United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-98/072 September 1998
Project Summary
Field Demonstration of Lead
Paint Abatement
Technologies in Residential
Housing
A study was conducted to demon-
strate lead-based paint (LBP) removal
from architectural wood components
in unoccupied residential housing us-
ing four technologies: granulated car-
bon dioxide (CO2) blasting, pelletized
CO2 blasting, encapsulant paint re-
mover, and wet abrasive blasting with
an engineered abrasive. The three
former technologies were demonstrated
on interior components, the latter on
exterior components. An X-ray fluores-
cence (XRF) spectrum analyzer (K-shell)
was used to quantify the change in
lead levels on the substrate before and
after paint removal. Inductively-coupled
plasma atomic emission spectroscopy
(ICP-AES) was used to quantify the
change in lead levels of airborne par-
ticulate and settled dust wipe samples
before and after paint removal. Aero-
dynamic particle size distributions of
lead paniculate were measured using
a multistage personal cascade impac-
tor.
The paint removal effectiveness of
the encapsulant paint remover and wet
abrasive blasting technologies were
comparable with overall residual lead
levels below the U.S. Housing and Ur-
ban Development (HUD) Guideline (1
mg/cm2); both technologies removed
the paint to bare substrate with no ap-
parent damage (minimal sanding prior
to painting) to the underlying substrate.
The estimated paint removal rate and
abatement cost were 10.3 and 134 ft2/
hour and $1.90 and $2.24/ft2, respec-
tively. The CO2 technologies yielded re-
sidual paint levels of >5 mg/cm2 and
rendered the substrate nonuseable for
its intended purpose. Although the air-
borne particulate and settled dust lev-
els varied with LBP abatement
technology, the encapsulant paint re-
mover technology consistently showed
the lowest levels.
This Project Summary was developed
by EPA's National Risk Management
Research Laboratory, Cincinnati, 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 Lead-Based Paint Poisoning Pre-
vention Act of 1971, as amended by the
Housing and Community Development Act
of 1987, established 1.0 milligram of lead
per square centimeter of surface area (mg/
cm2) as the federal threshold requiring
abatement of LBP on architectural com-
ponents in public and Indian housing de-
velopments nationwide. The Residential
Lead-Based Paint Hazard Reduction Act
of 1992 (commonly referred to as "Title
X") mandated the evaluation and reduc-
tion of LBP hazards in the nation's exist-
ing housing. Title X also established 0.5%
lead by weight as an alternative to the 1.0
mg/cm2 threshold.
Objectives
The overall objective of this study was
to demonstrate LBP removal from archi-
tectural wood components in unoccupied
residential housing using four technolo-
gies: (1) granulated carbon dioxide blast-
ing, (2) pelletized carbon dioxide blasting,
(3) encapsulant remover paint system, and
(4) wet abrasive blasting with an "engi-
neered abrasive."
Study Design
The study was conducted in unoccu-
pied single-family and two-family residen-
tial housing units in the City of Buffalo,
NY. Although the housing units were not
randomly selected, they did include differ-
ent housing components (e.g., baseboards,
door and window moldings), paint thick-
nesses, and lead levels. Each technology
was evaluated two or three times during a
Printed on Recycled Paper
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one-week period (depending on the logis-
tical and technical problems experienced).
Technologies Evaluated
Granulated and Palletized CO2 Blast-
Ing—-The granulated and pelletized CO2
blasting technologies are manufactured by
Alpheus Cleaning Technologies Corpora-
tion and by Cold-Jet Incorporated, respec-
tively. Although the technologies are similar
In principle, primary differences between
them are the size, density, and applica-
tion feed rate of the carbon dioxide blast-
ing media. One other primary difference is
that the Alpheus technology uses block
dry ice, which is shaved to create a fine,
crystalline blasting medium, whereas the
Cold-Jet technology uses uniform pellets.
The mechanism responsible for removal
of the paint coating is a combination of
several operations. First is the mechani-
cal abrasion caused by the movement of
one solid material against another. The
second is spalling of the material surface
that is caused by the rapid expansion of
the CO2 during sublimation. The third is
thermal fracturing where the significant
thermal differential between the substrate
and surface material causes these materi-
als to expand and contract at different
rates, resulting in fracturing of the coating.
Encapsulant Paint Remover Technol-
ogy—-The encapsulant paint remover is
manufactured by Kwick Kleen Industrial
Solvents, Inc. The spray-applied encap-
sulant paint remover is a two-part liquid
system consisting of potassium hydroxide
(13.2% by wt. in water) and a proprietary
polymer (9% by wt. in water).
The solutions are sprayed with an ap-
plicator gun that employs an external mix-
ing technique. The applicator gun facilitates
a flat spray pattern for uniform coverage
of the surface. The dwell or residence
time of the solution is dependent upon the
number of layers of paint, temperature,
and other environmental conditions. In the
present study, the dwell time was approxi-
mately 2 hours for the first application of
the encapsulant paint remover, and 1 hour
for each additional application. After the
paint is absorbed into the remover matrix,
the paint remover material is removed from
the surface with a putty knife. The encap-
sulant paint remover is reapplied if visible
paint remains on the surface. Following
removal of the paint remover waste, a
vacuum device equipped with a low-pres-
sure/low-volume sprayer is used to rinse
the surface with a trisodium phosphate
solution. The surface is then sprayed with
a "weak" acidic solution to neutralize wood
substrate.
Wet Abrasive Blasting with Chemical
Stabilizer Technology—This technology,
Turbo® Wet Abrasive Blasting System, is
manufactured by Keizer Technologies
Americas, Inc. The system uses conven-
tional blasting abrasives mixed with water
(80% abrasive to 20% water) in a pres-
sure vessel. The system combines an
abrasive medium and water to create a
slurry-mixture that is fed to a blast nozzle
much like a conventional blasting system.
In concept it both reduces the heat gener-
ated by friction and is a cohesive bond for
the dust created by the blasting process.
The paint coating is removed by the ki-
netic energy/mechanical abrasion of the
blast media striking the surface.
A chemical stabilizer, Blastox®, is added
at a 15 to 25% mixture to the abrasive/
water media prior to blasting of the sur-
face to create an "engineered abrasive."
Blastox®, manufactured by TDJ Group,
Inc., is a di- and tri-calcium silicate-based
material similar in chemical composition
to Type I cement. This calcium-silicate-
based material and lead in the paint waste
react to chemically stabilize the leachable
lead as lead silicate with stabilization
mechanisms similar to those of Portland
cement. Chemical substitution reactions
and physical encapsulation of the waste
are the two stabilization mechanisms that
reportedly render the lead nonleachable
based on EPA's Toxicity Characteristic
Leaching Procedure (TCLP).
Selection of Housing Units
A lead-based paint prescreening survey
was conducted among a pool of residen-
tial housing units in Buffalo, NY. The hous-
ing units selected for this study met the
following criteria:
1. Each housing unit had a minimum
lead-in-paint level of 2.0 mg/cm2
(arithmetic average of greater than
6.0 mg/cm2) on all components tar-
geted for paint removal. This level
exceeds the upper limit (1.3 mg/
cm2) of the inconclusive range for
the XRF instrument used during this
study.
2. Housing units for selected interior
lead paint removals had similar
properties including: chronological
age; architectural structure; aver-
age levels of lead in paint; and
amounts (i.e., square feet) and
types of building components tar-
geted for paint removal.
Sampling and Analytical
Methods
Thickness of Dry Paint Film
The measurement of dry film thickness
of the paint was made in accordance with
ASTM Method D 4138 - 88.
Lead in Paint Film
A SCITEC Corporation MAP-3 X-ray
fluorescence (XRF) spectrum analyzer was
used to determine the mass of lead per
unit area of painted substrate reported as
milligrams of lead per square centimeter
of surface (mg/cm2). The typical linear op-
erational range for the MAP-3 XRF is 0.2
to 10 mg lead/cm2 for the K-shell x-ray.1
The K-shell (or high-energy X-ray emis-
sion) was used for the measurements be-
cause it allows measurement of lead in
the deeper layers of multilayered paint.1
An evaluation of MAP-3 instruments, us-
ing a 15-second nominal reading time,
showed that the K-shell measured lead
levels with low bias on wood substrates,
provided that substrate correction was
used.2 The XRF measurements were made
using a single nominal reading time of 15
seconds. The inconclusive range of the
MAP-3 XRF instrument is <0.9 to >1.3
mg/cm2 (wood substrates).
The MAP-3 XRF instrument was cali-
brated and a fresh radioactive source (40
mCi Co57) was installed within 1 month
prior to use of the instrument. The manu-
facturer calibrated the instrument using
standard reference natural paint films
(SRM 2579) developed by MIST. Five con-
centration ranges were used 0.0001 to
3.53 mg lead/cm2. Because most of the
lead concentrations measured in the paint
film before paint removal exceed the maxi-
mum calibration standard, the correspond-
ing XRF measurements should be
interpreted as approximate or minimum
values.
Lead in Settled Dust
Wet wipe samples for settled lead-con-
taminated dust were collected in accor-
dance with the sampling procedures
specified in the HUD Guidelines3. The
samples were prepared for analysis in ac-
cordance with EPA SW-846 Method 3050
and analyzed by ICP-AES in accordance
with EPA SW-846 Method 6010.
Lead in Airborne Particulate
Personal Breathing Zone Samples—Per-
sonal breathing zone and work area air
samples were collected during each tech-
nology demonstration. The samples were
collected and prepared for analysis by ICP-
AES in accordance with NIOSH Method
7300.
Lead Particulate Aerodynamic Particle
Size Distribution—An 8-stage Marple Per-
sonal Cascade Impactor (Model 298) was
used to determine the aerodynamic par-
ticle size distribution of the lead particu-
late generated during each technology
demonstration. The samples were col-
lected and prepared for analysis by ICP-
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AES in accordance with NIOSH Method
7300.
Lead in Paint Chips
The paint chip samples were collected
from the substrate before paint removal in
accordance with the sampling procedures
specified in the HUD Guidelines.3 The
samples were prepared for analysis in ac-
cordance with EPA SW-846 Method 3050
and analyzed by ICP-AES in accordance
with EPA SW-846 Method 6010.
Lead in Soil
The samples were collected from the
perimeter of the housing units both before
and after the wet abrasive blasting tech-
nology in accordance with the sampling
procedures specified in the HUD Guide-
lines3. The samples were prepared for
analysis in accordance with EPA SW-846
Method 3050 and analyzed by ICP-AES
in accordance with EPA SW-846 Method
6010.
Wet Abrasive Blasting Debris
Single samples of the wet abrasive blast-
ing debris from the exterior lead abate-
ment demonstration were collected to
determine the leachable lead based on
TCLP. The samples were extracted in ac-
cordance with EPA SW-846 Method 1311
and digested in accordance with EPA SW-
846 Method 3015. The samples were then
analyzed in accordance with EPA SW-
846 Method 6010.
Statistical Methods
XRF Measurements and Lead in
Settled Dust, Air, and Soil
The relative change in lead concentra-
tion on the sampled building components
was measured by the ratio of the lead
concentration before paint removal to the
concentration after paint removal. This ra-
tio was calculated for each pair of before
and after measurements. These ratios
were then compared by taking the natural
logarithm and comparing the averages by
standard analysis of variance (ANOVA)
techniques.
XRF lead concentrations before and af-
ter paint removal were compared by using
a 2-factor ANOVA with Site and Room,
nested within Site, as the experimental
factors. The relative decrease in lead con-
centration was tested by calculating a 95%
confidence interval for the mean lead con-
centration before paint removal as a pro-
portion of the lead concentration after
removal.
Lead concentrations in settled dust be-
fore and after paint removal were com-
pared by using a 3-factor ANOVA with
Site, Room nested within Site,; and Loca-
tion (floor, wall) as the experimental fac-
tors. The relative increase in surface lead
concentration was tested by calculating a
95% confidence interval for the mean lead
concentration after paint removal as a pro-
portion of the lead concentration before
removal.
Airborne lead concentrations before and
during paint removal were compared by
using a 1-factor ANOVA with Site as the
experimental factor. The relative increase
in airborne lead concentration was tested
by calculating a 95% confidence interval
for the mean lead concentration during
paint removal as a proportion of the air-
borne lead concentration before removal.
Lead concentrations in the soil before
and after paint removal were compared
by using a one-factor ANOVA with Site as
the experimental factor. The relative in-
crease in lead concentration was tested
by calculating a 95% confidence interval
for the mean lead concentration after paint
removal as a proportion of the lead con-
centration before removal.
Results and Discussions
Encapsulant Paint Remover
Technology
Effectiveness of Paint Removal (XRF
Measurements)—Tablel presents descrip-
tive statistics for the XRF measurements
collected before and after paint removal
at each site. The encapsulant paint re-
mover system effectively removed the paint
to bare substrate with no apparent dam-
age, yielding a substrate that required little
preparation before painting. The average
paint removal rate was 10.3 ft2/hr (range 8
to 13ft2/hr).
The ANOVA results show that the mag-
nitude of the decrease in lead concentra-
tion on the sampled components varied
significantly by site (p=0.0122). Sites 4
and 5 showed similar decreases, whereas
the decrease at Site 3 was approximately
2 times higher than at Sites 4 and 5. This
is due primarily to the higher concentra-
tions of lead before paint removal at Site
3. Residual levels of lead contamination
after removal were essentially the same
at all three sites. The ANOVA results fur-
ther showed that the variation between
the rooms within each site was not statis-
tically significant (p=0.4496).
8-hr TWA Exposure Concentrations—
The 8-hr TWA exposure concentrations of
lead measured on the technology opera-
tor and helper ranged from 0.16 to 4.1 u.g/
m3. None of the calculated 8- hr TWA
concentrations exceeded the OSHA Ac-
tion Level of 30 u,g/m3.
Wet Abrasive Blasting
Technology
Effectiveness of Paint Removal (XRF
Measurements)—Table 2 presents de-
scriptive statistics for the XRF measure-
ments collected before and after paint
removal at each site. The wet abrasive
blasting paint remover technology effec-
tively removed the paint to bare substrate
with no apparent damage to the underly-
ing substrate. Thus, a substrate was pro-
duced that required little preparation before
painting (i.e., light sanding prior to paint-
ing. The average paint removal rate was
134 ft2/hr (range 133 to 135 ft2hr).
The ANOVA results show that the mag-
nitude of the decrease in lead concentra-
Table 1. XRF Measurements (K-Shell) Collected Before and After Paint Removal Using Encapsulant
Paint Remover
Site
No.
Lead Concentration (ma/cm2)
Mean
Minimum
Maximum
Before Paint Removal
3 64
4 64
5 32
Overall 160
14.7
9.6
9.2
11.3
7.2
4.2
6.1
4.2
26.9
16.6
18.9
26.9
After Paint Removal
3
4
5
Overall
64
64
32
160
0.7
1.1
0.8
0.8
ND"
ND
ND
ND
4.2
9.5
6.7
9.5
a Denotes that the XRF reading was < 0 after substrate correction.
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Table 2. XRF Measurements Collected Before and After Paint Removal Using Wet Abrasive Blasting
Technology
Site
No.
Lead Concentration (mg/cm2)
Mean
Minimum
Maximum
Before Paint Removal
8 64
9
Overall
64
128
20.4
8.2
14.3
0.7
2.5
0.7
43.0
20.7
43.0
After Paint Removal
8
9
Overall
64
64
128
0.8
1.0
0.93
NDa
ND
ND
3.0
2.5
3.0
* Denotes that the XRF reading was z 0 after substrate correction.
tion on the wood siding varied significantly
by site (p=0.0062). Specifically, the de-
crease in lead concentration after paint
removal at Site 8 was approximately 3
times greater than at Site 9. This is due
primarily to the higher lead concentrations
before removal at Site 8. Residual levels
of lead contamination after removal were
essentially the same at both sites. The
ANOVA results further showed that the
variability between areas within each site
was statistically significant (p=0.0561).
Figure 1 shows the differential particle
size distribution based on the lead par-
ticulate aerodynamic measurement using
the multistage cascade impactor. This
graph provides the lead particle mass con-
centration AC,) in each particle-size band
versus the geometric mean diameter
(GMDj), where GMDi = VD, x DM. The lead
particulate generated by the wet abrasive
blasting paint removal technology covers
a wide-size spectrum, where the larger
particles account for the greatest mass of
lead. The corresponding cumulative par-
ticle size distribution was determined by
preparing a log-probability plot of the par-
ticle size cut-point (Dp) versus the cumula-
tive percent of mass (mg/m3) less than the
Dp. The distribution of sample weights ap-
peared to approximate a lognormal distri-
bution with a mass median diameter
(MMD) of 15 u.m. That is, 50% of the
particle mass is borne by particles larger
than 50 urn. The calculated geometric stan-
dard deviation (GSD) was 6.3.
100
0.01
0.4 0.7 1.3 2.6 4.6 7.7 12 18 32
Particle Geometric Mean Diametewr (jim)
Figure 1. Differential particle size distribution for lead particulate generated during wet abrasive
blasting.
The 8-hr TWA exposure concentrations
of lead measured on the technology op-
erator and helper ranged from 171 to 198
u.g/m3. All of the calculated 8-hr TWA ex-
posure concentrations exceed both the
OSHA Action Level of 30 u.g/m3 and Per-
missible Exposure Limit of 50 u,g/m3, 8-hr
TWA.
TCLP Analyses of Blasted Debris—The
samples of the Blastox® debris collected
at Site 8 showed that the maximum con-
centration of lead (range 0.1 to 4.7 mg/L)
for the Toxicity Characteristic by TCLP
did not exceed the regulatory limit of 5.0
mg/L (40 CFR 261). The samples col-
lected at Site 9 showed lead concentra-
tions (26 to 33 mg/L) above 5.0 mg/L. The
results at Site 9 are inconsistent with pre-
vious TCLP analysis of Blastox® debris
from paint removal.4
Granulated and Palletized CO2
Blasting Technologies
Effectiveness of Paint Removal—Both
the granulated and pelletized CO2 blasting
technologies sporadically removed the
paint to base substrate, but they also
caused significant abrasion of the wood
substrate. That is, the underlying substrate
was textured and gouged. This condition
would render the abated substrate nonre-
usable as an architectural building com-
ponent.
Cost Analysis
A cost analysis was performed based
on the field data from the actual test dem-
onstrations. Table 3 summarizes the total
costs for application of these four tech-
nologies. The actual costs in terms of
square feet was calculated by dividing the
costs per site hour by the paint removal
rate (i.e., the rate of paint removal in
square feet abated per hour).
Conclusions
The following are the principal conclu-
sions reached during this study.
The encapsulant paint remover
technology effectively removed
lead-based paint from interior ar-
chitectural wood components to
bare substrate with no apparent
damage, yielding a substrate that
required little preparation prior to
painting.
The granulated and pelletized car-
bon dioxide blasting technologies
were not effective in removal of the
lead-based paint from interior ar-
chitectural wood components with-
out severe damage (abraded/
gouged) to the underlying substrate.
The wet abrasive blasting technol-
ogy with an abrasive mixed with
Blastox® (a di- and tri-calcium sili-
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Table 3. Estimated Costs Based on Square Feet of Surface Abated
Cost Factor
Wet Abrasive Blasting
with Chemical Stabilizer
Technology Type
Encapsulant
Paint Remover
Granulated
CO2 Blasting
Equipment/Materials/ $160/site hour
Waste Disposal
$4.32/site hour"
$30/site hour
Labor
Subtotal
Strip Rate
Removal Cost
$140/sitehour
$300/site hour
134ft2/hra
$2.24/ft2
$15/sitehour
$19.32/sitehour
10.3ft2/hra-<:
$1.88/ft2
$30/site hour
$60/site hour
140ft2/hra'd
$0.43/ft2
> Based on total ft2 stripped and total time observed.
b Based on chemical cost of $0.72/ft2 painted surface abated; 2 applications of paint stripper.
c Does not include the dwell time for the chemical to react with the paint. The average dwell time was 2 hr per
application.
d The strip rate was based on the total ft2 tested/total time of test.
cate based material) effectively re-
moved lead-based paint from exte-
rior architectural wood components
to bare substrate with no apparent
damage, yielding a substrate that
required little preparation prior to
painting.
The smallest increase in work area
contamination of settled lead dust
and airborne lead dust above
baseline levels resulted from the
encapsulant paint removal technol-
ogy.
The encapsulant paint remover
technology did not result in per-
sonal exposures to airborne lead
particulate above the OSHA Action
Level (30 |ig/m3). The airborne lead
particulate exposures generated
during granulated carbon dioxide
blasting, pelletized carbon dioxide
blasting, and wet abrasive blasting
technologies exceeded the OSHA
Action Level (12-, 13-, and 7-times,
respectively) as well as the Per-
missible Exposure Limit (50 ng/m3).
Recommendations
The encapsulant paint remover
technology can remove lead-based
paint from architectural wood com-
ponents without damage (only re-
quiring light sanding) to the
underlying substrate, as well as re-
quiring minimal worker protection
and environmental containment. It
is recommended that this technol-
ogy be included in a future study to
(1) further evaluate its efficacy on
interior architectural components in-
cluding more emphasis on decora-
tive "historic" wood substrates, (2)
confirm the adequacy of worker pro-
tection safeguards and environmen-
tal containments, and (3) obtain
more definitive estimates of perfor-
mance rates, hazardous waste gen-
eration, and overall usage costs of
this technology.
Both the granulated and pelletized
carbon dioxide blasting technolo-
gies (as demonstrated in this study)
do not appear to be viable tech-
nologies to remove lead-based paint
from architectural wood components
due to the resultant damage to the
underlying substrate. However,
these commercially available tech-
nologies offer outstanding environ-
mental gains regarding hazardous
waste minimization; i.e., these tech-
nologies do not generate second-
ary waste. Hence, it is
recommended that these technolo-
gies be included in a future study
to (1) evaluate their efficacy to re-
move lead-based paint from ma-
sonry surfaces of residential
housing units, (2) determine the
worker protection safeguards and
environmental containment require-
ments, and (3) determine the per-
formance rates and overall usage
costs of these technologies.
The wet abrasive blasting technol-
ogy can remove lead-based paint
from exterior architectural wood
components without damage (only
requiring light sanding) to the un-
derlying substrate, as well as po-
tentially offering outstanding
environmental gains regarding haz-
ardous waste minimization due to
the addition of Blastox® to the abra-
sive blasting media. It is recom-
mended that this technology be
included in a future study to (1)
evaluate its efficacy to remove lead-
based paint from masonry surfaces
of residential housing units, (2) fur-
ther evaluate the worker protection
safeguards and environmental con-
tainment requirements including an
evaluation of lead particulate expo-
sures during sanding of the abated
substrate (e.g., wood), (3) further
evaluate Blastox®-blasting debris as
a hazardous waste based on the
EPA TCLP, and (4) determine the
performance rate and overall us-
age cost of this technology.
References
1. Hardison, D. L., J. D. Neefers, and
E. D. Estes. Standard operating pro-
cedures for measurement of lead
in paint using the SCITEC MAP-3
X-ray fluorescence spectrophotom-
eter, EPA/600/8-91-412. Cincinnati,
OH: U.S. Environmental Protection
Agency, September 1991.
2. U.S. Environmental Protection
Agency. A field test of lead-based
paint testing technologies: Techni-
cal Report, EPA 747-R-95-002b,
1995.
3. U.S. Department of Housing and
Urban Development. Guidelines for
the evaluation and control of lead-
based paint hazards in housing,
Washington, D.C., June 1995.
4. Hock, V. F., C. M. Gustafson, D.
M. Cropek, and S. A. Drozdz. Dem-
onstration of lead-based paint re-
moval and chemical stabilization
using Blastox®, Technical Report
FEAP-TR-FE-94/Draft, U.S. Army
Center Public Works, Alexandria,
VA 22315, February 1995.
The full report was submitted in par-
tial fulfillment of Contract No. DACW88-
96-M-0277 by Environmental Quality
Management, Inc. This work was con-
ducted under sponsorship of the U.S.
Environmental Protection Agency and
the U.S. Army Construction Engineering
Research Laboratories (USACERL).
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Writers of this project summary are the staff of Environmental Quality Manage-
ment, Inc., Cincinnati, OH 45240.
Alva Edwards-Daniels is the EPA Project Officer (see below).
The complete report, entitled "Field Demonstration of Lead Paint Abatement
Technologies in Residential Housing," (Order No. PB98-172489; Cost: $36.00,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-605-6000
The EPA Project Officer can be contacted at:
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
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EPA/600/SR-98/072
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