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. I. .! Johns-Manviile . Sales Corporation Ken-Caryi Rancfi Denver. Colorado 8021 7 (303)979-1000 September S, 1978 Mr. John Marsh Director, Environmental Affairs Raybestos Manhattan Corp. 100 Oakviev Drive Trumbull, CT 06611 Dear Mr. Marsh-: The circumstances surrounding the work by Krishna Seshan of the University of California on asbestos fibers released from brake linings is unfortunately very typical of the irresponsible attitude towards environmental hacards and asbestos fiber in particular. The pattern includes initial release of the information in a sensational manner to the press with a promise that the complete work will be published at a later date in a respected journal. This is followed by editorials in and/or letters to the editors of other journals covering this same material which was released to the press. When the work is finally published, it is generally found to bear no resemblance to the promises made in the original releases. The allegations which were originally made are unfounded and in fact, the final paper may leave a totally different impression than was created in the initial releases. The final publication by Mr. Seshan which appeared in the July 19 78 issue of Environment a 1 Rese arch is a relatively straight-forward discussion on the use ot dark field electron microscopy to studv "deformed chrysotile". As he pointed out, however, the samples selected for brake------lining dusts did not represent the material which would be present in the air and heavily traveled a.reas . It is typical of the dust to which workers in a brake lining shop would be exposed The most significant point about Seshan's .article is that there is no reference whatsoever to the health effects of brake lining dust 3nd particularly the health effects that have been ascribed to `deformed chrysotile fibers in the advance publicity. Many of the newspaper articles reported that experts at the Mt. Sinai School of Medicine 07682 Mr. John Marsh Page 2 September 5, 1978 had determined that deformed cnrysotile was more biologically active than normal fibers. This is totally incorrect. In a paper by A. M. Langer, et al in the Journal of Toxicology and Environmental Health, 4_, 173-188 (1978), it is stated that: "It appears that the less mechanicallydegraded the surface of the fiber, the greater the biological response." The source of original opinion which was expressed by Mr. Seshan in the press is completely unknown at the present time. In the editorial which appeared in the April issue of the American Industrial Hygiene Association Journal, it is claimed that Mr. Seshan1s technique now resolved the controversy which purportedly exists concerning the fate of asbestos fibers during the normal wear of brake linings. Some contend that the fibers are destroyed, whereas others contend that a high percentage of the fibers remain intact. In all studies that I am aware of on brake lining dusts, the so-called deformed fibers observed by Mr. Seshan would have been included in the total determination of asbestos fibers remaining after brake lining wear. The techniques, therefore do not resolve such a controversy if, in fact, it does exist. In addition to Mr. Seshan's irresponsible handling of the information prior to publication, there are many points in his paper which indicate that he is not particularly well qualified in the field of electron diffraction. Very truly yours, ~~ C\ C? yfj. Jy P. Leineweber, Ph.D. Technical Director Health, Safety 8 Environment Dept. JPLrjh cc P. Kotin, M.D. E. M. Fenner D. Poutiatine ENVIRONMENT*!. RESEARCH 16,383 -- 392 (1978) On the Utility of Dark-Field Electron Microscopy in the Determination of the Degree of Deformation In Chrysotile-Asbestos: An Environmental Research Application ' . K. Seshan Department of Materials Science and Engineering. Materials and Molecular Research Division. Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 Received June 21, 1977 The degree of microcrystalline deformation in fibers of chrysotfle asbestos may be distin. guished using high resolution dark-field electron microscopy. This is demonstrated by com paring undeformed chrysotile with Union Internationale Conlre le Cancer (U1CO standard reference samples. The UICC samples are shown to be partially deformed as a result of milling in the mixing process. Samples of used and unused brake shoe lining dust were examined using this technique: it is shown that chrysotile asbestos in various stages of deformation--relatively undeformed to heavily deformed--survives in automobile brake drum dust. Such dark-field images can serve to identify the source of asbestos found in environmental pollution samples. . INTRODUCTION There is a controversy in the literature whether or not fibers of chrysotile asbestos survive in automobile brake drum dust: two studies (Rohl et al., 1976; Alste et al.. 1976) report that the fibers do survive and earlier work (Lynch, 1968; Hickish anti Knight, 1970) reports that they do not. The latter claim that the chrysotile is converted to forsterite under the high temperatures attained in the braking process. 'As high resolution dark-field electron microscope images are sensitive to the degree of deformation, they can be used to distinguish between deformed and undeformed fibers and thus to resolve these two differing sets of results. It is shown using this technique that chrysotile asbestos fibers in various states of deformation--relatively undamaged to heavily deformed and recrystallized--exist in automobile brake drum "dust. SAMPLE SELECTION AND PREPARATION Four samples were selected: (A) undeformed chrysotile ore samples from ser pentine outcrops of Calaveras County (California); (B) slightly deformed UICC reference standards of Canadian chrysotile milled during preparation to reduce fiber size (Timbrell et al., 1969); (C) unused brake lining dust, collected during burnishing prior to installation of new brake shoes; and (D) brake drum dust collected from the front and rear brake drums of a State vehicle obtained during brake shoe service (Seshan and Smith, 1977). . Samples were transferred directly to Formvar-coated electron microscope grids and coated with carbon on both sides. 383 0013-9351/78/1613 -- 03 8 3 S 0 J. 00/0 Copynfht 197S by Academic Pr|t iXriJc All rights of reproduction in any form rrlci 07684 | ir c 384 K. SESHAN EXPERIMENTAL As the high resolution dark field method is described in great detail elsewhere (Hirsch et al., 3969), only a very brief description is included here. An electron beam striking a polycrystalline specimen with grains of different orientation (e.g., A and B in Fig. 1) is diffracted into cones, causing the typical polycrystalline ring pattern. The high-resoiution dark-field method consists of tilting the incident beam so that the part of the diffracted ring passes through the optic axis of the micro scope (Fig. lb). The tilting is accomplished with the electronic beam tilt device. Then an aperture collects intensity only from those crystallites diffracting into this part of the ring, e.g., B (Fig. 1c). Various factors involved in the. interpretation of the diffraction patterns of chrysotile asbestos fiber bundles are shown in Fig. 2. The actual lattice of chrysotile is a defected, scrolled crystal with fiber axis along a (Yada, 1967). The reciprocal lattice of this crystal should be some-form of a spiral, equispaced along the a* axis. Zvyagin (1967) and Whittaker (1966) have studied diffraction effects from concentric cylinders. How deformation and shear w'ill affect the diffraction patterns has not, to the author's knowledge, been studied and is under study here. The simpler case of an undeformed defect-free chrysotile fiber, where the fiber is idealized as a series of concentric cylinders, as first proposed by Whittaker (1969), is shown in Fig. 2i. The reciprocal lattice then consists of X series of concentric rings; shown in Fig. 2ii (only the two rings in the 2kl layer are drawn). The electron diffraction pattern represents the intersection of the reflecting or Ewald sphere (ES, Fig. 2ii) with these rings (Hirsch et- al.. 1969). This ought to result in a series of spots as shown in the -2kl layer line. Streaked patterns are, however, obtained from single fibers of chrysotile (Yada, 1967; Seshan and Smith, 1977). The explanation for the streaking probably lies in refraction effects and the fiber shape (Yada, 1969); it could also result from the various faults produced during the Fic. I. Illustration of the high resolution dark-Gpld method: (a) The brighl-ficld image from a selected area of a polycrystal, illustrated with two grains, A and B. (b) The situation after gun lift: only a ponion of the diffracted intensity is collected by placing the objective aperture as shown, (c) The resulting high-resolution dark-field image with only favorably oriented grains, e.g.. B showing dif fracted intensity or "lighting up." J H M 07685 ` DEFORMATION OF CHRYSOTILE ASBESTOS . 385 it-:: t*cr:.-: Ftc. 2. Illustration of the real and reciprocal lattice of a defect-free chrysotile fiber (0 and (ii) idealized as a series of concentric cylinders. The actual structure is a defected spiral sheet (Yada. 1967). The reciprocal lattice of the ideal fiber is then a series of equispaced concentric rings along the o* axis, as in the 2kl tayer. when these rings intersect, the Ewald sphere (ES) spots ought to be produced as shown on the -2kl layer line. However, streaks are observed (Yada, 1967). arising proba bly from the spiral shape of the fiber defects and strains formed during the scrolling process. When a fiber bundle (fil?ers of different orientations) is imaged, the layer lines are smeared out. yielding a typical "arcuate" pattern as in Fig. 3b. ' gr6wth of the crystal. The influence of these faults on the diffraction patterns and their influence on deformation needs further study. When bundles of Fibers are involved, the streaks are replaced by arcs (Figs. 2iv and 3b), showing a strong tendency toward a texture and yielding the typical "arcuate" patterns observed by several researchers (e.g., Rohl et al., 1976). The dark-field image obtained by imaging any part of the arc, as shown in Figs. 1 and 3b, should yield uniform intensity, if the crystal is homogeneous. This is the case to be expected only in the case of the undeformed fibers--and is consistent with the experimental observations in Figs. 3a and 3b. . RESULTS Bright- and dark-field images of naturally occurring chrysotile (A)are shown in Fig. 3. The dark field is obtained by imaging a portion of the diffracted intensity, as explained above. The result is a uniform contrast, as would be expected from an undeformed crystal. The striking feature of the dark-field images is the great intensity along the hollow canals and this needs further investigation. The intensity difference cannot be explained on the basis of differences in absorption alone; it appears that some I rrr. JH'M 07 686 t Ftc. 3. Sample (A): naiurai chrysoiile. (a) and (b) Dark-field and difTraciion pattern. Nonce the unusually bright and undamaged internal canals: the crystal is homogeneous and undeformed. A faint outline of the objective aperture is seen in the diffraction pattern of Fig. 3b. (c) Illustrates the blistering as a result of exposure to the beam. . ' ', diffraction processes are operative: Notice that the canals are sometimes bright and sometimes dark. In the crystalline")iart, however, the intensity is uniform and it is clear that these fibers are free of gross deformation. Chrysotile fibers, like most sheet silicates, are beam-sensitive to 100-keV elec trons (Langeret a/.. 1974; Scshan, 1975). Precaution must therefore be exercised while obtaining the high resolution dark-field images, because upon focusing, the J HM n jam r-*' DEFORMATION OF CHRYSOTILE ASBESTOS 387 condenser, the fibers tend to become blistered. In the dark-field image shown in Fig. 3a, precaution was taken to prevent any beam damage; the condenser was not focused, and the beam was tilted in the dark field mode. The condenser was then ./ f,/ [r-rrf u \fl Fic. 4. Sample (B): UICC Standard Reference Canadian chrysolile. (a) and lb) Dark-field imay, hat illustrate that the ball milling during the mixing step converts the chrysolile into a fine-graimy olycrystal. The aperture is moved from one part of the ring to another, resulting in an eniucl; lifferenl set of grains lighting up. (c) The bright-field image from which little information can b, ibtained. jhm 0768a 388 K. SESHAN focused to obtain the diffraction pattern shown in Fig. 3b. The resulting beam damage is shown in Fig. 3c. The use of beam sensitivity to distinguish chrysotile from other non-beam-sensitive materials, e.g., the amphiboles, has been dis cussed by Langere/ al. H974). Dark- and bright-field images of deformed UlCC standards (B) are shown in Figs. 4a--4c). The effects of deformation are clearly seen in the dark-field images (4a and 4b) and in the electron diffraction patterns but not in the bright-field Fig. 5. Sample (Q: Burnishing dust from an automobile brake drum prior to installation, (a) Dark field, (b) diffraction pattern, and (c) bright field. Notice the well-preserved canal which shows up (the dark-field image) in (a), indicated by the arrow and arrowhead. This and the well-preserved diffraction pattern (b) shows that the fibers are not as deformed as the UlCC samples--a conclusion that cannot be inferred from the bright-field image (c). JH/, 07689 DEFORMATION OF CHRYSOT1JLE ASBESTOS 389 images (4c). The clear internal canals of the undeformed sample (A) are destroyed; there appear small submicron (100 A) areas which light up as if they were grains or microdomains of different orientations; consistent with this observation, the strongly textured diffraction patterns of the undeformed fibers (Fig. 3) are changed to those of a polycrystal. At the present the crystallographic and microstructural nature of the deformation is not clear and warrants further study. The effect of translating the aperture to a different part of the diffracted ring is shown in Figs. 4a and 4b. The result is that "grains" in a different orientation "light up" or show diffracted.intensity signifying that this is truly a diffraction effect. To isolate the effects of deformation during the braking process, unused brake shoe burnishing dust (Q was examined (Figs. 5a and 5b). The bright-field image (B) is not informative, whereas the dark-field image clearly shows some intact internal, canals (see arrow and arrowhead Fig. 5a) resembling the undeformed Fic. 6. Sample (D): Brake drum dust after use in a state vehicle, (a) Bright field and (b) dark field. Although the bright field is not distinctive, the high-resolution dark field and the selected area diffrac tion patterns are remarkably different. The crystal is quite inhomogeneous with very large grain sizes: this can happen for a varieity of reasons (see test). 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Sample (D): Automobile brake drum dust after use. (a) Dark field and (b) bright field. This shows that relatively undeformed fibers survive in the brake drum dust. The grain sizes in the darkfield images (a) are comparable to those in the burnishing dust (Fig. 5a) or the UICC samples (Fig. 4a), indicating little deformation during use. This preliminary study also shows the need to study details of the growth of the chrysotile asbestos and the nature of the defects involved, if all the diffraction and de/ormation effects are to be understood. ACKNOWLEDGMENTS I thank G. R. Smith of the Air Industrial Hygiene Laboratory (AJHL) Berkeley for bringing this problem to my attention and preparing the samples. 1 acknowledge useful discussions with him and Dr. Walter John and thank Professor L Washburn Cor encouragement. This work was supported financially by the U.S. Energy" Research and Development Administration. , `references Alste. L, Watson. D.. and Bagg. J. (1976). Airborne asbestos in the vicinity of a freeway. Atmos. Environ. 10, 583. Hatch. D. (1970). Possible alternatives to asbestos as a friction material. Ann. Occup. Hyg. 13. 25. "Hickish. D. E.. and Knight. K. L. (1970). Exposure to asbestos during brake maintenance. Ann. Occup. Hyg. 13, 17. Hirsch. P. B.. Howie. A.. Pashley. D. W., and Whelan. M. J. (1965). "Electron Microscopy of Thin Crystals." Butterworths. London. Longer, A. M., Mackler, A. D.. and Pooley. F. D. (1974). Electron microscopical investigation of asbestos fibers. Environ. Health Perspect. 9, 63. Lynch. J. R. (1968). Brake lining decomposition products. J. Air Pollul. Control Assoc. 18, 824. Rohl, A. N.. Longer. A. M., Wolff. M. S.. and Weisman. 1. (1976). Asbestos exposure during brake lining maintenance and repair. Environ. Res. 12, 110. Seshan. K., and Smith. G. R. (1977). Characterization of chrysotile asbestos in automobile brake drum 392 K. SE5HAN dust by transmission electron microscopy. "Proceedings 35th Annual Meeting of EMSA.'* Claitors. Baton Rouge. La. Timbrell, V. (1969). Characteristics of the international union against cancer standard reference samples of asbestos. Pneumoconiosis. In "Proceedings International Conference on Pneumoconiosis, Johannesburg," p. 28. In Oxford Univ. Press, England. Whittaker, E. J. W. (1966). Diffraction contrast in electron microscopy of Chrysotile. Acta Crysial- logr. 21, 4616. ` Yada. K. (1967). Study of chrysotile asbestos by a high resolution electron microscope. Acta Crystal- logr. 23. 704. Zvyagin. B. B. (1967). "Electron-Diffraction Analysis of Day Mineral Structures" Plenum. New York. / Automobile brake linings may be a health hazard ... Automob,ile brakes -- normally associated with To date. Seshan estimates, about 90 percent of) averting danger -- may, in fact, be producing the asbestos used in the United States is milled ' dangerous substances and releasing them into under heat and pressure. And. because of these the atmosphere, according to a researcher at the processing methods, most of the asbestos we University of California's Lawrence Berkeley breathe is deformed in some way or another. Still, Laboratory (LBL). many medical researchers in the U.S~ have The concern is being expressed by Krishna ignored the health problems connected with these Seshan, a materials science engineer at LBL's asbestos deformations, says Seshan. Materials and Molecular Research Division, who has shown that automobile brake drum linings produce substances that may be hazardous to our health. For that reason, Seshan, an expert in electron microscopy, was asked by the- California Department of Health's Air and Industrial Hygiene Laboratory to help develop a method of identifying The substances that Seshan has been studying asbestos fibers found commonly in air samples. are thin, single fibers of asbestos -- so thin, in fact, This investigation, claims Seshan, was the way in that even the most powerful microscopes which he was introduced to the health hazards of illuminated with visible light cannot detect their chrysotiie asbestos and how he eventually turned presence. Looking through an electron to the problem of automobile brake drums. microscope -- an instrument with as much as 10,000 times the resolution of conventional light microscopes -- Seshan found that the minute particles of dust created by automobile brake drums contain filaments of deformed "chrysotiie" asbestos, a type of asbestos that many researchers consider a health hazard. ""According to Seshan. most automobile brakes operate by grinding pads against a lining of heatresistant asbestos, an action that introouces wnat he terms "process defects" in the asbestos fibers heated and ground against hot brake drums. Such fibers had long been suspected by many scientists to be a constituent of brake drum dust. But other These fibers, according to public health officials, researchers contended that the high friction may not be particularly dangerous to the average developed in braking simply disintegrates the citizen since people driving cars breathe, at most, only small amounts of brake drum dust. The real hazard of chrysotiie asbestos, say these experts, is r to workers such as brake repairmen who use \ compressed air to blow asbestos fibers from tbrakes daily and may breathe as much as a million particles of asbestos in each cubic meter of air. Many medical experts, most notably Dr. Irving asbestos and leaves no asbestos fibers at all. Neither theory could be verified, because a microscopic technique capable of illuminating chrysotiie asbestos with their defects had not yet been applied. Seshan however, solved this controversy by employing a special microscopy technique. Setikoff of Mt. Sinai Hospital in New York City, Using what electron microscopists term a "dark contend that chrysotiie asbestos is hazardous to field image" -- a method of observing small lung tissue because such forms are minute and particles by looking at the diffracted or "scattered" rough enough to prevent the mucous covering of electrons -- Seshan managed to illuminate the the lung from dislodging it. Once in the lungs, tiny fibers. By doing this, he not only confirmed asbestos never dissolves. And this substance is that chrysotiie asbestos is present in automobile often found in the lungs of factory workers, brake drum dust, but also discovered that some of construction workers, auto mechanics, office the fibers show further significant damage. workers and even in the lungs of spouses and In a preliminary report on the project soon to be children of asbestos workers. published in the scientific journal, ENVIRON Asbestos, is a mineral, says Seshan. And MENTAL RESEARCH, Seshan concludes "that 4. approximately 900 million tons of this chrysotiie chrysotiie asbestos fibers in various states-of mineral are mined in theUnited States annually. deformation -- relatively undamayed to heavily Much of it is milled or woven into a blanket-like deformed and recrystallized -- exist in automobile 7 material, then used to insulate or fireproof brake drum dust." equipment such as steam pipes, roof linings and What this means, he says, is that some of the ship hulls. asbestos in brake drum dust may be more of a moro on A 26 . . . A-34 Am. ind. Hyg. Assoc. J. 09) Aonl, 1978 JHm 07694 BRAKE LININGS/ASBESTOS . .. health hazard than the ordinary chrysotile form, certainly introduces deformed asbestos into thi because much of it is further deformed. And atmosphere." deformation in asbestos fibers, say increasing numbers of scientists, may play a significant role in causing lung disease or cancer. Samples for the research were prepared by G.R Smith of the California State Health department*: Air and Industrial Hygiene Laboratory.'Lawrenci 'There are many factors that contribute to Berkeley Laboratory is operated by the Universitt environmental pollution," says Seshan. "But of California under contract with the U.S what we have shown is that brake drum dust Department of Energy. L now it's Andersen 2000 Inc., manufacturer of the Andersen widely-known Andersen samplers and Samplers control equipment line known as HEAF and CHEAF, has sold the sampler division in its entirety, including patents, tooling, manufacturing rights and existing contracts to Thomas P. Roth, who was President of Andersen 2000 Inc. for the past eight years. Mr. Roth announced that the sampler division will be changing its name from Andersen 2000 Instruments to Andersen Samplers Inc. and that plans are underway to expand the product line as rapidly as possible. Mr. Roth further stated that the sales rate this year indicates that the company will experience its best year since inception. The new company is located at 4215-C Wendell Drive, Atlanta, Georgia 30336. Phones: (404) 691-1910 and (800) -- 241-6898. A-26 Am. IM. Hn Assoc. J. (39) Apri. 197* JHM