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on
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1
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
REGION
VIII
999
18th
STREET
­
SUITE
500
DENVER,
COLORADO
80202­
2466
February
27,
2003
Mr.
Henry
Schuver
Office
of
Solid
Waste
(
5303W)
US
EPA
Ariel
Rios
Building
1200
Pennsylvania
Avenue,
NW
Washington
DC
20460­
0002
re:
Vapor
Intrusion
Guidance
Dear
Mr.
Schuver:

The
EPA
Regional
Risk
Assessors
have
reviewed
the
draft
Vapor
Intrusion
Guidance.
As
primary
users
of
this
guidance,
we
are
submitting
these
comments
as
we
believe
that
a
number
of
issues
must
be
resolved
before
Regional
Risk
Assessors
can
successfully
use
this
guidance
to
advise
our
Regional
Superfund
and
RCRA
Programs.
These
comments
have
been
endorsed
by
Regional
Risk
Assessors
in
all
10
EPA
Regions.

1.
Use
of
additive
risk
In
our
experience
it
is
common
that
multiple
chemicals
will
be
present
at
a
site.
Superfund
has
a
consistent
approach
to
evaluate
exposure
to
the
complete
mix
of
chemicals
for
both
cancer
and
non­
cancer
endpoints.
This
guidance
should
not
advocate
a
different
approach.
As
written
the
guidance
will
be
viewed
by
many
as
being
insufficiently
protective
of
the
public
health.
Accordingly,
we
recommend
that
the
Current
Human
Exposures
Under
Control
EI
determination
use
10­
5
cancer
risk
and
a
Hazard
Index
of
1
taking
into
account
all
the
chemicals
that
intrude
into
a
residence
and
that
footnote
2
on
page
10
be
replaced
with
a
specific
statement
that
additive
risk
is
to
be
used
when
making
an
EI
determination
for
a
site.
In
addition
to
avoid
confusion,
there
should
be
a
statement
acknowledging
that
risk­
based
screening
for
purposes
other
than
Current
Human
Exposures
Under
Control
EI
determinations
typically
use
a
cancer
risk
of
10­
6
and
a
Hazard
Quotient
of
0.1
for
both
RCRA
and
CERCLA
sites.

2.
Use
of
the
MCL
as
the
target
concentration
For
several
chemicals
the
MCL,
rather
than
a
risk­
based
concentration,
is
used
in
Tables
2
and
3.
This
is
not
helpful
to
the
user
who
needs
or
wishes
to
conduct
risk­
based
screening
at
specific
target
risk
levels.
The
current
tables
do
not
even
alert
the
user
to
the
fact
that
values
footnoted
as
representing
MCLs
exceed
the
target
risk
or
hazard
levels
of
the
tables.
We
recommend
that
the
tables
contain
only
risk­
based
values.
As
the
MCL
is
based
both
on
risk
assessment
and
risk
management
considerations,
using
the
MCL
as
the
target
concentration
blends
risk­
based
values
and
risk
management
objectives
in
the
guidance.
We
recommend
that
only
risk­
based
values
be
used
for
decision
making
under
this
guidance.
Printed
on
Recycled
Paper
2
3.
Clarify
how
the
guidance
applies
to
remedial
investigations
at
CERCLA
and
RCRA
sites
Section
D
is
confusing
on
the
application
of
the
guidance
at
CERCLA
and
RCRA
facilities.
The
first
sentence
states
that
the
guidance
is
to
be
used
for
making
Current
Human
Exposures
Under
Control
EI
determinations.
The
sentence
then
confuses
the
applicability
by
adding
the
clause
"
as
well
as
in
CERCLA
remedial
investigations
and
RCRA
facility
investigations"
and
then
contradicting
that
clause
in
the
next
sentences.
To
clarify
the
paragraph,
we
recommend
deletion
of
the
clause
"
as
well
as
in
CERCLA
remedial
investigations
and
RCRA
facility
investigations."
Absent
specific
guidance
to
the
contrary,
the
Regional
Risk
Assessors
will
use
the
ordinary
procedures
for
conducting
a
remedial
investigation,
a
screening
assessment,
and
a
baseline
risk
assessment
for
a
specific
site.
In
these
activities
we
believe
it
would
be
appropriate
to
use
the
screening
tables
but
not
the
risk
management
benchmarks
(
10­
5
cancer
risk
and
Hazard
Quotient
=
1
for
an
individual
chemical
as
in
the
draft
guidance).
In
both
the
CERCLA
and
RCRA
programs,
Regional
Risk
Assessors
generally
use
a
cancer
risk
of
10­
6
and
a
Hazard
Quotient
of
0.1
as
screening
values.

4.
Clarify
how
the
guidance
applies
to
an
occupational
setting
Section
D
1)
on
page
3
is
very
confusing
on
how
the
guidance
will
apply
to
an
occupational
setting.
Screening
for
impacts
from
the
subsurface
on
indoor
air
are
appropriate
whether
or
not
the
building
is
used
for
occupational
purposes.
The
vapor
intrusion
guidance
can
and
should
clarify
that
different
investigatory
and
remedial
actions
may
be
appropriate
at
these
facilities,
depending
on
the
use
of
hazardous
volatile
chemicals
in
the
facility.
We
recommend
a
clear
statement
such
as
"
The
screening
of
possible
exposures
using
this
guidance
will
apply
to
situations
where
any
hazardous
chemical
is
present
in
indoor
air
as
a
result
of
vapor
intrusion
from
subsurface
contamination."
Another
example
of
a
clear
statement
on
the
application
on
EPA
guidance
to
an
occupational
setting
can
be
found
in
the
March
2001
draft
Supplemental
Guidance
for
Developing
Soil
Screening
Levels
for
Superfund
Sites.
That
guidance
states
in
Section
4.3.3,
"
Although
both
OSHA
standards
and
SSLs
protect
the
health
of
workers
exposed
to
toxic
substances,
the
conditions
of
exposure
implicit
in
each
set
of
values
differ.
As
a
result,
OSHA
standards
are
not
suitable
substitutes
for
SSLs."

5.
Clarify
how
the
guidance
applies
to
existing
groundwater
plumes
(
page
18)
If
the
statement
that
the
guidance
"
is
intended
to
be
applied
to
existing
groundwater
plumes
as
they
are
currently
defined"
is
intended
to
mean
that
plumes
already
characterized
don't
need
to
be
newly
characterized
just
for
the
vapor
intrusion
pathway,
then
this
should
be
stated
clearly.
However,
there
should
also
be
a
statement
that
plumes
that
have
been
inadequately
or
partially
characterized
or
that
have
yet
to
be
characterized
are
subject
to
the
guidance.

6.
Clarify
when
the
guidance
requires
confirmatory
sampling
Section
C
(
page
9)
indicates
that
confirmatory
sampling
is
not
recommended
to
support
a
Current
Human
Exposures
Under
Control
EI
determination.
The
guidance
should
clarify
if
confirmatory
indoor
air
sampling
is
necessary
to
support
the
opposite
determination
and
before
some
action
is
initiated.

7.
Clarify
the
guidance
on
the
amount
of
data
adequate
for
decision
making
Printed
on
Recycled
Paper
3
We
interpret
the
guidance
(
last
sentence
of
Tier
2
­
Secondary
Screening
on
page
8)
to
indicate
that
a
single
value
exceeding
the
screening
value
is
sufficient
to
move
into
Tier
3.
If
that
is
not
correct,
then
the
guidance
needs
clarification.
We
recommend
that
the
guidance
provide
more
emphasis
that
multiple
lines
of
evidence
from
the
different
environmental
media
need
to
be
used
in
decision
making.
We
also
recommend
that
some
guidance
be
provided
on
how
to
resolve
situations
where
conflicting
data
are
present
from
different
environmental
media
or
different
locations
at
the
site.

8.
Decision
rule
on
appropriate
toxicity
reference
value
Appendix
D,
Section
5,
paragraph
3
explains
the
decision
rule
on
the
use
of
an
extrapolated
versus
a
non­
extrapolated
value
for
the
development
of
values
listed
in
Tables
2
and
3.
As
the
Tables
are
to
be
used
in
a
screening
decision,
we
recommend
using
the
lower
value
regardless
of
its
source.
The
risk
assessor
for
the
site
should
then
review
those
chemicals
whose
target
concentration
was
derived
by
a
toxicity
value
based
on
route­
to­
route
extrapolation
and
determine
the
reliability
and
appropriateness
of
application
of
the
extrapolated
value.

9.
Application
of
the
guidance
to
a
chemical
in
soil
and
a
situation
where
a
NAPL
is
present
Section
IV
A
states
the
guidance
applies
to
exposure
from
soil.
However,
Table
1
screens
out
chemicals
based
on
the
toxicity
of
the
pure
vapor
and
volatility
from
water
using
Henry's
Law.
For
a
chemical
that
volatilizes
from
bulk
soil
or
a
situation
where
a
NAPL
is
present,
the
appropriate
screening
value
would
be
only
the
toxicity
of
the
pure
vapor
(
the
column
entitled
"
Is
chemical
sufficiently
toxic?"
in
Table
1).
Table
1
should
clearly
indicate
that
the
NA
entry
reflects
a
determination
that
the
pathway
is
not
likely
to
pose
an
unacceptable
risk,
not
that
the
pathway
is
incomplete.
See
comment
below.

10.
Decisions
on
"
incomplete
pathway"
versus
"
pathway
does
not
pose
an
unacceptable
risk"
In
several
places
the
guidance
uses
these
determinations
interchangeably.
We
recommend
that
the
guidance
make
explicit
which
determination
applies.
A
determination
that
the
pathway
is
incomplete
is
a
risk
assessment
determination
stating
that
there
is
no
exposure
and
therefore
no
risk
from
that
pathway.
This
concept
is
well
understood
by
risk
assessors.
However,
a
decision
that
the
pathway
does
not
pose
an
unacceptable
risk
is
a
risk
management
determination
and
involves
a
host
of
factors
such
as
the
exposure
scenario
considered
and
the
risk
criterion
applied.

11.
Replacement
of
HEAST
values
in
Table
D­
1
and
quality
control
of
entries
in
the
tables
A
number
of
toxicity
values
are
taken
from
old
HEAST
sources
(
H
and
A
codes
in
the
table).
We
recommend
that
some
effort
be
expended
to
replace
these
values
with
EPA­
NCEA
provisional
values
that
have
enjoyed
at
least
some
level
of
external
peer
review.
As
we
expect
there
will
be
changes
in
toxicity
values
before
the
guidance
goes
to
final
form,
it
is
important
to
check
the
correctness
of
the
calculations
and
other
entries
in
the
tables.
As
one
example,
Table
D­
1
states
that
the
data
are
current
as
of
November
2002.
The
entry
for
1,1­
dichloroethylene
lists
the
source
as
an
EPA­
NCEA
provisional
value
when
the
new
IRIS
file
was
loaded
in
August
2002.
Printed
on
Recycled
Paper
4
12.
Discussion
of
TCE
(
page
D­
2)
The
third
sentence
in
the
third
paragraph
should
be
deleted
as
it
could
be
construed
to
mean
that
the
Superfund
Technical
Support
Center
continues
to
support
the
TCE
cancer
slope
factor
withdrawn
from
IRIS
in
July
1989.
If
new
language
is
used
to
replace
it,
it
should
state
that
the
Superfund
Technical
Support
Center
continued
to
support
the
use
of
the
withdrawn
value
until
the
external
review
draft
of
the
new
TCE
health
assessment
was
published
in
August
2001.

Sincerely,

EPA
Regional
Risk
Assessors
Regions
1,
2,
3,
4,
5,
6,
7,
8,
9,
and
10
cc.
Marianne
Horinko
Mike
Cook
Betsy
Southerland
Matt
Hale
Debbie
Newberry
