Document 6BN0BRxBNLNx3LQRvYrXYDow9

r fr-1 o( October 2, 1978 Sir Neville Stack Asbestos International Association 63 Gloucester Place London Will 3KL England Dear Jim: Enclosed is a copy of an unsigned article titled "Automobile EraJca Linings may be a Health Hazard" that appeared in the April, 197B issue of the American Industrial Hygiene Association Journal. Also enclosed is a copy of the paper by K. Seshan referred to in the article and comments on the article and Seshan's paper by Dr. Leineweter of Johns-Manyille. It would be appreciated if you would circulate these documents to the Chairman of the Priction Materials Advisory Panel and to other association members who might have an interest in the subject. Sincerely, (Signed) John H. Marsh /as Enclosures CC: J. P. Loineweber, Ph.D. HM 07681 ...-t . -* i` i ' t- ' k,,' i Johns-Manville Sales Corporation Ken-Caryi Rancr. Denver, Colorado 0217 (303)979-1000 September 5, 197S Mr. John Marsh Director, Environmental Affairs Ravbestos Manhattan Corp. 100 Oakview Drive Trumbull, CT 06611 Dear Mr. Marsh-: The circumstances surrounding the work by Krishna Sesh%n' of the University of California on asbestos fibers released from brake linings is unfortunately very typical of the irresponsible attitude towards environmental hatards 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 tnrigTrral "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 The allegations which were originally made are unfounded and in fact, the final paper may leave a totally different impression than was created in the initial releases.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 1978 issue of Environmental Research is a relatively, straight-forward discussion on the use ot dark field electron microscopy to stud'" "deformed chrvsotile". .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 areas. 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 and particularly the health effects that have been ascribed to deformed chrvsotile fibers in the advance publicity. Many of the newspaper articles reported that experts at the Mt. Sinai School of Medicine `Jhm 07682 Mr. John Marsh Page 2 September S, 1976 had determined that deformed c'nrysotile was more biologically active than normal fibers. This is totally incorrect. In a paper by A. M. Langer, et al in the Journal of Toxicologv 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 , --- Q, Jy P. Leineweber, Ph.D. Technical Director Health, Safety & Environment Dept. JPL : j h cc P. Kotin, M.D. E. M. Fenner D. Poutiatine 07683 ENVIRONMENTAL 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. Lau rence Berkeley Laboratory. University of California. Berkeley. California 94770 ,, Received June 21. 1977 Tlie degree of microcryslalline deformation in fibers of chrysotile asbestos may be distin guished using high resolution dark-field electron microscopy. This is demonstrated by com paring undeformed chrysotile with Union Internationale Contre le Cancer (UICO standard reference samples. The UlCC 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 arake Hmm bust- [WO studies (Rohl el at.. 1976; Alste et at.. 19761 r Hickish and Knigf and earlier work (Lynch, 1968; not. The latter claim that the chrysotile is conve h temperatures attained in the braking process. 'As high resolutit je images are sensitive 'to the. degree of deformai Anguish between deformed and undeformed fibers differing sets of results. It is shown using this t os fibers in various states of deformation--relati med and recrystallized--exist in automobile brakt PARATION Four samples we pentine outcrops of reference standards fiber size (Timbrell burnishing prior to collected from the f ysotile ore samples from ser(B) slightly deformed UICC during preparation to reduce lining dust, collected during s; and (D) brake drum dust Slate vehicle obtained during brake shoe service toesnan and omith, 19//). Samples were transferred directly to Formvar-coated electron microscope grids and coated with carbon on both sides. 383 0O13-935I/78/I613-W83S0J.0O/0 Copnj( <T) {*71 pf Academic MiJiic 384 k. seshan EXPERIMENTAL As the high resolution dark field method is described in great detail elsewhere (Hirsch el a!.. 1969), only a very brief description is included here. An electron beam striking a polycrystailine specimen with grains of different orientation (e.g., A and B in Fig. 1) is diffracted into cones, causing the typical polycrystailine 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. lc). 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 will 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 at 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 era/.. 1969). This ought to result in a series cf 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 't/ Id Ftc. 1. Mustration of the high resolution dark-figld method: (a) The brighl-field image from a selected area of a polycrystal, illustrated with two grains. A and B. (b) The situation after gun till: only a portion of the diffracted intensity is collected by placing the objective aperture as shown, (cl The resulting high-resolution dark-field image with only favorably oriented grains, e.g.. B showing dif fracted intensity or "lighting up." JHM 07685 ` DEFORMATION OF CHRYSOTILE ASBESTOS . 385 Fig. 2. Illustration of the real and reciprocal lattice of a defect-free chrysolile fiber (0 and (ii) idealized as a series of concentric cylinders. The actual structure is a defected spiral sheet (Yada. 19671. The reciprocal lattice of the ideal fiber is then a series of equispaced concentric rings along the fl" axis, as in the 23d layer, when these rings intersect, the Ewald sphere (ES) spots ought to be produced as shown on the -21d 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 proccsi. When a fiber bundle (fibers of different orientations! is imaged, the layer lines are smeared out. yielding a typical "arcuate" pattern as in Fig. 3b. grdwth of the crystal. The influence of these faults on the diffraction patterns and their influence on deformation tieesis 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 a/.. 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 J H M 07686 Ftc. 3. Sample (AY. natural chrysolite, (a) and (b) Dark-Held and diffraction pattern. Notice 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 arc operative: Notice that (he canals are sometimes bright and sometimes dark. In the crystalline"part, however, the intensity is uniform and it is clear that these fibers are free of gross deformation. Chrysocile fibers, like most sheet silicates, are beam-sensitive to 100-keV elec trons (Lingerer al.. 1974; Seshan, 1975). Precaution must therefore be exercised while obtaining the high resolution dark-field images, because upon focusing the JHM 07687 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 Ftc. 4. Sample (B): UICC Standard Reference Canadian chrysotile. (a) and (bl Dark-field ima^*. that illustrate that the ball milling during the mining step converts the chrysofile into a fine-gram*y polycrystaJ. The aperture is moved from one part of the nng to another, resulting in an cntiuf; different set of grains lighting up. (c) The brighl-ficld image from which little information can K obtained. 07683 388 K. 5E5HAN 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 chrysotiie from other non-beam-sensitive materials, e.g.. the amphiboles, has been dis cussed by Langer el al. <1974). Dark- and bright-field images of deformed U1CC 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 Fic. 5. Sample (Q: Burnishing dust from an automobile brake drum prior lo 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 U1CC samples--a conclusion that cannot be inferred from the bright-field image (c). JH/m 07689 'deformation of chrysotile 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 (Dl: 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 teat). jHm 07690 390 K. SESHAN chrysolile (Fig. 3). There are also small deformation domains which clearly re semble the UICC standard (B) samples. These fibers are therefore deformed less than the UICC standard samples (Fig. 4), as some intact internal canals can still be seen. It is impossible to derive this conclusion from the bright-field range. Samples of heavily deformed chrysotile fiber found in brake drum dust are shown in Fig. 6 in the bright and dark field. Whereas the effects of deformation are not evident in the bright-field image, the difference in the dark-field image is quite striking. The crystal is inhomogeneous. This is reflected in the electron diffraction pattern, now showing a number of spots (fug. 6c). The mottled contrast of black and bright areas could arise from one of several causes: severe surface deforma tion leading to uneven crystal thickness, conversion (or "grain growth" under heat and deformation) to a large grain polycrystal, or transformation of local areas into a new crystalline phase (e.g., forsterite).' Further investigation into carefully deformed chrysotile is required to decide which it is. It is, however, quite clear that these identifying effects are associated only with the samples found in the used brake drum dust. Undeformed and unaltered chrysotile is also found in the brake drum dust collected after use (sample D, Fig. 7). This was confirmed by electron diffraction patterns which were indexed after the camera constant was cajibrated using a co-dcposited gold standard, with the following results: Used brake dust Vada (1967) diameter (A) diameter (A) hU :.6: 2.60 130 2.34 2.30 220 1.49 1.4C 005 There is also clear dark-field evidence that not all the fibers are deformed. Figure 7 shows the dark- and bright-field images of fibers found in the brake drum .-dust: the dark-field image resembles that `of the UICC chrysotile asbestos (B, '' shown in Fig. 4) and those in the unused brake lining (C, shown Fig. 5). the "grain sizes" being the same as in the UICC samples. Based upon this observation, it is concluded that a variety of products ranging from almost undeformed to com pletely transformed chrysotile products exist in brake drum dust. DISCUSSION AND CONCLUSIONS It is demonstrated that high-resolution dark-field electron microscopy can dis tinguish the degree of deformation in chrysotile asbestos fibers. In particular, it has been shown that UICC standard chrysotile has undergone microdeformation as a result of ball milling in the preparation step. The dark-field method may then be used by environmental researchers to trace the origins of asbestos fibers. The dark-field images suggest that there are significant changes in the micro structure of chrysotile upon deformation, the cystallographic and microstructural details of which are complex and are worthy of further study. There are several references to the beam sensitivity of chrysotile (Yada. 1967; Langer ei al.. 1974). The utility of using this effect to distinguish chrysotile from other non-Oeam-semsUTve materials could be of value to environmental pollution research. . JHM 07691 DEFORMATION OF CHRYSOTILE ASBE5TOS 391 Fic. 7. 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 ail the diffraction and deformation effects are to be understood. ACKNOWLEDGMENTS I thank G. R. Smith of the Air Industrial Hygiene Laboratory (AiHL) Berkeley for bringing this problem to my attention and preparing the samples. I acknowledge useful discussions with him and Dr. Walter John and thank Professor J. Washburn for encouragement. This work was supported financially by the U.S. Energy'Research and Development Administration. * `references Alste. J.. 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. 0. 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. Linger. A. M.. Mackler. A. D.. and Pooley. F. D. (1974). Electron microscopical investigation of asbestos fibers. Environ. Health Prrspect. 9. 63. Lynch. J. R. (1968). Brake lining decomposition products. J. Air Pollut. Control Assoc. 18. 824. Rohl. A. N., Langer. A. M.. WollT. M. S.. and Weisman. 1. (1976). Asbestos exposure during brake lining maintenance and repair. Environ. Rts. 12, 110. Seshan. K.. and Smith. G. R. 11977). Characterization of chrysotile asbestos in automobile brake drum 392 K. SESHAK dust by transmission electron microscopy. "Proceedings 33th Annual Meeting of EMSA.*' Claitors. Baton Rouge, La. Timbre]), V. (J969). 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 Chrysolite. Acta Crystal* togr. 21. <1615. Yada, K. (1967). Study of chrysotile asbestos by a high resolution electron microscope. Acta Crystal bgr. 23. 704. Zvyagin. B. B. (1967). "Electron-Diffraction Analysis of Gay Mineral Structures'* Plenum. New York. Automobile brake linings may be a health hazard ... Automobile 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 (L3L). 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. The substances that Seshan has been studying are thin, single fibers of asbestos -- so thin, in fact, that even the most powerful microscopes illuminated with visible light cannot detect their presence. Looking through an electron microscope -- an instrument with as much as 10.CO0 times the resolution of conventional light microscopes -- Seshan found that the minute panicles of dust created by automobile brake drums contain filaments of deformed "chrysotile" asbestos, a type of asbestos that many researchers consider a health hazard. These fibers, according to public health officials, may not be panicularly dangerous to the average citizen since peoole driving cars breathe, at mos* only small amounts of brake drum dust. Tu ' hazard of chrysotr/e asbestos, say th*' to workers such as brake repairr comoressed air to blow asbestos brakes daily and mav breathe as much particies of asbestos in each cubic me 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 asbestos fibers found commonly in air samples. This investigation, claims Seshan, was the way in which he was introduced to the health hazards of chrysotile asbestos and how he eventually turned to the problem of automobile brake drums, ^^fccording to Seshan, most automobile brakes \ operate by grinding pads against a lining of heat- ' resistant asbestos, an actionrtnat introduces wnat ne 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 con** yent of brake drum dust. But other resea'"' \ntended that the high friction ** raking simply disintegrates the es no asbestos fibers at all. ould be verified, because a ue capable of illuminating jth their defects had not yet however, solved this ig 's 'special 'Tmcruscopy Many medical experts, most notably . Selikoff of Mt. Sinai Hospital in New Y; contend that chrysotile asbestos is hazari lung tissue because such forms are mmui rougn enough to prevent the mucous coveri. the lung from dislodging it. Once in the lui \ <v \)J A roscopists term a `dark ' " of observing small jracted or "scattered" led to illuminate the | not only confirmed asbestos never dissolves. And this substance often found in the lungs of factory worker; construction workers, auto mechanics, office . lesent in automobile lovered that some of licant damage. workers and even in the lungs of spouses and children of asbestos workers. e project soon to be ic journal, ENVIRON- Asbestos is a mineral, says Seshan. And Seshan concludes "that i approximately 900 million tons of this chrysotile c .joestos fibers in various states of mineral are mined~7n the United States annually. de ..>ation -- relatively undamaged to heavily Much of it is milled or woven into a blanket-like deformed and recrystalli2ed -- exist in automobile . material, then used to insulate cr 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 A-24 mart on A-26 . . Am tnd. Hrt. Assoc. / Apni. Wl JHm 07694 BRAKE UNINGS/ASBESTOS . . . health hazard than the ordinary chrysotile form, because much of it is further deformed. And deformation in asbestos fibers, say increasing numbers of scientists, may play a significant role in causing lung disease or cancer. "There are many factors that contribute to environmental pollution." says Seshan. "But what we have shown is that brake drum dust certainly introduces deformed asbestos into tl atmosphere." Samples for the research were prepared by G. Smith of the California State Health Department Air and Industrial Hygiene Laboratory. Lawren> Berkeley Laboratory is operated by the Universi of California under contract with the U..' Department of Energy. now it's Andersen 2000 Inc., manufacturer of the Andersen widely-known Andersen samplers and Samplers control equipment line known as HEAF and CHEAP, 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. Ant Ina HiJ Anoc. 1 OSI JHM 07(3S Aort 19X1 October 2, 1978 Sir Neville stack Asbestos International Association 63 Gloucester Place London Win 3HL England Dear Jim: Enclosed is a copy o' an unsigned article titled "Automobile Brake ` Linings may be a Health Hazard" that appeared in the April, 1978 issue of the American Industrial Hygiene Association Journal. Also enclosed is a copy of the paper by K. Seahan referred to in the article and comments on the article and Seshan's paper by Dr. Laineweter of Johns-Manvilla. It would be appreciated if you would circulate these documents to the Chairman of the Friction Materials Advisory Panel and to other association members who might have an interest in the subject. Sincerely, (Signed) John H. Marsh /as Enclosures CC: J. P. Laineweber, Ph.D. fHM 076fiI Johns-Manville Sales Corporation Ken-Caryi Rancn Denver. Colorado 6021 7 (303) 979-1000 September S, 197S Mr. John Marsh Director, Environmental Affairs Ravbestos Manhattan Corp. 100 Oakview Drive Trumbull, CT 06611 Dear Mr. Marsh-: The circumstances surrounding the work by Krishna Sesha,n" of the University of California on asbestos fibers / released from brake linings is unfortunately very typical of the irresponsible attitude towards environmental hazards 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 197S issue of Environmental Research 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 areas. 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 and 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 'JHM 07682 Mr. John Marsh Page 2 September S, 1976 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 Toxicologv and Environmental Health, , 173-188 (1978), it Is stated" that: It appears that the less mechanically degraded 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. Seshan's 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 1 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 , Jy P. Leineweber, Ph.D. Technical Director Health, Safety 5 Environment Dept. JPL : jh cc P. E. D. Kotin , M.D. M. Fenner Poutiatine 07683 ENVIRONMENTAL KJEStARCM 16, 383 -392 (1978) On the Utility of Dark-Field Electron Microscopy in the Determination of the Degree of Deformation In ChrysotileJksbestos: An Environmental Research Application .' K. Seshan Department of Materials Science and Engineering, Materials and Molecular Research Division. Lau rence 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 Contre le Cancer (U1CQ standard referepce 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 Hntm Hiict- ivvo studies (Rohl et at., 1976; Alstc ei al.. 19761 r pnd earlier work (Lynch. 1968; Hickish and Knigl chrysotile is conve not. The latter claim that the h temperatures attained in the braking process. 'As high resolutit jc images are sensitive to the degree of deformai iguish between deformed and undeformed fibers differing sets of results. It is shown using this t k os fibers in various states of deformation--relati med and recrystallized--exist in automobile braki S. PARATION Four samples we ysotile ore samples from ser- pentine outcrops ol (B) sligtuly deformed UICC reference standards during preparation to reduce fiber size (Timbrell burnishing prior to lining dust, collected during s; and (D) brake drum dust collected from the f State vehicle obtained during brake shoe service (i>esnan and bmitft, 191/). Samples were transferred directly to Formvar-coated electron microscope grids and coated with carbon on both sides. m 0013-9351/7S/1613--O3S3S02.00/0 Copynffti I97t by Academic PmiXdli:. 384 K. SESHAN EXPERIMENTAL As the high resolution dark field method is described in great detail elsewhere (Hirsch el al.. 1969), only a very brief description is included here. An electron beam striking a poiycrystalline 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-resoimion dark-field method consists oftilting 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. lc). 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 will affect the diffractioa 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 a 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 scries cf spots as shown in the -2kl layer line. Streaked patterns are, however, obtained from single fibers of chrysotile (Yada, 1967; Seshan and Si.iith, 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. 1- niustralion of the high resolution dark-Gg!d method: fa) The bnght-field image from a selected area of a polycrystal, illustrated with two grains. A and B. (bi The situation afler gun till: only a portion of the dilTraeled intensity is collected by placing Ihe 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 Fjc. 2. Illustration of the real and reciprocal lattice of a defect-free chrysotile fiber (fl and (iO 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 axis, as in the 2kl layer, when these rings intersect, the Ewaid 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 {fibers of different orientations) is imaged, the layer lines are smeared out. yielding a typical "arcuate'* pattern as in Ftg. 3b. growth 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 JH M 07686 Fic. 3. Sample (A): natural chrysotile. (a) and (b) Dark-field and diffraction pattern. Notice the unusuaU)1 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. (cl Illustrates the blistering as a result of exposure to (he beam. s diffraction processes are operative: Notice that the canals are sometimes bright and sometimes dark. In the crystalline""part, 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 (Lingerer al.. 1974; Seshan, 1975). Precaution must therefore be exercised while obtaining (he high resolution dark-field images, because upon focusing, the JHM 07687 DEFORMATION OF CHRYSOTIUE ASlZSTOS 387 condenser, the fibers tend to become blistered. In the dark-field image shown tin Fig. 3aT precaution was taken to prevent any beam damage; the condenser was not focused, and the beam was tilted in the dark field inode. The condenser was then Fic. 4. Sample (Bl: UICC Standard Reference Canadian chrysotiie. (a) and tbl Dark-Held imag* that illustrate that the ball milling dunng the mixing step converts the chrysoiilc into a fine-gram^ polycrystai. The aperture is moved from one part of the ring lo another, resulting in an cnttu-l', different set of grains lighting up. (c) The brighl-fieid image from which little information can K obtained. JHM 0768S 388 K. SE5HAN 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 Langer el at. (1974). Dark- and bright-field images of deformed UJCC standards (B) are shown in Figs. 4a-4c). The effects of deformation are cleariy s'een in the dark-field images (4a and 4b) and in the electron diffraction patterns but not in the bright-field Fig. 5. Sample (O: Burnishing dust from an automobile brake drum prior to installation, (a) Dark field. (b> diffraction pattern, and (c) bright field. Notice the weU-preserved canai which show* Up <fhe 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>. JHi\i 07689 DEFORMATION OF CHRYSOTILE 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 dear 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 (O 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 (Dl: Brake drum dual after use in a slate vehicle, (a) Bright field and (b) dart field. Although the bright field is not distinctive, the high-resolution dark field and the selected area difTraction patterns are remarkably different. The crystal is quite inhomogeneous with very large grain sizes; this can happen for a varicily of reasons (see test). jHm 07690 390 K. SESHAN chrysotile (Fig. 3). There are also small deformation domains which clearly re semble the UICC standard (B) samples. These fibers are therefore deformed less than the UICC standard samples (Fig. 4), as some intact internal canals can still be seen. It is impossible to derive this conclusion from the bright-field range. Samples of heavily deformed chrysotile fiber found in brake drum dust are shown in Fig. 6 in the bright and dark field. Whereas the effects of deformation are not evident in the bright-field image, the difference in the dark-field image is quite striking. The crystal is inhomogeneous. This is reflected in the electron diffraction --pattern, now showing a number of spots (Fig. 6c). The mottled contrast of black and bright areas could arise from ope of several causes: severe surface deforma tion leading to uneven crystal thickness, conversion (or "gTain growth" under heat and deformation) to a large grain polycrystal, or transformation oflocal areas into a new crystalline phase (e.g., forsterite).' Further investigation into carefully deformed chrysotile is required to decidi which it is. It is, however, quite clear that these identifying effects are associated only with the-samples found in the used brake drum dust. Undeformed and unaltered chrysotile is also found in the brake drum dust collected after use (sample D, Fig. 7). This was confirmed by electron diffraction pattems which were indexed after the camera constant was cajibrated using a co-dcposited gold standard, with the following results: Used Craxe dust Yada (1967} diameter (A) diameter (A) hkl 2.62 2.60 no 2.34 2.30 220 1.49 \.4C 005 There is also clear dark-field evidence that not all the fibers are deformed. Figure 7 shows the dark- and bright-field images of fibers found in the brake drum _idust: the dark-field image resembles that of the UICC chrysotile asbestos (B, ' shown in Fig. 4) and those in the unused brake lining <C, shown Fig. 5), the ''grain sizes" being the same as in the UICC samples. Based upon this observation, it is concluded that a variety of products ranging from almost undeformed to com pletely transformed chrysotile products exist in brake drum dust. DISCUSSION AND CONCLUSIONS It is demonstrated that high-resolution dark-field elecrfott microscopy can dis tinguish the degree of deformation in chrysotile asbestos fibers. In particular, it has been shown that UICC standard chrysotile has undergone microdeformation as a result of ball milling in the preparation step. The dark-field method may then be used by environmental researchers to trace the origins of asbestos fibers. The dark-field images suggest that there are significant changes in the micro structure of chrysotile upon deformation, the cystallographic and microstructural details of which are complex and are worthy of further study. There are several references to the beam sensitivity of chrysotile (Yada. 1967: Langer el a!., 19741. The utility of using this effect to distinguish chrysotile from other non-beam-sensitive materials could be of value to environmental pollution research. . JHM 07691 DEFORMATION OF CHRYSOTILE ASBESTOS 391 Ftc. 7. 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 deformation 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 J. Washburn for encouragement. This work was supported financially by the U.S. Energy'Research and Development Administration. - , 'references Alste. J.. 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. //yg. 13. 25. ^Htckish. D. E.. and Knight. K. L. (1970). Exposure to asbestos during brake maintenance. Ann.- Occup. Hyp. 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. (J968). Brake lining decomposition products../. Air Poliut. Control Assoc. 18, 824. Rohl. A. N.. Langcr, A. M.. WolfT. M. S.. and Weisman. I. (1976). Asbestos exposure during brake lining maintenance and repair. Environ. Rex. 12, 110. Seshan. K.. and Smith. G. R. (1977). Characterization ofchrysotile asbestos in automobile brake drum 392 K. SESHAN dust by transmission electron microscopy. "Proceedings 35th Annua) Meeting of EMSA." Claitorz. Baton Rouge. La. Timbrel!, V. (1969). Characteristics of the international union against cancer standard reference samples of asbestos. Pneumoconiosis. In "Proceedings Internationa) Conference oo Pneumoconiosis. Johannesburg," p. 28. In Oxford Univ. Press, England. Whittaker. E. J. W. (1966). Diffraction contrast in electron microscopy of Chrysotile. Acta Crystallogr. 21, 46)6. Yada. K. (1967). Study of chrysotile asbestos by a high resolution electron microscope. Acta Crystallogr. 23, 704. Zvyagin. B. B. (1967). "Electron-Diffraction Analysis of Clay Mineral Structures" Plenum. New York. Automobile brake linings may be a health hazard ... Automobile brakes --- normally associated with averting danger -- may, in fact be producing dangerous substances and releasing them into the atmosphere, according to a researcher at the University of California's Lawrence Berkeley Laboratory (L3U. The concern is being expressed by Krishna Sesnan, a materials science engineer at LBL's To date, Seshan estimates, about 90 percent of the asbestos used in the United States is milled under heat and pressure. And. because of these processing methods, most of the asbestos we breathe is deformed in some way or another. Still, many medical researchers in the U.S. have ignored the health problems connected with these 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. The substances that Seshan has been studying are thin, single fibers of asbestos -- so thin, in fact, that even the most powerful microscopes illuminated with visible light cannot detect their presence. Looking through an electron microscope -- an instrument with as much as 10,COO times the resolution of conventional light microscopes -- Seshan found that the minute particles of dust created by automobile brake drums contain filaments of deformed "chrysotile" asbestos, a type of asbestos that many researchers consider a health hazard. These fibers, according to public health officials, may not be particularly dangerous to the average citizen since people driving cars breathe, at most only small amounts of brake drum dust. T*' hazard of chrysotile asbestos, say th*' to workers such as brake repairr compressed air to blow asbestos brakes daily and may breathe as much panicles of asbestos in each cubic me Por 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 asbestos fibers found commonly in air samples. This investigation, claims Seshan, was the way in which he was introduced to the health hazards of chrysotile asbestos and how he eventually turned to the problem of automobile brake drums, ^^ccording to Seshan, most automobile brakes f operate by grinding pads against a lining of heat- | resistant asbestos, an actton~tfiat introouceswnat 1 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 con^^ient of brake drum dust. But other reseat intended that the high friction A Yaking simply disintegrates the [e$ no asbestos fibers at ail. ould be verified, because a ue capable of illuminating ith their defects had not yet however, solved this rig a special microscopy Many medical experts, most notably . Selikoff of Mt. Sinai Hospital in New Yv contend that chrysotile asbestos is hazan lung tissue because such forms are mmut rougn enough to prevent the mucous coveri. the lung from dislodging it. Once in the lut i Yoscopists term a "dark of observing small fraeted or "scattered" led to illuminate the * not only confirmed asbestos never dissolves. And this substance often found m the lungs of factory worker, . lesent in automobile tovered that some of construction workers, auto mechanics, office licant damage. workers and even in the lungs of spouses and children of asbestos workers. - -*%Li. e project soon to be Hie journal, ENV1RON- Asbestos, is a mineral, says Seshan, And Seshan concludes "that ^ approximately 900 million tons of this chrysotile c -dOestos fibers in various states of mineral are mined~in the United States annually. de ...ation -- relatively undamaged to heavily n Much of it is milled or woven into a blanket-like deformed and recrystailized -- exist in automobile l. material, then used to insulate or firsoroof 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 A-24 mor on A-26 . . Am. fntf. Hyg. Assoc. J. (3$) Apnl. 1978 JHm 07694 BRAKE UNINGS/AS8EST0S . . . health hazard than the ordinary chrysotile form, because much of it is further deformed. And deformation in asbestos fibers, say increasing numbers of scientists, may play a significant role in causing lung disease or cancer. `There are many factors that contribute to environmental pollution." says Seshan. "But what we have shown is that brake drum dust certainly introduces deformed asbestos into i atmosphere." Samples for the research were prepared by G Smith of the California State Health Oepartmen Air and Industrial Hygiene Laboratory. Lawref Berkeley Laboratory is operated by the Univers of California under contract with the U. Department of Energy. i> now it's Andersen 2000 Inc., manufacturer of the Andersen widely-known Andersen samplers and Samplers control equipment line known as HEAP and CHEAP, 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 __ 30335. Phones: (404) 691-1910 and (800) 241-6898. A-K m Hrt. *aoc- J. OS) Xori. 1971 JHM 0763s