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FRICTION MATERIALS STANDARDS INSTITUTE, 1NC.,E-210 ROJTE 4, PARAMUS, N. J. 07652^ *' *-'N . iV Jine 6, 1972 5C TO: Members of Asbestos Study Conmittee SU3JICT: Asbestos Fibers Emissions - Friction Materials A'seminar was held at the Illinois Institute of Technology Research Insti tute back in April of this year. Dr. Colin Harwood of MTRI was one of the advisors to the Illinois Pollution Control Board who was in favor of the pro posed 1971 regulations as written--that is to include a ban on the1' use of . asbestos in the brake lining of. vehicles manufactured after January 1, 1975 and sold for'use in*lllinoi3." n> The oages from, the IITRi paper are: pages 22, 25, 26,* 27, 28, 46, 49, 65, 66, 67, 68, 69, 70, 71, 72, 73. .. Your Chairman, Ur. I. H. Sfoaver, sent this data to me for distribution to the Conmittee. He conniented cn the paper: "The main issue I would have with Dr. Harwood's conclusion would have to do with whether or not the free fibers or fibrils released from friction material decomposition are truly hazardous in any way, and I. also believe he tends to underestimate the problems in non-asbestos containing braking systems.n Your Chairman believes that a meeting of the Committee should be called. I'm asking for a reply on the attached form, for which weeks not to call a meeting. From this l will try to arrive at a meeting date (perhaps late vkily or late August). .' ETIO/lmc E. I?. Drislane Executive Secretary SC-ALL-16160 2 PLAINTIFF'S EXHIBIT no. fe'-zir] SCF-ALLF-04020 MEETING SCHEDULE - AS0ESTOS STUDY COM ITTEE TO: Friction Materials Standards Institute, Inc. E-210 Route UL . Faramus, N. J. 07652 ft: Gentlemen: Concerning a proposed meeting of the Asbestos Study Committee, PLEASE DO NOT SCHEDULE IT FOR THE FOLLOWING WEEKS: . July 24-28 August 7-11 v August 14-18 . August 21-25 ' August 28-31_________ Additional Comments: ' _ By_ Company__ Date attachments such that the dust created is arrested at the source and collected in 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 industry may be utilised. Rules which relate more specifically to fabrication of asbestos products may be found m such publi cations as: . 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.u National insulation Manufacturers ' Association (NIMA). 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 5054 asbestos and may...he .up io-JOS, -and the industry that mararf'acturea these ma terials is ranked third (1969) in the consumption of asbestos fleers. 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. IT RESEARCH INSTITUTE Sources of Emission - Emission 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 196B Mileage life of brake linings Brake lining sets on new vehicles Pounds of asbestos per set of brake linings - 1,010.000,000,000 27.SOD 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 high temperatures at the brake lining/drura contact points actually reach degradation levels. Tests on brake linings, brake discs and clutches have demonstrated that the quantity of fiber emitted is some function of the severity of the braking conditions (see Table 3) . How ever. even at; the level of l5i. the total emissions must be considerable when the total tonnage in use is considered. Further, the emissions are likely to occur at places of ~hi<jh 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 and some work on roadsides has been done at Mt. Sinai, Mew York. The EPA study will establish the extent and nature of the asbestos lit RESEARCH INSTITUTE ' .. 25 Table 3 ASBESTOS EMISSIONS FROM BRAKE LININGS (Test Results by Electron Micrograph) Product Brand 1. Automobile A . drum brakes 2. It 3. 1 B C 4. If C 5. 0 French 6. tt E 7. II .F German 6. M C 9. Ift G 10. 1* ' H 11. Automobile clutch J 12. Automobile disk brake X 13. Bus drum brake L 14. M 15. Truck drum F brake (light) Test Mi* c hod Friction Ko. of Samples 6 Conditions Presence of of Tcsr-F Free Fibers 300-BOO Fev Z Free Fiber* <1 Friction Friction Friction Friction 6 250-800 None 0 5 300-700 Fev <1 1 700-900 Numerous *-*10 5 300-800 Fev cl Friction Friction 5 300-700 Fev 5 300-800' ' Fev <1 <1 Friction Friction Friction Dynamometer Dynamometer Dynamometer Friction Friction 2 100-500 1 2` 600-700 100-600 l normal driving 1 normal driving 1 city . driving 2 450-550 10 300-800 Fev Numerous Fev None Fev None None Few <1 v-15 Cl .0 C5 0 0 cl *Utl(jht estimated from fiber volume* 26 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 ' Modulus of Rigidity lb/in.2 Asbestos Fiber yarns Steel wool Mineral wool 550,000 180,000 50,000 25,000 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 changes required to accom modate the stresses end temperatures involved would result in IT RESEARCH INSTITUTE "' ' ' . 27 . . . i larger, more expensive components. Brakes - The recent adoption of disc brakes by the auto motive industry makes material substitution more plausible. x 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 'asbestos 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. I IT RESEARCH INSTITUTE I r~ i i i' ] j ] * 7I ] ,j ] 1 I T I X I 10. SPEC ir i.C 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 parti cles whose size is in excess of 5p with a variety of control devices (see Figure 10) . However, the efficiency does drop off considerably with decrease of particle size, for example, seeFigure n for lp. particles, (it should be noted that these graphs refer to spherical particles - information on fibrous particles is not presently available.) Nov 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 through will be 0.00001 g, or 10 4 ng. A* nd since 1 ng ^ 10 3 ' 7 fibers, then a total of 10 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-herring" 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. '' I it research institute 46 i f j 1 . 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 thei 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 Recycling of 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 indiscriminant 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 ASBESTOS AIR POLLUTION RESULTING FROM THE WEAR OF BRAKE LININGS By Colin F. Harwood, Ph.D. ABSTRACT Asbestos containing brake linings have been cited as a source of ambient air asbestos pollution. This paper reviews the suggestion and an estimate is presented which indicates that the asbestos emission from brake linings is significant. The ways in which this emission may be reduced or eliminated are briefly reviewed. IIT RESEARCH INSTITUTE 10 West 35th Street Chicago, Illinois 60616 111 RESEARCH INSTITUTE 65 ASBESTOS AIR POLLUTION RESULTING FROM THE WEAR OF BRAKE LININGS tmtrODUCTIQN V Recent interest in asbestos and the realization of its health hazard have raised the question of the extent to which people are exposed, to asbestos on a non-occupational basis. Measurements have been made on urban background levels and it has been shown that small but definite concentrations are to be found in areas.quite remote from any apparent source. . Since virtually every motor vehicles carries several pounds of asbestos contained in its -brake linings and since these are worn away to some degree every time the brakes are applied then it is reasonable to expect that they could present a significant emission source. This is especially acceptable when one considers the 100 million or so vehicles on the nations roads. The paper investigates the possible extent of such emissions and presents an estimate of the cont'ribution to urban asbestos concentrations. Possible means of reducing such emissions by use of an alternative or sealing the system are briefly reviewed. The Extent of the Emission 12 The best information available at the present time *. indicates that the percentage, of asbestos contained in the dust normally emitted from brake linings is of the order of .1/6. However, under conditions of severe breaking, this may rise to 15X. - ` The average brake friction material contains of the order of SOX asbestos, thus an explanation-is necessary to account for the discrepancy between the measured and theoretical values. The most likely' explanation results from the known facts with re gard to heat generated at friction surfaces. The work of Bowden and Tabor has shown that when two surfaces are placed together the contact area is dramatically less than the apparent area. MT RESEARCH INSTITUTE 66 . This me*ns that very large energy transfer takes place at thest contact points and extremely high temperatures are reached. In the case of brake linings, some evidence of these temperatures has been generated in unpublished work by the . General Motors Company^. In.this study, a small hole was cut through a brake shoe and the radiation collected from the ex posed shoe surface was monitored. The results suggested that under light braking temperatures of the order of 800-900C were found, while during heavy braking the temperature reached 1700-1800#C. The significance of this data to the present case is ' that it is known that asbestos decomposes above 500C^ to give forsterite (MgjSiO^), talc (Mg^Si^O^g (OH) 2) and water vapor. Acceptance of the value of 1% of asbestos emitted allows an estimate to be made of the effect of this emission on the quality of the atmosphere. Estimation of Urban Concentrations of Asbestos From Brakes Assumptions a. There are approximately 100 million* motor vehicles. b. Motor vehicles have an approximate average weight of 4 lbs of friction material, when new, of which 50% is asbestos. c. The average motor vehicle will require replacement of the brakes after three years of use at which -time -they -will -have ierst *50% ~of-their weight by abrasion. d. The dust emitted will contain 1% of asbestos fibers. e. Of the wear dust, 80% is emitted and 20% is lodged within the system. - The AAA claims there are 109,000.000 licenced vehicles in cluding 90.000,000 passenger vehicles and 19,000,000 trucks. Ill R t SEARCH INSTITUTE 67 mi filiation The total weight of brake linings in use is 1001 000,00.P.-X ,,,i _ 200.000 Tons. . 2000 . The quantity worn off these linings per year follows from the assumptions made in c. 1 50 200.000 _ . as 200.000 x q3- x V10n0n =- ------6------ Tons/yr. This wear dust contains 1% asbestos, hence emission is 200.000 6 ~ 100 2000 Tons/yr. 6 Allowing for the fact .that 20X is not emitted, the total emission is .thus 2000 80 6 x 100 1600 . = 270 Tons/yr. ' Effect on the Atmosphere There are no facts relating directly to asbestos on which one may judge the effect of these emissions on urban air. However, there has been a considerable amount of study done on the diffusion of other materials from automobiles, particularly lead and carbon monoxide. At a recent ACS Symposium in Minneapolis^ evidence was presented which placed the level for lead emission at *0.01 pg/m3 in Thule, Alaska and 2.5 pg/m3 in. New York City. Next to busy highways a level in excess of 50 pg/m may well be possible. In the light of this data the value of 2 I'.g/m^ for average urban air conditions, suggested by .Cm , seems -eminently treasonable. . f.nngi^ar< ng that 1.25 x 10 tons of lead are emitted in total from automobiles then the following factor is'used. Avg. Cone, asbestos in city air from automobiles - Ouantity of 2 itg/m3 city air asbestos emitted x 1.25 x 105 tons Pb from cars Applying this figure to the present case and assuming that 200 tons are emitted in city areas, then we get that: MT RESEARCH INSTITUTE 68 The evg. cone- - 200 ,, -------' 5 . 1.25xl05 3.2 x 10~3 pg/ro3 ` or ztt. 3.2 x ng/ro3 ^ A similar result is obtained using the dispersion factor for carbon monoxide. However, the values for lead are preferred since it is a particulate emission rather than a gas. The Significance of This Value The question of whether asbestos containing brake linings constitute a significant source of ambient air background, asbestos levels can now be considered. Firstly, it is pertinent to review the available evidence, on asbestos levels in ambient air. Perhaps the most up-to-date information is reported in a recent paper by Thompson and Morgan of the EPA7. Their data suggests that values 0.5-15 _ ng/rr.3 are appropriate to urban sites, while 0.1 ng/m3 is to be found in nonurban sites. They give a figure of 0.01 ng/m3 for remote sites. . . The California 5tate Health Department in collaboration with the School of Public Health, Berkeley, California, have tested ambient air for asbestos. Their results suggest values of 0.06 ng/m in remote sites and 3 ng/m near a ` source. . Nicholson* and Rohl 8 of the Mt. Sinai School of Medicine have alro been active in "the measurement o' asbestos in urban ambient air. The analysis of a large number of samples has revealed that 33% of the samples contained 0-0.9 ng/m3, 55% . contained 1.0-5.0 ng/m3 and 10% contained 5-20 ng/m3 and a few Were in excess of- this. All of the workers have been at pains to point out that the results are to be considered preliminary. Thus they should kc regarded not as final definite figures, but rather as good, IIT ICSEAKCH INSTITUTE 69 considered, preliminary findings- The similarity of the figures reported toy the various -workers does suggest that at least an order of magnitude has been established. 3* Consider now the estimate of 3.2 ng/m calculated pre / viously as the contribution from asbestos brake linings. Firstly, it should be stated that this figure is a conservative estimate and allowance has been made for the many factors which could re duce this figure. Secondly, although there is no reason to doubt the factor for the diffusion of lead, it should be realised that this figure is an average value for the whole of the city air. Consequently, much higher concentrations are to be expected in' ' certain areas of high brake usage. For example, near inter sections, tol\booths, etc. .* In the light of the evidence here presented, one must conclude that asbestos emitted from brake linings may be a major contributing factor in the overall ambient air concen tration. Further work is necessary to establish more definitely the major contributors to urban asbestos concentration levels. It is not possible to state with assurance how much these low concentrations of asbestos constitute a threat to the health o the general public. Medical evidence and opinion is widely divergent on this issue. However, asbestos has been rated as a hazardous substance by the EPA and as such it should be.treated with due respect. Emissions should be reduced or curbed wherever this is possible. To this end it is worth briefly reviewing how this may be achieyed. TECHHOLOGY of eliminating emissions The emission of asbestos to the atmosphere from asbestos containing brakes could be prevented in two ways: its use could be banned altogether, or, the brakes could be sealed. In the former case, an alternate would have to be found. II? RESEARCH INSTITUTE 70 Alternatives to Asbestos For a replacement to be as suitable as asbestos, it would have to fulfill a list of desirable features as: . Resist high temperatures without degradatioh or loss of frictional properties. Combine excellent friction characteristics without severe abrasion. . Provide great strength - asbestos fibers have a greater tensile strength than steel and yet are more flexible. Have relative economy. Of the materials which have been considered, sintered met'al with ceramics and fiberglass have been the most likely candi dates thus far. Sintered Metal - This material has been used and indeed has the desirable quality of being fade-free, for this reason it is still used in some racing cars. Hoveyer, it has several dis advantages. It tends to be noisy and brake screetch is a problem. They suffer from what is known* in the trade as "morning sickness", this means that the first stop is very severe, or, that the cold friction is high. Wear is higher than with asbestos and thus the brakes have to be replaced more frequently. Replacing the brakes is more difficult since all brakes are honed to fit the drum. Honing metal is more difficult than asbestos friction material. - Ceramic Metal (Cermets) - A sintered metal and ceramic composition has been developed and tried. Its use at this time seems to be restricted to the clutches on heavy-duty vehicles (tractors, etc.); in these cases it is usual to use buttons of the material rather than a complete annulus. Although to a lesser degree, ifsuffers from the same complaints as sintered metal with respect to noise, wear and severe first 8top, and in addition, it is relatively expensive. However, . . ....... I IT RESEARCH INSTITUTE 71 its anti-fade characteristics have led:to extensive testing. For example, the Ford Motor Company put inserts of ceramic ngjji at the position o maximum brake wear on their 19 SQ ' Thunderbird. The concept was abandoned, reportedly due to uneven braking leading to a directional pull when* braking. - Fiberglass - Attempts to use fiberglass instead of asbestos have been attempted since 1918. So far, no design has met the exacting standards required. As with the other materials, the first stop is harsh. Apparently the design is better for disc brakes than drums. A problem is the sensitivity of the brake to moisture. Owens-Corning are undertaking development* research .in this area. They are very guarded with regard to the status of their work, but state that they are actively engaged in developing a product. To date, no vehicles are known to employ fiberglass in their brake. friction product. Sealed Systems * Sealed systems have been seriously considered. Normally, cars rely on air cooling and the movement of air round the brake caused by. the motion of the car. However*with high performance cars, more cooling is required. This is achieved in a simple manner by fabricating a superstructure which scoops up air and directs it inside the brake drum. If a filter were added on the exiting side, this would cause a substantial reduction in emissions. t A more elaborate design'which has been used is to liquid cool the. brake system. This enables the braking system to be completely sealed and thus no emission are possible. The one problem area with this design is that the oil seals must be extremely reliable* However, with a well designed system problems due to overheating could be largely eliminated. I IT RESEARCH INSTITUTE 72 CONCLUSIONS An estimate has been made of the asbestos concentrations co be found in urban air resulting from the use of asbestos ^ containing brake materials. The results indicate that brake use may veil constitute a major source of asbestos background levels. The quantity in comparison to occupational levels is extremely low. A time weighted average occupational ex posure level of 5 f/cc would be of the order of 100,000 times greater than a background level of 3.0 ng/m^. The medical significance of these results is not known with any certainty- At the present time, no alternative to asbestos contain ing friction products is developed to the stage of finesse required by the industry. It is difficult tobelieve'that modem technology cannot overcome the problems presented by the use of alternates. The use of sealed brake units is a second possibility. Again there do not seem to be any insurmountable technologi cal problems, but no information is available as to the cost and time factors. . HT RESEARCH INSTITUTE 73 .