Document ID: EPA-HQ-RCRA-2006-0097-0083
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-05-25T04:00Z

Peer
Reviewer
Comments
on
the
Report
on
Potential
Risks
Associated
with
the
Use
of
Chat
from
Tri­
State
Area
in
Transportation
Projects
Prepared
for
Industrial
Economics,
Inc.
2067
Massachusetts
Ave.
Cambridge,
MA
02140
EPA
Contract
No.
68­
W­
02­
007
Work
Assignment
4­
36
Amendment
No.
1
Prepared
by
Sandra
J.
S.
Baird,
Ph.
D.
Menzie­
Cura
&
Associates,
Inc.
8
Winchester
Place,
Suite
202
Winchester,
MA
01890
April
26,
2006
MCA­
863D
Chat
Peer
Review
2
Sandra
J.
S.
Baird
Charge
Questions
1.
Are
you
aware
of
any
other
data/
studies
that
are
relevant,
particularly
with
respect
to
air
emissions
from
either
transportation,
construction
projects,
or
demolition
that
could
be
included
in
the
evaluation?

No.
I
recommend
a
literature
search
and
consultation
with
experts
in
the
field
to
get
better
information
on
the
amount
of
total
dust
emitted
during
the
various
processes,
e.
g.,
on
location
mixing,
milling,
and
then
estimate
fraction
due
to
the
aggregate
related
components.
Chat
Peer
Review
3
Sandra
J.
S.
Baird
2.
Does
the
report
present
the
available
data,
assumptions,
and
evaluation
in
a
complete
and
unbiased
manner?

The
report
does
a
satisfactory
job
of
presenting
data,
assumptions
and
the
evaluation
in
a
complete
and
unbiased
manner.
However,
there
is
room
for
improvement
in
the
completeness
and
clarity
of
the
data
and
the
presentation.
Specific
concerns
and
comments
are
presented
below
for
each
section.

Section
3.0
Problem
Formulation
Processes
and
their
related
exposure
pathways
are
missing
from
the
conceptual
model:
 
Mixing
of
asphalt
on
location
of
road
construction
site;
 
Milling
of
asphalt
on
location
of
road
construction
site;
and,
 
Weathering
of
asphalt
road
and
production
of
metal
containing
dust
as
the
asphalt
road
wears
over
time.
All
of
these
processes
have
the
potential
to
generate
dust
that
can
disperse
in
the
air
and
deposit
on
soil
and
surface
water
in
locations
near
the
site
of
the
road
construction.

The
report
should
include
information
in
the
text
and
Figure
3
about
the
locations
where
the
processing
activities
take
place,
e.
g.,
dry
sieving
and
washing
probably
take
place
at
a
central
location
removed
from
the
road
construction
site,
but
mixing
of
the
HMA
and
milling
occur
on
location
at
the
roadway.
Mixing
of
raw
or
washed
chat
with
the
binding
materials
to
create
asphalt
or
concrete
at
the
road
construction
site
is
likely
to
create
local
dust
and
possibly
discharges
of
wet
wastes
with
fine
particles.
I
recommend
that
Figure
3
be
expanded
to
explicitly
include
"
Mixing
of
HMA
(
or
cement)
on
location"
and
"
Milling/
recycling"
under
the
management
heading,
and
that
"
recycling"
be
separated
from
the
dry
sieving
and
washing
processes
in
Figure
2.
Recycling
includes
milling
and
should
be
included
in
Figure
3
as
noted
above
or
as
a
separate
process
in
Figure
2.
Figure
2
needs
to
be
expanded
to
include
production
of
asphalt
containing
dust
from
use
of
roads,
deposition
on
adjacent
soil,
potential
as
a
source
for
surface
water
ecological
exposure
and
potential
for
exposure
of
resident
in
yard
adjacent
to
road.

Figures
1­
3
should
provide
a
means
to
easily
identify
encapsulated
and
unencapsulated
chat
reuses,
as
these
are
discusses
separately
in
the
remainder
of
the
report.

Section
3.2.4
Recycling­
mentions
that
air
releases
during
the
recycling
process
would
be
episodic
and
of
limited
duration.
This
is
true.
However,
if
millings
occurs
next
to
a
residence,
the
dust
could
be
deposited
on
soil
in
a
yard
and
remain
there
as
a
potential
a
source
of
exposure
after
the
milling
project
is
completed.
I
think
that
the
report
dismisses
potential
for
exposure
during
the
milling
process
too
readily.
The
report
should
include
this
potential
exposure
pathway
or
present
more
information
supporting
the
assumption
that
this
pathway
is
not
a
potential
concern.
Section
3.3
states
the
assumption
that
milling
activities
are
assumed
to
be
subject
to
environmental
standards
for
air
emissions.
It
is
not
clear
from
this
description,
whether
the
authors
of
the
report
are
thinking
about
the
emissions
during
the
milling
process
on
the
roadway
or
the
emissions
during
the
preparation
of
the
milled
asphalt
for
another
use
that
most
likely
occurs
at
centralized
facility.
Note
this
pathway
is
explicitly
discussed
in
the
risk
characterization
section,
but
not
presented
in
the
conceptual
model.
Chat
Peer
Review
4
Sandra
J.
S.
Baird
Section
3.2.4
 
a
reference
is
needed
for
the
statement,
"
studies
indicate
that
metals
in
milled
asphalt
may
be
more
tightly
bound "
Or
this
statement
should
be
omitted.
If
kept,
the
statement
needs
to
summarize
the
context
in
which
it
is
being
made,
i.
e.,
is
it
referring
to
studies
of
laboratory
scale
milling
of
HMA
or
milled
asphalt
used
in
roads?

The
assumption
that
encapsulation
of
chat
removes
all
exposure
pathways
except
for
leaching
is
consistent
with
the
conceptual
model.
However,
if
this
assumption
is
incorrect,
the
environmental
consequences
could
be
significant.
This
assumption
should
be
tested
or
additional
supporting
studies
should
be
identified
from
the
literature.

Suggested
changes
for
the
text
to
improve
clarity
and
content:
1.
Section
3.1,
first
paragraph,
last
line
­
insert
size
of
respirable
particles
(
i.
e.,
~
30
um
and
smaller).
2.
Section
3.1,
last
paragraph,
2cd
line
­
inset
"(
0.425
mm)"
after
"
the
No.
40
sieve"

Section
4.0
Analysis:

Data:
Presentation
The
report
clarity
would
be
much
improved
if
the
conceptual
model
was
repeated
in
the
analysis
section
with
addition
of
table
numbers
indicating
the
location
of
the
data
presented
in
the
report
for
the
chat
reuses
and
exposure
pathways.

While
it
is
logical
for
the
report
to
present
the
data
for
the
total
metal
analyses
first
followed
by
the
leaching
analyses,
ultimately
the
user
of
this
analysis
will
be
considering
chat
reuses
and
associated
exposures
on
a
pathway
by
pathway
basis.
The
reader
must
flip
between
a
number
of
tables
to
follow
the
data
for
each
type
of
reuse.
This
makes
it
difficult
to
evaluate
the
data
for
each
reuse
in
the
data
section.
The
addition
of
a
table
summarizing
the
metal
concentrations
across
the
full
chat
life
cycle,
including
total
metal
and
TCLP
data
for
the
different
sources,
encapsulated
and
unencapsulated
along
with
the
soil
screening
and
toxicity
characterization
levels
would
aide
the
reader.

It
is
also
important
to
have
clear
linkages
across
total
metals
in
chat
and
metal
concentrations
in
the
exposure
media,
when
considering
the
development
of
criteria
for
chat
reuses.
The
addition
of
the
conceptual
model
with
data
tables
noted
would
aide
in
the
evaluation.

The
soil
screening
and
toxicity
characterization
levels
need
to
be
introduced
earlier
in
the
data
section
as
they
are
referred
to
as
the
data
is
presented.

Evaluation
Measures
of
variability
in
the
data
(
e.
g.,
standard
deviation)
need
to
be
included
in
all
data
tables
when
available.

The
summaries
of
the
data
from
the
various
reports
need
to
more
complete,
for
example:
Chat
Peer
Review
5
Sandra
J.
S.
Baird
 
The
summary
of
the
data
from
the
Tar
Creek
Superfund
site
(
page
4­
2),
says
that
the
levels
of
lead
in
15%
of
the
soil
samples
are
above
the
level
considered
safe
at
the
site
and
that
the
lead
and
cadmium
following
the
leach
test
are
below
the
toxicity
characteristic
levels;
but
the
levels
are
not
included.
Also
this
is
the
first
mention
of
the
toxicity
characteristic
level.
Add
a
footnote
defining
the
toxicity
characteristic
level,
the
levels
for
lead,
cadmium,
absence
of
one
for
zinc,
and
reference
the
source
of
these
levels
or
point
the
reader
to
a
table
with
these
levels.
There
is
no
table
containing
these
levels.
I
think
that
they
belong
in
the
table
with
the
other
human
health
values;
they
are
based
on
human
health
values.
 
Are
the
samples
presented
individually
in
Tables
1,
5
and
6,
matched
across
tests,
i.
e.,
is
the
series
of
numbers
always
presented
in
the
same
order
(
USACE,
2000)?
 
Section
4.1.1
Total
Concentration
Data
for
Encapsulated
Uses,
3rd
paragraph,
are
the
compacted
and
crushed
samples
from
the
same
chat
source?
 
Table
3
 
the
total
metal
concentration
of
the
raw
chat
measured
in
ODEQ
(
2005)
report,
should
be
included
in
this
table.
Likewise
for
TCLP
and
SPLP
results.
 
Table
4
­
the
total
metal
concentrations
for
the
milled
HMA
for
the
control
(
0%)
chat
should
be
included
in
this
table,
if
available.
Likewise
for
TCLP
and
SPLP
results.

Section
4.1.1,
page
4­
5,
3rd
paragraph
 
The
statement,
"
suggesting
that
weathering
of
the
broken
asphalt
piles
may
result
in
removal
and
migration
of
additional
metals
relative
to
asphalt
still
in
use
as
a
road
surface"
is
unsupported
by
evidence
presented
in
thus
far
in
the
report.
It
could
be
true
if,
the
same
source
of
chat
was
used
for
the
roads
sampled
by
USACE
in
the
USACE,
2000
study
and
the
Will
Rodgers
turnpike.
However,
the
reader
can
not
determine
if
the
roads
under
study
are
the
same
based
on
the
information
provided.
If
the
sources
of
chat
are
not
the
same
for
both
studies,
then
this
statement
should
be
removed.
It
would
provide
context
to
the
reader
to
have
information
on
the
age
of
the
roads
tested
by
USACE
(
2000)
and
the
piles
of
Will
Rodgers
milled
asphalt
discussed
in
this
paragraph
and
in
Table
2.

If
there
is
evidence
to
support
this
statement,
then
the
amount
of
metals
migrating
out
of
the
milled
asphalt
needs
to
be
studied
and
management
practices
may
need
to
be
developed
to
prevent
migration
of
metals
during
the
portion
of
the
chat
life
cycle
where
milled
chat
containing
asphalt
must
be
stored.

Section
4.1.1,
page
4­
6
­
data
on
unweathered
mix
When
lower
concentrations
of
total
metals
are
incorporated
into
the
mix,
where
to
the
remaining
(
non­
incorporated)
metals
go?
Are
they
in
the
wash,
sludge?
How
is
the
mix
handled?
Assuming
that
the
mix
is
made
on
location
at
the
road
construction
site,
it
appears
that
there
is
a
potential
for
exposure.
The
source
of
the
chat
(
Kenoyer
North
Site)
and
the
reason
for
selection
of
this
source
of
chat
(
high
end
of
lead
concentration
among
sites)
needs
to
be
mentioned
in
the
summary.
The
metals
concentrations
in
the
raw
chat
prior
to
incorporation
into
the
HMA
are
presented
in
Figure
4,
but
the
text
and
tables
do
not
provide
a
connection.

Section
4.1.5,
page
4­
20,
1st
paragraph­
the
discussion
of
the
soil
concentrations
adjacent
to
roads
constructed
with
chat
containing
asphalt
needs
to
be
moved
to
Section
4.1.1,
at
the
end
of
the
discussion
of
the
total
metals
concentrations
in
encapsulated
asphalt.
Note:
this
report
includes
the
statement
from
the
USACE
(
2000)
report
summary
suggesting
that
some
of
the
metals
found
Chat
Peer
Review
6
Sandra
J.
S.
Baird
in
the
soil
beside
the
roads
made
with
chat
may
be
from
past
use
of
sand
sized
chat
as
road
deicer.
This
statement
indicates
that
the
USACE
study
is
not
able
to
provide
reliable
information
about
the
release
of
metals
from
roads
incorporating
chat.
I
was
only
able
to
review
the
summary
report
(
USACE,
2000)
and
it
does
not
discuss
the
extent
of
use
of
chat
as
road
deicer
or
provide
information
about
whether
chat
was
used
as
a
deicer
on
specific
roads
in
the
study.
The
absence
of
a
reliable
study
for
this
exposure
pathway
adds
uncertainty
to
the
conclusion
of
this
report.

Although
the
USACE
study
has
limitations,
a
separate
line
of
evidence
of
metal
release
from
asphalt
is
found
in
the
study
by
Oklahoma
DEQ.
The
ODEQ
(
2005)
study
of
HMA
mixes
and
weathering
is
cited
in
this
report.
The
ODEQ
(
2005)
study
includes
measurement
of
lead
concentrations
that
can
be
wiped
off
of
asphalt
that
has
had
road
surface
wear
simulated
by
a
wet
or
dry
rutting
machine.
I
did
not
find
this
part
of
the
ODEQ
study
mentioned
in
this
report.
The
ODEQ
study
provides
information
indicating
the
lead
particles
can
be
wiped
from
the
surface
of
the
solid
HMA
following
simulated
road
wear
(
ODEQ,
2005,
page
8­
51).
They
report
concentrations
of
lead
ranging
from
7­
79
mg/
kg
per
445
sq.
inches
of
road
surface,
depending
on
mix
and
rutting
method.
While
it
is
difficult
to
extrapolate
the
cumulative
amount
of
lead
that
could
be
expected
to
be
shed
from
a
road
and
accumulate
in
the
soil
next
to
the
road
during
the
life
of
a
road
from
the
road
wear
simulation
results,
the
results
do
provide
evidence
that
metals
can
be
shed
from
HMA
containing
chat.
This
is
an
important
piece
of
information
for
evaluating
the
potential
environmental
impacts
of
chat
use
in
asphalt
roads
for
the
soil
pathway.

Screening
Criteria:
Human
health
screening
values
 
all
screening
values
are
based
on
non­
cancer
effects
and
all
individual
screening
values
use
a
HQ
of
one.
If
all
metals
were
present
in
a
media
at
the
screening
value,
then
the
HI,
the
total
of
the
HQs
for
each
metal
in
that
media
would
be
3;
greater
than
the
target
total
HI
of
1.
This
should
be
discussed
in
the
uncertainty
section.
The
use
of
screening
values
based
on
HQs
of
one
for
each
of
the
three
metals,
implicitly
assumes
that
1)
exposures
will
not
occur
at
the
full
screening
value
for
each
simultaneously,
or,
2)
if
exposures
are
assumed
to
occur
simultaneously
at
the
full
screening
value
for
each
of
the
three
metals,
then
the
effects
of
the
metals
are
not
additive
because
they
act
through
different
pathways
or
affect
different
target
organs.

In
addition,
the
potential
for
a
residential
receptor
to
be
exposed
from
more
than
one
pathway
needs
to
be
discussed.
The
use
of
HQs
of
one
(
i.
e.,
HQ=
1)
for
multiple
pathways,
could
result
in
a
greater
noncancer
hazard
than
anticipated.
The
data
on
leaching
of
metals
from
encapsulated
chat
suggests
that
there
is
not
likely
to
be
a
hazard
for
people
ingesting
groundwater
sources;
leaving
the
soil
exposure
pathways
as
the
principle
potential
exposure
pathways
for
residents.
Thus,
this
comment
is
intended
to
aide
in
completeness
of
the
report.
A
brief
discussion
of
the
limitations
of
screening
values
for
multiple
pathways
needs
to
be
included
in
the
discussion
in
the
health
effects
section
as
well
as
the
uncertainty
section
and
considered
during
the
development
of
criteria.

The
potential
for
less
than
additive,
additive
or
synergistic
effects
following
exposure
to
all
three
metals
needs
to
be
discussed.
ATSDR
(
2004a,
b),
as
part
of
their
series
of
interaction
profiles,
Chat
Peer
Review
7
Sandra
J.
S.
Baird
has
evaluated
the
potential
for
interaction
among
metals
that
frequently
occur
together
in
exposure
media.
The
potential
for
interactions
between
lead
and
cadmium
is
evaluated
in
ATSDR
(
2004a),
and
between
lead
and
zinc
in
ATSDR
(
2004b).
The
interaction
between
cadmium
and
zinc
was
not
evaluated;
neither
was
the
interaction
among
the
three
metals
together.
The
potential
for
interaction
is
evaluated
in
a
target
organ
by
target
organ
basis.
ATSDR's
evaluation
found
that
the
available
data
suggest
that
the
interaction
may
be
less
than
additive
for
combined
exposure
to
lead
and
zinc;
may
be
more
than
additive
for
neurological
and
testicular
effects
following
combined
exposure
to
lead
and
cadmium.
The
potential
for
interaction
to
increase
or
decrease
effects
increases
as
the
exposure
level
increases,
and
is
expected
to
be
low
at
exposures
in
the
range
of
a
HQ
of
one.

The
screening
values
for
lead
do
not
consider
the
background
exposure
level
to
lead,
as
would
be
done
in
a
risk
assessment
using
the
IEUBK
model
to
predict
blood
lead
levels
from
an
environmental
exposure.

Ecological
screening
values
 
no
comment.

Suggested
changes
to
the
text
to
improve
clarity
and
content:
1.
Section
4.1,
page
4­
2,
Sampling
and
metal
analysis
pf
chat
piles
in
the
Tar
Creek
Superfund
site.
(
ODEQ,
2002)
summary,
line
4
 
check
the
size
listed
in
the
parentheses
after
"
small
size
fractions",
I
think
that
it
should
be
<
0.425
mm,
not
<
0.0425
mm.
It
would
be
helpful
to
add
that
these
are
gravel
roads
and
that
the
chat
is
unencapsulated.
2.
Section
4.1,
page
4­
4,
2cd
line
 
check
spelling
and
context
of
the
use
of
"
root"
in
"
potential
root
of
exposure."
3.
The
number
of
significant
digits
needs
to
be
checked,
e.
g.,
page
4­
10,
the
TCLP
detection
limit
is
presented
as
0.500
mg/
L,
and
on
page
4­
11,
a
detection
limit
is
listed
as
0.00500
and
0.0100
mg/
L.
4.
Table
7
 
the
mean
of
the
lead
concentration
does
not
match
the
presented
data,
it
is
larger
than
any
single
presented
sample
result.
5.
Table
8
 
needs
to
have
the
detection
limit
of
0.5
mg/
L
included
in
the
table
notes.
6.
Table
9
 
needs
to
have
the
detection
limit
of
0.5
mg/
L
included
in
the
table
notes.
7.
Table
16
 
the
note
would
be
better
stated
at:
Values
in
bold
exceeded
the
TC
limits
of
5
mg/
L
and
1
mg/
L
for
lead
and
cadmium
respectively.
8.
Section
4.2.1
Health
screening
criteria
 
the
second
to
last
sentence
says
"
we
did
not
use
human
health
benchmarks
for
cancer
endpoints "
These
three
metals
are
only
evaluated
for
noncancer
effects.
Chat
Peer
Review
8
Sandra
J.
S.
Baird
3.
Are
the
conclusions
concerning
the
environmental
release
and
potential
environmental
and
public
impacts,
including
the
limitations
and
uncertainties,
supported
by
the
available
data?
In
particular,
while
the
report
findings
relied
on
several
studies
that
followed
specific
data
quality
objectives
and
methodologies,
are
the
laboratory
and
field
data
of
sufficient
power
to
support
the
findings?

Section
5.0
­
Risk
Characterization
The
conclusions
of
the
report
are
supported
by
the
available
data.
The
laboratory
data
appear
to
be
of
sufficient
power
to
support
the
findings.
The
TCLP
and
SPLP
data
with
detection
limits
greater
than
the
ecological
screening
values
do
not
have
sufficient
power
to
support
findings.

Section
5.3,
2cd
paragraph­
While
it
is
correct
that
the
milling
of
asphalt
roads
is
episodic
and
infrequent;
once
the
metal
containing
dust
lands
on
the
soil
adjacent
to
the
road
it
remains
in
the
soil
into
the
future.
Thus,
residents
and
ecologic
receptors
could
experience
long­
term
exposure
to
the
dust
generated
during
the
milling
process.

The
lack
of
data
on
air
emissions
during
construction
and
milling,
and
dust
deposition
on
soil
and
surface
water
is
a
considerable
source
of
uncertainty
in
evaluating
the
ecologic
and
human
health
implications
of
using
chat
in
asphalt.
These
pathways
are
most
likely
to
be
complete
at
locations
near
the
road
surface
or
storage
areas.
Thus,
the
extent
of
deposition
and
potential
health
implications
is
likely
to
be
limited
to
a
small
and
defined
area.

The
risk
characterization
section
needs
to
have
a
separate
uncertainty
section
that
includes
discussion
of
the
direction
of
bias
in
the
various
sources
of
uncertainty.
For
example,
there
is
uncertainty
in
the
prediction
of
leaching
from
asphalt
using
the
TCLP
method
that
was
designed
for
the
conditions
of
a
municipal
landfill.
Because
municipal
landfill
conditions
are
more
extreme
that
what
is
expected
for
a
road,
the
TCLP
data
are
biased
high,
i.
e.,
they
over
predict
the
amount
of
metal
that
would
be
leached
from
chat
uses.
It
would
be
useful
to
list
assumptions
and
sources
of
uncertainty
in
a
table
or
text
box
for
each
exposure
pathway
for
the
full
life
cycle
of
encapsulated
uses
for
both
residential
and
ecological
receptors.

Suggested
changes
to
the
text
to
improve
clarity
and
content:
1.
Section
5.1,
1st
paragraph­
define
pozzolanic
in
a
footnote.
2.
Check
the
current
footnote
indicators
and
actual
notes
in
this
section,
in
some
cases
the
footnote
text
does
not
appear
to
relate
to
the
text
statement.
Chat
Peer
Review
9
Sandra
J.
S.
Baird
4.
As
with
any
risk
assessment,
there
are
various
sources
of
uncertainty
associated
with
data
limitations
that
we
believe
are
identified
in
the
report.
Other
than
conducting
model
simulations
or
performing
additional
sampling,
can
you
recommend
alternate
approaches
or
changes
to
our
methodology
that
could
provide
a
more
thorough
characterization
of
these
uncertainties?

Determine
whether
the
chat
used
in
HMA
and
stored
at
the
site
of
the
road
construction
activities
would
be
washed
or
unwashed;
potential
risk
from
metals
in
dust
during
storage,
mixing,
road
surface
use
and
milling
is
likely
to
be
lower
if
washed
chat
is
used.

Conduct
additional
review
of
the
literature
including,
road
construction
management
for
estimates
of
duration
of
storage
of
surfacing
materials,
studies
done
to
develop
management
protocols
to
meet
local
air
standards
for
dust
control
during
road
construction,
studies
of
loss
of
road
surface
materials
(
e.
g.,
potential
for
generation
of
particles),
and
studies
of
roadway
dust
generation.
Chat
Peer
Review
10
Sandra
J.
S.
Baird
5.
The
Agency
was
directed
to
establish
criteria
for
the
safe
and
environmentally
protective
use
of
chat
for
cement
or
concrete
projects
and
transportation
construction
projects.
There
were
significant
data
limitations
as
well
as
resource
constraints
place
on
the
evaluation.
Does
this
type
of
analysis
lend
technical
support
to
the
nature
of
the
decision
to
establish
criteria
for
the
use
of
chat?
Can
you
propose
alternative
approaches
that
can
be
used
to
support
this
type
of
decision
in
situations
where
there
are
significant
data
or
time
limitations?

This
type
of
analysis
does
lend
technical
support
to
the
nature
of
the
decision
to
establish
criteria
for
chat.
The
analysis
was
able
to
clearly
determine
uses
of
chat
that
pose
unacceptable
ecological
and
human
health
risk.
Not
surprisingly,
analysis
of
uses
of
chat
that
do
not
fall
in
the
unacceptable
category
is
more
difficult.

The
report
does
not
explicitly
define
a
priori
criteria
that
are
to
be
used
to
support
decision
making.
The
use
of
ecological
and
human
health
screening
values
to
evaluate
hazard
from
identified
exposure
pathways
implies
a
criteria.
However,
criteria
for
inclusion
or
exclusion
of
an
exposure
pathway
are
not
defined
and
no
criteria
are
described
for
evaluating
the
cases
where
screening
values
for
a
pathway
are
exceeded
for
some
receptors
and
not
others.

Decisions
to
use
chat
for
particular
applications
may
be
made
on
a
case
by
case
basis.
The
decision
making
process
could
be
aided
by
development
of
a
summary
table
of
chat
uses,
including
all
processes
in
the
lifecycle,
that
summaries
1)
the
likelihood
of
an
exposure
pathway
resulting
in
exposures
greater
than
the
appropriate
benchmark,
and
2)
the
level
of
confidence
in
the
likelihood.
Chat
Peer
Review
11
Sandra
J.
S.
Baird
References
cited
in
the
peer
review
that
are
not
drawn
from
the
report.

Agency
for
Toxic
Substances
and
Disease
Registry
(
ATSDR).
2004a.
Interaction
profile
for:
arsenic,
cadmium,
chromium,
and
lead.
U.
S.
Department
of
Health
and
Human
Services,
Public
Health
Services.
Atlanta,
GA.

Agency
for
Toxic
Substances
and
Disease
Registry
(
ATSDR).
2004b.
Interaction
profile
for:
lead,
manganese,
zinc,
and
copper.
U.
S.
Department
of
Health
and
Human
Services,
Public
Health
Services.
Atlanta,
GA.