United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-91/003 Apr. 1991
&EPA Project Summary
Assessment of Asbestos
Removal Carried Out Using
EPA Purple Book Guidance
John R. Kominsky, Ronald Freyberg, Robert S. Amick, and
Thomas J. Powers
An evaluation was made of airborne
asbestos data collected before, during,
and after removal of spray-applied as-
bestos-containing fireproofing at three
university buildings. Each abatement
project was conducted in accordance
with the work practices and procedures
recommended by the U.S. Environmen-
tal Protection Agency in "Guidance for
Controlling Asbestos-Containing Mate-
rials in Buildings," (the Purple Book).
Containment barriers should be de-
signed so they effectively prevent a sig-
nificant increase in airborne concentra-
tions outside the work area during and
after abatement. An increase in asbes-
tos concentration outside the work area
could allow an abatement site to be
cleared when the level inside the con-
tainment is similarly elevated. This holds
true whether phase contrast microscopy
or transmission electron microscopy is
used for the clearance.
This Project Summary was devel-
oped by EPA's Risk Reduction Engi-
neering 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 Office of Pesticides and Toxic
Substances of the U.S. Environmental
Protection Agency (EPA) provides guidance
and information on the identification of as-
bestos-containing materials in buildings and
on the abatement actions for potential as-
bestos hazards.
The EPA guidance in effect at the time
of this study, entitled "Guidance for Con-
trolling Asbestos-Containing Materials in
Buildings," EPA 560/5-85-024 (June 1985),
known as the "Purple Book," contains rec-
ommendations for work practices and pro-
cedures to be used in performing asbes-
tos-abatement projects. The recommen-
dations include 1) constructing airtight
plastic containment barriers around the
work area, 2) using negative-pressure air
filtration systems, 3) wetting all asbestos-
containing material (ACM) prior to its re-
moval, 4) containerizing of ACM and as-
bestos-contaminated debris while it is wet,
5) conducting rigorous postabatement
cleanup with wet cleaning and high-effi-
ciency particulate air (HEPA) filtered
vacuuming techniques, and 6) performing
visual inspections and air monitoring to
determine asbestos-abatement completion
and work area decontamination.
The EPA guidance document recom-
mends that air monitoring for post-abate-
ment clearance be conducted after the
work area has passed a thorough visual
inspection. According to the EPA "Purple
Book" guidance, two methods for measur-
ing airborne asbestos can be used: trans-
mission electron microscopy (TEM) and
phase contrast microscopy (PCM). If TEM
is used, at least five samples from inside
and five samples from outside each homo-
geneous work area should be collected.
The average of the work-area concentra-
tions should be statistically (t-test) no larger
than the average of measured concentra-
tions outside the work area. If PCM is
used, at least five samples from inside
each homogeneous work area should be
collected, and none of the concentrations
should be higher than the reliable limit of
quantitation (approximately 0.01 f/cm3).
Although the Purple Book recommends
TEM as the method of choice based on its
sensitivity to smaller fibers and specificity
for asbestos, the decision to select an air
sampling protocol for determining suc-
cessful abatement completion is left to the
abatement project manager. Thus, the
determination of work-area cleanliness
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depends on which method is chosen for
measuring asbestos fibers.
Although the Purple Book contains the
latest EPA-recommended guidance for
work practices and procedures to be used
in performing asbestos-abatement projects,
it did not represent the latest EPA guid-
ance for clearance testing of an abatement
site at the time the study report was pre-
pared. This guidance is presented in the
final rule (October 30, 1987; 52 FR41826)
for the Asbestos Hazard Emergency Re-
sponse Act (AHERA) of 1986. The final
rule establishes TEM as the preferred ana-
lytical method to be used for analysis of
samples taken for clearance air monitoring
and also specifies a procedure for deter-
mining when an asbestos site is sufficiently
clean for the critical containment barriers
to be removed. The procedure requires
the collection of five samples from inside
and five samples from outside the abate
ment work area, but not necessarily outside
of the building. The average of the concen-
trations inside the work area must be sta
tistically (Z-test) no larger than the average
of measured concentrations outside the
work area.
Study Objectives
The following were the primary objec-
tives of the study:
To determine the effectiveness of
containment barriers in preventing the
release of asbestos fibers outside of
the work area.
To determine the effectiveness of fi-
nal cleanup procedures.
• To evaluate the TEM clearance crite-
ria for both the t-test and, to the
extent that the data allow, the Z-test.
To determine if an abated site meets
both TEM and PCM clearance crite-
ria and to evaluate whether PCM
provides false positives for clearance
decisions.
To determine if 0.8-u.m pore-size
mixed cellulose ester and 0.4-fim
pore-size polycarbonate membrane
filters produce equivalent estimates
of airborne asbestos concentrations.
Project Description
Site Selection
The three study sites, which were all
school buildings, were chosen based on
the following selection criteria:
1. No significant abatement of ACM had
occurred inside the building site within
the last 12 mo.
2. Each abatement site was in a differ-
ent geographical location or building.
3. The abatement project involved the
removal of spray-applied asbestos-
containing fireproofing from structural
members and decking.
4. The abatement project was governed
by written specifications that comply
with the minimum requirements in
the latest EPA guidance document
(the Purple Book).
5. The building owner and abatement
contractor agreed to cooperate with
the EPA and to provide access to
selected areas of the building.
Abatement Programs
The abatement contractors prepared
the work areas, removed the asbestos-
containing fireproofing, and conducted de-
contamination activities in accordance with
the latest EPA guidance (the Purple Book).
The abatement activities were performed
in three distinct stages: preparation, re-
moval, and decontamination. Work areas
were prepared by removing all movable
objects; turning off the ventilation and
electrical systems; sealing off all air ducts
and openings; covering the floors, walls,
and immovable objects with plastic sheet-
ing; installing HEPA-filtered, negative-
pressure air filtration systems; and con-
structing two entrance and egress con-
tamination-control facilities—one with
showers and change rooms for personnel
and the other for waste-material handling.
Suspended ceilings and carpeting were
either removed and disposed of as con-
taminated waste or cleaned and disposed
of by conventional means.
Workers wearing full protective cloth-
ing and approved respiratory protection
removed the fireproofing by first wetting
the material with an amended water solu-
tion and then scraping it off. The asbestos-
containing debris was placed in double 6-
mil polyethylene bags and disposed of at
an approved sanitary landfill. All substrate
surfaces from which asbestos was removed
were wire-brushed and wet-wiped repeat-
edly to remove as much of the fireproofing
material as possible. All stripped or poten-
tially contaminated surfaces were sprayed
with an asbestos sealant to bond any re-
sidual fibers to the substrate. During de-
contamination of the work area, all loose
debris was removed, as was the plastic
sheeting from the walls and floors. Decon-
tamination also involved two complete final
cleanups entailing wet-wiping or mopping
of the walls and floors. At Site 1, an 8-h
period elapsed between the final cleanings;
at Site 2, a 24-h period elapsed between
cleanings. The work areas were then vi-
sually inspected to assure the absence of
debris and visible dust on surfaces. When
the work area passed a thorough visual
inspection and air monitoring showed that
the total fiber concentrations were less
than 0.01 f/cm3 (by phase contrast micros-
copy), all remaining critical containment
barriers (on windows, doors, and vents)
were removed, and the area was consid-
ered acceptable for reoccupancy.
Sampling Strategy
At each of the three abatement sites,
area air samples were collected before,
during, and after removal of the spray-
applied asbestos-containing fireproofing.
Samples were collected inside the work
area (i.e., the abatement area); outside the
work area (i.e., the perimeter area outside
the abatement area); and from the ambi-
ent air (i.e., outside of the building). Side-
by-side samples were collected at each
location for separate PCM and TEM
analysis.
The preabatement air samples were
collected inside and outside the work area
before the containment barriers were con-
structed. The sampling was conducted
under static conditions (i.e., activity in the
area was minimal and the heating, venti-
lating, and air-conditioning system was not
in operation).
During the removal phase of the abate-
ment, air samples were collected outside
the work area at scheduled intervals and
under static sampling conditions.
The postabatement air samples out-
side the work area also were collected
under static sampling conditions. The
postabatement air samples inside the work
area were collected under aggressive
sampling conditions. The aggressive sam-
pling conditions were created by sweeping
all horizontal and vertical surfaces with a
hand-held, electric-powered, leaf blower
and then using floor fans to generate con-
tinuous air turbulence throughout sampling
period.
Sampling Methods
Two side-by-side area air samples were
collected at each sampling location inside
and outside the work area and outdoors.
Each pair of samples consisted of a 25-
mm, 0.4u.m pore size, Nuclepore* polycar-
bonate filter and a 25-mm, 0.8-u.m pore
size, Millipore mixed cellulose ester filter.
Each 25-mm filter was mounted on a 5-jim
pore size, mixed cellulose ester, backup
diffusing filter and cellulose support pad
and was contained in a three-piece cassette
with a 50-mm conductive cowl and face
cap. The filter cassettes were positioned 4
to 5 ft above the floor and were arranged in
a horizontal line by clipping them to a
Mention of trade names or commercial products does
not constitute endorsement or recommendation for
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sturdy stand. The filter cassettes were
placed approximately 5 cm apart and were
oriented in the same direction with the
filter face angled slightly downward. Dur-
ing sampling, the face cap was removed
to expose the full face of the filter to the
air stream.
The filter assembly was attached to an
electric-powered vacuum pump. An inline
calibrated precision rotameter was used
to regulate the air-flow rate through the
filter assembly at 8 to 12 L/min. The air
samples were generally collected for a
period of approximately 6 to 9 h to achieve
a minimum air volume of 3,000 L for each
sample; however, a limited number of
samples were collected for periods ex-
tending up to 17 h, which yielded air
volumes of approximately 11,000 L.
Methods of Analysis
Phase-Contrast Microscopy
The mixed cellulose ester membrane
filters were analyzed by PCM, and the
polycarbonate membrane filters were
analyzed by TEM. The PCM and TEM
analytical protocols are presented in the
Quality Assurance Project Plan (QAPP)
prepared for this research study.
The mixed cellulose ester filters were
prepared and analyzed for total fibers by
PCM in accordance with National Institute
of Safety and Health Method 7400.
Transmission Electron
Microscopy (TEM)
The polycarbonate membrane filters
were analyzed by TEM. The filters were
prepared and analyzed for asbestos fibers
by TEM in accordance with the Yamate
Revised Method. A TEM Level II analysis
was performed on all polycarbonate
samples collected in this study.
Quality Assurance
The QAPP contains the complete de-
tails of the quality assurance procedures
followed during this research project.
Specific quality assurance procedures
used to ensure the accuracy and precision
of the TEM analysis of air samples in-
cluded the use of lot blanks, field blanks,
and replicate TEM analyses.
Lot blanks are unused filters submit-
ted for prescreening analysis for back-
ground contamination before the start of
field work to determine the integrity of the
entire lot of filters purchased for EPA field
studies. Analysis of 100 lot blanks showed
an average background contamination of
1.8 asbestos structures per 10 grid open-
ings. The lot of filters was subsequently
considered "acceptable" for use because
the average asbestos structure count did
not exceed 3 structures per 10 grid open-
ings.
Field blanks are filters taken into the
field and handled in the same manner as
exposed air samples to check for contami-
nation that might not be a result of air
sampling. A total of 27 field blanks were
collected at Sites 1, 2, and 3. Because the
average asbestos structure count did not
exceed 3 asbestos structures per 10 grid
openings at any site, background contami-
nation was not considered a problem.
Replicate sample analysis provides a
means of quantifying analytical variability
introduced by the filter preparation proce-
dure and refers to the analysis of different
filter preparations from the same sample.
The replicate analyses showed no signifi-
cant tendency toward higher or lower struc-
ture counts.
Statistical Analysis Methods
Nonparametric statistical methods were
selected to analyze the data collected dur-
ing this study. Nonparametric procedures
analyze the relative ranks of the data rather
than the actual data values, and they do not
require any assumptions regarding the form
of the underlying statistical distribution of
the data.
The Kruskal-Wallis one-way analysis
procedure was used to examine the differ-
ences between airborne asbestos concen-
trations in the perimeter area before, dur-
ing, and after abatement. The Wilcoxon
rank sum test was used to make all other
comparisons.
The TEM clearance comparison was
made with the Student's t-test as recom-
mended in the Purple Book, and to the
extent the data allowed, with the Z-test
required in the AHERA final rule. Because
all three sites used negative-pressure air
filtration systems during abatement and the
makeup or "background"' air came from other
parts of the building rather than directly
from outdoors, the postabatement samples
inside the work area were compared with
the postabatement samples outside the work
area but within the building.
Results
Average airborne asbestos concentra-
tions and respective sample sizes are pre-
sented in Table 1. The results are pre-
sented for Sites 1, 2, and 3 by abatement
phase (before, during, and after); location
of sample (inside the work area, outside the
work area, and ambient); and microscopy
technique (TEM and PCM). Figure 1 pre-
sents average airborne asbestos concen-
trations graphically for Sites 1, 2, and 3
according to abatement phase and sample
location. The study report includes a de-
tailed presentation and discussion of the
results for each site, including plots of
structure lengths and diameters determined
by TEM analysis.
Conclusions
The following principal conclusions from
this study are presented for each study
objective.
Comparison of Concentrations
Outside the Work Area
Asbestos concentrations measured
outside the work area before, during, and
after abatement at Sites 1 and 3 did not
vary significantly. This indicates that the
containment barriers at these two sites
were effective in preventing the release of
asbestos fibers outside the work area. At
Site 2, however, the asbestos concentra-
tions measured after abatement were sig-
nificantly higher than those measured be-
fore and during abatement. The average
asbestos concentration after abatement
was approximately 80 times higher than
the average concentration before abate-
ment. These elevated asbestos concen-
trations suggest that 1) the containment
barrier was not effective at this site; 2)
work practices recommended in the Purple
Book were not followed; or 3) asbestos-
containing material outside the abatement
containment was disturbed, which resulted
in elevated asbestos concentrations in that
area.
Comparison of Work Area
Concentrations Before and After
Abatement
At Site 1, asbestos concentrations did
not increase significantly after abatement.
At Sites 2 and 3, however, asbestos con-
centrations did increase significantly after
abatement.
Final cleanup procedures can effectively
control postabatement airborne asbestos
concentrations inside the work area. The
higher postabatement concentrations may
be attributable to improper or inadequate
implementation of final cleanup procedures,
or they may be due to sampling conditions
(i.e., static conditions in the preabatement
phase versus aggressive conditions in the
postabatement phase, or both).
TEM Clearance Comparisons
Sites 1, 2, and 3 passed the TEM clear-
ance criteria for both the t-test recom-
mended in the Purple Book and Z-test
specified in the final rule under AHERA. At
Site 2, the increase in the postabatement
asbestos concentration outside the work
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Table 1. Average Airborne Asbestos Concentrations Before, During, and After Abatement at Sites
1, 2, and 3
Location
Ambient
Perimeter
Work area
Ambient
Perimeter
Work area
Ambient
Perimeter
Work area
Average Airborne Asbestos Concentration (s/crrfySample Size
Site 1 Site 2 Site 3
JEM PCM JEM PCM JEM PCM
Preabatement phase
0.0041/3 0.0007/3 0.0011/5 0.0012/5 0.0000/3 0.0020/3
0.0052/12 0.0003/12 0.0030/5 0.0014/5 0.0008/3 0.0040/3
0.0091/10 0.0000/10 0.0367/5 0.0012/5 0.0001/8 0.0020/8
0.0034/4
0.0089/31
0.0067/4
0.0057/5
0.0056/5
Durinq-abatement phase
0.0008/4 " 0.0005/5 0.0010/5
0.0023/31 0.0304/31 0.0015/31
0.0129/49 0.0106/61
0.0002/5
0.0022/5
0.0015/5
Postabatement phase
0.2410/7
0.3082/5
0.0027/7
0.0024/5
0.0000/3
0.0028/2
0.0023/7
0.0107/3
0.0074/5
0.0080/7
' Dashes indicate that no samples were collected.
Average Airborne Asbestos Concentration (s/cm3)
0.35
0.3
0.25
0.2
0.15
0.1
0.05
r Work Area
Perimeter
Outdoor
Pre Dur Post
Site 1
Pre Dur Post
Site 2
Pre Dur Post
Site 3
Figure 1.
Mean airborne asbestos concentrations before, during, and after abatement for
samples analyzed by TEMat sites 1, 2, and 3.
area, as noted in the preceding discus-
sion, enabled the site to pass both clear-
ance tests. Conversely, a comparison of
the postabatement concentrations inside
the work area with ambient concentrations
resulted in the site failing both clearance
tests. This single incident points up a seri-
ous limitation in the comparison of
postabatement asbestos concentrations
inside the work area with those outside the
work area.
Both the Purple Book and AHERA final
rule clearance strategies could allow an
abatement site to be cleared despite the
fact that the airborne asbestos concentra-
tion outside the work area is significantly
higher than preabatement building con-
centrations.
Comparison of TEM and PCM
Clearance Test Results
Sites 1,2, and 3 passed the TEM clear-
ance criteria based on both the t-test
(Purple Book) and the Z-test (AHERA final
rule). Sites 1 and 2 also passed the PCM
clearance criterion (0.01 f/cm3); however,
Site 3 failed. Thus, this study identified a
false positive PCM clearance situation
where a site failed PCM and passed TEM.
The differences in conclusions reached
by the two protocols are probably due to
the limited ability of PCM to distinguish
asbestos from nonasbestos materials. Air-
borne fiber concentrations estimated by
PCM reflect total fiber concentrations, not
just asbestos fiber concentrations; there-
fore, they may lead to erroneous conclu-
sions regarding abatement clearance.
Comparison of Concentrations
Measured on Mixed Cellulose Ester
and Polycarbonate Filters
The TEM analysis of 69 paired 0.8-jim
pore size mixed cellulose ester and 0.4-
u,m pore size polycarbonate membrane
filters revealed a statistically significant dif-
ference in asbestos concentrations on the
two filter types. This comparison was made
because the guidance in the Purple Book
allowed for the choice of either type of
filter. Asbestos concentrations on 0.4-jim
pore size polycarbonate filters were sig-
nificantly higher than those on 0.8-u,m pore
size mixed cellulose ester filters. The two
types of filters do not produce equivalent
estimates of airborne asbestos concentra-
tions. The difference in asbestos concen-
trations may be due to the differences in
the pore sizes or in the chemical composi-
tion of the two types of filters.
Recommendations
Because the elevated levels outside
the containment area at Site 2 would have
allowed a contaminated site to pass under
the AHERA sampling strategy, monitoring
of the contamination level outside the work
area during abatement or after abatement
should be strongly considered as a pre-
requisite to using this area as a clearance
reference point. If additional monitoring is
not considered reasonable, the guidance
should be revised to emphasize the impor-
tance of the location of the "outside"
samples.
The full report was submitted in fulfill-
ment of EPA Contract 68-03-4006 by PEI
Associates, Inc., under the sponsorship of
the U.S. Environmental Protection Agency.
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John R. Kominsky, Ronald Freyberg, and Robert S. Amick are with PEI Associates, Inc.,
Cincinnati, OH 45246.
Thomas J. Powers (also the EPA Project Officer, see below) is with the Risk Reduc-
tion Engineering Laboratory, Cincinnati, OH 45268.
The complete report, entitled "Assessment of Asbestos Removal Carried Out Using
EPA Purple Book Guidance," (Order No. PB91-148338/AS; Cost: $17.00, 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:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
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