1
ENVIRONMENTAL
PROTECTION
AGENCY
40
CFR
Part
141
[
FRL­_______­_______]

RIN
Drinking
Water
Contaminant
Candidate
List
2;
Notice
AGENCY:
Environmental
Protection
Agency.

ACTION:
Notice.

SUMMARY:
The
Safe
Drinking
Water
Act
(
SDWA),
as
amended
in
1996,
requires
the
Environmental
Protection
Agency
(
EPA)
to
publish
a
list
of
contaminants
which,
at
the
time
of
publication,
are
not
subject
to
any
proposed
or
promulgated
national
primary
drinking
water
regulations,
that
are
known
or
anticipated
to
occur
in
public
water
systems,
and
which
may
require
regulations
under
SDWA
(
section
1412
(
b)(
1)).
SDWA,
as
amended,
specifies
that
EPA
must
publish
the
first
list
of
drinking
water
contaminants
no
later
than
18
months
after
the
date
of
enactment,
i.
e.,
by
February
1998
(
henceforth
referred
to
as
the
1998
Contaminant
Candidate
List
or
the
1998
CCL),
and
every
five
years
thereafter.
Today's
notice
announces
EPA's
preliminary
2
decision
to
carry
over
the
remaining
51
contaminants
on
the
1998
CCL
as
the
draft
CCL
2,

provides
information
on
EPA's
efforts
to
expand
and
strengthen
the
underlying
CCL
listing
process
to
be
used
for
future
CCL
listings,
and
requests
comment
on
CCL­
related
activities
to
improve
the
drinking
water
contaminant
listing
process.
Today's
draft
CCL
includes
42
chemicals
or
chemical
groups
and
nine
microbiological
contaminants.
The
Agency's
approach
to
the
draft
CCL
2
is
to
continue
using
the
remaining
contaminants
on
the
1998
CCL
for
prioritizing
research
and
making
regulatory
determinations
while
working
with
the
National
Drinking
Water
Advisory
Council
(
NDWAC)
and
stakeholders
to
complete
a
review
of
the
National
Research
Council
(
NRC)
recommendations
for
developing
a
more
comprehensive
and
transparent
CCL
listing
process.
The
EPA
seeks
comment
on
the
range
of
CCL
issues
and
activities
addressed
in
this
notice.

DATES:
The
Agency
requests
comment
on
today's
notice.
Comments
must
be
received
or
postmarked
by
midnight
[
INSERT
DATE
60
DAYS
AFTER
DATE
OF
PUBLICATION
IN
THE
FEDERAL
REGISTER].

ADDRESSES:
Comments
may
be
submitted
electronically,
by
mail,
or
through
hand
delivery/
courier.
Follow
the
detailed
instructions
as
provided
in
section
I.
C
of
the
Supplementary
Information
section.
The
official
public
docket
for
this
action
is
located
at
EPA
West
Building,

Room
B102,
1301
Constitution
Avenue,
NW,
Washington,
DC.

FOR
FURTHER
INFORMATION
CONTACT:
For
questions
about
this
notice
contact
Dan
3
Olson
at
(
202)
564­
5239
or
e­
mail
olson.
daniel@
epa.
gov.
For
general
information
contact
the
EPA
Safe
Drinking
Water
Hotline
at
(
800)
426­
4791
or
e­
mail:
hotline­
sdwa@
epa.
gov.
The
Safe
Drinking
Water
Hotline
is
open
Monday
through
Friday,
excluding
legal
holidays,
from
9:
00
a.
m.

to
5:
30
p.
m.

SUPPLEMENTARY
INFORMATION
I.
General
Information
A.
Does
this
Notice
Impose
Any
Requirements
on
My
Public
Water
System?

Neither
this
draft
CCL
2
nor
the
final
CCL
2,
when
published,
imposes
any
requirements
on
anyone.
Instead,
it
notifies
interested
parties
of
the
availability
of
EPA's
Draft
CCL
2
and
seeks
comment
on
this
draft
list
as
well
as
EPA's
efforts
to
improve
the
contaminant
selection
process
for
future
CCLs.
Contaminants
on
the
list
may
become
the
subject
of
future
regulations.

At
that
time,
the
public
would
be
provided
additional
opportunities
to
comment
as
part
of
the
rule
making
process.

B.
How
Can
I
Get
Copies
of
Related
Information?

1.
Docket.
EPA
has
established
an
official
public
docket
for
this
action
under
Docket
ID
No.

OW­
2003­
0028.
The
official
public
docket
is
a
collection
of
materials
that
is
available
for
public
4
viewing
at
the
Water
Docket
in
the
EPA
Docket
Center,
(
EPA/
DC)
EPA
West,
Room
B102,

1301
Constitution
Avenue,
NW,
Washington,
DC.
The
EPA
Docket
Center
Public
Reading
Room
is
open
from
8:
30
a.
m.
to
4:
30
p.
m.,
Monday
through
Friday,
excluding
legal
holidays.

The
telephone
number
for
the
Public
Reading
Room
is
(
202)
566­
1744,
and
the
telephone
number
for
the
Water
Docket
is
(
202)
566­
2426.
For
access
to
docket
material,
please
call
(
202)
566­

2426
to
schedule
an
appointment.

2.
Electronic
access.
You
may
access
this
Federal
Register
document
electronically
through
the
EPA
Internet
under
the
Federal
Register
listings
at
http://
www.
epa.
gov/
fedrgstr/.

An
electronic
version
of
the
public
docket
is
available
through
EPA's
electronic
public
docket
and
comment
system,
EPA
Dockets.
You
may
use
EPA
Dockets
at
http://
www.
epa.
gov/
edocket/
to
submit
or
view
public
comments,
access
the
index
listing
of
the
contents
of
the
official
public
docket,
and
to
access
those
documents
in
the
public
docket
that
are
available
electronically.
Once
in
the
system,
select
"
search,"
then
key
in
the
appropriate
docket
identification
number.

Certain
types
of
information
will
not
be
placed
in
the
EPA
Dockets.
Information
claimed
as
confidential
business
information
(
CBI)
and
other
information
whose
disclosure
is
restricted
by
statute,
which
is
not
included
in
the
official
public
docket,
will
not
be
available
for
public
viewing
in
EPA's
electronic
public
docket.
EPA's
policy
is
that
copyrighted
material
will
not
be
placed
in
EPA's
electronic
public
docket
but
will
be
available
only
in
printed,
paper
form
in
the
official
public
docket.
Although
not
all
docket
materials
may
be
available
electronically,
you
may
still
access
any
of
the
publicly
available
docket
materials
through
the
docket
facility
identified
in
5
section
I.
B.
1.

For
public
commenters,
it
is
important
to
note
that
EPA's
policy
is
that
public
comments,

whether
submitted
electronically
or
in
paper,
will
be
made
available
for
public
viewing
in
EPA's
electronic
public
docket
as
EPA
receives
them
and
without
change,
unless
the
comment
contains
copyrighted
material,
CBI,
or
other
information
whose
disclosure
is
restricted
by
statute.
When
EPA
identifies
a
comment
containing
copyrighted
material,
EPA
will
provide
a
reference
to
that
material
in
the
version
of
the
comment
that
is
placed
in
EPA's
electronic
public
docket.
The
entire
printed
comment,
including
the
copyrighted
material,
will
be
available
in
the
public
docket.

Public
comments
submitted
on
computer
disks
that
are
mailed
or
delivered
to
the
docket
will
be
transferred
to
EPA's
electronic
public
docket.
Public
comments
that
are
mailed
or
delivered
to
the
Docket
will
be
scanned
and
placed
in
EPA's
electronic
public
docket.
Where
practical,
physical
objects
will
be
photographed,
and
the
photograph
will
be
placed
in
EPA's
electronic
public
docket
along
with
a
brief
description
written
by
the
docket
staff.

C.
How
and
to
Whom
Do
I
Submit
Comments?

You
may
submit
comments
electronically,
by
mail,
or
through
hand
delivery/
courier.
To
ensure
proper
receipt
by
EPA,
identify
the
appropriate
docket
identification
number
in
the
subject
line
on
the
first
page
of
your
comment.
Please
ensure
that
your
comments
are
submitted
within
the
specified
comment
period.
Comments
received
after
the
close
of
the
comment
period
will
be
marked
"
late."
The
EPA
is
not
required
to
consider
these
late
comments.
6
1.
Electronically.
If
you
submit
an
electronic
comment
as
prescribed
below,
EPA
recommends
that
you
include
your
name,
mailing
address,
and
an
e­
mail
address
or
other
contact
information
in
the
body
of
your
comment.
Also
include
this
contact
information
on
the
outside
of
any
disk
or
CD
ROM
you
submit,
and
in
any
cover
letter
accompanying
the
disk
or
CD
ROM.
This
ensures
that
you
can
be
identified
as
the
submitter
of
the
comment
and
allows
EPA
to
contact
you
in
case
EPA
cannot
read
your
comment
due
to
technical
difficulties
or
needs
further
information
on
the
substance
of
your
comment.
EPA's
policy
is
that
EPA
will
not
edit
your
comment,
and
any
identifying
or
contact
information
provided
in
the
body
of
a
comment
will
be
included
as
part
of
the
comment
that
is
placed
in
the
official
public
docket,
and
made
available
in
EPA's
electronic
public
docket.
If
EPA
cannot
read
your
comment
due
to
technical
difficulties
and
cannot
contact
you
for
clarification,
EPA
may
not
be
able
to
consider
your
comment.

a.
EPA
Dockets.
Your
use
of
EPA's
electronic
public
docket
to
submit
comments
to
EPA
electronically
is
EPA's
preferred
method
for
receiving
comments.
Go
directly
to
EPA
Dockets
at
http://
www.
epa.
gov/
edocket,
and
follow
the
online
instructions
for
submitting
comments.
Once
in
the
system,
select
"
search,"
and
then
key
in
Docket
ID
No.
OW­
2003­
0028.

The
system
is
an
"
anonymous
access"
system,
which
means
EPA
will
not
know
your
identity,

e­
mail
address,
or
other
contact
information
unless
you
provide
it
in
the
body
of
your
comment.

b.
E­
mail.
Comments
may
be
sent
by
electronic
mail
(
e­
mail)
to
OW­
Docket@
epa.
gov,

Attention
Docket
ID
No.
OW­
2003­
0028.
In
contrast
to
EPA's
electronic
public
docket,
EPA's
e­
mail
system
is
not
an
"
anonymous
access"
system.
If
you
send
an
e­
mail
comment
directly
to
the
Docket
without
going
through
EPA's
electronic
public
docket,
EPA's
e­
mail
system
automatically
captures
your
e­
mail
address.
E­
mail
addresses
that
are
automatically
captured
by
7
EPA's
e­
mail
system
are
included
as
part
of
the
comment
that
is
placed
in
the
official
public
docket,
and
made
available
in
EPA's
electronic
public
docket.

c.
Disk
or
CD
ROM.
You
may
submit
comments
on
a
disk
or
CD
ROM
that
you
mail
to
the
mailing
address
identified
in
section
I.
C.
2.
These
electronic
submissions
will
be
accepted
in
WordPerfect
or
ASCII
file
format.
Avoid
the
use
of
special
characters
and
any
form
of
encryption.

2.
By
mail.
Send
an
original
and
three
copies
of
your
comments
to:
Water
Docket,

Environmental
Protection
Agency,
Mail
Code:
4101T,
1200
Pennsylvania
Ave.,
NW,

Washington,
DC,
20460,
Attention
Docket
ID
number
OW­
2003­
0028.

3.
By
hand
delivery
or
courier.
Deliver
your
comments
to:
Water
Docket,
Environmental
Protection
Agency,
EPA
West
Building,
Room
B102,
1301
Constitution
Avenue,
NW,

Washington,
DC,
Attention
Docket
ID
number
OW­
2003­
0028.
Such
deliveries
are
only
accepted
during
the
Docket's
normal
hours
of
operation
as
identified
in
section
I.
B.
1.

D.
What
Should
I
Consider
as
I
Prepare
My
Comments
for
EPA?

You
may
find
the
following
suggestions
helpful
for
preparing
your
comments:

1.
Explain
your
views
as
clearly
as
possible.

2.
Describe
any
assumptions
that
you
used.

3.
Provide
any
technical
information
and/
or
data
you
used
that
support
your
views.
8
4.
If
you
estimate
potential
burden
or
costs,
explain
how
you
arrived
at
your
estimate.

5.
Provide
specific
examples
to
illustrate
your
concerns.

6.
Offer
alternatives.

7.
Make
sure
to
submit
your
comments
by
the
comment
period
deadline
identified.

8.
To
ensure
proper
receipt
by
EPA,
identify
the
appropriate
docket
identification
number
in
the
subject
line
on
the
first
page
of
your
response.
It
would
also
be
helpful
if
you
provided
the
name,
date,
and
Federal
Register
citation
related
to
your
comments.

II.
Background
and
Summary
of
Today's
Notice
This
section
summarizes
the
purpose
of
today's
notice
and
provides
a
brief
background
on
the
CCL
requirements
and
prior
activities
related
to
the
CCL.

A.
What
is
the
Purpose
of
Today's
Action?

The
drinking
water
CCL
is
the
primary
source
of
priority
contaminants
for
evaluation
by
EPA's
drinking
water
program.
Contaminants
on
the
CCL
are
currently
not
subject
to
any
proposed
or
promulgated
national
primary
drinking
water
regulation,
but
are
known
or
anticipated
to
occur
in
public
water
systems,
and
may
require
regulation
under
SDWA.
The
EPA
conducts
research
on
health,
analytical
methods,
treatment
technologies
and
effectiveness,
and
contaminant
occurrence
for
priority
drinking
water
contaminants
on
the
CCL.
The
Agency
also
develops
drinking
water
guidance
and
health
advisories,
and
makes
regulatory
determinations
for
9
priority
contaminants
on
the
CCL.

Today's
Federal
Register
notice
explains
why
EPA
is
carrying
over
the
remaining
51
contaminants
on
the1998
CCL
as
the
draft
CCL
2
and
provides
background
information
on
the
list.
Additionally,
this
notice
describes
efforts
to
improve
on
the
CCL
selection
process,
the
NRC
recommendations
to
EPA
on
developing
future
CCLs,
and
related
issues
being
evaluated
by
EPA
and
NDWAC
to
implement
the
NRC
recommendations.
(
The
NDWAC
provides
independent
advice,
consultations,
and
recommendations
to
EPA
on
matters
related
to
the
activities,
function,

and
policies
of
the
Agency
under
the
SDWA,
as
amended.
See
section
V
for
further
discussion
on
NDWAC.)
The
EPA
requests
comment
on
the
draft
CCL
2
and
on
the
process
for
developing
future
CCLs.

B.
The
Background
of
the
CCL.

The
SDWA
is
the
core
statute
addressing
drinking
water
at
the
Federal
level.
Under
SDWA,
EPA
sets
public
health
goals
and
enforceable
standards
for
drinking
water
quality.
In
1996,
Congress
amended
SDWA
to
emphasize
sound
science
and
risk­
based
priority­
setting.

Congress
also
changed
the
way
drinking
water
regulatory
priorities
are
set
by
establishing
the
CCL
requirements.
The
1996
SDWA
amendments
require
EPA
to
(
1)
publish
every
five
years
a
list
of
currently
unregulated
contaminants
in
drinking
water
that
may
pose
risks,
and
(
2)
make
determinations
on
whether
or
not
to
regulate
at
least
five
contaminants
on
a
five
year
cycle,
or
three
and
a
half
years
after
each
CCL
(
SDWA
§
1412
(
b)(
1)).

Following
the
1996
SDWA
Amendments,
EPA
sought
NDWAC's
recommendations
on
10
the
process
that
should
be
used
to
identify
contaminants
for
inclusion
on
the
CCL.
For
chemical
contaminants,
the
Agency
developed
screening
and
evaluation
criteria
based
on
recommendations
from
NDWAC
and
identified
262
potential
chemical
contaminants.
For
microbiological
contaminants,
NDWAC
recommended
that
the
Agency
seek
external
expertise
to
identify
and
select
potential
waterborne
pathogens.
As
a
result,
the
Agency
convened
a
workshop
of
microbiologists
and
public
health
experts,
developed
screening
and
evaluation
criteria
based
on
workshop
recommendations,
and
evaluated
an
initial
list
of
25
potential
microbiological
contaminants.

The
1998
CCL
process
benefitted
from
considerable
input
from
the
scientific
community
and
the
public
through
stakeholder
meetings
and
the
public
comments
received
on
the
draft
CCL
published
in
1997.
The
EPA
published
the
final
CCL
containing
50
chemical
and
10
microbiological
contaminants
in
March
of
1998
(
63
FR
10273).
A
detailed
discussion
of
how
EPA
developed
the
1998
CCL
is
presented
in
section
III
of
this
notice.

After
publication
of
the
final
1998
CCL,
EPA
began
collecting
occurrence
data
and
conducting
research
on
the
CCL
contaminants.
Data
collection
efforts
include
assessing
the
occurrence
of
contaminants
in
public
water
systems
through
the
Unregulated
Contaminant
Monitoring
Regulation
(
64
FR
50556),
as
well
as
evaluating
occurrence
data
from
national
surveys
and
considering
State­
level
contaminant
occurrence
information.
Research
efforts
focused
on
obtaining
the
information
needed
to
characterize
the
adverse
health
effects
of
contaminants,
drinking
water
treatment
options,
and
the
development
of
analytical
methods
to
detect
contaminants
in
drinking
water.

As
noted
above,
the
1996
SDWA
also
directs
EPA
to
select
at
least
five
contaminants
11
from
the
CCL
every
five
years
to
determine
if
regulating
the
contaminants
with
a
national
primary
drinking
water
regulation
would
present
a
meaningful
opportunity
for
health
risk
reduction
(
SDWA
§
1412
(
b)(
1)).
In
order
to
make
regulatory
determinations
on
contaminants,
EPA
must
have
sufficient
data
to
evaluate
when
and
where
contaminants
occur,
human
exposure,
and
the
risk
to
public
health.

On
July
18,
2003,
EPA
announced
its
final
determinations
for
a
subset
of
contaminants
on
the
1998
CCL
(
68
FR
42898),
which
concluded
that
sufficient
data
and
information
were
available
to
make
the
determination
that
a
regulation
was
not
appropriate
for
the
following
nine
contaminants:
Acanthamoeba,
aldrin,
dieldrin,
hexachlorobutadiene,
manganese,
metribuzin,

naphthalene,
sodium,
and
sulfate.

III.
Developing
Today's
Draft
Drinking
Water
Contaminant
Candidate
List
This
section
provides
the
approach
EPA
used
to
develop
the
draft
CCL
2,
explains
the
rationale
to
support
the
approach,
and
presents
the
draft
CCL2.

A.
Approach
and
Rationale
for
the
Draft
CCL
2.

The
EPA's
approach
for
the
draft
CCL
2
is
to
continue
to
use
contaminants
identified
on
the
1998
CCL
to
set
drinking
water
research
priorities
and
make
regulatory
determinations.
The
EPA
believes
that
it
is
appropriate
for
the
draft
CCL
2
to
be
based
on
the
1998
CCL
because
(
1)

in
developing
the
1998
CCL,
the
Agency
used
peer­
reviewed
data
and
information
to
evaluate
12
contaminants;
(
2)
EPA
relied
on
significant
input
from
experts
and
stakeholders
to
develop
a
high
quality
process
for
selecting
the
contaminants
on
the
CCL;
(
3)
the
Agency
has
invested
in
research
and
data
collection
activities
related
to
the
CCL,
and
is
preparing
to
make
regulatory
determinations
in
the
2006
time­
frame
using
the
data
collected
from
these
activities;
and
(
4)

continued
reliance
on
high
priority
contaminants
remaining
from
the
1998
CCL
allows
the
Agency
to
focus
resources
on
completing
ongoing
work
on
an
expanded
process
for
classifying
drinking
water
contaminants
based
on
recent
recommendations
of
the
National
Research
Council
(
NRC,

2001).
A
more
detailed
discussion
of
this
approach
follows.

1.
Organizing
and
extracting
data.

a.
Evaluating
available
chemical
contaminant
listings.
The
EPA
reviewed
contaminants
from
eight
well­
known
lists,
as
well
as
contaminants
recommended
by
stakeholders,
to
develop
the
1998
CCL
(
Table
II­
1).
These
lists
contained
chemicals
that
could
be
of
potential
concern
in
drinking
water.
In
addition,
EPA
evaluated
a
number
of
other
contaminants
identified
by
stakeholders
during
the
December
2­
3,
1996,
stakeholder
meeting
for
potential
inclusion
on
the
CCL.
In
the
process
of
creating
the
final
list,
EPA
removed
from
consideration
23
contaminants
suspected
of
being
endocrine
disruptors
and
35
pesticides,
because
both
groups
of
chemicals
were
the
focus
of
additional
data
collection
efforts
under
other
programs
in
the
Agency.
The
EPA
intends
to
consider
both
groups
of
chemicals
as
part
of
the
next
CCL
screening
and
evaluation
process.
13
Table
II­
1.
Initial
Chemical
Lists
Considered
for
Development
of
the
1998
CCL.

List
Description
1991
Drinking
water
priority
list
(
DWPL,
EPA,
1991)
56
contaminants
Health
advisories
(
HAs)
108
contaminants,
(
included
all
contaminants
with
HAs
or
HAs
under
development)

EPA's
Integrated
Risk
Information
System
database
48
contaminants,
based
on
a
risk­
based
screen
developed
by
EPA
for
the
1994
DWPL
Contaminants
identified
by
public
water
systems
22
"
non­
target"
contaminants
identified
by
public
water
systems
for
the
1994
DWPL
Agency
for
Toxic
Substances
and
Disease
Registry's
list
of
contaminants
found
at
Comprehensive
Environmental
Response,
Compensation
and
Liability
Act
sites
Top
50
contaminants
from
the
1995
list
of
275
prioritized
hazardous
substances
Stakeholder
summary
list
59
contaminants
proposed
as
candidates
by
participants
in
a
December
2­
3,
1997
stakeholder
meeting
Toxic
Release
Inventory
(
TRI)
list
51
contaminants
that
met
the
criteria
for
assessing
the
potential
to
occur
in
public
water;
derived
from
an
original
1994
TRI
list
of
343
chemicals
b.
Screening
chemical
contaminants.
In
1997,
EPA
developed
screening
criteria
to
evaluate
the
potential
occurrence
and
health
effects
of
chemical
contaminants
gathered
from
the
lists
based
on
the
recommendation
of
experts
in
the
drinking
water
field,
including
NDWAC.

These
screening
criteria
focused
on
the
following
two
questions:

1.
Is
a
given
contaminant
found
in
water
at
levels
of
health
concern?

2.
If
no
data
exists
on
contaminant
occurrence,
is
the
contaminant
likely
to
be
found
in
water
based
on
surrogates
for
occurrence?
14
An
affirmative
answer
to
either
question
moved
the
contaminant
to
the
health
effects
phase
of
the
evaluation.
Contaminants
met
the
criteria
if
the
available
data
indicated
occurrence
in
a
drinking
water
system
serving
a
population
of
100,000
or
more,
occurrence
in
two
or
more
States,
or
occurrence
in
10
or
more
small
public
water
systems
at
levels
that
would
trigger
concern
for
human
health.
If
a
contaminant
did
not
have
specific
occurrence
data,
EPA
assessed
the
potential
for
a
contaminant
to
occur
in
drinking
water
based
on
surrogates
for
occurrence.

Surrogates
for
occurrence
included:
TRI
release
estimates,
production
amounts
from
industry
data,
and
physical­
chemical
properties.
A
contaminant
was
considered
to
have
the
potential
to
occur
if,
using
the
TRI,
the
release
to
surface
water
was
in
excess
of
400,000
pounds
per
year
and
the
physical­
chemical
properties
indicated
persistence
and
mobility
of
the
contaminant.
A
contaminant
was
also
considered
to
have
the
potential
to
occur
if
the
production
volume
exceeded
10
billion
pounds
per
year,
and
physical­
chemical
properties
indicated
persistence
and
mobility
of
the
contaminant.

If
a
pollutant
met
the
occurrence
screening
criteria,
EPA
then
screened
it
for
potential
health
effects.
The
health
effects
phase
of
the
evaluation
had
one
major
criterion:
was
there
evidence,
or
was
there
suggestion,
that
the
contaminant
causes
adverse
human
health
effects?

This
criterion
was
met
if
a
contaminant
had
one
or
more
of
the
following
elements:
(
1)
listed
by
California
Proposition
65,
(
2)
addressed
by
an
EPA
Health
Advisory,
(
3)
considered
a
likely
(
based
on
animal
data)
or
known
(
based
on
human
data)
carcinogen
by
EPA
or
the
International
Agency
for
Research
on
Cancer,
(
4)
evaluated
by
more
than
one
human
epidemiological
study
(
indicating
adverse
effects),
(
5)
received
an
oral
value
in
EPA's
Integrated
Risk
Information
System,
(
6)
regulated
in
drinking
water
by
another
industrial
country,
(
7)
identified
as
a
member
15
of
a
chemical
family
of
known
toxicity,
or
(
8)
characterized
by
a
structural
activity
relationship
indicating
toxicity.
If
a
contaminant
had
none
of
these
elements,
then
EPA
did
not
include
it
in
the
1998
CCL.

A
contaminant
that
met
both
the
occurrence
screening
criteria
and
received
an
affirmative
response
to
any
of
the
above
health
effects
screening
elements
resulted
in
that
contaminant's
inclusion
into
the
draft
1998
CCL.

c.
Selecting
microbiological
contaminants.
In
May
of
1997,
at
the
recommendation
of
NDWAC,
EPA
convened
a
workshop
on
microbiology
and
public
health
to
develop
a
list
of
pathogens
for
possible
inclusion
in
the
1998
CCL
(
62
FR
52193).
Participants
included
experts
from
academia,
the
drinking
water
industry,
EPA,
and
other
Federal
agencies.
The
EPA
prepared
and
distributed
a
list
of
25
microorganisms
(
6
protozoa,
8
viruses,
7
bacteria,
and
4
algal
toxins)

for
initial
consideration
by
workshop
members.
Microorganisms
were
included
on
this
initial
list
if
they
were
identified
in
disease
outbreak
data,
if
published
literature
documented
the
occurrence
of
known
or
suspected
pathogens
in
water,
or
if
other
information
suggested
the
possibility
of
a
public
health
risk.
The
workshop
participants
established
screening
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.

All
of
the
microorganisms
included
on
the
initial
EPA
list,
as
well
as
other
organisms
that
arose
during
the
discussions,
were
evaluated
against
these
criteria.
The
results
of
the
deliberations
of
the
microbiology
workshop
were
adopted
by
NDWAC
and
subsequently
utilized
by
the
Agency
to
select
13
microbiological
contaminants
placed
on
the
draft
1998
CCL.
16
2.
Input
from
stakeholders,
experts,
and
the
public.

The
EPA
relied
on
significant
input
from
experts
and
stakeholders
to
develop
a
high
quality
process
for
selecting
the
contaminants
on
the
1998
CCL.
The
Agency
sought
stakeholder
input
from
a
number
of
sources
and
at
several
different
junctures
in
the
CCL
development
process.
First,
EPA
convened
a
day­
long
meeting
of
over
50
experts,
including
representatives
from
industry,
academia,
consultants,
and
other
government
agencies
to
review
a
draft
of
the
strategy
for
developing
the
CCL.
The
EPA
also
convened
NDWAC
to
review
the
strategy
and
make
recommendations
on
the
development
of
the
CCL.
Experts
on
the
NDWAC
met
numerous
times
to
discuss
the
CCL
process
and
data
on
potential
contaminants.

As
mentioned
in
the
prior
section,
EPA
also
relied
on
the
advice
of
nationally
recognized
experts
in
the
field
of
microbiology,
during
a
separate
meeting,
to
classify
microbiological
contaminants.
These
experts
identified
and
selected
the
microbiological
contaminants
for
initial
consideration.

Additionally,
EPA
consulted
with
the
Agency's
Science
Advisory
Board
which
is
a
public
advisory
group
that
provides
extramural
scientific
information
and
advice
to
EPA.

The
draft
CCL
containing
58
chemical
and
13
microbiological
contaminants
was
published
on
October
6,
1997
(
62
FR
52193).
The
EPA
requested
comment
on
the
approach
used
to
develop
the
CCL,
and
on
whether
specific
contaminants
should
be
on
the
list.
The
EPA
received
71
comments
from
many
segments
of
the
drinking
water
community
including
trade
associations,

environmental
groups,
industries,
chemical
manufacturers,
State
and
local
health
regulatory
agencies,
water
utilities,
and
private
citizens.
Commenters
provided
data
and
information
on
17
specific
contaminants
and
included
suggestions
on
the
process
for
future
CCL
development.

Based
on
these
comments,
EPA
removed
10
chemical
and
4
microbiological
contaminants,
and
added
2
chemical
and
1
microbiological
contaminant
to
the
final
list.
The
final
1998
CCL
contained
50
chemical
and
10
microbiological
contaminants
and
was
published
on
March
2,
1998
(
63
FR
10273).

3.
Research
and
data
collection
for
contaminants
on
the
1998
CCL.

The
EPA
has
made
data
collection
and
research
on
the
CCL
contaminants
a
priority
and
continues
to
collect
information
and
conduct
research
in
the
areas
of
health
effects,
analytical
methods,
treatment,
and
occurrence.
As
noted
previously,
the
Agency
is
preparing
to
make
regulatory
determinations
in
the
2006
time­
frame
using
the
data
collected
from
these
activities.

a.
Research
on
health
effects,
treatment,
and
analytical
methods.
The
Drinking
Water
Research
Program's
Multi­
Year
Plan
identifies
over
50
projects
for
contaminants
on
the
CCL.

These
projects
are
scheduled
for
completion
in
the
next
two
years
and
span
three
research
areas:

health
effects,
treatment,
and
analytical
methods.
The
results
of
these
activities
will
provide
the
information
needed
to
characterize
potential
health
impacts,
assess
the
ability
to
detect
selected
contaminants
in
drinking
water,
and
verify
treatment
capability
and
cost.

b.
Data
collection
on
occurrence.
To
assess
whether
the
CCL
contaminants
are
occurring
in
drinking
water
systems,
EPA
identified
occurrence
priorities
and
determined
whether
analytical
methods
were
available
to
monitor
for
priority
CCL
contaminants.
Because
SDWA
requires
EPA
to
limit
monitoring
requirements
to
30
contaminants
in
any
5­
year
cycle,
only
a
18
subset
of
the
CCL
contaminants
were
monitored
in
the
first
round
of
data
collection.
Data
will
be
available
for
use
from
the
first
five­
year
cycle
of
monitoring
in
mid­
2004.
The
second
cycle
of
data
collection
is
expected
to
begin
in
2006
and
will
be
completed
in
mid­
2010,
after
EPA
proposes
and
promulgates
a
new
list
of
contaminants
for
monitoring.
Research
is
also
underway
to
develop
methods
for
contaminants
currently
without
adequate
analytical
methods,
or
where
the
current
analytical
method
detection
limit
was
above
the
known
adverse
health
effect
level
of
concentration.
Completion
of
these
methods
will
allow
EPA
to
make
regulatory
determinations
in
the
future.

Because
data
from
ongoing
research
and
data
collection
activities
will
become
available
in
the
next
few
years,
EPA
believes
that
it
is
appropriate
to
maintain
current
focus
on
gathering
this
information
in
preparation
for
making
regulatory
determinations
in
2006.

4.
Development
of
an
improved
classification
process
for
future
CCLs.

Continued
focus
on
many
of
the
priority
contaminants
from
the
1998
CCL
allows
the
Agency
to
target
resources
to
complete
its
ongoing
work
on
an
expanded
process
for
classifying
drinking
water
contaminants,
so
that
contaminants
identified
in
many
more
sources
can
be
effectively
screened.

After
the
1998
CCL
was
published,
the
Agency
asked
the
National
Research
Council,
the
operating
arm
of
the
National
Academy
of
Sciences,
to
review
the
1998
CCL
selection
process
and
provide
recommendations
on
how
the
process
could
be
improved.
These
recommendations
were
developed
over
several
years
and
provided
to
the
Agency
in
late
2001
(
see
section
IV).
On
19
balance,
the
NRC
found
the
1998
CCL
to
be
an
important
first
step
and
noteworthy
effort
to
identify
and
select
unregulated
chemical
and
microbiological
drinking
water
contaminants.
As
with
any
new
initiative,
the
NRC
identified
a
number
of
opportunities
to
strengthen
and
expand
the
analytical
process
upon
which
the
1998
CCL
was
based.
The
NRC
recommendations
focused
on
developing
a
larger
initial
list
(
universe)
and
on
identifying
new
approaches
for
screening
larger
numbers
of
potential
CCL
contaminants.
While
the
NRC
recommendations
greatly
expand
the
universe
of
contaminants
and
suggest
a
change
in
the
manner
in
which
contaminants
are
selected
for
the
CCL,
they
are
based
on
the
same
fundamental
principles
used
in
developing
the
1998
CCL
­­
a
focus
on
health
impacts
and
occurrence.
The
NRC
approach
addresses
the
expansion
of
the
universe
of
contaminants
and
recommends
a
process
that
combines
expert
judgement
with
the
use
of
computerized
data
sources
and
classification
processes
to
screen
contaminants
(
see
section
IV.
C
for
more
information).
The
use
of
automated
classification
processes
would
allow
EPA
to
evaluate
many
more
contaminants
than
experts
alone
can
evaluate
in
the
absence
of
these
processes.
The
much
broader
and
more
complex
approach
recommended
by
the
NRC
may
enable
EPA
to
gather
information
from
sources
that
were
not
used
to
develop
the
1998
CCL,
and
thus
strengthen
the
Agency's
ability
to
identify
emerging
contaminants.

The
EPA
agrees
that
an
approach
that
combines
expert
judgement
with
automated
classification
processes
should
be
explored.
The
Agency
is
continuing
to
assess
and
refine
the
approach
recommended
by
the
NRC.
The
Agency
believes
that
the
CCL
proposed
today
is
sound,
and
should
continue
to
be
the
source
of
contaminants
for
making
additional
regulatory
determinations
in
the
near
term.
This,
however,
should
not
be
interpreted
to
mean
that
EPA
is
restricted
to
the
contaminants
on
this
CCL
for
making
regulatory
determinations.
The
EPA
may
20
add
contaminants
to
this
list
and
make
regulatory
determinations
for
any
unregulated
contaminant
not
on
today's
CCL,
as
necessary,
to
address
an
urgent
threat
to
public
health.

B.
The
Draft
CCL
2.

Table
II­
2
lists
the
contaminants
on
the
draft
CCL
2.
These
contaminants
are
identified
by
name
and,
where
available,
the
Chemical
Abstracts
Service
Registry
Number
(
CASRN).
The
draft
CCL
2
consists
of
nine
microbiological
contaminants
and
42
chemical
contaminants
or
contaminant
groups.

Table
II­
2.
Draft
Drinking
Water
CCL
2.

Microbiological
Contaminant
Candidates
Adenoviruses
Aeromonas
hydrophila
Caliciviruses
Coxsackieviruses
Cyanobacteria
(
blue­
green
algae),
other
freshwater
algae,
and
their
toxins
Echoviruses
Helicobacter
pylori
Microsporidia
(
Enterocytozoon
and
Septata)

Mycobacterium
avium
intracellulare
(
MAC)

Chemical
Contaminant
Candidates
CASRN
1,1,2,2­
tetrachloroethane
79­
34­
5
1,2,4­
trimethylbenzene
95­
63­
6
1,1­
dichloroethane
75­
34­
3
1,1­
dichloropropene
563­
58­
6
Chemical
Contaminant
Candidates
CASRN
21
1,2­
diphenylhydrazine
122­
66­
7
1,3­
dichloropropane
142­
28­
9
1,3­
dichloropropene
542­
75­
6
2,4,6­
trichlorophenol
88­
06­
2
2,2­
dichloropropane
594­
20­
7
2,4­
dichlorophenol
120­
83­
2
2,4­
dinitrophenol
51­
28­
5
2,4­
dinitrotoluene
121­
14­
2
2,6­
dinitrotoluene
606­
20­
2
2­
methyl­
Phenol
(
o­
cresol)
95­
48­
7
Acetochlor
34256­
82­
1
Alachlor
ESA
&
other
acetanilide
pesticide
degradation
products
N/
A
Aluminum
7429­
90­
5
Boron
7440­
42­
8
Bromobenzene
108­
86­
1
DCPA
mono­
acid
degradate
887­
54­
7
DCPA
di­
acid
degradate
2136­
79­
0
DDE
72­
55­
9
Diazinon
333­
41­
5
Disulfoton
298­
04­
4
Diuron
330­
54­
1
EPTC
(
s­
ethyl­
dipropylthiocarbamate)
759­
94­
4
Fonofos
944­
22­
9
p­
Isopropyltoluene
(
p­
cymene)
99­
87­
6
Linuron
330­
55­
2
Chemical
Contaminant
Candidates
CASRN
22
Methyl
bromide
74­
83­
9
Methyl­
t­
butyl
ether
(
MTBE)
1634­
04­
4
Metolachlor
51218­
45­
2
Molinate
2212­
67­
1
Nitrobenzene
98­
95­
3
Organotins
N/
A
Perchlorate
14797­
73­
0
Prometon
1610­
18­
0
RDX
121­
82­
4
Terbacil
5902­
51­
2
Terbufos
13071­
79­
9
Triazines
and
degradation
products
of
triazines
including,
but
not
limited
to
Cyanazine
21725­
46­
2
and
atrazine­
desethyl
6190­
65­
4
Vanadium
7440­
62­
2
IV.
The
National
Research
Council's
Recommended
Approach
for
Developing
Future
CCLs
This
section
summarizes
the
NRC
recommendations
to
EPA
for
developing
future
CCLs
and
discusses
other
issues
related
to
contaminant
selection
and
prioritization.

The
EPA
sought
the
advice
of
the
NRC
in
response
to
comments
received
during
the
development
of
the
1998
CCL,
which
indicated
a
need
for
a
broader,
more
systematic
approach
for
selecting
contaminants.

The
Agency
asked
the
NRC
to
address
three
key
topics
related
to
drinking
water
23
contaminant
selection
and
prioritization:

1.
What
approach
should
be
used
to
develop
future
CCLs?

2.
How
best
should
EPA
assess
emerging
drinking
water
contaminants
and
related
databases
to
support
future
CCL
efforts?

3.
What
approach
should
EPA
use
to
set
priorities
for
contaminants
on
the
CCL?

The
NRC's
findings
and
recommendations
on
these
topics
were
published
in
the
following
three
NRC
reports:
Setting
Priorities
for
Drinking
Water
Contaminants
(
NRC,
1999a),

Identifying
Future
Drinking
Water
Contaminants
(
NRC,
1999b),
and
Classifying
Drinking
Water
Contaminants
for
Regulatory
Consideration
(
NRC,
2001).
The
discussion
in
today's
notice
focuses
on
the
2001
report,
which
synthesizes
key
findings
from
the
prior
reports.

In
its
report
entitled
Classifying
Drinking
Water
Contaminants
for
Regulatory
Consideration,
the
NRC
recommended
that
EPA
use
a
two­
step
process
for
generating
future
CCLs.
The
first
step
in
the
process
is
to
select
contaminants
from
a
broad
universe
of
chemical,

microbiological,
and
other
types
of
potential
drinking
water
contaminants
for
inclusion
on
a
preliminary
CCL
(
PCCL),
based
on
a
screening
assessment
of
human
health
impacts,
occurrence
data,
and
expert
judgement
(
NRC,
2001).
The
second
step
in
the
process
is
to
use
a
classification
algorithm
(
a
formula
or
set
of
steps
for
solving
a
particular
problem),
in
conjunction
with
expert
judgement,
to
select
from
the
PCCL
contaminants
to
be
included
on
the
CCL.
The
NRC
believes
that
this
process
of
selecting
contaminants
for
future
CCLs
will
result
in
a
more
systematic,

transparent,
and
comprehensive
approach
to
classifying
drinking
water
contaminants.

A.
Screening
the
Universe
of
Contaminants.
24
The
NRC
suggests
that
the
universe
of
potential
drinking
water
contaminants
could
contain
tens
of
thousands
contaminants
and
recommends
that
EPA
consider
a
range
of
contaminants
including
naturally
occurring
substances,
emerging
waterborne
pathogens,
chemical
agents,
byproducts,
degradates
of
chemical
agents,
radionuclides,
and
biological
toxins
as
part
of
the
universe.
The
NRC's
approach
to
assembling
the
universe
is
to
begin
with
data
sources
that
are
currently
available
and
to
work
with
the
public,
the
drinking
water
industry,
and
the
scientific
community
to
develop
a
strategy
for
assessing
contaminants
that
are
not
found
in
existing
databases
or
lists
(
NRC,
2001).
This
approach
could
greatly
expand
on
the
number
of
contaminants
to
be
reviewed
and
the
number
of
databases
and
lists
to
be
searched.

B.
Compiling
the
PCCL.

The
NRC
further
suggested
that
EPA
develop
a
well­
conceived
set
of
screening
criteria
that
can
be
applied
rapidly
and
routinely,
in
conjunction
with
expert
judgement,
to
screen
the
universe
of
potential
drinking
water
contaminants
to
a
much
smaller
PCCL.

To
compile
the
PCCL,
the
NRC
recommends
an
approach
that
relies
on
health
effects
and
occurrence
information.
The
NRC
suggests
a
screening
process
that
selects
contaminants
from
a
hierarchy
of
information
based
on
the
following
criteria
related
to
both
health
effects
and
occurrence:

1.
Contaminants
that
are
demonstrated
to
cause
adverse
health
effects
and
are
demonstrated
to
occur
in
drinking
water.

2.
Contaminants
that
have
the
potential
to
cause
adverse
health
effects
and
are
25
demonstrated
to
occur
in
drinking
water.

3.
Contaminants
that
are
demonstrated
to
cause
adverse
health
effects
and
that
have
the
potential
to
occur
in
drinking
water.

4.
Contaminants
that
have
the
potential
to
cause
adverse
health
effects
and
that
have
the
potential
to
occur
in
drinking
water.

The
NRC
advises
EPA
to
acquire
input
from
the
public
and
other
"
stakeholders"
on
the
PCCL.
This
approach
will
assist
EPA
in
making
any
policy
judgements
about
the
PCCL
and
will
encourage
transparency
in
the
process.

C.
Contaminant
Selection
from
the
PCCL
to
the
CCL.

The
second
step
is
the
selection
of
drinking
water
contaminants
on
the
PCCL
for
inclusion
on
the
CCL.

The
NRC
evaluated
a
number
of
screening
and
assessment
processes
and
recommended
that
EPA
consider
the
prototype
classification
method,
combined
with
expert
judgement,
as
an
effective
approach
for
selecting
contaminants.
Prototype
classification
uses
computer­
based
computational
tools
to
weigh
selected
contaminant
characteristics
(
also
called
attributes)
against
the
characteristics
of
drinking
water
contaminants
that
are
known
to
occur
in
drinking
water
and
are
recognized
as
having
negative
health
impacts.
These
attributes
could
include
various
measures
of
toxicity,
occurrence,
and
surrogates
for
these
measures
where
primary
data
do
not
exist.
A
prototype
classification
algorithm
would
need
to
be
"
trained"
to
recognize
features
of
contaminants
that
should
be
on
the
CCL
by
inputting
key
information
about
contaminants
that
we
26
know
should
and
should
not
be
on
the
CCL.

For
demonstration
purposes,
the
NRC
used
a
prototype
classification
approach
known
as
a
"
neural
network."
Neural
networks
are
being
used
in
investment
analysis
to
predict
foreign
exchange
rates,
credit
worthiness,
and
signature
analysis.
The
approach
relies
on
expert
judgement
to
determine
which
attributes
should
be
used
to
characterize
the
contaminants
and
the
relative
importance
of
the
attributes.
The
neural
network
then
uses
mathematical
formulas
to
evaluate
attributes
of
contaminants
against
those
of
known
contaminants
and
makes
a
prediction
based
on
the
importance
placed
on
the
contaminants'
attributes.

In
addition
to
suggesting
a
sample
prototype
classification
method,
the
NRC
also
identified
possible
attributes
for
use
in
comparing
the
characteristics
of
potential
contaminants.

They
suggested
the
following
attributes:
potency,
severity,
prevalence,
magnitude,
and
persistence­
mobility.
The
NRC
considered
these
attributes
because
of
their
applicability
to
both
chemicals
and
microbes,
and
noted
that,
after
additional
analysis
and
advice,
EPA
might
well
determine
that
other
attributes
were
more
appropriate
for
developing
the
CCL.

D.
Virulence
Factor
Activity
Relationships
for
Assessing
Emerging
Waterborne
Pathogens.

The
NRC
also
addressed
the
issue
of
how
best
to
examine
emerging
waterborne
pathogens,
opportunistic
microorganisms,
and
other
newly
identified
microorganisms
in
Classifying
Drinking
Water
Contaminants
for
Regulatory
Consideration
(
NRC,
2001).
The
panel
recognized
several
difficulties
in
classifying
microbiological
drinking
water
contaminants.

These
include
difficulties
in
characterizing
microbiological
contamination
of
drinking
water,
27
identifying
the
organism
responsible
for
outbreaks,
and
developing
databases
for
emerging
pathogens.
The
NRC
recommended
that
EPA
explore
virulence
factor
activity
relationships
(
VFARs)
to
address
this
problem.
The
VFAR
principle
can
be
described
as
comparing
the
gene
structure
of
newly
identified
waterborne
pathogens
to
pathogens
with
known
genetic
structures
which
have
been
associated
with
human
disease.

Virulence
factors
are
defined
broadly
by
the
NRC
as
the
ability
of
a
pathogen
to
persist
in
the
environment,
gain
entry
into
a
host
(
e.
g.,
humans),
reproduce,
and
cause
disease
or
other
health
problems
either
because
of
its
architecture
or
because
of
its
biochemical
compounds.
A
number
of
virulence
factors
are
known,
including
the
ability
of
a
microbe
to
move
within
a
host
under
its
own
power,
the
ability
of
mechanisms
to
protect
the
microbe
against
the
body's
defenses
(
e.
g.,
anti­
phagocytosis
mechanisms),
the
ability
of
a
microbe
to
adhere
or
attach
to
the
surface
of
a
host
cell,
and
the
ability
of
microbes
to
produce
toxins
that
injure
host
cells.

Genetic
information
in
the
form
of
gene
sequences
has
been
stored
in
several
computerized
"
libraries"
or
"
gene
banks"
for
the
use
of
the
research
community.
The
NRC
described
several
of
these
gene
banks
and
provides
a
list
of
microorganisms
whose
genomes
have
already
been
studied.
The
NRC
noted
that
the
genetic
information
of
additional
microbes
are
being
added
to
gene
banks
at
a
rapid
pace
(
NRC,
2001).

The
NRC
also
recommended
that
EPA
explore
the
use
of
gene
chip
technology
(
also
referred
to
as
biochips,
deoxyribonucleic
acid
(
DNA)
chips,
DNA
microarrays,
and
gene
arrays)

to
assist
in
classifying
drinking
water
contaminants.
Gene
chips
are
devices
not
much
larger
than
postage
stamps.
Thousands
of
tiny
cells
are
typically
placed
on
a
glass
wafer.
Each
holds
deoxyribonucleic
acid,
or
DNA,
from
a
different
human
or
microbiological
gene.
The
array
of
28
cells
on
a
gene
chip
makes
it
possible
to
carry
out
a
large
number
of
genetic
tests
on
a
sample
at
one
time.
At
the
moment,
the
devices
are
used
in
pharmaceutical
laboratories
to
investigate
which
genes
are
involved
in
various
normal
and
disease
processes
and
to
speed
up
the
process
of
finding
new
drugs.

The
NRC
believed
that
this
approach
has
major
and
far
reaching
potential
and
indicated
that,
in
the
near
future,
microarrays
could
be
developed
that
are
labeled
with
genes
for
a
variety
of
virulence
factors
and
could
be
used
to
assay
drinking
water
samples
for
the
presence
of
genetic
virulence
factors
of
concern.

The
NRC
recognized
that
use
of
the
VFAR
approach
to
identify
potential
waterborne
pathogens
would
require
a
multi­
year
commitment
and
significant
cooperation
and
collaboration
by
EPA
and
other
participating
organizations
before
the
technology
can
be
used
to
develop
the
CCL.

V.
Implementation
of
the
National
Research
Council
Recommendations
The
NRC
recommendations
provided
a
possible
framework
for
evaluating
a
larger
number
of
contaminants
and
making
decisions
about
contaminants
for
which
data
are
limited
through
the
use
of
innovative
technologies
and
expert
advice.
In
making
these
recommendations,
the
NRC
stressed
that
more
work
is
needed
in
the
area
of
research
and
encouraged
EPA
to
explore
different
approaches
for
effective
implementation.

The
EPA
has
requested
the
assistance
of
NDWAC
to
evaluate
and
provide
advice
on
the
NRC's
recommended
classification
process.
This
section
describes
the
role
played
by
NDWAC
in
29
assisting
EPA's
evaluation
and
implementation
of
the
NRC
recommendations
and
the
development
of
the
classification
approach.

A.
The
National
Drinking
Water
Advisory
Council
Background
and
Charge.

As
previously
noted,
the
1974
SDWA
established
NDWAC
to
provide
independent
advice,
consultations,
and
recommendations
to
EPA
on
matters
related
to
the
activities,
functions,

and
policies
of
the
Agency
under
SDWA.
To
assist
in
this
process,
the
NDWAC
forms
work
groups
of
experts
to
perform
assessments
of
specific
drinking
water
issues.
The
work
groups
prepare
reports
and
recommendations
that
the
NDWAC
considers
when
making
its
recommendations
to
EPA.
The
NDWAC
CCL
Work
Group
began
its
deliberations
in
September,

2002.
The
Work
Group
is
comprised
of
21
recognized
technical
and
public
health
experts
representing
an
array
of
backgrounds
and
perspectives.

The
NDWAC
CCL
Work
Group
is
charged
with
discussing,
evaluating,
and
providing
advice
to
the
Agency
on
methodologies,
activities,
and
analysis
needed
to
implement
the
NRC
recommendations
on
an
expanded
approach
for
the
CCL
listing
process.
The
EPA
is
working
with
the
NDWAC
CCL
Work
Group
to
explore
issues
related
to
a
contaminant
classification
approach
including
(
1)
collecting
and
organizing
the
data,
(
2)
screening
the
contaminants
in
the
universe
to
compile
the
PCCL,
(
3)
classifying
contaminants
from
the
PCCL
to
the
CCL,
and
(
4)

developing
the
VFAR
concept
and
classifying
microorganisms.
The
NDWAC
CCL
Work
Group
is
currently
discussing
and
evaluating
the
issues
related
to
implementing
the
NRC
recommendations.
EPA
is
assisting
the
NDWAC
CCL
Work
Group
by
conducting
analyses
and
30
investigations
that
inform
the
Work
Group
discussions.
The
NDWAC
CCL
Work
Group
expects
to
present
its
recommendations
to
the
NDWAC
in
2004.

The
NDWAC
CCL
Work
Group
and
EPA
have
made
great
progress
in
evaluating
the
NRC
recommendations.
The
EPA
recognizes
that
the
recommended
approach
would
require
a
significant,
sustained
effort
to
screen
many
more
data
sources
for
potential
CCL
contaminants
and
to
adapt
computer
programs
for
environmental
contaminant
selection.
The
efforts
to
date
have
provided
substantial
information
about
the
scope
of
the
effort
and
the
challenges
ahead.

B.
Ongoing
Analysis
of
the
Classification
Approach.

1.
Organizing
and
extracting
data.

The
NRC
recommended
that
EPA
begin
by
considering
a
broad
universe
of
chemical,

microbiological,
and
other
types
of
potential
drinking
water
contaminants
and
contaminant
groups.
The
NRC
projects
that
the
scope
of
the
universe
could
be
on
the
order
of
tens
of
thousands
of
contaminants,
which
represent
a
dramatically
larger
set
of
substances
to
be
initially
considered
in
terms
of
types
and
numbers
of
contaminants
than
that
used
for
the
creation
of
the
1998
CCL
(
262
contaminants
from
8
data
sources).
Considering
that
there
is
no
comprehensive
list
of
potential
drinking
water
contaminants,
and
limited
data
on
health
effects,
occurrence,
and
other
related
data
for
many
of
the
potential
contaminants,
EPA
is
challenged
with
defining
the
universe
of
potential
drinking
water
contaminants,
determining
how
it
will
identify
data
sources,

and
identifying
what
approach
it
will
use
for
extracting
information.
31
Based
on
the
NRC
recommendations,
EPA
is
considering
two
guiding
principles
for
construction
of
the
CCL
universe:
(
1)
the
universe
should
include
those
contaminants
that
have
demonstrated
or
potential
occurrence
in
drinking
water,
and
(
2)
the
universe
should
include
those
contaminants
that
have
demonstrated
or
potential
adverse
health
effects.
These
inclusionary
principles
apply
to
selection
of
contaminants
to
be
included
in
the
CCL
universe.
The
proposed
process
involves
the
identification
of
information
and
data
sources
and
the
development
of
a
means
of
extracting
data
to
be
merged
into
a
CCL
universe
data
set.

The
NDWAC
CCL
Work
Group
and
EPA
have
identified
a
number
of
data
sources
as
potentially
useful
resources.
The
data
sources
vary
widely
in
their
intended
use
(
e.
g.,
research,

survey,
and
compliance
monitoring);
type
of
data
(
e.
g.,
concentrations,
health
effects,
chemical
information,
microbiological
occurrence,
environmental
fate,
and
genetic
sequences);
data
format;

availability;
and
possible
applicability
to
the
universe
of
contaminants.
The
data
sources
include
the
following:

°
Databases
recommended
by
the
NRC
(
NRC
1999a,
1999b,
and
2001)

°
Databases
required
by
SDWA
1412(
b)

°
Chemical
structure
databases
(
e.
g.,
molecular
structure
information
used
for
predictive
toxicology)

°
Chemical
property
databases
(
e.
g.,
chemical
boiling
point
and
solubility)

°
Bibliographic
databases
(
i.
e.,
references
to
published
literature)

°
Subscription/
commercial
databases
°
Genomic
sequence
databases
°
International
databases
32
°
Other
sources
of
information
recommended
by
NDWAC
and
other
organizations
In
addition
to
data
availability
and
extraction
issues,
EPA
must
also
address
data
quality
concerns.
The
Agency
is
required
under
SDWA
to
use
the
best
available
peer­
reviewed
science
and
data
collected
by
accepted
methods
or
best
available
methods.
While
the
standards
of
quality
depend
on
the
use
to
which
the
data
is
put,
and
screening
level
analyses
require
less
rigorous
standards
than
some
other
uses
(
e.
g.,
rule
development),
the
data
used
to
define
the
CCL
universe
of
contaminants
must
nonetheless
be
accurately
characterized
and
its
quality
clearly
understood.

To
satisfy
these
quality
assurance
objectives,
EPA
is
in
the
process
of
developing
a
Quality
Assurance
Project
Plan
to
cover
all
phases
of
the
CCL
process,
from
defining
the
universe
of
contaminants
to
making
regulatory
determinations.

2.
Compiling
the
PCCL.

The
NRC
recommended
that
EPA
develop
a
set
of
screening
criteria
that
could
be
applied
rapidly
and
routinely,
in
conjunction
with
expert
judgement,
to
screen
the
universe
of
potential
drinking
water
contaminants
for
inclusion
on
the
PCCL.
The
NRC
considered
this
a
significant
challenge,
but
did
not
deliberate
extensively
on
the
criteria
to
be
used
for
this
screening.
Thus,

this
screening
step
has
become
an
area
of
significant
analysis
by
EPA
and
the
NDWAC
CCL
Work
Group.
Work
to
develop
a
process
and
criteria
for
screening
is
ongoing,
as
is
the
analysis
of
methods
that
would
enable
the
screening
of
contaminants
with
little
or
no
primary
data
or
information.

In
addition
to
exploring
screening
criteria,
EPA
is
evaluating
how
expert
judgement
could
33
be
used
to
quickly
reduce
a
broad
universe
to
a
manageable
set
of
contaminants
for
the
PCCL.

While
the
NRC
reports
only
provided
a
conceptual
recommendation
for
screening
the
universe
to
a
PCCL,
the
NRC
indicated
that
the
process
should
not
involve
an
extensive
analysis
of
data.
The
NRC
suggested
that
EPA
develop
coarse
screening
criteria
that
can
eliminate
chemicals
with
low
production
volume
and
low
potential
for
adverse
health
effects,
unless
expert
judgement
of
health
effects
would
place
a
chemical
on
the
PCCL.

As
previously
described,
EPA
is
coordinating
efforts
with
the
NDWAC
CCL
Work
Group
to
develop
a
list
of
occurrence
databases
to
be
used
in
the
analysis
and
will
evaluate
available
human
exposure
or
potential
human
exposure
databases
such
as
production
and
use
databases,

environmental
release
databases,
and
environmental
media
and
biological
tissues
monitoring
databases.
The
toxicological
or
health
effects
databases
being
evaluated
include
health
assessment
databases
and
waterborne
disease
outbreak
databases
as
well
as
other
information.

For
health
effects
screening,
EPA
is
focusing
on
contaminants
that
may
be
potent
at
levels
near
those
found
in
drinking
water
and
substances
with
irreversible
or
life
threatening
health
effects.
The
NDWAC
CCL
Work
Group
is
considering
a
number
of
options
for
processing
data
and
information
in
order
to
examine
the
relationship
between
adverse
health
effects
and
occurrence
in
drinking
water
to
make
decisions
on
movement
to
the
PCCL.

3.
Classifying
contaminants
from
the
PCCL
to
the
CCL.

The
challenge
of
classifying
a
potentially
large
number
of
contaminants
for
movement
from
the
PCCL
to
the
CCL
raises
the
question
of
what
kind
of
process
or
method
is
best
suited
34
for
performing
this
task.
The
NRC
panel
recommended
the
use
of
a
prototype
classification
approach
combined
with
expert
judgement.
The
EPA
has
asked
NDWAC
for
advice
in
this
area
and
is
exploring
several
alternative
models
including:
artificial
neural
networks,
classification
and
regression
trees,
logistic
regression
(
a
specific
form
of
a
generalized
linear
model),
and
multivariate
adaptive
regression
splines.
Work
is
ongoing
to
identify
and
test
models
and
conduct
trial
classifications
using
a
subset
of
the
contaminants
that
will
be
in
the
universe.

Use
of
the
prototype
classification
approach
necessitates
assigning
a
score
to
each
attribute
for
a
given
contaminant.
Attributes
are
descriptive
properties
which
allow
different
types
of
contaminants
to
be
compared
in
a
consistent
manner.
The
NRC
recommended
the
following
attributes:
potency
(
i.
e.,
the
amount
of
a
contaminant
that
is
needed
to
cause
illness);

severity
(
i.
e.,
the
seriousness
of
the
health
effect);
prevalence
(
i.
e.,
how
common
does
or
would
a
contaminant
occur
in
water);
magnitude
(
i.
e.,
the
concentration
or
expected
concentration
of
a
contaminant
relative
to
a
level
that
causes
a
perceived
health
effect);
and
persistence­
mobility
(
i.
e.,

a
surrogate
for
occurrence
when
occurrence
information
is
unavailable).
The
EPA
and
NDWAC
CCL
Work
Group
are
examining
the
five
attributes
recommended
by
the
NRC,
as
well
as
exploring
other
possible
attributes.

The
EPA
and
NDWAC
CCL
Work
Group
are
also
exploring
how
attributes
(
e.
g.,

potency)
for
a
given
contaminant
might
be
scored
using
differing
data
elements
(
e.
g.,
the
reference
dose
(
RfD),
the
no
observable
adverse
effect
level
(
NOAEL),
and
the
lowest
observable
adverse
effect
level
(
LOAEL)),
so
that
the
score
for
an
attribute
would
reflect
the
degree
of
the
health
effect
or
occurrence
relative
to
other
contaminants.

The
NDWAC
CCL
Work
Group
and
EPA
have
undertaken
significant
analysis
with
35
regard
to
the
severity
attribute.
For
example,
the
following
range
of
scores
was
used
by
the
NRC
to
represent
the
severity
of
a
given
contaminant
for
health
effects
as
follows:

0.
No
effect
1.
Changes
in
organ
weights
with
minimal
clinical
significance
2.
Biochemical
changes
with
minimal
clinical
significance
3.
Pathology
of
minimal
clinical
significance
4.
Cellular
changes
that
could
lead
to
disease;
minimal
functional
change
5.
Significant
functional
changes
that
are
reversible
6.
Irreversible
changes,
treatable
disease
7.
Single
organ
system
pathology
and
function
loss
8.
Multiple
organ
system
pathology
and
function
loss
9.
Disease
likely
leading
to
death
10.
Death
The
EPA
and
NDWAC
CCL
Work
Group
are
exploring
ways
that
the
severity
scale
provided
by
the
NRC
might
be
modified
so
that
effects
in
the
middle
of
the
scale
(
e.
g.,
4­
8)
would
be
more
easily
differentiated
and
to
allow
for
appropriate
scoring
of
reproductive
and
developmental
effects.
The
EPA
and
NDWAC
CCL
Work
Group
are
also
examining
possible
approaches
to
scoring
chemicals
that
lack
information
on
a
critical
effect
for
severity.

Similarly,
EPA
is
engaged
in
substantial
technical
analysis
with
the
NDWAC
CCL
Work
Group
of
a
possible
scoring
methodology
for
the
attribute
potency.
The
NRC
suggested
that
potency
could
be
measured
in
terms
of
the
RfD,
the
NOAEL,
the
LOAEL,
or
by
other
measures.

Additional
issues
and
challenges
the
NDWAC
CCL
Work
Group
is
considering
include:
36
1.
Which
data
elements
are
best
suited
to
estimate
the
score
for
an
attribute?
For
example,
for
the
attribute
potency,
values
exist
for
RfDs,
NOAELs,
and
LOAELs.

2.
In
what
order
should
data
for
a
given
contaminant
be
considered
given
the
quality,

confidence,
and
certainty
of
data
sources?
For
example,
should
EPA
score
a
contaminant
using
an
RfD
over
an
oral
LOAEL
if
both
are
available?

3.
If
no
RfD
or
LOAEL
is
available,
then
which
value
should
be
used
to
score
a
contaminant?

4.
Should
EPA
review
all
types
of
data
elements
even
when
an
RfD
exists?

5.
How
should
contaminants
be
scored
when
data
from
different
sources
suggest
conflicting
scores?

6.
When
should
surrogates
be
used
in
place
of
the
preferred
data
elements?
For
example,

using
production
and
release
data
to
estimate
the
potential
for
occurrence
may
be
a
better
approximation
than
limited
sampling
in
one
location.

7.
How
should
surrogates
be
expressed
and
scored?

8.
For
the
health
effects
attributes,
which
populations
should
be
targeted
in
scoring
(
e.
g.,

adults,
children,
or
sensitive
subpopulations)?
Is
it
possible
to
make
that
distinction
given
the
data
that
are
available?

9.
Should
an
assessment
of
certainty
and
confidence
be
incorporated
into
the
scoring
process
to
reflect
the
quality
of
the
data?

10.
How
should
scoring
for
occurrence
data
elements
be
addressed?

11.
How
should
subjectivity
of
severity
scoring
process
be
addressed?
For
example,

some
disorders
are
treatable
depending
upon
when
treatment
is
initiated.
How
should
37
treatability
be
accounted
for
without
subjectively
referring
to
a
person's
ability
to
obtain
medical
treatment?

12.
What
data
quality
guidelines
would
be
appropriate
for
classifying
contaminants
from
a
PCCL
to
the
CCL?
Would
different
guidelines
for
screening
contaminants
be
appropriate
from
a
CCL
universe
to
a
PCCL?

13.
Which
models
or
other
approaches
would
be
best
suited
for
classification
given
the
scoring
approach?

4.
The
virulence
factor
activity
relationship
concept
and
classifying
microorganisms.

The
VFAR
process
offers
a
possible
alternative
to
identifying
and
characterizing
microbiological
contaminants
that
lack
information.
As
previously
discussed,
the
VFAR
concept
can
be
described
as
comparing
the
gene
structure
of
newly
identified
waterborne
pathogens
to
pathogens
with
known
genetic
structures
that
have
been
associated
with
human
disease.
The
NRC
recommends
the
use
of
the
VFAR
approach
for
assessing
emerging
waterborne
pathogens,

opportunistic
microorganisms,
and
other
newly
identified
microorganisms.
While
this
approach
may
offer
significant
improvements
for
the
future,
it
may
not
be
sufficiently
developed
in
time
for
the
next
CCL
(
i.
e.,
the
2008
CCL).
Some
of
the
challenges
to
overcome
include
the
ability
of
microbiological
genes
to
exhibit
considerable
adaptability
by
frequently
gaining
or
losing
genetic
elements.
The
presence
of
multiple
genetic
elements,
together
with
the
relative
frequency
of
chromosomal
recombinations,
results
in
highly
dynamic
genes
that
make
predictability
difficult.

Researchers
have
mapped
about
100
entire
genomes
of
bacteria
and
viruses,
and
the
38
number
of
mapped
genomes,
especially
of
pathogens,
is
growing
rapidly.
Researchers
store
the
information
in
several
computerized
libraries,
or
gene
banks.
Sophisticated
computer
software
programs
can
sort
and
match
genetic
information
in
these
libraries,
which
can
allow
researchers
to
predict
the
ability
of
a
microbe
to
produce
virulence
factors,
and
compare
a
microbe
to
known
pathogens.
Some
waterborne
pathogens
have
similar
toxins,
surface
proteins,
and
mechanisms
of
infection,
and
some
of
the
genes
for
these
factors
have
been
identified.

The
NDWAC
CCL
Work
Group
and
EPA
are
exploring
a
means
of
using
gene
banks
for
drinking
water
applications.
For
example,
EPA
searched
for
genetic
sequences
associated
with
virulence
using
the
National
Center
for
Biotechnology
Information's
GenBank
database.
The
database
contains
a
large
list
of
such
sequences,
most
of
which
are
associated
with
pathogens
or
microbes
used
in
laboratory
studies.
Initial
findings
indicate
that
some
relevant
sequence
data
are
available,
however,
the
data
were
in
a
form
that
proved
difficult
to
use
for
this
purpose.

The
EPA
is
also
coordinating
efforts
with
the
NDWAC
CCL
Work
Group
to
evaluate
an
approach
based
on
bioinformatics
to
extract
relevant
information
from
databases
and
literature
sources
on
known
waterborne
pathogen
gene
sequences.
The
information
could
provide
the
gene
sequences
needed
to
demonstrate
the
potential
use
of
gene
chip
technology
in
performing
VFAR
analysis.

The
EPA
is
also
exploring
alternative
approaches
to
screen
microbes
for
the
next
CCL,

given
the
uncertainty
surrounding
the
time
frame
for
a
fully
developed
VFAR
approach.
For
example,
EPA
is
exploring
an
approach
that
would
construct
a
microbiological
universe,
define
microbiological
attributes,
and
score
the
attributes.

The
EPA
believes
that
the
NRC
recommendations
hold
substantial
promise
and
is
39
exploring
ways
to
take
the
recommendations
beyond
the
conceptual
framework
to
development
and
implementation.
Additionally,
EPA
is
working
with
the
NDWAC
CCL
Work
Group
to
define
the
dimensions
of
the
microbiological
universe
as
part
of
a
step­
wise
process
for
defining
the
CCL.
The
EPA
welcomes
comments
on
these
and
other
relevant
microbiological
issues
to
assist
the
Agency
in
addressing
the
NRC
recommendations.

VI.
Request
for
Comment
The
EPA
seeks
comments
on
the
range
of
CCL
issues
and
activities
addressed
in
this
notice.
EPA
is
also
requesting
comment
on
its
decision
to
carry
over
the
remaining
contaminants
on
the
1998
CCL
as
the
draft
CCL
2.
The
Agency
is
asking
for
public
comments
on
the
following
questions
related
to
the
process
for
developing
the
2008
CCL:

1.
Which
data
sources
should
the
Agency
use
to
assemble
the
universe
of
potential
CCL
contaminants?

2.
Should
the
Agency
adopt
the
general
framework
of
moving
from
a
broad
universe
of
potential
candidates
to
a
PCCL
and
finely
to
a
CCL?

3.
If
so,
what
criteria
should
be
used
for
inclusion
of
a
contaminant
on
the
PCCL,
and
in
selecting
contaminants
from
the
PCCL
to
the
CCL?

4.
How
should
EPA
address
contaminants
that
lack
data
on
toxicity,
occurrence,
and
exposure?

In
addition,
the
Agency
welcomes
comments
on
other
aspects
of
the
approach
40
recommended
by
the
NRC.

The
EPA
expects
that
public
comments
on
these
and
other
relevant
issues
will
assist
the
Agency
in
addressing
remaining
questions
posed
by
the
NRC
and
the
NDWAC
and
welcomes
comments
from
the
public.
The
Agency
recognizes
that,
while
the
draft
CCL
2
has
not
been
compiled
using
the
new
approach
recommended
by
the
NRC,
many
of
the
underlying
principles
and
objectives
remain
the
same.
Information
and
comments
submitted
on
this
notice
will
be
considered
in
determining
the
final
CCL
2
list,
as
well
as
in
the
development
of
future
CCLs
and
in
the
Agency's
efforts
to
set
drinking
water
priorities
in
the
future.

VIII.
References
NRC.
1999a.
Setting
Priorities
for
Drinking
Water
Contaminants.
National
Academy
Press,

Washington,
D.
C.
http://
www.
nap.
edu/
catalog/
6294.
html
NRC.
1999b.
Identifying
Future
Drinking
Water
Contaminants.
National
Academy
Press,

Washington,
D.
C.
http://
www.
nap.
edu/
catalog/
9595.
html
NRC.
2001.
Classifying
Drinking
Water
Contaminants
for
Regulatory
Considerations.
National
Academy
Press,
Washington,
D.
C.

http://
books.
nap.
edu/
books/
0309074088/
html/
index.
html
41
[
Drinking
Water
Contaminant
Candidate
List
2;
Notice
­
Page
41
of
41]

EPA.
1991.
Priority
List
of
Substances
Which
May
Require
Regulation
Under
the
Safe
Drinking
Water
Act.
Notice.
Federal
Register
Vol
56,
No.
9,
p.
1470.
January
14,
1991.

EPA.
1997a.
EPA
Drinking
Water
Microbiology
and
Public
Health
Workshop.
Washington,

D.
C.,
EPA,
Office
of
Ground
Water
and
Drinking
Water,
May
20­
21,
1997.

Dated:

Benjamin
Grumbles,

Acting
Assistant
Administrator,
Office
of
Water.
