[Federal Register Volume 63, Number 40 (Monday, March 2, 1998)]
[Notices]
[Pages 10274-10287]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-5313]



[[Page 10273]]

_______________________________________________________________________

Part III





Environmental Protection Agency





_______________________________________________________________________



Announcement of the Drinking Water Contaminant Candidate List; Notice

  Federal Register / Vol. 63, No. 40 / Monday, March 2, 1998 / 
Notices  

[[Page 10274]]



ENVIRONMENTAL PROTECTION AGENCY

[W-97-11; FRL-5972-5]


Announcement of the Drinking Water Contaminant Candidate List

AGENCY: U.S. Environmental Protection Agency (EPA).

ACTION: Notice.

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

SUMMARY: The Safe Drinking Water Act (SDWA), as amended in 1996, 
requires the Environmental Protection Agency (EPA) to publish a list of 
contaminants which, at the time of publication, are not subject to any 
proposed or promulgated national primary drinking water regulation 
(NPDWR), that are known or anticipated to occur in public water systems 
and which may require regulations under the SDWA [section 1412(b)(1)]. 
The SDWA, as amended, specifies that EPA must publish the first list of 
contaminants (Drinking Water Contaminant Candidate List, or CCL) not 
later than 18 months after the date of enactment, i.e., by February 
1998, and every five years thereafter. The SDWA, as amended, also 
specifies that the CCL must be published after consultation with the 
scientific community, and after notice and opportunity for public 
comment.
    A draft CCL was published in the October 6, 1997 edition of the 
Federal Register (62 FR 52193) in order to seek comment from the 
public. Seventy-one comments were received. The comments have been 
reviewed and considered in creating the final CCL presented in today's 
notice. The CCL is divided among contaminants which are identified as 
priorities for drinking water research, those which need additional 
occurrence data, and contaminants which are priorities for 
consideration for the development of future drinking water regulations 
and guidance. The CCL includes 50 chemical and 10 microbiological 
contaminants/contaminant groups.
    The full record for this notice has been established under docket 
number W-97-11, and includes supporting documentation as well as all 
comments received in response to the October 6, 1997 notice. The full 
record is available for inspection from 9:00 a.m. to 4:00 p.m., Monday 
through Friday, excluding legal holidays at the Office of Water Docket, 
East Tower Basement, USEPA Headquarters, 401 M Street, S.W., 
Washington, D.C. For access to the docket, please call 202-260-3027 to 
schedule an appointment.

FOR FURTHER INFORMATION CONTACT: For general information, please 
contact the EPA Safe Drinking Water Hotline. The toll-free number is 
800-426-4791. The Hotline operates from 9:00 a.m. to 5:30 p.m., Monday 
through Friday, excluding legal holidays. For specific information on 
the Contaminant Candidate List and the contaminant identification 
process, please contact Ms. Evelyn Washington, at the U.S. 
Environmental Protection Agency, Office of Ground Water and Drinking 
Water, Mailcode 4607, Washington, D.C. 20460, phone: 202-260-3029, fax: 
202-260-3762, email: [email protected].

EPA Regional Offices

I. JFK Federal Bldg., Room 2203, Boston, MA 02203. Phone: 617-565-3602, 
Jerry Healey
II. 290 Broadway, Room 2432, New York, NY 10007-1866. Phone: 212-637-
3880, Walter Andrews
III. 841 Chestnut Street, Philadelphia, PA 19107. Phone: 215-566-5775, 
Jeff Hass
IV. 61 Forsyth Street, SW, Atlanta GA 30303. Phone: 404-562-9480, 
Janine Morris
V. 77 West Jackson Blvd., Chicago, IL 60604-3507. Phone: 312-886-4239, 
Kim Harris
VI. 1445 Ross Avenue, Dallas, TX 75202. Phone: 214-665-7150, Larry 
Wright
VII. 726 Minnesota Ave., Kansas City, KS 66101. Phone: 913-551-7410, 
Stan Calow
VIII. One Denver Place, 999 18th Street, suite 500, Denver, CO 80202. 
Phone: 303-312-6627, Rod Glebe
IX. 75 Hawthorne Street, San Francisco, CA 94105. Phone: 415-744-1884, 
Bruce Macler
X. 1200 Sixth Avenue, Seattle, WA 98101. Phone: 206-553-1893, Larry 
Worley

SUPPLEMENTARY INFORMATION:

Abbreviations Used in This Notice

AMA--American Medical Association
AWWARF--American Water Works Association Research Foundation
CAA--Clean Air Act
CASRN--Chemical Abstract Services Registry Number
CCL--Contaminant Candidate List
CERCLA--Comprehensive Environmental Response, Comprehensive and 
Liability Act
CPVC--Chlorinated Polyvinyl Chloride
DBPR--Microbiological and Disinfection Byproducts Regulations
DWEL--Drinking Water Equivalent Level
DWPL--Drinking Water Priority List
EDSTAC--Endocrine Disruptor Screening and Testing Advisory Committee
EPA--Environmental Protection Agency
ESWTR--Enhanced Surface Water Treatment Rule
FIFRA--Federal Insecticide, Fungicide, and Rodenticide Act
FQPA--Food Quality Protection Act
FR--Federal Register
GWDR--Ground Water
GW--Ground Water Disinfection Rule
IRIS--Integrated Risk Information System
MCL--Maximum Contaminant Level
MCLG--Maximum Contaminant Level Goal
MTBE--Methyl-t-butyl Ether
NAS--National Academy of Sciences
NAWQA--National Water Quality Assessment Program
NDWAC--National Drinking Water Advisory Council
NOAEL--No-Observed-Adverse-Effect-Level
NPDWR--National Primary Drinking Water Regulations
NPL--National Priority List
NSF--National Sanitation Foundation
OPP--EPA's Office of Pesticide Programs
OPPTS--EPA's Office of Pollution Prevention and Toxic Substances
PGWDW--Pesticides in Ground Water Database
PVC--Polyvinyl Chloride
RfD--Reference Dose
SAB--EPA's Science Advisory Board
SAP--Science Advisory Panel
SDWA--Safe Drinking Water Act
SWTR--Surface Water Treatment Rule
TTHM--total trihalomethane
TSCA--Toxic Substances Control Act
UCMR--Unregulated Contaminant Monitoring Regulations
WHO--World Health Organization

Table of Contents

I. Background
II. Drinking Water Contaminant Candidate List
    Table 1. Drinking Water Contaminant Candidate List
III. Changes Made to Create the Final Contaminant Candidate List 
Based on Comments Received on the Draft
    A. Acetochlor, Metolachor, and Alachlor ESA
    B. Acetone and Cumene
    C. Aldicarbs and Nickel
    D. Aluminum
    E. Dimethoate
    F. DTBB
    G. Methyl Bromide
    H. Microorganisms
    I. MTBE
    J. Organotins
    K. Perchlorate
    L. Rhodamine WT
    M. Sodium
    N. Triazines
    O. Zinc
IV. Continuing Work in Preparation for Future CCLs
    A. Pesticides Deferred
    B. Endocrine Disruptors

[[Page 10275]]

    C. Development of the Contaminant Selection Process
V. Data, Research Needs and Next Steps
    Table 2. Next Steps for the CCL
VI. Other Requirements
VII. References

I. Background

    The Safe Drinking Water Act (SDWA), as amended in 1996, requires 
the Environmental Protection Agency (EPA) to publish a list of 
contaminants that are known or anticipated to occur in public water 
systems, and which may require regulation under the SDWA [section 
1412(b)(1)]. The SDWA, as amended, also specifies that EPA must publish 
this list of contaminants (Drinking Water Contaminant Candidate List, 
or CCL) not later than 18 months after the date of enactment (i.e., by 
February 1998), and publish a new CCL every five years thereafter. The 
SDWA requires that the list of contaminants include those which, at the 
time of publication, are not subject to any proposed or promulgated 
national primary drinking water regulation (NPDWR). The list must be 
published after consultation with the scientific community, including 
the Science Advisory Board, after notice and opportunity for public 
comment, and after consideration of the occurrence database established 
under section 1445(g). The unregulated contaminants considered for the 
list must include, but not be limited to, substances referred to in 
section 101(14) of the Comprehensive Environmental Response, 
Compensation, and Liability Act of 1980 (CERCLA), and substances 
registered under the Federal Insecticide, Fungicide, and Rodenticide 
Act (FIFRA).
    Today's notice is being published pursuant to the requirements in 
section 1412(b)(1). The contaminants included are not subject to any 
proposed or promulgated national primary drinking water regulation, are 
known or anticipated to occur in public water systems, and may require 
regulation under the SDWA. During the development of the CCL, the 
Agency consulted with stakeholders, including the National Drinking 
Water Advisory Council's (NDWAC) Working Group on Occurrence & 
Contaminant Selection, which includes microbiologists, toxicologists, 
public health scientists, and engineers, and consulted with other 
members of the scientific community including the Science Advisory 
Board (SAB). A draft CCL was published in the October 6, 1997 edition 
of the Federal Register (62 FR 52193) to seek comment from the public.
    Seventy-one comments were received in response to the notice on the 
draft CCL; 66 comments were received by the due date, and an additional 
5 comments were received later. The majority were supportive of the CCL 
process and the development of this first CCL, and provided suggestions 
on specific contaminants that should be included on, or excluded from, 
the CCL. The comments, data, and information provided were taken into 
consideration in preparing the final CCL presented in today's notice. 
Modifications to the CCL presented in today's notice were also reviewed 
by the National Drinking Water Advisory Council (NDWAC), and the NDWAC 
Working Group on Occurrence & Contaminant Selection.
    The Agency believes the CCL presented in today's notice is a first 
step toward improving risk assessment, strengthening science and data, 
and achieving better decision-making and future priority setting. The 
CCL is designed to be responsive to each of the requirements noted 
above of the SDWA, as amended, and is consistent with the goals of the 
Drinking Water Redirection Strategy. The CCL is the result of a 
concerted effort of screening a larger set of contaminants to a subset 
of those of most concern.
    This final CCL will be the primary source of priority contaminants 
for the Agency's drinking water program. The list is divided among 
priorities for drinking water research, priorities for additional 
occurrence data collection, and those contaminants which are priorities 
for consideration for Agency determinations of whether or not to 
regulate specific contaminants by August 2001.
    The SDWA does not preclude the Agency from taking action on a 
contaminant not included on the CCL. The EPA can decide to monitor, 
develop guidance, or conduct research, for a contaminant not included 
on the CCL. The Agency can also develop regulations to address an 
urgent threat to public health under SDWA [section 1412(b)(1)(D)]. The 
Agency is also not precluded from modifying the CCL prior to the due 
date of the next CCL, which is February 2003.

II. Drinking Water Contaminant Candidate List

    The following table includes the contaminants, microbiological and 
chemical, presented as the Drinking Water Contaminant Candidate List. 
The chemical contaminants in the table are identified by name and 
Chemical Abstracts Service Registry Number (CASRN). The CCL includes 50 
chemical and 10 microbiological contaminants/contaminant groups.

           Table 1.--Drinking Water Contaminant Candidate List          
------------------------------------------------------------------------
                      Microbiological contaminants                      
-------------------------------------------------------------------------
Acanthamoeba (guidance expected for contact lens wearers)               
Adenoviruses                                                            
Aeromonas hydrophila                                                    
Caliciviruses                                                           
Coxsackieviruses                                                        
Cyanobacteria (blue-green algae), other freshwater algae, and their     
 toxins                                                                 
Echoviruses                                                             
Helicobacter pylori                                                     
Microsporidia (Enterocytozoon & Septata)                                
Mycobacterium avium intracellulare (MAC)                                
------------------------------------------------------------------------


                                                                        
                  Chemical contaminants                        CASRN    
1,1,2,2-tetrachloroethane...............................         79-34-5
1,2,4-trimethylbenzene..................................         95-63-6
1,1-dichloroethane......................................         75-34-3
1,1-dichloropropene.....................................        563-58-6
1,2-diphenylhydrazine...................................        122-66-7
1,3-dichloropropane.....................................        142-28-9
1,3-Dichloropropene.....................................        542-75-6

[[Page 10276]]

                                                                        
2,4,6-trichlorophenol...................................         88-06-2
2,2-dichloropropane.....................................        594-20-7
2,4-dichlorophenol......................................        120-83-2
2,4-dinitrophenol.......................................         51-28-5
2,4-dinitrotoluene......................................        121-14-2
2,6-dinitrotoluene......................................        606-20-2
2-methyl-Phenol (o-cresol)..............................         95-48-7
Acetochlor..............................................      34256-82-1
Alachlor ESA & other acetanilide pesticide degradation                  
 products...............................................             N/A
Aldrin..................................................        309-00-2
Aluminum................................................       7429-90-5
Boron...................................................       7440-42-8
Bromobenzene............................................        108-86-1
DCPA mono-acid degradate................................        887-54-7
DCPA di-acid degradate..................................       2136-79-0
DDE.....................................................         72-55-9
Diazinon................................................        333-41-5
Dieldrin................................................         60-57-1
Disulfoton..............................................        298-04-4
Diuron..................................................        330-54-1
EPTC (s-ethyl-dipropylthiocarbamate)....................        759-94-4
Fonofos.................................................        944-22-9
Hexachlorobutadiene.....................................         87-68-3
p-Isopropyltoluene (p-cymene)...........................         99-87-6
Linuron.................................................        330-55-2
Manganese...............................................       7439-96-5
Methyl bromide..........................................         74-83-9
Methyl-t-butyl ether (MTBE).............................       1634-04-4
Metolachlor.............................................      51218-45-2
Metribuzin..............................................      21087-64-9
Molinate................................................       2212-67-1
Naphthalene.............................................         91-20-3
Nitrobenzene............................................         98-95-3
Organotins..............................................             N/A
Perchlorate.............................................             N/A
Prometon................................................       1610-18-0
RDX.....................................................        121-82-4
Sodium..................................................       7440-23-5
Sulfate.................................................      14808-79-8
Terbacil................................................       5902-51-2
Terbufos................................................      13071-79-9
Triazines & degradation products of triazines                           
 (including, but not limited to Cyanazine 21725-46-2,                   
 and atrazine-desethyl 6190-65-4).......................                
Vanadium................................................       7440-62-2
------------------------------------------------------------------------

III. Changes Made to Create the Final Contaminant Candidate List Based 
on Comments Received on the Draft

    The criteria which EPA used to select the contaminants for the CCL 
are described in detail in the October 6, 1997 notice (62 FR 52193) on 
the draft CCL. In general, the criteria for including a contaminant on 
the CCL consisted of determinations of whether the occurrence, or 
anticipated occurrence, of a contaminant was likely at levels of 
concern to human health. The October notice solicited input from the 
public and specifically requested comments on (1) the approach EPA used 
to create the list and suggestions on the process for future lists; (2) 
contaminants on the list; (3) data needs categories; and (4) whether to 
include perchlorate on the CCL.
    EPA received 71 comments, 66 by the deadline and 5 additional late 
comments. The majority of comments were supportive of the CCL process, 
and the development of this first CCL. Comments were received from a 
number of segments of the stakeholder community, including equipment 
manufacturers, consultants, chemical manufacturers, trade associations, 
environmental groups, state regulatory agencies, water utilities, and 
private citizens. Commenters provided data and information on specific 
contaminants and included suggestions on the process for future CCL 
development, as well as feedback on the data and research needs 
indicated for the contaminants on the CCL. Roughly 60 issues were 
raised by the comments, both contaminant-specific and related to the 
development of a process for identifying contaminants for future CCLs. 
The comments, data, and information provided were taken into 
consideration in preparing the final CCL presented in today's notice. 
Proposed changes to the CCL were also reviewed by the NDWAC Working 
Group on Occurrence & Contaminant Selection, and the NDWAC full-
Council.
    A number of comments indicated that many did not understand the 
function of the CCL. The CCL is not the list of contaminants for which 
the Agency has made a determination to regulate. The CCL is a list of 
priority contaminants (not otherwise addressed) for drinking water 
program activities which include those for: (1) drinking water 
research, (2) monitoring, (3) guidance development, as well as those 
for (4) selection and regulatory determination by the year 2001. The 
next steps likely to occur with regard to any given contaminant are 
discussed in more detail in Section V in today's notice.
    Despite the support expressed for the development of this first 
CCL, commenters advised that more robust criteria are needed for future 
CCL

[[Page 10277]]

development and for contaminant selection. The Agency agrees with these 
commenters and will continue to work to develop a contaminant 
identification process for chemical and microbiological contaminants to 
be used to develop future CCLs. Section IV.C. of today's notice 
provides additional information on how the Agency plans to develop 
these processes.
    The following is a summary of the significant public comments 
received that led to changes to the CCL. The remainder of this section 
responds to the more significant comments, and indicates how the CCL 
was changed in response to these comments. A complete report of 
responses to all comments received on the notice of the draft CCL can 
be found in the docket.

A. Acetochlor, Metolachor, and Alachlor ESA

    A number of commenters supported the inclusion of acetochlor, 
metolachor, and alachlor ESA (the sulfonic acid degradate of alachlor) 
on the CCL, while others indicated that they should not be included. 
Three commenters indicated that acetochlor should have low priority for 
regulation, and that the Agency should consider deleting it from the 
CCL. The commenters argued that under the Acetochlor Registration 
Project, the EPA has established very conservative triggers for its 
potential cancellation of use as a pesticide. The commenters went on to 
indicate that in 175 community water systems monitored since March 
1995, acetochlor detections have occurred in only 20% of samples, that 
no system had an average mean concentration exceeding 2 ppb, which is 
one of the triggers, and that additional monitoring data will indicate 
that concentrations found in public water systems are far below 140 
ppb.
    One commenter argued that metolachlor should not be included on the 
CCL. That although it is detected in water, it is rarely above the 
lifetime health advisory level of 70 ppb, and the detections in most 
cases are associated with point sources. The commenter stated that data 
collected under the Unregulated Contaminant Monitoring Regulations is 
available on a state-by-state basis, and the results reported from 3 
States also indicate no detections above the lifetime health advisory 
level of 70 ppb. Another commenter suggested that alachlor ESA should 
not be included on the CCL, as it, too, should have a low priority for 
regulation based on concentrations in water not exceeding 6370 ppb.
    Other commenters argued that metolachor, acetochlor, and alachlor 
ESA should be kept on the CCL since States reported finding these 
contaminants in water. One commenter added that the metolachor ESA and 
metolachor OA degradation products should be included on the CCL also, 
since all have been found in ground water.
    One commenter also pointed out that metolachlor, acetochlor, and 
alachlor do not have a common mode of action, and thus cannot be 
grouped together to develop a single standard to address all 
acetanilide pesticides.
EPA Response
    The Agency disagrees with the commenters who believe it is 
inappropriate to include acetochlor, metolachor, and alachlor ESA on 
the CCL. By including these contaminants on the CCL, the Agency has not 
yet made a determination with respect to regulating any of them. In 
light of the reported occurrences of these contaminants in water, the 
drinking water program needs to determine what action is appropriate to 
ensure the protection of public health even if the action may be only 
the development of guidance for States and public water systems. The 
Office of Water will evaluate further the available toxicity and 
occurrence information for these pesticides in order to determine 
appropriate concentration values adequate to protect against risks 
associated with exposure through drinking water. With respect to 
metolachlor specifically, the Agency believes it is appropriate to 
include it on the CCL. The data collected under the Unregulated 
Contaminant Monitoring Regulations is being collected from all States 
and will be compiled and evaluated as additional information is 
collected and evaluated for all contaminants on the CCL.
    The Agency agrees that it is appropriate to include other 
acetanilide pesticide degradation products in addition to alachlor ESA, 
since they, too, have been found in ground water. However, at this 
time, the Agency has not yet determined which are the most important to 
include; therefore, EPA has decided to include alachlor ESA & other 
acetanilide pesticide degradation products as a group of contaminants 
on the CCL. The determination of which degradation products are of most 
concern will be determined as we learn more about these contaminants as 
a class. The Agency also agrees with the commenter that because 
alachlor, acetochlor, and metolachlor do not have a common mode of 
action, they are not at this time appropriate contaminants to be 
grouped together to develop a single approach addressing all 
acetanilide pesticides. Contrary to earlier statements, acetanilide 
pesticides are not likely candidates for development of ``total 
standards'' in the foreseeable future. However, the Agency is 
interested in the development of ``total standards,'' or standards that 
address classes of compounds, where appropriate, and as the state of 
the science improves.

B. Acetone and Cumene

    Two commenters remarked that outdated oral reference doses (RfD) 
from the Integrated Risk Information System (IRIS) for acetone and 
cumene were used in developing the draft CCL and that analyses should 
be done with current information. The Chemical Manufacturers 
Association's Acetone Panel submitted comments about acetone and 
recommended that it should not be included on the final CCL. The reason 
given, in addition to the outdated RfD, was that outdated information 
concerning levels of acetone detected in the environment, including 
data from old National Priority List (NPL) sites had been used in the 
Agency's evaluation and that this did not provide a reliable basis for 
estimating likely levels of acetone in drinking water or sources of 
drinking water. The Panel believes more relevant information shows that 
acetone is unlikely to be present in drinking water or sources of 
drinking water at levels of concern.
    The Chemical Manufacturers Association's Cumene Panel submitted 
comments about cumene and recommended that it should not be included on 
the final CCL. The reason given, in addition to the outdated RfD, was 
that concentrations of cumene detected in the environment were not at 
levels of concern, and it is rarely detected in drinking water or 
sources of drinking water.
EPA Response
    The Agency agrees with the commenters that the current IRIS values 
should be used in the evaluations for developing the CCL. The updated 
value for acetone has not been posted on the IRIS database; however, 
the Agency has acknowledged the new value of 0.9 mg/kg/day previously 
in a notice concerning section 313 of the Emergency Planning and 
Community Right-to-Know Act (60 FR 31644). The updated value for cumene 
has been posted on the IRIS database, and is 0.1 mg/kg/day.
    The occurrence data from the U.S. Geological Survey's National 
Water Quality Assessment Program (NAWQA) indicates that acetone was 
detected at a

[[Page 10278]]

frequency of greater than 10% of the samples collected; however, the 
concentrations found did not exceed their reporting level of 0.2 
g/l. When the current IRIS values are used for acetone and 
cumene, and compared to the available occurrence data, neither meets 
the criteria set forth for identifying contaminants for the CCL, and 
therefore, acetone and cumene have been removed from the CCL.

C. Aldicarbs and Nickel

    EPA received a number of comments encouraging the inclusion of 
aldicarbs and nickel on the CCL, while a few commented that it was 
inappropriate to include these contaminants, despite the Agency's 
existing statutory obligation with regard to these contaminants.
EPA Response
    In the case of aldicarbs (aldicarb, aldicarb sulfoxide, aldicarb 
sulfone) and nickel, the Agency has determined that it is inappropriate 
to include these contaminants on the CCL. The 1996 Amendments to SDWA 
explicitly reenacted the requirements for regulation of these 
contaminants [section 1412 (b)(2)]. In response to an administrative 
petition from the manufacturer Rhone-Poulenc, the Agency issued an 
administrative stay of the effective date of the maximum contaminant 
levels (MCLs) for aldicarbs, and they never became effective. NPDWRs 
for nickel were promulgated on July 17, 1992, but the MCL was later 
vacated and remanded in response to a lawsuit from the Nickel 
Development Institute and other industry parties.
    The Agency intends to complete regulatory action for both aldicarbs 
and nickel. The time-frame of completing action for these contaminants 
is likely to be the same time-frame required by SDWA for regulatory 
determinations for contaminants on the CCL. When considering the nature 
and type of work necessary to complete action on these contaminants, 
the effort for aldicarbs is anticipated to be less extensive than that 
required for nickel; thus, regulations for aldicarbs are likely to be 
completed prior to regulations for nickel.

D. Aluminum

    EPA received four comments recommending that aluminum not be 
included on the CCL. One commenter stated that regulations would be 
premature at this time, due to the need for additional information on 
the risk of adverse effects and occurrence in drinking water. Other 
commenters argued that there was no scientific health basis for the 
inclusion of aluminum on the CCL, and that the World Health 
Organization (WHO) stated in 1995 that there is an inadequate basis for 
revising existing guidelines for aluminum below the 200 g/l 
standard used to control taste and odor effects. The commenters also 
explained that the source of aluminum in drinking water is primarily 
linked to the use of alum as a flocculent in water treatment, and the 
implications of regulating aluminum at lower levels could cause 
deleterious effects on water quality.
    An additional commenter felt that aluminum should be included on 
the CCL based on new literature on the relationship of aluminum to 
Alzheimer's Disease, elderly mental impairment, and childhood learning 
disabilities. The commenter disagreed with the need for additional data 
on the health impacts of aluminum. The commenter contends that much 
more is actually known today about how aluminum causes neurological 
injury than is known for lead, and that there is as much data on the 
health effects of aluminum as was ever available for lead.
EPA Response
    The Agency disagrees with the commenters who indicated that 
aluminum should not be on the CCL. The Agency believes it is 
appropriate to include aluminum on the CCL because of the new 
developments and research on aluminum epidemiology indicating a 
potential link between aluminum and adverse neurological effects. It is 
clear that additional studies are needed to characterize the risk of 
this contaminant from exposure through drinking water.
    Due to aluminum's widespread occurrence and the recent studies 
indicating some association with Alzheimer's like symptoms and other 
potential neurotoxic effects, the Agency believes aluminum warrants 
further investigation. It is also EPA's opinion that additional data 
are needed to determine an adequate no-observed-adverse-effect-level 
(NOAEL) for potential chronic neurotoxicity. The inclusion of a 
contaminant on the CCL does not necessarily mean that the contaminant 
will be regulated. Contaminants on the CCL include those priorities for 
which the Agency must make a determination of whether or not to 
regulate by the year 2001, and priority contaminants for which the 
Agency will gather additional data and conduct research. At this time, 
the EPA has included aluminum among the contaminants for which 
additional research is needed.

E. Dimethoate

    One commenter suggested that dimethoate be deleted from the CCL. 
The major reasons given were that dimethoate did not meet the 
occurrence criteria, because data used in the Agency's analysis from 
the Pesticides in Ground Water Database (PGWDB) report were recorded 
erroneously, and that the IRIS values lack critical evaluation and 
therefore should not be considered in evaluating whether a contaminant 
should be included on the CCL.
EPA Response
    The Agency agrees with the commenter on the point raised about the 
occurrence data, but not on the point raised about the use of IRIS 
values. Based on the faulty occurrence data, dimethoate has therefore 
been removed from the CCL.
    In general, the RfD 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 effects during a lifetime. The 
health assessment information and RfD values on a chemical substance 
are included in IRIS only after a comprehensive review of chronic 
toxicity data by U.S. EPA health scientists from several program 
offices and the Office of Research and Development. The Agency believes 
it is entirely appropriate to use RfD values reported to IRIS in the 
absence of drinking water health advisory values in the derivation of 
health levels of concern for determining if a contaminant should be 
included on the CCL.
    However, according to EPA's Office of Pesticide Programs (OPP), the 
office that prepared the PGWDB report, and the Georgia Department of 
Natural Resources, the data reported for the State of Georgia are 
incorrect. The laboratory analysis sheets from the Georgia Ground Water 
Management Laboratory Program indicate dimethoate was not detected in 
any samples in the State. By eliminating the occurrence data from the 
PGWDB report for the State of Georgia and replacing it with this new 
information, which the Agency feels is appropriate, dimethoate no 
longer meets the criteria for inclusion on the CCL, and has therefore 
been removed.

F. DTBB

    DTBB, also known as 2,6-di-tert-butyl-p-benzoquinone, is a 
contaminant that appears to be associated with sewage contamination of 
ground water, and is

[[Page 10279]]

considered by some to be a good indicator of such contamination. DTBB 
was determined not to meet the criteria for the CCL per se, but was 
included on the draft list nevertheless, because of the persistent 
nature of the contaminant, and its potential to serve as an indicator. 
One commenter stated that coliforms and nitrate already serve the 
purpose as indicators of contamination, and that it was pointless to 
include DTBB on the CCL, since it, in fact, did not meet the criteria.
EPA Response
    The Agency agrees with the commenter and has removed DTBB from the 
CCL. DTBB does not meet criteria set forth for identifying contaminants 
for the CCL, and since there are currently acceptable indicators of 
sewage contamination in the use of total coliforms, its inclusion is 
unnecessary.

G. Methyl Bromide

    Several commenters supported the inclusion of methyl bromide on the 
CCL. The principal reason cited by commenters was the widespread use of 
methyl bromide as a fumigant and its likely occurrence in drinking 
water sources. One commenter indicated that although the frequency of 
detection in samples was less than 0.1% in ambient water monitoring 
conducted by the U.S. Geological Survey, methyl bromide should be 
considered for inclusion because the environmental significance may 
warrant it.
EPA Response
    Methyl bromide, which is also known as bromomethane, was included 
on the draft CCL based on input from stakeholders that it was found in 
drinking water. In response to the comments, EPA has reevaluated the 
available information on methyl bromide occurrence. Contrary to 
assertions of likely widespread occurrence in source water due to its 
use as a fumigant, the U.S. Geological Survey ambient water monitoring 
indicates it occurs at less than 0.1% frequency, at very low 
concentrations (less than 0.2 g/l). However, unregulated 
contaminant monitoring data collected from States indicates methyl 
bromide occurred in 0.8% of the public water systems. One explanation 
for this apparent anomaly could be that the finished water occurrence 
comes not from its use as a fumigant, but that methyl bromide is 
associated with the disinfection processes used for drinking water 
treatment. Nevertheless, methyl bromide met the criteria for inclusion 
on the CCL; the concentrations reported (maximum 29 g/l) in 
the unregulated contaminants database exceeded the health level of 0.8 
g/l.
    Methyl bromide is a gas produced by both manmade and natural 
sources. Methyl bromide is primarily used for soil fumigation (87%), 
but its other agricultural uses include: commodity and quarantine 
treatment (8%), and structural fumigation (5%). When used as a soil 
fumigant, methyl bromide is injected into the soil at a depth of 12 to 
24 inches. About 50 to 95% of the methyl bromide injected in the soil 
eventually enters the atmosphere. About 80 to 95% of the amount used 
for commodity treatments, and well over 90% used for structural 
fumigation eventually enters the atmosphere. A significant quantity of 
methyl bromide used for agricultural purposes is known to escape to the 
atmosphere due to its volatile nature. Therefore, the U.S. Geological 
Survey data indicating less than 0.1% frequency of occurrence is 
consistent with what would be expected to present in ground water due 
to methyl bromide's use as a fumigant.
    Methyl bromide is also considered a Class I ozone depleting 
substance, and as such, its use is being phased out around the world by 
the Montreal Protocol, and in the U.S., by the Clean Air Act (CAA). The 
Montreal Protocol is an international treaty developed to protect the 
earth from the detrimental effects of ozone depletion, and to control 
the production and trade of ozone depleting substances on a global 
basis. Title VI of the CAA, as amended in 1990, requires that certain 
ozone depleting substances be phased out in the U.S. within seven 
years. Under the CAA, the EPA has prohibited the production and 
importation of methyl bromide starting January 1, 2001. As a result, 
given methyl bromide's lack of persistence, occurrence in source waters 
will likely decrease even more.
    If methyl bromide is a disinfection byproduct, EPA has a number of 
rules and activities currently in place and under development to 
address it. In 1979, EPA issued an NPDWR establishing an MCL for the 
total trihalomethanes (TTHMs) disinfection byproducts. The Agency is 
also in the process of updating the disinfection byproducts regulation. 
In 1994, EPA proposed a revised standard for TTHMs and a new standard 
for haloacetic acids. The TTHMs were regulated not only to control 
trihalomethanes, but also to protect against other similar byproducts. 
Because of structural similarity, steps to reduce formation of TTHMs 
would also reduce formation of methyl bromide. The treatment technique 
of enhanced coagulation, included in the 1994 proposed DBPR, will 
remove disinfection byproduct precursors, thus reducing the levels of 
disinfection byproducts in finished waters. Although methyl bromide is 
not a TTHM, for which an MCL is explicitly established, the Agency 
believes it would be effectively controlled under the DBPR. However, it 
is not clear whether methyl bromide is being formed due to 
disinfection.
    Because it cannot be determined whether methyl bromide is being 
formed due to disinfection, and its use as a fumigant cannot be 
completely dismissed as source of drinking water contamination, the 
Agency has decided to retain methyl bromide on the CCL. At the January 
7, 1998 meeting, the NDWAC Working Group on Occurrence & Contaminant 
Selection concurred with the EPA recommendation to delete methyl 
bromide because it was being addressed in ongoing rulemakings for 
disinfection byproducts. However, at the February 2, 1998 meeting, the 
full NDWAC recommended the Agency retain methyl bromide on the CCL 
after receiving comment that because it is a mono-halogenated compound, 
it was not specifically regulated with the TTHM family which are tri-
halogenated compounds, and that it may not turn out to be a 
disinfection byproduct. At the meeting, EPA was insufficiently lucid in 
explaining the connection between the TTHM byproducts and the control 
of similar byproducts. Nonetheless, after further consideration of the 
NDWAC recommendation, and given the uncertainties about the source, EPA 
has concluded that methyl bromide should remain on the CCL.
    Since methyl bromide is a gas, most health studies have used the 
inhalation route of exposure, and the effects of oral exposure have 
received limited attention. In 1989, EPA classified methyl bromide as a 
Group D carcinogen (not classifiable) due to inadequate bioassay data. 
At the time of the IRIS assessment, also in 1989, a chronic oral study 
was not available, therefore an additional uncertainty factor of 10 
(total uncertainty of 1,000) was applied to the RfD calculation. 
However, since the IRIS assessment, a 2-year rat feeding study showed 
no evidence of carcinogenicity, and a National Toxicology Program 
inhalation study, conducted in 1992, found no evidence of 
carcinogenicity. The Agency will also explore the potential sources of 
drinking water contamination, and the expected impact of the prohibited 
production and importation of methyl bromide which begins in January 1, 
2001. Methyl bromide is listed on the Research Priorities portion of 
the CCL to

[[Page 10280]]

allow the Agency time to better determine the drinking water risk due 
to this contaminant.

H. Microorganisms

    Many commenters stated that the rationale for the inclusion of 
microorganisms appeared to be inconsistent. They suggested that other 
microorganisms would have been included had the criteria been used 
consistently. It was not the intention of EPA, nor the participants of 
the EPA Drinking Water Microbiology and Public Health Workshop, to 
develop a comprehensive list of all possible agents of waterborne 
disease. The intent was to list what were considered the most important 
agents (or potential agents) of waterborne disease. The Agency 
recognizes that the Workshop participants could have established 
different lists of reasonable criteria for selecting pathogens, and 
believes that the ultimate decisions represent the best (albeit 
sometimes subjective) judgment of the panel. Nevertheless, the Agency 
believes that the process for developing the current CCL for 
microorganisms by this group of nationally recognized experts in the 
field of microbiology was reasonable and credible.
    EPA believes that regulations that are currently in effect [Surface 
Water Treatment Rule (SWTR), Total Coliform Rule (TCR)] or are now 
under development [e.g., Groundwater Disinfection Rule (GWDR), Enhanced 
Surface Water Treatment Rule (ESWTR), and Disinfection Byproducts 
Regulations (DPBR)] will address a number of the microorganisms that 
commenters have suggested. Generally, if a microorganism has not 
caused, or not expected to cause, a waterborne outbreak in the U.S., or 
if the organism is known to be susceptible to disinfection or 
filtration required by current or upcoming regulations, the organism 
has not been included on the CCL.
Protozoa
    Several commenters supported the draft CCL, which included 
Toxoplasma gondii, Cyclospora cayetanensis, and two microsporidia--
Enterocytozoon and Septata. One commenter suggested the addition of 
Entamoeba histolytica to the CCL, primarily because of its virulence. 
One commenter suggested that EPA add Isospora belli to the final CCL.
EPA Response
    After further consideration, EPA has decided to remove Toxoplasma 
and Cyclospora from the final CCL. Toxoplasma gondii is about the same 
size as Giardia, and Cyclospora cayetanensis is larger than 
Cryptosporidium. The Agency believes that the upcoming M/DBPR to 
control Giardia and Cryptosporidium will also control these larger 
organisms. Microsporidia remains on the CCL for the reasons indicated 
in the preamble to the draft CCL, including the ineffectiveness of 
chlorination and filtration.
    The Agency recognizes that Entamoeba histolytica can be virulent. 
Even though the commenter cites an article stating that dogs and 
perhaps pigs may be reservoirs for E. histolytica (Benenson 1995), 
animals are probably not major host reservoirs, in contrast to the 
situation for Giardia and Cryptosporidium. Thus, if sewage treatment 
practices are adequate, the potential for source water contamination is 
probably low, as suggested by the fact that the organism has not caused 
a significant waterborne disease outbreak since the early 1950s (the 
one reported exception in the U.S. was a small outbreak in 1984 
associated with untreated well water). Importantly, the cyst is large 
(10-15m). It is slightly larger than a Giardia cyst, and much 
larger than microsporidia spores that infect humans (1-5m) to 
which the commenter compares E. histolytica. Thus, EPA believes that 
regulations that control for Giardia and Cryptosporidium should also 
control E. histolytica. For these reasons, E. histolytica was not 
included on the final CCL. The Agency has also decided not to include 
Isospora belli for the reasons given in the preamble of the draft CCL, 
especially for the fact that its oocysts are 30 x 12m, larger 
than Giardia cysts, and any rule to control Giardia and Cryptosporidium 
should also control this organism.
Viruses
    The draft CCL included the following viruses: caliciviruses, 
adenoviruses, coxsackieviruses, echoviruses, and the hepatitis A virus. 
Several commenters suggested that EPA add rotaviruses, hepatitis E 
virus, and bacteriophage to the final CCL.
EPA Response
    The final CCL remains the same as the draft, except that the 
hepatitis A virus has been removed. Hepatitis A was removed because it 
is being addressed by current regulations, or regulations under 
development. As a matter of policy, all viruses are regulated as a 
class under EPA's SWTR and are going to be regulated as a class under 
the GWDR, and the Agency does not believe that additional research is 
needed to demonstrate the efficacy of disinfection for this organism. 
In contrast, the Agency believes that additional research is needed on 
the impact of treatment for the other viruses that remain on the CCL.
    EPA did not include rotaviruses on the final CCL, primarily because 
they are vulnerable to disinfection and should always be associated 
with fecal contamination. Thus, the Agency believes that EPA's SWTR, 
plus the upcoming GWDR, should adequately control these viruses.
    EPA excluded the hepatitis E virus from the final CCL because the 
Agency does not regard the virus as a significant public health threat 
in the U.S. and believes that current sewage treatment practices are 
sufficient to eliminate significant risk of waterborne transmission. 
EPA recognizes that hepatitis E is a major problem in some developing 
countries, especially for pregnant women. However, there is no evidence 
that the organism is a problem in the U.S. Rare cases have occurred in 
the U.S., usually among travelers returning from an area where the 
disease is endemic (Mast and Krawczynski 1996). Structurally, the 
organism is a small, single-stranded RNA virus similar to the 
caliciviruses, coxsackieviruses, and echoviruses, all of which remain 
on the CCL, because of evidence of outbreaks and occurrence in finished 
waters.
    Bacteriophage were excluded from the CCL because they are not 
pathogenic to humans. However, EPA recognizes that they may be useful 
as an indicator of fecal contamination. EPA has decided not to include 
indicators of fecal contamination or of pathogens on the final CCL. 
However, the Agency will consider indicators in the context of 
regulations to control pathogens on the CCL. For example, the Agency is 
considering two bacteriophage--the somatic coliphage and the male-
specific coliphage--as an indicator of fecal contamination under the 
Groundwater Disinfection Rule.
Bacteria
    The draft CCL included the following bacteria: Helicobacter pylori, 
Legionella, Mycobacterium avium complex, and Aeromonas hydrophila. 
Commenters urged EPA to include additional bacteria, including 
Pseudomonas aeruginosa, Shigella, Salmonella, Vibrio, Arcobacter, 
Campylobacter, Yersinia, and E. coli O157:H7, and that if these enteric 
bacterial pathogens were not included on the CCL, then H. pylori and A. 
hydrophila should not be included either, because both are sensitive to 
disinfection also.

[[Page 10281]]

EPA Response
    The final CCL does not include the enteric bacterial pathogens that 
commenters suggested EPA add (Shigella, Salmonella, Vibrio, Arcobacter, 
Campylobacter, Yersinia, and E. coli O157:H7). The Agency's reasons for 
excluding these organisms are that they are all sensitive to 
disinfection and are all associated with fecal contamination. Thus, EPA 
regards total coliforms as an adequate indicator for these organisms. 
Moreover, the SWTR requires all surface water systems to disinfect, and 
the forthcoming GWDR is likely to require systems that have wells 
vulnerable to fecal contamination to disinfect or provide other 
corrective action. The Agency regards these regulatory tools as 
sufficient to control for the above pathogens.
    With regard to P. aeruginosa, the preamble to the draft CCL 
indicated that the participants of the EPA Drinking Water Microbiology 
and Public Health Workshop could not agree on whether to include this 
organism on the draft CCL. There was controversy among participants 
about its public health significance and its potential health risk via 
the waterborne route. Therefore, participants recommended that EPA 
conduct a complete literature search on the topic before deciding 
whether to include this organism on the final list. The Agency has not 
yet completed this search. Because of this lack of information, EPA has 
decided to defer a decision on P. aeruginosa and not include it on the 
CCL. However, should the literature search suggest that regulatory 
action may be necessary, EPA will increase the priority of research in 
this area, if appropriate.
    With regard to Helicobacter, following the meeting of the panel, an 
article was published indicating that Helicobacter is sensitive to 
chlorine (Johnson, Rice and Reasoner 1997). However, EPA decided not to 
remove Helicobacter from the CCL because of the large number of people 
in the U.S. affected by peptic ulcers (about 20 million people) and 
gastritis, the poor survival rate of individuals with gastric cancer, 
and ignorance about the mode of transmission of the organism. 
Helicobacter pylori has been implicated in the cause of these three 
diseases. The Agency believes that, in spite of the recent disinfection 
data, it would be improper to remove Helicobacter from the CCL for 
these reasons.
    With regard to Aeromonas hydrophila, EPA recognizes that this 
organism is sensitive to disinfection in source and finished waters. 
However, unlike the fecal pathogens listed above, A. hydrophila  may 
enter the distribution system either as a result of inadequate 
treatment or a break in the water distribution system, and grow as part 
of the biofilm on the pipes or in the sediment, which may protect it 
from disinfectants. In addition, A. hydrophila  is not necessarily 
associated with fecal contamination. Thus, the total coliforms rule may 
not be adequate as an indicator for this organism. Moreover, systems 
which are not required to disinfect (or take other corrective action) 
under the forthcoming Groundwater Disinfection Rule because they are 
considered not vulnerable to fecal contamination, may still be 
vulnerable to A. hydrophila. For these reasons, EPA does not believe 
that this organism can be treated in the same manner as E coli O157:H7 
and other fecal bacteria listed by the commenter. Thus, the final CCL 
includes A. hydrophila .
    EPA removed Legionella in ground water from the final CCL. It was 
removed because: (1) the Agency intends to address the control of this 
organism under the Groundwater Disinfection Rule, and (2) the Agency 
does not believe that high priority research is needed in this area to 
regulate this organism.
Algae and Their Toxins
    Several commenters strongly urged EPA to add algae, especially the 
blue-green algae, plus their toxins (e.g., mycotoxin) to the CCL. One 
commenter suggested that Pfiesteria piscicida be included on the final 
CCL, as well.
EPA Response
    In the preamble to the draft CCL, EPA stated that certain species 
of blue-green algae produce toxins that could be harmful if ingested at 
high enough concentrations, but that algal control was best handled 
through good watershed management practices. The Agency continues to 
regard this strategy as reasonable. However, the Agency has decided to 
add the algae and their toxins to the final CCL because: (1) pathogenic 
algae and their toxins are not necessarily associated with fecal 
contamination and thus may not be effectively controlled by the SWTR or 
ESWTR, and (2) some data suggest that current treatment techniques may 
be particularly inadequate in controlling algal toxins. Placement of 
this group of contaminants on the CCL will make them a priority for 
research to determine what triggers toxic algal growth in source water 
and the effectiveness of water treatment practices.
    EPA is aware that Pfiesteria piscicida has been implicated in 
adverse health effects in humans. Apparently at least 13 researchers 
who worked with dilute toxic cultures of this organism and 10 fishermen 
sustained mild to serious health effects by water contact or by 
inhaling toxic aerosols. Symptoms include skin rashes, reddening of the 
eyes, severe headaches, blurred vision, nausea/vomiting, breathing 
difficulties, kidney and liver problems, short-term memory loss, 
confusion, and other problems. The organism has a complicated life 
cycle, with about 24 stages. Pfiesteria's habitat is estuarine or 
brackish water. Current data indicate that, like most other 
dinoflagellates, the organism grows poorly in fresh water and does not 
elaborate toxins in this milieu, thus, there is no evidence that 
Pfiesteria  occurs or could occur in drinking water. Moreover, the size 
ranges from 5-450 m, with the dormant cyst stages 7-60 
m in diameter. Thus filtration that is effective for removing 
Cryptosporidium (4-6 m) should be effective for removing 
Pfiesteria. For these reasons, EPA believes that Pfiesteria  does not 
represent a health threat in drinking water systems, and thus did not 
include Pfiesteria  on the final CCL.

I. MTBE

    A number of commenters agreed with the inclusion of methyl-t-butyl 
ether (MTBE) on the CCL, and some indicated that MTBE should be 
included among the contaminants for which determinations will be made 
by 2001. Another commenter suggested it should not be included on the 
CCL but should be included in the forthcoming Unregulated Contaminant 
Monitoring rulemaking, due in 1999.
EPA Response
    The Agency agrees that MTBE should remain on the CCL. However, as 
with all the contaminants on the list, EPA has not made a determination 
with respect to regulating MTBE. Although there are serious limitations 
in the MTBE data, there is some evidence to support a concern for 
potential human hazard. MTBE has been found in some drinking water 
wells but it is uncertain whether the concentrations are at levels of 
health concern. Given the potential health hazard and need for 
additional data, MTBE meets the criteria for placement on the CCL.
    The inclusion of a contaminant on the CCL does not mean that the 
contaminant will be regulated. As noted earlier, contaminants on the 
CCL include those for which the Agency must make a determination of 
whether or not to regulate by 2001 pursuant to the requirements of the 
SDWA, but it also includes the Agency's research

[[Page 10282]]

priorities, contaminants for which monitoring is necessary to gather 
additional data. MTBE will remain on the CCL since the Agency needs 
additional occurrence data.
    At this time, the EPA has not included MTBE among the contaminants 
for which determinations will be made by 2001. As stated earlier, MTBE 
needs additional health and occurrence data, and as such, it will be 
one of the priority contaminants for which the Agency will gather such 
data. There are no data on the effects on humans of drinking MTBE 
contaminated water. Therefore, EPA is continuing to evaluate the 
available health information and is doing additional research to seek 
more definitive estimates of potential risks to humans from drinking 
water. One of the mechanisms for gathering occurrence data is to 
include a contaminant in the forthcoming Unregulated Contaminant 
Monitoring rulemaking to be issued in August 1999. The Agency is also 
not precluded from using other means of gathering occurrence data which 
may include conducting special studies. The data collection and 
evaluation efforts will assist in determining what the appropriate 
action should be with respect to MTBE. Placing MTBE in this category 
does not prevent the Agency from selecting it to make a determination 
of whether or not to regulate by 2001; however, at this time, it is not 
likely that the necessary data will be collected and evaluated in time 
to make a determination by this date.
    To facilitate data collection and evaluation efforts for MTBE, an 
Agency-wide task force has been formed and has prepared a draft 
Oxygenates in Water Research Strategy. The Strategy identifies current, 
or soon to be started, research in areas that include environmental 
occurrence, source characterization, transport and transformation, 
exposure, toxicity, and treatment. The Strategy will also identify key 
areas of research that are still necessary to build a stronger, more 
informed scientific database to support health risk assessment and risk 
management decisions with respect to fuel oxygenates, including MTBE.
    On October 7, 1997, EPA convened a day-long meeting of over 50 
experts--including representatives from industry, academia, 
consultants, and other government agencies--to review a draft of the 
Strategy. The information produced in this workshop is being used to 
help revise the draft of the Strategy, which will serve as a blueprint 
to assist in coordinating efforts by various organizations, public and 
private, in addressing the issues related to oxygenates in water. The 
Agency will also publish the Strategy in the Federal Register this 
Spring, to seek additional public comment on the research priorities 
identified.

J. Organotins

    Four commenters argued that organotins, specifically the mono- and 
di-organotins, the only types used as polyvinyl-chloride (PVC) heat 
stabilizers, should not be included on the CCL. The commenters 
maintained that, due to evidence of low toxicity and low migration 
(thus, low risk to consumers), mono- and di-organotins, especially 
mono- and di-methyltins, should not be of concern to drinking water, 
particularly in light of the National Sanitation Foundation (NSF) 
certification program for plumbing materials. Other commenters 
indicated that it was premature for the Agency to regulate organotins, 
but thought it prudent that the Agency keep informed of the issue.
EPA Response
    EPA disagrees with the commenters who suggest that organotins 
should be deleted from the CCL. It should be emphasized that retaining 
organotins on the CCL does not necessarily mean that they will be 
regulated. The Agency believes that organotins, including mono- and di-
organotins which are used as heat stabilizers in PVC and chlorinated 
polyvinyl-chloride (CPVC) pipes, are of sufficient concern to warrant 
further investigation. The Agency is aware of the NSF certification 
program, and has noted that many States require the use of NSF-
certified material in the construction of new buildings. The Agency 
agrees with the NDWAC Working Group recommendation that an assessment 
of the toxicological data underlying the action levels established by 
the NSF needs to be made along with assessment of other available 
information on organotins, before these compounds can be disregarded as 
of concern. The Agency requested this information from the NSF, and 
learned that due to confidentiality agreement, NSF cannot disclose this 
information, therefore we have not yet been able to assess the 
toxicological data.
    There are numerous concerns about the occurrence and toxicological 
significance of various species of organotins in drinking water. A 
recent report indicates that unlike PVC systems, new CPVC systems have 
the potential to contaminate drinking water with organotin compounds 
for a longer period of time after installation (Forsyth and Jay 1997). 
There has been a report concerning tributyltin contamination of 
drinking water from PVC pipes, and tributyltin is of far more 
toxicological significance than mono- and di-organotins (Sadiki et al, 
1996). There is also concern about the recent reports of teratogenic 
potential of dibutyltin (Ema et al, 1996). The Canadian Government is 
concerned about organotin contamination of drinking water and has 
launched a national survey.
    In view of these concerns, the Agency believes that organotins, 
including mono- and diorganotins, should remain on the CCL until the 
Agency can perform its own in-depth evaluation of the occurrence and 
toxicological data of the contaminants of this class.

K. Perchlorate

    The majority of comments on perchlorate indicated support for its 
inclusion on the CCL. Commenters pointed out that the information on 
the occurrence of perchlorate in drinking water supplies was sufficient 
to raise concern over the potential impact on public health. A few 
commenters expressed concern that perchlorate should not be regulated 
or that there was not sufficient information at present to warrant its 
regulation, and that a health advisory would be more appropriate.
EPA Response
    The Agency agrees with commenters that sufficient information 
exists to raise concern over the potential health effects and 
occurrence of perchlorate in drinking water supplies. Despite 
significant data gaps regarding health effects, occurrence, and 
treatment technologies, perchlorate has been found in a number of 
drinking water supplies at levels of health concern, and as a result is 
included on the final CCL.
    The Agency understands that the extent of actual or even potential 
perchlorate contamination is unclear for many parts of the country, and 
that for some areas of the country perchlorate contamination may not be 
an issue. However, perchlorate has been detected in a number of 
drinking water supplies to date and warrants further evaluation. 
Placement of perchlorate on the CCL means that the Agency will make it 
a priority to conduct further investigation and evaluation of the 
health effects and national occurrence of perchlorate in drinking water 
supplies.
    Perchlorate has been placed in the categories of needing additional 
health effects, treatment research, and occurrence information. Several 
toxicological and occurrence studies are planned or are underway, which 
will assist the Agency in filling these data

[[Page 10283]]

gaps on perchlorate. At this time, the Agency has not made a 
determination to issue a health advisory or to regulate perchlorate. 
The additional data obtained from these health effects and occurrence 
studies will provide a sound scientific basis for future EPA decisions 
of whether to regulate perchlorate or not, to prepare a health advisory 
or guidance, or to include perchlorate in the Unregulated Contaminant 
Monitoring rulemaking. Placing perchlorate in these categories does not 
preclude the Agency from selecting it to make a determination of 
whether or not to regulate by 2001, but at this time it is unlikely 
that perchlorate will be included among those for which determinations 
will be made by 2001.

L. Rhodamine WT

    A few commenters argued that Rhodamine WT be removed from the CCL. 
The commenters stated that Rhodamine WT has a very specialized purpose. 
They also noted that it is certified by the NSF and that the 
certification is reviewed by EPA. They also stated that data for 
including Rhodamine WT were questionable, and that the contaminant had 
no specific health effect.
EPA Response
    EPA agrees with the commenters and has removed Rhodamine WT from 
the CCL. Rhodamine WT was placed on the draft CCL because it was 
detected in ground water above the NSF Standard 60 concentration of 
0.1g/L for drinking water. However, three concentrations have 
been established under the NSF Standard 60; 0.1g/L for 
drinking water, 10g/L for water entering a drinking water 
plant (prior to treatment and distribution), and 100 g/L for 
ground water not associated with drinking water production. These 
concentration values were developed under the Agency's former Additives 
Program which was subsequently privatized and turned over to NSF in the 
1980's.
    The maximum concentration of available occurrence data was 28 
g/L detected in ground water, and, as such, should be compared 
to the recommended value of 100 g/L for ground water, not the 
value for drinking water. Given this comparison, the maximum 
concentration of 28 g/l is well below the recommended value 
for ground water of 100 g/L. When the NSF guidance regarding 
the use of Rhodamine WT as a fluorescent tracer in water flow studies 
is followed the Agency does not anticipate any adverse health effects 
resulting from the use of Rhodamine WT.

M. Sodium

    Many commenters were opposed to including sodium on the CCL, 
primarily due to their contention that sodium in drinking water is not 
a public health concern because of its extremely low level in drinking 
water, and its small contribution to overall sodium intake. Commenters 
also noted that controlling sodium in public water systems would be 
cost-prohibitive and produce marginal or nonexistent health benefits. 
Commenters argued that food, which is the major source of sodium, is 
allowed to average 440 mg/day under a ``salt-restricted'' medically-
supervised diet, and that controlling sodium content in food would 
address salt-restriction more directly. Commenters also strongly 
disagreed with the use of EPA's DWEL of 20 mg/l as the public health 
criteria for determining whether to include sodium on the CCL. The 
commenters mentioned a more up-to-date, 1996 report published by the 
American Medical Association (AMA) showing a lack of association 
between sodium and blood-pressure, except for older individuals with 
existing hypertension. Other commenters argued for the inclusion of 
sodium, citing studies linking it to hypertension and the need to 
maximize protection of salt-sensitive individuals as a sensitive 
subpopulation.
EPA Response
    The issue of sodium posed a unique challenge for the Agency 
priority setting and contaminant candidate listing process. Information 
from commenters on each side made important points. On the one hand, 
high levels of salt intake can be associated with hypertension in some 
individuals. On the other hand, sodium levels in drinking water are 
unlikely to be a significant contribution to adverse health effects.
    This low level of concern is compounded by the legitimate 
criticisms of EPA's 20 mg/l guidance level that was used in this 
process. EPA believes this guidance level for sodium needs updating, 
and is probably low. If a health benchmark for drinking water were 
established using current information and current drinking water health 
assessment procedures, it would likely be higher. This revision could 
establish a new level at which sodium occurrence would not meet the 
criteria for inclusion on the CCL as a drinking water contaminant of 
concern. There was insufficient time to complete a reassessment of the 
sodium guidance in advance of the CCL issuance.
    Given the state of the data, EPA faced a dilemma on whether or not 
to list sodium. A decision not to list would be justified by the fact 
that much is known about sodium and it does not appear to be a drinking 
water risk comparable to other priority contaminants. In fact, this was 
the logic supporting the decision not to include sodium on the previous 
drinking water priority list in 1991. However, a decision to list 
sodium would afford EPA the opportunity to address the confusion 
surrounding the current guidance for sodium in drinking water.
    In the end, EPA decided to include sodium on the CCL, primarily as 
a vehicle to reexamine and correct the current, outdated guidance. 
Therefore, sodium is listed, not as a Regulatory Determinations 
Priority, but as a Research Priority to allow time to evaluate and 
revise the Agency guidance. When this is completed, EPA will reevaluate 
whether sodium merits retention on the CCL for any further action.

N. Triazines

    Many commenters applauded EPA's intention to address triazines and 
their metabolites as a group a ``good first step'' to addressing these 
compounds. A number of commenters indicated that we should include 
other triazine degradation products such as deisopropyl atrazine and 
diaminochlorotriazine (same as diamino atrazine) because they too are 
common degradation products of atrazine as well as simazine, and are 
found at higher concentrations than atrazine-desethyl. Once commenter 
expressed concern that additional information was being considered and 
evaluated by the Agency under the OPP Special Review program, and that 
these reviews should be completed before triazines are considered for 
the CCL.
EPA Response
    The Agency agrees with the points raised by the commenters 
regarding the triazine degradation products. As a result, the EPA has 
decided to include triazines and their degradation products (including 
but not limited to: cyanazine and atrazine-desethyl) on the CCL as a 
group to include all potential risks from this class of compounds. 
Stakeholders, through the regulatory reassessment process in developing 
the redirection strategy, and through the development of this draft 
CCL, have requested that the Agency address triazine pesticides as a 
group, which includes all parent and degradate compounds, as opposed to 
each triazine as an individual contaminant.
    The EPA has been studying the mechanism of carcinogenicity of this

[[Page 10284]]

group of analogues along with their degradation products, and will 
continue to study these chemicals as a group to characterize their risk 
in drinking water. The Agency regulated atrazine in 1991 and simazine 
in 1992. The Agency may ultimately develop regulations for the mixtures 
of triazines either through the revision of existing regulations or the 
development of new ones.
    EPA disagrees with the notion that triazines should be excluded 
from the CCL until after the completion of the Special Reviews. The 
triazines are included in the Priority Group 1 of pesticide tolerances 
that will be examined first under the Food Quality Protection Act 
(FQPA) tolerance reassessment (62 FR 42020). The work being 
accomplished by OPP in their review efforts will certainly be factored 
into EPA's decisions regarding triazines, as with all pesticides on the 
CCL.

O. Zinc

    Two commenters were opposed to the inclusion of zinc on the CCL. 
The commenters argued that zinc did not meet the criteria for inclusion 
on the CCL, and is generally non-toxic to animals and humans. They 
pointed out that zinc is used in a wide variety of products, and is 
also an essential element. One commenter stated that the Agency had not 
considered zinc's beneficial qualities when deciding whether it should 
be included on the CCL, and that the WHO and EPA have both stated that 
deficiency of zinc is more of a concern than over-exposure. The 
commenter further argued that the history of the substitution from the 
1988 DWPL was not considered, and that the HA value used in the 
Agency's analysis was from a ``7-yr old draft'' which was not available 
for comment and therefore the explanation behind the Agency's HAL of 
2,000 g/l was not available for comment.
EPA Response
    The EPA agrees with the commenter on the point raised that zinc 
does not meet the criteria for inclusion on the CCL, and has removed 
zinc from the CCL. The Agency has determined that the number of public 
water systems with zinc levels above 1,000 g/l is 4, and none 
had occurrence levels above 2,000 g/l, and, as a result, zinc 
doesn't meet the criteria for inclusion on the CCL. The criterion for a 
contaminant to be included on the CCL was ``occurrence at the health 
level of concern in 10 or more small public water systems.'' The action 
of removing zinc from the CCL was due to its lack of occurrence in 
water systems at health levels of concern, not due to its lack of 
toxicity. It is known that daily exposure to zinc of approximately 60 
mg/l (60,000 g/l) or more can effect copper metabolism, and 
result in deleterious health effects.

IV. Continuing Work in Preparation for Future CCLs

    In the Federal Register notice on the draft CCL, the Agency 
deferred action on a number of pesticides, and contaminants implicated 
as endocrine disruptors, in anticipation of impending resolution 
specific to these two groups of contaminants. Action on these 
contaminants continues to be deferred and these contaminants will be 
reconsidered when the next CCL is developed. The Agency is also 
resuming work on a contaminant identification process to be used in the 
development of future CCLs. Further discussion of these three topics 
follows.

A. Pesticides Deferred

    In developing the CCL, the SDWA requires EPA to consider substances 
registered as pesticides under FIFRA. During the development of the 
CCL, the Agency's Office of Ground Water and Drinking Water sought 
assistance from OPP in determining what pesticides should be priorities 
for the drinking water program. In response to the request, OPP 
provided recommendations for a number of pesticides based on physical-
chemical properties, occurrence and extent of use, using the Ground 
Water (GW) Risk score. The GW-Risk score is a calculated potential of 
pesticides to leach to ground water. Pesticides with a GW-Risk of 2.0 
or greater were included for initial consideration in developing the 
draft CCL.
    However, later during the data evaluation and screening phase of 
the CCL development, the decision was made to defer pesticides 
identified by the GW-Risk of 2.0 or greater for which no additional 
information was available. Inclusion on the CCL would be deferred 
pending further evaluation of the potential of these pesticides to 
occur at levels of health concern. The Agency is working to develop a 
tool to estimate concentrations in ground and surface waters based on 
physical-chemical properties and pesticide use volumes, and will then 
compare the estimated concentrations with health advisory levels or 
calculated health levels based on reference doses or cancer potency.
    It was anticipated that the tool to estimate concentrations of 
pesticides in ground and surface waters would be completed and 
available in time to reevaluate the inclusion of the additional 
pesticides prior to completing the CCL. However, the Agency believes it 
is important to have this tool peer-reviewed prior to its use, which 
would increase the time necessary for its development beyond the time 
available. Therefore, EPA did not attempt to complete this work before 
finalizing the CCL in today's notice. As a result, action on these 
pesticides remains deferred until the next CCL.
    On December 10, 1997, the Science Advisory Panel (SAP) met to 
discuss drinking water exposure assessment issues with the OPP. The 
objective of the meeting was to obtain SAP's recommendation on the 
approaches and models developed by OPP to determine short-term and 
long-term potential exposures from pesticides in drinking water. The 
issues of monitoring requirements, and assessing impacts of exposure to 
mixtures were also part of the discussion. The approaches and models 
developed by OPP and the forthcoming SAP's recommendations on these 
issues are of particular importance to the Office of Water in that the 
outcome will be used in the drinking water program as well.

B. Endocrine Disruptors

    During the development of the draft CCL, the Agency initially 
considered, then later deferred, a number of contaminants implicated or 
suspected as substances which disrupt the function of the endocrine 
system. As stated in the notice of the draft CCL, EPA issued an interim 
assessment in February 1997, pending a more extensive review expected 
to be issued by the National Academy of Sciences (NAS), determining 
that, while effects have been found in laboratory animal studies, a 
causal relationship between exposure to a specific environmental agent 
and an adverse health effect in humans operating via endocrine 
disruption has not been established, with a few exceptions. Further 
research is needed before such effects can be demonstrated.
    Under the SDWA, as amended, the Agency is also required to 
establish a program to screen endocrine disrupting contaminants. 
Additional authority to assess endocrine disruptors is also provided 
through the recently enacted FQPA. EPA's Office of Prevention, 
Pesticides, and Toxic Substances (OPPTS) has the Agency lead on 
endocrine disruptor screening and testing issues, and is actively 
engaged in research and regulatory initiatives to respond to the 
growing scientific and public concern over endocrine disruptors. Also, 
the Endocrine Disruptor Screening and Testing Advisory Committee 
(EDSTAC) has

[[Page 10285]]

been established to provide advice and counsel to the Agency in 
implementing a screening and testing strategy required under the FQPA 
and SDWA. EDSTAC will complete its recommendations for a screening and 
testing strategy by March 1998. The recommendations will be peer-
reviewed jointly by the SAB and the FIFRA SAP.
    As a result, pending completion of the EDSTAC's recommendations and 
the additional review of endocrine disruptors by the NAS, EPA has not 
included contaminants for inclusion on this first CCL based solely on 
the possibility of endocrine disruption (although several contaminants 
implicated as endocrine disruptors were considered for other reasons). 
As stated in the notice on the draft CCL, the Agency will continue to 
follow this issue closely and reconsider this category of potential 
contaminants in the development of future CCLs.

C. Development of the Contaminant Selection Process

    This CCL is largely based on knowledge acquired over the last few 
years and other readily available information, but an enhanced, more 
robust approach to data collection and evaluation will be developed for 
future CCLs. The Agency will also resume work on the contaminant 
identification and the contaminant selection process. The CCL, and the 
identification and selection process will serve as the cornerstones of 
the Agency's regulatory development process. In addition to developing 
the CCL, and the identification and selection process, the Agency 
intends to obtain resources in order to acquire better data and 
information, improve analytical capability, and seek additional 
stakeholder involvement.
    The next steps for improving the contaminant identification and 
selection process include an American Water Works Association Research 
Foundation (AWWARF) project utilizing a series of workshops in which 
established decision-making tools would be employed to develop a 
process to identify emerging pathogens of concern for consideration, 
regulation, and future research. The work is expected to begin in June/
July 1998. A project with the NAS will also be undertaken to solicit 
input on criteria for listing and selecting chemical contaminants for 
future CCLs. A panel is currently being formed and work is expected to 
begin in summer of 1998. The development of the identification and the 
selection process will be completed in consultation with the NDWAC and 
the Working Group on Occurrence & Contaminant Selection, and their 
future involvement is likely to include reviewing products from AWWARF 
and NAS in 1999. The CCL is a critical input to shaping the future 
direction of the drinking water program, and improvements to the 
process will be made with each successive cycle of publishing the list.

V. Data, Research Needs and Next Steps

    Table 2 divides the CCL into categories to represent the next steps 
and data needs for each contaminant. Sufficient data are needed to 
conduct analyses on extent of exposure and risk to populations via 
drinking water in order to determine appropriate Agency action 
(development of health advisories, or regulations, or no action) for 
many of these contaminants. If sufficient data are not available, they 
must be obtained before such an assessment can be made. The data and 
information required will be gathered by research or monitoring 
programs, and are not likely to be available for analyses to be 
completed prior to 2001. Thus, the contaminants for which sufficient 
data exist at the time of publishing the CCL are likely to be those 
from which the determinations will be made by 2001.
    However, it should be noted that the groupings in Table 2 are based 
on current information, and some movement of contaminants between 
categories can be expected as more information is evaluated and 
analyzed. The Regulatory Determination Priorities category in Table 2 
will be used to select 5 or more contaminants for which the Agency must 
determine, by August 2001, whether or not regulations should be 
developed. To make these determinations, further analysis of data 
currently available, or data that will become available within a short 
period, is required to prepare supporting documents addressing health 
criteria, cost and benefit assessments, and analyses of analytical 
methods, occurrence, and treatment technology and feasibility. For 
contaminants in the category, there may also be some short-term 
research needs, such as bench-scale treatability studies, that must 
also be completed. The next steps for the Agency regarding the 
contaminants in this category are to determine which contaminants to 
address first, and outline plans of action to work towards making 
determinations for five or more by August 2001.
    The contaminants in the Research Priorities category have 
significant data gaps in areas of health, treatment, or analytical 
methods. For these contaminants, the research, or data gathering, and 
subsequent analysis needed are not expected to be complete within the 
3\1/2\ years, by August 2001, in order to make determinations of 
whether regulation of these contaminants is necessary. These are EPA's 
priority contaminants for research and data gathering. Some of these 
research needs are currently being addressed by EPA or other agencies 
(e.g., Department of Defense for perchlorate), while other needs are 
newly identified.
    The contaminants in the Occurrence Priorities category have 
significant data gaps in occurrence data. The Unregulated Contaminant 
Monitoring Regulations (UCMR) will be the primary source for data for 
most contaminants included in this category; however, some contaminants 
may be more appropriate for special studies or surveys, or joint data 
gathering efforts with other Agencies. Also, for some contaminants, 
suitable analytical methods must be developed prior to obtaining the 
occurrence data necessary.
    The next steps for the Agency are to develop short- and long-term 
research plans on health, treatment, and methods, to develop the UCMR 
proposal (expected August 1998) for gathering occurrence data, and to 
plan for special occurrence studies, where appropriate. The Agency will 
also use its FIFRA and Toxic Substances Control Act (TSCA) authorities, 
as appropriate, to conduct studies and obtain data necessary for 
decision-making.

[[Page 10286]]



                                        Table 2.--Next Steps for the CCL                                        
----------------------------------------------------------------------------------------------------------------
                                               Research priorities                                              
      Regulatory      ---------------------------------------------------------------------      Occurrence     
    determination                                                      Analytical methods        priorities     
      priorities          Health research       Treatment research          research                            
----------------------------------------------------------------------------------------------------------------
Acanthamoeba           Aeromonas hydrophila   Adenoviruses           Adenoviruses           Adenoviruses.*      
 (guidance)            Cyanobacteria (Blue-   Aeromonas hydrophila   Cyanobacteria (Blue-   Aeromonas           
1,1,2,2-                green algae), other   Cyanobacteria (Blue-    green algae), other    hydrophila.        
 tetrachloroethane      freshwater algae,      green algae), other    freshwater algae,     Cyanobacteria (Blue-
1,1-dichloroethane      and their toxins       freshwater algae,      and their toxins       green algae), other
1,2,4-                 Caliciviruses           and their toxins      Caliciviruses           freshwater algae,  
 trimethylbenzene      Helicobacter pylori    Caliciviruses          Helicobacter pylori     and their toxins.* 
1,3-dichloropropene    Microsporidia          Coxsackieviruses (ICR  Microsporidia          Caliciviruses.*     
2,2-dichloropropane    Mycobacterium avium     data)                 1,2-diphenylhydrazine  Coxsackieviruses    
Aldrin                  intercellulare (MAC)  Echoviruses (ICR       2,4,6-trichlorophenol   (ICR data).        
Boron                  1,1-dichloropropene     data)                 2,4-dichlorophenol     Echoviruses (ICR    
Bromobenzene           1,3-dichloropropane    Helicobacter pylori    2,4-dinitrophenol       data).             
Dieldrin               Aluminum               Microsporidia          2-methyl-Phenol        Helicobacter        
Hexachlorobutadiene    DCPA mono-acid & di-   Mycobacterium avium    Acetochlor              pylori.*           
p-Isopropyltoluene      acid degradates        intracellulare (MAC)  Alachlor ESA           Microsporidia.*     
Manganese              Methyl bromide         Aluminum               Fonofos                1,2-                
Metolachlor            MTBE                   MTBE                   Perchlorate             diphenylhydrazine.*
Metribuzin             Perchlorate            Perchlorate            RDX                    2,4,6-              
Naphthalene            Sodium (guidance)                                                     trichlorophenol.*  
Organotins                                                                                  2,4-dichlorophenol.*
Triazines &                                                                                 2,4-dinitrophenol.* 
 degradation products                                                                       2,4-dinitrotoluene. 
 (incl., but not                                                                            2,6-dinitrotoluene. 
 limited to Cyanazine                                                                       2-methyl-phenol.*   
 and atrazine-                                                                              Alachlor ESA* and   
 desethyl)                                                                                   Acetochlor.*       
Sulfate                                                                                     DCPA mono-acid & di-
Vanadium                                                                                     acid degradates.   
                                                                                            DDE.                
                                                                                            Diazinon.           
                                                                                            Disulfoton.         
                                                                                            Diuron.             
                                                                                            EPTC.               
                                                                                            Fonofos.*           
                                                                                            Linuron.            
                                                                                            Molinate.           
                                                                                            MTBE.               
                                                                                            Nitrobenzene.       
                                                                                            Perchlorate.*       
                                                                                            Prometon.           
                                                                                            RDX.*               
                                                                                            Terbacil.           
                                                                                            Terbufos.           
----------------------------------------------------------------------------------------------------------------
The groupings in Table 2 are based on current information, and some movement of contaminants between categories 
  can be expected as more information is evaluated and analyzed. *Suitable analytical methods must be developed 
  prior to obtaining occurrence data.                                                                           

VI. Other Requirements

    The CCL is a notice and not a regulatory action; therefore, the 
following statutes and executive orders are not applicable at this 
time: the Regulatory Flexibility Act, Small Business Regulatory 
Enforcement Fairness Act, Paperwork Reduction Act, Unfunded Mandates 
Reform Act; and Executive Order 12866. For any contaminants selected 
for rule-making, all necessary analysis will be conducted in accordance 
with the rule-making process.
    Executive Order 13045, Protection of Children from Environmental 
Health Risks and Safety Risks, requires that Federal Agencies identify 
and assess health risks and safety risks that disproportionately affect 
children, and ensure that its policies, programs, activities, and 
standards address disproportionate health and safety risks to children. 
The SDWA also requires the Agency to select priorities for regulation 
while considering risks to sensitive subpopulations, such as infants 
and children.
    The impact on sensitive populations will be addressed in the 
contaminant selection process, and will be a component of the Agency's 
determination of whether or not to regulate a given contaminant. In 
preparation for addressing the issues of sensitive subpopulations, the 
Agency is sponsoring several activities to determine water intake by 
age group, by demographic distribution, and by innate or developed 
sensitivity to potential drinking water contaminants. The Agency is 
also collaborating with the Center for Disease Control and Prevention 
on a study of six major cities to determine the most sensitive 
populations for drinking water manifested during major outbreaks of 
illness from incidents of water. Other research also is underway to 
determine the extent of vulnerable populations including children and 
the immunologically impaired.

VII. References

Benenson, A.S. 1995. Control of Communicable Diseases Manual (16th 
ed.). pp. 10-13. American Public Health Assoc., Washington.
Ema, M., R. Kurosaka, H. Amano, and Y. Ogawa. 1996. Comparative 
Developmental Toxicity of Di-, Tri-and Tetrabutyltin Compounds after 
Administration during Late Organogenesis in Rats. J. Appl. Toxicol., 
16(1), 71-76.
Forsyth, D.S., and B. Jay. 1997. Organotin Leachate in Drinking 
Water from Chlorinated Polyvinyl Chloride (CPVC) Pipe. Appl. 
Organometallic Chem., 11:551-558.
Johnson, C.H., E.W. Rice and D.J. Reasoner. 1997. Inactivation of 
Helicobacter pylori by chlorination. Appl. Environ. Microbiol. 
63:4969-4970.

[[Page 10287]]

Mast, E.E., and K. Krawczynski. 1996. Hepatitis E: An Overview. 
Annual Rev. Med. 47:257-266.
Midgley, J.P., A.G. Matthew, C.M.T. Greenwood, and A.G. Logan. 1996. 
Effect of Reduced Dietary Sodium on Blood Pressure. J. Amer. Med. 
Assoc., 275 (20): 1590-1597.
RDA. 1989. Recommended Dietary Allowances, tenth edition. National 
Research Council, National Academy Press, Washington, D.C., 284 pp.
Sadiki, Abdel-Iiah, D. Williams, R. Carrier and B. Thomas. 1996. 
Pilot study of the Contamination of Drinking Water by Organotin 
Compounds from PCV Materials. Chemosphere, 32:2389-2398.
U.S. EPA. 1995. ``Acetone; Toxic Chemical Release Reporting; 
Community Right-to-Know, Final Rule,'' 60 FR No. 116, 31643-31646, 
June 16.
U.S. EPA. 1996. ``Drinking Water Program Redirection Strategy,'' 
Office of Water. EPA 810-R-96-003, June.
U.S. EPA. 1997. ``Announcement of the Draft Drinking Water 
Contaminant Candidate List; Notice,'' 62 FR No. 193 52194-52219, 
October 6.
U.S. EPA. 1998. ``Response to Comment Document.'' Office of Ground 
Water and Drinking Water.

(Authority: 42 U.S.C. 300f-300j-25)

    Dated: February 6, 1998.
Robert Perciasepe,
Assistant Administrator, Office Water, Environmental Protection Agency.
[FR Doc. 98-5313 Filed 2-27-98; 8:45 am]
BILLING CODE 6560-50-P