90B The identification of asbestos in bulk samples by

Kenneth S Basden BSc, PhD, ASTC, CPEng, CChem, MIE(Aust), MRACI, MAusIMM, FInstE, FAIE

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Author information Kenneth Spencer Basden has the following qualifications: ASTC (Associate of the Sydney Technical College majoring in Mining Engineering – Geology – Metallurgy, 1950); BSc (Applied Chemistry, UNSW, 1954); PhD (Mining Engineering, UNSW, 1960) and is a corporate member of the following professional institutes: member – Institution of Engineers, Australia; member – Royal Australian Chemical Institute; member – Australasian Institute of Mining and Metallurgy; fellow – The Institute of Energy (UK); and fellow – Australian Institute of Energy. He is a Chartered Engineer (UK), and a Chartered Chemist and Chartered Professional Engineer in Australia and an active member of a number of other learned societies. After working at the BHP Steelworks, Newcastle in several departments, in 1951 Dr Basden joined the University of New South Wales as a Technical Officer in the School of Mining Engineering and Applied Geology. He was appointed Lecturer, Mining Engineering in 1954 and a Senior Lecturer in Fuel Technology, School of Chemical Engineering and Industrial Chemistry in 1964. In 1986 he was appointed a foundation Senior Lecturer in a newly-established Department of Mineral Processing and Extractive Metallurgy in the School of Mines before retiring in February 1987. Before retirement Dr Basden taught and examined in over 40 individual subjects in mining engineering, chemical engineering, fuel technology, applied chemistry, mineral processing and mechanical engineering, and in the Departments of Mechanical Engineering at Sydney University and the University of California, Berkeley. He also has published numerous papers and has supervised and examined many Masters’ and PhD theses. Since retirement Dr Basden has been an active consultant through the University of New South Wales. His areas of expertise are in workplace atmospheres (largely concerning asbestos exposure where he appears for plaintiffs on matters of foreseeability and preventability), ambient and indoor air pollution and design performance of industrial air pollution control equipment. Dr Basden can be contacted at: PO Box 148 LAWSON NSW 2783 AUSTRALIA Telephone: 61 (02) 4757 3156 Fax: 61 (02) 4757 3704 Email: [email protected]

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TABLE OF CONTENTS

THE IDENTIFICATION OF ASBESTOS IN BULK SAMPLES Introduction ................................................................................................................... [90B.70] Points of relevance for members of the legal profession .......................................... [90B.100] The nature of asbestos .............................................................................................. [90B.130] Mineralogical principles of use in asbestos identification .......................................... [90B.150] Sample examination ................................................................................................... [90B.250] Concluding comments ................................................................................................ [90B.340] Addendum 2009 ......................................................................................................... [90B.400] Australian Standard AS 4964–2004 ................................................................... 90B.415 AS 4964–2004 Appendix B ................................................................................ 90B.415

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ABBREVIATIONS

Abbreviations ACGIH ............................................American Conference of Governmental Industrial Hygienists AHERA ...........................................Asbestos Hazard Emergency Response Act (USA) AIHA ...............................................American Industrial Hygiene Association ASTM ..............................................American Society for Testing and Materials EDAX ..............................................an acronym for “energy dispersive analysis by X-ray”, and now is believed to be a trade name owned by a particular manufacturer of electron microscopy equipment. (See next entry, and WDS later in this tabulation.) EDS..................................................an acronym for “energy dispersive spectrometry”, and is a term used in preference to that of the entry above when using equipment not manufactured by the owner of the EDAX trade name MMMF ............................................Man-made mineral fibres NATA...............................................National Association of Testing Authorities Australia NIOSH.............................................National Institute of Occupational Safety and Health NVLAP............................................National Voluntary Laboratory Accreditation Program (USA) OSHA ..............................................Occupational Safety and Health Administration of the US Department of Labor PLM.................................................polarised light microscope or polarised light microscopy SAED...............................................selected area electron diffraction SEM.................................................scanning electron microscope SM ...................................................stereomicroscope TEM.................................................transmission electron microscopy USEPA.............................................United States Environmental Protection Agency WDS ................................................wavelength dispersive spectrometry (used in electron microscopic examinations)

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GLOSSARY

Glossary actinolite — a monoclinic amphibole occurring at the iron-rich end of the isomorphous series tremolite-actinolite. Fibrous varieties constitute a species of asbestos. amorphous — means “without form” or a non-crystalline or glassy state. amosite — an acronym for Asbestos Mines of South Africa (with -ite added to imply a mineral) to denote a fibrous variety of the grunerite-cummingtonite isomorphous series of monoclinic amphibole minerals. It is a commercial variety of asbestos. amphibole — a grouping of silicate minerals in which the silicates form chains as opposed to rings or sheets or other forms such as frameworks. The other grouping of chain silicates, besides the amphiboles, is the pyroxenes (which are of no concern in asbestos identification). analyser — the uppermost of two polarising screens in the polarised light microscope. See Figure 1 at [90B.100]. anisotropic — this means that various properties (in this context the refractive index, but elsewhere properties such as thermal and electrical conductivity) are different, in different directions through the material concerned (which in this context is a crystal of a mineralogical species). Minerals crystallising in any system other than the isometric system are anisotropic. anthophyllite — an orthorhombic amphibole, the fibrous variety of which constitutes a type of asbestos. asbestos — a name given to any one of six fibrous varieties of minerals: chrysotile, amosite, crocidolite, fibrous anthophyllite, fibrous tremolite or fibrous actinolite. asbestosis — a recognised pathological condition of pneumoconiosis caused by the inhalation of airborne asbestos fibres. back focal plane — the area of plane on the side of a lens which is opposite to the side on which the object is lying, within which the object has come to a sharp focus. Bertrand lens — a lens which may be introduced as required into the barrel of a microscope to bring into focus the back focal plane of the objective lens. (See Figure 1). Its purpose is to observe interference figures from appropriately-oriented mineral fragments or sections, and is not used in asbestos identification procedures. biaxial — minerals which exhibit two optic axes; namely those crystallising in the orthorhombic, monoclinic and triclinic systems. birefringence — the numerical value between the maximum and minimum refractive indices in those materials where double refraction occurs. bivalent — having a valency of two. An example would be ferrous as opposed to ferric iron, the latter being trivalent. chlorite — a group of allied minerals consisting of hydrated silicates of aluminium, iron and magnesium, formed as alteration products of other minerals. chrysotile — a principal asbestos species consisting of the fibrous form of the mineral serpentine. (Pronounced in Australia and the UK as KRISE-O-TILE where both Is are long as in “icon”; but in the USA it is pronounced as CHRIS-O-TEEL where the I is short, such as in “if”.) ©

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compensator — a device for measuring the retardation, or the distance that the wave front of a slower ray has fallen behind that of the faster ray in doubly-refracting or anisotropic substances. The usual compensator is a quartz wedge employed with relevant knowledge and skill, but other more expensive and elaborate compensators (such as tilting plate compensators) are in existence. The retardation is manifested in terms of a polarisation colour, and the compensator serves to allocate a retardation distance in nanometres (nm) to the colour as observed. (Note that the retardation distance in nm does not correspond to the wavelength of the polarisation colour as observed, but is related to it by certain principles of physical optics.) In so doing some subsidiary information is obtained such as whether or not the substance is length slow or length fast, and if the thickness is known or can be measured then birefringence can be calculated as indicated in the text of this chapter at [90B.180]. (The latter point is not significant for asbestos identification, but it is for natural and artificial organic fibres.) crocidolite — the fibrous form of the mineral riebeckite and an important asbestos species. (The pronunciation both in Australia and the USA is KROW-SID-O-LITE where the first I is short and the second is long, as in “if” and “icon” respectively.) cummingtonite — the magnesium-rich end member of the monoclinic amphibole isomorphous series cummingtonite-grunerite, of which the fibrous variety constitutes amosite asbestos. double refraction — a property of anisotropic substances to divide a beam of light into two plane polarised components having mutually perpendicular vibration directions, and to propogate these through the substance with different velocities. extinction — the condition which exists when an optically anisotropic substance appears dark when observed between crossed polars. extinction angle — the angle at which extinction occurs compared with a N-S or E-W reference line such as a pronounced crystallographic or morphological feature. In the case of asbestos the feature concerned is the length of the fibre. See Figure 3 at [90B.160]. first order red plate — one of the microscope accessory plates consisting of a slice of gypsum (or some other suitable mineral) cut to the exact thickness to give a retardation (see compensator above) of 550 nm when observed between crossed polars. This produces a red colour which occurs at the end of the first band of colours seen with increasing thicknesses, hence is called first order red. If a fibre is observed simultaneously in such an orientation that its slow direction (for example) corresponds to that of the plate, (and this direction is marked thereon for that purpose) an additive effect occurs, so the combined retardation pushes the observed colour up into the blue zone at the start of the second order. If the fibre is rotated 90 degrees so the fast direction of the fibre parallels the slow direction of the plate, a subtractive effect occurs so the net retardation is reduced to a correspondence within a yellow first order band which underlies the red. This is the reason for the amosite fibres being either blue or yellow in their respective orientations in Figures A3 and A4 at [90B.460], and also for the blues and yellows for the NW oriented and NE oriented respectively cellulose fibres of Figure A11 at [90B.500]. glass fibre or glass wool — loose wool-like material made entirely of glass, and used for thermal insulation purposes. Other categories of fine glass fibres are for weaving into cloth principally for reinforcement in plastic objects, frequently referred to as “fibreglass objects”. graticule (or eyepiece graticule) — a disc of glass fitting into the focal plane of the eyepiece (or one of the eyepieces if a binocular microscope, as virtually all of them are today) and onto which is engraved an appropriate pattern, ranging from simple “cross-hairs” to complex arrangements of rectangles, squares, etc. Usually one or both of one of the horizontal or ©

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GLOSSARY

vertical lines is graduated, and when this is calibrated with a stage micrometer (see below) it gives an accurate scale (usually in micrometres, m) by means of which the size of objects on the microscope slide may be measured. Care must be taken to utilise the scale so obtained only with the objective lens and eyepiece combination for which the calibration was performed. grunerite — the iron-rich end member of the monoclinic amphibole isomorphous series cummingtonite-grunerite, of which the fibrous variety constitutes amosite asbestos. interference figures — these are observed in appropriately-oriented mineral fragments or thin sections by means of a Bertrand lens with crossed polars in strongly convergent light. They are not used in asbestos identification. Further information is given in “Mineralogical Principles of Use in Asbestos Identification” at [90B.150] and following paragraphs. isomorphous — “of the same form”. The name given to two or more mineral species which crystallise with very similar structures and lattice dimensions so that they may inter-mingle in all proportions, providing crystals of mixed chemical composition. isotropic — various properties (in this context the refractive index) are the same in all directions throughout the substance concerned. See anisotropic above for more details. kaolinite — a fine crystalline form of a hydrated aluminium silicate resulting chiefly from the alteration of felspars by appropriate geological processes. It is one of the clay minerals. lattice spacing — in the mineralogical context, the distances between various layers of atoms, or groupings of atoms when looked at in different directions, throughout the crystal. It is these which are measured indirectly, along with the intensity of the reflected X-ray, in XRD. (Actually it is the angle at which the X-ray is reflected which is measured for diagnostic purposes, but this is governed by the lattice spacing for a given X-ray wavelength through a well-known equation, called the Bragg Equation.) lizardite — another name for the massive variety of serpentine. mineral wool (or rock wool or slag wool) — is made from molten rocks or slag, which then is converted into its fluffy fine form of a multitude of fine fibres, usually by a blowing process. morphology — the form, shape or appearance of the substance concerned. normal — at right angles. optic axis — a direction through a crystal along which a ray of light may pass without undergoing double refraction. In anisotropic crystals there is only one such direction for “uniaxial” crystals, or there are two for “biaxial” crystals. For further information see uniaxial and biaxial in this Glossary. pleochroism — a property exhibited by some anisotropic materials, in which different brightnesses or different colours are exhibited when the specimen is rotated by the rotating stage, in plane polarised light only (ie with the polariser in place but with the analyser removed). polarisation colour — a colour produced by an anisotropic material when observed between crossed polars. It is a function of the birefringence and thickness. As the thickness of an anisotropic material increases (as best illustrated by means of a quartz wedge–see under compensator, above) the colours pass through a series of bands marked by the appearance of a red at regular intervals; but the bands after three or four series degenerate into alternate greens and pinks which on further increasing thickness merge into a uniform parchment white. The reds, and later the pinks, are chosen arbitrarily to designate the divisions between orders of ©

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colours, as they occur at regular intervals corresponding to retardations of 550 nm and integer multiples thereof. Thus the bands of colour that occur between the reds (although the first starts from a black) are called first, second, third, etc orders of polarisation colour. These are illustrated in textbooks of optical mineralogy by a chart known as a Michel-Lèvy chart. polariser — the lowermost of two polarising screens in the polarised light microscope. See Figure 1 at [90B.100]. quartz wedge — a thin wedge of quartz cemented between glass protecting plates and mounted in a holder which slides into and out of the accessory slot at an angle of 45 degrees to the planes of polarisation of the polariser and analyser. For its use see under compensator, above. refractive index — the ratio of the velocity of light in a vacuum to its velocity in the defined direction in the medium (or crystal etc) concerned. However, because of known mathematical relationships it can be measured in ways other than by measuring the velocity of light in or through the substance and in a vacuum, and then dividing the former into the latter. retardation — see under compensator, above. serpentine — a mineral of which the fibrous form is chrysotile asbestos. stereomicroscope — a binocular microscope which magnifies the object in 3-dimensions. The usual arrangement is for there to be two complete microscopes joined together in the one body with the optic axis of each converging on the specimen at an angle of 12 degrees. However some models have only a single objective lens (as opposed to the two in the configuration just mentioned) but two eyepieces, and the beam is split at the objective back focal plane so that one side enters one eyepiece and vice versa. Modern instruments, which are a marvel of optical clarity, have in-built parfocal zoom magnification mechanisms and inverting prisms so the image appears “right-way-up”, and is not inverted as with normal microscopes. This facilitates manipulative operations such as teasing and selecting fibres with forceps and needles. stage micrometer — a microscope slide on which has been placed by a micro-engraving or micro-photographic process a scale of length of one or two millimetres, subdivided into tenths and hundredths (or even to five thousandths) of a millimetre. This is a real measure such as a ruler, so the image when observed can be used to calibrate an eyepiece graticule (see above). This in turn can then be used to measure the size of objects being viewed. tremolite — a monoclinic amphibole occurring at the magnesium-rich end of the isomorphous series tremolite-actinolite. Fibrous varieties constitute a species of asbestos. At the time of the Second World War and for several years thereafter, fibrous tremolite was referred to as “Italian Asbestos” as it was mined in Piedmont and Lombardy in northwest Italy, and also to distinguish it from “Canadian Asbestos” which was a synonym for chrysotile. uniaxial — an anisotropic mineral containing one only optic axis. In practice this means members of the tetragonal, hexagonal and trigonal crystallographic systems. units of measurement — in microscopy the usual unit of measurement of particle sizes or fibre diameters is the micrometre ( m) which is one millionth of a metre or one thousandth of a millimetre. This is the same as the older (but now unused) term “micron” which had the symbol “ ” and which is now deprecated because of the world-wide adoption of the SI system of measurement which utilises specific prefixes attached to the basic unit (in this case the metre which is the unit of length). When dealing with light wavelengths, or retardation distances (see compensator above) the unit is the nanometre (nm) which is one thousandth of a micrometre. Older literature refers to this unit as the now deprecated “milli-micron”. To give a rough ©

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GLOSSARY

indication of these sizes, a human hair varies from about 70 to 100– m; the limit of visibility of a particle by the naked eye is about 40 m; pollen grains range from about 10 to 100 m, and bacteria range from about 0.5 to 50 m (although the majority are in the lower half of this range). The limit of resolution of the optical microscope is about 0.25 m or 250 nm, and the wavelength of visible light is from 0.4 to 0.7 m (or 400 to 700 nm, for blue and red respectively).

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THE IDENTIFICATION OF ASBESTOS IN BULK SAMPLES Introduction [90B.70] Asbestos has featured dramatically in recent litigation. Most of the cases are workers’ compensation related, brought by workers and others (including “bystanders”) who had been exposed over varying periods of time to airborne asbestos fibres. As a consequence of such exposure, the persons concerned now are suffering from one or more of the asbestos related diseases of asbestosis, mesothelioma or lung cancer (or already have died from these illnesses whereupon the actions are brought by dependants), and are suing former originators of the asbestos contamination for appropriate damages. Of concomitant concern are matters related to current sources of asbestos exposure. Such sources, at the present time, in general are the results of asbestos utilisation practices which were common or uncontrolled for many years until the mid-to-late 1970s, and principally consist of a large range of asbestos-based thermal, electrical and acoustic insulating materials, decorative surface coatings and a variety of building products and industrial components. This chapter is concerned with the methods of identification of asbestos, and how it may be distinguished from other fibrous materials which frequently are used for related purposes. Often when the presence of asbestos has been established, and depending upon the friability and state of preservation of the product in which it occurs, extensive and very costly removal operations are undertaken by specially-licenced firms of asbestos removalists. Accordingly, it follows that if a wrongful identification has been made, either an expensive removal exercise would be conducted needlessly or a possible health threat would remain in situ unchecked, until properly identified and treated at some future time. Consequently, the potential for further aspects of litigation could be present; namely an action brought by some party against an asbestos analyst for a wrongful identification of an alleged asbestos-containing product, or analyst versus analyst where their findings differ and one charges the other with defamation because of implied or alleged incompetence. In fact, the present writer has been involved in two such incidents where the findings of others have had to be contradicted; but so far, at the time of writing, neither has been the subject of a cross challenge likely to end up in court. This chapter is not concerned with the related aspects of airborne asbestos fibre concentration determinations (by membrane filtration and phase contrast microscopy) on the one hand, or asbestos removal procedures on the other. Both of these topics are dealt with in detail in the Worksafe Australia Code of Practice and Guidance Notes (Worksafe Australia (1988)), and the latter is further dealt with in appropriate legislation which has been, (or is about to be), introduced in each of the Australian States and the ACT. A listing of the relevant Acts and Regulations, and related documentation for the States and Commonwealth, is provided on pp 78–81 of the Worksafe Australia publication.

[90B.80] Various methods for the identification of asbestos have been proposed. Direct chemical analysis, of course, is of no use at all because it would be unable to distinguish between the fibrous and non-fibrous forms of the mineral species (of which the fibrous form would constitute a type of “asbestos”) on the one hand, and the many different mineral species ©

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with the same or nearly the same empirical formulae on the other. Accordingly various “non chemical” properties, which apply not only to asbestos and to other natural and “artificial” minerals, but also to other materials (such as natural and “artificial” fabric threads, polymers, plant and insect hairs, etc) are used. There are two exceptions to this statement; (i) the “combustion behaviour” of a suspected asbestos fibre when it is approached by a micro-flame as observed by a low power or binocular microscope; and (ii) the energy dispersive X-ray spectra of certain cations indicating their relative concentrations in association with the visual morphology in transmission electron microscopy (TEM). Therefore, methods such as X-ray diffraction (XRD), differential thermal analysis (DTA) and infrared absorption (IRA) have been proposed and used in the past (and under some conditions are used to-day, particularly XRD). However these methods require a relatively large analytical sample which consists entirely of the asbestos or suspected asbestos component; or if it is mixed with other substances, then the suspected asbestos component must occupy a substantial proportion of the total. The reason for this is that its identifying characteristics as yielded by the procedure concerned could be masked by those originating from the constituents comprising the remainder of the sample if the proportion of the latter is too large. However, NIOSH Method 9000 of February 1984 (NIOSH (1984)) is for the XRD determination of chrysotile in bulk samples from 100 per cent down to one per cent of chrysotile, but points out that certain other minerals if present in the sample, such as antigorite, chlorite, kaolinite, bemenite and brushite could cause interference. In fact some laboratories in the USA are using XRD to quantify chrysotile in samples particularly in the vicinity of the one per cent level. (This level is significant in the USA for the reasons set out at [90B.350].) As a consequence of the matters just discussed, there remains the most effective and hence universally-employed procedure: optical or light microscopy, or more specifically the polarising light microscopy (PLM) branch of the technique of light microscopy. This method makes use of the various optical properties of the asbestos or non-asbestos fibres, which themselves are dictated by the mineralogical constitution or molecular structure of the substances concerned.

[90B.90] Electron microscopy (whether scanning or transmission, SEM or TEM respectively) while being able to show fibres including many below the resolution limit of the optical microscope, also if fitted with additional analytical facilities, may give some further information about the fibre structure and composition. This already has been alluded to at [90B.70] above. The additional analytical facilities are energy dispersive spectrometry (EDS) and wavelength dispersive spectrometry (WDS) which may be used with both SEM and TEM, and selected area electron diffraction (SAED) with the TEM. For example, a TEM fitted with provisions for both EDS and SAED is capable of providing the following information: (1) high resolution images of the fibres concerned, distinguishing features measuring one nanometre (nm) or less; (2) from the SAED analysis, information about symmetry characteristics and lattice constants can be calculated; (3) the EDS analysis can provide a semi-quantitative to approximately quantitative analysis of elements of atomic mass greater than sodium, provided that proper calibration and data interpretation are undertaken. Various manufacturers of the equipment provide software programmes which are claimed to provide quantitative results. However, the instrument concerned would cost many hundreds of thousands of dollars (probably approaching a million) at 1995 prices so the cost of performing an analysis, including the sample preparation time, would be substantial and could amount to many ©

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