Title 40


Appendix E to Subpart E of Part 763 - Interim Method of the Determination of Asbestos in Bulk Insulation Samples

40: : Appendix E

Appendix E to Subpart E of Part 763 - Interim Method of the Determination of Asbestos in Bulk Insulation Samples Section 1. Polarized Light Microscopy 1.1 Principle and Applicability

Bulk samples of building materials taken for asbestos identification are first examined for homogeneity and preliminary fiber identification at low magnification. Positive identification of suspect fibers is made by analysis of subsamples with the polarized light microscope.

The principles of optical mineralogy are well established. 1 2 A light microscope equipped with two polarizing filters is used to observe specific optical characteristics of a sample. The use of plane polarized light allows the determination of refractive indices along specific crystallographic axes. Morphology and color are also observed. A retardation plate is placed in the polarized light path for determination of the sign of elongation using orthoscopic illumination. Orientation of the two filters such that their vibration planes are perpendicular (crossed polars) allows observation of the birefringence and extinction characteristics of anisotropic particles.

Quantitative analysis involves the use of point counting. Point counting is a standard technique in petrography for determining the relative areas occupied by separate minerals in thin sections of rock. Background information on the use of point counting 2 and the interpretation of point count data 3 is available.

This method is applicable to all bulk samples of friable insulation materials submitted for identification and quantitation of asbestos components.

1.2 Range

The point counting method may be used for analysis of samples containing from 0 to 100 percent asbestos. The upper detection limit is 100 percent. The lower detection limit is less than 1 percent.

1.3 Interferences

Fibrous organic and inorganic constituents of bulk samples may interfere with the identification and quantitation of the asbestos mineral content. Spray-on binder materials may coat fibers and affect color or obscure optical characteristics to the extent of masking fiber identity. Fine particles of other materials may also adhere to fibers to an extent sufficient to cause confusion in identification. Procedures that may be used for the removal of interferences are presented in Section

1.4 Precision and Accuracy

Adequate data for measuring the accuracy and precision of the method for samples with various matrices are not currently available. Data obtained for samples containing a single asbestos type in a simple matrix are available in the EPA report Bulk Sample Analysis for Asbestos Content: Evaluation of the Tentative Method. 4

1.5 Apparatus 1.5.1 Sample Analysis

A low-power binocular microscope, preferably stereoscopic, is used to examine the bulk insulation sample as received.

Microscope: binocular, 10-45X (approximate). • Light Source: incandescent or fluorescent. • Forceps, Dissecting Needles, and ProbesGlassine Paper or Clean Glass Plate

Compound microscope requirements: A polarized light microscope complete with polarizer, analyzer, port for wave retardation plate, 360° graduated rotating stage, substage condenser, lamp, and lamp iris.

Polarized Light Microscope: described above. • Objective Lenses: 10X, 20X, and 40X or near equivalent. • Dispersion Staining Objective Lens (optional) • Ocular Lens: 10X minimum. • Eyepiece Reticle: cross hair or 25 point Chalkley Point Array. • Compensator Plate: 550 millimicron retardation. 1.5.2 Sample Preparation

Sample preparation apparatus requirements will depend upon the type of insulation sample under consideration. Various physical and/or chemical means may be employed for an adequate sample assessment.

Ventilated Hood or negative pressure glove box. • Microscope SlidesCoverslipsMortar and Pestle: agate or porcelain. (optional) • Wylie Mill (optional) • Beakers and Assorted Glassware (optional) • Certrifuge (optional) • Filtration apparatus (optional) • Low temperature asher (optional) 1.6 Reagents 1.6.1 Sample Preparation • Distilled Water (optional)Dilute CH3COOH: ACS reagent grade (optional) • Dilute HCl: ACS reagent grade (optional) • Sodium metaphosphate (NaPO3)6 (optional) 1.6.2 Analytical Reagents

Refractive Index Liquids: 1.490-1.570, 1.590-1.720 in increments of 0.002 or 0.004.

Refractive Index Liquids for Dispersion Staining: high-dispersion series, 1.550, 1.605, 1.630 (optional). • UICC Asbestos Reference Sample Set: Available from: UICC MRC Pneumoconiosis Unit, Llandough Hospital, Penarth, Glamorgan CF6 1XW, UK, and commercial distributors. • Tremolite-asbestos (source to be determined) • Actinolite-asbestos (source to be determined) 1.7 Procedures Note:

Exposure to airborne asbestos fibers is a health hazard. Bulk samples submitted for analysis are usually friable and may release fibers during handling or matrix reduction steps. All sample and slide preparations should be carried out in a ventilated hood or glove box with continuous airflow (negative pressure). Handling of samples without these precautions may result in exposure of the analyst and contamination of samples by airborne fibers.

1.7.1 Sampling

Samples for analysis of asbestos content shall be taken in the manner prescribed in Reference 5 and information on design of sampling and analysis programs may be found in Reference 6. If there are any questions about the representative nature of the sample, another sample should be requested before proceeding with the analysis.

1.7.2 Analysis Gross Examination

Bulk samples of building materials taken for the identification and quantitation of asbestos are first examined for homogeneity at low magnification with the aid of a stereomicroscope. The core sample may be examined in its container or carefully removed from the container onto a glassine transfer paper or clean glass plate. If possible, note is made of the top and bottom orientation. When discrete strata are identified, each is treated as a separate material so that fibers are first identified and quantified in that layer only, and then the results for each layer are combined to yield an estimate of asbestos content for the whole sample. Sample Preparation

Bulk materials submitted for asbestos analysis involve a wide variety of matrix materials. Representative subsamples may not be readily obtainable by simple means in heterogeneous materials, and various steps may be required to alleviate the difficulties encountered. In most cases, however, the best preparation is made by using forceps to sample at several places from the bulk material. Forcep samples are immersed in a refractive index liquid on a microscope slide, teased apart, covered with a cover glass, and observed with the polarized light microscope.

Alternatively, attempts may be made to homogenize the sample or eliminate interferences before further characterization. The selection of appropriate procedures is dependent upon the samples encountered and personal preference. The following are presented as possible sample preparation steps.

A mortar and pestle can sometimes be used in the size reduction of soft or loosely bound materials though this may cause matting of some samples. Such samples may be reduced in a Wylie mill. Apparatus should be clean and extreme care exercised to avoid cross-contamination of samples. Periodic checks of the particle sizes should be made during the grinding operation so as to preserve any fiber bundles present in an identifiable form. These procedures are not recommended for samples that contain amphibole minerals or vermiculite. Grinding of amphiboles may result in the separation of fiber bundles or the production of cleavage fragments with aspect ratios greater than 3:1. Grinding of vermiculite may also produce fragments with aspect ratios greater than 3:1.

Acid treatment may occasionally be required to eliminate interferences. Calcium carbonate, gypsum, and bassanite (plaster) are frequently present in sprayed or trowelled insulations. These materials may be removed by treatment with warm dilute acetic acid. Warm dilute hydrochloric acid may also be used to remove the above materials. If acid treatment is required, wash the sample at least twice with distilled water, being careful not to lose the particulates during decanting steps. Centrifugation or filtration of the suspension will prevent significant fiber loss. The pore size of the filter should be 0.45 micron or less. Caution: prolonged acid contact with the sample may alter the optical characteristics of chrysotile fibers and should be avoided.

Coatings and binding materials adhering to fiber surfaces may also be removed by treatment with sodium metaphosphate. 7 Add 10 mL of 10g/L sodium metaphosphate solution to a small (0.1 to 0.5 mL) sample of bulk material in a 15-mL glass centrifuge tube. For approximately 15 seconds each, stir the mixture on a vortex mixer, place in an ultrasonic bath and then shake by hand. Repeat the series. Collect the dispersed solids by centrifugation at 1000 rpm for 5 minutes. Wash the sample three times by suspending in 10 mL distilled water and recentrifuging. After washing, resuspend the pellet in 5 mL distilled water, place a drop of the suspension on a microscope slide, and dry the slide at 110 °C.

In samples with a large portion of cellulosic or other organic fibers, it may be useful to ash part of the sample and view the residue. Ashing should be performed in a low temperature asher. Ashing may also be performed in a muffle furnace at temperatures of 500 °C or lower. Temperatures of 550 °C or higher will cause dehydroxylation of the asbestos minerals, resulting in changes of the refractive index and other key parameters. If a muffle furnace is to be used, the furnace thermostat should be checked and calibrated to ensure that samples will not be heated at temperatures greater than 550 °C.

Ashing and acid treatment of samples should not be used as standard procedures. In order to monitor possible changes in fiber characteristics, the material should be viewed microscopically before and after any sample preparation procedure. Use of these procedures on samples to be used for quantitation requires a correction for percent weight loss. Fiber Identification

Positive identification of asbestos requires the determination of the following optical properties.

• Morphology • Color and pleochroism • Refractive indices • Birefringence • Extinction characteristics • Sign of elongation Table 1-1 lists the above properties for commercial asbestos fibers. Figure 1-1 presents a flow diagram of the examination procedure. Natural variations in the conditions under which deposits of asbestiform minerals are formed will occasionally produce exceptions to the published values and differences from the UICC standards. The sign of elongation is determined by use of the compensator plate and crossed polars. Refractive indices may be determined by the Becke line test. Alternatively, dispersion staining may be used. Inexperienced operators may find that the dispersion staining technique is more easily learned, and should consult Reference 9 for guidance. Central stop dispersion staining colors are presented in Table 1-2. Available high-dispersion (HD) liquids should be used.

Table 1-1 - Optical Properties of Asbestoc Fibers

Mineral Morphology, color a Refractive indices b Birefring- ence Extinction Sign of elonation
α γ
Chrysotile (asbestiform serpentine) Wavy fibers. Fiber bundles have splayed ends and “kinks”. Aspect ratio typically >10:1. Colorless 3, nonpleochroic 1.493-1.560 1.517-1.562 f (normally 1.556) .008 | to fiber length +
(length slow)
Amosite (asbestiform grunerite) Straight, rigid fibers. Aspect ratio typically >10:1. Colorless to brown, nonpleochroic or weakly so. Opaque inclusions may be present 1.635-1.696 1.655-1.729 f (normally 1.696-1.710 .020-.033 | to fiber length +
(length slow)
Crocidolite (asbestiform Riebeckite) Straight, rigid fibers. Thick fibers and bundles common, blue to purple-blue in color. Pleochroic. Birefringence is generally masked by blue color 1.654-1.701 1.668-1.717 3e (normally close to 1.700) .014-.016 | to fiber length
(length fast)
Anthophyllite-asbestos Straight fibers and acicular cleavage fragments. d Some composite fibers. Aspect ratio <10:1. Colorless to light brown 1.596-1.652 1.615-1.676 f .019-.024 | to fiber length +
(length slow)
Tremolite-actinolite-asbestos Normally present as acicular or prismatic cleavage fragments. d Single crystals predominate, aspect ratio <10:1. Colorless to pale green 1.599-1.668 1.622-1.688 f .023-.020 Oblique extinction, 10-20° for fragments. Composite fibers show | extinction +
(length slow)