Document KGBLYndgQmj70ed9vZmOdDxxQ

J 123 E S TIE G E L STREET. MANHEIM, PENN. 17545 Raybestos^Manhattsn June 1, 1972 l H. WEAVER r* o<cto COTOC PLAINTIFF'S EXHIBIT AB-233 Mr. E. W. Drislane, Executive Secretary Friction Materials Standards Institute, Inc Bergen Mall Office Center, E.210 Route #4 . Paramus, N'.J. 07652 # tear Ed: , The., attarhri material concerning automotive emissions of asbestos fibre vss received from -Illinois Institute- of Tuchnology Research Institute yesterday and probably will be of interest to ether members of the FK5I Asbestos Study Committee . I suggest that you circulate it to them. this material was forwarded by Dr. Colin F. Harwood of IXTRI as a supplement to information presented at a seminar on asbestos they conducted April 4 through 7. Very little attention was devoted to automotive emission sources during the seminar. The main issue I would have with Dr. Harwood's conclusion would have to do with whether or not the free fibres or fibrils released from friction material decomposition are truly hazardous in any way, and I also believe he tends to underestimate the problems involved in non asbestos containing braking systems. Since it appears unnecessary and probably impossible to schedule an Asbestos Study Committee meeting in June and I will be away the first two weeks in July, I think it might be prudent to tentatively schedule a meeting late in July, preferably during the last week. By that time -I expect there will be a number of subjects worthwhile reviewing. "If you agree, kindly canvass the other members and pick a date. As far as I know, I will be available arjtine during the week of July 24. I am also open the week after that in the event this suits the others better. Best r J Teaver J attachments such that the dust created is arrested at the source and collected m filter bags. Commercial devices are available but normally firms with a sincere interest in pollution control, design and fabricate^their own devices. Two examples of such " devices are shown in Figures 6 and 7, These control hoods work on the high velocity, low volume principle and can be readily adapted to industrial vacuum cleaner systems. . When arrest-at-the-source systems are not possible, tech niques similar to those employed by the asbestos spraying ` .ndustry may be utilized. Rules which relate more specifically to fabrication of asbestos products may be found in such pufall---- cations ass , 1. "Recommended Practices for Fabricating*, Handling and Construction Industries,- Health.and Safety Council-Asbestos Cement Products Association. ------- 2. "Recommended Health Safety Practices for Handling and Applying Thermal Insulation Products Containing .. Asbestos," National Insulation Manufacturers ' * . Association (NIMA). j ' 3. The Asbestos Research Council - Control and Safety Guides (London, England). 4. "Recommendations for Handling Asbestos," Engineering Equipment Users Association (EEUA), E.E.U.A. Hand-- , book No. 33. __ ' ------- 3.3.3 Friction Material Applications Typical friction materials contain 30 to 5056 asbestos and may be up to 70%, and the industry that manufactures these ma terials is ranked third (1969) in the consumption of asbestos fibers. Crysotile is the preferred variety because it has better frictional properties than amphibol asbestos and does not exert so much wear on the opposing surface. The major uses of asbestos-containing friction materials include brake linings, brake discs and clutch facings. These products have been applied to a wide variety of industrial and commercial products. 11T RESEARCH INSTITUTE 22 % Sources of Emission - Errussion of asbestos from friction materials results from normal day-to-day usage. An idea of the scope of this source can be gained from the estimation that the average automobile wears out 3 to 4 sets of brake linings, and ** 1 to 2 sets of clutch facings during its lifetime and that commercial public transport vehicles wear out many more sets. Data concerning motor vehicle brake linings for the whole of the United States are given in the following: Vehicle miles during 1968 Mileage life of brake linings itake lining sets on new vehicles Pounds of asbestos per set of brake linings 1,010,000,000,000 27,500 10,718,000 3 Tests performed on brake linings have indicated that under conditions of normal usage, considerable alteration of the asbestos occurs. It is reported that most of-the dust collected from brake drums appears non-fibrous and is Similar in appearance to thermally degraded asbestos. The suggestion is that hxgh temperatures at the brake lining/drua contact points actually reach degradation levels. Tests cn brake linings, brake discs.and clutches have demonstrated that the quantity of fiber emittedjls^nome function^ of the severity of the braking conditions (see Table 3) . How ever, even at the level of 1%, the total emissions must be considerable when the total tonnage in use is considered. Further, the emissions are likely to occur at places of high density population and restricted ventilation. That is, in busy main streets of towns surrounded by large buildings. The effect of different braking conditions and different types of friction materials on asbestos emissions is the subject of a study being sponsored by the Environmental Protection Agency. Other studies are being conducted in California ar.d some work on roadsides has been done at Mt. Sinai, New York. The E?A study will establish the extent and nature of the asbestos MT RESEARCH INSTITUTE 25 Table 3 ASBESTOS EMISSIONS FROM BRAKE LININGS (Test Results by Electron Micrograph) - Product - Brand 1. Automobile A drum brakes 2. M B 3. tl C 4. . ft 5. - H 6. II 7. II 8. II 9. II 10. II C D" French E .F German G C H. 11. Automobile clutch J 12. Automobile disk brake K 13. Bus drum brake L 14. M 15. Truck drum 7 brake (light) Test Method Friction Friction Friction Friction Friction Friction Friction Friction Friction Friction Dynamometer Dynamometer Dynamometer Friction Friction No. of Samples 6 Conditions Presence of of Tcr.r-F Free Fibers 300-800 Few 6 250-800 None 5 300-700 Few 1 700-900 Numerous 5 300-800- Few 5 300-700 5 300-800' Few Few 2 1 2` 1 1 1 2 10 100-500 600-700 100-600 normal driving normal driving city driving 450-550 300-800 Few Numerous Few None Few None None Few Z Frc Fiber <1 0 <1 --10 <1 <1 <1 <1 --15 <1 0 <5 0 0 <1 Weight estimated from fiber volume. :J *I 26 J-s l emitted from brake drums, disc brakes and clutches of vehicles operating under real conditions. Hopefully the situation will be more clearly understood at the end of those studies. _ Emission Control Techniques ' Emission at Overhaul - To avoid blowing the accumulated dust into the atmosphere at the time of overhaul devices have been suggested for extraction of the dust from brake and/or clutch housings by suction. Of the devices tried, a simple hand-held vacuum cleaner has proven to be the most flexible unit. Changes to the original design have been limited to the addition of a disposable paper bag inserted in the original cloth bag. The paper bag may be easily sealed before removal to prevent emission. Substitution - Beyond the adaptation of better cleaning practices during brake and clutch maintenance, as mentioned above, additional controls seem to be limited to improve design of brake and clutch assemblies and/or substitution of other materials for asbestos. . The high temperature properties and exceptional tensile strength of asbestos have resulted in very compact and economi cal design. These same unique properties which make asbestos applicable to friction materials also make the application of substitute materials very difficult. The tensile strength and modules of rigidity of asbestos as compared to several candidate substitute materials follows:' Tensile Strength lb/in.2 Asbestos 550,000 Fiber yarns 180,000 Steel wool 50,000 .Mineral wool 25,000 Modulus of iaiditv lb/in.^ 30,000,000 3.000,000 100,000 60,000 There is no doubt that substitution of other materials for asbestos is possible, but the design chances required to accom modate the stresses and temperatures involved would result in- 117 RESEARCH INSTITUTE V 27 larger, more expensive components. Brakes - The recent adoption of disc brakes by the auto motive industry makes material substitution more plausible. ^ Disc brakes are capable of greater energy dissipation than similar sized drum brakes because the design results in con siderably lower heating rates. This is due to the fact that at-- any one time the friction pad contacts only a section of the disc surface. The lower operating temperatures permit the use . _ of friction materials which do not contain asbestos. Another- - feature of disc brake design which has reduced the need of asbestos materials is the lower strength requirement of the friction material. Clutches - The substitution of-other-material" for `asbestj^s__2 in clutch facings of traditional design could only be done by changes in size and design. Two changes in clutch design which have reduced the requirement for asbestos-containing friction . materials are the advent of the automatic transmission and the redesign of manual clutch friction surface. The clutch surface of the automatic transmission is im mersed in an oil bath which virtually eliminates airborne pollutants. Further, the cooling affect of the oil bath reduces the requirement for high-temperature capability materials. Automatic transmission clutch facings may be made from either sintered metals or fibrous cellulose materials. . ____ Many manual clutches have redesigned friction surfaces which consist of numerous small circular pads or discs attached to the clutch face as opposed to the standard annular ring friction surface. These small pads act in the same manner as the disc brakes friction pad. Thus, lower stresses and oper ating temperatures associated with the new design reduce the need for asbestos-containing friction materials. UT RESEARCH INSTITUTE 28 .10 cgprTPTC PROBLEMS 10.1 Emission Levels In understanding control techniques and their efficiencies, it is important not to be confused with efficiencies quoted on a weight basis and those based on a particle count basis. Firstly, considering efficiency based on a weight basis, it is relatively easy to get a very high efficiency with parbi- cles whose size is in excess of 5/x with a variety of control devicesr (see Figure 10) . However, the efficiency does drop off considerably with decrease of particle size, for example, see Figure 11 for l#x particles. (It should be noted that these graphs refer to spherical particles - information on fibrous particles is not presently available.) ..,------- . ------ ------- - ^ Now consider what these apparent high efficiencies mean in terms of numbers of fibers. It can be assumed that 10 average fibers of asbestos weigh approximately 1* ng. ^ If 1 g of asbestos material approaches a filter rated at even as high as 99.999% efficiency, then the quantity passing 4 3 through will be 0.00001 g, or 10 ng. And since 1 ng ^ 10 fibers, then a. total of 107 fibers will pass through the filter for every 1 g of material impinging upon it. This is a situation not frequently brought out, but is very _ significant when exposure levels are monitored in terms of fibers per cubic centimeter. . - Thus the quoting of efficiency in terms of mass efficiency is a "red-herringH statement that flatters to deceive. It bears no obvious relation to the number of fibers being emitted. However, based on tests which actually measure the number of fibers being emitted, it would seem that both fabric filters and high efficiency wet scrubbers are capable of reducing the fiber counts to acceptable levels. British experience is that 0.2 f/cc is routine and Johns Manville finds that 1 f/cc is an acceptable value when the results are averaged over a time period. , "' NT RESEARCH INSTITUTE The medical evidence as to the size of fiber responsible for adverse"health'effects is not positive nor is the question of whether fibrils of fibers are most hazardous. Until the medical questions are fully resolved, it would seem premature to impose inflexible or overly rigid regulations. This has been the view held by the Federal occupational health authorities in assessing their standards. It would seem that thgi approach-in limiting exposure to that which is possi ble using good modern technology is sensible. The same may be said for their monitoring techniques. . 10.2 Water Pollution Recyclingof waste water is possible and is practiced in certain segments of the industry. The question of the damage done to streams, rivers, and lakes by indiscrirainant dumping of asbestos containing waste waters needs careful study. One must remember it is a natural material which will appear in water in any case. On the other hand, there is evidence that asbestos particles ingested into the stomach may cause stomach cancer. Again, until medical evidence is clear, it would seem sensible to recycle water whenever this can be accomplished. IIT RESEARCH INSTITUTE 49 ^ c_ -JK