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:
Screening
Assessment
of
Central
Nervous
System
Hazardous
Air
Pollutants
from
Wood­
Fired
Industrial
Boilers
FROM:
Scott
Jenkins
Risk
and
Exposure
Assessment
Group
(
C404­
01)

TO:
Dave
Guinnup,
Leader
Risk
and
Exposure
Assessment
Group
(
C404­
01)

Background
The
EPA
performed
a
screening
assessment
to
evaluate
acute
and
chronic
non­
cancer
risks
due
to
emissions
of
central
nervous
system
(
CNS)
toxicants
from
uncontrolled
wood­
fired
industrial
boilers.
This
document
describes
the
results
of
that
screening
assessment.

Methods
The
present
analysis
utilized
the
SCREEN3
model
with
characteristic
defaults
where
data
were
not
available.
Engineering
judgement
was
used
to
develop
plant
parameters
(
Table
1)
and
emission
rates
(
Table
2)
for
three
different
sized
model
facilities
within
the
Large
Solid
Fuel
Fired
Boiler
subcategory.
ll
CNS
HAP
for
which
emission
rates
from
wood­
fired
boilers
are
available
were
evaluated.
he
range
of
predicted
HAP
concentrations
was
determined
by
using
the
plant
parameters
listed
in
table
1
and
the
emission
rates
listed
in
table
2.
Acute
and
chronic
toxicity
dose­
response
values
were
taken
from
the
EPA
Air
Toxics
website
(
http://
www.
epa.
gov/
ttn/
atw/
toxsource/
summary.
html)
as
of
10/
01/
2003.
For
HAP
with
more
than
one
acute
dose­
response
value,
the
most
health­
protective
was
chosen.
Health­
protective
assumptions
were
made
for
model
input
parameters
where
data
were
lacking.
The
rural
dispersion
option
was
chosen
and
the
emission
source
was
assumed
to
be
a
point
source.
The
default
ambient
air
temperature
(
293
K)
was
used
and
the
receptor
height
was
0
m.
The
full
worst­
case
meteorology
default
was
chosen.
Building
downwash
was
not
expected
to
be
significant
for
these
sources,
and
therefore
was
not
calculated.
Simple,
flat
terrain
was
assumed
and
the
automated
distance
option
was
chosen
with
measurement
points
between
100
m
and
50,000
m.
The
maximum
predicted
pollutant
concentration
occurred
beyond
100
m
for
all
three
model
facilities.
2
Table
1.
Plant
Parameters
Used
for
Screen3
Modeling
Parameter
Large
Facility
Parameters
Medium­
sized
Facility
Parameters
Small
Facility
Parameters
Stack
Height
(
m)
70
15
37.5
Stack
Diameter
(
m)
3.0
1.0
2.0
Stack
Gas
Exit
Velocity
(
m/
s)
8.5
22
13.6
Stack
Gas
Exit
Temp.
(
K)
485
425.5
425.5
Table
2.
Typical
Uncontrolled
HAP
Emission
Rates
(
g/
s)
HAP
Large
Facility
Medium
Facility
Small
Facility
Carbon
Disulfide
7.15E­
03
2.86E­
03
1.60E­
04
1,1,1­
Trichloroethane
8.94E­
04
3.58E­
04
2.00E­
05
Styrene
8.94E­
04
3.58E­
04
2.00E­
05
Tetrachloroethene
2.15E­
03
8.59E­
04
4.80E­
05
Xylenes
1.79E­
04
7.15E­
05
4.00E­
06
Toluene
2.46E­
02
9.84E­
03
5.50E­
04
Selenium
4.47E­
05
1.79E­
05
1.00E­
06
Mercury
8.94E­
05
3.58E­
05
2.00E­
06
Manganese
3.18E­
01
1.27E­
01
7.10E­
03
Results
Table
3
lists
the
maximum
predicted
acute
HAP
concentrations
and
their
corresponding
hazard
quotient
values
for
wood­
fired
plants.
Hazard
quotient
values
were
calculated
by
dividing
the
maximum
predicted
1­
hour
HAP
concentration
by
the
appropriate
dose­
response
value
(
see
methods).
The
maximum
acute
hazard
quotient
value
is
0.00003.

Table
3.
Predicted
Acute
HAP
concentrations
and
HQ
Values
HAP
Large
Facility
Max
Predicted
[
]
µ
g/
m3
Medium
Facility
Max
Predicted
[
]
µ
g/
m3
Small
Facility
Max
Predicted
[
]
µ
g/
m3
Dose­
Response
Values
µ
g/
m3
Large
Facility
HQ
Medium
Facility
HQ
Small
Facility
HQ
Carbon
Disulfide
1.90E­
02
3.77E­
02
7.84E­
04
3100
6.11E­
06
1.21E­
05
2.53E­
07
1,1,1­
Trichloroethane
2.37E­
03
4.71E­
03
9.80E­
05
11000
2.15E­
07
4.28E­
07
8.91E­
09
Styrene
2.37E­
03
4.71E­
03
9.80E­
05
21000
1.13E­
07
2.24E­
07
4.67E­
09
Tetrachloroethene
5.69E­
03
1.13E­
02
2.35E­
04
1400
4.06E­
06
8.07E­
06
1.68E­
07
Xylenes
4.74E­
04
9.42E­
04
1.96E­
05
4300
1.10E­
07
2.19E­
07
4.56E­
09
Toluene
6.52E­
02
1.29E­
01
2.69E­
03
3800
1.71E­
05
3.41E­
05
7.09E­
07
Selenium
1.18E­
04
2.35E­
04
4.90E­
06
100
1.18E­
06
2.35E­
06
4.90E­
08
Mercury
2.37E­
04
4.71E­
04
9.80E­
06
1000
2.37E­
07
4.71E­
07
9.80E­
09
Manganese
8.41E­
01
1.67E+
00
3.48E­
02
50000
1.68E­
05
3.34E­
05
6.96E­
07
3
Table
4
lists
the
maximum
predicted
chronic
HAP
concentrations
and
their
corresponding
hazard
quotient
values
for
wood­
fired
plants.
Hazard
quotient
values
were
calculated
by
dividing
the
maximum
predicted
chronic
HAP
concentration
by
the
RfC
or
other
appropriate
dose­
response
value.
The
hazard
quotient
for
manganese
is
the
only
hazard
quotient
that
exceeds
1.0.
All
other
hazard
quotients
are
insignificant.
A
total
hazard
index
was
calculated
by
summing
all
of
the
hazard
quotients.
The
total
hazard
index
values
are
1.4
(
large),
2.7
(
medium),
and
0.06
(
small).
Without
manganese,
the
hazard
index
values
fall
to
0.0002
(
large),
0.0005
(
medium),
and
0.000009
(
small).

Table
4.
Predicted
Chronic
HAP
Concentrations
and
HQ
Values
HAP
Large
Facility
Max
Predicted
[
]
µ
g/
m3
Medium
Facility
Max
Predicted
[
]
µ
g/
m3
Small
Facility
Max
Predicted
[
]
µ
g/
m3
Dose­
Respons
e
Values
Large
Facility
HQ
Medium
Facility
HQ
Small
Facility
HQ
Carbon
Disulfide
1.52E­
03
3.01E­
03
6.27E­
05
700
2.17E­
06
4.30E­
06
8.96E­
08
1,1,1­
Trichloroethane
1.90E­
04
3.77E­
04
7.84E­
06
1000
1.90E­
07
3.77E­
07
7.84E­
09
Styrene
1.90E­
04
3.77E­
04
7.84E­
06
1000
1.90E­
07
3.77E­
07
7.84E­
09
Tetrachloroethene
4.55E­
04
9.04E­
04
1.88E­
05
270
1.68E­
06
3.35E­
06
6.97E­
08
Xylenes
3.79E­
05
7.53E­
05
1.57E­
06
430
8.82E­
08
1.75E­
07
3.65E­
09
Toluene
5.21E­
03
1.04E­
02
2.16E­
04
400
1.30E­
05
2.59E­
05
5.39E­
07
Selenium
9.48E­
06
1.88E­
05
3.92E­
07
20
4.74E­
07
9.42E­
07
1.96E­
08
Mercury
1.90E­
05
3.77E­
05
7.84E­
07
0.09
2.11E­
04
4.18E­
04
8.71E­
06
Manganese
6.73E­
02
1.34E­
01
2.78E­
03
0.05
1.35E+
00
2.67E+
00
5.57E­
02
OAQPS:
ESD:
REAG:
SJenkins:
bmiles:
C404­
01:
2/
25/
04
4
