United
States
Environmental
Protection
Agency
November
2002
EPA530­
F­
02­
052
www.
epa.
gov/
osw
Evaluating
the
Vapor
Intrusion
into
Indoor
Air
The
Environmental
Protection
Agency
(
EPA)
issues
a
draft
guidance
to
help
determine
if
the
vapor
intrusion
exposure
pathway
poses
a
significant
risk
to
human
health.

Action
EPA
issues
a
draft
guidance
that
provides
current
technical
and
policy
recommendations
on
determining
if
the
vapor
intrusion
pathway
poses
an
unacceptable
risk
to
human
health
at
cleanup
sites.
This
guidance
is
not
intended
to
provide
recommendations
for
delineating
extent
of
risk
or
eliminating
risk.

The
guidance
is
suggested
for
use
at
the
Resource
Conservation
and
Recovery
Act
(
RCRA)
Corrective
Action
sites,
National
Priorities
List
and
Superfund
Alternative
sites
and
Brownfields
sites,
but
is
not
recommended
for
use
at
Subtitle
I
Underground
Storage
Tank
sites
at
this
time.

EPA
recommends
that
program
implementers
consider
the
use
of
this
draft
guidance
as
a
screening
approach
in
implementing
the
RCRA
and
CERCLA
programs.
Although
the
document
is
still
in
draft
and
EPA
is
requesting
comment
on
it,
it
has
gone
through
extensive
agency
review,
and
believe
it
is
a
technically
sound
product.
While
we
hope
to
receive
useful
comments
that
will
result
in
improvements
when
the
draft
is
finalized,
we
believe
the
document
in
its
current
state
provides
the
best
guidance
and
information
currently
available
on
these
issues.
Implementers
should
remember,
of
course,
that
this
document
serves
as
guidance
only
and
should
not
be
construed
in
any
fashion
as
mandatory.

Vapor
intrusion
is
a
rapidly
developing
field
of
science
and
policy.
This
draft
guidance
is
intended
to
aid
in
evaluating
the
potential
for
human
exposure
from
this
pathway
given
the
state­
of­
the­
science
at
this
time.
EPA
will
continue
to
explore
this
area
in
efforts
to
improve
the
state­
of­
the­
science
of
this
complex
exposure
pathway.
A
workgroup
of
EPA
and
State
representatives
is
currently
being
organized
to
evaluate
this
pathway
over
the
next
several
years.
As
the
state­
of­
the­
science
improves,
this
guidance
will
revised
as
appropriate.

EPA
and
State
site
managers
are
encouraged
to
contact
EPA's
Office
of
Solid
Waste
to
join
the
workgroup
and/
or
provide
the
workgroup
with
relevant
site
information
that
can
be
added
to
the
Office
of
Solid
Waste
and
Emergency
database
to
facilitate
these
efforts.

Background
In
December
2001,
EPA
issued
the
draft
RCRA
Environmental
Indicator
Supplemental
Guidance
for
Evaluating
the
Vapor
Intrusion
Into
Indoor
Air
Pathway.
The
current
guidance
replaces
the
2001
document,
but
does
not
replace
the
State
guidance.

Vapor
intrusion
is
the
migration
of
volatile
chemicals
from
the
subsurface
into
overlying
buildings.
Volatile
chemicals
in
buried
wastes
and/
or
contaminated
groundwater
can
emit
vapors
that
may
migrate
through
subsurface
solid
and
into
air
spaces
of
overlying
buildings.

In
extreme
cases,
the
vapors
may
accumulate
in
dwellings
or
occupied
buildings
to
levels
that
may
pose
near­
term
safety
hazards,
acute
health
effects
or
aesthetic
problems
In
most
cases,
however,
the
chemical
concentrations
are
low,
or
depending
on
site­
specific
conditions,
vapors
may
not
be
present
at
detectable
concentrations.

For
More
Information
This
fact
sheet,
the
Federal
Register
notice,
and
other
documents
related
to
this
action
are
generally
available
on
the
Internet
when
the
rule
is
published.
See:
<
http://
www.
epa.
gov/
epaoswer/
hazwaste/
recycle/
fertiliz/
index.
htm>.
For
additional
information,
contact
the
RCRA
Call
Center.
Callers
within
the
Washington
Metropolitan
Area
must
dial
703­
412­
9810
or
TDD
703­
412­
3323
(
hearing
impaired).
Long­
distance
callers
may
call
1­
800­
424­
9346
or
TDD
1­
800­
553­
7672.
