Journal of Exposure Science and Environmental Epidemiology (2008) 18, 20–30 r 2008 Nature Publishing Group All rights reserved 1559-0631/08/$30.00 www.nature.com/jes Using environmental forensic microscopy in exposure science JAMES R. MILLETTE, RICHARD S. BROWN AND WHITNEY B. HILL MVA Scientific Consultants, 3300 Breckinridge Blvd, Suite 400, Duluth, Georgia, USA Environmental forensic microscopy investigations are based on the methods and procedures developed in the fields of criminal forensics, industrial hygiene and environmental monitoring. Using a variety of microscopes and techniques, the environmental forensic scientist attempts to reconstructthe sources and the extent of exposure based on the physical evidence left behind after particles are exchanged between an individual and the environmentshe or she passes through. This article describes how environmental forensic microscopy uses procedures developed for environmental monitoring, criminal forensics and industrial hygiene investigations. It provides key references to the interdisciplinary approach used in microscopic investigations. Case studies dealing with lead, asbestos, glass fibers and other particulate contaminants are used to illustrate how environmental forensic microscopy can be veryuseful in the initial stages of a variety of environmental exposure characterization efforts to eliminate some agents of concern and to narrow the field of possible sources of exposure. Journal of Exposure Science and Environmental Epidemiology (2008) 18, 20–30; doi:10.1038/sj.jes.7500613; published online 7 November 2007 Keywords: dust, particulate, soil, indoor environment, exchange principle. Introduction microscopy procedures used in comparing physical evidence including dust and specific particle types such as hairs, fibers Dust can be used as a metric for residential and building and mineral grains have been presented by Palenik (1988), exposure assessment and source characterization (Lioy et al., Saferstein (1995, 2006) and Petraco and Kubic (2003). 2002a). By using forensictechniques that have been In describing how dust can be used as a metric for developed by criminologists (now called forensic scientists) residential and building exposure and source characteriza- over many years, the field of environmental forensic tions, it has been suggested that from microscopic dust microscopy has come a long way in identifying sources of analyses, information is frequently obtained from one or indoor and outdoor contaminants and in improving how the more different microenvironments occupied or passed total human exposure is assessed in residential and office through by an individual or individuals over the course of environments. a day (Lioy et al., 2002a). This same concept is often referred Environmental forensic microscopy is the use of micro- to as the exchange principle by criminologists (forensic scopy following forensic procedures to characterize particles scientists) when describing the premise of their forensic trace and materials involved in environmental studies. The evidence studies. The Locard Exchange Principle was procedures used in environmental forensic investigations are proposed in the 1930s by Edmund Locard, the director of generally the same as the criminal forensic science approach the crime laboratory in Lyon, France. Locard’s Exchange to trace evidence analysis. Samples of the particles (dust, dirt, Principle states that whenever two objects come into contact, soil or suspensions in liquid) in question are collected and a transfer of material will occur (Locard, 1930). By analyzed by different microscopy techniques to identify the recognizing, documenting and examining the nature and particles and to determine possible sources. The procedure extent of this evidentiary exchange, Locard observed that then involves comparing the results of the analyses with criminals could be associated with particular locations, items cataloged information about particles that are emitted or of evidence and victims (Chisum and Turvey, 2000). In his released from suspect sources. In some situations, a writings on the subject of physical evidence and crime comparison is made of sample particle types to particles reconstruction, Locard wrote, ‘‘ythe criminologist recreates obtained from the suspect source(s). Guidelines for basic the criminal from traces the latter leaves behind, just as the archaeologist reconstructs prehistoric beings from his finds’’ 1. Address all correspondence to: Dr. J. R. Millette, MVA Scientific (Locard, 1930). On the basis of the Exchange Principle, Consultants, 3300 Breckinridge Blvd, Suite 400, Duluth, Georgia 30096, Locard built the first crime lab in the attic of Lyons Police USA. Tel.: 770-662-8509. Fax: 770-662-8532. Department, which later became the Institute of Criminalis- E-mail: [email protected] Received 5 March 2007; accepted 22 June 2007; published online 7 tics at the University of Lyons. The Exchange Principle is November 2007 widely regarded as a cornerstone of the forensic sciences and Environmental Forensic Microscopy Millette et al Locard’s successful use of the Principle with scientific acterization of soil minerals is just one part of the methods led to the creation of forensic laboratories in many examination of dust and dirt particle samples. Dusts always countries. In environmental forensic particulate studies, the contain particles other than soil minerals. Among these may goal is to recognize, examine and document the nature and be biological substances such as pollen grains, skin cells, extent of the particles left behind after an interaction between plant fragments, combustion products (soot), building two environments or an environment and an individual. In materials such as paint flakes, construction debris and metal other words, the environmental forensicscientist attempts to flakes; and fibers (both natural and man-made). Microscopic reconstruct the sources and the extent of exposure based on forensicexaminations of hairs and fabricfibers have been the physical evidence left behind. long established procedures in tracing criminal evidence An illustration of the Exchange Principle and environ- evaluations (Saferstein, 1995). In the environmental and mental forensic microscopy is the case of dust that had industrial hygiene areas, standard procedures for the analysis accumulated on surfaces in an attic several feet below an of one particular fiber, asbestos, have been well documented asbestos-containing fireproofing. Investigators had concluded for a variety of media; air, dust, water and bulk building that a fallout from the fireproofing was the primary source of materials (Millette and Bandli, 2005). Some of these methods the asbestos fibers found in the dust based on the facts that have been adapted for the characterization and monitoring of the dust was the same color as the fireproofing and no other various types of glass fibers such as fiberglass, mineral wool, asbestos-containing products were apparent in the attic. It slag wool and rock wool. Ceramic fibers are also the subject was also apparent that chunks of debris had fallen from the of health concerns, and microscopy methods to characterize fireproofing to the surfaces in some areas. Although it them in some media are available. In the investigation of appeared fairly straightforward, another investigator insisted sooty deposits, the American Society for Testing and that the asbestos fibers in the dust were the result of Materials Method 6602 (ASTM, 2003) is a standard infiltration of fibers from other sources from inside and procedure that serves as an excellent basis for environmental perhaps outside of the building. Samples of the dust were sent forensic microscopy investigations where soot might be to a laboratory, and an environmental forensic microscopy involved. This ASTM standard was designed primarily for analysis of the dust was performed. The analysis showed that the determination of carbon black among soot particles and the dust contained particles of gypsum, vermiculite and other dark particles but provides the framework for the chrysotile asbestos including some where the three particle microscopy studies necessary to determine the identity of all types were combined in small aggregates. The aggregated particles and possible sources of surface contamination. particles were consistent with the composition of the Microscopic examination first by stereomicroscope and then fireproofing: gypsum binder, vermiculite filler and chrysotile polarized light microscope is used to sort out the various asbestos. The analysis did not find evidence of other asbestos- particle types present and to determine the approximate containing products such as floor tile fragments. The relative percentages by volume of the different components. conclusion of the forensic analysis was that the primary Transmission electron microscope analysis is used in source of asbestos in the dust on the attic surfaces was the conjunction with energy-dispersive x-ray analysis (TEM– asbestos-containing fireproofing. An exchange had taken place EDS) to identify the ‘‘fine’’ (small) size fraction of the dark between the building product and the attic environment. particulate and is especially useful in differentiating between various carbon soots. If a significant amount of fine (small) particulate such as soot is determined by polarized light Background: combining disciplines microscopy (PLM), additional analysis by TEM–EDS is necessary to confirm the presence of aciniform soot and to The methods used in environmental forensicinvestigations