Document gY9yj7EQzr4b3OZejzeVevoN

. ~n/l LXl . A*-A A/. ____ ^4iAV 05 1983 ASBESTOS IDENTIFICATION ^ AND MEASUREMENT 5-^3 ROCEEDINGS OF A TOPICAL SYMPOSIUM APRIL 9, 1979 OES PLAINES, IL I. Sponsored by THE AMERICAN CONFERENCE OF GOVERNMENTAL INDUSTRIAL HYGIENISTS i I % 4. Lynch, J.R. and H.E. Ayer Meaaurement of Dust Exposures in the Asbestos Textile Industry. Ain. Ind. Hyg. Assoc. J- 27 (September/October 1966). 5. Edwards. R.G. et ai Dust Counting Variability. Am. 7nd. Hyg. Assoc H. 27 (November/December 19681 6. Lynch. J.R. and J.E. Ayer Motes and Fibers in the Air of Asbestos Processing Plants and Hygienic Criteria for Airborne Asbestos. Reprint from Inhaled Particles and Vapor* II (proceedings of an internal symposium organised by the British Occupational Hygiene Society). Pergamon Press, NY: 1966. 7: Orable. J.V.: Quantitative Determination of Chyroolile, Amosite, and Craddolite by X-Ray Diffraction. Am. Ind. Hyg. Assoc J. 27 (MayJane 1966). 8: Lynch. JJL and H.E. Ayer Msaaonment of Asbestos Exposure J. of Occupational. Medicine 10 (January 19681 9. Edwards, G.H. and JL Lynch; The Method Used by the USPHS for Enumeration of Asbestos Dost on Membrane Filters. Am. Occupational Hyg. 2: 1-4 (Psrgamon Press. 19ttL 10. Renahaw, PJt et ab Urn Use of Midget Impingers and Membrane Filters for Determining Particle Counta. Am. Ind. Hyg. Aston /. (Mmch/April 19681 11. Keenan. R.G. and JJL Lynch: Techniques for the Detection. Identification, and Analysis of Fibers. Am. Ind. Hyg. Assoc. J. 31 (September/October 19701 12. Lynch. JJL et ak The Interrelationships of Selected Asbestos Exposure Indices. Am. Ind. Hyg. Aasoe. J. 31 (September/October 19701 131 Occupational Kxpotute to Asbestos. NIQSH <19721USGPO HSM72-1<067. 14. LFE Corporation: StatisticalEvaluation ofthe Procedure for Counting Asbestos Fibers on membrane Filters. Report submitted to the Asbestos Information Assoc, ofNorth America, Suita 16-11.22 E. 40th St. New York. NY 10016. 15. Symposium on Electron Microscopy of Microfiber*. August 1976. USGPO 017-012- . L . j-mot eoetnoa tor Estimating Airborne Asbestos Dust. October 1976 Secretary. N.H. & M.R.C., P.O. Box 100, Woden. , C"*"**. A.C.T. 2606, Australia. 17- "fj**"* Recommended Asbestos Standard. DH^P 77 lS"ber 19?a USGPO N108^ 18. Zumwalde, R.D. and J.M. Dement: Reviewand Evaluation of Analytical Methods for Environmental Studies of Fibrous Particulate Exposures. USGPO NIOSH-DHEW 77-204. May 1971 - 19. Baron, P-A^ PhJX: The Use of Light Scatteringforthe DetectionofFilter Samples of Fibrous Aerosols. DH2V NIOSH 78-105. Jaaaasy 1978. 20. Lsvino. IU, BID. (editor): Asbestos: An Information Resource. DREW N1H 79-1681. May 197& 21. Samudra, A.V. et aL Electrr.. Microscope Meaaaramant of Airborne Asbestos Concentrations--A Provisional Methodology Manual. EPA 600/2-77-178. Rarissd Jane 1978. 22. Gmvatt, C.C. et ah Proceedings of Workshop on Asbestos: Definitions and Measurement Methods. NBS Special Pah. Number 506.' November 1978. 23L Iaide). NA et ah USPHS/NWSH Filter Method far Bvnlaating Airborne Asbestos Fiber*. DKEW NIOSH 79-127. February 1979. Evaluation of Asbestos in Insolation DR. WALTER C. McCRONE McCrone Research Institute. Chicago. IL The Enviwmaentoi Protection Agency has undertaken the fourrfination of a nationwide effortto elinrinateapoaaihlsthroattothehealthof drool children poaad by the past uas ofaabestoscontaining materials in thenotion's schools. The purpose. eatanL and tMasafttdo effort can bebest ascertained by contacting theEPA(80Q/424-9065; in Washington. DlC. caD864-1404). It Is therefore important to have the tools and tachniqnea available for rapid and dependable analysis of insulating, sound-proofing, and other materials used in schools for sshestiform minerals. The task of (denning up the nation's schools makes Hercules* took of denning the Augean stables seemlike a Sunday picnic,and thecortwill be monumental. Each school and each materialin each school most bo considered by informed experts who can decide tbs best solution to the problem. Removal is very costly and conld, in some cases, actually increasethehazard. Leaving wdlsnoo^h alone shouldbethe recommendation unless contraindicated, for mm:--pt by high friability as a high probability of ifistubance. Then sncapanlation (sealing in with spray finishes) or isolation (such asinstalling a lowered ceding) aboold be considered. Bach situation must, however, be considered huSviduaDy. Anyone who must decide what to do must have reliableinformation on which tobase his decision. In particular, ho mart know the composition of each passible asbestas-caatainuig material. Ideally, he should know: 1. what asbeetifann substances are presents; 2. in what proportion; 3. what other substances an present (eg.. ceDolosic fibers, mineral wool, other glass fibers, vermiculile. talc; perlite, diatomaceoos earth, organic fibers, days, glass powder, quartz, gypsum,* tc.h and 4. size ranges for each substance. 5 LLA 002049 The third of these points is important because some ofthese substances are already known to be unbealthful and, the way matters are going, the others may well be declared hazardous in the future. Knowing what is present permits a more intelligent evaluation of the overall situation and may eliminate the need for a later more complete analysis. Even the chemical analytical problem is formidable and many laboratories will be involved. McCrone Associates' twolaboratoriesin Chicago sod London have analyzed thouranda of samples of insulation, acoustical tDe, wallboard, and other construction and decorative materials. Our staff has sampled hundreds oflocations and advised many of the institatiops involved as to what we think they should do based on our analyses. Finally, the McCrone Research Institute leaches the methods wo fed best serve the analyst who wishes to analyze `these materials. Polarized light microscopy Our method of choice is polarized tight microscopy. There is. in fact, no other method capable ofdoing the job. Even the minimal jobof detecting chrysotOe. amoeite, and croridolitecan only bo dan* microscopically. Certainly the identification ofground glass, mineral wool,glass wool, diatomaceous earth, micas, days, perlite, Lizardite, antigorite, other amphiboles. ceUolosic fibers, organic fibers, etc. requires the microscope. Part of the reason ia that almost the only differences between many substances are microscopic shape or optical features: e.glixardite, antigorite. and chiysatQe; perlite, diploma, and quartz; cotton, wood fibers, and linen; or silk, human heir, and horse hair. X-ray diffraction may help in some cases butit does not differentiate between fibrous and nonfibrous varieties of the same minerals. Furthermore, it cant identify amorphous snhstaucsa such as diatoms, partite, glass or cTganic fibers; nor is it useful fur particle size mesenement All ofthese analyses are quickly accomplished microscopically. Another season ia that asbestne minerals were discovered, characterised, and namedbeforex-ray or alectron diffraction and other modem instrumentalmethods were invented. In fact,only rfisminl analysis and microscopy wen then available; the dttferantiatian of the various amphihnlto and the three eoiplentinencanonlybe quickly, confidently, and concinaxvdy done by piinMii tight mtfiuHV|iy The determination of chemical composition is net very practical on single-particles ia a mixture even aside from the fact that many different substances can have identical chemicalcomposition,e-g. riebeckiteand croridotits; granerito or cummingtonite and amosila; lizardite or antigorite and chrysotfle; fibrous and nonfibrous tremoKle, fibrous and nonfibrous actinolhe. or fibrous and nonfibrous feriruactinotite. Sampling The first and a major problem faced by the mirroccopist is sampling. Insolation, especially in microscopic samples, is far from a uniform material containing a precise percentage offibers throughout The wide variation often found in the results from different laboratories or even the same laboratory can in most cases be explained by sample variation. The initial sample should be large enough to be representative and the microscopist must make every effort to take a representative milligram range sample. This is very difficult A sampling procedure recommended by the EPA that works very well for friable samples is to press a 35 mm film cannister completely through all layers to yield a core of material. This cannister should be carefully labeled and sent to the laboratory. Then each sample should be divided in half(with careful attention to layering if present). One-half(after drying and weighing) should bo placed in a small 100 ml beaker with about 50 ml of 10% HaSO*. Only the cementicious campcmentswfll dissolve, leaving the fibrous and other more Inert materials in suspension. The latter can be showed to settle forseve.nl minutes, the solution decanted, and water washed by nsuspensian and deamiatioa several times. Finally, the washed particles shoold be resuspended by agitation to give a uniformly mixed composition. A few drops can then be removed by eyedropper and several onodrop samples can be placed on microscope slides. These; after drying, can be need farmicroscopical identification of the partvrlea present. To give more quantitative results the remaining sample, after rexwval of the eyedropper samples, should be filtered, dried, and weighed. This will allow calculation ofthe ftcementicious materialand, by nticroecopy on the residue, the percentages of the When the budget allows, the above procedures would yield mare accurate and more reproducible quantitative results, la most cases, the budget does not permit the horary of doing each a complete job InirirH the original ounce sample submitted to the laboratory ia usually sampled at 10-20 . regularly spared locations with fine forceps, and I the accumulated sample is dispersed on a microscope slide hr an appropriate iounermion liquid. It is the variation in composition of such samples ftsa lands to corresponding variations in analytical results. One should expectthat repoat analyses made ia this waymay vary fay up to 50%. Any single1-5 mgsampleoften no asbestos in <M|irl*i containing as much as 50% of that substance in the overall sample. Identification Nomatterhow tbofinalmicroscopepreparation is obtained, we now have the problem of identifying each component. This iabest doneby dMil pihdwil fight methods together with dispersion staining; a specialized petrographic procedure A well-trained mineralogist may not need dispersion staining although most would find it easiur to apply to asbestos identification than classical optical crystallography. Any microscopist not trained in mineralogy will find dispersion staining far simpler and, indeed, the 6 aft 002050 only method that can be'learned in a 3*6 day coarse or an one's own in any reasonable time. substitutional solid solution--in this hh Fe**1 with Mg1* --can cause d , $, and ^ to vary. Are aabestiform minerals present? Generally, this means--Is chzysotile, amosite (fibrous' cummingtonite or grunerite), or crocidolite (fibrous riebeckite) present? The actual analysis proceeds by adding a Cargille refractive index liquid (nO 1.550. high dispersion) to one of the slide samples after complete drying. The particles should be dispersed in this liquid by tearing aggregates apart, using two fine needles before covering with a coveralip. In this Squid, chryeotile has distinctive shape--very fine flexible fibrils (often curly) pins straight handles of such fibrils--and distinctive dispersion staining colors*--usually blue-magenta parallel to the fiber axis and blue perpendicular. Different samples of chryeotile. however, may vary somewhat in/fe, the wavelength at whichparticle and liquid have thesamerefractiveindex.Parallel to the lengthArranges from about 440-560nm and perpendicular to the length from about 5604360 ansb form-nii is usually dose to 100-120 ms. The presence of chrysolite and other fibrous particles often obscured by a covering oflarge numbers of other particles. This is eaparially troublesome because most such particles an so different in refractive index from the mounting liquid that they appear bright white with tbs central stop. Trying to see the asbestos is like trying to set white driving at night with an oncoming stream of can with high-beam headlights. Often one can bo pretty sure the Although the refractive indices of amosite and other amphiboles may vary over a wide range, most of these minerals are not from commercial sources. Nearly all amosite actually used in insulation commercially has the opticalproperties given above. It in liquid>0*1.680 low birefringentfibers show lower go colors close together in the yellow to golden magenta, crocidolite is strongly indicated. Ifthey ahow a negativeaigu ofelongation (higher ^parallel to the length) and blue absorption colors with pleochroism (blue parallel, gray-blue perpendicular), crocidolite is present. Further confirmation can be obtained by mountinga third cample in Cargille refractive index liquid xO*t CroddoBte will show go colors doss to 485 nm (golden magenta) parallel to the length and about 455 (golden yellow) perpendicular. Again, some parallel movement of tbeAd.*f colon should be expseted teraroddofites from difterant sources. Weahouldemphasise thatdispersion stainingis method farrapid refractive lades detmwiii/m To ho certain tha colon obssrved n a particular asbestneia present one mustbe certain the dispersion staining data an coaafeteat with particte rise and shape as *&aa thardatieouhip between tha optical properties and the crystallographic axes. With samite. far example, the crosswise index must be Cv oblique extinction views and a forviewsshowingparallel particles are covering obscured fibers because of their pattern. 1 have described this as the milky Are other aabestiform minerate present? way effect. Sometimes a stray fibril may poke its way outintotheliquid to showdispersion staining It during tbs above examination, anomalous results wereobserved, thatis,highly fibrouswith colors. It is always a haip in sueh situations to * colors in other than the proscribed ranges for examine the "milky way" with crossed polars chrysotile, amosite, v>d croddoBte. then fibrous since the underlying fibers often thou become tremofite. fibrous --tinolite, or antfaophyllitemay visible and recognizable as fibers. Grossed polars also brip to locate smaller fibers and small he present Those are rarely found, however, in inmtoiwi When these anomalous results woo percentages of fibers. Every sample should be obtained, youshould havacharacterisadthafibets I quickly scannsrf with croeeod palms bribes the absence of asbestos is reported. in those Bquida as to refractive indices rristivt to those Squids and rrHnrtion angtea IfaD of the Amosite and crocidotits ara both vary pals y-n--. i-- fibers ahow parallel extinction, they are .ifthe pose I in liquid 1.560. because thairnfractivsindicae are so much higher. Crocidolite. of eoun Tremolite will ahow strong cokes in sQ usually shows a Use sheasprion color. If i orientations in 1.605 high dispersion Squid. Tbs anisotropic fibers with refractive indict obliqueestinctioo view(ca. 15-18)*)willsnow higher than 1JS0 are present, the analysis is perpndBcolsrbucn. 440run; ydtew)sndg nearly oomctetecl parallel ( go ca. 680 nm; pate blueX Tbs psroilsl If bightT index anistropic fibers are present, extinction viewshows |* parallri tothelength (go another simple is mounted in CargiBe Squid nD ca. 480 run; golden yellow)and 9 psrpsndiadsrCle =1.680 ant examined with *t*"8-- staining. Most animate* used far buildings will show s leaf ca. 530 nm; rod magenta). ActinoUte has similar1 morphology and optics about 460 nm(goldenyritow)paralleltotbsingth and about 600 nm (blue-mageuta)> 660 nm (prie blue) perpendicular to the length depending on except that the indices an aD higher than tremoBte. ActinoHte may also show ptenchmam (green to colorless). It is beat stwfiad in high fiber orientation. A pcrpenoicalar O&660 nm dispersion liquid 1.630 in which 4 and f oaths corresponds to the at vibration direction which obfique extinction view show magenta (a* ca. 50 usually shows oblique extinction of about U'xb 600nro perpendicular to the length corresponds tod nm) and gulden ysDow ( As cn. 445 nm), respectively. On the parallel extinction view t* on the view showing parallelextinction. Higher ar lower values for any one of the three vibration directions should mean higher or lower values for all throe As with most silicate minerals. Oengthwise) shows * ca. 470 am or golden magenta and d (perpendicular)shown fteca.496' nm. also golden magenta although with more red. Tremolite, actinolite, and fenroactinolite are The dispersion staining colors mentioned throughout this paper are those obtained by using the central stop rather than the annular. - Lift 002051 sf I parts of a continuous solid solution ssriss in ths same manner as ths amosite minerals, cummingtonite and grunierite. The name to use for a given amphiboie depends directly on the optical properties, as shown in Table 1. Identification of interfering substances A few common substances show dispersion staining colors similar to those ofchrysotile, and some are elongated as well These include ontigorite and Ussrdite (polymorphs of ebryso- tiltl, quarts, tale, paper fibers, and hairs. AH of thsss show dispersion staining colors in 1.550and til except talcand paperfibers show colorssimilar to chrysotile. Antigarit* in 1.550 high disperxion liquid shows Xfor .parallel to ths length, aboot 485 nm (golden ysllow),;uft>rffand* crosswise ore ca. BOO nm (gulden magenta) and 520 on (red- magenta), respectively. Utnrdito is plstdflv (often a lamellar aggregate) with* (fecai 100 ntn. pale blue) perpendicular to the plate; it generally hours undulose extinction. Thed and jr indiceslie in the plans of the plots and both shows near5'0 nm in the UiO diapaision liquid (rad magenta). Quarts, although usually glassy flaksa, shows bins and msgsntacsntnd atopcolors very similar to cbrysotOe in the 1J5J50 liquid. Theshape ia very different. however, and someisotropicviewe show only blua Talc fibsn are derived by cleavage from large talc plates; I turva never seen rolled tak plated aa fiber*. Thedispersion staining colors aretherefore always verypole yellow (fees. 360 nm) parallel to the length. Iliey may aleo showJexSfiOnm farthe perpendicular dneto but, if an edge, they wfll haw* *645nm (blue-green). Tapping gently on the covanfip with a needle will usually bounce these needleefrom the380-380nm view tothe360645 nm view. This ia a very useful technique far quartz and other mineral grains aawelL Animal and human- hair may also have refractive indices in the same range ae chrysotile, and if finely fibrilated, by electric razor for example, can be confitsiagly similar. Such fibrilated fibers an, however, ran; they also usually show mdanin pigment particles and sufficiently different indices to avoid confusion. Paper fibers also show a crosswise index dose to 1J6 (but lower) and the lengthwise index is much higher, hence shows a yellow color. Usually also the morphology of paper fibers is distinctive. Identification of other asbestos substitutes A number of substances an often used as aabsatns substitutes, ag. wollsstonits, glass wool, mineral wool, polyester and paper fibers. WoUastomt*. a low birefringant (1X014)mineral, ia tridiuk sad thereforeshorn obUqut extinction in all views. U boa refractive indices ha the same range aa UemoBta and authaphyBito but, fD*fuoatel?v1lis 4 index is nearly parallel to the length, hence eomeviewe show positive and soma negative signs of elongation (anthophyOite and tnimolite always show a positive sign). The dispersion staining colonfarwoHaatonftainiJOS liquid art: parallel, 429 nm (yellow); perpendicular. 410 nm (pole yellow), end 632 nm (red-magenta). Gloss fibers, usually aa mineral wool, an often found in insulation. Different samples vary widely in refractive indsa and may show diapenioa staining colon bi any oftbo standard Uqatda from 1.55 to 1.6& Generally, however, minersl wool has low indices < 1.55, and is often coated with a colored (yellow, orange to red) resin. It is always isotropic or very slightly Ureftingent due to strain. Another unusual constituent found in seven] recent samples ia a polyester fiber. Hie very high birefringence, uniform cylindrical crossaction, and conaManbla length make fids easy to distinguish. The radices am about 1.53 TABLE I Optical Proportion of tbo Amphibolm CN Mineral Refractive Indices O5 Extinction Sign (aver.) angle elonre'u optic Tresolite 1.603-1.620 1.627-1.642 0.023 19-21 + - 86-80 Actinollte 1.620-1.667 1.642-1.686 0.020 15-19 + - 80-70 Ferroactinolit* 1.667-1.683 1.686-1.702 0.019 10-15 + - 7C-65 Cusinctoaiee 1.633-1.664 1.654-1.687 0.022 15-21 + + 103-92 Crunerite 1.666-1.686 1.687-1.729 0.933 10-15 92-82 Klebeckltc 1.654-1.698 1.666-1.712 0.014 10-20 - - 40-90 Anthophyllit 1.606-1.648 1.626-1.670 0.021 0 * 66-120 \ : i 8 002052 lib perpendicular (lees than chprsotile) and 1.71 parallel (greater than crocidolite). Identification of other poaaihle nonfibrous constituents of insulation Possible additional constituents of insulation etc. include ground glass, perlite(a heat-expanded volcanic lava), diatomaceous earth, vermiculite, and mica. Of these, ground glass, perlite, and diatoms are isotropic and characteristically shaped. Vermiculite, a clay, and the micas are very thin, flat plates often nearly isotropic but with turned-up higher birefringent edges. Vermiculite will have indices less than 1.55 and the micas above 1.55 and often above 1.605. If colored brownish-gray the mica is biotite with higher indices than colorless muscovite, another common mica. til Other materials may well be found as time goes on but the observations made during the analytical procedure described above should uncover such substances, since they will not fit the data given here. All things considered, a careful microscopiat, confident with dispersion staining, should have no difficulty in identifying asbestos and most other substances associated with it. Acknowledgement Although folly responsible personally for the ideas expressed here, the author acknowledges with gratitude the constructive appraisal by his colleagues at McCrone Associates: John Deity. Lucy McCrone. Mark Paknik. and Ian Stewart Asbestos and the Electron Hicroacope IAN M. STEWART Manager, Electron Optics Group, Walter C. McCrone Associates, Inc* Chicago, 1L I first learned aboutthismeetingtwoweeksago, when I saw the provisional program, and my immediate reaction was that the ACGIH was going to wish oa us in electron microscopy the name "raw deal,'* if1 may call it that as they had wished oa us with light microscopy. 1 noted that there was to be a paper on the use ofthe scanning electron microscope to characterise asbestos but not one on transmission electron microscopy. 1 felt that this eras similar to using phase contrast microscopy to tackle a mineralogical problem which is more appropriately tackled by a petrographic microscope, so I called Mr. Kelley to ask tom what he was doing to us. He very kindly suggested that 1 come along and present my views in the general discussion at this meeting and so 1 came prepared with one or two slides to do this. When 1 arrived, however. Jim Ferguson told ms that I was to present my views a little more formally, so hoe they are. Criteria for Asbestos identification Let me say from the outset that 1 should not be regarded as an antr-scanwmg electron microscope man. There are many stiuations in which the scaning electron microscope is the appropriate too! to use, but I do not believe that the asbestos situation is necessarily one of them. My reasons for saying thisarethat, likeDr. McCrone. 1 behave that the main criteria by which one must identify asbestos are crystallographic with chemistry as a secondary consideration, and the scaninng electron microscope is unfartunatly lading in its ability to give crystallographic characterization from particles oftire sizes which are going to be of interest to oa. An additional problem in many scanning electron microscopes is that of resolution. Although manufacturers currently will claim that resolutions are better than 100 A (10nm) for their microscopes, they do reserve the right to select the specimens on which they demonstrate this resolution, and their samples are generally those with very clearly defined features and very high contrast This situation does not normallyprevail with asbestos fibers down to unit fibril dimensions. Having brought in tha term "unit fibril.'' let me define it This term is applied generally to ctoryaotfle asbeatoa. It ia the smallest chryaotile fiber which can existas a singleentity and has an approximate diameter of 3Q&8SQ A <30-35 nmk Fibers of tneae dimensions are quits common in environmental samples but onedoes generally see larger fibers in the workplace. However, as control procedures improve; it is to be hoped that the larger fibers will be less prevalent in the workplace, in which case we wiD have to concentrate on the very fine fibers which are not visible and thus cannot be characterized by the light microscope. How tha do we go abaut characterizing these fine fibrils with the electron microscope? As I have mentioned, the principal criterion ia a crystallographic one. Bower, one may summarize the three main criteria for identification of a fiber as asbestos under three headings: morphology, crystallography, and chemiatry. Morphology Clearly, since yon are interested hi controlling asbestos fibers, the particle ia question must have the morphology ofa fiber. I wOl not at the present time go into the various semantics of defining a fibs. But I sri0 say that, at tins time, everyone concerned with this problem is utilizing (I almost said accepting) the federaldefinition ofa fiberas a particle with an aspect ratio greaterthan 3:1. Itia quite possible that this may stimulate some discussion. However, though one may argue the semantira ofa fiber from a mineralogist's point of view, the final criterion to decide what will be called a fiber for regulatory purposes mustonlybe the biological significance ofthe particles's aspect ratio This is a subject on which I am notqualified 9 LLA 002053