Attachment A
EXPOSURE OF CUSTODIAL EMPLOYEES TO
AIRBORNE ASBESTOS
A Technical Report by
Arthur R. Wlckman, Principal Investigator
Daryl W. Roberts, Project Manager
Terry L. Hopper, Industrial Hygiene Supervisor
Missouri Department of Health
Bureau of Environmental Epidemiology
for
U.S. Environmental Protection Agency
Office of Pesticides and Toxic Substances
under
EPA Project No. J1007468-01-0
EPA Grant Administrator: David Treece
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ABSTRACT
The objective of this study was to evaluate the occupational
exposure of custodians to airborne asbestos during routine activities.
The sample population included eight custodians working in six public
buildings in Missouri. Forty-seven personal samples and 91 area
samples were collected and analyzed by transmission electron
microscopy using direct preparation techniques. Personal samples
resulted in an arithmetic mean of 0.0009 structures/cubic centimeter
(s/cc) and area samples resulted in an arithmetic mean of 0.0003 s/cc.
The highest personal sample concentration was 0.0255 s/cc, or 26% of
the OSHA action level of 0.1f/cc.
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INTRODUCTION
The goal of this study was to assess the exposure of custodians
to airborne asbestos fibers as they conduct routine custodial activities
in buildings where asbestos containing materials (ACM) are present.
The study was designed to provide quantitative exposure data in the
range of the current OSHA action level, 0.1 fiber/cubic centimeter
(f/cc). Exposures did not involve the intentional disruption of ACM, as
might occur with maintenance personnel, plumbers, electricians, and
asbestos abatement workers. As studied here, custodial exposure was
incidental and unintentional, often involving the redispersal of
asbestos dust which had accumulated on surfaces after previously
being released from its original source material. The study related
exposure levels to the type of custodial activity involved, such as
vacuuming, dust mopping, and stripping of vinyl asbestos tiles.
METHODS
STUDY DESIGN. Samples were collected for three consecutive
days on each of two visits to six.selected sites. Forty-seven personal
samples were collected from the eight custodians involved in the study.
These samples represented full shift exposures, and were computed as
an eight hour time weighted average (8 hr. TWA). In addition to the
personal samples, area samples were taken when a custodian was
involved in a specific task. Six categories of custodial activities were
monitored during area sampling: stripping vinyl asbestos tile (VAT),
buffing VAT, vacuuming, dust mopping, dry broom sweeping, and hand
dusting. These area samples provided information on the concentration
of asbestos rendered airborne by the particular custodial activity. The
area samples also gave information regarding the tasks during the day
which contributed to the 8 hr. TWA exposure recorded on the
custodian's personal sample. Custodians were instructed to perform
their work routinely but in as much as possible to schedule their work
so that the six relevant tasks would be performed at some time during
the three day sampling periods.
SITE SELECTION. A list of potential sites for this study was
generated from the records of the Missouri Department of Health. The
Department maintains records of asbestos inspections for
approximately 2900 public buildings in Missouri, inspected since 1988
under state law 701.122, RSMo 1991. The criteria used to determine
potential building sites was the presence of accessible, friable, and
Exposure of Custodial Employees Page 3 of 22
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extensive ACM which was damaged to some degree. Managers of these
buildings were contacted to determine the nature of custodial services
in the building. Buildings were identified in which custodians worked
routinely in the presence of ACM. Visits were made to each of the
sites, with the result that six sites and eight custodians meeting the
exposure criteria of the study were chosen. These sites are listed
below:
Student Union. Missouri Western State College, St. Joseph (MWSC). This
site had 10,000 square feet of asbestos sprayed onto the underside of
roof and metal trusses on two floors. Custodial and maintenance areas
of the building were directly exposed to this insulation. The space
between the suspended ceiling and the metal trusses served as the
return air plenum on both floors. Some damaged areas were visible in
the sprayed on insulation. This material was friable and subjected to
airstream abrasion. Two janitors worked here full time.
Dallas County Courthouse, Buffalo (Dallas CC). This building had
approximately 20,000 square feet of ceiling area throughout that
contained asbestos. About 90% of this ceiling had been painted with
latex paint rendering it non-friable. The remaining 10% of ceiling area
was not painted and was friable. Isolated areas of ceiling were
damaged to the point of releasing fibers. Hallways in the building
served as the return air plenum, which created a continuous flow of air
over this ACM. Floors throughout the building were vinyl asbestos tile.
Two half-time janitors were employed here.
Independence Power and Light Generating Station, Independence (IP&L). An
extensive amount of TS) was present on the steam pipes of this coal
fired electrical power plant, some in significantly damaged condition.
A definitive quantity of TSI was not determined, but amount was
estimated as hundreds of linear feet. A program of asbestos removal
and/or abatement, by outside contractors occurred periodically at the
plant, but not during the period of this study. Approximately 75% of
asbestos had been removed from the plant. Remaining TSI is subjected
to strong air currents and vibration from operations of the plant.
Floors in office areas contained vinyl asbestos floor tiles. Two
janitors worked here -spending 'time' both' in the generating plant and in
the office areas.
Franklin County Courthouse. Union (Franklin CC). This building had 2700
square feet of hidden spline ceiling tile throughout which contained
asbestos. Approximately 5% of the ceiling was damaged and friable.
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Five hundred linear feet of hot water pipes in the basement were
wrapped with TSI, some of which was in damaged condition. Two full-
time and two part-time custodians worked in the building.
Western Missouri Medical Center. Warrensburg (WMMC). This building
had 36,000 square feet of ceiling containing asbestos. The ceiling had
been painted and was not friable. Approximately 25% of ceiling area
had been cut to allow access for equipment, lights, mirrors, etc,
Isolated spots in the ceiling showed damage. In some damaged areas,
there was expected fiber release from the many openings into the
ceiling. Approximately 7,200 square feet of flooring was VAT. The
building also had approximately 150 thermal system joints packed with
asbestos, of which 15 were damaged. Four full-time janitors were
employed.
Ha// of Waters (City Hall), Excelsior Springs (Ex Spr). This building
served as the city's municipal building. Prior to the 1960's it had also
been used as a center for therapeutic mineral bath treatments. The
building had an extensive system of hot water pipes insulated with
asbestos throughout. The total amount of TSI could not be determined
accurately, but was estimated at several thousand linear feet. Varying
degrees of damage existed In this material. Air chases in certain areas
of the building were built around these insulated pipes, which created
the possibility of widespread dispersal of asbestos fibers. One full
time custodian worked here.
MATERIALS Materials were selected in accordance with the
NIOSH Method 7402 protocols for asbestos fiber collection. All
samples were collected -on Millipore 0.045 micron mixed cellulose
ester filters using open faced 25 mm preloaded cassettes. Personal
sampling pumps were SKC Model 224-PCXR3 which were calibrated on
site to a flow range between 2.0 and 2.5 liters per minute. Area
samples were collected using Gilian Aircon 520 high volume samplers,
Calibrated to 10 liters per minute. Calibration of the air samplers was
performed using a Gilian Gilibrator electronic flow meter with a
representative filter in line. Pumps were calibrated at the beginning
and end of each sample collected.
SAMPLE ANALY^ig Analysis of the samples was performed by
transmission electron microscopy using direct transfer methods.
Analysis was conducted according to the non-mandatory protocols of
the Asbestos Hazard Emergency Response Act (AHERA) method, as
described in 40 CFR 763, Appendix A, Subpart E. QuanTEM Laboratory,
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Oklahoma City, Oklahoma, served as the principal analytical laboratory.
QuanTEM's role Involved the analysis of 156 samples and the
repreparation of 7 samples. Included in the laboratory report were the
following factors: structure type (free fibers, bundles, clusters, or
matrices), species of asbestos (chrysotile/amphibole), the count of
fibers less than or greater than 5 microns, and the length and diameter
of all structures identified as asbestos. Quality control analysis was
performed by Professional Service Industries (PSI) at their Pittsburg,
Pennsylvania facility. All analysis was performed at or below a level
of sensitivity of 0.005 s/cc.
QUALITY ASSURANCE/QUALITY CONTROL. In order to define
the background contamination of the filters in the production lots, two
lot blanks were selected at random from each of the 2 production lots.
They were submitted for analysis without opening the cassettes. One
field blank was selected for each day of sampling. Field blanks were
handled in the same fashion as field samples, including removal of the
cover in the field and connection to the pump tubing. This was a
control for contamination occurring in the field but not resulting from
air sampling. Nineteen duplicate area samples were collected side by
side. The duplicate samples were sent to an external laboratory, PSI,
for analysis. Results from the external laboratory were compared to
results from the primary analytical laboratory. The degree of
agreement between the two was used to define the overall precision of
the sampling and analytical techniques. In order to test intra-
laboratory analyst reliability, ^preparations were done on seven (7)
samples at the primary laboratory.
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RESULTS
A total of 138 samples were collected, of which 47 (34%) were
personal samples and 91 (66%) were area samples. Collection volumes
averaged 1309 liters (SD +/- 302 L). Average analytical sensitivity
was 0.0044 s/cc (SD +/• 0.0007s/cc). Seventeen samples (12.3%)
were rejected as too dirty to count (TDTC) using the AHERA counting
rules for TEM analysis by direct preparation. The remaining 121
samples were divided between 38 personal samples and 83 area
samples. No asbestos structures were counted in 99 (81.8%) of the
samples. Detectable asbestos structures were found in 22 (18.2%) of
samples, with total concentrations ranging from 0.0029 s/cc to 0.1247
s/cc. When a level of interest was established at total concentrations
of 0.005 s/cc or greater, detectable asbestos structures were reported
in 12 (9.9%) samples.
ARITHMETIC MEAN VALUES Table 1 gives the arithmetic mean
values for personal and area samples. These are reported first for all
samples, and then for samples from each of the sites. The mean 8 hr-
TWA for all personal samples was 0.0009 s/cc (SD W- 0.0043). The
mean total concentration value for all area samples was 0.0033 s/cc
(SD +/- 0.0147). Standard deviations were calculated based on total
concentration for area samples, and on 8 hr-TWA's for personal
samples.
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Table 1: Arithmetic means, as structures/cubic centimeter, of personal and area
aamplaa.
Total Cane. flHr TWA
< B u
>S a Sample Sign SO
All Site*
Personal
Area
Dallas CC
Personal
Area
Exc. Spr.
0.0019
0.0020
WMMC
O.0018
MWSC
Personal
Area
IPftL
Personal
Area
Franklin CC
Area
0.0064 0.0009
0.0033
0.0472 0.0099
0.0176
Personal 0.0202
Area 0.0011
Personal 0
Area 0.0009
0 0
0 0
0 0
0 0
Personal O
000
0.0054
0.0030
0.0364
0.0160
0.0008
0
0
0
0
0
0
0
0 13
0.0010
0.0003
0.0108
0.0016
0.0192
0.0009
0
0.0009
0
0
0
0
0
0
38
83
3
14
0.0010
0.0003
0
0
12
14
8
11
0
0.0043
0.0147
0.0136
0.0329
5
16
6 0
15
0
0
0
0
a o
1. The category of total concentration Is composed of structures <5ji and
2. Standard deviations (SO) were calculated from total concentrations for area
samplesand from 8Hr-TWA concentrations for personal samples.
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As indicated in Table 1, sample results are skewed based on the
building in which sampling occurred. Three buildings accounted for all
reported asbestos structures. Two buildings, Dallas County Courthouse
and Excelsior Springs City Hall, accounted for all values reported at a
total concentration level of 0.005 s/cc or greater. Figure 1 graphically
depicts this skewed distribution with respect to the personal samples.
Eight hour TWA's in Figure 1 were based on asbestos structures greater
than 5u in length.
Figure 1: Arithmetic mean concentrations of fiber lengtha<5|t, £5u, and of
BHr-TWA's for personal samples grouped by building collection site.
1. Calculations of 8 Hr-TWA's were baaed on the concentration
of asbestos structures
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- PERSONAL SAMPLES Detectable asbestos structures were found
in 6 (15.8%) of the analyzed personal samples. Listed in Table 2 are the
personal samples with total concentrations 2 0.005 s/cc. Eight hour
TWA's were calculated using asbestos structures greater than 5u.,
following the OSHA definition of fiber length. Sample #79, from Dallas
County Courthouse, was the only personal sample which met the criteria
for both concentration 0>0.005sfcc) and fiber length
Table 2: Results of personal samples with total concentrations a).005s/cc.
ID # Site
79 Dallas CC0.0598
120 Ex Spr 0.0098
74 Dallas CC0.0495
176 Ex Spr 0.0450
112 Ex Spr 0.0414
Concentration
0.0276 0.0874
0.0049 0.0147
0.0000 0.0495
0.0000
O.OOOO
0.0450
0.0414
Total
BHr-TWA
0.0255
0.0042
0.0000
0.0000
0.0000
Sample #79. The composition of custodial work during this personal
sample was as follows: Sweeping (7%), dust mopping (7%), dusting
(7%), miscellaneous activities (45%), and stripping VAT (34%). The
miscellaneous category included activities such as wet mopping,
emptying trash, and glass cleaning. The custodian was also involved in
sweeping and dusting in a small store room that contained
approximately 12 square feet of a friable asbestos ceiling. Although
this sweeping and dusting were of short duration (five minutes), the
activity was very dusty. Area sampling (sample #81) in this room
during the cleanup did not confirm the presence of airborne 'asbestos.
The custodian also stripped wax from approximately 300 square feet of
vinyl asbestos floor tiles for a period of one hour using a rotary
stripper and stripping solution. Area sampling of this operation
recorded levels of airborne asbestos concentrations of 0.0043 s/cc
(structure _sjze 25u). From observations of custodial work during the
day, the elevated, concentration..of this, personal sample is.most like/ly
attributable to the dusting and sweeping of the store room, despite the
negative results of sample #81.
Sample # 120 The composition of custodial work during this personal
sample was as follows: Sweeping (11%), dust mopping (22%),
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miscellaneous (60%), vacuuming (7%). The custodian cleaned a seldom
used storage room during this sampling period. Asbestos containing
materials in this area included significantly damaged thermal system
insulation located above the storage area. Approximately 15 minutes
was spent sweeping the area with a dry broom. This area had a large
accumulation of dust and was seldom cleaned. The majority of other
work on this day involved little generation of dust.
DISTRIBUTION OF CUSTODIAL TIME. Custodial activities were
monitored during each personal sampling period. Time spent on each
activity has been averaged for all personal samples. Figure 2 gives the
distribution of time, by percentage, spent on each of the listed job
classes.
Figure 2: Average percentage distribution of an 8 hour workday on each
task during personal sampling.
The distribution of work time, indicated in Figure 2 gives an
approximation of the actual job exposure of custodians on an average day.
A job such as dry broom sweeping, "sweep," which is high in exposure
potential, occupies only about 4% of the work day. Thus the contribution
of dry broom sweeping to daily exposure is low.
AREA SAMPLES^ Area samples were collected in seven categories
of custodial work. The numbers of samples distributed among these
categories were as follows: Sweeping (5); buffing (8); dust mopping (32);
dusting (8); stripping vinyl asbestos floor tile (5); vacuuming (12); and
miscellaneous (13). Detectable asbestos structures were found in 16
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(19.3%) of the analyzed area samples. Figure 3 gives the mean
concentrations of area samples categorized by building location.
Figure 3: Arithmetic mean <<5n, £5|i, and total) concentrations of area
samples listed by collection site.
The means for area samples given here follow the trend established
for personal samples in Figure 1. That is, Dallas County Courthouse shows
the highest airborne concentration and the length of fibers is primarily
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Figure * gives the arithmetic mean of area samples categorized by job
class. Three means are given for each job class (<5|i, £5u,, and total
structure count). Of these three means, the mean for structures &5u, is
the most relevant for comparison to occupational standards. As seen in
previous figures, airborne asbestos fibers are primarily <5jj. in length.
Figure 4: Arithmetic mean concentrations for area samples, categorized by
job class. Calculations are made for means of structures <5\i,
and for total structure counts.
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Listed in Table 3 are the 7 area samples with concentrations at or
above 0.005 s/cc. Because these samples are Intended to represent
ambient concentrations, as compared to personal exposures, TWA's have
not been calculated. - Six of the seven of these samples were collected at
the Dallas County Courthouse.
Table 3. Results of area samples with total concentrations at or above 0.005
ID #
78
80
26
<5fi
0.1118
0.0258
0.0300
2 7 0.0240
0.0129
0.0043
0.0000
0.0048
Total Cone. Site Job note
0.1247 Dallas CC Sweeping In fumcace room with
In room.
0.0301 Dallas CC Stripping VAT down to exposed
tile.
.0.0300 Dallas CC Vacuum beneath paint encapsulated
ACM surfaced ceiling.
0.0288 Dallas CC Dry buffing on VAT with poor wax
seal.
2 5 0.0096
surfaced ceiling.
75
poor wax
113
187
0.0000 0.0096 Dallas CC Dust mop beneath paint
encapsulated ACM
0.0096 0.0000 0.0096 Dallas CC Dustmop on VAT with
coat.
0.0050 0.0000 0.0050 Ex Spr 45 minutes vacuuming.
minutes background.
Sample ft 78. Area sample #78 was collected during the cleaning of a
mechanical and air handling room. The concrete ceiling of this room was
identified as having a surface coating of friable asbestos in the
Department of Health's 1988 inspection. This surfacing had been removed
at the time this study was conducted. Remnants of the original surface
have been covered with paint. Debris on the floor and oth'eV horizontal
surfaces of the room appeared to contain remnants of asbestos surfacing.
The custodian worked in this room for approximately 90 minutes. Area
sample #78 was collected concurrently with personal sample #74.
Personal sample #74 which does not indicate a-high personal exposure,
had an 8 hr-TWA of 0.0000 s/cc.
Sample # 90. Area sample #80 was collected during the stripping of
approximately 300 square feet of VAT floor. Stripping was done by
applying a chemical stripper solution to the old floor wax, followed by
removal using a rotary stripper/buffer machine. The stripper/buffer
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machine was operated for one hour, resulting in the complete removal of
wax and some direct abrasion of the VAT. This sample was collected as
an area sample associated with the personal sample #79, which had an
8 hr-TWA of 0.0255 s/cc.
Sample # 27. Area sample #27 was collected during the dry buffing of
1000 square feet of VAT. This floor was not frequently buffed and was
poorly coated with wax at the time of sampling. The procedure for buffing
the floor consisted of an initial cleaning with an oil impregnated dust
mop. This was followed by rotary buffing using a nylon pad. The operation
required one hour. The area sample was collected in association with
personal sample #24, which was rejected from analysis as too dirty to
count.
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REJECTED SAMPLES. Samples that were too dirty to count
represented 12.3% of the samples collected (19. 1% of personal samples
and 8.8% of area samples). These samples are listed in Table 4.
Table 4: Samples too dirty to count (TDTC) by AHERA counting rules for TEM, by
probable source of overexposure.
ID a
T vn e
Probable Source of Qverexooaure
17
19
23
24
28
178
42
44
46
91
84
5
6
7
129
131
134
Personal
Personal
Area
Personal
Area
Area
Personal
Area
Personal
Area
Area
Personal
Personal
Area
Personal
Area
Personal
Dallas CC
Dallas CC
Dallas CC
Dallas CC
Dallas CC
Ex Spr
Franklin CC
Franklin CC
Franklin CC
Franklin CC
Franklin CC
IP&L
IP&L
IP&L
IP&L
IP&L
IP&L
No Identified probable source of overexposure
Very dusty mechanlcal/furance room cleanup
Very dusty mechanical/furnace room cleanup
Very dusty mechanical/furnace room cleanup
Very dusty mechanical/furnace room cleanup
Very dusty store room, with TS1 on pipes above area
Very dusty basement hallway cleanup
Very dusty basement hallway cleanup
Includes dusting Venetian blinds
Includes non-routine sweeping back stairs and dusting
Vicinity of old ACM ceiling tile, seldom cleaned
Extremely dusty, fly ash at coal power plant
Extremely dusty, fly ash at coal power plant
Dusting rails in area of coal lired boiler
Mostly dustmopplng, ongoing construction on boilers
Includes dustmopping In construction area
replace VAT and dustmop In construction area
ASBESTOS STRUCTURE LENGTH AND WIDTH. Length and width
measurements of 115 structures identified as asbestos were made.
Arithmetic mean value for length of all structures was 2.45u, (SD W-1.94
s/cc). The range of length data was 0,5n to 9.5u. Nine structures were
measured at £5u, length. Arithmetic mean width was 0.14|i (SD +/- 0.18
s/cc). The range of width data was 0.1u to 1.75u. Lengths and widths
were compared for asbestos structures collected at Dallas County
Courthouse and Excelsior Springs City Hall, the two primary sites at
which recordable asbestos structures were collected. No significant
differences were found in length or width of structures coming from these
two sites (p=0.05). Asbestos structures were proportionately divided in
the following categories: Bundles, 7%; fibers, 15%; matrices, 78%.
QUALITY CONTROL SAMPLES. Nineteen samples were collected
side-by-side for duplicate analysis at PSI, No significant difference was
found between the original samples and the duplicates (p-0.05).
Repreparations were done on seven samples. No significant difference
was found between the original sample and the reprepared sample
(p-0,05). One asbestos structure was found on a field blank, which gave a
total concentration of 0.0045 s/cc. No explanation for this occurrence
Exposure of Custodial Employees
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was made. No other asbestos structures were found on field blanks or
production lot blanks.
DISCUSSION
As an occupational group, custodial exposure to asbestos has not
received the same attention which has been focused on persons whose
work directly disturbs ACM in buildings. This paucity of research data
has recently been noted in the comprehensive review of asbestos exposure
research undertaken by the Health Effects Institute - Asbestos Research
(HEI-AR.1991). From the limited data currently available, estimates of
the occupational exposure of custodians to asbestos vary greatly. Sawyer
(1977) measured levels of airborne asbestos resulting from custodial
dusting of book shelves beneath a friable 20% chrysotile ceiling in a Yale
University building. Concentration levels, as counted by polarized light
microscopy, ranged from 1.6 fibers/cubic centimeter (f/cc) lor dry
sweeping to 4.0 f/cc for dry dusting. These concentrations would indicate
a significant health hazard" if they were representative of normal
custodial exposures. By contrast, one of the mean values of ambient
concentration recorded in EPA's Public Buildings Study (1988) was
0.00073 structures/cubic centimeter (s/cc). The samples that
contributed to this mean were collected in areas of public buildings with
significantly damaged ACM. Samples were subsequently analyzed by
transmission electron microscopy (TEM). If predictions of custodial
exposure were- made based on the deposition and resuspension of asbestos
dust, as measured in the Public Buildings Study, it would be.reasonable to
estimate that exposures would be quite low, well below the OSHA action
level.
Concern has been expressed that routine custodial exposure may be a
significant health hazard (HEI-AR, 1991; Indoor Air Review, 1991;
Bricher, 1990). Catherine Oliver's review (1991) of the pulmonary
radiographs and lung functions of custodians has focused attention on this
issue. In Oliver's study, pulmonary radiographs and spirometric
measurements were reviewed from a cohort of custodial employees who
had been occupation ally exposed to asbestos in the Boston Public Schools.
The prevalence of pleural plaques and pulmonary restrictions, in excess of
background rates,..was. attributed to custodial occupational exposure, to
asbestos. Pleural plaques are considered diagnostic traits of asbestos
exposure. Advocates of custodial employees have called for more
stringent controls of ACM in buildings to ensure occupational health
protection.
Exposure of Custodial Employees Page 17 of 22
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The OSHA asbestos standard was used in this study for comparison to
the obtained analytical results, with the acknowledgment that OSHA uses
phase contrast microscopy (PCM) for analysis rather than TEM. The
OSHA/PCM standard was used in the absence of a comparable TEM
standard. In this study the arithmetic mean for all personal samples with
fibers longer than 5 microns, is 0.0009 s/cc, 8 hour TWA. This mean is
below the OSHA action level of 0.1 f/cc (95% Upper Confidence Level of
0.029 s/cc). In the case of the highest exposure building, Dallas County
Courthouse, the building mean for personal exposure was 0.0099 s/cc,
from Table 1. The 95% Upper Confidence Level for this mean is 0.032
s/cc, or 32% of the action level. The personal sample with the highest
measured concentration, also from Dallas County Courthouse, was 0.0255
s/cc, Table 2, or 26% of the OSHA action level.
Mean values for all area samples was 0.0033 s/cc, with the mean for
the area samples from Dallas County Courthouse at 0.0176 s/cc. These
means included fibers of all lengths. Among individual area sample
results, the highest concentration, 0.1247 s/cc, came from a sample
collected during the dry broom sweeping of a furnace room at the Dallas
County Courthouse. The ceiling of this room was originally coated with a
friable asbestos surfacing material. This surfacing had been scraped off
within the last five years and replaced with decorative paint. Debris and
dust in the room were evident and cleanup of the room was rarely done,
occurring less than once per year. Rve additional area samples at Dallas
County Courthouse also registered concentrations exceeding 0.005 s/cc.
The custodial activities conducted during each of these sampling periods
are described in the Job Notes, Table 3.
Included in the miscellaneous category of Figure 5 are two instances
of small scale replacement of VAT flooring and the replacement of three
damaged suspended ceiling tiles beneath a sprayed-on asbestos
fireproofing. The miscellaneous category also included a high proportion
.of activities, such as wet.mopping and moving equipment, when custodial
exposure could not reasonably be expected to be higher than that of
general building occupants.
Exposure of Custodial Employees Page 18 of 22
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REJECTED SAMPLES. The use of direct preparation TEM analysis
presented difficulties in the assessment of custodial exposure to
asbestos. In the custodial occupational environment, small concentrations
of asbestos fibers were suspended in higher background concentrations of
non-asbestos building dusts. In order to detect low concentrations of
asbestos efficiently, it was necessary to draw a minimum volume
(approximately 1000L) of air through the filter. In dusty environments,
this volume of air caused .the excessive buildup of dust on the filter. When
25% of the filter's grid area was obscured, the concentration of asbestos
was considered too dirty to count (TOTC) by AHERA counting rules.
This problem was apparent in the attempts made in this study to
collect peak custodial exposures. An example of this was the cleanup of
the mechanical room at Dallas County Courthouse. The cleanup of this
room, which reportedly had not been cleaned in the last three years, was
not part of the custodian's routine duty. However, in an effort to define a
"worst case scenario" for custodial exposure, the custodian was requested
to clean this room during trie study. A total of 7 samples (4 area, 3
personal) were collected. Of these 7 samples, 2 personal samples and 2
area samples were rejected as too dirty to count. The highest
concentration for the samples which could be counted was 0.0874 s/cc,
8 hr-TWA.
Other samples that were TDTC are described in Table 4. From the
right column of Table 4, it can be seen that overexposed samples
generally occurred in association with the clean up of areas in buildings
described as having a large amount of background dust. With the exception
of Independence Power and Light, these areas of the buildings were
excessively dusty because they were seldom, if ever, cleaned. These
exposures have been considered episodic, or non-routine, rather than
routine. Independence Power and Light was an exception to this, because
excessive dust in the plant was due to the operation of the coal fired
boilers, rather than to long periods between custodial services. This is a
type of exposure which is routine"," but 'applicable to only lirtiifed industrial
populations.
Exposure of Custodial Employees Page 19 of 22
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LIMITATIONS OF DATA in discussing the results of this study, a
distinction should be made between the two classes of samples collected.
Personal samples, which are taken in the breathing zone of the custodian
for an 8 hour work shift, represented actual occupational exposure. Area
samples represented a potential exposure to building occupants who are in
the vicinity of custodial activity for a time duration of approximately two
hours. Area samples do not represent occupational exposure and can not
be related to occupational standards. They did however, give an indication
of the concentrations of airborne asbestos fibers generated during
custodial work.
The present data can be used to assessed custodial exposure during
tasks which were routinely performed on a daily, weekly, or monthly
cycle. The data can not be used to make a valid assessment of tasks which
fall under the general duties of custodians, but which are done on a non-
routine basis. Routine exposures to custodians were reported to fall at or
below the values obtained at Dallas County Courthouse, 0.0099 s/cc. The
evaluation of custodial exposure levels for non-routine tasks can not be
made from this data.
STUDY BIAS. A bias was established in this study which
emphasized the occupational exposure of custodians to ACM. Work
regimes were scheduled so that air sampling would predominately include
activities which had the potential to dislodge or resuspend asbestos
fibers. The buildings themselves were selected with a bias toward those
buildings with damaged, friable ACM. The study did not attempt to define
the "average" exposure of custodians. The rationale for the study's bias
was to focus attention on those routine custodial activities which
directly involved ACM and to document the resultant level of custodial
exposure.
CONCLUSION
This study determined that custodians who performed routine
activities in buildings which contained friable, asbestos materials were
not exposed to levels of airborne asbestos which approached the OSHA
action level of 0.1 f/cc. The arithmetic mean value for 38 personal
samples, analyzed by TCM,- was-0.0009 s/cc, 8 hr-TWA for structure
lengths £5u,. The study attempted to bias sampling in order to maximize
the number of occurrences in which custodians worked with asbestos
containing materials. Even with this bias, resulting exposure levels were
well below the OSHA action level.
Exposure of Custodial Employees Page 20 of 22
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A proportion of samples (12.3%) were rejected from analysis as too
dirt/ to count. These samples predominantly reflect collections made
under non-routine conditions. Hypothetically, the rejected samples
contain higher asbestos content than the analyzed samples. The
conclusion remains firm, however, that during routine activities the
exposure of custodians is very low and does not pose a significant risk for
the development of asbestos related diseases.
Exposure of Custodial Employees Page 21 of 22
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REFERENCES
Bricher, Julie Larson. 1990. The Third Wave Risk. Asbestos Issues.
August, pp. 8-17.
EPA. 1988. Assessing Asbestos Exposure in Public Buildings. EPA 560/5-
88-002.
Health Effects Institute-Asbestos Research (HEI-AR). 1991. Asbestos in
Public and Commercial Buildings: A literature review and synthesis
of current knowledge. HEI-AR, Cambridge, Mass.
Indoor Air Review* 1991. Victims Group Says Asbestos Report 'Short-
Changes' Public. Vol. 1, #8, p.29.
Oliver, C. L; Sprinca, N. L'u.and Greene, R. 1991. Asbestos-Related
Disease in Public School Custodians. American Journal of
industrial Medicine. Vol 19, pp. 303-316.
Sawyer, R. 1977. Asbestos Exposure in a Yale Building: Analysis and
Resolution. Environmental Research. Vol 13:1, pp. 146-168.
Exposure of Custodial Employees Page 22 of 22
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