United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/053 Aug. 1986
Project Summary
Assessment of Assay
Methods for Evaluating
Asbestos Abatement
Technology
Mark A. Karaffa, Robert S. Amick, Ann Crone, and Thomas J. Powers
Two analytical methods and two sam-
pling schemes were evaluated for their ef-
fectiveness in a project to remove air-
entrainable asbestos from Columbus East
High School in Columbus, Indiana. The
two analytical methods were phase con-
trast microscopy (PCM) and transmission
electron microscopy (TEM). The sampling
schemes included a static method and an
aggressive one using a leaf blower.
The study results indicated that the
building abatement did meet the PCM
specifications in effect at the time, allow-
ing acceptance of the work and reoc-
cupancy. However, the TEM results re-
vealed airborne asbestos concentrations
averaging four times outdoor levels with
peak values near 1 million asbestos struc-
tures/m3. Aggressive sampling amplified
the significance of the situation, produc-
ing average airborne asbestos concentra-
tions that were 50 times the outdoor
levels, with peak concentrations near 1.5
million asbestos structures/m3 of air.
As a result of this study, TEM coupled
with aggressive sampling is the currently
recommended method of choice for post-
abatement clearance.
This Project Summary was developed
by EPA's Water Engineering Research Lab-
oratory, 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 in-
formation at back).
Introduction
The Technical Assistance Program of
the Office of Pesticides and Toxic Sub-
stances of the U.S. Environmental Pro-
tection Agency (EPA) provides guidance
and information on the identification of
asbestos-containing materials in buildings
and on the correction of potential asbestos
hazards. Four EPA Guidance Documents
contain much of the technical informa-
tion about asbestos in nonindustrial set-
tings. 1'2'3'4 These documents describe
how to establish an asbestos identification
and control program, provide background
information and direction to school of-
ficials and building owners on exposure
assessment, and develop and implement
an asbestos abatement program. The
most recent asbestos guidance from EPA
not only emphasizes recent experience
and new information on asbestos control
but also introduces and discusses criteria
for developing an appropriate asbestos
control plan.
Considerable scientific uncertainty still
surrounds the effectiveness of specific
abatement actions in reducing the risk of
exposure to airborne asbestos. One critical
concern among those responsible for as-
bestos abatement is how clean the con-
tractor leaves a building (or building area)
after removing the asbestos material or
after completing work that could have dis-
turbed an asbestos-containing material
(e.g., encapsulation, enclosure, or special
maintenance operations). The two criteria
recommended by the EPA guidance
(1983)3 that was in effect at the outset
of this study were visual inspection of the
worksite and air monitoring after comple-
tion of the project. Visual inspection
should detect incomplete removal, dam-
age caused by abatement activity, and
(most important) the presence of debris or
dust left by inadequate cleanup of the
work area. Air monitoring by the mem-
brane filter collection technique and phase-
contrast microscopic (PCM) analysis are
recommended to supplement the visual in-
spection and to determine whether ele-
vated levels of airborne fibers generated
during the removal process have been suf-
-------
ficiently reduced. This currently recom-
mended optical microscopic technique is
one of two methods specified by the Na-
tional Institute for Occupational Safety
and Health (NIOSH) to determine airborne
fiber concentrations; it is used by the
Occupational Safety and Health Adminis-
tration (OSHA) to measure total airborne
fibers in occupational environments.
The EPA-recommended air-monitoring
methodology for determining abatement
completion (NIOSH Method No. P&CAM
239) was as follows:
Air sampling should begin after the
project has been completed and all
surfaces in the abatement site have
been cleaned, perferably within 48
hours after abatement work is finish-
ed. A minimum of three air monitors
per worksite and at least one per room
is recommended. Air is drawn through
a membrane filter for about 8 hours
at a flow rate of approximately 2 liters
per minute."A total air volume of ap-
proximately 1,000 liters collected at
the specified flow rate should be
sampled. After the sampling, a sec-
tion of the filter is mounted on a
microscope slide and treated to form
a transparent, optically homogeneous
gel. The fibers are sized and counted
by using a phase-contrast microscope
at 400 to 450X magnification. For
counting purposes, a fiber is defined
as a particle with a physical dimension
longer than 5 micrometers and a
length-to-diameter ratio of 3 to 1 or
greater.3
This method is intended to give an index
of the.airborne concentration of fibers of
specified dimensions in an atmosphere
known or suspected to contain asbestos;
it is not designed to count fibers less than
5 \xn long or to differentiate asbestos
fibers from other fibrous particulates.
The most significant limitation of the
PCM method 6ompared with transmission
electron microscopy (TEM) and scanning
electron microscopy (SEM) is that PCM is
limited in the detection of fine particles
(i.e., those with submicron diameters or
lengths less than 5 ^m) that may be toxi-
cologically significant. For example, in
glove-box tests of simulated industrial
mechanical operations on asbestos-con-
taining products (drilling, sawing, and san-
ding), the PCM method counted fewer
than 1 percent of the fibers counted by
TEM.5 Although conditions of this glove-
box study were obviously different from
asbestos abatement activities, some con-
cern existed about the relative merits and
capabilities of the different analytical
methods used to determine representative
fiber concentrations. Another study esti-
mated that small asbestos fibers (i.e.,
fibers less than 0.2 ^m wide and 5 \*m long
that are not detected by the PCM method)
were present at 50 to 100 times the con-
centration of the larger, optically visible
fibers.6
Study Objective
The objective of this research project
was to identify and quantify the fine frac-
tion of airborne asbestos fibers present in
building atmospheres after an asbestos
remedial activity. The project focused" on
the adequacy of EPA's previously recom-
mended PCM method of analysis and sam-
ple collection technique. The PCM method
was compared with TEM methods, and
the feasibility of an alternative aggressive
sampling technique was investigated. The
results of this study established the advan-
tages and limitations of applying PCM and
TEM analytical methods, both separately
and in conjunction with an aggressive
sampling technique, to the evaluation of
air quality following asbestos abatement.
This project was conducted during the
postabatement phase of asbestos removal.
Reliable methods of air sampling and anal-
ysis permit the use of monitoring results
to be included in evaluating the efficacy
of asbestos abatement methods and in
developing better technical guidance for
abatement contractors, building owners,
and other parties directly responsible for
remedial asbestos programs.
Active or recently completed abatement
sites were selected 'for monitoring be-
cause they provided an excellent opportu-
nity to collect real world data, and because
the monitoring tasks could be arranged
with minimum lead time and coordination.
The conditions in a work area while the
final air samples are collected can influ-
ence the results of a postabatement as-
sessment. After an abatement action, the
air is usually sampled while the area is
sealed off, before ventilation is restored,
and after at least a 24-hr settling period
following the final wet cleaning. Conse-
quently, this monitoring technique may fail
to detect residual fibers that have settled
on horizontal surfaces during this static
condition or that were missed by the
cleaning.
Residual asbestos fibers constitute a
potential exposure hazard because they
could be reentrained later, when the air in
the area is agitated by personnel traffic,
air flow from ventilation systems, and
custodial activities. Thus for more accu-
rate characterization of postabatement fi-
ber concentrations, the work area should
experience appreciable air movement to
simulate actual use conditions during air J
monitoring. *
The introduction of air turbulence into
the work area during the collection of sta-
tionary air samples is termed "agressive
sampling." This method entails the crea-
tion of air movement by the use of blowers,
fans, brooms, or compressed air streams
to entrain any paniculate matter that may
be present. The advantages of the aggres-
sive sampling technique over the static (or
nonaggressive) sampling are that the for-
mer reflects worst-case conditions and
that the testing requires a relatively short
period. The disadvantages are that this
technique is not readily standardized or
reproducible, nor does it reflect normal ex-
posure levels to occupants. As with the
static sampling method, no criteria have
been established to define an acceptable
or safe level of fibers in a nonoccupational
environment. The research on fiber con-
centration levels using the PCM and TEM
methods is continuing so that the before-
, during-, and after-abatement criteria can
be developed within the next 2 years.
Project Description
Site Select/on
Air monitoring was conducted at two
selected sites from which friable asbestos
building materials had been removed: Site
1, Columbus East High School, Columbus,
Indiana; and Site 2, the U.S. EPA Environ-
mental Research Laboratory in Corvallis,
Oregon.
This report describes only the results of
the air monitoring survey conducted at
Site 1. The monitoring data from Site 2
and the significance of these data are the
subject of a separate report. These se-
lected sites met the following criteria:
• The abatement plan involved the
removal of friable, spray-applied, as-
bestos-containing material.
• The contractors carried out the work
area preparation, removal, and decon-
tamination in accordance with EPA-
recommended specifications and
requirements.1
• Multiple work areas containing ho-
mogeneous asbestos material were
available for monitoring.
• The building owner and abatement
contractor agreed to cooperate with
EPA and to provide access to select-
ed areas of the building.
Abatement Program
A multiphase asbestos abatement and
renovation program was conceived and
implemented. The first abatement phase
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was conducted during the summer of
1984 and included the following areas:
Academic Building:
Third floor - all rooms
North and south large-group instruc-
tional rooms (sidewall enclosures)
Mechanical penthouses
Stairwells and elevator shafts
Industrial arts
TV studio/publications
Music rooms
Auditorium
Gymnasium:
Storage rooms
Mechanical room
Concessions
Restrooms
Sources of friable, asbestos-containing
fireproofing were controlled by removing
the material or by placing it in airtight en-
closures in areas where complete removal
and replacement were not feasible. Deci-
sions regarding the most appropriate con-
trol method for each Phase I subspace
were based on EPA-recommended assess-
ment factors for evaluating the potential
for fiber release.3
Asbestos-containing fireproofing insula-
tion had been spray-applied to steel beams
and columns on the first, second, and third
floors and in mechanical areas. The range
of asbestos concentration for this moder-
ately friable material was 30 to 60 percent
chrysotile asbestos, based on an analysis
of 17 representative bulk samples by polar-
ized-light microscopy and dispersion stain-
ing.7 Throughout these areas, there was
a considerable amount of overspray on
sections of the corrugated steel deck pan
between the treated beams. The treated
beams were largely concealed by a su-
spended lay-in or interlocking steel panel
ceiling, but in some areas, the construc-
tion design rendered the fireproofed beams
visible and exposed.
The structural beams on the lower level
had also been sprayed with friable mater-
ial, but it contained no asbestos. Many of
these beams had been enclosed by drywall
and therefore were not visible. Other
beams on the lower level were concealed
above suspended ceilings, and still others
were exposed (visible).
Asbestos-containing fireproofing was
also found in the gymnasium on the ceil-
ing above the mezzanine level and in the
mechanical equipment and storage rooms.
The spray-applied material on beams above
the suspended ceiling on the lower level
of the gymnasium contained mostly fi-
brous glass and no asebestos fibers.
Procedures
The procedures followed for the removal
and enclosure of the asbestos-containing
fireproofing at Site 1 were consistent with
those described in the EPA guidance docu-
ments, and they complied with EPA and
OSHA asbestos regulations. Detailed spe-
cifications describing the scope of work,
the work sequence, and specific perfor-
mance criteria for the abatement contrac-
tor were prepared by the project team and
distributed as part of the bid package. The
technical job specifications for the removal
and enclosure of the asbestos-containing
fireproofing were based on the Guide
Specifications for the Abatement of As-
bestos Releases From Spray- or Trowel-
Applied Materials in Buildings and Other
Structures, published by the Foundation of
the Wall and Ceiling Industry.8
An industrial hygiene technician was on-
site throughout the entire abatement pro-
ject. The field technician was under the
direct supervision of a certified industrial
hygienist, who made weekly inspections
of the job site and was available for con-
sultation. The first phase of the asbestos
abatement program began on May 30 and
was completed (excluding final renovation
items) by August 11, 1984. The second
phase of the abatement program was com-
pleted during the summer months of 1985,
and the third phase will be completed dur-
ing the summer of 1986.
Abatement Activities
The abatement activities were performed
in three distinct stages: preparation, re-
moval, and decontamination. Each of the
building areas included in Phase I were
isolated as separate abatement work areas.
Some work areas comprised multiple
rooms (e.g., the third-floor classroom area
and the music area), and some consisted
of a single room (e.g., the penthouses,
storage rooms, and the TV studio). Each
work area was prepared by turning off the
ventilation and electrical systems; sealing
off all air ducts and openings; covering the
floors, walls, and immovable objects with
plastic sheeting; installing high-efficiency-
particulate-air- (HEPA-) filtered exhaust
units; and constructing worker decontam-
ination facilities. Suspended ceilings and
carpeting were removed and disposed of
as contaminated waste, or they were
cleaned and disposed of by conventional
means. Workers wearing full protective
equipment and approved air-purifying res-
pirators removed the fireproofing by first
wetting it with an amended water solution
and then scraping it off. The asbestos-
containing debris was placed in double
6-mil plastic bags and disposed of at a
local EPA-approved sanitary landfill. All
substrate materials from which asbestos
was removed were wire-brushed and wet-
wiped repeatedly to remove as much of
the fireproofing material as possible. A dry
removal method that did not use the
amended water solution was used in the
TV studio room to prevent damage to the
acoustical panels and electronic equip-
ment in this area.
All stripped or potentially contaminated
surfaces were sprayed with an approved
asbestos sealant to bond any residual
fibers to the substrata The work area was
decontaminated by removing all loose de-
bris, removing the plastic sheeting from
the walls and floors, and repeatedly wet-
wiping or mopping the walls and floors.
When the work area had passed a thor-
ough visual inspection and air monitoring
showed that the fiber concentrations were
less than 0.05 fiber/cm3 (the clearance
level of the contractor's specifications),
the barriers and HEPA-filtered exhaust
units were removed, and the area was
opened for occupancy by other tradesman
responsible for various components of the
renovation, for example, fireproofers, pain-
ters, electricians, plasterers, and heating,
ventilating, and air conditioning (HVAC)
installers.
Monitoring Approach
Samples for subsequent PCM and TEM
analysis were collected from two or three
representative locations within each de-
signated work area after completion of all
abatement activities but before any appli-
cation of replacement fibrous material (e.g.,
nonasbestos fireproofing). Plastic sheeting
on walls and floors had been removed, the
substrate had been sprayed with a sealant,
and HEPA-filtered exhaust units had been
removed. Air sampling was not conducted
until the abatement area had passed a rig-
orous visual inspection by the onsite in-
dustrial hygienist and architect. In each
designated work area, first static and then
aggressive sampling techniques were used.
To summarize briefly, filter holders contain-
ing either 0.8-^m Millipore mixed-cellulose
ester filters (PCM) or 0.4-^m Nuclepore
polycarbonate filters (TEM) were posi-
tioned (1.4 to 1.7 m) 4.5 to 5.5 ft above
the floor at arbitrary locations. Battery-
powered sampling pumps were used to
draw air through the filters. The constant-
flow pumps were calibrated to 2 to 3 L/m
and were operated for 6 to 8 hr/test, de-
pending on the contractor's schedule.
Samples were collected from several in-
door work areas and at outdoor locations
during each monitoring period.
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In addition to the postabatement moni-
toring, limited preabatement monitoring
was conducted in an area of the audito-
rium to take advantage of the one oppor-
tunity available for preabatement monitor-
ing in the abatement program schedule.
Two PCM and two TEM preabatement
samples were obtained and analyzed.
Upon completion of each monitoring
survey, samples were submitted to the ap-
propriate laboratory for preparation or
analysis. The Nuclepore filters were hand-
carried to EPA for carbon coating before
they were transported to the laboratory for
TEM analysis.
Methods of Air Sampling
and Analysis
Overview of Sampling Strategy
Samples designated for PCM and TEM
analysis were collected with both aggres-
sive and static methods in seven different
work areas. Samples were also collected
from the surrounding environment outside
the building. Each work area consisted of
a specific room or rooms and adjacent hall-
ways, closets, or other spaces that were
treated as a separate component of the
total abatement project. The building areas
sampled included the auditorium, gymnas-
ium, industrial arts rooms, music rooms,
projection booth, TV studio, and elevators.
These sampling locations were not select-
ed as part of a study design; selection was
dictated by the contractor's abatement se-
quence and schedule. After completion of
abatement efforts in the individual work
areas, representative PCM and TEM sam-
ples were collected. All outdoor air sam-
ples were collected in the parking lot ad-
jacent to the school building, except for
one that was collected on the roof of the
building.
All postabatement air samples were col-
lected while the work area was still iso-
lated (i.e., containment barriers were in
place) but after (1) the substrate had been
sprayed with a sealant, (2) the plastic
sheeting covering the walls and floor had
been removed, and (3) all surfaces had
been wet-wiped. Because of timing, limit-
ed preabatement monitoring in one area
of the auditorium was conducted before
any abatement activity in the auditorium.
Insofar as possible, outdoor and indoor air
sampling was conducted concurrently, but
inclement weather or equipment availabil-
ity sometimes made this impossible.
Whenever possible, side-by-side sam-
ples, (one PCM and one TEM) were col-
lected in each work area under static and
aggressive sampling conditions. Accessi-
bility restrictions prevented aggressive
sampling in some areas. As each building
area became available, sampling was per-
formed in the following sequence. Sam-
ples designated for both PCM and TEM
analysis were collected under nonaggres-
sive conditions approximately 1 to 24 hr
following a satisfactory visual inspection
of the of work area by the architect and
onsite industrial hygienist, depending on
the contractor's schedule for final clean-
ing. Immediately afterward or on the
following day, samples for PCM and TEM
analysis were again collected, this time
under aggressive conditions (i.e., turbulent
air movement). Placement of the sampling
equipment within each work area was the
same during both static and aggressive
sampling. The number of samples per work
area was not specified by study design,
but efforts were made to collect at least
two of each type of sample within each
work area.
Sampling Equipment
Samples for PCM analysis were collect-
ed on 37-mm Millipore, Type AA, mixed-
cellulose ester membrane filters (0.8-jum
pore size). The filters were preassembled
in three-stage polystyrene cassettes by
the manufacturer. Samples for TEM
analysis were collected on 37-mm
Nuclepore polycarbonate membrane fil-
ters (0.4 fjm pore size). The polycarbonate
membrane filter was supported within a
three-stage polystyrene cassette by
means of a support pad and backup filter
(mixed-cellulose ester membrane, 5-//m
pore size). Each sample cassette was
sealed with a cellulose shrink band to
prevent air from entering the sides of the
unit during sampling.
Battery-operated personal sampling
pumps equipped with rotameters and/or
constant-flow controls were used to draw
air through the sample filters. All sampling
pumps were calibrated with a soap-film
flowmeter before and after sample collec-
tion. The rotameter setting of each cali-
brated sampling pump was noted to pro-
vide a visual indication of proper pump
functioning, and the settings were check-
ed periodically throughout the sampling
period.
Sample Collection and Handling
Samples designated for both PCM and
TEM analysis were collected at a known
flow rate of approximately 2 to 3 L/min
(LPM). Sampling duration was 6 to 8 hr.
The average sample volume per filter was
1,200 L.
All samples were collected open-faced
(i.e., with the face cap of the cassette de-
vice removed) to expose the maximum ef-
fective surface area of the filter. During
sampling, the face caps were carefully
stored in clean, resealable, plastic bags. 4
The filter cassettes were positioned at "
breathing zone height (1.4 to 1.7 m, or 4.5
to 5.5 ft above the floor) and were sup-
ported by taping the end of the sampling
hose to the wall or clipping it to an adjust-
able tripod. The sample cassettes were
also positioned so that the membrane fil-
ters were angled approximately 45 de-
grees toward the floor.
At the end of the sampling period, each
filter cassette was turned upright (i.e., the
filter plane was parallel to the floor), the
sampling pump was turned off, the face
cap of the three-stage filter cassette was
repositioned tightly on the cassette, the
cassette was disconnected from the sam-
pling hose, a plastic plug was inserted into
the cassette outlet, and the cassette was
placed face-up in a box for transport. All
PCM and TEM filter samples were main-
tained in this upright position from the
time of collection until they were carbon-
coated or analyzed by the appropriate
laboratory.
The PCM analysis equipment was avail-
able at the Columbus East site, and a por-
tion of the PCM samples (final clearance
samples collected under static conditions)
were analyzed onsite shortly after comple-
tion of sampling. Rapid reporting of these
sample results was essential so that the
building areas could be released to the
contractor for additional nonabatement
work and renovation. The remaining PCM
filters were hand-carried to the laboratory,
where they were subsequently analyzed.
The TEM samples were submitted to the
EPA Project Officer (or his representative)
and hand-carried to EPA in Cincinnati,
where they were carbon-coated. The TEM
samples were then either shipped by over-
night courier or hand-carried to the lab-
oratory for analysis.
Static Sampling
Samples for PCM and TEM analysis
were collected under static conditions for
comparison with similar samples collected
under aggressive conditions. The sampling
condition was considered static when air
movement in the work area was negligible
and/or minimized to the greatest possible
extent. Under this condition, asbestos
fibers (or any other particulate matter) will
settle out if given sufficient time. Any work
area, no matter how contaminated, can be
totally "clean" as defined by PCM as long
as enough time is allowed to elapse before
static sampling. The probability of reen-
trainment of these asbestos fibers is much
lower under static conditions than under
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conditions of typical building use (aggres-
sive sampling conditions). In this study,
static sampling conditions existed when
the work area was sealed off, all ventila-
tion was shut off, and personnel access
was prohibited. These are the typical con-
ditions under which air monitoring is con-
ducted at a work site following asbestos
removal and decontamination.
Aggressive Sampling
Samples for PCM and TEM analysis
were also collected under agressive sam-
pling conditions. Aggressive conditions
were created by introducing air turbulence
into the sampling area by intermittent use
of a hand-held electric blower. The air
movement created was much greater than
would exist under conditions of normal
building use. Under these aggressive sam-
pling conditions, most asbestos fibers
susceptible to entrainment will become
airborne and remain suspended for the
duration of the sampling period, as long
as the use of fans or the hourly introduc-
tion of air turbulence is continued. Thus
an aggressive environment provided the
best possible setting for high or "worst-
case" airborne asbestos fiber concentra-
tions following abatement. Figure 1 com-
pares airborne fiber concentrations for
PCM and TEM under static and aggressive
conditions.
The blower used in this study was a 1-hp
electric power blower (Figure 2). The air-
flow rate at the blower outlet is approx-
imately 8.5 m3/min (300 ft3/min). The
electric blower was equipped with a two-
piece plastic tube extension and concen-
trator nozzle that enabled the operator to
direct the airstream at objects and sur-
faces within the sampling area.
Aggressive sampling conditions were
created in each of the work areas sampled
by an initial blow-down of all surfaces,
followed by hourly agitation with the
blower throughout the duration of the
sampling period. During aggressive sam-
pling, all containment barriers isolating the
work area were intact, and building air-
handling systems remained off. In some in-
stances, it was necessary for the contrac-
tor to remove the HEPA filtration units for
use in another active work area..Figure 3
shows the aggressive sampling procedure
in progress. The sequence of operations
is summarized below:
1. A technician entered the work area,
positioned the sampling equipment,
and started the sampling pumps.
2. Using a back-and-forth motion, the
technician directed the airstream of
the electric blower at all surfaces
within the sampling area (walls,
floors, ceilings, all structures be-
tween walls, ceilings, and floors, and
any other exposed surfaces within
the enclosed area). The technician
then exited from the sampling area.
3. After approximately 1 hr, the techni-
cian reentered the work area and
repeated the blow-down of all sur-
faces. This procedure was then re-
peated hourly for the duration of the
sampling period. Unless actively en-
gaged in manipulating the electric
blower, the technician did not remain
within the enclosure.
4. At the end of the sampling period,
samples were collected, sampling
pumps were turned off, and the sam-
pling equipment was removed from
the area.
The technician used appropriate respir-
atory protection and decontamination
procedures.
Methods of Analysis
Phase-Contrast Microscopy
All PCM samples were analyzed in ac-
cordance with NIOSH Method No. P&CAM
239.9 This optical microscopic technique
is the method the OSHA uses to measure
Aggressive
TEM
Aggressive
PCM
Static
TEM
Static
PCM
Ambient TEM
Ambient PCM
I Range 1
25% 75%
Percentiles
.001 .005 .010 .050 .100 .500
106Fibers/m3
Figure 1. Comparison of airborne fiber concentrations measured by TEM and PCM under aggressive and static conditions.
5
1 00
2.00
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total airborne fibers in occupational en-
vironments. The EPA guidance document
pertaining to asbestos in buildings recom-
mends a visual inspection followed by air
monitoring by the membrane filter collec-
tion technique and PCM analysis as one
method for evaluating satisfactory com-
pletion of asbestos abatement and decon-
tamination of the work site.3
Airborne fiber concentrations are deter-
mined by NIOSH Method No. P&CAM 239
through microscopic examination of the
fibers collected on a mixed-cellulose ester
membrane filter. A triangular wedge con-
stituting approximately one-eighth of the
entire surface area of the 37-mm-diameter
filter is removed from the sample cassette,
mounted on a microscope slide, and ex-
amined. The filter wedge is rendered into
an optically transparent homogeneous gel
by the use of a slidemounting solution of
1:1 (by volume) dimethyl phthalate and
diethyl oxalate. A microscope equipped
with a phase-contrast condenser is used
to size and count the fibers at 400 to
450X magnification. Only those fibers
longer than 5 pan with a length-to-width
ratio of 3 to 1 or greater are counted.
Fibers are sized by comparing fiber length
with the diameters of the calibrated circles
of a Porton reticle. Sample analysis con-
tinues until at least 20 fibers or 100 micro-
scopic fields have been counted. Micro-
scopic field areas generally range from
0.003 to 0.006 mm2.
Transmission Electron Microscopy
Nuclepore filters were prepared and ana-
lyzed for asbestos content by TEM in ac-
cordance with the Methodology for the
Measurement of Airborne Asbestos by
Electron Microscopy.™ The current TEM
methodology was developed particularly
for application to samples collected from
a volume of air in which the asbestos con-
centration is considered a minor compo-
nent of the total particulate loading. Car-
bon coating of the samples was perform-
ed by the EPA staff. Sample preparation
and analyses were completed by the TEM
laboratory.
Three levels of TEM analysis are describ-
ed in the methodology. Briefly summariz-
ed, Level I TEM analysis involves examina-
tion of the particulates deposited on the
sample filter by a 100-kV TEM. Asbestos
structures (fibers, bundles, clusters, and
matrices) are counted, sized, and identi-
fied as to asbestos type (chrysotile, amphi-
bole, ambiguous, or no identity) by mor-
phology and by observing the selected
area electron diffraction (SAED) patterns.
The width-to-length ratio of each particle
that is counted is recorded. Level II TEM
analysis consists of a Level I analysis plus
chemical elemental identification by
energy-dispersive spectrum (EDS) analysis.
Energy-dispersive analysis is used to deter-
mine the spectrum of the X-rays generated
by an asbestos structure. X-ray elemental
analysis is used for further categorization
Figure 2. Electric blower used for aggressive sampling.
6
of the amphibole fibers, identification of
the ambiguous fibers, and confirmation or
validation of chrysotile fibers. All Nucle-
pore samples collected in this study were
analyzed by Level II TEM.
Results
Air Monitoring Results
The results of TEM analyses of samples
collected under static and aggressive con-
ditions are compared in Figures 4 and 5.
The measured fiber concentrations after
abatement varied widely under both static
and aggressive sampling conditions, re-
gardless of the analytical method used. For
example, fiber concentrations determined
by PCM ranged from less than 2,000 to
90,000 fibers/m3 for static sampling and
from 2,000 to 110,000 fibers/m3 for ag-
gressive sampling. Similarly, concentra-
tions determined by TEM ranged from
6,000 to 583,000 fibers/m3 for static
sampling and from 14,700 to 1.27 million
fibers/m3 for aggressive sampling.
Statistical Comparisons
Statistical Method of Analysis
The Mann-Whitney test was used to de-
termine whether the observed differences
in analytical methods and sampling con-
ditions were statistically significant.11 Use
of the Mann-Whitney test required no prior
assumption regarding the nature of the
underlying probability distribution function
of measurements of asbestos fiber
concentrations.
Analytical Methods
Table 1 compares the asbestos fiber
levels detected by the PCM and TEM
methods of analysis under various sam-
pling conditions. PCM and TEM concen-
trations relate to different fiber popula-
tions, as defined by their detection limits
and by their standard protocols. Based on
the application of the Mann-Whitney test
and the assumption that the fiber/volume
concentrations are comparable, the dif-
ference between PCM and TEM results is
statistically significant (i.e., p <0.02) for
ambient sampling and for indoor sampling
under static and aggressive conditions.
The ratios of TEM/PCM concentrations for
static sampling were 6.5 for ambient sam-
ples and 5.2 for indoor samples. For ag-
gressive sampling, the ratio of TEM/PCM
was 9.8.
Sampling Conditions
The difference between the geometric
average fiber concentrations under static
and aggressive sampling conditions (Table
1) was statistically significant (i.e., p
-------
Figure 3. Aggressive sampling in progress.
Table 1. Comparison of Asbestos Fiber Levels* Detected by PCM and JEM Analyses
Under Various Sampling Conditions
Sampling Conditions
Analytical Technique
PCM analysis, fibers/m3
TEM analysis
Asbestos fibers/m3
Asbestos structures/m3
Outdoor
(Ambient)
2,000+110?
13,000 110]
15,000
Postabatement
Static
8,000 120]
42,000 [26]
64,000
Postabatement
Aggressive
27,000 [14]
266,000 [20]
725,000
*AH values are geometric means.
+Below limit of reliable quantitation 1 = 21,000 fibers/m3). Detection limit = fibers/m3.
*[ ] = number of samples.
<0.001) for PCM and TEM. The ratio of ag-
gressive to static fiber concentrations was
3.4 for PCM analyses and 6.3 for TEM
analyses.
Indoor Versus Ambient Samples
Also included in Table 1 are the PCM and
TEM analyses for samples collected in the
ambient atmosphere. For samples analyzed
by PCM, the geometric mean fiber concen-
tration was 8,000 fibers/m3 for indoor
samples compared with 2,000 fibers/m3
for ambient samples—a ratio of 4.1.
However, the PCM method is not suffi-
ciently sensitive for effective detection of
these ambient and indoor (static) concen-
trations because they are below the lower
limit of reliable quantitation by the method.
Consequently, the observed differences
between the two sample groups are prob-
ably not meaningful.
For the TEM samples collected indoors
under static conditions, the geometric
mean asbestos fiber concentration was
42,000 fibers/m3 compared with 13,000
fibers/m3 for ambient samples—a ratio of
3.2. The observed difference between
these indoor, static TEM concentrations
and the ambient TEM concentrations was
statistically significant (p = 0.009). The
ratio of indoor asbestos concentrations
under aggressive sampling conditions to
ambient asbestos concentrations was
20.5.
TEM Data from Static and
Aggressive Sampling Conditions
Figures 4 and 5 present data from the
TEM asbestos analysis reports. Figure 4
is the static TEM measurement, and
Figure 5 is the aggressive TEM analysis.
The analysis includes:
• Types of asbestos fibers observed.
• Number of other fibrous structures.
• Numbers of nonfibrous asbestos
particles.
• Diameters and lengths of fibers ob-
served by analyst.
• Total asbestos structures per cubic
centimeter of air.
The structural analysis data for each
TEM sample were entered into EPA's DEC
POP 11/70 computer in Cincinnati and
transferred to the IBM 3081 at EPA's Na-
tional Computer Center in North Carolina.
The data were processed by using the
statistical analysis system (SAS) and plot-
ted by use of the TELLAGRAF system.
Length-to-width plots were made for the
fibers.
Conclusions and Recommendations
The following conclusions resulted from
this study:
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Figure 4. Results o1 TEM analysis under static conditions. Plot of fiber length and diameter for
a static postabatement air sample in Room M112. Total asbestos structures/cc of
air = 0.067.
The aggressive sampling technique
used in this problem-definition study
revealed that air-entrainable asbestos
remained at this site immediately after
completion of abatement actions. The
mean asbestos fiber concentration dur-
ing aggressive sampling, as determin-
ed by TEM, was about 6 times that of
the mean asbestos fiber concentrations
during static sampling.
2. The fiber concentrations measured
under aggressive sampling conditions
were higher than those measured un-
der static conditions regardless of the
analytical method used. The ratio of ag-
gressive to static fiber concentrations
during PCM analyses was 3.4, whereas
this ratio during TEM analyses was 6.3.
The average PCM concentration during
aggressive sampling conditions was
0.03 fiber/cm3-less than the NIOSH-
recommended occupational limit of 0.1
fiber/cm3. This 8-hr time-weighted av-
erage is frequently cited in abatement
contractor specifications as the final
postabatement acceptance criterion.
3. The study results clearly demonstrate
that under similar sampling conditions,
TEM analysis detects more fibers than
PCM. The ratio of TEM/PCM concen-
trations for static sampling was 6.5 for
ambient samples and 5.2 for indoor
samples; the ratio for aggressive sam-
pling was 9.8.
4. Concentrations of work area asbestos
fibers that were determined by TEM
and measured by both aggressive and
static sampling methods were signifi-
cantly higher than ambient TEM con-
centrations. The actual environmental
conditions that exist in a building after
reoccupancy, reactivation of ventilation
systems, and the return to typical us-
age patterns are somewhere between
the static and aggressive sampling
conditions.
The following recommendations are based
on the study findings:
1. TEM should be recommended as the
analytical method of choice for mea-
suring airborne asbestos fiber concen-
trations for final clearance testing in at-
mospheres of buildings that have un-
dergone asbestos abatement. How-
ever, the current TEM protocols are
very time-consuming and expensive for
routine use in large surveys.
2. PCM analyses should be conducted as
a preliminary check to determine whe-
ther additional cleaning is necessary
before final clearance testing by TEM.
The PCM analyses are relatively inex-
pensive and can be performed quickly.
3. & criterion should be established to de-
fine an acceptable asbestos fiber con-
centration in building areas after asbes-
tos abatement, but not until a standard-
ized TEM protocol and an aggressive
sampling procedure have been devel-
oped and validated. Once developed,
these methods should be required for
all postabatement assessments.
4. Research should continue in the areas
of asbestos measurement, sampling,
hazard assessment, and abatement
control technology so that asbestos
hazards in buildings can be effectively
reduced. One important research ave-
nue should be the development of
quicker, less expensive methods for
monitoring the atmosphere in buildings
after asbestos abatement.
8
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5. Falgout, D. Environmental Release of
Asbestos From Commercial Product
Shaping. Engineering-Science, Fairfax,
Virginia. EPA/600/S2-85/044. August
1985.
6. Chatfield, E.J. Measurement of As-
bestos Fibre Concentrations in Ambi-
ent Atmospheres. Study No. 10, On-
tario Research Foundation. 1983.
7. PEDCO Environmental, Inc. Inventory
of Friable Asbestos-Containing Mater-
ials in Columbus East High School with
Recommendations for Corrective Ac-
tion. Final Report, Volume I. January
1984.
8. Association of the Wall/Ceiling Indus-
tries International, Inc. Guide Specifi-
cations for the Abatement of Abestos
Release From Spray-or-Trowel-Applied
Materials In Buildings and Other Struc-
tures. The Foundation of the Wall and
Ceiling Industry, Washington, D.C.
December 1981.
9. National Institute for Occupational
Safety and Health. Asbestos Fibers in
Air. NIOSH Method No. P&CAM 239.
NIOSH Manual of Analytical Methods,
Second Ed., Vol. 1. U.S. Department of
Health, Education, and Welfare, Cincin-
nati, Ohio. April 1977.
10. Yamate, G., S.C. Agarwal, and R.D.
Gibbons. Methodology for the Mea-
surement of Airborne Asbestos by
Electron Microscopy (Draft). Prepared
by NT Research Institute for the Of-
fice of Research and Development,
U.S. Environmental Protection Agen-
cy, Research Triangle Park, North Car-
olina. July 1984.
11. Mosteller, F., and R.E.K. Rourke. Sturdy
Statistics: Nonparametrics and Order
Statistics, Addison Wesley, Reading,
Massachusetts, 1973.
The full report was submitted in fulfill-
ment of Contract No. 68-03-3197 by PEI
Associates, Inc. under the sponsorship of
the U.S. Environmental Protection Agency.
Figure 5. Results of JEM analysis under aggressive Conditions. Plot of fiber length and
diameter for an aggressive postabatement air sample in Room M112. Total asbestos
structdres/cc of air = 1.112.
References
1. U.S. Environmental Protection Agency.
Asbestos-Containing Materials in
School Buildings: A Guidance Docu-
ment, Part 1. Office of Toxic Sub-
stances, Washington, D.C. 20460.
March 1979.
2. Sawyer, R.N., and D.M. Spooner. As-
bestos-Containing Materials in School
Buildings: A Guidance Document, Part
2. Office of Toxic Substances, U.S. En-
vironmental Protection Agency, Wash-
ington, D.C. 20460. March 1979.
3. U.S. Environmental Protection Agency.
Guidance for Controlling Friable As-
bestos-Containing Materials in Build-
ings. Office of Toxic Substances, Wash-
ington, D.C. EPA 560/5-83-002. March
1983.
4. U.S. Environmental Protection Agency.
Guidance for Controlling Asbestos-
Containing Materials in Buildings. EPA
560/5-85-024. June 1985.
-------
Mark A. Karaffa, Robert S. Amick, and Ann Crone are with PEI Associates, Inc..
Cincinnati. OH 45246-0100; the EPA author Thomas J. Powers (also the EPA
Project Officer, see below) is with the Water Engineering Research Laboratory,
Cincinnati, OH 45268.
The complete report, entitled "Assessment of Assay Methods for Evaluating
Asbestos Abatement Technology," {Order No. PB 86-194 446/AS; Cost:
$11.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, MA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
10
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