[Federal Register Volume 62, Number 193 (Monday, October 6, 1997)]
[Notices]
[Pages 52194-52219]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-26433]



[[Page 52193]]

_______________________________________________________________________

Part III





Environmental Protection Agency





_______________________________________________________________________



Announcement of the Draft Drinking Water Contaminant Candidate List; 
Notice

  Federal Register / Vol. 62, No. 193 / October 6, 1997 / Notices  

[[Page 52194]]



ENVIRONMENTAL PROTECTION AGENCY

[FRL-5904-7]


Announcement of the Draft Drinking Water Contaminant Candidate 
List

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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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 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. Today's notice announces the draft CCL, provides background on 
how it was developed, and seeks comment on various aspects of 
developing the final CCL. The CCL will be the source of priority 
contaminants for drinking water research, monitoring, guidance 
development, and for selection of candidates for drinking water 
regulation. The draft CCL includes 58 chemical and 13 microbiological 
contaminants.

DATES: Submit comments on or before December 5, 1997.

ADDRESSES: Send written comments to the Comment Clerk, docket number W-
97-11, Water Docket (MC4101), USEPA, 401 M. St., SW, Washington, DC 
20460. Please submit an original and three copies of your comments and 
enclosures (including references). Comments must be received or 
postmarked by midnight December 5, 1997.
    Commenters who want EPA to acknowledge receipt of their comments 
should enclose a self-addressed, stamped envelope. No facsimiles 
(faxes) will be accepted. Comments may also be submitted electronically 
to [email protected]. Electronic comments must be submitted as 
an ASCII file avoiding the use of special characters and any form of 
encryption. Electronic comments must be identified by the docket number 
W-97-11. Comments and data will also be accepted on disks in 
WordPerfect in 5.1 format or ASCII file format. Electronic comments on 
this notice may be filed online at many Federal Depository Libraries.
    The full record for this notice has been established under docket 
number W-97-11, and includes supporting documentation as well as 
printed, paper versions of electronic comments. The full record is 
available for inspection from 9 to 4 p.m. Monday through Friday, 
excluding legal holidays at the Water Docket, Room M2616, Headquarters, 
USEPA, 401 M. Street, SW, Washington, DC. For access to docket 
materials, please call 202/260-3027 to schedule an appointment. 
Additionally, a few critical pieces of the record have been made 
available at each Regional Office.

FOR FURTHER INFORMATION CONTACT: For general information, please 
contact the EPA Safe Drinking Water Hotline. The toll-free number is 
800-426-4791. For specific information on the CCL 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, DC 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. 345 Courtland Street, NE, Atlanta GA 30365. 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:

Table of Contents

I. Background
II. Draft Drinking Water Contaminant Candidate List
    Table 1. Draft Drinking Water Contaminant Candidate List
III. Identification of Contaminants for the Draft Drinking Water 
Contaminant Candidate List
    A. Role of NDWAC Working Group
    B. Microbiological Contaminants Identified for the Draft CCL
    Table 2. Initial List of Microorganisms Developed by EPA for 
Consideration by the Workshop on Microbiology and Public Health
    1. Protozoa
    2. Viruses
    3. Bacteria
    4. Microbiological Indicators
    5. Future Activities Planned for Microbiological Contaminants 
and the CCL
6. Possible Impacts From Other Regulatory Activity
    C. Chemical Contaminants Identified for the Draft CCL
    1. The Initial List of Chemical Contaminants Considered
    Table 3. Initial List of Chemical Contaminants Considered during 
Development of the Draft CCL
    a. 1991 Drinking Water Priority List
    b. Health Advisories
    c. Integrated Risk Information System
    d. Non-Target Analytes in Public Water Supply Samples
    e. CERCLA Priority List
    f. Stakeholder Responses
    g. Toxic Release Inventory
    h. Pesticides Identified by Office of Pesticide Programs
    Table 4. Pesticides Deferred
    i. Safe Drinking Water Hotline
    Table 5. Contaminants Identified by the Safe Drinking Water 
Hotline
    j. Endocrine Disruptors
    Table 6. Contaminants Identified as Suspected of Endocrine 
Disruption
    2. Development and Application of the Criteria
    a. Criteria for Occurrence
    b. Criteria for Health
    3. Additional Specific Contaminants Included
    a. Aldicarb, Aldicarb sulfoxide, and Aldicarb sulfone
    b. Nickel
    c. Sulfate
IV. Contaminants on the CCL Which Are of Specific Interest
    A. Aluminum
    B. MTBE
    C. Organotins
    D. Rhodamine WT
    E. Sodium
    F. Zinc
    G. 2,6-di-tert-butyl-p-benzoquinone (DTBB)
    H. Contaminants to be Considered as Groups
    I. Contaminants for Which Unregulated Contaminant Data are or 
Will Be Available
    Table 7. Contaminants with Unregulated Contaminant Monitoring 
Data
V. Request for Comment
    A. Data and Research Needs
    Table 8. Data Needs for Chemical Contaminants Included on the 
Draft CCL
    B. Perchlorate

[[Page 52195]]

VI. Development of the final Drinking Water Contaminant Candidate 
List, the Contaminant Identification Method, and the Contaminant 
Selection Process
VII. Summary of Other Related Activity Required by the SDWA
    A. Contaminant Selection and Regulatory Determination
    B. The National Contaminant Occurrence Database
    C. Unregulated Contaminant Monitoring Regulation
VIII. Summary of Concurrent Regulatory Activity Required by the SDWA
    A. Radon
    B. Other Radionuclides
    C. Arsenic
    D. Sulfate
    E. Disinfectants and Disinfection Byproducts
IX. Other Requirements
X. References

Abbreviations Used in this Notice

    ACWA-Association of California Water Agencies
ATSDR--Agency of Toxic Substances and Disease Registry
AWWARF--American Water Works Association Research Foundation
CASRN--Chemical Abstract Services Registry Number
CCL--Contaminant Candidate List
CDC-Center for Disease Control and Prevention
CERCLA--Comprehensive Environmental Response, Comprehensive and 
Liability Act
CIM--Contaminant Identification Method
D/DBP--Disinfectants and Disinfection Byproducts
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
GW--Ground Water
HA--Health Advisory
HSDB--Hazardous Substances Data Base
IARC--International Agency for Research on Cancer
ICR--Information Collection Request
IESWTR--Interim Enhanced Surface Water Treatment Rule
IRIS--Integrated Risk Information System
LTESWTR--Long-term Enhanced Surface Water Treatment Rule
MCL--Maximum Contaminant Level
MCLG--Maximum Contaminant Level Goal
NAS--National Academy of Sciences
NCOD--National Contaminant Occurrence Database
NDWAC--National Drinking Water Advisory Council
NIPDWR--National Interim Primary Drinking Water Regulations
NPDWR--National Primary Drinking Water Regulations
NPL--National Priority List
NRC--National Research Council
OGWDW--EPA's Office of Ground Water and Drinking Water
OPP--EPA's Office of Pesticide Programs
OPPTS--EPA's Office of Pollution Prevention and Toxic Substances
PWS--Public Water Systems
RDA--Recommended Daily Allowance
RfD--Reference Dose
RQ--Reportable Quantity
SAB--EPA's Science Advisory Board
SDWA--Safe Drinking Water Act
STORET--Storage and Retrieval Database
SWTR--Surface Water Treatment Rule
TRI--Toxic Release Inventory
WHO--World Health Organization

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 regulations under the SDWA (section 
1412(b)(1)). The SDWA, as amended, specifies that EPA must publish this 
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 publish a CCL every five years thereafter. The SDWA 
also 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).
    Prior to the 1996 Amendments, the SDWA required the EPA to publish 
a drinking water priority list (DWPL) of contaminants every three years 
which were known or anticipated to occur in drinking water and which 
may have required regulation under the SDWA. In response to these 
previous amendments, EPA published two DWPLs which served as candidates 
for regulation. The first DWPL was published on January 22, 1988 (53 FR 
1892), and the second was published on January 14, 1991 (56 FR 1470).
    The 1996 Amendments to the SDWA were developed and enacted during 
the time of the Presidential initiative intended to substantially 
improve the existing regulatory system to move the Nation toward a new 
and better environmental management system for the 21st century. During 
the two-year period prior to the 1996 Amendments, EPA developed a 
National Drinking Water Program Redirection Strategy (EPA, 1996a) to 
(1) establish priorities for setting safety standards based on health 
risks and sound science; (2) support strong, flexible partnerships 
among EPA, States, local governments and other stakeholders to protect 
public health; and (3) promote effective community-based source water 
protection. The Redirection Strategy provides an overall framework for 
the development of the CCL, as well as for other drinking water program 
activities.
    The Agency believes the draft CCL presented in today's notice is 
the result of a commendable effort of screening a larger set of 
contaminants to the subset of those of most concern. The draft CCL is a 
first step toward improving risk assessment, strengthening science and 
data, and achieving better decision-making and future priority setting. 
Today's notice announces the draft CCL, provides background on how it 
was developed, summarizes detailed material available in the docket and 
used to develop the list, seeks comment on the methods used to develop 
the draft CCL, and seeks comment on developing the final CCL. The draft 
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 
redirection strategy.
    Today's notice is being published pursuant to the requirement in 
section 1412(b)(1) that the CCL be subjected to prior notice and 
opportunity for public comment. The contaminants included are not 
subject to any proposed or promulgated national primary drinking water 
regulation,1 are known or anticipated to occur in public 
water systems, and may require regulations under the SDWA. During the 
development of the draft CCL, the Agency consulted with stakeholders, 
including the National Drinking Water Advisory Council's Working Group 
on Occurrence & Contaminant Selection, which includes microbiologists, 
toxicologists, public health scientists, and engineers, and with other 
members of the scientific community including the Science Advisory 
Board (SAB). The Agency plans for a more in-depth consultation with the 
SAB during the

[[Page 52196]]

fall of 1997. The occurrence database, which is to be established under 
section 1445(g) by August 1999, was not considered since it is 
currently under development; however, occurrence data from other 
sources was considered.
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    \1\ With the exception of nickel, aldicarb and its degradates, 
and sulfate, which are considered special cases. Refer to later 
sections of this notice for rationale for inclusion.
---------------------------------------------------------------------------

    The final CCL, after publication in February 1998, will be the 
source of priority contaminants for the Agency's drinking water 
program. Priorities for drinking water research, occurrence monitoring, 
guidance development, including the development of health advisories, 
will be drawn from the CCL. The CCL will also serve as the list of 
contaminants from which the Agency will make determinations of whether 
or not to regulate specific contaminants. This first 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.

II. Draft Drinking Water Contaminant Candidate List

    The following table includes the contaminants, microbiological and 
chemical, presented as the draft Drinking Water Contaminant Candidate 
List. The contaminants were identified as described by Section III of 
today's notice. The contaminants in the table are identified by name 
and Chemical Abstracts Service Registry Number (CASRN). The draft CCL 
includes 58 chemical contaminants/contaminant groups and 13 
microbiological contaminants.

        Table 1.--Draft Drinking Water Contaminant Candidate List       
------------------------------------------------------------------------
                   Chemical contaminants                        CASRN   
------------------------------------------------------------------------
1,1,2,2-tetra-chloroethane.................................      79-34-5
1,2,4-trimethylbenzene.....................................      95-63-6
1,1-dichloro-ethane........................................      75-34-3
1,1-dichloro-propene.......................................     563-58-6
1,2-diphenylhydrazine......................................     122-66-7
1,3-dichloropropane........................................     142-28-9
1,3-Dichloropropene (telone or 1,3-D)......................     542-75-6
2,4,6-trichlorophenol......................................      88-06-2
2,2-dichloro-propane.......................................     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
2,6-di-tert-butyl-p-benzoquinone (DTBB)....................     719-22-2
2-methyl-Phenol (o-cresol).................................      95-48-7
Acetochlor.................................................   34256-82-1
Acetone....................................................      67-64-1
Alachlor ESA (a degradation product of alachlor)                        
Aldicarbs*                                                              
Aldrin.....................................................     309-00-2
Aluminum...................................................    7429-90-5
Atrazine-desethyl, a degradation product of triazines......    6190-65-4
Boron......................................................    7440-42-8
Bromobenzene...............................................     108-86-1
Cyanazine..................................................   21725-46-2
p-Cymene (p-isopropyltoluene)..............................      99-87-6
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
Dimethoate.................................................      60-51-5
Disulfoton.................................................     298-04-4
Diuron.....................................................     330-54-1
EPTC (s-ethyl-dipropylthiocarbamate).......................     759-94-4
Fonofos....................................................     944-22-9
Hexachloro-butadiene.......................................      87-68-3
Isopropylbenzene (cumene)..................................      98-82-8
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
Nickel*                                                                 
Nitrobenzene...............................................      98-95-3
Organotins                                                              
Prometon...................................................    1610-18-0
RDX........................................................     121-82-4
Rhodamine WT                                                            
Sodium.....................................................    7440-23-5
Sulfate*                                                                
Terbacil...................................................    5902-51-2
Terbufos...................................................   13071-79-9
Vanadium...................................................    7440-62-2
Zinc.......................................................    7440-66-6
Microbiological Contaminants:                                           
  Acanthamoeba (guidance expected for contact lens wearers).............
  Adenoviruses..........................................................
  Aeromonas hydrophila..................................................
  Caliciviruses.........................................................
  Coxsackieviruses......................................................
  Cyclospora cayetanensis...............................................
  Echoviruses...........................................................
  Helicobacter pylori...................................................
  Hepatitis A virus.....................................................
  Legionella (in ground water)..........................................
  Microsporidia (Enterocytozoon & Septata)..............................
  Mycobacterium avium intracellulare (MAC)..............................
  Toxoplasma gondii.....................................................
------------------------------------------------------------------------
*Included on the CCL as special cases, not subject to the criteria used 
  to identify other contaminants.                                       

III. Identification of Contaminants for the Draft Drinking Water 
Contaminant Candidate List

    Drinking water contamination generally occurs from: (1) 
Contaminants that find their way into drinking water sources from 
industrial waste releases, agricultural runoff, atmospheric deposition, 
and other pollution sources; (2) contaminants formed during the 
treatment of water supplies (e.g., disinfection by-products); and (3) 
materials used for treatment, storage, and distribution of water. EPA 
has considered all of these sources in identifying microbiological and 
chemical contaminants for this draft CCL. Figure 1 provides a graphical 
representation of how today's draft CCL was developed.

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    The National Drinking Water Advisory Council's (NDWAC) Working 
Group on Occurrence & Contaminant Selection played an integral part in 
the development of the CCL by providing recommendations for the 
criteria, and the contaminants for initial consideration. Also, during 
the development of the CCL, the Agency sought the expertise of 
microbiologists for input on microorganisms to include on the CCL. The 
following sections describe the role of the NDWAC Working Group and 
describe the approach used to develop the CCL for microorganisms and 
chemical contaminants.

A. Role of NDWAC Working Group

    After enactment of the recent SDWA amendments, and in keeping with 
the redirection strategy, EPA held its first stakeholder meeting on 
approaches to developing CCLs on December 2 and 3, 1996 in Washington, 
D.C. Participants, including public water system professionals, state 
regulatory officials, public health officials, environmental groups and 
other stakeholders, with a range of interests, explored issues 
concerning the identification of potential drinking water contaminants 
for consideration for the first CCL as well as the factors to consider 
for future CCL development. One result of the meeting was the 
recommendation that the February 1998 CCL be the first topic addressed 
by the NDWAC Working Group on Occurrence & Contaminant Selection.
    In 1975, pursuant to the SDWA [Section 1446(a)], NDWAC was 
established under the Federal Advisory Committee Act to provide 
practical and independent advice, consultation, and recommendations to 
EPA on the activities, functions and policies related to the SDWA. At 
its meeting held on November 13 and 14, 1996, NDWAC decided that 
working groups should be formed on the following subjects: Small 
Systems Capacity Building; Operator Certification; Source Water 
Protection; Consumer Confidence Reports; Drinking Water State Revolving 
Fund; and Occurrence & Contaminant Selection. The NDWAC Occurrence & 
Contaminant Selection Working Group has been integral to developing the 
criteria and identifying contaminants for the draft CCL published 
today.
    At the recommendation of the Working Group, the Agency sought 
expertise on microbiological contaminants and convened a workshop of 
microbiologists. The input from the workshop was adopted by the Working 
Group for use in developing the draft CCL. The approach used to 
identify microorganisms for the CCL is explained in more detail in 
section III.B.
    In addition to microorganisms, the Working Group developed 
recommendations on chemical contaminants. The recommendations addressed 
which contaminants to include for initial consideration, and the 
criteria for use in determining which contaminants should be included 
on the draft CCL. The recommendations were developed over a series of 
meetings with the Working Group followed by the endorsement by the full 
NDWAC. The details concerning the contaminants included for initial 
consideration, and development and use the identification criteria are 
contained in section III.C.

B. Microbiological Contaminants Identified for the Draft CCL

    On May 20-21, 1997, EPA utilized a workshop on microbiology and 
public health to develop a list of pathogens for possible inclusion on 
the first CCL. Taking part in this workshop were invited experts 
representing academia, EPA and other federal agencies, and the water 
industry. In preparation, EPA scientists prepared and distributed a 
list of microorganisms for initial consideration by workshop members 
(see Table 2.). Inclusion of organisms on this initial list was based 
on disease outbreak data, published literature documenting the 
occurrence of known or suspected pathogens in water, and other 
information. A summary of the workshop proceedings is in the docket.
Table 2. Initial List of Microorganisms Developed by EPA for 
Consideration by the Workshop on Microbiology and Public Health

Protozoa

Microsporidia
Toxoplasma
Cyclospora
Acanthamoeba
Naegleria
Isospora

Viruses

Hepatitis E
Astroviruses
Coxsackie/Echo viruses
Adenovirus 40/41
Norwalk virus and other caliciviruses
Rotavirus

Bacteria

Helicobacter pylori
Mycobacterium (MAC)
E. coli O157:H7
Aeromonas hydrophila
Pseudomonas aeruginosa
Acrobacter
Campylobacter

Algal Toxins

Anaebaena flos-aquae
Aphanizomenon flos-aque
Microcystis aeruginosa
Schizothrix calcicola
    Workshop participants established a set of baseline criteria for 
deciding whether an organism should appear on the CCL. These criteria 
were (1) public health significance, (2) known waterborne transmission, 
(3) occurrence in source water, (4) effectiveness of current water 
treatment, and (5) adequacy of analytical methods. Organisms on the EPA 
list mentioned above, as well as other organisms that arose during the 
discussions, were evaluated against these criteria.
    The CCL published today includes the list of pathogens identified 
by the workshop and subsequently adopted by the NDWAC as 
recommendations for the CCL. Algal toxins were considered to be of 
minimal public health significance, and therefore were not included on 
the draft CCL. The following sections identify the organisms selected, 
the rationale for why a pathogen was included on the CCL, and the 
rationale why certain pathogens were not included.
1. Protozoa
    The following protozoa are included on the CCL: Cyclospora 
cayetanensis, Toxoplasma gondii, the two microsporida--Enterocytozoon 
and Septata, and Acanthamoeba. It is recommended that EPA develop 
guidance for controlling Acanthamoeba, for individuals who wear contact 
lenses. The rationale for their selection follows.
    C. cayetanensis has caused waterborne outbreaks in other countries 
and one documented outbreak in the U.S. Thus, it may be a significant 
public health risk. Disease symptoms include watery diarrhea, abdominal 
cramping, decreased appetite, and low-grade fever (Huang et al., 1995). 
In HIV-infected persons, the disease may be chronic and constant (Soave 
and Johnson, 1995). The occurrence of this organism in natural waters 
and its animal host range are unknown. However, C. cayetanensis is 
transmitted by the fecal-oral route, and so its presence in water is 
likely. The morphology of C. cayetanensis suggests that the organism is 
relatively resistant to disinfectants, but due to its large size (7-
10m in diameter) it may be removed satisfactorily by 
filtration. Cyclospora is included on the CCL because it has caused 
waterborne disease outbreaks in the U.S. and other countries.
    Toxoplasma gondii causes a common infection of mammals and birds, 
but the complete life cycle only occurs in wild

[[Page 52199]]

and domestic cats. The organism infects a high percentage of the human 
population (50 percent in some areas of the U.S.) but, while 
subclinical infections are prevalent, illness is rare (Fishback, 1992). 
However, illness may be severe in fetuses and AIDS patients. Symptoms 
include fever, swelling of lymph glands in the neck, blindness and 
mental retardation in fetuses, and encephalitis in AIDS patients 
(Fishback, 1992). There have been two documented outbreaks of 
toxoplasmosis--in Panama and British Columbia--both linked 
epidemiologically to drinking water. Chlorination of unfiltered surface 
waters is not effective against Toxoplasma (Benenson et al., 1982). 
However, due to their large size (11x12m), filtration may be 
effective in controlling this organism. Toxoplasma is included on the 
CCL because it poses a significant public health risk, can be 
transmitted via the waterborne route, and because a reasonable 
potential exists for completing the needed research in the next few 
years for controlling this organism.
    Microsporidia are a large group of protozoan parasites that are 
common in the environment and multiply only inside cells (Cali, 1991). 
Five species of microsporidia have been reported to cause disease in 
humans, but only two are significant in water: Enterocytozoon bieneusi 
and Septata intestinalis. Both are common in people with AIDS 
(Goodgame, 1996) and occur chiefly in AIDS patients (Bryan, 1995), 
although infections have been reported in otherwise healthy persons 
(Weber et al., 1994). Symptoms may include diarrhea (sometimes severe 
and chronic), and illness involving the respiratory tract, urogenital 
tract, eyes, kidney, liver or muscles (Bryan, 1995; Goodgame, 1996; 
Cali, 1991).
    Microsporidia that infect humans produce small (1-5m), 
very resistant spores (Waller, 1979; Cali, 1991). They are shed in 
bodily fluids, including urine and feces, and thus have a strong 
potential to enter water sources. However, no waterborne outbreak has 
yet been reported and there is no published evidence of waterborne 
transmission. Chlorine is probably not effective against microsporidia, 
given that other protozoan spores (cysts, oocysts) are resistant to 
chlorine. Thus, effective filtration and watershed control may be 
needed to control this organism in drinking water. E. bieneusi and S. 
intestinalis are included on the CCL because they pose a significant 
risk to immuno-compromised individuals and may not be removed 
effectively by filtration because of their small size (the spores are 
somewhat smaller than Cryptosporidium oocysts).
    Acanthamoeba are a group of free-living amoeba that are common in 
soil and water, including drinking water (Sawyer, 1989; Gonzalez de la 
Cuesta et al., 1987). Some Acanthamoeba species are pathogenic and can 
cause inflammation of the eye's cornea (especially in individuals who 
wear soft or disposable contact lenses (Seal et al., 1992)), and 
chronic encephalitis in the immuno-compromised population (Kilvington, 
1990). To date, no case of waterborne disease has been reported. 
However, Acanthamoeba cysts are relatively resistant to chlorine (De 
Jonkheere and Van der Voorde, 1976). Because drinking water is not a 
suspected route of transmission, workshop members did not include 
Acanthamoeba on their list. However, as stated above, the Workshop 
participants and the NDWAC recommend that EPA issue guidance to educate 
the public about the potential problem with contact lenses.
    Two protozoa that were on the initial list for consideration 
developed by EPA (Naegleria fowleri, Isospara belli), and two that were 
not (Entamoeba histolytica, Blastocystis hominis) were also considered 
by the workshop, but were not included on the CCL. The reasons for 
excluding them follow.
    N. fowleri is a free-living amoeba, about 8-15m in size, 
found in soil, water, and decaying vegetation. Although it is common in 
many surface waters, it rarely causes disease. All disease incidents 
have been associated with swimming in natural or manmade, warm fresh 
waters; drinking water is not a suspected route of transmission. The 
route of infection is via inhalation rather than by ingestion. For this 
reason, it was not included on the CCL.

I. belli causes gastrointestinal illness, primarily in AIDS 
patients and children. There have been no documented cases of 
waterborne transmission. However, the organism is transmitted by 
the fecal-oral route, so its presence in water is possible. 
Filtration is probably effective in removing I. belli oocysts, 
given their large size (30x12m). This organism was not 
included on the CCL because of the lack of documentation on 
waterborne transmission and the belief that not enough is known 
about the organism for developing potential regulations within a 
three-year time-frame.

    E. histolytica is not considered to be a significant health problem 
in the U.S. In contrast to the situation for Giardia and 
Cryptosporidium, animals are not host reservoirs for E. histolytica. 
Thus, the potential for source water contamination is relatively low, 
especially if sewage treatment practices are adequate. Moreover, the 
organism has not caused a significant waterborne disease outbreak since 
the early 1950s. Thirdly, the cyst is large (10-15m), slightly 
larger than a Giardia cyst; thus, filtration should be effective for 
removing this organism. For these reasons, this organism was not 
included on the CCL.
    B. hominis was not included on the CCL because its clinical 
significance has not been determined and very little is known about its 
potential for waterborne transmission or its occurrence in water.
2. Viruses
    The following viruses are included on the CCL: caliciviruses, 
adenoviruses, coxsackieviruses, echoviruses, and the hepatitis A virus. 
The rationale for their inclusion follows.
    The caliciviruses are a common cause of acute, but mild, 
gastrointestinal illness in the U.S. Between 1980 and 1994, 14 
waterborne disease outbreaks with more than 9,000 associated cases 
caused by the Norwalk virus and other caliciviruses were reported. 
Thus, their public health significance is high. However, because 
adequate recovery and assay methods for the caliciviruses are not yet 
available, information about the occurrence of these viruses in water 
or the effectiveness of water treatment is lacking. It is believed that 
current research programs might fill the research gap in the near-term 
to allow development of regulations, if necessary, to control this 
group of organisms.
    Most of the adenoviruses are respiratory pathogens. However, 
serotypes 40 and 41 are important causes of gastrointestinal illness, 
especially in children. However, all types may be shed in the feces, 
and may be spread by the fecal-oral route. Although adenoviruses have 
been detected in water, data on their occurrence in water are meager. 
No drinking water outbreaks implicating these viruses have been 
reported. Both the respiratory and gastrointestinal adenoviruses are 
recommended for the CCL because of their high public health 
significance and data which suggest that adenoviruses are relatively 
resistant to disinfectants.
    The coxsackieviruses are readily found in wastewater and surface 
water, and sometimes in drinking water (Hurst, 1991). Although they 
have not caused a documented outbreak of waterborne disease, 
coxsackieviruses produce a variety of illnesses in humans, including 
the common cold, heart

[[Page 52200]]

disease, fever, aseptic meningitis, gastrointestinal problems, and many 
more, some of which can be serious (Melnick, 1992). Coxsackieviruses 
are included on the CCL because they are found more frequently in water 
than other viruses and are associated with a number of illnesses.
    The echoviruses, like the coxsackieviruses, are readily detected in 
water, including treated drinking water. They are associated with 
milder illnesses than the coxsackieviruses, and have not caused a 
documented outbreak. Echoviruses are included on the CCL because, like 
the coxsackieviruses, they are found more frequently in water than 
other viruses and are associated with a number of illnesses.
    The hepatitis A virus has caused at least 11 waterborne disease 
outbreaks of infectious hepatitis since 1980. Therefore, it has a high 
public health significance. The virus has been found in contaminated 
drinking water, and is somewhat resistant to chlorination (Peterson et 
al., 1983). For these reasons, it is also included on the CCL.
    Three viruses that were on the initial list for consideration 
developed by EPA (rotaviruses, hepatitis E virus, and astroviruses) and 
two that were not (picobivirna and picotrivirna) were also considered 
by the workshop participants, but were not included on the CCL. The 
reasons for not including them follow.
    Rotaviruses cause acute gastroenteritis, primarily in children. 
Almost all children have been infected at least once by the age of five 
years (Parsonnet, 1992), and in developing countries, rotavirus 
infections are a major cause of infant mortality. Rotaviruses are 
spread by fecal-oral transmission and have been found in ambient water, 
ground water, and tap water (Gerba et al., 1985; Gerba, 1996). However, 
only a single waterborne disease outbreak has been reported in the U.S. 
and only several have been documented outside the U.S. (Gerba et al., 
1985). Rotaviruses are readily inactivated by chlorine, chlorine 
dioxide, and ozone, but apparently not by monochloramine (Berman and 
Hoff, 1984; Chen and Vaughn, 1990, Vaughn et al., 1986; 1987). 
Rotaviruses were not included on the CCL because they are not regarded 
as an important public health problem in the U.S., and because of their 
vulnerability to disinfectants.
    Hepatitis E virus is an important agent of hepatitis in 
underdeveloped countries, but apparently not in the U.S. The virus is 
transmitted by the fecal-oral route (Dreesman and Reyes, 1992) and 
probably a majority of cases are waterborne. Even though the disease is 
apparently not a health concern in the U.S., one investigation found 
that 21.3% of blood donors in Baltimore were sero-positive (Thomas et 
al., 1997), suggesting previous exposure to the organism. Infections 
are mild and self-limiting except for pregnant women, who have a 
fatality rate of up to 39%. No data from disinfection studies have been 
published. Hepatitis E virus was not included on the CCL because it is 
not regarded as a significant public health threat in the U.S., and 
because current sewage treatment practices are judged sufficient to 
eliminate risk of waterborne transmission.
    Astroviruses are found throughout the world and cause illness in 1-
3 year old children and in AIDS patients, but rarely in healthy adults 
(Kurtz and Lee, 1987; Grohmann et al., 1993). Symptoms are mild and 
typical of gastrointestinal illness, but the disease is more severe and 
persistent in the severely immuno-compromised. Astroviruses are 
transmitted by the fecal-oral route and have been detected in water and 
have been associated anecdotally with waterborne disease outbreaks 
(Cubitt, 1991; Pinto et al., 1996). The astroviruses were not included 
on the CCL because of the mildness of the illness and the lack of 
adequate documentation about the occurrence in water and potential as a 
waterborne disease agent.
    The picobivirna and picotrivirna viruses are of public health 
significance outside the U.S., and are not regarded as being a 
waterborne problem in the U.S. and are adequately removed from effluent 
water by current sewage treatment practices. Picobivirna and 
picotrivirna viruses were not included on the CCL for these reasons.
3. Bacteria
    The following bacteria are included on the CCL: Helicobacter 
pylori, Legionella, Mycobacterium avium complex, and Aeromonas 
hydrophila. The rationale for their identification follows.
    H. pylori has been closely associated with peptic ulcers, gastric 
carcinoma, and gastritis (Peterson, 1991; Nomura et al., 1991; 
Parsonnet et al., 1991, Cover and Blaser, 1995). Data about its 
distribution in the environment are scarce, but the organism has been 
found in sewage (Sutton et al., 1995) and has been linked to ambient 
water and drinking water by epidemiological tests and other means 
(Klein et al., 1991; Shahamat et al., 1992; Shahamat et al., 1993; 
Hulten et al., 1996). The number of people in the U.S. that have 
antibodies against H. pylori, and thus have been exposed to the 
organism, is high. Helicobacter is thought to be vulnerable to 
disinfectants. H. pylori is included on the CCL because of its public 
health significance in the U.S. and the possibility of waterborne 
transmission.
    Legionella pneumophila and other Legionella species cause 
Legionnaires Disease (a type of pneumonia) and Pontiac Fever (a mild, 
nonpneumonic illness). Legionnaires Disease, which has a 15% mortality 
rate, typically results from the inhalation of aerosols of water 
containing the organism. Legionella are abundant and naturally 
occurring in surface water; thus they are not necessarily associated 
with fecal contamination. They have also been detected in ground water. 
Small numbers can occur in the finished waters of systems employing 
full treatment (U.S. EPA, 1989b) and can colonize plumbing systems, 
especially warm ones. Aerosols from fixtures, such as showerheads, may 
cause the disease via inhalation. Aerosols from cooling towers, hot 
tubs, and pools have also caused a number of outbreaks. Direct person-
to-person spread has not been documented (Yu et al., 1983). Ozone, 
chlorine dioxide, and ultraviolet light are effective in controlling 
Legionella, but data for chlorine are inconsistent (States et al., 
1990). Legionella in surface water are already regulated under EPA's 
Surface Water Treatment Regulations (40 CFR part 141, subpart H). 
Legionella in ground water is included on the CCL because of their 
public health significance in the U.S. and the possibility of 
waterborne transmission via ground water.
    Mycobacterium avium complex (MAC; also known as the Mycobacterium 
avium intracellulare complex) is common in the environment and can 
colonize water systems and plumbing systems (du Moulin and Stottmeier, 
1986; du Moulin et al., 1988). It is known to cause pulmonary disease 
and other diseases, especially in individuals with a weakened immune 
system (e.g., AIDS patients). Drinking water has been epidemiologically 
linked to infections in hospital patients (du Moulin and Stottmeier, 
1986). MAC is relatively resistant to chlorine disinfection (Pelletier 
et al., 1988). MAC is included on the CCL because of its high public 
health significance, its ability to colonize on pipes, and its relative 
resistance to chlorine.
    Aeromonas hydrophila can cause wound infections and septicemia in 
people with a weakened immune system, and some evidence suggests that 
it causes gastrointestinal disease in

[[Page 52201]]

healthy people. The organism is common in water and is not necessarily 
associated with fecal contamination. It is vulnerable to disinfectants. 
A. hydrophila is included on the CCL primarily because it is common in 
source water.
    Pseudomonas aeruginosa is a free-living bacterium that is common in 
water. People at risk include patients with profound neutropenia, 
cystic fibrosis, severe burns, and those with foreign devices installed 
(Hardalo and Edberg, 1997). The organism has also caused numerous 
outbreaks of dermatitis in recreational waters, e.g., pools, 
whirlpools, and hot tubs (Kramer et al., 1996). Because of differing 
opinions among the microbiologists who participated in the workshop 
about its public health significance and its potential health risk via 
the waterborne route, a decision could not reach on whether to include 
P. aeruginosa on their list. Rather, it was recommended that EPA 
conduct a complete literature search on the topic before the Agency 
decides whether to include this organism on the final list. The 
literature search will be conducted prior to publishing the final CCL.
    Four bacteria that were on the initial list for consideration 
developed by EPA (Escherichia coli O157:H7, Campylobacter, Arcobacter, 
and the cyanobacteria) and four that were not (Salmonella, Shigella, 
Vibrio cholerae and other Vibrio species, and Yersinia enterocolitica) 
were also considered by the workshop, but were not included on the CCL. 
The reasons for excluding them follow.
    E. coli O157:H7, Campylobacter, Salmonella, Shigella, V. cholerae, 
and Y. enterocolitica have all caused waterborne disease in the U.S. 
and are regarded as significant health risks. They were not included on 
the CCL because current treatment practices were deemed to be adequate 
in controlling these organisms. Arcobacter was not included on the CCL 
because its health significance and the possibility of waterborne 
transmission are unknown, and because current treatment practices were 
judged likely in controlling this organism.
    Cyanobacteria (also known as blue-green algae) are generally not 
considered an important health risk. However, certain species may 
produce neurotoxins (which affects the nervous system), hepatotoxins 
(which affects the liver), and other types of toxins which, if ingested 
at high enough concentrations, may be harmful. High concentrations of 
toxins associated with a bloom of Schizothrix calcicola may have been 
responsible for an outbreak of gastroenteritis in 1975 (Lippy and Erb, 
1976). However, little evidence exists that ambient levels found in 
most water supplies pose a health risk to the normal population. The 
cyanobacteria was not included on the CCL because the problem is 
thought to be best handled through good watershed management practices 
to prevent algal growth in source waters.
4. Microbiological Indicators
    Indicators of fecal contamination or of pathogens were not 
addressed at the workshop. EPA is involved, however, in a project with 
the International Life Sciences Institute to begin an evaluation of 
which microbiological indicators are most appropriate for various types 
of environmental waters. Currently, the Agency uses total coliform 
bacteria as the sole indicator of microbiological drinking water 
quality.
5. Future Activities Planned for Microbiological Contaminants and the 
CCL
    EPA is attempting to develop a more formal framework for 
identifying, selecting and prioritizing pathogens (and their 
indicators) for research and possible regulation, and for future CCLs. 
To date, the identification of pathogens for the CCL has been 
relatively informal. In contrast, a more objective approach for 
contaminant identification and selection in the future may be based on 
a numerical scoring procedure such that contaminants with higher scores 
would have greater priority for regulation, research and guidance 
development than those that have lower scores.
6. Possible Impacts From Other Regulatory Activity
    Pathogens that are included on the final CCL, will be candidates 
for regulatory control, guidance development, and additional research 
over the next five years. These organisms may be controlled, however, 
by regulations currently under development such as the Enhanced Surface 
Water Treatment Rule, the Ground Water Disinfection Rule. If pathogens 
on the CCL are determined to be controlled by these regulations, they 
will be withdrawn from the CCL.

C. Chemical Contaminants Identified for the Draft CCL

    As stated earlier, the NDWAC Working Group on Occurrence & 
Contaminant Selection played an integral part in developing the draft 
CCL presented in today's notice. At the initial Working Group meeting 
held on April 3-4, 1997, the Agency proposed a number of lists of 
contaminants as a logical starting point for developing the draft CCL. 
Some lists originate from other Agency programs, while others were 
developed in anticipation of future DWPLs. The Agency also proposed 
that the initial list would need to be reduced to a smaller list of 
priority contaminants that would become the CCL.
    In April, the Working Group identified 32 contaminants thought to 
be those most important for inclusion on the first CCL, other 
contaminants for initial consideration, and criteria to be used to 
evaluate and screen all contaminants initially considered. During this 
April meeting, and two subsequent meetings, held on June 23 and July 
17, 1997, the Working Group developed these recommendations which were 
approved by the full NDWAC, and subsequently adopted by the Agency, to 
use in screening the initial list to the contaminants to today's draft 
CCL. Summaries of the meetings are provided in the docket. The 
following sections provide the rationale for the initial list of 
contaminants considered and a summary of the development and 
application of the criteria used to evaluate the contaminants on the 
initial list to develop the draft CCL.
1. The Initial List of Chemical Contaminants Considered
    Ten lists of chemical contaminants were considered to be logical 
starting points for developing the first CCL. Of the ten, eight lists 
were ultimately combined to serve as the initial list of contaminants 
to be considered for the CCL. Some contaminants appear on more than one 
of the eight lists. The initial list of contaminants considered, as 
well as those eliminated or deferred from consideration, are in Table 
3. The following sections provide a description of each of the lists 
and the rationale behind including it with, or excluding it from, the 
initial list of contaminants considered.

[[Page 52202]]



                             Table 3.--Initial List of Chemical Contaminants Considered During Development of the Draft CCL                             
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                            Contaminant lists considered                                
                                                          ----------------------------------------------------------------------------------------------
                 Contaminant                    CAS No.                 Health                                       Stakeholder                        
                                                           1991 DWPL  advisories  IRIS  (3)   PWS (4)    CERCLA (5)    summary     TRI list  OPP ranking
                                                              (1)         (2)                                          list (6)      (7)          (8)   
--------------------------------------------------------------------------------------------------------------------------------------------------------
                         Contaminants Identified as Initial Candidates for the CCL during April 3-4, 1997 Working Group Meeting                         
--------------------------------------------------------------------------------------------------------------------------------------------------------
Inorganics:                                                                                                                                             
  Aluminum..................................    7429-90-5           .........  .........  ...........            ...........
  Zinc......................................    7440-66-6           .........  .........  ...........  ...........      ...........
Pesticides:                                                                                                                                             
  Acetochlor................................   34256-82-1  .........       .........  .........  ...........        .........      
  Alachlor ESA..............................  ...........  .........  ..........  .........  .........  ...........        .........      
  Butylate..................................    2008-41-5  .........           .........  ...........  ...........  .........      
  Chlorpyrifos..............................    2921-88-2  .........           .........  ...........        .........  ...........
  DCPA (Dacthal)............................    1861-32-1           .........  .........  ...........        .........  ...........
  DCPA di-acid degradate....................    2136-79-0      ..........  .........  .........  ...........  ...........  .........      
  DCPA mono-acid degradate..................     887-54-7      ..........  .........  .........  ...........  ...........  .........  ...........
  DDE.......................................      72-55-9  .........  ..........      .........        ...........  .........  ...........
  Diazinon..................................     333-41-5  .........       .........  .........  ...........  ...........  .........      
  Diuron....................................     330-54-1  .........       .........  .........  ...........        .........      
  Endosulfan................................     115-29-7  .........  ..........      .........  ...........        .........      
  EPTC (s-ethyl-dipropylthio-carbamate).....     759-94-4  .........  ..........      .........  ...........  ...........  .........      
  Malathion.................................     121-75-5  .........       D   .........  ...........  ...........  .........  ...........
  Methyl parathion..........................     298-00-0  .........           .........  ...........  ...........  .........  ...........
  Metolachlor...............................   51218-45-2               .........  ...........        .........      
  Metribuzin................................   21087-64-9               .........  ...........        .........      
  Prometon..................................    1610-18-0           .........  .........  ...........  ...........  .........      
  Propanil..................................     709-98-8  .........  ..........      .........  ...........  ...........  .........  ...........
  Tebuthiuron...............................   34014-18-1  .........       .........  .........  ...........  ...........  .........  ...........
  Terbacil..................................    5902-51-2  .........       .........  .........  ...........  ...........  .........      
  Triazines (total) (9).....................  ...........  .........  ..........  .........  .........  ...........        .........  ...........
  Triazine degradation products (9),                                                                                                                    
   atrazine-desethyl........................    6190-65-4  .........  ..........  .........  .........  ...........        .........      
  Triazines (unregulated) (9)...............  ...........  .........  ..........  .........  .........  ...........        .........  ...........
   Trifluralin..............................    1582-09-8               .........  ...........  ...........  .........      
Organics:                                                                                                                                               
  2-methyl-Phenol (o-cresol)................      95-48-7  .........  ..........      .........  ...........  ...........  .........  ...........
  Acetone...................................      67-64-1  .........  ..........      .........  ...........  ...........  .........  ...........
  Ethylene glycol...........................     107-21-1  .........           .........  ...........  ...........      ...........
  Methyl ethyl ketone (MEK).................      78-93-3           .........  .........  ...........            ...........
   Methyl-t-butyl ether (MTBE)..............    1634-04-4           .........  .........  ...........            ...........
  Nitrobenzene..............................      98-95-3      ..........      .........  ...........  ...........  .........  ...........
  Phenol....................................     108-95-2  .........           .........  ...........  ...........      ...........
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Additional Contaminants Considered for the CCL                                                     
--------------------------------------------------------------------------------------------------------------------------------------------------------
Inorganics:                                                                                                                                             
  Ammonia...................................    7664-41-7  .........       .........  .........  ...........            ...........
  Ammonium nitrate..........................    6484-52-2  .........  ..........  .........  .........  ...........  ...........      ...........
  Ammonium sulfamate........................    7773-06-0  .........       .........  .........  ...........  ...........  .........  ...........
  Ammonium sulfate..........................    7783-20-2  .........       .........  .........  ...........  ...........      ...........
  Boron.....................................    7440-42-8           .........  .........  ...........  ...........  .........  ...........
  Carbon disulfide..........................      75-15-0  .........  ..........  .........  .........  ...........  ...........      ...........
  Carbonyl sulfide..........................     463-58-1  .........  ..........  .........  .........  ...........  ...........      ...........
  Cobalt....................................    7440-48-4  .........  ..........  .........  .........  ...........  ...........      ...........
  Hydrochloric acid.........................    7647-01-0  .........  ..........  .........  .........  ...........  ...........      ...........
  Hydrogen fluoride.........................    7664-39-3  .........  ..........  .........  .........  ...........  ...........      ...........
  Manganese.................................    7439-96-5      ..........  .........  .........                  ...........
  Metam-sodium..............................     137-42-8  .........  ..........      .........  ...........  ...........  .........  ...........
  Molybdenum................................    7439-98-7           .........  .........  ...........  ...........  .........  ...........
  Phosphoric acid...........................    7664-38-2  .........  ..........  .........  .........  ...........  ...........      ...........
  Phosphorous...............................    7723-14-0  .........       .........  .........        ...........      ...........
  Sodium....................................    7440-23-5  .........       .........  .........  ...........  ...........  .........  ...........
  Strontium.................................    7440-24-6           .........  .........  ...........  ...........  .........  ...........
  Vanadium..................................    7440-62-2           .........  .........  ...........  ...........  .........  ...........
Pesticides:                                                                                                                                             
  1,3-Dichloropropene (telone or 1,3-D).....     542-75-6               .........  ...........        .........      
  2,4,5-T...................................      93-76-5           .........  .........  ...........  ...........  .........  ...........
  2,4-DB....................................      94-82-6  .........  ..........  .........  .........  ...........  ...........  .........      
  2,4-DP....................................     120-36-5  .........  ..........  .........  .........  ...........        .........  ...........

[[Page 52203]]

                                                                                                                                                        
  4-Nitrophenol (p-Nitrophenol).............     100-02-7           .........  .........  ...........  ...........  .........  ...........
  Acephate..................................   30560-19-1  .........       .........  .........  ...........        .........  ...........
  Acifluofen................................   50594-66-6           .........  .........  ...........        .........      
  Aldrin....................................     309-00-2  .........       .........  .........        ...........  .........             
  Ametryn...................................     834-12-8  .........       .........  .........  ...........        .........      
  Amitraz...................................   33089-61-1  .........  ..........  .........  .........  ...........        .........  ...........
  Asulam....................................    3337-71-1      ..........  .........  .........  ...........  ...........  .........      
  Bensulfuron methyl........................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Bentazon..................................   25057-89-0           .........  .........  ...........  ...........  .........      
  Benzidine.................................      92-87-5  .........  ..........  .........  .........        ...........  .........  ...........
  Bromacil..................................     314-40-9           .........  .........  ...........        .........      
  Bromoxynil................................    1689-84-5  .........  ..........      .........  ...........  ...........  .........      
  Cadre.....................................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Caprolactum...............................     105-60-2  .........  ..........      .........  ...........  ...........  .........  ...........
  Captan....................................     133-06-2  .........  ..........      .........  ...........  ...........  .........  ...........
  Carbaryl..................................      63-25-2  .........           .........  ...........  ...........  .........  ...........
  Carboxin..................................    5234-68-4  .........       .........  .........  ...........  ...........  .........  ...........
  Chloramben................................     133-90-4  .........       .........  .........  ...........        .........  ...........
  Chlorimuron ethyl.........................   90982-32-4  .........  ..........  .........  .........  ...........  ...........  .........      
  Chlorothalonil............................    1897-45-6  .........           .........  ...........  ...........  .........  ...........
  Chlorsulfuron.............................   64902-72-3  .........  ..........  .........  .........  ...........  ...........  .........      
  Clopyralid................................    1702-17-6  .........  ..........  .........  .........  ...........        .........  ...........
  Cyanazine.................................   21725-46-2               .........  ...........        .........      
  Cyromazine................................   66215-27-8      ..........  .........  .........  ...........        .........  ...........
  DDD.......................................      72-54-8  .........  ..........  .........  .........        ...........  .........  ...........
  DDT.......................................      50-29-3  .........  ..........      .........        ...........  .........  ...........
  Diazinon--oxypyrimidine...................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Dicamba...................................    1918-00-9           .........  .........  ...........        .........      
  Dichlobenil...............................    1194-65-6  .........  ..........  .........  .........  ...........        .........  ...........
  Dieldrin..................................      60-57-1  .........       .........  .........              .........  ...........
  Dimethoate................................      60-51-5  .........  ..........      .........  ...........        .........  ...........
  Dimethrin.................................      70-38-2  .........       .........  .........  ...........  ...........  .........  ...........
  Diphenamid................................     957-51-7  .........       .........  .........  ...........  ...........  .........  ...........
  Disulfoton................................     298-04-4  .........       .........  .........        ...........  .........  ...........
  Endosulfan sulfate........................    1031-07-8  .........  ..........  .........  .........        ...........  .........  ...........
  Ethalfluralin.............................   55283-68-6  .........  ..........  .........  .........  ...........  ...........  .........      
  Ethofumesate..............................   26225-79-6  .........  ..........  .........  .........  ...........        .........  ...........
  Ethoprop..................................   13194-48-4  .........  ..........  .........  .........  ...........        .........  ...........
  Ethylenethiourea (ETU)....................      96-45-7           .........  .........  ...........  ...........  .........      
  Fenamiphos................................   22224-92-6  .........       .........  .........  ...........        .........      
  Fluazifop-p-butyl.........................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Fluometuron...............................    2164-17-2  .........       .........  .........  ...........  ...........  .........      
  Fomesafen.................................   72178-02-0      ..........  .........  .........  ...........  ...........  .........  ...........
  Fonofos...................................     944-22-9  .........           .........  ...........        .........  ...........
  Halofenozide..............................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Halosulfuron..............................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Hexazinone................................   51235-04-2  .........  ..........  .........  .........  ...........        .........      
  Imazamethabenz............................   81405-85-8  .........  ..........  .........  .........  ...........  ...........  .........      
  Imazapyr..................................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Imazaquin.................................   81335-37-7  .........  ..........  .........  .........  ...........  ...........  .........      
  Imazethapyr...............................   81335-77-5  .........  ..........  .........  .........  ...........        .........      
  Imidacloprid..............................  ...........  .........  ..........  .........  .........  ...........        .........  ...........
  Lactofen..................................   77501-63-4      ..........  .........  .........  ...........  ...........  .........  ...........
  Linuron...................................     330-55-2  .........  ..........      .........  ...........  ...........  .........  ...........
  Maneb (ETU precursor).....................   12427-38-2  .........  ..........      .........  ...........  ...........  .........  ...........
  MCPA......................................      94-74-6  .........       .........  .........  ...........        .........  ...........
  MCPP......................................      93-65-2  .........  ..........  .........  .........  ...........        .........  ...........
  Metalaxyl.................................   57837-19-1      ..........  .........  .........  ...........  ...........  .........  ...........
  Methazole.................................   20354-26-1  .........  ..........  .........  .........  ...........  ...........  .........      
  Methomyl..................................   16752-77-5      ..........      .........  ...........        .........  ...........
  Metsulfuron methyl........................   74223-64-6  .........  ..........  .........  .........  ...........        .........      
  Molinate..................................    2212-67-1  .........  ..........      .........  ...........  ...........  .........  ...........
  MSMA......................................    2163-80-6  .........  ..........  .........  .........  ...........  ...........  .........      
  Napropamide...............................   15299-99-7  .........  ..........  .........  .........  ...........        .........  ...........
  Nicosulfuron..............................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Norflurazon...............................   27314-13-2  .........  ..........  .........  .........  ...........        .........      

[[Page 52204]]

                                                                                                                                                        
  Paraquat..................................    4685-14-7  .........           .........  ...........  ...........  .........      
  Pendimethalin.............................   40487-42-1  .........  ..........      .........  ...........  ...........  .........      
  Primisulfuron methyl......................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Prometryn.................................    7287-19-6  .........  ..........  .........  .........  ...........  ...........  .........      
  Pronamide.................................   23950-58-5  .........       .........  .........  ...........  ...........  .........  ...........
  Propachlor................................    1918-16-7  .........       .........  .........  ...........        .........      
  Propargite................................    2312-35-8  .........  ..........      .........  ...........  ...........  .........  ...........
  Propazine.................................     139-40-2  .........           .........  ...........  ...........  .........      
  Propham...................................     122-42-9  .........       .........  .........  ...........  ...........  .........  ...........
  Propiconazole.............................   60207-90-1  .........  ..........  .........  .........  ...........        .........  ...........
  Propoxur (Baygon).........................     114-26-1  .........       .........  .........  ...........  ...........  .........  ...........
  Prosulfuron...............................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Pyrazon...................................    1698-60-8  .........  ..........  .........  .........  ...........        .........  ...........
  Pyrithiobac-Na............................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Rimsulfuron...............................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Sethoxydim................................   74051-80-2  .........  ..........  .........  .........  ...........  ...........  .........      
  Sulfentrazone.............................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Sulfometuron methyl.......................   74222-97-2  .........  ..........  .........  .........  ...........  ...........  .........      
  Tebufenozide..............................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Terbufos..................................   13071-79-9  .........           .........  ...........        .........  ...........
  Terbufos sulfone..........................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Thiazopyr.................................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Thifensulfuron methyl.....................   79277-27-3  .........  ..........  .........  .........  ...........  ...........  .........      
  Thiodicarb................................   59669-26-0      ..........  .........  .........  ...........  ...........  .........  ...........
  Triallate.................................    2303-17-5  .........  ..........      .........  ...........  ...........  .........  ...........
  Triasulfuron..............................   82097-50-5  .........  ..........  .........  .........  ...........        .........      
  Triberuron methyl.........................  ...........  .........  ..........  .........  .........  ...........  ...........  .........      
  Vernolate.................................    1929-77-7  .........  ..........  .........  .........  ...........  ...........  .........      
Organics:                                                                                                                                               
  1,1,1,2-tetra-chloroethane................     630-20-6           .........  .........  ...........  ...........  .........  ...........
  1,1,1-trichloropropane....................  ...........  .........       .........  .........  ...........  ...........  .........  ...........
  1,1,2,2-tetra-chloroethane................      79-34-5           .........  .........  ...........  ...........  .........  ...........
  1,1-dichloro-ethane.......................      75-34-3      ..........  .........  .........  ...........  ...........  .........  ...........
  1,1-dichloro-propene......................     563-58-6           .........  .........  ...........  ...........  .........  ...........
  1,2,3-trichloro-propane...................      96-18-4           .........  .........  ...........  ...........  .........  ...........
  1,2,4-trimethylbenzene....................      95-63-6  .........  ..........  .........  .........  ...........  ...........      ...........
  1,2-diphenyl-hydrazine....................     122-66-7      ..........  .........  .........  ...........  ...........  .........  ...........
  1,3,5-trichlorobenzene....................     108-70-3  .........       .........  .........  ...........  ...........  .........  ...........
  1,3-butadiene.............................     106-99-0  .........  ..........  .........  .........  ...........  ...........      ...........
  1,3-dichloro-benzene......................     541-73-1      ..........  .........  .........  ...........  ...........  .........  ...........
  1,3-dichloropropane.......................     142-28-9           .........  .........  ...........  ...........  .........  ...........
  1,3-dichloropetan-3-OL,...................  ...........  .........  ..........  .........      ...........  ...........  .........  ...........
  1,3-dinitrobenzene........................      99-65-0  .........       .........  .........  ...........  ...........  .........  ...........
  1,4-dioxane...............................     123-91-1  .........           .........  ...........            ...........
  1,4-dithiane..............................     505-29-3  .........       .........  .........  ...........  ...........  .........  ...........
  1-methyl -2-Pyrrolidinone.................     872-50-4  .........  ..........  .........      ...........  ...........  .........  ...........
  2,2-dichloro-propane......................     594-20-7           .........  .........  ...........  ...........  .........  ...........
  2,4,6-trichlorophenol.....................      88-06-2  .........       .........  .........  ...........  ...........  .........  ...........
  2,4-dichlorophenol........................     120-83-2  .........       .........  .........  ...........  ...........  .........  ...........
  2,4-dinitrophenol.........................      51-28-5      ..........  .........  .........  ...........  ...........  .........  ...........
  2,4-dinitrotoluene........................     121-14-2           .........  .........  ...........  ...........  .........  ...........
  2,6-dinitrotoluene........................     606-20-2           .........  .........  ...........  ...........  .........  ...........
  2,6-di-tert-butyl-p-benzoquinone (DTBB),                                                                                                              
   (2,6-bis(1,1-dimethylethyl)2,5-                                                                                                                      
   cyclohexadiene-1,4-dione)................     719-22-2  .........  ..........  .........      ...........  ...........  .........  ...........
  2-methanoxy ethanol.......................     109-86-4  .........  ..........  .........  .........  ...........  ...........      ...........
  3-chloro-1-propene........................     107-05-1  .........  ..........  .........      ...........  ...........  .........  ...........
  4,4'-isopropylidenediphenol (bisphenol A).      80-05-7  .........  ..........  .........  .........  ...........  ...........      ...........
  4-methyl-Phenol (p-cresol)................     106-44-5  .........  ..........  .........      ...........  ...........  .........  ...........
  Acetaldehyde..............................      75-07-0  .........  ..........  .........  .........  ...........  ...........      ...........
  Acetamide.................................      60-35-5  .........  ..........  .........      ...........  ...........  .........  ...........
  Acetonitrile..............................      75-05-8  .........  ..........  .........  .........  ...........  ...........      ...........
  Acrylic acid..............................      79-10-7  .........  ..........  .........  .........  ...........  ...........      ...........
  Acrylonitrile.............................     107-13-1           .........  .........  ...........  ...........      ...........

[[Page 52205]]

                                                                                                                                                        
  Aniline...................................      62-53-3  .........  ..........      .........  ...........  ...........  .........  ...........
  Azulene...................................     275-51-4  .........  ..........  .........      ...........  ...........  .........  ...........
  Benzaldehyde..............................     100-52-7  .........  ..........  .........      ...........  ...........  .........  ...........
  Benzaldehyde, 3-hydroxy-..................     100-83-4  .........  ..........  .........      ...........  ...........  .........  ...........
  Benzamide, N-acetyl-......................    1575-95-7  .........  ..........  .........      ...........  ...........  .........  ...........
  Benzamide,N-ethyl-........................     614-17-5  .........  ..........  .........      ...........  ...........  .........  ...........
  Benzeneacetamide, N,N-dimethyl-a-phenyl-..  ...........  .........  ..........  .........      ...........  ...........  .........  ...........
  Benzeneacetonitrile.......................     140-29-4  .........  ..........  .........      ...........  ...........  .........  ...........
  Benzofluoranthene.........................   56832-73-6  .........  ..........  .........  .........        ...........  .........  ...........
  Bis-2-chloroisopropyl ether...............   39638-32-9  .........       .........  .........  ...........  ...........  .........  ...........
  Bornyl acetate............................      76-49-3  .........  ..........  .........      ...........  ...........  .........  ...........
  Bromobenzene..............................     108-86-1           .........  .........  ...........  ...........  .........  ...........
  Catechol..................................     120-80-9  .........  ..........  .........  .........  ...........  ...........      ...........
  Chlorodifluoromethane HCFC-22.............      75-45-6  .........  ..........  .........  .........  ...........  ...........      ...........
  Chlorophenol 2-...........................      95-57-8  .........       .........  .........  ...........  ...........  .........  ...........
  Creosote..................................    8001-58-9  .........  ..........  .........  .........        ...........  .........  ...........
  Cresol mixed isomers......................    1319-77-3  .........  ..........  .........  .........  ...........  ...........      ...........
  Cymene p-(p-isopropyltolunene)............      99-87-6  .........       .........  .........  ...........  ...........  .........  ...........
  Decabromodiphenyl oxide...................    1163-19-5  .........  ..........  .........  .........  ...........  ...........      ...........
  Dibenzo(a,h)anthracene....................      53-70-3  .........  ..........  .........  .........        ...........  .........  ...........
  Dichloro CFC-114..........................      76-14-2  .........  ..........  .........  .........  ...........  ...........      ...........
  Dichloro-difluoromethane..................      75-71-8           .........  .........  ...........            ...........
  DichloroHCFC141-b.........................     171-00-6  .........  ..........  .........  .........  ...........  ...........      ...........
  Diethanolamine............................     111-42-2  .........  ..........  .........  .........  ...........  ...........      ...........
  Diisoamylene..............................  ...........  .........  ..........  .........      ...........  ...........  .........  ...........
  Diisopropyl methylphosphonate.............    1445-75-6  .........       .........  .........  ...........  ...........  .........  ...........
  Dimethyl methylphosphonate................     756-79-6  .........       .........  .........  ...........  ...........  .........  ...........
  Diphenylamine.............................     122-39-4  .........       .........  .........  ...........  ...........  .........  ...........
  Ethanone, 1-[4-(hydroxy-1-methylethyl)                                                                                                                
   phenyl]-.................................  ...........  .........  ..........  .........  .........  ...........  ...........  .........  ...........
  Ethyl ether...............................      60-29-7  .........  ..........      .........  ...........  ...........  .........  ...........
  Ethylene..................................      74-85-1  .........  ..........  .........  .........  ...........  ...........      ...........
  Fog oil...................................  ...........  .........       .........  .........  ...........  ...........  .........  ...........
  Formaldehyde..............................      50-00-0  .........           .........  ...........  ...........      ...........
  Formic acid...............................      64-18-6  .........  ..........  .........  .........  ...........  ...........      ...........
  Freon 113.................................      76-13-1  .........  ..........  .........  .........  ...........  ...........      ...........
  Glufosinate ammonium......................   77182-82-2  .........  ..........  .........  .........  ...........        .........  ...........
  Glycol ethers.............................     111-46-6  .........  ..........  .........  .........  ...........  ...........      ...........
  HCFC-11142-b..............................  ...........  .........  ..........  .........  .........  ...........  ...........      ...........
  Hexachloro-butadiene......................      87-68-3           .........  .........        ...........  .........  ...........
  Hexachloroethane..........................      67-72-1           .........  .........  ...........  ...........  .........  ...........
  Hexanoic acid.............................     142-62-1  .........  ..........  .........      ...........  ...........  .........  ...........
  Hexazinone................................   51235-04-2  .........       .........  .........  ...........  ...........  .........  ...........
  HMX (cyclotetramethylene tetranitramine)..    2691-41-0  .........       .........  .........  ...........  ...........  .........  ...........
  Hydroperoxide, 1,1-dimethylethy...........     l75-91-2  .........  ..........  .........      ...........  ...........  .........  ...........
  Iron,tricarbonyl-[n-(phenyl-2-                                                                                                                        
   pyridinylmethylene)-benze namide-N,N.....  ...........  .........  ..........  .........      ...........  ...........  .........  ...........
  Isophorone................................      78-59-1           .........  .........  ...........  ...........  .........  ...........
  Isopropylbenzene (cumene).................      98-82-8  .........           .........  ...........  ...........      ...........
  Isopropyl methyl-phosphonic acid..........    1832-54-8  .........       .........  .........  ...........  ...........  .........  ...........
  Maleic hydrazide..........................     123-33-1  .........       .........  .........  ...........  ...........  .........  ...........
  Merphos oxide.............................      78-48-8  .........       .........  .........  ...........  ...........  .........  ...........
  Methane, tert-butoxyisopropoxy-...........  ...........  .........  ..........  .........      ...........  ...........  .........  ...........
  Methanol..................................      67-56-1  .........  ..........      .........  ...........  ...........      ...........
  Methyl bromide............................      74-83-9  .........  ..........  .........  .........  ...........  ...........  .........  ...........
  Methyl isobutyl ketone (MIBK).............     108-10-1      ..........  .........  .........  ...........            ...........
  Methyl methacrylate.......................      80-62-6  .........  ..........  .........  .........  ...........  ...........      ...........
  Methylene bis phenylisocyanate............     101-68-8  .........  ..........  .........  .........  ...........  ...........      ...........

[[Page 52206]]

                                                                                                                                                        
  Other fuel oxygenates (TAME, DIPE, ETBE)..           na  .........  ..........  .........  .........  ...........        .........  ...........
  n-Butanol.................................      71-36-3  .........  ..........      .........  ...........  ...........      ...........
  n-Hexane..................................     110-54-3  .........       .........  .........  ...........  ...........  .........  ...........
  Naphthalene...............................      91-20-3           .........  .........  ...........            ...........
  nitro-Cyclopentane........................  ...........  .........  ..........  .........      ...........  ...........  .........             
  Nitrocellulose............................    9004-70-0  .........       .........  .........  ...........  ...........  .........  ...........
  Nitroglycerine............................      55-63-0  .........  ..........  .........  .........  ...........  ...........      ...........
  Nitroquanidine............................  ...........  .........       .........  .........  ...........  ...........  .........  ...........
  o-Chlorotoluene...........................      95-49-8           .........  .........  ...........  ...........  .........  ...........
  Octatriene, 3,7-dimethyl-1,3,6-...........   13877-91-3  .........  ..........  .........      ...........  ...........  .........  ...........
  Organotins (tributyl, methyl tin, etc.)...  ...........  .........  ..........  .........  .........  ...........        .........  ...........
  P-Chlorotoluene...........................     106-43-4           .........  .........  ...........  ...........  .........  ...........
  Pentachloroethane.........................      76-01-7  .........       .........  .........  ...........  ...........  .........  ...........
  Propylbenzene n-..........................     103-65-1  .........       .........  .........  ...........  ...........  .........  ...........
  Propylene glycol..........................      57-55-6  .........  ..........  .........  .........  ...........        .........  ...........
  Propylene oxide...........................      75-56-9  .........  ..........  .........  .........  ...........  ...........      ...........
  Rhodamine WT..............................  ...........  .........  ..........  .........  .........  ...........        .........  ...........
  RDX (cyclo trimethylene trinitramine).....     121-82-4  .........       .........  .........  ...........  ...........  .........  ...........
  Terbuthylazine............................    5915-41-3  .........  ..........  .........      ...........  ...........  .........  ...........
  Tetrahydrofuran...........................     109-99-9      ..........  .........  .........  ...........        .........  ...........
  Tetranitromethane (TNM)...................     509-14-8  .........       .........  .........  ...........  ...........  .........  ...........
  Trichlorofluoromethane....................      75-69-4  .........       .........  .........  ...........  ...........  .........  ...........
  Triethylbenzene...........................   25340-18-5  .........       .........  .........  ...........  ...........  .........  ...........
  Trinitrotoluene (TNT).....................     118-96-7  .........       .........  .........  ...........  ...........  .........  ...........
  Vinyl acetate.............................     108-05-4  .........  ..........  .........  .........  ...........  ...........      ...........
--------------------------------------------------------------------------------------------------------------------------------------------------------
1. 1991 Drinking water Priority List, but does not include disinfection by-products or crytosporidium for which regulations are being under the M/DBP   
  rules.                                                                                                                                                
2. Health Advisories developed under EPA's Health Advisory Program. Does not include contaminants regulated under the SDWA.                             
3. Contaminants from IRIS based on a risked-based screen developed by EPA.                                                                              
4. Contaminants identified in public water systems samples as non-targets.                                                                              
5. First 50 contaminants of the 1995 ATSDR Ranked CERCLA priority chemicals list.                                                                       
6. Stakeholder Summary List consists of specific contaminants proposed as candidates by participants of EPA's December 2-3, 1997 Stakeholder Meeting on 
  the Contaminant Identification Method.                                                                                                                
7. The TRI List was derived from chemicals with significant health effects as found in IRIS.                                                            
8. The OPP Ranking is a ranking of pesticides from highest to lowest potential to leach to ground water.                                                
9. Stakeholders requested that the Agency address tirazines as a class of contaminants including their degradates, as opposed to addressing them as     
  individual contaminants.                                                                                                                              

    a. 1991 Drinking Water Priority List. The SDWA, as amended in 1986, 
required EPA to publish a triennial list of priority contaminants, the 
DWPL, which may require regulation. The first list containing 53 
contaminants/contaminant group was published on January 2, 1988 (53 FR 
1892). Since none of the contaminants had been selected for regulation, 
EPA revised and updated the 1988 list three years later. The revised 
and updated list, published on January 14, 1991 (56 FR 1470), contained 
50 substances carried over from the 1988 list and 27 new substances, 
bringing the total number of contaminants/contaminant groups to 77, 
including one microorganism.
    In consideration of the statutory requirements and the time frame 
for rulemaking in the SDWA at the time, EPA used the following criteria 
to select contaminants for the DWPL: (1) occurrence or the potential 
occurrence of the substance in public water systems; (2) documented or 
suspected adverse health effects; and (3) the availability of 
sufficient information on the substance so that a regulation could be 
developed within the statutory time frame. The contaminants were 
selected from the following groups: disinfectants and their byproducts, 
the first group of 100 contaminants on the 1987 CERCLA priority list of 
hazardous substances (52 FR 12866), design analytes of the EPA National 
Pesticide Survey conducted between 1987-1990, pesticides with high 
potential for leaching in groundwater, substances recommended by the 
States and EPA regions, unregulated contaminants monitored under 
Section 1445 of the SDWA, and certain substances reported frequently 
and at high concentrations in drinking water. The selection of 
contaminants was made with the assistance of the DWPL workgroup which 
consisted of representatives from various programs within the Agency, 
the National Toxicology Program, the U.S. Geological Survey, and the 
Agency for Toxic Substances and Disease Registry.
    For development of the draft CCL, the Agency selected contaminants 
from the 1991 DWPL that were not specifically addressed by other 
regulations under development. Thus, all contaminants specifically 
addressed by the disinfectants and disinfection byproducts regulation 
were eliminated from consideration.
    b. Health advisories. The Health Advisories (HAs) are prepared for 
contaminants that have the potential to cause adverse human health 
effects and

[[Page 52207]]

which are known or anticipated to occur in drinking water, but for 
which no national regulations currently exist. Each HA contains 
information on the nature of the adverse health effects of the 
contaminant and the concentrations that would not be anticipated to 
cause an adverse effect following various periods of exposure. HAs also 
summarize available data on occurrence, pharmacokinetics, environmental 
fate, health effects, available analytical methods, and treatment 
techniques for the contaminant. HA concentration levels include a 
margin of safety to protect sensitive members of the population (e.g., 
children, the elderly, pregnant women).
    The Office of Water Health Advisory Program was initiated to 
provide information and guidance to individuals and agencies concerned 
with potential risk from drinking water contaminants. HAs are used only 
for guidance and are not legally enforceable, and are subject to change 
as new information becomes available. For purposes of developing the 
draft CCL, all contaminants with HAs, or HAs under development, were 
considered.
    c. Integrated Risk Information System. The Integrated Risk 
Information System (IRIS) is an EPA on-line database containing health 
risk and EPA regulatory information. IRIS lists chemicals of interest 
or concern for which the Agency has reached consensus regarding adverse 
health effects. When available, a reference dose (RfD) for non-cancer 
health effect resulting from oral exposure is reported with information 
about how the RfD was derived and any uncertainty regarding the source 
studies. An RfD is an estimate of a daily exposure to the human 
population that is likely to be without appreciable risk of adverse 
effect over a lifetime of exposure. For carcinogens, a carcinogenic 
assessment, or cancer potency factor, is reported for both oral and 
inhalation exposure. The cancer potency factor is the estimated risk to 
the human population of cancer effects over a lifetime of exposure.
    In 1992, in anticipation of the next DWPL, the Agency developed a 
list of chemicals based on a risk-based screen of chemicals in IRIS. 
There were approximately 600 chemicals in the IRIS database in 1992, 
and 312 were selected for further screening. The 312 were chosen 
because they had defined toxicity via the oral route of exposure and 
did not have NPDWRs. The 312 chemicals were screened using the 
following categories: (1) using Storage and Retrieval (STORET) data, 
chemicals were identified with concentration in water that exceeded the 
drinking water equivalent level (DWEL) which was derived from the 
reference dose or cancer potency; (2) chemicals were identified that 
were produced in quantities exceeding one billion pounds per year; (3) 
pesticides were identified with use exceeding 1000 tons per year; and 
(4) chemicals were identified that were reported in the Toxic Release 
Inventory (TRI) database as discharged to surface water in excess of 
100 tons per year. Sixteen chemicals met the STORET criteria; nine, the 
production criteria; 31, the pesticides criteria; and 6, the TRI 
criteria. A total of 48 individual chemicals were identified, and some 
were identified by more than one screen. All 48 contaminants were 
included on the initial list for consideration.
    d. Non-Target Analytes in Public Water Supply Samples. In 
anticipation of the 1994 DWPL, the Agency consulted with analytical 
laboratories that routinely analyze samples for public water systems to 
determine what contaminants were occurring that were not currently 
regulated. A list of contaminants tentatively identified in 1991 from 
drinking water samples collected for compliance monitoring was 
developed. These contaminants, also referred to as non-targets 
analytes, are compounds identified by the spikes found on the 
chromatograph. The concentrations for these compounds were not 
measured. These non-target analytes represent the monitoring experience 
of several water systems with operations in various states. The 
contaminants included on the initial list for consideration are a 
subset of 23 contaminants chosen from the larger list of non-targets 
analytes. The 23 contaminants were chosen because they were considered 
to be related to possible anthropogenic sources.
    e. CERCLA Priority List. In developing the CCL, the SDWA requires 
EPA to consider substances referred to in section 101(14) of the 
CERCLA. CERCLA requires the Agency for Toxic Substances and Disease 
Registry (ATSDR) to prepare a list in the order of priority of 
hazardous substances which are most commonly found at facilities on the 
CERCLA National Priority List (NPL).
    In 1995, ATSDR developed a list of 275 hazardous substances ranked 
by the order of priority. (ATSDR, 1996) To develop this list, ATSDR 
considered 750 of 2800 substances present at NPL sites and ranked them 
based on the following three criteria, which were combined to result in 
a total score. These criteria were: (1) Frequency of occurrence at NPL 
sites, (2) toxicity, and (3) potential for human exposure. The number 
of NPL sites at which a substance was identified in any medium was used 
to indicate the frequency of occurrence. EPA's Reportable Quantity (RQ) 
was used to assess the toxicity of candidate substance. If a RQ was not 
available, the RQ methodology was applied to candidate substances to 
establish a Toxicity/Environmental Score. The human exposure component 
was based on two parts: the concentration of the substance in the 
environmental media and the exposure status of population. EPA included 
the top 50 substances from the 1995 CERCLA prioritized list of 275 
substances for consideration for the draft CCL.
    f. Stakeholder responses. In December 1996, the EPA convened its 
first stakeholder meeting on the contaminant identification process. At 
that meeting, EPA requested input on what contaminants to include on 
its first CCL. At the December meeting, and following, participants 
have provided input to the Agency on contaminants for inclusion on, or 
exclusion from, the CCL. Some stakeholders provided information on 
health effects or occurrence, or both, while others listed 
contaminants. All contaminants suggested by stakeholders were included 
for initial consideration except those which already had NPDWRs, or 
which were included under other regulatory activity mentioned in 
section VIII of this notice.
    g. Toxic Release Inventory. Another source of available information 
which could serve as a predictor of anticipated occurrence in drinking 
water, is the TRI. This data base, established under the Emergency 
Planning and Community Right-to-Know Act of 1986, contains information 
from manufacturing facilities in the United States regarding transfers 
and releases of toxic and hazardous materials to air, ground and water. 
The most recent report analyzed data gathered for calendar year 1994 
from 22 chemical categories and included 343 separate chemicals from 
23,000 facilities which met certain thresholds requiring submission of 
data. (U.S. EPA, 1997c).
    In order to assess the potential for a chemical to be a contaminant 
in public water systems, EPA conducted an analysis of the release and 
emissions data. Each of the four categories of emissions or discharges 
were assigned a threshold value above which the contaminant was deemed 
to fit within the criteria of the SDWA, as a contaminant anticipated to 
occur in public water systems. The threshold did not attempt to 
attribute differences in reactivity, solubility, mobility or

[[Page 52208]]

toxicity of the pollutants at this stage of the contaminant evaluation 
process, but involved simply determining a gross anticipation factor. 
If a contaminant was released via an on-site discharge to the 
environment, EPA judged that it was reasonable to anticipate it as a 
contaminant in public water systems to varying degrees, depending upon 
the media receiving the discharge.
    The overall analysis of the above TRI criteria resulted in 58 
chemicals from the various discharges meeting the criteria. Where a 
release was close to the threshold, it was included in the tally. 
Several chemicals met the criteria but were excluded because there is 
an existing standard (e.g., hydrofluoric acid--fluoride is regulated) 
or a standard under consideration (sulfuric acid--there is regulatory 
activity currently underway regarding sulfate). Other contaminants such 
as ammonia, hydrochloric acid, or methanol were not believed to 
represent a significant threat to drinking water due to limited 
persistence, leaving 51 contaminants. Of the 51 contaminants, 49 met 
the criteria for air release, 21 from stack emissions, 38 for fugitive 
emissions, 11 via underground injection, 13 from land release, and 30 
for surface water releases. All 51 were included for initial 
consideration in Table 3.
    h. Pesticides identified by Office of Pesticide Programs. In 
developing the CCL, the SDWA requires EPA the consider substances 
referred to in the FIFRA. During the development of the draft CCL, the 
Agency's Office of Ground Water and Drinking Water sought assistance 
from the Office of Pesticide Programs (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. (U.S. EPA, 1997b) The list of pesticides, based on 
physical-chemical properties, occurrence and extent of use, was ranked 
using the Ground Water (GW) Risk score, a calculated potential to leach 
to ground water. Pesticides with a GW Risk of 2.0 or greater were 
included for initial consideration in developing the CCL (see Table 3).
    However, later during the data evaluation and screening phase of 
the draft CCL development, the decision was made to defer some of the 
pesticides identified by the OPP GW Risk of 2.0 or greater. The 
pesticides in Table 4 include those where the GW Risk value of 2.0 or 
greater was the only factor for inclusion on the CCL. The decision was 
made, that for these cases, inclusion on the CCL would be deferred 
pending further evaluation of the potential of these pesticides to 
occur at levels of health concern. Many new pesticides for which no 
other data exists are included in Table 4.
Table 4. Pesticides Deferred
Asulam
bensulfuron methyl
bentazon
bromacil
Cadre
chlorimuron ethyl
chlorsulfuron
Diazinon--oxypyrimidine
Dicamba
Ethylenethiourea (ETU)
Fenamiphos
Fluometuron
Halofenozide
Halosulfuron
Hexazinone
Imazamethabenz
Imazapyr
Imazaquin
Imazethapyr
MCPA (Methoxone)
Methsulfuron methyl
Nicosulfuron
Norflurazon
Primisulfuron methyl
Prometryn
Propazine
Prosulfuron
Pyrithiobac-Na
Rimsulfuron
Sulfentrazone
Sulfometuron methyl
Tebufenozide
Terbufos sulfone
Thiazopyr
Triasulfuron

    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 then compare the estimated concentrations 
with health advisory levels or calculated health levels based on 
reference doses or cancer potency. The model is expected to be 
completed and available for use at the end of 1997, and at that time 
the Agency will reevaluate the inclusion for the additional pesticides 
on Table 4 on the CCL.
    On August 4, 1997, EPA announced its schedule for reassessing 
tolerances for pesticide residues on raw and processed foods (62 FR 
42020). Publication of this schedule was pursuant to the requirements, 
as established by the Food Quality Protection Act of 1996 (FQPA). Under 
this new law, EPA is required to reassess all existing tolerances and 
exemptions from tolerances for both active and inert ingredients. EPA 
is directed to give priority review to pesticides that appear to 
present risk concerns based on current data. Many of the pesticides 
included in today's notice are included among the first group of 
reassessments.
    In reassessing tolerances, EPA must consider the aggregate exposure 
to the pesticide, including drinking water; cumulative effects from 
other pesticides with a common mode of toxicity; whether there is an 
increased susceptibility from exposure to the pesticide to infants and 
children; and whether the pesticide produces an effect in humans 
similar to an effect produced by a naturally occurring estrogen or 
other endocrine effects.
    i. Safe Drinking Water Hotline. The Hotline provides information 
about EPA's drinking water regulations and other related drinking water 
and ground water topics to the public, the regulated community, and 
State and local officials. The Hotline assists callers with questions 
on the regulations and programs developed in response to the Safe 
Drinking Water Act, and inquiries about the levels and health effects 
of specific contaminants found in or suspected to be in drinking water 
from public water systems and private wells, and handles requests for 
drinking water publications (fact sheets, pamphlets, health advisories, 
etc.). The Safe Drinking Water Hotline receives hundreds of calls each 
week, and a large percentage of the calls come from private citizens, 
consultants, educators, researchers, and health care professionals from 
across the country. The Hotline provided a list of contaminants that 
were not currently regulated or proposed for regulation for which 
callers had expressed concern or interest (see Table 5).
Table 5. Contaminants Identified by the Safe Drinking Water Hotline
Calcium
Phosphates
1,1,1-dichloroethane
Gasoline
Perchlorate
Total Petroleum Hydrocarbons
    The Hotline did not ascertain if the calls were due to a general 
question or inquiry, or if they were related to a contamination 
incident. At the April 3-4, 1997 Working Group meeting, the decision 
was made not to include the Hotline list for initial consideration, and 
that a list from the Hotline would only be useful if it captured 
concerns or reports of contamination.
    The Agency will attempt to capture Hotline inquiries concerning 
contamination incidents for future CCL development. Perchlorate, a 
contaminant discussed later in this notice, probably should have been

[[Page 52209]]

included for initial consideration. The fact that perchlorate was on 
the Hotline list, and no other, may indicate that such a list from the 
Hotline could be useful if the nature of the inquiry can be recorded.
    j. Endocrine disruptors. A list of contaminants was developed which 
included those suspected of having adverse effects on endocrine 
function (see Table 6). For several years, the Agency has been 
concerned that chemicals may be disrupting the endocrine (i.e., 
hormonal) systems of humans and wildlife. It has also been hypothesized 
that endocrine disruption might result in cancer, harm to male and 
female reproductive systems, thyroid damage, or other adverse 
consequences. In February 1997, EPA issued an assessment and analysis 
of this concern (U.S. EPA, 1997a). The report represents an interim 
assessment pending a more extensive review expected to be issued by the 
National Academy of Sciences (NAS) later this year.
Table 6. Contaminants Identified as Suspected of Endocrine Disruption
Amitrole
Benomyl
Dicofol (Kelthane)
Esfenvalerate
Ethylparathion
Fenvalerate
Kepone
Mancozeb
Metiram
Mirex
Nitrofen
Oxychlordane
Parathion
Permethrin
Synthetic pyrethroids
Transnonachlor
Tributyltin oxide
Vinclozolin
Zineb
Ziram
Octachlorostyrene
PBBs
Penta- to nonyl-phenols

    In brief, the report found 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. The exceptions include incidents of chemical exposure in 
the workplace and exposure to the drug DES. 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. OPPTS is actively 
engaged in research and regulatory initiatives to respond to the 
growing scientific and public concern over endocrine disruptors.
    The Endocrine Disruptor Screening and Testing Advisory Committee 
(EDSTAC) has been established to provide advice and counsel to the 
agency in implementing a screening and testing strategy required under 
the FQPA and SDWA. EDSTAC is composed of a balanced representation from 
industry, government, environmental and public health groups, labor, 
academia, and other interested stakeholders. During its deliberations, 
the Committee will consider human health, ecological, estrogenic, 
androgenic, anti-estrogenic, anti-androgenic, and thyroid effects of 
pesticides, industrial chemicals, and important mixtures. 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 Scientific Advisory Panel.
    EPA is also involved in concurrent effort to coordinate activities 
with the European Union, the Organization of Economic and Community 
Development, and the United Nations Environmental Program concerning 
global research programs, and international harmonization of endocrine 
disruptor screening and testing methods for chemicals and pesticides.
    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 initial consideration for the draft CCL based 
solely on the possibility of endocrine disruption (although several 
contaminants implicated as endocrine disruptors were considered for 
other reasons). The Agency will continue to follow this issue closely 
and reconsider this category of potential contaminants in the 
development of future CCLs.
2. Development and Application of the Criteria
    Criteria were developed by the NDWAC Working Group for use in 
screening and evaluating chemical contaminants for the draft CCL, with 
the exception of aldicarbs, nickel, and sulfate which are discussed in 
section III.C.3. The general premises of the criteria were: (1) The 
contaminants included for initial consideration be those on EPA's 
initial list, without NPDWRs, and (2) that occurrence, or anticipated 
occurrence, of the contaminant be evaluated first, before evaluating 
its health effects information. The criteria, presented below, were 
used to screen and evaluate chemical contaminants for the purpose of 
developing today's draft CCL. Data used to evaluate and screen 
contaminants were obtained from STORET, the Hazardous Substances 
Database (HSDB), IRIS, published literature, and various EPA reports 
and documents. The data used in the evaluation and screening are 
included in the docket for today's notice.
    These criteria, as well as the conceptual approach to the 
Contaminant Identification Method (CIM) presented in the December 2-3, 
1996 Stakeholders meeting, will serve as the basis for developing a 
more robust contaminant identification method for future CCL 
development. The search results on each element of the criteria for 
contaminants considered during the development of the CCL can be found 
by using the Occurrence Table, the Health Table, and the Comments Table 
included in the docket for today's notice.
    a. Criteria for occurrence. For the occurrence portion of the 
criteria, an affirmative response to any of the following elements 
would result in moving to the health portion of the criteria for 
further consideration. If all of the occurrence elements had a negative 
response, the contaminant was eliminated from further consideration. 
The two main elements to the occurrence portion of the criteria were as 
follows: (1) Was the contaminant looked for and found in drinking 
water, or in a major drinking water source, or in ambient water at 
levels that would trigger concern about human health? (2) if the 
contaminant was not looked for, is it likely to be found in water based 
on surrogates for occurrence?
    To judge whether a contaminant was looked for and found in drinking 
water, according to the criteria, it would need to be included in a 
major survey which was defined as one which included a population of 
100,000 or more, 2 or more states, or 10 or more small public water 
systems, or a data set such as EPA's Unregulated Contaminants Database. 
To judge whether a contaminant was looked for and found in a major 
drinking water source, or in ambient water, any source of occurrence 
data could be used. A source of drinking water was considered to be 
major if it supplied a population of 100,000 or

[[Page 52210]]

more, or 2 or more states. Levels that would trigger concern about 
human health were defined as concentrations in samples within an order 
of magnitude of the level that is likely to cause health effects, or at 
least \1/2\ of samples at 50% of level that is likely to cause health 
effects. Contaminants were considered to have met the criteria if the 
data available indicated occurrence at a population of 100,000 or more; 
or in 2 or more states; or in 10 or more small public water systems at 
levels that would trigger concern about human health.
    If the contaminant was not looked for using the data available, it 
was evaluated to determine if it was likely to be found in water based 
on surrogates for occurrence. The elements considered as surrogates for 
occurrence included: TRI releases, or production volumes, coupled with 
physical-chemical properties, or the OPP GW Risk value. In order for a 
contaminant to meet this criterion as likely to be found in water using 
TRI, the release to surface water was in excess of 400,000 pounds per 
year, and the physical-chemical properties indicated persistence & 
mobility of the contaminant. The quantity of 400,000 pound per year was 
based on the top 15 TRI chemicals with the largest discharges to 
surface water as reported in 1995. In order for a contaminant to meet 
this criterion as likely to be found in water using production, the 
volume was in excess of 10 billion pounds per year, and physical-
chemical properties indicated persistence and mobility.
    For a contaminant to meet this criteria as likely to be found in 
water using OPP GW Risk, the value was 2.0 or greater. However, late 
during the data evaluation and screening phase of the CCL development, 
the decision was made to defer contaminants identified under this 
element until a more in-depth analysis could be performed that would 
include risk to both surface and ground water, and a component to 
address health.
    b. Criteria for health. For the health portion of the criteria, an 
affirmative response to any of the following elements resulted in 
including the contaminant on the first CCL, if it also met the 
occurrence criteria. A negative response to every question resulted in 
the contaminant being eliminated from consideration for the CCL. The 
health portion of the criteria had one major component; was there 
evidence, or suspicion, that the contaminant causes adverse human 
health effects? This portion of the criteria was met if a contaminant 
had one or more of the following elements: (1) Listed by California 
Proposition 65, (2) an EPA Health Advisory, (3) a likely (based on 
animal data) or known (based on human data) carcinogen by EPA or 
International Agency for Research on Cancer (IARC), (4) more than one 
human epidemiological study (indicating adverse effects), (5) an oral 
value in IRIS, (6) regulated in drinking water by another industrial 
country, (7) a member of a chemical family of known toxicity, or (8) 
structural activity relationship indicating toxicity.
    As the contaminants were being screened and evaluated, the factors 
for health which proved to be the most useful were those that provided 
a health level of concern as a concentration that could be compared to 
the levels of occurrence found in water, such as an EPA Health 
Advisory, an oral value in IRIS, or a regulatory level from another 
industrial country. Being listed by California Proposition 65, or a 
member of a chemical family of known toxicity had limited utility in 
determining which contaminants to include on the CCL.
3. Additional Specific Contaminants Included
    Aldicarbs, nickel, and sulfate are also on the draft CCL. The SDWA, 
as amended, did not specifically mention aldicarbs and nickel, but 
since the Agency has existing obligations for completing regulatory 
action on these contaminants pursuant to the SDWA, as amended 1986, it 
was thought to be prudent to include them on the CCL to make clear the 
intention to address these responsibilities. Sulfate is included on the 
CCL, since the Agency must make a determination to regulate or not by 
August 2001, along with at least four more contaminants. The following 
sections provide the rationale for the inclusion of aldicarbs, nickel, 
and sulfate on the draft CCL.
    a. Aldicarb, aldicarb sulfoxide, and aldicarb sulfone. EPA 
promulgated a final NPDWR for aldicarb, aldicarb sulfoxide and aldicarb 
sulfone on July 1, 1991 (56 FR 30266). EPA set the maximum contaminant 
level goal (MCLG) at 0.001 mg/l and maximum contaminant levels (MCLs) 
of 0.003 mg/l for aldicarb, 0.004 mg/l for aldicarb sulfoxide, and 
0.002 mg/l for aldicarb sulfone. In response to an administrative 
petition from the manufacturer Rhone-Poulenc, the Agency issued an 
administrative stay of the effective date of the MCLs, i.e., the MCLs 
never became effective, but monitoring is required. Rhone-Poulenc also 
filed a petition for judicial review, and the court stayed its 
proceedings while EPA proceeded administratively, but required 
quarterly reports. On agreement of the parties, the judicial 
proceedings have been dismissed. An updated health advisory was issued 
in 1995 incorporating data from a human study conducted in 1992 by 
Rhone Poulenc. The aldicarbs were not subject to the criteria used to 
identify other chemical contaminants and are being included on the CCL 
to signify the Agency's intention to complete the regulatory activity 
for these contaminants. At this point, however, the time frame of 
completing action relative to aldicarbs has not been determined.
    b. Nickel. NPDWRs for nickel including an MCLG and an MCL of 0.1 
mg/l were proposed on July 25, 1990 (55 FR 30370) and finalized on July 
17, 1992 (57 FR 31776). In September, 1992, the Nickel Development 
Institute and other industry parties filed a petition for review in the 
U.S. Court of Appeals for the D.C. Circuit challenging the MCLG and MCL 
for nickel. The petitioners raised objections over EPA's methodology 
for determining the MCLG for nickel. Specifically, they raised 
questions concerning the derivation of the relative source contribution 
factor and the need for a 3-fold uncertainty factor that EPA applied 
due to the lack of adequate data on the effects of nickel ingestion on 
reproductive systems. Because the MCL for nickel was based directly on 
the MCLG, the petitioners also challenged the nickel MCL.
    EPA and the petitioners entered into discussions in an attempt to 
settle this litigation but could not agree on the merits of the 
petitioners' challenges. Nevertheless, EPA agreed that it did not fully 
address in the public record the petitioner's comments on the proposed 
methodology for deriving the MCLG for nickel, and agreed to take a 
remand of the MCLG and MCL for nickel. Accordingly, on February 9, 
1995, EPA and the nickel industry petitioners filed a joint motion for 
a voluntary remand of the nickel MCL and MCLG. By orders of February 
23, 1995 and March 6, 1995, the court granted this motion and vacated 
and remanded the nickel MCLG and MCL (and dismissed the lawsuit). No 
other aspects of the NPDWRs for nickel were vacated, including 
monitoring requirements and identification of best available 
technologies for nickel. A notice of this action was published in June 
1995 (60 FR 33929).
    To provide guidance for the period prior to new regulations for 
nickel, the EPA updated and issued a health advisory for nickel. Nickel 
was not subject to the criteria used to identify other chemical 
contaminants and is

[[Page 52211]]

being included on the CCL to signify the Agency's intention to complete 
regulatory action for this contaminant. The time frame of completing 
action on nickel has not yet been determined.
    c. Sulfate. As noted above, by August, 2001 the Agency must decide 
whether or not to regulate sulfate. The date for making a determination 
about sulfate coincides with the date by when determinations must be 
made for 5 or more contaminants from the first CCL. Sulfate was not 
subject to the criteria used to identify other contaminants; however, 
it has been included, given these special circumstances.

IV. Contaminants on the CCL Which Are of Specific Interest

    A number of contaminants included on the draft CCL may be of 
particular interest. The following sections attempt to provide 
additional information for a few of the contaminants that seem to be of 
most interest. Data obtained and evaluated for developing the draft CCL 
and referred to in the following discussion can be found in the docket 
for this notice.

A. Aluminum

    There is intense interest from some for development of drinking 
water regulations for aluminum. Aluminum currently has a secondary MCL 
of 50 to 200 ``g/l based on organoleptic properties. There 
have been a few epidemiological studies in Canada that emphasize the 
need to determine if regulations for this contaminant should be 
developed based on health effects. At present, based on the work in 
Canada, it appears that the most sensitive population is the elderly. 
To determine if aluminum is of health concern to the elderly and to 
other possible sensitive groups like children, the EPA collaborated 
with Health Canada on a workshop on aluminum held September 3 and 4, 
1997. This workshop was planned to help define the need for chronic 
animal studies and the use of appropriate animal models to better 
characterize the risk of this contaminant in drinking water. The Agency 
will continue to work to determine if aluminum is of health concern, 
and the appropriate action to address this concern.

B. MTBE

    MTBE (methyl-t-butyl ether) is a fuel additive used in many 
locations throughout the United States to reduce carbon monoxide and 
ozone forming precursors associated with the combustion of fossil 
fuels. There is evidence of contamination of drinking water; however 
the extent of contamination of drinking water supplies on a national 
scale is unclear at this time (IAOF, 1997). The Agency is in the 
process of revising the HA for MTBE that will incorporate updated 
health effects information, and has completed a research strategy to 
guide efforts at improving the understanding of the occurrence and 
health effects of MTBE (U.S. EPA, 1997e). As more PWSs across the 
country voluntarily monitor for MTBE, and if it is found at levels of 
concern nationally, the Agency does have the capacity to make a 
determination to develop regulations to monitor and/or control MTBE 
prior to the 2001, SDWA deadline for selecting at least 5 contaminants 
for determination.

C. Organotins

    Organotins represent a class of contaminants which include, methyl 
tin, tributyltin, and others. The organotins of concern are those that 
result from use in heat stabilizing PVC piping for the in-home 
distribution of water. There are a few cases of tributyltin 
contamination of drinking water in the U.S. (Sadiki, 1996). It has been 
reported that the Canadian government is concerned about organotin 
contamination and has planned a national survey of drinking water in 
Canada to assess the danger to human health.
    The concentrations of concern for human health are not known at 
this time, however tributly tin and other organotins are known to be 
toxic to aquatic life. On August 7, 1997, the Agency published a notice 
of ambient water quality criteria document for tributyltin (TBT) and a 
request for comments (62 FR 42554). Ambient water quality criteria are 
for the protection of aquatic organisms and guidance to States and 
others, and may form the basis for enforceable State water quality 
standards developed pursuant to Section 304(a)(1) of the Clean Water 
Act.

D. Rhodamine WT

    Rhodamine WT is a fluorescent dye widely used as a tracer to 
measure ground water flow. Rhodamine WT has been certified by the 
National Sanitation Foundation for use in tracing water under the 
conditions that it not exceed concentrations in drinking water of 0.1 
g/l and that exposure be infrequent. Rhodamine WT was detected 
in ground water above the 0.1 g/l value; however the 
conditions under which the detections occurred are unclear. Rhodamine 
WT appears to be a contaminant that the Agency may need to observe more 
closely in terms of its health effects, and possible occurrence in 
drinking water.

E. Sodium

    At present, the Agency has no NPDWR or HA value for sodium. All 
that is currently available is a guidance DWEL of 20 mg/l. DWELs are 
unenforceable guidance levels describing a lifetime exposure 
concentration of a contaminant that is considered protective of adverse 
non-cancer health effects, and it also assumes that all of the exposure 
to a contaminant is from a drinking water source. In addition, EPA has 
a non-enforceable criterion for dissolved solids and salinity for 
ambient waters of 250 mg/l.
    The DWEL is based on a 1965 American Heart Association 
recommendation of a 20 mg/l sodium level to protect genetically 
susceptible people on low sodium diets, assuming a total dietary intake 
of 500 mg/day. Naturally occurring sodium in food with no salt added 
averages about 440 mg/day. The additional 60 mg that would increase the 
intake to the typical level for a restricted diet of 500 mg/day must 
take into account all other non-food sources, such as drugs, water, 
etc. A concentration in drinking water of up to 20 mg/l of sodium is 
compatible with this diet.
    Since a significant percentage of the U.S. population is attempting 
to reduce their sodium intake, the Agency believes that sodium levels 
in drinking water could be an important issue. This is particularly 
true for locations where many of the residents using the water may be 
susceptible to adverse health effects from exposure to this 
contaminant. The Agency believes that all consumers are able to use 
water for drinking if the sodium concentration is maintained at or 
below 20 mg/l, but nearly half of the nation's water supplies have 
natural or added sodium above these levels.
    The inclusion of sodium on the CCL is controversial, but it is 
expected that guidance will be developed for those who need it, and 
that including it on the CCL will be a mechanism to develop an Agency 
position on the issue of sodium in drinking water.

F. Zinc

    Zinc is used as a dietary supplement, main ingredient in lozenges, 
and corrosion inhibitor. There is intense interest over including zinc 
on the CCL, but there are also indications of health effects associated 
with increased levels of zinc consumption.
    The Agency is aware that zinc is an essential element for which the 
Food

[[Page 52212]]

and Nutrition Board of the National Research Council has established a 
Recommended Dietary Allowance (RDA). Zinc can also cause adverse health 
effects at high doses and the zinc RfD (0.3 mg/kg/day) is higher than 
the RDA for adult men and women. While deriving RfDs, EPA must also 
keep in mind the fact that excess exposure to an essential trace 
element, such as zinc, can also cause adverse health effects. The 
present RfD for zinc represents a balance between the essential 
requirement for zinc and the toxic effects of too much zinc; however, 
the Agency is currently working on revising the risk assessment 
procedures for essential elements. The World Health Organization (WHO) 
is also in the process of developing a document on the risk assessment 
of essential trace elements, and EPA will consider the WHO document 
when it is available.

G. 2,6-di-tert-butyl-p-benzoquinone (DTBB)

    DTBB is a contaminant that appears to be associated with sewage 
contamination of ground water. A ground water study concluded that DTBB 
was a good indicator of such contamination because, among other 
reasons, it does not biodegrade readily (Barber, 1988). DTBB was 
determined not to meet the criteria for the draft CCL per se, but was 
included nevertheless, because of the recalcitrant nature of the 
contaminant, its association with sewage contamination, its potential 
health impacts, and its potential to serve as an indicator of other 
contamination.

H. Contaminants to be Considered as Groups

    Stakeholders, through the regulatory reassessment process and the 
development of this draft CCL, have requested that the Agency, address 
triazine pesticides as a group which includes all parent and degradates 
compounds as opposed to each triazine as an individual contaminant. The 
triazine pesticides include; cyanazine, propazine, etc., and atrazine 
and simazine (which are both currently regulated), and are often 
substituted for one another for similar agricultural use.
    The USEPA regulated atrazine in 1991 and simazine in 1992. 
Cyanazine and atrazine-desethyl, a degradation product of triazines, 
were identified for the draft CCL using the criteria discussed earlier, 
and because of the common effect of triazine pesticides and degradates, 
Office of Ground Water and Drinking Water (OGWDW) and OPP are 
coordinating to have atrazine and simazine, and possibly other 
triazines, if warranted, addressed as a group. A triazine special 
review was initiated by OPP which will culminate in a proposed decision 
on the labeling and agricultural use triazine. The proposal is expected 
during the summer of 1998. The triazines are also included in the 
Priority Group 1 of pesticide tolerances that will be examined first 
under the FQPA tolerance reassessment (62 FR 42020).
    The Agency is concerned about triazines in water and the exposure 
of sensitive populations, including children, and OGWDW will work 
closely with OPP to characterize the risk of triazines in food and 
water. EPA has been studying the mechanism of carcinogenicity of this 
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 may ultimately develop regulations for 
the mixtures of triazines either through the revision of existing 
regulations or the development of new ones. The same may occur for 
other families of pesticides, such as the acetanilide pesticides, which 
include acetochlor, metolachor, alachlor (which is currently 
regulated), given their common effects and agricultural uses.

I. Contaminants for Which Unregulated Contaminant Data Are or Will Be 
Available

    Unregulated contaminant monitoring data which have been collected a 
number of contaminants during 1988-1991, and additional monitoring data 
collected during 1993-1995 (see Table 7). These monitoring data can 
serve in evaluating whether these contaminants should be included on 
the CCL. The data collected during 1988-1991 have been preliminarily 
evaluated by the Agency; however, further analysis is necessary to 
determine if a contaminant in fact meets the criteria used to develop 
the draft CCL. The data collected during 1993-1995, are not yet 
available; however, during the comment period, and prior to publishing 
the CCL by February 1998, the Agency will attempt to obtain and 
evaluate this data to determine if the contaminant should remain on the 
CCL. Contaminants that do not meet the criteria as presented in today's 
notice, or as modified subsequent to the comment period of the notice, 
will not be included on the final CCL to be published by February 1998.
Table 7. Contaminants with Unregulated Contaminant Monitoring Data
1,3-dichloro-benzene
1,2,4-trimethyl-benzene
1,3-dichloropropene
1,3-dichloro-propane
1,1,2,2-tetrachloro-ethane
1,1-di-chloro-ethane
1,1-dichloro-propene
1,2,3-trichloro-propane
2,2-dichloro-propane
bromobenzene
bromomethane
carbaryl
o-chorotoluene
p-chlorotoluene
cumene
cymene
dichloro-difluoromethane
hexachlorobutadiene
metolachlor
metribuzan
naphthalene
n-propylbenzene
trichlorofluoro-methane

V. Request for Comment

    The purpose of today's notice is to present the draft CCL and seek 
comment on various aspects of its development. The Agency requests 
comment on the approach used to develop the CCL, and on the 
contaminants included. The Agency also requests comment on the data and 
research needs categories the contaminants have been divided into, in 
Table 8. Any data supporting comments or that can be used by the Agency 
in developing the final CCL are also requested. In addition to comments 
on contaminants considered for the draft CCL, the Agency seeks comment 
on the inclusion of perchlorate on the final CCL. The following 
sections provide more detail on the data and research needs and the 
issue of perchlorate.

A. Data and Research Needs

    The microbiological contaminants included on the CCL all have 
research needs of one sort or another in the area of analytical 
methods. The meeting summary of the Workshop on Microbiology and Public 
Health, held May 20-21, 1997, provided more detail of the research 
needed for microorganisms.
    For the chemical contaminants on the draft CCL, Table 8 divides 
them into categories to represent the 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 a given contaminant. 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

[[Page 52213]]

prior to 2001. Thus, the contaminants for which sufficient data exists 
at the time of publishing the CCL, are likely to the those from which 
the determinations will be made by 2001.

                    Table 8.--Data Needs for Chemical Contaminants Included on the Draft CCL                    
----------------------------------------------------------------------------------------------------------------
                                        Need additional health      Need additional          Need both health   
    Sufficient health effects and       effects data, but not     occurrence data, but    effects and occurrence
        occurrence data exist              occurrence data      not health effects data            data         
----------------------------------------------------------------------------------------------------------------
1,1,2,2-tetrachloroethane; 79-34-5...  Aluminum; 7429-90-5....  1,2-diphenylhydrazine;   2,6-di-tert-butyl-p-   
                                                                 122-66-7.                benzoquinone (DTBB);  
                                                                                          719-22-2              
1,2,4-trimethylbenzene; 95-63-6......  Vanadium; 7440-62-2....  2,4,6-trichlorophenol;   .......................
                                                                 88-06-2.                                       
1,1-dichloro-ethane; 75-34-3                                    2,2-dichloro-propane;    DCPA mono-acid         
                                                                 594-20-7.                degradate; 887-54-7   
1,1-dichloro-propene; 563-58-6                                  2,4-dichlorophenol; 120- DCPA di-acid degradate;
                                                                 83-2.                    2136-79-0             
1,3-dichloropropane; 142-28-9                                   2,4-dinitrophenol; 51-   Organotins             
                                                                 28-5.                                          
1,3-Dichloropropene; 542-75-6                                   2,4-dinitrotoluene; 121- .......................
                                                                 14-2                                           
Boron; 7440-42-8                                                2,6-dinitrotoluene; 606- .......................
                                                                 20-2                                           
Bromobenzene; 108-86-1                                          2-methyl-phenol; 95-48-  .......................
                                                                 7                                              
Cyanazine; 21725-46-2                                           Acetochlor; 34256-82-1   .......................
atrazine-desethyl (a triazine                                   Acetone 67-64-1          .......................
 degradation product); 6190-65-4.                                                                               
p-Cymene; 99-87-6                                               Alachlor ESA (an         .......................
                                                                 alachlor degradation                           
                                                                 product).                                      
Hexachloro-butadiene; 87-68-3                                   Aldrin; 309-00-2         .......................
cumene; 98-82-8                                                 DDE; 72-55-9             .......................
Manganese; 7439-96-5                                            Diazinon; 333-41-5       .......................
Methyl bromide; 74-83-9                                         Dieldrin; 60-57-1        .......................
Metolachlor; 51218-45-2                                         Dimethoate; 60-51-5      .......................
Metribuzin; 21087-64-9                                          Disulfoton, 298-04-4     .......................
Naphthalene; 91-20-3                                            Diuron; 330-54-1         .......................
Sodium; 7440-23-5                                               Fonofos; 944-22-9                               
Zinc; 7440-66-6                                                 Linuron; 330-55-2        .......................
                                                                MTBE; 1634-04-4........                         
                                                                Molinate; 2212-67-1....                         
                                                                Nitrobenzene; 98-95-3..                         
                                                                Prometon; 1610-18-0....                         
                                                                RDX; 121-82-4..........                         
                                                                Rhodamine WT...........                         
                                                                Terbacil; 5902-51-2....                         
                                                                Terbufos; 13071-79-9...                         
                                                                EPTC; 759-94-4.........                         
----------------------------------------------------------------------------------------------------------------

    B. Perchlorate
    Additional information and comment is sought on the inclusion of 
perchlorate on the final CCL. Perchlorate is being mentioned in this 
notice because EPA received information that it had been detected in 
water in the Colorado River and in wells in California, but the 
information came too late in the process of developing the draft CCL to 
evaluate it as had been done for the other contaminants. The 
information the Agency has received regarding perchlorate's occurrence, 
health effects, source of contamination and treatment that has been 
included in the docket. This information, and any other submitted in 
response to comments, as well as additional data that the Agency may 
obtain, will be considered to determine whether perchlorate should be 
included on the final CCL.

VI. Development of the Final Drinking Water Contaminant Candidate List, 
the Contaminant Identification Method, and the Contaminant Selection 
Process

    Between now and the publication of the final CCL, the Agency will 
evaluate comments received during the comment period for this notice 
and re-evaluate the criteria used to develop the draft CCL and revise 
the CCL, as appropriate. The final CCL will be published by February 
1998.
    In addition to publishing the final CCL, the Agency will also 
resume work on the CIM and the contaminant selection process. The 
development of the CIM and the selection process will be completed in 
consultation with the NDWAC Working Group on Occurrence & Contaminant 
Selection. The next meeting of the Working Group will likely be later 
this fall. The CCL, CIM and the selection process will serve as the 
cornerstones of the Agency's regulatory development process. In 
addition to developing the CCL, CIM and the selection process with the 
Adminstration policy in mind, the Agency intends to obtain resources to 
improve the screening process in order to acquire better information, 
improve analytical capability, and seek additional stakeholder 
involvement. The CCL is a critical input to shaping the future 
direction of the drinking water program, and improvements will be made 
with each successive cycle of publishing the list.

VII. Summary of Other Related Activity Required by the SDWA

    After the CCL is developed and in accordance with the SDWA, as 
amended, the Agency will determine whether or not regulation is needed 
for at least five contaminants. This step of contaminant selection is 
then followed by proposal and ultimate promulgation of regulations for 
those contaminants for which a determination has been made to regulate. 
Two tools provided for in the SDWA, as amended, that relate to 
development of the CCL, are the

[[Page 52214]]

occurrence database and unregulated contaminant monitoring. In 
identifying contaminants for inclusion on the CCL, and selecting 
contaminants for determination, the National Drinking Water Contaminant 
Occurrence Database must be considered. The primary mechanism for 
obtaining the occurrence data for the database is the Unregulated 
Contaminant Monitoring Requirements provision. Figure 2 provides a 
representation of the relationship among these various elements. The 
SDWA requirements for contaminant selection, the occurrence database 
and unregulated contaminant monitoring are presented below to give the 
reader a sense of what these requirements entail and how they relate to 
the CCL and to each other.

BILLING CODE 6560-50-P

[[Page 52215]]

[GRAPHIC] [TIFF OMITTED] TN06OC97.001



BILLING CODE 6560-50-C

[[Page 52216]]

A. Contaminant Selection and Regulatory Determination

    The SDWA, as amended in 1996, requires EPA to make determinations 
of whether or not to regulate no fewer than five contaminants from the 
CCL five years after enactment (i.e., by August 2001), and every five 
years thereafter (section 1412(b)(1)); which is also three and a half 
years following each CCL. Any of the contaminants from the CCL that the 
Agency decides to regulate are subject to proposed NPDWRs within 24 
months of this decision to regulate, and final NPDWRs within 18 months 
of the proposal. The SDWA also requires that EPA give priority to 
selecting contaminants for regulation that present the greatest public 
health concern, including vulnerable populations such as infants, the 
elderly, and those with serious illness. Three criteria must be 
considered when deciding whether or not to regulate a contaminant: (1) 
Could the contaminant adversely affect public health, (2) is it known 
or substantially likely to occur in public water systems with a 
frequency and at levels posing a threat to public health, and (3) will 
regulation of the contaminant present a meaningful opportunity for 
health risk reduction.
    The Agency will be developing a contaminant selection process that 
will address the criteria mentioned above in concert with the 
contaminant identification method. The contaminant selection process 
will be used to select contaminants from the CCL for which 
determinations will be made, while the CIM will be used to develop the 
CCL. A conceptual approach for the CIM was presented on December 2-3, 
1996, at an EPA sponsored stakeholders meeting (U.S. EPA, 1996b) 
However, in order to meet the February 1998 deadline for finalizing the 
CCL, further work on the CIM was delayed in favor of developing the 
draft CCL presented in today's notice. The Agency, in collaboration 
with the NDWAC Working Group on Occurrence & Contaminant Selection, 
will resume work on the CIM and the contaminant selection process 
during the fall of 1997. Knowledge gained during the development of 
this draft CCL, as well as the feedback received since the December 
1996 stakeholders meeting, will be factored into the development.

B. The National Contaminant Occurrence Database

    The SDWA, as amended in 1996, requires EPA to establish a national 
drinking water contaminant occurrence database (NCOD) to be assembled 
by August 1999 [section 1445(g)]. The database is to include the 
occurrence of both regulated and unregulated contaminants, and, once 
established, is to be used to support the Administrator's 
determinations for future regulations. The requirements for developing 
the CCL also include consulting the occurrence database. Since the 
database is currently under development, and will not be available for 
the development of this first CCL, the Agency consulted other sources 
of occurrence data. Once available, however, the NCOD will be used not 
only to develop future CCLs and support future determinations of the 
need for regulations, but to develop future regulations.
    A Stakeholder meeting was held on May 21-22, 1997, in Washington, 
D.C., on the NCOD to discuss and obtain input from the public, states, 
and the scientific community on database design and structure, input 
parameters and requirements, and the uses and interpretation of the 
data. This meeting was the first of several expected to take place in 
the near future regarding the NCOD development.

C. Unregulated Contaminant Monitoring Regulation

    The SDWA, as amended, requires EPA to list and develop regulations 
for monitoring of certain unregulated contaminants by August 1999, and 
every 5 years thereafter (section 1445(a)(2)). This provision was first 
introduced with the 1986 amendments to the SDWA and has been 
substantially modified by the 1996 amendments. The SDWA requires that 
the list of unregulated contaminants not exceed 30, and that the 
monitoring data be collected and maintained in the NCOD. Criteria for 
determining which contaminants on the CCL will be chosen for the 
unregulated contaminant monitoring list will be developed as part of 
this regulation.
    Contaminants on the CCL that need additional occurrence data will 
be used as the principal source of contaminants for the list of 
unregulated contaminants. The unregulated contaminant monitoring 
provision of the SDWA will be used as a tool to gather the contaminant 
occurrence data necessary for determining the need for drinking water 
regulations.

VIII. Summary of Concurrent Regulatory Activity Required by the 
SDWA

    In addition to the requirements for the CCL and contaminant 
selection, the SDWA, as amended 1996, also contain specific provisions 
with regard to radon, arsenic, sulfate, and disinfectants and 
disinfection byproducts. The SDWA, as amended, did not specify a new 
time frame for finalizing rulemaking for other radionuclides, however, 
EPA and the Bull Run Coalition have entered into a consent decree with 
the court establishing timetables to finalize this rulemaking. 
Regulatory activity for radon, other radionuclides, arsenic, sulfate, 
and disinfectants and disinfection byproducts are not affected by 
today's notice, but are summarized below to provide the reader with an 
update on the status these specific activities.

A. Radon

    The SDWA, as amended in 1996, contains specific provisions for 
regulating radon in drinking water (section 1412(b) (13)). First, EPA 
is required to withdraw the proposed rule for radon which was published 
in 1991 and to re-propose a drinking water regulation for radon by 
August 6, 1999, and issue final regulations by August 6, 2000. The 
SDWA, as amended, also requires EPA to: (1) Arrange for the NAS to 
prepare a peer reviewed risk assessment for radon that evaluates the 
health effects of radon in drinking water under conditions likely to be 
experienced through residential exposure and to assess the risk 
reduction benefits from various mitigation measures to reduce radon 
levels in indoor air; (2) make available for public comment a health 
risk reduction and cost analysis comparing costs and benefits of 
various possible MCL in advance of proposing a radon regulation; and 
(3) establish an alternative-MCL, if the MCL is set at a level that is 
more stringent than necessary to reduce the contribution of radon in 
indoor air originating from drinking water to a level equal to the 
national average concentration of radon in outdoor air. States will 
have the option to comply with the less stringent alternative-MCL if 
they implement a multi-media radon risk reduction program that 
accomplishes greater health protection than would be achieved by 
complying with the more stringent MCL alone.
    A notice was published in the Federal Register on August 6, 1997, 
to withdraw the radon proposed rule. (62 FR 42221) The NAS risk 
assessment is scheduled to be complete by July 1998, and the HRRCA is 
due by February 1998. In addition, EPA held stakeholder meetings on 
June 26, 1997, in Washington, D.C., and on September 2, 1997, in San 
Francisco, and has scheduled an additional stakeholder meeting in 
Boston later this fall to obtain input from the public.

[[Page 52217]]

B. Other Radionuclides

    On July 18, 1991, EPA proposed NPDWRs for radionuclides in public 
water supplies (56 FR 33050). EPA proposed MCLs for Radium-228 at 20 
pCi/l, Radium-226 at 20 pCi/l, Uranium at 30 pCi/l (20 g/l), 
adjusted gross alpha at 15 pCi/l (excluding Ra-226, U, and Rn-222), and 
beta and photon emitters (excluding Ra-228) at 4 mrem ede/yr; MCLGs 
were proposed at zero.
    Comments on the proposed rule were received from approximately 600 
individuals and organizations. Due to concerns by commenters and 
Congress over the most effective way to regulate radon and other 
radionuclides together, the proposed rule was put on hold, pending 
passage of amendments to the SDWA, so that EPA could gain further 
clarification of Congress' intent.
    The SDWA, as amended in 1996, did not specify a new time frame for 
finalizing rulemaking for radionuclides, as it did for radon. However, 
an existing consent decree providing deadlines for regulating 
radionuclides was amended in 1996 to provide that EPA would, by 
November 2000, finalize a rule for Uranium; and finalize a rule for Ra-
226, Ra-228, alpha and beta/photon emitters, or publish its reasons for 
not taking final action as to these contaminants. An Agency Workgroup 
has been formed and is process of evaluating all current data and 
information, which will lead to finalizing elements of the proposed 
rule or to re-proposing NPDWRs for radionuclides.

C. Arsenic

    In 1975, EPA established National Interim Primary Drinking Water 
Regulations (NIPDWR), setting an MCL for Arsenic at 50 g/l. In 
1985, EPA proposed an MCLG of 50 g/l, requesting comment on 
alternate MCLGs of 100 g/l and 0 g/l. However, the 
SDWA, as amended in 1986, converted the interim standard into a NPDWR, 
subject to revision by 1989. When the Agency failed to meet the 
statutory deadline for promulgating an arsenic regulation, a citizen's 
group filed suit to compel EPA to do so. EPA entered into a consent 
decree to, in part, issue the arsenic regulation. The consent decree 
was amended several times to extend the deadlines and with passage of 
the 1996 Amendments was dismissed as to arsenic.
    The SDWA, as amended, requires EPA to conduct additional research 
on arsenic in order to reduce the uncertainty in assessing the health 
effects of low exposure levels; to propose a NPDWR for arsenic by 
January 1, 2000; and to issue a final regulation by January 1, 2001. 
(Sec. 1412(b)(12)) EPA developed a research plan, made it available for 
public comment, and had it peer reviewed in January 1997. The revised 
research plan will be available this fall. In addition, EPA issued a 
joint request for research proposals with the American Water Works 
Association Research Foundation (AWWARF) and the Association of 
California Water Agencies (ACWA). EPA, AWWARF and ACWA awarded almost 
$3 million in grants and contracts this summer, for up to three years. 
This spring, EPA also funded an Interagency Agreement, with the 
National Research Council (NRC) of the NAS to review EPA's risk 
assessment, determine the adequacy of EPA's current MCL for protecting 
human health and surface water quality criteria, and identify 
priorities for research to fill data gaps. The NRC report will be 
submitted to EPA in mid-to-late 1998. In May, 1997, EPA convened an 
expert panel to evaluate the scientific literature on the genetic and 
carcinogenic effects of arsenic in order to comment on arsenic's mode 
of action and the data supporting models extrapolating to low dose 
arsenic exposures. The final report is now being considered by EPA's 
IRIS Update Group.

D. Sulfate

    A December 20, 1994 proposed sulfate regulation contained both MCLG 
and MCL levels for sulfate of 500 mg/l and included 4 alternative 
compliance options designed to allow flexible implementation. 
Thereafter, the Agency's drinking water redirection effort concluded 
that sulfate was a relatively low risk contaminant, and further 
regulatory activity was suspended. The SDWA, as amended, requires 
completion of a study to resolve risk questions and requires the Agency 
to make a determination within 5 years of enactment of the Amendments, 
by August 6, 2001, of whether or not to regulate sulfate. Any of the 
contaminants from the CCL that the Agency decides to regulate are 
subject to proposed NPDWRs within 24 months of this decision to 
regulate, and final NPDWRs within 18 months of the proposal. In 1997 
the Agency entered into an Interagency Agreement with the Center for 
Disease Control and Prevention (CDC). EPA and CDC are currently waiting 
for completion of the peer review of the jointly planned health risk 
study for sulfate. The study results, due in February 1999, will serve 
as input for EPA's contaminant identification and selection protocol to 
decide whether or not to regulate sulfate, and will be publicly 
available. In addition, prior to deciding on the need to regulate 
sulfate, the Agency would need to make a determination on the adequacy 
of existing occurrence data for sulfate and, if inadequate, consider 
approaches for filling data gaps.

E. Disinfectants and Disinfection Byproducts

    Microorganisms identified for the CCL are not specifically targeted 
by the following regulations, however they may be indirectly 
controlled. Any microorganism identified for the CCL which is 
determined later to be adequately, although indirectly, controlled by 
the following regulations, will be subsequently withdrawn from the CCL.
    Under the Surface Water Treatment Rule (SWTR) promulgated on June 
29, 1989, (54 FR 27486), EPA set MCLGs of zero for Giardia lamblia, 
viruses and Legionella; and promulgated NPDWRs for all public water 
systems (PWSs) using surface water sources or groundwater sources under 
the direct influence of surface water. The SWTR includes treatment 
technique requirements for filtered and unfiltered systems that are 
intended to protect against the adverse health effects of exposure to 
Giardia lamblia, viruses, and Legionella, as well as many other 
pathogenic organisms.
    In 1992, EPA initiated a negotiated rulemaking to develop 
disinfectant and disinfection byproducts regulations. The Regulatory 
Negotiating Committee met from November 1992 through June 1993 and 
included representatives of State and local health and regulatory 
agencies, public water systems, elected officials, consumer groups and 
environmental groups. One of the major goals addressed by the Committee 
was to develop an approach that would reduce the level of exposure from 
disinfectants and disinfection byproducts without undermining the 
control of microbiological pathogens. To accomplish this, the Committee 
agreed to the development of three sets of regulations: a two-staged 
Disinfectant/Disinfection Byproducts Rule (D/DBP), an Enhanced Surface 
Water Treatment Rule (ESWTR), and an Information Collection Rule (ICR). 
The purpose of the ICR is to collect occurrence and treatment 
information to evaluate the need for possible changes to the current 
SWTR, existing microbial treatment practices, and also evaluate the 
need for future regulation for disinfectants and disinfection 
byproducts.
    EPA would first develop an Interim-ESWTR (IESWTR) that would only 
apply to systems serving 10,000 people or more, the committee agreed 
that a

[[Page 52218]]

Long-Term-ESWTR (LTESWTR) may be needed for systems serving fewer than 
10,000 people when the results of more research and water quality 
monitoring became available. The LTESWTR could include additional 
refinements for larger systems.
    The ICR was proposed on February 10, 1994 (59 FR 6332) and 
promulgated on May 14, 1996 (61 FR 24354). The D/DBP regulations and 
the IESWTR were proposed on July 29, 1994 (59 FR 38668, 59 FR 38832). 
The SDWA, as amended, requires EPA to promulgate an IESWTR and a Stage 
I D/DBP Rule by November 1998. In addition, the SDWA requires EPA to 
promulgate a final ESWTR and a Stage II D/DBP rule by November 2000 and 
May 2002, respectively [section 1412(b)(2)(C)].
    In light of new information that has become available in several 
key areas related to issues put forth in the D/DBP Stage 1 proposal, 
the Agency initiated a series of public meetings in May 1996. These 
meetings were designed to exchange information on issues related to the 
development of the IESWTR and the Stage 1 D/DBP rule and the impact of 
the ICR data not being available. In order to facilitate moving in an 
expedited fashion to meet the deadlines in the 1996 Amendments, and to 
maximize stakeholder participation, the Agency subsequently established 
an advisory committee to collect, share, and analyze new information 
and data as well as to build consensus on the regulatory implications 
of this new information. After evaluation of the new data and 
information, the committee made recommendations on a number of major 
issues. These recommendations and a discussion of the pertinent issues 
will be published in a Federal Register Notice planned for later this 
fall.

IX. 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. As contaminants are selected for 
rulemaking, all necessary analysis will be conducted in accordance with 
the rulemaking 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 risk 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 CDC 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 contamination. Other 
research also is underway to determine the extent of vulnerable 
populations including children and the immunologically impaired.

X. References

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That will be The Subject of Toxicological Profiles and Support 
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Micropollutants in Sewage-Contaminated Groundwater. Environ. Sci. 
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Sulzer. 1982. Oocyst-transmitted toxoplasmosis associated with 
ingestion of contaminated water. New Engl. J. Med., 307:666-669.
    Berman, D., and J.C. Hoff. 1984. Inactivation of simian 
rotavirus SA11 by chlorine, chlorine dioxice, and monochloramine. 
Appl. Environ. Microbiol., 48:317-323.
    Bryan, R.T. 1995. Microsporidiosis as an AIDS-related 
opportunistic infection. Clin. Infect. Dis., 21(Suppl 1):62-65.
    Cali. A. 1991. General Microsporidium Features and Recent 
Findings on AIDS Isolates. J. Protozool., 38:625-630.
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simian rotaviruses by chlorine dioxide. Appl. Environ. Microbiol., 
56:1363-1366.
    Cover, T.L., and M.J. Blaser. 1995. Helicobacter pylori: A 
Bacterial Cause of Gastritis, Peptic Ulcer Disease, and Gastric 
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Waterborne Viral Infections. Water Science and Tehnol., 24:197-203.
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Destruction of Cysts of Pathogenic and Nonpathogenic Naegleria and 
Acanthamoeba by chlorine. Appl. Environ. Microbiol., 31:294-297.
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Protozoa: Cryptosporidia, Microsporidia, Isospora, and Cyclospora. 
Ann. Intern. Med., 1214:429-441.
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    (Authority: 42 U.S.C. 300f-300j-25)

    Dated: September 29, 1997.
Robert Perciasepe,
Assistant Administrator, Office Water, Environmental Protection Agency.
[FR Doc. 97-26433 Filed 10-3-97; 8:45 am]
BILLING CODE 6560-50-P