Document 37QeKO4nKYwe5pzyYM1wbvzZD

PLAINTIFF'S EXHIBIT ftu* ject: Asbestos Exposures from Brake Drum Work Case: 48306-3 MEMORANDUM FOR FILE Bell Laboratories date. August 30, 1976 trom. G. D. Kenney Summary: Samples were taken at five different garages in two separate operating companies to try and estimate exposures to asbestos by employees changing brakes. The concentrations found ranged from 0.04 to 0.3 fibers/cc. Two ambient samples for asbestos had values of 0.25 and 0.4 fibers/cc. The samples were ana lyzed using the procedure of phase contrast microscopy. Standards: The present standard for asbestos promulgated by OSHA is 2 fibers per cubic centimeter greater than five micrometers in length (f/cc.). This two fiber limit refers to ar. eight hour time weighted average standard.' This standard also included a ten fiber/cc ceiling concentration which is not to be exceeded. Procedures: Air samples for asbestos fibers were taken using the NI0SH recommended procedures.* The fibers were collected by pulling air through small filters using u battery powered pump. The filters used were 37 milli meter cellulose ester membrane filters having a 0.8 micrometer nominal pore diameter. The sampling pumps used were Mine Safety Appliance Model G sampling pumps. The air was pulled through the filters at a rate of 1.8 liters per minute. The filters were sent to the Kettering Laboratory for analysis. The procedure used for analysis was to count the fibers collected on the filter using a phase contrast microscope at a magnifica tion of 40C to 450 X. * NIOSH Manual of Analytical Methods HEW Publication Hu. 75-121, 1975. CONFIDENT! At 003959 1 -2- Both personal and general room air samples were collected for these operations. Results: The results of these samples are presented in Table I appended to the end of this report. At garage number 1 the employee was only engaged in inspecting the brake drums for wear. The total time it took to complete the inspection was twenty five minutes. In inspecting the drums the dust accumulated on the shoes and mechanical parts was cleaned off using a whisk broom. The vehicle inspected was a light duty van. At garage number 2 the employee was changing the brakes on the front of a light duty van and inspecting the rear brakes for wear. This particular employee cleaned the drums by blowing out the dust using compressed air. This operation of using compressed air took about thirty seconds per wheel. During this time the employee was actually encompassed in a cloud of the dust. The total time taken to complete this job was 45 minutes. At the third garage the employees were changing the front brakes on a lightweight sedan, and inspecting the rear drums. In this operation the drums and backing plate were cleaned using an aerosol consisting of common solvents. Relatively little dust was generated using this process. The excess dust in the brake drum was disposed of by dumping the dust on the floor. The excess dust laden solvent v/as caught in a drip pan. The total time required to perform the job was 30 r.'nutes. At the forth garage the operation was to change the rear brakes of a medium duty truck. This job varied from the others in that the mechanic had to pull the rear axles as well as turn the brake drums in addition to installing new brakes. Excess dust in the brake drums was dumped in a garbage can. The remaining dust on the backing plates and in the drums was clean ed out using an aerosol mixture. The total time required to change the brakes on this truck was about four hours. At the fifth garage the employees were changing the brakes on a light van. All the dust in the drums and on the backing plates v/as cleaned out using an aerosol mixture. CONFIDENT!/.!. 003960 -3- The employee performing this work was wearing a nonapproved filter mask. In this particular case after the brakes had been mounted on the backing plates the brake shoes were sanded or buffed using a piece of sandpaper by the employee. The total time to complete the job was 85 minutes. Discussion of Results: From the Table I it is seen that the exposure levels do not vary greatly from garage to garage, except for the levels found in Garage H4. The most probable explanation for the lower values in this garage is, as explained before, that the work involved included operations and times where no asbestos exposure occurred. As a result these time weighted samples will be lower than found in the other garages. The levels reported here agree tolerably well with those re ported by Hickish and Knight.* They reported exposures ranging from 0.03 to 1.12 fibers/cc in changing brakes on lightweight cars. The average exposure level was O.38 fibers/cc. The levels however are much lower than those reported by NIOSH.t Samples taken during the blowout of automobile drum brake assemblies, beveling of new truck brake linings and the grinding of used truck linings gave results of 10.5, 37-3, and 3-75 fibers per cubic centimeter respectively. These measurements were taken to try and get the peak levels during exposure. The most probable explanation for the discrepancy between the results reported here and those by NIOSH is a difference in sampling times. The sampling periods were not reported in the article. If it is assumed that the samples reported by NIOSH were taken only for the time that the actual job, such as blow ing out the drum assemblies took place then the sampling period would only last for 2 to 3 minutes. Performing some calculations assuming a 3 minute sampling time and a 1. liter per minute flow rate only 17 fibers counted out of 100 fields would be necessary to get a concentration of 10 f/cc. The numbers of fibers counted in the samples taken here ranged from 3 to 16 fibers per 10d fields The most difficult results to explain are the values obtained for the ambient samples. The respective values for these samples are 0.25 and 0.h. The 0.4 value is the highest concentration found for any of the results. * Hickish, 1). E. and Knight, K. L. : Exposure to Asbestos during brake maintenace. Ann. Occup. Hyg. 13: 17-21, 1970. t NIOSH Issues Asbestos Dust Alert for Workers Exposed Servic ing Brakes; Occ. Safety and Health Reporter, BNA, 5:348-49, 1975. 003961 1 One possible explanation would be contamination of the filters. H*wever, blank filters, handled in the same way as the samples but through which no air was passed, did not rive nigh values. This would eliminate the possibility of gross contamination'of the filters. Another possible explanation for these results is that the ambient sampling sites were situated so as to be in the path of the dust laden air from the garage. Both ambient sampling sites, however, were at least V5 feet from the nearest open ing to the garages and located upwind of the openings. A third possible explanation is that a mistake was made in the counting of these samples. A recount of the ambient sample at garage 113 by two different person.- gave results of 0.38 and 0.9 fibers/cc. Although a relatively wide-spread exists between the numbers, such ranges are not uncommon in asbestos counting. The recounts seem to confirm that the first count is relatively accurate. The question then is what is the significance of these ambient resuits. If the values are true than an argument can be made that the exposures to asbestos during a brake changing operation is no greater or even less than the employees ambient exposure. The problem is that with the present method of phase co: microscopy it is impossible to qualify whether the fiber being counted is in fact an asbestos fiber. With the present ; hod any particle with an aspect ratio (length of fiber to wider, cf fiber) of 3 to 1 or greater and having a length greater than five micrometers is to be counted. Therefore it is possible that the fibers in the ambient samples and for that matter the personal and general air samples are not of the asbestos form type. With the present samples ana analysis it is impossible to state whether this is true. Bulk samples of brake drum dust were taken to try and determine if the dust contained asbestos. According to the analytical laboratories the amount of asbestos, if present in the samples, was below the analytical sensitivity of the me'... ' used. The sensitivity limit for the method as reported by the lab is 5*. In a report by Jacko and Du Charr.e they repor. d the asbestos concentration in brake duct as about one perce t.* This would explain the nega-.ive results found in the camples taken here. * Jacko, M. ()., Du Chnrir.cMeasurements from B.rak. Mobile Pour-cos. EI'A licp w; eh I.inir. i:c. 3-0*1-00 ~cion.~: Kmis' ion. frem Golectea ifidential 003962 5- The final question is how do these results compare with the present OSHA standard for asbestos. The present eight hour time weighted average standard for asbestos is two (2) fibers/cc. The sample values are well below this level of 2 fibers/cc.' Perhaps a more Important question is does an exposure to asbestos exist, if so then medical examinations of the exposed employees must be initiated. With the present results an interpretation that an exposure does exist must be made. Copy to W. J. Schreibeis G. M. Wilkening G. D. Kenney CONFIDENTIAL 003963 Sample Ident. Garage 81 Personal Sample Gen. Air Ambient Garage 82 Personal Sample Gen. Air Garage 8 3 Personal Sample Gen. Air Ambient Garage #4 Personal Sample General Air Garage 85 Personal Sample General Air Table I Sample pd. Minutes 30 30 32 45 41 35 35 63 232 230 100 102 Concentration f/cc 0.15 0.22 0.25 0.13 0.07 0.3 0.3 0.4 0.04 0.06 0.2 O.l L 003964