Document KqbXNzprbdvGMNw3wXRVn6o6
FILE NAME Brakes BRK
DATE 2007
DOC BRK196
DOCUMENT DESCRIPTION Journal Article - Heavy Equipment Maintenance Exposure Assessment
Journal of Occupational and Environmental Hygiene 4 525 ISSN 1545-9624 print / 1545-9632 online Copyright '2007 JOEH LLC
DOI 15459620701411109 15459620701411109
537
Heavy Equipment Maintenance Exposure Assessment Using a Activity Model to Estimate Surrogate Values
for Replacement of Missing Data
Fred W. Boelter John W. Spencer and Catherine E. Simmons,,
Boelter Associates Inc. Park Ridge Illinois 2Environmental Profiles Inc. Baltimore Maryland
,
This study on four pieces of heavy construction equipment was conducted to determine the concentration of airborne asbestos fibers during frame maintenance and repair activities which included aggressive techniques that resulted in visible dust from work involving friction products and gaskets Despite execution of a carefully planned sampling strategy approximately 10 47 of the samples collected could not be analyzed due to overloading orfilter damage To include the overloaded samples in the data analysis surrogate values were estimated following a activity model Twelve term personal samples 2 short 30min personal samples and 31 term area samples were modeled Personal and area weighted average data , were analyzed both with and without the estimated surrogate values and compared A total of 444 samples were collected over 9 days Four experienced heavy equipment mechanics removed and replaced friction products and gaskets Samples were analyzed using NIOSH Method 7400 Phase Contrast Microscopy followed by NIOSH Method 7402 Transmission Electron Microscopy Sample data information including the surrogate values for the shift TWA personal sample results
ranged from 0.002 to 0 064 asbestosflcc Personal short
min sample results including the two surrogate values ranged from 0 038 to 0 561 asbestos flcc shift TWA area samples including the 31 surrogate values ranged from 0.005 to 0.039 asbestos flcc Area air sample results at the end of the project were similar to levels measured before the start of the project No fiber concentration buildup within the work area was indicated over the day study Allshift personal and area TWA sample results were below 0.1 flcc and shortterm min personal samples were below 1.0 flcc Statistical results of the sample data with and without the surrogate values were consistent Use of the activity model reduced the uncertainty associated with this data analysis and provided a consistent logical process for estimating surrogate values to replace missing data
Keywords
containing chrysotile exposure assessment friction products gaskets activity model
e
E. Address correspondence to Catherine Simmons Boelter As-
sociates Inc. 1300 Higgins Road Suite 301. Park Ridge IL 60068-
5772 mail cximmons@boulterassociates.com cximmons@boulterassociates.com cximmons@boulterassociates.com
INTRODUCTION
A sbestos has been used in certain applications of engine gaskets and friction products in high- and lowspeed automobiles trucks buses light duty equipment and heavy construction equipment Workers involved in repair or replacement of gaskets and friction products used in heavy construction equipment are potentially exposed to asbestos fibers The authors anticipated and hypothesized that resulting airborne asbestos fiber levels would be below 0.1 cc 8hr weighted average TWA and 1.0 cc min shortterm exposure limit STEL The hypothesis was based on the previous work experience of the authors and results of published studies discussed herein
Conducting an assessment for asbestos exposures on mcchanics performing maintenance activities on heavy equipment presents a number of challenges to sample collection and analysis The analytical methods used to determine the concentration of fibers are sensitive to the presence of other particles on the filters Activities such as welding cutting using torches
and grinding may render the filter overloaded with particulate
matter the result being that the sample cannot be analyzed This study experienced a percentage of samples that were affected by these activities and as a result 10 of the samples could not be analyzed To overcome problems associated with filter overloading and damage the authors chose to apply a activity model commonly used in historical exposure assessment to estimate surrogate values for replacement of the missing data 123
The study was conducted during June 2003 and performed in heavy equipment repair facility by independent mechanics with extensive experience working on heavy equipment The work spanned a period of 9 days and was conducted on four pieces of Caterpillar heavy equipment A D8 Dozer D8 a
12E Motor Grader 12E a 930 Wheel Loader 930 and a 955 Track Loader 955
Brakes chutches and engines determined likely to be original equipment with asbestos containing components were
Journal of Occupational and Environmental Hygiene
July 2007
525525
dismantled cleaned and reassembled The gaskets brake linings and clutch linings were removed and replaced
METHODS
Work Layout and Ventilation
The repair facility was constructed of a steel frame and metal skin and was fitted with two large sectional steel overhead
doors The interior was unfinished and the dimensions were
17.1 m wide by 18.3 m long with a roof that varied from 3.7 m at the side wall to 8.5 m at the apex Figure 1 shows the location of the equipment during the work and the location of the overhead doors The D8 was in Location A throughout the study Sequentially the 12E 930 and 955 were placed in Location B and worked on during the study Figure 1 shows the layout of the facility and the location of equipment
The repair facility was not equipped with a mechanical ventilation system The study was conducted under routine conditions with doors being opened only for entry and exit of personnel The overhead doors were opened only to move equipment and supplies in and out of the repair facility or for a few minutes following work activities such as operating the diesel engines welding and grinding or other activities that generated dense smoke or fume A mounted fan was used by the mechanics at various times to provide air movement inside the repair facility
Prior to and following work activities the effective ventila tion rate reported as the number of air changes per hour of the facility was determined by using carbon dioxide CO2 tracer gas The American Society for Testing and Materials ASTM
Office
N
lets
Location A
me18.3
18.3
Bay
,
Bay 2
Location B
[
Overhead Doors
Ff
LJ
a
l
+ meters eens oa
FIGURE 1. equipment
Layout of repair facility and location of heavy
Method E 741-00 Standard Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution
was followed as a guideline
guideline
SAMPLING STRATEGY AND ANALYTICAL METHODS
he facility owners removed interfering construction equipment and cardboard boxes from the repair facility Ten background air samples were collected for approximately 145 min at 2 min on the day prior to the start of repair activities Five samples were collected inside the facility and five were collected outside the facility to establish background
fiber concentrations
Personal and area air samples were collected each day with sample pumps started prior to the initiation of work activities and were stopped at the end of the day after completion of work Consecutive term samples were collected on each mechanic and at each area sampling location Samples were combined into TWAS over the whole sampling period to
achieve shift TWA concentrations
The short personal monitoring periods were for 30 min and were collected during activities when the mechanics were directly impacting the containing gasket or friction material These samples were collected to reflect peak exposure concentrations from activities conducted over a short period of time
To determine average room fiber concentrations in air a procedure based on Environmental Protection Agency EPA asbestos guidance documents was used The occupied volume of the repair facility was subdivided into 40.320 modules The volume of each module equaled 0.03 mOnly areas between the floor and a height of 3.7 m were included in the random generation of area sample locations as this is the zone where the mechanics worked Eight of the modules were selected using a random number generator A sample cassette was located in the center of the respective module for the duration of each day of testing Area saruples were collected and analyzed using the same methods as the personal samples
All background personal and area saniples were collected and analyzed following National Institute for Occupational Safety and Health NIOSH Method 7400 for collection and analysis by PCM All air samples were collected at a rate of approximately 2 min Samples with results above the limit of detection LOD by phase contrast microscopy PCM were subsequently analyzed by NIOSH Method 7402 Transmission
Electron Microscopy TEM to identify fiber type TEM
analysis determines the fraction of asbestos fibers present on the PCM filters This fraction was then multiplied by the PCM fibers per cubic centimeter cc result in accordance with NIOSH Method 7402 to obtain a PCM equivalent PCME asbestos cc All samples above the PCM LOD in the study were subsequently analyzed by TEM
For sample results below the LOD the PCM LOD value was used in the TWA calculation and statistical analyses
526 526 526
Journal of Occupational and Environmental Hygiene
July 2007
Missinty Data
* v
Determine time period Total and tasks or activities performed
Break down the individual
tasks or activities along with the corresponding time for
each separate one
Task 1 Time 1
Task 2 Time 2
Task 3 Time 3
Review available results
.
for same tasks or similar activities
Select sample result value representative of each task or activity and document the process used
Perform TWA calculation to estimate a surrogate
value for the missing data point The sum of time
for all tasks or activities should equal Ttotal
Is the surrogate value reasonable when compared to
values of similar activities If not evaluate
Combine surrogate value with other measurement to obtain the shift
TWA estimate
FIGURE 2.
Process framework for the
activity
model
used
to
determine an
estimated
surrogate
value
for missing data
"
Note
This
value
may be based on an average mean maximum or some other value Although not used in the model for this paper commercial software for
stochastic modeling is available to assist with selection of a representative value
Journal of Occupational and Environmental Hygiene
'
July 2007
527
For example if a sample was analyzed by PCM and resulted in < 0.045 cc a value of 0.045 cc was used as the value for
PCM and PCME For samples analyzed by TEM and where
the result after multiplying the PCM result by the TEM fraction
was
below
the
PCM
LOD
the
PCM
LOD
was
used
as
the value
value
in the TWA calculation and statistical analysis
Surrogate values for missing overloaded and damaged filters samples were estimated by using a activity model This model is consistent with methods described by Leidel
et 10 and Mulhausen and Damiano where professional
judgment is used to make inferences about exposure concentrations and the use of estimated surrogates in place of
missing data The process usedin this studyis consistent with the worker activity model described by Ramachandran and Vincent and Ramachandran which is used for
retrospective exposure assessments Figure 2 describes the
*
step process that determined the estimated surrogate value to replace the missing sample data point
Bulk Samples Bulk samples of friction and gasket materials and debris
created during the brake and clutch removal process were collected and analyzed for asbestos content and mineral type by polarized light microscopy PLM in accordance with guidelines set forth in EPA Method for Determination of Asbestos in Bulk Building Materials
Statistical Methods
Descriptive statistical functions were performed to summarize personal and area data Industrial bygiene inferential statistics of the TWA shift personal sample
TABLE 1. TWA PCME Personal and Area Samples Daily Statistics Personal TWA Samples
Area Samples
Day
Data Set
xt
Mia
Max
Mean
Std Dev
a
Min
Max
Mean
1
AFS
2
.0.002
0.041
0.024
0.028
0
1
APS
1
BFS
2
AFS
1
_
_
0.007
3
0.002
0.033
0.016
3
0.005
0.007
0.006
0.017 0.001
3
0.004
0.006
0.005
8
0.006
0.008
0.006
8
0.005
0.006
0.006
2233
APS
2233
BFS
0
_
_
3
0.005
0.007
0.006
_
0.001
0
_
_
_
8
0.005
0.006
0.006
2233
AFS
2
0.020
0.028
0.024
0.006
8
0.005
0.022
0.014
2233
APS
3
BFS
2
0.015
0.046
0.030
4
0.013
0.036
0.024
0.022 0.010
0
_
8
0.005
0.022
0.014
4
AFS
4
APS
4
BFS
1
_
0.005
2
0.008
0.009
0.008
3
0.005
0.007
0.006
_
0.001
0.001
0
_
_
8
0.013
0.018
0.014
8
0.007
0.007
0.007
5
AFS
5
APS
0
3
0.046
0.055
0.052
0.005
0
_
4
0.03
0.04
0.036
BFS
6
AFS
6
APS
6
BFS
7
AFS
7
APS
7
BFS
8
AFS
8
APS
00
BFS
9
AFS
3
0.045
...
0.011
1
_
4
0.011
3
0.014
0
3
0.014
3
0.010
0 oT
3
0.010
4
0.008
0.064
0.012
ao
0.012 0.022
_
0.022 0.017
0.017 0.019
0.053
*
0.011 0.011 0.011 0.017
0.017 0.012
_
0.012 0.014
0.010 0.001
0.001
0.004
0.004 0.004
0.004
0.005
8
0.034
0.039
0.036
5
0.007
0.010
0.008
3
0.007
0.010
0.008
8
0.007
0.010
0.008
8
0.009
0.022
0.015
0_
8
0.009
0.022
0.015
8
b.009
0.019
0.011
0
_
8
0.009
0.019
0.011
8
0.008
0.017
0.011
9
APS
a
BFS
0
_
_
4
0.008
0.019
0.014
---
0.005
0
_
_
8
0.008
0.017
0.011
Total AFS
0.002
0.041
0.014
0.009
0.005
0.022
0.011
Total APS
0.008
0.055
0.022
0.003
0.004
0.040
0.016
Total BFS
0.002
0.064
0.018
0.005
0.005
0.039
0.013
AFS =: TWA shift analyzed data > 390 min APS = TWA partial shift analyzed data 390 min BFS --- TWA analyzed plus modeled data
Std Dev
0.001 0.001 0.000
_
0.000 0.005
_
0.005
0.002 0.000
0.004
0.001 0.001 0.001 0.001 0.004
.
0.004 0.004
0.004
0.003
0.003 0.002 0.001 0.002
528
Journal of Occupational and Environmental Hygiene
July 2007
data and short min personal sample data were also
determined
RESULTS
Ventilation
The effective ventilation rate with all doors closed was 0.13 air changes per hour ACH and averaged 4.7 ACH with both overhead repair facility doors open
Background Air Samples Ten samples were collected 5 inside outside but only
the inside facility samples were analyzed Results ranged from 0.012-0.025 total fibers by PCM These samples were further analyzed by TEM and no asbestos fibers were detected PCME of 0.009 asbestos cc in any of the five samples
Bulk Samples The removed and replaced brake materials from all four
pieces of equipment contained from 15 to 95 chrysotile asbestos Bulk sample analysis for asbestos in brake debris collected from all four machines yielded either nondetectable or less than % chrysotile asbestos Removed and replaced gasket materials positive for asbestos ranged from % to 85
chrysotile
Personal and Area Samples A total of 434 personal and area samples were collected
during work activities and analyzed 192 area samples 101 long personal samples and 138 short samples seven approximately 10 of the 434 samples were
overloaded with particulate matter and could not be analyzed Three samples were excluded from the data compilation and statistical analysis due to pump faults that resulted in sample times less than 30 min or sample time uncertainty
Shift and Short Personal Samples shift monitoring periods ranged from 6.5 hr to 9.5 hr
with over half of the samples in the hr time period shift sample collection ranged from one sample collected over a full
shift to collection of five samples averaged to determine the
shift TWA From the 101 personal samples a total of 30 shift averaged personal samples were expected For this study a minimum sampling time of 390 min defined a fullshift personal sample Twenty averaged personal samples
met the shift criteria and are described as Data Set AFS
full shift The remaining nine personal TWAs were less than 390 min due to one or more overloaded samples The partialshift samples are described as Data Set APS partial shift
Sample filters that overloaded with particulate matter or were damaged resulted in inconclusive data which then resulted in TWA samples failing to meet the selected shift time criteria To avoid loss of the missing sample data points a activity model Figure 2 was used to estimate surrogate asbestos fibers values The estimated surrogate value for cach missing data point was then entered into the PCME TWA calculation The results of including the surrogate values into the PCME TWAs are described as Data Set BFS full shift
Personal shift TWAS by PCM analysis ranged from 0.005 cc to 0.049 cc with an arithmetic average value of 0.027 cc Partial TWAs by PCM analysis ranged from
0.10
0.09
0.08
0.07
Fibers 0.06 0.05
Asbetos
0.04 0.03
0.02
0.01
0.00
*
APS
AFS APS BFS AFS APS
APS APS AFS AFS BFS APS
AFS
5
Day Day
DayDay Day
DaDyay
Day
Day
Day
Day Day
Day Day Day Day Day Day
5
6
Day Day Day Day
BFSAFS
APS APS
-
BFS
AFS APS
BFS
BFS AFS APS BFS
BFS APS BFS
Day Day Day Day Day
AFS APS BFS AFS APS
APS BFS
Day Day
FIGURE 3. TWA personal sample asbestos libers by day and data set Note The solid circle on the graph indicates the average value The line extending through the circle indicates the range of the data AFS indicates Data Set TWA data 390 minutes APS indicates
Sample Data Set TWA partial data 390 minutes BFS indicates Data Set TWA shift data including surrogate modeled data
Analysis by NIOSH 7400 followed by NIOSH 7402 Note The maximum value for Data Set BFS is different from AFS because one of the AFS
samples included an OL sample that when replaced with the surrogate value the TWA was lower
Journal of Occupational and Environmental Hygiene
July 2007
529
530
TABLE II Daily TWA Personal Sample Results with Activity Descriptions Data Set BFS
Sample Information
.
.
Date
Day 1 Day 1 Day 1
Day 2
Day 2
Day 2
Day 3
Day 3
Day 3
Day 3
Person
Sampled
Mechanic # Mechanic # Mechanic 4
Mechanic 2
Mechanic 3
Mechanic 4
Mechanic #
Mechanic 2 Mechanic 3 Mechanic 4
Activity
D8 - Cable control disassembly removed wheels and brake
D8 - Removed and replaced right cable control brake 12 E- Removed and replaced the air filter exhaust and intake manifolds valve cover and
-
engine head
D8 - Removed parts to access the track brakes Assisted with disconnection of the cable
control unit from the body of the dozer 12E 12E removed and replaced rear brakes D8 - Removed and replaced left cable control brake disconnected cable control unit from
body of D8 12E Removed and replaced rear brakes cleaned engine head and block replaced head gasket
and engine head removed radiator connections and gaskets 12E -- Removed and replaced rear brakes cleaned engine head and block replaced head gasket
and engine head removed radiator connections and gaskets
~
D8 --- Removed the left and right track brake bands replaced left brake band
D8 - Removed and replaced clutch and cable puller linkage
12E - Machine fluids replaced oil filter crank case breather and air filter parts and gaskets and
engine cover replaced 930 Removed and replaced the wheels four brake caliper
Surrogate Estimated
Value Time min
0 131 123
0
0
0
0
162 162
*
o
assemblies and brake pads Day 4 Mechanic 2 D8 -- Track band brake replacement and adjustment Assisted with the rernoval of clutch using 350
overhead hoist
the master clutch Assisted with the removal of clutch using
223
Day Mechanic 3 D8 --- Removed parts 10 access
,
overhead hoist
4 Mechanic 4 955 -- Removed engine cowling exhaust manifold rocker art assembly valve cover engine
0
Day studs air intake manifold and air filter radiator hose connection water thermostat and the
-
engine head along with associated gaskets
access to the rear brake bands Disassembled and removed the
64
Day 5 Mechanic # 955 -- Removed parts to gain
steering clutch linkages and assisted Mechanic 4
5 Mechanic 3 D8 - Removed and replaced clutch drive and driven plate friction linings
155
DDaayy 5 Mechanic # 955 Removed gaskets from the intake manifold exhaust manifold valve covei radiator hose 279
pipe connection and the oil cooler pump Replaced ferrules seals gaskets and engine
head
6 Mechanic # D8 - Assisted with replacement of clutch 955 -- Removed three left side brake band assemblies
0
Day
Removed band brake D8 Removed and replaced clutch and cable puller linkage
0
Day 6 Mechanic 2 955 --
0
Day 6 Mechanic # D8 - Reinstalled the clutch assembly and clutch linkaagire intake manifold exhaust manifold 0
Day 6 Mechanic 4 955 -- Reassembled with gaskets the valve assembly
connection surfaces and air filter assemble
thermostat oil cooler surface radiator pipe
Total Sample Time min
490 536 494
509
409
509
405
511
512
504
517
520
493
422
493 499
336
438 574 576
Results
PCME TWA
N Asbestos Fibers
}
0.002
4
0.033
3
0.007
2
0.005
2
0.007
0.005
3
0.028
3
0.036
3
0.013
3
0.020
2
0.007
3
0.008
2
0.005
5
0.045
5
0.052
5
0.064
a
0.011
4
0.012
5
0.012
5
0.011
Journal Day 7 Mechanic # 955 - Removal of left side brake bands replaced the oil cooler radiator pipe gaskets and
0
radiator fan and fan guard of
Day 7 Mechanic # D8 - Reassembled the clutch linkage and installed the transmission inter assembly with
its original gasket 955 -- Assisted mechanic #
Ocupationl Day 7 Mechanic # D8 - Removed the pony engine exhaust pipe pony engine supply tube water manifold pipe
exhaust and air intake manifold and cylinder heads Removed gaskets and cleaned engine
head and flanged surfaces
Day 8 Mechanic # 955 - Installed right- and side brake bands and steering linkages
547
and Day 8 Mechanic # 955 - Installed the brake bands on the right and left side Reinstalled brake and steering
540
linkages D - Assisted with installation of engine head
.
.
Day & Mechanic 4 D8 - Cleaned the exhaust manifolds front and rear cylinder heads removed and
482
Envirometal replacedgaskets
Day 9 Mechanic # 955 - Completed steering clutch and brake linkage installation and adjusted brakes
489
D8 - Assisted Mechanic #
Day 9 Mechanic # 955 - Completed steering clutch and brake linkage installation adjusted biakes D8 Assisted
494
Hygien Mechanics # and 4 with engine assembly and replaced.exhaust replaced.exhaust stack
Day 9 Mechanic # D8 --- Drained and replaced oil installed seats levers and steering linkages in cab
502
Day 9 Mechanic 4 D8 - Cleaned valve cover surfaces installed replacement valve cover gaskets Reinstalled fuel
0
496
lines exhaust and water manifold gaskets and air intake pipe Cleaned the pony
July engine exhaust pipe flange and replaced gasket Removed and replaced the fuel filter and gaskets
20 7 The amount time that the activity model was used to estimate a surrogate value for inclusion in the TWA 6 The total amount of time this mechanic worked on Day 6
0.016 0.014 0.022
0.011 0.010
.
0.017 0.019 0.013 0.008 0.018
TABLE III Short Min Personal Sample
Daily Statistics
Day
Data Set
m
Min
Max
1 2 3
5 5 6 7 8 9 Total AST Total BST
AST AST AST AST AST BST AST AST AST AST
4
0.044
6
0.044
13
0.044
0.043
18
0.043
20
0.043
23
0.043
30
0.043
29
0.044
9
0.045
0.043
0.038
0.046 0.045 0.561 0.045 0.413
0.413
0.099 0.170
0.180
0.045 0.561 0.561
Notes AST indicates analyzed data only BST indicates analyzed plus
modeled data
Minimum values were all less than the limit of detection for the sampling
method
0.011 cc to 0.176 cc with an arithmetic average value of 0.053 cc The minimum PCME value result for data sets AFS and BFS was 0.002 asbestos cc and 0.008 asbestos cc for Data Set APS The maximum PCME values were 0.041 for Data Set AFS 0.055 for Data Set APS and 0.064 asbestos cc for Data Set BFS The means were similar with Data Set AFS at 0.014 asbestos cc Data Set APS at 0.022 asbestos cc and Data Set BFS at 0.018 asbestos cc Table I and Figure 3
present the daily statistics for personal PCME TWA samples and Data Sets AFS APS and BFS A comprehensive list of work activities and sample information for shift TWAS
representing Data Set BFS values are presented in Table II One hundred and thirty short samples were
collected Of those 136 samples were analyzed Two samples
on Day 5 were overloaded with particulate matter and could not be analyzed The analyzed samples are designated as Data Set AST short term The activity model was used to estimate surrogate values for the two missing data points and the combination of these values and the analyzed samples are designated as Data Set BST
All short samples were collected for 30 min except for one min sample Table III and Figure 4 present the sample data grouped and analyzed by day The range of results of the min short samples for Data Set AST by PCM analysis was less than the LOD < 0.043 cc to 0.561 cc The
range of results for Data Sets AST and BST by PCME analysis
were less than the detection limits of 0.043 and 0.038 asbestos
cc to 0.561 asbestos cc for both PCME data sets Mean
values were not calculated due to the high fraction of censored
data
Gasket and friction excursion limit samples were grouped and analyzed to determine exposure concentrations for the various activities Data were grouped to evaluate the results by a variable such as perceived aggressive activities including scraping hammering riveting abrasive cutting and cleaning surfaces using a die grinder or compressed air The PCM and PCME results of the sample data grouped by activity are presented in Table IV
1.00
0.80
0.60
Fibers
Asbetos 0.40 0.40
+
0.00
AST
Day
5AST
Day
FIGURE 4. Short personal sample results by day Note The solid diamond on the graph indicates the average value The line extending through the diamond indicates the range of the data AST indicates Data Set A BST indicates Data Set B. Sample Analysis by NIOSH 7400 followed by NIOSH 7402
e
532
Journal of Occupational and Environmental Hygiene
July 2007
TABLE IV Short Personal Samples by PCM and TEM
.
Sample InformationA
Activity
Analysis by NIOSH 7400
Phase Contrast
Microscopy PCM
Analysis by NIOSH 7400
PCM and NIOSH 7402 Transmission
Electron Microscopy TEM
NC Min Max Avg Std Dev Min Max Avg
Std Dev
Friction Work
Band brake removal
'
Removal of rivets and friction lining from
brake band or brake shoe
Cutting band with abrasive disc Removal of disc brake assembly Brake replacement and adjustment Rivet replacement of friction lining to
bands or shoes
Drilling of brake lining Clutch removal replacement and adjustment D8 only
Rivet removal from drive and driven
17
=4
2 5 28 4
1 28
2
plates D8 only
Cleaning scraping compressed air
4
cleaning of drive and driven plates D8
only
Rivet replacement of friction linings to
6
drive and driven plates D8 only
Related Work
Removal of exhaust and intake
13
manifold manifold gaskets
Scraping cleaning of engine head
13
engine block and manifold surfaces
Wiping cleaning parts
8
Use of compressed air to clean engine
8
parts
Replacement of engine parts and gaskets
12
0.043 0.044
0.077 0.044
0.048 0.044
0.049
0.044 0.043 0.043
0.561 0.044 0.104 0.044
0.305 0.044 0.047 0.044
0.043
0.201
0.038 0.079
0.190 0.230 0.210
,
0.151 0.211 0.180
.
0.048 0.207 0.156
0.044 0.048 0.045
0.045 0.413 0.143
0.045 0.045
'
199 0.199
0.065 0.064
0.045 0.074 0.050
0.010 0.000
0.043
= 0.044
0.058 0.044
0.045 0.044
0.362 0.000 0.012 0.001
0.049 0.044 0.043 0.043
0.561 0.044 0.045 0.044
0.305 0.044 0.044 0.044
0.050
0.043
0.099
0.038 0.048
0.028
0.150 0.184 0.167
0.026
0.150 0.211 0.170
0.056
0.044 0.207 0.127
0.001
0.044 0.045 0.044
0.125
0.054 0.054
0.045 0.413 0.116
;
0.045 0.045
0.094 0.094
0.051 0.051
0.010
0.045 0.045 0.045
0.004 0.000 0.362 0.000 0.001 0.001
0.013 0.024 0.029
0.069
0.000 0.114 0.017 0.017 0.000
* All samples were collected for 30 min at approximately 2 mm except for one min sample during brake drilling
B
For
all
samples
less
than
the
PCM
LOD
the
PCM
LOD
is
the
value
used
in
statistical
calculations
Seventeen short samples included work under two activities and are included in the analyses for both
Further inferential statistical analysis of personal shift term TWA Data Sets AFS and BFS and the short-
terro min data set was conducted For the short 30-
min data 96 of the 138 samples were less than the LOD Inclusion of data points less than the LOD censored data
would bias the statistical results toward the low end To be
conservative and avoid the bias associated with analyzing censored data only samples above the LOD were included in the analysis of the short min data By excluding the censored values from the short min data set analysis only the upper bound values of the inferential statistics are reported Each data set was determined to be lognormally distributed The geometric mean GM geometric standard deviation GSD percentile value X 95 upper tolerance limit 95 UTL 95 exceedance fraction point estimate
and 95 upper confidence limit were calculated The results
of these analyses are presented in Table V.
Area Samples Seventy TWA area samples were calculated from the
results of 192 area samples Of these 41 area sample results were shift TWA samples with the remainder composed of 31 partial TWA area samples Sample sets are designated the same as the shift personal samples with Data Set AFS representing shift TWA samples Data Set APS representing partial TWA samples and Data Set BFS which represented all of the data from the previous two data sets plus the estimated surrogate values for the missing data
points The range of PCM sample results for Data Set AFS was
0.003 to 0.047 total cc with an arithmetic average value of
0.020 cc The range of PCM sample results for Data Set APS was 0.003 to 0.066 cc with an arithmetic average value of 0.022 cc The overall statistics for the shift PCME data sets AFS and BFS were similar with minimum values of 0.005
Journal of Occupational and Environmental Hygiene
July 2007
533
TABLE V. Inferential Statistical Analysis Samples
Shift Personal
TWA PCME Samples Data Set AFS
Occupational exposure limit OEL cc Number of samples N Geometric mean cc Geometric standard deviation cc
95 cc UTL 95 UCL of 95 cc Exceedance fraction point estimate %
Exceedance fraction 95 UCL
0.1 N 21
0.011 1.98 0.035
0.057
0.07 1.14
Shift Personal
TWA PCME Samples Data Set BFS
0.1 N = 30
0.013 2.17 0.047 0.074 0.45 2.50
AFSTWA AFSTWA AFSTWA shift analyzed data 390 min
BBFS
BBFS
.
TWA
shift
analyzed
plus
modeled
data
'
Analyzed
data
from
Data
Set
AST
above
the
LOD
only
Only
upper
bound
statistics
reported
Short Min PCME Personal
Samples
1 N = 48
0.261 0.359 0.03 0.23
and 0.005 asbestos cc maximum values of 0.022 and 0.039
asbestos cc and arithmetic average values of 0.011 and 0.013 asbestos cc for data sets AFS and BFS respectively Table I
and Figure 5 present the PCME data by day Figure 5 shows that the arithmetic average asbestos cc air level by the end of the study was essentially the same as the beginning asbestos cc background level These results indicated no buildup of asbestos fibers in air from one day to the next
All TWA samples were below an hr TWA of 0.1 cc All
short min samples were 1 below cc
DISCUSSION
The The majority of the activities conducted during this study were according to the mechanics typical for the study vicing required However a few unusual practices were also monitored One unusual practice the cutting of the brake band resulted in the highest value for the short min samples 0.561 asbestos cc The brake band cutting took approximately 2.5 min and was necessary because the bolts holding the brake band on could not removed This activity
0.10
0.09
0.08
0.07
0.06
Fibers 0.05
Asbetos 0.04
0.03
0.02
0.01
0.00 Background
Background
Background
1-
BFS
APS
BFS
22 333 4
BFS 5
5
BFS
BFS
66 77 88
BFS
BFS
8 8 9- 0
FIGURE 5. TWA area sample asbestos fibers by day and data set Note The solid square on the graph indicates the average
value The line extending through the square indicates the range of the data AFS indicates Data Set TWA data 390 minutes APS indicates
Data Set TWApartial shift data 390 minutes BFS indicates Data Set TWA shift data including surrogate modeled values Sample
Analysis by NIOSH 7400 followed by NIOSH 7402
*
534
Journal of Occupational and Environmental Hygiene
July 2007
Results
PCM
total cc
PCME
asbestos cc
Work Activities Analyzed Values and Surrogate Values Personal Sample Information for Mechanic # on Day 5
Sample
Time
Duration
Analyzed Surrogate shift
min Value Value Value TWA
Mechanic removed radiator fan conducted scraping and used a die grinder and abrasive disc on manifolds and valve cover surfaces Five short samples collected on this mechanic on this
7:42 to 8:46
64 OLA
day included the same or similar activities described for this time period An average of the four short samples 0.413 0.270 0.080 0.046 and 0.077 asbestos cc was used as the surrogate
value 0.172 asbestos cc Mechanic used a die grinder and scrapers on oil cooler surfaces and air intake pipe flange
8:46 to 9:18
33 OLA
Four short samples collected on this mechanic on this day included the same or similar
activities described for this time period An average of the four short samples 0.413 0.270
0.080 0.046 and 0.077 asbestos cc was used as the surrogate value 0.172 asbestos cc
Mechanic used a chisel hammer and die grinder on water pump flange radiator head flange 9:19 to 10:07 48 0.26 0.16
exhaust manifold on engine head air intake on engine bead valve mechanism assembly broom
cleaned the floor wiped down work table and used a solvent to clean and wipe engine head
surface
Mechanic used a die grinder and scrapers on the engine block surfaces Conducted parts inventory 10:07 to 11:48 101 0.019 0.016
Used a grinder on the equipment frame to allow clearance to install engine head Mechanic replaced head gasket assembled ferrules and seals installed head to engine block
11:48 14:50 182 OLA
tightened engine head bolts with torque wrench and helped Mechanic # remove brake bands for
5 min No short samples were collected on this mechanic during this time period To
determine the surrogate value we took the air sample result on Mechanic # 0.058 asbestos cc
for the brake work and used this value for the 5 min Mechanic 4 assisted him Lunch break was
included during this sample and was for 37 min There was no exposure during lunch For the remainder of the time 140 min a value of 0.016 asbestos fibers was the surrogate This
surrogate value was based on the results of four samples collected on Mechanic # on Days & and
9 while he performed the same activities during reassembly of the D8 which ranged from 0.008 to 0.016 asbestos cc Using the weighted average TWA calculation for the above value the
result is 0.014 asbestos cc for the 182 min
Mechanic completed tightening engine head bolts with a torque wrench replaced valve mechanisms 14:50 to 16:01 71 0.043 0.040
and engine head gasket
Once the surrogate values were determined for the three OL samples described above they were
499
averaged with the remainder of the air samples for this mechanic on this day The total work time
was 499 min and the TWA result was 0.064 asbestos cc The activities for this mechanic on this
day were similar to his activities on Days 7 and 8. The TWA results for those days were 0.022 and 0.017 asbestos cc Based on comparing the TWA results on Days 7 and 9 to the TWA for this mechanic on Day 4. surrogate values were likely biased on the high side Because the goal was to compare results with 0.1 cc as an br TWA the bias was reasonable without being unreasonably
conservative
0.177
0.177
0.014
0.064
AOL indicates sample was overloaded with particulate matter and could not be analyzed
535
was also conducted a second time on another brake band on
the D8 and the sample result was 0.049 asbestos cc Exposures with the highest numerical values occurred on
Days 1 3 and 5 of the study Activities on Day 1 included removal of brake bands and removal and replacement of rivets and friction lining on the brake bands Day 3 activities focused on the brakes and clutch systems on the D8 end engine rebuild on the 12E and brake removal and replacement on the 930. Day 5 activities included rivet removal cleaning and
replacement on the drive and driven plates removal and
replacement of end engine containing gaskets Days 1 3 and 5 were also the days when 32 air samples
approximately 70 of all the overloaded samples were overloaded and could not be analyzed To overcome the inability to include the overloaded samples and to reduce uncertainty associated with evaluation of the data a timeactivity model to estimate surrogate values for the missing data was applied There was also a large data set with multiple samples for each task or similar tasks
As shown in Figure 2 the authors relied on the analyzed data to assist with determination of the surrogate value Also for most of the overloaded sample periods there were one or more short min samples collected on the same mechanic during the applicable time frame that were available for use in the model For each estimate made by following the model described in Figure 2 the authors chose conservative values in recognition that short samples with their higher limits of detection are likely biased high and are not necessarily
good predictors of term exposures Therefore the
estimated surrogate results are also likely biased toward higher
,
exposure values
Because the authors were interested in comparing the results with the maximum likely TWAS it was determined that conservative but reasonable estimations would be prudent To determine whether each surrogate TWA value was reasonable the result was compared with the TWA result of other mechanics performing similar activities To illustrate the process Table VI presents the results of using the activity model
to estimate values for three samples on Mechanic 4 on Day 5
of the project The pattern of results of TWA personal samples in Figure 3
is similar to the pattern of the results for TWA area samples in Figure 5. The similarity in patterns was expected and indicates that the area samples though much lower in concentration are reflective of the work activities conducted on each day of the study Results also indicate that the average value of the shortterm samples over the day study were consistent as shown in Figure 4
The PCME mean and range for each data set on each day and demonstrate the consistency of these values throughout the study However the authors would caution users of the timeactivity model for replacement of missing data that there may not always be this level of consistency for all data sets
Two published studies provided extensive PCM total fiber data regarding airborne exposures during maintenance and brake lining replacement in automobiles and other types
of vehicles Neither of the published studies included analysis to confirm fiber type in the air samples The PCM total fiber results of our study were within the exposure range of these previously published studies
In comparison a number of published studies provided a smaller volume of data regarding exposures to asbestos while removing and replacing gaskets Although not all of the studies provided TEM analysis results some did provide hr TWAs The results of this study were consistent with the previously published studies where hr TWAS by PCM or fiber identification was included as part of sample analyses using
NIOSH method 7402
CONCLUSIONS
Repair Repair and maintenance of heavy construction equipment involving containing friction products and gaskets resulted in exposure concentrations below 0.1 cc as an hr TWA and below 1 cc as a min short sample
Average asbestos cc air concentrations in the repair facility work environment by the end of the day study were essentially the same as background levels measured before the study indicating no buildup of asbestos fibers in air from one day to the next
A activity model approach to estimate surrogate values for replacement of missing data is an option to consider for exposure assessments when the ability to resample activities is not possible
ACKNOWLEDGMENTS
The authors wish to thank Caterpillar Inc. for funding this study Caterpillar is a defendant in asbestos personal injury claims Caterpillar did not influence the exposure assessment protocols that were developed or conducted We also want to thank the team of professionals who
assisted with the study and the professional and diligent heavy
equipment mechanics of Hoerr Machinery for sharing their knowledge skill and experience
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