UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
OFFICE
OF
AIR
QUALITY
PLANNING
AND
STANDARDS
EMISSION
STANDARDS
DIVISION
RESEARCH
TRIANGLE
PARK,
NC
27711
February
25,
2004
MEMORANDUM
SUBJECT:
Development
of
Central
Nervous
System
and
Respiratory
System
Lookup
Tables
for
Industrial
Boilers
FROM:
Scott
Jenkins
Risk
and
Exposure
Assessment
Group
(
C404­
01)

TO:
David
E.
Guinnup,
Leader
Risk
and
Exposure
Assessment
Group
(
C404­
01)

Background:

The
EPA
has
developed
risk­
based
lookup
tables
for
emissions
of
central
nervous
system
toxicants
and
respiratory
toxicants
from
industrial
boilers.
The
present
draft
memo
describes
the
development
of
these
tables
and
how
facilities
might
utilize
them.

Methods:

Table
development:
The
lookup
tables
(
see
appendix)
are
based
on
the
SCREEN3
atmospheric
dispersion
model.
SCREEN3
is
a
screening­
level
Gaussian
dispersion
model
used
to
predict
worst­
case
1­
hour
concentrations
on
the
centerline
of
the
plume
downwind
from
a
source.
SCREEN3
calculates
the
ambient
concentration
per
g/
s
of
emissions
assuming
no
deposition
or
atmospheric
reactions.
Predicted
1­
hour
concentrations
from
SCREEN3
are
multiplied
by
0.08,
as
described
in
the
EPA
Air
Toxics
Risk
Assessment
Reference
Library,
to
derive
a
predicted
worst­
case
chronic
concentration
(
annual
average).
Engineering
judgment
was
used
to
develop
the
facility
parameters
that
formed
the
basis
for
the
lookup
tables
(
Table
1).
These
parameters
represent
approximate
averages
based
on
an
engineering
analysis
of
available
facility
data.
Stack
height
and
fenceline
distance
vary
in
the
tables.
SCREEN3
model
runs
were
conducted
using
worst­
case
meteorology
defaults
and
local
flat
terrain.

Table
1
Parameter
Value
Stack
Diameter
(
m)
2.0
Stack
Gas
Exit
Velocity
(
m/
s)
13.6
2
Stack
Gas
Exit
Temp.
(
K)
425.5
To
develop
the
respiratory
lookup
table,
SCREEN3
model
runs
were
conducted
for
each
combination
of
stack
height
and
fenceline
distance
to
determine
the
emission
rate
of
HCl
in
pounds
per
hour
which
would
result
in
a
maximum
hazard
quotient
(
HQ)
value
equal
to
1.0
outside
the
facility
area.
To
develop
the
CNS
table,
SCREEN3
model
runs
were
conducted
for
each
combination
of
stack
height
and
fenceline
distance
to
determine
the
emission
rate
of
manganese
in
pounds
per
hour
which
would
result
in
a
maximum
HQ
value
equal
to
1.0
outside
the
facility
area.

Application
of
the
Lookup
Tables:
To
use
the
respiratory
lookup
table
a
facility
would
estimate
the
emission
rates
of
HCl,
Cl2,
and/
or
any
other
respiratory
toxicants
to
be
included
in
the
assessment
and
then
calculate
a
toxicity­
weighted
emission
rate
expressed
in
equivalents
of
HCl
according
to
equation
1.

TWERHCl
=

(
ERi
x(
RfCHCl/
RfCi)
Eqn.
1
ERi
=
Emission
rate
of
pollutant
i,(
lb/
hr)

RfCi
=
Reference
concentration
for
pollutant
i,(
µ
g/
m3)

RfCHCl
=
Reference
concentration
for
HCl,(
µ
g/
m3)
TWERHCl
=
Toxicity­
weighted
emission
rate
expressed
in
HCl
equivalents,
(
lb/
hr)

Calculated
toxicity­
weighted
emission
rates
will
then
be
compared
to
the
allowable
toxicityweighted
emission
rate
in
the
table.
To
determine
the
correct
value
from
the
table,
a
source­
wide
average
value
could
be
used
for
stack
height
and
the
minimum
distance
between
any
stack
at
the
affected
source
and
the
property
boundary
could
be
used
for
fenceline
distance.

To
use
the
CNS
lookup
table
a
facility
would
estimate
the
emission
rates
of
Mn
and/
or
any
other
CNS
toxicants
to
be
included
in
the
assessment
and
then
calculate
a
toxicity­
weighted
emission
rate
expressed
in
equivalents
of
Mn
as
described
for
HCl
above.
Calculated
toxicity­
weighted
emission
rates
will
then
be
compared
to
the
allowable
toxicity­
weighted
emission
rate
in
the
table.
To
determine
the
correct
value
from
the
table,
a
source­
wide
average
value
could
be
used
for
stack
height
and
the
minimum
distance
between
any
stack
at
the
affected
source
and
the
property
boundary
could
be
used
for
fenceline
distance.

Attachment
OAQPS:
ESD:
REAG:
SJenkins:
bmiles:
x5648:
C404­
01:
2­
25­
04
Draft
Document
3
Appendix:
Allowable
toxicity­
weighted
emission
rate
expressed
in
HCl
equivalents
(
lbs/
hr)

fenceline
(
m)

Stack
ht.(
m)
50
100
150
200
250
500
1000
1500
2000
3000
5000
5
114.9
114.9
114.9
114.9
114.9
144.3
287.3
373.0
373.0
373.0
373.0
10
188.5
188.5
188.5
188.5
188.5
195.3
328.0
453.5
434.4
434.4
434.4
20
386.1
386.1
386.1
386.1
386.1
386.1
425.4
580.0
602.7
602.7
602.7
30
396.1
396.1
396.1
396.1
396.1
396.1
436.3
596.2
690.6
807.8
816.5
40
408.1
408.1
408.1
408.1
408.1
408.1
448.2
613.3
715.5
832.2
966.0
50
421.4
421.4
421.4
421.4
421.4
421.4
460.6
631.0
746.3
858.2
1002.8
60
435.5
435.5
435.5
435.5
435.5
435.5
473.4
649.0
778.6
885.0
1043.4
70
450.2
450.2
450.2
450.2
450.2
450.2
486.6
667.4
813.8
912.4
1087.4
80
465.5
465.5
465.5
465.5
465.5
465.5
500.0
685.9
849.8
940.9
1134.8
100
497.5
497.5
497.5
497.5
497.5
497.5
527.4
723.6
917.1
1001.2
1241.3
200
677.3
677.3
677.3
677.3
677.3
677.3
682.3
919.8
1167.1
1390.4
1924.6
Allowable
toxicity­
weighted
emission
rate
expressed
in
manganese
equivalents
(
lbs/
hr)

fenceline
(
m)

Stack
ht.(
m)
50
100
150
200
250
500
1000
1500
2000
3000
5000
5
0.29
0.29
0.29
0.29
0.29
0.36
0.72
0.93
0.93
0.93
0.93
10
0.47
0.47
0.47
0.47
0.47
0.49
0.82
1.13
1.09
1.09
1.09
20
0.97
0.97
0.97
0.97
0.97
0.97
1.06
1.45
1.51
1.51
1.51
30
0.99
0.99
0.99
0.99
0.99
0.99
1.09
1.49
1.73
2.02
2.04
40
1.02
1.02
1.02
1.02
1.02
1.02
1.12
1.53
1.79
2.08
2.42
50
1.05
1.05
1.05
1.05
1.05
1.05
1.15
1.58
1.87
2.15
2.51
60
1.09
1.09
1.09
1.09
1.09
1.09
1.18
1.62
1.95
2.21
2.61
70
1.13
1.13
1.13
1.13
1.13
1.13
1.22
1.67
2.03
2.28
2.72
80
1.16
1.16
1.16
1.16
1.16
1.16
1.25
1.71
2.12
2.35
2.84
100
1.24
1.24
1.24
1.24
1.24
1.24
1.32
1.81
2.29
2.50
3.10
200
1.69
1.69
1.69
1.69
1.69
1.69
1.71
2.30
2.92
3.48
4.81
Draft
Document
6
