Document ID: EPA-HQ-OAR-2004-0084-0007
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2004-07-07T04:00Z

DC_
DOCS\
182920.2
[
W97]
ADDENDUM
TO
PETITION
TO
REMOVE
MIBK
FROM
THE
HAP
LIST
Submitted
by
the
Chemical
Manufacturers
Association
Ketones
Panel
May
26,
1999
In
April,
1997,
the
Ketones
Panel
(
Panel)
of
the
Chemical
Manufacturers
Association
(
CMA)
submitted
a
petition
asking
the
U.
S.
Environmental
Protection
Agency
(
EPA)
to
remove
methyl
isobutyl
ketone
(
MIBK)
from
the
list
of
chemicals
that
are
regulated
as
hazardous
air
pollutants
(
HAPs)
under
section
112
of
the
Clean
Air
Act
(
CAA).
Under
Section
112,
EPA
is
required
to
remove
a
substance
from
the
HAP
list
if
"
there
is
adequate
data
on
the
health
and
environmental
effects
of
the
substance
to
determine
that
emissions,
ambient
concentrations,
bioaccumulation
or
deposition
of
the
substance
may
not
reasonably
be
anticipated
to
cause
any
adverse
effects
to
human
health
or
adverse
environmental
effects."
CAA
§
112(
b)(
3).
This
addendum
briefly
reviews
the
toxicity
and
exposure
data
on
MIBK,
including
the
results
of
supplemental
air
dispersion
modeling
studies
recently
conducted
by
the
Panel,
and
explains
why
MIBK
should
be
delisted
as
a
HAP.

I.
Health
and
Environmental
Effects
Data
Because
MIBK
has
been
widely
used
for
many
years,
its
potential
effects
on
human
health
and
the
environment
have
been
extensively
studied.
This
body
of
data
is
discussed
at
length
in
the
Petition,
and
copies
of
the
relevant
studies
were
submitted
to
EPA
along
with
the
Petition.
EPA
recently
reviewed
the
data
on
the
potential
health
and
environmental
effects
of
MIBK
to
determine
whether
facilities
should
continue
to
report
their
MIBK
releases
under
Section
313
of
the
Emergency
Planning
and
Community
Right­
to­
Know
Act
(
EPCRA).
Although
EPA
decided
that
releases
of
MIBK
should
continue
to
be
reported
under
EPCRA
because
of
MIBK's
status
as
a
volatile
organic
compound
(
VOC),
the
Agency
found
that
MIBK
did
not
pose
direct
toxicity
concerns.

In
the
Federal
Register
notice
discussing
the
Agency's
review
of
the
MIBK
data
for
purposes
of
the
EPCRA
decision,
1
EPA
made
the
following
statements:

 
"
MIBK
has
low
acute
and
chronic
(
systemic)
toxicity
in
that
effects
occur
only
at
high
doses."
2
 
"
MIBK
exposure
does
not
appear
to
be
associated
with
genotoxicity
in
vitro
or
in
vivo."
3
 
"
MIBK
has
low
direct
environmental
toxicity."
4
1
64
Fed.
Reg.
8769
(
February
23,
1999).

2
Id.
at
8772
3
Id.
at
8770
4
Id.
at
8772
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182920.2
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2
 
"
MIBK
is
of
low
concern
with
respect
to
aquatic
toxicity
based
on
measured
toxicity
data
and
quantitative
structure
activity
relationship
(
QSAR)
analysis."
5
 
"
There
is
low
concern
for
a
potential
for
developmental
effects
for
the
general
population
following
acute
inhalation
exposures
to
MIBK."
6
Thus,
the
only
concern
raised
by
the
Agency
during
its
EPCRA
review
was
that
MIBK
is
a
VOC
and
can
therefore
contribute
to
ozone
formation.
As
the
Agency
has
acknowledged,
however,
section
112(
b)(
2)
of
the
Clean
Air
Act
makes
it
clear
that
a
compound
should
not
be
listed
as
a
HAP
solely
because
it
is
a
VOC.
7
II.
Exposure
Assessment
Although
MIBK
has
low
toxicity,
all
chemicals
can
cause
adverse
effects
at
sufficiently
high
exposure
levels.
In
considering
whether
MIBK
should
be
delisted
as
a
HAP,
EPA
must
determine
whether
"
emissions,
ambient
concentrations,
bioaccumulation
or
deposition"
of
MIBK
will
produce
high
enough
exposure
levels
to
cause
adverse
effects.
Based
on
input
from
Agency
staff,
the
Ketones
Panel
conducted
an
extensive
exposure
assessment
to
determine
whether
the
public
is
exposed
to
potentially
hazardous
levels
of
MIBK,
or
whether
such
exposures
are
likely
to
occur
if
MIBK
is
delisted
as
HAP.
Based
on
this
assessment,
it
is
clear
that
MIBK
cannot
"
reasonably
be
anticipated
to
cause
any
adverse
effects
to
human
health."
The
Panel
also
has
conducted
fugacity
modeling
(
Mackay
Level
I
and
Level
III)
to
evaluate
the
environmental
fate
of
MIBK
emissions.
These
modeling
exercises
show
that
predicted
environmental
concentrations
are
orders
of
magnitude
below
levels
of
concern
for
potential
adverse
environmental
effects.
The
results
of
the
Panel's
exposure
assessments
are
summarized
below.

A.
Inhalation
is
the
Only
Potential
Route
of
Significant
Exposure
In
light
of
anticipated
ambient
concentrations
(
described
further
below),
it
is
clear
that
humans
would
not
be
expected
to
ingest
any
appreciable
amounts
of
MIBK
resulting
from
air
emissions.
Further,
because
of
MIBK's
ready
biodegradation
and
volatilization
from
water,
it
is
highly
unlikely
that
humans
will
be
exposed
to
significant
levels
of
MIBK
in
drinking
water.
In
addition,
given
its
lack
of
persistence
and
low
bioaccumulation
potential,
MIBK
emitted
to
the
air
would
be
highly
unlikely
to
concentrate
in
food
sources.
Finally,
dermal
absorption
is
likely
to
be
insignificant
compared
to
inhalation,
because
dermal
absorption
is
a
less
efficient
exposure
route
for
humans
and
ambient
concentrations
of
MIBK
are
not
high
enough
to
make
this
route
toxicologically
relevant.
Thus,
as
explained
further
in
the
Petition,
inhalation
is
the
only
route
of
human
exposure
with
potential
significance.

5
Id.
at
8771
6
Id.
at
8772
7
See
Petition
Section
II.
C.
DC_
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3
B.
An
Inhalation
Reference
Concentration
(
RfC)
is
the
Relevant
Benchmark
for
Evaluating
Exposure
Levels
It
is
well­
recognized
that
MIBK
has
low
acute
toxicity.
Thus,
in
order
to
evaluate
whether
MIBK
emissions
may
pose
a
human
health
risk,
ambient
concentrations
of
MIBK
should
be
compared
to
an
inhalation
reference
concentration
(
RfC)
for
MIBK.
An
RfC
is
intended
to
represent
the
exposure
level
to
which
even
a
sensitive
individual
could
be
exposed
for
a
lifetime
without
"
an
appreciable
risk
of
deleterious
effects."
8
The
IRIS
database
does
not
currently
include
an
inhalation
reference
concentration
for
MIBK.
However,
as
explained
in
the
Petition,
the
Ketones
Panel
has
calculated
an
RfC
for
MIBK
based
on
EPA's
1994
guidance.
9
The
RfC
is
based
on
subchronic
inhalation
studies
in
rats
and
mice
sponsored
by
the
Ketones
Panel
as
part
of
a
testing
program
under
Section
4
of
TSCA.
This
study
also
was
used
by
EPA
to
calculate
the
composite
score
for
MIBK
as
part
of
the
proposed
relative
hazard
ranking
for
MIBK
and
other
compounds
under
Section
112(
g)
of
the
Clean
Air
Act.
Based
on
this
study,
the
calculated
RfC
for
MIBK
is
2.4
mg/
m3.
This
RfC
represents
a
conservative
estimate
of
the
concentration
of
MIBK
in
air
to
which
an
individual
could
be
exposed
for
a
lifetime
without
adverse
effect,
and
is
based
on
total
uncertainty
and
modifying
factors
of
1,000.
This
RfC
reflects
MIBK's
low
chronic
toxicity
and,
as
discussed
below,
far
exceeds
anticipated
human
exposures.

C.
The
Highest
Exposure
Levels
Are
Found
Around
Stationary
Sources
As
explained
in
the
Petition,
MIBK
is
a
highly
efficient
solvent
that
dissolves
a
wide
variety
of
resins
and,
therefore,
is
widely
used
in
surface
coatings,
adhesives,
and
inks.
10
It
also
is
used
as
a
solvent
in
cleaning
fluids
and
dewaxing
agents,
and
as
an
extraction
medium
for
fats,
oils,
waxes
and
resins.
The
vast
majority
of
MIBK
emissions
are
from
industrial
operations.
Although
it
is
also
used
in
consumer
products
and
in
applications
such
as
traffic
paint,
emissions
from
these
products
are
widely
dispersed
and
are
not
high
enough
to
produce
appreciable
airborne
concentrations.
This
fact
is
confirmed
by
ambient
monitoring
studies
that
are
discussed
more
fully
in
the
Petition.
11
In
these
studies,
MIBK
typically
was
not
detected
except
in
industrial
areas
where
it
was
found
in
the
low
parts
per
billion
range.
Thus,
based
on
information
about
the
usage
of
MIBK
and
data
from
ambient
air
monitoring
studies,
it
is
clear
that
the
highest
exposure
levels
are
found
around
stationary
sources
that
emit
MIBK.

8
See
EPA
Office
of
Research
and
Development,
"
Methods
for
Derivation
of
Inhalation
Reference
Concentrations
and
Application
of
Dosimetry,"
EPA
No.
600/
8­
90/
066F
(
October
1994)
at
p.
1­
3.

9
See
Petition
Section
III.
C.
7
and
Appendix
B.

10
In
its
EPCRA
review,
EPA
noted
that
"
MIBK
has
strong
solvent
power
and
is
a
good
solvent
for
many
natural
and
synthetic
resins."
64
Fed.
Reg.
8770.

11
See
Petition
Section
IV.
B.
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182920.2
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4
D.
Sources
Emitting
Less
than
144,000
Pounds
a
Year
Cannot
Realistically
Pose
a
Risk
The
Panel
retained
an
outside
consulting
firm,
ENSR
Corporation,
to
evaluate
potential
exposure
levels
from
industrial
releases.
Based
on
consultations
with
Agency
modelers,
ENSR
developed
an
approach
for
identifying
the
universe
of
sources
that
could
potentially
produce
ground­
level
concentrations
that
exceed
the
RfC.
12
As
discussed
below,
this
analysis
shows
that
sources
with
annual
emissions
less
than
144,000
pounds
cannot
realistically
be
expected
to
produce
ground­
level
concentrations
of
MIBK
that
exceed
the
RfC.

ENSR
used
the
following
approach,
based
on
input
from
EPA
staff,
to
make
this
determination.
First,
ENSR
designed
a
near
"
worst­
case"
hypothetical
facility
­­
a
source
configuration
that
would
tend
to
maximize
ground­
level
concentrations
of
MIBK.
In
this
model,
all
emissions
are
assumed
to
be
emitted
from
a
single
vent
located
in
the
center
of
a
small
onestory
building
that
is
5
meters
high
and
20
meters
square.
To
maximize
aerodynamic
downwash
(
and,
consequently,
ground­
level
concentrations),
the
model
also
assumed
that
the
vent
is
flush
with
the
roof
(
a
release
height
of
5
meters)
and
that
emissions
have
no
momentum
or
buoyancy
that
would
result
in
plume
rise.

This
configuration
was
then
modeled
using
EPA's
SCREEN3
model
to
determine
maximum
annual
average
ground­
level
concentrations
of
MIBK.
As
discussed
in
the
ENSR
Report
dated
August,
1999,13
SCREEN3
indicates
that,
with
this
source
configuration,
the
maximum
ground­
level
concentrations
of
MIBK
would
occur
at
a
point
located
18
meters
from
the
downwind
edge
of
the
building.
ENSR
then
determined
that,
in
order
to
produce
groundlevel
concentrations
of
MIBK
at
this
point
that
exceed
the
RfC,
the
facility
would
have
to
emit
more
than
144,000
pounds
per
year
of
MIBK.

There
are
several
layers
of
conservatism
built
into
this
estimate,
such
that
emissions
much
higher
than
144,000
pounds
per
year
probably
would
be
required
before
any
persons
would
be
exposed
to
ambient
concentrations
of
MIBK
above
the
RfC.
First,
it
is
highly
unlikely
that
human
receptors
would
be
found
just
18
meters
from
the
building
edge.
Under
the
screening
approach
used
by
ENSR,
however,
the
distance
to
the
site
boundary
is
not
relevant,
since
this
approach
is
designed
to
predict
maximum
ground­
level
concentrations
regardless
of
whether
they
would
occur
on­
site
or
off­
site.
Second,
it
would
be
difficult
(
if
not
impossible)
for
a
small
building
like
the
one
assumed
in
the
screening
model
to
house
even
a
moderate­
sized
coating
or
other
solvent­
based
industrial
operation.
The
actual
source
data
gathered
by
ENSR
indicates
that
facilities
with
significant
solvent
emissions
are
larger
and
have
higher
release
heights
than
the
model
facility,
and
that
emissions
are
usually
released
from
several
points
rather
than
from
a
single
vent
­­
all
of
which
would
tend
to
produce
lower
ground­
level
concentrations.
Thus,
it
can
be
concluded
with
considerable
confidence
that
sources
which
emit
less
than
144,000
12
The
approach
described
here
is
the
same
approach
used
by
the
Panel
to
support
the
separate
petition
to
remove
methyl
ethyl
ketone
(
MEK)
from
the
HAP
list.

13
A
copy
of
ENSR's
1999
Study
is
attached
as
Appendix
I
to
this
Petition
Addendum.
DC_
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182920.2
[
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5
pounds
of
MIBK
cannot
be
expected
to
produce
ground­
level
concentrations
that
exceed
the
RfC,
and
thus
cannot
be
expected
to
pose
a
risk
to
human
health.

E.
Modeling
Results
for
All
Sources
Above
144,000
Pounds
Show
No
Exceedances
of
the
RfC
ENSR
has
conducted
two
types
of
modeling
to
evaluate
ambient
concentrations
of
MIBK
around
all
sources
that
reported
more
than
144,000
pounds
of
MIBK
emissions
in
1996.
This
analysis
shows
that
predicted
maximum
off­
site
concentrations
are
well
below
the
RfC
at
all
of
these
sources.
ENSR
has
modeled
26
different
facilities
and
found
that
none
produced
off­
site
concentrations
that
would
be
anticipated
to
cause
adverse
health
effects.

The
1997
Study:
In
1997,
ENSR
conducted
site­
specific
air
dispersion
modeling
for
all
sources
that
had
reported
MIBK
emissions
of
300,000
pounds
or
more
(
the
1997
Study).
14
ENSR
contacted
each
of
these
facilities
(
13
based
on
1994
TRI
data)
to
gather
information
that
could
be
used
to
model
maximum
off­
site
concentrations
and
also
obtained
additional
information
from
public
sources
(
including
Title
V
permit
applications).
One
facility
was
excluded
because
it
discovered
that
it
had
incorrectly
calculated
its
1994
air
emissions.
ENSR
obtained
the
necessary
site
data
for
10
of
the
remaining
12
facilities,
including
the
top
two
emitters.
The
remaining
2
facilities
were
modeled
using
a
more
generic
approach
described
in
the
ENSR
1997
study
report.

Using
this
data,
ENSR
performed
an
air
dispersion
modeling
analysis
for
each
facility
using
EPA's
"
Tiered
Modeling
Approach
for
Assessing
Risks
Due
to
Sources
of
Hazardous
Air
Pollutants"
(
1992).
This
approach
uses
three
successively
rigorous
modeling
techniques.
Tier
1
requires
only
limited
source
information
and
an
EPA
look­
up
table,
and
provides
the
most
conservative
predictions
of
maximum
concentrations.
Tier
2
requires
additional
source
information
and
an
EPA
screening
level
computer
program,
and
generates
predictions
that
are
somewhat
more
realistic
than
Tier
1
predictions.
Tier
3,
which
requires
extensive
data
from
the
source
and
uses
EPA's
most
advanced
dispersion
modeling
techniques,
provides
the
most
realistic
predicted
maximum
concentrations.
Because
each
successive
tier
provides
a
less
conservative
(
and
more
realistic)
prediction,
Tier
3
modeling
was
not
performed
for
a
facility
if
Tier
2
modeling
predicted
maximum
annual
concentrations
below
1.0
mg/
m3.

The
results
of
this
study
are
detailed
in
the
1997
ENSR
Report.
Tier
3
modeling
was
performed
for
5
sites,
and
this
modeling
showed
that,
for
each
of
these
facilities,
predicted
maximum
off­
site
concentrations
were
well
below
the
calculated
RfC.
No
facility
had
a
Tier
3
maximum
off­
site
concentration
above
0.5
mg/
m3.
For
the
other
5
facilities
included
in
the
1997
Study,
Tier
2
concentrations
were
all
below
1.0
mg/
m3.
Because
of
the
conservative
nature
of
Tier
2
estimates,
actual
off­
site
concentrations
around
these
facilities
are
expected
to
be
much
lower
than
Tier
2
values.

14
A
copy
of
ENSR's
report
of
the
1997
Study
was
included
with
the
Petition
as
Appendix
I.
DC_
DOCS\
182920.2
[
W97]
6
The
1999
Study:
ENSR
has
recently
prepared
a
second
study
(
the
1999
Study)
15
that
updates
the
1997
Study
based
on
more
recent
emissions
data,
and
also
examines
all
sources
reporting
air
emissions
greater
than
144,000
pounds
in
the
1996
TRI
database,
excluding
only
those
that
had
already
been
modeled
in
the
previous
study.
This
second
ENSR
study
again
demonstrates
that
there
is
not
a
single
facility
in
the
U.
S.
that
produces
off­
site
concentrations
of
MIBK
that
are
anticipated
to
exceed
the
health
benchmark.

Only
9
facilities
reported
MIBK
emissions
at
or
above
300,000
pounds
in
1996.16
All
9
facilities
were
addressed
in
the
1997
Study.
As
discussed
in
the
1999
Study,
ENSR
used
a
simple
scaling
approach
to
update
the
previous
modeling
for
all
12
top
emitters
included
in
the
previous
study.
Because
emissions
generally
decreased
from
1994
to
1996,
predicted
off­
site
concentrations
were
lower
than
estimated
in
the
earlier
study
in
most
cases.
In
all
cases,
predicted
maximum
off­
site
concentrations
remained
substantially
below
the
RfC.
See
1999
Study,
Table
1.

ENSR
then
evaluated
all
the
other
facilities
that
reported
annual
MIBK
emissions
of
greater
than
144,000
pounds
on
the
1996
TRI.
For
these
sources
(
those
over
144,000
pounds
that
were
not
addressed
in
the
1997
report),
ENSR
used
Tier
3
modeling,
which
involves
the
application
of
sequential
meteorological
data
with
the
ISC
Short­
Term
model
(
ISCT3).
ISCT3
was
applied
to
each
of
the
sources
with
emissions
greater
than
144,000
pounds
using
site­
specific
meteorological
data
downloaded
from
EPA's
Technology
Transfer
Network
(
TTN).
Wherever
available,
five
years
of
meteorological
data
were
simulated
for
each
site,
so
that
worst­
case
dispersion
climatology
was
used.

Because
it
was
impractical
to
obtain
site­
specific
information
other
than
meteorological
data
for
each
source,
ENSR
again
used
the
conservative
source­
receptor
configuration
used
in
the
SCREEN3
modeling
discussed
above
(
Section
II.
D).
Thus,
model
runs
were
based
on
1996
TRI
emission
rates
using
the
very
conservative
assumptions
that
the
source
has
a
single
roof­
level
vent
in
the
center
of
a
one­
story
building
5
meters
high
and
20
meters
wide.
Again,
the
parameters
assumed
no
plume
rise,
and
no
consideration
was
given
to
whether
the
highest
predicted
impact
was
inside
or
outside
facility
boundaries.
Notwithstanding
the
layers
of
conservatism
built
into
this
approach,
the
modeling
showed
that
the
maximum
predicted
concentration
for
each
facility
was
below
the
calculated
RfC.
Thus,
EPA
can
conclude
with
a
great
deal
of
confidence
that
there
is
no
facility
in
the
country
that
produces
off­
site
levels
of
MIBK
that
are
anticipated
to
cause
adverse
health
effects.

Further,
to
illustrate
the
conservative
nature
of
the
SCREEN3
Modeling,
ENSR
conducted
SCREEN3
modeling
for
all
facilities
for
which
it
had
previously
conducted
Tier
3
modeling
using
site­
specific
data.
A
comparison
of
results
is
presented
in
Table
4
of
the
1999
15
The
1999
Study
is
included
as
Appendix
I
to
this
Petition
Addendum.

16
A
table
showing
the
distribution
of
1996
TRI
data
across
reporting
ranges
is
attached
as
Appendix
II
to
this
Petition
Addendum.
This
table
can
be
compared
to
table
4
in
the
Petition
(
p.
41)
which
presents
the
same
analysis
based
on
1994
TRI
data.
Note
also
the
previous
discussion
in
this
Addendum
concerning
one
facility
that
overstated
its
1994
emissions.
DC_
DOCS\
182920.2
[
W97]
7
ENSR
Study,
and
it
shows
that
modeling
results
based
on
site­
specific
data
typically
are
five­
toten
fold
(
or
more)
below
the
SCREEN3
modeling
results
based
on
conservative
default
assumptions.
This
comparison
adds
to
the
confidence
that
no
facilities
have
emissions
that
produce
fenceline
concentrations
above
the
RfC.

F.
It
is
Highly
Unlikely
that
Future
Emissions
of
MIBK
Will
Produce
Levels
of
Concern
If
MIBK
is
removed
from
the
list
of
HAPs,
use
of
MIBK
may
increase.
For
several
reasons,
however,
MIBK
emissions
are
unlikely
to
increase
substantially.
First,
MIBK
will
continue
to
be
regulated
as
a
VOC.
If
a
company
wishes
to
increase
its
usage
of
MIBK
substantially,
it
likely
will
trigger
either
new
source
review
(
NSR)
or
prevention
of
significant
deterioration
(
PSD)
permitting
requirements
under
the
Clean
Air
Act.
In
either
case,
the
facility
would
be
required
to
install
control
technology
to
minimize
emissions.
Even
if
a
facility
does
not
trigger
NSR
or
PSD
review,
VOC
emissions
are
subject
to
other
types
of
federal
and
state
regulation
that
will
limit
increases
in
MIBK
emissions.

Second,
MIBK
is
used
primarily
in
paints
and
coatings
and,
to
a
lesser
extent,
in
inks
and
adhesives.
In
these
and
other
solvent
applications,
MIBK
is
rarely
used
by
itself.
Typically,
MIBK
is
part
of
a
solvent
blend
that
must
be
carefully
formulated
to
achieve
the
proper
performance
characteristics,
including
such
things
as
evaporation
rate,
surface
tension,
solvent
balance,
and
flash
point.
Although
there
is
flexibility
to
increase
the
use
of
MIBK
in
many
solvent
blends,
there
are
inherent
limits
on
the
amount
of
MIBK
(
or
any
other
single
solvent)
that
can
be
used
in
any
formulation.

Finally,
modeling
data
discussed
above
show
that,
even
if
MIBK
emissions
were
to
increase
significantly,
ambient
concentrations
would
be
expected
to
remain
well
below
levels
of
concern.
Actual
monitoring
data
in
a
number
of
areas,
including
industrial
areas,
indicate
that
ambient
concentrations
of
MIBK
are
extremely
low.
The
air
dispersion
modeling
studies
conducted
by
ENSR
show
that,
in
most
cases,
estimated
maximum
annual
off­
site
concentrations
around
facilities
emitting
MIBK
should
be
below
the
RfC
by
an
order
of
magnitude
or
more.

In
obtaining
these
modeled
ambient
concentrations,
ENSR
used
a
very
conservative
source­
receptor
configuration,
the
same
configuration
used
in
Screen3
modeling.
Model
runs
were
based
on
a
hypothetical
industrial
source
with
a
single
roof­
level
stack
at
5
m.
The
effect
of
plume
rise
was
negated
by
setting
stack
temperature
to
ambient,
the
stack
diameter
to
0.01
m
and
the
exit
velocity
to
0.01
m/
sec.
The
MIBK
concentrations
obtained
using
these
conservative
assumptions
are
considerably
higher
than
would
be
obtained
using
site­
specific
source­
receptor
data.
To
evaluate
the
effect
of
using
such
conservative
assumptions,
ENSR
again
ran
the
dispersion
models
for
facilities
previously
addressed
in
ENSR's
1997
dispersion
modeling
study,
this
time
both
with
and
without
site­
specific
data.
The
inclusion
of
site­
specific
data
in
the
evaluation
of
these
facilities
reduced
the
predicted
maximum
annual
MIBK
concentrations
by
a
factor
of
6
to
28.
The
results
in
table
3
would
be
in
all
likelihood
similarly
reduced
with
the
inclusion
of
more
realistic
site­
specific
source­
receptor
data.
Therefore,
even
significant
increases
in
MIBK
emissions
would
not
pose
an
appreciable
risk
to
human
health
or
the
environment.
DC_
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182920.2
[
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8
G.
Fugacity
Modeling
Results
Demonstrate
that
Environmental
Concentrations
of
MIBK
Are
Orders
of
Magnitude
Below
Levels
of
Concern
for
Environmental
Effects
The
Panel
also
has
recently
performed
fugacity
modeling
(
Mackay
Level
I
and
Level
III)
to
evaluate
the
fate
of
MIBK
in
air,
water,
soil
and
sediment.
17
The
results
of
this
modeling
can
be
used
to
determine
whether
environmental
concentrations
might
be
expected
to
approach
levels
of
concern
for
environmental
effects.
Similar
to
the
ENSR
studies,
very
conservative
assumptions
were
used.
Even
so,
the
most
conservative
case
shows
environmental
concentrations
of
MIBK
as
follows:
air,
192
ng/
m3;
soil,
0.00891
ng/
g;
sediment,
0.00315
ng/
g;
and
water,
7.791
ng/
L.
These
concentrations
are
well
below
levels
that
might
be
expected
to
pose
hazards
to
human
health
or
the
environment.
Stated
differently,
the
PEC/
PNEC
ratio18
in
every
case
is
several
orders
of
magnitude
below
the
target
of
one.

The
fugacity
modeling
does
not
address
transformation
products,
but
this
is
not
a
likely
source
of
concern
because
the
principal
transformation
product
is
believed
to
be
acetone,
19
which
is
not
listed
as
a
HAP.
Further,
any
degradation
products
of
MIBK
in
air
would
be
produced
far
downwind
from
facility
boundaries,
after
the
emissions
have
been
greatly
dispersed
and
MIBK
concentrations
have
become
vanishingly
small.

III.
Conclusion
The
potential
for
MIBK
to
cause
adverse
effects
on
human
health
or
the
environment
has
been
extensively
studied.
The
body
of
data
demonstrates
that
MIBK
has
low
acute
and
chronic
toxicity
as
well
as
low
environmental
toxicity.
Extensive
modeling
studies
have
been
conducted
using
multiple
conservative
assumptions
to
estimate
maximum
ambient
concentrations
that
may
result
from
industrial
releases.
These
modeling
results
consistently
demonstrate
that
ambient
concentrations
are
well
below
levels
of
concern
for
health
or
environmental
effects.
Accordingly,
MIBK
meets
the
criteria
for
removal
from
the
HAPs
list.

17
The
modeling
results
and
analysis
are
presented
in
a
report
prepared
by
Dr.
Charles
Staples
of
Assessment
Technologies,
Inc.
A
copy
of
this
report
is
attached
as
Appendix
III
to
this
Petition
Addendum.

18
This
is
the
ratio
of
the
predicted
exposure
concentration
(
PEC)
to
the
predicted
no
effect
concentration
(
PNEC)
in
each
environmental
medium.
A
PEC/
PNEC
ratio
below
one
signifies
that
exposures
are
below
conservatively­
calculated
safe
levels.

19
P.
H.
Howard,
Handbook
of
Environmental
Fate
and
Exposure
Data
for
Organic
Chemicals
Vol.
II.,
341­
348
(
1990).