DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
PUBLIC HEALTH SERVICE
CENTER FOR DISEASE CONTROL
NATIONAL INSTITUTE FOR OCCUPATIONAL SAFETY AND HEALTH
5600 FISHERS LANE
ROCKVILLE, MARYLAND 20852
August 8, 1975
Dear Colleague:
This communication is intended to alert you to recently gathered information indicating a potential health hazard for persons exposed to asbestos during the servicing of motor vehicle brake and clutch assemblies.
On July 21, 1975, the National Institite for Occupational Safety and Health convened a meeting of government and university scientists, industry
representatives, and labor union officials to discuss the present state of
knowledge with respect to this problem. Data was presented by investigators
from the Mount Siani School of Medicine in New York City indicating that
workers engaged in the maintenance and repair of automobile and truck brake
linings are exposed to potentially hazardous levels of airborne asbestos
dust. Specific brake servicing operations studied included blow-out of
automobile drum brake assemblies, grinding of used truck brake linings, and
bevelling of new truck brake linings. Average peak asbestos air concentrations for these three activities based on personal samples taken within ten feet of the operator were, respectively, 10.5, 3.75, and 37.3 fibers (>5 microns in length) per ml. An analysis of samples of brake drum dust revealed that almost all of the asbestos fibers found were shorter than 0.4 microns in length.
Previous studies of the extent of asbestos emissions from automobile brake
lining wear showed that only a very small fraction of the original asbestos
content of the brake lining is found in brake drum dust
1-3. It was presumed that this is due to thermal degradation of the fibers during braking. The present findings indicate that enough asbestos is preserved to produce significant exposures during certain brake servicing procedures.
The full extent of asbestos-related disease in brake servicing personnel
is not known at present because this particular occupational group has not been studied systematically up to now. However, a review of the
scientific literature on the association between asbestos exposure and
mesothelial tumors of the pleura and peritoneum has revealed at least
four cases of these rare tumors in persons who were employed in jobs
involving automobile brake servicing 4-6.
For your information and guidance, we are enclosing pertinent references,
estimates of the population at risk, a NIOSH interim recommendation for
brake and clutch servicing procedures, and a copy of the Department of
Labor standard covering exposure to asbestos in the work place.
The environmental studies of brake lining servicing operations outlined
above together with observations of mesothelial tumors in persons so
employed affirms the necessity for instituting and maintaining recommended
control measures in this industry so that the health hazards of asbestos
are minimized.
[signature]
J. William Lloyd, Sc.D., Director
Office of Occupational Health
Surveillance and Biometrics
Estimates of the Workforce Potentially Exposed to Asbestos in the Manufacturing and Servicing of Brake Linings and Clutches
Auto Mechanics
833,535
Garage Workers
67,679
Manufacture
(original and rebuilding)
6,657
907,871
[Source:] from 1972 Census of Manufacturers, 1972 County
Business Patterns, and Census of Population: 1970 Occupation by
Industry (all are Department of Commerce, Census Bureau publications)
Recommended (Interim) Procedures for Asbestos Brake and Clutch Servicing
The National Institute for Occupational Safety and Health (NIOSH) has
research underway concerning dust exposures during brake and clutch
servicing. Due to preliminary data demonstrating significant asbestos
exposures during presently used cleaning techniques, NIOSH has reviewed
alternate techniques whereby asbestos exposures are reduced. The following are interim procedures recommended by NIOSH to minimize dust exposures.
If possible, an area shall be designated for all brake and clutch
repairs. Entrances into this area shall be posted with an asbestos
exposure warning sign as follows:
Asbestos
Dust Hazard
Avoid Breathing Dust
Wear Assigned Protective Equipment
Do Not Remain in Area Unless Your Work Requires It
Breathing Asbestos Dust May Cause Asbestosis and Cancer
During brake servicing, an air purifying respirator, either single use or with replaceable particulate filter(s), as approved by the Mining Enforcement and Safety Administration (formerly Bureau of Mines) or NIOSH, shall be worn during all procedures following removal of the wheels including reassembly. During manual clutch servicing, such a respirator shall be worn during removal and cleaning of the clutch,
pressure plate and housing assembly and during installation of the new
clutch assembly.
Dust shall first be cleaned from brake drums, brake backing plates, brake assemblies and clutch assemblies using an industrial type vacuum cleaner equipped with a high efficiency filter system (>99% efficiency for 0.3 µm diameter aerosols). After vacuum cleaning, any remaining dust shall be removed using a rag soaked in water and wrung until nearly dry. Under no circumstances shall compressed air or dry brushing be used for cleaning.
During arcing and riveting operations, an approved respirator, as described in (2) above, shall be worn. Grinding (arcing) machines shall be provided with local exhaust ventilation such that worker exposures are maintained at least below the 1976 OSHA asbestos standard (29 CFR 1910.1001).* a minimum, the dust bag of the arcing machine shall be removed and replaced with the hose of the high efficiency industrial vacuum described in (3) above.
Industrial vacuum cleaner bags containing asbestos dust and cloths
used for wiping brake and clutch assemblies shall be sealed in plastic bags and labeled with the following warning label printed in letters,
of sufficient size and contrast to be readily visible and legible:
Caution
Contains Asbestos Fibers
Avoid Breathing Dust
Breathing Asbestos Dust May Cause Asbestosis and Cancer
All asbestos waste shall be disposed of in accordance with the OSHA asbestos regulation, 29 CFR 1910.1001(h). During removal of vacuum
bags, an approved respirator, as described in (2) shall be worn.
All floor cleaning in areas where brakes and clutches are repaired
shall be done with the high efficiency industrial vacuum cleaner as
described in (3) above. Grinding (arcing) machines shall also be cleaned with such a vacuum cleaner and any remaining dust wiped with a damp cloth. An approved respirator, as described in (2) above, shall be used during this cleaning.
Although adherence to the above procedures should minimize any
contamination of work clothing, it is required that the appropriate
portions of the OSHA regulations on asbestos (29 CFR 1910.1001(d)
(3 and 4)) concerning special clothing, change rooms, etc. be followed.
NOTE: adherence to the above procedures should minimize exposures to mechanics during brake and clutch servicing. These are interim recommendations and are subject to revision pending results of ongoing NIOSH research.
Prepared By
Division of Field Studies and Clinical Investigations
National Institute for Occupational Safety and Health
Cincinnati, Ohio
*Section 1910.1001 of the Code of Federal Regulations was formerly Section 1910.93a. This change was noted in the Federal Register, May 28, 1975.
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