Announcement of the Draft Drinking Water Contaminant Candidate List

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.

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

\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.

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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 demogr

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