Anal. Chem. 1997, 69, 307R-327R
Industrial Hygiene Martin Harper,*,† Clifford R. Glowacki,‡ and Paul R. Michael§
SKC, Inc., 863 Valley View Road, Eighty Four, Pennsylvania 15330, Ashland Chemical Inc., 5200 Blazer Parkway, Dublin, Ohio 43017, and Monsanto Company, 800 North Lindbergh Boulevard, St. Louis, Missouri 63167 Review Contents General Reviews Monitoring Instruments Spectrometry Chromatography Miscellaneous Sensors Dusts, Aerosols, and Fibers Dusts Aerosols Fibers Radiation Dosimetry Sorbents and Filter Media Biological Monitoring Quality Assurance Conclusions Literature Cited
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Two years have elapsed since the last industrial hygiene review article was published (A1). The number of papers reviewed then was over 2000 published in the prior two years, and this has increased to over 2600 in the past two years. Of this total, around 800 have been included in this review as being of direct relevance to the practitioners of occupational and environmental hygiene chemistry. Typically, the industrial hygienist is devoted to the anticipation, recognition, evaluation, and control of chemical and physical stressors whose presence or action may lead to undesirable outcomes such as injury or death. The main functions of industrial hygiene chemistry (apart from using chemical knowledge to anticipate hazards) are screening for chemical stressors during the recognition phase and monitoring of specific hazard concentrations during the evaluation and control phases. Industrial hygiene has outgrown its roots in the manufacturing industry to include hazards of other workplaces, such as offices, and even the home and outdoor environments. The techniques of monitoring for the presence of hazards are similar whatever the environment. The control limits may be regulated in the workplace by the Occupational Safety and Health Administration (OSHA) or recommended by the National Institute for Occupational Safety and Health (NIOSH), the Threshold Limit Value (TLV) Committee of the American Conference of Governmental Industrial Hygienists (ACGIH), the Workplace Environmental Exposure Levels (WEEL) Committee of the American Industrial Hygiene Association (AIHA), in-house corporate industrial hygiene limits, or other government agencies worldwide, such as the Health and Safety Executive in the United Kingdom. Standards for the the home and office environment are generally recommended by bodies such as the American Society of Heating, Refrigeration and Air †
SKC, Inc. Ashland Chemical Co. § Monsanto Co. ‡
S0003-2700(97)00011-5 CCC: $14.00
© 1997 American Chemical Society
Conditioning Engineers (ASHRAE) or the Environmental Protection Agency (EPA), which also mandates ambient and emission air standards. Typically, these standards refer to a concentration of hazardous substance in air, either in terms of parts per million by volume (ppm) or weight per unit volume (e.g., mg/m3), as the most often encountered route of exposure is through the respiratory system. However, it is well known that significant contributions to exposure can occur through dermal exposure (e.g., pesticides) or through ingestion (e.g., leaded paint fragments). In these cases, it is often useful to measure the body burden of a chemical or its metabolite to determine an estimate of total exposure. This type of study is increasingly common and forms the subject of the largest grouping of articles in this review, concerned with biological monitoring through analysis of exhaled breath, urine, or blood. In addition, it is possible to estimate the contribution from dermal exposure by the analysis of surfaces, often by means of wipe samples. Airborne hazards include gases, vapors, and solid or liquid aerosol particulates including dusts, mists, and fibers. Monitoring requires sampling and analysis. The ideal monitor would sample and analyze immediately and continuously on-site with clear warning of excessive exposures. It would be portable, i.e., lightweight, unobtrusive, and self-powered. It would be selective and sensitive, yet responsive, to the broadest range of hazardssin short, the kind of instrument so far only seen in science fiction movies. Yet the pace of progress leads us ever closer to this goal. There are diffusive samplers that require no pump, including some that can give on-site readout. There is a new generation of pumps that are far smaller and lighter than ever before. New chemical sensors coupled with appropriate hardware can give audible alarms. Two sections of this review deal with advances in directreading instrumentation, the first with classical techniques of spectrometry and chromatography and the second with novel chemical sensors. In addition, a separate section deals with methods of radiation dosimetry, since many of these methods are designed for the collection and measurement of radioactive gases or aerosols. Traditional methods of taking time-weighted average samples by concentration of the contaminants in media such as filters, liquid reagents, or porous solid sorbents are still important and make up the bulk of techniques used or recommended for use by regulatory bodies. These are reviewed in a section devoted to methods for aerosols, dusts, and vapors and a section devoted to methods for gases and vapors. The section on biological monitoring concentrates on reviewing new or improved analytical methodologies or on the development of novel indicators of exposure. Finally, a section is included on quality assurance, since none of the data gathered by any of the methods described in any of the other sections is of value unless its quality can be assured. Analytical Chemistry, Vol. 69, No. 12, June 15, 1997 307R
GENERAL REVIEWS There are a number of review papers covering general areas of industrial hygiene sampling and analysis. Kennedy et al. (B1) and Blachere et al. (B2) published guidelines for analytical method development and evaluation, and the methods were reviewed by Eller (B3). The EPA published a report on personal air sampling and air monitoring requirements at hazardous waste sites (B4), Humphrey et al. examined air monitoring techniques used in support of cleanup activities (B5), and Loudon et al. reviewed the use of various on-site warning techniques (B6). Four reviews covered analysis of pollutants in indoor air (B7-B10). Laird comprehensively reviewed the equipment required for air sampling and surface contamination (B11), as did Namiesnik and Zaslawska (B12), Prokhorova and Khobotova (B13), Lioy (B14), Boyko (B15), and Meyer and Kelling (B16). Saarinen reviewed organic air sample collection and analysis using styrene as an example (B17). Wen et al. reviewed methods for monitoring arsenic, phosphorus, and sulfur compound exposures in the semiconductor industry (B18), as did Nakano (B19). This latter study included detection tubes as well as instrumental analyses. Uhlik (B20) also reviewed detector tubes. Wabeke (B21) and Bzdega et al. (B22) reviewed carbon monoxide monitoring. Koochaki et al. reviewed monitoring of biochemical aerosols (B23), and Samara reviewed methods for sampling various organic particulates (B24). In the field of chemical analysis of samples, Krylov (B25) and Drugov (B26) reviewed the use of chromatography. Atomic adsorption was reviewed in a book edited by Tsalev (B27), and electroanalytical methods were reviewed by Ashley (B28). Finally, the reader should refer to the following, more specific, sections, where further information on some of these aspects of sampling and analysis may be found. MONITORING INSTRUMENTS The measurement of environmentally important materials in the workplace, in ambient air, and in emissions using laboratory and field instrumentation contributed a large number of publications to the industrial hygiene literature in the last two years. Most of these were easily sorted into two general categories, spectroscopic and chromatographic, which will be addressed first. The remaining papers will be included under a “miscellaneous” section. Spectrometry. Infrared spectrometry (IR), especially Fourier transform IR (FT-IR), was the technique of choice for a majority of authors measuring the environment with a spectroscopic technique. Meng and Meng (C1) reviewed the application of FTIR in occupational hygiene analysis. Ahonen and co-workers (C2) compared a portable FT-IR with adsorption tubes for the determination of mixtures of organic solvents and reported a correlation coefficient of 0.978. The correlation degrades as the solvent concentration approaches the FT-IR detection limit of 1 mg/m3. Open path (OP) FT-IR was the subject of reports by several teams. Park et al. (C3), Samanta and Todd (C4), Drescher and co-workers (C5), and Kuile and associates (C6) used this technique for tomographical reconstruction of workplace concentrations and for imaging the spacial distribution of gases in the workplace. Coanalysis and spectral subtractions in OPFT-IR were the subject of a publication by Pescatore and associates (C7). Other reports of the use of OPFT-IR included the use of a low-resolution system by Griffiths et al. (C8) and indoor air assessment by Chaffin et al. (C9). Limitations with the use of OPFT-IR for process emissions 308R
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were reported by David et al. (C10), and Sato (C11) discussed the problem of humidity in OPFT-IR. FT-IR calibration (C12), application to disease diagnosis (C13), and strategies (C14) were also the subjects of articles. The use of an ion mobility analyzer array with selective chemical ionization was reported by Meng et al. (C15). The system was used to monitor indoor environments with 200 ms sampling intervals for a variety of volatile organic compounds (VOCs). Ion mobility spectrometry was also used for the on-site monitoring on nicotine vapors in the air during the manufacture of transdermal systems by Eiceman et al. (C16). Proton transfer reaction mass spectrometry was used by Hansel and co-workers (C17) to monitor common organic constituents of contaminated air at parts per billion (ppb) concentrations in air exhaled by smokers, in patients with cirrhosis of the liver, and at a road crossing. Spanel and Smith (C18) studied the reactions of NO+ and O2+ as potential routes for trace gas analysis. UV and UV-IR were used by Liu et al. (C19) for the determination of 2-naphthol and by Dankner et al. (C20) for hydrocarbons and toxic gases. The comparison of gravimetric and spectroscopic methods was the subject of work by Hekmat et al. (C21), and tunable diode lasers were applied to the chemical analysis of gases by Bechara and associates (C22). Atomic absorption, graphite furnace atomic absorption, and inductively coupled emission spectrometries were used to determine a variety of metals is different matrices, including lead and cadmium in dust (C23), metals in coarse and respirable industrial dust (C24), heavy elements in gaseous effluents (C25), metallic fumes and aerosols (C26), and hazardous and radioactive elements (C27). Nejedly and co-workers (C28) found that the elemental compositions of split samples analyzed by PIXE, PESA, EDXRF, and IC agreed within 20% for coarse and fine air particulates. Finally, X-ray fluorescence was used to evaluate the extent of lead contamination on carpeted surfaces by Bero et al. (C29). Chromatography. Gas chromatography, either alone or interfaced with other instrumentation, remains the most popular chromatographic technique. Table 1 summarizes the literature. Ion chromatographic methods were reported for the determination of fluoride in arc welding fumes (C55) and for the continuous measurement of gaseous nitrous and nitric acids and particulate nitrite and nitrate (C56). Ion chromatography was also combined with ICP-AES by Takaya and Sawatari (C57) for the speciation of vanadium(IV) and vanadium(V). HPLC was used by Kussak et al. (C58) for the determination of aflatoxins in airborne dust from feed factories. In other work, Dabill and co-workers (C59) evaluated the effect of pressure on gas monitoring equipment that was being used in pressurized tunnels and determined that the instruments are affected by both static and transient overpressurization. In an interesting paper, Kar and Dasgupta (C60) directly measured phenols in the gas phase at ppm levels using a loop-supported liquid film with micellar electrokinetic chromatography and direct UV detection. Finally, Kanagasabapathy et al. (C61) used supercritical extraction to recover polycyclic aromatic hydrocarbons (PAHs) from XAD-2 sampling media. Miscellaneous. A number of the articles did not fit conveniently within the previous sections. These are presented in Table 2 for ease of review and economy of space.
Table 1. Instrumental Methods Based on Gas Chromatography topica
analyte
GC HS/GC/MS GC GC/MS GC/MS TD/GC GC GC GC
RDX VOCs diphenylhydroxypropane VOCs chloropyrifos organic solvent vapor 1,2-epoxypropane BETX toluene, R-pinene, 1,4-dichlorobenzene benzene BETX odorous compounds VOCs PCBs, methylsulfonyl PCBs VOCs VOCs VOCs CO2, O2 VOCs
Zhong et al. Yang and Pawliszyn Koran et al. Dai et al. Mori et al. Kanno and Sugimoto Zhou Bertolino et al. Tang and Otson
C30 C31 C32 C33 C34 C35 C36 C37 C38
Burroughs and Woodfin Pashinsky Karpe et al. Overton et al. Janak et al.
C39 C40 C41 C42 C43
Mattinen et al. Laguna et al. Mapelli et al. Borossay et al. Baykut
C44 C45 C46 C47 C48
VOCs rat’s breath pyrethroids 1,2,4-triazole VOCs VOCs
Chai and Pawliszyn Raymer et al. Class et al. Khasanova Yang and Pawliszyn Merten et al.
C49 C50 C51 C52 C53 C54
GC GC TD/GC/MS GC GC/AED GC GC GC/MS GC GC/MS (mobile) SPE/GC/MS GC/MS GC/MS GC GC GC/MS
author(s)
ref
a GC, gas chromatography; HS, head space; MS, mass spectroscopy; TD, thermal desorption; AED, atomic emission detection; SPE, solid phase extraction.
SENSORS Several reviews described the use of chemosensors in motor vehicle exhaust control (D1), recommended routine maintenance and calibration procedures (D2), and discussed the response of gas sensors to specific functional groups and molecular geometries (D3). Another review by Vo-Dinh (D4) deals with recent advances in chemical and biosensors based on surface-enhanced Raman scattering (SERS) and the application of this technique for the qualitative and quantitative determination of important environmental and biological compounds. Sensors and sensor arrays are finding utility in the evaluation of indoor air and in locating the source(s) of odor in a variety of locations. Single-sensor construction and use are reported by
Nishiguchi (D5) and Myamoto et al. (D6). Multisensors and arrays were used to track sources of indoor air contaminants in offices, schools, hospitals, and private homes by Fogarty (D7), in an “animal house” by Watanabe and Tsuji (D8), and in a wind tunnel (D9) without regard for the actual chemical identity of the odorant. A paper by Hedderich (D10) reports the use of an array of 39 different gas sensors for the specific detection of compounds in vehicles and garages, while Steiner and Kist (D11) used arrays of 2-100 sensors inside consumer electronic products. Mchardy et al. (D12) discussed the construction and use of a sensor for toxic metals in workplace air, Posner et al. (D13) were able to detect diazinon in greenhouse air at 5-10 µg/m3, and Shi and associates described a unique distributed optical fiber sensor for the measurement of methane (D14). Electrically “wired” tyrosinase was used to construct a sensor for the detection of respiratory poisons by Robinson and coworkers (D15), and polyphenol oxidase was used to detect trace (ppb) levels of phenol (D16). In a report on the detection of “alarm molecules” (D17), the authors remind us of the necessity of challenging sensors with a fresh sample either by natural air movement or through mechanical means. Several papers described the use of sensors of various types for the measurement of specific organic compounds in air and in water. Ellis et al. reported on very sensitive (ppb) sensors based on conductive polymer films for the detection of hydrazine and methylhydrazine in ambient and vacuum environments (D18). A remote, miniaturized optical fiber gas sensor was combined with surface plasmon resonance spectroscopy by Niggemann and coworkers (D19) to detect tetrachloroethene. Microfabricated surface acoustic wave chemical sensor arrays were used to measure binary and tertiary mixtures of solvents (D20). Sensors based on acoustic wave technology can be calibrated by the procedure reported by Grate and associates (D21). Soluble phthaloctamines (D22) and polymer benzo[15]crown-5 complexes (D23) were shown to be useful for the detection of “organic solvents” (D22) and benzene (D23) in air. The crown complexes were also used to detect ethanol and dichloromethane in water. Brehmer et al. (D24) also reported on a humidity sensor constructed from UV cross-linked polymer on a metal oxide substrate.
Table 2. Miscellaneous Instrumental Methods topic
author(s)
ref
laminar flow sensor for a personal sampling pump instantaneous measurement of sulfur dioxide test chamber measurement with solvent-containing coatings real-time PAH monitor emission cell for VOCs, a review time-averaged toxic metals monitoring air quality telemetering system paper tape monitor for TDI passive samples for ammonia review of TVOC methods determination of sulfur trioxide and iron oxide dust in workplace air direct measurement of hazardous materials by PID determination of inorganic chloramines in air measurement of ppb mercury vapor portable apparatus for the measurement of organophosphorus compounds in air analysis of phosphine and arsine in air review of optical remote sensing configuration calibration of VOC instruments real-time colorimetric measurement of airborne pollutants electrochemical detection of hydrogen sulfide problems with the Rustrak Ranger data logger determination of ionogenic compounds in air by capillary isotachophoresis
Weber et al. Watanabe and Ikeda Kieburg Wilson et al. Wolkoff Townsend et al. Shibata Dharmarajan Kasper and Paxbaum Hodgson Sojka Budovich et al. Lorberau Bardey Milinkovic et al. Maeda Todd and Ramachandran Mouradian and Flannery Kirollos et al. Schiavon et al. Gressel et al. Pavlas
C62 C63 C64 C65 C66 C67 C68 C69 C70 C71 C72 C73 C74 C75 C76 C77 C78 C79 C80 C81 C82 C83
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The use of sensors based on electrochemical principles, primarily amperometric, was reported by several authors (D25D28) for specific compounds, such as hydrogen peroxide, ethanol, hydrogen cyanide, and hydrogen chloride, and general categories of compounds, like the ever-present “organic solvents”. Kitzelmann and Gottschalk published a review of amperometric sensor principles and perspectives (D29). Finally, potentiodynamic gas sensors for solvents that cannot be detected by amperometric techniques, such as perchloroethylene and benzene, were described by Baltruschat et al. (D30). The application of sensors to the detection of very light gases was the subject of a number of papers. Six groups reported on the measurement of carbon monoxide (D31-D36), and oxygen (D37), ozone (D38), hydrogen sulfide (D39), and sulfur dioxide (D40) were each the subject of one publication. DUSTS, AEROSOLS, AND FIBERS The sampling of aerosols and solids, including fibers, and the subsequent determination of the particulate mass, composition, and adsorbed/absorbed compounds, was the subject of hundreds of publications in 1996. It is beyond the scope of this review to mention all of them. This section reports on approximately 100 selected papers and is divided into sections for solids, aerosols, and fibers. Solids are defined as materials that are not liquids, condensed vapors, or fibers. Aerosols are liquid droplets and condensed vapors or fumes, and the term fibers is self-explanatory. Dusts. Papers dealing with the sampling and characterization of solids constitute the largest group in this section, by far. Many of the papers might be considered generic in content, in that they report on a sampling technique or determination that might be applied to a wide variety of solid types. Other papers are very specific, concentrating on the determination of individual inorganic or organic species associated with the solid. We will deal with the former group of papers first. Passive or direct-reading dust monitors were the subject of several publications. Vinzents (E1) reported on a passive monitor comprised of transparent sticky foils. Tsai et al. (E2), Koch et al. (E3), Rudolf (E4), Cantrell et al. (E5), and Peluso (E6) all described the construction, use, and calibration of direct-reading dust monitors. Their work was accomplished in both laboratory and field environments such as foundries and underground coal mines. Measurement strategies were discussed by Wegleitner et al. (E7), while Maynard (E8) described sampling errors associated with Higgins and Dewell type cyclones. Both Wu et al. (E9) and Groves et al. (E10) compared different samplers and methods in workplace environments. The field performance of a new design of a total inhalable dust sampling head and an evaluation of the characteristics of a multinozzle impactor were the subjects of papers by Marley (E11) and Gudmudsson et al. (E12), respectively. Sioutas and co-workers (E13) developed and evaluated a prototype ambient particulate concentrator. Papers by Chow (E14) and Lillquist et al. (E15) deal with ambient and stack sampling for particulate. Chow’s work is an extensive review encompassing 987 references. Lillquist finds that the pressure corrections required by the U.S. EPA’s reference methods for PM10 are without “chemical, physiological, or toxicological basis” and impose more stringent compliance standards on cities at higher elevations. Experimental methods to determine the minimum explosible concentrations for dusts were evaluated by Chawla and associates 310R
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(E16), while Vincent et al. (E17) concentrated on the speciation of inhalable particulates into inhalable, thoracic, and respirable fractions. Moving from the macro- to the microscale, Tourmann and coworkers (E18) illustrated the toxicological and environmental relevance of single-particle analyses. The authors used laser desorption/ionization mass spectrometry to examine the surfaces of quartz-containing coal mine dusts. They learned that most dusts are rendered harmless by protective and biopersistant clay layers and that the presence of iron-containing mineral particles appears to be a determinant toxicity parameter. The sampling and analysis of diesel exhausts in aboveground and underground (coal, zinc, and potash mines) workplaces is the subject of several publications. Sampling procedures were evaluated in three reports (E19-E21), and analysis and exposure issues were addressed in the others (E22-E24). Issues associated with the collection and characterization of inorganic particulates were the subject of 25 reports. Several reviews (E25-E27) and individual papers (E28-E30) dealt with silica, and others looked at the special needs of dust monitoring in the coal mining industry (E31-E36). Many methods were described for the quantitation of specific elements associated with solid particles. Roig-Navarro et al. (E37) described the application of the azomethine-H method for the determination of boron in ceramics factories. Numerous authors reported on methods for the generic analyte “metals” (E38, E39) and specific metals such as lead (E40-E44), cobalt (E45), aluminum (E46), and nickel (E47). The determination of organic compounds adsorbed and/or absorbed on solids was the subject of a significant number of papers. Notoe et al. (E48) and Gundel et al. (E49) reported on improved methods for PAHs. Pfaeffli determined phthalic anhydride in powder-coating dust (E50), while other authors reported on less common determinations, such as potato antigens (E51), tobacco smoke (E52), flour (E53), microorganisms (E54), nicotine (E55), and β-glucans (E56). Aerosols. Only two review articles, one by Kenny (E57) which reported on developments in workplace sampling, and the other by Sadhra et al. (E58) that focused on the sampling and analysis of colophony, a pine rosin, were found in the literature. Other articles described equipment and instrument improvements and their application to the measurement of specific materials in the environment. Equipment improvements and evaluations were described by Gorner et al. (E59) for a CIP-10 sampler, Rumyantsev and Yakovlev (E60) for an automated monitoring system, Chein and Lundgren (E61) for a high-output, size-selective aerosol generator, and Chandra and McFarland (E62) for shrouded and unshrouded probes. Bartley and co-workers (E63) developed performance tests for aerosol samplers, Tsai et al. (E64) proposed an impaction model for aspiration efficiencies, Izmerov and Tkatchev (E65) discussed the issues and prospects for international standardization of aerosol measurement methods, and Ramachandran and associates (E66) conducted an in-depth assessment of particle size distributions in workers’ exposures, while Werner et al. (E67) investigated the impact of introducing workplace standards based on the inhalable fraction. Other authors described the sampling and analysis of specific materials. These materials include petroleum oil mist (E68), mineral oil (E69), bioaerosols (E70-E72), metal-working fluids
Table 3. Methods for Determining Radon and Radon Progeny subject
author(s)
ref
review with 18 references measurement of thoron progeny soil gas radon concentrations surveys with charcoal and liquid scintillation counting radioactive contamination of buildings SSNTD calibration and equilibrium factor new “three count” measurement technique measurement using the PICO-RAD detector and liquid scintillation spectrometer analysis by continuous R spectroscopy method comparison and evaluation rapid measurement in buildings method comparison, γ ray spectroscopy and liquid scintillation determination of absolute concentration active measurement method response characteristics of CR-39 materials monitoring method using CR-39 Franco-Russian track detectors passive detector for retrospective measurements measurements with a cellulose nitrate detector in situ level characterization review entitled “Where from and what to do?” automated remote site monitoring continuous monitoring absolute determination by pseudocoincidence techniques event counting practical applications of electret ionization chambers optimization of electret ionization chambers equilibrium factors for a LR115 detector comparative study of methods measurement by R spectroscopy detection systems for building, soil, and water review of measuring techniques calibration factor for LR-115 detectors long-term environmental monitoring Argonne analysis system passive track detectors theoretical model of adsorption on charcoal integrated measurement using rotation filters sensitivity of combined charcoal and etched track technique
Piesch Yamasaki and Iida Hutter Schoenhofer et al. Spicka and Mertens Gil and Marques Tian et al. Koga et al. Peter Knutson et al. Soavi Gorzkowski et al. Teterev et al. Shweikani and Durrani Espinosa et al. Hadler et al. Klein et al. Meesen et al. Uvarov and Kulakov Klein et al. Joensson Renken and Cousins Tokonami et al. Mattsson et al. Bolton and Macarthur Kunzmann et al. Kunzmann et al. Nikezic and Baixeras Baixeras et al. Erees et al. Streil et al. Sato Srivastava et al. Peter and Krizman Lucas Farid Scarpitta Pressyanov Sutej
F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26 F27 F28 F29 F30 F31 F32 F33 F34 F35 F36 F37 F38 F39
(E73), and metals such as nickel (E74, E75), lead (E76), and aluminum (E77). Fibers. Most of the papers dealing with fibers reported on issues associated with the accurate determination of asbestos in the environment. Almost half of the reports involved sampling and sample preparation. The other works investigated fiber sizing and analysis, reported on the comparison of NIOSH and WHO methods, and presented the results of a round robin. Two review articles involving test methods for asbestos in construction materials (E78) and workplace exposures (E79) were also published. Sampling and sample preparation were discussed by several authors. Kohyama et al. (E80) provided a method for total sample preparation for the determination of asbestos and other fibers, while Kauffer and co-workers (E81) and Sahle and Laszlo (E82) presented studies on the effects of direct and indirect sample preparation for the transmission electron microscopy analysis of asbestos. Kauffer et al. also reported on a new static collection device for the thoracic fraction in a separate paper (E83), and Baron and associates (E84) studied the effect of nonuniform air flow in the inlet of the fiber sampling cassette on fiber deposition in the cassette. The generation of replicate filter samples of asbestos fibers in air was the subject of a paper by Skogstad et al. (E85) that reported replicate samples with a coefficient of variation
