&EPA
Environmental Monitoring Office of Pesticides EPA 600/4-85-049
Systems Laboratory and Toxic Substances November 1985
Research Triangle Park, NC 27711 Washington, DC 20460
Research and Development & Toxic Substances
Measuring Airborne Asbestos
Following An
Abatement Action
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MEASURING AIRBORNE ASBESTOS FOLLOWING
AN ABATEMENT ACTION
Quality Assurance Division
Environmental Monitoring Systems Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
and
Exposure Evaluation Division
Office of Toxic Substances
Office of Pesticides and Toxic Substances
U.S. Environmental Protection Agency
Washington, D.C. 20460
November 1985
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ACKNOWLEDGMENTS
Many individuals contributed their time and effort to the
preparation of this guidance document. The primary author is Dale L.
Keyes of Environmental Sciences, Tucson, Arizona. Michael Beard (Office
of Research and Development, Quality Assurance Division) and Joseph
Breen (Office of Toxic Substances, Exposure Evaluation Division) served
as Coauthors and Task Managers, and directed the report preparation
process.
The material presented here is based in part on the results of a
conference held in March 1984 and sponsored jointly by EPA and the
National Bureau of Standards on post-abatement air monitoring for
asbestos. The conference brought together government officials,
research scientists, asbestos experts, abatement contractors, and others
to share ideas and experiences. A draft of the guidance document
incorporating the conference results together with other information was
prepared and reviewed by several persons acting as official peer
reviewers. The reviewers are:
Daniel Baxter, Science Applications, Inc.
Wolfgang Brandner, EPA Region VII
Lester Breslow, University of California
Jay Carter, National Institute of Occupational Saftey and Health
Eric Chatfield, Ontario Research Foundation
William Ewing, Georgia Tech. Research Institute
Peter Frasca, Electron Microscope Service Lab
Richard Lee, U.S. Steel
Marshall Marcus, Marcus Associates
Anthony Natale, Duall Incorporated
Bertram Price, National Economic Research Associates
Tony Restaino, EPA Region V
John Small, National Bureau of Standards
Gerald Spencer, The Survey Group, Inc.
Eric Steel, National Bureau of Standards
Ian Stewart, McCrone Associates
Their effort in reviewing the first draft and in offering valuable
comments is greatly appreciated.
Others providing valuable comments on various drafts of the
document include Jean Chesson of Battelle Memorial Institute, William
Nicholson of Mt. Sinai School of Medicine, Roger Wilmoth of
EPA/ORD-Cincinnati, David Mayer of EPA/OPTS-Washington, and Ralph Sposato
of EPA/ORD-RTP.
This report was prepared under subcontract to the Research Triangle
Institute. Personnel there are also acknowledged for their assistance
in the technical editing process.
The material contained within the document is guidance and does not
constitute a Federal regulation.
11
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TABLE OF CONTENTS
Acknowledgments ii
Nontechnical Summary of the Guidance v
Chapter 1 - Introduction and Purpose 1-1
Chapter 2 - Overview of Technical Guidance 2-1
2.1 The Process for Releasing the Contractor 2-1
2.2 Analyzing Air Samples for Asbestos 2-1
2.3 Air Sampling Procedures 2-4
2.4 Air Testing Criteria for Determining Work Site
Cleanliness After Abatement 2-5
2.5 Quality Assurance Practices 2-6
Chapter 3 - Sample Analysis 3-1
3.1 The Asbestos Measurement Problem 3-1
3.2 Analysis by Phase Contrast Microscopy (PCM) 3-1
3.3 Analysis by Transmission Electron Microscopy (TEM) 3-3
3.4 Analysis by Scanning Electron Microscopy (SEM) 3-5
3.5 Comparison of the Three Methods for Post-Abatement
Air Testing 3-7
Chapter 4 - Air Sampling Procedures 4-1
4.1 Sampling Equipment 4-1
4.1.1 Filter Media 4-1
4.1.2 Filter Cassettes 4-1
4.1.4 Flow-Controlled Pumps and Orifices 4-2
4.2 Sampling Procedures 4-2
4.2.1 Checking Filter Assemblies 4-2
4.2.2 Measuring Airflow 4-2
4.2.3 Determining Sampling Times and Volumes 4-5
4.2.4 Field Operations - 4-6
4.3 Sampling Strategy 4-6
Chapter 5 - Air Testing Criteria for Determining Work-Site
Cleanliness After Abatement 5-1
5.1 The Rationale for the Recommended Release Criteria 5-1
5.2 Statistical Considerations for Using Release
Criteria 5-3
111
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TABLE OF CONTENTS (con.)
Page
5.3 TEM Release Criterion 5-4
5.3.1 Sampling Volume and Time 5-4
5.3.2 The Number and Location of Samplers 5-4
5.3.3 Comparing Measured Levels of Airborne Asbestos . . . 5-8
5.3.4 Recommended Actions if the Work Site Fails 5-8
5.4 PCM Release Criterion 5-9
5.4.1 Sampling Volume and Time 5-9
5.4.2 The Number and Location of Samplers 5-9
5.4.3 Comparing Measured Levels of Asbestos to the
Lowest Quantifiable Level 5-9
5.4.4 Recommended Actions if the Work Site Fails 5-9
5.5 Example Applications of the Two Release Criteria 5-9
5.5.1 PCM Example 5-11
5.5.2 TEM Example 5-11
Chapter 6 - Quality Assurance Practices 6-1
References R-l
Appendix A - A Random Number Procedure for Selecting a
Representative Work-site Sample A-l
IV
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NONTECHNICAL SUMMARY OF THE GUIDANCE
One of the most critical points in an asbestos abatement project is
knowing when the work has been completed, the contractor can be
released, and the building can be reoccupied. This decision should be
based on two factors: (1) satisfactory performance of the abatement
work, and (2) thorough cleaning of the work site. As outlined below,
these factors should be evaluated by visually inspecting the work site,
and by measuring the level of airborne asbestos there. The evaluation
should be conducted by the asbestos program manager or the technical
advisor assigned to monitor the abatement work.
Visual Inspection
Once the contractor has completed the abatement work but
before any containment barriers have been dismantled, the
project monitor should thoroughly inspect the work site for
incomplete abatement and for evidence of dust and debris.
Additional abatement and/or work-site cleaning is needed
if the work site fails the visual inspection.
Air Testing
Air testing should be conducted after the interior
plastic barriers have been removed but before the final
barriers separating the work site from the rest of the
building have been taken down.
Three methods for measuring airborne asbestos are
available: phase contrast microscopy (PCM), scanning
electron microscopy (SEM), and transmission electron
microscopy (TEM). TEM is the best method for measuring
the types of fibers expected to be present at abatement
work sites, but PCM is more available and practical in
many localities. SEM lacks a standard analytical protocol,
laboratory testing programs, and standard reference
materials for judging the accuracy of SEM analyses.
Regardless of which method is used, air samples
should be taken "aggressively". This means., _air blowers
should be used to dislodge fibers from surfaces, and
fans should be used to keep them suspended.
At least five samples should be taken inside the work
site, and, if TEM is used for sample analysis, another
five outside the work site should be collected.
Specified sampling equipment, flow rates, and sampling
volumes should be used.
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One of two alternative criteria should be used to
determine if the work site has been adequately cleaned:
For TEM, the average level of airborne asbestos for the
samples inside the work site should be no higher than the
average for the samples outside the work site.
For PCM, the level of airborne fibers for each of the
samples inside the work site should be less than PCM's limit
of reliable quantification (0.01 or fewer fibers per cubic
centimeter if the minimum recommended volume of air is
collected).
If the work site fails the air test, it should be
recleaned and retested.
The following chapters discuss various technical issues regarding
the air test. Specifications are provided for air sampling and detailed
guidelines are presented for using either TEM or PCM to analyze the
samples. The information is designed for asbestos program managers and
technical program advisors.
VI
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CHAPTER 1
INTRODUCTION AND PURPOSE
Asbestos-containing material (ACM) in buildings is a potential
concern for a growing number of building owners. EPA estimates that
31,000 schools and 733,000 public and commercial buildings contain
friable (easily crumbled) asbestos (USEPA, 1984a and 1984b). ACM which
is damaged, disturbed, or deteriorated will release asbestos fibers and
possibly create a health hazard for building occupants.
Many building owners have undertaken or are considering some form
of abatement (removal, enclosure, encapsulation, or repair of the ACM).
Although EPA's "Friable Asbestos-Containing Materials in Schools;
Identification and Notification Rule" (40 CFR Part 763) does not require
that schools take corrective action when asbestos is detected, the
parent and employee notification requirements of the Rule have
stimulated the majority of school districts to do so (USEPA, 1984a).
Owners of many other types of buildings also have developed asbestos
control programs.
EPA has published several guidance documents to assist building
owners in understanding the relevant technical issues, determining if
asbestos is present, planning a control program if necessary, and
choosing a course of action. The latest update of the EPA guidance is:
"Guidance for Controlling Asbestos-Containing Materials in Buildings,
1985 Edition," June 1985 (USEPA, 1985).
Once ACM has been detected in a building and the need for abatement
determined, conducting the abatement action in a safe and thorough
manner is crucial. Releasing the abatement contractor is the final step
in the abatement process (although a continuing operations and
maintenance program may be necessary until the building is demolished*).
This guidance document addresses the question of what criteria can be
used to judge when the contractor can be released. It supplements and
extends previous EPA guidance by recommending specific procedures for
using air monitoring in making these judgments. The material is
presented in technical language, and is thus directed to asbestos
program managers, technical program advisors, and others involved
with asbestos abatement work and air testing.
The guidance offered here is based in part on the results of a
two-day conference sponsored jointly by EPA and the National Bureau of
Standards (NBS) held in March 1984. The evidence presented and the
conclusions reached by the conference participants have been examined in
light of other information reported in the open literature and
government studies. In this sense, the guidance document reflects the
interpretation and judgment of EPA in addition to the collective
experience and knowledge of the conference participants.
See USEPA 1985 for a description of special O&M programs for
buildings with ACM.
1-1
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EPA will continue to gather data and conduct research on the
subject of air monitoring for asbestos following an abatement project.
To this end, the experience of asbestos program managers, asbestos
consultants, abatement contractors, and others working on asbestos
control projects could prove to be highly informative. Any information
on measurements of airborne asbestos in buildings with ACM made by phase
contrast microscopy, scanning electron microscopy, or transmission
electron microscopy may be forwarded to:
U.S. Environmental Protection Agency
Environmental Monitoring Systems Laboratory
Quality Assurance Division (MD-77)
Re: Asbestos Monitoring Data
Research Triangle Park, N.C. 27711
EPA is especially interested in measurements of airborne asbestos
made inside the work site during ACM abatement activities, and, once the
abatement is completed, after each work-site cleaning by the abatement
contractor prior to his release. It would be appreciated if data
forwarded to EPA include basic information such as asbestos fiber
concentration, sample volume, analytical procedure, number and type of
asbestos fibers counted, sample preparation technique (direct or
indirect).
1-2
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CHAPTER 2
OVERVIEW OF THE TECHNICAL GUIDANCE
The guidance offered here addresses the question of how to
determine when an asbestos abatement work site has been sufficiently
cleaned. It is set within the larger framework of determining when the
abatement work is completed and when to release the contractor, but it
focusses specifically on the use of air sampling and analysis to
determine work-site cleanliness. Procedures for conducting post-
abatement air sampling are specified and methods for measuring airborne
asbestos and interpreting the results are recommended.
Following are summaries of each major topic in the guidance
document, preceded by a brief discussion of the process for releasing
the abatement contractor. The major topics include analyzing air
samples for asbestos, air sampling procedures, criteria for determining
work-site cleanliness, and quality assurance practices.
2.1 THE PROCESS FOR RELEASING THE CONTRACTOR
The most recent EPA guidance on controlling ACM in buildings (USEPA
1985) describes a two-part process for determining when an abatement
project is complete and the contractor can be released. As illustrated
in Figure 2-1, the two steps are: (1) a visual test to determine if the
ACM has been properly abated and if the work site is free of debris and
dust, and (2) an air test to determine if residual asbestos fibers
generated during abatement have been reduced below a predetermined
level, that is, to determine if the air-test release criterion has been
met. The asbestos program manager or the person appointed to monitor
the abatement work should be responsible for conducting the visual test
and overseeing the air test.
The visual test is designed, first, to spot any incomplete
abatement work. If the ACM is surfacing material, abatement could mean
removal, encapsulation, or enclosure (USEPA, 1985). If the ACM is pipe
or boiler insulation, abatement could mean removal, patching, or
replacement of the protective jacket (USEPA, 1985). In any case, the
quality and thoroughness of the work is reviewed. Deficiencies should be
corrected before proceeding with the next phase of the inspection.
The second role of the visual inspection is to detect obvious signs
of inadequate work-site cleaning. The abatement contractor should clean
all plastic barriers at the work site using wet cleaning or HEPA
vacuuming techniques (USEPA, 1985). The inspector should use damp
cloths and a flashlight to check for debris and dust (USEPA, 1985).
The air test is designed to detect asbestos fibers which were not
removed by the cleaning procedures. Before the test is conducted, all
plastic barriers are removed except those covering vents, windows,
doors, and all entries to the work site. This will allow any fibers
trapped between the plastic and floors, walls, and/or ceilings to become
2-1
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Abatement Action
is
Abatement
Complete?
Wet-Clean and/or
HEPA-Vacuum
Work Site
Is Work Site
Visually Clean?
Remove All But
Final Plastic
Barriers
Measure Airborne Asbestos
Wet-Clean and/or
HEPA-Vacuum
Work Site
No
Yes
Is Level
Low Enough?
Release Contractor
Figure 2-1. The process for releasing the contractor.
2-2
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airborne before testing is begun. If the air test criterion is met, the
contractor is released. Otherwise, the work site must be thoroughly
recleaned.
2.2 ANALYZING AIR SAMPLES FOR ASBESTOS
Three microscopic methods are currently being used to analyze
airborne asbestos: phase contrast microscopy (PCM), scanning electron
microscopy (SEM), and transmission electron microscopy (TEM). Because
asbestos fibers are small (especially those found in buildings with ACM)
and difficult to distinguish from other types of fibers, the detection
and accurate identification of asbestos requires sophisticated methods
of analysis.
TEM is the best method for measuring airborne asbestos. It can
detect the very thin fibers (typically down to 0.0025 |Jm diameter) found
in buildings with ACM and in the ambient atmosphere, and it has the
capability of identifying asbestos unambiguously. In addition, a
standard protocol for TEM analysis has been developed by EPA, and
standard reference materials for instrument calibration and accuracy
checks are available from the National Bureau of Standards (NBS). PCM
is less sensitive to thin fibers and less specific for asbestos. When
used according to the National Institute of Occupational Safety and
Health (NIOSH) protocols, PCM cannot detect fibers smaller than 0.25 (Jm in
diameter, and cannot distinguish asbestos from other types of fibers. As
a result, PCM results can only be considered an index of airborne asbestos
levels. However, the method has a well-developed protocol, and NIOSH
operates a testing program for PCM laboratories. SEM is somewhat more
sensitive and specific than PCM but less so than TEM. Significantly, no
standard protocol nor NBS standard reference materials are available for
SEM. As a result, SEM analyses are currently of unknown reliability.
Anyone using SEM for measuring airborne asbestos should require the
analytical laboratory to document the relationship between SEM and either
PCM or TEM results.
With respect to method availability, cost, and "turnaround time"
(i.e., the time between submission of samples and receipt of results),
PCM is superior on all accounts. It is by far the most available and
(by a factor of 2-10 depending on the level of analysis) the least
expensive. The turnaround time is usually less than 6 hours compared
with 6-24 hours for SEM and 2-7 days for TEM. Note, however, that
availability, cost, and time factors may change significantly in the
future.
RECOMMENDATIONS
Either TEM or PCM should be used to analyze air
samples for asbestos fibers. TEM is the method of
choice but PCM is more practical. Without standard
protocols and reference materials, SEM results are
difficult to evaluate.
2-3
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Use TEM according to the updated EPA protocol
(direct sample preparation, if possible; Level I
analysis may be sufficient), and PCM according to
the NIOSH P&CAM 239 (or, alternatively, NIOSH 7400)
protocol.
2.3 AIR SAMPLING PROCEDURES
Air sampling is conducted by drawing air through a filter at a
known rate. Typically, flow-controlled pumps and either cellulose ester
or polycarbonate filters (depending on the method of sample analysis)
are used. Specific sampling procedures should be followed in order to
assure reliablity of the results.
In addition to the use of appropriate sampling equipment, the
sampling plan must be carefully designed to account for normal
variability in asbestos levels from location-to-location and over
time. One of the most important factors which influence the
degree of variability in air measurements is the pattern of air movement.
Under conditions of limited movement, many fibers will settle out of the
air. Measurements of airborne asbestos under these conditions are likely
to be lower than if all the fibers were suspended. Artificial agitation
of the air in a building is one way to keep the fibers suspended.
RECOMMENDATIONS
Use constant-flow sampling pumps and the following
filters:
For PCM analysis: cellulose ester filters
with 0.8-1.2 pm pore size.
For TEM analysis: polycarbonate filters with
0.4 [jm pore size.
Use the specified procedures for testing and
operating sampling equipment.
Sample at a flow rate of between 2 and 12 liters per
minute (L/min).
Sample aggressively:
Use forced-air equipment such as a leaf blower
to initially dislodge fibers from surfaces.
Use fans as specified to keep fibers suspended
during sampling.
2-4
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2.4 AIR TESTING CRITERIA FOR DETERMINING WORK-SITE CLEANLINESS
AFTER ABATEMENT
Regardless of which method is used to analyze air samples for
asbestos, the results of the analyses can only be used for releasing a
contractor if a criterion is available against which the results can be
compared. In other words, how low do the measured asbestos levels have
to be in order for the work site to be declared sufficiently clean?
Since an abatement contractor could not be expected to reduce
asbestos levels below those in the air entering the work site, the level
of airborne asbestos in the ambient air (or in the make-up air if
negative pressure ventilation is used at the work site [USEPA, 1985])
appears to be a reasonable reference. This is the case for TEM. PCM,
however, is not sufficiently sensitive to thin fibers nor specific for
asbestos to reliably measure asbestos outside the abatement work site.
A criterion based on the limit of reliable quantification of the
analytical method is more appropriate for PCM.
The recommended number of TEM samples and the minimum sampling
volume needed to compare measured asbestos levels at the work site
against the reference level should take into account the expected
variability in TEM measurements, how low the reference asbestos level is
likely to be, and the detection limit of the TEM method. Sampling
requirements for PCM should be at least as rigorous as those for TEM,
considering PCM's low sensitivity to thin fibers and lack of specificity
for asbestos.
RECOMMENDATIONS
If TEM is used:
Collect five samples within and five outside
the work site, each of at least 3000 liters.
(Use blank filters and duplicate samples for
reliability checks as specified.)
Analyze the samples and express the results as
f/cc (or ng/m3 if an indirect sample
preparation is necessary).
Compare the averages of the inside and outside
levels using the statistical t-test.
Release the contractor if the inside level is
not statistically higher than the outside
level; otherwise, have the entire work site
recleaned and retested.
2-5
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If PCM is used:
Collect at least five samples per work site or
one per room, whichever is greater, each of at
least 3,000 liters. (Use blank filter and
duplicate samples for reliability checks as
specified.)
Analyze the samples.
Release the contractor if none of the samples
are above the PCM limit of reliable
quantification (0.01 f/cc if 3,000 liters are
sampled); otherwise, have the entire work site
recleaned and retested.
2.5 QUALITY ASSURANCE PRACTICES
Measuring airborne asbestos is a sophisticated and exacting
process. Errors may be introduced at any one of the many data
collection and analysis steps. To guard against this possibility
and to assure reliable results, a formal quality assurance
program should be adopted.
RECOMMENDATIONS
Be sure that all persons and organizations involved
in sampling and analysis are trained and/or
experienced. Check references and documented
levels of performance.
Use field and laboratory blanks to check for fiber
contamination, coded sample labels to avoid analyst
bias, duplicate analyses to confirm analytical
precision, and a second laboratory to spot-check
the accuracy of results. Be sure that all
equipment setup, operation, and calibration
procedures are followed.
Assign responsibility for security of the samples
to specific persons at each stage of the analysis.
Document each step in the passage of the sample
from the field to the laboratory to the building
owner.
Check and document laboratory results. The
building owner should retain all test results and
records documenting the testing process. Filters
should also be saved in case additional analyses
need to be conducted in the future.
2-6
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CHAPTER 3
SAMPLE ANALYSIS
Three options for analyzing air samples for asbestos were
summarized in Chapter 2: PCM, SEM, and TEM. The recommended option is
TEM based on its superior technical capabilities. However, PCM is a
more practical alternative in many localities. SEM needs development
of a standardized protocol and standard reference materials. The
rationale for these guidelines is presented more fully in this chapter.
3.1 THE ASBESTOS MEASUREMENT PROBLEM
Analyzing a sample of air for asbestos is a technically challenging
problem. Asbestos fibers are extremely small and may number several
million for an average size room when friable ACM is present (Chesson, et
al., 1985a). Thus, only a small fraction of the asbestos fiber popula-
tion can be observed and counted. Significant errors can be introduced
when the results of the sample analysis are extrapolated to the entire
room. Furthermore, fibers of asbestos may closely resemble those of
hair, cloth, fibrous glass, paper, and other nonasbestos materials. As
a result, identifying and counting asbestos fibers requires sophisti-
cated instruments, highly trained technicians, and rigorous quality
assurance practices.
3.2 ANALYSIS BY PHASE CONTRAST MICROSCOPY (PCM)
The Occupational Safety and Health Administration (OSHA) has
adopted a standard protocol for measuring exposure to airborne asbestos
in the industrial workplace. This protocol, P&CAM 239, (Leidel et al.,
1979) was developed by the National Institute of Occupational Safety and
Health (NIOSH) and specifies PCM as the measurement method-. The NIOSH
protocol further specifies that only fibers with a 3:1 aspect ratio and
longer than 5 micrometers ([Jm) in length should be counted.
The NIOSH protocol involves collecting airborne fibers on a
standard 37-millimeter (mm), 0.8-[Jm pore-size cellulose ester filter. A
pie-shaped section of filter is then analyzed by dissolving the filter
and counting the fibers with PCM at 400X magnification." Phase contrast
increases the light contrast between the object and the background, thus
enhancing the microscopist's ability to see fibers. Normally, 100
NIOSH has published a revised protocolNIOSH 7400 (NIOSH, 1984).
OSHA is now reviewing this revised protocol, but has not adopted it
yet.
3-1
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microscopic fields or 100 fibers are counted, whichever occurs first.*
PCM, as employed in the NIOSH protocols, has two serious limitations
for measuring airborne asbestos. First, PCM can not distinguish asbestos
from nonasbestos fibers; all elongated particles with the required length
and aspect ratio are counted. PCM-measured fibers thus can only serve as
an index of asbestos fibers. Second, only particles larger than about
0.25 l-im in diameter can be detected owing to inherent limits of resolution
of PCM, and only particles longer than 5 [Jm are counted due to the
counting protocol.
These are not serious limitations for the use of PCM in asbestos
workplace settings where asbestos fibers are a significant fraction of
all airborne fibers. Moreover, variation over time in levels of
PCM-measured fibers and asbestos fibers appears to be correlated in the
asbestos workplace; that is, the higher the level of PCM fibers, the
higher the level of asbestos. These relationships are borne out by
studies of the health of workers in asbestos industries in which levels
of PCM-measured fibers serve as the index of exposure to asbestos (NEC,
1984).
With one exception, conditions in buildings with friable ACM are
believed to be quite different. Although evidence is limited, asbestos
fibers appear to be smaller in size (fewer fiber bundles) and a smaller
fraction of all airborne fibers than those in asbestos industry settings
(Chatfield,1983). A recent study of schools with friable ACM found very
low correlations of fiber levels measured by PCM compared with asbestos
levels measured by SEM and TEM (Chesson et al., 1985a).
The exception to this general rule may be fiber levels generated
during asbestos abatement activities. Levels of both PCM and asbestos
fibers are likely to be elevated during abatement, especially during
removal of friable ACM. In this sense, the abatement work site may
approximate conditions in the asbestos industry workplace. Thus, OSHA
requires measurements of airborne fibers by PCM during abatement
projects as an indication of asbestos exposure.
The justification for using PCM-measured fibers as the basis for
determining when the abatement worksite has been sufficiently cleaned,
that is, as the release criterion, follows from the above argument. If
levels of both PCM and asbestos fibers are elevated during abatement
activities, then removing PCM fibers should remove asbestos fibers as
well. In other words, work-site cleaning practices which reduce levels
of airborne cellulose, hair, and other large fibers detected by PCM
should likewise reduce levels of residual asbestos fibers. However,
this rationale rests on logical deduction; no simultaneous measurements
of PCM and SEM or TEM levels during an abatement action and following
work site cleaning operations have been made to test the rationale.
A minimum of 10 fibers needs to be counted for reliable quantifi-
cation (Leidel et al., 1979). Counting more than 100 fibers
or 100 fields would be unnecessarily time-consuming and would add
little to the reliability of the results.
3-2
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Of the three methods for measuring airborne asbestos, PCM is the
least expensive (about $25-$50 per sample) and the most readily
available. In addition, results of PCM analysis can usually be
communicated to the building owner in less than 6 hours. Finally, the
NIOSH protocol has been extensively tested and an active laboratory
evaluation program, the Proficiency Analytical Testing (PAT) Program, is
maintained by NIOSH.*
3.3 ANALYSIS BY TRANSMISSION ELECTRON MICROSCOPY (TEM)
The limit of a microscope's ability to detect objects is related to
the wavelength of the source of "illumination". Since electrons have a
much shorter wavelength than does light, the electron microscope is
inherently superior to the optical microscope for detecting small fibers
typical of asbestos fiber populations found in buildings with ACM.
Of the two types of electron microscopy used for measuring airborne
asbestos, TEM is considered the method of choice (Chatfield, 1983; Steel
and Small, 1985). Following the EPA provisional methodology for TEM
analysis (Samudra et al., 1978), fibers are collected on a 0.4 [Jm pore
size polycarbonate filter (or on a 0.45 (Jm pore size cellulose ester
filter if significant levels of contaminating organic materials are
present in the air). Sample preparation involves either (1) direct
transfer of collected fibers from the polycarbonate filter to an
electron microscope (EM) grid after the filter is first carbon-coated,
or (2) an indirect transfer whereby a section of the cellulose ester
filter is ashed, the asbestos fibers are sonicated in water and
refiltered on a polycarbonate filter, and then carbon-coated and
transferred to the EM grid.** Direct transfer is preferred since it
does not cause fiber breakage. The mounted fibers are then examined at
20,OOOX magnification, identified as asbestos, measured, and counted.
The mass of each fiber may also be estimated if estimates of mass
concentration are desired. No more than 100 fibers or 10 grid openings
need to be observed.
TEM is the method of choice for analyzing asbestos based on its
sensitivity to the smallest fibers and on its specificity for asbestos.
Since the sample of fibers is mounted on an extremely thin substrate on
the EM grid, electrons can pass through the substrate, be diffracted by
the fibers and other materials, and be refocussed into an image on a
fluorescent screen, all without substantial back-scatter of electrons.
This allows high electron beam voltage (approximately 100 kilovolts) and
high magnification of the specimen (up to 100,OOOX). Extremely thin
asbestos fibers (typically 0.0025 [Jm in diameter) can be detected.
The results of the PAT program should be used in selecting a
laboratory for PCM analysis. Call (513) 841-4357 for a copy of the
latest evaluation results.
A direct transfer technique for cellulose ester filters has also been
reported (Burdett and Rood, 1983).
3-3
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TEM can be used to indicate the likely presence of asbestos in a
population of fibers based on fiber shape and configuration alone.
However, in order to confirm the identity of the fibers, chemical and
crystal analysis of individual fibers is needed. The relevant
analytical techniques are known as energy dispersive X-ray spectrometry
(EDXA or EDS) and selective area electron diffraction (SAED). In EDXA,
X-rays emitted from interactions between the electron beam and the
fibers are analyzed, and in SAED, the electron diffraction patterns
created by the same interactions are analyzed.
A TEM instrument outfitted with EDXA and SAED capabilities is
sometimes called an analytical electron microscope. The high electron
beam voltage characteristic of TEM combined with the thinness of the
fiber substrate on the EM grid allows EDXA and SAED to be performed on
single fibers. Although each fiber observed is not always subjected to
EDXA and SAED analysis, the preliminary identification of asbestos-like
fibers combined with chemical and crystal analysis of a representative
subset of fibers allows the fiber population to be characterized with a
high level of confidence. In addition, SAED can be performed visually
(by quickly observing the diffraction pattern on the fluorescent screen)
or quantitatively (by photographing the diffraction pattern at an angle
and measuring the photograph). The latter is a definitive means of
identifying asbestos.
The extreme sensitivity of TEM does make the task of detecting and
assessing thick fibers (larger than about 1.0 |Jm) and fiber clusters and
bundles more difficult. Because thin fibers greatly outnumber thick
ones in air samples from buildings with friable ACM (Chatfield, 1983;
Chesson et al., 1985), counting fibers on the EM grid may stop before
any large fibers are observed. Although the failure to observe thick
fibers will not significantly affect fiber counts, it will bias downward
the estimation of fiber mass, since a single large fiber may equal the
mass of several thousand small fibers. Likewise, fiber clusters and
bundles may be infrequently found. However, the clusters and bundles
are so difficult to accurately measure and are so large in mass compared
to individual fibers that the revised EPA protocol specifies that the
presence of clusters and bundles be noted but not included in fiber
counts or estimates of mass concentrations (Yamate, 1984).
Scanning transmission electron microscopy (STEM) has been employed
by some laboratories to aid in identifying large fibers. STEM is
performed by scanning the field of view at a lower magnification
(typically 1000X). Not all transmission electron microscopes have
scanning capabilities.
Given the complexity and sophistication of the TEM analysis for
asbestos, the need for highly skilled microscopists and detailed
protocols is apparent. Early attempts to compare analyses of the same
air sample by several laboratories revealed that the analytical results
varied by several orders of magnitude (USEPA, 1977a). Since then,
efforts to standardize sample preparation and analysis protocols and to
develop strict quality assurance practices have greatly improved the
reliability of asbestos analyses by TEM. A recent study by the NBS
revealed that TEM microscopists in the study had a greater than 90
3-4
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percent chance of identifying chrysotile fibers longer than 1 pm (Steel
and Small, 1985). However, the authors also noted that instrument
characteristics (especially, the mechanical stage, image quality, and
electron diffraction capabilities) can be a significant source of error.
On the other hand, the availability of NBS standard reference materials
for asbestos (Small et al., 1985) and the use of special counting
procedures like the one described by the NBS authors (Steel and Small,
1985) can be used to evaluate the reliability and accuracy of TEM
results.
The major disadvantages to using TEM for post-abatement clearance
monitoring are the cost and time for analysis. Partly because few
laboratories currently offer TEM services, costs for analysis may be $500
or higher per sample, and the time until results are received may be
several days. To reduce the cost and turnaround time, EPA has proposed
three levels of TEM analysis (Yamate, 1984):
Level I - Identification of asbestos fibers is based on fiber
morphology and the observed SAED pattern on the
fluorescent screen.
Level II - Analysis of the chemical composition of each fiber by
EDXA is added to the Level I procedures.
Level III - Quantitative analysis of SAED patterns from a few
representative fibers is added to Level II procedures.
Where asbestos is known to be present, fibers which appear to be
asbestos-like by shape and by qualitative analysis of crystal structure
(i.e., visual SAED) can reasonably be assumed to be asbestos. This is
the case for abatement work sites in buildings with ACM. As a result,
Level I analysis should be sufficient for post-abatement testing
purposes. However, where definitive confirmation of airborne asbestos is
needed, for legal or other purposes, a Level II or III analysis will be
necessary. Thus, if only Level I analysis is employed, EM grids for all
samples should be archived for future Level II or III analysis as may be
needed.
3.4 ANALYSIS BY SCANNING ELECTRON MICROSCOPY (SEM)
As an electron microscopic method, SEM holds promise for greater
sensitivity to thin fibers and better specificity for asbestos as
compared with light microscopy. Technically, however, it currently
falls short of TEM's capabilities. SEM differs from TEM in that the
fiber substrate mounted on the EM grid is considerably thicker. As a
result, electrons bombarding the specimen are scattered and reflected
rather than being transmitted. The thick substrate also reflects and
scatters electrons which are detected as "noise" by the microscope. As
a result, the object being viewed must be larger than a TEM-observed
object in order to be seen. In terms of fiber dimensions, the limit of
resolution obtained under typical conditions is a fiber diameter of
0.20 pm.
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SEM is also less powerful than TEM in its ability to distinguish
asbestos from other types of fibers. SAED is not feasible with SEM due
to the thick substrate and the signal noise problem noted above.
Chemical analysis with EDXA is possible (for fibers with a diameter of
at least 0.20 urn), but EDXA alone does not provide definitive evidence
for asbestos. (Some nonasbestos fibrous materials have similar chemical
compositions.) However, in a setting such as an asbestos abatement work
site where airborne asbestos is likely to be present, morphological
identification of asbestos-like fibers by SEM combined with detection of
asbestos-like chemical compositions for a few of these fibers would be
strong support for the presence of asbestos.
Without doubt, SEM can be superior to PCM for indicating the
presence of airborne asbestos. In addition, the scanning feature of SEM
used at a magnification of 1,000-2,OOOX provides a useful means of
rapidly observing fields of view and locating large fibers, clusters,
and bundles.
Unlike PCM and TEM, no standardized protocol for sample preparation
and analysis using SEM is currently available. Although samples are
usually collected on 0.4-0.8 pm pore size polycarbonate filters,
cellulose ester filters have also been employed.* Likewise, most
laboratories use a relatively simple protocol for sample preparation
(generally, direct carbon coating of the filter), but the specific
features of the protocol differ significantly among laboratories. The
same is true for instrument specifications (e.g., raster scan rate,
magnification, electron beam strength) and fiber identification and
counting procedures.** Without standardized protocols, it is not
possible to characterize analytical accuracy and reliability of SEM
results. It is difficult to know how much confidence can be placed in
the results of an SEM analysis until (1) a standardized protocol is
developed, evaluated, and adopted, (2) NBS reference materials are made
available for calibrating instruments and procedures, and (3) a
laboratory evaluation program is initiated. EPA and NBS are both
initiating programs which address these deficiencies.
Based on evidence presented at the NBS/EPA conference (NBS/EPA,
1984), SEM service for asbestos analysis appears to be more available
than TEM but less available than PCM. In addition, both the cost and
time of analysis appear to be intermediate between PCM and TEM.
Polycarbonate filters are preferred since problems with signal noise
are fewer than with cellulose ester filters.
An example of an SEM protocol developed by Verein Deutscher Ingenieur
appears in Spurny (1985).
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3.5 COMPARISON OF THE THREE METHODS FOR POST-ABATEMENT TESTING
As summarized in Table 3-1, PCM, TEM, and SEM offer clear if not
easy choices for measuring airborne asbestos following an abatement
project. PCM is currently the most widely used technique, due to its
history of use for meeting OSHA workplace exposure standards and to its
availability. Since OSHA monitoring is required for many asbestos
removal projects, it seems only natural to many building owners to
specify a PCM-based criterion for determining project completion. Not
only is PCM the most popular method, the PCM analytical protocol and the
laboratories offering PCM service are the best characterized. Finally,
PCM's low cost and short turnaround time make it an attractive choice
when contractors are waiting to complete an abatement project. But PCM
measurements are, at best, only rough indicators of asbestos
contamination following abatement.
TEM is distinguished from PCM on all characteristics. It is more
sensitive to thin fibers and more specific for asbestos, on the one
hand, and less available, more costly, and more time consumptive on the
other. With respect to method characterization and development, TEM has
shown substantial improvement during the last few years. The
availability of qualified laboratories offering TEM service also should
improve as the demand for service increases. This should put downward
pressure on future costs and turnaround times. In the short term,
however, users of TEM for determining the completion of abatement
projects will be faced with relatively high costs and long delays in
obtaining results of analyses. Specifying EPA Level I analysis may
mitigate these problems to some extent, as suggested by the low end of
the cost and time estimates for TEM in Table 3-1. (A portion of the
range of cost and time estimates for TEM reflects direct compared with
indirect methods of sample preparation.)
SEM appears to lie between PCM and TEM on most characteristics: it
is potentially more sensitive to thin fibers and more specific for
asbestos than PCM but less so than TEM; it is more readily available
(and popular) than TEM but less so than PCM; and estimates for both cost
and time of analysis are higher than for PCM but lower than for TEM.
SEM's greatest handicap is inadequate method characterization, including
the lack of a standardized protocol for sample preparation and analysis.
Efforts by EPA and NBS to evaluate the utility of SEM, to provide
standard reference materials, and to develop a laboratojy testing
program should improve SEM characterization.
It is important to note that the estimates in Table 3-1 assume
up-to-date instruments, skilled analysts, good operating conditions, and
strict quality assurance practices. Where these assumptions do not
hold, the estimates of method sensitivity and specificity may not apply.
In addition, both TEM and SEM can be conducted with various degrees of
sophistication. The three EPA levels of analysis reflect this for TEM,
as does the range of cost and time estimates for SEM. For example, SEM
could be conducted with reduced sensitivity in order to detect
3-7
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TABLE 3-1. COMPARISON OF METHODS FOR MEASURING AIRBORNE ASBESTOS
PCM
SEM
TEM
Standard
Methods
Quality
Assurance
NIOSH P&CAM 239
Method"
Proficiency
Analytical Test-
ing Program; no
NBS reference
materials.
No standard
method.
No lab testing,
or NBS reference
materials .
EPA provisional
method & update**
Limited lab test-
ing, NBS refer-
ence materials
available.
Cost
Availability
Time
Requirements
Sensitivity
(Thinnest
Fiber Visible)
Specificity
$25-50
Most available.
1 hr preparation
& analysis, <6
hrs. turnaround
0.15 pm at best;
0.25 pm typical.
Not specific for
asbestos.
Collection
Filters
0.8-1.2 pm
cellulose ester.
$50-300
Less available.
4 hr preparation
& analysis, 6-24
hrs. turnaround
0.05 pm at best;
0.20 pm typical.
More specific
than PCM but not
definitive for
asbestos (SEM
with EDXA)
0.4-0.8 pm poly-
carbonate best,
cellulose ester
also used.
$200-600
Least available.
4-24 hr prep-
aration & anal-
ysis, 2-7 days
turnaround
0.0002 pm at best;
0.0025 pm typical.
Definitive for
asbestos (Level
III TEM with
EDXA & SAED)
0.4 pm polycarbon-
ate, or 0.45 pm
cellulose ester
if organic con-
taminants present.
* Leidel et al., 1979. NIOSH 7400 (NIOSH, 1984) is an alternative.
** Samudra et al., 1978; Yamate, 1984.
Source: Based on information from the EPA/NBS conference on post-
abatement air monitoring (NBS/EPA, 1985), the open literature, and
government reports, and on peer review comments.
3-8
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PCM-equivalent fibers (i.e., fibers with diameters greater than 0.25 jJra
and at least 5 (Jm in length) and without EDXA analysis to distinguish
nonasbestos fibers from those that are asbestos-like. Such an analysis
may cost as little as $50 and take only a few hours, but obviously would
provide no more information than a PCM analysis. A more sophisticated
SEM analysis, which counts all fibers 0.020 |Jm or more in diameter and
which uses EDXA on some fibers, would likely approach the high end of
the cost and time range ($300) and requires more than one day for
analysis.
Whichever method of measuring airborne asbestos is chosen, the
exact specifications of the analysis (sensitivity, specificity, cost,
and turnaround time) should be clearly communicated to the laboratory.
Limits of fiber resolution should then be verified by the laboratory.
To summarize:
(1) If PCM is selected as the method of analysis, the results
should be reliable, the cost modest, and the turnaround time
rapid. Strictly speaking, however, the results can only
indicate success in removing large airborne fibers of both
asbestos and other compositionthe relationship between PCM
fibers and asbestos fibers in this situation rests solely on
deduction.
(2) If TEM is selected as the method of analysis, the results
should be reliable and should indicate the level of all
asbestos fibers; but the cost will be high and the turnaround
slow. (Remember, the specificity of a Level II or III
analysis is higher than that of Level I, but cost and
turnaround time are also higher.)
(3) If SEM is selected as the method of analysis, the results
should indicate the level of most airborne asbestos fibers
(although some nonasbestos fibers may also be counted and the
smallest fibers will not be counted), and the cost and
turnaround time will be between those for PCM and TEM; but
the results will not necessarily be reliable.
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CHAPTER 4
AIR SAMPLING PROCEDURES
This chapter describes recommended air sampling equipment and
procedures for use in post-abatement clearance monitoring. As
summarized in Chapter 2, the recommended approach is "aggressive
sampling." Specifications for aggressive sampling are provided,
including the characteristics of forced-air equipment. The volume of
sampled air needed to evaluate alternative release criteria is also
discussed. The number of samplers and their location within the work
site are noted here and discussed more fully in Chapter 5.
4.1 SAMPLING EQUIPMENT
In the sampling process, air is drawn through a filter at a known
rate by a flow-controlled pump. The sampler components are described
below.
4.1.1 Filter Media
The selection of a filter for sample collection will depend on
which method is used to analyze the sample for asbestos. When PCM is
employed, the filter should be cellulose ester with a pore size of
0.8-1.2 [jm, as specified in the P&CAM 239 protocol (Leidel et al.,
1979)." When either TEM or SEM is used, the first choice in filter
media is polycarbonate with a pore size of 0.4 |Jm. When substantial
quantities of airborne organic materials are present, a 0.45 pm
cellulose ester filter is recommended together with the indirect method
of sample preparation for TEM (Yamate, 1984). Cellulose ester filters
have also been used for SEM analysis, although they tend to cause
additional background "noise" problems (see Chapter 3). Select the
proper filter type and check each filter lot for low background asbestos
counts prior to sampling. (See Chapter 6 for additional information on
quality assurance.)
4.1.2 Filter Cassettes
Commercial filters are sold as filter and cassette combinations.
If cassettes are loaded with filters outside the manufa-eturers'
facilities, loading should take place only under clean laboratory
conditions (i.e., either in a clean room or on a class 100 clean bench
with a laminar-flow hood). In order to obtain a uniform distribution of
collected particulates across the surface of the collecting filter, a
5.0 pro pore-size cellulose ester backing filter should be placed behind
The new NIOSH Method 7400 prescribes the use of 25-mm diameter
rather than the more common 37-mm diameter filters (NIOSH, 1984).
Since the area of a 25-mm filter is 45 percent less than that of a
37-mm filter, 45 percent less air needs to be sampled to achieve the
same fiber density (f/mm2) on the filter.
4-1
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the collecting filter. This is followed by the cellulose support pad
and the cassette base (see Figure 4-1). The filters should be sealed
evenly without wrinkles.
The movement of air through the filter may cause a significant
buildup of static charge on the cassettes. The static charge, in turn,
is likely to affect the distribution of fibers on the filter and may
cause fibers to collect on the cassette walls rather than on the filter.
To guard against static buildup, the European Reference Method for
Asbestos Measurement published by the Occupational Medicine and Health
Laboratory recommends that a metal cowl or electrically conductive
cassette be used in conjunction with the sampling train (OMHL, 1984).
4.1.3 Flow-Controlled Pumps and Orifices
Air samples should be collected using constant flow sampling pumps.
A typical pump and sampling train is shown in Figure 4.2. Critical
orifices are used because they are convenient and accurate in
controlling flow. However, slight changes in size and shape of the
orifice due to wear or accumulation of particles will change the orifice
characteristics. Therefore, orifices should be monitored before,
during, and after use in sampling. Pump and filter combinations must be
matched to flow rate requirements since some filters produce high back
pressure which limits pump capacity. Double orifice pumps can be used
for collecting samples on two types of filters simultaneously.
4.2 SAMPLING PROCEDURES
4.2.1 Checking Filter Assemblies
The cassette assembly and sampling train should be checked for
leaks before use. This can be accomplished by connecting the train to a
metered vacuum reservoir. The apparatus must pass a leak check of less
than 4 percent of the average sampling rate at a vacuum equal to or
greater than the maximum value reached during the sample run (USEPA,
1977c). Alternatively, a rotameter can be used to check for leaks (see
Section 4.2.2).
4.2.2 Measuring Airflow
In most applications, a high quality rotameter with arbitrary unit
graduations is sufficient to monitor the sample flow rate through the
sampling apparatus. When rotameters are not used, flow measurement
devices such as mass flow meters and dry gas meters may be employed.
The flow measuring device should be inserted behind (downstream of) the
filter and the pump assembly. All measurement equipment should be
capable of ranges at least 1.5 times and readable to at least 0.01 of
the desired flow rate. All flow measurement equipment should be
calibrated against standards of higher accuracy before and after
sampling. Specific calibration procedures for dry gas meters, mass flow
meters, and rotameters are found in EPA, 1977b.
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Collection Filter
Backing Filter
~-^Pad
Figure 4-1. Filter and cassette assembly.
4-3
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Orifice
Detail
Brass Disk 0.209" Dia.
1/16" Thick Center
Drilled No. 68 & Soft
Soldered in Place Drill No. 4
(0.2090")
8 Turns of
1/4" Copper
Tubing Wound
4" Diameter
Gelman Filter Holders
Model 4202 47 mm Open
Faced Magnetic
Clamp, Medium
Utility 3-Finger
Jaw Vinylized
36" Long Rod
3 foot 1/4" x 3/16"
Rubber Vacuum Tubing
Swagelok B-2-MHC4T
Hose Connector to Male
Pipe 1/8" Male Pipe to
1/4" I.D. Tubing
Thomas Industries Inc.
Pump Model 107CA18
Tube Fitting, Male Elbow 90°
1/8" Male Pipe Threaded to
1/4" Tube
Swagelok B-200-2-4
Elapsed Time
Indicator
WW Grainger
6x136
"^"n
7 Day
Programmable Timer
Grainger 2E214
Power Cord
Figure 4-2. Typical pump.
4-4
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4.2.3 Determining Sampling Times and Volumes
Regardless of which method is used for sample analysis, a minimum
of about 3,000 liters (L) of air should be filtered at a rate of 2-12
L/min. The total sampling volume needed will depend on the criterion
used to determine abatement project completion (see Chapter 5). For
example, if the criterion is 0.01 PCM fibers per cubic centimeter
(f/cc), then the total volume required to detect fiber levels this low
is 2,850 liters:
- (10 f/100 fields) (855 mm2/filter) (1 L) _ . T
~ (0.01 f/cc) X (0.003 mnrVfield) X (lOOOcc) Z" L
where: (a) 10 f/100 fields is the minimum fiber loading on the filter
required for reliable quantification by the P&CAM 239 Method
(Leidel et al., 1979).*
(b) 0.01 f/cc is the release criterion.
(c) 855 mm2/filter and 0.003 mm2/field are, respectively, the
area of a 37-mm diameter filter and the area of each viewing
field. (Some optical microscopes have viewing fields as large
as 0.006 mm2. Larger fields of view will improve [decrease]
the limit of reliable quantification for a given sampling
volume. )
At 2-12 L/min, collecting 2,850 liters would require sampling for
about 24 hours (2 L/min) or about 4 hours (12 L/min).
Likewise for TEM, a volume of 3,054 liters would be needed to
detect asbestos levels down to, for example, 0.005 asbestos f/cc:**
_ (1 f/10 gd.sq.) (855 mm2/filter) (1 L) ,
V ~ (0.005 f/cc) X (0.0056 mm* /gd.sq.) X (lOOOcc) JU°4 L
where: (a) 1 f/10 gd.sq. is the minimum fiber loading (per 10 grid
squares) for fiber detection.
(b) 0.01 f/cc is the release criterion.
(c) 855 mm2/filter and 0.0056 mm2/gd.sq. are, respectively, the
area of a 37-mm filter and the area of one grid square, 75 |Jm
on a side in a 200 mesh EM grid. (Grid squares may vary in
size from 0.0056 to 0.0081 mm2. Larger squares will improve
[lower] the detection limit for the same sampling volume.)
These examples point out the need to estimate sampling volumes on
the basis of how many fibers need to be collected for reliable measurement
The NIOSH 7400 Method lowers the minimum fiber loading to 5 f/100
fields (NIOSH, 1984).
If an indirect sample transfer technique is used, additional dilution
terms must be added to the equation. This will increase the minimum
sampling volume needed to detect one fiber.
4-5
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at the air level selected as the release criterion. The number of fibers
is based on the limit of reliable quantification for PCM and on the
theoretical detection limit for TEM. The former is the preferred
measure of the minimum required fiber loading on the filters. Unfortu-
nately, data on which to base an estimate of the limit of reliable
quantification for TEM are not available.
4.2.4 Field Operations
Samplers should be located in a room or area so that they are not
unduely influenced by the configuration of the space or by each other.
For example, samplers should not be placed in room corners, under
shelves, or in other locations where airflow is restricted.
Once the sampling equipment is in place, the location, time, filter
number, pump number, and other pertinent information are recorded. (See
Chapter 6 for a detailed discussion of quality assurance requirements.)
The end cap is removed from the front of the cassette and the pump is
started. Normally, the cassette face is oriented in a downward position
to prevent contamination of the filter by large particles falling from
the ceiling. In a clean work site, however, the ceilings should be free
of any large particles. Placing the filter cassette in an upward
position is thus feasible. This has the added advantage of preventing
the collected fibers from becoming dislodged from the filter when the
vacuum is released. After the pump is started, the flow rate is
recorded and verified after 15-30 minutes of operation to guard against
leaks or constrictions in the sampling train. Timers are frequently
used when the sampling time exceeds a few hours. When the pump needs to
be shut off for any reason, the cassette should first be oriented in an
upright position (if sampling has been conducted with the filter facing
downward) to preclude the chance of collected fibers falling from the
filter when the vacuum is released.
When the requisite sampling volume has been reached, the time,
intermediate flow rate checks, and the final flow rate are recorded.
Samples on cellulose ester filters are usually mailed to the laboratory
for analysis without further treatment. The polycarbonate filters
should be treated with special care. They should be hand carried to the
laboratory if possible. To guard against fiber loss from polycarbonate
filters, keep the filters in a horizontal position with the collection
surface up.
4.3 SAMPLING STRATEGY
Guidelines for the number of sampling locations needed to evaluate
the various release criteria are described in Chapter 5. Regardless of
which criteria is selected, air sampling to evaluate compliance should
be conducted "aggressively", that is, after any settled fibers have been
resuspended and while fans are operated to keep them airborne.
Aggressive sampling should begin after the work site has been
wet-cleaned and HEPA-vacuumed (see Chapter 2) and all plastic except the
4-6
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final containment barrier removed. (That is, plastic should remain on
windows, doors, and air vents.) Any negative filtration units used
during abatement should remain on. The samplers are located as
indicated by the sampling design. Before any sampling begins, floor,
ceilings, and walls are swept with the exhaust from a high-speed air
circulating device such as a 1-horsepower, electrically operated leaf
blower. This activity should continue until the exhaust has been swept
across all surfaces, or for at least 5 minutes per 1,000 square feet of
floor area. Stationary fans (20-inch minimum in size) on 2-meter high
stands are then placed at central locations so as to induce area-wide
circulation. In addition, they are directed at the ceiling and operated
at low speeds so as to avoid high rates of air flow in the vicinity of
the sampling equipment. One fan should be used for each 10,000 cubic
feet of space. The fan(s) should be left on for the duration of
sampling. Aggressive sampling greatly increases the probability that
fibers, if present, will be dislodged and distributed in a relatively
homogeneous manner throughout the air space.
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CHAPTER 5
AIR TESTING CRITERIA FOR DETERMINING WORK-SITE
CLEANLINESS AFTER ABATEMENT
The overall process for determining when an abatement contractor
can be released was outlined in Chapter 2 and is discussed in more
detail in the updated EPA guidance document on controlling asbestos in
buildings (USEPA, 1985). A two-phased approach is recommended: visual
inspection followed by air testing. Air testing is designed to
determine whether the work-site has been cleaned adequately. The measure
of work-site cleanliness will depend on which method is chosen for
measuring asbestos fibers. The recommended criteria are:
If TEM is used, the average of measured work-site levels should
be statistically no larger than the average of measured levels
outside the work site.
If PCM is used, all measured work-site levels should be no
higher than 0.01 f/cc (or less, if a lower level of reliable
quantification is used).
The basis for these recommendations is presented in this chapter.
The discussion includes the rationale for each of the two release
criteria, and the statistical basis for applying them.
Recommendations for the required sampling volumes and the number
and location of air samplers follow from the choice of release criteria.
As summarized in Chapter 2, sampling design recommendations are:
If TEM is used, at least five samples inside and five samples
outside each homogeneous work site should be collected. Sampling
volume should be at least 3,000 liters.
If PCM is used, at least five samples inside each homogeneous
work site should be collected. Sampling volume should be at
least 3,000 liters.
5.1 THE RATIONALE FOR THE RECOMMENDED RELEASE CRITERIA_
The objective of measuring airborne asbestos following an abatement
project is to assure that asbestos fibers released during the abatement
action have been reduced to an acceptable level. Unfortunately, no
safe level of exposure to asbestos exists. Any exposure to the fibers
carries some risk. The point is to reduce levels to the lowest level
technically possible. Hence, the lowest airborne asbestos level that can
be attained within practical limitations depends upon the technological
feasibility in the analytical methodologies.
5-1
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Since outdoor levels are typically very low compared with levels in
buildings with ACM, outdoor levels would appear to be the next best
basis of comparison. However, where negative air ventilation systems
are used during abatement, the make-up or "background" air comes from
other parts of the building rather than directly from outdoors. In this
situation, the more appropriate reference point is the level of asbestos
in air outside the work site but inside the building. Thus, the
recommended release criterion, if TEM is used, involves comparisons
between measurements of asbestos inside the work site with those
outside, either outdoors or immediately outside the work site.
The use of PCM requires additional considerations. Since PCM used
according to the NIOSH protocol detects many types of fibers other than
asbestos and is not sensitive enough to detect the very small fibers
typical of asbestos in the ambient environment, outdoor fiber measurements
using PCM provide little if any information on ambient asbestos. The same
is true for airborne asbestos inside buildings other than at the
abatement work site.
As an alternative to inside-outside comparisons, the recommended
release criterion for use with PCM involves comparing work-site asbestos
levels with the PCM limit of reliable quantification. Since the lowest
level of airborne fibers quantifiable with PCM depends on the volume of
air collected, the criterion could, in concept, specify any level of
fibers.* A level of 0.01 f/cc is recommended as the least stringent
level that should be considered.
Regardless of which method for measuring asbestos is used, the
release criterion should be specified in terms of fiber rather than mass
concentrations. The number of fibers rather than their mass is believed
to be a better indicator of health effects (NEC, 1984). In addition,
mass concentrations are unduly influenced by a few large fibers. Thus, in
principle, a superficial cleaning of the work site could significantly
reduce levels of asbestos mass by removing primarily a few large fibers,
while leaving the concentration of total asbestos fibers almost unchanged.
However, if an indirect sample preparation is used for TEM analysis in
which fibers may be broken thus increasing the number of fibers in the
sample, the concentration of fibers measured is likely to be higher than
that in the air. Under these conditions, mass concentration is the
preferred measure of asbestos levels.
The asbestos measurement protocol for PCM specified by NIOSH (P&CAM
239) requires that at least 10 fibers be collected for 100 fields of
view on the filter. This corresponds to a sample volume of about
3,000 liters (see Section 4.3.3). Thus, if a very stringent release
criterion (very low concentration of asbestos) were desired, a very
large sampling volume would be specified.
5-2
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5.2 STATISTICAL CONSIDERATIONS FOR USING RELEASE CRITERIA
If samples of air are taken in the same general area but at
slightly different locations or at different times at the same location,
the measurements of sampled material will differ. Likewise, side-by-side
samples taken at the same location and time will vary. Thus,' measure-
ments of airborne asbestos at an abatement worksite will be variable
irrespective of abatement activities or post-abatement cleaning efforts.
The task at hand is to understand this variability, and, using standard
statistical procedures, to determine whether two measurements are truly
different or differ only due to normal (expected) variability.
The variability of measurements of airborne asbestos has two
components sampling and analytic variability. Sampling variability is
due to random fluctuations in the constituents of an air mass, and to
systematic factors such as air circulation patterns in a room. Analytic
variability is associated with the instruments and procedures used to
sample air and analyze the samples.
Recent EPA research studies provide information on the magnitude of
sampling and analytic variability for measurements of airborne asbestos
using TEM (USEPA, 1983; Chesson et al., 1985a; 1985b). The results of
the analyses of variability in these studies are expressed as the
coefficient of variation (CV). The CV is simply the standard deviation
of a series of measurements divided by the mean value.*
The first study (USEPA, 1983) produced estimates of sampling
variability. A CV of 0.88 was found in simultaneous measurements of
airborne asbestos among rooms with ACM in 25 school buildings within a
single school district. Since the measurements of asbestos were
adjusted for between-school variation in mean asbestos levels, the
measurements can be considered reflective of spatial variability in a
single area. Variability over time was estimated as the CV for average
weekly levels of asbestos in three different schools (CV = 0.42).
Spatial and time variability combined would thus be a CV of about 1.0.**
The other two studies (Chesson et al., 1985a; 1985b) estimated the
analytic component of variability. Using the variation between
laboratories in 49 pairs of TEM measurements of asbestos as the
indicator, analytic variability was estimated as a CV of-about 1.0.
Based on these limited studies, expected variability in asbestos
levels at a single location (e.g., an abatement work site) as measured
by TEM may be characterized by a CV of between^1.0 and 1.5.
Since the variability of measurements of airborne asbestos tends to
be larger if the average value is high, a high standard deviation
may reflect a high variability and/or a high mean for the
measurements. Dividing the standard deviation by the mean thus
allows the variability of measurements with large means to be
compared with the variability of those with small means.
CV's are combined by taking the square root of the sum of each CV(
squared.
5-3
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This information on the normal or expected variability of asbestos
fibers is used in the following sections to calculate the required
number of samples for determining compliance with the TEM release
criterion. (A different approach is used for the PCM criterion.) Of
course, the actual variation in asbestos levels at any site is
calculated directly from the measurements at that site. The degree of
expected variability is assumed solely for the purpose of determining
sample design specifications before the measurements are made.
5.3 TEM RELEASE CRITERION
As noted previously, the recommended criteria for releasing the
abatement contractor if TEM is used involves comparing asbestos levels
at the work site with those measured outside. Only if the asbestos
levels inside are not statistically larger than those outside the work
site, would the contractor be released.
5.3.1 Sampling Volume and Time
The required sampling volume is determined by the lowest level of
asbestos to which the work-site environment must be reduced. As shown
in Table 5-1, typical ambient asbestos levels are on the order of 0.001
in rural areas and somewhat higher in urban areas. Based on these data,
enough air must be sampled to detect a concentration of approximately
0.005 f/cc. As described in Chapter 4, a volume of at least 3,000
liters per sample is required if the sample preparation involves direct
transfer to the EM grid, more if the indirect sample preparation
technique is used. At a rate of 2-12 L/min, sampling would require from
3.5 to 21 hours.
5.3.2 The Number and Location of Samplers
The number of samples needed to reliably determine compliance with
the release criterion depends on several factors. Table 5-2 lists these
factors and illustrates their influence on sample size.
The first two factors are the expected errors regarding decisions
on satisfactory cleaning of the abatement work site. These are the
probabilities that no difference between levels inside and outside the
work site will be detected when the work-site asbestos levels are
actually too high (false negatives), or that a difference will be
detected when the work-site levels are actually low enough (false
positives).
The third factor ("inside-to-outside multiple") is related to the
false positive and negative error rates. Since small differences
between inside and outside asbestos levels are more difficult to detect
than large differences, more samples are needed to maintain the same
rates of making errors in decisions. For example, as shown in Table
5-2, if the CV for TEM is 1.5, seven samples are required to detect a
5-fold difference between inside and outside levels with a 10-percent
chance of making a wrong decision. However, only four samples are
required to detect a 10-fold difference. In other words, if seven
5-4
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TABLE 5-1
REPORTED LEVELS OF AMBIENT ASBESTOS FIBERS MEASURED BY TEM-
Setting
Level (f/cc)
Reference
Urban
Urban
0-0.024
Rural 0-0.004
Industrial 0.0002-0.011
Rural
0-0.045
(most below
0.01)
0-0.003
Murchio, 1973. "Asbestos Fibers
in the Ambient Air of California,"
California Air Resources Board.
Same
John et al., 1976. "Experimental
Determination of the Number and
Size of Asbestos Fibers in Ambient
Air," NTIS Report # PB-254086
Chatfield, 1983. "Measurement of
Asbestos Fibre Concentrations in
the Ambient Atmosphere," Royal
Commission on Asbestos.
Same
All TEM analyses reported to have been made following direct sample
preparation procedures.
5-5
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TABLE 5-2
NUMBER OF SAMPLES REQUIRED TO TEST COMPLIANCE
WITH THE TEM RELEASE CRITERION
False False Inside-to-
Positive Negative Outside
Rate Rate Multiple
0.10 0.10 5
0.10 0.10 7
0.10 0.10 10
Number of Samples
CV=1.0 CV=1.5 CV=2.0
4 79
4 57
3 45
0.10 0.05 5 5 9 12
0.10 0.05 7 5 7 9
0.10 0.05 10 4 5 7
Source: Based on the method used in Breen et al., 1985 (Table 5)
5-6
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samples are used, there is at most a 10-percent chance that the work
site would pass the air test when levels inside were actually five times
higher than outside. If the true multiple is larger than 5 and seven
samples were collected, the likelihood of passing is less than 10
percent. The inside-to-outside multiple is selected when planning the
air test. A multiple in the range of 5 to 10 is typically used.
The final factor is the coefficient of variation. As discussed in
Section 5.3, the CV expresses the relative variation in asbestos
measurements for samples at the same site. As shown in Table 5-2, the
higher the CV, the larger the sample size must be.
Table 5-2 indicates that the number of required samples varies from
4 to 12. To make the task of air testing following an abatement project
practical, a minimum sample size of 5 is recommended. This corresponds
to false positive and negative error rates of 0.10 each, an
inside-to-outside multiple of 5, and a CV of between 1.0 and 1.5.
The recommended sample size of 5 applies to samples inside as well
as outside the work site. Thus, a total of at least 10 samples would be
required if TEM is employed. In selecting the location of the 10 air
samplers, the following guidelines should be considered:
For indoor locations, first determine if the work site is
homogeneous. "Homogeneous" refers to contiguous areas with the
same type of ACM and in which one type of abatement process was
performed. For example, an auditorium with accoustical ceiling
plaster containing chrysotile that was removed would qualify as
homogeneous. Similarly, a corridor and connecting rooms on a
single floor would be homogeneous if all areas contained the same
type of ACM and the same abatement method were used. Separate
floors within a building and separate buildings are usually
considered different work sites. Collect five samples in each
homogeneous work site.
Place the samplers within the homogeneous work site so as to
collect representative samples. If the work site is a single
room, disperse the samplers throughout the area. If the work site
contains up to five rooms, place at least one sampler in each
room. If the work site contains more than five rooms, select a
representative sample of rooms. The random number procedure in
Appendix A is one way to select a representative sample. Place
each sampler so that it is subject to normal air circulation;
avoid room corners, obstructed locations, and sites near windows,
doors, or vents. Samplers placed outside the work site but within
the building should be located to avoid any air that might escape
through the containment barriers. Minimum recommendations are at
least 50 feet from the entrance to the work site, and 25 feet
from the plastic barriers.
Outdoor samplers should be placed at ground level (about 6 feet
high), if possible, and away from obstructions that may
influence wind patterns. If access to electricity and concerns
about security dictate a roof-top site, avoid locations near
vents or other structures on the roof.
5-7
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The above guidelines are designed to assure that representative
samples of airborne asbestos are collected.
5.3.3 Comparing Measured Levels of Airborne Asbestos
The appropriate statistical test for comparing levels of asbestos
measured at the work site with those measured outside is known as the
"difference between means" using Student's "t" test:
Compute the natural logarithm of fiber concentration for each
sample.
Compute means of the log-transformed data for inside samples
and for outside samples.
Form the ratio:
Where:
Y. = the average of log concentrations inside the work site
Y = the average of log concentrations outside the work site
S = {[I(Y.. - Y.)2 + Z(Y - - Y )2] / (n. + n -
ij i °J o i o
n. = number of samples inside the work site
n = number of samples outside the work site
o
Then compare t to 1.86 if 10 samples were collected
(the 95 percentile point of a "t" distribution with
8 [n. + n - 2] degrees of freedom). If t exceeds 1.86,
the work site fails the test (consult a statistics text
for the appropriate t value if the degrees" of freedom are
other than 8).
The fiber level data is log-transformed because frequency distri-
butions of asbestos levels usually are highly skewed. The transformed
data are adequately approximated by a normal distribution on which
standard statistical methods can be used.
5.3.4 Recommended Actions If the Work Site Fails
For each homogeneous work site which fails the test (i.e., average
asbestos levels inside the work site are statistically greater than
those outside), the entire work site should be thoroughly recleaned.
Wet cleaning methods should be used (see Section 2.1 and the companion
EPA guidance document [EPA, 1985]). New samples (at least 5) should be
5-8
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collected in the work site and analyzed for asbestos as described above.
This process should be repeated until the work site passes the test.
Note that for an abatement project with more than one homogeneous work
site (as defined in Section 5.3.2), the release criterion should be
applied to each work site independently.
5.4 PCM RELEASE CRITERION
The contractor release criterion recommended for use with PCM
employs PCM's limit of reliable quantification as opposed to asbestos
levels outside the work site for comparison purposes. As a result, some
of the specifications for using the PCM criterion differ significantly
from those for TEM.
5.4.1 Sampling Volume and Time
A minimum of 3,000 liters of air should be collected by each
sampler. Since PCM can only be used as an indirect measure of asbestos,
the sampling requirements should be at least as stringent as those for
TEM. Based on the illustration in Chapter 4, a sampling volume of about
3000 liters will allow the PCM method to reliably quantify fibers levels
as low as about 0.01 f/cc.
5.4.2 The Number and Location of Samplers
The recommended minimum number of samplers is five per homogeneous
work site, or one per room, whichever is greater. Again, the rationale
is that the minimum requirements for the PCM test should be at least as
stringent as the TEM requirements since PCM is only an indirect
indicator of asbestos. (In fact, the PCM specifications are slightly
more stringent for work sites with more than five rooms.) All of the
guidelines for locating samplers discussed in Section 5.3.2 (except the
need for outside samplers) apply to PCM as well.
5.4.3 Comparing Measured Levels of Asbestos to the Lowest
Quantifiable Level
The recommended test for the PCM release criterion is that each of
the five or more samples must be less than the PCM limit of reliable
quantification. If 3,000 liters is the sampling volume,-this limit is
approximately 0.01 f/cc. Using each sample in the test is more
stringent than averaging the sample values and using the mean, as
illustrated in Table 5-3. As shown, the probability that the work site
would pass the test is only about 0.12 if the true asbestos levels is
actually equal to 0.01 f/cc, due to variation in PCM measurements.
Thus, the work site needs to be cleaned so that the actual air level is
lower than 0.01 f/cc to be assured that it will pass the test.
5.4.4 Recommended Actions If the Work Site Fails
As with the TEM criterion, each homogeneous work site should be
completely recleaned if it fails the test. Recleaning is followed by
resampling and reanalyzing the samples.
5-9
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TABLE 5-3
THE PROBABILITY OF CONTRACTOR RELEASE FOR DIFFERENT
PCM FIBER LEVELS IN THE WORK SITE*
Actual Fiber Level Probability of Release
(f/cc)
0.001
0.002
0.003
0.004
0.005
0.01
0.02
0.05
0.998
0.94
0.81
0.64
0.49
0.12
0.01
0.0003
A negative binomial distribution and a CV of 1.0 to 1.25 are
assumed for PCM fiber levels.
5-10
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5.5 EXAMPLE APPLICATIONS OF THE TWO RELEASE CRITERIA
Examples of how the recommended PCM and TEM criteria for contractor
release are applied will illustrate the guidelines described in this
chapter and problems that may arise in certain situations. The following
examples assume that 3,000 liters of air are filtered by each sampler.
5.5.1 PCM Example
Work Site: Five school classrooms, one auditorium, and one
connecting corridor. Samplers are located in each area
(seven samplers altogether).
Release Criterion: All measurements must be less than 0.01
f/cc.
PCM Results: <0.01, <0.01, <0.01, 0.045, <0.01, <0.01,
<0.01 f/cc.
Interpretation of Results: Work site fails.
First PCM Retesting Results (after recleaning the entire work
site): <0.01, <0.01, 0.012, <0.01, <0.01, <0.01, <0.01
Interpretation of Results: Work site fails.
Second Retesting Results: All seven samples, <0.01 f/cc.
Interpretation of Results: Work site passes.
In this example, all PCM samples in the first test were below the
release criterion except the fourth sample, which is significantly
higher (0.045 f/cc). According to the guidelines, the entire work site
should be recleaned. Some may argue that only the room with the high
measurement should be recleaned. However, the seven PCM measurements
only represent a sample of the entire work site. Air samplers placed in
other locations may also show high levels. In addition, the low
sensitivity and specificity of the PCM test argues for a comprehensive
response if the test fails. (Remember that a work site could pass the
PCM test while failing the more sensitive and specific.TEM test.) The
example also shows that one sample in the first retest (the third sample
this time) was still above the 0.01 f/cc criterion. The fact that the
work site again failed to pass the test could reflect either inadequate
cleaning and/or normal variability in PCM measurements of airborne
fibers. Nevertheless, a second recleaning and retesting is recommended.
Note that the five or more samplers need not be placed at the same
locations for retesting.
5.5.2 TEM Example
Work Site: The entire first floor of an office building
(30 offices, two rest rooms, a reception area, and a
connecting corridor). The five work site air samplers are
5-11
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placed in three offices, one rest room, and the corridor.
The five outside samplers are placed in two stairwells
between the first and second floors.
Release Criterion: The average of inside samples must be
statistically no greater than the average of the outside
samples.
TEM Results:
Fiber Level Natural Log of Mean of
(f/cc) Fiber Level Logs
-3.48 (Y.)
Inside
Samples
Outside
Samples
0.073
0.032
0.008
0.057
0.026
<0.005*
0.010
0.024
0.009
0.015
-2.62
-3.44
-4.83
-2.86
-3.65
-5.30
-4.61
-3.73
-4.71
-4.20
-4.5i (YO;
Difference of means test:
71 . - Y
^j °J o
n - 2
o
= {^
[(2.98^ 2.26)]1/2 _
(-3.48) - (-4.51)
t =
0.809
Interpretation of Results: Work site fails because
t > 1.86.
5-12
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ERRATUM
This sheet replaces the TEM release calculations in example 5.5.2 on
pages 5-12 and 5-13 of the document "Measuring Airborne Asbestos Following
An Abatement Action." (EPA 600/4-85-049)
Difference of means test:
(p. 5-12)
S =
[Z(Yii - Y^2
- Y )2
OJ O'
n + n - 2
[2.98 + 1.381 1
L5 + 5- 2j
/2 =
J
0.738
Note:
= 1.38
t =
= (-3.48) - (-4.51) = 2.21
Vnj + Vn0 0.738 /(V5 + V5)
Interpretation of results: Work site fails because t > 1.86.
Difference of means test:
(Retest, p. 5-13)
S =
f(4.80 + 1.38)1 l/2
L ~ J
= 0.879
(-4.17) - (-4.51)
t =
0.879/(V5 + V5)
0.612
Interpretation of Results: Work site passes because t < 1.86.
-------
TEM Retesting Results (after recleaning the entire work
site):
Fiber Level Natural Log of
(f/cc) Fiber Level
Inside 0.081
Samples <0.005~'
0.011
0.025
0.008
-2.51
-5.30
-4.51
-3.69
-4.82
Mean of
Logs
-4.17
Outside Same as before (no new sampling is needed)
Samples
* Assumed to be 0.005 for purposes of calculation.
Difference of means test:
2.26)!1/2
_ F(4.80 +
"L 8
= 0.940
t = (-4.17) - (-4.51) =
0.57
0.940
Interpretation of Results: Work site passes because
t < 1.86.
This example illustrates how the use of average fiber concentra-
tions in the TEM criterion influences the results. After the initial
cleaning, levels inside the work site were significantly higher than
those immediately outside. Since the t-test is greater than 1.86
(2.01), the entire work site is recleaned. The second set of work-site
samples reveals lower air levels with one exceptionthe first sample
(0.081 f/cc) is higher than any of the samples in the first or second
rounds of testing. However, the mean of all second round samples is
lower than the mean of the first, and the contractor is released since
the t-test is less than 1.86 (0.57). Some may be concerned about the
single high level found during the second round of sampling, and would
argue for another recleaning of the work site. Recall, however, that TEM
measurements are expected to be highly variable, and that a single high
value is not necessarily a cause for concern. On the other hand, a
simple rule such as "if any single value is more than 'x' times the mean
for all values, the work site must be recleaned" could be used as a
supplement to the recommended TEM criterion. Such a rule would help
guard against the possibility of a single contaminated room in an
otherwise clean work site.
5-13
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CHAPTER 6
QUALITY ASSURANCE PRACTICES
Regardless of which method for measuring airborne asbestos is used,
reliable results can be obtained only if the collection, transfer,
handling, analysis, interpretation, and documentation of the data follow
specified procedures. Procedures for data collection, analysis, and
interpretation were described in Chapters 3, 4, and 5; procedures for
transferring and handling the data are included in this chapter. In
order to insure that all of these procedures are carefully followed, a
quality assurance (QA) program is essential.
Following are the key elements of a comprehensive QA program.
Training and Experience
Everyone involved with measuring airborne asbestos
should be properly trained and should understand his or
her role.
Only qualified air sampling firms and analytical
laboratories should be hired. As noted previously,
NIOSH's Proficiency Analytical Testing Program is a good
source of information on qualifications of laboratories
offering PCM services. Information should be requested
from each PCM or TEM laboratory on:
the laboratory's quality control program.
the lowest fiber counts (f/cc) that are routinely
reported.
the thinnest fibers that are routinely detected.
Quality Control Checks
All sampling equipment should be calibrated and checked
as described in Section 4.2.
All analytical instruments should be calibrated with NBS
reference materials, and checked as described in Leidel,
et al., 1979, or NIOSH, 1984 (PCM), and Yamate, 1984
(TEM).
One field blank and one laboratory blank per work site
should be analyzed to check for asbestos contamination
of blank filters.
All labels on filters should be coded to avoid possible
bias by laboratory analysts.
6-1
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One filter per work site should be split for duplicate
analysis by a second laboratory. Where the duplicate
analysis is significantly different, procedures used by
either or both laboratories should be investigated until
the source of the discrepancy is identified and
corrected.
Data Handling Chain-of-Custody
Responsibility for samples should be assigned to an
individual at each stage of the testing process.
Each step in the transfer of the data from field to
laboratory to building owner should be recorded.
Documentation
All testing procedures and test results should be
documented.
Unused filters and portions of filters should be saved
for possible reanalysis at a later date.
6-2
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REFERENCES
Burdett, G. J., and Rood, A. P. 1983. "Membrane Filter, Direct
Transfer Technique for the Analysis of Asbestos Fibers or Other
Inorganic Particles by Transmission Electron Microscopy," Environ.
Sci. Technol., 17, 643-648.
Chatfield, E. J. 1983. Measurement of Asbestos Fibre Concentrations in
Ambient Atmospheres. Ontario, Canada: Ontario Research
Foundation.
Chesson, J., Margeson, D. P., Ogden, J., Reichenbach, N. G., Bauer, K.,
Constant, P. C., Bergman, F. J., Rose, D. P., Atkinson, G. R., and
Lentzen, D. E. 1985a. Evaluation of Asbestos Abatement
Techniques, Phase 1: Removal. Final Report. Washington, DC:
Office of Toxic Substances and Environmental Monitoring Systems
Laboratory, U.S. Environmental Protection Agency. Contracts
68-01-3938 and 68-02-3767.
Chesson, J., Margeson, D. P., Ogden, J., Bauer, K., Constant, P. C.,
Bergman, F. J., and Rose, D. P. 1985b. Evaluation of Asbestos
Abatement Techniques; Phase 2: Encapsulation. Draft Report.
Washington, B.C.: Office of Toxic Substances, U.S. Environmental
Protection Agency. Contracts 68-01-6721 and 68-02-3938.
Chesson, J., Price, B. P., Stroup, C. R., and Breen, J. J., 1985.
Statistical Issues in Measuring Airborne Asbestos Levels Following
an Abatement Program. American Chemical Society Symposium on
Environmental Applications of Chemometrics in Philadelphia in
August 1984. (To appear in forthcoming proceedings volume.)
National Research Council. 1984. Asbestiform Fibers, Non-occupational
Health Risks. Washington, B.C.: National Academy Press.
Leidel, N. A., Boyer, S. G., Zumwalde, R. D., and Busch, K. A. 1979.
USPHS/NIOSH Membrane Filter Method for Evaluating Airborne Asbestos
Fibers. Washington, D.C.: National Institute of Occupational
Safety and Health.
NBS/EPA. 1985. Proceedings of the Workshop on the Monitoring and
Evaluation of Airborne Asbestos Levels Following an Abatement
Program. Cosponsored by U.S. Environmental Protection Agency and
National Bureau of Standards. Held at NBS, Gaithersburg, Maryland,
March 12-13, 1984.
NIOSH. 1984. Fibers, Method 7400. Cincinnati, Ohio: National
Institute of Occupational Safety and Health.
OMHL. 1984. MDHS 39, Methods for the Determination of Hazardous
Substances, Asbestos Fibers in Air, Determination of personal
exposure by the European Reference version of the membrane filter
method, Health and Safety Executive. London: Occupational
Medicine and Hygiene Laboratory.
R-l
-------
Samudra, A., Harwood, C. F., and Stockham, J. D. 1978. Electron
Microscope Measurement of Airborne Asbestos Concentration: A
Provisional Methodology Manual. Washington, D.C.: Office of
Research and Development. U.S. Environmental Protection Agency.
EPA 600/2-77-178.
Small, J. A., Steel, E. B., and Sheridan, P. J. 1985. "Analytical
Standards for the Analysis of Chrysotile Asbestos in Ambient
Environments," Anal. Chem., 57, 204-208.
Spurny, K. R. 1985. "Measurement of Asbestos and Other Mineral Fibers
in Ambient and Indoor Air," Proceedings of the Workshop on the
Monitoring and Evaluation of Airborne Asbestos Levels Following an
Abatement Program. Cosponsored by U.S. Environmental Protection
Agency and National Bureau of Standards. Held at NBS,
Gaithersburg, Maryland, March 12-13, 1984.
Steel, E. B., and Small, J. A. 1985. "Accuracy of Transmission
Electron Micrscopy for the Analysis of Asbestos in Ambient
Environments," Anal. Chem., 57, 209-213.
USEPA. 1977a. Montgomery County Asbestos Study. RTP, N.C.: Office of
Research and Development, USEPA.
USEPA. 1977b. Quality Assurance Handbook for Air Pollution Measurement
Systems, Vol. II: Ambient Air Specific Methods. Washington, D.C.:
Office of Research and Development, USEPA. EPA-600/4-77-027a.
USEPA. 1977c. "Method 5: Determination of Particulate Emissions From
Stationary Sources," Federal Register, Vol. 42, No. 160, pp.
41776-41781. (40 CFR 60, Appendix A, Method 5.)
USEPA. 1983. Airborne Asbestos Levels in Schools. Washington, D.C.:
Office of Toxic Substances, USEPA. EPA 560/5-83-003
USEPA. 1984a Evaluation of the EPA Asbestos-in-Schools Identification
and Notification Rule. Washington, D.C.: Office of Toxic
Substances, USEPA. EPA 560/5-84-005.
USEPA. 1984b. Asbestos in Buildings: National Survey of
Asbestos-Containing Friable Materials. Washington, D.C.: Office
of Toxic Substances, USEPA. EPA 560/5-84-006.
USEPA. 1985. Guidance for Controlling Asbestos-Containing Materials in
Buildings, 1985 Edition. Washington, D.C.: Office of Toxic
Substances, USEPA. EPA 560/5-85-024.
Yamate, G., Agarwal, S. C., and Gibbons, R. D. 1984. Methodology for
the Measurement of Airborne Asbestos by Electron Microscopy. Draft
Report. Washington, D.C.: Office of Research and Development,
U.S. Environmental Protection Agency. Contract 68-02-3266.
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APPENDIX A
A RANDOM NUMBER PROCEDURE FOR SELECTING A
REPRESENTATIVE WORK-SITE SAMPLE
A table of random numbers can be used to pick a sample of rooms for
air testing as follows. (A table of random numbers is simply many
sequences of single-digit numbers presented in a random order.)
(1) If the number of rooms is less than 10, each room is
assigned a unique single-digit number. Rooms with
numbers corresponding to the first five numbers in a
selected random number sequence in the table constitute
the air test sample.
(2) If the number of rooms is greater or equal to ten (but
less than 100), each room is assigned a unique two-digit
number. The random number table is then considered
sequences of two-digit numbers. The first five room
numbers to appear in a selected sequence constitutes the
air test sample.
(3) Similarly, if the number of rooms is greater than or
equal to 100, each room is assigned a unique three-digit
number and the random number table is considered
sequences of three-digit numbers.
Tables of random numbers can be found in any statistics textbook,
such as: Snedecor, G. W., and Cochran, W. G., 1976. Statistical
Methods (6th Ed.). Iowa State U. Press, Ames Iowa. 593 pp.
A-l
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing/
1. REPORT NO.
EPA 600/4-85-049
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Measuring Airborne Asbestos Following an Abatement
Action
5. REPORT DATE
November 1985
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
D.L. Keyes, J.J. Breen, and M.E. Beard
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Sciences, 6845 North Cocopas Road
Tucson, Arizona, 85718, under contract to the
Research Triangle Institute, P.O. Box 12194,
Research Triangle Park, N.C. 27709
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-3767
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Office of Research and Development
Environmental Monitoring Systems Laboratory
Research Triangle Park, N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
One of the most critical points in an asbestos abatement project is knowing
when the work has been completed, the contractor can be released, and the building
can be reoccupied. This decision should be based on two factors: (1) satisfactory
performance of the abatement work, and (2) thorough cleaning of the work site. As
outlined herein, these factors should be evaluated by virtually inspecting the work
site and by measuring the level of airborne asbestos there. The evaluation should
be conducted by the asbestos program manager or the technical advisor assigned to
monitor the abatement work.
This report discusses various technical issues regarding the air test. Speci-
fications are provided for air sampling and detailed guidelines are presented for
using either TEM or PCM to analyze the samples. The information is designed for
asbestos program managers and technical program advisors.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATi I leld/Group
Airborne Asbestos
Asbestos Abatement
Asbestos-Containing Materials
Asbestos Control Program
Asbestos Exposure
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (Tins Report I
21. NO. OF PAGES
20. SECURITY CLASS (Tim pj.ro
22. PRICE
EPA Form 2220-1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
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