United States
Environmental Protection
Agency
Industrial-Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-062 August 1982
Project Summary
Emissions and Residue
Values from Waste Disposal
During Wood Preserving
B. DaRos, R. Merrill, H. K. Willard, and C. D. Wolbach
Agency restrictions on the discharge
of wastewater generated during the
preservation of wood has resulted in
the increased use of evaporation
techniques for water removal by the
wood preserving industry. This report.
which further details the type of work
described in EPA report 600/2-81-
066 "Wood Preserving Industry Mul-
timedia Emission Inventory." dis-
cusses emissions and residues that
were measured during thermal (pan)
evaporation, spray pond evaporation.
and direct thermal destruction of
organic components in the wastewater.
The information presented includes
plant and evaporation device descrip-
tions, wastewater and residue handling
procedures, sampling and analytical
results, and conclusions and recom-
mendations. Also presented are quali-
tative descriptions of the fugitive
emissions and residues that occur
during normal processing operations.
It was concluded that toxic materials
are both emitted and disposed as
residues. This includes organic com-
pounds (phenols and polynuclear
aromatic hydrocarbons) that were
emitted to the atmosphere during
thermal (pan) evaporation. Similar
organic emissions from the spray
pond were below detectable levels.
Contrarily, solid residues from evapo-
rators had low concentrations of toxic
organic constituents while residues
in spray ponds contained much higher
levels than the feed wastewater.
Fugitive organic emissions from the
retort and vacuum vents were highly
concentrated although limited in
duration. Thermal destruction of
wastewater sludge by cofiring in an
industrial wood-fired boiler was 96.1
to 99.99+ percent complete for the
measured organics. Chlorinated dioxin
and furan components were measured
in both sludge and ash wastes, but
varied too much to determine removal
or generation rates.
Sludges produced from each process
contained a significant toxic organic
fraction. Waste sludge must be recy-
cled back to the process for reuse or
disposed in a manner cognizant of the
toxic components identified.
This Project Summary was devel-
oped by EPA's Industrial Environ-
mental Research Laboratory, Cincin-
nati, OH, to announce key findings of
the research project that is fully
documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
The wood preserving industry pri-
marily produces utility poles, railroad
ties, and construction materials, chem-
ically treated to enhance the useful
life—usually with creosote, penta-
chlorophenol (penta) or waterborne
salts. Conditioning and preserving the
wood generates a wastewater stream
of wood extracts and toxic preservative
components. To dispose of this waste in
accordance with Environmental Protec-
tion Agency (EPA) regulations, the
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industry generally discharges effluent
to POTWs or uses evaporation (thermal
or pan methods, cooling towers, and
solar and spray ponds) in conjunction
with oil/water separation and other in-
plant modifications. This report sum-
marizes the results of test programs to
quantify the release of organic species
1) from the pan evaporator treatment
system to the air, 2) of similar emissions
and residues to land from a spray pond
and 3) of emissions and ash from
preserving oil-laden wastewater dis-
posal in an industrial steam boiler.
Other residue discharges were also
characterized for these systems.
Conclusions
The results of this program confirmed
that the discharge of organic compounds
during wastewater evaporation in
thermal (pan) evaporates occurred and
in greater amounts than usually pre-
dicted. The toxic organic content of
wastewater charged to the evaporators
was many times higher than that of
similar wastewater reported in litera-
ture. Spray pond emissions were such
that the cryogenic sampling systems did
not yield enough sample material to
detect the low volatility components of
the wastewater if present. Therefore, of
the evaporation systems studied, therm-
al (pan) evaporation had the most emis-
sions and spray ponds the least. Solid
residues in spray ponds have much
higher concentrations of toxic organic
constituents while residues in evapor-
ators contained much lower concentra-
tions than the feed wastewater.
The destruction of the organic com-
pounds in an industrial steam boiler is a
viable disposal option. The system
tested accomplished a 96.1 to 99.99+
percent destruction efficiency of the
phenols and PNAs measured; certain
chlorinated dioxins and furans were
present in the preserving waste feed
and ash streams. No generation or
destruction efficiency could be deter-
mined for such dioxin or furan constit-
uents due to limited analytical reliability.
Industrywide, the air emissions from
onsite treatment of wastewater handling
had been estimated at <100 metric
tons/year, based on the reported mass
of volatile organic compounds contained
in wastewater requiring treatment.
However, PNAs and other aromatic
compounds were emitted at rates up to
12 kg/hr for the plant tested (which
uses two thermal evaporators). The
wide variation in pollutant releases (<2
to 11,300 g/hr and ~0 to 52,000 ppm)
within one day or less for individual
sources precludes establishing exact
mass emissions. Measured fugitive
emissions, although of high concentra-
tion, were apparently of relatively short
duration. Thus, although localized
emissions do occur, the wood preserving
industry in total does not emit as much
organic material as some other industry
segments. Table 1 presents a summary
of the organic materials discharged
from the evaporation devices.
Solid residues produced from each
process must be recycled back to the
process for reuse or disposed in a
manner cognizant of the toxic compo-
nents identified and quantified.
Recommendations
If evaporation technology is to be
employed, it must be recognized that
the thermal (pan) evaporation system is
an emitter of organic components to the
atmosphere and its minimal use would
lessen air emittants.
Regardless of the evaporator used,
care should be taken' to develop oil/
water separation techniques which
minimize oil and sludge carryover to the
evaporator. A program should be
conducted to establish the best available
separation systems or to develop meth-
ods to enhance the operation of existing
systems. Systems with potential ap-
plicability include chemical flocculation,
solvent extraction, biological pretreat-
ment, and land application. A pre-
liminary study (EPA-600/2-81-043)
has covered parts of the first three
mentioned treatments. Disposal of
residue from systems that minimized air
emissions must be accomplished by
modes (preferrably by reuse) that do not
adversely impact the land.
The destruction of wood preserving
wastes by cofiring in boilers can be
accomplished with minimal environ-
mental impacts. It is recommended that
industry pursue such disposal. Also a
program should be conducted to deter-
mine the proper injection (atomization)
methods, and the residence times and
temperatures necessary to satisfactorily
destroy the organics in the waste at
higher loadings. Such an incineration
study could productively be extended to
include the ash and a variety of sludges.
Further analysis of the most toxic bypro-
ducts (possibly furans) should be
extended for better speciation and
quantification of the chlorinated di-
benzodioxins and chlorinated dibenzo-
furans. Careful evaluation should be
conducted of the partitioning of these
organic components in ash, especially
where no baghouse is used.
Fugitive emission and residue studies
should be extended to include the
duration of emission or floyvrates and
extent of onsite land (qr subsoil)
contamination. Such information could
be utilized along with the existing
concentration values to quantify these
pollutant sources.
If further testing of very low level
emissions from ponds is undertaken, it
is recommended that surface emissions
be sampled separately from spray drift
sampling. Surface emissions can be
analyzed from samples of the air layer
above the surface. This air layer
contains all pollutants emitted if the
surface is enclosed by a film bubble that
excludes all surrounding air transfer.
Particle or aerosol drift can be better
sampled by a high volume collection
device.
Wood Preserving Program
Onsite Wastewater Disposal
by Evaporation
Excess wastewater is most easily
managed onsite by water removal
treatment. The practice of using evap-
oration to achieve water removal is
reviewed below as well as a model
which predicts pollutant losses associ-
ated with such practices. Results of a
program funded by EPA lERL-Ci and
reported as 600/2-81-066 indicated
that organic components of the wood
preserving wastewater could be dis-
charged to the air during evaporation. In
Table 1. Summary of Emissions and Residues of Organic Compounds*
Emission Emissions Residues
concentration rate concentration
Source (ppm or fig/g) g/hr yg/g
Thermal evaporator
Spray pond evaporation
Retort emissions/ residues
Vacuum vent emissions
36 to 1.500
<1
220 to 3.700
22.000 to 52.000
1.8 to 11.300
0 to 20.000
75
48,000
2.100 to 14,000
* Organic constituents include volatile and semivolatile (PNAs) compounds only.
Residues include only separately wasted material, not recycled streams.
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a mathematical expression developed
for the evaporation rate of these organic
chemical pollutants, diffusivity in-
creased as a function of increased
temperature, which would then drive
higher-molecular-weight compounds
out of solution. This evaporation model
applies to both solar ponds (quiescent
lagoons) and thermal (pan) heated
evaporators, and indicates emissions
from thermal evaporators should be
higher.
Thermal evaporators apply heat
directly to accelerate evaporation. The
wastewater is contained in a tank or
lined pond and heated by an external
source such as boiler steam, or by using
a cooling fluid to condense vapor from
the retort before recycling to the
evaporator
Another way to enhance evaporation
is to increase liquid surface area for
greater liquid-air contact. One such
device is a spray pond which isa lined or
unlined lagoon with a pumping system
and nozzles to spray the contained
wastewater. Less land is required for
evaporation of a given waste than is
needed for solar ponds. The evaporation
rate of organic compounds from sprayed
wastewater was estimated using the
equation for the evaporation rate of a
free-falling drop. Diffusivity and partial
pressure, as well as air resistance, were
included in the evaporation model that
applies to spray ponds and cooling
towers.
With cooling tower evaporation using
Boulton conditioning, wastewater is
condensed from the retort and sent
through an oil/water separator, and is
then added to the cooling water that
recirculates through the condenser and
cooling tower The waste heat promotes
evaporation. For processes without
Boulton conditioning, there is insuffi-
cient waste heat to evaporate the
wastewater generated. A field test at a
cooling tower site had found low-
molecular-weight compounds being
emitted to the atmosphere while non-
volatile organics remained in solution.
Another evaporation process used by
the industry is land irrigation. Waste-
water is sprayed onto a field and part of
the droplets evaporate, after which time
solar evaporation occurs as the water
percolates into the soil
Each of the wastewater treatment
processes described produces a residual
sludge. The amount of solid waste
material generated depends on the
treatment technologies employed. This
material is typically disposed of in
landfills (usually onsite if land is
available). Incineration of solid waste is
a very limited practice at preserving
plants.
Characterization of Chemical
Discharges from Thermal (Pan)
Evaporators
Field tests were conducted at a wood
preserving plant (Plant A) equipped for
thermal (pan) evaporation to determine
the organic residues and emissions
from two evaporators, one of which is
for wastewater containing penta and
the other for creosote wastes.
The plant used two treating cylinders
(one with penta, the other creosote) and
Boulton conditioning. Oil/water sep-
arators recovered oil for reuse, routing
the remaining wastewater to its respec-
tive evaporator. Steam was then pumped
through coils in the tanks to boil the
wastewater, driving off the water. Post
evaporation oil/preservative was re-
turned to the work tanks while a resi-
dual sludge was subsequently landf illed
in drums.
Source emission sampling was con-
ducted at the evaporator outlets; total
hydrocarbons and specific low-molecu-
lar-weight hydrocarbons were measured
at each emission point. The EPA Method
5 sampling train was used with XAD-2
resms for nonvolatile organics; volatile
organics were measured by field gas
chromatography (GC). Grab samples
also were taken of each evaporator's
contents, of the treating solutions,
penta in treating oil and creosote, and of
both fractions from each oil/water
separator.
Emissions concentrations were cal-
culated by dividing the amount of each
component collected in the resins by
the water volume in the impinger train
as water vapor was the major carrier
gas. Waste generation rates were
based on plant information and field
confirmed with measurements. Volume
emission rates were computed from the
rate of wastewater volume change in
each evaporator.
Because emission mass and concen-
trations reported for the field tests were
at times well above their predicted
levels, a new model for predicting
emissions was developed. In thermal
evaporation, the concentration of the
emitted specie varied in a cyclic pattern
depending on when in the evaporation
cycle the sample was taken. This was
modeled as a series of physical mech-
anisms, each dependent on the distri-
bution of the particular component in
the sludge, water, and oil.
The results of this study confirm that
all organic species analyzed in the
wastewater stream are emitted to the
atmosphere during pan evaporation.
The emissions rate of all organics
measured and of specific components is
highly variable and is cyclic (highest just
after charging) due to the once or twice-
a-day charging of the evaporators from
the oil/water separators. The rate of
emitted organics during the test period
varied from 11,300 to 1.8 g/hr for each
evaporator (see Table 2). Mass dis-
charges of organic material was not
time weighted with the exception of a
creosote charge. In that case, 65
percent of the daily charged organics
were emitted in 3 hours. The concentra-
ted residue consists of treating oil that
was recycled back to the working tanks
and a residual sludge (2 to 3 percent)
that contained toxic compounds.
Characterization of Chemical
Discharges from a Spray
Pond
Field tests were conducted at a wood
treating plant (Plant B) with a spray
pond to determine the organic emissions
from the pond, the resulting sludge, and
the wastewater input. The program
focused on determining if organic
emissions were discharged during
evaporation and if the transport mech-
anisms could be established. Cryogenic
sampling and resin trapping methods
also were compared.
The plant used two treating cylinders
(one with penta, the other with creosote)
and a closed steaming process. Individ-
ual oil/water separators, operated
manually, recovered the treating form-
ulation for reuse from each wastewater
stream. Creosote wastewater was
discharged directly into the spray pond,
but penta wastewater was treated
further by a three-zone gravity separator
and skimming device before discharge.
Sprays were operated 24 hr/day.
The field tests included sampling to
determine characteristic of the air
above the spray pond using cryogenic
and resin trapping methods, and taking
grab samples of pond wastewater and
sludge.
Toxic organic constituents contained
in the wastewater discharged into the
pond became concentrated in the
bottom sludge layer. Concentrations of
penta and PNAs evidently decreased in
the pond liquid layer as they were far
below the influent levels. Ultimate
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Table2. Loading and Emitted Organic Compounds: PNAs, Penta 3 Phenol
Combined
Process Unit Creosote Penta Industry Average
Evaporator Evaporator Wastewater**
Flow (g/hr) (g/hr) (g/hr)
Average hourly rate
fed to evaporators
130
2,300
21
Exhaust emissions
rates measures
minimum
maximum
other sample
140
1,100*
960*
1.8
1 1.300*
8.0
* Measurements taken shortly after new charge addition.
**Value based on EPA-EGD data on wastewater requiring disposal by evaporation or
equivalent.
sludge disposal was not monitored, but
is anticipated to be affected after
several years.
Emission rates could not be deter-
mined due to the detection limits of the
sampling and analytical methodology.
Although the system used is currently
the best way to determine organic
emissions from surface waters, the
sampling system's limited volume and
location (above surface) combined with
low pond evaporation rates prevented
the detection of low and medium
volatile compounds.
Characterization of Chemical
Discharges from Cofiring
Wastes in a Boiler
Field tests were conducted at a wood
preserving facility (Plant C) using a 18
kg/hr pile-burning watertube boiler to
cofire wood waste and penta/creosote
wastewater. To determine the destruc-
tion and removal efficiencies of organic
compounds in the wastewater, inputs
(wood waste and sludge) and output
(hopper ash, baghouse ash, bottom ash,
and stack gases) were analyzed. Data
for a material balance evaluation was
collected.
The facility used six retorts and a
steaming process to treat wood with
penta, creosote, or waterborne pre-
servatives. Individual oil/water sepa-
rators handled wastewater from each
treating process, recovering the pre-
servative fraction for reuse. The remain-
ing wastewater and sludge was routed
to a storage tank until enough had
accumulated to be fired in the steam
boiler. The boiler, consisting of a
furnace and auxiliary cell, was fueled
using two metering bins and a contin-
uously operating screw conveyor. Fuel
is stored in either a wet or dry wood fuel
silo, or on a waste wood slab pile.
The field tests included a preliminary
characterization of the gas stream,
isokinetic source sampling of the flue
gas, determination of total hydrocarbons
and specific low-molecular-weight
hydrocarbons, composite sampling of
the bottom ash, hopper ash and waste-
water sludge, and grab samples of the
baghouse ash, treating penta in oil, and
bulk treating creosote. The EPA Method
5 sampling train was used with XAD-2
resins for nonvolatile organics. A field
GC was used to determine volatile
emissions.
Air emission rates and ash estimates
for naphthalene and phenol are sum-
marized in Table 3. Other components
were not detected in air emissions.
Based on these emissions, destruction
efficiencies of 96.1 to 99.99+ percent
were calculated.
Due to the high toxicity of some
isomers, analyses for chlorodibenzo-
furans (CDF) and chlorodibenzodioxins
(CDD) were undertaken. No CDF or CDD
were detected in the air emissions. Ash,
sludge, and penta in oil samples were
analyzed by three laboratories using
split samples. Both CDFs and CDDs
were found in the treating penta
solution, waste sludge and the ash.
Although these materials were detected,
the quantities measured were not
consistent and evidently depended on
the analyzing laboratory's procedure.
Extraction and cleanup procedures
were quite different between the labs
as were spiked sample recovery and
detection limits. Unfortunately the
toxicity of CDDs and CDFs are quite
isomer specific while the results
reported do not contain isomer data that
is clearly independent of contamination
and also reproducible. In terms of
specific monomers, TCDDs are evidently
generated in the process while OCDDs
are reduced. The highly toxic isomer 2,
3, 7, 8-TCDD has not conclusively been
demonstrated as present and apparently
is not in ash samples. Values determined
are in the range reported for combustion
ash and especially of wood preserving
waste ash from other sources (see Table
4). Measurements of Mono-CDD, Di-
CDD, and Tri-CDD monomers are
significant as this is only the second
time combustion source measurements
have had positive values reported. Table
4 contains typical data for the three
laboratories.
Evaluation of Fugitive
Emission and Residue
Sources
Fugitive emissions measured were
cylinder spillage and vapors released
during unloading/charging operations,
emissions from valves, fittings during
transfer or preservative formulation, or
open vessels, and vacuum vent exhaust
during the treating cycles. These
sources also are close to employee work
areas. Air samples were collected
directly above the access doors during
unloading/charging using EPA Method
5 and XAD-2 cartridges; the fugitive
emissions released appeared as a dense
white plume. Emissions from preserv-
ative transport on the plant site were not
tested.
Fugitive residues measured included
treating liquid spillage and deposition.
Samples of accumulated spillage were
collected directly falling from the access
doors of the penta and creosote treating
cylinders.
Emissions resulting from pressure
release and vacuum exhaust during the
treating process were characterized.
Grab samples from a vacuum vent
common to both penta and creosote
treating cylinders were analyzed onsite
for total hydrocarbons; Table 1 sum-
marizes these and other hydrocarbon
results. The grab samples also were
tested for low-molecular-weight hydro-
carbons—benzene, toluene, and ethyl-
benzene. Significant concentrations of
organic compounds were found to be
emitted, and the vacuum vent was
determined as the greatest fugitive air
emission source with rates varying from
0 to 360 g/min of organics. The most
significant solid fugitive discharges
were retort drippings and spray pond
residues.
The final disposal of residues which
accumulate in treatment lagoons,
holding ponds or tanks depends on site
specific management practices. When
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Table3. Rates of Discharge and Efficiency of Destruction for Naphthalene and Phenol
Test 2
Naphthalene
Phenol
Solid rate
Test 3
Naphthalene
Phenol
Solid rate
Test 4
Naphthalene
Phenol
Solid rate
Feed
(g/sec)
0.10
0.10
79
0.08
0.08
79
0.05
0.11
79
Bottom ash
(g/sec)
>5 x W5
>5 x 70-7
>5
>9 x iO's
>4 x /CT6
>5
>4.8 x 70~5
>3 x 70~6
>5
Mech. hop.
(g/sec)
>J >
>7 *
>70
>7.7
>7 >
>70
>2.2
>7 >
>70
: 70""
: 70~6
x 70~4
'• 10'6
x 70~5
= 70~6
Baghouse
(g/sec)
>5>
>2.5
>5
>1.9
c 70~5
x 70~9
x 70"5
>7 x 70"6
>5
>2.5
>7.5
>5
x W'5
x 7CT6
Gas
(g/sec)
3.9 x 70~3
2.9 x ;o~5
re.ssr
7 x /o'3
>7.9 x 70"5
(6,85)*
1.10* W'3
1 6 x 70"5
P. or
Total out
(g/sec)
3.9x 70~3
2.9 x /O"5
7 x ;o~3
>2 x 70"5
7. 7 x 70~3
7.6x 70'5
Efficiency
(percent)
96.1
99.97
98.7
>99.99
97.8
99.99
Assumptions: Feedrate, all cases=79 g/sec sludge; ash quantity is 5 g/sec total, but some unburned organics were observed in
the mechanical hopper thus >10g is used.
*Sm3/sec (23°C and 1 atm).
Table 4. CDD Values in Penta and Ash Reported from Combustion Sources
Reporting source
This project (Plant A)
Ash
Lab A (d-2)
Lab A (d-3)
Lab A (d-4)
Lab C (d-2)
Bottom ash
Baghouse (fly)
Treating Solution
Lab A
LabB
Multiple sources wood
preserving waste ash
Lab combustion of
penta (smoke)
Lab combustion of
penta, 2, 4, 6 tri-.
and 2, 3. 4, 6-tetra-
chlorophenol (ash)
Oil combustion (Swiss)
TCDD
4
.8
3.3
10
960
1.1
i*
5.2
17
100
PCDD
32
2.6
6
20
1.400
33.
i
14 '
58
160
HiCDD
81
8.7
10
40
2,000
570
1,540
9-27
56
74
180
HpCDD
(U9/9)
117
42
4
100
640
260
17,000
90-135
172
18
130
OCDD
198
96
1
140
210
4,000
>1 7.000
575-2,510
710
6
40
TCDD
CDD
.009
.005
.10
.032
.18
.0002
small
0
.005
.1
.16
OCDD
CDD
.45
.61
.032
.45
.04
.82
>.5
.8:9
.74
.035
.066
*i = Interference precludes determining values
the equipment is part of the processing
plant, the accumulated material is
recycled if possible. On the other hand,
holding lagoons and spray ponds may be
cleaned only occasionally or else
residue may accumulate until the
lagoon is bypassed by some alternative
device. In the latter case, residues may
require removal to prevent impacting
future land use. For the field sites
surveyed, Plants A and C currently
transfer residual sludge or ash to onsite
landfills by direct hauling. Plant B's
residue impacts the environment as a
continuous minor land application is
effected indirectly through lagoon
bottom buildup. The character of this
material is presented in Table 5. Plant A
had a similar practice that was aban-
doned for evaporation.
The high values of spray pond
components in Table 5 indicate that
incoming waste eventually decreases in
concentration while the bottom sludge
increases. Higher molecular weight
organics are not emitted very rapidly at
low temperatures. Thus it is assumed
that toxic organics settle onto the
lagoon bottom and remain therefor some
period of time. Residues are thereby
slowly transferred to land, albeit with
undocumented environmental effects.
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Table 5. Characterization of wood preserving solid residues (concentrations in g/g)
Sample location
Cylinder
Spillage and Dnppage
Pan Evaporator Sludge
Evaporation Pond
Incineration Ash
Compound
Pentachlorophenol
Phenol
Fluoranthene
Naphthalene
Benzo(a)anthracene
Benzo(a)pyrene
Benzofluoranthenes
Chrysene
A cenaphthylene
Anthracene
Benzol g. h, ijperylene
Fluorene
Phenanthrene
Dibenzo(a,h)anthracene
lndeno(1.2,3-c,d)pyren
Pyrene
Benzene
Toluene
Ethylbenzene
Other PNAs
COO
CDF
*Not detectable.
** Abandon pond.
Penta
treating
1,800
<10
JOS
125
70
28
40
68
13
51
>40
125
235
<10
<10
82
0.1
0.3
<0.3
Creosote
treating
1,100
<20
310
1.350
940
220
600
780
126
1,350
40
1,850
2.150
20
50
1,000
7
<1
<1
Penta
treating
620
1.2
2.0
1.1
0.5
.05
0.2
0.4
.05
.5
.1
3
3.1
2.5
*
*
3.4
#
0.7
#
1.8
6.9
*
*
1.4
O.3
—
—
Bottom
ash
0.5
0.8
36
12
2.8
0.5
3.4
0.7
2.5
1.9
—
0.5
19
—
—
—
Mechanical
hopper ash
2.7
0.1
0.9
6
0.1
0.1
0.1
0.2
0.1
0.1
—
0.1
0.5
—
—
—
0.4-2.3
0.1-1.1
B. DaRos, R. Merrill. H. K. Willard, and C. D. Wolbach are with Acurex Corp.,
Mountain View, CA 94042.
Donald Wilson is the EPA Project Officer (see below).
The complete report, entitled "Emissions and Residue Values from Waste
Disposal During Wood Preserving." (Order No. PB 82-234 246; Cost: $19.50.
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
OUSGPO: 1982 — 559-092/0496
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Center for Environmental Research
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