California Code of Regulations › Title 8 - Industrial Relations › Division 1 - Department of Industrial Relations › Chapter 4 - Division of Industrial Safety › Subchapter 7 - General Industry Safety Orders › Group 16 - Control of Hazardous Substances › Article 110 - Regulated Carcinogens › Appendix J - Polarized Light Microscopy of Asbestos Non-Mandatory

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
Method number: ID-191
Matrix: Bulk
Collection Procedure: Collect approximately 1 to 2
						  grams of each type of material and place into separate 20 mL scintillation
						  vials.
Analytical Procedure: A portion of each separate phase
						  is analyzed by gross examination, phase-polar examination, and central stop
						  dispersion microscopy.
Commercial manufacturers and products mentioned in this
						  method are for descriptive use only and do not constitute endorsements by
						  USDOL-OSHA. Similar products from other sources may be substituted.
1. Introduction
This method describes the collection and analysis of
						  asbestos bulk materials by light microscopy techniques including phase-polar
						  illumination and central-stop dispersion microscopy. Some terms unique to
						  asbestos analysis are defined below:
Amphibole: A family of minerals whose crystals are
						  formed by long, thin units which have two thin ribbons of double chain silicate
						  with a brucite ribbon in between. The shape of each unit is similar to an "I
						  beam". Minerals important in asbestos analysis include cummingtonite-grunerite,
						  crocidolite, tremolite-actinolite and anthophyllite.
Asbestos: A term for naturally occurring fibrous
						  minerals. Asbestos includes chrysotile, cummingtonite-grunerite asbestos
						  (amosite), anthophyllite asbestos, tremolite asbestos, crocidolite, actinolite
						  asbestos and any of these minerals which have been chemically treated or
						  altered. The precise chemical formulation of each species varies with the
						  location from which it was mined. Nominal compositions are listed:
Chrysotile
						  Mg3Si2O5(OH)4
Crocidolite (Riebeckite asbestos)
						  Na2Fe32+Fe23+Si8O22(OH)2
Cummingtonite-Grunerite asbestos (Amosite)
						  (Mg,Fe)7Si8O22(OH)2
Tremolite-Actinolite asbestos
						  Ca2(Mg,Fe)5Si8O22(OH)2
Anthophyllite asbestos
						  (Mg,Fe)7Si8O22(OH)2
Asbestos Fiber: A fiber of asbestos meeting the
						  criteria for a fiber. (See section
						  3.5. of this Appendix)
Aspect Ratio: The ratio of the length of a fiber to its
						  diameter usually defined as "length : width", e.g. 3:1.
Brucite: A sheet mineral with the composition
						  Mg(OH)2.
Central Stop Dispersion Staining (microscopy): This is
						  a dark field microscope technique that images particles using only light
						  refracted by the particle, excluding light that travels through the particle
						  unrefracted. This is usually accomplished with a McCrone objective or other
						  arrangement which places a circular stop with apparent aperture equal to the
						  objective aperture in the back focal plane of the microscope.
Cleavage Fragments: Mineral particles formed by the
						  comminution of minerals, especially those characterized by relatively parallel
						  sides and moderate aspect ratio.
Differential Counting: The term applied to the practice
						  of excluding certain kinds of fibers from a phase contrast asbestos count
						  because they are not asbestos.
Fiber: A particle longer than or equal to 5 µm
						  with a length to width ratio greater than or equal to 3:1. This may include
						  cleavage fragments. (see section
						  3.5 of this appendix).
Phase Contrast: Contrast obtained in the microscope by
						  causing light scattered by small particles to destructively interfere with
						  unscattered light, thereby enhancing the visibility of very small particles and
						  particles with very low intrinsic contrast.
Phase Contrast Microscope: A microscope configured with
						  a phase mask pair to create phase contrast. The technique which uses this is
						  called Phase Contrast Microscopy (PCM).
Phase-Polar Analysis: This is the use of polarized
						  light in a phase contrast microscope. It is used to see the same size fibers
						  that are visible in air filter analysis. Although fibers finer than 1 µm
						  are visible, analysis of these is inferred from analysis of larger bundles that
						  are usually present.
Phase-Polar Microscope: The phase-polar microscope is a
						  phase contrast microscope which has an analyzer, a polarizer, a first order red
						  plate, and a rotating phase condenser all in place so that the polarized light
						  image is enhanced by phase contrast.
Sealing Encapsulant: This is a product which can be
						  applied, preferably by spraying, onto an asbestos surface which will seal the
						  surface so that fibers cannot be released.
Serpentine: A mineral family consisting of minerals
						  with the general composition
						  Mg3Si2O5(OH)4
						  having the magnesium in brucite layer over a silicate layer. Minerals important
						  in asbestos analysis included in this family are chrysotile, lizardite,
						  antigorite.
1.1. History
Light microscopy has been used for well over 100 years
						  for the determination of mineral species. This analysis is carried out using
						  specialized polarizing microscopes as well as bright field microscopes. The
						  identification of minerals is an on-going process with many new minerals
						  described each year. The first recorded use of asbestos was in Finland about
						  2500 B.C. where the material was used in the mud wattle for the wooden huts the
						  people lived in as well as strengthening for pottery. Adverse health aspects of
						  the mineral were noted nearly 2000 years ago when Pliny the Younger wrote about
						  the poor health of slaves in the asbestos mines. Although known to be injurious
						  for centuries, the first modern references to its toxicity were by the British
						  Labor Inspectorate when it banned asbestos dust from the workplace in 1898.
						  Asbestosis cases were described in the literature after the turn of the
						  century. Cancer was first suspected in the mid 1930's and a causal link to
						  mesothelioma was made in 1965. Because of the public concern for worker and
						  public safety with the use of this material, several different types of
						  analysis were applied to the determination of asbestos content. Light
						  microscopy requires a great deal of experience and craft. Attempts were made to
						  apply less subjective methods to the analysis. X-ray diffraction was partially
						  successful in determining the mineral types but was unable to separate out the
						  fibrous portions from the non-fibrous portions. Also, the minimum detection
						  limit for asbestos analysis by X-ray diffraction (XRD) is about 1%.
						  Differential Thermal Analysis (DTA) was no more successful. These provide
						  useful corroborating information when the presence of asbestos has been shown
						  by microscopy; however, neither can determine the difference between fibrous
						  and non-fibrous minerals when both habits are present. The same is true of
						  Infrared Absorption (IR).
When electron microscopy was applied to asbestos
						  analysis, hundreds of fibers were discovered present too small to be visible in
						  any light microscope. There are two different types of electron microscope used
						  for asbestos analysis: Scanning Electron Microscope (SEM) and Transmission
						  Electron Microscope (TEM). Scanning Electron Microscopy is useful in
						  identifying minerals. The SEM can provide two of the three pieces of
						  information required to identify fibers by electron microscopy: morphology and
						  chemistry. The third is structure as determined by Selected Area Electron
						  Diffraction -- SAED which is performed in the TEM. Although the resolution of
						  the SEM is sufficient for very fine fibers to be seen, accuracy of chemical
						  analysis that can be performed on the fibers varies with fiber diameter in
						  fibers of less than 0.2 µm diameter. The TEM is a powerful tool to
						  identify fibers too small to be resolved by light microscopy and should be used
						  in conjunction with this method when necessary. The TEM can provide all three
						  pieces of information required for fiber identification. Most fibers thicker
						  than 1 µm can adequately be defined in the light microscope. The light
						  microscope remains as the best instrument for the determination of mineral
						  type. This is because the minerals under investigation were first described
						  analytically with the light microscope. It is inexpensive and gives positive
						  identification for most samples analyzed. Further, when optical techniques are
						  inadequate, there is ample indication that alternative techniques should be
						  used for complete identification of the sample.
1.2. Principle
Minerals consist of atoms that may be arranged in
						  random order or in a regular arrangement. Amorphous materials have atoms in
						  random order while crystalline materials have long-range order. Many materials
						  are transparent to light, at least for small particles or for thin sections.
						  The properties of these materials can be investigated by the effect that the
						  material has on light passing through it. The six asbestos minerals are all
						  crystalline with particular properties that have been identified and cataloged.
						  These six minerals are anisotropic. They have a regular array of atoms, but the
						  arrangement is not the same in all directions. Each major direction of the
						  crystal presents a different regularity. Light photons travelling in each of
						  these main directions will encounter different electrical neighborhoods,
						  affecting the path and time of travel. The techniques outlined in this method
						  use the fact that light traveling through fibers or crystals in different
						  directions will behave differently, but predictably. The behavior of the light
						  as it travels through a crystal can be measured and compared with known or
						  determined values to identify the mineral species. Usually, Polarized Light
						  Microscopy (PLM) is performed with strain-free objectives on a bright-field
						  microscope platform. This would limit the resolution of the microscope to about
						  0.4 µm. Because OSHA requires the counting and identification of fibers
						  visible in phase contrast, the phase contrast platform is used to visualize the
						  fibers with the polarizing elements added into the light path. Polarized light
						  methods cannot identify fibers finer than about 1 µm in diameter even
						  though they are visible. The finest fibers are usually identified by inference
						  from the presence of larger, identifiable fiber bundles. When fibers are
						  present, but not identifiable by light microscopy, use either SEM or TEM to
						  determine the fiber identity.
1.3. Advantages and Disadvantages
The advantages of light microcopy are:
(a) Basic identification of the materials was first
						  performed by light microscopy and gross analysis. This provides a large base of
						  published information against which to check analysis and analytical
						  technique.
(b) The analysis is specific to fibers. The minerals
						  present can exist in asbestiform, fibrous, prismatic, or massive varieties all
						  at the same time. Therefore, bulk methods of analysis such as X-ray
						  diffraction, IR analysis, DTA, etc. are inappropriate where the material is not
						  known to be fibrous.
(c) The analysis is quick, requires little preparation
						  time, and can be performed on-site if a suitably equipped microscope is
						  available.
The disadvantages are:
(a) Even using phase-polar illumination, not all the
						  fibers present may be seen. This is a problem for very low asbestos
						  concentrations where agglomerations or large bundles of fibers may not be
						  present to allow identification by inference.
(b) The method requires a great degree of
						  sophistication on the part of the microscopist. An analyst is only as useful as
						  his mental catalog of images. Therefore, a microscopist's accuracy is enhanced
						  by experience. The mineralogical training of the analyst is very important. It
						  is the basis on which subjective decisions are made.
(c) The method uses only a tiny amount of material for
						  analysis. This may lead to sampling bias and false results (high or low). This
						  is especially true if the sample is severely inhomogeneous.
(d) Fibers may be bound in a matrix and not
						  distinguishable as fibers so identification cannot be made.
1.4. Method Performance
1.4.1. This method can be used for determination of
						  asbestos content from 0 to 100% asbestos. The detection limit has not been
						  adequately determined, although for selected samples, the limit is very low,
						  depending on the number of particles examined. For mostly homogeneous, finely
						  divided samples, with no difficult fibrous interferences, the detection limit
						  is below 1%. For inhomogeneous samples (most samples), the detection limit
						  remains undefined. NIST has conducted proficiency testing of laboratories on a
						  national scale. Although each round is reported statistically with an average,
						  control limits, etc., the results indicate a difficulty in establishing
						  precision especially in the low concentration range. It is suspected that there
						  is significant bias in the low range especially near 1%. EPA tried to remedy
						  this by requiring a mandatory point counting scheme for samples less than 10%.
						  The point counting procedure is tedious, and may introduce significant biases
						  of its own. It has not been incorporated into this method.
1.4.2. The precision and accuracy of the quantitation
						  tests performed in this method are unknown. Concentrations are easier to
						  determine in commercial products where asbestos was deliberately added because
						  the amount is usually more than a few percent. An analyst's results can be
						  "calibrated" against the known amounts added by the manufacturer. For
						  geological samples, the degree of homogeneity affects the precision.
1.4.3. The performance of the method is analyst
						  dependent. The analyst must choose carefully and not necessarily randomly the
						  portions for analysis to assure that detection of asbestos occurs when it is
						  present. For this reason, the analyst must have adequate training in sample
						  preparation, and experience in the location and identification of asbestos in
						  samples. This is usually accomplished through substantial on-the-job training
						  as well as formal education in mineralogy and microscopy.
1.5. Interferences
Any material which is long, thin, and small enough to
						  be viewed under the microscope can be considered an interference for asbestos.
						  There are literally hundreds of interferences in workplaces. The techniques
						  described in this method are normally sufficient to eliminate the
						  interferences. An analyst's success in eliminating the interferences depends on
						  proper training.
Asbestos minerals belong to two mineral families: the
						  serpentines and the amphiboles. In the serpentine family, the only common
						  fibrous mineral is chrysotile. Occasionally, the mineral antigorite occurs in a
						  fibril habit with morphology similar to the amphiboles. The amphibole minerals
						  consist of a score of different minerals of which only five are regulated by
						  federal standard: amosite, crocidolite, anthophyllite asbestos, tremolite
						  asbestos and actinolite asbestos. These are the only amphibole minerals that
						  have been commercially exploited for their fibrous properties; however, the
						  rest can and do occur occasionally in asbestiform habit.
In addition to the related mineral interferences, other
						  minerals common in building material may present a problem for some
						  microscopists: gypsum, anhydrite, brucite, quartz fibers, talc fibers or
						  ribbons, wollastonite, perlite, attapulgite, etc. Other fibrous materials
						  commonly present in workplaces are: fiberglass, mineral wool, ceramic wool,
						  refractory ceramic fibers, kevlar, nomex, synthetic fibers, graphite or carbon
						  fibers, cellulose (paper or wood) fibers, metal fibers, etc.
Matrix embedding material can sometimes be a negative
						  interference. The analyst may not be able to easily extract the fibers from the
						  matrix in order to use the method. Where possible, remove the matrix before the
						  analysis, taking careful note of the loss of weight. Some common matrix
						  materials are: vinyl, rubber, tar, paint, plant fiber, cement, and epoxy. A
						  further negative interference is that the asbestos fibers themselves may be
						  either too small to be seen in Phase Contrast Microscopy (PCM) or of a very low
						  fibrous quality, having the appearance of plant fibers. The analyst's ability
						  to deal with these materials increases with experience.
1.6. Uses and Occupational Exposure
Asbestos is ubiquitous in the environment. More than
						  40% of the land area of the United States is composed of minerals which may
						  contain asbestos. Fortunately, the actual formation of great amounts of
						  asbestos is relatively rare. Nonetheless, there are locations in which
						  environmental exposure can be severe such as in the Serpentine Hills of
						  California.
There are thousands of uses for asbestos in industry
						  and the home. Asbestos abatement workers are the most current segment of the
						  population to have occupational exposure to great amounts of asbestos. If the
						  material is undisturbed, there is no exposure. Exposure occurs when the
						  asbestos-containing material is abraded or otherwise disturbed during
						  maintenance operations or some other activity. Approximately 95% of the
						  asbestos in place in the United States is chrysotile.
Amosite and crocidolite make up nearly all the
						  difference. Tremolite and anthophyllite make up a very small percentage.
						  Tremolite is found in extremely small amounts in certain chrysotile deposits.
						  Actinolite exposure is probably greatest from environmental sources, but has
						  been identified in vermiculite containing, sprayed-on insulating materials
						  which may have been certified as asbestos-free.
1.7. Physical and Chemical Properties
The nominal chemical compositions for the asbestos
						  minerals were given in Section
						  1. Compared to cleavage fragments
						  of the same minerals, asbestiform fibers possess a high tensile strength along
						  the fiber axis. They are chemically inert, noncombustible, and heat resistant.
						  Except for chrysotile, they are insoluble in Hydrochloric acid (HCl).
						  Chrysotile is slightly soluble in HCl. Asbestos has high electrical resistance
						  and good sound absorbing characteristics. It can be woven into cables, fabrics
						  or other textiles, or matted into papers, felts, and mats.
1.8. Toxicology (This Section is for Information Only
						  and Should Not Be Taken as OSHA Policy)
Possible physiologic results of respiratory exposure to
						  asbestos are mesothelioma of the pleura or peritoneum, interstitial fibrosis,
						  asbestosis, pneumoconiosis, or respiratory cancer. The possible consequences of
						  asbestos exposure are detailed in the NIOSH Criteria Document or in the OSHA
						  Asbestos Standards 29 CFR
						  1910.1001,
						  29 CFR
						  1926.1101, and
						  29 CFR
						  1915.1001.
2. Sampling Procedure
2.1. Equipment for sampling
(a) Tube or cork borer sampling device
(b) Knife
(c) 20 mL scintillation vial or similar vial
(d) Sealing encapsulant
2.2. Safety Precautions
Asbestos is a known carcinogen. Take care when
						  sampling. While in an asbestos-containing atmosphere, a properly selected and
						  fit-tested respirator should be worn. Take samples in a manner to cause the
						  least amount of dust. Follow these general guidelines:
(a) Do not make unnecessary dust.
(b) Take only a small amount (1 to 2 g).
(c) Tightly close the sample container.
(d) Use encapsulant to seal the spot where the sample
						  was taken, if necessary.
2.3. Sampling Procedure
Samples of any suspect material should be taken from an
						  inconspicuous place. Where the material is to remain, seal the sampling wound
						  with an encapsulant to eliminate the potential for exposure from the sample
						  site. Microscopy requires only a few milligrams of material. The amount that
						  will fill a 20 mL scintillation vial is more than adequate. Be sure to collect
						  samples from all layers and phases of material. If possible, make separate
						  samples of each different phase of the material. This will aid in determining
						  the actual hazard. DO NOT USE ENVELOPES, PLASTIC OR PAPER BAGS OF ANY KIND TO
						  COLLECT SAMPLES. The use of plastic bags presents a contamination hazard to
						  laboratory personnel and to other samples. When these containers are opened, a
						  bellows effect blows fibers out of the container onto everything, including the
						  person opening the container.
If a cork-borer type sampler is available, push the
						  tube through the material all the way, so that all layers of material are
						  sampled. Some samplers are intended to be disposable. These should be capped
						  and sent to the laboratory. If a non-disposable cork borer is used, empty the
						  contents into a scintillation vial and send to the laboratory. Vigorously and
						  completely clean the cork borer between samples.
2.4. Shipment
Samples packed in glass vials must not touch or they
						  might break in shipment.
(a) Seal the samples with a sample seal over the end to
						  guard against tampering and to identify the sample.
(b) Package the bulk samples in separate packages from
						  the air samples. They may cross-contaminate each other and will invalidate the
						  results of the air samples.
(c) Include identifying paperwork with the samples, but
						  not in contact with the suspected asbestos.
(d) To maintain sample accountability, ship the samples
						  by certified mail, overnight express, or hand carry them to the
						  laboratory.
3. Analysis
The analysis of asbestos samples can be divided into
						  two major parts: sample preparation and microscopy. Because of the different
						  asbestos uses that may be encountered by the analyst, each sample may need
						  different preparation steps. The choices are outlined below. There are several
						  different tests that are performed to identify the asbestos species and
						  determine the percentage. They will be explained below.
3.1. Safety
(a) Do not create unnecessary dust. Handle the samples
						  in HEPA- filter equipped hoods. If samples are received in bags, envelopes or
						  other inappropriate container, open them only in a hood having a face velocity
						  at or greater than 100 fpm. Transfer a small amount to a scintillation vial and
						  only handle the smaller amount.
(b) Open samples in a hood, never in the open lab
						  area.
(c) Index of refraction oils can be toxic. Take care
						  not to get this material on the skin. Wash immediately with soap and water if
						  this happens.
(d) Samples that have been heated in the muffle furnace
						  or the drying oven may be hot. Handle them with tongs until they are cool
						  enough to handle.
(e) Some of the solvents used, such as THF
						  (tetrahydrofuran), are toxic and should only be handled in an appropriate fume
						  hood and according to instructions given in the Safety Data Sheet (SDS).
3.2. Equipment
(a) Phase contrast microscope with 10x, 16x and 40x
						  objectives, 10x wide-field eyepieces, G-22 Walton-Beckett graticule, Whipple
						  disk, polarizer, analyzer and first order red or gypsum plate, 100 Watt
						  illuminator, rotating position condenser with oversize phase rings, central
						  stop dispersion objective, Kohler illumination and a rotating mechanical stage.
						  (see Figure 1. of this appendix)
(b) Stereo microscope with reflected light
						  illumination, transmitted light illumination, polarizer, analyzer and first
						  order red or gypsum plate, and rotating stage.
(c) Negative pressure hood for the stereo
						  microscope
(d) Muffle furnace capable of 600 °C
(e) Drying oven capable of 50 -- 150 °C
(f) Aluminum specimen pans
(g) Tongs for handling samples in the furnace
(h) High dispersion index of refraction oils (Special
						  for dispersion staining.)
n = 1.550
n = 1.585
n = 1.590
n = 1.605
n = 1.620
n = 1.670
n = 1.680
n = 1.690
(i) A set of index of refraction oils from about
						  n=1.350 to n=2.000 in n=0.005 increments. (Standard for Becke line
						  analysis.)
(j) Glass slides with painted or frosted ends 1x3
						  inches 1mm thick, precleaned.
(k) Cover Slips 22x22 mm, #1 ½
(
l
) Paper clips or dissection
						  needles
(m) Hand grinder
(n) Scalpel with both #10 and #11 blades
(o) 0.1 molar HCl
(p) Decalcifying solution (Baxter Scientific
						  Products)
Ethylenediaminetetraacetic Acid, Tetrasodium 0.7
						  g/l
Sodium Potassium Tartrate 8.0 mg/liter
Hydrochloric Acid 99.2 g/liter
Sodium Tartrate 0.14 g/liter
(q) Tetrahydrofuran (THF)
(r) Hotplate capable of 60 deg.C
(s) Balance
(t) Hacksaw blade
(u) Ruby mortar and pestle
3.3. Sample Pre-Preparation
Sample preparation begins with pre-preparation which
						  may include chemical reduction of the matrix, heating the sample to dryness or
						  heating in the muffle furnace. The end result is a sample which has been
						  reduced to a powder that is sufficiently fine to fit under the cover slip.
						  Analyze different phases of samples separately, e.g., tile and the tile mastic
						  should be analyzed separately as the mastic may contain asbestos while the tile
						  may not.
(a) Wet Samples
Samples with a high water content will not give the
						  proper dispersion colors and must be dried prior to sample mounting. Remove the
						  lid of the scintillation vial, place the bottle in the drying oven and heat at
						  100 °C to dryness (usually about 2 h). Samples which are not submitted to
						  the lab in glass must be removed and placed in glass vials or aluminum weighing
						  pans before placing them in the drying oven.
(b) Samples With Organic Interference -- Muffle
						  Furnace
These may include samples with tar as a matrix, vinyl
						  asbestos tile, or any other organic that can be reduced by heating. Remove the
						  sample from the vial and weigh in a balance to determine the weight of the
						  submitted portion. Place the sample in a muffle furnace at 500 °C for 1 to
						  2 h or until all obvious organic material has been removed. Retrieve, cool and
						  weigh again to determine the weight loss on ignition. This is necessary to
						  determine the asbestos content of the submitted sample, because the analyst
						  will be looking at a reduced sample.
NOTE: Heating above 600 °C will cause the sample to
						  undergo a structural change which, given sufficient time, will convert the
						  chrysotile to forsterite. Heating even at lower temperatures for 1 to 2 h may
						  have a measurable effect on the optical properties of the minerals. If the
						  analyst is unsure of what to expect, a sample of standard asbestos should be
						  heated to the same temperature for the same length of time so that it can be
						  examined for the proper interpretation.
(c) Samples With Organic Interference -- THF
Vinyl asbestos tile is the most common material treated
						  with this solvent, although, substances containing tar will sometimes yield to
						  this treatment. Select a portion of the material and then grind it up if
						  possible. Weigh the sample and place it in a test tube. Add sufficient THF to
						  dissolve the organic matrix. This is usually about 4 to 5 mL. Remember, THF is
						  highly flammable. Filter the remaining material through a tared silver
						  membrane, dry and weigh to determine how much is left after the solvent
						  extraction. Further process the sample to remove carbonate or mount
						  directly.
(d) Samples With Carbonate Interference
Carbonate material is often found on fibers and
						  sometimes must be removed in order to perform dispersion microscopy. Weigh out
						  a portion of the material and place it in a test tube. Add a sufficient amount
						  of 0.1 M HCl or decalcifying solution in the tube to react all the carbonate as
						  evidenced by gas formation; i.e., when the gas bubbles stop, add a little more
						  solution. If no more gas forms, the reaction is complete. Filter the material
						  out through a tared silver membrane, dry and weigh to determine the weight
						  lost.
3.4. Sample Preparation
Samples must be prepared so that accurate determination
						  can be made of the asbestos type and amount present. The following steps are
						  carried out in the low-flow hood (a low-flow hood has less than 50 fpm
						  flow):
(1) If the sample has large lumps, is hard, or cannot
						  be made to lie under a cover slip, the grain size must be reduced. Place a
						  small amount between two slides and grind the material between them or grind a
						  small amount in a clean mortar and pestle. The choice of whether to use an
						  alumina, ruby, or diamond mortar depends on the hardness of the material.
						  Impact damage can alter the asbestos mineral if too much mechanical shock
						  occurs. (Freezer mills can completely destroy the observable crystallinity of
						  asbestos and should not be used). For some samples, a portion of material can
						  be shaved off with a scalpel, ground off with a hand grinder or hack saw
						  blade.
The preparation tools should either be disposable or
						  cleaned thoroughly. Use vigorous scrubbing to loosen the fibers during the
						  washing. Rinse the implements with copious amounts of water and air-dry in a
						  dust-free environment.
(2) If the sample is powder or has been reduced as in
						  (1) above, it is ready to mount. Place a glass slide on a piece of optical
						  tissue and write the identification on the painted or frosted end. Place two
						  drops of index of refraction medium n=1.550 on the slide. (The medium n=1.550
						  is chosen because it is the matching index for chrysotile.) Dip the end of a
						  clean paper-clip or dissecting needle into the droplet of refraction medium on
						  the slide to moisten it. Then dip the probe into the powder sample. Transfer
						  what sticks on the probe to the slide. The material on the end of the probe
						  should have a diameter of about 3 mm for a good mount. If the material is very
						  fine, less sample may be appropriate. For non-powder samples such as fiber
						  mats, forceps should be used to transfer a small amount of material to the
						  slide. Stir the material in the medium on the slide, spreading it out and
						  making the preparation as uniform as possible. Place a cover-slip on the
						  preparation by gently lowering onto the slide and allowing it to fall
						  "trapdoor" fashion on the preparation to push out any bubbles. Press gently on
						  the cover slip to even out the distribution of particulate on the slide. If
						  there is insufficient mounting oil on the slide, one or two drops may be placed
						  near the edge of the coverslip on the slide. Capillary action will draw the
						  necessary amount of liquid into the preparation. Remove excess oil with the
						  point of a laboratory wiper.
Treat at least two different areas of each phase in
						  this fashion. Choose representative areas of the sample. It my be useful to
						  select particular areas or fibers for analysis. This is useful to identify
						  asbestos in severely inhomogeneous samples.
When it is determined that amphiboles may be present,
						  repeat the above process using the appropriate high-dispersion oils until an
						  identification is made or all six asbestos minerals have been ruled out. Note
						  that percent determination must be done in the index medium 1.550 because
						  amphiboles tend to disappear in their matching mediums.
3.5. Analytical procedure
NOTE: This method presumes some knowledge of mineralogy
						  and optical petrography.
The analysis consists of three parts: The determination
						  of whether there is asbestos present, what type is present, and the
						  determination of how much is present. The general flow of the analysis
						  is:
(1) Gross examination.
(2) Examination under polarized light on the stereo
						  microscope.
(3) Examination by phase-polar illumination on the
						  compound phase microscope.
(4) Determination of species by dispersion stain.
						  Examination by Becke line analysis may also be used; however, this is usually
						  more cumbersome for asbestos determination.
(5) Difficult samples may need to be analyzed by SEM or
						  TEM, or the results from those techniques combined with light microscopy for a
						  definitive identification.
Identification of a particle as asbestos requires that
						  it be asbestiform. Description of particles should follow the suggestion of
						  Campbell. (Figure 1. of this appendix)
Click
						  here to view image
Figure 1. Particle definitions showing mineral
						  growth habits. From the U.S. Bureau of Mines
For the purpose of regulation, the mineral must be one
						  of the six minerals covered and must be in the asbestos growth habit. Large
						  specimen samples of asbestos generally have the gross appearance of wood.
						  Fibers are easily parted from it. Asbestos fibers are very long compared with
						  their widths. The fibers have a very high tensile strength as demonstrated by
						  bending without breaking. Asbestos fibers exist in bundles that are easily
						  parted, show longitudinal fine structure and may be tufted at the ends showing
						  "bundle of sticks" morphology. In the microscope some of these properties may
						  not be observable. Amphiboles do not always show striations along their length
						  even when they are asbestos. Neither will they always show tufting. They
						  generally do not show a curved nature except for very long fibers. Asbestos and
						  asbestiform minerals are usually characterized in groups by extremely high
						  aspect ratios (greater than 100:1). While aspect ratio analysis is useful for
						  characterizing populations of fibers, it cannot be used to identify individual
						  fibers of intermediate to short aspect ratio. Observation of many fibers is
						  often necessary to determine whether a sample consists of "cleavage fragments"
						  or of asbestos fibers.
Most cleavage fragments of the asbestos minerals are
						  easily distinguishable from true asbestos fibers. This is because true cleavage
						  fragments usually have larger diameters than 1 µm. Internal structure of
						  particles larger than this usually shows them to have no internal fibrillar
						  structure. In addition, cleavage fragments of the monoclinic amphiboles show
						  inclined extinction under crossed polars with no compensator. Asbestos fibers
						  usually show extinction at zero degrees or ambiguous extinction if any at all.
						  Morphologically, the larger cleavage fragments are obvious by their blunt or
						  stepped ends showing prismatic habit. Also, they tend to be circular rather
						  than filiform.
Where the particles are less than 1 µm in
						  diameter and have an aspect ratio greater than or equal to 3:1, it is
						  recommended that the sample be analyzed by SEM or TEM if there is any question
						  whether the fibers are cleavage fragments or asbestiform particles. Care must
						  be taken when analyzing by electron microscopy because the interferences are
						  different from those in light microscopy and may structurally be very similar
						  to asbestos. The classic interference is between anthophyllite and biopyribole
						  or intermediate fiber. Use the same morphological clues for electron microscopy
						  as are used for light microscopy, e.g. fibril splitting, internal longitudinal
						  striation, fraying, curvature, etc.
(1) Gross examination:
Examine the sample, preferably in the glass vial.
						  Determine the presence of any obvious fibrous component. Estimate a percentage
						  based on previous experience and current observation. Determine whether any
						  prepreparation is necessary. Determine the number of phases present. This step
						  may be carried out or augmented by observation at 6 to 40 x under a stereo
						  microscope.
(2) After performing any necessary pre-preparation,
						  prepare slides of each phase as described above. Two preparations of the same
						  phase in the same index medium can be made side-by-side on the same glass for
						  convenience. Examine with the polarizing stereo microscope. Estimate the
						  percentage of asbestos based on the amount of birefringent fiber
						  present.
(3) Examine the slides on the phase-polar microscopes
						  at magnifications of 160 and 400x. Note the morphology of the fibers. Long,
						  thin, very straight fibers with little curvature are indicative of fibers from
						  the amphibole family. Curved, wavy fibers are usually indicative of chrysotile.
						  Estimate the percentage of asbestos on the phase-polar microscope under
						  conditions of crossed polars and a gypsum plate. Fibers smaller than 1.0
						  µm in thickness must be identified by inference to the presence of
						  larger, identifiable fibers and morphology. If no larger fibers are visible,
						  electron microscopy should be performed. At this point, only a tentative
						  identification can be made. Full identification must be made with dispersion
						  microscopy. Details of the tests are included in the appendices.
(4) Once fibers have been determined to be present,
						  they must be identified. Adjust the microscope for dispersion mode and observe
						  the fibers. The microscope has a rotating stage, one polarizing element, and a
						  system for generating dark-field dispersion microscopy (see Section
						  4.6. of this appendix). Align a
						  fiber with its length parallel to the polarizer and note the color of the Becke
						  lines. Rotate the stage to bring the fiber length perpendicular to the
						  polarizer and note the color. Repeat this process for every fiber or fiber
						  bundle examined. The colors must be consistent with the colors generated by
						  standard asbestos reference materials for a positive identification. In
						  n=1.550, amphiboles will generally show a yellow to straw-yellow color
						  indicating that the fiber indices of refraction are higher than the liquid. If
						  long, thin fibers are noted and the colors are yellow, prepare further slides
						  as above in the suggested matching liquids listed below:
Type of
									 asbestos
Index of
									 refraction
Chrysotile
n = 1.550.
Amosite
n = 1.670 or 1.680.
Crocidolite
n = 1.690.
Anthophyllite
n = 1.605 and 1.620.
Tremolite
n = 1.605 and 1.620.
Actinolite
n = 1.620.
Where more than one liquid is suggested, the first is
						  preferred; however, in some cases this liquid will not give good dispersion
						  color. Take care to avoid interferences in the other liquid; e.g., wollastonite
						  in n=1.620 will give the same colors as tremolite. In n=1.605 wollastonite will
						  appear yellow in all directions. Wollastonite may be determined under crossed
						  polars as it will change from blue to yellow as it is rotated along its fiber
						  axis by tapping on the cover slip. Asbestos minerals will not change in this
						  way.
Determination of the angle of extinction may, when
						  present, aid in the determination of anthophyllite from tremolite. True
						  asbestos fibers usually have 0 deg. extinction or ambiguous extinction, while
						  cleavage fragments have more definite extinction.
Continue analysis until both preparations have been
						  examined and all present species of asbestos are identified. If there are no
						  fibers present, or there is less than 0.1% present, end the analysis with the
						  minimum number of slides (2).
(5) Some fibers have a coating on them which makes
						  dispersion microscopy very difficult or impossible. Becke line analysis or
						  electron microscopy may be performed in those cases. Determine the percentage
						  by light microscopy. TEM analysis tends to overestimate the actual percentage
						  present.
(6) Percentage determination is an estimate of occluded
						  area, tempered by gross observation. Gross observation information is used to
						  make sure that the high magnification microscopy does not greatly over-or
						  under-estimate the amount of fiber present. This part of the analysis requires
						  a great deal of experience. Satisfactory models for asbestos content analysis
						  have not yet been developed, although some models based on metallurgical
						  grain-size determination have found some utility. Estimation is more easily
						  handled in situations where the grain sizes visible at about 160x are about the
						  same and the sample is relatively homogeneous.
View all of the area under the cover slip to make the
						  percentage determination. View the fields while moving the stage, paying
						  attention to the clumps of material. These are not usually the best areas to
						  perform dispersion microscopy because of the interference from other materials.
						  But, they are the areas most likely to represent the accurate percentage in the
						  sample. Small amounts of asbestos require slower scanning and more frequent
						  analysis of individual fields.
Report the area occluded by asbestos as the
						  concentration. This estimate does not generally take into consideration the
						  difference in density of the different species present in the sample. For most
						  samples this is adequate. Simulation studies with similar materials must be
						  carried out to apply microvisual estimation for that purpose and is beyond the
						  scope of this procedure.
(7) Where successive concentrations have been made by
						  chemical or physical means, the amount reported is the percentage of the
						  material in the "as submitted" or original state. The percentage determined by
						  microscopy is multiplied by the fractions remaining after pre-preparation steps
						  to give the percentage in the original sample. For example:
Step 1. 60% remains after heating at 550 °C for 1
						  h.
Step 2. 30% of the residue of step 1 remains after
						  dissolution of carbonate in 0.1 m HCl.
Step 3. Microvisual estimation determines that 5% of
						  the sample is chrysotile asbestos.
The reported result is:
R = (Microvisual result in percent) x (Fraction
						  remaining after step 2) x (Fraction remaining of original sample after step
						  1)
R = (5) x (.30) x (.60) = 0.9%
(8) Report the percent and type of asbestos present.
						  For samples where asbestos was identified, but is less than 1.0%, report
						  "Asbestos present, less than 1.0%." There must have been at least two observed
						  fibers or fiber bundles in the two preparations to be reported as present. For
						  samples where asbestos was not seen, report as "None Detected."
4. Auxiliary Information
Because of the subjective nature of asbestos analysis,
						  certain concepts and procedures need to be discussed in more depth. This
						  information will help the analyst understand why some of the procedures are
						  carried out the way they are.
4. 1. Light
Light is electromagnetic energy. It travels from its
						  source in packets called quanta. It is instructive to consider light as a plane
						  wave. The light has a direction of travel. Perpendicular to this and mutually
						  perpendicular to each other, are two vector components. One is the magnetic
						  vector and the other is the electric vector. We shall only be concerned with
						  the electric vector. In this description, the interaction of the vector and the
						  mineral will describe all the observable phenomena. From a light source such a
						  microscope illuminator, light travels in all different direction from the
						  filament.
In any given direction away from the filament, the
						  electric vector is perpendicular to the direction of travel of a light ray.
						  While perpendicular, its orientation is random about the travel axis. If the
						  electric vectors from all the light rays were lined up by passing the light
						  through a filter that would only let light rays with electric vectors oriented
						  in one direction pass, the light would then be POLARIZED.
Polarized light interacts with matter in the direction
						  of the electric vector. This is the polarization direction. Using this property
						  it is possible to use polarized light to probe different materials and identify
						  them by how they interact with light.
The speed of light in a vacuum is a constant at about
						  2.99 x 10(8) m/s. When light travels in different materials such as air, water,
						  minerals or oil, it does not travel at this speed. It travels slower. This
						  slowing is a function of both the material through which the light is traveling
						  and the wavelength or frequency of the light. In general, the more dense the
						  material, the slower the light travels. Also, generally, the higher the
						  frequency, the slower the light will travel. The ratio of the speed of light in
						  a vacuum to that in a material is called the index of refraction (n). It is
						  usually measured at 589 nm (the sodium D line). If white light (light
						  containing all the visible wavelengths) travels through a material, rays of
						  longer wavelengths will travel faster than those of shorter wavelengths, this
						  separation is called dispersion. Dispersion is used as an identifier of
						  materials as described in Section
						  4.6.
4.2. Material Properties
Materials are either amorphous or crystalline. The
						  difference between these two descriptions depends on the positions of the atoms
						  in them. The atoms in amorphous materials are randomly arranged with no long
						  range order. An example of an amorphous material is glass. The atoms in
						  crystalline materials, on the other hand, are in regular arrays and have long
						  range order. Most of the atoms can be found in highly predictable locations.
						  Examples of crystalline material are salt, gold, and the asbestos
						  minerals.
It is beyond the scope of this method to describe the
						  different types of crystalline materials that can be found, or the full
						  description of the classes into which they can fall. However, some general
						  crystallography is provided below to give a foundation to the procedures
						  described.
With the exception of anthophyllite, all the asbestos
						  minerals belong to the monoclinic crystal type. The unit cell is the basic
						  repeating unit of the crystal and for monoclinic crystals can be described as
						  having three unequal sides, two 90 deg. angles and one angle not equal to 90
						  deg.. The orthorhombic group, of which anthophyllite is a member has three
						  unequal sides and three 90 deg. angles. The unequal sides are a consequence of
						  the complexity of fitting the different atoms into the unit cell. Although the
						  atoms are in a regular array, that array is not symmetrical in all directions.
						  There is long range order in the three major directions of the crystal.
						  However, the order is different in each of the three directions. This has the
						  effect that the index of refraction is different in each of the three
						  directions. Using polarized light, we can investigate the index of refraction
						  in each of the directions and identify the mineral or material under
						  investigation. The indices alpha, beta, and gamma are used to identify the
						  lowest, middle, and highest index of refraction respectively. The x direction,
						  associated with alpha is called the fast axis. Conversely, the z direction is
						  associated with gamma and is the slow direction. Crocidolite has alpha along
						  the fiber length making it "length-fast". The remainder of the asbestos
						  minerals have the gamma axis along the fiber length. They are called
						  "length-slow". This orientation to fiber length is used to aid in the
						  identification of asbestos.
4.3. Polarized Light Technique
Polarized light microscopy as described in this section
						  uses the phase-polar microscope described in Section
						  3.2. A phase contrast microscope is
						  fitted with two polarizing elements, one below and one above the sample. The
						  polarizers have their polarization directions at right angles to each
						  other.
Depending on the tests performed, there may be a
						  compensator between these two polarizing elements. Light emerging from a
						  polarizing element has its electric vector pointing in the polarization
						  direction of the element. The light will not be subsequently transmitted
						  through a second element set at a right angle to the first element. Unless the
						  light is altered as it passes from one element to the other, there is no
						  transmission of light.
4.4. Angle of Extinction
Crystals which have different crystal regularity in two
						  or three main directions are said to be anisotropic. They have a different
						  index of refraction in each of the main directions. When such a crystal is
						  inserted between the crossed polars, the field of view is no longer dark but
						  shows the crystal in color. The color depends on the properties of the crystal.
						  The light acts as if it travels through the crystal along the optical axes. If
						  a crystal optical axis were lined up along one of the polarizing directions
						  (either the polarizer or the analyzer) the light would appear to travel only in
						  that direction, and it would blink out or go dark. The difference in degrees
						  between the fiber direction and the angle at which it blinks out is called the
						  angle of extinction. When this angle can be measured, it is useful in
						  identifying the mineral. The procedure for measuring the angle of extinction is
						  to first identify the polarization direction in the microscope. A commercial
						  alignment slide can be used to establish the polarization directions or use
						  anthophyllite or another suitable mineral. This mineral has a zero degree angle
						  of extinction and will go dark to extinction as it aligns with the polarization
						  directions. When a fiber of anthophyllite has gone to extinction, align the
						  eyepiece reticle or graticule with the fiber so that there is a visual cue as
						  to the direction of polarization in the field of view. Tape or otherwise secure
						  the eyepiece in this position so it will not shift.
After the polarization direction has been identified in
						  the field of view, move the particle of interest to the center of the field of
						  view and align it with the polarization direction. For fibers, align the fiber
						  along this direction. Note the angular reading of the rotating stage. Looking
						  at the particle, rotate the stage until the fiber goes dark or "blinks out".
						  Again note the reading of the stage. The difference in the first reading and
						  the second is an angle of extinction.
The angle measured may vary as the orientation of the
						  fiber changes about its long axis. Tables of mineralogical data usually report
						  the maximum angle of extinction. Asbestos forming minerals, when they exhibit
						  an angle of extinction, usually do show an angle of extinction close to the
						  reported maximum, or as appropriate depending on the substitution
						  chemistry.
4.5. Crossed Polars with Compensator
When the optical axes of a crystal are not lined up
						  along one of the polarizing directions (either the polarizer or the analyzer)
						  part of the light travels along one axis and part travels along the other
						  visible axis. This is characteristic of birefringent materials.
The color depends on the difference of the two visible
						  indices of refraction and the thickness of the crystal. The maximum difference
						  available is the difference between the alpha and the gamma axes. This maximum
						  difference is usually tabulated as the birefringence of the crystal.
For this test, align the fiber at 45 deg. to the
						  polarization directions in order to maximize the contribution to each of the
						  optical axes. The colors seen are called retardation colors. They arise from
						  the recombination of light which has traveled through the two separate
						  directions of the crystal. One of the rays is retarded behind the other since
						  the light in that direction travels slower. On recombination, some of the
						  colors which make up white light are enhanced by constructive interference and
						  some are suppressed by destructive interference. The result is a color
						  dependent on the difference between the indices and the thickness of the
						  crystal. The proper colors, thicknesses, and retardations are shown on a
						  Michel-Levy chart. The three items, retardation, thickness and birefringence
						  are related by the following relationship:
R = t (n gamma - n alpha)
R = retardation, t = crystal thickness in µm,
						  and
n alpha, gamma = indices of refraction.
Examination of the equation for asbestos minerals
						  reveals that the visible colors for almost all common asbestos minerals and
						  fiber sizes are shades of gray and black. The eye is relatively poor at
						  discriminating different shades of gray. It is very good at discriminating
						  different colors. In order to compensate for the low retardation, a compensator
						  is added to the light train between the polarization elements. The compensator
						  used for this test is a gypsum plate of known thickness and birefringence. Such
						  a compensator when oriented at 45 deg. to the polarizer direction, provides a
						  retardation of 530 nm of the 530 nm wavelength color. This enhances the red
						  color and gives the background a characteristic red to red-magenta color. If
						  this "full-wave" compensator is in place when the asbestos preparation is
						  inserted into the light train, the colors seen on the fibers are quite
						  different. Gypsum, like asbestos has a fast axis and a slow axis. When a fiber
						  is aligned with its fast axis in the same direction as the fast axis of the
						  gypsum plate, the ray vibrating in the slow direction is retarded by both the
						  asbestos and the gypsum. This results in a higher retardation than would be
						  present for either of the two minerals. The color seen is a second order blue.
						  When the fiber is rotated 90 deg. using the rotating stage, the slow direction
						  of the fiber is now aligned with the fast direction of the gypsum and the fast
						  direction of the fiber is aligned with the slow direction of the gypsum. Thus,
						  one ray vibrates faster in the fast direction of the gypsum, and slower in the
						  slow direction of the fiber; the other ray will vibrate slower in the slow
						  direction of the gypsum and faster in the fast direction of the fiber. In this
						  case, the effect is subtractive and the color seen is a first order yellow. As
						  long as the fiber thickness does not add appreciably to the color, the same
						  basic colors will be seen for all asbestos types except crocidolite. In
						  crocidolite the colors will be weaker, may be in the opposite directions, and
						  will be altered by the blue absorption color natural to crocidolite. Hundreds
						  of other materials will give the same colors as asbestos, and therefore, this
						  test is not definitive for asbestos. The test is useful in discriminating
						  against fiberglass or other amorphous fibers such as some synthetic fibers.
						  Certain synthetic fibers will show retardation colors different than asbestos;
						  however, there are some forms of polyethylene and aramid which will show
						  morphology and retardation colors similar to asbestos minerals. This test must
						  be supplemented with a positive identification test when birefringent fibers
						  are present which cannot be excluded by morphology. This test is relatively
						  ineffective for use on fibers less than 1 µm in diameter. For positive
						  confirmation TEM or SEM should be used if no larger bundles or fibers are
						  visible.
4.6. Dispersion Staining
Dispersion microscopy or dispersion staining is the
						  method of choice for the identification of asbestos in bulk materials. Becke
						  line analysis is used by some laboratories and yields the same results as does
						  dispersion staining for asbestos and can be used in lieu of dispersion
						  staining. Dispersion staining is performed on the same platform as the
						  phase-polar analysis with the analyzer and compensator removed. One polarizing
						  element remains to define the direction of the light so that the different
						  indices of refraction of the fibers may be separately determined. Dispersion
						  microscopy is a dark-field technique when used for asbestos. Particles are
						  imaged with scattered light. Light which is unscattered is blocked from
						  reaching the eye either by the back field image mask in a McCrone objective or
						  a back field image mask in the phase condenser. The most convenient method is
						  to use the rotating phase condenser to move an oversized phase ring into place.
						  The ideal size for this ring is for the central disk to be just larger than the
						  objective entry aperture as viewed in the back focal plane. The larger the
						  disk, the less scattered light reaches the eye. This will have the effect of
						  diminishing the intensity of dispersion color and will shift the actual color
						  seen. The colors seen vary even on microscopes from the same manufacturer. This
						  is due to the different bands of wavelength exclusion by different mask sizes.
						  The mask may either reside in the condenser or in the objective back focal
						  plane. It is imperative that the analyst determine by experimentation with
						  asbestos standards what the appropriate colors should be for each asbestos
						  type. The colors depend also on the temperature of the preparation and the
						  exact chemistry of the asbestos. Therefore, some slight differences from the
						  standards should be allowed. This is not a serious problem for commercial
						  asbestos uses. This technique is used for identification of the indices of
						  refraction for fibers by recognition of color. There is no direct numerical
						  readout of the index of refraction. Correlation of color to actual index of
						  refraction is possible by referral to published conversion tables. This is not
						  necessary for the analysis of asbestos. Recognition of appropriate colors along
						  with the proper morphology are deemed sufficient to identify the commercial
						  asbestos minerals. Other techniques including SEM, TEM, and XRD may be required
						  to provide additional information in order to identify other types of
						  asbestos
Make a preparation in the suspected matching high
						  dispersion oil, e.g., n=1.550 for chrysotile. Perform the preliminary tests to
						  determine whether the fibers are birefringent or not. Take note of the
						  morphological character. Wavy fibers are indicative of chrysotile while long,
						  straight, thin, frayed fibers are indicative of amphibole asbestos. This can
						  aid in the selection of the appropriate matching oil. The microscope is set up
						  and the polarization direction is noted as in Section
						  4.4. Align a fiber with the
						  polarization direction. Note the color. This is the color parallel to the
						  polarizer. Then rotate the fiber rotating the stage 90 deg. so that the
						  polarization direction is across the fiber. This is the perpendicular position.
						  Again note the color. Both colors must be consistent with standard asbestos
						  minerals in the correct direction for a positive identification of asbestos. If
						  only one of the colors is correct while the other is not, the identification is
						  not positive. If the colors in both directions are bluish-white, the analyst
						  has chosen a matching index oil which is higher than the correct matching oil,
						  e.g. the analyst has used n=1.620 where chrysotile is present. The next lower
						  oil (Section
						  3.5.) should be used to prepare
						  another specimen. If the color in both directions is yellow-white to
						  straw-yellow-white, this indicates that the index of the oil is lower than the
						  index of the fiber, e.g. the preparation is in n=1.550 while anthophyllite is
						  present. Select the next higher oil (Section
						  3.5.) and prepare another slide.
						  Continue in this fashion until a positive identification of all asbestos
						  species present has been made or all possible asbestos species have been ruled
						  out by negative results in this test. Certain plant fibers can have similar
						  dispersion colors as asbestos. Take care to note and evaluate the morphology of
						  the fibers or remove the plant fibers in pre-preparation. Coating material on
						  the fibers such as carbonate or vinyl may destroy the dispersion color.
						  Usually, there will be some outcropping of fiber which will show the colors
						  sufficient for identification. When this is not the case, treat the sample as
						  described in Section
						  3.3. and then perform dispersion
						  staining. Some samples will yield to Becke line analysis if they are coated or
						  electron microscopy can be used for identification.
5. References
5.1. Crane, D.T., Asbestos in Air, OSHA method ID160,
						  Revised November 1992.
5.2. Ford, W.E., Dana's Textbook of Mineralogy; Fourth
						  Ed.; John Wiley and Son, New York, 1950, p. vii.
5.3. Selikoff, I.J., Lee, D.H.K., Asbestos and Disease,
						  Academic Press, New York, 1978, pp. 3,20.
5.4. Women Inspectors of Factories. Annual Report for
						  1898, H.M. Statistical Office, London, p. 170 (1898).
5.5. Selikoff, I.J., Lee, D.H.K., Asbestos and Disease,
						  Academic Press, New York, 1978, pp. 26,30.
5.6. Campbell, W.J., et al, Selected Silicate Minerals
						  and Their Asbestiform Varieties, United States Department of the Interior,
						  Bureau of Mines, Information Circular 8751, 1977.
5.7. Asbestos, Code of Federal Regulations,
						  29 CFR
						  1910.1001 and
						  29 CFR
						  1926.58.
5.8. National Emission Standards for Hazardous Air
						  Pollutants; Asbestos NESHAP Revision, Federal Register, Vol. 55, No. 224, 20
						  November 1990, p. 48410.
5.9. Ross, M. The Asbestos Minerals: Definitions,
						  Description, Modes of Formation, Physical and Chemical Properties and Health
						  Risk to the Mining Community, Nation Bureau of Standards Special Publication,
						  Washington, D.C., 1977.
5.10. Lilis, R., Fibrous Zeolites and Endemic
						  Mesothelioma in Cappadocia, Turkey, J. Occ Medicine, 1981,
						  23,(8),548-550.
5.11. Occupational Exposure to Asbestos -- 1972, U.S.
						  Department of Health Education and Welfare, Public Health Service, Center for
						  Disease Control, National Institute for Occupational Safety and Health,
						  HSM-72-10267.
5.12. Campbell,W.J., et al, Relationship of Mineral
						  Habit to Size Characteristics for Tremolite Fragments and Fibers, United States
						  Department of the Interior, Bureau of Mines, Information Circular 8367,
						  1979.
5.13. Mefford, D., DCM Laboratory, Denver, private
						  communication, July 1987.
5.14. Deer, W.A., Howie, R.A., Zussman, J., Rock
						  Forming Minerals, Longman, Thetford, UK, 1974.
5.15. Kerr, P.F., Optical Mineralogy; Third Ed.
						  McGraw-Hill, New York, 1959.
5.16. Veblen, D.R. (Ed.), Amphiboles and Other Hydrous
						  Pyriboles -- Mineralogy, Reviews in Mineralogy, Vol 9A, Michigan, 1982, pp
						  1-102.
5.17. Dixon, W.C., Applications of Optical Microscopy
						  in the Analysis of Asbestos and Quartz, ACS Symposium Series, No. 120,
						  Analytical Techniques in Occupational Health Chemistry, 1979.
5.18. Polarized Light Microscopy, McCrone Research
						  Institute, Chicago, 1976.
5.19. Asbestos Identification, McCrone Research
						  Institute, G & G printers, Chicago, 1987.
5.20. McCrone, W.C., Calculation of Refractive Indices
						  from Dispersion Staining Data, The Microscope, No 37, Chicago, 1989.
5.21. Levadie, B. (Ed.), Asbestos and Other Health
						  Related Silicates, ASTM Technical Publication 834, ASM, Philadelphia
						  1982.
5.22. Steel, E. and Wylie, A., Riordan, P.H. (Ed.),
						  Mineralogical Characteristics of Asbestos, Geology of Asbestos Deposits, pp.
						  93-101, SME-AIME, 1981.
5.23. Zussman, J., The Mineralogy of Asbestos,
						  Asbestos: Properties, Applications and Hazards, pp. 45-67 Wiley,
						  1979.
1. New
						  Appendix J to section
						  5208 filed 5-3-96; operative 7-3-96
						  (Register 96, No. 18).
2. Change without regulatory effect repealing
						  and adopting new Figure 1 filed 5-19-2008 pursuant to section
						  100, title 1, California Code of
						  Regulations (Register 2008, No. 21).
3. Amendment of item 3.1.(e)
						  filed 5-6-2013; operative 5-6-2013 pursuant to Labor Code section
						  142.3(a)(4)(C).
						  Submitted to OAL for printing only pursuant to Labor Code section
						  142.3(a)(4)
						  (Register 2013, No. 19).
4. Amendment of item 3.1.(e) refiled
						  11-6-2013; operative 11-6-2013 pursuant to Labor Code section
						  142.3(a)(4)(C).
						  Submitted to OAL for printing only pursuant to Labor Code section
						  142.3(a)(4)
						  (Register 2013, No. 45).
5. Repealer of 11-6-2013 order by operation
						  of law 5-6-2014 pursuant to Labor Code 142.3 (Register 2014, No.
						  19).
6. Amendment of item 3.1.(e) filed 5-5-2014; operative 5-6-2014
						  pursuant to Government Code section
						  11343.4(b)(3)
						  (Register 2014, No. 19).
Note: Authority cited: Section
							 142.3. Labor
							 Code. Reference: Section
							 142.3, Labor
							 Code.