Document ba9evOM7g80Y43QdY6qoO37DO
FILE NAME Brakes BRK
DATE 2006
DOC BRK155
DOCUMENT DESCRIPTION Journal Article - Asbestos Exposures During Reprocessing of Automobile Brakes and Clutch - International Journal of Occupational and Environmental Health
Original Articles
Asbestos Exposures during Reprocessing of
Automobile Brakes and Clutches
KIYOSHI SAKAI DMSC NAOMI HISANAGA MD EIJI SHIBATA MD DMSC YUICHIRO ONO MD DMSC YASUHIRO TAKEUCHI MD DMSC
Asbestos exposures of workers in three small factories
reprocessing automobile brakes and clutches in Japan were investigated Airborne asbestos was collected on a membrane filter using an air sampler From 1982 to 1989 asbestos counting was performed on 295 samples 198 personal and 97 stationary using phase contrast microscopy Only chrysotile asbestos was detected Workers who reprocessed automobile brakes and clutches were exposed to asbestos concentrations of 0.025-76.4 fibers Geometric mean asbestos concentrations during attaching linings to brake shoes and attaching facings to clutch disks were 0.859 fibers cm and 0.780 fibers respectively Concentrations during stripping worn brake linings and clutch facings were 0.484 fibers and 0.382 fibers respectively Machine grinding and leveling of new brakelining surfaces represent potential sources of heavy
asbestos exposures unless enclosures and local ventila-
tion are efficient Key words asbestos automobile brake and clutch reprocessing small industry
INT J OCCUP ENVIRON HEALTH 95-106
n Japan during the early 1980s reprocesing at least 400 companies were involved in the reprocessing of auto-
mobile brakes and clutches In 1982 of the 400
companies 190 that employed 1,611 workers were
organized to a form society of reprocessing companies
Companies employing fewer than ten workers com-
Received from the Nagoya City Public Health Research Institute
Nagoya Japan KS the Center for Health Care Aichi University of
Education Kariya Aichi Japan NH the Department of Health and
Psychosocial Medicine Aichi Medical University School of Medicine
Nagakute Aichi Japan ES the Department of Public Health
Fujita Health University School of Medicine Toyoake Aichi Japan
YO and the Department of Occupational and Environmental
Health Nagoya University Graduate School of Medicine Nagoya Japan YT
Address correspondence and reprint requests to Kiyoshi Sakai Nagoya City Public Health Research Institute 1-11 Hagiyama Mizuho Nagoya 467-8615 Japan telephone 81-52-841-1511 fax 81-52-841-1514 mail k-sakai@ma.medias.ne.jp
prised 75 of this society Of the member companies
33 had been founded between 1955 and 1964 and
59 after 1965. The number of member companies increased with the widespread use of automobiles in Japan Meanwhile the number of reprocessed automobile parts increased with every passing year Brakes and clutches in particular were the principal reprocessed parts In 1982 approximately 17,500 tons of asbestos were used for manufacturing brake linings clutch facings and disk pads The chrysotile contents of these brake linings and clutch facings usually ranged from
40 to 60
Although there are numerous reports of airborne asbestos concentrations in automobile repair and serv-
ice shops there are very few reports of asbestos
exposure levels in factories that reprocess brakes and clutches
Langer and McCaughey,,reported the case of a repair worker who contracted mesothelioma Levin et al presented the case of a clutch refabricator who had asbestosis and lung cancer and the chrysotile concentration in lung tissue of this patient exceeded the reference values by a large margin Dahlqvist et al reported that the degree of airway closure was posi-
tively correlated with an increased cumulative exposure to asbestos even after controlling for age height smoking and exposure to diesel exhaust Lemen15 stated that the alleged controlled use of asbestos taining brakes posed a health risk to workers users and their families Thus workers reprocessing automo-
bile brakes and clutches are at risk for asbestos
health disorders
From 1982 to 1989 we determined the airborne
asbestos concentrations in three small factories
that reprocessed automobile brakes and clutches As mentioned previously available information about
asbestos exposures in the automobile clutch- and
reprocessing industry is very limited The results
of our study which was conducted in the 1980s can provide valuable information for the risk assessment of asbestos diseases in this industry
95
TABLE 1 Survey Dates and Numbers of Samples
No. Samples
Dates
Factory Personal Stationary
1982
July 16 July 27
October 12
<<<
5
580
A
6
580
A
8
580
1983 June 11 June 18 June 22
August 24
1984
July 9 July 15 July 18
1985
July 16 July 17 July 18
1989 August 11
ABAC
1627
0502
ABAC
1627
0502
--
1627
0502
ABAC
1627
0502
ABC
-- -----
ABC
30
-- -----
ABC
-- -----
--
21
68
ABC
20
68
ABC
24
0
B
0
10
TOTAL
198
97
MATERIALS AND METHODS
Materials
Between 1982 and 1989 sampling was repeatedly performed in three factories in Nagoya that reprocessed
automobile brakes and clutches Table 1 shows the
number of samples used for measurement on each day
A total of 295 198 personal and 97 stationary samples
was obtained
Personal Sampling
Personal samples were collected from the breathing zone of each worker either throughout a single operation or throughout two different operations The samples were collected on membrane filters Millipore type AA 0.8 ...mpore size 47 mm diameter using a personal sampler Roken type Sibata Scientific Technology Personal samplers were attached to workers lapels The sampling flow rate was 1.0 min and
depending on the duration of the operation sampling
times ranging from 4 to 135 min were set Subjects were selected from among workers reprocessing automobile
brakes and clutches
Stationary Sampling
Stationary samples were taken according to the Working Environment Measurement Standards of Japan More than five fixed sampling points were set up in a given unit work area The samples were collected on membrane filters Millipore type AA 0.8 ...mpore size 47 mm diameter using an open filter holder
Model 3400 Sartorius Sampling was performed at a flow rate of 10 min using a suction pump Model IP30L Sibata Scientific Technology sampling times ranged from 15 to 60 minutes The samples were obtained from a height of 0.5-1.5 m above the workplace floor There were five unit work areas one in fac-
tory A and two each in factories B and C.
Counting Method
Asbestos particles were counted using a contrast microscope BHB Olympus in accordance with the standardized method developed by the Japan Asso-
ciation ofIndustrial Health To elaborate a small por-
tion of each filter was cut and mounted a on glass slide
with a medium consisting of dimethyl phthalate and diethyl oxalate 1 and then covered with a cover glass Up to more than 100 fibers or 20 areas within the given graticule field at a magnification of 400 were counted Only the fibers that met the following criteria were counted length greater than 5 mdiameter less
than 3 ...mand aspect ratio greater than 1
The detection limit for personal sampling when collecting 60 L of air and counting 20 areas within the given graticule field was 0.006 fibers and that for stationary sampling when collecting 600 L of air and counting 20 areas within the given graticule field was 0.0006 fibers
Identification of Asbestos
A transmission electron microscope 800 HITACHI
equipped with an dispersive ray analyzer EDXA KEVEX was used for identification of asbestos during the analysis of some samples Asbestos was morphologically e.g. the hollow structure of chrysotile identified with the help of EDXA
Mean Asbestos Concentrations
The mean asbestos concentration of each operation was obtained in the following manner
1. Where more than two samples were obtained from an operation on any day of measurement the mean asbestos concentration of that operation in the factory on that particular day was calculated as a geo-
metric mean because airborne asbestos concentrations
distribute normally 2. The mean asbestos concentration of an operation
was obtained by calculating the geometric mean of the obtained geometric mean asbestos concentrations on the day of measurement
Calculation of Evaluation Values and Control Class Classification
The values of asbestos concentration measured by stationary sampler at a unit work area were processed fol-
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Sakai et al
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TABLE 2 Profiles of Surveyed Factories as of 1983
Factory
Floor Area
m
No. of
Workers
Average Monthly
Reprocessing
Amounts Pieces
Brake
Clutch
ABC
300
20 10
19.600
1,700
ABC
362
20 10
27,500
300
ABC
452
19 7
12,500
4,000
Number in parentheses is number of workers handling friction materials directly
Working Hours per Day
7.3 7.5 7.8
No. Local Exhaust Ventilators
in Factory
8 7 26
lowing the Working Environment Evaluation Stan-
dards of the Japanese government After calculating geometric mean GM and geometric standard devia-
tion GSD of measured concentrations the first evaluation value El and the second evaluation value E2 were calculated by the following formulas
LogEl = logGM + 1.645 ^
logGSD+ 0.084
LogE2 = logGM + 1.151 ^ log2GSD + 0.084
If we measure airborne asbestos concentration by stationary sampler at every possible point and time during working hours in a unit work area we will get an
infinite number of concentration values The El is a
statistically estimated concentration corresponding to 5 percentile points from the highest value among
them The E2 is the estimated arithmetic mean of infi-
nite asbestos concentration values
The next step is sorting unit work areas into three control classes based on comparisons among E1 E2 and an administrative control level ACL explained in the Discussion section The sorting criteria for con-
trol classes 1 2 and 3 are E1 < ACL E2 < ACL E1
and ACL < E2 respectively The measures required for control classes 1 2 and
3 are 1 maintaining the present good condition 2 an effort to reduce exposure further and 3 immediate
action to reduce exposure respectivel1y8
Reports to Employers
The result of each assessment of the working environment was reported to the respective employer The
reports consisted of the determined airborne asbestos concentrations and recommendations for measures to
reduce asbestos exposures of workers
RESULTS
Profiles ofFactories
The three surveyed factories had begun to function around 1955 and were comparatively large companies in the brake- and reprocessing industry Factories A and B were located in areas having both smallscale factories and private homes However factory C
was located in a residential area Factory A was a one-
story structure and factories B and C were storied structures Table 2 shows the characteristics of each fac-
tory In 1983 27 of the 57 workers directly handled automotive friction materials and the remaining workers did not Ages and employment periods were available for 52 of these 57 workers The mean ages range of the male and female workers were 42 19-71 years and 44 34-54 years respectively The mean employment periods range of the male and female workers were 15 1-34 years and 8 0.5-28 years respectively
The work processes and the amounts of time spent on
various operations in the three factories were similar The work processes and operations remained unchanged through the 1980s and the work was carried out on a regular basis The labels of the friction materials specified the asbestos content 50 and contained a hazard warning The weights of the brake linings and the clutch facings that were mainly used were 0.23 piece and 0.22 piece respectively It
was estimated that every month 4.8 tons of friction
materials were utilized at factory A 6.3 tons at factory B and 3.7 tons at factory C.
Asbestos substitutes were not used at that time
In the present study environment measurements were obtained only in the summer On the days
of measurement the doors and windows of factories A
and B were kept open However the doors and windows of factory C were kept closed in some workplaces throughout the day because of conditioning Only a few workers used personal respiratory protective equipment
Processes
Figure 1 illustrates the sequence of operations during
the reprocessing of automobile brakes and clutches
The main process consisted of four steps
Step 1. Stripping used brakes and clutches to pieces 1 and 2 in Figure ) Used drum brakes are heated in a furnace to burn off the glue that bonds the brake linings and the shoes The iron shoes are stripped off the worn asbestos linings Figure 2A The rivets binding the clutch facing and the disk are loosened using a drilling machine Figure 2B The iron disks are then stripped off the worn clutch facings
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reprocessing Asbestos Exposures
97
Figure Sequence of operations in the reprocessing of brakes and
clutches Boxed numbers indicate
processprocess numbers in Table 3
eens cneeeannecaneeeeneneteeeeeseeceenny
po poe
Used brakes
;
1
Heating in furnace to burn off the glue } that bonds the linings and the shoes
;
Dismantling |
ee eee ee
eee cen
eee nee
;
oy
Loosening rivets
*
2|
poceeeecccay
ee
eae
'
Scrap
Anti treatment
;
_ Adjusting distortion
H
; | New brake linings | | Brake shoes |
| Clutch disks | New clutch facings |
holes
;
Drilling
5|
: Gluing linings onto shoes
Attaching facings
[Co
: Adjusting
| Reprocessed brakes and clutches
Step 2. Cleaning the brake shoes and clutch disks 3 in Figure ) The recovered brake shoes and clutch disks are polished by shot blasting or using a hand brush After polishing the shoes and disks are painted to impart anti properties to them and adjusted if
any distortion is observed
Step 3. Reassembling brakes and clutches 4 and 5 in Figure ) New linings are glued onto the brake shoes
The reassembled brakes are cured in an oven at tem-
peratures of 200-300 C. The new lining surfaces are ground with a grindstone Figure 2C or band grinders Figure 2D Holes are drilled into the new facings Figure 2E which are subsequently riveted to
the clutch disks
Step 4. Visual check and packing 6 in Figure 1 The reprocessed brakes and clutches are visually inspected and then packaged
Asbestos Levels in Personal Samples
Table 3 presents the asbestos concentrations in the per-
sonal samples which are classified by operation
Asbestos was detected in all the air samples and chrysotile was the only fiber type detected The highest geometric mean concentration of asbestos 44.2 fibers was found when grinding brake linings
using a band grinder even though a local exhaust ven-
tilator was in use This operation was performed in factory A only The geometric mean asbestos concentrations during the attaching of linings to brake shoes and the attaching of facings to clutch disks were 0.859 fibers and 0.780 fibers respectively The heaviest exposure observed during the attaching of brake linings to shoes 4.80 fibers was due to drilling the lining The heaviest exposure observed during the attaching of clutch facings 3.15 fibers to clutch disks was due to the riveting on of a clutch facing In 2000 the Japan Society for Occupational Health JSOH recommended 0.15 fibers as a reference value corresponding to an individual excess lifetime risk of cancer among 1,000 workers relevant description is given in the Discussion section The geometric mean asbestos concentration exceeded 0.15 fibers in the following operations grinding
98
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Figure Operations comprising reprocessing of brakes and
clutches
A. Stripping worn linings from
brake shoes on a table after
heating used brakes in a
furnace
B. Loosening of the rivets in used clutch using a drilling
machine
C. Grinding the lining of a
reassembled brake with a
grindstone
D. Grinding the lining of reassembled brake using a band grinder
E. Drilling holes in a new clutch facing for the riveting
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TABLE 3 Mean Airborne Asbestos Concentrations in Personal Samples Corresponding to the Various Operations
Factory A
Factory B
Process No and Operation
Sampling
Duration Min
Mean Range
Asbestos Concentration Fibers
Geometric
No.t Mean Range
Sampling
Duration Min
Asbestos Concentration
Fibers
Geometric
Mean Range No. Mean Range
Stripping worn brake linings 1
54 10-70
3
0.350 0.11-0.80 47
5-60
2
0.695 0.220-1.17
Stripping worn clutch facings 2
-
0
-
59 =~ 56-70
1
0.524
_
Cleaning 3 Adjusting and
polishing
Painting
02
49 36-60
2
0.098 0.08-0.116
62 60-63
02
0.100 0.10-0.10 62 62-62
1
0.144
_
Reassembling brakes 4 Gluing linings to
brake shoes
Attaching linings to
shoes
Grinding linings with a grindstone
Grinding linings with a band grinder
64
60-68
1
0.135
55
40-61
30
5-76
3
55 15-135 6
1.739 0.12-4.80 50 49-50 0.867 0.22-2.42 46 12-60
10 = 10-10
2
44.2
12.0-76.4
_
2
0.157 0.149-0.165
1
0.234
-
3
0.782 0.120-1.39
0
_
Reassembling clutches 5
Drilling holes into
clutch facings
42 10-62
4
0.793 0.155 2.40 30 15-60
2
0.383 0.12-0.646
Attaching facings to
disks
55 15-72
3
0.397 0.155-0.64 58 49-67
2
1.669 0.187-3.15
Visual checking and packing 6
22
_
1
0.13
_
48 15-67
3
0.129 0.095-0.153
Combination
71 = 24-135 12
0.159 0.027-0.33 55 35-63 10 0.190 0.09 0.32
The number in parentheses indicates the process number in Figure 1 Number of days of measurement of airborne asbestos concentrations #Arithmetic mean of the geometric mean for each measurement day when more than two samples were obtained for an operation on a day of measurement then the mean asbestos concentration of the operation on that day was expressed as the geo-
metric mean for each factory
brake linings with a grindstone drilling holes into clutch facings gluing linings onto brake shoes and stripping worn brake linings and clutch facings The geometric mean asbestos concentrations were less than 0.15 fibers in the remaining operations
During the grinding of the linings with a grindstone the geometric mean asbestos concentration in factory C was 0.287 fibers compared with 0.867 fibers cmin factory A and 0.782 fibers in factory B.
The differences in asbestos concentrations between
factories were large during operations such as drilling holes into clutch facings and attaching brake linings to shoes and clutch facings to disks When the asbestos concentrations during the same operation were compared among the three factories factory C always had the lowest geometric mean asbestos concentrations except when worn brake linings were stripped A majority of the grinders and drills and a blasting machine were equipped with local exhaust ventilators in factory C in contrast factories A and B had very few
such local exhaust ventilators Only factory C had a local exhaust ventilation duct in the workplace in which worn brake linings were stripped however the size and the location of the duct were not appropriate The workplace in factory C was frequently cleaned using a vacuum cleaner Accumulation of deposited
dust was observed on all the flat surfaces of the machines as well as on the floors of factories A and B.
Asbestos Exposure Levels in Stationary Samples
Table 4 summarizes the asbestos concentrations in the
one unit work area in factory A and two each in factories B and C. Measurements were repeatedly per-
formed in the five unit work areas from 1982 to 1989 Of 15 unit work areas 14 were classified as Control Class 3 that is the mean concentration of airborne
chrysotile in the unit work area exceeded the administrative control level 0.15 fibers and measures were needed to improve the working environment
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TABLE 3 continued
Process No and Operation
Factory C
Sampling
Duration Min
Asbestos Concentration
Fibers
Geometric
Mean Range No.t Mean Range
Factory D
Sampling
Duration Min
Asbestos Concentration
Fibers
Geometric
Mean Range No. Mean Range
Stripping worn brake linings 1
41
4-60
3
0.477 0.120-1.11 47
4-70
8
0.467 0.11-1.17
Stripping worn clutch facings 2
Cleaning 3 Adjusting and
polishing
Painting
60
_
1
60 60-61
2
_
0
Reassembling brakes 4
Gluing linings to
brake shoes
0
Attaching linings to
shoes
32
9-62
3
Grinding linings with a grindstone
Grinding linings with a band grinder
37
9-61
2
-
0
Reassembling clutches 5
Drilling holes into
clutch facings
65
Attaching facings to
disks
52
1
0.065
43-60
1
Visual checking and packing 6
Combination
60
_
1
63 60-85
7
0.24
-
59 57-90 = 2
0.355 0.24-0.524
0.047 0.033-0.06 58 36-61
4
0.068 0.033-0.116
_
58 60-63
3
0.113 0.10-0.144
58 40-68
3
0.149 0.135 0.165
0.188 0.07-0.334 34
5-76
7
0.503 0.07-4.80
0.287 0.090-0.483 46
9-135 11
0.689 0.090-2.42
-
10 = 10-10
2 44.2
12.0-76.4
0.152
-
0.07
_
0.142 0.05-0.21
46 10-80
7
55 15-72
6
46 15-67
5
63 24-135 29
0.451 0.12-2.40 0.546 0.152-3.15
0.114 0.07-0.153 0.165 0.027-0.33
The operations nearest to the sampling locations 0.3-5 m were the basis of classification of the stationary samples and the highest geometric mean concentration of asbestos 1.253 fibers was obtained during the operation of attaching clutch facings to disks The geometric mean concentration exceeded the OEL 0.15 fibers in the following operations drilling holes in clutch facings grinding brake linings with a grindstone stripping worn brake linings and clutch facings attaching brake linings to shoes visual inspection and packaging and gluing linings to brake
shoes The asbestos concentration in a locker room in
factory B was 1.72 fibers The locker room was situated close to the workplace where brakes were
reassembled
Attaching brake linings to shoes in factory A produced asbestos concentrations of 0.26 fibers 0.24 fibers and 0.08 fibers 1 m 2 m and 3 m away from the operator respectively In factory A grinding brake linings with a grindstone produced asbestos con-
centrations at distances of 1 m and 2 m from the oper-
ator of 3.5 fibers and 1.2 fibers respectively
Thus airborne asbestos concentrations deceased as the distance from the operator increased
LONG TRENDS
Figure 3 shows the trends observed from 1982 to 1985 in the geometric mean asbestos concentrations corresponding to the various operations in the personal sam-
ples from factory A. Asbestos exposure levels had a ten-
dency to decrease The geometric mean of the asbestos concentrations in the unit work area in factory A also decreased Figure 4 showed the trends observed from 1983 to 1985 with regard to the geometric mean asbestos concentrations corresponding to the various operations in the personal samples from factories B and C. Although the asbestos exposure levels in factory C decreased with every passing year the asbestos exposure levels fluctuated in factory B. In the personal samples
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reprocessing Asbestos Exposures
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TABLE 4 Airborne Asbestos Concentrations in Individual Unit Work Area
Unit Work Area No.
1
Factory
A
Story
First
Date
7/16/82 7/27/82 6/22/83 7/9/84 7/16/85
Asbestos Concentration fibers
Geometric Mean Geometric Standard
Deviation
First Evaluation
Value
Second Evaluation
Value
1.96 1.66 0.483 1.89 0.356 2.07 0.189 1.70 0.178 3.43
5.14 1.49 1.29 0.510 1.43
3.85 1.06 0.877 0.379 0.763
2
B
First
6/18/83 7/15/84 7/17/85 8/11/89
0.598 3.34 0.125 1.69 1.17 2.55 0.554 2.23
4.60 0.334 5.87 2.25
2.49 0.249 3.62 1.48
3
B
Second
7/15/84
0.144 1.22
8/11/89
0.132 1.49
0.257 0.297
0.216 0.233
4
C
First
8/24/83 7/18/84
0.155 1.43 0.045 2.55
0.329 0.227
0.262 0.140
5
C
Second
8/24/83
0.174 1.39
7/18/84
0.145 2.61
0.360 0.751
0.289 0.458
Comparison with Administrative Control Level amended in 2004 0.15fibers 0.15fibers
Control Class
3 3 3 3 3
3 3 3 3
3 33
32 2
33 3
the asbestos exposure levels were expressed as the geometric mean asbestos concentrations corresponding to
the operation anda large variation in the asbestos con-
centrations was observed among the operations
Relationship between Personal and Area
Concentrations
Figure 5 shows the relationship between the geomet-
ric mean airborne asbestos concentrations deter-
mined with personal and stationary samplers at only 13 unit work areas because there were no personal
samples obtained in the other two unit work areas The personal sample data were reclassified into groups according to the unit work area and the day of measurement Although large discrepancies were observed with regard to the mean asbestos concentrations of the personal and stationary samples at some
unit work areas the mean asbestos concentrations of
the personal samples significantly increased along with those of the stationary samples at the unit work areas p 0.01 The mean asbestos concentrations of the personal samples tended to be higher than those of the stationary samples
10
m
/
fibers
fibers
fibers
(
1
concentration
concentration
concentration
concentration
concentration concentration
concentration concentration concentration concentration
|
0.1
Asbestos
Asbestos
Asbestos Asbestos
Asbestos
Asbestos
1982 1983 0.01 1982
1982
1982
1983
1982
1982
1983
1984
1985
1984
1985
1984
1985
Fixingbrakelinings onto shoes o
linings
with
grindstone
t}Gr-iGnrdiinndging brake linings with a grindstone
-- X Drilling holes into clutch facing
@-Fixing clutch facings to disks
Figure Trends of geometric mean
asbestos concentrations from 1982
in
classi-
personal to 1985 in
samplsampeles s clclasi-assi-
fied by operations in factory A.
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fibers
conetraion 0.1 ;
Asbetos
0.01
1983 1983
1984
1985
Aug. Jun
Jul
Jul
1 Grinding brake linings with a grindstone in Factory B
Visual inspection and packaging in Factory B
- A Stripping worn brake linings in Factory C -Fixing -Fixing brake linings onto shoes in Factory C
Figure Trends of geometric mean asbestos concentrations from 1983 to 1985 in personal samples classified by operation in factories B and C.
10.00
Y 0.66K -0.31 -0.31 r = 0.67
Y
cm 1.00 cm
cm
fibers fibers
fibers
samples
samples
samples
samples 0.10
Stationary
Stationary
Stationary
Stationary
Stationary
[e)
fo) fe)
re)
808808
0.01 0.01
0.10
1.00
Personal samples fibers X
10.00
Figure Relationship between geometric mean asbestos concentrations of personal and stationary samples at 13 unit work areas
DISCUSSION
Comparison with Reference Values and Administrative
Control Levels
In Japan there have been two kinds of occupational
health standards for airborne asbestos One is the occu-
pational exposure limit OEL recommended by the Japan Society for Occupational Health JSOH This is
defined as the reference value for the mean exposure concentration at or below which adverse health effects
caused by the substance do not appear in most workers working for eight hours a day 40 hours a week under a moderate workload The OEL promulgated by acade-
mia is not legally enforceable The JSOH has revised its
OEL for asbestos three times It was 2 mg until
1973.20 In 1974 it was amended to ) crocidolite 0.2 fibers and 2 other types of asbestos 2 fibers and 10 fibers as ceiling limit ceiling limit is an
average concentration for 15 minutes which should not
21
be exceeded at any time during a workday In 1996 it became crocidolite 0.2 fibers and chrysotile 2 fibers and remaining types of asbestos were noted
as under consideration.22 In 2000 JSOH abandoned the
conventional OEL for asbestos and changed it to reference values corresponding to an individual excess lifetime risk of cancer based on an average model Regarding chrysotile JSOH recommends 0.15 fibers and 0.015 fibers as reference values corresponding to the aforementioned risk among
1,000 and 10,000 workers respectively
The other standard for asbestos is the administrative
control level.18 The Japanese government has developed a unique environment control system
The administrative control level is an indicator to assess
whether hazardous substances in a workplace are controlled well or the workplace requires engineering con-
trol measures In 1984 the government issued the administrative control levels as a enforceable stan-
dard by an administrative notification later it was changed to an enforceable standard by the Working Environment Evaluation Standard 1988. The admin-
istrative control level for asbestos was 2 fibers The
administrative control level was lowered to 0.15 fibers
cmin 2004.25 Therefore the personal exposure levels
are research data and the airborne levels in the unit
work areas are government data The geometric mean asbestos concentrations in the
personal samples exceeded reference value 0.15 fibers during four processes namely stripping worn brake linings stripping worn clutch facings reassembling brakes and reassembling clutches In the personal samples the geometric mean asbestos concentration estimated when grinding linings with a band grinder 44.2 fibers was the highest among all the operations The machine grinding of brake linings was the most potent source of heavy asbestos exposure In this study regarding the personal sampling we focused on measuring the asbestos exposure concentrations by operations We did not conduct a time study to elaborate the time that a worker spent for each operation within a day Therefore the weighted average con-
centrations of asbestos exposure are unavailable
There were 15 unit work areas in this study because the measurements were performed repeatedly in five unit work areas of the working environment The
second evaluation values exceeded the administrative
control limit 0.15 fibers in 14 of the 15 unit work areas This means that the working environments in those unit work area were unacceptable condition
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reprocessing Asbestos Exposures
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TABLE 5 Airbone Asbestos Exposure Levels during Brake Maintenance or Repair Work Reported in the Literature
Product Operation
No. of | Sampling
Samples Time Min
Asbestos Concentration
Fibers
Meant
Range
Year of Publication
Reference
Brakes
Drilling holes
1
Grinding linings
7
Renewing used linings by grinding
3-5 ft away
10
Renewing used linings by grinding
10 ft away
2
Renewing used linings by grinding
25 ft away
2
Beveling new linings 3-5 ft away
5
Beveling new linings 8 ft away
2512-
Beveling new linings 12 ft away
2
Beveling new linings 30 ft away
2512-
Punching rivets into brake linings
3-5 fl away
2
Light grindings of new linings before
installation
2
0.6
1983
5
_
0.9-29.2
3.8
1.7-7.0
1976
7
1.5
1.2-1.7
0.8 37.3
0.6 0.4 0.3
0.6-1.0 23.7-72.0
0.3-0.5
_
1.5
0.9-2.0
3.7
2.7-4.7
Light grinding of new lining before
installation
1
4.8
_
1976
8
Grinding new linings before installation
-2537520
Renewing used linings by grinding
-25377520
_
2-10
2.7
3.8
1.7-7.0
Beveling new linings
-2537 520
2-10
37.5
23.7-72.0
Brake pad machining
-2537 520
10
0.55
0.04-0.83
1986
9
Riveting off and on truck
-2537 520
60
0.10
_
1986
10
Grinding by hand passager
-2537 520
60
0.12
Machine grinding passager
-2537 520
60
0.06
_
Loosening rivets from brake linings
-25377520
5-29
0.3
0.1-1.6
1987
11
Punching rivets into brake linings
-25377520
3-60
0.7
0.1-3.5
Grinding brake linings with machine
exhaust ventilation not in use
5
4-27
56
0.3-125
Grinding brake linings with machine
exhaust ventilation in use
30
4-33
1.5
0.1-5.9
Bevelling edges of brake linings with file
7
2-5
0.4
0.1-0.9
Assembling of brakes
7
6-41
0.2
0.1-0.4
Grinding of brake drums
6
3-26
0.2
0.1-0.3
Reprocessing brakes +
17
77-135
0.05 0.05-
1999
12
Clutches reprocessingt
7
125
0.05 0.05 0.04
1999
12
Personal samples stationary samples arithmetic mean geometricmean The opening brushing and cleaning of brakes and clutches were excluded
In those workplaces the following measures were rec-
ommended to reduce asbestos exposures industrial
hygiene engineering measures better housekeeping practices and personal protective equipment
Comparison with Previous Reports
There have been seven previous reports of airborne asbestos concentrations in automobile repair and service industries To the best of our knowledge the only report focusing on factories reprocessing automobile brakes and clutches was from a study of airborne asbestos exposures in bonding workshops where
the used brakes that were collected from brake service
stations in Australia were employed The authors reported that the geometric means of the asbestos concentrations in bonding workshops were less than
0.17 fibers These values are much lower than those estimated in this study They described that the
low exposure levels could be attributed to the recent
use of wet methods which have replaced the traditional dry methods
Table 5 summarizes the airborne asbestos concen-
trations during automobile brake- and reprocessing work and brake maintenance or repairs
described in the literature Boillat and Lob have
reported asbestos concentrations measured during the drilling and grinding of brake linings they found values ranging from 0.3 to 29.2 fibers Rohl et al.6 reported that the average asbestos concentration was 37.3 fibers in the vicinity of the operator during the beveling of truck brake shoes on a grinding
machine The airborne asbestos concentration 9 m
away from this operation was 0.3 fibers Lorimer et
104
Sakai et al
www.ijoeh.com www.ijoeh.com J INT OCCUP ENVIRON HEALTH
al reported that asbestos concentrations during the grinding of a new lining before installation were 2.7 and 4.8 fibers Cheng et al reported that asbestos concentrations during brake machining ranged from 0.04 to 0.83 fibers with a mean of 0.55 fibers Rodelsperger et al.9 reported that the mean asbestos concentration during the machine grinding of brake linings was 0.06 fibers During the machine grinding of brake linings Kauppinen et
al found a mean asbestos concentration of 56
fibers in the absence of exhaust ventilation and a mean concentration of 1.5 fibers when exhaust ventilation was present they also reported concentrations of up to 125 fibers during the grinding of brake linings with a machine There are large differ-
ences among the airborne asbestos concentrations esti-
mated in similar operations in the previous reports
The low asbestos levels could be attributed to better
control of the working environment Our results and previous reports demonstrate that machine grinding and beveling of the new brake lining surface can become the sources of heavy asbestos exposure unless
the enclosure and local ventilation are efficient
Asbestos Exposures in Individual Factories
The operations in the individual factories remained unchanged in the 1980s however the asbestos exposure levels then decreased in factories A and C but not in factory B. The geometric mean asbestos concentrations of the personal samples tended to be higher than those of the stationary samples at unit work areas This might be due to the distances between asbestos emission sources and sampling points The personal sampling points were closer to the emission sources than were the stationary sampling points The asbestos concentrations in factory C were lower than those in
the others this could have been due to the presence of
a larger number of local exhaust ventilators and frequent cleaning of the workshop
Limitations and Significance of This Study
This study has a couple of limitations First it may not be representative of all workers exposed to asbestos in factories across Japan that reprocess automobile brakes and clutches because the factories in this study were not selected randomly and the number of the study subjects was small Second this study was conducted during the summer and it is known that the asbestos concentrations in such factories may be higher during
the winter because of poor natural ventilation which
occurs when windows and doors are kept closed to maintain warm temperatures in the workplace Despite
these limitations since asbestos exposures in the auto-
mobile brake- and reprocessing industry have not been sufficiently elucidated to date the informa-
tion presented by the present study could be useful for retrospective exposure assessments in this industry
In Japan automobile brake pads and linings and clutch facings containing asbestos were banned in October 2004. In addition products containing crocidolite or amosite were legally prohibited from import manufacture supply and use in 1995.26 The government also banned products containing more than % chrysotile such as automobile brake pads and linings and clutch facings except for specified products for
which substitutes were unavailable in October 2004.27
containing automobile friction materials continue to be manufactured and used in industrializing countries28 however these countries are phasing out
the use of asbestos If used brakes and clutches are
reprocessed in industrializing countries asbestos expo-
sures should be monitored and the measures necessary to reduce such exposures taken
References
1. Japan Automobile Times The register book of rebuilders on automobiles in 1982. Tokyo Japan Automobile Times 17-20 In Japanese
2. The Environment Agency of Japan Manual for Controlling Asbestos Emission An Enlarged Edition Tokyo Japan Gyosei 1988 16-34 In Japanese
3. Japanese Standards Association Brake Linings and Pads for
Automobiles Japanese Industrial Standards JIS D 4411. 1975
In Japanese 4. Japanese Standards Association Clutch facings for automobiles
Japanese Industrial Standards JIS D 4311. 1975. In Japanese 5. Boillat MA Lob M. Risk of asbestosis in workers employed in
replacing automobile brake linings Schweiz Med Wochenschr 1354-9 In French
6. Rohl AN Langer AM Wolff MS Weisman I. Asbestos exposure during brake lining maintenance and repair Environ Res 1976
12 110-28
7. Lorimer WV Rohl AN Miller A Nicholson WJ Selikoff IJ
Asbestos exposure of brake repair workers in the United States
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8. Cheng VKI O'Kelly FJ Asbestos exposure in the motor vehicle
repair and servicing industry in Hong KongJ Soc Occup Med 1986 104 6
9. R^delspergerK Jahn H Br^...ckelB Manke Paur R Woitowitz
H Asbestos dust exposure during brake repair Am J Ind Med
1986 63
72
10. Kauppinen T Korhonen K. Exposure to asbestos during brake maintenance of automotive vehicles by different methods Am
Ind Hyg AssoJc. 499-504
11. Yeung P Patience K Apthorpe L Willcocks D. An Australian
study to evaluate worker exposure to chrysotile in the automo-
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12. Langer AM McCaughey WTE Mesothelioma in a brake repair
worker Lancet 8307 1101 3
13. Levin JL O'Sullivan MF Corn CJ Williams MG Dodson RF
Asbestosis and small cell lung cancer in a clutch refabricator J
Occup Environ Med 602
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14. Dahlqvist M Alexandersson R Hedenstierna G. Lung function and exposure to asbestos among vehicle mechanics Am J Ind
Med 59-68
15. Lemen RA Asbestos in brakes exposure and risk of disease Am
J Ind Med 229
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16. Ministry of Labour Working environment measurement stan-
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Occupational Safety and Health http://www.jicosh.gr.jp/eng-
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html >
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17. Japan Association of Industrial Health Recommendation of
Occupational Exposure Limits 1979 Appendix 2. Measurement of exposure to asbestos fibers Jpn J Ind Health 1979 491-2 In Japanese 18. Ministry of Labor Working Environment Evaluation Standards Ministry of Labor Notification No.79 1988. See the homepage of Japan International Center for Occupational Safety and
Health http://www.jicosh.gr.jp/english/law/WorkingEnviron http://www.jicosh.gr.jp/english/law/WorkingEnviron mentEvaluationStandard>s
19. Japan Society for Occupational Health Recommendation of Occupational Exposure Limits 2000 200J1 Occup Health
2000 213-38
Japan Association of Industrial Health Recommendation of
Occupational Exposure Limits 1973 Jpn J Ind Health 1973 280-6 In Japanese 21. Japan Association of Industrial Health Recommendation of
Occupational Exposure Limits 1974 Jpn J Ind Health 57-66 In Japanese 22. Japan Society for Occupational Health Recommendation of Occupational Exposure Limits 1996 199J7 Occup Health
134-47
23. Japan Society for Occupational Health Proposal of reference
value on individual's increased lifetime risk of developing
cancer asbestos Sangyo Eiseigaku Zasshi Formerly Jpn J Ind
Health 177-86 Japanese
24. Koshi S. A basic framework of working environment control for
occupational health in Japan Ind Health 149-65
Ministry of Health labor and Welfare Revised Working Envi-
ronment Evaluation Standards Ministry of Health Labor and
Welfare Notification No.369 2004. In Japanese
26. Revised Enforcement Order of the Industrial Safety and Health
Law Cabinet Order No.9 1995. In Japanese
27. Revised Enforcement Order of the Industrial safety and Health
Law Cabinet Order No.457 2003. In Japanese
28. Giannasi F Thebaud A. Occupational exposures to
asbestos in Brazil IntJOccup Environ Health 150
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chrysotile asbestos a critical review Ind Health 1999
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www.ijoeh.com INT J OCCUP ENVIRON HEALTH