below must be corrected for the sample 
dilution.
    a. Calculate chlorine dioxide concentration.

[ClO2 (mg/l)]=13490 x 5/4 x (B-D) x N

    b. Calculate chlorite concentration.

[ClO2 (mg/l)] = 16863  x  D  x  N

    c. Calculate chlorate concentration.

[ClO3 (mg/l)] = 13909  x  [E-(A+B)]  x  N

    d. Calculate yield (in %).

TP29JY94.009

    3. Determine excess chlorine. This calculation must be corrected 
for sample dilution.
    a. Calculate chlorine concentration.

[Cl2 (mg/l)] = {A - [(B-D)/4]}  x  N  x 35453

    b. Using the concentrations of chlorine dioxide, chlorite, and 
chlorate calculated above (2.a.-c.), calculate excess chlorine.

TP29JY94.010

    4. Determine whether CT credit can be taken.
    a. If % Yield  95% and % Excess Chlorine  5%, 
CT credit may be taken.
    b. If % Yield  90% but < 95%, and/or % Excess chlorine > 
5% but < 10%, the system may take immediate corrective action and then 
remeasure. CT credit may be taken if a subsequent measurement performed 
on the same day shows a yield  95% and % Excess Chlorine 
 5%.
    c. If % Yield < 90% or excess chlorine > 10%, the system may not 
take CT credit for that day and for any subsequent days until a 
subsequent measurement shows a yield  95% and % Excess 
Chlorine  5%.
    Best Available Technology: EPA identifies the best means available 
for achieving compliance with the MRDL for chlorine dioxide as control 
of treatment processes to reduce disinfectant demand, and control of 
disinfection treatment processes to reduce disinfectant levels.

D. Enhanced Coagulation and Enhanced Softening Requirements

    In addition to meeting MCLs and MRDLs, some water suppliers must 
also meet treatment requirements to control the organic material 
(disinfection byproduct precursors (DBPPs)) in the raw water that 
combines with disinfectant residuals to form DBPs. Subpart H systems 
using conventional treatment are required to control for DBPPs 
(measured as total organic carbon (TOC)) by using enhanced coagulation 
or enhanced softening. A system must remove a certain percentage of TOC 
(based on raw water quality) prior to the point of continuous 
disinfection. Systems using ozone followed by biologically active 
filtration or chlorine dioxide which meets specific criteria would be 
required to meet the TOC removal requirements prior to addition of a 
residual disinfectant. Systems able to reduce TOC by a specified 
percentage level have met the DBPP treatment technique requirement. If 
the system does not meet the percent reduction, it must determine its 
alternative minimum TOC removal level, which is further explained in 
Section IX. The State approves the alternative minimum TOC removal 
possible for the system on the basis of the relationship between 
coagulant dose and TOC in the system.
1. Applicability
    Subpart H systems using conventional treatment must use enhanced 
coagulation or enhanced softening to remove TOC unless they meet one of 
the criteria in a. through d. below. Systems using chlorine dioxide 
that achieve a 95 percent yield of chlorine dioxide and have no more 
than five percent excess chlorine would be required to meet the TOC 
removal requirements prior to the addition of another residual 
disinfectant.
    a. The system's treated water TOC level, prior to the point of 
continuous disinfection, is less than 2.0 mg/l.
    b. The system's source water TOC level, prior to any treatment, is 
less than 4.0 mg/l; the alkalinity is greater than 60 mg/l; and not 
later than the effective dates for compliance for the system, either 
the TTHM annual average is no more than 0.040 mg/l and the THAA annual 
average is no more than 0.030 mg/l, or the system has made a clear and 
irrevocable financial commitment not later than the effective date for 
compliance for Stage 1 to technologies that will limit the levels of 
TTHMs and THAAs to no more than 0.040 mg/l and 0.030 mg/l, 
respectively. Systems must submit evidence of the clear and irrevocable 
financial commitment, in addition to a schedule containing milestones 
and periodic progress reports for installation and operation of 
appropriate technologies, to the State for approval not later than the 
effective date for compliance for Stage 1. These technologies must be 
installed and operating not later than the effective date for Stage 2.
    c. The system's TTHM annual average is no more than 0.040 mg/l and 
the THAA annual average is no more than 0.030 mg/l and the system uses 
only chlorine for disinfection.
    d. Systems practicing softening and removing at least 10 mg/l of 
magnesium hardness (as CaCO3), except those that use ion exchange, 
are not subject to performance criteria for the removal of TOC.
2. Enhanced Coagulation Performance Requirements
    Systems Not Practicing Softening. Systems that use either (1) ozone 
followed by biological filtration or (2) chlorine dioxide and meet the 
performance requirements for CT credit must reduce TOC by the amount 
specified in Table VIII-4 before the addition of a residual 
disinfectant. All other systems must reduce the percentage of TOC in 
the raw water by the amount specified in Table VIII-4 prior to 
continuous disinfection, unless the State approves a system's request 
for an alternative minimum TOC removal level.
    Required TOC reductions for Subpart H systems, indicated in Table 
VIII-4, are based upon the specified source water parameters.
    Systems Practicing Softening. Systems that use either (1) ozone 
followed by biological filtration or (2) chlorine dioxide and meet the 
performance requirements for CT credit must reduce TOC by the amount 
specified in the far-right column of Table VIII-4 (Source Water 
Alkalinity >120 mg/l) for the specified source water TOC before the 
addition of a residual disinfectant. All other systems practicing 
softening are required to meet the percent reductions in the far-right 
column of Table VIII-4 (Source Water Alkalinity >120 mg/l) for the 
specified source water TOC prior to continuous disinfection, unless the 
State approves a system's request for an alternative minimum TOC 
removal level. Systems removing more than 10 mg/l of magnesium hardness 
(as CaCo3) are considered to be practicing enhanced softening, and 
are not subject to performance criteria for the removal of TOC (see 
paragraph D.1.(d) above). 

   Table VIII-4.--Required Removal of TOC by Enhanced Coagulation for   
            Subpart H Systems Using Conventional Treatment\1\           
                              [In percent]                              
------------------------------------------------------------------------
                                         Source water alkalinity (mg/l) 
 Source water total organic carbon (mg/ --------------------------------
                   l)                       0-60     >60-120    >120\2\ 
------------------------------------------------------------------------
>2.0-4.0...............................       40.0       30.0       20.0
>4.0-8.0...............................       45.0       35.0       25.0
>8.0...................................       50.0       40.0      30.0 
------------------------------------------------------------------------
\1\Systems meeting at least one of the conditions in Sec.               
  141.135(a)(1)(i)-(iv) are not required to operate with enhanced       
  coagulation.                                                          
\2\Systems practicing softening must meet the TOC removal requirements  
  in this column.                                                       

3. Alternative Performance Criteria
    a. Non-softening systems. Non-softening Subpart H conventional 
treatment systems that cannot achieve the TOC removals required above 
due to unique water quality parameters or operating conditions must 
apply to the State for alternative performance criteria. The system's 
application to the State must include, as a minimum, results of bench- 
or pilot-scale testing for alternate performance criteria. Alternative 
TOC removal criteria may be determined as follows:
    (1) bench- or pilot-scale testing used to determine alternative TOC 
removal criteria must be based on quarterly measurements and must be 
conducted at pH levels no greater than those indicated in Table VIII-5, 
dependent on the alkalinity of the water,
    (2) the alternative TOC removal criteria will be no less than the 
percent removal determined by the alternative enhanced coagulation 
level (AECL), where an incremental addition of 10 mg/l of alum (or an 
equivalent amount of ferric salt) results in a TOC removal of 0.3 mg/l 
(determined as a slope),
    (3) once approved by the State, this new requirement (alternative 
TOC removal criteria) supersedes the minimum TOC removal required in 
Table VIII-4 and remains effective until the State approves a new 
value, and
    (4) if the TOC removal is consistently less than 0.3 mg/l of TOC 
per 10 mg/l of incremental alum dose at all dosages of alum, the water 
is deemed to contain TOC not amenable to enhanced coagulation and the 
system may then apply to the State for a waiver of enhanced coagulation 
requirements. 

     Table VIII-5.--Alternate Enhanced Coagulation Level Maximum pH     
------------------------------------------------------------------------
                Alkalinity (mg/l as CaCO3)                   Maximum pH 
------------------------------------------------------------------------
0-60.......................................................          5.5
60-120.....................................................          6.3
>120-240...................................................          7.0
>240.......................................................         7.5 
------------------------------------------------------------------------

    The system may then operate at any coagulant dose or pH necessary 
to achieve the minimum TOC removal determined under the testing. For 
example, a system may choose to use lower levels of alum and depress 
the pH further instead of adding higher levels of alum at the higher 
pH.
    b. Softening systems. During the negotiation, the Committee was not 
able to develop alternative performance criteria for Subpart H 
softening systems. In Section IX of this Notice, EPA solicits comments 
on what these criteria should include.
4. Compliance Determinations
    Compliance for systems required to operate with enhanced 
coagulation or enhanced softening is based on a running annual average, 
computed quarterly, of normalized monthly TOC percent reductions. A 
system is in compliance if the normalized running annual average is at 
least 1.00. For Subpart H systems using conventional treatment but not 
required to operate enhanced coagulation or enhanced softening, 
compliance with the DBPP treatment technique is based on continuing to 
meet the avoidance criteria in paragraph 1 above. Example VIII-1 below 
shows how to determine compliance with the enhanced coagulation (or 
enhanced softening) requirements for systems that do not require 
alternative TOC removal requirements.

Example VIII-1

    The system conducts the required monitoring for 12 months. 
Complete data are included only for the most recent quarter of 
monitoring.
    (1) Using the procedure explained in Sec. 141.135(b), the system 
determines the percent TOC removal, which is equal to:

(1 - (treated water TOC/source water TOC))  x  100

    (2) Determine the required monthly TOC percent removal (from 
either the table in Sec. 141.135(a)(2)(i) or from 
Sec. 141.135(a)(3). Note that seasonal water quality variations may 
require systems to determine required TOC removals from both 
sections (i.e., both Step 1 and Step 2 levels) during any one year.
    (3) Divide 1) by 2).
    (4) Add together the results of 3) for the last 12 months and 
divide by 12.
    (5) If 4) <1.00, the system is not in compliance.

    In the report below, the system is in compliance with the TOC 
removal requirements. 

                                                                                                                
                                                                                                                
                                                                              Source                            
               Month                  Treated       Source     (1-a./b.)      water      Reqd. TOC      c./d.   
                                     TOC(mg/l)    TOC(mg/l)      x  100     alkalinity  removal (%)             
                                             a.           b.           c.                        d.           e.
                                                                                                                
----------------------------------------------------------------------------------------------------------------
January...........................  ...........  ...........  ...........  ...........  ...........         1.10
February..........................  ...........  ...........  ...........  ...........  ...........         0.94
March.............................  ...........  ...........  ...........  ...........  ...........         1.03
April.............................  ...........  ...........  ...........  ...........  ...........         1.07
May...............................  ...........  ...........  ...........  ...........  ...........         0.98
June..............................  ...........  ...........  ...........  ...........  ...........         1.24
July..............................  ...........  ...........  ...........  ...........  ...........         1.10
August............................  ...........  ...........  ...........  ...........  ...........         1.07
September.........................  ...........  ...........  ...........  ...........  ...........         1.02
October...........................          4.6          8.2           44           70           40         1.10
November..........................          4.0          6.1           34           75           35         0.98
December..........................          4.4          6.2           29           85           35         0.83
Last 12 mos.......................          N/A          N/A          N/A          N/A          N/A   =
                                                                                                     12.48 1.00, the system is in compliance.                                                             

    EPA solicits comment on how the following situations should be 
handled in compliance determinations.

--when the monthly source water TOC is less than 2.0 mg/l and enhanced 
coagulation is not required.
--when seasonal variations cause the system to determine that TOC is 
not amenable to any level of enhanced coagulation and the system would 
be eligible for a waiver of enhanced coagulation requirements.

EPA believes that assigning a value of 1.00 for these months is a 
reasonable approach.
5. CT Credit.
    Systems required to operate with enhanced coagulation or enhanced 
softening may not take credit for compliance with CT requirements prior 
to sedimentation unless they meet one of the following criteria:
    a. Systems may include CT credit during periods when the water 
temperature is below 5 deg.C and the TTHM and HAA5 quarterly averages 
are no greater than 40 g/l and 30 g/l, respectively.
    b. Systems receiving disinfected water from a separate entity as 
their source water shall be allowed to include credit for this 
disinfectant in determining compliance with the CT requirements. If the 
TTHM and HAA5 quarterly averages are no greater than 40 g/l 
and 30 g/l, respectively, systems may use the measured ``C'' 
(residual disinfectant concentration) and the actual contact time (as 
T10). If the TTHM and HAA5 quarterly averages are greater than 40 
g/l and 30 g/l, respectively, systems must use a 
``C'' (residual disinfectant concentration) of 0.2 mg/l or the measured 
value, whichever is lower; and the actual contact time (as T10). 
This credit shall be allowed from the disinfection feed point, through 
a closed conduit only, and ending at the delivery point to the 
treatment plant.
    c. Systems using chlorine dioxide as an oxidant or disinfectant may 
include CT credit for its use prior to enhanced coagulation or enhanced 
softening if the following standards are met: the chlorine dioxide 
generator must generate chlorine dioxide on-site at a minimum 95 
percent yield from sodium chlorite; and the generated chlorine dioxide 
feed stream applied from the chlorine dioxide generator must contain 
less than five percent (by weight) chlorine, measured as the weight 
ratio of chlorine to chlorine dioxide, chlorite, and chlorate in such 
feed stream. Compliance with these standards must be demonstrated by 
monitoring.

E. Requirement for Systems to Use Qualified Operators

    Under the proposed rule, each PWS must be operated by qualified 
personnel who meet the requirements specified by the State. This 
proposed requirement is similar to the requirement in the Surface Water 
Treatment Rule. States must develop operator qualifications if they do 
not already have them and they must require that systems be operated by 
personnel who meet these qualifications. In addition, the State must 
maintain a register of qualified operators. The appropriate criteria 
for determining if an operator is qualified depend upon the type and 
size of the system.

F. Analytical Method Requirements

    Disinfection By-Products. Disinfection by-products must be measured 
by the methods listed in Table VIII-6: 

      Table VIII-6.--Proposed Methods for Disinfection By-products      
------------------------------------------------------------------------
                 Contaminant                           Methods          
------------------------------------------------------------------------
Trihalomethanes (4).........................  \1\502.2, \2\524.2,       
                                               \3\551.                  
Haloacetic Acids (5)........................  \2\552.1, \4\6233 B.      
Bromate, Chlorite...........................  \5\300.0.                 
------------------------------------------------------------------------
\1\EPA Method 502.2 is in the manual ``Methods for the Determination of 
  Organic Compounds in Drinking Water'', EPA/600/4-88/039, July 1991,   
  NTIS publication PB91-231480.                                         
\2\EPA Methods 524.2 and 552.1 are in the manual ``Methods for the      
  Determination of Organic Compounds in Drinking Water--Supplement II'',
  EPA/600/R-92/129, August 1992, NTIS PB92-207703.                      
\3\EPA Method 551 is in the manual ``Methods for the Determination of   
  Organic Compounds in Drinking Water--Supplement I'', EPA/600/4-90/020,
  July 1990, NTIS PB91-146027.                                          
\4\Standard Method 6233 B is in ``Standard Methods for the Examination  
  of Water and Wastewater,'' 18th Edition, American Public Health       
  Association, American Water Works Association, and Water Environment  
  Federation, 1992.                                                     
\5\EPA Method 300.0 is in the manual ``Methods for the Determination of 
  Inorganic Substances in Environmental Samples'', EPA/600/R/93/100,    
  August 1993, with revisions. See Section IX for revisions.            

    All measurements listed in this section must be conducted by a 
laboratory certified by EPA or the State. To receive certification, the 
laboratory must:
    (1) Use the promulgated method(s).
    (2) On an annual basis, successfully analyze appropriate 
performance evaluation (PE) samples provided by EPA or the State.
    Disinfectant Residuals. The three disinfectant residuals are 
measured and reported as follows: chlorine as free or total chlorine; 
chloramines as combined or total chlorine; and chlorine dioxide as 
chlorine dioxide. Residual disinfectant concentrations must be measured 
by the methods listed in Table VIII-7. 

            Table VIII-7.--Proposed Methods for Disinfectants           
------------------------------------------------------------------------
      Disinfectant measurement               Proposed methods\1\        
------------------------------------------------------------------------
Chlorine as free or total residual   4500-Cl DAmperometric Titration.   
 chlorine, chloramines as combined   4500-Cl FDPD Ferrous Titrimetric.  
 or total residual chlorine.         4500-Cl GDPD Colorimetric.         
Chlorine as free residual chlorine.  4500-Cl HSyringaldazine (FACTS).   
Chlorine or Chloramines as total     4500-Cl ELow-Level Amperometric.   
 residual chlorine.                  4500-Cl IIodometric Electrode.     
Chlorine Dioxide as residual         4500-ClO2 CAmperometric Titration. 
 chlorine dioxide.                   4500-ClO2 DDPD.                    
                                     4500-ClO2 EAmperometric Titration. 
------------------------------------------------------------------------
\1\Proposed methods are in ``Standard Methods for the Examination of    
  Water and Wastewater,'' 18th Edition, American Public Health          
  Association, American Water Works Association, and Water Environment  
  Federation, 1992.                                                     

    Residual disinfectant concentrations for chlorine and chloramines 
may also be measured by using DPD colorimetric test kits if their use 
is approved by the State. Measurement for disinfectant residual 
concentration must be conducted by a party approved by the State.
    Other Parameters--Total Organic Carbon, Alkalinity and Bromide. 
Other parameters that are monitored to meet treatment technique 
requirements must be measured using the methods listed in Table VIII-8.

    Table VIII-8.--Proposed Analytical Methods for Other Parameters     
------------------------------------------------------------------------
             Parameter                              Method              
------------------------------------------------------------------------
Total Organic Carbon...............  5310 CPersulfate-Ultraviolet       
                                      Oxidation\1\                      
                                     5310 DWet Oxidation\1\             
Alkalinity.........................  2320 B\1\, 310.1\2\, D-1067-       
                                      88BTitrimetric\3\                 
                                     I-1030-85Electrometric\4\          
Bromide............................  300.0Ion Chromatography\5\         
------------------------------------------------------------------------
\1\Standard Methods 2320 B, 5310 B and 5310 C are in Standard Methods   
  for the Examination of Water and Wastewater, 18th Edition, American   
  Public Health Association, American Water Works Association, and Water
  Environment Federation, 1992.                                         
\2\EPA Method 310.1 is in the manual ``Methods for Chemical Analysis of 
  Water and Wastes'', EPA/600/4-79-020, March 1983, NTIS PB84-128677.   
\3\Method D-1067-88B is in the ``Annual Book of ASTM Standards'', Vol.  
  11.01, American Society for Testing and Materials, 1993.              
\4\Method I-1030-85 is in Techniques of Water Resources Investigations  
  of the U.S. Geological Survey, Book 5, Chapter A-1, 3rd ed., U.S.     
  Government Printing Office, 1989.                                     
\5\EPA Method 300.0 is in the manual ``Methods for the Determination of 
  Inorganic Substances in Environmental Samples'', EPA/600/R/93/100--   
  Draft, June 1993.                                                     

    Measurement for these parameters must be conducted by a party 
approved by the State.

G. Public Notice Requirements

    Standard provisions for public notice apply to this rule. These 
provisions are explained in Section XIV of this preamble. There is only 
one acute violation, which occurs when the chlorine dioxide MRDL is 
exceeded in the distribution system (or if the system fails to take the 
required samples in the distribution system).

H. Variances and Exemptions

    Standard provisions for variances and exemptions apply to this 
rule. These provisions are explained in Section XI of this preamble.

I. Reporting and Recordkeeping Requirements for PWSs

    Reporting: EPA has proposed reporting requirements designed to 
document compliance with the treatment and monitoring requirements 
described above. These requirements are specified in Sec. 141.134(b) of 
the proposed rule. Systems required to sample quarterly or more 
frequently must report monitoring information to the State within 10 
days after the end of each quarter in which samples were collected. 
Systems required to sample less frequently than quarterly must report 
monitoring information to the State within 10 days after the end of 
each required monitoring period in which samples were collected.
    Recordkeeping: There are no additional recordkeeping requirements 
for systems.

J. State Implementation Requirements

    Records Kept by States: EPA is proposing to add several 
requirements to Sec. 142.14, Records Kept by States. These include 
records of the currently applicable or most recent State 
determinations, including supporting information and an explanation of 
the technical basis for each decision.

--Records of systems that are installing GAC or membrane technology.
--Records of systems that are required, by the State, to meet 
alternative TOC performance criteria (alternate enhanced coagulation 
level).
--Records of Subpart H systems using conventional treatment meeting any 
of the enhanced coagulation or enhanced softening exemption criteria.
--Register of qualified operators.
--Records of systems with multiple wells considered to be one treatment 
plant.

    Reports by States: EPA is proposing to add several requirements to 
Sec. 142.15, Reports by States. These requirements include:

--Reports of systems that must meet alternative minimum TOC removal 
levels.
--Reports of extensions granted for compliance with MCLs in Sec. 141.64 
and the date by which compliance must be achieved.
--A list of systems required to monitor for various disinfectants and 
disinfection byproducts.
--A list of all systems using multiple ground water wells which draw 
from the same aquifer and are considered a single source for monitoring 
purposes.

    Special Primacy Requirements: EPA is proposing to add several 
requirements to Sec. 142.16, Special Primacy Requirements. These 
requirements include how the State will:

--Determine the interim treatment requirements for those systems 
electing to install GAC or membrane filtration.
--Qualify operators of community and nontransient-noncommunity public 
water systems subject to this regulation.
--Approve alternative TOC minimum removal levels.
--Approve parties to conduct pH, alkalinity, temperature and residual 
disinfectant concentration measurements.
--Approve DPD colorimetric test kits for free and total chlorine 
measurements.
--Define the criteria to use to determine if multiple wells are being 
drawn from a single aquifer and therefore be considered a single source 
for compliance with monitoring requirements.

IX. Basis for Key Specific Criteria of Proposed Rule

A. 80/60 TTHM/HAA5 MCLs, Enhanced Coagulation Requirements, and BAT

1. Basis for Umbrella Concept vs. Individual MCLs
    The proposed rule would establish limits for two DBP class sums 
(i.e., TTHMs and the sum of five HAA species [HAA5]) rather than 
individual DBPs. In performing the regulatory impact analysis (RIA), 
TTHM and HAA5 data were generated that were believed to represent 
occurrence data with conventional drinking water treatment as well as 
that achievable with the use of advanced technologies. However, 
individual DBPs could not be reliably predicted over the range of TOC 
and bromide levels that are found in surface waters before and after 
treatment.
    In addition to the inability to characterize individual DBP 
formation, the Negotiating Committee was concerned that individual DBPs 
cannot all be controlled simultaneously without adverse impacts. While 
precursor removal processes (i.e., coagulation, precipitative 
softening, GAC, and nanofiltration) can remove TOC, they do not remove 
bromide (except for nanofiltration to a limited extent). Such processes 
are best for controlling the formation of chloroform and least 
effective for controlling the formation of bromoform (Summers et al., 
1993). Amy and colleagues found that increasing the bromide-to-TOC 
ratio (e.g., by reducing TOC with a precursor-removal technology) 
yielded a higher percentage of brominated THM species (Amy et al., 
1991). Symons and colleagues speculated that this phenomenon is due to 
the following: (1) after treatment to lower TOC, a water may be 
``precursor-limited''; (2) THM formation kinetics favor bromine 
incorporation; (3) thus bromine consumes most of the active precursor 
sites, leaving few for chlorine substitution (Symons et al., 1993).
    In an enhanced coagulation study of 16 waters nationwide, the 
median reduction in TTHMs was 50 percent (JAMES M. MONTGOMERY, 
CONSULTING ENGINEERS, INC., 1991 and Means et al., 1993). Because this 
technology removed TOC but not bromide, chloroform levels were well 
reduced (median of 65 percent), while bromodichloromethane values were 
not as well reduced (for 15 of the waters the median reduction was 28 
percent; this THM level, though, went up six percent in the sixteenth 
water). For the more brominated species (dibromochloromethane and 
bromoform), the THM levels decreased in some waters and increased in 
others. Again, the increase in formation of these brominated THMs was 
attributed to the change in bromide-to-TOC ratio and/or competition 
between bromine and chlorine for precursors. For the raw waters in this 
study (median TOC of 4.3 mg/L and bromide of 0.09 mg/L), chlorination 
(at 20  deg.C for 16 hr) yielded median values of 77 g/L 
chloroform, 17 g/L bromodichloromethane, 6 g/L 
dibromochloromethane, 0.2 g/L bromoform, and 124 g/L 
TTHMs. For the coagulated/settled waters, chlorination yielded median 
values of 26 g/L chloroform, 12 g/L 
bromodichloromethane, 6 g/L dibromochloromethane, 0.3 
g/L bromoform, and 56 g/L TTHMs. These data 
demonstrate that enhanced coagulation can reduce TTHMs, with varying 
impacts on individual species. While not all chemical species were 
significantly reduced, the overall theoretical cancer risk from THMs is 
lower. This may also apply to HAA5 and other byproducts.
    In the aforementioned coagulation study, the median raw- and 
settled-water DCAA levels were 28 and 14 g/L, respectively 
(JAMES M. MONTGOMERY, CONSULTING ENGINEERS, INC., 1991 and Means et 
al., 1993). For the waters tested, the median reduction in DCAA was 61 
percent, which was comparable to the reduction in chloroform. For 
dibromoacetic acid (DBAA), the median raw- and settled-water levels 
were 1.2 and 1.6 g/L, respectively (JAMES M. MONTGOMERY, 
CONSULTING ENGINEERS, INC., 1991). For the three waters in this study 
with very high bromide levels, DBAA was reduced from a range of 16 to 
52 g/L in the chlorinated raw waters to a range of 11 to 30 
g/L in the chlorinated coagulated/ settled waters.
    These types of data indicate that while it is feasible for systems 
utilizing enhanced coagulation to reduce TTHM and HAA5 levels, it is 
not possible to reduce all of the individual THMs and HAAs to the same 
extent. Using precursor control technologies, which can remove TOC but 
not bromide, there is a feasible limit on being able to minimize the 
formation of each individual THM or HAA. Alternatively, using 
alternative disinfectants (e.g., ozone/chloramines), one can 
significantly reduce the formation of all THMs and HAAs. However, as 
discussed in Section VI.C., there are concerns with the byproducts of 
alternative disinfectants.
    Utilizing the DBP class sums, though, the Technologies Working 
Group (TWG) was able to evaluate the benefits of enhanced coagulation 
with the DBPRAM. For surface waters that filter but do not soften, 
using conventional filtration treatment and chlorine, it was determined 
that the median, 75th, and 90th percentile TTHMs are 46, 68, and 90 
g/L, respectively. With enhanced coagulation for all surface 
water systems that filter but do not soften, it was predicted that 
median, 75th, and 90th percentile TTHMs would drop to 29, 41, and 58 
g/L, respectively. Similarly, using conventional treatment and 
chlorine, it was determined that the median, 75th, and 90th percentile 
HAA5 levels are 28, 47, and 65 g/L, respectively. With 
enhanced coagulation, it was predicted that median, 75th and 90th 
percentile HAA5 levels would drop to 17, 26, and 37 g/L, 
respectively.
    In order to comply with MCLs of 80 g/L TTHMs and 60 
g/L HAA5, the TWG assumed that a utility would design the 
treatment process to achieve levels less than 80 percent of the MCL 
values (i.e., 64 g/L TTHMs and 48 g/L HAA5) as an 
operating margin of safety. Such TTHM and HAA5 levels should be 
attainable for approximately 90 percent of the systems when using 
enhanced coagulation with chlorine, based upon the predicted 90th 
percentile levels above. Similarly, GAC10 with chlorine was predicted 
to result in comparable levels of TTHMs and HAA5. Note, though, that 
for some waters the HAA levels may exceed the THM concentrations 
(Grenier et al., 1992) and that compliance with both sets of DBP 
classes may require additional treatment changes. For example, the 
DBPRAM predicted that for these surface-water systems using enhanced 
coagulation, the maximum TTHM would be 80 g/L while the 
maximum HAA5 level would be 81 g/L.
    Enhanced coagulation can be used to remove the precursors for other 
DBPs as well as those associated with THMs and HAAs. Reckhow and Singer 
demonstrated that the formation potential (a measure of precursor 
levels) of THMs, di-, and trichloroacetic acid, dichloroacetonitrile, 
1,1,1-trichloropropanone, and TOX could all be reduced with enhanced 
coagulation (Reckhow et al., 1990). Thus, enhanced coagulation can be 
used to control other DBPs as well, even though they are not part of 
this proposed D/DBP Rule.
    In a full-scale evaluation of enhanced coagulation performed during 
the 35-utility DBP study, the alum dose was raised from 10 to 40 mg/L 
(Metropolitan Water District of So. Calif. et al, 1989). Removal of TOC 
(raw water TOC of 3 mg/L--a low-alkalinity water) through coagulation 
and settling increased from 25 to 50 percent. Chlorination (at 25 
deg.C for 24 hr) of settled/filtered water during the low-alum-dose 
test yielded 86 g/L TTHMs, 50 g/L HAA5, and 9.4 
g/L chloral hydrate. Chlorination of settled/filtered water 
during the high-alum-dose test yielded 55 g/L TTHMs, 29 
g/L HAA5, and 6.0 g/L chloral hydrate. By enhancing 
the coagulation process at this utility, the levels of TTHMs, HAA5, and 
chloral hydrate were all reduced (compared to the low-alum-dose test) 
by 36-42 percent. In the 35-utility study, the overall correlation 
between the occurrence of chloral hydrate and chloroform in the 
treatment plant effluents of all the systems was good (correlation 
coefficient of 0.85) (Metropolitan Water District of So. Calif. et al., 
1989). Chloral hydrate has been postulated to form as an intermediate 
in the conversion of ethanol to chloroform (Beibar et al., 1973). By 
removing THM and HAA precursors during enhanced coagulation, chloral 
hydrate should be controlled as well.
2. Basis for Level of Stringency in MCLs, BAT, and Concurrent Enhanced 
Coagulation Requirements
    The Safe Drinking Water Act directs EPA to set the MCL as close to 
the MCLG as is technically and economically feasible to achieve and to 
specify in the rule such best available technology (BAT). Systems 
unable to meet the MCL after application of BAT can get a variance (see 
Section XI for a discussion of variances). Systems that obtain a 
variance must meet a schedule approved by the State for coming into 
compliance. Systems are not required to use BAT in order to comply with 
the MCL but can use other technologies as long as they meet all 
drinking water standards and are approved by the State.
    For chemicals classified as B2 carcinogens, EPA must set standards 
as close to zero (the MCLG) as is technically and economically feasible 
to achieve by the BAT. EPA has classified three THMs (chloroform, 
bromodichloromethane, and bromoform) and one of the HAAs 
(dichloroacetic acid) as probable human carcinogens (i.e., B2 
carcinogens) based on evidence of carcinogenicity in animals. EPA is 
also concerned with the potential risks of chlorination byproducts 
other than THMs or HAAs, indicated in part by the presence of THMs and 
HAAs. A TTHM MCL and HAA MCL would limit exposure from different THMs 
and HAAs as well as other chlorinated DBPs.
    EPA is proposing a combined limit for only five of the HAAs 
(HAA5)--monochloroacetic acid, dichloroacetic acid, trichloroacetic 
acid, monobromoacetic acid, and dibromoacetic acid--because currently 
available data enable EPA to predict only their combined occurrence.
    How BAT is defined determines the level at which MCLs are set for 
TTHMs and HAA5. Per agreement with the Negotiating Committee, EPA is 
proposing either enhanced coagulation or shallow bed GAC (GAC10) with 
chlorine as the primary and residual disinfectant. The TWG considered 
GAC10 as roughly equivalent to enhanced coagulation in removing organic 
precursors to DBPs. The Negotiating Committee considered it appropriate 
to define chlorination for primary and residual disinfection within the 
BAT definition because 1) chlorine is an effective disinfectant for 
inactivating most microbial pathogens originating in the source water 
and for limiting contamination in the distribution system, and 2) 
health risks from DBPs from use of alternate disinfectants are not as 
yet as well characterized as they are for DBPs of chlorination. 
However, as noted above, alternate disinfectants (such as ozone) may be 
used to achieve D/DBPR compliance.
    As discussed previously, based on model predictions by the DBPRAM, 
most systems in the U.S. would be able to achieve a TTHM level of 80 
g/l or an HAA5 level of 60 g/l if they were to apply 
the proposed BATs. The Negotiating Committee agreed to propose the MCLs 
accordingly. Alternative BATs and corresponding MCLs were considered 
but not included for the reasons discussed below.
    Including a more effective precursor removal technology such as 
GAC20 or membrane filtration in the BAT would result in significantly 
lower MCLs. Setting such MCLs would probably result in much greater use 
of alternative disinfectants, such as ozone and chloramines because 
these technologies would be significantly less expensive than the BAT 
for achieving the MCL. While much greater use of such technology may be 
appropriate, some members of the Negotiating Committee did not consider 
this increased use desirable, at least until more was known concerning 
health risk associated with DBPs formed from use of alternative 
disinfectants. For the same reasons, alternative disinfectants were not 
included in the BAT definition(s).
    Setting the MCLs for TTHMs and HAA5 at 80 and 60 g/l, 
respectively, should lead to substantially lower TTHM and HAA levels 
than those being achieved under the existing TTHM MCL. The TWG 
estimated that, for surface water systems serving over 10,000 people 
that do not soften, the median concentration for TTHMs and HAA5 would 
drop from about 46 g/l to 31 g/l and 28 g/l 
to 20 g/l, respectively, as a result of such regulations. As 
part of today's proposal, EPA is also proposing that all systems using 
surface water sources which use sedimentation and filtration must 
operate with either enhanced coagulation or enhanced softening unless 
they meet certain water quality conditions (discussed in the following 
section of the preamble). This requirement was set in conjunction with 
the MCLs for TTHMs and HAA5 for the following reasons:
    (1) A substantial amount of precursors to disinfection DBPs could 
be removed at low cost and within a short period of time, regardless of 
which disinfectants were used. Thus, any health effects associated with 
DBPs that might otherwise be formed would be reduced quickly and at low 
costs.
    (2) Reducing precursors would lead to lower TTHM and HAA5 levels 
and thereby diminish the incentive for many systems to shift toward use 
of alternative disinfectants in order to comply with the new MCLs, 
thereby limiting concerns from any potential associated health risks.
    (3) Enhanced coagulation and enhanced softening will also 
significantly reduce disinfectant demand, thereby allowing utilities to 
use less disinfectant while still maintaining a residual in the 
distribution system. Maintaining a residual is important for 
identifying when contamination occurs into the distribution system 
(indicated by the absence of a residual) and for limiting bacterial 
growth.
    While lowering DBP precursors and disinfectant demand can provide 
obvious benefits, there are also associated potential downside risks. 
Since water treatment plant operators often apply disinfectant dosages 
in order to maintain a residual in the distribution system, if the 
disinfectant demand is lowered, lower disinfectant dosages could 
inadvertently lead to lower levels of inactivation of pathogens 
originating in the source water and increased microbial risk. To 
prevent such risks, compensating treatment must be provided where 
appropriate. EPA is therefore concurrently proposing possible 
amendments to the SWTR to address such concerns in today's Federal 
Register.
    Another concern with precursor removal is that, in waters with high 
bromide concentrations, it is possible (as previously discussed) to 
increase the concentrations of certain brominated DBPs even though the 
group concentrations of the TTHMs and HAA5 may decrease. Since the 
health risks associated with many of the brominated DBPs are currently 
unknown, it remains unclear whether the benefits of lowering the 
concentrations of chlorinated DBPs outweigh the possible downside risks 
of increasing certain brominated DBPs. Nevertheless, since only a small 
percentage of systems may experience increased concentrations of 
certain brominated DBPs from enhanced coagulation, the Negotiating 
Committee reached a consensus that setting a national requirement for 
precursor removal by enhanced coagulation or enhanced softening would 
be appropriate.
    The Committee could not reach consensus on whether to require 
systems to use technologies such as GAC20 or membrane technology in 
conjunction with setting lower MCLs, as was done for enhanced 
coagulation with the proposed Stage 1 MCLs. Some members did not 
consider it appropriate without a better understanding of the impacts 
of such a requirement. Installation and use of GAC20 or membrane 
technology involve greater costs and time to begin implementing than 
enhanced coagulation. Some Committee members believed that, depending 
on source water quality, use of alternative disinfectants may be 
significantly more cost-effective for reducing health risks from DBP 
levels than GAC20 or membrane technology. Also, these members believed 
that use of alternative disinfectants instead of GAC20 or membranes may 
pose fewer ecological impacts. However, other members believed that 
GAC20 or membranes would substantially improve water quality and should 
be required. The Committee did not reach consensus.
    If GAC20 or membrane technology were required under Stage 1, bench- 
and pilot-scale studies would need to be conducted prior to design and 
installation. Such studies would probably require at least several 
years to complete for most systems. Under the ICR (59 FR 6332), large 
systems with high TOC levels will be required to conduct bench- or 
pilot-scale studies to evaluate the treatment effectiveness of GAC or 
membrane technology. These studies will enable systems to design and 
install GAC or membrane technologies, if required by the Stage 2 D/
DBPR, in a shorter time than otherwise would be possible under the 
Stage 2 rule. Bench- or pilot-scale studies initiated under the ICR 
will in part simulate the same initial actions that many utilities will 
take in the future and reduce the time needed to come into compliance 
if GAC20 or membrane technology are required.

3. Basis for enhanced coagulation and softening criteria

    a. Enhanced coagulation. Removal of organic carbon in conventional 
drinking water treatment by the addition of alum or iron salts has been 
demonstrated by laboratory research, pilot-scale, demonstration plant, 
and full-scale studies. Until recently, there have been limited data 
available on the removal of organic carbon (measured as TOC) using 
natural organic carbon matrices. Much of the developmental work for the 
removal of TOC by coagulation and sedimentation has been done in the 
laboratory using synthetic mixtures of humic materials. Researchers 
have demonstrated that natural TOC exhibits a wide range of responses 
to treatment with high doses of alum and iron salts. A key indication 
of the ability of TOC to be removed by coagulation is the molecular 
weight distribution of the organic carbon. A large proportion of high 
molecular weight organic carbon is much easier to remove than an 
organic carbon that is predominantly low molecular weight material. 
Unfortunately, the procedure to determine TOC molecular weight 
distribution is cumbersome, is only being used in research 
applications, and is not generally available in water treatment plants 
or to consulting firms.
    Even though TOC removal has been practiced for some time at 
conventional, full-scale plants, there has not been a standard method 
to evaluate the potential for a water treatment plant to remove TOC 
during the coagulation/sedimentation process. As a result of the work 
of the TWG of the Negotiating Committee, a number of alternatives for 
defining enhanced coagulation have been evaluated. The term optimized 
coagulation was not used to describe the process of incremental removal 
of TOC by coagulants to avoid confusion with optimized coagulation for 
particle removal practiced by many water utilities.
    The majority of the data for removal of TOC in drinking water 
treatment has been developed with the use of aluminum sulfate 
(AlSO4  14H2O). Iron salts are also effective for 
removing TOC and equivalent dosages for iron salts were developed on 
the basis of TOC removal by alum. Research has demonstrated that 
polyaluminum chloride and cationic polymers are not effective for 
removing the same degree of TOC as either alum or iron salts. Cationic 
polymers (as well as anionic and nonionic polymers) have been proven to 
be valuable in creating settlable floc when high dosages of alum or 
iron salts are used. Specific organic polymers have been shown to 
remove color in water treatment applications, but significant TOC 
removal by organic polymers has not been demonstrated on a widespread 
basis. Other coagulation process arrangements that result in the 
required removals for enhanced coagulation are acceptable. For example, 
sludge blanket clarifiers with or without powdered activated carbon 
have been shown to remove significant levels of TOC.
    The TWG attempted to define what percent TOC removals could be 
achieved by most systems treating surface water and using coagulation/
sedimentation processes using elevated, but not unreasonable, amounts 
of coagulant dose. The intent was to define enhanced coagulation in 
such a manner that (a) significant TOC reductions would be achieved and 
(b) the criteria could easily be enforced with minimal State 
transactional costs. A TOC-based performance standard was therefore 
desirable. It was not considered appropriate to base a performance 
standard on what all systems would be expected to be able to achieve 
since some waters are especially difficult to treat. Under such a 
standard many systems with easier to treat waters might not be 
motivated to reduce their TOC to the extent that was reasonably 
achievable. On the other hand, setting a standard based on what many 
systems would not be able to readily achieve would introduce large 
transactional costs to States enforcing the rule. To address these 
concerns the TWG developed a two-step standard for enhanced 
coagulation. The first step includes performance criteria which, if 
achieved, would define compliance. The second step would allow systems 
that have difficult to treat waters to demonstrate to the State, 
through a specific protocol, alternative performance criteria for 
achieving compliance.
    The TWG examined case histories of TOC removal with alum and 
developed the 4X3 matrix shown below (Table IX-1) as the initial step 
for defining enhanced coagulation. The TWG members and other experts 
consulted during this process attempted to specify criteria by which 
about 90 percent of the water utilities employing conventional 
treatment and required to operate enhanced coagulation would be able to 
meet the TOC removal percentages listed, without unreasonable addition 
of alum. While limited empirical data were used to develop these 
criteria, the 90 percent compliance objective with the step 1 criteria 
is not statistically based. Establishing criteria at the anticipated 90 
percent level, versus (for example) a 50 percent level with more 
stringent percent TOC removal requirements, was expected to result in 
much lower transactional costs to the State (because fewer evaluations 
of experimental data to establish alternative criteria would be 
required) without significantly higher TOC levels in treated waters 
nationally.
    Systems not practicing conventional treatment were excluded from 
enhanced coagulation requirements because they were generally expected 
to (a) have higher quality source waters with lower TOC levels than 
waters treated by conventional water treatment plants, and (b) not have 
treatment that could be expected to achieve significant TOC reduction 
(e.g., most ground water supplies, direct filtration, diatomaceous 
earth filtration, and slow sand filtration).

Table IX-1.--Required Removal of TOC by Enhanced Coagulation for Subpart
                H Systems Using Conventional Treatment\2\               
                              [In percent]                              
------------------------------------------------------------------------
                                          Source Water Alkalinity(mg/l) 
 Source Water Total Organic Carbon (mg/ --------------------------------
                  l)                       0-60      >60-120    >120\1\ 
------------------------------------------------------------------------
>2.0-4.0...............................       40.0       30.0       20.0
>4.0-8.0...............................       45.0       35.0       25.0
>8.0...................................       50.0       40.0      30.0 
------------------------------------------------------------------------
\1\Systems practicing softening must meet the TOC removal requirements  
  in this column.                                                       
\2\Systems meeting at least one of the conditions in Sec.               
  141.135(a)(1)(i)-(iv) are not required to operate with enhanced       
  coagulation.                                                          

    The percent removals required as part of the initial compliance 
determination were developed in recognition of the general trends in 
TOC coagulation research that removals of TOC were more difficult the 
higher the alkalinity (due to the difficulty of reaching the optimum 
coagulation pH for TOC, usually between 5.5 and 6.5). It is also fairly 
well established that TOC removal by coagulation is generally easier 
the higher the initial TOC in the water. More information on the 
practice of removing TOC in a wide variety of source waters would have 
been helpful for developing the proposed criteria. EPA solicits comment 
on whether the TOC percent removal levels in Table IX-1 indicated above 
are representative of what 90 percent could be expected to achieve with 
elevated, but not unreasonable, coagulant addition.
    About 10 percent of the utilities required to operate enhanced 
coagulation are not expected to achieve the percent removals in Table 
IX-1. The purpose of the second step in the definition of enhanced 
coagulation is to determine the point of diminishing returns for the 
addition of coagulant for TOC removal.
    Some waters contain TOC composed mostly of highly mineralized 
organic carbon with most of the molecular weight fraction in the low 
range. It is known that this kind of TOC can be very difficult to 
remove. It is not the intent of this rule to require the addition of 
very high concentrations of coagulants with little removal of TOC. 
Therefore, the second step in the definition of enhanced coagulation 
allows utilities to avoid such a situation. It requires the evaluation 
of incremental addition of coagulant in a bench- or pilot-scale test 
and measurement of the amount of TOC removed by 10 mg/L increments of 
coagulant. Per recommendation of the TWG, EPA is proposing that the 
point of diminishing returns for coagulant addition be defined as the 
alternate enhanced coagulation level (AECL) at 0.3 mg/L of TOC removed 
per 10 mg/L of alum added or equivalent addition of iron coagulant, and 
that the percent TOC removal achieved at this point be defined, if 
approved by the State, as the alternative minimum TOC removal level (to 
that indicated in Table IX-1) that could be met for demonstrating 
compliance.

                Table IX-1a.--Coagulant Dose Equivalents                
                                 [mg/l]                                 
------------------------------------------------------------------------
                         Coagulant                               Dose   
------------------------------------------------------------------------
Aluminum sulfate 14H2O.............................           10
Ferric chloride 6H2O...............................          9.1
Ferric chloride............................................          5.5
Ferric sulfate 9H2O................................          9.5
------------------------------------------------------------------------

    The guidance manual contains a bench-scale method for demonstrating 
alternative performance criteria under step 2 of the enhanced 
coagulation definition (EPA, 1994). The method described therein is 
patterned after the ASTM D 2035-80 method for ``Standard Practice for 
Coagulation-Flocculation Jar Test of Water.''
    The bench-/pilot-scale procedure for determining alternative 
percent TOC removal requirements does not require the use of a 
laboratory filtration step. Experience has shown that most TOC is 
removed during coagulation/sedimentation. Also, not requiring 
laboratory filtration eliminates a point of possible contamination. TOC 
is known to leach from some commercially available filters. Not 
specifying laboratory filtration also avoids the issue of requiring a 
particular type of filter for the bench-scale studies. During the 
development of this proposed rule, no consensus could be reached on the 
use of membrane filters with various pore diameters versus glass fiber 
filters.
    If a utility wishes to include the TOC removal in the filtration 
process as part of compliance with enhanced coagulation, under step 2, 
filtration would then have to be part of the bench-/pilot-scale study. 
Using filtration in the treatment plant as part of compliance with 
enhanced coagulation TOC removal would also require that continuous 
disinfection for CT credit would not be allowed until after the 
filters.
    EPA solicits comment on whether filtration should be required as 
part of the bench-/pilot-scale procedure for determination of Step 2 
enhanced coagulation. If so, what type of filter should be specified 
for bench-scale studies?
    Figure IX-1 shows three examples of the types of curves anticipated 
to result from a step 2 analysis and are based on actual data collected 
during the TWG evaluation. Curve A represents a water containing a TOC 
highly susceptible to removal by coagulation/sedimentation. Step 2 is 
met at an alum dosage of 40 mg/L. Note that due to its low alkalinity 
(<60 mg/L), the percent removal of TOC at this point (57%) is actually 
more than is required under step 1 (45%). In this case, the utility is 
only required to remove TOC to the level specified in step 1, 45%, 
although removal of higher levels of easily removed TOC is encouraged.

BILLING CODE 6560-50-P

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BILLING CODE 6560-50-C
    Curve B is probably more typical of waters that fall into the step 
2 evaluation (alkalinity 60-120). Note that the slope of 
0.3/10 is located at a dosage of 25 mg/L of alum and results in a TOC 
removal of 26%. The method used to determine the actual slopes of 
portions of Curve B was to draw it on graph paper and count squares. 
Curve fitting programs with instantaneous slope determinations may be 
available to improve the precision of this task. If the specified TOC 
removal in Table IX-1 had been followed, 31 mg/L of alum would have 
been added to achieve the required 30% removal. Curve C shows a water 
with a TOC that is not amenable to removal by coagulation. A slope of 
0.3/10 is never reached.
    Once a TOC percent removal is established at the slope of 0.3/10, a 
utility may operate its water treatment plant with any combination of 
acid and coagulant to achieve that percent TOC removal. Utilities may 
find that the least-cost approach to achieving a specific TOC percent 
removal may be with both sulfuric acid and a metal salt coagulant. 
Other utilities may wish to avoid the concerns with handling sulfuric 
acid and use alum or ferric salts to depress pH and produce a metal 
hydroxide precipitate.
    EPA solicits comment on whether a slope of 0.3 mg/L of TOC removed 
per 10 mg/L of alum added should be considered representative of the 
point of diminishing returns for coagulant addition under Step 2. EPA 
also solicits comment on how the slope should be determined (e.g., 
point-to point, curve-fitting). If the slope varies above and below 
0.3/10, where should the Step 2 alternate TOC removal requirement be 
set--at the first point below 0.3/10? At some other point?
    The requirement to add alum at 10 mg/L increments until the 
``maximum pH'' is reached was developed to ensure that enough alum was 
added to adequately test if TOC removal was feasible and to add it in 
small enough increments to notice significant changes in the slope of 
the coagulant dose-TOC removal curve. The maximum pH varies depending 
on the alkalinity due to the difficulty in changing pH at the higher 
alkalinities. Because alum coagulation of natural organic material is 
most effective at a pH level between 5.5 and 6.5, large amounts of acid 
would be required for high alkalinity waters to achieve this optimal 
pH, followed by large amounts of base to raise the pH of the water up 
to 8.0 before distributing to ensure compliance with the lead/copper 
rule.
    It is well demonstrated that the concentrations and characteristics 
of TOC in source waters will change over time. In some source waters, 
the rate of change could be rapid (such as during storm events). Other 
source waters have a generally consistent TOC concentration and 
characteristic due to storage of source water in reservoirs. EPA 
proposes that, under guidance, the bench- or pilot-scale evaluation of 
enhanced coagulation be performed on at least a quarterly basis, for 
one year, to reflect seasonal changes in source water quality. 
Currently, the proposed rule does not specify the frequency at which 
the bench- or pilot-scale evaluation should be conducted because such 
frequency of testing may not be warranted for all waters.
    EPA solicits comment on how often bench- or pilot-scale studies 
should be performed to determine compliance under step 2. Should such 
frequency and duration of testing be included in the rule or left to 
guidance (i.e., allow the State to define what testing would be needed 
on a case by case basis for each system)? Is quarterly monitoring 
appropriate for all systems? What is the best method to present the 
testing data to the primacy agency that reflects changing influent 
water quality conditions and also keeps transactional costs to a 
minimum? How should compliance be determined if the system is not 
initially meeting the percent TOC reduction requirements because of a 
difficulty to treat waters and a desire to demonstrate alternative 
performance criteria?
    b. Enhanced softening. In general, there is much less data on the 
removal of TOC during the softening process when compared to 
conventional treatment. Based on the data available to the TWG, the 
definition of enhanced softening is (a) the percent TOC removals 
indicated for high alkalinity waters (> 120 mg/l) in Table IX-1, or (b) 
the achievement of 10 mg/L magnesium removal during the softening 
process. There are limited data on the use of ferrous salts at the high 
pH levels of softening, but not enough to specify in this rule.
    The calcium carbonate precipitate typically created during 
softening is relatively dense and completely unlike the amorphous 
aluminum and ferric hydroxide precipitates created in conventional 
coagulation processes. It is the amorphous or gelatinous nature of the 
aluminum and ferric hydroxides with their high surface areas that give 
them their ability to absorb and remove TOC. Softening is carried out 
at a wide range of pH levels, generally between 9.5 and 11.0. Above a 
pH of about 10.5, magnesium precipitates as magnesium hydroxide (which 
has very similar characteristics to alum and ferric precipitates). The 
TWG determined that if a softening process could not achieve the 
percent TOC removals shown in Table IX-1 under the alkalinity column of 
>120 mg/L and it was practicing magnesium precipitation, there was 
little more that could be done to enhance TOC removal. It is 
anticipated that the vast majority of softening utilities will be able 
to comply with these enhanced softening requirements. Not enough data 
were available to the TWG to determine whether alternative enhanced 
coagulation criteria needed to be defined and, if so, what they should 
be.
    EPA solicits comment on whether data are available on the use of 
ferrous salts in the softening process which can help define a step 2 
for enhanced softening. For softening plants, is enhanced softening 
properly defined by the percent removals in Table IX-1 or by 10 mg/L 
removal of magnesium hardness reported as CaCO3? Is there a step 2 
definition? Can ferrous salts be used at softening pH levels to further 
enhance TOC removals?
    c. Preoxidation credit. Except for the conditions described below, 
disinfection credit for the purpose of complying with the ESWTR is not 
allowed prior to enhanced coagulation. The reason for these limitations 
is the production of higher levels of DBPs when disinfectants are used 
prior to the precursor removal step.
    A number of water treatment plants add oxidants to the influent to 
the treatment plant to control a variety of water quality problems. The 
regulation allows the continuous addition of oxidants to control these 
problems. The limitation on disinfection credit prior to enhanced 
coagulation, except for the conditions described below, is expected to 
keep the addition of disinfectants to the minimum necessary to control 
the water quality problems that can be controlled by oxidation.
    EPA solicits comments on whether preoxidation is necessary in water 
treatment to control water quality problems such as iron, manganese, 
sulfides, zebra mussels, Asiatic clams, taste and odor. Will allowing 
preoxidation before precursor removal by enhanced coagulation generate 
excessive DBP levels?
    Ozone. Disinfection credit for ozone is allowed prior to enhanced 
coagulation if it is followed by biologically active filtration (BAF) 
because many of the organic DBPs formed by ozone are generally removed 
by a biological process. In order to maintain a filter in a 
biologically active mode, virtually no chlorine, chlorine dioxide, or 
chloramines can be added to the filter influent.
    EPA solicits comments on whether biologically active filtration 
following ozonation is sufficient to remove most byproducts believed to 
result from ozonation. What parameters, if any, should be measured in 
and/or out of the filter to demonstrate a biologically active filter, 
or alternatively, that ozone byproducts are adequately being removed? 
For example, would it be sufficient to demonstrate greater than 90 
percent removal of formaldehyde to establish that a filter is 
biologically active and that predisinfection credit could therefore be 
given?
    Chlorine dioxide. Due to the wide variation in the application of 
chlorine dioxide generation technology, it is common for water 
treatment plants to apply chlorine dioxide along with an excess of free 
chlorine. Technologies do exist to produce high purity chlorine 
dioxide, but these technologies are not universally used. EPA is 
proposing to allow disinfection credit for chlorine dioxide prior to 
enhanced coagulation in the same manner as for ozone and BAF if the 
system can demonstrate the generation of high purity chlorine dioxide.
    Under the proposal, a system using chlorine dioxide could get 
disinfection credit if the following standards are met: the chlorine 
dioxide generator must generate chlorine dioxide on-site at a minimum 
95 percent conversion efficiency (yield) from sodium chlorite; and the 
generated chlorine dioxide feed stream applied from the chlorine 
dioxide generator must contain less than five percent (by weight) free 
chlorine residual, measured as the weight ratio of free residual 
chlorine (i.e., hypochlorous acid) to chlorine dioxide in such feed 
stream. Compliance with these standards must be demonstrated on an 
ongoing basis for each generator in use. By meeting these standards, 
chlorite and chlorate (chlorine dioxide generation byproducts) will be 
limited and free residual chlorine will not be available to react with 
the organic precursors prior to TOC removal and the potential for 
halogenated organic DBP production is limited.
    EPA solicits comments on whether disinfection credit should be 
allowed for chlorine dioxide used prior to enhanced coagulation if 
virtually no halogenated organic DBPs are formed. Should some other 
limit, in addition to or in lieu of that proposed, be set (e.g., 5 
g/L TTHMs) on DBPs formed by high purity chlorine dioxide to 
ensure sufficient control for the production of excessive halogenated 
organic DBPs if disinfection credit were to be allowed with chlorine 
dioxide prior to enhanced coagulation?
    Disinfection credit during cold water months. It is well 
established that temperature plays a critical role in the production of 
DBPs and that DBP concentrations are the lowest in winter months. The 
cold water temperature months are also the most difficult time for 
utilities to meet CT requirements, because longer contact times with a 
disinfectant are needed to overcome the poorer inactivation 
efficiencies.
    Figure IX-2 plots the required CT values for inactivation of 
Giardia cysts for free chlorine at various pH and log inactivation 
levels. The family of curves clearly indicates a significant change in 
slope below a temperature of 5 deg. C indicating that it is much more 
difficult to achieve a log inactivation of Giardia cysts in water below 
this temperature.

BILLING CODE 6560-50-P

TP29JY94.026


BLLING CODE 6560-50-C
    NSERT FIGURE IX-2 HERE.
    EPA is proposing that systems be allowed to add a disinfectant 
before enhanced coagulation when water temperatures are less than or 
equal to 5 deg.C. In order to ensure that excessive DBPs are not 
produced by this special case and to more cost effectively balance 
chemical and microbial risks, exercise of this provision would only be 
allowed if the TTHM and HAA5 winter quarterly averages in the 
distribution system served by the treatment plant are less than 40 and 
30 ug/l, respectively.
    EPA solicits comment on the appropriateness of this provision or 
alternative means for addressing this issue.
    d. Basis for Avoiding Enhanced Coagulation or Enhanced Softening 
Requirements. The purpose of the treatment technique for control of 
disinfection byproduct precursors (DBPPs) is to remove one of the 
factors which result in the production of DBPs upon subsequent 
disinfection. Criteria have been established which allow systems to 
forgo the requirement to implement enhanced coagulation for control of 
DBPPs. These criteria were generally established to either recognize 
low potential of certain waters to produce DBPs or to account for types 
of water which contain TOC that is difficult to remove by enhanced 
coagulation. Implementation of enhanced coagulation in difficult to 
treat waters generally costs much more than the average case used to 
develop the national costs for this rule, and may introduce other water 
quality problems.
    TOC <2.0 mg/L. If a water contains less than 2.0 mg/L TOC before 
continuous disinfection, it does not have to implement enhanced 
coagulation. This level is calculated each quarter as a running annual 
average, based on monthly (or quarterly, if the system has qualified 
for reduced monitoring) treated water (i.e., prior to continuous 
disinfection) TOC measurements. The basis for this criterion is related 
to the purpose of the enhanced coagulation requirement (which is to 
reduce the presence of organic matter when chlorine or other 
disinfectants are added to the water). A TOC of less than 2.0 mg/L 
would be expected, in general, to produce TTHM and HAA5 levels upon 
chlorination that are less than 40 and 30 g/L, respectively. 
This criterion would apply to high quality source waters and to systems 
with water treatment plants which have installed a precursor removal 
process other than enhanced coagulation prior to continuous 
disinfection. High quality surface waters with TOC levels less than 2.0 
mg/L account for less than 20 percent of the total number of utilities 
using surface water in the U.S.
    Systems with other installed precursor removal technologies include 
a water treatment plant with granular activated carbon in a post-filter 
adsorber configuration, e.g., Cincinnati, Ohio. As long as the TOC is 
less than 2.0 mg/L before continuous disinfection, it is not important 
which precursor removal technology is employed.
    40/30/<4/>60. It is harder to remove organic matter by enhanced 
coagulation in waters with alkalinities greater than 60 mg/L as 
CaCO3 and TOC levels less than 4.0 mg/L. To compensate for this 
phenomenon, systems with these water quality characteristics are 
permitted to apply alternate disinfectants before any precursor removal 
step and, if the TTHM and HAA5 levels produced are less than 40 and 30 
g/L, respectively, the utility would not have to implement 
enhanced coagulation. Source water TOC, source water alkalinity and 
TTHM and HAA5 levels are calculated each quarter as running annual 
averages, based on monthly measurements.
    In addition to allowing systems that already meet these criteria to 
avoid enhanced coagulation, the Committee also agreed to allow systems 
that were installing alternative disinfection technology that would 
allow the system to meet these criteria to avoid enhanced coagulation. 
The technology must be installed prior to the compliance date for Stage 
2 D/DBPR. For example, a system that already had a TOC of less than 4.0 
mg/l and an alkalinity of greater than 60 mg/l would be allowed to 
avoid enhanced coagulation if the system committed to installation of 
ozonation. This commitment must include a clear and irrevocable 
financial commitment not later than the effective date for compliance 
with Stage 1 D/DBPR to technologies that will limit the levels of TTHMs 
and HAA5 to no more than 0.040 mg/l and 0.030 mg/l, respectively. 
Systems must submit evidence of the financial commitment, in addition 
to a schedule containing milestones for installation and operation of 
appropriate technologies, to the State for approval. Violation of the 
approved schedule will constitute a violation of the National Primary 
Drinking Water Regulation.
    The schedule must be enforceable, but should only contain 
significant milestones. Types of schedule items that should be included 
as enforceable include award contract, begin construction, end 
construction, pilot operations, and full compliance. The schedule 
should allow for minor slippage, but must require compliance by the 
compliance date for Stage 2. The State may also require periodic 
progress reports, but EPA recommends that these not be part of the 
enforceable schedule (and thus be a basis for finding the system in 
violation for late submission or failure to submit).
    The cost of employing enhanced coagulation to waters of this type 
is higher than the base case examined as part of the regulatory impact 
analysis for this rule. It is assumed that systems with this type of 
water quality will, in general, achieve more cost effective reduction 
of DBPs by use of alternative treatment strategies than by use of 
enhanced coagulation. The overall purpose of this rule is to reduce the 
levels of both DBPs that are known and DBPs which are not known. The 
criterion in this section is expected to accomplish these goals.
    40/30 with Chlorine. It is possible that some types of TOC do not 
produce significant levels of DBPs upon chlorination. To account for 
this fact, systems which use chlorine (and meet the CT requirements 
under the SWTR or ESWTR) and which achieve running annual averages of 
less than 40 and 30 g/L for TTHM and HAA5, respectively, do 
not have to employ enhanced coagulation. The type of precursors 
normally encountered in surface waters will produce TTHMs and THAAs 
higher than the concentrations of 40 and 30 g/L if the TOC 
level is greater than 2.0 mg/L and CT requirements are met. It is 
expected that this criterion will not be applicable to many surface 
water systems.
4. Basis for GAC Definitions
    Treatment with granular activated carbon (GAC) has been found by 
many researchers to remove organic DBP precursors. For water treatment 
applications, GAC is typically placed in a gravity filter, not unlike 
granular media filters for particle removal, and operated in a downflow 
mode. The design parameters most often specified for the use of GAC are 
empty bed contact time (EBCT) and regeneration frequency (or 
equivalently, carbon use rate). During the development of this proposed 
rule, GAC was defined at two levels of treatment to facilitate the 
development of national cost data as well as project expected national 
DBP levels resulting from the use of GAC treatment.
    GAC10 means granular activated carbon filter beds with an empty-bed 
contact time of 10 minutes based on average daily flow and a carbon 
regeneration frequency of every 180 days. The GAC10 definition, which 
was recommended by the TWG, was meant to specify the design and 
operating conditions of GAC that would be necessary to remove 
approximately the same amount of DBP precursors (measured as TOC) as 
that achieved by enhanced coagulation. As discussed previously, the 
Negotiating Committee agreed that enhanced coagulation or GAC10, used 
in conjunction with chlorine as the sole disinfectant, should be the 
BATs corresponding to the Stage 1 MCLs of 80 and 60 g/l for 
TTHMs and HAA5, respectively.
    GAC20 means granular activated carbon filter beds with an empty-bed 
contact time of 20 minutes based on average daily flow and a carbon 
regeneration frequency of every 60 days. The GAC20 definition, 
recommended by the TWG, was meant to specify the conditions by which at 
least 90% of the systems in the U.S. would be able to use this 
technology, with chlorine as the sole disinfectant, and comply with the 
Stage 2 MCLs of 40 and 30 g/l for TTHMs and HAA5, 
respectively. The ability of systems to use GAC20 and achieve such 
performance was tested and confirmed by the TWG using national TOC 
occurrence data obtained from the Water Industry Data Base (WIDB) and 
the Water Treatment Plant Simulation Model (USEPA 1992; USEPA, 1994).
    The Water Treatment Plant Simulation Model predicts the production 
of TTHMs and HAA5 based on water quality and treatment conditions. GAC 
performance in the model is based on equation parameters developed as 
part of a TOC removal study at Jefferson Parish, Louisiana. Jefferson 
Parish is proposed as representative of the ``general case'' for TOC 
removal. TOC removal has been demonstrated to be higher at Jefferson 
Parish than at Manchester, NH; Miami, FL; and the Metropolitan Water 
District of Southern California. TOC removal was lower at Jefferson 
Parish than at Philadelphia, PA; Cincinnati, OH; and Shreveport, LA.
    The TWG participants who developed these definitions also thought 
that it would be conceivable for GAC10 to be employed in a filter media 
replacement mode. GAC20 was clearly not compatible in a filter media 
replacement mode and would have to be applied as post-filter adsorbers.
    EPA solicits comment on whether GAC10 and GAC20 are reasonable 
definitions of GAC performance? Do they span the expected level of GAC 
applications in drinking water treatment for the control of TTHMs and 
HAA5? Is it appropriate to consider Jefferson Parish, Louisiana, TOC 
removal by GAC representative of the ``general case'' of TOC removal?
5. Basis for Monitoring Requirements
    Monitoring for disinfection byproducts, disinfectant residuals, and 
total organic carbon must be conducted during normal operating 
conditions. Systems may not change their operating conditions for the 
sole purpose of meeting an MCL or MRDL and then change back to an 
operating regime that would not meet limits. For example, a system may 
not reduce disinfectant feed temporarily to meet the chlorine MRDL and 
the TTHM and HAA5 MCLs (or chlorine dioxide MRDL and chlorite MCL) and 
then immediately revert to a higher feed. However, systems are allowed 
to modify operations to address changing conditions and to protect 
human health. For example, systems must modify operations to address 
changes in source water quality or emergency conditions (such as 
earthquakes and floods). Such modifications have been made for 
legitimate reasons and are included as ``normal operations''.
    Failure to monitor in accordance with the monitoring plan is a 
monitoring violation. Where compliance is based on a running annual 
average of monthly or quarterly samples or averages and the system's 
failure to monitor makes it impossible to determine compliance with 
MCLs or MRDLs, this failure to monitor will be treated as a violation 
for the entire period covered by the annual average. Systems whose 
monitoring is substantially complete will not be in violation for the 
entire period covered by the annual average. Substantially complete 
means that the State is able to determine MCL/MRDL compliance. For 
example, a system that missed a few percent of its MRDL compliance 
samples due to inability to sample at required locations (or took all 
necessary samples, but had minor deviations from its monitoring plan) 
would be able to determine compliance. These systems would be in 
violation of monitoring requirements, but only for the month or quarter 
(depending on the particular requirement). A system that did not take 
samples or took samples at locations that would be expected to produce 
results that are not representative (e.g., not taking TTHM samples at 
the point of maximum residence time) is in violation for the entire 
period covered by the annual average.
    a. TTHMs and HAA5. In general, monitoring requirements for TTHMs 
and HAA5 follow closely the requirements contained in the 1979 TTHM 
rule. In that rule, there were provisions for routine and reduced 
monitoring. In this proposal, the Agency has included the same 
frequency of monitoring for routine monitoring for Subpart H systems 
serving at least 10,000 people as in the 1979 TTHM rule, although the 
Committee did not reach consensus on these specific requirements. See 
below for (1) further discussion and (2) requests for comment on the 
monitoring requirements. Subpart H systems serving 10,000 or more 
persons must take four water samples each quarter for each treatment 
plant in the system, with at least 25 percent of the samples taken at 
locations within the distribution system that represent the maximum 
residence time of the water in the system. The remaining samples must 
be taken at locations within the distribution system that represent the 
entire system, taking into account the number of persons served, 
different sources of water, and different treatment methods employed.
    Initial monitoring for ground water systems serving at least 10,000 
people will be less than what is required under the 1979 TTHM rule, 
because of the generally lower byproduct formation shown over the life 
of the 1979 rule. Systems that use a chemical disinfectant must take 
one water sample each quarter for each treatment plant in the system, 
taken at locations within the distribution system that represent the 
maximum residence time of the water in the system. Routine samples must 
be taken at locations meant to reflect the highest possible TTHM and 
HAA5 levels (i.e., at the maximum residence time in the distribution 
system). If those samples are below the MCL, the Agency believes that 
the system should be considered in compliance.
    The Agency is also requiring systems not regulated under the 1979 
TTHM rule to meet the requirements of this proposed rule. Community 
water systems serving fewer than 10,000 people will be covered, as will 
nontransient noncommunity water systems, a category that did not exist 
in 1979. Nontransient noncommunity water systems must sample at the 
same frequency and location as community water systems of the same 
size.
    Routine samples for these systems must be taken at locations meant 
to reflect the highest TTHM and HAA5 levels (i.e., at the maximum 
residence time in the distribution system). If those samples are below 
the MCL, the Agency believes that the system should be considered in 
compliance. Subpart H systems serving from 500 to 9,999 persons must 
take one water sample each quarter for each treatment plant in the 
system, taken at a point in the distribution system that represents the 
maximum residence time in the distribution system.
    Subpart H systems serving fewer than 500 persons must take one 
sample per year for each treatment plant in the system, taken at a 
point in the distribution system reflecting the maximum residence time 
in the distribution system and during the month of warmest water 
temperature, when the formation rate of TTHMs and HAA5 is the fastest. 
This monitoring requirement will allow for a worst case sample, but 
will limit the monitoring burden for these very small systems.
    Systems using only ground water sources not under the direct 
influence of surface water that use a chemical disinfectant and serve 
less than 10,000 persons must sample once per year for each treatment 
plant in the system, taken at a point in the distribution system 
reflecting the maximum residence time in the distribution system and 
during the month of warmest water temperature, as with very small 
Subpart H systems.
    All ground water systems may, with State approval, consider 
multiple wells drawing water from the same aquifer as one plant for the 
purposes of determining monitoring frequency. This provision is the 
same as was in the 1979 TTHM rule. EPA requests comment on whether any 
additional regulatory requirements, guidance, or explanation is 
required to define ``multiple wells''. It was the intention of the 
Committee that multiple wells include both individual wells and well 
groups. This was done because many ground water systems are extremely 
decentralized, with multiple entry points to the distribution system, 
unlike most Subpart H systems with only one or several entry points. 
Also, EPA requests comment on whether there should be an upper limit of 
sampling frequency for systems that either cannot determine that they 
are drawing water from a single aquifer or are drawing water from 
multiple aquifers. For example, should a system that must draw water 
from many aquifers to satisfy demand be allowed to limit monitoring as 
if they were drawing from no more than four aquifers (routine sampling 
would thus be limited to four samples per quarter from systems serving 
at least 10,000 people or to four samples per year for systems serving 
fewer than 10,000 people)? Does EPA need to develop any additional 
guidance for any other aspect of this requirement?
    Systems monitoring less frequently than one sample per quarter per 
plant must increase monitoring to one sample per treatment plant per 
quarter until the system meets criteria for reduced sampling if the 
sample (or the average of the annual samples, when more than one sample 
is taken) exceeds the MCL.
    Systems may sample more frequently than one sample per quarter and 
more frequently than required, but must take at least 25 percent of the 
samples at a location reflecting the maximum residence time in the 
distribution system. The remaining samples must be taken at locations 
representative of at least average residence time in the distribution 
system. Any public water system that samples once per quarter or less, 
but more frequently than the frequency required in this section, must 
take all of its samples at a location reflecting the maximum residence 
time in the distribution system.
    Taken together, these requirements attempt to balance TTHM and HAA5 
formation, system size and source characteristics, and system 
monitoring costs. As the number of required samples decreases, the 
system is required to take samples at locations (and times, in some 
cases) where the highest levels would be expected.
    Reduced TTHM and HAA5 Monitoring. Some systems are not able to 
reduce monitoring. Any Subpart H system which has a source water TOC 
level, before any treatment, of greater than 4.0 mg/l may not reduce 
its monitoring. Subpart H systems serving fewer than 500 people may not 
reduce their monitoring to less than one sample per plant per year. 
Should there be any exceptions that would allow systems with a TOC> 4.0 
mg/l to reduce monitoring (e.g., the system has installed 
nanofiltration)?
    Systems may reduce monitoring (1) if they have a running annual 
averages for TTHMs and HAA5 that are no more than 0.040 mg/l and 0.030 
mg/l, respectively, or (2) for systems using ground water not under the 
direct influence of surface water that serve fewer than 10,000 persons 
and are required to take only one sample per year, if either (a) the 
average of two consecutive annual samples is no more than 0.040 mg/l 
and 0.030 mg/l, respectively, for TTHMs and HAA5 or (b) any annual 
sample is less than 0.020 mg/l and 0.015 mg/l, respectively, for TTHMs 
and HAA5. Systems must meet these requirements for both TTHMs and HAA5 
to qualify for reduced monitoring. The system may reduce monitoring 
only after the system has completed at least one year of monitoring. 
This standard is more stringent than that in the TTHM rule, in which 
the system had only to demonstrate that the TTHM concentrations would 
be ``consistently below'' the MCL. The Negotiating Committee felt that 
a more objective set of criteria were necessary.
    Reduced monitoring frequency. Subpart H systems serving 10,000 
persons or more that are eligible for reduced monitoring may reduce the 
monitoring frequency for TTHMs and HAA5 to one sample per quarter per 
treatment plant, with samples taken at a point in the distribution 
system reflecting the maximum residence time in the distribution 
system. Subpart H systems serving between 500 to 9,999 persons that are 
eligible for reduced monitoring may reduce the monitoring frequency for 
TTHMs and HAA5 to one sample per year per treatment plant, with samples 
taken at a point in the distribution system reflecting the maximum 
residence time in the distribution system and during the month of 
warmest water temperature.
    Systems using only ground water not under the direct influence of 
surface water and serving 10,000 persons or more that are eligible for 
reduced monitoring may reduce the monitoring frequency for TTHMs and 
HAA5 to one sample per year per treatment plant, with samples taken at 
a point in the distribution system reflecting the maximum residence 
time in the distribution system and during the month of warmest water 
temperature. Systems using only ground water sources not under the 
direct influence of surface water and serving fewer than 10,000 persons 
may reduce the monitoring frequency for TTHMs and HAA5 to one sample 
per three-year monitoring cycle, with samples taken at a point in the 
distribution system reflecting the maximum residence time in the 
distribution system and during the month of warmest water temperature.
    EPA believes that this procedure of taking worst-case samples less 
frequently will adequately identify systems with TTHM and HAA5 
problems, since systems have to meet relatively stringent criteria to 
be eligible for reduced monitoring. Systems which are on a reduced 
monitoring schedule may remain on that reduced schedule as long as the 
average of all samples taken in the year (for systems which must 
monitor quarterly) or the result of the sample (for systems which must 
monitor no more frequently than annually) is no more than 75 percent of 
the MCLs. Systems that do not meet these levels must resume monitoring 
at routine frequency. Also, the State may return a system to routine 
monitoring at the State's discretion.
    During the negotiated rulemaking, the Association of State Drinking 
Water Administrators (ASDWA) expressed the opinion that the reduced 
monitoring for ground water systems serving fewer than 10,000 people 
could be expanded beyond what is in the proposal. These are the systems 
usually having multiple ground water sources, whose quality is unlikely 
to change with respect to DBP precursors and are most likely to benefit 
from reduced monitoring. The additional options presented below both 
have as a basis the demonstration that the ground water source in 
question has a minimal likelihood of having precursor material that 
could combine with chlorine to form any significant concentrations of 
THMs or HAA5s. Each option would rely on having each entry point of the 
system go through three years of routine monitoring to qualify for 
reduced monitoring. After this period, if the entry points meet 
additional criteria, then the entry points would be subject to minimal 
additional monitoring. Option one would reduce the monitoring to once 
every nine years for THMs and HAA5s in the distribution system. This 
option would minimize the expense of THM and HAA5 monitoring for these 
systems. Option two, which specifies even more restrictive criteria, 
would exempt systems from any additional THM and HAA5 monitoring as 
long as the TOC criteria are met. This option offers the largest cost 
savings and eliminates the need for tracking and enforcing monitoring 
requirements on those systems that have historically had the poorest 
monitoring compliance records and are least likely to have significant 
levels of DBPs. The Agency would like to receive comments on the 
following two options.
    Option One: Any ground water system serving fewer than 10,000 
people that has a raw water TOC of less than 1.0 mg/l, and has both 
TTHM and HAA5 values less than 25 percent of the MCLs (20 g/l 
and 15 g/l, respectively) after three years of routine and 
reduced monitoring, can reduce the monitoring for TTHMs and HAA5s to 
one sample every nine years, taken at the maximum distribution system 
residence time during the warmest month.
    Option Two: Any ground water system serving fewer than 10,000 
people that has a raw water TOC of less than 0.5 mg/l, and has both 
TTHM and HAA5 values less than 25 percent of the MCLs (20 g/l 
and 15 g/l, respectively) after three years of routine and 
reduced monitoring, is exempt from the distribution system monitoring 
requirements for TTHMs and HAA5s for as long as TOC monitoring is 
conducted once every three years and the raw water TOC remains less 
than 0.5 mg/l.
    These options are not mutually exclusive, that is, both could be 
used simultaneously or some hybrid could be developed. The Agency seeks 
comment on whether either or both of these options are reasonable in 
adequately protecting the public health and should therefore be 
considered as criteria for reduced monitoring. Are there other options 
for reduced monitoring that should be considered? What are they?
    Consensus was not reached on certain key aspects of monitoring and 
compliance determination. Some members of the Negotiating Committee 
expressed concerns about the following issues, especially (but not 
solely) as related to TTHMs and HAA5 monitoring:

--Is the monitoring frequent enough to adequately determine variations 
in sample results caused by time and/or location in the distribution 
system? If not, what is a more appropriate monitoring schedule? Should 
requirements differ for systems based on population served, raw water 
source, or other factors? If so, should the proposed requirements be 
changed? How should they be changed? If requirements should not be 
based on these factors, what should the requirements be?
--Does averaging of sample results taken in various locations and 
averaging over the course of a year to determine compliance adequately 
protect individuals that are in locations that may regularly have 
higher than average levels? If it does not, how should the proposed 
requirements be changed?

EPA solicits comment on the above issues.
    b. Basis for TOC Monitoring Requirements With Enhanced Coagulation 
or Enhanced Softening. In order to demonstrate that the necessary DBPP 
removal is accomplished (either the percentage specified in Table IX-1 
or the alternative minimum TOC removal level determined by the AECL), 
systems must monitor TOC on a monthly basis, with both source water and 
treated water (prior to continuous disinfection) samples taken. At the 
same time, systems must monitor for source water alkalinity. Compliance 
is based on a running annual average, computed quarterly. Specifics on 
compliance calculations are included in Section VIII.

B. Bromate MCL and BAT

    During the D/DBP negotiated regulation, ozone was evaluated as an 
alternative disinfectant to chlorine. In particular, the use of ozone 
for primary disinfection and chloramines for residual disinfection were 
considered as a disinfection scenario to significantly minimize the 
formation of THMs, HAAs, and TOX (Metropolitan Water District of So. 
Calif. et al., 1989; Ferguson et al., 1991; Glaze et al., 1993, in 
press; Miltner, 1993; and Jacangelo et al., 1989). In addition, when a 
``cancer-risk bubble'' was evaluated by examining the theoretical risks 
contributed by five compounds that have been classified as B2 (i.e., 
``probable human'') carcinogens (i.e., chloroform, 
bromodichloromethane, bromoform, dichloroacetic acid [DCAA], and 
bromate), it was shown that the production of bromate during ozonation 
may present less of a theoretical cancer risk than the sum of the risks 
from the individual chlorination DBPs. However, such a determination 
largely depended upon the risk attributed to DCAA (which had not been 
finally established by EPA). Also, the ability to detect bromate at 
risk levels equivalent to risk levels for chlorinated DBPs greatly 
obscures this analysis.
    As part of the TWG evaluation of different technologies that might 
be used to comply with the D/DBP Rule, ozone/chloramines were evaluated 
under a possible enhanced SWTR scenario for large systems using surface 
waters that filter but do not soften. It was predicted that TTHMs would 
range from 4 to 62 g/L, with median, 75th, and 90th percentile 
values of 15, 23, and 30 g/L, respectively. In addition, it 
was predicted that HAA5 would range from 2 to 133 g/L, with 
median, 75th, and 90th percentile values of 16, 26, and 41 g/
L, respectively. The TWG believed that use of alternative disinfectants 
would provide a feasible means of not only achieving the Stage 1 
criteria of 80 g/L TTHMs and 60 g/L HAA5 but also 
allow some systems the means of complying with a proposed Stage 2 
criteria of 40 g/L TTHMs and 30 g/L HAA5. As 
discussed previously (Section VI.C.1.b.ii), the TWG also conducted an 
analysis of bromate occurrence with use of ozone technology and 
determined that most systems, allowing for modifications in treatment 
if necessary, such as lowering of pH, could achieve a bromate level of 
10 g/L (Krasner et al., 1993).
    A major issue, however, is the ability to determine low levels of 
bromate during compliance monitoring and concern that the risk from 
bromate could exceed the risk from chlorinated DBPs for which risk 
estimates are available. While Haag and Hoigne discussed the 
theoretical basis for the formation of bromate in their 1983 paper 
(Haag et al., 1983), an analytical method sensitive enough to determine 
if bromate was indeed formed in ozonated drinking water was not 
available until a few years ago (Pfaff et al., 1990). In addition, the 
initial ion chromatography (IC) method was unable to adequately resolve 
low levels of bromate from very high amounts of chloride. Because most 
waters high in bromide can have very high levels of chloride 
(Metropolitan Water District of So. Calif. et al., 1989), Kuo and 
colleagues developed a modification to the IC method in order to remove 
chloride prior to bromate analysis (Kuo et al., 1990). This 
modification permitted quantitation of bromate down to a concentration 
of 10 g/L; subsequently quantitation has been lowered in 
several research laboratories to 3 or 5 g/L (Gramith et al., 
1993). Using two different labor-intensive concentration methods prior 
to IC analysis at EPA research facilities, quantitation for bromate was 
lowered to less than 1.0 g/L (Sorrell et al., 1992 and 
Hautman, 1992).
    Currently, though, a minimum quantitation level for bromate by 
conventional IC is probably about 10 g/L in laboratories that 
might perform compliance monitoring. During the D/DBP negotiated 
rulemaking, some members of the Negotiating Committee expressed concern 
that setting an MCL at 10 g/L would exceed the theoretical 
10-4 risk level for bromate of 5 g/L. The regulation of 
bromate, at this time, represents an unresolved issue. However, the 
Negotiating Committee was willing to propose an MCL for bromate of 10 
g/L with the following qualifications and reservations:
    1. EPA is seeking data to show that a lower quantitation level (at 
least down to 5 g/L) can be obtained by those laboratories 
that will perform compliance monitoring for bromate in natural drinking 
water matrices. Whether this improvement in sensitivity is accomplished 
by improvements to the official EPA method 300.0 (USEPA, 1993) or an 
alternative analytical method, such data would need to demonstrate 
appropriate precision and accuracy, including a linear calibration 
curve for the range of values to be measured, quantitative and precise 
measurements at the MCL (U.S. Office of the Federal Register, 1987), 
intra- and interlaboratory reproducibility, as well as freedom from 
potential interferences in natural matrices (e.g., other anions in 
water such as chloride, and other ozone byproducts such as organic 
acids). In addition, this methodology would need to be demonstrated in 
a number of ozonated drinking water matrices and tested in several 
laboratories nationwide. If the improved methodology uses equipment 
and/or reagents that are not currently required for EPA method 300.0, 
data to indicate the commercial availability and costs of these items 
would also need to be presented.
    2. In addition, EPA is soliciting comments on a treatment technique 
that could ensure that bromate can be kept below 5 g/L, even 
if quantitation at 5 g/l is not achievable under routine 
laboratory conditions. A possible treatment technique that could ensure 
that all systems be able to produce 5 g/L bromate 
(the theoretical 10-4 risk level), would be to construct a matrix 
of predicted bromate concentration as a function of bromide 
concentration levels, ozone disinfection conditions (CT), and pH levels 
under which ozonation occurs. As the bromide and/or inactivation 
criterion increased, the pH of ozonation might need to be decreased to 
ensure that the bromate concentration was kept below 5 g/l. 
Under a treatment requirement, if a system used ozone, it would be 
required to operate within the specified matrix conditions for bromide, 
CT, and pH levels to achieve compliance. This matrix would need to 
consider ozone residuals sufficient to meet CT criteria for a possible 
ESWTR.
    Other treatment techniques which allow ozone to meet disinfection 
and oxidation requirements while minimizing bromate formation are also 
solicited. In addition, any proposed treatment technique must be field-
tested in a number of representative natural water matrices. A number 
of parameters which can affect bromate formation and must be evaluated 
in establishing a treatment technique include TOC, bromide, alkalinity, 
pH, ammonia, and hydrogen peroxide levels of the water, as well as the 
temperature and ozone contact time (Krasner et al., Jan. 1993; Amy et 
al., 1992-3; Haag et al., 1983; Glaze et al., Jan. 1993; Krasner et 
al., 1991; Miltner, Jan. 1993; Krasner et al., 1993; Gramith et al., 
1993; Miltner et al., 1992; Siddiqui et al., 1993; and Von Gunten et 
al., 1992). Because the hydrodynamics of the ozone contactor can 
significantly affect bromate formation (Krasner et al., Jan. 1993; 
Krasner et al., 1991; and Gramith et al., 1993), the treatment 
technique may need to be evaluated at pilot-, demonstration-, and/or 
full-scale. (Bench-scale testing can be used in preliminary evaluations 
of ozone/bromide/bromate chemistry, but such experiments cannot provide 
the sole basis for determining an appropriate treatment technique.)
    Evaluation of the treatment technique will also require 
quantitation of bromate concentrations that are 5 
g/L. Thus, appropriate quality assurance and control will be 
required to ensure that the data are precise and accurate.
    3. Because the proposed bromate MCL of 10 g/L was 
determined to be feasible based upon studies performed to date, if 
sufficient data are presented to EPA to indicate that a lower MCL and/
or an appropriate treatment technique can be obtained, the feasibility 
and nationwide regulatory impact would need to be considered. For 
example, the cost of chemical addition to lower the pH of water before 
ozonation and to raise the pH prior to distribution was not considered 
in developing the national cost data for systems using ozone to meet 
the D/DBP Rule. This cost for pH adjustment could be significant for 
systems with high alkalinity. EPA requests comment on the cost impact 
that this requirement would have on systems with both high alkalinity 
and high bromide levels. The effect of a treatment technique would also 
need to be evaluated in terms of other water quality impacts. 
Therefore, if a treatment technique is developed, EPA would revise the 
regulatory impact analysis to reflect new costs and other water quality 
impacts. EPA requests comment on the relative costs of adjusting pH to 
reduce bromate formation versus the costs of other technologies to meet 
the MCLs in this proposed rule.
    The following limited data suggest that a significant increase in 
sensitivity of the method for measuring bromate may indicate that other 
disinfectant/oxidants produce bromate, and/or that bromate may be a 
contaminant in some source waters. In a study conducted to test a more 
sensitive method for measuring bromate (Hautman, 1992), a bromate 
concentration of 0.4 g/L was measured in one of the nine 
source waters tested (i.e., before the point of disinfection/
oxidation). However, the researcher did not rule out the possibility of 
sample contamination of this source water. Theoretical and limited data 
suggest that chlorine dioxide can react with bromide in the presence of 
sunlight to form brominated DBPs, including possibly bromate (Cooper, 
1990 and Kruithof, 1992). Likewise, under alkaline conditions, bromide 
reacts with hypochlorite to form hypobromite which then 
disproportionates to bromate (Bailar et al, 1973). When the 
hypochlorite solutions from 14 drinking water utilities were surveyed 
for the presence of oxyhalides (Bolyard et al., 1992), bromate was 
measured in nine of the hypochlorite solutions, at levels of 4 to 51 
mg/L. However, the chlorinated drinking water samples did not contain 
bromate at concentrations above the 10 g/L quantitation level. 
Based on this information, if the MCL for bromate is lowered, analyses 
for the occurrence of bromate may need to be extended to sources other 
than ozonated water.
    4. EPA plans to convene a second meeting of interested parties to 
develop a consensus on the second stage of the D/DBP Rule in 1998. It 
is anticipated that by that time, measurement for bromate at 
concentrations <10 g/L may be practical, more health effects 
data on this DBP will be available, and the treatment to control 
bromate formation will be appropriately developed and field tested. EPA 
solicits comments on the feasibility of developing a treatment 
technique requirement for bromate, lowering the MCL based upon improved 
analytical techniques, and the time frame under which such alternative 
standards could be developed.
    In the proposed D/DBP Rule, bromate compliance will be based on a 
running annual average value. This schedule is analogous to that used 
for THMs and HAAs. Because carcinogens represent a risk based upon a 
lifetime exposure, temporary peaks in exposure should not affect the 
lifetime cancer risk. Unlike THMs and HAAs, though, bromate will be 
measured monthly rather than quarterly and at the entry point to the 
distribution system rather than in the distribution system. THMs and 
HAAs can increase in a distribution system as DBP precursors continue 
to react with the residual disinfectant, especially if free chlorine is 
used. Because ozone and other active oxidant residuals (e.g., hydroxyl 
radicals) are short-lived, bromate formation should be complete within 
the treatment plant. Once in the distribution system, bromate should be 
stable (Glaze et al., 1993, in press), so analyzing samples in the 
distribution system will provide no additional information. Because 
there are many water quality parameters and treatment plant operations 
that can affect bromate formation, it was not clear whether quarterly 
monitoring would be adequate to capture the variability in bromate 
formation (Krasner et al., Jan. 1993, Miltner, Jan. 1993, and Gramith 
et al., 1993). However, EPA is proposing reduced bromate monitoring 
where a utility's average raw water bromide level is less than 0.05 mg/
L. This reduction is based on limited data to date to suggest that 
under typical drinking water ozonation conditions of water with 
0.05 mg/L bromide (based on pilot- and full-scale data) that 
bromate will typically not be formed at levels of 5 to 10 g/L 
or higher (Krasner et al., 1993).

C. Chlorite MCL and BAT

    Chlorite is formed as a result of treating source water with 
chlorine dioxide. Many utilities use chlorine dioxide because of 
specific water quality characteristics that make the water difficult to 
treat. These characteristics include high hardness, TOC, and bromide 
concentrations. For example, at high pHs (above 9.0), chlorine is much 
less effective as a disinfectant and ozone residuals cannot be 
maintained in solution long enough for effective disinfection. Systems 
now using chlorine dioxide may not be able to meet the standards 
proposed in this regulation, since in some cases, even expensive 
precursor removal technologies such as GAC or membrane technology may 
not be able to remove precursors adequately to meet DBP MCLs and, in 
other cases, systems may not be able to use the technologies due to 
site restrictions (e.g., membranes not feasible due to water limits--
system cannot afford loss of significant amounts of water as membrane 
reject).
    While research is underway on how to reduce chlorite residuals at 
the treatment plant, e.g., using ferrous iron (Griese et al., 1992), 
additional work is required. At this time, the only means for reducing 
chlorite levels is to control the use of chlorine dioxide.
    During the negotiations, EPA had not yet established a reference 
dose for chlorite and, therefore, no MCLG was considered at that time. 
However, EPA's Office of Water staff stated that they interpreted the 
available health effects data to indicate the toxicological endpoint of 
concern as oxidative stress to red blood cells. This effect is 
considered reversible, lasting a matter of a few weeks or months.
    Based on considerations that the health effect was of relatively 
short duration, and that some systems might require chlorine dioxide, 
the Negotiating Committee agreed to propose a conditional MCL of 1.0 
mg/l. This MCL was selected based on a recommendation from the TWG that 
1.0 mg/l is the lowest level achievable by typical systems using 
chlorine dioxide, and taking into consideration the monitoring 
requirements to determine compliance.
    In agreeing to propose 1.0 mg/l as the MCL for chlorite, the 
Negotiating Committee set certain qualifications and reservations:
    (1) If EPA proposed a MCLG for chlorite of 1.0 mg/l or higher, the 
proposed MCL would be set at the MCLG value. If EPA proposed a MCLG for 
chlorite of less than 1.0 mg/l based on EPA's reference dose, the 
proposed MCL would be set at 1.0 mg/l based on technological 
feasibility considerations.
    (2) Additional research would be conducted including a two-
generation reproductive effects study in animals and a clinical study 
of humans exposed to chlorite to determine what minimum levels of 
exposure can be considered safe. It was agreed that these studies would 
be completed in time for consideration of possible changes to the MCL 
under the final Stage 1 rule. If the studies indicate that a level of 
1.0 mg/l of chlorite is safe, the MCL would remain at 1.0 mg/l. If the 
studies indicate that a level of 1.0 mg/l of chlorite is not safe or, 
if such a study is not conducted, the MCL would be reevaluated.
    Based on a consideration that the health effect is reversible and 
relatively short term in duration, the Negotiating Committee agreed 
that systems would determine compliance by monitoring for chlorite 
three times per month. Samples would be taken at the following 
locations: one near the first customer, one in a location 
representative of average residence time, and one near the end of the 
distribution system reflecting maximum residence time. Monitoring would 
be conducted in the distribution system since the concentration of 
chlorite is likely to increase in the distribution system. If the 
monthly average of the three distribution system samples exceeded the 
MCL, the system would be in violation for that month. In agreeing to 
propose these requirements, the Negotiating Committee assumed that, if 
a system were out of compliance during one month but achieved 
compliance during the following month, that any health effects that 
might occur from the short term exposure would cease once the system 
achieved compliance.
    After the Negotiating Committee agreed to propose the above MCL and 
monitoring requirements at its last meeting in June, 1993, EPA's 
Reference Dose Committee met and determined a different toxicological 
endpoint for chlorite. The Reference Dose Committee determined that 
chlorite poses an acute developmental heath effect, which is a 
neurobehavioral effect: depressed exploratory behavior. Based on the 
new reference dose, the MCLG for chlorite would be 0.08 mg/l (see 
section V of this preamble). The derivation of the MCLG includes a 
1,000-fold uncertainty factor to account for use of a LOAEL instead of 
a NOAEL from an animal study. EPA does not believe that the proposed 
MCL of 1.0 mg/l and monitoring requirements agreed to by the 
Negotiating Committee are adequate to protect the public from the acute 
developmental health effect, unless new data indicate otherwise.
    EPA is concerned about proposing an MCL significantly above the 
MCLG, especially since the MCLG is based on acute health risks. EPA is 
proposing this level to honor the agreement of the Negotiating 
Committee. However, EPA solicits comment on the following approaches 
for promulgating a final rule.
    (1) EPA could promulgate an MCL at the MCLG. Based on currently 
available information, an MCL of 0.08 mg/l would probably rule out the 
use of chlorine dioxide as a disinfectant, since it does not appear 
possible for systems to meet simultaneously disinfection requirements 
and the resultant chlorite MCL. If new data become available indicating 
a NOAEL of 1 mg/kg/day, the highest resultant MCLG and corresponding 
MCL would likely be no more than 0.3 mg/l. An MCL of 0.3 mg/l for 
chlorite ion would allow some systems to be able to use chlorine 
dioxide. However, other water systems, because of water quality 
parameters that affect chlorine dioxide demand and chlorite ion 
control, will not be able to find a feasible operating region to use 
chlorine dioxide, at least on a year-round basis. EPA would be 
concluding that other technologies besides chlorine dioxide are 
feasible for those systems for meeting the Stage 1 D/DBPR and SWTR (or 
ESWTR, if such a rule is necessary), taking cost into consideration for 
systems currently using chlorine dioxide. A regulatory impact analysis 
will have to be prepared to evaluate technical feasibility, production 
of other DBPs based on a different disinfectant, and cost 
considerations.
    (2) EPA could promulgate an MCL lower than the proposed MCL of 1.0 
mg/l, but above the MCLG, depending upon all data that became available 
in the near term. In doing so, EPA would be concluding that risks from 
other alternatives are commensurate at this level, or that other 
technologies, taking costs into consideration, are not available at the 
0.08 mg/l level, but are available at a higher level. EPA would thus be 
indicating that some systems must use chlorine dioxide to meet 
disinfection requirements, but can maintain compliance by making 
operational modifications that are not available to all systems. This 
approach would more narrowly limit the use of chlorine dioxide to 
systems with very specific source water or other characteristics if use 
of chlorine dioxide were considered essential versus use of other 
disinfectants.
    (3) Depending on new data that become available, EPA could 
promulgate an MCL at the proposed MCL of 1.0 mg/l if the Agency 
determined that the systems currently using chlorine dioxide could not 
meet disinfection requirements in any other feasible manner, taking 
cost into consideration.
    As part of any of the above approaches, EPA could accelerate the 
promulgation of NPDWRs for chlorine dioxide and chlorite if the Agency 
believed it necessary to avoid acute health effects. Also, as part of 
the final rule, EPA would consider the appropriateness of the proposed 
monitoring requirements and public notification language in light of 
the acute health effect. Monitoring changes could include increasing 
the sampling frequency, changing the location of monitoring, and/or 
changing the determination of compliance. These changes may result in 
requirements similar to those for chlorine dioxide (e.g., daily 
measurements within the distribution system to determine compliance).
    In making its final decision, EPA will consider a number of 
factors: the risk which would be posed from chlorite and chlorine 
dioxide compared to the risk from other contaminants if chlorine 
dioxide were not used, the uncertainty in those risk estimates, the 
feasibility of using other means of control, and the cost of those 
other control mechanisms.
    EPA requests comments on the above approaches for regulating 
chlorite. Specifically, EPA requests comment on the following:

--Is the basis for EPA's MCLG and concern for acute health effects 
appropriate? See Section V. for a complete discussion.
--In light of the proposed MCLG and concern for acute health risks that 
were not apparent during the negotiations, should EPA accelerate the 
promulgation of NPDWRs for chlorine dioxide and chlorite? If so, should 
EPA set the MCL at the proposed MCLG? Should EPA wait until more data 
become available, as agreed upon during the negotiations, before 
promulgating an MCL? Such data will be available through CMA. CMA is 
conducting health effects studies to fill data gaps for chlorine 
dioxide and chlorite. EPA will evaluate these data (which are scheduled 
to be available prior to rule promulgation) to help determine what 
changes to the MRDLG and MRDL may be warranted.
--Are there any particular water quality characteristics for systems 
currently using chlorine dioxide which make it ineffective to use any 
other disinfection technology?
What are the lowest chlorite levels these systems can achieve? What 
technologies would need to be adopted and at what costs if such systems 
with these particular water quality characteristics would no longer use 
chlorine dioxide to meet the other regulatory criteria proposed herein?
--Should EPA set the chlorite MCL at a level so that chlorine dioxide 
remains a viable disinfection alternative for some systems even if this 
level is above the MCLG? If so, what would be the rationale for doing 
so?
--Is 1.0 mg/l the lowest level that systems needing chlorine dioxide 
can reliably achieve?
--How should EPA change the compliance monitoring requirements for 
chlorite to reflect concern about acute effects? Should such changes 
include increasing the frequency or changing the location of monitoring 
to be similar to those for chlorine dioxide? How would the MCL be 
affected by changes in the monitoring requirements?
--How should EPA change the public notification requirements for 
chlorite to reflect concern about acute effects?

D. Chlorine MRDL and BAT

    The chlorine MRDL has been set at the MRDLG of 4.0 mg/l, with 
compliance being based on a running annual average of monthly averages 
of samples taken in the distribution system. A running annual average 
was used as the basis for compliance because health effects are long 
term (see Section V.).
    There will be no additional monitoring required by Subpart H 
systems to comply with this requirement, since samples that are already 
required to be taken by systems to comply with the Surface Water 
Treatment Rule (see 40 CFR 141.74) may be used to demonstrate 
compliance with the MRDL. The samples required under the SWTR are used 
to demonstrate compliance with the requirement for maintenance of a 
residual in the distribution system (in effect, a floor or minimum); 
the samples required under this rule would set a maximum or ceiling for 
chlorine levels.
    Additional monitoring is required for systems that use only ground 
water not under the direct influence of surface water to comply with 
this requirement, since samples are not already required to be taken by 
these systems. However, this sampling may be required to comply with 
the forthcoming Ground Water Disinfection Rule (GWDR) to be proposed at 
a later date. If such monitoring is required by the GWDR, one set of 
samples will be allowed to be used to demonstrate compliance with both 
the MRDL in this rule and the distribution system monitoring 
requirements in the GWDR.
    Since compliance is based on an annual average, the MRDL does not 
apply to individual samples, which are allowed to be higher than the 
MRDL. In addition, allowing individual samples to exceed the MRDL gives 
the system operator the flexibility to address short-term 
microbiological problems caused by distribution system line breaks, 
storm runoff events, source water contamination, or cross connections.
    EPA believes that it is essential that system operators are aware 
of the flexibility that this rule gives them in addressing specific 
microbiological threats without worrying about violating an MRDL. For 
this reason, the definition of ``maximum residual disinfectant level'' 
proposed today in Sec. 141.2 specifically allows higher disinfectant 
levels for the two disinfectants with long-term, but not short-term, 
effects (chlorine and chloramines), while pointing out that increasing 
levels of chlorine dioxide to address short-term problems is not 
allowed (because of the short-term health effects--see Section V.). The 
Agency believes that even if systems must increase disinfectant levels 
to address specific contamination problems, they will be able to meet 
the MRDL on an annual basis.

E. Chloramine MRDL and BAT

    The chloramine MRDL has been set at the MRDLG of 4.0 mg/l, with 
compliance based on a running annual average of monthly averages of 
samples taken in the distribution system. A running annual average was 
used as the basis for compliance because health effects are long term 
(see Section V.). The Negotiating Committee considered a range of 4 to 
6 mg/l and chose 4 mg/l. This decision was based on compliance being 
determined by a running annual average rather than by individual 
samples. Also, 4 mg/l was thought to be the lowest feasible MRDL for 
some systems that would not compromise microbial protection. Residual 
disinfectant demand could be reduced by additional precursor removal, 
but the Negotiating Committee agreed that precursor removal beyond that 
achieved by enhanced coagulation or enhanced softening should not be 
required in Stage 1. EPA requests comment on what level would be 
feasible to achieve by most systems without increasing microbial risk.
    There will be no additional monitoring required by Subpart H 
systems to comply with this requirement, since samples that are already 
required to be taken by systems to comply with the Surface Water 
Treatment Rule (see 40 CFR 141.74) may be used to demonstrate 
compliance with the MRDL. The samples required under the SWTR are used 
to demonstrate compliance with the requirement for maintenance of a 
residual in the distribution system (in effect, a floor or minimum); 
the samples required under this rule would set a maximum or ceiling for 
chloramine levels.
    Additional monitoring is required for systems that use only ground 
water not under the direct influence of surface water to comply with 
this requirement, since samples are not already required to be taken by 
these systems. However, this sampling may be required to comply with 
the forthcoming Ground Water Disinfection Rule (GWDR) to be proposed at 
a later date. If such monitoring is required by the GWDR, one set of 
samples will be allowed to be used to demonstrate compliance with both 
the MRDL in this rule and the distribution system monitoring 
requirements in the GWDR.
    Since compliance is based on an annual average, the MRDL does not 
apply to individual samples, which are allowed to be higher than the 
MRDL. In addition, allowing individual samples to exceed the MRDL gives 
the system operator the flexibility to address short-term 
microbiological problems caused by distribution system line breaks, 
storm runoff events, source water contamination, or cross connections.
    EPA believes that it is essential that system operators are aware 
of the flexibility that this rule gives them in addressing specific 
microbiological threats without worrying about violating an MRDL. For 
this reason, the definition of ``maximum residual disinfectant level'' 
proposed today in Sec. 141.2 specifically allows higher disinfectant 
levels for the two disinfectants with long-term, but not short-term, 
effects (chlorine and chloramines), while pointing out that increasing 
levels of chlorine dioxide to address short-term problems is not 
allowed (because of the short-term health effects--see Section V.). The 
Agency believes that even if systems must increase disinfectant levels 
to address specific contamination problems, they will be able to meet 
the MRDL on an annual basis.

F. Chlorine Dioxide MRDL and BAT

    EPA has proposed the MRDLG for chlorine dioxide at 0.3 mg/L (see 
section V of this preamble). The derivation of the MRDLG includes an 
uncertainty factor of three to address one data gap (i.e., lack of a 2-
generation reproduction study). In the near future, it is tentatively 
planned that health effects studies on the impact of chlorine dioxide 
in drinking water will be performed to resolve the data gap concerning 
reproductive effects.
    Chlorine dioxide is used in Europe as a residual disinfectant, 
while in the U.S. it is used for disinfection or oxidation within the 
treatment plant. Because chlorine dioxide residuals are short-lived, 
they are typically not detected in distribution systems. When chlorine 
dioxide residuals are analyzed, the presence of other oxidants (e.g., 
chlorine, chlorite, and chlorate) must be subtracted out from a total 
oxidant measurement. In a method where the value is obtained by 
difference, there is a limit to how low a quantitative measurement can 
be made. The PQL for chlorine dioxide residuals is probably in the 
range of 0.5 to 1.0 mg/L.
    Systems must monitor for chlorine dioxide daily since there are 
acute health effects. Monitoring must be conducted at the entrance to 
the distribution system, since the concentration of chlorine dioxide 
will not increase in the distribution system. If monitoring indicates 
that the concentration of chlorine dioxide exceeds the MRDL, the system 
is then required to conduct additional monitoring in the distribution 
system. This monitoring consists of three samples taken the day 
following an exceedance of the MRDL at specific locations within the 
distribution system considered to be those most likely to have the 
highest levels and depend on the type and location of residual 
disinfection. For systems that use chlorine dioxide or chloramines to 
maintain a residual in the distribution system, or that use chlorine 
with no booster chlorination after the water enters the distribution 
system, three samples must be taken as close as possible to the first 
customer at intervals of at least six hours. For systems that use 
chlorine to maintain a disinfectant residual in the distribution 
system, and have one or more locations within the distribution system 
where additional chlorine is added (i.e., booster chlorination), 
samples must be taken at the following locations: One as close as 
possible to the first customer, one in a location representative of 
average residence time, and one near the end of the distribution system 
reflecting maximum residence time. These additional samples must be 
taken each day following any sample taken at the entrance to the 
distribution system that exceeds the MRDL.
    Compliance is based on samples taken both at the entrance to the 
distribution system and in the distribution system. If one or more of 
the samples taken in the distribution system exceed the MRDL, the 
system has an acute violation and must take immediate corrective action 
to lower the level of chlorine dioxide and make appropriate public 
notification. If two consecutive samples taken at the entrance to the 
distribution system exceed the MRDL (and none of the required samples 
taken in the distribution system exceed the MRDL), the system has a 
nonacute violation and must take corrective action to lower the level 
of chlorine dioxide and make appropriate public notification. If a 
required sample is not taken, the system must treat it as if the sample 
had been taken and exceeded the MRDL. Therefore, failure to take one or 
more of the additional distribution system samples the day following a 
sample taken at the entrance to the distribution system that exceeds 
the MRDL is considered an acute violation. Failure to take a sample at 
the entrance to the distribution system the day following a sample 
taken at the entrance to the distribution system that exceeds the MRDL 
is considered a nonacute violation.
    The Negotiating Committee agreed to propose 0.8 mg/L as the MRDL 
for chlorine dioxide with certain qualifications and reservations:
    (1) A two-generation reproductive study would be completed for 
consideration in the final Stage 1 rule. If this study indicates there 
is no concern from reproductive effects at the proposed MRDL, unless 
public comments otherwise influence the Agency, then the proposed MRDL 
would remain the same as proposed (0.8 mg/l).
    (2) If no new health effects studies become available on 
reproductive effects, the chlorine dioxide MRDL will be reassessed. It 
will be necessary to re-examine the tradeoffs and regulatory impacts of 
a lower chlorine dioxide MRDL in light of the positive aspects of 
chlorine dioxide disinfection and control of chlorination DBPs. EPA 
would probably promulgate a final MRDL that is the higher of the MRDLG 
or the detection level because the health effects are acute. Issues 
that would be considered include new information on health effects of 
other disinfectants.
    As part of the above approaches, EPA could accelerate the 
promulgation of an NPDWRs for chlorine dioxide if the Agency believed 
it necessary to avoid acute health effects. In making its final 
decision, EPA will consider a number of factors: The risk which would 
be posed from chlorite and chlorine dioxide compared to the risk from 
other contaminants if chlorine dioxide were not used, the uncertainty 
in those risk estimates, the feasibility of using other means of 
control, and the cost of those other control mechanisms.
    EPA requests comments on the above approaches for regulating 
chlorite. Specifically, EPA requests comment on the issues identified 
earlier in the chlorite subsection.
    Regardless of the final MRDL value, the Negotiating Committee 
agreed on the following monitoring program to protect against the risk 
of a reproductive endpoint due to short-term exposure to a high dose of 
chlorine dioxide: the entry point to the distribution system will be 
measured daily. If any day's value exceeds the MRDL, sampling will be 
initiated in the distribution system. If the second-day plant effluent 
is also above the MRDL, but distribution system samples are less than 
the MRDL, then the utility will be in violation (but this would not be 
considered an acute violation); the lower concentration of chlorine 
dioxide in the distribution system will minimize the risk to consumers 
due to the lower level of exposure. If chlorine dioxide is detected at 
a level greater than the MRDL in the distribution system, then the 
utility would be considered in acute violation because the risk to 
susceptible consumers (i.e., pregnant women) is higher. By monitoring 
chlorine dioxide residuals daily in the treatment plant, utilities can 
work best at minimizing exposure in the distribution system.

G. Basis for Analytical Method Requirements

    The SDWA directs EPA to set an MCL for a contaminant ``if, in the 
judgment of the Administrator, it is economically and technologically 
feasible to ascertain the level of such contaminant in water in public 
water systems.'' [SDWA section 1401(1)(c)(ii)] To make this threshold 
determination for the disinfectants and disinfection by-products (DBPs) 
proposed today, EPA evaluated the availability, costs, and performance 
of analytical techniques which measure these disinfectants and DBPs. 
This evaluation is discussed below. EPA also considered the ability of 
laboratories to measure consistently and accurately at the maximum 
residual disinfectant level (MRDL) or the maximum contaminant level 
(MCL) of each contaminant. The ability to measure consistently and 
accurately at 25 and 50 percent of the total trihalomethane (TTHM) and 
haloacetic acid (HAA5) MCLs was also evaluated in order to ensure that 
measurements for allowing reduced monitoring can be made reliably.
    The reliability of analytical methods is critical at the MRDL or 
MCL and at levels which allow reduced monitoring. Therefore, each 
analytical method was evaluated for lack of bias (i.e. accuracy or 
recovery) and precision (good reproducibility) at these concentrations 
for each contaminant. The primary purpose of the evaluation was to 
determine: (1) Whether analytical methods exist to measure 
disinfectants and DBPs; (2) reasonable expectations of technical 
performance by analytical laboratories at the MRDL or MCL levels and at 
the levels which allow reduced monitoring for TTHMs and HAA5; and (3) 
analytical costs.
    In selecting analytical methods, EPA considered the following 
factors:
    (a) Reliability (i.e., precision/accuracy) of the analytical 
results;
    (b) Specificity in the presence of interferences;
    (c) Availability of enough equipment and trained personnel to 
implement a national monitoring program (i.e., laboratory 
availability);
    (d) Rapidity of analysis to permit routine use; and
    (e) Cost of analysis to water supply systems.
    Several analytical methods are described and discussed below. EPA 
refers readers to the published methods for additional information on 
the precision, accuracy and quality control requirements of the 
proposed analytical methods.
1. Disinfectants
    Today's rule proposes monitoring requirements to ensure compliance 
with proposed maximum residual disinfectant levels for chlorine, 
chloramines, and chlorine dioxide. Analytical methods, most of which 
have been in use for years, exist to measure these residuals. There are 
additional analytical techniques available for measuring disinfectant 
residuals (AWWARF, 1992) that are not proposed in today's rule because 
they are not written in a standard format that is readily available to 
the public. Nine disinfectant methods are proposed in today's rule 
(Table IX-2). Most of the proposed methods are in use, because they 
were promulgated with the Surface Water Treatment Rule (SWTR). (54 FR 
27486, June 29, 1989)

            Table IX-2.--Proposed Methods for Disinfectants             
------------------------------------------------------------------------
     Disinfectant measurement                 Proposed methods          
------------------------------------------------------------------------
Chlorine as free or total residual   4500-Cl DAmperometric Titration.   
 chlorine, chloramines as combined   4500-Cl FDPD Ferrous Titrimetric.  
 or total residual chlorine.         4500-Cl GDPD Colorimetric.         
Chlorine as free residual chlorine.  4500-Cl HSyringaldazine (FACTS).   
Chlorine or Chloramines as total     4500-Cl ELow-Level Amperometric.   
 residual chlorine.                  4500-Cl IIodometric Electrode.     
Chlorine Dioxide as residual         4500-ClO2 C Amperometric Titration.
 chlorine dioxide.                   4500-ClO2 DDPD.                    
                                     4500-ClO2 EAmperometric Titration. 
------------------------------------------------------------------------
Proposed methods are in ``Standard Methods for the Examination of Water 
  and Wastewater,'' 18th Edition, American Public Health Association,   
  American Water Works Association, and Water Environment Federation,   
  1992.                                                                 

    The disinfectant residual methods proposed in today's rule were 
selected based on evaluations that included the results of an 
evaluation made for the methods that were promulgated with the SWTR. In 
today's rule, EPA proposes to withdraw Standard Method 408F, which was 
promulgated for measurement of chlorine residual under the SWTR. EPA is 
also proposing two methods (Standard Methods 4500-Cl H and 4500-Cl I) 
that were inadvertently omitted from the SWTR. Methods 4500-Cl H and I 
would be approved for compliance monitoring under the SWTR and the D/
DBP rule. In addition, EPA proposes to update all of the disinfectant 
methods, which were promulgated in 1989 with the SWTR, to the versions 
that will be promulgated with the D/DBP rule. This update will allow 
laboratories to use the most recent versions of these methods for all 
compliance monitoring of disinfectant residuals.
    Standard Method 408F was dropped from the 17th and subsequent 
editions of Standard Methods because it is difficult to use, and 
because there are several other available methods that are superior to 
it. Since EPA believes few, if any, laboratories use Method 408F, 
withdrawal should have little effect on the regulated community.
    In evaluating disinfectant residual methods for use under the SWTR 
EPA considered, but did not promulgate, five EPA and two Standard 
Methods. The seven methods were rejected for the following reasons. EPA 
methods 330.1 to 330.5 for free and total chlorine measurement were not 
promulgated because equivalent methods published by Standard Methods, 
which contained more up-to-date and complete descriptions of required 
analytical procedures, were available. The five EPA methods have not 
been updated since 1979, while new editions of Standard Methods are 
issued periodically to include all applicable improvements made to the 
methods during the interim. Standard Method 4500-Cl B (Iodometric I) 
was not promulgated with the SWTR because it cannot measure chlorine 
accurately at concentrations of less than 1 mg/L. Standard Method 4500-
Cl C (Iodometric II) was not promulgated because it is not sensitive 
enough for drinking water analyses. For these same reasons, EPA is not 
proposing these seven methods in today's rule.
    EPA is aware that all of the disinfectant methods proposed today 
are subject to interferences, especially when used to measure low 
concentrations of disinfectant residuals. However, when procedures 
specified in the methods are followed, the methods can be used to 
indicate compliance with the minimum disinfectant residual 
concentrations proposed in today's rule (AWWARF, 1992). EPA is 
soliciting information on improvements which may have been made to 
these methods, but that are not reflected in the 18th edition of 
Standard Methods. EPA is also seeking information on new methodology 
that may be applicable for compliance monitoring. New methods must 
provide demonstrated advantages over the current methods and have the 
potential for being distributed in a standard format in the time frame 
of this regulation.
    EPA is aware that several vendors manufacture or may manufacture 
test kits that are based on DPD colorimetric Standard Methods 4500-Cl G 
and 4500-ClO2 D. If Methods 4500-Cl G and 4500-ClO2 D are 
promulgated under the D/DBP rule, EPA proposes that kits using the same 
chemistry as these methods be approved for compliance monitoring for 
chlorine and chlorine dioxide, respectively, provided the State also 
approves of their use.
    EPA believes that the analytical methods being proposed today are 
within the technical and economic capability of many laboratories. For 
example, utility laboratories are currently using the proposed 
disinfectant methods to measure disinfectant residuals under the SWTR. 
The analytical cost is estimated at $10 to $20 per sample. Costs will 
vary with the laboratory, analytical technique selected, number of 
samples, and other factors. EPA believes these costs are affordable.
    Below is a description of the analytical methods proposed for 
compliance with the proposed MRDLs. The three disinfectant residuals 
are measured and reported as follows: chlorine as free or total 
chlorine; chloramines as combined or total chlorine; and chlorine 
dioxide as chlorine dioxide. For information on the precision and 
accuracy of these methods, EPA refers the readers to the written 
methods and to AWWARF, 1992. EPA requests public comments on the 
technical adequacy of these proposed analytical techniques.
    a. Amperometric Titration Method (SM 4500-Cl D) for chlorine and 
chloramines. Free residual chlorine is measured by adjusting the pH of 
the sample to between 6.5 and 7.5 followed by titration to the endpoint 
with a phenylarsine oxide reducing solution. Total residual chlorine is 
measured by adding potassium iodide to the sample, adjusting the pH to 
between 3.5 and 4.5, and titrating with phenylarsine oxide to the 
endpoint. Chloramines, as combined chlorine, are determined by 
subtracting the result of the free residual chlorine measurement from 
the total residual chlorine measurement in the same sample. A 
microammeter is used to detect the endpoints in each titration. 
Commercial titrators are considered to have detection limits as low as 
20 g/L (as Cl2), but the limit of detection depends on 
the type of water sample (AWWARF, 1992). Since interferences may 
account for a high percentage of the instrument response at low 
concentrations, results in samples with low concentrations of free or 
total chlorine should be used with caution (AWWARF, 1992). EPA believes 
the working range for this method adequately covers the proposed MRDLs 
for free, combined, and total chlorine residuals.
    b. Low Level Amperometric Titration Method (SM 4500-Cl E) for 
chlorine and chloramines measured as total residual chlorine. This 
method utilizes the same principle as the amperometric titration method 
listed above. This method modifies SM 4500-Cl D by using a more dilute 
concentration of phenylarsine oxide titrant and a graphical procedure 
to determine the endpoint. Use of this method is recommended when the 
total chlorine residual is less than or equal to 0.2 mg/L as Cl2. 
This method will show a positive bias if other oxidizing reagents are 
present in the water sample. Since SM 4500-Cl E is only applicable to 
measuring total residual chlorine, it cannot be used to differentiate 
between free and combined residual chlorine.
    c. DPD Ferrous Titrimetric Method (SM 4500-Cl F) for chlorine and 
chloramines. When the proper sample pH is chosen, this method can 
differentiate between free chlorine, monochloramine, dichloramine, and 
total chlorine. The color produced by the reaction of the chlorine 
species with the DPD dye slowly disappears as the sample is titrated 
with ferrous ammonium sulfate. The amount of titrant corresponds to the 
concentration of chlorine species being measured. This method is 
proposed for the determination of free, combined, and total residual 
chlorine.
    d. DPD Colorimetric Method (SM 4500-Cl G) for chlorine and 
chloramines. The method utilizes the same principle as SM4500-Cl F 
except that the color produced is read by a colorimeter and the 
concentrations of free and total chlorine are calculated after 
standardization. Combined residual chlorine is the sum of the 
monochloramine and dichloramine measurements. Total residual chlorine 
is the sum of free and combined residual chlorine. This method is 
proposed for the determination of free, combined, and total residual 
chlorine.
    e. Syringaldazine (FACTS) Method (SM 4500-Cl H) for chlorine. The 
reagent, syringaldazine, is oxidized by free chlorine on a 1:1 basis to 
produce a color which is determined colorimetrically. The pH of the 
sample must be maintained at approximately 6.7 to stabilize the color 
formed. This method is proposed for the determination of free residual 
chlorine.
    f. Iodometric Electrode Technique (SM 4500-Cl I) for chlorine and 
chloramines. This method involves the direct potentiometric (electrode) 
measurement of iodine released when potassium iodide is added to an 
acidified sample containing chlorine. A platinum-iodide electrode pair 
is used in combination to measure the liberated iodine. This method is 
proposed for the determination of total residual chlorine.
    g. Amperometric Method I (SM 4500-ClO2 C) for chlorine dioxide 
residuals. This titration method is an extension of SM 4500-Cl D (which 
measures chlorine). By sequentially performing four titrations at 
different sample pH with phenylarsine oxide, four chemicals (free 
chlorine, monochloramine, chlorite, and chlorine dioxide) may be 
determined by a method of differences. This method is proposed for the 
determination of chlorine dioxide residuals.
    h. DPD Method (SM 4500-ClO2 D) for chlorine dioxide. This 
method is an extension of the DPD method for chlorine (SM 4500-Cl F). 
Chlorine dioxide appears in the first step of this procedure, but only 
to the extent of one-fifth of its available oxidation/reduction 
potential. This potential arises from the reduction of chlorine dioxide 
in the sample to chlorite. After a pH adjustment and the addition of a 
buffer, a color is produced which corresponds to the chlorine dioxide 
content of the sample. This method is proposed for the determination of 
chlorine dioxide residuals.
    i. Amperometric Method II (4500-ClO2 E) for chlorine dioxide. 
This titration method is similar to SM 4500-ClO2 C which is 
described above. The method can measure chlorine dioxide in samples 
which contain free chlorine and other interfering compounds. The method 
can measure a wide range of chlorine dioxide concentrations in drinking 
water samples. Dilute (0.1 to 10 mg/L) and concentrated (10 to 100 mg/
L) concentrations of chlorine dioxide are measured by varying the size 
of the drinking water sample and the concentration of the titrating 
solution. This method is proposed for the determination of chlorine 
dioxide residuals.
2. By-Products
    Six analytical methods for measurement of inorganic and organic 
disinfection by-products (Table IX-3) are proposed and discussed in 
parts 3 and 4.

       Table IX-3.--Proposed Methods for Disinfection By-products       
------------------------------------------------------------------------
                Contaminant                           Methods\1\        
------------------------------------------------------------------------
Trihalomethanes.............................  502.2, 524.2, 551.        
Haloacetic Acids............................  552.1, 6233 B.            
Bromate, Chlorite...........................  300.0.                    
------------------------------------------------------------------------
\1\EPA Method 502.2 is in the manual ``Methods for the Determination of 
  Organic Compounds in Drinking Water'', EPA/600/4- 88/039, July 1991,  
  NTIS publication PB91-231480. EPA Method 551 is in the manual         
  ``Methods for the Determination of Organic Compounds in Drinking      
  Water--Supplement I'', EPA/600/4-90/020, July 1990, NTIS PB91-146027. 
  EPA Methods 524.2 and 552.1 are in the manual ``Methods for the       
  Determination of Organic Compounds in Drinking Water--Supplement II'',
  EPA/600/R-92/129, August 1992, NTIS PB92-207703. EPA Method 300.0 is  
  in the manual ``Methods for the Determination of Inorganic Substances 
  in Environmental Samples'', EPA/600/R/93/100--Draft, June 1993.       
  Standard Method 6233 B is in ``Standard Methods for the Examination of
  Water and Wastewater,'' 18th Edition, American Public Health          
  Association, American Water Works Association, and Water Environment  
  Federation, 1992.                                                     

3. Organic By-Product Methods
    EPA is proposing five methods (Table IX-3) for the analysis of two 
classes of organic disinfection by-products--total trihalomethanes 
(TTHMs) and haloacetic acids (five) (HAA5). Compliance with the 0.08 
mg/L TTHM MCL will be determined by summing the concentration of each 
of four trihalomethanes (bromoform, chloroform, dibromochloromethane 
and bromodichloromethane) as measured in a drinking water sample by EPA 
Methods 502.2 or 524.2 or 551. EPA is also proposing to withdraw 
approval of two EPA methods which use older technology and have been 
superseded by Methods 502.2 and 551.
    Compliance with the HAA5 MCL of 0.060 mg/L will be determined by 
summing the concentration of each of five haloacetic acids (mono-, di-, 
and trichloroacetic acids; mono- and dibromoacetic acids) as measured 
in a drinking water sample with EPA Method 552.1 or Standard Method 
6233 B. The haloacetic analytical methods can also measure a sixth 
haloacetic (bromochloroacetic) acid. Since this acid may be considered 
in a future disinfection by-product control regulation, EPA encourages, 
but does not require, water systems to measure and report occurrences 
of bromochloroacetic acid in samples analyzed for HAA5 MCL compliance 
monitoring.
    EPA believes the analytical methods being proposed today are within 
the technical capability of many laboratories and within the economic 
capability of the regulated community. The analytical cost for 
trihalomethane (THM) analysis is estimated to be from $50 to $100 per 
sample. There is generally no additional cost for THM measurements if 
Method 502.2 or 524.2 is used to measure volatile organic compounds 
(VOCs) in the same sample. The analytical cost for haloacetic acid 
analysis is estimated at $150 to $250 per sample; adding 
bromochloroacetic acid to the analysis should not significantly change 
the cost. Actual costs may vary with the laboratory, analytical 
technique selected, the total number of samples, and other factors.
    Today's proposed requirements would impose little or no extra 
trihalomethane monitoring on community water systems serving 
populations of 10,000 or more because most of these systems must 
routinely monitor for THMs under the Trihalomethane rule [44 FR 68264, 
November 29, 1979]. Monitoring for haloacetic acids will increase each 
system's analytical costs but EPA believes these costs are affordable.
    With the exception of EPA Method 551, the proposed methods for 
measuring trihalomethanes are in widespread use. More than 700 
laboratories are presently certified to measure THMs. Many of these 
laboratories use Methods 502.2 and 524.2 to comply with VOC and THM 
monitoring requirements and MCLs. EPA believes there is adequate 
laboratory capacity for trihalomethane analysis. EPA expects that many 
of these laboratories will become certified to conduct analysis of 
haloacetic acids in drinking water samples.
    The methods for measuring haloacetic acids are new and not in 
widespread use. These compounds have been included in several of EPA's 
Water Supply (WS) performance evaluation (PE) studies, and the number 
of participants has increased with each successive study. In the WS 31 
study, twenty-five laboratories reported data for all five of the 
haloacetic acids covered in today's proposed rule, compared to sixteen 
laboratories in the WS 29 study. These data were produced using a 
liquid-liquid extraction method. Based on the available PE data, EPA 
believes the haloacetic acid methods can provide reliable data at the 
proposed MCLs. EPA is aware that many utility laboratories are 
developing analytical capability for haloacetic acids, and commercial 
laboratories are receiving requests from utilities for haloacetic acid 
analyses. Therefore, EPA believes there will be adequate laboratory 
capability by the time compliance monitoring for haloacetic acids is 
required.
    a. Trihalomethane Methods. Presently EPA Methods 501.1, 501.2, 
502.2, and 524.2 are approved for compliance with total trihalomethane 
monitoring requirements under 40 CFR 141.30. For reasons discussed 
below, EPA proposes to withdraw Methods 501.1 and 501.2, and to approve 
a new method (EPA Method 551) for trihalomethane compliance 
measurements.
    Method 502.2, Volatile Organic Compounds in Water by Purge and Trap 
Capillary Column Gas Chromatography with Photoionization and 
Electrolytic Conductivity Detectors in Series, and Method 524.2, 
Measurement of Purgeable Organic Compounds in Water by Capillary Column 
Purge and Trap Capillary Column Gas Chromatography/Mass Spectrometry, 
are widely used for THM and VOC analyses. Readers are referred to 
previous notices, 52 FR 25690 (July 8, 1987) and 56 FR 3548 (January 
30, 1991), for discussions and descriptions of these methods. Method 
502.2 requires a photoionization detector and an electrolytic 
conductivity detector, configured in series, to measure aromatic or 
unsaturated VOCs by photoionization, and other VOCs and THMs by 
electrolytic conductivity. If only THMs are to be determined in a 
sample, Method 502.2 may be used without the photoionization detector.
    EPA proposes to withdraw approval of EPA Methods 501.2 and 501.1 
for TTHM compliance monitoring. Method 501.2, which uses a liquid-
liquid extraction technique, and Method 501.1, which uses a purge-and-
trap sparging technique, have not been updated since 1979. Both methods 
use packed column technology. Packed columns have less resolving power 
than capillary columns, which often limits their use to very simple 
analyses. This is one of the reasons that Methods 501.1 and 501.2 are 
only promulgated for trihalomethane monitoring.
    Packed column technology is becoming obsolete, and capillary 
columns are required in most modern gas chromatographic methods that 
have been developed for compliance monitoring. In a rule which was 
published on August 3, 1993 (58 FR 41344), EPA encourages the use of 
capillary column methods for THM analysis, and announces discontinuance 
of technical support for packed column methods. As laboratories replace 
their gas chromatographs over the next few years, EPA believes most, if 
not all, laboratories will acquire capillary column instruments because 
they offer greater flexibility in the number of analytes that can be 
measured [W.L. Budde, 1992].
    The Agency has promulgated (58 FR 41344) two capillary column 
methods (EPA Methods 502.2 and 524.2) that can replace Method 501.1. 
Today EPA is proposing a capillary column method (EPA Method 551) for 
trihalomethane monitoring that can replace Method 501.2. Withdrawal of 
EPA Methods 501.1 and 501.2 would not become effective until 18 months 
after today's rule is promulgated, so laboratories would be able to use 
these methods for several more years. EPA does not believe that 
withdrawal of the methods will adversely affect laboratories over this 
time frame.
    EPA Method 551, Determination of Chlorination Disinfection 
Byproducts and Chlorinated Solvents in Drinking Water by Liquid- Liquid 
Extraction and Gas Chromatography with Electron Capture Detection, is 
proposed for THM compliance measurements. It is a liquid-liquid 
extraction method applicable to the determination of a variety of 
halogenated organic compounds.
    In Method 551 the ionic strength of a 35-mL drinking water sample 
aliquot is adjusted using sodium chloride, and the sample is extracted 
with 2-mL of methyl-tert-butyl ether. If only THMs are to be measured, 
pentane can be used as the extracting solvent provided the quality 
control requirements specified in Method 551 are met. When pentane is 
used, Method 551 is very similar to liquid-liquid extraction Method 
501.2. EPA believes laboratories wishing to use liquid-liquid 
extraction to measure THMs will prefer Method 551 to Method 501.2.
    b. THM-Sample Dechlorination. All of the promulgated and proposed 
methods for THM compliance analysis require that the THM formation 
reaction be halted by addition of a reagent that removes all free 
chlorine from the sample. EPA provides the following guidance to help 
laboratories correctly preserve samples for compliance with proposed 
and existing (40 CFR 141.30 and 141.133) THM monitoring requirements. 
The Agency believes that this guidance is warranted because many 
preservation procedures are available, depending on the method, and 
because laboratories may wish to measure VOCs and THMs in a single 
analysis.
    Laboratories must carefully follow the preservation procedure 
described in each method, especially the order in which reagents are 
added to the sample. The methods allow analysts to choose among four 
reagents (ammonium chloride, ascorbic acid, sodium sulfite, or sodium 
thiosulfate) to dechlorinate a water sample. These reagents remain 
available for use but, with one exception, EPA strongly recommends the 
use of sodium thiosulfate for the analyses of THMs, since EPA has the 
most performance data with this chemical. The exception is that 
ascorbic acid should be used when sulfur dioxide will interfere with 
analyses that are performed using a mass spectrometer. Samples 
dechlorinated with ascorbic acid must be acidified immediately, as 
directed in the method.
    c. Haloacetic Acid Methods. Standard Method 6233 B and EPA Method 
552.1 are relatively new, use capillary columns, and are proposed today 
for measurement of five haloacetic (monochloroacetic, dichloroacetic, 
trichloroacetic, monobromoacetic and dibromoacetic) acids. As discussed 
above, EPA recommends that bromochloroacetic acid also be measured with 
these methods.
    Standard Method 6233 B, Micro Liquid-Liquid Extraction Gas 
Chromatographic Method for Haloacetic Acids, was developed by several 
laboratories, including EPA. The analytical procedures used in Method 
6233 B are equivalent and very similar to those used in the 30-mL 
extraction option, which is described in EPA Method 552, Determination 
of Haloacetic Acids in Drinking Water by Liquid-Liquid Extraction, 
Derivatization, and Gas Chromatography with Electron Capture Detection. 
EPA considered proposing both methods; however, Method 552 contains a 
30-mL and a 100-mL extraction option. EPA believes that the 100-mL 
extraction option uses a quantitation and calibration procedure that 
will not produce acceptable results for compliance with today's 
monitoring requirements. Also, the performance data for the 30-mL 
extraction option is more completely presented in Method 6233 B. For 
purposes of today's rule, EPA believes that Method 6233 B is more 
complete and easier to use than Method 552. Laboratories, which have 
been using the 30-mL extraction option in Method 552, will have no 
trouble switching to Method 6233 B. If EPA revises Method 552, it may 
be approved in the final rule.
    In Method 6233 B, the pH of a 30-mL drinking water sample is 
adjusted to 0.5 or less, and the ionic strength of the sample is 
increased by adding sodium sulfate. The acids are extracted into 3-mL 
of methyl-tert-butyl ether (MTBE). Exactly 2-mL of the extract is 
transferred to a volumetric flask and the volume is reduced to 
approximately 1.7-mL.
    The haloacetic acids, which have been concentrated in the MTBE 
extract, are converted to methyl esters using a dilute solution of 
diazomethane in MTBE. The extract, which now contains the methyl esters 
of the haloacetic acids, is analyzed using capillary column gas 
chromatography with electron capture detection.
    The analytical method is calibrated and the haloacetic acids are 
quantitated using standards with a known concentration of each 
haloacetic acid. These standards are called aqueous procedural 
standards because they are prepared in reagent water and treated 
exactly like a drinking water sample. This means that the standards are 
carried through the extraction, derivatization, and chromatographic 
steps of the method. Aqueous standards which are analyzed in this way 
automatically correct for the method bias that occurs when any of the 
haloacetic acids are not completely extracted from the drinking water 
sample with the solvent MTBE.
    EPA Method 552.1, Determination of Haloacetic Acids and Dalapon in 
Drinking Water by Ion-Exchange Liquid-Solid Extraction and Gas 
Chromatography with an Electron Capture Detector, is a liquid-solid 
extraction method which does not require the use of diazomethane. It is 
proposed today for five haloacetic acids.
    In Method 552.1, a 100-mL sample aliquot is adjusted to pH 5.0 and 
extracted with a preconditioned miniature anion exchange column. The 
haloacetic acids are eluted from the column with small aliquots of 
acidic methanol. After the addition of a small volume of MTBE as a co-
solvent, the acids are converted to their methyl esters directly in the 
acidic methanol. The methyl esters are partitioned into the MTBE phase 
and identified and measured by capillary column gas chromatography with 
electron capture detection.
4. Inorganic By-Product Method
    EPA is proposing Method 300.0, Determination of Inorganic Anions by 
Ion Chromatography, for analysis of the inorganic disinfection by-
products covered in today's proposed rule--bromate and chlorite (Table 
IX-3). Method 300.0 must be modified as specified below to adequately 
measure bromate at the MCL proposed in today's rule. This method is 
presently approved for the analysis of nitrate and nitrite in drinking 
water under 40 CFR 141.23. The method is described below; additional 
information may be found in the May 22, 1989 notice [54 FR 22097].
    Method 300.0 requires an ion chromatograph and an ion 
chromatographic column. Ion chromatography is conducted in many 
laboratories because it can simultaneously measure many anions of 
interest--bromide, chloride, fluoride, nitrate, nitrite, 
orthophosphate, sulfate, bromate, chlorite, and chlorate. Method 300.0 
specifies the two columns that are required to separate and measure the 
ions of interest. The AS9 column is used to measure chlorite, chlorate, 
and bromate. This column has the advantage that it separates the 
chlorate ion from the nitrate ion.
    EPA believes that Method 300.0 is within the technical capability 
of many laboratories and within the economic capability of the 
regulated community. The analytical cost of bromate and chlorite 
analysis is estimated to range from $50 to $100 per sample. Actual 
costs may vary with the laboratory, the total number of samples, and 
other factors. EPA believes the analytical costs for bromate and 
chlorite ion monitoring are affordable.
    Under the requirements set forth in this proposed rule, monitoring 
for the bromate ion would apply to water systems using ozone in the 
treatment train. Monitoring for the chlorite ion would apply to systems 
using chlorine dioxide. Since utilities rarely use both ozone and 
chlorine dioxide, most systems will use Method 300.0 to measure only 
bromate or only chlorite for compliance with the MCLs proposed in 
today's rule.
    EPA WS PE studies indicate that an increasing number of 
laboratories have the capability to measure bromate and chlorite. The 
lowest concentration of the bromate ion in a PE sample to date was 30 
g/L in WS 31. Twenty-three laboratories reported data and 65% 
of them were within 50% of the true value. Chlorite ion 
concentrations have ranged from 100 to 460 g/L in studies WS 
29 through WS 31. The percentage of laboratories successfully meeting 
50% of the true value acceptance criteria ranged from 85 to 
96%. These data indicate that adequate laboratory capacity will be 
available by the time the compliance monitoring requirements proposed 
in this rule become effective.
    EPA has evaluated Method 300.0, modifications to the method, and 
the results from PE studies to determine the feasibility of obtaining 
reliable measurements at the MCLs proposed in today's rule for chlorite 
and bromate. Based on this evaluation, EPA believes that Method 300.0 
can easily provide reliable data at the proposed MCL for chlorite. To 
reliably measure bromate at the proposed MCL, Method 300.0 must be 
modified to improve the sensitivity of the analysis. The modifications, 
which are discussed below, involve changes to the injection volume and 
to the eluent.
    a. Bromate Ion. EPA is aware that the current version of Method 
300.0 is not sensitive enough to measure bromate ion concentrations at 
the proposed MCL. Method 300.0 is more sensitive to bromate if a weaker 
ion chromatographic eluent is used. In a recent EPA study, Hautman & 
Bolyard [1992] successfully used a borate, rather than a carbonate, 
eluent to chromatographically measure bromate ion concentrations in 
drinking water. This alternate eluent reduced baseline noise, thereby 
increasing the method sensitivity. The detection limit for bromate can 
be further reduced by increasing the volume of sample that is injected 
into the ion chromatograph (from 50 to 200 L) and by further 
decreasing the concentration of the borate eluent to 18mM NaOH/72 mM 
H3BO3 [Hautman, 1993]. These are acceptable modifications to 
Method 300.0. The quality control requirements, which must be met when 
a weaker eluent or a larger sample injection volume is used, are 
specified in the method.
    A few utility, university, and commercial laboratories are 
analyzing ozonated drinking water for low concentrations of the bromate 
ion. According to verbal communications with EPA, some of these 
laboratories are able to quantitate bromate down to concentrations of 5 
to 10 g/L, and they can detect bromate down to concentrations 
of 1 to 2 g/L. In order to achieve this sensitivity, the 
laboratories are using the modifications mentioned above and, in some 
cases, the laboratories are also treating the samples to remove a 
chloride interference [Kuo et al., 1990].
    Based on the information presented above, EPA believes that Method 
300.0 with the appropriate modifications can be used to reliably 
determine compliance with the proposed MCL for bromate. Whether 
laboratories are able to reliably measure bromate ion concentrations at 
levels below the proposed MCL under routine operating conditions is 
presently unknown. Laboratory performance data will be collected as 
part of the proposed Information Collection Rule (ICR) (59 FR 6332) so 
EPA will be able to more accurately determine laboratory capabilities 
for measuring bromate prior to promulgation of today's proposed rule.
    EPA is aware of efforts to develop more sensitive techniques for 
measuring bromate ion concentrations in drinking water. Two studies 
have demonstrated the capability to measure bromate levels of <1 
g/L using sample concentration techniques prior to injection 
into the ion chromatograph [Hautman, 1992; Sorrell & Hautman, 1992]. 
However, these techniques are labor-intensive and not generally 
available to laboratories that do routine analyses using ion 
chromatography. Efforts are underway to develop an automated sample 
concentration technology which may be applicable to routine analyses 
[Joyce & Dhillon, 1993]. EPA solicits comments on whether use of a 
sample concentration technology prior to ion chromatographic analysis 
should be considered as a new methodolgy or a modification to Method 
300.0 under today's rule. EPA also solicits comments on the 
applicability of sample concentration technology to today's proposed 
MCL for bromate.
    EPA is aware that high concentrations of the chloride ion interfere 
with the measurement of the bromate ion. There are currently two 
solutions to this interference problem. The first solution is based on 
a recent study [Hautman & Bolyard, 1992] that successfully used a 
borate eluent to chromatographically separate bromate and chloride. The 
study demonstrated that these conditions can be used to measure other 
anions for which ion chromatography is an approved compliance 
monitoring technique. The second solution to the chloride interference 
is to remove chloride from the sample by filtering it through a silver 
filter before injecting it into the ion chromatograph [Kuo et al., 
1990]. Both of these solutions are permitted as part of EPA Method 
300.0 provided the quality control requirements, which are specified in 
the method, are met.
    EPA prefers the first solution (borate as eluent) to the chloride 
interference problem, because it lowers the baseline noise, thereby 
increasing the method's sensitivity for all anions in the analytical 
scope of the method. However, in some waters, chloride ion 
concentrations are too high, and a silver filter must be used to remove 
excess chloride. EPA cautions that silver will leach from the filters 
into the sample. If the leachate is not removed from the sample, it 
will contaminate the ion chromatographic column. Since a contaminated 
column cannot be used to measure chloride or bromide ion 
concentrations, the leachate must be removed by filtering the sample 
through an ion chromatographic chelate cartridge prior to injection 
into the ion chromatograph [Hautman, 1992]. Another alternative is to 
dedicate an ion chromatographic column to bromate analysis, since 
silver interferes only with the analysis of chloride and bromide, not 
bromate, ions.
    Compliance with the bromate MCL under today's rule is determined by 
analyzing samples collected at the entrance point to the distribution 
system. EPA does not believe an ozone residual will exist at this 
sampling point, so the reactions that cause bromate formation should be 
complete. Bromate does not decompose after it is produced. As a result, 
Method 300.0 does not require the use of a preservative for bromate 
samples. EPA is soliciting any data that demonstrate the need for a 
preservative in samples collected at this sampling point for 
measurement of bromate.
    b. Chlorite Ion. EPA considered other available methods for the 
measurement of the chlorite ion. For example, chlorite ion, chlorate 
ion, and the disinfectant chlorine dioxide can be measured by 
amperometric or potentiometric measurements of iodine, which is formed 
from the reaction of these chemicals with iodide ion. EPA recognizes 
that these methods may be useful to utility operators for routine 
operational monitoring of unit processes. Their use is encouraged for 
such work when an ion chromatograph is not available at the treatment 
plant. However, EPA does not believe that these methods are suitable 
for compliance monitoring, because chlorite is determined by a method 
of differences rather than direct measurement. EPA believes that the 
ion chromatography method is the compliance technique of choice, 
because it provides a direct measurement of each inorganic DBP anion. 
Method 300.0 is also a very versatile method with an analytical scope 
that includes several other ions that are commonly present in drinking 
water samples. Therefore, Method 300.0 is the only method proposed for 
chlorite ion monitoring in today's rule.
    Utilities using chlorine dioxide as a disinfectant or oxidant will 
have the ions, chlorite and chlorate, in the treated water. Using 
Method 300.0, chlorate can be measured along with chlorite at little or 
no extra cost. Since chlorate may be considered in a future 
disinfection by-product control regulation, utilities are encouraged, 
but not required, to obtain data on chlorate concentrations in their 
water.
    Since the chlorite ion reacts with free residual chlorine and with 
metal ions such as nickel and iron, it is not stable in some drinking 
water matrices [Hautman & Bolyard, 1992]. Method 300.0 addresses this 
problem by requiring the addition of ethylenediamine (EDA) as a 
preservative, if samples cannot be analyzed for the chlorite ion within 
10 minutes of sample collection. If the chlorite ion is measured in 
samples with a chlorine dioxide residual, the sample must also be 
sparged with nitrogen at the time of collection to remove the chlorine 
dioxide residual. EPA is interested in learning whether there are 
vendors who are willing, or would be willing in the future, to sell 
high purity chlorite standards to laboratories performing analyses for 
chlorite.

. Other Parameters--Total Organic Carbon, Alkalinity and Bromide

     Table IX-4.--Proposed Analytical Methods for Other Parameters      
------------------------------------------------------------------------
             Parameter                            Method\1\             
------------------------------------------------------------------------
Total Organic Carbon...............  5310 CPersulfate-Ultraviolet       
                                      Oxidation.                        
                                     5310 DWet Oxidation.               
Alkalinity.........................  2320 B, 310.1, D-1067-             
                                      88BTitrimetric.                   
                                     I-1030-85Electrometric.            
Bromide............................  300.0Ion Chromatography.           
------------------------------------------------------------------------
\1\EPA Method 300.0 is in the manual ``Methods for the Determination of 
  Inorganic Substances in Environmental Samples'', EPA/600/R/93/100--   
  Draft, June 1993. EPA Method 310.1 is in the manual ``Methods for     
  Chemical Analysis of Water and Wastes'', EPA/600/4-79-020, March 1983,
  NTIS PB84-128677. Standard Methods 2320B, 5310B and 5310C are in      
  Standard Methods for the Examination of Water and Wastewater, 18th    
  Edition, American Public Health Association, American Water Works     
  Association, and Water Environment Federation, 1992. Method D-1067-88B
  is in the ``Annual Book of ASTM Standards'', Vol. 11.01, American     
  Society for Testing and Materials, 1993. Method I-1030-85 is in       
  Techniques of Water Resources Investigations of the U.S. Geological   
  Survey, Book 5, Chapter A-1, 3rd ed., U.S. Government Printing Office,
  1989.                                                                 

    Total organic carbon, alkalinity, and bromide are not covered by 
proposed MRDLs or MCLs in today's rule. As explained in Sections VIII 
and IX of this notice, EPA is proposing monitoring requirements for 
some or all of these parameters at systems that need to use the results 
to comply with certain treatment requirements. To ensure accurate 
measurement of these parameters, EPA proposes the following analytical 
methods.
    a. Total organic carbon (TOC) methods. Several analytical methods 
exist to measure total organic carbon; two Standard Methods are 
proposed in today's rule (Table IX-4). TOC measurements are conducted 
in many laboratories. In a recent EPA Water Pollution PE study (WP 30), 
541 laboratories reported TOC data. EPA believes this response 
indicates an adequate potential laboratory capability to comply with 
the requirements of today's rule. EPA believes these methods are within 
the technical and economic capability of many laboratories. The 
analytical cost for TOC analyses is estimated to range from $50 to $75 
per sample. Actual costs may vary with the laboratory, analytical 
technique selected, the total number of samples, and other factors. EPA 
believes that the costs for TOC monitoring are affordable.
    Today's rule proposes monitoring for TOC, not dissolved organic 
carbon (DOC). TOC is the sum of the undissolved and dissolved organic 
carbon in the water sample. DOC is differentiated from TOC by filtering 
the sample with a very fine (0.45-m) filter. Today's rule 
specifies that TOC samples are not to be filtered except to remove 
turbidity, which is known to interfere with accurate TOC measurement 
when the sample turbidity is greater than 1 NTU. A TOC sample can be 
filtered to remove turbidity provided a prewashed, glass-fiber filter 
with a large (5- to 10-m) pore size is used. As an alternative 
to filtering, the TOC sample can be diluted with organic-free reagent 
water in order to reduce the turbidity interference. EPA solicits 
comments on the proposed turbidity threshold, and on the sample 
filtration procedure as described above and in the proposed methods.
    EPA has evaluated several methods to determine the feasibility of 
obtaining reliable TOC measurements. To meet today's proposed 
requirements, a TOC method must have a detection limit of at least 0.5 
mg/L, and more importantly achieve a reproducibility of 0.1 
mg/L over a range of approximately 2 to 5 mg/L. This reproducibility is 
required because some systems will have to reliably measure 0.3 mg/L 
differences in TOC removal in several jar test samples to which 
progressively greater amounts of coagulant have been added [R. Miltner, 
1993]. Reliable measurement of 0.3 mg/L differences requires that the 
error bars on the analysis approach 0.1 mg/L. When 
calculated as a percent, this precision requirement becomes 
5% at 2 mg/L of TOC, and 2% at 5 mg/L of TOC. 
Data presented in Standard Method 5310 C indicate that this is 
feasible, and Standard Method 5310 D is close to this level of 
performance.
    In a PE sample prepared for EPA's Water Pollution WP 27 study, 26 
EPA and State laboratories achieved a precision of 0.33 mg/
L on a TOC sample spiked at about 5 mg/L. In WP 30, a mean value of 
8.74 0.79 mg/L was measured by the 541 laboratories that 
reported results. A subset of 27 EPA and State laboratories in WP 30 
reported a precision of 0.4 mg/L on the same sample. EPA 
solicits comment on what precision can be routinely expected on 
differential TOC measurements of jar test samples. EPA is also 
interested in new methods or modifications to the methods proposed 
today that would improve the reproducibility of TOC measurement.
    EPA considered, but is not proposing, Standard Method 5310 B 
because the stated detection limit is 1 mg/L, which is 0.5 mg/L greater 
than the required TOC detection limit. EPA is aware that the 
instrumentation used in Method 5310 B is being improved. If this work 
is successful, EPA will consider the next version of Method 5310 B (or 
its equivalent) for promulgation in the final rule. The two methods 
proposed today for TOC measurements are described below.
    Persulfate-Ultraviolet Oxidation Method (SM 5310 C) measures 
organic carbon via infrared absorption of the carbon dioxide gas that 
is produced when the organic carbon in the sample is simultaneously 
reacted with a persulfate solution and irradiated with ultraviolet 
light. Inorganic carbon is removed from the sample prior to analysis by 
acidification with phosphoric or sulfuric acid. Chloride and low sample 
pH can impede the analysis; precautions are specified in the method. 
The lower limit of detection of the method is 0.05 mg/L.
    Wet-Oxidation Method (SM 5310 D) has a detection limit of 0.10 mg/L 
and is subject to the same interferences as the persulfate-ultraviolet 
method. Persulfate and phosphoric acid are added to the sample; the 
sample is then purged with pure oxygen to remove inorganic carbon. The 
purged sample is sealed in an ampule and combusted for four hours in an 
oven at a temperature that causes persulfate to oxidize organic carbon 
to carbon dioxide. The ampule is opened inside a TOC-analyzer, and TOC 
is measured via infrared absorption of carbon dioxide.
    b. Alkalinity Methods. With two minor exceptions, EPA is proposing 
all of the methods (Table IX-4) which are currently approved under 40 
CFR 141.89 for measurement of alkalinity. The exceptions are that EPA 
is proposing more recent versions of the alkalinity methods, which are 
published by Standard Methods and the American Society of Testing and 
Materials (ASTM). In today's rule, EPA is proposing Method 2320 B, 
which is in the 18th edition of Standard Methods, and Method D1067-88B, 
which is in the 1993 Annual Book of ASTM Standards, in lieu of the 
versions cited at 40 CFR 141.89. There are no technical difference 
between the proposed versions and the currently approved versions.
    EPA is also aware that EPA Method 310.1, which uses the same 
technology as Methods 2320 B and D1067-88B, has not been updated since 
1983. The references in the EPA method are becoming obsolete, and the 
equivalent methods from ASTM and Standard Methods are updated more 
regularly. To allow laboratories the use of only the most current 
versions of equivalent methods, EPA may not promulgate Method 310.1 
with the final D/DBP rule, and EPA also may withdraw approval of it 
under 40 CFR 141.89.
    To accurately measure alkalinity, the sample pH at the source where 
the sample was collected must be recorded. It is important to 
accurately measure carbon dioxide gas, which is dissolved in the sample 
and is a major contributor to the alkalinity of the sample. To minimize 
loss of carbon dioxide, the sample is collected in an air tight 
container, and agitation of the sample is kept to a minimum.
    EPA believes that the proposed alkalinity methods, which have been 
used for years, are within the technical and economic capability of 
many laboratories. The analytical cost of alkalinity analysis is 
estimated to range from $5 to $10 per sample. Actual costs may vary 
with the laboratory, analytical technique selected, the total number of 
samples and other factors. EPA believes the analytical costs for 
alkalinity monitoring are affordable.
    EPA believes the working range for each method adequately covers 
the requirements proposed for alkalinity monitoring in today's rule. 
All procedures and precautions listed below and in the methods must be 
followed carefully. Descriptions and more information on the methods 
are in the notices of August 18, 1988 [53 FR 31516] and October 19, 
1990 [55 FR 42409].
    c. Bromide Method. EPA Method 300.0, Determination of Inorganic 
Anions by Ion Chromatography, is proposed for measurement of bromide 
ion. This method is described above under inorganic by-product methods 
for chlorite and bromate. EPA believes the working range for this 
method adequately covers the requirements proposed for bromide 
monitoring in today's rule.
    EPA believes that Method 300.0 is within the technical and economic 
capability of many laboratories. The analytical cost of bromide 
analysis is estimated to range from $50 to $100 per sample. However, if 
other anions, such as fluoride or chloride, are measured in the same 
sample, the additional cost for bromide analysis should be minimal. 
Actual costs may vary with the laboratory, analytical technique 
selected, the total number of samples, and other factors. EPA believes 
the analytical costs for bromide ion monitoring are affordable.
6. Sources and Scope of Future Analytical Methods
    The Standard Methods proposed in today's rule are published in the 
18th edition of Standard Methods. EPA is aware that these methods will 
be updated when the 19th edition is published. EPA is also gathering 
additional performance data on several EPA methods which are proposed 
in today's rule. EPA will obtain these data from occurrence studies, 
from laboratory certification performance evaluation sample analyses 
and from other sources. To support pollution prevention goals and to 
generally improve the safety and efficiency of analytical methods, EPA 
is working to reduce the volume of solvents and the amounts of 
potentially hazardous reagents in EPA methods. Thus, EPA may revise, 
improve, or expand several EPA methods prior to promulgation of the D/
DBP rule. Examples of methods that EPA or other organizations might 
change are discussed below.
    EPA may refine the solvent extraction and sample preservation 
procedures in Method 551, which is proposed today for trihalomethanes. 
EPA may also extend approval of EPA Method 551 to compliance 
measurements of six chemicals currently regulated under 40 CFR 141.24. 
The six contaminants are: carbon tetrachloride, trichloroethylene, 
tetrachloroethylene, 1,2-dibromoethane (EDB), 1,2-dibromo-3-
chloropropane (DBCP), and 1,1,1-trichloroethane. EPA may revise Method 
552, merge it with Method 552.1, and approve it for the analysis of 
haloacetic acids. EPA may revise Method 300.0 to improve the detection 
limits for bromate and to further eliminate some of the interference 
problems in the method. The Standard Methods organization may 
incorporate more sensitive instrumentation in later versions of TOC 
method 5310 B.
    To accommodate future improvements in analytical methods, EPA 
proposes that the methods in the then current editions of books 
published by Standard Methods and ASTM and the then current versions of 
EPA methods be cited in the final D/DBP rule provided no unacceptable 
changes are in the later versions of these methods.

H. Basis for Compliance Schedule and Applicability to Different Groups 
of Systems, Timing With Other Regulations

    Under the negotiated rulemaking the Negotiating Committee agreed to 
propose three rules: (a) an information collection requirements rule 
(ICR) (59 FR 6332), (b) an ``interim'' enhanced surface water treatment 
rule (ESWTR) (proposed in today's Federal Register), and c) 
Disinfection/Disinfection By-products (D/DBP) regulations, proposed 
herein today. Table IX-5 indicates the schedule agreed to by the 
Negotiating Committee by which these rules would be proposed, 
promulgated, and become effective. Compliance dates for the ICR are 
indicated under the columns of the Stage 2 D/DBP rule and ESWTR to 
reflect the relationship between these rules.
    The Negotiating Committee agreed that more data, especially 
monitoring data, should be collected under the ICR to assess possible 
shortcomings of the SWTR and develop appropriate remedies, if needed, 
to prevent increased risk from microbial disease when systems began 
complying with the Stage 1 D/DBP regulations. It was also agreed that 
EPA would propose an interim ESWTR (proposed elsewhere in today's 
Federal Register) pertaining to systems serving greater than 10,000 
people, including a wide range of regulatory options. Data gathered 
under the ICR would form the basis for (a) promulgating the most 
appropriate criteria among the options presented in the proposed 
interim ESWTR, and (b) proposing at a later date a long-term ESWTR 
pertaining to all system sizes. Both of these rules, if needed, would 
be proposed and promulgated so as to be in effect at the same time that 
systems of the respective size categories would be required to comply 
with new regulations for D/DBPs.
    The Negotiating Committee also agreed that additional data on the 
occurrence of disinfectants, disinfection byproducts (DBPs), potential 
surrogates for DBPs, source water and within treatment conditions 
affecting the formation of DBPs, and bench-pilot scale information on 
the treatability for removal of DBP precursors would be beneficial for 
developing the Stage 2 D/DBP regulatory criteria.
    Prior to promulgating the interim ESWTR, EPA intends to issue a 
Notice of Availability to: (a) discuss the pertinent data collected 
under the ICR rule, (b) discuss additional research that would 
influence determination of appropriate regulatory criteria, (c) discuss 
criteria EPA considered appropriate to promulgate in the interim ESWTR 
(which would be among the regulatory options of the proposed interim 
ESWTR) and (d) solicit public comment on the intended criteria to be 
promulgated.
    The Negotiating Committee believed that the December 1996 scheduled 
date for promulgating the Stage 1 D/DBP Rule was within the shortest 
time possible by which the interim ESWTR, if necessary, could also be 
promulgated. EPA is proposing that the Stage 1 D/DBP regulations and 
the interim ESWTR (if necessary) become effective on the same date of 
June 30, 1998 for systems using surface water and serving greater than 
10,000 people.

   TABLE IX-5.--Proposed D/DBP, ESWTR, ICR Rule Development Schedule    
------------------------------------------------------------------------
  Time line    Stage 1 DBP rule    Stage 2 DBP rule         ESWTR       
------------------------------------------------------------------------
12/93.......  ..................  Propose             Propose           
                                   information         information      
                                   collection          collection       
                                   requirements for    requirements for 
                                   systems >100k.      systems >10k.    
3/94........  Propose required    Propose Stage 2.    Propose interim   
               enhanced            MCLs for TTHMs      ESWTR for systems
               coagulation for     (40 g/     >10k.            
               systems with        l), HAA5 (30                         
               conventional        g/l),                       
               treatment. MCLs-    BAT is precursor                     
               TTHMs (80g/l), HAA5        chlorination.                        
               (60g/l),                                        
               bromate,                                                 
               chlorite.                                                
               Disinfectant                                             
               limits.                                                  
6/94........  ..................  Promulgate ICR....  Promulgate ICR.   
8/94........  Close of public     ..................  Public comment    
               comment period.                         period for       
                                                       proposed ESWTR   
                                                       closes.          
10/94.......  ..................  Systems >100k       Systems >100k     
                                   begin ICR           begin ICR        
                                   monitoring.         monitoring.      
1/95........  ..................  ..................  Systems 10-100k   
                                                       begin source     
                                                       water monitoring.
10/95.......  ..................  SW systems >100k,   ..................
                                   GW systems >50k                      
                                   begin bench/pilot                    
                                   studies unless                       
                                   source water                         
                                   quality criteria                     
                                   met.                                 
11/95.......  ..................  ..................  NOA for monitoring
                                                       data, direction  
                                                       of interim ESWTR.
1/96........  ..................  ..................  Systems >10k      
                                                       complete ICR     
                                                       monitoring. End  
                                                       NOA public       
                                                       comment period.  
3/96........  ..................  Systems complete    Systems >100k     
                                   ICR monitoring.     complete ICR     
                                                       monitoring.      
12/96.......  Promulgate Stage 1  ..................  Promulgate interim
                                                       ESWTR for systems
                                                       >10k.            
6/97........  ..................  Notice of           Propose long-term 
                                   availability for    ESWTR for systems
                                   Stage 2             <10k, possible   
                                   reproposal.         changes for      
                                                       systems >10k.    
10/97.......  ..................  Complete and        ..................
                                   submit results of                    
                                   bench/pilot                          
                                   studies.                             
12/97.......  ..................  Initiate            ..................
                                   reproposal--begin                    
                                   with 3/94                            
                                   proposal.                            
6/98........  Effective.          Close of public     Interim ESWTR     
               Effective for SW    comment period.     effective for    
               systems serving                         systems >10k.    
               greater >10k,                           1994-6 monitoring
               extended                                data used to     
               compliance date                         determine        
               for GAC or                              treatment level. 
               membrane                                                 
               technology.                                              
12/98.......  ..................  Propose for CWSs,   Publish long-term 
                                   NTNCWSs.            ESWTR.           
6/00........  Stage 1 limits      Promulgate Stage 2  Long-term ESWTR   
               effective for       for all CWSs,       effective for all
               surface water       NTNCWSs.            system sizes.    
               systems <10k, GW                                         
               systems <10k.                                            
1/02........  Stage 1 limits      Stage 2 effective,  ..................
               effective for GW    compliance for                       
               systems >10k        GAC/membranes by                     
               unless Stage 2      2004.                                
               criteria                                                 
               supersede.                                               
------------------------------------------------------------------------

    Although the Agency anticipates that the ICR will be promulgated 
later than the date indicated in Table IX-5, EPA believes that the 
long-term schedule will be adhered to and the final D/DBPR will be 
promulgated in December, 1996.
    EPA is proposing that systems using surface water and serving fewer 
than 10,000 people comply with the Stage 1 D/DBP regulations by June 
30, 2000 to allow such systems to also come into compliance with the 
final ESWTR. EPA believes that the June 30, 2000 compliance date 
reflects the shortest time possible that would allow for the final 
ESWTR to be proposed, promulgated, and become effective; thereby 
providing the necessary protection from any downside microbial risk 
that might otherwise result when systems of this size attempt to 
achieve compliance with the Stage 1 D/DBP rule.
    EPA is also proposing that systems using ground water and serving 
greater than 10,000 people would be required to achieve compliance with 
the Stage 1 D/DBP rule by June 30, 2000. EPA believes this is the 
earliest date possible by which all ground water systems of this size 
could be expected to achieve compliance with both the GWDR and the 
Stage 1 D/DBP rule. Many ground water systems would be expected to be 
able to achieve compliance by an earlier date but others, due to 
recently installing or upgrading disinfection to meet the GWDR, would 
require some period of monitoring for DBPs in order to adjust their 
treatment processes to also meet the Stage 1 D/DBP standards.
    For the same reasons as stated above, EPA is proposing that systems 
using ground water and serving 10,000 or less people be required to 
meet the Stage 1 D/DBP rule beginning January 1, 2002. The delayed date 
for the ground water systems serving 10,000 or less people is because 
of the much large number of such systems in this size category, and the 
time necessary for States and systems to implement the GWDR.

I. Basis for Qualified Operator Requirements and Monitoring Plans

    EPA believes that systems that must make treatment changes to 
comply with requirements to reduce the microbiological risks and risks 
from disinfectants and disinfection byproducts should be operated by 
personnel who are qualified to recognize and react to problems. 
Therefore, in today's proposal, the Agency is requiring that all 
systems regulated under this rule be operated by an individual who 
meets State-specified qualifications, which may differ based on size 
and type of the system. Subpart H systems already are required to be 
operated by qualified operators under the provisions of the SWTR (40 
CFR 141.70(c)). Current qualification programs developed by the States 
should, in many cases, be adequate to meet this requirement for Subpart 
H systems. In the upcoming Ground Water Disinfection Rule, the Agency 
may require some or all ground water systems to also be operated by 
qualified operators. If so, the qualification programs for Subpart H 
systems may be modified to account for the differences between Subpart 
H systems and ground water systems. Also, States must maintain a 
register of qualified operators.
    EPA encourages States which do not already have operator license 
certification programs in effect to develop such programs. The 
Negotiating Committee and Technologies Working Group believed that 
properly trained personnel were an essential first step in ensuring 
safer drinking water.
    Also, systems are required to develop and follow monitoring plans 
for monitoring required under this proposed rule. Systems may update 
these plans for reasons including changes to the distribution system or 
changes in treatment.

J. Basis for Stage 2 Proposed MCLs

    EPA is proposing lower MCLs for TTHMs and total haloacetic acids 
(THAAs) for Stage 2 to indicate the desire to further decrease exposure 
from these chemicals but also to lower the exposure from other 
byproducts resulting from chlorine reacting with naturally occurring 
organics. Systems which lower the levels of TTHMs and THAAs are also 
likely to lower the levels of many other chlorination byproducts, some 
of which may pose additional health risks.
    The proposed 40/30 MCL is based on what would be achievable by most 
systems if they were to use the ``best available technology'' (BAT) 
proposed for Stage 2. The Negotiating Committee agreed that the BAT in 
Stage 2 for controlling TTHMs and THAAs include either enhanced 
coagulation and shallow bed granular activated carbon (GAC10) or deep 
bed granular activated carbon (GAC20) and chlorine as the primary and 
residual disinfectant.
    One of the major reasons for defining BAT as including chlorine 
versus, for example, defining BAT as including alternative 
disinfectants, is to recognize the many benefits of chlorine as a 
disinfectant, especially in preventing microbial disease. In addition 
to being a strong primary disinfectant, a chlorine residual in the 
distribution system helps prevent bacterial growth and is an excellent 
marker (when there is an absence of chlorine) for indicating potential 
contamination from outside sources into the distribution system. EPA 
believes that chlorine should be included in the BAT definition at 
least until there is more health effects information on byproducts 
formed by use of alternative disinfectants.
    Currently it is not clear whether risks from chlorination 
byproducts are more significant than those formed from use of 
alternative disinfectants. The Negotiating Committee agreed that EPA 
would repropose Stage 2 requirements in 1998 to consider new 
information that would become available, especially data on the health 
effects of alternative disinfectants.

X. Laboratory Certification and Approval

    EPA recognizes that the effectiveness of today's proposed 
regulations depends on the ability of laboratories to reliably analyze 
the regulated disinfectants and disinfection byproducts at the proposed 
MRDL or MCL, respectively. Laboratories must also be able to measure 
the trihalomethanes and haloacetic acids at the proposed monitoring 
trigger levels, which are between 25 and 50 percent of the proposed 
MCLs for these compound classes. EPA has established a drinking water 
laboratory certification program that States must adopt as a part of 
primacy. (40 CFR 142.10(b)). EPA has also specified laboratory 
requirements for analyses, such as alkalinity and disinfectant 
residuals, that must be conducted by approved parties. (40 CFR 141.89 
and 141.74). EPA's ``Manual for the Certification of Laboratories 
Analyzing Drinking Water'', EPA/570/9-90/008, specifies the criteria 
which EPA uses to implement the drinking water laboratory certification 
program.
    Today EPA is proposing MCLs for total trihalomethanes, total 
haloacetic acids (HAA5), bromate, and chlorite. EPA is proposing that 
only certified laboratories be allowed to analyze samples for 
compliance with the proposed MCLs. For the disinfectants and other 
parameters in today's rule, which have MRDLs or monitoring 
requirements, EPA is requiring that analyses be conducted by a party 
acceptable to the State.
    Performance evaluation (PE) samples, which are an important tool in 
EPA's laboratory certification program, are provided by EPA or the 
States to laboratories seeking certification. To obtain and maintain 
certification, a laboratory must use a promulgated method and at least 
once a year successfully analyze an appropriate PE sample. In the 
drinking water PE studies, EPA has samples for bromate, chlorite, five 
haloacetic acids, four trihalomethanes, free chlorine, and alkalinity. 
EPA has total chlorine and total organic carbon samples in the 
wastewater PE studies and has the potential to provide these samples 
for drinking water studies. Due to the lability of chlorine dioxide, 
EPA does not expect a suitable PE sample can be designed for chlorine 
dioxide measurements.

A. PE-Sample Acceptance Limits for Laboratory Certification

    Historically, EPA has set minimum PE acceptance limits based on one 
of two criteria: statistically derived estimates or fixed acceptance 
limits. Statistical estimates are based on laboratory performance in 
the PE study; fixed acceptance limits are ranges around the true 
concentration of the analyte in the PE sample. Today's proposed rule 
combines the advantages of these approaches by specifying 
statistically-derived acceptance limits around the study mean, within 
specified minimum and maximum fixed criteria.
    EPA believes that specifying statistically-derived PE acceptance 
limits with upper and lower bounds on acceptable performance will 
provide the flexibility necessary to reflect improvement in laboratory 
performance and analytical technologies. The proposed acceptance 
criteria will maintain minimum data quality standards (the upper bound) 
without artificially imposing unnecessarily strict criteria (the lower 
bound). Therefore, EPA is proposing the following acceptance limits for 
measurement of bromate, chlorite, each haloacetic acid, and each 
trihalomethane in a PE sample.
    EPA proposes to define acceptable performance for each chemical 
measured in a PE sample from estimates derived at a 95% confidence 
interval from the data generated by a statistically significant number 
of laboratories participating in the PE study. However, EPA proposes 
that these acceptance criteria not exceed 50% nor be less 
than 15% of the study mean. If insufficient PE study data 
are available to derive the estimates required for any of these 
compounds, the acceptance limit for that compound will be set at 
50% of the study true value. The true value is the 
concentration of the chemical that EPA has determined was in the PE 
sample.
    EPA recognizes that when using multianalyte methods, the data 
generated by laboratories that are performing well will occasionally 
exceed the acceptance limits. Therefore, to be certified to perform 
compliance monitoring using a multianalyte method, laboratories are 
required to generate acceptable data for at least 80% of the regulated 
chemicals in the PE sample that are analyzed with the method. If fewer 
than five compounds are included in the PE sample, data for each of the 
analytes in that sample must meet the minimum acceptance criteria in 
order for the laboratory to be certified.

B. Approval Criteria for Disinfectants and Other Parameters

    Today's rule proposes MRDLs for the three disinfectants--chlorine, 
chloramines, and chlorine dioxide. In addition, monitoring requirements 
(under conditions explained in sections VIII and IX of this notice) are 
being proposed for total organic carbon (TOC), alkalinity, and bromide; 
there are no MCLs proposed for these parameters. In previous rules (40 
CFR 141.28, .74, and .89), EPA has required that measurements of 
alkalinity, disinfectant residuals, pH, temperature, and turbidity be 
made with an approved method and conducted by a party approved (not 
certified) by the State. In today's rule, EPA proposes that samples 
collected for compliance with today's requirements for alkalinity, 
bromide, residual disinfectant, and TOC only be conducted with approved 
methods and by a party approved by the State.

C. Other Laboratory Performance Criteria

    For all contaminants and parameters proposed for monitoring in 
today's rule, the States may impose other requirements for a laboratory 
to be certified or a party to be approved to conduct compliance 
analyses. EPA solicits suggestions for other optional or mandatory 
performance criteria that EPA or the States should consider for 
certification or approval of laboratories.

XI. Variances and Exemptions

A. Variances

    Under section 1415(a)(1)(A) of the SDWA, a State which has primary 
enforcement responsibility (primacy), or EPA as the primacy agent, may 
grant variances from MCLs to those public water systems that cannot 
comply with the MCLs because of characteristics of the water sources 
that are reasonably available. At the time a variance is granted, the 
State must prescribe a compliance schedule and may require the system 
to implement additional control measures. The SDWA requires that 
variances only be granted to those systems that have installed BAT (as 
identified by EPA in the regulations). Furthermore, before EPA or the 
State may grant a variance, it must find that the variance will not 
result in an unreasonable risk to health (URTH) to the public served by 
the public water system. The levels representing an URTH for each of 
the contaminants and disinfectants in this proposal will be addressed 
in subsequent guidance. In general, the URTH level would reflect acute 
and subchronic toxicity for shorter term exposures and high 
carcinogenic risks for long-term exposures (as calculated using the 
linearized multistage model in accordance with the Agency's risk 
assessment guidelines; see URTH Guidance, 55 FR 40205, October 2, 
1990).
    Under section 1413(a)(4), States that choose to issue variances 
must do so under conditions, and in a manner, that are no less 
stringent than EPA allows in section 1415. Of course, a State may adopt 
standards that are more stringent than the EPA standards. Before a 
State may issue a variance, it must find that the system is unable to 
(1) Join another water system or (2) develop another source of water 
and thus comply fully with all applicable drinking water regulations.
    EPA specifies BATs for variance purposes. EPA may identify as BAT 
different treatments under section 1415 for variances than BAT under 
section 1412 for MCLs. EPA's section 1415 BAT findings may vary 
depending on a number of factors, including the number of persons 
served by the public water system, physical conditions related to 
engineering feasibility, and the costs of compliance with MCLs. In this 
proposal, EPA is not proposing a different BAT for variances under 
section 1415.

B. Exemptions

    Under section 1416(a), EPA or a State may exempt a public water 
system from any requirements related to an MCL or treatment technique 
of an NPDWR, if it finds that (1) Due to compelling factors (which may 
include economic factors), the PWS is unable to comply with the 
requirement; (2) the exemption will not result in an unreasonable risk 
to health; and (3) the PWS was in operation on the effective date of 
the NPWDR, or for a system that was not in operation by that date, only 
if no reasonable alternative source of drinking water is not available 
to the new system.
    If EPA or the State grants an exemption to a public water system, 
it must at the same time prescribe a schedule for compliance (including 
increments of progress) and implementation of appropriate control 
measures that the State requires the system to meet while the exemption 
is in effect. Under section 1416(a)(2), the schedule must require 
compliance within one year after the date of issuance of the exemption. 
However, section 1416(b)(2)(B) states that EPA or the State may extend 
the final date for compliance provided in any schedule for a period not 
to exceed three years, if the public water system is taking all 
practicable steps to meet the standard and one of the following 
conditions applies: (1) The system cannot meet the standard without 
capital improvements that cannot be completed within the period of the 
exemption; (2) in the case of a system that needs financial assistance 
for the necessary implementation, the system has entered into an 
agreement to obtain financial assistance; or (3) the system has entered 
into an enforceable agreement to become part of a regional public water 
system. For public water systems which serve less than 500 service 
connections and which need financial assistance for the necessary 
improvements, EPA or the State may renew an exemption for one or more 
additional two-year periods if the system establishes that it is taking 
all practicable steps to meet the requirements above.
    Under section 1416(d), EPA is required to review State-issued 
exemptions at least every three years and, if the Administrator finds 
that a State has, in a substantial number of instances, abused its 
discretion in granting exemptions or failed to prescribe schedules in 
accordance with the statute, the Administrator, after following 
established procedures, may revoke or modify those exemptions and 
schedules. EPA will use these procedures to scrutinize exemptions 
granted by States and, if appropriate, may revoke or modify exemptions.
    In addition to the conditions stated above, EPA solicits comment on 
whether exemptions to this rule should be granted if a system could 
demonstrate to the State, that due to unique water quality 
characteristics, it could not avoid through the use of BAT the 
possibility of increasing its total health risk by complying with the 
Stage 1 regulations. EPA solicits comment on when such situations might 
occur. For example, such situations might occur for systems with 
elevated bromide levels in raw water. In this case, it is possible that 
the use of BAT could result in the increase of total risk due to 
increased concentrations of brominated byproducts in the finished 
water. EPA also solicits comment on what specific conditions, if any, 
should be met for a system to be granted an exemption under such a 
provision. What provisions should EPA require of States to grant these 
exemptions? Should such exemptions be granted for a limited period but 
be renewable by the State if no new health risk information became 
available?

XII. State Implementation

    The Safe Drinking Water Act provides that States may assume primary 
implementation and enforcement responsibilities. Fifty-five out of 57 
jurisdictions have applied for and received primary enforcement 
responsibility (primacy) under the Act. To implement the federal 
drinking water regulations, States must adopt their own regulations 
which are at least as stringent as the federal regulations. This 
section describes the regulations and other procedures and policies 
that States must adopt to implement this proposed rule.
    To implement this proposed rule, States are required to adopt the 
following regulatory requirements:

--Section 141.32, Public Notification;
--Section 141.64, MCLs for Disinfection Byproducts;
--Section 141.65, MRDLs for Disinfectants;
--Subpart L, Disinfectant Residuals, Disinfectant Byproducts, and 
Disinfection Byproduct Precursors.

    In addition to adopting regulations no less stringent than the 
federal regulations, EPA is proposing that States adopt certain 
requirements related to this regulation in order to have their program 
revision applications approved by EPA. In several instances, the 
proposed NPDWRs provide flexibility to States in implementing of the 
monitoring requirements of this rule.
    EPA is also proposing changes to State recordkeeping and reporting 
requirements. EPA's proposed changes are discussed below.

A. Special Primacy Requirements

    To ensure that a State program includes all the elements necessary 
for an effective and enforceable program, a State application for 
program revision approval must include a description of how the State 
will:
    (1) Determine the interim treatment requirements for systems 
granted additional time to install GAC and membrane filtration.
    (2) Qualify operators of community and nontransient noncommunity 
water systems subject to this regulation. Qualification requirements 
established for operators of systems subject to 40 CFR Part 141 Subpart 
H (Filtration and Disinfection) may be used in whole or in part to 
establish operator qualification requirements for meeting Subpart L 
requirements if the State determines that the Subpart H requirements 
are appropriate and applicable for meeting Subpart L requirements.
    (3) Approve percentage reduction of TOC levels lower than those 
required in Sec. 141.135(a)(3) (i.e., how the State will approve 
alternate enhanced coagulation levels).
    (4) Approve parties to conduct analyses of water quality parameters 
(pH, alkalinity, temperature, bromide, and residual disinfectant 
concentration measurements). The State's process for approving parties 
performing water quality measurements for systems subject to Subpart H 
requirements may be used for approving parties measuring water quality 
parameters for systems subject to Subpart L requirements, if the State 
determines the process is appropriate and applicable.
    (5) Approve alternate analytical methods for measuring residual 
disinfectant concentrations for chlorine and chloramines. State 
approval granted under Subpart H (Sec. 141.74(a)(5)) for the use of DPD 
colorimetric test kits for free chlorine testing would be considered 
acceptable approval for the use of DPD test kits in measuring free 
chlorine residuals as required in Subpart L.
    (6) Define criteria to use in determining if multiple wells are to 
be considered as a single source. Such criteria will be used in 
determining the monitoring frequency for systems using only ground 
water not under the direct influence of surface water.

B. State Recordkeeping

    The current regulations in Sec. 142.14 require States with primacy 
to keep various records, including analytical results to determine 
compliance with MCLs, MRDLs, and treatment technique requirements; 
system inventories; sanitary surveys; State approvals; enforcement 
actions; and the issuance of variances and exemptions. In this rule, 
States would be required to keep additional records of the following, 
including all supporting information and an explanation of the 
technical basis for each decision:
    (1) Records of determinations made by the State when the State has 
allowed systems additional time to install GAC or membrane filtration. 
These records must include the date by which the system is required to 
have completed installation.
    (2) Records of systems that apply for alternative TOC performance 
criteria (alternate enhanced coagulation levels). These records must 
include the results of testing to determine alternative limits.
    (3) Records of systems that are required to meet alternative TOC 
performance criteria (alternate enhanced coagulation levels). These 
records must include the alternative limits and rationale for 
establishing the alternative limits.
    (4) Records of Subpart H systems using conventional treatment 
meeting any of the enhanced coagulation or enhanced softening exemption 
criteria.
    (5) Records of systems with multiple wells considered to be one 
treatment plant for purposes of determining monitoring frequency.
    (6) Register of qualified operators.
    Pursuant to Sec. 141.133(d), Subpart H systems serving more than 
3,300 people are required to submit monitoring plans to the State. EPA 
solicits comment on whether the State should be required to keep this 
plan on file at the State after submission to make it available for 
public review.

C. State Reporting

    EPA currently requires in Sec. 142.15 that States report to EPA 
information such as violations, variance and exemption status, and 
enforcement actions. In addition to the current reporting requirements, 
EPA is proposing under Sec. 142.15(c) that States also report:
    (1) A list of all systems required to monitor for various 
disinfectants and disinfection byproducts;
    (2) A list of all systems for which the State has granted 
additional time for installing GAC or membrane technology and the basis 
for the additional time;
    (3) A list of laboratories that have completed performance sample 
analyses and achieved the quantitative results for TOC, TTHMs, HAA5, 
bromate, and chlorite;
    (4) A list of all systems using multiple ground water wells which 
draw from the same aquifer and are considered a single source for 
monitoring purposes;
    (5) A list of all Subpart H systems using conventional treatment 
which are not required to operate with enhanced coagulation, and the 
reason why enhanced coagulation is not required for each system, as 
listed in Sec. 141.135(a)(1)(A)-(D); and
    (6) A list of all systems with State-approved alternate performance 
standards (alternate enhanced coagulation levels).
    EPA believes that the State reporting requirements contained in 
this proposal are necessary to ensure effective oversight of State 
programs. Public comments on these proposed reporting requirements are 
requested. EPA particularly requests comment from the States on whether 
the proposed reporting requirements are reasonable.

XIII. System Reporting and Recordkeeping Requirements

    The current system reporting regulations, 40 CFR 141.31, require 
public water systems to report monitoring data to States within ten 
days after the end of the compliance period. No changes are proposed to 
those requirements.
    Specific data required by this rule to be reported by public water 
systems are included in Sec. 141.134. These data are required to be 
submitted quarterly for any monitoring conducted quarterly or more 
frequently, and within 10 days of the end of the monitoring period for 
less frequent monitoring. Systems that are required to do extra 
monitoring because of the disinfectant used have additional reporting 
requirements specified. This applies to systems that use chlorine 
dioxide (must report chlorine dioxide and chlorite results) and ozone 
(must report bromate results).
    Subpart H systems that use conventional treatment are required to 
report either compliance/noncompliance with disinfection byproduct 
precursor (TOC) removal requirements or report which of the enhanced 
coagulation/enhanced softening exemptions they are meeting. There are 
additional requirements for systems that cannot meet the required TOC 
removals and must apply for an alternate enhanced coagulant level. 
These requirements are included in Sec. 141.134(b)(6).
    Calculation of compliance with the TOC removal requirements is 
based on normalizing the percent removals over the most recent four 
quarters, since compliance is based on that period. Normalization is 
necessary since source water quality changes will change the percent 
removal requirements. To illustrate this process, EPA has developed a 
sample reporting and compliance calculation sheet that will be included 
in the (to be developed) guidance manual. An example of calculations 
using the sheet is included in Section VIII (Description of the 
Proposed D/DBP Rule).

XIV. Public Notice Requirements

    Under Section 1414(c)(1) of the Act, each owner or operator of a 
public water system must give notice to persons served by it of: (1) 
Any violation of any MCL, treatment technique requirement, or testing 
provision prescribed by an NPDWR; (2) failure to comply with any 
monitoring requirement under section 1445(a) of the Act; (3) existence 
of a variance or exemption; and (4) failure to comply with the 
requirements of a schedule prescribed pursuant to a variance or 
exemption.
    The 1986 Amendments required that EPA amend its current public 
notification regulations to provide for different types and frequencies 
of notice based on the differences between violations which are 
intermittent or infrequent and violations which are continuous or 
frequent, taking into account the seriousness of any potential adverse 
health effects which may be involved. EPA promulgated regulations to 
revise the public notification requirements on October 28, 1987 (52 FR 
41534). The regulations state that violations of an MCL, treatment 
technique, or variance or exemption schedule (``Tier 1 violations'') 
contain health effects language specified by EPA which concisely and in 
non-technical terms conveys to the public the adverse health effects 
that may occur as a result of the violation. States and water utilities 
remain free to add additional information to each notice, as deemed 
appropriate for specific situations. Today's proposed rule contains 
specific health effects language for the contaminants which are in 
today's proposed rulemaking. EPA believes that the mandatory health 
effects language is the most appropriate way to inform the affected 
public of the health implications of violating a particular EPA 
standard. The proposed mandatory health effects language in 
Sec. 141.32(e) describes in non-technical terms the health effects 
associated with the proposed contaminants.
    Under this rule, Sec. 141.135 prescribes treatment technique 
requirements. Violations of these requirements are considered Tier 1 
violations. Tier 2 violations include monitoring violations, failure to 
comply with an analytical requirement specified by an NPDWR, and 
operating under a variance or exemption.
    EPA requests comment on its proposed rule language. Of particular 
interest is the acute violation language in Sec. 141.32(e)(85) for 
violations of the chlorine dioxide MCL. Also of interest is the 
language in Sec. 141.32(e)(86) for violations of the TTHM and HAA5 MCLs 
and the enhanced coagulation treatment technique requirement.

XV. Economic Analysis

A. Executive Order 12866

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), the 
Agency must determine if the regulatory action is ``significant'' and 
therefore subject to OMB review and the requirements of the Executive 
Order. The Order defines ``significant regulatory action'' as one that 
is likely to result in a rule that may:
    (1) Have an annual effect on the economy of $100 million or more or 
adversely affect in a material way the economy, a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local, or tribal governments or 
communities;
    (2) Create a serious inconsistency or otherwise interfere with an 
action taken or planned by another agency;
    (3) Materially alter the budgetary impact of entitlements, grants, 
user fees, or loan programs or the rights and obligations of recipients 
thereof; or
    (4) Raise novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
the Executive Order.
    Pursuant to the terms of Executive Order 12866, it has been 
determined that this rule is a ``significant regulatory action'' 
because it will have an annual effect on the economy of $100 million or 
more. As such, this action was submitted to OMB for review. Changes 
made in response to OMB suggestions or recommendations will be 
documented in the public record.

B. Predicted Cost Impacts On Public Water Systems

1. Compliance Treatment Cost Forecasts
    Compliance treatment cost forecasts were estimated by the TWG. The 
basis for these estimates presented herein are described in the 
Regulatory Impact Analysis (USEPA, 1994). Tables XV-1 through XV-3 
present summaries of the estimated total national costs of installing 
and operating treatment to comply with both Stage I and Stage II 
requirements. Table XV-1 is a summary of estimated cost impacts for all 
public water supplies affected (i.e., community and nontransient 
noncommunity systems) and represents a combination of the estimates 
indicated in Table XV-2 for community systems and Table XV-3 for 
nontransient noncommunity systems.

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    The rule would affect about 51,500 ``non-purchased'' community 
water systems and 24,500 ``non-purchased'' nontransient noncommunity 
water systems. Non-purchased water systems are those that produce and/
or treat water for distribution. Of the affected community water 
systems, about 95% serve fewer than 10,000 persons. It is estimated 
that all but four of the affected nontransient noncommunity water 
systems serve fewer than 10,000 persons. As a group, the systems 
serving fewer than 10,000 persons are projected to account for about 40 
percent of the total annual cost of installing and operating treatment 
to comply with the rule and about 55 percent of the total cost of 
monitoring and reporting to comply with the rule. In terms of the 
Regulatory Flexibility Act, this rule will have a significant impact on 
a substantial number of small systems. Following EPA guidance, the 
Regulatory Flexibility Act Analysis will be presented within the 
Regulatory Impact Analysis.
    The Stage II DBP Rule--as proposed--would apply only to non-
purchased community and NTNC surface water systems serving more than 
10,000 persons. The impact of the Stage II requirements on these 
systems will result in a combined total annual cost (Stage I + Stage 
II) for installing and operating treatment facilities of $1.77 billion 
per year. If the Stage II requirements were extended to cover all 
systems, the result would be a combined total annual cost (Stage I + 
Stage II) for installing and operating treatment facilities of $2.56 
billion per year. Monitoring and state implementation costs have not 
been estimated for Stage II. Under this extended Stage II scenario, 
systems serving fewer than 10,000 persons would account for nearly 40 
percent of the total annual cost of installing and operating treatment. 
In terms of the total annual cost of installing and operating 
treatment, the Stage II extended scenario would be about one-and-one-
half times as expensive as Stage I. The same ratio applies to both size 
categories of systems, i.e., those serving greater or fewer than 10,000 
people.
2. Compliance Treatment Forecast
    Tables XV-4 and XV-5 present summaries of the national forecasts of 
treatment choices that were made to support the development of the 
national treatment cost estimates. The DBPRAM, a Monte Carlo simulation 
model of influent variability combined with a treatment model to 
predict treatment performance, was used to seed this analysis. 
Initially, the DBPRAM provided a default set of most likely compliance 
choices based on a least cost algorithm based on estimated costs of 
different unit processes (Gelderloos et al., 1992; Cromwell et al., 
1992; USEPA, 1992). These choices were then adjusted via a consensus 
process reflecting the combined judgement of the TWG (USEPA, 1994). 
While some technologies, such as chlorine dioxide, were recognized as 
possible means for achieving compliance, insufficient data were 
available to predict such compliance choices. However, the TWG believed 
that failure to consider compliance choices other than those listed in 
Tables XV-4 and XV-5 would not significantly affect the total national 
cost compliance cost estimates.

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    Regarding Table XV-4, the DBPRAM predicted that 60 percent of all 
systems using surface water would at least use enhanced coagulation to 
comply with the Stage 1 requirements. Among the systems using enhanced 
coagulation, 10% would also use chloramines as their residual 
disinfectant (with chlorine used as the primary disinfectant), 6% would 
also use ozone as their primary disinfectant and chloramines as their 
residual disinfectant, 1% would also use GAC10, and 1% would also use 
GAC20. Among the systems not using enhanced coagulation, 3% would use 
chloramines as a residual disinfectant (with chlorine as the primary 
disinfectant), 5% would use ozone as their primary disinfectant and 
chloramines as their residual disinfectant, and 4% would use membrane 
technology. The predicted compliance choices for systems serving 10,000 
people or less are almost the same as those for systems serving greater 
than 10,000 people. One notable difference is that because of large 
economies of scale for GAC20, no systems serving 10,000 people or less 
are predicted to use GAC20; rather all such systems (6%) requiring 
substantial precursor removal are predicted to use membrane technology.
    Regarding Table XV-5, the DBPRAM predicted that for systems using 
ground water and seeking to comply with the Stage 1 requirements, 8% 
would use chloramines as their residual disinfectant (with chlorine as 
the primary disinfectant), 4% would use membrane technology, and 0.04% 
would use ozone for primary disinfection with chloramines for residual 
disinfection. While 2% of systems serving greater than 10,000 people 
were predicted to use ozone and chloramines, no systems serving 10,000 
people or less were predicted to use this technology (for these sized 
systems membranes were considered a preferred option to ozone and 
chloramines because of the likely lower system level cost and ease of 
use).
    Unlike for surface water supplies, all large ground water systems 
with high DBP precursor levels are predicted to use membrane technology 
in lieu of GAC. This is because large ground water systems are assumed 
to use multiple wells, each being of small enough size to be more cost 
effectively treated with membrane technology than by GAC.
    The percentage of systems affected by the DBP regulations is 
markedly less among those using ground waters than those using surface 
waters. This is because (1) Most ground waters have much lower levels 
of DBP precursors than surface waters, and (2) most ground waters 
(i.e., those not under the direct influence of surface water as assumed 
in this analysis) are not considered vulnerable to contamination by 
protozoa and therefore require much less disinfection. Also, some 
ground water systems which are adequately protected will be able to 
avoid disinfection altogether and thereby avoid needing to meet any 
regulatory requirements pertaining to DBPs.
3. DBP Exposure Estimates
    Table XV-6 presents three computer generated profiles of exposure 
reflecting the baseline condition, the Stage I rule, and the Stage II 
rule. The change in exposure is characterized in terms of TOC, TTHMs, 
and HAA5. These data are applicable only to large systems (>10,000 
population) which filter but do not soften. The median and 95th 
percentile values for effluent TOC are shown to be reduced from 2.5 and 
4.9 mg/l under baseline conditions to 2.2 and 3.8 mg/l at Stage I, and 
2.0 and 3.3 mg/l at Stage II. The median and 95th percentile values for 
TTHMs are shown to be reduced from 46 and 104 g/l under 
baseline conditions to 31 and 58 g/l at Stage I, and 22 and 30 
g/l at Stage II. The median and 95th percentile values for 
effluent HAA5 are shown to be reduced from 28 and 86 ug/l under 
baseline conditions to 20 and 43 g/l at Stage I, and 14 and 22 
g/l at Stage II.

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    Quantitative changes in exposure from TOC and DBPs were not 
predicted for ground water systems because of insufficient data. 
Treatment changes that ground water systems make to comply with the DBP 
regulations are likely to result in lower reductions of national median 
TOC and DBP levels than in surface water supplies. This is because of 
the much smaller percentage of ground water systems that are affected. 
However, the resultant change from the DBP regulations on the 95th 
percentile of TOC and DBP levels in ground water systems may be more 
significant than in surface water systems. This is because membrane 
filtration, which would be used in the systems with poorest quality, 
can remove greater than 90% of TOC, resulting in probably similar 
reductions of TTHMs and HAA5 (USEPA 1992).
4. System Level Cost Estimates
    Tables XV-7 and XV-8 present the unit cost estimates that were 
utilized for each of the different treatment technologies in each 
system size category. The unit cost estimates were derived from a cost 
model described in the Cost and Technology document (USEPA 1992) and 
adjusted per discussion among TWG to reflect site specific factors 
(USEPA 1994). For systems in size categories serving greater than 
10,000 people the estimated system level costs for achieving compliance 
ranged from $0.01/1000 gallons (chlorine/chloramines) to $1.87/1000 
gallons (membrane technology). For systems in size categories serving 
less than 10,000 people the estimated system level costs for achieving 
compliance ranged from $.03/1000 gallons (chlorine/chloramines) to 
$3.49/1000 gallons. Although some technologies are listed as costing 
more than $3.49/1000 gallons in the smallest size categories (because 
of large economies of scale), no such technologies would be used 
because compliance could be achieved with membrane technology.

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5. Effect on Household Costs
    Table XV-9 summarizes cost impacts at the household level contained 
in Figures XV-1 through XV-4 for systems having to install and operate 
treatment. The impacts presented for Stage II represent the cumulative 
cost per household of both Stage I and Stage II. The household impacts 
are based solely upon the community water system analysis since the 
nontransient noncommunity systems typically do not serve households. 
These household impacts do include, however, the households in 
purchased water systems that are served by the affected non-purchased 
water systems. These household costs reflect only the cost of treatment 
and do not include the cost of monitoring. Note also that costs of an 
Enhanced Surface Water Treatment Rule, if such a rule should become 
necessary, are not included.

                         Table XV-9.--Stage 1 and Stage 2 Household Cost Impact Summary                         
----------------------------------------------------------------------------------------------------------------
                                                    Large        Small        Large        Small                
                Type of system                     surface      surface       ground       ground       Totals  
                                                  water\1\     water\1\     water\1\     water\1\               
----------------------------------------------------------------------------------------------------------------
Number of systems..............................         1395         4562         1316       44,310       51,583
Number of households (in millions).............           56          6.4           19         12.3         93.7
$/household/yr.                                                                                                 
(4) Number of households expected to pay                                                                        
 specific increased costs for compliance with                                                                   
 stage 1 (in millions)                                                                                          
    0..........................................         16.8          1.8         16.0         10.6         45.2
    >0-10......................................         30.8          2.4          2.0          1.0         36.2
    >10-20.....................................          4.5          1.1          0.2         None          5.8
    >20-40.....................................          2.2          0.1          0.2          0.1          2.6
    >40........................................          1.7          1.0          0.6          0.6          3.9
                                                                                                                
                                                                                                                
(4) Number of households expected to pay                                                                        
 specific increased costs for compliance with                                                                   
 stage 1 and stage 2 (in millions)                                                                              
    0..........................................         13.4        (\2\)        (\2\)        (\2\)         13.4
    >0-10......................................         25.2        (\2\)        (\2\)        (\2\)         25.2
    >10-20.....................................          6.2        (\2\)        (\2\)        (\2\)          6.2
    >20-40.....................................          6.7        (\2\)        (\2\)        (\2\)          6.7
    >40........................................          4.5        (\2\)        (\2\)        (\2\)          4.5
----------------------------------------------------------------------------------------------------------------
\1\Large systems serve 10,000 or more persons. Small systems serve fewer than 10,000 persons. Surface water     
  systems are Subpart H systems. Ground water systems are systems using only ground water not under the direct  
  influence of surface water.                                                                                   
\2\Today's Stage 2 D/DBP Rule proposal only applies to Subpart H systems serving at least 10,000 persons. As    
  proposed, there are no household compliance costs for other systems.                                          


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    EPA estimates that about 45 million households (48% of the total 
served by community water systems) will incur no treatment costs for 
compliance with Stage I. Of 49 million households incurring treatment 
costs for compliance with Stage I, 45.5 million will incur costs of 
less than $50 per year, 1.3 million will incur costs of $50 to $100 per 
year, 1.0 million will incur costs of $100 to $200 per year, 0.8 
million will incur costs of $200 to $300 per year, and 0.2 million will 
incur costs of more than $300 per year.
    EPA estimates that 13.4 million of the 56 million households served 
by large surface water systems (24% of the total) will incur no 
treatment costs for compliance with Stage II as proposed (applying only 
to large surface water systems). Of the nearly 43 million households 
incurring treatment costs for compliance with Stage II as proposed, 
39.8 million will incur costs of less than $50 per year, 2.2 million 
will incur costs of $50 to $100 per year, and 0.8 million will incur 
costs of $100 to $200 per year.
    EPA estimates that 36.3 million households (39% of the total served 
by community water systems) will incur no treatment costs for 
compliance with Stage II if extended to all systems. Of the 57.2 
million households incurring treatment costs for compliance with an 
extended Stage II, 48.6 million will incur costs of less than $50 per 
year, 2.7 million will incur costs of $50 to $100 per year, 2.6 million 
will incur costs of $100 to $200 per year, 2.5 million will incur costs 
of $200 to $300 per year, and 0.8 million will incur costs of more than 
$300 per year. Annual household costs above $200 are projected 
predominantly for small systems that may be required to install 
membrane treatment. Some of these systems could find that there are 
less expensive options available, such as connecting into a larger 
regional water system.
    Impacts on Low Income Families. The Negotiating Committee had 
several discussions of the impact of the DBP regulatory proposals on 
low income households and reviewed the impact estimates specifically in 
this light. An analysis was presented that focused exclusively on the 
impact on low income households, using data on families enrolled in the 
Aid to Families with Dependent Children (AFDC) program as an 
illustration.
    Based on the 1992 Statistical Abstract of the United States, there 
were 4.2 million AFDC families (this represents about one- third of all 
families below the poverty line). In the absence of information to 
suggest otherwise, it was assumed that these families are distributed 
across water system types and sizes in the same proportion as the total 
population. The analysis was performed to illustrate the impact of the 
Stage II DBP requirements under the assumption that the 40/30 
requirement was extended to all water systems. Results are presented in 
Figure XV-5.
    The results in Figure XV-5 show the distribution of impacts in 
terms of the number of households that would have a given level of 
impact on their household income in terms of the percent of AFDC 
income. Based on the current level of AFDC payments, a $22 per year 
increase in the water bill is equivalent to 0.5 percent of AFDC income.

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    With the given assumptions about the distribution of AFDC 
households, it is projected that 1.7 million of the 4.2 million AFDC 
families would be served by water systems that are unaffected by the 
DBP regulations. This reflects a general characteristic of the 
regulation of DBPs--that it is not going to be a problem in many 
systems that have fortunate circumstances regarding raw water 
characteristics.
    Another 1.8 million of the 4.2 million AFDC families are projected 
to be served by water systems that will incur costs of less than $22 
per household per year, or less than 0.5 percent of AFDC income. This 
reflects another feature of the DBP rule--that impacts might not be too 
severe in many large urban water systems with moderate levels of DBPs 
and economies of scale. It is noted, however, that the current Stage II 
cost estimates are based upon generous use of alternative 
disinfectants. If use of alternative disinfectants becomes unacceptable 
or inadequate for meeting other concurrent criteria (such as DBP 
precursor removal), greater use of alternative precursor removal 
technologies becomes necessary as a means of achieving compliance and 
utilities could incur expenses several times as great.
    About one-sixth of the 4.2 million AFDC households (0.7 million) 
are projected to be served by water systems that will incur costs of 
more than $22 per household per year, or more than 0.5 percent of AFDC 
income. These estimates are also based on an assumption of extensive 
use of alternative disinfectants that are less expensive than precursor 
removal technologies.
    Important patterns are illustrated in Figure XV-5. Most of the 
700,000 households are concentrated in large systems near the low end 
of the scale. Nearly 75 percent (514,000 of the total 700,000 
households) are projected to be served by large water systems. Among 
these 514,000 households, over 75 percent (390,000) will face costs of 
less than 2 percent of AFDC income; nearly half (248,000) will face 
costs of less than 1 percent of AFDC income. Less than one-quarter of 
AFDC households in large systems (124,000) will face costs between 2 
percent and 4.5 percent of AFDC income. None will face costs greater 
than 4.5 percent of AFDC income. Again, these estimates assume use of 
alternate disinfectants rather than more costly precursor removal 
technologies.
    At the extreme right-hand side of Figure XV-5, the most extreme 
impacts on AFDC households are indicated to occur in small water 
systems. Given the assumptions of this analysis, it is projected that 
there will be 147,000 AFDC households in small communities that will 
face costs of between 6.0 and 7.0 percent of AFDC income. This impact 
is more likely to occur in small rural communities in declining 
economic regions. Realistically, it is not clear that such communities 
could raise the required capital without some form of government 
assistance that might reduce the final cost per household.
6. Monitoring and State Implementation Costs, Labor Burden Estimates
    Table XV-10 summarizes the monitoring and state implementation cost 
and labor burden estimates. In compliance with the Paperwork Reduction 
Act, EPA estimates the total labor burden of complying with monitoring 
and reporting requirements to be 1.5 million hours over six years, 
averaging 250,000 hours per year. This estimate equates to an average 
of 4 hours per system per year. The labor burden for State program 
implementation is estimated to total 2.5 million hours over six years, 
averaging 416,666 hours per year. This estimate implies a per State 
average of 7,440 hours per year. However, the implementation work load 
will not be staggered evenly over the six year period or by State.

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    The total cost of compliance with the monitoring requirements is 
estimated to be $283 million over six years, averaging $47 million per 
year. The total cost of state implementation is estimated to be $82 
million over six years, averaging $14 million per year. The cost of 
monitoring and of state implementation will not be evenly spread over 
the six year period.

C. Concepts of Cost Analysis

    The Negotiating Committee reviewed the cost of capital assumptions 
normally employed by EPA in analyzing drinking water regulations. EPA 
typically assumes a 7 percent interest rate and a 20-year term. These 
assumptions result in a Capital Recovery Factor of 0.09439. The Capital 
Recovery Factor is multiplied times the capital cost to arrive at the 
amount of the annual payment required including principal and interest. 
During the negotiation, it was pointed out that the standard EPA 
assumption is too low for investor owned utilities considering other 
carrying costs of capital investment (e.g., taxes, depreciation), 
although it be reasonable for municipal utilities considering current 
interest rates. It was also noted that the standard EPA assumption is 
too low an estimate for the cost of capital in small investor owned 
systems and other small private systems (e.g., homeowner's 
associations, trailer parks, etc.) considering differences in credit 
risk and access to capital.
    An analysis was presented by a member of the Negotiating Committee 
indicating that a Capital Recovery Factor of 0.17172 is appropriate for 
large investor owned utilities and that a Capital Recovery Factor of 
0.20105 is appropriate for small privately owned water systems. Based 
on current interest rates for municipal bonds, the TWG determined that 
Capital Recovery Factors of 0.09439 and 0.10185 are appropriate for 
large and small municipally owned water systems, respectively. EPA and 
NAWC data on the mix of ownership types by system size were then used 
to develop weighted composite Capital Recovery Factors for use in the 
analysis. The results are summarized as follows:

------------------------------------------------------------------------
                                                  Capital               
          Category              Ownership of      recovery    Composite 
                                   systems        factors      factors  
------------------------------------------------------------------------
<1,000......................  priv 87.........      0.20105      0.18815
                              publ 13.........      0.10185             
1,000-10,000................  priv 25.........      0.20105      0.12665
                              publ 75.........      0.10185             
10,000-100,000..............  priv 14.........      0.17172      0.10522
                              publ 86.........      0.09439             
100,000+....................  priv 17.5.......      0.17172      0.10792
                              publ 82.5.......     0.09439              
------------------------------------------------------------------------

Capital costs are based on the EPA Cost and Technology Document which 
represents fourth quarter 1991 costs. These costs were not adjusted for 
inflation, but very little inflation has occurred since then.

D. Benefits

    Despite the enormous uncertainties for estimating reductions in 
risk resulting from different regulatory strategies, the Negotiating 
Committee recognized that the existing risks could be large, and 
therefore should be reduced. The Negotiating Committee reached a 
consensus that the Stage 1 requirements were of sufficient benefit to 
be proposed for all system sizes, but could not agree on Stage 2 
reductions. Until extensive epidemiological and toxicological studies 
have been completed, it is not possible to draw definitive quantitative 
conclusions regarding the precise extent of cancer and non-cancer 
adverse health effects resulting from disinfection byproducts.
    Nevertheless, based on exposure estimates described above, an 
analysis was developed to provide some quantitative indication of the 
range of possibilities implied by the Stage I and Stage II proposals in 
terms of the cost-per-case-of-cancer-avoided. Toxicological and 
epidemiological analyses can be applied to the exposures predicted by 
the DBPRAM to suggest a range of annual cancer incidence that might be 
avoided if systems were to comply with the proposed D/DBP regulations.
    During the regulatory negotiations, some negotiators argued that 
the national baseline incidence of cancer attributed to DBPs in 
drinking water may be less than 1 case per year; others argued that 
over 10,000 cases per year are linked to DBPs. The lower bound baseline 
risk estimate was based on the maximum likelihood estimates of 
toxicological risk (best case estimates as opposed to upper 95% 
confidence bound estimates) associated with THM levels (i.e., 
chloroform, bromoform, bromodichloromethane, and dibromochloromethane) 
predicted by the DBPRAM (USEPA, 1994). Not included in the lower bound 
estimate were any risks resulting from exposure to HAAs or other DBPs. 
Although dichloroacetic acid has been classified as a probable human 
carcinogen (see Section V of this preamble), risks have not been 
included for this chemical because the Agency has not yet quantified 
its carcinogenic potential. Also, since cancer bioassays are only 
currently underway for the brominated HAAs, potential risks from their 
exposure could not be quantified. No national risk estimates were 
possible for bromate because of the lack of national occurrence data or 
model to predict bromate formation.
    An upper bound base-line estimate of over 10,000 cancer cases per 
year was considered based upon the central tendency estimate of the 
pooled relative risks from a meta-analysis study which statistically 
combined the results of ten previously published epidemiology studies 
(Morris et al. 1992). The basis for estimating risks from the meta-
analysis was questioned by some members of the Negotiating Committee, 
including EPA, because (a) the studies used in the meta-analysis were 
of different design and thus not subject to a meta-analysis and (b) 
potential confounding factors or bias may not have been adequately 
controlled (Farland and Gibb, 1993; Craun 1993; Murphy 1993). Also, the 
epidemiologic studies used in the meta-analysis considered exposure to 
populations before the advent of the 1979 MCLs for TTHMs; that 
regulation significantly reduced exposure to chlorinated DBPs (McGuire 
et al 1989). Other members of the Negotiating Committee, however, 
commented that many of the ``biases'' noted in studies used in the 
meta-analysis would tend to underestimate cancer risks and that, taken 
as a whole, these studies are highly suggestive of a link between DBPs 
and certain cancers. They also noted that current THM rules do not 
apply to most public water systems (those serving fewer than 10,000 
people) which serve about 20% of the U.S. population. Also, these rules 
do not necessarily control many other DBPs which may be of health risk 
significance.
    While research is needed to establish better risk estimates 
associated with disinfected water, the above estimates appear to 
reasonably bound the potential for cancer risk (it should be noted, 
however, using the upper bound of the meta-analysis estimate would have 
resulted in a higher baseline cancer risk estimate). In order to 
estimate the benefits of reducing DBP exposure, EPA made certain 
assumptions. All assumptions are based on results of DBPRAM estimates 
of conditions in large surface water systems that filter but do not 
soften. These systems represent about 80 percent of the population 
served by surface water systems and over 50 percent of the population 
served by all public water systems. However, this analysis does not 
address the benefits to consumers using smaller systems. One approach 
used was to assume that the percent reduction in TTHM and HAA5 median 
effluent concentrations reflects an equivalent percent reduction in 
cancer risk. A second approach was to assume that the percent reduction 
in median TOC effluent concentration reflects an equivalent percent 
reduction in cancer risk. These alternatives were evaluated under the 
assumption that there would be no compromising the SWTR risk goal of no 
more than one case of giardiasis per 10,000 people per year. In other 
words, this microbial treatment objective was used to constrain the 
DBPRAM model while predicting a) the baseline levels of TTHMs, HAA5, 
and TOC under the existing SWTR, and b) the new concentrations of 
TTHMs, HAA5, and TOC resulting from systems attempting to meet the 
Stage 1 and Stage 2 requirements (USEPA, 1994). This modeling 
constraint, which is in effect an ESWTR consistent with the objectives 
of the SWTR, avoids increases in microbial risk and simplifies the 
benefits analysis. The preamble to the proposed ESWTR, elsewhere in 
today's Federal Register, discusses how the DPBRAM has also been used 
to predict increases in microbial risk that might result if systems 
complied with more stringent DBP standards without an ESWTR.
    In Stage 1, the DBPRAM predicted that the baseline median TTHM and 
HAA5 effluent concentrations would be reduced by 33 and 29 percent, 
respectively, while the TOC effluent concentration would be reduced by 
12 percent. Assuming that the change in the median effluent TTHM and 
HAA5 levels reflects the same changes in exposure from cancer risk 
(relative to the respective toxicological and epidemiological baseline 
risk levels previously alluded to), the Stage I proposal would result 
in avoidance of between 0.29 to 0.33 cases per year and 2,900 to 3,300 
cases per year. The lower bound of cancer cases avoided per year is 
likely to be understated because, in the absence of risk estimates 
available for other DBPs, it is assumed that all cancer cases caused by 
exposure to DBPs can be represented by the maximum likelihood 
toxicological risk estimate from exposure to THMs alone.
    Under the assumptions described above and assuming that the change 
in median effluent TOC reflects the same changes in exposure from 
cancer risk, the Stage I proposal would result in avoidance of between 
0.12 and 1,200 cases of cancer per year. In Stage 2, the change in 
median TTHM and HAA5 effluent concentrations was a reduction of 48 and 
50 percent, respectively, from the baseline prior to Stage 1, while the 
change in TOC effluent concentration was a reduction of 18 percent. 
Assuming the change in median effluent TTHM and HAA5 levels reflects 
the same change in exposure from cancer risk, the Stage II proposal 
would result in a cumulative (Stage 1 plus 2) avoidance of between 0.50 
to 0.52 cases per year and 5,000 to 5,200 cases per year. Assuming the 
change in median effluent TOC reflects the change in exposure from 
cancer risk, the Stage II proposal would result in cumulative avoidance 
of between 0.2 and 2,000 cases of cancer per year.
    If the total annual cost of treatment is $1.04 billion to meet 
Stage I targets, then the cost per case of cancer avoided ranges 
between $8.67 billion and $867,000 per case, based on changes in median 
effluent TOC. If based on Stage I changes in median effluent TTHMs and 
THAAs, the cost per case of cancer avoided ranges between $3.59 billion 
and $359,000. Assuming that DBPs other than THMs pose some cancer risk, 
the upper bound cost estimates per cancer case avoided are likely to be 
overstated. Similarly, until more conclusive epidemiology data become 
available, the lower bound cost estimate per case will remain highly 
controversial. If one were to assume there is a 10 percent chance that 
the baseline cancer risks suggested by Morris et al. (1992) were true, 
then the estimated costs per case of cancer avoided would range from 
$8.67 million per case (based on changes in median TOC) to $3.59 
million per case (based on changes in median TTHMs). The lack of better 
evidence for causality in the epidemiological studies would indicate 
there is a possibility that the associations cited in the Morris study 
are due to omitted variables or deficiencies in the data, in which case 
the cost effectiveness may be even worse than these estimates.
    In principle, the cost-effectiveness of the rule should be 
evaluated in terms of the expected (mean) outcome and the likelihood of 
this and other outcomes. Quantitative data on the likelihood of 
different outcomes are unavailable, however, and as a result EPA has 
been able to quantify the expected cost effectiveness only in terms of 
the ranges reported here. EPA believes that likely cost-effectiveness 
outcomes will fall in this range. Whether the expected cost 
effectiveness of the proposal is closer to the high-end or low-end 
estimates depends primarily on whether future epidemiological or 
toxicological studies can provide stronger evidence of a causal effect 
of exposure to disinfected (e.g., chlorinated) water on cancer risks.
    Cost-effectiveness will be affected by the size and the water 
quality of a particular system, and the technology used for achieving 
compliance. Economies of scale for technologies used to achieve 
compliance will make household compliance costs higher in smaller 
systems than in larger systems (see Table XV-8). However, because many 
large systems will already have reduced exposure from DBPs under the 
existing TTHM standard (which only pertains to systems serving greater 
than 10,000 people), reductions in exposure from DBPs in many small 
systems is also likely to be greater than in larger system. Although 
the data are limited, this presumption appears to be supported by 
Figures VI-11 and VI-13 in section VI of this preamble. Figures VI-11 
and VI-13 suggest that a substantial number of systems serving less 
than 10,000 people have much higher TTHM (and DBP) concentrations than 
systems serving 10,000 people or greater. EPA solicits data and comment 
on the extent to which reductions in exposure can be expected to differ 
between systems serving 10,000 people or more and systems serving less 
than 10,000 people.
    For systems using enhanced coagulation, the technology most likely 
to be used to achieve compliance among surface water supplies (see 
Table XV-4), there are relatively small differences in economies of 
scale (see Tables XV-6 and XV-7) and small differences in cost 
effectiveness between small and large systems. Table XV-4 indicates 
that approximately 17% of the surface water supplies serving fewer than 
10,000 people will use technologies (ozone or membrane technology) that 
would result in significantly higher household costs than those 
expected in most larger-sized systems. Similarly, Table XV-5 indicates 
that approximately 4% of the ground water supplies serving fewer than 
10,000 people will use a technology (membrane technology) that would 
result in significantly higher household costs than in most larger-
sized systems. Depending on the reductions in exposure, which would be 
very significant in systems using membrane technology, the cost-
effectiveness in some small systems is likely to be substantially less 
than in larger-sized systems. EPA solicits comments on what data and 
approaches could be used for estimating differences in cost-
effectiveness for large versus small systems complying with Stage 1 
requirements.
    Maintaining the assumptions as described above, if the total annual 
cost of treatment is $2.56 billion to meet Stage II targets (extended 
to all systems), then the cost per case of cancer avoided ranges 
between $5.3 billion and $512,000 if based on changes in median TTHM 
and HAA5 effluent concentrations. If based on Stage II changes in 
median effluent TOC, the cost per case of cancer avoided ranges between 
$12.8 billion and $1.28 million per case.
    Under the above assumptions, the Stage 1 requirements are 
significantly more cost effective than the Stage 2 requirements for 
reducing risk, whatever that risk may be. Despite the enormous 
uncertainties for estimating reductions in risk resulting from 
different regulatory strategies, the Negotiating Committee believed 
that the Stage 1 requirements were of sufficient benefit to be proposed 
for all system sizes. Some negotiators argued that Stage 2 controls 
should only be proposed now for larger systems and revisited when more 
information became available; others argued that such controls should 
be put in place sooner. The ultimate decision was to propose Stage 2 
rules but to provide an opportunity for consideration of more data at a 
second regulatory negotiation (or similar proceeding) before Stage 2 is 
finalized.

XVI. Other Requirements

A. Consultation with State, Local, and Tribal Governments

    Two Executive Orders (E.O. 12875, Enhancing Intergovernmental 
Partnerships, and E.O 12866, Regulatory Planning and Review) explicitly 
require Federal agencies to consult with State, local, and tribal 
entities in the development of rules and policies that will affect 
them, and to document what they did, the issues that were raised, and 
how the issues were addressed.
    As described in section II of today's rule, SDWA section 1412 
requires EPA to promulgate NPDWRs for at least 25 contaminants every 
three years. The contaminants listed in today's rule are being proposed 
in response to that Congressional mandate.
    To comply with this rule, PWSs will need to meet specified levels 
for total trihalomethanes, haloacetic acids, certain other byproducts, 
and certain disinfectants. To meet these standards, certain systems 
will need to employ enhanced coagulation, enhanced precipitative 
softening, and/or other treatment technologies. The total annual cost 
of the rule, including monitoring, is expected to be about $1.1 billion 
per year. Systems serving more than 10,000 persons are expected to come 
into compliance in 1998 and 2000 and bear $700 million of the cost. 
Systems serving fewer than 10,000 persons are expected to come into 
compliance in the years 2000 to 2002 and bear about $400 million of the 
total cost.
    The Agency first sought public input to the rule in a strawman rule 
published in October 1989. Comments received in response to the 
strawman rule are summarized in section IV of today's rule. In June 
1991 EPA issued a status report designed to update the public on the 
Agency's thinking on rule criteria. Comments were also received on the 
status report; they, too, are summarized in section IV.
    In 1992, EPA considered entering into a negotiated rulemaking on 
this rule primarily because no clear path for addressing all the major 
issues associated with the rule was apparent. EPA hired a facilitator 
to explore this option with external stakeholders and, in November 
1992, decided to proceed with the negotiation. The 18 negotiators, 
including EPA, met from November 1992 until June 1993 at which time 
agreement was reached on the content of the proposed rule. Today's 
proposed regulatory and preamble language has been agreed to by the 17 
negotiators who remained at the table through June 1993. A summary of 
those negotiations is contained in section IV.
    The negotiators included persons representing State and local 
governments. At the table were:
    (1) Association of State Drinking Water Administrators, a group 
representing state government officials responsible for implementing 
the regulations,
    (2) Association of State and Territorial Health Officials, a group 
representing statewide public health interests and the need to balance 
spending on a variety of health priorities,
    (3) National Association of Regulated Utilities Commissioners, a 
group representing funding concerns at the state level,
    (4) National Association of County Health Officials, a group 
representing local government general public health interests,
    (5) National League of Cities, a group representing local elected 
and appointed officials responsible for balancing spending needs across 
all government services,
    (6) National Association of State Utility Consumer Advocates, a 
group representing consumer interests at the state level, and
    (7) National Consumer Law Center, a group representing consumer 
interests at the local level.
    In addition, several associations representing public municipal and 
investor-owned water systems also served on the committee.
    As part of the negotiation process, each of these representatives 
was responsible for obtaining endorsement from their respective 
organization on the positions they took at the negotiations and on the 
final signed agreement. During the negotiations, the group heard from 
many other parties who attended the public negotiations and were 
invited to express their views. As is true with any negotiation, all 
sides presented initial positions which were ultimately modified to 
obtain consensus from all sides. However, all parties mentioned above 
signed the final agreement on behalf of their associations. This 
agreement reflected basic consensus that the cost of the rule was 
offset by its public health benefits and its promotion of responsible 
drinking water treatment practices.
    The only original negotiator who did not sign the agreement left 
the negotiations in March 1993. That negotiator represented the 
National Rural Water Association (NRWA), a group representing primarily 
small public and private water systems. NRWA believed that since 
systems serving populations under 10,000 persons are not subject to the 
current trihalomethane standard, it would be more reasonable to require 
that small systems comply with the current trihalomethane standards 
rather than the standards proposed today. NRWA objected to the costs of 
the rule on small systems given its belief that the risks to humans 
from D/DBP are poorly understood. NRWA in its letter of resignation 
stated that ``[t]here is insufficient good, reliable scientific data 
showing clear risks to human health from the levels of D/DBP found on 
average in drinking water.'' It should be noted that although NRWA 
objected to the cost of the rule, they had supported an option with 
approximately the same estimated cost earlier in the negotiation 
process. The NRWA position that small systems should meet the current 
trihalomethane standard was rejected by the remaining negotiators, 
several of whom also represent small water systems.
    The contents of today's proposed rule has been available to the 
public for several months as part of the regulatory negotiation 
signature process. EPA has briefed numerous groups, including 
government organizations, on its contents. The Agency has received 
several letters from public water systems objecting to the cost of the 
proposed rule and questioning its potential health benefit. These 
letters are contained in the public docket supporting today's rule. The 
Agency recognizes that many persons are concerned whether the proposed 
rule is warranted. The technical issues are complex. The process needed 
to develop a common level of understanding among the negotiators as to 
what was known and unknown and what are reasonable estimates of 
potential costs and benefits was time-consuming. It is unreasonable to 
expect persons not at the negotiating table to have that same level of 
understanding and to all share the same view. However, the discussions 
throughout the negotiated rulemaking process were informed by a broad 
spectrum of opinions. The Agency believes this consensus proposal is 
not only the preferred approach but one which will generate informed 
debate and comment.

B. Regulatory Flexibility Act

    The Regulatory Flexibility Act, 5 U.S.C. 602 et eq., requires EPA 
to explicitly consider the effect of proposed regulation on small 
entities. By policy, EPA has decided to consider regulatory 
alternatives if there is any economic impact on any number of small 
entities. The Small Business Administration defines a ``small water 
utility'' as one which serves fewer than 3,300 people. If there is a 
significant effect on a substantial number of small systems, the Agency 
must seek means to minimize the effects.
    In accordance with the Regulatory Flexibility Act EPA has conducted 
a Regulatory Flexibility Analysis indicating what the predicted impacts 
on small systemns could be and how such impacts could be minimized. A 
detailed description of this effort is available in the Regulatory 
Impact Analysis (USEPA, 1994). Following is a summary of the key 
elements of the Regulatory Flexibility Analysis.
    Throughout the negotiated rulemaking process, small systems were 
defined as those serving fewer than 10,000 persons. This definition was 
used because there is an existing SDWA standard of 0.10 mg/l for total 
trihalomethanes that applies only to systems serving at least 10,000 
persons. Systems serving fewer than 10,000 persons are presently 
unregulated with respect to disinfection byproducts. There are, as a 
result, two different baseline conditions from which water systems will 
approach additional disinfection byproduct control. The major impact 
will be the requirement to install and operate water treatment 
equipment to meet specific standards of quality in the delivered water. 
These requirements pertain primarily to systems that actually treat 
water. Systems that purchase treated water from another source may see 
an increase in their wholesale costs, but a data base sufficient to 
track all the wholesale treated water transactions in the country does 
not exist. Impacts are therefore evaluated in terms of the systems that 
treat water. The data with which to characterize the capacities and 
flows of these facilities does exist and provides an adequate basis for 
assessing total capital and operating costs.
    EPA estimates that there are a total of 76,051 community and 
nontransient noncommunity water systems that treat water. Of these, an 
estimated 73,336 (96%) serve fewer than 10,000 persons. Despite their 
overwhelming dominance in terms of industry structure, these systems 
provide water to only 22 percent of the total population served by 
public water supplies.
    Of the total 68,171 small groundwater systems, it is estimated that 
8,324 (12%) will have to modify treatment to comply with the Stage 1 
proposal. The TWG forecast that 5,403 (8%) systems will comply with the 
very inexpensive technology of chloramines while 2,921 (4%) systems 
will require more expensive membrane treatment systems. Use of these 
technologies by small systems will result in total capital costs of 
$1.1 billion.
    Of the total 5,165 small surface water systems, it is estimated 
that 3,611 (70%) will have to modify treatment to comply with the Stage 
1 proposal. The TWG forecast that 3,318 (64%) systems will comply with 
cost effective combinations of enhanced coagulation, chloramines, and 
ozone. Another 293 (6%) systems will require more expensive membrane 
treatment systems. This will result in total capital costs of $0.6 
billion.
    EPA believes that the proposed rule could have a significant impact 
on a substantial number of small systems. Therefore, the Agency has 
attempted to provide less burdensome alternatives to achieve the rule's 
goals for small systems wherever possible. These considerations, 
discussed in greater detail in Section IX of this preamble and in the 
Regulatory Impact Analysis (USEPA, 1994), include:
    (a) Less routine monitoring. Small systems are required to monitor 
less frequently for such contaminants as TTHMs and HAA5. Also, ground 
water systems (the large majority of small systems) are required to 
monitor less frequently than Subpart H systems of the same size.
    (b) Reduced monitoring. There are reduced monitoring provisions for 
systems that meet specified prerequisites. EPA believes that many small 
systems will qualify for this reduced monitoring.
    (c) Extended compliance dates. Systems that use only ground water 
not under the direct influence of surface water serving at least 10,000 
people and Subpart H systems serving fewer than 10,000 people have 42 
months from promulgation of this rule to comply. Systems that use only 
ground water not under the direct influence of surface water serving 
fewer than 10,000 people have 60 months from promulgation of this rule 
to comply. These staggered compliance dates will allow smaller systems 
to learn from the experience of larger systems on how to most cost 
effectively comply with the Stage 1 D/DBP rule. Larger systems will 
generate a significant amount of treatment and cost effectiveness data 
under the Information Collection Rule and in their efforts to achieve 
compliance with the Stage 1 requirements. EPA intends to summarize this 
information and make it available through guidance documents that will 
assist smaller systems in achieving compliance with both the Stage 1 D/
DBP rule and long-term ESWTR.
    The staggered compliance dates for smaller systems will also enable 
them to consider any new Stage 2 requirements, scheduled to be proposed 
in 1998, while achieving compliance with the Stage 1 requirements. The 
delayed compliance schedule should facilitate the selection of the most 
cost effective means for achieving compliance with both the Stage 1 and 
Stage 2 requirements.
    (d) The Negotiating Committee considered other options for systems 
serving less than 10,000 people. These ranged from requiring smaller 
systems to meet the same compliance schedule as for larger systems to 
only extending the existing TTHM standard to systems serving less than 
10,000 people. The Negotiating Committee rejected the former option for 
the above reasons and to enable the development of an ESWTR (i.e., the 
long-term ESWTR rather than the interim ESWTR) that would be more 
reasonable for smaller systems to comply with (see proposed ESWTR in 
today's Federal Register, and the proposed Information Collection Rule, 
59 FR 6332; February 10, 1994). The Negotiating Committee rejected the 
latter option, over the objections of the National Rural Water 
Association, because it believed that all systems should be subject to 
the same level of protection. Also, setting only a TTHM standard in the 
absence of other criteria could lead to increased exposure from other 
DBPs that might pose greater health risks.

C. Paperwork Reduction Act

    The information collection requirements in this proposed rule have 
been submitted for approval to the Office of Management and Budget 
(OMB) under the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. An 
Information Collection Request document has been prepared by EPA (ICR 
No. 270.33) and a copy may be obtained from Sandy Farmer, Information 
Policy Branch (MC:2136), EPA, 401 M Street SW., Washington, DC 20460, 
or by calling (202) 260-2740.
    The reporting and recordkeeping burden for this proposed collection 
of information will be phased-in starting in 1997. The specific burden 
anticipated for each category of respondent, by year, is shown below:

1997

Public Water Systems--monitoring and reporting
    Hours per respondent: 0
    Total hours: 0
Public Water Systems--recordkeeping
    Hours per respondent: 0
    Total hours: 0
State Program Costs--reporting
    Hours per respondent: 2,650
    Total hours: 148,424
State Program Costs--recordkeeping
    Hours per respondent: 1,500
    Total hours: 84,000

1998

Public Water Systems--monitoring and reporting
    Hours per respondent: 5.3
    Total hours: 328,605
Public Water Systems--recordkeeping
    Hours per respondent: .05
    Total hours: 3,319
State Program Costs--reporting
    Hours per respondent: 11,643
    Total hours: 652,032
State Program Costs--recordkeeping
    Hours per respondent: 600
    Total hours: 33,640

1999

Public Water Systems--monitoring and reporting
    Hours per respondent: 3.9
    Total hours: 239,424
Public Water Systems--recordkeeping
    Hours per respondent: .04
    Total hours: 2,418
State Program Costs--reporting
    Hours per respondent: 9,119
    Total hours: 510,672
State Program Costs--recordkeeping
    Hours per respondent: 0
    Total hours: 0

    Send comments regarding the burden estimate or any other aspect of 
this collection of information, including suggestions for reducing this 
burden, to Chief, Information Policy Branch (MC:2136), EPA, 401 M 
Street, SW, Washington, DC 20460; and to the Office of Information and 
Regulatory Affairs, OPM, Washington, DC 20503, marked ``Attention: Desk 
Officer for EPA.'' The final rule will respond to any OMB or public 
comments on the information collection requirements contained in the 
proposal.

D. National Drinking Water Advisory Council and Science Advisory Board

    In accordance with section 1412 (d) and (e) of the Act, the Agency 
has submitted this proposed rule to the Science Advisory Board, 
National Drinking Water Advisory Council (NDWAC), and the Secretary of 
Health and Human Services for their review. The Agency will take their 
comments into account in developing the final rule. NDWAC supported the 
use of regulatory negotiation to develop this rule.

XVII. Request for Public Comment

    The proposed rule represents criteria that were agreed to be 
proposed by the Negotiating Committee. Part A of this Section lists the 
parts of the rule for which members of the Negotiating Committee, 
including EPA, requested comment. Part B of this Section lists the 
parts of the rule that pertain to small systems for which EPA requests 
public comments but which were not requested by Members of the 
Negotiating Committee. Members of the Negotiating Committee agreed not 
to file negative comments on the settled portions of the proposed rule 
or the preamble to the extent that they have the same substance and 
effect as the recommended rule and preamble. Each member of the 
Negotiating Committee may comment in support of the settled portions of 
the proposed rule. Each member of the Negotiating Committee may comment 
fully on or respond to comments solicited in the preamble or on issues 
that were not the subject of negotiations. The public at large is 
invited to comment on all aspects of the rule or preamble including the 
appropriateness of numerical criteria, monitoring requirements, and 
applicability. EPA will consider all public comments received in 
developing the final rule.

A. Request for Comment

Section V
    The appropriateness of adopting the term ``MRDLG'' in lieu of MCLGs 
for disinfectants in the final rule.

--Any additional data on known concentrations of chlorine in drinking 
water, food, and air.
--The following issues concerning chlorine: placing chlorine in 
Category III for developing an MRDLG, selection of the specified study 
and NOAEL as the basis for the MRDLG, the 80% RSC, the appropriateness 
of the UF of 100, and the cancer classification for chlorine.
--Any additional data on known concentrations of chloramines in 
drinking water, food, and air.
--The following issues concerning chloramines: the proposed MRDLG for 
chloramines and the RSC of 80%, the significance of the findings of 
immunotoxicity for setting the RfD instead of the NTP study, the 
significance of the finding of mononuclear cell leukemia in female F344 
rats, the significance of the finding of tubular cell neoplasms in 
high-dose exposed mice, and whether the adjusted MRDLG, which takes 
into account the measurement of monochloramine as total chlorine, is 
appropriate.
--The significance of the epidemiological studies with chlorine and 
chloramines as indicators of risk. EPA recognizes that there are 
different interpretations of these epidemiological studies and 
specifically solicits comment on the rationale for EPA's 
interpretations. EPA further requests comments on the studies 
suggesting a reproductive risk related to disinfectant byproduct 
exposure.
--Any additional data on known concentrations of chlorine dioxide, 
chlorate, and chlorite in drinking water, food, and air.
--For chlorine dioxide, the SAB's suggestion that a child's body weight 
of 10 kg and water consumption of 1 L/d may be more appropriate for 
setting the MRDLG than the adult parameters, given the acute nature of 
the toxic effect. EPA also requests comment on the appropriateness of 
the 300-fold uncertainty factor, the studies selected as the basis for 
the RfD, and the 80% relative source contribution.
--For chlorite, the SAB's suggestion that EPA consider basing the MCLG 
on the child body weight of 10 kg and water consumption of 1 L/day 
instead of the adult default values. EPA requests comments on the SAB's 
suggestion, along with the study selected as the basis for the MCLG, 
the uncertainty factor and the RSC of 80%.
--The decision not to propose an MCLG for chlorate at this time.
--Any additional data on known concentrations of chloroform in drinking 
water, food, and air.
    The basis for the proposed MCLG for chloroform.

--Any additional data on known concentrations of BDCM in drinking 
water, food, and air.
--The basis of the proposed MCLG for BDCM and the use of tumor data of 
large intestine and kidney, but not liver, in quantitative estimation 
of carcinogenic risk of BDCM from oral exposure.
--Any additional data on known concentrations of DBCM in drinking 
water, food, and air.
--The basis for the proposed MCLG for DBCM, the RSC of 80%, and the 
cancer classification for DBCM.
--Any additional data on known concentrations of bromoform in drinking 
water, food, and air.
--The different viewpoints between IARC and EPA regarding bromoform's 
carcinogenic potential.
--The basis for the proposed MCLG for bromoform.
--Any additional data on known concentrations of DCA in drinking water, 
food, and air.
--The basis for the proposed MCLG for DCA in drinking water and the 
cancer classification of Group B2.
--Any additional data on known concentrations of TCA in drinking water, 
food, and air.
--The basis for the MCLG and the cancer classification for TCA.
--Any additional data on known concentrations of CH in drinking water, 
food, and air.
--For CH, the Category II approach for setting an MCLG, the extra 
safety factor of 1 instead of 10 for a Category II contaminant, and 
whether the endpoint of liver weight increase and hepatomegaly is a 
LOAEL or NOAEL given the lack of histopathology.
--Any additional data on known concentrations of bromate in drinking 
water, food, and air.
--The MCLG of zero for bromate based on carcinogenic weight of evidence 
and the mechanism of action for carcinogenicity related to DNA adduct.
Section VIII
--The timetable for promulgation of the final rule and the compliance 
dates therein.
--How monitoring and compliance requirements should be split among 
wholesalers and retailers of water. Does Sec. 141.29 (consecutive 
systems) provide the State adequate flexibility and authority to 
address individual situations? Are any specific federal regulatory 
requirements necessary to handle such situations? If so, what are they?
--How the following situations should be handled in compliance 
determinations.
--When the monthly source water TOC is less than 2.0 mg/l and enhanced 
coagulation is not required.
--When seasonal variations cause the system to determine that TOC is 
not amenable to any level of enhanced coagulation and the system would 
be eligible for a waiver of enhanced coagulation requirements.

EPA believes that assigning a value of 1.00 for these months is a 
reasonable approach.
Section IX
--Whether exemptions to this rule should be granted if a system could 
demonstrate to the State, that due to unique water quality 
characteristics, it could not avoid through the use of BAT the 
possibility of increasing its total health risk by complying with the 
Stage 1 regulations. When might such situations occur? What specific 
conditions, if any, should be met for a system to be granted an 
exemption under such a provision. What provisions should EPA require of 
States to grant these exemptions? Should such exemptions be granted for 
a limited period but be renewable by the State if no new health risk 
information became available?
--Whether the TOC percent removal levels in Table IX-1 are 
representative of what 90 percent of systems required to use enhanced 
coagulation could be expected to achieve with elevated, but not 
unreasonable, coagulant addition.
--Whether filtration should be required as part of the bench-/pilot-
scale procedure for determination of Step 2 enhanced coagulation. If 
so, what type of filter should be specified for bench-scale studies?
--Whether a slope of 0.3 mg/L of TOC removed per 10 mg/L of alum added 
should be considered representative of the point of diminishing returns 
for coagulant addition under Step 2. EPA also solicits comment on how 
the slope should be determined (e.g., point-to point, curve-fitting). 
If the slope varies above and below 0.3/10, where should the Step 2 
alternate TOC removal requirement be set--at the first point below 0.3/
10? At some other point?
--Whether any additional regulatory requirements, guidance, or 
explanation is required to define ``multiple wells''. EPA requests 
comment on whether there should be an upper limit of sampling frequency 
for systems that either cannot determine that they are drawing water 
from a single aquifer or are drawing water from multiple aquifers. For 
example, should a system that must draw water from many aquifers to 
satisfy demand be allowed to limit monitoring as if they were drawing 
from no more than four aquifers (routine sampling would thus be limited 
to four samples per quarter from systems serving at least 10,000 people 
or to four samples per year for systems serving fewer than 10,000 
people)? Does EPA need to develop any additional guidance for any other 
aspect of this requirement?
--How often bench-or pilot-scale studies should be performed to 
determine compliance under step 2. Should such frequency of testing be 
included in the rule or left to guidance? Is quarterly monitoring 
appropriate for all systems? What is the best method to present the 
testing data to the primacy agency that reflects changing influent 
water quality conditions and also keeps transactional costs to a 
minimum? How should compliance be determined if the system is not 
initially meeting the percent TOC reduction required because of 
difficult to treat water and a desire to demonstrate alternative 
performance criteria?
--Whether data are available on the use of ferrous salts in the 
softening process which can help define a step 2 for enhanced 
softening. For softening plants, is enhanced softening properly defined 
by the percent removals in Table IX-1 or by 10 mg/L removal of 
magnesium? Is there a step 2 definition? Can ferrous salts be used at 
softening pH levels to further enhance TOC removals?
--Whether preoxidation is necessary in water treatment to control water 
quality problems such as iron, manganese, sulfides, zebra mussels, 
Asiatic clams, taste and odor. Will allowing preoxidation before 
precursor removal by enhanced coagulation generate excessive DBP 
levels?
--Whether biologically active filtration following ozonation is 
sufficient to remove most byproducts believed to result from ozonation? 
What parameters should be measured in and/or out of the biologically 
active filter to demonstrate that ozone byproducts are being removed? 
For example, would it be sufficient to demonstrate greater than 90 
percent removal of formaldehyde to establish that a filter is 
biologically active?
--Whether disinfection credit should be allowed for chlorine dioxide 
used prior to enhanced coagulation if virtually no halogenated organic 
DBPs are formed. Should some other limit, in addition to or in lieu of 
that proposed, be set (e.g., 5 /L TTHMs) on DBPs formed by 
high purity chlorine dioxide to ensure sufficient control for the 
production of excessive halogenated organic DBPs if disinfection credit 
were to be allowed with chlorine dioxide prior to enhanced coagulation?
--The appropriateness of allowing systems to add a disinfectant before 
enhanced coagulation when water temperatures are less than or equal to 
5  deg.C if excessive DBPs are not produced or identification of 
alternative means for addressing this issue.
--Whether GAC10 and GAC20 reasonable definitions of GAC performance? Do 
they span the expected level of GAC applications in drinking water 
treatment for the control of TTHMs and THAAs? Is the Jefferson Parish, 
Louisiana TOC removal representative of the ``general case'' of TOC 
removal?
--Whether any Subpart H systems with a TOC >4.0 mg/l should be allowed 
to reduce monitoring? Under what conditions (e.g., system has installed 
nanofiltration)?
--Whether reduced monitoring for ground water systems serving fewer 
than 10,000 people could be expanded beyond what is in the proposal. 
The additional options presented below would rely on having each entry 
point of the system go through three years of routine monitoring to 
qualify for reduced monitoring. After this period, if the entry points 
meet additional criteria, then the entry points would be subject to 
minimal additional monitoring.

    Option One: Any ground water system serving fewer than 10,000 
people that has a raw water TOC of less than 1.0 mg/l, and has both 
TTHM and HAA5 values less than 25 percent of the MCLs (20 g/l 
and 15 g/l, respectively) after three years of routine and 
reduced monitoring, can reduce the monitoring for TTHMs and HAA5s to 
one sample every nine years, taken at the maximum distribution system 
residence time during the warmest month.
    Option Two: Any ground water system serving fewer than 10,000 
people that has a raw water TOC of less than 0.5 mg/l, and has both 
TTHM and HAA5 values less than 25 percent of the MCLs (20 g/l 
and 15 g/l, respectively) after three years of routine and 
reduced monitoring, is exempt from the distribution system monitoring 
requirements for TTHMs and HAA5s for as long as TOC monitoring is 
conducted once every three years and the raw water TOC remains less 
than 0.5 mg/l.
    These options are not mutually exclusive, that is, both could be 
used simultaneously or some hybrid could be developed. The Agency seeks 
comment on whether either or both of these options are reasonable in 
adequately protecting the public health and should therefore be 
considered as criteria for reduced monitoring. Are there other options 
for reduced monitoring that should be considered? What are they?

--Comment on the cost impact of pH adjustment on systems with both high 
alkalinity and high bromide levels.
--Comment on the relative costs of adjusting pH to reduce bromate 
formation versus the costs of other technologies to meet the MCLs in 
this proposed rule.
--Whether the monitoring is frequent enough to adequately determine 
variations in sample results caused by time and/or location in the 
distribution system? If not, what is a more appropriate monitoring 
schedule? Should requirements differ for systems based on population 
served, raw water source, or other factors? If so, should the proposed 
requirements be changed? How should they be changed? If requirements 
should not be based on these factors, what should the requirements be? 
Does averaging of sample results taken in various locations over the 
course of a year to determine compliance adequately protect individuals 
that are in locations that may regularly have higher than average 
levels? If it does not, how should the proposed requirements be 
changed?
--Data to show that a lower quantitation level (at least down to 5 
g/L) can be obtained by those laboratories that will perform 
compliance monitoring for bromate in natural drinking water matrices. 
If the improved methodology uses equipment and/or reagents that are not 
currently required for EPA method 300.0, data to indicate the 
commercial availability and costs of these items would also need to be 
presented.
--A treatment technique that could ensure that bromate can be kept 
below 5 g/L, even if quantitation at 5 g/l is not 
achieveable under routine laboratory conditions.
--Other treatment techniques which allow ozone to meet disinfection and 
oxidation requirements while minimizing bromate formation.
--The feasibility of developing a treatment technique requirement for 
bromate, lowering the MCL based upon improved analytical techniques, 
and the time frame under which such alternative standards could be 
developed.
--The following approaches for promulgating a final rule for chlorite:

    (1) An MCL at the MCLG.
    (2) An MCL lower than the proposed MCL of 1.0 mg/l, but above the 
MCLG, depending upon all data that became available in the near term.
    (3) Depending on new data that become available, EPA could 
promulgate an MCL at the proposed MCL of 1.0 mg/l if the Agency 
determined that the systems currently using chlorine dioxide could not 
meet disinfection requirements in any other feasible manner, taking 
cost into consideration.
--The approaches for regulating chlorite. Specifically, EPA requests 
comment on the following:
--Is the basis for EPA's MCLG and concern for acute health effects 
appropriate? See Section V. for a complete discussion.
--Are there any particular water quality characteristics for systems 
currently using chlorine dioxide which make it ineffective to use any 
other disinfection technology? What are the lowest chlorite levels 
these systems can achieve? What technologies would need to be adopted 
and at what costs if such systems with these particular water quality 
characteristics would no longer use chlorine dioxide to meet the other 
regulatory criteria proposed herein?
--Should EPA set the chlorite MCL at a level so that chlorine dioxide 
remains a viable disinfection alternative for some systems even if this 
level is above the MCLG? If so, what would be the rationale for doing 
so?
--Is 1.0 mg/l the lowest level that systems needing chlorine dioxide 
can reliably achieve?
--How should EPA change the compliance monitoring requirements for 
chlorite to reflect concern about acute effects? Should such changes 
include increasing the frequency or changing the location of monitoring 
to be similar to those for chlorine dioxide? How would the MCL be 
affected by changes in the monitoring requirements?
--How should EPA change the public notification requirements for 
chlorite to reflect concern about acute effects?
--What level of residual chloramine would be feasible to achieve by 
most systems without increasing microbial risk.
--Information on improvements which may have been made to disinfectant 
methods to measure low concentrations of disinfectant residuals, but 
that are not reflected in the 18th edition of Standard Methods. EPA is 
also seeking information on new methodology that may be applicable for 
compliance monitoring.
--The technical adequacy of the analytical methods proposed for 
compliance with the proposed MRDLs.
--For bromate, whether use of a sample concentration technology prior 
to ion chromatographic analysis should be considered as a new 
methodolgy or a modification to Method 300.0 under today's rule. EPA 
also solicits comments on the applicability of sample concentration 
technology to today's proposed MCL for bromate.
--Data that demonstrate the need for a preservative in samples 
collected at the entrance point to the distribution system for 
measurement of bromate.
--The proposed turbidity threshold of 1 NTU to remove turbidity, which 
is known to interfere with accurate TOC measurement when the sample 
turbidity is greater than 1 NTU, and on the sample filtration procedure 
described in Section IX and in the proposed methods.
--What precision can be routinely expected on differential TOC 
measurements of jar test samples. EPA is also interested in new methods 
or modifications to the methods proposed today that would improve the 
reproducibility of TOC measurement.
Section X
--Other optional or mandatory performance criteria that EPA or the 
States should consider for certification of laboratories, or approval 
of analysts.
Section XI
--Whether exemptions to this rule should be granted if a system could 
demonstrate to the State, that due to unique water quality 
characteristics, it could not avoid through the use of BAT the 
possibility of increasing its total health risk by complying with the 
Stage 1 regulations. When might such situations occur? What specific 
conditions, if any, should be met for a system to be granted an 
exemption under such a provision. What provisions should EPA require of 
States to grant these exemptions? Should such exemptions be granted for 
a limited period but be renewable by the State if no new health risk 
information became available?
Section XII
--The proposed State reporting requirements. EPA particularly requests 
comment from the States on whether the proposed reporting requirements 
are reasonable.
--Whether the State should be required to keep the monitoring plan on 
file at the State after submission to make it available for public 
review?
Section XIV
--The proposed public notification rule language. Of particular 
interest is the acute violation language in Sec. 141.32(e)(85) for 
violations of the chlorine dioxide MCL. Also of interest is the 
language in Sec. 141.32(e)(86) for violations of the TTHM and HAA5 MCLs 
and the enhanced coagulation treatment technique requirement.
Section XV
--Data and comment on the extent to which reductions in exposure to 
TTHMs and DBPs can be expected to differ between systems serving 10,000 
people or more and systems serving less than 10,000 people.
Section XVI
--The burden estimate or any other aspect of this collection of 
information, including suggestions for reducing this burden.

B. Request for Additional Public Comments by EPA

    The Negotiating Committee considered several regulatory options for 
systems serving less than 10,000 people. These ranged from requiring 
smaller systems to meet the same compliance schedule as for larger 
systems to only extending the existing TTHM standard to systems serving 
less than 10,000 people. The Negotiating Committee rejected the former 
option for reasons discussed in Section XVI of this preamble. The 
Negotiating Committee rejected the latter option, over the objections 
of the National Rural Water Association (which was initially 
represented on the Negotiating Committee but then withdrew from the 
negotiations), because it believed that all systems should be subject 
to the same level of protection. Also, setting only a TTHM standard in 
the absence of other criteria could lead to increased exposure from 
other DBPs that might pose greater health risks.
    EPA recognizes that several factors still make it significantly 
more difficult for smaller systems than larger systems to achieve 
compliance with the Stage 1 requirements. Because the larger systems 
already have substantial experience with lowering TTHM levels, they 
will be more familiar than smaller systems with available technologies 
and operating conditions for lowering DBP levels. Because of economies 
of scale, the costs for systems to achieve the same incremental 
reduction in DBPs is substantially greater in smaller systems than in 
larger systems. For about 4% of systems serving less than 3,300 people 
(and less than 1% of the U.S. population receiving public drinking 
water), costs for compliance are estimated to be about $300 per 
household per year. For these reasons, EPA remains concerned about the 
ability of small communities to afford compliance and is interested in 
comments on this issue as well. Specifically, EPA is interested in 
further comment on alternative regulatory approaches for various small 
and medium system sizes.
    The parties reached consensus on the approach for staggered 
compliance schedules for systems serving fewer than 10,000 people 
(i.e., June 2000 for systems using surface water and ground water under 
the direct influence of surface water that serve fewer than 10,000 
people and January 2002 for ground water systems serving fewer than 
10,000 people). EPA is interested in comments on these important 
issues. Again, EPA recognizes the problems faced by small- and medium-
sized systems and is interested in further comment on alternative 
compliance approaches and possible solutions for various small and 
medium system sizes (e.g., <1,000; 1,000-3,300; >3,300-10,000).
    Because of the Agency's commitment to develop rules based on the 
best reasonably available scientific data, EPA intends to conduct 
research on the best way to reduce exposure from both DBPs and 
pathogens in small systems cost effectively. Based on information 
collected under the ICR, EPA intends to also refine models to more 
accurately predict occurrence of DBPs as a function of different 
treatment technologies, including those used by small systems. EPA 
intends to use available data in refining its estimates and solicits 
additional data on the occurrence of DBPs in drinking water systems, 
the concentration of pathogens in source water, and the effectiveness 
of treatment on microbial contaminants, especially for smaller systems. 
Also, as part of the major research effort leading to negotiation of 
the Stage 2 D/DBP rule, EPA intends to investigate technologies to 
determine whether small systems will be able to comply with D/DBP 
regulations at lower costs in future years.

XVIII. References and Public Docket

    References in this section are organized by type. Subsection A 
lists Federal Register references. Subsection B lists analytical method 
references. Subsection C lists health criteria document references. 
Subsection D lists other references.

A. Federal Register References

    1. U.S. Environmental Protection Agency. National Interim 
Primary Drinking Water Regulations; Control of Trihalomethanes in 
Drinking Water. Vol. 44, No. 231. November 29, 1979. pp. 68624-
68707.
    2. U.S. Environmental Protection Agency. National Revised 
Primary Drinking Water Regulations, Volatile Synthetic Organic 
Chemicals in Drinking Water; Advanced Notice of Proposed Rulemaking. 
Vol. 47, No. 43, Thursday, Mar. 4, 1982--Part IV. pp. 9350-9358.
    3. U.S. Environmental Protection Agency. National Interim 
Primary Drinking Water Regulations; Trihalomethanes. Vol. 48, No. 
40. Monday, Feb. 28, 1983. pp. 8406-8414.
    4. U.S. Environmental Protection Agency. National Primary 
Drinking Water Regulations; Synthetic Organic Chemicals, Inorganic 
Chemicals and Microorganisms: Proposed Rule. Vol. 50, No. 219. 
Wednesday, Nov. 13, 1985--Part IV. pp. 46936-47025.
    5. U.S. Environmental Protection Agency. National Primary 
Drinking Water Regulations--Synthetic Organic Chemicals; Monitoring 
for Unregulated Contaminants; Final Rule. Vol. 52, No. 130. July 8, 
1987--Part II. pp. 25690-25717.
    6. Federal Register. U.S. Environmental Protection Agency. 
Drinking Water Regulations; Public Notification; Final Rule. Vol. 
52, No. 208. Wednesday, Oct. 28, 1987--Part II. pp. 41534-41550.
    7. U.S. Environmental Protection Agency. National Primary 
Drinking Water Regulations. Maximum Contaminant Level Goals and 
National Primary Drinking Water Regulations for Lead and Copper. 
Vol. 53, No. 160. Thursday, Aug. 18, 1988. pp. 31516-31578.
    8. U.S. Environmental Protection Agency. National Primary and 
Secondary Drinking Water Regulations; Proposed Rule. Vol. 54, No. 
97. Monday, May 22, 1989. pp. 22062-22160.
    9. U.S. Environmental Protection Agency. Drinking Water; 
National Primary Drinking Water Regulations; Filtration, 
Disinfection; Turbidity, Giardia lamblia, Viruses, Legionella, and 
Heterotrophic Bacteria; Final Rule. Part II. Vol. 54, No. 124. 
Thursday, June 29, 1989. pp. 27486-27541.
    10. U.S. Environmental Protection Agency. National Primary 
Drinking Water Regulations; Synthetic Organic Chemicals and 
Inorganic Chemicals; Proposed Rule. Vol. 55, No. 143. Wednesday, 
July 25, 1990--Part II. pp. 30370-30448.
    11. U.S. Environmental Protection Agency. Notice of Availability 
of Proposed Guidance for Determining Unreasonable Risk to Health. 
Vol. 55, No. 191. Tuesday, Oct. 2, 1990. p. 40205.
    12. U.S. Environmental Protection Agency. National Primary 
Drinking Water Regulations: Lead and Copper. Notice of Availability 
with Request for Comments. Vol. 55, No. 203. Friday, Oct. 19, 1990. 
pp.42409-42413.
    13. U.S. Environmental Protection Agency. National Revised 
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. Vol. 56, No. 20. Wednesday, 
Jan. 30, 1991. pp. 3526-3597.
    14. U.S. Environmental Protection Agency. National Primary and 
Secondary Drinking Water Regulations; Synthetic Organic Chemicals 
and Inorganic Chemicals; Final Rule. Vol. 57, No. 138. Friday, July 
17, 1992--Part III. pp. 31776-31849.
    15. U.S. Environmental Protection Agency. Intent to Form an 
Advisory Committee to negotiate the Drinking Water Disinfection By-
Products Rule and Announcement of Public Meeting. Vol. 57, No. 179. 
September 15, 1992. pp. 42533-42536.
    16. U.S. Environmental Protection Agency. Establishment and Open 
Meeting of the Negotiated Rulemaking Advisory Committee for 
Disinfection By-Products. Vol. 57, No. 220. November 13, 1992. p. 
53866.
    17. U.S. Environmental Protection Agency. National Primary 
Drinking Water Regulations: Analytical Techniques (Trihalomethanes); 
Final Rule. Vol. 58, No. 147. August 3, 1993. pp. 41344-41345.
    18. U.S. Environmental Protection Agency. Executive Order 12866: 
Regulatory Planning and Review. Vol. 58, No. 190. October 4, 1993. 
51735-51744.

B. Analytical Methods

    1. APHA. 1992. American Public Health Association. Standard 
Methods for the Examination of Water and Wastewater (18th ed.). 
Washington, D.C. (Including: 4500 Cl D,E,F,G,H,I; 4500 ClO2 
C,D,E; 5310 C,D; 6233B; 2320 B)
    2. ASTM. 1993. Methods D-1067-88B, D-2035-80. Annual Book of 
ASTM Standards. Vol. 11.01, American Society for Testing and 
Materials.
    3. U.S. EPA. 1993. EPA Method 300.0. The Determination of 
Inorganic Anions by Ion Chromatography in the manual ``Methods for 
the Determination of Inorganic substances in Environmental 
Samples,'' EPA/600/R/93/100.
    4. U.S. EPA. 1983. EPA Method 310.1. Methods of Chemical 
Analysis of Water and Wastes. Envir. Monitoring Systems Laboratory, 
Cincinnati, OH. EPA 600/4-79-020. 460 pp.
    5. U.S. EPA. 1988. EPA Method 502.2. Methods for the 
Determination of Organic Compounds in Drinking Water. EPA 600/4-88-
039. PB91-231480. Revised July 1991.
    6. U.S. EPA. 1992. EPA Methods 524.2, 552.1. Methods for the 
Determination of Organic Compounds in Drinking Water--Supplement II. 
EPA 600/R-92/129. PB92-207703.
    7. U.S. EPA. 1990. EPA Methods 551, 552. Methods for the 
Determination of Organic Compounds in Drinking Water--Supplement I. 
EPA 600/4-90-020. PB91-146027.
    8. USGS. 1989. Method I-1030-85. Techniques of Water Resources 
Investigations of the U.S. Geological Survey. Book 5, Chapter A-1, 
3rd ed., U.S. Government Printing Office.

C. Health Criteria Documents

    1. USEPA. 1993b. Draft Drinking Water Health Criteria Document 
for Bromate. Office of Science and Technology, Office of Water. Sep. 
30, 1993.
    2. USEPA. 1994b. U.S. Environmental Protection Agency. Draft 
Drinking Water Health Criteria Document for Chloramines. Office of 
Science and Technology, Office of Water.
    3. USEPA. 1994e. U.S. Environmental Protection Agency. Draft 
Drinking Water Health Criteria Document for Chlorinated Acetic 
Acids/Alcohols/Aldehydes and Ketones. Office of Science and 
Technology, Office of Water.
    4. USEPA. 1994a. U.S. Environmental Protection Agency. Draft 
Drinking Water Health Criteria Document for Chlorine, Hypochlorous 
Acid and Hypochlorite Ion. Office of Science and Technology, Office 
of Water.
    5. USEPA. 1994c. U.S. Environmental Protection Agency. Final 
Draft Drinking Water Health Criteria Document for Chlorine Dioxide, 
Chlorite and Chlorate. Office of Science and Technology, Office of 
Water. March 31, 1994.
    6. U.S. Environmental Protection Agency. 1994d. Health and 
Ecological Criteria Div., OST. Final Draft for the Drinking Water 
Criteria Document on Trihalomethanes. Apr. 8. 1994.

D. Other References

    1. Aieta, E. M., & Berg, J. D. 1986. A Review of Chlorine 
Dioxide in Drinking Water Treatment. Jour. AWWA, 78:6:62 (June 
1986).
    2. Aieta, E. M.; Roberts, P. V.; & Hernandez, M. 1984. 
Determination of Chlorine Dioxide, Chlorine, Chlorite, and Chlorate 
in Water. Jour. AWWA, 76:1:64 (Jan. 1984).
    3. Alavanja M, Goldstein I, Susser M. 1978. A Case-Control Study 
of gastrointestinal and urinary tract cancer mortality and drinking 
water chlorination. In: Water Chlorination: Environmental Impact and 
Health Effects, Vol. 2. R.L. Jolley et al., editors. (Ann Arbor: Ann 
Arbor Science Publishers). pp. 395-409.
    4. Amy, G., et al. Nation-wide Survey of Bromide Ion 
Concentrations in Drinking Water Sources. Progress reports to 
AWWARF, University of Colorado at Boulder, Dept. of Civil, 
Environmental, and Architectural Engineering, Boulder, Colo. (1992-
93).
    5. Amy, G. L.; Chadik, P. A.; & Chowdhury, Z. 1987. Developing 
Models for Predicting Trihalomethane Formation Potential and 
Kinetics. Jour. AWWA, 79:7:89 (July 1987).
    6. Amy, G. L.; Tan, L.; & Davis, M. K. 1991. The Effects of 
Ozonation and Activated Carbon Adsorption on Trihalomethane 
Speciation. Water Res., 25:2:191 (Feb. 1991).
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Comparison of Methods (BDOC and AOC) and Correlations with Chemical 
Surrogates. Proc. 1992 AWWA Ann. Conf. (Water Research), pp. 523-
542, Vancouver, B.C.
    8. Aschengrau A, Zierler S, Cohen A. 1993. Quality of Community 
Drinking Water and the Occurrence of Late Adverse Pregnancy 
Outcomes. Arch Env Health 48:105-113.
    9. Atlas, E.; Schauffler, S. 1991. Analysis of Alkyl Nitrates 
and Selected Halocarbons in the Ambient Atmosphere Using a Charcoal 
Preconcentration Technique, Environ. Sci. Technol., Vol. 25, No. 1, 
pp. 61-7.
    10. AWWA Water Industry Data Base (WIDB). 1990. American Water 
Works Association. User's Guide.
    11. AWWA Water Industry Data Base (WIDB). 1991. AWWA, Denver, 
CO.
    12. AWWA Water Quality Division Disinfection Committee. 1992. 
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    15. AWWARF, 1992. AWWA Research Foundation. Disinfectant 
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toxicity of chlorine dioxide and related compounds in drinking water 
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Technique for the Analysis of Bromate at Low Levels in Drinking 
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    195. Spitzer, W.O. 1991. Editorial. Meta-meta-analysis: 
Unanswered questions about aggregating data. J. Clin. Epidemiol. 
44:103-107.
    196. Stevens, A.A. 1981. ``Reaction Products of Chlorine 
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    199. Summers, R. S., et al. 1993. Effect of Separation Processes 
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    201. Symons, J.M., et al. 1993. Measurement of THM and Precursor 
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List of Subjects

40 CFR Part 141

    Intergovernmental relations, Reporting and recordkeeping 
requirements, Water supply.

40 CFR Part 142

    Adminstrative practice and procedure, Reporting and recordkeeping 
requirements, Water supply.

    Dated: June 7, 1994.
Carol M. Browner,
Administrator.

    For the reasons set out in the preamble, chapter I of title 40 of 
the Code of Federal Regulations is proposed to be amended as follows:

PART 141--NATIONAL PRIMARY DRINKING WATER REGULATIONS

    1. The authority citation for part 141 continues to read as 
follows:

    Authority: 42 U.S.C. 300f, 300g-1, 300g-2 300g-3, 300g-4, 300g-
5, 300g-6, 300j-4 and 300j-9.

    2. Section 141.2 is amended by adding the following definitions in 
alphabetical order to read as follows:

    Note: The definition for ``subpart H systems'' has been proposed 
(59 FR 6332, February 10, 1994) and is included in this proposal for 
the convenience of the reader.


Sec. 141.2  Definitions.

* * * * *
    Biologically active filtration (BAF) means conventional filtration 
treatment or direct filtration preceded by continuous application of 
ozone (in possible combination with hydrogen peroxide), but no other 
continuous chemical disinfectant, utilizing filtration media and rate 
(i.e., empty bed contact time) sufficient to remove substantial levels 
of biodegradeable ozone byproducts.
    Enhanced coagulation means the addition of excess coagulant for 
improved removal of disinfection byproduct precursors by conventional 
filtration treatment.
    Enhanced softening means the improved removal of disinfection 
byproduct precursors by precipitative softening.
* * * * *
    GAC10 means granular activated carbon filter beds with an empty-bed 
contact time of 10 minutes based on average daily flow and a carbon 
reactivation frequency of every 180 days.
    GAC20 means granular activated carbon filter beds with an empty-bed 
contact time of 20 minutes based on average daily flow and a carbon 
reactivation frequency of every 60 days.
* * * * *
    Haloacetic acids (five) (HAA5) mean the sum of the concentrations 
in milligrams per liter of the haloacetic acid compounds 
(monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, 
monobromoacetic acid, and dibromoacetic acid), rounded to two 
significant figures after addition.
* * * * *
    Maximum residual disinfectant level (MRDL) means a level of a 
disinfectant added for water treatment that may not be exceeded at the 
consumer's tap without an unacceptable possibility of adverse health 
effects. For chlorine and chloramines, a PWS is in compliance with the 
MRDL when the running annual average of monthly averages of samples 
taken in the distribution system, computed quarterly, is less than or 
equal to the MRDL. For chlorine dioxide, a PWS is in compliance with 
the MRDL when daily samples are taken at the entrance to the 
distribution system and no two consecutive daily samples exceed the 
MRDL. MRDLs are enforceable in the same manner as maximum contaminant 
levels under section 1412 of the Safe Drinking Water Act. There is 
convincing evidence that addition of a disinfectant is necessary for 
control of waterborne microbial contaminants. Notwithstanding the MRDLs 
listed in Sec. 141.65, operators may increase residual disinfectant 
levels of chlorine or chloramines (but not chlorine dioxide) in the 
distribution system to a level and for a time necessary to protect 
public health to address specific microbiological contamination 
problems caused by circumstances such as distribution line breaks, 
storm run-off events, source water contamination, or cross-connections.
    Maximum residual disinfectant level goal (MRDLG) means the maximum 
level of a disinfectant added for water treatment at which no known or 
anticipated adverse effect on the health of persons would occur, and 
which allows an adequate margin of safety. MRDLGs are nonenforceable 
health goals and do not reflect the benefit of the addition of the 
chemical for control of waterborne microbial contaminants.
* * * * *
    Subpart H systems means public water systems using surface water or 
ground water under the direct influence of surface water as a source 
that are subject to the requirements of subpart H of this part.
* * * * *
    Total Organic Carbon (TOC) means total organic carbon in mg/l 
measured by methods specified in subpart L of this part using heat, 
oxygen, ultraviolet irradiation, chemical oxidants, or combinations of 
these oxidants that convert organic carbon to carbon dioxide, rounded 
to two significant figures.
* * * * *
    3. Subpart B is amended by revising Sec. 141.12 to read as follows:


Sec. 141.12  Maximum contaminant levels for total trihalomethanes.

    The maximum contaminant level of 0.10 mg/l for total 
trihalomethanes (the sum of the concentrations of bromodichloromethane, 
dibromochloromethane, tribromomethane (bromoform), and trichloromethane 
(chloroform)) applies to Subpart H community water systems which serve 
a population of 10,000 people or more until [insert date 18 months 
after date of publication of the final rule in the Federal Register]. 
This level applies to community water systems that use only ground 
water not under the direct influence of surface water and serve a 
population of 10,000 people or more until [insert date 42 months after 
date of publication of the final rule in the Federal Register]. 
Compliance with the maximum contaminant level for total trihalomethanes 
is calculated pursuant to Sec. 141.30. After [insert date 42 months 
after date of publication of the final rule in the Federal Register], 
this section expires.
    4. Section 141.30 is amended by adding paragraph (g) to read as 
follows:


Sec. 141.30  Total trihalomethanes sampling, analytical and other 
requirements.

* * * * *
    (g) The requirements in paragraphs (a) through (f) of this section 
apply to Subpart H community water systems which serve a population of 
10,000 or more until [insert date 18 months after date of publication 
of the final rule in the Federal Register]. The requirements in 
paragraphs (a) through (f) of this section apply to community water 
systems which use only ground water not under the direct influence of 
surface water that add a disinfectant (oxidant) in any part of the 
treatment process and serve a population of 10,000 or more until 
[insert date 42 months after date of publication of the final rule in 
the Federal Register]. After [insert date 42 months after date of 
publication of the final rule in the Federal Register], this section 
and Appendix A (Summary of Public Comments and EPA responses on 
Proposed Amendments to the National Interim Primary drinking Water 
Regulations for Control of Trihalomethanes in Drinking Water), Appendix 
B (Summary of Major Comments), and Appendix C (Analysis of 
Trihalomethanes) of this part expire.
    5. Section 141.32 is amended by revising paragraph (a) introductory 
text; removing the word ``MCLs'' and adding, in its place, the words 
``MCLs and MRDL(s)'' in paragraph (a)(1)(iii); removing the words 
``maximum contaminant level'' and adding, in its place, the words 
``maximum contaminant level and maximum residual disinfectant level'' 
in paragraph (c); and adding paragraphs (a)(1)(iii)(E) and (e)(83) 
through (88) to read as follows:

Subpart D--Reporting, Public Notification and Recordkeeping


Sec. 141.32  Public notification.

* * * * *
    (a) Maximum Contaminant Levels (MCLs), Maximum Residual 
Disinfectant Levels (MRDLs), treatment technique, and variance and 
exemption schedule violations. The owner or operator of a public water 
system which fails to comply with an applicable MCL, MRDL, or treatment 
technique established by this part or which fails to comply with the 
requirements of any schedule prescribed pursuant to a variance or 
exemption, shall notify persons served by the system as follows:
    (1) * * *
    (iii) * * *
    (E) Violation of the MRDL for chlorine dioxide as defined in 
Sec. 141.65 and determined according to Sec. 141.133(b)(2)(iii)(B).
* * * * *
    (e) * * *
    (83) Chlorine. The United States Environmental Protection Agency 
(EPA) sets drinking water standards and has determined that chlorine is 
a health concern at certain levels of exposure. The Safe Drinking Water 
Act requires disinfection for all public water systems. This chemical 
is used to disinfect drinking water. Chlorine is added to drinking 
water to kill bacteria and other disease-causing microorganisms. 
Chlorine is also added to provide continuous disinfection throughout 
the distribution system. However, at high doses for extended periods of 
time, chlorine has been shown to damage blood in laboratory animals. 
EPA has set a drinking water standard for chlorine to protect against 
the risk of these adverse effects. Drinking water which meets this EPA 
standard is associated with little to none of this risk and should be 
considered safe with respect to chlorine.
    (84) Chloramines. The United States Environmental Protection Agency 
(EPA) sets drinking water standards and has determined that chloramines 
are a health concern at certain levels of exposure. The Safe Drinking 
Water Act requires disinfection for all public water systems. This 
chemical is used to disinfect drinking water. Chloramines are added to 
drinking water to kill bacteria and other disease-causing 
microorganisms. Chloramines are also added to provide continuous 
disinfection throughout the distribution system. However, at high doses 
for extended periods of time, chloramines have been shown to damage 
blood and the liver in laboratory animals. EPA has set a drinking water 
standard for chloramines to protect against the risk of these adverse 
effects. Drinking water which meets this EPA standard is associated 
with little to none of this risk and should be considered safe with 
respect to chloramines.
    (85) Chlorine dioxide. The United States Environmental Protection 
Agency (EPA) sets drinking water standards and requires disinfection of 
drinking water. The Safe Drinking Water Act also requires disinfection 
of all public water systems. Chlorine dioxide is used in water 
treatment to kill bacteria and other disease-causing microorganisms and 
can be used to control tastes and odors. However, at high doses, 
chlorine dioxide in drinking water has been shown to damage blood in 
laboratory animals. Also, high levels of chlorine dioxide given to 
pregnant laboratory animals in drinking water have been shown to cause 
delays in development of the nervous system of their offspring. These 
effects may occur as a result of a short term exposure to excessive 
chlorine dioxide levels. To protect against such potentially harmful 
exposures, EPA requires chlorine dioxide monitoring at the treatment 
plant, where disinfection occurs, and at representative points in the 
distribution system serving water users. EPA has set a drinking water 
standard for chlorine dioxide to protect against the risk of these 
adverse effects.

    Note: In addition to paragraph (e)(85) of this section, systems 
must include either paragraph (e)(85)(i) or paragraph (e)(85)(ii) of 
this section. Systems with a violation at the treatment plant, but 
not in the distribution system, are required to use the language in 
paragraph (e)(85)(i) of this section and treat the violation as a 
nonacute violation. Systems with a violation at the treatment plant 
and in the distribution system are required to use the language in 
paragraph (e)(85)(ii) of this section and treat the violation as an 
acute violation.

    (i) The chlorine dioxide violations reported today are the result 
of exceedances at the treatment facility only, and do not include 
violations within the distribution system serving users of this water 
supply. Continued compliance with chlorine dioxide levels within the 
distribution system minimizes the potential risk of these violations to 
present consumers or
    (ii) The chlorine dioxide violations reported today include 
exceedances of the EPA standard within the distribution system serving 
water users. Violations of the chlorine dioxide standard within the 
distribution system may harm human health based on short-term 
exposures. Certain groups, including pregnant women, may be especially 
susceptible to adverse effects of excessive chlorine dioxide exposure. 
The purpose of this notice is to advise that such persons should 
consider reducing their risk of adverse effects from these chlorine 
dioxide violations by seeking alternate sources of water for human 
consumption until such exceedances are rectified. Local and State 
health authorities are the best source for information concerning 
alternate drinking water.
    (86) Disinfection byproducts and treatment technique for DBPs. The 
United States Environmental Protection Agency (EPA) sets drinking water 
standards and requires the disinfection of drinking water. The Safe 
Drinking Water Act also requires disinfection for all public water 
systems. However, when used in the treatment of drinking water, 
disinfectants combine with organic and inorganic matter present in 
water to form chemicals called disinfection byproducts (DBPS). EPA has 
determined that a number of DBPs are a health concern at certain levels 
of exposure. Certain DBPs, including some trihalomethanes (THMs) and 
some haloacetic acids (HAAs), have been shown to cause cancer in rats. 
Other DBPs have been shown to damage the liver and the nervous system, 
and cause reproductive or developmental effects in laboratory animals. 
There is also some evidence that exposure to certain DBPs may produce 
adverse effects in people. EPA has set standards to limit exposure to 
THMs, HAAs, and other DBPs.
    (87) Bromate. The United States Environmental Protection Agency 
(EPA) sets drinking water standards and has determined that bromate is 
a health concern at certain levels of exposure. Bromate is formed as a 
by-product of ozone disinfection of drinking water. Ozone reacts with 
naturally occurring bromide in the water to form bromate. Bromate has 
been shown to produce cancer in rats. EPA has set a drinking water 
standard to limit exposure to bromate.
    (88) Chlorite. The United States Environmental Protection Agency 
(EPA) sets drinking water standards and has determined that chlorite is 
a health concern at certain levels of exposure. Chlorite is formed from 
the breakdown of chlorine dioxide, a drinking water disinfectant. 
Chlorite in drinking water has been shown to damage blood cells and the 
nervous system. EPA has set a drinking water standard for chlorite to 
protect against these effects. Drinking water which meets this standard 
is associated with little to none of these risks and should be 
considered safe with respect to chlorite.

Subpart F--Maximum Contaminant Level Goals

    6. Subpart F is amended by adding new Secs. 141.53 and 141.54 to 
read as follows:


Sec. 141.53  Maximum contaminant level goals for disinfection 
byproducts.

    (a) MCLGs are zero for the following contaminants:
    (1) Chloroform;
    (2) Bromodichloromethane;
    (3) Bromoform;
    (4) Bromate; and
    (5) Dichloroacetic acid.
    (b) MCLGs for the following contaminants are as indicated: 

------------------------------------------------------------------------
                                                              MCLG(mg/l)
                        Contaminant                                     
------------------------------------------------------------------------
Chloral hydrate.............................................        0.04
Chlorite....................................................        0.08
Dibromochloromethane........................................        0.06
Trichloroacetic acid........................................        0.3 
------------------------------------------------------------------------

Sec. 141.54  Maximum residual disinfectant level goals for 
disinfectants.

    The MRDLGs for disinfectants are as follows: 

------------------------------------------------------------------------
               Disinfectant residual                     MRDLG (mg/l)   
------------------------------------------------------------------------
Chloramines.........................................          4 (as Cl2)
Chlorine............................................          4 (as Cl2)
Chlorine dioxide....................................       0.3 (as ClO2)
------------------------------------------------------------------------

Subpart G--National Revised Primary Drinking Water Regulations: 
Maximum Contaminant Levels

    7. Subpart G is amended by adding Secs. 141.64 and 141.65 to read 
as follows:


Sec. 141.64  Maximum contaminant levels for disinfection byproducts.

    (a) The following Maximum Contaminant Levels (MCLs) for 
disinfection byproducts apply to community water systems and 
nontransient, noncommunity water systems; compliance dates are 
indicated in paragraph (d)(1) of this section: 

------------------------------------------------------------------------
                       Contaminant                           MCL (mg/l) 
------------------------------------------------------------------------
Bromate...................................................         0.010
Chlorite..................................................         1.0  
Haloacetic acids (five) (HAA5)............................         0.060
Total trihalomethanes (TTHM)..............................         0.080 
------------------------------------------------------------------------

    (b)(1) For Subpart H systems that serve more than 10,000 people, 
the HAA5 and TTHM MCLs (the Stage 1 MCLs) in paragraph (a) of this 
section will be superseded by the MCLs (the Stage 2 MCLs) in paragraph 
(b) of this section 18 months after publication of the final MCLs in 
paragraph (b) of this section in the Federal Register with compliance 
as indicated in paragraph (d)(2) of this section. The MCLs in paragraph 
(a) of this section continue to apply for all other systems. 

------------------------------------------------------------------------
                       Contaminant                           MCL (mg/l) 
------------------------------------------------------------------------
Haloacetic acids (five)...................................         0.030
Total trihalomethanes.....................................         0.040 
------------------------------------------------------------------------

    (2) Prior to the publication of the final MCLs in paragraph (b) of 
this section in the Federal Register, the Administrator shall conduct a 
second regulatory negotiation or similar proceeding intended to develop 
a consensus rulemaking through negotiation to review these levels. The 
Administrator shall provide notice to the public of the availability of 
the monitoring data collected in accordance with Secs. 141.140 through 
141.142 and the results of health effects research relating to 
disinfectants and disinfection byproducts completed during the period 
1994-1996. Thereafter, the Agency shall initiate the second regulatory 
negotiation or similar proceeding to ensure that the affected interests 
that participated in the 1993 negotiated rulemaking participate fully 
with the Agency in the evaluation of the proposed Stage 2 MCLs in light 
of the monitoring data, health effects research, and other information 
developed since the proposal of the Stage 2 MCLs. If the second 
negotiated rulemaking or similar proceeding produces a consensus among 
the affected interests, the Agency will proceed in accordance with that 
consensus. The Agency agrees to take action on the proposed Stage 2 
MCLs by December 31, 1998, and to publish notice of that action in the 
Federal Register. If data prior to this second rulemaking warrants 
earlier action on acute health effects, a meeting shall be convened to 
review the results of these data and to develop recommendations.
    (c)(1) The Administrator, pursuant to Section 1412 of the Act, 
hereby identifies the following as the best technology, treatment 
techniques, or other means available for achieving compliance with the 
maximum contaminant levels for disinfection byproducts identified in 
paragraph (a) of this section: 

------------------------------------------------------------------------
     Disinfection byproduct         Best available technology (stage 1) 
------------------------------------------------------------------------
TTHMs............................  Enhanced coagulation or enhanced     
                                    softening or GAC10, with chlorine as
                                    the primary and residual            
                                    disinfectant.                       
HAA5.............................  Enhanced coagulation or enhanced     
                                    softening or GAC10, with chlorine as
                                    the primary and residual            
                                    disinfectant.                       
Bromate..........................  Control of ozone treatment process to
                                    reduce production of bromate.       
Chlorite.........................  Control of treatment processes to    
                                    reduce disinfectant demand and      
                                    control of disinfection treatment   
                                    processes to reduce disinfectant    
                                    levels.                             
------------------------------------------------------------------------

    (2) The Administrator, pursuant to Section 1412 of the Act, hereby 
identifies the following as the best technology, treatment techniques, 
or other means available for achieving compliance with the maximum 
contaminant levels for disinfection byproducts identified in paragraph 
(b) of this section: 

------------------------------------------------------------------------
     Disinfection byproduct         Best available technology (stage 2) 
------------------------------------------------------------------------
TTHMs............................  Enhanced coagulation or enhanced     
                                    softening, and GAC10; or GAC20; with
                                    chlorine as the primary and residual
                                    disinfectant.                       
HAA5.............................  Enhanced coagulation or enhanced     
                                    softening, and GAC10; or GAC20; with
                                    chlorine as the primary and residual
                                    disinfectant.                       
------------------------------------------------------------------------

    (d) Compliance dates for community water systems and nontransient 
noncommunity water systems. (1) Compliance with the MCLs in paragraph 
(a) of this section. Subpart H systems serving 10,000 or more persons 
must comply with the MCLs contained in paragraph (a) of this section 
beginning [insert date 18 months after date of publication of the final 
rule in the Federal Register]. Subpart H systems serving fewer than 
10,000 persons or systems using only ground water not under the direct 
influence of surface water serving 10,000 or more persons must comply 
with the MCLs in paragraph (a) of this section beginning [insert date 
42 months after date of publication of the final rule in the Federal 
Register]. Systems using only ground water not under the direct 
influence of surface water serving fewer than 10,000 persons must 
comply with paragraph (a) of this section beginning [insert date 60 
months after date of publication of the final rule in the Federal 
Register].
    (2) Compliance with the MCLs in paragraph (b) of this section. 
Subpart H systems serving 10,000 or more persons must comply with the 
listed MCLs or alternative requirements as developed under the 
negotiated rulemaking or similar process contained in paragraph (b) of 
this section beginning 18 months after date of publication of the final 
MCLs in paragraph (b) of this section in the Federal Register.
    (3) A system that is installing GAC or membrane technology to 
comply with this section may apply to the State for an extension of up 
to 42 months past the dates in paragraphs (d) (1) or (2) of this 
section, but not to exceed 60 months from the date of publication of 
the final rule in the Federal Register. In granting the extension, 
States must set a schedule for compliance and may specify any interim 
measures that the system must take. Failure to meet the schedule or 
interim treatment requirements constitutes a violation of National 
Primary Drinking Water Regulations.


Sec. 141.65  Maximum residual disinfectant levels.

    (a) The maximum residual disinfectant levels (MRDLs) are as 
follows:

------------------------------------------------------------------------
               Disinfectant residual                     MRDL (mg/l)    
------------------------------------------------------------------------
Chloramines.........................................        4.0 (as Cl2)
Chlorine............................................        4.0 (as Cl2)
Chlorine dioxide....................................      0.8 (as ClO2) 
------------------------------------------------------------------------

    (b) The Administrator, pursuant to Section 1412 of the Act, hereby 
identifies the following as the best technology, treatment techniques, 
or other means available for achieving compliance with the maximum 
residual disinfectant levels identified in paragraph (a) of this 
section: control of treatment processes to reduce disinfectant demand 
and control of disinfection treatment processes to reduce disinfectant 
levels.
    (c) Compliance dates. (1) CWSs and NTNCWSs. Subpart H systems 
serving 10,000 or more persons must comply with this section beginning 
[insert date 18 months after date of publication of the final rule in 
the Federal Register]. Subpart H systems serving fewer than 10,000 
persons or systems using only ground water not under the direct 
influence of surface water serving 10,000 or more persons must comply 
with this subpart beginning [insert date 42 months after date of 
publication of the final rule in the Federal Register]. Systems using 
only ground water not under the direct influence of surface water and 
serving fewer than 10,000 persons must comply with this subpart 
beginning [insert date 60 months after date of publication of the final 
rule in the Federal Register].
    (2) Transient NCWSs. Subpart H systems serving 10,000 or more 
persons and using chlorine dioxide as a disinfectant or oxidant must 
comply with the chlorine dioxide MRDL beginning [insert date 18 months 
after date of publication of the final rule in the Federal Register]. 
Subpart H systems serving fewer than 10,000 persons and using chlorine 
dioxide as a disinfectant or oxidant or systems using only ground water 
not under the direct influence of surface water serving 10,000 or more 
persons and using chlorine dioxide as a disinfectant or oxidant must 
comply with the chlorine dioxide MRDL beginning [insert date 42 months 
after date of publication of the final rule in the Federal Register]. 
Systems using only ground water not under the direct influence of 
surface water and serving fewer than 10,000 persons and using chlorine 
dioxide as a disinfectant or oxidant must comply with the chlorine 
dioxide MRDL beginning [insert date 60 months after date of publication 
of the final rule in the Federal Register].
    8. A new Subpart L is proposed to be added to read as follows:

Subpart L--Disinfectant Residuals, Disinfection Byproducts and 
Disinfection Byproduct Precursors

Sec.
141.130  General requirements.
141.131-141.132  [Reserved]
141.133  Analytical and monitoring requirements.
141.134  Reporting and recordkeeping requirements.
141.135  Treatment technique for control of Disinfection Byproduct 
Precursors (DBP).

Subpart L--Disinfectant Residuals, Disinfection Byproducts and 
Disinfection Byproduct Precursors


Sec. 141.130  General requirements.

    (a) The requirements of this subpart L constitute national primary 
drinking water regulations. Subpart L of this part establishes criteria 
under which community water systems (CWSs) and nontransient, 
noncommunity water systems (NTNCWSs) which add a chemical disinfectant 
to the water in any part of the drinking water treatment process must 
modify their practices to meet MCLs and MRDLs in Secs. 141.64 and 
141.65 and must meet the treatment technique requirements for 
disinfection byproduct precursors in Sec. 141.135. In addition, subpart 
L of this part establishes criteria under which transient NCWSs that 
use chlorine dioxide as a disinfectant or oxidant must modify their 
practices to meet the MRDL for chlorine dioxide in Sec. 141.65. MCLs 
for TTHMs and HAA5 and treatment technique requirements for 
disinfection byproduct precursors are established to limit the levels 
of known and unknown disinfection byproducts which may have adverse 
health effects. These disinfection byproducts may include chloroform; 
bromodichloromethane; dibromochloromethane; bromoform; dichloroacetic 
acid; trichloroacetic acid; and chloral hydrate 
(trichloroacetaldehyde).
    (b) Compliance dates. (1) CWSs and NTNCWSs. Unless otherwise noted, 
compliance with the requirements of this subpart shall begin as 
follows: Subpart H systems serving 10,000 or more persons must comply 
with this subpart beginning [insert date 18 months after date of 
publication of the final rule in the Federal Register]. Subpart H 
systems serving fewer than 10,000 persons or systems using only ground 
water not under the direct influence of surface water serving 10,000 or 
more persons must comply with this subpart beginning [insert date 42 
months after date of publication of the final rule in the Federal 
Register]. Systems using only ground water not under the direct 
influence of surface water serving fewer than 10,000 persons must 
comply with this subpart beginning [insert date 60 months after date of 
publication of the final rule in the Federal Register].
    (2) Transient NCWSs. Subpart H systems serving 10,000 or more 
persons and using chlorine dioxide as a disinfectant or oxidant must 
comply with any requirements for chlorine dioxide in this subpart 
beginning [insert date 18 months after date of publication of the final 
rule in the Federal Register]. Subpart H systems serving fewer than 
10,000 persons and using chlorine dioxide as a disinfectant or oxidant 
or systems using only ground water not under the direct influence of 
surface water serving 10,000 or more persons and using chlorine dioxide 
as a disinfectant or oxidant must comply with any requirements for 
chlorine dioxide in this subpart beginning [insert date 42 months after 
date of publication of the final rule in the Federal Register]. Systems 
using only ground water not under the direct influence of surface water 
and serving fewer than 10,000 persons and using chlorine dioxide as a 
disinfectant or oxidant must comply with any requirements for chlorine 
dioxide in this subpart beginning [insert date 60 months after date of 
publication of the final rule in the Federal Register].
    (c) Each CWS and NTNCWS regulated under paragraph (a) of this 
section must be operated by qualified personnel who meet the 
requirements specified by the State and are included in a State 
register of qualified operators.
    (d) Control of Disinfection Byproducts. (1) All CWS and NTNCWS must 
comply with MCLs in Sec. 141.64.
    (2) All CWS and NTNCWS must comply with monitoring requirements in 
Sec. 141.133.
    (e) Control of Disinfectant Residuals. (1) All CWS and NTNCWS must 
comply with MRDLs in Sec. 141.65. All transient NCWSs that use chlorine 
dioxide as a disinfectant or oxidant must comply with the chlorine 
dioxide MRDL in Sec. 141.65.
    (2) All CWS and NTNCWS must comply with monitoring requirements in 
Sec. 141.133. All transient NCWSs that use chlorine dioxide as a 
disinfectant or oxidant must comply with the chlorine dioxide 
monitoring requirements in Sec. 141.133.
    (3) Not withstanding the MRDLs in Sec. 141.65, systems may increase 
residual disinfectant levels in the distribution system of chlorine or 
chloramines (but not chlorine dioxide) to a level and for a time 
necessary to protect public health, to address specific microbiological 
contamination problems caused by circumstances such as, but not limited 
to, distribution line breaks, storm run-off events, source water 
contamination, or cross-connections.


Secs. 141.131-141.132  [Reserved]


Sec. 141.133  Analytical and monitoring requirements.

    (a) Analytical Requirements. Only the analytical method(s) 
specified in this paragraph (a), or otherwise approved by EPA, may be 
used to demonstrate compliance with the requirements of this subpart. 
These methods are effective for compliance monitoring [insert date 30 
days after date of publication of the final rule in the Federal 
Register].
    (1) Disinfection Byproducts. (i) Disinfection byproducts must be 
measured by the methods listed below: 

                       Approved Methods for Disinfection Byproduct Compliance Monitoring                        
----------------------------------------------------------------------------------------------------------------
                                                                           Methodology\2\                       
                                                   -------------------------------------------------------------
               Byproduct measured\1\                     EPA                                                    
                                                     method\3\     TTHMs\4\    HAA5\5\     Chlorite     Bromate 
----------------------------------------------------------------------------------------------------------------
P&T/GC/ElCD & PID.................................  502.2\6\              X                                     
P&T/GC/MS.........................................  524.2                 X                                     
LLE/GC/ECD........................................  551                   X                                     
LLE/GC/ECD........................................  \7\6233 B     ..........          X                         
SPE/GC/ECD........................................  552.1         ..........          X                         
IC................................................  300.0         ..........  ..........          X          X  
----------------------------------------------------------------------------------------------------------------
\1\X indicates method is approved for measuring specified disinfection byproduct.                               
\2\P&T=purge and trap; GC=gas chromatography; ElCD=electrolytic conductivity detector; PID=photoionization      
  detector; MS=mass spectrometer; LLE=liquid/liquid extraction; ECD=electron capture detector; SPE=solid phase  
  extractor; IC=ion chromatography                                                                              
\3\As set forth in Methods for the Determination of Organic Compounds in Drinking Water, USEPA, 1988 (revised   
  July 1991) (available through National Technical Information Service (NTIS), EPA/600/4-88/039, PB91-231480)   
  for Method 502.2; Methods for the Determination of Organic Compounds in Drinking Water-Supplement II, USEPA,  
  1992, (available through NTIS, EPA/600/R-92/129, PB92-207703), for Methods 524.2 and 552.1; Methods for the   
  Determination of Organic Compounds in Drinking Water-Supplement I, USEPA, July 1990 (available through        
  National Technical Information Service (NTIS), EPA/600/4-90/020, PB91-146027) for Method 551; and Methods for 
  the Determination of Inorganic Substances in Environmental Samples, EPA/600/R/93/100--August 1993 for Method  
  300.0.                                                                                                        
\4\Total trihalomethanes.                                                                                       
\5\Total haloacetic acids.                                                                                      
\6\If TTHMs are the only analytes being measured in the sample, then a PID is not required.                     
\7\Method 6233 B, as set forth in Standard Methods for the Examination of Water and Wastewater, 1992 (18th Ed.),
  American Public Health Association et al.                                                                     

    (ii) Analysis under this section for disinfection byproducts shall 
be conducted by laboratories that have received certification by EPA or 
the State after meeting the following conditions. To receive 
certification to conduct analyses for the contaminants in 
Sec. 141.64(a) (1) through (4), the laboratory must: annually analyze 
performance evaluation (PE) samples provided by EPA Environmental 
Monitoring Systems Laboratory or equivalent State samples, and achieve 
quantitative results on a minimum of 80% of the analytes included in 
each PE sample. The acceptance limit is defined as the 95% confidence 
interval calculated around the mean of the PE study data between a 
maximum and minimum acceptance limit of +/-50% and +/-15% of the study 
mean.
    (2)(i) Disinfectant Residuals. Residual disinfectant concentrations 
for free chlorine, combined chlorine (chloramines), and chlorine 
dioxide must be measured by the methods listed below:

                        Approved Methods for Disinfectant Residual Compliance Monitoring                        
----------------------------------------------------------------------------------------------------------------
                                                                  Residual measured\1\                          
                                       -------------------------------------------------------------------------
             Methodology                    Standard          Free        Combined        Total       Chlorine  
                                            method\2\       chlorine      chlorine      chlorine       dioxide  
----------------------------------------------------------------------------------------------------------------
Amperometric Titration................  4500-Cl D                   X             X             X   ............
Amperometric Titration................  4500-Cl E         ............  ............            X   ............
DPD Ferrous Titrimetric...............  4500-Cl F                   X             X             X   ............
DPD Colorimetric......................  4500-Cl G                   X             X             X   ............
Syringaldazine (FACTS)................  4500-Cl H                   X   ............  ............  ............
Iodometric Electrode..................  4500-Cl I         ............  ............            X   ............
Amperometric Titration................  4500-ClO2 C       ............  ............  ............            X 
DPD Method............................  4500-ClO2 D       ............  ............  ............            X 
Amperometric Titration (proposed).....  4500-ClO2 E       ............  ............  ............           X  
----------------------------------------------------------------------------------------------------------------
\1\X indicates method is approved for measuring specified disinfectant residual.                                
\2\As set forth in Standard Methods for the Examination of Water and Wastewater, 1992 (18th Ed.), American      
  Public Health Association et al.                                                                              

    (ii) Residual disinfectant concentrations for chlorine and 
chloramines may also be measured by using DPD colorimetric test kits if 
approved by the State. Measurement for residual disinfectant 
concentration must be conducted by a party approved by EPA or the 
State.
    (3) Additional Analytical Methods. Systems required to analyze 
parameters not included in paragraphs (a)(1) and (2) of this section 
shall use the following methods. Measurement for these parameters must 
be conducted by a party approved by EPA or the State.
    (i) Alkalinity. All methods allowed in Sec. 141.89(a) for measuring 
alkalinity.
    (ii) Bromide. EPA method 300.0.
    (iii) Total Organic Carbon-Method 5310 C (Persulfate-ultraviolet 
Oxidation Method) or Method 5310 D (Wet-oxidation Method) as set forth 
in Standard Methods for the Examination of Water and Wastewater, 1992 
(18th Ed.), American Public Health Association et al. Samples shall not 
be filtered prior to this analysis. For compliance monitoring, TOC and 
not dissolved organic carbon (DOC) data are required.
    (b) Routine monitoring requirements for disinfection byproducts, 
disinfectant residuals, and total organic carbon. All samples must be 
taken during normal operating conditions. Failure to monitor in 
accordance with the monitoring plan required under the provisions of 
Sec. 141.133(d) is a monitoring violation. Where compliance is based on 
a running annual average of monthly or quarterly samples or averages 
and the system's failure to monitor makes it impossible to determine 
compliance with MCLs or MRDLs, this failure to monitor will be treated 
as a violation for the entire period covered by the annual average.
    (1) Disinfection byproducts. (i) TTHMs and HAA5. (A) Subpart H 
systems serving 10,000 or more persons shall take four water samples 
each quarter for each treatment plant in the system. At least 25 
percent of all samples collected each quarter, including those samples 
taken in excess of the required frequency, shall be taken at locations 
within the distribution system that represent the maximum residence 
time of the water in the system. The remaining samples shall be taken 
at locations within the distribution system that represent the entire 
system, taking into account the number of persons served, different 
sources of water, and different treatment methods employed.
    (B) Systems using only ground water sources not under the direct 
influence of surface water that use a chemical disinfectant and serve 
10,000 or more persons shall take one water sample each quarter for 
each treatment plant in the system. Samples shall be taken at locations 
within the distribution system that represent the maximum residence 
time of the water in the system. At least 25 percent of all samples 
collected each quarter, if samples are taken in excess of the required 
frequency, shall be taken at locations within the distribution system 
that represent the maximum residence time of the water in the system. 
The remaining samples must be taken at locations representative of at 
least average residence time in the distribution system. Multiple wells 
within a system drawing water from a single aquifer shall, with State 
approval in accordance with criteria developed under Sec. 142.16(f)(6), 
be considered one treatment plant for determining the minimum number of 
samples required.
    (C) Subpart H systems serving from 500 to 9,999 persons shall take 
one water sample each quarter for each treatment plant in the system. 
Samples shall be taken at a point in the distribution system that 
represents the maximum residence time in the distribution system. At 
least 25 percent of all samples collected each quarter, if samples are 
taken in excess of the required frequency, shall be taken at locations 
within the distribution system that represent the maximum residence 
time of the water in the system. The remaining samples must be taken at 
locations representative of at least average residence time in the 
distribution system.
    (D) Subpart H systems serving fewer than 500 persons shall take one 
sample per year for each treatment plant in the system. Samples shall 
be taken at a point in the distribution system reflecting the maximum 
residence time in the distribution system and during the month of 
warmest water temperature. If the sample (or average of the annual 
samples, if more than one sample is taken) exceeds the MCL, the system 
must increase monitoring to one sample per treatment plant per quarter, 
taken at a point in the distribution system reflecting the maximum 
residence time in the distribution system, until the system meets 
criteria in paragraph (c) of this section for reduced monitoring.
    (E) Systems using only ground water sources not under the direct 
influence of surface water that use a chemical disinfectant and serve 
less than 10,000 persons shall sample once per year for each treatment 
plant in the system. Samples shall be taken at a point in the 
distribution system reflecting the maximum residence time in the 
distribution system and during the month of warmest water temperature. 
If the sample (or the average of the annual samples, when more than one 
sample is taken) exceeds the MCL, the system must increase monitoring 
to one sample per treatment plant per quarter, taken at a point in the 
distribution system reflecting the maximum residence time in the 
distribution system, until the system meets criteria in paragraph (c) 
of this section for reduced sampling. Multiple wells drawing water from 
a single aquifer shall, with State approval in accordance with criteria 
developed under Sec. 142.16(f)(6), be considered one treatment plant 
for determining the minimum number of samples required.
    (ii) Chlorite. Community and nontransient noncommunity water 
systems using chlorine dioxide, for disinfection or oxidation, shall 
take three samples each month in the distribution system. One sample 
must be taken at each of the following locations: near the first 
customer, in a location representative of average residence time, and 
near the end of the distribution system (reflecting maximum residence 
time in the distribution system). Any additional sampling must be 
conducted in the same manner (i.e., three-sample sets, at the specified 
locations).
    (iii) Bromate. Community and nontransient noncommunity systems 
using ozone, for disinfection or oxidation, shall take one sample per 
month for each treatment plant in the system using ozone. Samples must 
be taken monthly at the entrance to the distribution system while the 
ozonation system is operating under normal conditions.
    (iv) Compliance. (A) TTHMs and HAA5. For systems monitoring 
quarterly, compliance with MCLs in Sec. 141.64 shall be based on a 
running annual arithmetic average, computed quarterly, of quarterly 
arithmetic averages of all samples collected by the system as 
prescribed by this section under paragraphs (b)(1)(i)(A), (B), and (C) 
of this section. If the arithmetic average of quarterly averages 
covering any consecutive four-quarter period exceeds the MCL, the 
supplier of water shall report to the State pursuant to Sec. 141.134 
and notify the public pursuant to Sec. 141.32. Systems on a reduced 
monitoring schedule whose annual average exceeds the MCL will revert to 
routine monitoring immediately. For systems monitoring less frequently 
than quarterly, compliance shall be based on an average of samples 
taken that year under the provisions of Sec. 141.133(b)(1)(i)(D) 
through (E) or Sec. 141.133(c)(1)(iii)(C). If the average of these 
samples exceeds the MCL, the system must increase monitoring to once 
per quarter per treatment plant. All samples taken and analyzed under 
the provisions of this section must be included in determining 
compliance, even if that number is greater than the minimum required. 
If, during the first year following the effective date, any individual 
quarter's average will cause the running annual average of that system 
to exceed the MCL, the system is out of compliance at the end of that 
quarter.
    (B) Bromate. Compliance shall be based on a running annual 
arithmetic average, computed quarterly, of monthly samples (or, for 
months in which the system takes more than one sample, the average of 
all samples taken during the month) collected by the system as 
prescribed by paragraph (b)(1)(iii) of this section. If the average of 
samples covering any consecutive four-quarter period exceeds the MCL, 
the system shall report to the State pursuant to Sec. 141.134 and 
notify the public pursuant to Sec. 141.32. If a PWS fails to complete 
12 consecutive months' monitoring, compliance with the MCL for the last 
four-quarter compliance period shall be based on an average of the 
available data.
    (C) Chlorite. Compliance shall be based on a monthly arithmetic 
average of samples as prescribed by paragraph (b)(1)(ii) of this 
section. If the arithmetic average of samples covering any month 
exceeds the MCL, the system shall report to the State pursuant to 
Sec. 141.134 and notify the public pursuant to Sec. 141.32.
    (2) Disinfectant residuals. (i) Chlorine and chloramines. (A) 
Subpart H systems must measure the residual disinfectant level at the 
same points in the distribution system and at the same time as total 
coliforms are sampled, as specified in Sec. 141.21. Systems may use the 
results of residual disinfectant concentration sampling conducted under 
Sec. 141.74(b)(6)(i) for unfiltered systems or Sec. 141.74(c)(3)(i) for 
systems which filter, in lieu of taking separate samples.
    (B) Community and nontransient noncommunity systems using only 
ground water not under the direct influence of surface water must 
measure the residual disinfectant level at the same points in the 
distribution system and at the same time as total coliforms are 
sampled, as specified in Sec. 141.21.
    (ii) Chlorine Dioxide. (A) Routine Monitoring. Community, 
nontransient noncommunity, and transient noncommunity water systems 
must monitor for chlorine dioxide only if chlorine dioxide is used by 
the system for disinfection or oxidation. If monitoring is required, 
systems shall take daily samples at the entrance to the distribution 
system. For any daily sample that exceeds the MRDL, the system is 
required to take samples in the distribution system the following day 
at the locations required by paragraph (b)(2)(ii)(B) of this section, 
in addition to the sample required at the entrance to the distribution 
system.
    (B) Additional Distribution System Monitoring. On each day 
following a routine sample monitoring result that exceeds the MRDL, the 
system is required to take three chlorine dioxide distribution system 
samples.
    (1) If chlorine dioxide or chloramines are used to maintain a 
disinfectant residual in the distribution system, or if chlorine is 
used to maintain a disinfectant residual in the distribution system and 
there are no disinfection addition points after the entrance to the 
distribution system (i.e., no booster chlorination), three samples 
shall be taken as close to the first customer as possible at intervals 
of at least six hours.
    (2) If chlorine is used to maintain a disinfectant residual in the 
distribution system and there are one or more disinfection addition 
points after the entrance to the distribution system (i.e., booster 
chlorination), one sample shall be taken at each of the following 
locations: as close to the first customer as possible, in a location 
representative of average residence time, and as close to the end of 
the distribution system as possible (reflecting maximum residence time 
in the distribution system).
    (C) CT credit prior to enhanced coagulation or enhanced softening. 
Subpart H systems required to operate enhanced coagulation or enhanced 
softening under the provisions of Sec. 141.135 may receive credit for 
compliance with CT requirements specified by the State if the following 
monitoring is completed and the criteria in Sec. 141.135(a)(2)(i)(B)(3) 
are met.
    (1) For each chlorine dioxide generator, the system must 
demonstrate that the generator is achieving at least 95 percent 
chlorine dioxide yield and producing no more than five percent chlorine 
by measuring a minimum of once per week. Measurements shall be 
conducted by using Standard Method 4500-ClO22 E. Chlorine dioxide 
yield and chlorine presence shall be measured as described in Aieta et 
al, Journal AWWA, 76:1, pp.66 and 67, respectively. Guidance on 
generator effluent sampling, safety, dilutions, replication, and the 
measurement of these and related species may be found in [cite Hoehn's 
upcoming AWWARF report] and in Aieta et al, Journal AWWA, 76:1, pp.64 
through 70, as noted.
    (2) On any day that a generator fails to achieve at least 95 
percent chlorine dioxide yield and no more than five percent chlorine, 
and on subsequent days until these conditions are achieved, the system 
may not receive credit for compliance with CT requirements in subpart H 
of this part.
    (3) On any day that a generator fails to achieve at least 95 
percent chlorine dioxide yield but achieves at least 90 percent 
conversion efficiency and/or produces more than five percent chlorine 
but less than 10 percent, the system may take immediate corrective 
action to achieve a minimum of 95 percent chlorine yield and a maximum 
of five percent chlorine. If subsequent measurements conducted on the 
same day demonstrate at least 95 percent chlorine dioxide yield and no 
more than five percent chlorine, the system may receive credit for 
compliance with CT requirements in subpart H of this part on that day. 
If the generator continues to fail to demonstrate at least 95 percent 
chlorine dioxide yield and no more than five percent chlorine, the 
system may not receive credit for compliance with CT requirements in 
subpart H of this part on that day.
    (4) After achieving the conditions in paragraph (b)(2)(ii)(C)(1) of 
this section, the system may operate no more than one week without 
measurement. If however, in the interim, the system changes generator 
operating conditions (e.g., changes chlorine dioxide dose, changes 
conditions to match changing plant flow rate) or generator conditions 
(e.g., a new batch of sodium chlorite or a different ratio of chlorite 
to chlorine or acid is used), the system shall remeasure for chlorine 
dioxide yield and chlorine presence and meet the conditions in 
paragraphs (b)(2)(ii)(C)(1) or (3) of this section to receive CT 
credit.
    (iii) Compliance. (A) Chlorine and chloramines. (1) Compliance 
shall be based on a running annual arithmetic average, computed 
quarterly, of quarterly averages of all samples collected by the system 
as prescribed in this section. If the average of quarterly averages 
covering any consecutive four-quarter period exceeds the MRDL, the 
system shall report to the State pursuant to Sec. 141.134 and notify 
the public pursuant to Sec. 141.32.
    (2) In cases where systems switch between the use of chlorine and 
chloramines for residual disinfection during the year, compliance shall 
be determined by including together all monitoring results of both 
chlorine and chloramines in calculating compliance pursuant to 
paragraph (b)(2)(iii)(C)(1) of this section. Reports submitted pursuant 
to Sec. 141.134 will clearly indicate which residual disinfectant was 
analyzed for each sample.
    (B) Chlorine dioxide. (1) Acute violations. Compliance shall be 
based on consecutive daily samples collected by the system as 
prescribed in this section. If any daily sample taken at the entrance 
to the distribution system exceeds the MRDL, and on the following day 
one (or more) of the three samples taken in the distribution system 
exceed the MRDL, the system will be in violation of the MRDL and shall 
take immediate corrective action to lower the level of chlorine dioxide 
below the MRDL and will notify the public pursuant to the procedures 
for acute health risks in Sec. 141.32(a)(1)(iii)(E). Failure to take 
samples in the distribution system the day following an exceedance of 
the chlorine dioxide MRDL at the entrance to the distribution system 
shall also be considered an MRDL violation and the system shall notify 
the public of the violation in accordance with the provisions for acute 
violations under Sec. 141.32(a)(1)(iii)(E).
    (2) Nonacute violations. Compliance shall be based on consecutive 
daily samples collected by the system as prescribed in this section. If 
any two consecutive daily samples taken at the entrance to the 
distribution system exceed the MRDL and all distribution system samples 
taken are below the MRDL, the system will be in violation of an MRDL 
and shall take corrective action to lower the level of chlorine dioxide 
below the MRDL at the point of sampling and will notify the public 
pursuant to the procedures for nonacute health risks in Sec. 141.32. 
Failure to monitor at the entrance to the distribution system the day 
following an exceedance of the chlorine dioxide MRDL at the entrance to 
the distribution system shall also be considered an MRDL violation and 
the system shall notify the public of the violation in accordance with 
the provisions for nonacute violations under Sec. 141.32.
    (3) Disinfection Byproduct Precursors (DBPP). (i) Subpart H 
systems. Community and nontransient noncommunity systems which use 
conventional filtration treatment (as defined in Sec. 141.2) must 
monitor each treatment plant water source for TOC prior to any 
continuous disinfection treatment; except that systems using ozone 
followed by biologically active filtration (as defined in Sec. 141.2) 
may measure TOC in the treated water following biological filtration 
but before the addition of a residual disinfectant and systems using 
chlorine dioxide that meet the standards for including CT credit for 
its use prior to enhanced coagulation or enhanced softening contained 
in Sec. 141.135(a)(2)(i)(B)(3) or Sec. 141.135(a)(2)(ii)(B)(3) may 
measure TOC in the treated water at any point prior to the continuous 
addition of any other disinfectant. All systems required to monitor 
under paragraph (b)(3) of this section must also monitor for TOC in the 
source water prior to any treatment at the same time as monitoring for 
TOC in the treated water. These samples (source water and treated 
water, prior to disinfection) are referred to as paired samples. At the 
same time as the source water sample is taken, all systems must monitor 
for alkalinity in the source water prior to any treatment.
    (ii) Frequency. All systems required to monitor under paragraph 
(b)(3)(i) of this section must take one paired sample per month per 
plant at a time representative of normal operating conditions and 
influent water quality. At the same time, the system must take a source 
water alkalinity sample in order to make the appropriate calculations 
required to comply with Sec. 141.135.
    (iii) Compliance. Compliance shall be determined as specified by 
Sec. 141.135(b). Systems may begin monitoring to determine whether Step 
1 TOC removals can be met 12 months prior to the compliance date for 
the system. This monitoring is not required and failure to monitor 
during this period is not a violation. However, any system that: Does 
not monitor during this period, and then determines in the first 12 
months after the compliance date that it is not able to meet the Step 1 
requirements in Sec. 141.135(a)(2) and must therefore apply for 
alternate performance criteria, is not eligible for retroactive 
approval of alternate performance criteria as allowed pursuant to 
Sec. 141.135(a)(3). Systems may apply for alternate performance 
criteria any time after the compliance date.
    (c) Reduced monitoring requirements for disinfection byproducts, 
disinfectant residuals, and total organic carbon. Systems may reduce 
monitoring, except as otherwise provided, in accordance with the 
following.
    (1) Disinfection byproducts. (i) Chlorite. Systems required to 
analyze for chlorite may not reduce monitoring.
    (ii) Bromate. Systems required to analyze for bromate may reduce 
monitoring from monthly to once per quarter, if the system demonstrates 
that the average raw water bromide concentration is less than 0.05 mg/l 
based upon representative monthly measurements for one year.
    (iii) TTHMs and HAA5. (A) Any Subpart H system which has a source 
water TOC level, before any treatment, of greater than 4.0 mg/l may not 
reduce its monitoring.
    (B) Systems may reduce monitoring if they have a running annual 
average for TTHMs and HAA5 that is no more than 0.040 mg/l and 0.030 
mg/l, respectively, with the following exceptions. Systems using ground 
water not under the direct influence of surface water that serve fewer 
than 10,000 persons and are required to take only one sample per year 
may reduce monitoring if either: the average of two consecutive 
representative annual samples is no more than 0.040 mg/l and 0.030 mg/l 
for TTHMs and HAA5, respectively, or any representative annual sample 
is less than 0.020 mg/l and 0.015 mg/l for TTHMs and HAA5, 
respectively. Systems using surface water or ground water under the 
direct influence of surface water in whole or in part that serve fewer 
than 500 persons may not reduce their monitoring to less than one 
sample per year. Systems must meet the requirements for reduction of 
monitoring for both TTHMs and HAA5 to qualify for reduced monitoring. 
The system may reduce monitoring only after the system has completed at 
least one year of monitoring in accordance with paragraph (b)(1)(i) of 
this section.
    (C) Reduced monitoring frequency. (1) Subpart H systems serving 
10,000 persons or more that are eligible for reduced monitoring in 
paragraph (c)(1)(iii)(B) of this section may reduce the monitoring 
frequency for TTHMs and HAA5 to one sample per quarter per treatment 
plant. Samples shall be taken at a point in the distribution system 
reflecting the maximum residence time in the distribution system.
    (2) Systems using only ground water not under the direct influence 
of surface water and serving 10,000 persons or more that are eligible 
for reduced monitoring in paragraph (c)(1)(iii)(B) of this section may 
reduce the monitoring frequency for TTHMs and HAA5 to one sample per 
year per treatment plant. Samples shall be taken at a point in the 
distribution system reflecting the maximum residence time in the 
distribution system and during the month of warmest water temperature.
    (3) Subpart H systems serving between 500 to 9,999 persons that are 
eligible for reduced monitoring may reduce the monitoring frequency for 
TTHMs and HAA5 to one sample per year per treatment plant. Samples 
shall be taken at a point in the distribution system reflecting the 
maximum residence time in the distribution system and during the month 
of warmest water temperature.
    (4) Systems using only ground water sources not under the direct 
influence of surface water and serving fewer than 10,000 persons, may 
reduce the monitoring frequency for TTHMs and HAA5 to one sample per 
three year monitoring cycle, with this three-year cycle beginning on 
the January 1 following the quarter in which the system qualifies for 
reduced monitoring. Samples shall be taken at a point in the 
distribution system reflecting the maximum residence time in the 
distribution system and during the month of warmest water temperature.
    (D) Systems on a reduced monitoring schedule may remain on that 
reduced schedule as long as the average of all samples taken in the 
year (for systems which must monitor quarterly) or the result of the 
sample (for systems which must monitor no more frequently than 
annually) is no more than 0.060 mg/l and 0.045 mg/l for TTHMs and HAA5, 
respectively. Systems that do not meet these levels must resume 
monitoring at the frequency identified in Sec. 141.133(b)(1) in the 
quarter immediately following the quarter in which the system exceeded 
75 percent of either MCL.
    (E) The State may return a system to routine monitoring at the 
State's discretion.
    (2) Disinfectant residuals. Monitoring for disinfectant residuals 
may not be reduced.
    (3) TOC. Subpart H systems with a treated water TOC of less than 
2.0 mg/l for two consecutive years, or less than 1.0 mg/l for one year, 
may reduce monitoring for both TOC and alkalinity to one paired sample 
per plant per quarter.
    (d) Monitoring plans. (1) Each system required to monitor under 
this subpart must develop and implement a monitoring plan. The system 
shall maintain the plan and make it available for inspection by the 
State and the general public no later than 30 days following the 
applicable effective dates in Sec. 141.130(b). All Subpart H systems 
serving more than 3300 people shall submit a copy of the monitoring 
plan to the State no later than the date of the first report required 
under Sec. 141.134. The State may also require the plan to be submitted 
by any other system. The plan must include at least the following 
elements.
    (i) Locations for collecting samples for any parameters included in 
this subpart.
    (ii) How the system will calculate compliance with MCLs and MRDLs.
    (2) After review, the State may require changes in any plan 
elements.


Sec. 141.134  Reporting and recordkeeping requirements.

    (a) Systems required to sample quarterly or more frequently must 
report to the State within 10 days after the end of each quarter in 
which samples were collected. Systems required to sample less 
frequently than quarterly must report to the State within 10 days after 
the end of each monitoring period in which samples were collected.
    (b) Systems required to monitor for the following compounds must 
report the following information.
    (1) TTHMs and HAA5.
    (i) Systems monitoring for TTHMs and HAA5 under the requirements of 
Secs. 141.133(b) or (c) on a quarterly or more frequent basis must 
report at least the following information. The State may choose to 
perform paragraphs (b)(1)(i)(C) through (E) of this section in lieu of 
having the system report that information.
    (A) the number of samples taken during the last quarter,
    (B) the location, date, and result of each sample taken during the 
last quarter,
    (C) the arithmetic average of all samples taken in the last 
quarter,
    (D) the arithmetic average of the arithmetic averages reported 
under paragraph (b)(1)(i)(C) of this section for the last four 
quarters, and
    (E) whether the MCL was exceeded.
    (ii) Systems monitoring for TTHMs and HAA5 under the requirements 
of Sec. 141.133(b) or (c) less frequently than quarterly (but at least 
annually) must report at least the following information. The State may 
choose to perform paragraphs (b)(1)(ii)(C) through (D) of this section 
in lieu of having the system report that information.
    (A) the number of samples taken during the last year,
    (B) the location, date, and result of each sample taken during the 
last quarter,
    (C) the arithmetic average of all samples taken over the last year, 
and
    (D) whether the MCL was exceeded.
    (iii) Systems monitoring for TTHMs and HAA5 under the requirements 
of Sec. 141.133(c) less frequently than annually must report at least 
the following information:
    (A) the location, date, and result of the last sample taken, and
    (B) whether the MCL was exceeded.
    (2) Systems monitoring for chlorite under the requirements of 
Sec. 141.133(b) must report at least the following information. The 
State may choose to perform paragraphs (b)(2)(iii) through (iv) of this 
section in lieu of having the system report that information.
    (i) the number of samples taken each month for the last 3 months,
    (ii) the location, date, and result of each sample taken during the 
last quarter,
    (iii) for each month in the reporting period, the arithmetic 
average of all samples taken in the month, and
    (iv) whether the MCL was exceeded, and which month it was exceeded.
    (3) Systems monitoring for bromate under the requirements of 
Sec. 141.133(b) or (c) must report at least the following information. 
The State may choose to perform paragraphs (b)(3)(iii) through (iv) of 
this section in lieu of having the system report that information.
    (i) the number of samples taken during the last quarter,
    (ii) the location, date, and result of each sample taken during the 
last quarter,
    (iii) the arithmetic average of the monthly arithmetic averages of 
all samples taken in the last year, and
    (iv) whether the MCL was exceeded.
    (4) Systems monitoring for chlorine or chloramines under the 
requirements of Sec. 141.133(b) must report at least the following 
information:
    (i) the number of samples taken during each month of the last 
quarter,
    (ii) the monthly arithmetic average of all samples taken in each 
month for the last 12 months, and
    (iii) the arithmetic average of all monthly averages for the last 
12 months, and
    (iv) whether the MRDL was exceeded.
    (5) Systems monitoring for chlorine dioxide under the requirements 
of Sec. 141.133(b) must report at least the following information:
    (i) the dates, results, and locations of samples taken during the 
last quarter,
    (ii) whether the MRDL was exceeded, and
    (iii) whether the MRDL was exceeded in any two consecutive daily 
samples and whether the resulting violation was acute or nonacute.
    (6) Disinfection Byproduct Precursors and enhanced coagulation or 
enhanced softening.
    (i) Reports from systems monitoring monthly or quarterly for TOC 
under the requirements of Sec. 141.133(b)(3) and required to meet the 
enhanced coagulation or enhanced softening requirements in Sec. 141.135 
(a)(2) or (a)(3) must include at least the following information. The 
State may choose to perform paragraphs (b)(6)(i) (C) through (E) of 
this section in lieu of having the system report that information.
    (A) the number of paired (raw water and treated water, prior to 
continuous disinfection) samples taken during the last quarter,
    (B) the location, date, and result of each paired sample taken 
during the last quarter and the associated source water alkalinity,
    (C) for each month in the reporting period that paired samples were 
taken, the arithmetic average of the percent reduction of TOC for each 
paired sample and the required TOC percent removal,
    (D) calculations for determining compliance with the TOC percent 
removal requirements, as provided in Sec. 141.135(b)(1), and
    (E) whether the system is in compliance with the enhanced 
coagulation or enhanced softening percent removal requirements in 
Sec. 141.135(a) for the last four quarters.
    (ii) Systems monitoring monthly or quarterly for TOC under the 
requirements of Sec. 141.133(b) and meeting one or more of the criteria 
in Sec. 141.135(a)(1) for avoiding the requirement for enhanced 
coagulation and enhanced softening must report at least the following 
information. The State may choose to perform paragraphs (b)(6)(ii) (D) 
through (I) of this section in lieu of having the system report that 
information.
    (A) the criterion that the system is using to avoid enhanced 
coagulation or enhanced softening,
    (B) the number of paired samples taken during the last quarter,
    (C) the location, date and result of each sample (identified as 
either source water or treated water) taken during the last quarter,
    (D) the monthly arithmetic average (or quarterly sample result) of 
all treated water samples taken in the quarter and the running annual 
arithmetic average based on monthly averages (or quarterly samples) 
(for systems meeting the criterion in Sec. 141.135(a)(1)(i) for 
avoiding enhanced coagulation or enhanced softening),
    (E) the monthly arithmetic average of all treated water samples 
taken for each month of the quarter, the quarterly average of the 
monthly averages, and the running annual average of the quarterly 
averages (for systems meeting the criterion in Sec. 141.135(a)(1)(ii) 
for avoiding enhanced coagulation or enhanced softening),
    (F) the running annual average of alkalinity of the source water 
(for systems meeting the criterion in Sec. 141.135(a)(1)(ii) for 
avoiding enhanced coagulation or enhanced softening),
    (G) the running annual average for both TTHMs and THAAs (for 
systems meeting the criterion in Sec. 141.135(a)(1) (ii) or (iii) for 
avoiding enhanced coagulation or enhanced softening),
    (H) the running annual average of the amount of magnesium hardness 
removal (in mg/l) (for systems meeting the criterion in 
Sec. 141.135(a)(1)(iv) for avoiding enhanced coagulation or enhanced 
softening),
    (I) whether the system is in compliance with the particular 
criterion in Sec. 141.135(a)(1) (i) through (iv) that the system is 
using to avoid enhanced coagulation or enhanced softening.


Sec. 141.135  Treatment technique for control of Disinfection Byproduct 
Precursors (DBP).

    (a)(1) Subpart H systems using conventional filtration treatment 
(as defined in Sec. 141.2) must operate with enhanced coagulation or 
enhanced softening to achieve the TOC percent removal levels specified 
in this section unless the system meets at least one of the criteria 
listed in paragraphs (a)(1)(i) through (iv) of this section:
    (i) The system's treated TOC level, measured according to 
Sec. 141.133(b)(3), is less than 2.0 mg/l, calculated quarterly as a 
running annual average.
    (ii) The system's source water TOC level, measured as required by 
Sec. 141.133(b)(3), is less than 4.0 mg/l, calculated quarterly as a 
running annual average; the source water alkalinity, measured according 
to Sec. 141.133(a)(4), is greater than 60 mg/l, calculated quarterly as 
a running annual average; and, prior to the effective date for 
compliance in Sec. 141.130, either the TTHM and HAA5 running annual 
averages are no greater than 0.040 mg/l and 0.030 mg/l, respectively, 
or the system has made a clear and irrevocable financial commitment not 
later than the effective date for compliance in Sec. 141.30(b) to use 
of technologies that will limit the levels of TTHMs and HAA5 to no more 
than 0.040 mg/l and 0.030 mg/l, respectively. Systems must submit 
evidence of a clear and irrevocable financial commitment, in addition 
to a schedule containing milestones and periodic progress reports for 
installation and operation of appropriate technologies, to the State 
for approval not later than the effective date for compliance in 
Sec. 141.30(b) of this part. These technologies must be installed and 
operating not later than the effective date for Stage 2 of the 
Disinfectant/Disinfection Byproduct Rule. Violation of the approved 
schedule will constitute a violation of the National Primary Drinking 
Water Regulation.
    (iii) The TTHM and HAA5 running annual averages are no greater than 
0.040 mg/l and 0.030 mg/l, respectively, and the system uses only 
chlorine for disinfection.
    (iv) Systems practicing softening and removing at least 10 mg/l of 
magnesium hardness (as CaCO3), calculated quarterly as a running 
annual average, except those that use ion exchange, are not subject to 
performance criteria for the removal of TOC.
    (2) Enhanced coagulation performance requirements.
    (i) Systems not practicing softening. (A) Systems (except those 
noted in paragraph (a)(2)(i)(D) of this section) must achieve the 
percent reduction of TOC specified in paragraph (a)(2)(i)(E) of this 
section between the raw water source and the treated water prior to 
continuous disinfection, unless the State approves a system's request 
for alternative performance standards under paragraph (a)(3) of this 
section. Continuous disinfection is defined as the continuous addition 
of a chemical disinfectant for the purposes of achieving a level of 
inactivation credit to meet the minimum inactivation/removal treatment 
requirements of subpart H of this part.
    (B) Continuous disinfection does not include: the addition of a 
chemical disinfectant for filter maintenance (when applied 
intermittently), or the use of a disinfectant (other than provided for 
in paragraph (a)(2)(i)(C) of this section) as an oxidant for the 
purposes of controlling water quality problems such as iron, manganese, 
sulfides, zebra mussels, Asiatic clams, taste, and odor. In determining 
compliance with the CT requirements specified by the State, the system 
shall not include any credit for disinfectants used either for filter 
maintenance or for controlling water quality problems except as allowed 
below in paragraphs (a)(2)(i)(B)(1) through (4) of this section.
    (1) Systems may include CT credit during periods when the water 
temperature is below 5  deg.C and the TTHM and HAA5 quarterly averages 
are no greater than 0.040 mg/l and 0.030
mg/l, respectively.
    (2) Systems receiving disinfected water from a separate entity as 
their source water shall be allowed to include credit for this 
disinfectant in determining compliance with the CT requirements. If the 
TTHM and HAA5 quarterly averages are no greater than 0.040 mg/l and 
0.030 mg/l, respectively, systems may use the measured ``C'' (residual 
disinfectant concentration) and the actual contact time (as T10). 
If either the TTHM or HAA5 quarterly average is greater than 0.040 mg/l 
or 0.030 mg/l, respectively, systems must use a ``C'' (residual 
disinfectant concentration) of 0.2 mg/l or the measured value, 
whichever is lower; and the actual contact time (as T10). This 
credit shall be allowed from the disinfection feedpoint, through a 
closed conduit only, and ending at the delivery point to the treatment 
plant.
    (3) Systems using chlorine dioxide as an oxidant or disinfectant 
may include CT credit for its use prior to enhanced coagulation or 
enhanced softening if the following standards are met: the chlorine 
dioxide generator must generate chlorine dioxide on-site and minimize 
the production of chlorine as shown by complying with monitoring and 
performance standards in Sec. 141.133(b)(2)(ii)(C).
    (4) Systems using ozone and biologically active filtration may 
include CT credit for its use prior to enhanced coagulation or enhanced 
softening.
    (C) Systems not required to operate with enhanced coagulation may 
continue to include, in compliance calculations, continuous addition of 
a chemical disinfectant for the purposes of achieving a level of 
inactivation credit to meet the minimum inactivation/removal treatment 
requirements of subpart H of this part, even when such addition is also 
made for the purpose of controlling water quality problems.
    (D) Systems using ozone and biologically active filtration must 
achieve the TOC percent reduction specified in paragraph (a)(2)(i)(E) 
of this section before the addition of a residual disinfectant. Systems 
using chlorine dioxide that meet the requirements for including CT 
credit specified in paragraph (a)(2)(i)(B)(3) of this section must 
achieve the TOC percent reduction specified in paragraph (a)(2)(i)(E) 
of this section before the addition of a residual disinfectant.
    (E) Required TOC reductions, indicated in the table below, are 
based upon specified source water parameters measured in accordance 
with Sec. 141.133(b)(3). 

  Required Removal of TOC by Enhanced Coagulation for Subpart H Systems 
                    Using Conventional Treatment\2\                     
------------------------------------------------------------------------
                                         Source water alkalinity (mg/l) 
                                        --------------------------------
 Source water total organic carbon (mg/                         >120\1\ 
                  l)                        0-60     >60-120   (percent)
                                         (percent)  (percent)           
------------------------------------------------------------------------
>2.0-4.0...............................      40.0       30.0       20.0 
>4.0-8.0...............................      45.0       35.0       25.0 
>8.0...................................      50.0       40.0      30.0  
------------------------------------------------------------------------
\1\Systems practicing softening must meet the TOC removal requirements  
  in this column.                                                       
\2\Systems meeting at least one of the conditions in Sec. 141.135(a)(1) 
  (i) through (iv) are not required to operate with enhanced            
  coagulation.                                                          

    (ii) Systems practicing softening. (A) Systems (except those noted 
in paragraph (a)(2)(ii)(D) of this section) must achieve the percent 
reduction of TOC specified in paragraph (a)(2)(ii)(E) of this section 
between the raw water source and treated water prior to continuous 
disinfection. Continuous disinfection is defined as the continuous 
addition of a chemical disinfectant for the purposes of achieving a 
level of inactivation credit to meet the minimum inactivation/removal 
treatment requirements of subpart H of this section.
    (B) Continuous disinfection does not include: the addition of a 
chemical disinfectant for filter maintenance (when applied 
intermittently), or the use of a disinfectant (other than provided for 
in paragraph (a)(2)(ii)(C) of this section) as an oxidant for the 
purposes of controlling water quality problems such as iron, manganese, 
sulfides, zebra mussels, Asiatic clams, taste, and odor. In determining 
compliance with the CT requirements in subpart H of this part, the 
system shall not include any credit for disinfectants used either for 
filter maintenance or for controlling water quality problems except as 
allowed by paragraphs (a)(2)(ii)(B) (1) through (4) of this section.
    (1) Systems may include CT credit during periods when the water 
temperature is below 5 deg.C and the TTHM and HAA5 quarterly averages 
are no greater than 0.040 mg/l and 0.030 mg/l, respectively.
    (2) Systems receiving disinfected water from a separate entity as 
their source water shall be allowed to include credit for this 
disinfectant in determining compliance with the CT requirements. If the 
TTHM and HAA5 quarterly averages are no greater than 0.040 mg/l and 
0.030 mg/l, respectively, systems may use the measured ``C'' (residual 
disinfectant concentration) and the actual contact time (as T10). 
If either the TTHM or HAA5 quarterly average is greater than 0.040 mg/l 
or 0.030 mg/l, respectively, systems must use a ``C'' (residual 
disinfectant concentration) of 0.2 mg/l or the measured value, 
whichever is lower; and the actual contact time (as T10). This 
credit shall be allowed from the disinfection feed point, through a 
closed conduit only, and ending at the delivery point to the treatment 
plant.
    (3) Systems using chlorine dioxide as an oxidant or disinfectant 
may include CT credit for its use prior to enhanced coagulation or 
enhanced softening if the following standards are met: the chlorine 
dioxide generator must generate chlorine dioxide on-site and minimize 
the production of chlorine as shown by complying with monitoring and 
performance standards in Sec. 141.133(b)(2)(ii)(C).
    (4) Systems using ozone and biologically active filtration may 
include CT credit for its use prior to enhanced coagulation or enhanced 
softening.
    (C) Systems not required to operate with enhanced softening may 
continue to include, in compliance calculations, continuous addition of 
a chemical disinfectant for the purposes of achieving a level of 
inactivation credit to meet the minimum inactivation/ removal treatment 
requirements of subpart H of this part, even when such addition is also 
made for the purpose of controlling water quality problems.
    (D) Systems using ozone and biologically active filtration must 
achieve the TOC percent reduction specified in paragraph (a)(2)(ii)(E) 
of this section before the addition of a residual disinfectant. Systems 
using chlorine dioxide that meet the requirements for including CT 
credit specified in paragraph (a)(2)(ii)(B)(3) of this section must 
achieve the TOC percent reduction specified in paragraph (a)(2)(ii)(E) 
of this section before the addition of a residual disinfectant.
    (E) Required TOC reductions are indicated in the table in paragraph 
(a)(2)(i)(E) of this section. Systems practicing softening are required 
to meet the percent reductions in the far-right column (Source water 
alkalinity >120 mg/l) for the specified source water TOC.
    (3) Non-softening Subpart H conventional treatment systems that 
cannot achieve the TOC removals required by paragraph (a)(2) of this 
section due to water quality parameters or operating conditions must 
apply to the State, within three months of failure to achieve the TOC 
removals required by paragraph (a)(2) of this section, for alternative 
performance criteria. If the State approves the alternate performance 
criteria, the State may make those criteria retroactive for the 
purposes of determining compliance. If the State does not approve the 
alternate performance criteria, the system must meet the TOC removals 
contained in paragraph (a)(2)(i)(E) of this section.
    (i) Such application must include, as a minimum, results of bench- 
or pilot-scale testing for alternate enhanced coagulation level. 
``Alternate enhanced coagulation level'' is defined as coagulation at a 
coagulant dose and pH as determined by the method outlined in paragraph 
(a)(3)(ii) of this section such that an incremental addition of 10 mg/l 
of alum (or equivalent amount of ferric salt) results in a TOC removal 
of 0.3 mg/l. The percent removal of TOC at this point on the 
``coagulant dose versus TOC removal'' curve is then defined as the 
minimum TOC removal required for the system. Once approved by the 
State, this minimum requirement supersedes the minimum TOC removal 
required by the table in paragraph (a)(2)(i)(E) of this section. This 
requirement will be effective until such time as the State approves a 
new value based on the results of a new bench- and pilot-scale test 
triggered by changes in source water quality. Failure to achieve State-
set alternative minimum TOC removal levels is a violation of paragraph 
(a)(3) of this section.
    (ii)(A) Bench- or pilot-scale testing of enhanced coagulation shall 
be conducted by using representative water samples and adding 10 mg/l 
increments of alum (or equivalent amounts of ferric salt) until the pH 
is reduced to a level less than or equal to the enhanced coagulation 
maximum pH shown in the table below. 

                    Enhanced Coagulation Maximum pH                     
------------------------------------------------------------------------
                                                                 Maximum
                  Alkalinity (mg/l as CaCO3)                        pH  
------------------------------------------------------------------------
0-60...........................................................      5.5
>60-120........................................................      6.3
>120-240.......................................................      7.0
>240...........................................................     7.5 
------------------------------------------------------------------------

    (B) For waters with alkalinities of less than 60 mg/l for which 
addition of small amounts of alum or equivalant addition of iron 
coagulant drives the pH below 5.5 before significant TOC removal 
occurs, the system must add necessary chemicals to maintain the pH 
between 5.3 and 5.7 in samples until the TOC removal of 0.3 mg/l per 10 
mg/l alum added or equivalant addition of iron coagulant is reached.
    (iii) The system may operate at any coagulant dose or pH necessary 
(consistent with other NPDWRs) to achieve the minimum TOC percent 
removal determined under paragraph (a)(3)(i) of this section.
    (iv) If the TOC removal is consistently less than 0.3 mg/l of TOC 
per 10 mg/l of incremental alum dose at all dosages of alum or 
equivalant addition of iron coagulant, the water is deemed to contain 
TOC not amenable to enhanced coagulation. The system may then apply to 
the State for a waiver of enhanced coagulation requirements.
    (b) Compliance calculations. (1) Subpart H systems other than those 
identified in paragraph (b)(2) of this section shall comply with the 
TOC compliance requirements contained in paragraph (a) of this section. 
Systems shall calculate compliance quarterly by the following method:
    (i) Determine actual monthly TOC percent removal, equal to: (1-
(treated water TOC/source water TOC))  x  100.
    (ii) Determine the required monthly TOC percent removal (from 
either the table in paragraph (a)(2)(i)(E) of this section or from 
paragraph (a)(3) of this section).
    (iii) Divide paragraph (b)(1)(i) of this section by paragraph 
(b)(2)(ii) of this section.
    (iv) Add together the results of paragraph (b)(1)(iii) of this 
section for the last 12 months and divide by 12.
    (v) If paragraph (b)(1)(iv) of this section <1.00, the system is 
not in compliance with the TOC percent removal requirements.
    (2) Subpart H systems using conventional treatment but not 
operating enhanced coagulation must comply with the DBP precursor 
treatment technique identified in paragraphs (a)(1) (i) through (iv) of 
this section.
    (c) Treatment technique requirements for Disinfection Byproduct 
Precursors. The Administrator identifies the following as treatment 
techniques to control the level of disinfection byproduct precursors in 
drinking water treatment and distribution systems: For Subpart H 
systems using conventional treatment, enhanced coagulation or enhanced 
softening.
PART 142--NATIONAL PRIMARY DRINKING WATER REGULATIONS 
IMPLEMENTATION 
    1. The authority citation for Part 141 continues to read as 
follows:

    Authority: 42 U.S.C. 300g, 300g-1, 300g-2 300g-3, 300g-4, 300g-
5, 300g-6, 300j-4 and 300j-9.
    2. Section 142.14 is amended by adding paragraphs (d)(12) and 
(d)(13) to read as follows: 
Sec. 142.14  Records kept by states.

* * * * *
    (d) * * *
    (12) Records of the currently applicable or most recent State 
determinations, including all supporting information and an explanation 
of the technical basis for each decision, made under the following 
provisions of 40 CFR part 141, subpart L for the control of 
disinfectants and disinfection byproducts. These records must also 
include interim measures toward installation.
    (i) States must keep records of systems that are installing GAC or 
membrane technology in accordance with Sec. 141.64(d)(3). These records 
must include the date by which the system is required to have completed 
installation.
    (ii) States must keep records of systems that are required, by the 
State, to meet alternative minimum TOC removal requirements in 
accordance with Sec. 141.135(a)(3). Records must include the 
alternative limits and rationale for establishing such limits.
    (iii) States must keep records of Subpart H systems using 
conventional treatment meeting any of the enhanced coagulation or 
enhanced softening exemption criteria in Sec. 141.135(a)(1).
    (iv) States must keep a register of qualified operators that have 
met the State requirements developed under Sec. 142.16(f)(2).
    (13) Records of systems with multiple wells considered to be one 
treatment plant in accordance with Sec. 141.133(b)(1).
* * * * *
    3. Section 142.15 is amended by adding paragraphs (c)(5) through 
(c)(8) to read as follows:


Sec. 142.15  Reports by states.

* * * * *
    (c) * * *
    (5) Reports of systems that must meet alternative minimum TOC 
removal levels and the alternate performance criteria specified in 
Sec. 141.135(a)(3).
    (6) Any extensions granted for compliance with MCLs in Sec. 141.64 
as allowed by Sec. 141.64(c)(3) and the date by which compliance must 
be achieved.
    (7) A list of systems required to monitor for various disinfectants 
and disinfection byproducts.
    (8) A list of all systems using multiple ground water wells which 
draw from the same aquifer and are considered a single source for 
monitoring purposes.
* * * * *
    4. Section 142.16 is amended by adding paragraph (f) to read as 
follows:


Sec. 142.16  Special primacy requirements.

* * * * *
    (f) Requirements for States to adopt 40 CFR part 141, subpart L. In 
addition to the general primacy requirements elsewhere in this part, 
including the requirement that State regulations be at least as 
stringent as federal requirements, an application for approval of a 
State program revision that adopts 40 CFR part 141, subpart L, must 
contain a description of how the State will accomplish the following 
program requirements:
    (1) Section 141.64(d)(3) (interim treatment requirements). 
Determine the interim treatment requirements for those systems electing 
to install GAC or membrane filtration and granted additional time to 
comply with Sec. 141.64(a).
    (2) Section 141.130(c) (qualification of operators). Qualify 
operators of community and nontransient-noncommunity public water 
systems subject to this regulation. Qualification requirements 
established for operators of systems subject to 40 CFR part 141, 
Subpart H--Filtration and Disinfection, may be used in whole or in part 
to establish operator qualification requirements for meeting 
requirements of subpart L of this part if the State determines that the 
requirements of subpart H of this part are appropriate and applicable 
for meeting requirements of subpart L of this part.
    (3) Approve alternative TOC removal levels, as allowed under the 
provisions of Sec. 141.135(a).
    (4) Section 141.133(a)(2) (State approval of parties to conduct 
analyses). Approve parties to conduct pH, alkalinity, temperature, and 
residual disinfectant concentration measurements. The State's process 
for approving parties performing water quality measurements for systems 
subject to requirements of subpart H of this part may be used for 
approving parties measuring water quality parameters for systems 
subject to requirements of subpart L of this part, if the State 
determines the process is appropriate and applicable.
    (5) Section 144.133(a)(2) (DPD colorimetric test kits). Approve DPD 
colorimetric test kits for free and total chlorine measurements. 
Approval granted under Sec. 141.74(a)(5) for the use of such test kits 
for free chlorine testing would be considered acceptable approval for 
the use of DPD test kits in measuring free chlorine residuals as 
required in subpart L of this part.
    (6) Section 141.133(b)(3)(ii)(C) (multiple wells as a single 
source). Define the criteria to determine if multiple wells are being 
drawn from a single aquifer and therefore be considered a single source 
for compliance with monitoring requirements.

[FR Doc. 94-17651 Filed 7-28-94; 8:45 am]
BILLING CODE 6560-50-P