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ENVIRONMENTAL FORENSIC MICROSCOPY
CHAPTER 13
E N V I R O N M E N TA L F O R E N S I C MICROSCOPY Jam e s R . Mill e t te an d Richard S . Brow n
13.1 Introduction 13.2 Sampling and Analysis Equipment 13.2.1 Air Sampling 13.2.2 Surface Dust Sampling 13.2.2.1 Microscopy Equipment 13.3 Determining the Nature of Contaminants 13.3.1 Particle Analysis 13.3.2 Product Identification by Microscopy 13.3.2.1 Sampling 13.3.2.2 Analysis 13.4 Measuring the Extent of a Specific Contaminant 13.4.1 Asbestos 13.4.1.1 Vermiculite Analysis 13.4.2 Nonasbestos Fibers 13.4.2.1 ISO Method 14966 13.4.2.2 Glass Fibers 13.4.2.3 Ceramic Whiskers 13.4.3 Nonfibrous Particulate 13.5 Case Studies—Examples of Environmental Forensic Microscopy Investigations 13.5.1 Elevated Lead in a Child 13.5.2 A Spot Called Ralph 13.5.3 Automobiles with a Sooty Deposition—1 13.5.4 Automobiles with a Sooty Deposition—2 13.5.5 WTC Signature Search References 1 3 .1
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INTRODUCTION
Environmental forensic microscopy is the application of microscopy to the identification, collection, and analysis of small particles and the interpretation of the analyses performed as they pertain to environmental investigations
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and litigation. Environmental investigations are generally assessments of the nature and extent of a contaminant. Microscopy is most useful in examining, classifying, and identifying particulate contaminants. Determining the nature of a contaminant and measuring the extent of a contaminant are two fundamentally, although often overlapping, questions. Often the questions put to the environmental forensic microscopist are “What is this dust?” and “Where did it come from?” However, the environmental forensic microscopist may also be asked to quantify the amount of a specific contaminant in several samples in an effort to determine the extent of the problem and to establish a procedure for further sampling and analysis. Answering the two questions has given rise to different sets of methods. In answering the question about how much of a specific contaminant is present, that contaminant must be sorted and identified. Other particles comprising the matrix of the sample may be ignored. In answering the questions about the nature of a contaminant dust, a broader range of knowledge may be required to sort the various contaminants into appropriate classes or categories. Environmental forensic microscopy measurement methods tend to be fairly specific with a designated set of counting rules defined so that different analysts can get comparable numerical results. Environmental forensic microscopy methods dealing with the nature of a contaminant sample tend to be less formalized because they must take into account a vast variety of potential particle types. In answering the question “What is this dust?”, the microscopist cannot ignore all the particle types but one. The microscopist must allow the constituents of the sample to dictate which basic standard microscopy procedures and other techniques he or she will use in solving the analytical problem. When dealing with an environmental particle contamination situation of unknown origin, the forensic investigation of the nature of the contaminant naturally takes place first. However, in some situations where the nature of the contaminant is known, measurement methods may be employed first. 13. 2
S A M P L I N G A N D A N A LY S I S E Q U I P M E N T
The sampling and analysis methods used in environmental forensic investigations are drawn primarily from the criminal forensics, industrial hygiene, and environmental monitoring areas. Combining various aspects of these disciplines allows the investigator to generate a procedure that fits the varied and sometimes very complex environmental situation. 13.2.1 AIR SAMPLING Collecting samples of airborne particles for environmental forensic investigations usually is done using membrane filter sampling cassettes. Various types of membrane filters are used in environmental and industrial hygiene
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Figure 13.1 Scanning electron microscope images of filters used to collect airborne particles. Spheres of 5 micrometers and 1 micrometer are overlaid to show how small particles would appear on the filter surface.
sampling. These include filters made of mixed cellulose ester polymer, polycarbonate polymer, glass fiber filters, quartz fiber filters, silver membrane filters, and polyvinyl chloride (PVC) filters. Figure 13.1 shows a comparison of the surfaces of the various filter types. Spheres representing particles of 5 micrometer diameter and 1 micrometer diameter are overlaid on the images. With the glass fiber filters, particles can be lost in the filter thickness. Backwashing the glass filter to remove the particles produces a sample that contains glass fiber fragments. It is clear why microscopists prefer air samples collected on polycarbonate (PC) filters. The PC filters have a flat surface because they are a “straight through” filter rather than a tortuous path design that is found in the other filter types.
13.2.2 SURFACE DUST SAMPLING Surface dust particle collection techniques, varying according to situation, are chosen to maximize probative value and when possible to preserve a
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portion for future analysis. Common particle collection techniques for environmental forensic microscopy investigations of surface particulate include scraping, brushing, taping with cellophane tape on a slide or post-it notes, scoop and bag techniques, wipe sampling, and vacuuming with either a microvac (air cassette) or large-scale vacuuming (Ness, 1994; Millette and Few, 2001). Sample collection procedures with cotton or polyester balls, wipes, and tape slides for outdoor surfaces are described in the ASTM Standard Practice D6602 (ASTM, 2003). ASTM D6602 is a standard procedure that serves as an excellent basis for environmental forensic microscopy investigations where soot might be involved. This ASTM standard was designed primarily for the determination of carbon black among soot particles and other dark particles but provides the framework for the microscopy studies necessary to determine the identity of all particles and possible sources of surface contamination.
13.2.2.1 Microscopy Equipment Microscopic analyses in environmental forensic investigations are accomplished utilizing a combination of visible light, infrared light, and electron microscopy. The light microscopy usually is performed with polarized light microscopy (PLM), but may involve phase contrast (PCM), darkfield, or fluorescence microscopy. Infrared microscopy is done using Fourier transform infrared microspectroscopy (micro-FTIR). FTIR is very useful when identifying organic molecules such as plastics and polymers. Scanning electron microscopy (SEM) allows the analyst to see particles that are smaller than can be seen with light microscopy, and when equipped with an x-ray analysis unit, allows the analyst to determine the elemental composition of the particles. Transmission electron microscopy (TEM) also allows the analyst to see particles that are smaller than can be seen with light microscopy, and when equipped with electron diffraction capabilities and an x-ray analysis unit, allows the analyst to determine the crystal structure and elemental composition of the particles. ASTM Practice D6602 lists different types of microscopes that can be used to investigate environmental particles: a stereobinocular microscope, capable of 1 to 60× magnification; a polarized light microscope (PLM), equipped with objectives in the 4 to 100× range of magnification (for a total magnification between 40 and 1000×); a transmission electron microscope (TEM), equipped with a suitable camera; and a scanning electron microscope (SEM), equipped with energy or wavelength dispersive analysis equipment (EDS or WDS). A TEM equipped with selected area electron diffraction (SAED) and EDS is referred to as an analytical electron microscope (AEM).
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13. 3
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D E T E R M I N I N G T H E N AT U R E O F C O N TA M I N A N T S
For questions involving the nature of particulate contaminants, the general procedure in environmental forensic investigations is the same as the general forensic science approach to trace analysis; that is, to collect samples of the particles (dust, dirt, or suspensions in liquid) in question, evaluate the samples to classify and identify the particles, identify possible sources, and then to compare the sample particle types to the suspect source(s) particle types (see Table 13.1).
13.3.1
PARTICLE ANALYSIS
The McCrone Particle Atlas is the standard reference for environmental forensic microscopical particle analysis (McCrone, 1973). Published first in 1972, this six-volume set (now available only on CD-ROM) contains thousands of images of different types of particles and information about their microscopical characteristics observable by light and electron microscopy. There are also clear discussions of various topics important to the proper use of PLM in identifying particles including birefringence, refractive index, and dispersion staining. Another useful reference atlas for the forensic microscopist was published by Petraco and Kubic (2003). Illustrations and information about the morphological characteristics of pollen grains can be found in Faegri, Iversen, and Waterbolk (1964). Images and information about the appearances of fungal spores can be found in Hawksworth et al. (1995). Images of soil minerals can be found in Graves (1979), Krumbein and Pettijohn (1938), Palenik (1979), and Hopen (2004), along with useful information about the identification of soil minerals as individual (detrital) grains. Images of soot have been published by Medalia and Rivin (1982), Huffman et al. (2000), and Clague et al. (1999). Images of aciniform flare combustion can be seen in Kostiuk, Johnson, and Thomas (2004). Although environmental forensic microscopical particle analysis of dusts may seem daunting due to the many types of particles possible, it has been found that for most common situations such as normal residential and
Collect Analyze Identify particle type Identify possible sources Compare sample particles to suspect source(s) Report Interpret findings as they pertain to law/science
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Table 13.1 General forensic science approach to trace evidence analysis.
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building dust, the particles can be classified using approximately 20 categories (Millette, Lioy et al., 2003; Turner, Millette et al., 2005).
13.3.2 PRODUCT IDENTIFICATION BY MICROSCOPY Product identification is a special case of environmental forensic microscopy because it involves, in addition to particle classifications, the combining of the results of several analytical techniques to determine the composition of a product and then compare the overall results to product formula information. The same process may be used to compare dust particles with building products or other man-made compounds. Sections 13.3.2.1 and 13.3.2.2 describe the general procedures used for product identification when matching asbestos-containing products with manufacturers’ formulae. 13.3.2.1 Sampling Sampling involves removing the material in a manner that will maintain the layer structure and integrity of layered samples. This can be accomplished with a polycarbonate tube used as a cork borer or by carefully cutting through the product down to the substrate, wrapping in paper and cushioning the sample so as the product cannot be crushed or crumbled. Wet samples should be thoroughly air dried prior to packaging to discourage fungal and mold growth. Sampling a variety of products having different physical dimensions and cohesion requires the person doing the sampling to be creative and cognizant of the type of analysis that will be performed. Chain-of-custody forms must accompany the samples to the laboratory. Once the sample reaches the laboratory the packing is carefully removed and the sample’s condition “as received” can be recorded, in some cases, with photographs. Examination with reflected light under low magnification is performed to determine if the sample represents a single product or multiple products displayed as multiple layers. If multiple layers are present, the color and layer sequence can be documented with a photograph. The layers are examined as individual products as the analysis continues. Each sample is split into four vials. One vial is sent to each analysis station for PLM, SEM-EDS, TEM, or acid-soluble weight percent. Quality control for each analysis is checked by comparing the results of each examination for a particular sample against each other. For instance, a sample that contained chrysotile as identified by PLM should also have chrysotile characterized by SEM and identified by TEM. Should an ingredient that was determined to be a major component of a sample not be observed by each of the microscopical techniques, a review of the analysis would be undertaken to determine why. Some particles, such as montmorillonite clay, may be of a
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Table 13.2
Acoustical plaster Ceiling tiles Fireproofing Pipe insulation
Diatoms Kaolinite Montmorillonite Fiberglass® Quartz and soil minerals Iron chromite Chrysotile Amosite Crocidolite Tremolite, actinolite, anthophyllite Fly-ash
Mineral wool (soluble in some procedures) Calcium carbonate Portland cement
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Common asbestoscontaining product types that have been tested for product ID.
Starch Perlite Pumice Hair Lithopone Titanium dioxide Mineral wool (soluble in some procedures) Cotton/paper cellulose fibers Vermiculite Mica
Calcium and magnesium silicates Gypsum Sodium silicates
Table 13.3 Acid insoluble particle types.
Table 13.4 Common acid soluble particles.
low percentage that when combined with other ingredients, such as Portland cement, may be difficult to find. Here looking at the acid insoluble material collected on the filter may be necessary to confirm the presence of the clay. 13.3.2.2 Analysis A combination of microscopy techniques is used to analyze asbestoscontaining building materials. Polarized light microscopy (PLM) is used in combination with stereobinocular microscopy to estimate the volume percent of the constituents. Table 13.2 lists some common product types that are the subjects of product identification. Tables 13.3 and 13.4 list the common constituents that are readily identified using polarized light microscopy. A description of the sample includes color and number of layers present. A portion of the sample is placed into a refractive index liquid of known value. The sample is observed using the PLM to note relative refractive index, color, pleochroism, birefringence, morphology, and relative abundance. Particles such as paint, calcium carbonate, Portland cement, synthetic calcium silicate, synthetic magnesium silicate, asbestos, paper fiber, synthetic fiber, glass fibers, mineral wool fibers (slag and rock wools), starch, and clays can be characterized and their volume percentage estimated. Scanning electron microscopy coupled with energy-dispersive x-ray spectrometry (SEM-EDS) is used to analyze a portion of the sample to complement
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the PLM analysis. The sample is prepared by adding a few milligrams to a clean glass vial (disposable plastic pressure fit cap half-dram vials work well). Add one drop of collodian and 15 to 20 drops of amyl acetate. Using clean forceps, crush and stir the sample in the vial. Using a clean glass Pasteur pipette, mix gently and draw a few drops of the mixture into the pipette. Deposit onto a 12 millimeter diameter carbon planchet controlling the loading of solids by adding and removing the mixture until a light loading of the sample particulate has been deposited on the planchet. Allow to dry three to four hours and carbon coat. Analysis is carried out at 500× magnification. Find a heavily loaded area and collect an image and an EDS spectrum at 100× magnification to get a representation of the elements present. Search the majority of the planchet with a combination of secondary electron and backscattered electron imaging. Collect EDS spectra and images of particles that represent each type of constituent present. The SEM-EDS is especially useful when looking at glass fibers, Portland cement, gypsum, mineral wools, heavy metals, paint, perlite, and pumice. Clays such as montmorillonite and kaolinite can be differentiated if there are a minimum of interfering materials present. Diatoms, synthetic magnesium silicates, and calcium silicates can also be characterized by morphology and elemental composition. Transmission electron microscopy coupled with an energy dispersive x-ray spectrometer and capable of electron diffraction (AEM) is useful to characterize and identify mineral fibers (such as asbestos), clays, pigments, and other very fine, thin particles that may present themselves. The sample is prepared as a drop mount directly on a carbon film copper grid support and placed directly into the AEM. Collect EDS spectra and images of particles that represent each type of constituent present. To determine the acid-soluble weight percent, approximately 250 milligrams of the sample is weighed and dissolved in warm 10% hydrochloric acid. The undissolved particles are recovered by filtering through a preweighed polycarbonate filter (0.4 micrometer pore size). The insoluble fraction will typically contain clays, glass fibers, perlite, pumice, polymers, paint fragments, and other acid insoluble materials (see Table 13.2). Occasionally, difficult or complex samples will require the analysis of the acid insoluble particles collected on the polycarbonate filter by PLM, SEM, and AEM. Occasionally multilayered samples will require all the forementioned analyses performed on each layer. Some particles will actually be aggregates such as concrete or paint flakes and will require further testing. The final report involves matching results of particle classification to formulae that have been obtained from manufacturers and entered into a database. The formula information from various manufacturers varies considerably. So complex were the terms used to describe processes and so varied between manufacturers were the terms and proprietary names for ingredients that in
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one case hundreds of hours were needed to analyze documents associated with the formulas and a dictionary of terms was created to decipher the formulae (Hopen, Millette et al., 1999).
13. 4
MEASURING THE EXTENT OF A S P E C I F I C C O N TA M I N A N T
13.4.1 ASBESTOS There are quite a few standard microscopical methods for determining quantities of one environmental contaminant: asbestos. The asbestos methods use one of four types of microscopy: polarized light microscopy (PLM), phase contrast microscopy (PCM), transmission electron microscopy (TEM), or scanning electron microscopy (SEM). The TEM analysis includes characterization of fiber crystal structure by selected area electron diffraction (SAED). Methods for both types of electron microscopy (SEM and TEM) utilize an energy dispersive x-ray spectrometer (EDS) to analyze the fibers for their elemental composition. Many methods have been developed for determining asbestos levels in bulk building materials or concentrations in airborne samples, and some have been developed for asbestos in surface dust samples (Millette and Hays, 1994; ASTM, 2002). Because a chapter was devoted to asbestos in Volume 1 of Environmental Forensics: Contaminant Specific Guide (Van Orden, 2006), and additional information on available asbestos analysis methods can be found in Millette and Bandli (2005) and Millette (2006), only one asbestos-related environmental forensic microscopy method will be considered here. 13.4.1.1 Vermiculite Analysis Environmental forensic microscopy can be used to determine if a sample of vermiculite can be traced to a specific mine in Libby, Montana. Vermiculite products originating from the mine near Libby, Montana are currently in millions of homes and businesses across the nation. Associated with the Libby vermiculite are fibrous amphiboles including tremolite-asbestos. Many of these amphiboles occur in the asbestiform habit. Recent studies of the health of former mine workers and residents of Libby, Montana have shown an increased incidence of asbestos-related lung disease (ATSDR, 2001). The former W.R. Grace vermiculite mine and milling operations and numerous residences and commercial properties in Libby have been added to the U.S. Environmental Protection Agency’s (EPA) National Priorities List for immediate environmental remediation. Because other vermiculite products are not contaminated with fibrous amphiboles, it is an important environmental forensic question to determine
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whether a particular vermiculite material is from Libby or not. The USEPA Research Method for Sampling and Analysis of Fibrous Amphibole in Vermiculite Attic Insulation (VAI) (USEPA, 2004) can be used to analyze a sample of vermiculite for fibrous amphiboles that are characteristic of Libby vermiculite. In the EPA VAI Method (sometimes called the Cincinnati Method), samples are processed/separated using a water density gradient into three fractions: floats, sinks, and suspended particles. The EPA VAI Method contains the procedures for making two measurements of amphibole in VAI. Light microscopy is used to analyze the sinks fraction because denser particles that sink to the bottom may contain large amphibole fiber bundles. Electron microscopy is used to analyze the suspended particle fraction because some fine amphibole fibers may be suspended in the water. Using the cone and quartering technique replicate subsamples of approximately 10 grams each are produced from the original ziplock bag of material (usually a one-gallon container). These subsamples are dried for two hours at 100 degrees and weighed using an analytical balance. Following the methods described in EPA/600/R-04/004, the denser particles (sinks) are separated from the less dense particles (floats). The sinks are dried overnight on a hot plate at 60 degrees and weighed. The sinks are examined at low magnification utilizing a stereobinocular microscope. Fiber bundles are picked with tweezers. The total weight of fiber bundles is determined for each subsample. Representative fiber bundles are then analyzed by polarized light microscopy (PLM). Representative fiber bundles from one of the subsamples may also be examined and analyzed by scanning electron microscopy (SEM) coupled with an energy dispersive x-ray spectrometry (EDS) system. If no fibers are found by stereobinocular microscopy, the suspended particle fractions are prepared from the subsamples using the liquid suspensions after the floats and sinks have been removed. The suspensions are brought up to a volume of one liter and sonicated for two minutes. The suspensions are then agitated by bubbling filtered oxygen for one minute through the liquid using a 10 ml glass pipette at a flow rate of approximately 4 liters per minute. One- and 10-milliliter aliquots of each suspension are removed and filtered through 0.2 mm pore size polycarbonate filters. The filters are prepared and analyzed following the standard procedures as described in ISO 13794. Analyses are performed on a transmission electron microscope with an x-ray analysis system.
13.4.2
NONASBESTOS FIBERS
13.4.2.1 ISO Method 14966 The International Standards Organization (ISO, 2002) Method 14966 uses an SEM-EDS approach for determination of the concentration of inorganic
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fibrous particles in the air. It was designed to consider various types of fibers longer than 5 micrometers in length. With the ISO method, an analyst may count fibers on air filters and determine concentrations of different fiber types based on their elemental composition. The method specifies the use of goldcoated, capillary-pore, track-etched membrane filters, through which a known volume of air has been drawn. Using energy-dispersive x-ray analysis, the method can discriminate between fibers with compositions consistent with those of the asbestos varieties (e.g., serpentine and amphibole), gypsum, and other inorganic fibers. Annex C provides a summary of fiber types that can be measured. Information is included about fibers of mullite (Al6Si2O13), willemite (Zn2SiO4), sillimanite (Al2SiO5), dumortierite (Al7O3(BO3)(SiO4)), wollastonite (CaSiO3), and several zeolites; industrial crystalline fibers such as silicon carbide (SiC), zirconia (ZrO2), and tungsten (W); inorganic amorphous fibers such as glass wool, rock wool, and slag wool, ceramic, and quartz. ISO 14966:2002 is applicable to the measurement of the concentrations of inorganic fibrous particles in ambient air. The method is also applicable for determining the numerical concentrations of inorganic fibrous particles in the interior atmospheres of buildings. It is important to note that the ability of the method to detect and classify fibers with widths lower than 0.2 micrometers is limited. If airborne fibers in the atmosphere being sampled are predominantly less than 0.2 micrometers in width, a transmission electron microscopy method is recommended. 13.4.2.2 Glass Fibers Glass fibers found in airborne samples collected on membrane filters can be analyzed by phase contrast microscopy using the “B” rules of the National Institute of Occupational Safety and Health (NIOSH) 7400 method (NIOSH, 1994a). Although the phase contrast method does not identify the type of fiber counted, it does provide a useful system for monitoring airborne concentrations in areas where glass fibers are manufactured or products are fabricated with the fibers. In situations where mixtures of fibrous materials are anticipated, the PCM method should be augmented with additional microscopical procedures such as polarized light microscopy (PLM) or electron microscopy. Although not a standard method, surface dust samples were analyzed for glass fibers by Schneider et al. (1990). They used gelatinous foils to collect the samples and then analyzed them by light microscopy. 13.4.2.3 Ceramic Whiskers There are four standard microscopy measurement methods related to airborne ceramic whiskers including silicon carbide and silicon nitride fibers (ASTM, 2001a,b,c,d). The scanning electron microscopy method for single-
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crystal ceramic whiskers (SCCW) is a method that has the ability to distinguish among many different types of fibers based on energy dispersive x-ray spectrometry (EDS) analysis. This test method may be appropriate for other man-made mineral fibers (MMMF). This test method is applicable to the quantification of fibers on a collection filter that are greater than 5 micrometers (mm) in length, less than 3 mm in width, and have an aspect ratio equal to or greater than 5 : 1. The data are directly convertible to a statement of concentration per unit volume of air sampled. This test method is limited by the diameter of the fibers visible by SEM (typically greater than 0.10 to 0.25 mm in width) and the amount of coincident interference particles. The transmission electron method is applicable to the quantification of fibers on a collection filter that are greater than 0.5 mm in length and have an aspect ratio equal to or greater than 5 : 1.
13.4.3 NONFIBROUS PARTICULATE There is a standard procedure for determining particle size information on samples of environmental particulate emissions. Administered by the Louisiana Department of Environmental Quality (LDEQ), the Louisiana Environmental Laboratory Accreditation Program (LELAP) is recognized by the National Environmental Laboratory Accreditation Program (NELAP). Under the LELAP program, samples of particulate from industrial emissions that have been collected on filters (PC filters are preferred although they do have a temperature limit) are analyzed for total particle sizing by automated scanning electron microscopy. The analyses are performed using a scanning electron microscope operating in automated mode under the control of an x-ray analysis system utilizing a standard operating procedure. Figure 13.2 shows a dispersion of lead-rich particles in the backscattered electron mode and Figure 13.3 shows how the automated sizing procedure assigns dimensional values to all the particles. Approximately 1000 to 2000 particles from each sample are individually sized and classified according to five client-requested size categories, typically, 0.5–2.5, 2.5–5.0, 5.0–7.5, 7.5–10.0 and >10 mm. The particle size data are presented in terms of particle number and in terms of estimated mass. The assumption is made that the particles are all of similar density and therefore the particle volume distribution is equivalent to the particle mass distribution. Automated Particle Analysis is a useful environmental forensic microscopy tool. Digital imaging under computer control with the scanning electron microscope makes possible the morphological and chemical analysis of hundreds or thousands of particles without intervention by the microscopist. With computer control of the electron beam and the sample position, digital images
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Figure 13.2 Backscattered electron image of lead ore dust sized by automated scanning electron microscopy.
Figure 13.3 Same image field as Figure 13.2 after the microscope computer has applied conditions of particle definitions for automated particle sizing. A full color version of this figure is available at books.elsevier.com/ companions/ 9780123695222.
can be acquired into computer memory and the image searched for particles based on computer programs that recognize image contrast. Size and shape calculations can be made and recorded for each particle found and the electron beam can be driven back to the particle for chemical analysis by energy dispersive x-ray spectrometry. Automated SEM particle analysis has been used extensively in the investigation of leaded particles in soil (Cotter-Howells and
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Thornton, 1991; Hunt et al., 1991, 1998; Rybicka, Wilson, and McHardy, 1994; Thornton et al., 1994; Franck and Herbarth, 2002; Pirrie, 2003) and in other types of environmental forensic studies including the size of urban air particles ( Jambers, De Bock, and Van Grieken, 1995) and those involving cement particles and grout (Millette and Brown, 2002).
13.5
CASE STUDIES—EXAMPLES OF E N V I R O N M E N TA L F O R E N S I C M I C R O S C O PY I N V E S T I G AT I O N S
13.5.1 ELEVATED LEAD IN A CHILD It is well known that young children can be exposed to lead by ingesting lead paint dust that is generated by the deterioration, sanding, or scraping of leadbased paints in the home. Other sources of lead present in homes include deposits of particles from the use of leaded gasoline and from industrial sources like smelting. In one case, finding a child with elevated blood lead raised the concern that the child was ingesting lead-based paint dust. However, x-ray fluorescence testing of the paint in the home detected no lead. Samples of the dust were collected on adhesive notes and sent to the laboratory for analysis by SEM-EDS. The results showed the source of the lead in dust was lead-containing fly ash (Millette, Brown et al., 1991). A search of the neighborhood resulted in sampling piles of material at a nearby industrial site (see Figure 13.4). The SEM-EDS showed lead-containing fly ash consistent with that found within the home (see Figure 13.5). The So-Green company apparently had been paid to receive tons of electric arc fly ash from a company in another state and was turning it into a product to be sold as a fertilizer. Unfortunately the fertilizer business was not keeping up with the shipments of fly ash and large piles were accumulating around the facility. The site was
Figure 13.4 Piles of electric-arc fly ash at the So-Green site. A full color version of this figure is available at books.elsevier.com/ companions/ 9780123695222.
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Figure 13.5 Backscattered electron image of fly ash and leadrich particle (white) typical of particles found in homes surrounding the So-Green facility.
ultimately declared a Superfund site. In other cases involving concern over lead particulate, samples were collected from homes and analyzed by SEMEDS. The leaded particles were classified as lead paint (Pb-Cr, Pb-Zn), auto exhaust (Pb-Br), industrial lead (Pb+metals), soil lead (Pb-Si, Al and/or Ca), and undetermined (Pb-only) based on the other elements associated with the lead in the particle. In one project, lead-arsenate particles were found in household dust (Millette et al., 1995). In another project, lead-chlorine particles from PVC electric cable covering were found in an office building (Ghazi and Millette, 2005).
13.5.2
A SPOT CALLED RALPH
In a courthouse in South Carolina a mysterious stain appeared in the new carpet. Employees even gave the spot a name—“Ralph.” At first it was the size of a half dollar but it grew after cleaning to about 2 square feet. Environmental mold specialists initially tested the stain in the carpet and determined that it was not caused by mold. A section of the stain was cut from the carpet and delivered to the environmental forensic microscopy laboratory for inspection. Analysis by light and scanning electron microscopy showed that the carpet contained a variety of particles typical of the particles often found in office dusts. A sticky substance was also found on the carpet fibers. FTIR analysis of the sticky material showed that it was consistent with corn syrup. It is apparent that someone spilled a soft drink on the carpet and the stain was caused by office dust particles adhering to the sticky drink residue. Efforts to clean the stain removed the dark office dust particles but did not completely remove the sticky drink residue. In fact, the cleaning efforts spread the sticky residue, which collected more office dirt over time and therefore appeared to grow in size. Not surprisingly, the newspaper reporter who interviewed the laboratory
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Figure 13.6 Dark “sooty” looking deposit on an automobile trunk surface.
after the findings were made public was disappointed that the stain called “Ralph” was not something exotic, just something caused by a spilled soft drink.
13.5.3 AUTOMOBILES WITH A SOOTY DEPOSITION—1 The ASTM standard, D4610, states “Microbial growth is a major cause of discoloration and deterioration of paint films.” This is true not only of painted house surfaces but also of automobile finishes. Environmental forensic microscopy investigations of what is causing the dark “sooty” layer on light colored automobiles such as the one shown in Figure 13.6 were performed using the ASTM D6602 standard (ASTM, 2003a). A clear cellophane tape is applied to the surface of the auto, removed, and placed on a microscope slide. The use of a PLM microscope at magnifications from 50 to 400× showed that the darkening agent on the automobile shown in Figure 13.6 was a biological growth (see Figure 13.7). A cotton ball is used to collect a sample for analysis by transmission electron microscopy of the darkening agent if it is suspected of being soot. The TEM analysis is the only way to differentiate various types of aciniform soots including carbon black that have particle sizes in the nanometer range. In a similar case, a residential mailbox was reportedly covered with soot from a nearby power plant. The environmental forensic investigation showed that the darkening agent on the mailbox was not soot but a sooty mold.
13.5.4 AUTOMOBILES WITH A SOOTY DEPOSITION—2 Cars parked in an industrial area were becoming coated with “black, sticky debris.” The debris was described as “sticky and difficult to wash off” and
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Figure 13.7 PLM image of the mold/ biofilm material causing the darkening shown in Figure 13.6.
Figure 13.8 Brightfield reflected light image of black debris from parked automobile (Sooty Deposition 2). A full color version of this figure is available at books. elsevier.com/companions/ 9780123695222.
scratched the automobile painted finish if rubbed. Samples were collected with tape and sent for microscopical examination. The black, sticky debris was examined using a combination of polarized light microscopy (PLM), scanning electron microscopy-energy dispersive x-ray spectrometry (SEM-EDS), and Fourier transform microspectroscopy (FTIR), and was found to consist primarily of metal particles, quartz sand, and a resinous material (see Figures 13.8, 13.9, and 13.10). Aggregates were extracted with drops of acetone on a glass slide and the acetone soluble fraction was redeposited on a reflective e-glass slide for FTIR analysis. Samples from exhaust vents of a nearby metal casting industry were collected. The residue from the exhaust vents was found to be similar in physical and elemental composition to the black debris appearing on the parked automobiles.
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Figure 13.9 Transmitted light image using crossed polarizers of quartz particles in black debris.
Figure 13.10 Backscattered electron image of inorganic particles comprising black debris.
13.5.5 WTC SIGNATURE SEARCH The dust cloud generated by the collapse of the World Trade Center (WTC) towers on September 11, 2001 was a complex mixture of building material particles (Millette et al., 2001; Lioy et al., 2002a; Yin et al., 2004). In April 2005, there remained questions about where the dust particles had settled and how to determine which residences in New York City still required cleaning of the WTC dust. EPA conducted a study to determine if a WTC Dust Signature Protocol could be used to determine where residue of the WTC dust remained.
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Figure 13.11 Brightfield transmitted light image of WTC dust showing glass fibers, cement particles, and gypsum.
Figure 13.12 Secondary electron image of WTC dust showing glass fibers, cement particles, and gypsum.
They asked a number of independent laboratories to test a proposed protocol based on work done by the U.S. Geological Survey (Lowers et al., 2005; Meeker et al., 2005). Based on the fact that glass fibers, cement particles, and gypsum were the major components of the WTC dust (see Figures 13.11 and 13.12), the USGS protocol involved elemental mapping of calcium and sulfur by computer-controlled scanning electron microscopy—x-ray analysis (SEMEDS) and an independent analysis for slag wool fibers. In the summer of 2005, based on the work of the various laboratories, the EPA decided that the Computer Controlled SEM/EDS analysis was not reproducible between labs and proposed a method based only on Slag Wool Analysis by SEM-EDS (USEPA, 2005). The proposed protocol was sent out to a Peer Review Panel. In October
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2005, the peer review panel (Crane et al., 2005) concluded, “EPA has not made the case that its proposed analytical method can reliably discriminate background dust from dust contaminated with WTC residue.” The USEPA is proceeding with a $7 million Test and Clean Program that covers the area south of Canal Street and west of Pike-Allen Streets in New York City. Instead of a decision based on a WTC dust signature, a cleaning decision will be based on the finding of elevated levels of one of four contaminants of concern. Dust samples will be analyzed for asbestos, man-made vitreous fiber (MMVF), lead, and polycyclic aromatic hydrocarbons (PAH). The proposed EPA Criteria for determining whether an accessible area is to be cleaned are: 䊏
Asbestos—5000 structures/cm2
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MMVF—5000 fibers/cm2
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Lead—40 mg/ft 2
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PAHs—150 mg/M2
Standard methods exist for the analysis, in surface dust, of asbestos (ASTM, 2003b), lead (NIOSH, 1994b; USEPA, 1996; OSHA, 2002), and PAHs (USEPA, 1986), but no standard method currently exists for the analysis of MMVF in surface dust. It is anticipated that a method for MMVF in surface dust will be developed by combining the ASTM microvac TEM method for asbestos in dust (ASTM, 2003) with analytical procedures developed by the U.S. Geological Survey (Lowers and Meeker, 2005) using the scanning electron microscope to classify the glass fibers. A method using PLM identification of the glass fibers is also possible. There is no advantage to using the TEM for glass fiber analysis because although asbestos and other naturally occurring mineral fibers are characterized by their crystalline structure, which can be examined by electron diffraction, man-made vitreous fibers are amorphous; that is, they are glassy, with no discernible crystalline array (US Navy, 1997).
REFERENCES ASTM. (2001a) Standard Practice for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environment. American Society for Testing and Materials, Method D6058-96. Conshohocken, PA. ASTM. (2001b) Standard Test Method for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environment by Transmission Electron Microscopy. American Society for Testing and Materials, Method D6056-96. Conshohocken, PA.
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ASTM. (2001c) Standard Test Method for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environment by Scanning Electron Microscopy. American Society for Testing and Materials, Method D6059-96. Conshohocken, PA. ASTM. (2001d) Standard Test Method for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environment by Phase Contrast Microscopy. American Society for Testing and Materials, Method D6057-96. Conshohocken, PA. ASTM. (2003a) Sampling and Testing of Possible Carbon Black Fugitive Emissions or Other Environmental Particulate, or Both. American Society for Testing and Materials, Method D6602. Conshohocken, PA. ASTM. (2003b) Standard Test Method for Microvacuum Sampling and Indirect Analysis of Dust by Transmission Electron Microscopy for Asbestos Structure Number Surface Loading. American Society for Testing and Materials, Method D5755-03. Conshohocken, PA. ATSDR. (2001) Libby Environmental Health Update. Agency for Toxic Substances and Disease Registry, January 12, 2001. Clague, A.D.H., Donnet, J.B., Wang, T.K., and Peng, J.C.M. (1999) A Comparison of Diesel Engine Soot with Carbon Black. Carbon 37, 1553–1565. Cotter-Howells, J. and Thornton, I. (1991) Sources and pathways of environmental lead to children in a Derbyshire mining village. Environmental Geochemistry and Health 13(2), 127–135. ISSN: 0269-4042 (Paper) 1573–2983 (Online). DOI: 10.1007/BF01734304. Crane, D., Ehrenfeld, F., Gunter, M., McConnell, E., Su, S., Webber, J., and Wilhelmi, J. (2005) Peer Review of the U.S. Environmental Protection Agency’s Final Report on the World Trade Center (WTC) Dust Screening Study. Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC., EPA Contract No. 68-C-02-060, Task Order 107. Faegri, K., Iversen, J., and Waterbolk, H.T. (1964) Textbook of Pollen Analysis. Hafner Publishing Company, New York, 237. Franck, U. and Herbarth, O. (2002) Using scanning electron microscopy for statistical characterization of the diameter and shape of airborne particles at an urban location. Environmental Toxicology 17, 98–104. Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/tox.10037. Ghazi, A.M. and Millette, J.R. (2005) Environmental forensic application of lead isotope ratio determination: A case study using laser ablation, Sector ICP-MS. Environmental Forensics 5(2), 97–108.
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Graves, W.J. (1979) A mineralogical soil classification technique for the forensic scientist. JFSCA 24, 323–338. Hawksworth, D.L., Kirk, P.M., Sutton, B.C., and Pegler, D.N. (1995) Ainsworth and Bisby’s Dictionary of the Fungi. CABI International, Oxon, UK, 616. Hopen, T.J., Millette, J.R., Boltin, W.R., and Brown, R.S. (1999) A dictionary of terms related to additives found in asbestos building products. Microscope 47(3), 163–171. Hopen, T.J. (2004) The value of soil evidence. In Trace Evidence Analysis, M.M. Houck, ed. Elsevier Academic Press, Boston, 105–122. Huffman, G.P., Huggins, F.N., Shah, N., Huggins, R., Linak, W.P., Miller, C., Pugmire, R.J., Meuzelaar, H.L.C., Seehra, M.S., and Manivannan, A. (2000) Characterization of fine particulate matter produced by combustion of residual fuel oil. Journal of the Air & Waste Management Association 50, 1106–1114. Hunt, A., Johnson, D.L., and Thornton, I. (1991) Descriptive apportionment of lead in house dust by automated SEM. Water, Air and Soil Pollution, 57–77. Hunt, A., Hawkins, J., Gilligan, E., and Bhatiab, S. (1998) A comparison of the lead particle content of indoor dust before and after a lead paint abatement: A new source of lead recontamination. Indoor and Built Environment 7, 32–46 (DOI: 10.1159/000024558). ISO. (1999) Ambient air—determination of asbestos fibres—indirect-transfer Transmission electron microscopy method. International Standards Organization, Method 13794. ISO. (2002) Ambient air-determination of numerical concentration of inorganic fibrous particles—Scanning electron microscopy method. International Standards Organization, Method 14966. Jambers, W., De Bock, L., and Van Grieken, R. (1995) Recent advances in the analysis of individual environmental particles. A review. The Analyst 120, 681– 692. DOI: 10.1039/AN9952000681. Kostiuk, L.W., Johnson, M.R., and Thomas, G.P. (2004) University of Alberta flare research project final report November 1996—September 2004. University of Alberta, Department of Mechanical Engineering. Krumbein, W.C. and Pettijohn, F.J. (1938) Manual of Sedimentary Petrography. Appleton-Century-Crofts, New York, 439–441. Lioy, P.J., Weisel, C.P., Millette, J.R., Eisenreich, S., Vallero, D., Offenberg, J. et al. (2002a) Characterization of the dust/smoke aerosol that settled east of the
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World Trade Center (WTC) in Lower Manhattan after the collapse of the WTC 11 September 2001. Environmental Health Perspectives 110(7), July 2002, 703–714. Lowers, H.A., and Meeker, G.P. (2005) Particle atlas of World Trade Center dust. US Geological Survey, Open File Report 2005-1165. Lowers, H.A., Meeker, G.P., and Brownfield, I.K. (2005) Analysis of background residential dust for World Trade Center signature components using scanning electron microscopy and x-ray microanalysis. US Geological Survey, Open File Report 2005-1073. McCrone, W.C., Delly, J.G., and Palenik, S.J. (1973) The Particle Atlas, 2nd Ed. Ann Arbor Science Publishers, Inc., Ann Arbor, Michigan, ISBN: 0250400081. Medalia, A.I. and Rivin, D. (1982) Particulate carbon and other components of soot and carbon black. Carbon 20, 481–492. Meeker, G.P., Bern, A., Lowers, H., and Brownfield, I.K. (2005) Determination of a diagnostic signature for World Trade Center dust using scanning electron microscopy point counting techniques. US Geological Survey, Open File Report 2005-1031. Millette, J.R., Brown, R.S., Barnett, J., and Mount, M.D. (1991) Scanning electron microscopy of post-it notes used for environmental sampling. NAC Journal, 32–35. Millette, J.R. and Hays, S.M. (1994) Settled Asbestos Dust: Sampling and Analysis. Lewis Publishers, Boca Raton. Millette, J.R., Brown, R.S., and Mount, M.D. (1995) Lead arsenate. Microscope 43(4), 187–191. Millette, J.R. and Few, P. (2001) Sample collection procedures for microscopical examination of particulate surface contaminants. Microscope 49(1), 21–27. Millette, J.R., Boltin, R., Few, P., and Turner, W. Jr. (2002) Microscopical studies of World Trade Center disaster dust particles. Microscope 50(1), 29–35. Millette, J.R. and Brown, R.S. (2002) Examining the fine particle component of grout dust by automated SEM. Microscope 50(1), 1–3. Millette, J.R., Lioy, P.J., Wietfeldt, J., Hopen, T.J., Gipp, M., Padden, T. et al. (2003) A microscopical study of the general composition of household dirt. Microscope 51(4), 201–207. Millette, J.R. and Bandli, B.R. (2005) Asbestos identification using available standard methods. Microscope 53(4), 179–185.
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Millette, J.R. (2006) Chapter 2: Asbestos analysis methods. In Asbestos: Risk Assessment, Epidemiology, and Health Effects, R.F. Dodson and S.P. Hammar, eds. CRC, Taylor & Francis, Boca Raton, 9–38. Ness, S.A. (1994) Surface and Dermal Monitoring for Toxic Exposures. Van Nostrand Reinhold, New York, 561. NIOSH. (1994a) Asbestos and other fibers by phase contrast microscopy (PCM). NIOSH Manual of Analytical Methods, Method 7400, 4e, 94–113. NIOSH. (1994b) Lead surface wipe samples. NIOSH Manual of Analytical Methods, Method 9100, 4e. OSHA. (2002) Metal and metalloid particles in workplace atmospheres (ICP Analysis). Occupational Safety and Health Administration, Method ID-125G. Palenik, S.J. (1979) The determination of geographical origin of dust samples. In The Particle Atlas, 2e, Volume 5, W.C. McCrone, J.G. Delly, and S.J. Palenick, eds. Ann Arbor Science Publishers Inc., Ann Arbor, 1347–1361. Petraco, N. and Kubic, T. (2003) Color Atlas and Manual of Microscopy for Criminalists, Chemists, and Conservators. CRC Press, New York, 328. Pirrie, D., Power, M.R., Rollinson, G., Camm, G.S., Hughes, S.H., Butcher, A.R., and Hughes, P. (2003) The spatial distribution and source of arsenic, copper, tin and zinc within the surface sediments of the Fal Estuary, Cornwall, UK. Sedimentology 50(3), 579–595. Rybicka, E.H., Wilson, M.J., and McHardy, W.J. (1994) Chemical and mineralogical forms and mobilization of copper and lead in soils from a Cu-smelting area in Poland. Journal of Environmental Science and Health, Part A. A29, 3, 531–546. Schneider, T., Nielsen, O., Bredsdorff, P., and Linde, P. (1990) Dust in buildings with man-made mineral fiber ceiling boards. Scandinavian Journal of Work Environment and Health 16, 434–439. Thornton, I., Watt, J.M., Davies, D.J.A., Hunt, A., Cotter-Howells, J., and Johnson, D.L. (1994) Lead contamination of UK dusts and soils and implications for childhood exposure: An overview of the work of the Environmental Geochemistry Research Group, Imperial College, London, England 1981–1992. Environmental Geochemistry and Health 16, 113–122; 10.1007/BF01747907. Turner, W.L., Millette, J.R., Boltin, W.R., and Hopen, T.J. (2005) A standard approach to the characterization of common indoor dust constituents. Microscope 53(4), 169–177. USEPA. (1986) Polynuclear Aromatic Hydrocarbons. U.S. Environmental Protection Agency, Method 8310.
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USEPA. (2004) Research Method for Sampling and Analysis of Fibrous Amphibole in Vermiculite Attic Insulation. U.S. Environmental Protection Agency, EPA/600/ R-04/004. USEPA. (2005) Final Report on the World Trade Center (WTC) Dust Screening Method Study. U.S. Environmental Protection Agency, August 17, 2005. US Navy Environmental Health Center. (1997) Man-made vitreous fibers. Technical Manual, NEHIC-TM6290.91-REVA. Van Orden, D. (2006) Asbestos. In Environmental Forensics: Contaminant Specific Guide, R.D. Morrison and B.L. Murphy, eds. Elsevier, Amsterdam, 19–31. Yiin, L.M., Millette, J.R., Vette, A., Ilacqua, V., Quan, C., Gorczynski, J. et al. (2004) Comparisons of the dust/smoke particulate that settled inside the surrounding buildings and outside on the streets of southern New York City after the collapse of the World Trade Center, September 11, 2001. Journal of the Air & Waste Management Association 54, 515–528.
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Figure 13.1 Scanning electron microscope images of filters used to collect airborne particles. Spheres of 5 micrometers and 1 micrometer are overlaid to show how small particles would appear on the filter surface.
Figure 13.2 Backscattered electron image of lead ore dust sized by automated scanning electron microscopy.
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Figure 13.3 Same image field as Figure 13.2 after the microscope computer has applied conditions of particle definitions for automated particle sizing. A full color version of this figure is available at books.elsevier.com/ companions/ 9780123695222.
Figure 13.4 Piles of electric-arc fly ash at the So-Green site. A full color version of this figure is available at books.elsevier.com/ companions/ 9780123695222.
Figure 13.5 Backscattered electron image of fly ash and leadrich particle (white) typical of particles found in homes surrounding the So-Green facility.
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Figure 13.6 Dark “sooty” looking deposit on an automobile trunk surface.
Figure 13.7 PLM image of the mold/ biofilm material causing the darkening shown in Figure 13.6.
Figure 13.8 Brightfield reflected light image of black debris from parked automobile (Sooty Deposition 2). A full color version of this figure is available at books. elsevier.com/companions/ 9780123695222.
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Figure 13.9 Transmitted light image using crossed polarizers of quartz particles in black debris.
Figure 13.10 Backscattered electron image of inorganic particles comprising black debris.
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Figure 13.11 Brightfield transmitted light image of WTC dust showing glass fibers, cement particles, and gypsum.
Figure 13.12 Secondary electron image of WTC dust showing glass fibers, cement particles, and gypsum.
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E N V I R O N M E N TA L F O R E N S I C MICROSCOPY Jam e s R . Mill e t te an d Richard S . Brow n
13.1 Introduction 13.2 Sampling and Analysis Equipment 13.2.1 Air Sampling 13.2.2 Surface Dust Sampling 13.2.2.1 Microscopy Equipment 13.3 Determining the Nature of Contaminants 13.3.1 Particle Analysis 13.3.2 Product Identification by Microscopy 13.3.2.1 Sampling 13.3.2.2 Analysis 13.4 Measuring the Extent of a Specific Contaminant 13.4.1 Asbestos 13.4.1.1 Vermiculite Analysis 13.4.2 Nonasbestos Fibers 13.4.2.1 ISO Method 14966 13.4.2.2 Glass Fibers 13.4.2.3 Ceramic Whiskers 13.4.3 Nonfibrous Particulate 13.5 Case Studies—Examples of Environmental Forensic Microscopy Investigations 13.5.1 Elevated Lead in a Child 13.5.2 A Spot Called Ralph 13.5.3 Automobiles with a Sooty Deposition—1 13.5.4 Automobiles with a Sooty Deposition—2 13.5.5 WTC Signature Search References 1 3 .1
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INTRODUCTION
Environmental forensic microscopy is the application of microscopy to the identification, collection, and analysis of small particles and the interpretation of the analyses performed as they pertain to environmental investigations
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and litigation. Environmental investigations are generally assessments of the nature and extent of a contaminant. Microscopy is most useful in examining, classifying, and identifying particulate contaminants. Determining the nature of a contaminant and measuring the extent of a contaminant are two fundamentally, although often overlapping, questions. Often the questions put to the environmental forensic microscopist are “What is this dust?” and “Where did it come from?” However, the environmental forensic microscopist may also be asked to quantify the amount of a specific contaminant in several samples in an effort to determine the extent of the problem and to establish a procedure for further sampling and analysis. Answering the two questions has given rise to different sets of methods. In answering the question about how much of a specific contaminant is present, that contaminant must be sorted and identified. Other particles comprising the matrix of the sample may be ignored. In answering the questions about the nature of a contaminant dust, a broader range of knowledge may be required to sort the various contaminants into appropriate classes or categories. Environmental forensic microscopy measurement methods tend to be fairly specific with a designated set of counting rules defined so that different analysts can get comparable numerical results. Environmental forensic microscopy methods dealing with the nature of a contaminant sample tend to be less formalized because they must take into account a vast variety of potential particle types. In answering the question “What is this dust?”, the microscopist cannot ignore all the particle types but one. The microscopist must allow the constituents of the sample to dictate which basic standard microscopy procedures and other techniques he or she will use in solving the analytical problem. When dealing with an environmental particle contamination situation of unknown origin, the forensic investigation of the nature of the contaminant naturally takes place first. However, in some situations where the nature of the contaminant is known, measurement methods may be employed first. 13. 2
S A M P L I N G A N D A N A LY S I S E Q U I P M E N T
The sampling and analysis methods used in environmental forensic investigations are drawn primarily from the criminal forensics, industrial hygiene, and environmental monitoring areas. Combining various aspects of these disciplines allows the investigator to generate a procedure that fits the varied and sometimes very complex environmental situation. 13.2.1 AIR SAMPLING Collecting samples of airborne particles for environmental forensic investigations usually is done using membrane filter sampling cassettes. Various types of membrane filters are used in environmental and industrial hygiene
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Figure 13.1 Scanning electron microscope images of filters used to collect airborne particles. Spheres of 5 micrometers and 1 micrometer are overlaid to show how small particles would appear on the filter surface.
sampling. These include filters made of mixed cellulose ester polymer, polycarbonate polymer, glass fiber filters, quartz fiber filters, silver membrane filters, and polyvinyl chloride (PVC) filters. Figure 13.1 shows a comparison of the surfaces of the various filter types. Spheres representing particles of 5 micrometer diameter and 1 micrometer diameter are overlaid on the images. With the glass fiber filters, particles can be lost in the filter thickness. Backwashing the glass filter to remove the particles produces a sample that contains glass fiber fragments. It is clear why microscopists prefer air samples collected on polycarbonate (PC) filters. The PC filters have a flat surface because they are a “straight through” filter rather than a tortuous path design that is found in the other filter types.
13.2.2 SURFACE DUST SAMPLING Surface dust particle collection techniques, varying according to situation, are chosen to maximize probative value and when possible to preserve a
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portion for future analysis. Common particle collection techniques for environmental forensic microscopy investigations of surface particulate include scraping, brushing, taping with cellophane tape on a slide or post-it notes, scoop and bag techniques, wipe sampling, and vacuuming with either a microvac (air cassette) or large-scale vacuuming (Ness, 1994; Millette and Few, 2001). Sample collection procedures with cotton or polyester balls, wipes, and tape slides for outdoor surfaces are described in the ASTM Standard Practice D6602 (ASTM, 2003). ASTM D6602 is a standard procedure that serves as an excellent basis for environmental forensic microscopy investigations where soot might be involved. This ASTM standard was designed primarily for the determination of carbon black among soot particles and other dark particles but provides the framework for the microscopy studies necessary to determine the identity of all particles and possible sources of surface contamination.
13.2.2.1 Microscopy Equipment Microscopic analyses in environmental forensic investigations are accomplished utilizing a combination of visible light, infrared light, and electron microscopy. The light microscopy usually is performed with polarized light microscopy (PLM), but may involve phase contrast (PCM), darkfield, or fluorescence microscopy. Infrared microscopy is done using Fourier transform infrared microspectroscopy (micro-FTIR). FTIR is very useful when identifying organic molecules such as plastics and polymers. Scanning electron microscopy (SEM) allows the analyst to see particles that are smaller than can be seen with light microscopy, and when equipped with an x-ray analysis unit, allows the analyst to determine the elemental composition of the particles. Transmission electron microscopy (TEM) also allows the analyst to see particles that are smaller than can be seen with light microscopy, and when equipped with electron diffraction capabilities and an x-ray analysis unit, allows the analyst to determine the crystal structure and elemental composition of the particles. ASTM Practice D6602 lists different types of microscopes that can be used to investigate environmental particles: a stereobinocular microscope, capable of 1 to 60× magnification; a polarized light microscope (PLM), equipped with objectives in the 4 to 100× range of magnification (for a total magnification between 40 and 1000×); a transmission electron microscope (TEM), equipped with a suitable camera; and a scanning electron microscope (SEM), equipped with energy or wavelength dispersive analysis equipment (EDS or WDS). A TEM equipped with selected area electron diffraction (SAED) and EDS is referred to as an analytical electron microscope (AEM).
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For questions involving the nature of particulate contaminants, the general procedure in environmental forensic investigations is the same as the general forensic science approach to trace analysis; that is, to collect samples of the particles (dust, dirt, or suspensions in liquid) in question, evaluate the samples to classify and identify the particles, identify possible sources, and then to compare the sample particle types to the suspect source(s) particle types (see Table 13.1).
13.3.1
PARTICLE ANALYSIS
The McCrone Particle Atlas is the standard reference for environmental forensic microscopical particle analysis (McCrone, 1973). Published first in 1972, this six-volume set (now available only on CD-ROM) contains thousands of images of different types of particles and information about their microscopical characteristics observable by light and electron microscopy. There are also clear discussions of various topics important to the proper use of PLM in identifying particles including birefringence, refractive index, and dispersion staining. Another useful reference atlas for the forensic microscopist was published by Petraco and Kubic (2003). Illustrations and information about the morphological characteristics of pollen grains can be found in Faegri, Iversen, and Waterbolk (1964). Images and information about the appearances of fungal spores can be found in Hawksworth et al. (1995). Images of soil minerals can be found in Graves (1979), Krumbein and Pettijohn (1938), Palenik (1979), and Hopen (2004), along with useful information about the identification of soil minerals as individual (detrital) grains. Images of soot have been published by Medalia and Rivin (1982), Huffman et al. (2000), and Clague et al. (1999). Images of aciniform flare combustion can be seen in Kostiuk, Johnson, and Thomas (2004). Although environmental forensic microscopical particle analysis of dusts may seem daunting due to the many types of particles possible, it has been found that for most common situations such as normal residential and
Collect Analyze Identify particle type Identify possible sources Compare sample particles to suspect source(s) Report Interpret findings as they pertain to law/science
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Table 13.1 General forensic science approach to trace evidence analysis.
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building dust, the particles can be classified using approximately 20 categories (Millette, Lioy et al., 2003; Turner, Millette et al., 2005).
13.3.2 PRODUCT IDENTIFICATION BY MICROSCOPY Product identification is a special case of environmental forensic microscopy because it involves, in addition to particle classifications, the combining of the results of several analytical techniques to determine the composition of a product and then compare the overall results to product formula information. The same process may be used to compare dust particles with building products or other man-made compounds. Sections 13.3.2.1 and 13.3.2.2 describe the general procedures used for product identification when matching asbestos-containing products with manufacturers’ formulae. 13.3.2.1 Sampling Sampling involves removing the material in a manner that will maintain the layer structure and integrity of layered samples. This can be accomplished with a polycarbonate tube used as a cork borer or by carefully cutting through the product down to the substrate, wrapping in paper and cushioning the sample so as the product cannot be crushed or crumbled. Wet samples should be thoroughly air dried prior to packaging to discourage fungal and mold growth. Sampling a variety of products having different physical dimensions and cohesion requires the person doing the sampling to be creative and cognizant of the type of analysis that will be performed. Chain-of-custody forms must accompany the samples to the laboratory. Once the sample reaches the laboratory the packing is carefully removed and the sample’s condition “as received” can be recorded, in some cases, with photographs. Examination with reflected light under low magnification is performed to determine if the sample represents a single product or multiple products displayed as multiple layers. If multiple layers are present, the color and layer sequence can be documented with a photograph. The layers are examined as individual products as the analysis continues. Each sample is split into four vials. One vial is sent to each analysis station for PLM, SEM-EDS, TEM, or acid-soluble weight percent. Quality control for each analysis is checked by comparing the results of each examination for a particular sample against each other. For instance, a sample that contained chrysotile as identified by PLM should also have chrysotile characterized by SEM and identified by TEM. Should an ingredient that was determined to be a major component of a sample not be observed by each of the microscopical techniques, a review of the analysis would be undertaken to determine why. Some particles, such as montmorillonite clay, may be of a
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Table 13.2
Acoustical plaster Ceiling tiles Fireproofing Pipe insulation
Diatoms Kaolinite Montmorillonite Fiberglass® Quartz and soil minerals Iron chromite Chrysotile Amosite Crocidolite Tremolite, actinolite, anthophyllite Fly-ash
Mineral wool (soluble in some procedures) Calcium carbonate Portland cement
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Common asbestoscontaining product types that have been tested for product ID.
Starch Perlite Pumice Hair Lithopone Titanium dioxide Mineral wool (soluble in some procedures) Cotton/paper cellulose fibers Vermiculite Mica
Calcium and magnesium silicates Gypsum Sodium silicates
Table 13.3 Acid insoluble particle types.
Table 13.4 Common acid soluble particles.
low percentage that when combined with other ingredients, such as Portland cement, may be difficult to find. Here looking at the acid insoluble material collected on the filter may be necessary to confirm the presence of the clay. 13.3.2.2 Analysis A combination of microscopy techniques is used to analyze asbestoscontaining building materials. Polarized light microscopy (PLM) is used in combination with stereobinocular microscopy to estimate the volume percent of the constituents. Table 13.2 lists some common product types that are the subjects of product identification. Tables 13.3 and 13.4 list the common constituents that are readily identified using polarized light microscopy. A description of the sample includes color and number of layers present. A portion of the sample is placed into a refractive index liquid of known value. The sample is observed using the PLM to note relative refractive index, color, pleochroism, birefringence, morphology, and relative abundance. Particles such as paint, calcium carbonate, Portland cement, synthetic calcium silicate, synthetic magnesium silicate, asbestos, paper fiber, synthetic fiber, glass fibers, mineral wool fibers (slag and rock wools), starch, and clays can be characterized and their volume percentage estimated. Scanning electron microscopy coupled with energy-dispersive x-ray spectrometry (SEM-EDS) is used to analyze a portion of the sample to complement
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the PLM analysis. The sample is prepared by adding a few milligrams to a clean glass vial (disposable plastic pressure fit cap half-dram vials work well). Add one drop of collodian and 15 to 20 drops of amyl acetate. Using clean forceps, crush and stir the sample in the vial. Using a clean glass Pasteur pipette, mix gently and draw a few drops of the mixture into the pipette. Deposit onto a 12 millimeter diameter carbon planchet controlling the loading of solids by adding and removing the mixture until a light loading of the sample particulate has been deposited on the planchet. Allow to dry three to four hours and carbon coat. Analysis is carried out at 500× magnification. Find a heavily loaded area and collect an image and an EDS spectrum at 100× magnification to get a representation of the elements present. Search the majority of the planchet with a combination of secondary electron and backscattered electron imaging. Collect EDS spectra and images of particles that represent each type of constituent present. The SEM-EDS is especially useful when looking at glass fibers, Portland cement, gypsum, mineral wools, heavy metals, paint, perlite, and pumice. Clays such as montmorillonite and kaolinite can be differentiated if there are a minimum of interfering materials present. Diatoms, synthetic magnesium silicates, and calcium silicates can also be characterized by morphology and elemental composition. Transmission electron microscopy coupled with an energy dispersive x-ray spectrometer and capable of electron diffraction (AEM) is useful to characterize and identify mineral fibers (such as asbestos), clays, pigments, and other very fine, thin particles that may present themselves. The sample is prepared as a drop mount directly on a carbon film copper grid support and placed directly into the AEM. Collect EDS spectra and images of particles that represent each type of constituent present. To determine the acid-soluble weight percent, approximately 250 milligrams of the sample is weighed and dissolved in warm 10% hydrochloric acid. The undissolved particles are recovered by filtering through a preweighed polycarbonate filter (0.4 micrometer pore size). The insoluble fraction will typically contain clays, glass fibers, perlite, pumice, polymers, paint fragments, and other acid insoluble materials (see Table 13.2). Occasionally, difficult or complex samples will require the analysis of the acid insoluble particles collected on the polycarbonate filter by PLM, SEM, and AEM. Occasionally multilayered samples will require all the forementioned analyses performed on each layer. Some particles will actually be aggregates such as concrete or paint flakes and will require further testing. The final report involves matching results of particle classification to formulae that have been obtained from manufacturers and entered into a database. The formula information from various manufacturers varies considerably. So complex were the terms used to describe processes and so varied between manufacturers were the terms and proprietary names for ingredients that in
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one case hundreds of hours were needed to analyze documents associated with the formulas and a dictionary of terms was created to decipher the formulae (Hopen, Millette et al., 1999).
13. 4
MEASURING THE EXTENT OF A S P E C I F I C C O N TA M I N A N T
13.4.1 ASBESTOS There are quite a few standard microscopical methods for determining quantities of one environmental contaminant: asbestos. The asbestos methods use one of four types of microscopy: polarized light microscopy (PLM), phase contrast microscopy (PCM), transmission electron microscopy (TEM), or scanning electron microscopy (SEM). The TEM analysis includes characterization of fiber crystal structure by selected area electron diffraction (SAED). Methods for both types of electron microscopy (SEM and TEM) utilize an energy dispersive x-ray spectrometer (EDS) to analyze the fibers for their elemental composition. Many methods have been developed for determining asbestos levels in bulk building materials or concentrations in airborne samples, and some have been developed for asbestos in surface dust samples (Millette and Hays, 1994; ASTM, 2002). Because a chapter was devoted to asbestos in Volume 1 of Environmental Forensics: Contaminant Specific Guide (Van Orden, 2006), and additional information on available asbestos analysis methods can be found in Millette and Bandli (2005) and Millette (2006), only one asbestos-related environmental forensic microscopy method will be considered here. 13.4.1.1 Vermiculite Analysis Environmental forensic microscopy can be used to determine if a sample of vermiculite can be traced to a specific mine in Libby, Montana. Vermiculite products originating from the mine near Libby, Montana are currently in millions of homes and businesses across the nation. Associated with the Libby vermiculite are fibrous amphiboles including tremolite-asbestos. Many of these amphiboles occur in the asbestiform habit. Recent studies of the health of former mine workers and residents of Libby, Montana have shown an increased incidence of asbestos-related lung disease (ATSDR, 2001). The former W.R. Grace vermiculite mine and milling operations and numerous residences and commercial properties in Libby have been added to the U.S. Environmental Protection Agency’s (EPA) National Priorities List for immediate environmental remediation. Because other vermiculite products are not contaminated with fibrous amphiboles, it is an important environmental forensic question to determine
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whether a particular vermiculite material is from Libby or not. The USEPA Research Method for Sampling and Analysis of Fibrous Amphibole in Vermiculite Attic Insulation (VAI) (USEPA, 2004) can be used to analyze a sample of vermiculite for fibrous amphiboles that are characteristic of Libby vermiculite. In the EPA VAI Method (sometimes called the Cincinnati Method), samples are processed/separated using a water density gradient into three fractions: floats, sinks, and suspended particles. The EPA VAI Method contains the procedures for making two measurements of amphibole in VAI. Light microscopy is used to analyze the sinks fraction because denser particles that sink to the bottom may contain large amphibole fiber bundles. Electron microscopy is used to analyze the suspended particle fraction because some fine amphibole fibers may be suspended in the water. Using the cone and quartering technique replicate subsamples of approximately 10 grams each are produced from the original ziplock bag of material (usually a one-gallon container). These subsamples are dried for two hours at 100 degrees and weighed using an analytical balance. Following the methods described in EPA/600/R-04/004, the denser particles (sinks) are separated from the less dense particles (floats). The sinks are dried overnight on a hot plate at 60 degrees and weighed. The sinks are examined at low magnification utilizing a stereobinocular microscope. Fiber bundles are picked with tweezers. The total weight of fiber bundles is determined for each subsample. Representative fiber bundles are then analyzed by polarized light microscopy (PLM). Representative fiber bundles from one of the subsamples may also be examined and analyzed by scanning electron microscopy (SEM) coupled with an energy dispersive x-ray spectrometry (EDS) system. If no fibers are found by stereobinocular microscopy, the suspended particle fractions are prepared from the subsamples using the liquid suspensions after the floats and sinks have been removed. The suspensions are brought up to a volume of one liter and sonicated for two minutes. The suspensions are then agitated by bubbling filtered oxygen for one minute through the liquid using a 10 ml glass pipette at a flow rate of approximately 4 liters per minute. One- and 10-milliliter aliquots of each suspension are removed and filtered through 0.2 mm pore size polycarbonate filters. The filters are prepared and analyzed following the standard procedures as described in ISO 13794. Analyses are performed on a transmission electron microscope with an x-ray analysis system.
13.4.2
NONASBESTOS FIBERS
13.4.2.1 ISO Method 14966 The International Standards Organization (ISO, 2002) Method 14966 uses an SEM-EDS approach for determination of the concentration of inorganic
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fibrous particles in the air. It was designed to consider various types of fibers longer than 5 micrometers in length. With the ISO method, an analyst may count fibers on air filters and determine concentrations of different fiber types based on their elemental composition. The method specifies the use of goldcoated, capillary-pore, track-etched membrane filters, through which a known volume of air has been drawn. Using energy-dispersive x-ray analysis, the method can discriminate between fibers with compositions consistent with those of the asbestos varieties (e.g., serpentine and amphibole), gypsum, and other inorganic fibers. Annex C provides a summary of fiber types that can be measured. Information is included about fibers of mullite (Al6Si2O13), willemite (Zn2SiO4), sillimanite (Al2SiO5), dumortierite (Al7O3(BO3)(SiO4)), wollastonite (CaSiO3), and several zeolites; industrial crystalline fibers such as silicon carbide (SiC), zirconia (ZrO2), and tungsten (W); inorganic amorphous fibers such as glass wool, rock wool, and slag wool, ceramic, and quartz. ISO 14966:2002 is applicable to the measurement of the concentrations of inorganic fibrous particles in ambient air. The method is also applicable for determining the numerical concentrations of inorganic fibrous particles in the interior atmospheres of buildings. It is important to note that the ability of the method to detect and classify fibers with widths lower than 0.2 micrometers is limited. If airborne fibers in the atmosphere being sampled are predominantly less than 0.2 micrometers in width, a transmission electron microscopy method is recommended. 13.4.2.2 Glass Fibers Glass fibers found in airborne samples collected on membrane filters can be analyzed by phase contrast microscopy using the “B” rules of the National Institute of Occupational Safety and Health (NIOSH) 7400 method (NIOSH, 1994a). Although the phase contrast method does not identify the type of fiber counted, it does provide a useful system for monitoring airborne concentrations in areas where glass fibers are manufactured or products are fabricated with the fibers. In situations where mixtures of fibrous materials are anticipated, the PCM method should be augmented with additional microscopical procedures such as polarized light microscopy (PLM) or electron microscopy. Although not a standard method, surface dust samples were analyzed for glass fibers by Schneider et al. (1990). They used gelatinous foils to collect the samples and then analyzed them by light microscopy. 13.4.2.3 Ceramic Whiskers There are four standard microscopy measurement methods related to airborne ceramic whiskers including silicon carbide and silicon nitride fibers (ASTM, 2001a,b,c,d). The scanning electron microscopy method for single-
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crystal ceramic whiskers (SCCW) is a method that has the ability to distinguish among many different types of fibers based on energy dispersive x-ray spectrometry (EDS) analysis. This test method may be appropriate for other man-made mineral fibers (MMMF). This test method is applicable to the quantification of fibers on a collection filter that are greater than 5 micrometers (mm) in length, less than 3 mm in width, and have an aspect ratio equal to or greater than 5 : 1. The data are directly convertible to a statement of concentration per unit volume of air sampled. This test method is limited by the diameter of the fibers visible by SEM (typically greater than 0.10 to 0.25 mm in width) and the amount of coincident interference particles. The transmission electron method is applicable to the quantification of fibers on a collection filter that are greater than 0.5 mm in length and have an aspect ratio equal to or greater than 5 : 1.
13.4.3 NONFIBROUS PARTICULATE There is a standard procedure for determining particle size information on samples of environmental particulate emissions. Administered by the Louisiana Department of Environmental Quality (LDEQ), the Louisiana Environmental Laboratory Accreditation Program (LELAP) is recognized by the National Environmental Laboratory Accreditation Program (NELAP). Under the LELAP program, samples of particulate from industrial emissions that have been collected on filters (PC filters are preferred although they do have a temperature limit) are analyzed for total particle sizing by automated scanning electron microscopy. The analyses are performed using a scanning electron microscope operating in automated mode under the control of an x-ray analysis system utilizing a standard operating procedure. Figure 13.2 shows a dispersion of lead-rich particles in the backscattered electron mode and Figure 13.3 shows how the automated sizing procedure assigns dimensional values to all the particles. Approximately 1000 to 2000 particles from each sample are individually sized and classified according to five client-requested size categories, typically, 0.5–2.5, 2.5–5.0, 5.0–7.5, 7.5–10.0 and >10 mm. The particle size data are presented in terms of particle number and in terms of estimated mass. The assumption is made that the particles are all of similar density and therefore the particle volume distribution is equivalent to the particle mass distribution. Automated Particle Analysis is a useful environmental forensic microscopy tool. Digital imaging under computer control with the scanning electron microscope makes possible the morphological and chemical analysis of hundreds or thousands of particles without intervention by the microscopist. With computer control of the electron beam and the sample position, digital images
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Figure 13.2 Backscattered electron image of lead ore dust sized by automated scanning electron microscopy.
Figure 13.3 Same image field as Figure 13.2 after the microscope computer has applied conditions of particle definitions for automated particle sizing. A full color version of this figure is available at books.elsevier.com/ companions/ 9780123695222.
can be acquired into computer memory and the image searched for particles based on computer programs that recognize image contrast. Size and shape calculations can be made and recorded for each particle found and the electron beam can be driven back to the particle for chemical analysis by energy dispersive x-ray spectrometry. Automated SEM particle analysis has been used extensively in the investigation of leaded particles in soil (Cotter-Howells and
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Thornton, 1991; Hunt et al., 1991, 1998; Rybicka, Wilson, and McHardy, 1994; Thornton et al., 1994; Franck and Herbarth, 2002; Pirrie, 2003) and in other types of environmental forensic studies including the size of urban air particles ( Jambers, De Bock, and Van Grieken, 1995) and those involving cement particles and grout (Millette and Brown, 2002).
13.5
CASE STUDIES—EXAMPLES OF E N V I R O N M E N TA L F O R E N S I C M I C R O S C O PY I N V E S T I G AT I O N S
13.5.1 ELEVATED LEAD IN A CHILD It is well known that young children can be exposed to lead by ingesting lead paint dust that is generated by the deterioration, sanding, or scraping of leadbased paints in the home. Other sources of lead present in homes include deposits of particles from the use of leaded gasoline and from industrial sources like smelting. In one case, finding a child with elevated blood lead raised the concern that the child was ingesting lead-based paint dust. However, x-ray fluorescence testing of the paint in the home detected no lead. Samples of the dust were collected on adhesive notes and sent to the laboratory for analysis by SEM-EDS. The results showed the source of the lead in dust was lead-containing fly ash (Millette, Brown et al., 1991). A search of the neighborhood resulted in sampling piles of material at a nearby industrial site (see Figure 13.4). The SEM-EDS showed lead-containing fly ash consistent with that found within the home (see Figure 13.5). The So-Green company apparently had been paid to receive tons of electric arc fly ash from a company in another state and was turning it into a product to be sold as a fertilizer. Unfortunately the fertilizer business was not keeping up with the shipments of fly ash and large piles were accumulating around the facility. The site was
Figure 13.4 Piles of electric-arc fly ash at the So-Green site. A full color version of this figure is available at books.elsevier.com/ companions/ 9780123695222.
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Figure 13.5 Backscattered electron image of fly ash and leadrich particle (white) typical of particles found in homes surrounding the So-Green facility.
ultimately declared a Superfund site. In other cases involving concern over lead particulate, samples were collected from homes and analyzed by SEMEDS. The leaded particles were classified as lead paint (Pb-Cr, Pb-Zn), auto exhaust (Pb-Br), industrial lead (Pb+metals), soil lead (Pb-Si, Al and/or Ca), and undetermined (Pb-only) based on the other elements associated with the lead in the particle. In one project, lead-arsenate particles were found in household dust (Millette et al., 1995). In another project, lead-chlorine particles from PVC electric cable covering were found in an office building (Ghazi and Millette, 2005).
13.5.2
A SPOT CALLED RALPH
In a courthouse in South Carolina a mysterious stain appeared in the new carpet. Employees even gave the spot a name—“Ralph.” At first it was the size of a half dollar but it grew after cleaning to about 2 square feet. Environmental mold specialists initially tested the stain in the carpet and determined that it was not caused by mold. A section of the stain was cut from the carpet and delivered to the environmental forensic microscopy laboratory for inspection. Analysis by light and scanning electron microscopy showed that the carpet contained a variety of particles typical of the particles often found in office dusts. A sticky substance was also found on the carpet fibers. FTIR analysis of the sticky material showed that it was consistent with corn syrup. It is apparent that someone spilled a soft drink on the carpet and the stain was caused by office dust particles adhering to the sticky drink residue. Efforts to clean the stain removed the dark office dust particles but did not completely remove the sticky drink residue. In fact, the cleaning efforts spread the sticky residue, which collected more office dirt over time and therefore appeared to grow in size. Not surprisingly, the newspaper reporter who interviewed the laboratory
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Figure 13.6 Dark “sooty” looking deposit on an automobile trunk surface.
after the findings were made public was disappointed that the stain called “Ralph” was not something exotic, just something caused by a spilled soft drink.
13.5.3 AUTOMOBILES WITH A SOOTY DEPOSITION—1 The ASTM standard, D4610, states “Microbial growth is a major cause of discoloration and deterioration of paint films.” This is true not only of painted house surfaces but also of automobile finishes. Environmental forensic microscopy investigations of what is causing the dark “sooty” layer on light colored automobiles such as the one shown in Figure 13.6 were performed using the ASTM D6602 standard (ASTM, 2003a). A clear cellophane tape is applied to the surface of the auto, removed, and placed on a microscope slide. The use of a PLM microscope at magnifications from 50 to 400× showed that the darkening agent on the automobile shown in Figure 13.6 was a biological growth (see Figure 13.7). A cotton ball is used to collect a sample for analysis by transmission electron microscopy of the darkening agent if it is suspected of being soot. The TEM analysis is the only way to differentiate various types of aciniform soots including carbon black that have particle sizes in the nanometer range. In a similar case, a residential mailbox was reportedly covered with soot from a nearby power plant. The environmental forensic investigation showed that the darkening agent on the mailbox was not soot but a sooty mold.
13.5.4 AUTOMOBILES WITH A SOOTY DEPOSITION—2 Cars parked in an industrial area were becoming coated with “black, sticky debris.” The debris was described as “sticky and difficult to wash off” and
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Figure 13.7 PLM image of the mold/ biofilm material causing the darkening shown in Figure 13.6.
Figure 13.8 Brightfield reflected light image of black debris from parked automobile (Sooty Deposition 2). A full color version of this figure is available at books. elsevier.com/companions/ 9780123695222.
scratched the automobile painted finish if rubbed. Samples were collected with tape and sent for microscopical examination. The black, sticky debris was examined using a combination of polarized light microscopy (PLM), scanning electron microscopy-energy dispersive x-ray spectrometry (SEM-EDS), and Fourier transform microspectroscopy (FTIR), and was found to consist primarily of metal particles, quartz sand, and a resinous material (see Figures 13.8, 13.9, and 13.10). Aggregates were extracted with drops of acetone on a glass slide and the acetone soluble fraction was redeposited on a reflective e-glass slide for FTIR analysis. Samples from exhaust vents of a nearby metal casting industry were collected. The residue from the exhaust vents was found to be similar in physical and elemental composition to the black debris appearing on the parked automobiles.
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Figure 13.9 Transmitted light image using crossed polarizers of quartz particles in black debris.
Figure 13.10 Backscattered electron image of inorganic particles comprising black debris.
13.5.5 WTC SIGNATURE SEARCH The dust cloud generated by the collapse of the World Trade Center (WTC) towers on September 11, 2001 was a complex mixture of building material particles (Millette et al., 2001; Lioy et al., 2002a; Yin et al., 2004). In April 2005, there remained questions about where the dust particles had settled and how to determine which residences in New York City still required cleaning of the WTC dust. EPA conducted a study to determine if a WTC Dust Signature Protocol could be used to determine where residue of the WTC dust remained.
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Figure 13.11 Brightfield transmitted light image of WTC dust showing glass fibers, cement particles, and gypsum.
Figure 13.12 Secondary electron image of WTC dust showing glass fibers, cement particles, and gypsum.
They asked a number of independent laboratories to test a proposed protocol based on work done by the U.S. Geological Survey (Lowers et al., 2005; Meeker et al., 2005). Based on the fact that glass fibers, cement particles, and gypsum were the major components of the WTC dust (see Figures 13.11 and 13.12), the USGS protocol involved elemental mapping of calcium and sulfur by computer-controlled scanning electron microscopy—x-ray analysis (SEMEDS) and an independent analysis for slag wool fibers. In the summer of 2005, based on the work of the various laboratories, the EPA decided that the Computer Controlled SEM/EDS analysis was not reproducible between labs and proposed a method based only on Slag Wool Analysis by SEM-EDS (USEPA, 2005). The proposed protocol was sent out to a Peer Review Panel. In October
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2005, the peer review panel (Crane et al., 2005) concluded, “EPA has not made the case that its proposed analytical method can reliably discriminate background dust from dust contaminated with WTC residue.” The USEPA is proceeding with a $7 million Test and Clean Program that covers the area south of Canal Street and west of Pike-Allen Streets in New York City. Instead of a decision based on a WTC dust signature, a cleaning decision will be based on the finding of elevated levels of one of four contaminants of concern. Dust samples will be analyzed for asbestos, man-made vitreous fiber (MMVF), lead, and polycyclic aromatic hydrocarbons (PAH). The proposed EPA Criteria for determining whether an accessible area is to be cleaned are: 䊏
Asbestos—5000 structures/cm2
䊏
MMVF—5000 fibers/cm2
䊏
Lead—40 mg/ft 2
䊏
PAHs—150 mg/M2
Standard methods exist for the analysis, in surface dust, of asbestos (ASTM, 2003b), lead (NIOSH, 1994b; USEPA, 1996; OSHA, 2002), and PAHs (USEPA, 1986), but no standard method currently exists for the analysis of MMVF in surface dust. It is anticipated that a method for MMVF in surface dust will be developed by combining the ASTM microvac TEM method for asbestos in dust (ASTM, 2003) with analytical procedures developed by the U.S. Geological Survey (Lowers and Meeker, 2005) using the scanning electron microscope to classify the glass fibers. A method using PLM identification of the glass fibers is also possible. There is no advantage to using the TEM for glass fiber analysis because although asbestos and other naturally occurring mineral fibers are characterized by their crystalline structure, which can be examined by electron diffraction, man-made vitreous fibers are amorphous; that is, they are glassy, with no discernible crystalline array (US Navy, 1997).
REFERENCES ASTM. (2001a) Standard Practice for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environment. American Society for Testing and Materials, Method D6058-96. Conshohocken, PA. ASTM. (2001b) Standard Test Method for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environment by Transmission Electron Microscopy. American Society for Testing and Materials, Method D6056-96. Conshohocken, PA.
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ASTM. (2001c) Standard Test Method for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environment by Scanning Electron Microscopy. American Society for Testing and Materials, Method D6059-96. Conshohocken, PA. ASTM. (2001d) Standard Test Method for Determining Concentration of Airborne Single-Crystal Ceramic Whiskers in the Workplace Environment by Phase Contrast Microscopy. American Society for Testing and Materials, Method D6057-96. Conshohocken, PA. ASTM. (2003a) Sampling and Testing of Possible Carbon Black Fugitive Emissions or Other Environmental Particulate, or Both. American Society for Testing and Materials, Method D6602. Conshohocken, PA. ASTM. (2003b) Standard Test Method for Microvacuum Sampling and Indirect Analysis of Dust by Transmission Electron Microscopy for Asbestos Structure Number Surface Loading. American Society for Testing and Materials, Method D5755-03. Conshohocken, PA. ATSDR. (2001) Libby Environmental Health Update. Agency for Toxic Substances and Disease Registry, January 12, 2001. Clague, A.D.H., Donnet, J.B., Wang, T.K., and Peng, J.C.M. (1999) A Comparison of Diesel Engine Soot with Carbon Black. Carbon 37, 1553–1565. Cotter-Howells, J. and Thornton, I. (1991) Sources and pathways of environmental lead to children in a Derbyshire mining village. Environmental Geochemistry and Health 13(2), 127–135. ISSN: 0269-4042 (Paper) 1573–2983 (Online). DOI: 10.1007/BF01734304. Crane, D., Ehrenfeld, F., Gunter, M., McConnell, E., Su, S., Webber, J., and Wilhelmi, J. (2005) Peer Review of the U.S. Environmental Protection Agency’s Final Report on the World Trade Center (WTC) Dust Screening Study. Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC., EPA Contract No. 68-C-02-060, Task Order 107. Faegri, K., Iversen, J., and Waterbolk, H.T. (1964) Textbook of Pollen Analysis. Hafner Publishing Company, New York, 237. Franck, U. and Herbarth, O. (2002) Using scanning electron microscopy for statistical characterization of the diameter and shape of airborne particles at an urban location. Environmental Toxicology 17, 98–104. Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/tox.10037. Ghazi, A.M. and Millette, J.R. (2005) Environmental forensic application of lead isotope ratio determination: A case study using laser ablation, Sector ICP-MS. Environmental Forensics 5(2), 97–108.
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Figure 13.1 Scanning electron microscope images of filters used to collect airborne particles. Spheres of 5 micrometers and 1 micrometer are overlaid to show how small particles would appear on the filter surface.
Figure 13.2 Backscattered electron image of lead ore dust sized by automated scanning electron microscopy.
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Figure 13.3 Same image field as Figure 13.2 after the microscope computer has applied conditions of particle definitions for automated particle sizing. A full color version of this figure is available at books.elsevier.com/ companions/ 9780123695222.
Figure 13.4 Piles of electric-arc fly ash at the So-Green site. A full color version of this figure is available at books.elsevier.com/ companions/ 9780123695222.
Figure 13.5 Backscattered electron image of fly ash and leadrich particle (white) typical of particles found in homes surrounding the So-Green facility.
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Figure 13.6 Dark “sooty” looking deposit on an automobile trunk surface.
Figure 13.7 PLM image of the mold/ biofilm material causing the darkening shown in Figure 13.6.
Figure 13.8 Brightfield reflected light image of black debris from parked automobile (Sooty Deposition 2). A full color version of this figure is available at books. elsevier.com/companions/ 9780123695222.
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Figure 13.9 Transmitted light image using crossed polarizers of quartz particles in black debris.
Figure 13.10 Backscattered electron image of inorganic particles comprising black debris.
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Figure 13.11 Brightfield transmitted light image of WTC dust showing glass fibers, cement particles, and gypsum.
Figure 13.12 Secondary electron image of WTC dust showing glass fibers, cement particles, and gypsum.
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