Document ID: EPA-HQ-OAR-2003-0161-0124
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-04-07T04:00Z

Date:
March
8,
2006
From:
Thomas
Holloway
Subject:
National
Emission
Standards
for
Magnetic
Tape
Manufacturing
Operations 
Summary
of
Public
Comments
and
EPA
Responses
To:
Lynn
Dail
ESD/
CCPG
(
C539­
03)
U.
S.
Environmental
Protection
Agency
(
EPA)
Research
Triangle
Park,
NC
27711
I.
Introduction
On
October
24,
2005,
the
U.
S.
Environmental
Protection
Agency
(
EPA)
proposed
taking
no
further
action
at
this
time
to
revise
the
national
emission
standards
for
hazardous
air
pollutants
(
NESHAP)
for
magnetic
tape
manufacturing
operations,
based
on
findings
from
the
residual
risk
review
and
technology
review
for
the
source
category.
In
the
proposed
action,
EPA
requested
public
comment
on
the
residual
risk
review
and
technology
review
and
on
issues
of
delisting
the
source
category
and
conducting
future
technology
reviews.
The
purpose
of
this
memorandum
is
to
present
a
summary
of
the
public
comments
received
and
EPA's
responses
to
the
comments.

By
the
end
of
the
public
comment
period,
comments
from
five
entities
had
been
received.
The
commenters
(
and
the
document
numbers
assigned
to
their
comments)
are
listed
below:

STAPPA/
ALAPCO
(
EPA­
HQ­
OAR­
2003­
0161­
0107)
The
American
Chemistry
Council
(
EPA­
HQ­
OAR­
2003­
0161­
0108)
Residual
Risk
Coalition
(
EPA­
HQ­
OAR­
2003­
0161­
0109)
Alliance
of
Automobile
Manufacturers
(
EPA­
HQ­
OAR­
2003­
0161­
0110)
The
AN
Group
(
EPA­
HQ­
OAR­
2003­
0161­
0111)

II.
Summary
of
Comments
and
Responses
A.
Residual
Risk
Determination
Comment:
Commenters
EPA­
HQ­
OAR­
2003­
0161­
0108,
­
0109,
and
­
0110
(
hereafter
referred
to
as
commenters
0108,
0109,
and
0110)
supported
EPA's
decisions
for
the
magnetic
tape
source
category.
The
commenters
0108,
0109,
and
0110
supported
EPA's
conclusion
that
no
changes
to
the
existing
NESHAP
for
magnetic
tape
manufacturing
were
required
to
satisfy
the
requirements
of
section
112(
f).
The
commenters
noted
that
EPA
correctly
reviewed
the
magnetic
tape
sources,
followed
the
tiered
risk
assessment
approach
described
in
its
Residual
Risk
Report
to
Congress,
and,
using
a
conservative
methodology,
determined
that
no
source
in
the
category
had
a
maximum
individual
cancer
risk
exceeding
the
1­
in­
1­
million
level
for
triggering
promulgation
of
a
residual
risk
standard
under
section
112(
f).
2
Commenters
0108
and
0109
stated
that
EPA
was
correct
to
focus
its
section
112(
f)
residual
risk
analysis
on
the
sources
in
the
magnetic
tape
source
category
subject
to
section
112(
d)
requirements,
and
not
consider
risk
from
outside
that
source
category.
According
to
the
commenters,
the
statutory
language
and
construction
of
section
112(
f)
shows
that
Congress
was
directing
EPA
to
perform
residual
risk
analyses
for
individual
source
categories.

Response:
We
acknowledge
the
commenters'
support
for
our
health­
protective
methodology
and
our
conclusions
in
the
proposed
notice.
Because
risks
from
the
magnetic
tape
source
category
did
not
exceed
the
statutory
trigger
of
1
in
1
million,
we
agree
that
it
was
appropriate
to
limit
our
analysis
to
the
source
category
rather
than
also
considering
risks
from
other
sources.
However,
we
do
not
agree
that
our
section
112(
f)
residual
risk
analyses
must
always
focus
only
on
the
sources
in
the
magnetic
tape
source
category
subject
to
section
112(
d)
requirements
or
that
Congress
intended
to
limit
all
residual
risk
analyses
to
the
individual
source
categories
in
question.
As
we
stated
in
the
preamble
to
the
Coke
Ovens
residual
risk
rule,
"
EPA
disagrees
that
section
112(
f)
precludes
EPA
from
considering
emissions
other
than
those
from
the
source
category
or
subcategory
entirely."
Rather,
we
have
concluded
that,
when
the
statutory
risk
trigger
is
exceeded,
the
two­
step
approach
set
forward
in
the
Benzene
NESHAP
remains
the
approach
that
we
should
follow
in
determinations
under
section
112(
f).
At
the
first
step,
when
determining
"
acceptable
risk,"
we
will
consider
risks
that
result
from
emissions
from
the
source
category
only.
However,
during
the
second
step,
we
must
determine
whether
additional
reductions
should
be
required
to
protect
public
health
with
"
an
ample
margin
of
safety."
One
of
the
factors
that
we
can
consider
in
this
second
step
is
environmental
levels
of
hazardous
air
pollutants
(
HAP)
due
to
emissions
from
sources
outside
the
source
category
being
assessed.
This
could
include
ambient
background
concentrations
of
HAP,
as
well
as
co­
location
of
other
emission
sources
that
augment
the
identified
risks
from
the
source
category.

B.
Delisting
the
Source
Category
At
proposal,
we
requested
comment
on
whether
it
would
be
appropriate
to
delist
the
magnetic
tape
source
category
under
section
112(
c)(
9)
based
on
the
possibility
that
HAP
emissions
from
the
source
category
would
be
sufficiently
low
even
in
the
absence
of
maximum
achievable
control
technology
(
MACT)
standards.

Comment:
Commenter
EPA­
HQ­
OAR­
2003­
0161­
0107
(
hereafter
referred
to
as
commenter
0107)
opposed
delisting
the
magnetic
tape
source
category,
stating
that
if
the
source
category
was
delisted,
there
would
be
nothing
to
prevent
sources
from
increasing
their
HAP
emissions
substantially
or
changing
their
processes
to
emit
new
HAP,
resulting
in
HAP
levels
unacceptable
to
public
health
and
the
environment.
The
commenter
indicated
that
such
an
approach
ignores
the
possibility
that
HAP
emissions
were
reduced
to
an
acceptable
level
because
of
the
MACT
requirements
and
that
emissions
could
increase
again
without
the
MACT
standard
in
place.
Furthermore,
the
commenter
believed
that
Congress
did
not
intend
for
the
residual
risk
review
to
result
in
delisting
of
regulated
source
categories;
if
Congress
had
wanted
to
make
delistings
dependent
on
or
linked
to
the
outcome
of
the
residual
risk
process,
it
would
have
specifically
mandated
this
in
the
CAA,
which
it
did
not.
3
Commenters
0108
and
0109
argued
that
delisting
a
source
category
does
not
affect
the
applicability
of
an
existing
NESHAP
and
cited
the
delisting
action
following
the
Asbestos
NESHAP
as
support
for
their
argument.
They
also
noted
that
EPA
said
in
its
proposal
that
no
further
section
112(
d)(
6)
reviews
are
required
unless
there
is
a
significant
change
to
the
source
category.
Consequently,
the
commenters
saw
no
benefit
in
delisting
the
magnetic
tape
source
category.
However,
they
were
not
opposed
to
such
an
action.

Commenter
0110
supported
delisting
the
magnetic
tape
source
category
under
the
authority
of
section
112(
c)(
9)
based
on
EPA's
finding
of
negligible
risks
(
0.01
in
1
million).
The
commenter
stated
that
EPA's
request
for
comment
implied
that
it
interpreted
the
CAA
to
allow
delisting
on
the
basis
of
low
risk
only
before
a
MACT
standard
is
issued;
however,
section
112(
c)(
9)
provides
EPA
with
the
authority
to
delist
a
source
category
whenever
the
Administrator
makes
a
determination
that
the
risks
are
below
the
risk
criteria
in
the
CAA
and
does
not
limit
this
authority
to
sources
not
yet
subject
to
a
MACT
standard
or
a
generally
available
control
technology
(
GACT)
standard.
According
to
the
commenter,
limiting
EPA's
discretion
to
delist
source
categories
prior
to
issuing
MACT
or
GACT
standards
also
conflicts
with
the
required
sequence
of
duties
under
section
112,
which
does
not
require
EPA
to
conduct
a
risk
analysis
until
a
residual
risk
evaluation
is
required
8
years
after
MACT
standards
are
issued;
consequently,
EPA
is
unlikely
to
have
sufficient
data
on
which
to
base
a
delisting
decision
until
many
years
after
MACT
standards
have
been
promulgated.
Furthermore,
the
commenter
stated
it
is
possible
that
source
categories
found
to
be
low­
risk
after
MACT
standards
were
imposed
may
have
been
low­
risk
before
the
standards
were
imposed,
especially
magnetic
tape
facilities,
where
the
risk
assessment
showed
risks
two
orders
of
magnitude
below
the
statutory
criteria
for
delisting
under
section
112(
c)(
9).
Finally,
the
commenter
noted
that
if
EPA
was
concerned
that
the
source
category
would
exceed
risk
levels
if
MACT
controls
were
not
applicable,
it
could
use
section
112(
c)(
9)
to
keep
in
place
those
MACT
requirements
needed
to
sustain
the
low­
risk
determination
and
delisting.
According
to
the
commenter,
those
requirements
could
be
established
as
part
of
the
delisting
decision
and
maintained
in
the
title
V
permit,
as
was
done
in
the
NESHAP
for
Plywood
and
Composite
Wood
Products.

Response:
Based
on
our
risk
assessment
of
the
magnetic
tape
source
category,
we
have
concluded
that
these
sources
are
low­
risk
and,
therefore,
that
no
further
standards
are
required
to
protect
public
health
with
an
ample
margin
of
safety
or
to
protect
the
environment.
However,
we
agree
with
the
commenter
who
argues
that
this
conclusion
is
based,
at
least
in
part,
on
the
fact
that
the
MACT
requirements
for
these
sources
limit
HAP
emissions.
Further,
we
disagree
with
the
comment
that
delisting
will
not
affect
the
viability
of
the
existing
NESHAP.
The
commenter
cited
the
delisting
action
following
the
Asbestos
NESHAP
as
support
for
their
argument,
noting
that
the
applicability
of
that
rule
was
not
affected
by
delisting.
However,
the
Asbestos
NESHAP
was
established
under
part
61,
which
is
not
directly
relevant
in
this
situation
since
the
Magnetic
Tape
NESHAP
is
a
part
63
rule.
If
we
delist
this
source
category,
it
is
our
conclusion
that
existing
magnetic
tape
sources
would
no
longer
be
subject
to
the
NESHAP
and,
thus,
HAP
emissions
would
no
longer
be
limited
by
this
rule.
If
sources
begin
emitting
HAP
at
levels
exceeding
those
allowed
under
the
NESHAP,
risks
could
increase,
and
the
basis
for
our
finding
that
the
source
category
is
low­
risk
could
be
compromised.
We
have
already
documented
that
emissions
from
magnetic
tape
manufacturing
operations
were
substantially
higher
at
promulgation,
compared
to
more
recent
emissions
estimates
(
after
the
standards
were
4
implemented).
As
noted
in
the
October
24,
2005
proposal
(
70
FR
61419),
HAP
emissions
at
promulgation
were
estimated
to
be
4,060
megagrams
per
year
(
Mg/
yr)
(
4,470
tons
per
year
[
tpy]),
while
HAP
emissions
in
2000
were
estimated
to
be
468
Mg/
yr
(
516
tpy) 
a
difference
of
almost
90
percent.
(
These
HAP
emissions
estimates
include
methyl
ethyl
ketone,
which
has
since
been
delisted
as
a
HAP.)
Therefore,
since
compliance
with
the
MACT
standard
is
part
of
the
basis
for
our
low­
risk
determination,
we
believe
that
it
would
be
inappropriate
to
delist
the
magnetic
tape
source
category.

Contrary
to
one
commenter's
contention,
we
did
not
intend
to
imply
through
our
request
for
comments
that
we
interpret
section
112(
c)(
9)
of
the
CAA
to
apply
only
before
a
MACT
standard
has
been
promulgated.
We
were
simply
seeking
comment
on
the
use
of
section
112(
c)(
9)
after
the
MACT
standard.
However,
as
we
argue
above,
use
of
section
112(
c)(
9)
to
delist
the
magnetic
tape
source
category
is
neither
necessary
nor
appropriate,
and
we
agree
with
the
commenters
who
suggested
that
there
would
be
no
benefit
to
delisting
this
source
category.
Further,
we
do
not
agree
that
section
112(
c)(
9)
provides
us
the
authority
to
impose
requirements
less
stringent
than
MACT
in
order
to
sustain
a
low­
risk
determination
and
delisting.

C.
Future
Technology
Reviews
At
proposal,
we
requested
comment
on
"
the
notion
that,
barring
any
unforeseeable
circumstances
which
might
substantially
change
this
source
category
or
its
emissions,
we
would
have
no
obligations
to
conduct
future
technology
reviews
under
CAA
section
112(
d)(
6)."
We
suggested
this
approach
because
of
the
low­
risk
finding
for
this
source
category
under
section
112(
f).

Comment:
Commenter
0107
disagreed
that
low
risk
from
a
source
category
at
this
time
should
absolve
EPA
of
its
obligation
to
conduct
future
technology
reviews.
The
commenter
stated
that,
without
periodic
reviews
of
source
categories
and
technology
in
the
future
reviews,
EPA
would
not
be
aware
of
any
technologies
that
have
been
developed
or
any
"
unforeseeable
circumstances"
related
to
the
source
category
to
which
EPA
refers
in
the
notice.
Furthermore,
the
commenter
believed
that
Congress
did
not
intend
for
the
residual
risk
review
to
result
in
the
removal
of
EPA's
obligation
to
conduct
future
technology
reviews
under
section
112(
d)(
6);
if
Congress
had
wanted
to
make
technology
reviews
dependent
on
or
linked
to
the
outcome
of
the
residual
risk
process,
it
would
have
specifically
mandated
this
in
the
CAA,
which
it
did
not.

Commenters
0108,
0109,
and
0110
stated
that
EPA
has
no
obligation
to
conduct
a
technology
review
in
the
case
of
Magnetic
Tape.
According
to
the
commenters,
because
the
residual
risk
provisions
of
the
CAA
were
not
triggered
by
the
magnetic
tape
source
category's
remaining
low
risk,
even
an
initial
technology
review
was
unnecessary.
The
commenters
noted
that
EPA
only
used
the
results
of
the
section
112(
f)(
2)
residual
risk
analysis
to
conclude
that
future
section
112(
d)(
6)
technology
reviews
would
not
be
required.
The
commenters
stated
that
EPA's
use
of
a
formal
technology
review
as
the
basis
for
its
conclusion
under
section
112(
d)(
6)
that
the
NESHAP
did
not
need
to
be
revised
was
inconsistent
with
EPA's
prior
stated
position
in
the
Coke
Ovens
residual
risk
rule
(
70
FR
20009)
on
determining
the
need
for
a
technology
review
under
section
112(
d)(
6).
Commenter
0109
stated
that
if
the
Coke
Ovens
criteria
for
when
a
technology
review
is
not
"
necessary"
under
the
CAA
are
sound
for
subsequent
technology
5
reviews,
then
they
are
also
sound
for
initial
reviews,
as
in
the
case
of
Magnetic
Tape.
Commenter
0108
stated
that,
where
the
ample
margin
of
safety
set
in
the
residual
risk
rule
is
largely
based
on
cost
or
technical
feasibility,
then
further
future
review
under
section
112(
d)(
6)
may
remain
viable,
and
additional
controls
may
not
be
precluded
if
feasible,
cost­
effective
control
measures
are
identified
in
the
future.

Response:
We
stated
in
the
preamble
to
the
Coke
Ovens
residual
risk
rule
that
if
the
ample
margin
of
safety
analysis
for
the
section
112(
f)
standard
is
not
based
at
all
on
the
availability
or
cost
of
particular
control
technologies,
then
advances
in
air
pollution
control
technology
should
not
justify
revising
the
MACT
standard
pursuant
to
section
112(
d)(
6)
because
the
section
112(
f)
standard
would
continue
to
assure
an
adequate
level
of
safety.
We
agree
that
a
technology
review
is
required
every
8
years.
However,
if
the
ample
margin
of
safety
analysis
for
a
section
112(
f)
standard
shows
that
remaining
risk
for
non­
threshold
pollutants
falls
below
1
in
1
million
and
for
threshold
pollutants
falls
below
a
similar
threshold
of
safety,
then
further
revision
should
not
be
needed
because
an
ample
margin
of
safety
has
already
been
assured.
In
these
situations,
the
development
of
new
technology,
or
of
inexpensive
control
strategies,
would
generally
not
cause
us
to
require
additional
risk
reductions
for
a
source
category.
If
the
availability
and/
or
costs
of
technology
are
part
of
the
rationale
for
the
ample
margin
of
safety
determination,
it
is
reasonable
to
conclude
that
changes
in
those
costs
or
in
the
availability
of
technology
could
alter
our
conclusions
regarding
the
ample
margin
of
safety.
For
this
reason,
we
agree
with
the
comment
that
subsequent
technology
reviews
would
be
appropriate
and
revisions
may
also
be
appropriate
if
the
ample
margin
of
safety
established
by
the
residual
risk
process
considers
cost
or
technical
feasibility.

We
disagree
with
the
comment
that
we
should
not
have
conducted
an
initial
technology
review
under
section
112(
d)(
6)
for
the
magnetic
tape
source
category.
As
we
noted
in
the
preamble
to
the
Coke
Ovens
residual
risk
rule,
we
believe
that
the
findings
that
underlie
a
section
112(
f)
determination
should
be
key
factors
in
making
any
subsequent
section
112(
d)(
6)
determinations.
As
indicated
by
the
inclusion
of
the
word
"
subsequent"
in
this
rationale,
we
believe
that
we
are
obligated
to
perform
the
initial
section
112(
d)(
6)
analysis.
The
timing
requirements
for
the
initial
section
112(
d)(
6)
analysis
coincide
with
those
for
the
residual
risk
analysis.
Thus,
it
is
appropriate
for
us
to
conduct
both
analyses
at
the
same
time
and
for
the
results
of
the
risk
analysis
to
impact
future
section
112(
d)(
6)
technology
reviews,
even
though
these
results
do
not
negate
either
the
need
to
perform
the
initial
review
or
the
need
to
perform
subsequent
reviews
under
section
112(
d)(
6).

D.
General
Approach
to
Technology
Reviews
Comment:
Commenters
0108,
0109,
and
0110
stated
that
action
is
not
necessarily
required
under
section
112(
d)(
6)
even
if
a
residual
risk
rule
does
not
reduce
cancer
risks
for
all
persons
to
a
level
below
1
in
1
million.
Commenters
0108
and
0109
noted
that
EPA
had
already
rejected
such
a
"
bright
line"
approach
under
section
112(
f)
in
the
Coke
Ovens
residual
risk
rule;
instead,
it
serves
as
a
trigger
point
to
evaluate
whether
additional
reductions
are
necessary
to
provide
an
ample
margin
of
safety.
Commenter
0110
cited
the
legislative
history
of
the
1990
amendments
to
the
CAA
as
support
that
Congress
had
rejected
provisions
requiring
sources
to
meet
a
1­
in­
1­
million
standard.
According
to
commenter
0110,
EPA's
proposed
interpretation
of
6
section
112(
d)(
6)
of
requiring
successive
reviews
unless
sources
achieve
this
risk
level
implies
that
sources
must
meet
a
1­
in­
1­
million
standard
to
avoid
future
regulation,
and
if
Congress
had
intended
this
"
technology­
based"
downward
revision
of
the
standard,
there
would
have
been
no
need
for
section
112(
f).

Noting
that
EPA's
risk
estimates
are
upper
bound
estimates
that
likely
overstate
risks,
commenters
0108
and
0109
stated
that
a
"
bright
line"
approach
should
not
be
employed
under
section
112(
d)(
6)
any
more
than
it
should
be
employed
under
section
112(
f);
instead,
they
stated
that
EPA
should
make
determinations
of
whether
a
technology
review
is
necessary
on
a
case­
bycase
basis
for
each
category.

Commenter
0110
stated
that
section
112(
d)(
6)
should
be
more
appropriately
viewed
as
a
regulatory
backstop
authority,
similar
to
the
case­
by­
case
"
MACT
hammer"
provisions
of
section
112(
j),
to
ensure
that
available
advances
in
technology
will
be
applied
in
the
event
EPA
fails
to
issue
residual
risk
standards
under
section
112(
f).
The
commenter
stated
that
once
EPA
has
established
a
residual
risk
standard
under
section
112(
f)
that
is
"
acceptable"
or
"
safe"
and
protective
with
an
"
ample
margin
of
safety,"
then
it
must
find
that
a
separate
revision
of
the
MACT
standard
under
section
112(
d)(
6)
is
not
necessary.

Response:
We
agree
with
the
commenters
who
indicated
that
a
revision
is
not
necessarily
required
under
section
112(
d)(
6)
even
if
cancer
risks
are
greater
than
or
equal
to
1
in
1
million.
For
example,
it
may
be
the
case
that
a
technology
review
is
performed,
but
no
change
in
the
standard
results
from
that
review.
However,
we
disagree
with
the
commenters'
assertion
that
the
1­
in­
1­
million
risk
level
should
not
be
used
to
determine
the
need
for
a
subsequent
technology
review
under
section
112(
d)(
6)
of
the
CAA.
Section
112(
f)(
2)
of
the
CAA
sets
a
cancer
risk
cutoff
of
1
in
1
million
for
determining
whether
residual
risk
standards
must
be
promulgated.
If
individual
cancer
risks
for
the
source
category
fall
below
1
in
1
million,
no
further
risk
reductions
are
necessary
regardless
of
the
feasibility
or
costs
of
those
further
reductions.
In
the
preamble
to
the
residual
risk
rule
for
Coke
Ovens,
we
have
applied
a
similar
logic
to
the
need
for
subsequent
technology
reviews
under
section
112(
d)(
6).
As
we
stated
in
the
Coke
Ovens
rule,
if
the
ample
margin
of
safety
analysis
for
a
section
112(
f)
standard
shows
that
the
remaining
risk
for
non­
threshold
pollutants
falls
below
1
in
1
million
and
for
threshold
pollutants
falls
below
a
similar
threshold
of
safety,
then
no
further
revision
would
be
needed,
regardless
of
costs
and
feasibility,
because
an
ample
margin
of
safety
has
already
been
assured.

E.
Context
of
the
Residual
Risk
Program
Comment:
Commenter
0109
strongly
recommended
that
EPA
carefully
lay
out
the
context
and
framework
of
the
residual
risk
program
in
the
determination
for
each
source
category.
The
commenter
stated
that
this
was
especially
important
because
of
the
unique
nature
of
the
program
compared
to
other
EPA
programs
with
which
the
public
is
familiar.

The
commenter
specifically
recommended
that
EPA
mention
the
two­
stage
regulatory
process
(
MACT
and
residual
risk)
used
to
control
HAP
emissions
from
major
stationary
sources
and
to
determine
whether
the
MACT
technology
controls
provide
an
ample
margin
of
safety.
The
commenter
noted
that
the
residual
risk
program
is
different
from
other
EPA
programs,
in
7
that
additional
controls
will
be
necessary
for
only
some
of
the
listed
categories
of
sources,
because
in
some
cases,
the
cancer
risk
will
be
less
than
the
1­
in­
1­
million
trigger,
or,
if
it
is
greater,
EPA
may
determine
that
the
current
emission
level
provides
the
public
with
an
ample
margin
of
safety.

The
commenter
also
recommended
that
EPA
put
into
the
proper
context
the
relatively
small
contribution
of
major
stationary
sources
to
the
risks
from
air
toxics­­
about
11
percent
in
1999
and
expected
to
be
even
smaller
as
sources
come
into
compliance
with
the
latest
MACT
rules.

Finally,
the
commenter
recommended
that
EPA
present
the
risks
from
air
toxics
in
context
with
the
risks
from
ambient
(
criteria)
air
pollutants
to
make
clear
to
the
public
how
the
air
toxics
risk
estimates
are
much
more
conservative
and
to
avoid
any
misperceptions
by
the
public
that
the
risk
estimates
for
ambient
air
pollutants
are
comparable
to
the
risk
estimates
for
air
toxics.
Without
a
program
of
public
education
on
this
issue,
the
commenter
indicated
the
public
may
incorrectly
believe
that
the
ample
margin
of
safety
decisions
in
the
residual
risk
rules
are
less
stringent
than
EPA
knows
them
to
be,
resulting
in
public
lawsuits
against
EPA's
decisions
or
overregulation
by
EPA
to
compensate
for
the
gap
in
public
knowledge.
The
commenter
recommended
that
EPA
include
preamble
language
in
future
EPA
decisions
describing
the
criteria
it
used
to
determine
the
ample
margin
of
safety
and
presenting
the
incremental
risk/
incremental
cost
approach
in
the
fuller
context
for
the
residual
risk
program.

Response:
We
agree
that
it
is
important
to
provide
context
for
any
residual
risk
rule.
In
the
preamble
of
the
current
rule,
we
describe
the
MACT
program
and
its
impact
on
the
magnetic
tape
source
category.
We
also
describe
our
statutory
authority
and
our
obligations
to
assess
risks
to
human
health
and
the
environment
under
section
112(
f)
of
the
CAA,
as
well
as
the
requirement
to
further
regulate
categories
of
sources
if
any
of
the
estimated
individual
cancer
risks
exceed
the
statutory
trigger
level
of
1
in
1
million.

However,
while
we
agree
that,
on
a
national
average
basis,
population
risk
levels
are
dominated
by
the
impacts
of
mobile
source
emissions,
we
disagree
with
the
commenter's
contention
that
it
is
appropriate
to
draw
the
general
conclusion
that
all
major
stationary
sources
make
relatively
small
contributions
to
individual
risk
levels
in
their
neighborhoods.
Rather,
the
risks
posed
by
any
individual
major
stationary
source
depend
upon
a
number
of
factors,
including
emission
rates
at
the
source,
proximity
of
exposed
populations
to
the
emission
source,
the
specific
HAP
emitted,
local
meteorological
conditions,
and
terrain
conditions
surrounding
the
source.
Therefore,
the
relative
contribution
of
a
particular
major
stationary
source
to
overall
individual
risk
levels
in
its
vicinity
will
vary
dramatically
depending
on
the
local
conditions
at
and
around
that
specific
source.
This
variability
is
not
captured
by
the
national
average
contribution
of
major
sources
to
population
risk
levels
mentioned
by
the
commenter.

We
agree
that
our
risk
assessment
for
the
magnetic
tape
source
category
appropriately
contains
a
number
of
health­
protective
assumptions,
resulting
in
a
screening
assessment
that
is
designed
to
overestimate,
rather
than
underestimate,
risks.
The
results
demonstrate
negligible
risks
for
potential
chronic
cancer,
chronic
noncancer,
and
acute
noncancer
health
endpoints.
Also,
no
significant
human
health
multipathway
or
ecological
risks
were
identified.
Had
the
8
resulting
risks
been
determined
to
be
non­
negligible,
a
more
refined
analysis
with
site­
specific
data
would
have
been
conducted.
Such
an
assessment
would
be
more
data­
intensive;
however,
it
would
also
present
a
more
accurate
estimate
of
risks
which
could
then
be
used
as
the
basis
for
regulatory
action.
However,
since
the
findings
of
the
screening
risk
assessment
for
the
magnetic
tape
source
category
were
negative
(
i.
e.,
the
statutory
cancer
risk
trigger
level
was
not
exceeded),
it
was
not
necessary
to
conduct
a
more
refined
risk
assessment
using
more
site­
specific
data.
Since
these
activities
were
not
relevant
to
this
action,
a
complete
discussion
of
them
in
the
context
of
a
full
discussion
of
the
residual
risk
program
was
not
deemed
necessary
or
appropriate.
The
details
of
our
risk
assessment
can
be
found
in
the
docket
in
the
memo
titled,
"
Residual
Risk
Assessment
for
the
Magnetic
Tape
Manufacturing
Source
Category."

F.
IRIS
Data
for
Acrylonitrile
Comment:
According
to
commenter
EPA­
HQ­
OAR­
2003­
0161­
0111
(
hereafter
referred
to
as
commenter
0111),
EPA
should
not
have
relied
on
the
outdated
unit
cancer
risk
value
for
acrylonitrile
contained
in
EPA's
Integrated
Risk
Information
System
(
IRIS)
in
conducting
its
residual
risk
assessment
of
the
magnetic
tape
manufacturing
industry.
Although
EPA
concluded
that
there
were
no
issues
to
be
addressed
regarding
acrylonitrile
because
the
facility
emitting
acrylonitrile
presented
a
potential
cancer
risk
of
only
1
in
100
million,
the
commenter
stated
that
it
was
inappropriate
for
EPA
to
use
the
acrylonitrile
value
in
IRIS
in
its
assessment
because
EPA
was
already
aware
the
value
was
severely
out­
of­
date.
According
to
the
commenter,
the
IRIS
profile
itself
indicates
that
there
are
one
or
more
significant
new
studies
based
on
a
screeninglevel
review
of
the
more
recent
toxicology
literature.
The
commenter
also
noted
that
EPA
was
aware
that
numerous
new
studies
had
been
conducted
on
assessing
the
cancer
risk
from
acrylonitrile
because
its
staff
were
briefed
on
an
assessment
of
those
new
studies,
received
copies
of
the
assessment
report,
and
attended
a
peer
review
meeting
on
the
report.
The
commenter
also
noted
that
a
summary
of
the
cancer
assessment
was
published
in
October
2005.

Response:
We
agree
that
our
IRIS
assessment
for
acrylonitrile
does
not
consider
studies
published
after
1991,
and
we
are
currently
developing
an
assessment
that
includes
newer
information.
Our
staff
reviewed
the
assessment
described
(
and
funded)
by
the
commenter
and
concluded
that
it
does
not
conform
with
EPA
science
policy,
as
per
EPA's
Guidelines
for
Carcinogen
Risk
Assessment
(
EPA­
630/
P­
03­
001F),
in
three
ways.
First,
the
assessment
concludes
that
the
mode
of
action
is
nonlinear,
but
is
unable
to
identify
a
nonlinear
mechanism.
Second,
the
assessment
provides
a
supplemental
linear
unit
risk
value
but
bases
it
upon
animal
data
rather
than
human
data.
Third,
the
animal­
based
linear
value
was
not
documented
adequately
for
us
to
confirm
the
calculations.
Therefore,
we
conclude
that
the
current
IRIS
assessment
represents
the
best
available
science
at
this
time.