Document ID: EPA-HQ-RCRA-2002-0033-0042
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2003-06-23T04:00Z

Reply
to
Attn
of:
WCM­
121
February
26,
2003
OSWER
Docket
Environmental
Protection
Agency
Mailcode:
5305­
G
1200
Pennsylvania
Avenue,
NW
Washington,
D.
C.
20460
Attention
Docket
ID
No.
RCRA­
2002­
0033
Thank
you
for
this
opportunity
to
comment
on
the
OSWER
Draft
Guidance
for
Evaluating
the
Vapor
Intrusion
to
Indoor
Air
Pathway
from
Groundwater
and
Soils
(
Subsurface
Vapor
Intrusion
Guidance).
This
draft
guidance
is
to
be
used
to
conduct
screening
evaluations
of
this
pathway,
and
in
EPA's
determination
for
the
Current
Human
Exposure
Under
Control
Environmental
Indicator
for
RCRA
and
NPL
sites.
We
have
three
primary
issues
we
would
like
to
bring
to
your
attention,
for
consideration
when
the
draft
guidance
is
revised.
We
encourage
that
it
be
revised
as
soon
as
practicable.

1.
The
revised
guidance
should
be
applicable
to
occupational
exposures.

The
draft
guidance
states
that
"
EPA
does
not
expect
this
guidance
be
used
for
settings
that
are
primarily
occupational"
(
page
3).
An
OSWER
policy
excluding
occupational
settings
would
depart
markedly
from
past
and
current
practices
at
Superfund
and
RCRA
sites.
For
example,
the
peer
review
draft
of
the
Supplemental
Guidance
for
Developing
Soil
Screening
Levels
for
Superfund
Sites,
March
2001,
has
an
entire
chapter
on
the
occupational
setting,
including
the
appropriate
exposure
assumptions
to
be
used
when
estimating
occupational
exposures
to
contamination
in
soil.

EPA
has
previously
made
clear
that
it
would
not
rely
on
OSHA
standards.
One
of
the
clearest
statements
and
the
supporting
logic
for
this
approach
can
be
found
in
Section
4.3.3
in
the
2001
document
cited
above:
[
a]
lthough
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.

Risk­
based
screening
for
impacts
from
the
subsurface
on
indoor
air
are
appropriate
whether
or
not
the
building
is
used
for
occupational
purposes.
Frequency
and
duration
variables
in
the
equations
(
in
Appendix
D)
for
calculating
target
indoor
air
concentrations
can
be
adjusted
for
occupational
exposures,
as
they
are
for
RCRA
and
CERCLA
sites
when
evaluating
other
media
exposures.
The
vapor
intrusion
guidance
should
acknowledge
that
investigatory
and
remedial
actions
may
necessarily
be
different
at
occupational
facilities,
depending
on
their
use
of
hazardous
volatile
chemicals
and
other
building­
specific
circumstances.
2
We
recommend
that
the
guidance
include
a
clear
statement
to
this
effect:

The
screening
evaluation
of
potential
exposures
using
this
guidance
will
apply
to
situations
where
any
hazardous
chemical
may
be
present
in
indoor
air
as
a
result
of
vapor
intrusion
from
subsurface
contamination.

2.
The
revised
guidance
should
emphasize
risk­
based
concentrations
for
screening
evaluations.

Changes
are
needed
in
two
sections
of
the
draft
guidance.

A)
Tables
2a­
c
and
3a­
c,
risk­
based
screening
tables:

These
tables
are
segregated
by
three
target
inhalation
cancer
risks
and
a
target
hazard
quotient
no
higher
than
1.0,
in
each
table.
Concentrations
of
groundwater
are
provided
in
the
tables,
to
represent
consequent
target
risks
and
hazards
in
indoor
air,
using
specific
attenuation
coefficients
from
soil
gas
to
indoor
air.
Where
groundwater
MCLs
represent
indoor
air
concentrations
higher
than
the
table­
specific
target
risks
or
hazards,
they
nonetheless
are
used
in
the
tables
instead
of
risk­
based
groundwater
concentrations.
These
are
footnoted,
indicating
that
they
represent
MCLs,
but
the
user
is
not
alerted
to
either
1)
the
actual
inhalation
risk/
hazard
that
the
MCL
represents;
or
2)
the
actual
risk­
based
groundwater
concentration
representing
the
table­
specific
risk/
hazard.
This
is
not
helpful,
and
potentially
misleading
to
the
user
who
needs
or
wishes
to
conduct
risk­
based
screening
at
specific
target
risk/
hazard
levels,
and
is
inconsistent
with
EPA's
policy
of
transparency
in
making
risk
estimates.

The
MCLs
in
these
tables
should
be
replaced
with
risk­
based
concentrations
corresponding
to
the
target
risks/
hazards
specific
to
each
table.
Footnotes
could
be
provided
to
indicate
MCL
concentrations
for
those
chemicals
with
MCLs,
so
if
a
risk
management
decision
is
made
to
use
MCLs
for
protection
of
indoor
air
intrusion,
that
information
is
available.
Using
MCLs
in
a
risk­
based
screening
exercise
replaces
risk
assessment
techniques
with
predetermined
risk
management
decisions,
and
in
this
case,
in
a
highly
nontransparent
manner.
It
could
result
in
the
screening
out
of
chemicals
that
should
continue
to
be
evaluated.

B)
Page
D­
6,
last
paragraph,
target
groundwater
concentrations:

This
text
instructs
the
user
to
substitute
the
MCL
as
the
target
groundwater
concentration
for
protection
of
vapor
intrusion:

If
the
calculated
groundwater
target
concentration
is
less
than
the
MCL
for
the
compound,
the
target
concentration
is
set
as
the
MCL.

As
a
risk­
based
screening
tool,
the
guidance
could
suggest
that
the
replacement
of
a
calculated
risk­
based
groundwater
concentration
with
the
MCL
may
be
considered,
but
only
as
a
risk
management
option.
The
MCL
should
be
provided
for
informational
purposes,
but
not
as
a
required
target
groundwater
concentration
for
protection
of
inhalation
via
the
vapor
intrusion
pathway.
3
3.
There
should
be
no
limitation
of
applicability
of
the
guidance
to
plumes
based
on
their
degree
of
prior
characterization.

On
page
18,
the
following
statement
is
made:

Finally,
this
guidance
is
intended
to
be
applied
to
existing
groundwater
plumes
as
they
are
currently
defined
(
e.
g.,
MCLs,
State
Standards,
or
Risk­
Based
Concentrations).

Conversations
with
representatives
of
OSWER
indicated
that
the
intention
of
this
language
was
to
discourage
reevaluation
of
already­
characterized
plumes
where
drinking
water,
but
not
vapor
intrusion,
had
been
considered.
In
addition,
plumes
that
have
not
yet
been
defined
would
seem
to
be
excluded
by
the
statement.
These
should
be
regional
decisions,
based
on
site­
specific
circumstances.
The
guidance
should
resist
being
overly
prescriptive
in
this
matter.

We
believe
these
recommendations
for
changes
to
the
draft
vapor
intrusion
guidance
will
serve
to
make
a
valuable
document
even
more
useful
and
our
screening
and
Environmental
Indicator
decisions
more
transparent.

Thank
you
for
the
opportunity
to
provide
our
comments.

Sincerely,
Sincerely,

/
signed/
/
signed/

Michael
Gearheard,
Director
Richard
Albright,
Director
Office
of
Environmental
Cleanup
Office
of
Waste
and
Chemicals
Management