Anal. Chem. 1995, 67, 349R-376R
Industrial Hygiene John E. Adkinr, Jr.* and Norman W. Henry, 111 Sabine River Works, E. 1. DuPont de Nemours and Company, Inc., P.0. Box 1089, Orange, Texas 77631- 1089, and Haskell Laboratory for Toxicology and Industrial Medicine, E. 1. DuPont de Nemours and Company, Inc., P.O. Box + 50, Elk-ton Road, Newark, Delaware 19714 Review Contents
General Reviews Monitoring Instruments Statistical Considerations and Multigas Analyzers Instruments for Gases and Aerosols Instruments for Dusts and Fumes Specific Techniques Specific Compounds Gas Monitoring Sensors Aerosols, Dusts, and Fibers Aerosols Dusts Fibers Sorbents and Filter Media Derivatizations Specific Chemical Analyses Polynuclear Aromatic Hydrocarbons Biological Monitoring Passive Dosimeters Sampling Strategy Quality Assurance and Quality Control Indoor Air Quality Future Needs and Trends Conclusions
Table 1. OSHA Sampling Devices
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Two years have elapsed since the last industrial hygiene review article was published ( A I ) . That review covered the prior four years of industrial hygiene chemistry scientiiic literature, and over 2000 abstracts and papers were reviewed. For the past two years, through October 1994, there have been another two thousandplus articles published in the field of industrial hygiene chemistry! Talk about your information explosion! This field encompasses both the workplace and community environments where industrial processes and environmental emissions contribute to the overall atmospheric gIobal air quality. Dusts, mists, particulates, aerosols, fibers, vapors, and gases are all part of the multitude of potential contaminants released in the air which may cause harm or injury to workers or people in the community. Monitoring these contaminants is one of the primary functions of the industrial hygienist. By evaluating airborne concentrations of these contaminants and comparing the results to government standards such as the Occupational Safety and Health Administration’s permissible exposure limits (PELs), industrial hygienists can implement control procedures and practices to reduce worker exposure and improve the quality of the air in our work and community environments. One area of concern during the last two years has been indoor air quality. Workers in offices, public buildings, and homes have experienced exposure problems from various indoor air contaminants that cause irritation, sensitization, and diseases such as sick building syndrome. Because of the diverse construction and building materials used in these places, it is difficult to identify 0003-2700/95/0367-0349$15.50/0 0 1995 American Chemical Society
sampling device solid sorbent (treated and untreated) bubbler
passive monitor direct reader impregnated filter sampling bag
% use
40 33
8.5 8.5 5
5
and quantify levels of exposure. Many of these problems can be attributed to poor maintenance of existing ventilation, air conditioning, and humid~cationsystems. However, it is not the intent of this review article to discuss or resolve these problems, but to share the latest trends and developments in improving air monitoring techniques for the practicing analytical industrial hygiene chemist. Industrial hygiene monitoring involves both sampling and analysis. Each of these functions is dependent on the other for determining accurate reproducible results for evaluating exposure to airborne contaminants. Many airborne contaminants lack adequate warning properties for detection; therefore, specific, sensitive detectors are needed to alert workers and the public of imminent danger. Other contaminants may not be hazardous but still can cause harm if airbome concentrations exceed regulatory limits. This review article will discuss some of the new detectors, sensors, and sampling and analytical methods that help identify and quantitate airborne contaminants in the environment. Included in this review will be information on instrumentation for gas monitoring, sensors, sorbents and filter media, derivatizing agents, detector tubes, specific chemical analyses, biological monitoring, passive dosimetry, sampling strategy, calibration techniques, quality assurance/quality control, and future trends. An interesting article by Cee and Ku (A2) looks at inorganic gas and vapor sampling from an OSHA perspective. Approximately 83% of the sampling systems used in OSHA analytical methods require the use of a sampling pump. Impingers are no longer used by OSHA for monitoring inorganic gases and vapors, and they are trying to minimize the use of bubblers. Current OSHA usage of sampling systems for capturing inorganic gases and vapors is shown in Table 1. This same article summarized the results of a NIOSH Occupational Exposure Survey (A3) of direct-reading instrument use, as shown in Table 2. OSHA methods for the analysis of halogens and chlorine dioxide are listed also, along with appropriate collection media. Combination sampling devices are described for particulate- and vapor-phase sampling, using a Teflon filter and carbon bead tubes for sampling phosphine, ammonia, sulfur dioxide, and iodine. OSHA methods are listed for each gas. During the development of sampling and analytical methods for inorganic gases or vapors, OSHA conducts experiments for detection limits, collection efficiency, breakthrough, sample stability, precision and accuracy, humidity or Analytical Chemistty, Vol. 67, No. 12, June 15, 1995 349R
Table 2. NIOSH Occupational Exposure Survey direct-reading instrumentddevices
570 use
detector tubes electrochemical mass measure gas chromatographic monitor other fibrous aerosol infrared gas monitor ultraviolet gas monitor
31.2 16.8 16.4 11.1
9.1 6.8
5.2 2.8
other environmental effects, other tests needed for the particular sampling device (e.g., for passive monitors: face velocity, reverse diffusion, etc.), and interferences. Methods for generating test atmospheres are described. Passive monitors have been used by OSHA to monitor substances such as carbon monoxide, ethylene oxide, formaldehyde, mercury, nitrous oxide, and radon. Validation methods by OSHA @4), NIOSH (A5-A7), and the U.K. Health and Safety Executive (A8, A9) are referenced. GENERAL REVIEWS One of the most prevalent sampling and analytical techniques used in industrial hygiene monitoring is the adsorption of organic chemical vapors in air onto charcoal, followed by solvent desorption and gas chromatographic analysis. Several reviews have described the application of these techniques to indoor air analysis (B1,B2), and a Russian review reported on the determination of harmful substances in the air at chemical plants (B3). Driscoll reviewed the use of portable toxic gas monitoring instruments using photoionization detectors for hydrocarbons and toxic gases. He also described the use of gas chromatography for field laboratory analyses (B4). Atmospheric nitric acid vapors, nitric oxide, particulate nitrates, and particulate organic carbon are atmospheric pollutants which easily undergo physical or chemical changes while an integrated sample is being collected. A review of manual sampling methods for these pollutants, including the filter pack method, diffusion denuders, and tandem filter sampling, is presented by Appel (B5). A number of recent projects at the National Institute for Occupational Safety and Health have dealt with the development of sampling and analytical methods for compounds present in workplace air as vapor and aerosol particles and are included in an extensive review of the simultaneous collection of vapors and aerosols with special emphasis on isocyanate sampling, by Streicher et al. (B6). Aerosol particles are most frequently collected by filtration or inertial impaction. One strategy invoked in several instances consisted of a filter for particle collection followed by an appropriate second stage for vapor collection. For organophosphorus pesticides, the second stage was a sorbent tube. For gaseous HF, it was alkaline-impregnated hydrogen sultite. Isocyanate aerosol cannot be collected on a filter because the isocyanates can be lost through reaction with other compounds present in the aerosol particle or simultaneously collected on the filter. The isocyanate is derivatized rapidly on collection, using filters and sorbents impregnated with derivatizing reagent, as well as impingers and bubblers containing solutions of derivatizing reagent, to collect the isocyanate aerosol. The combination of an impinger followed by a reagent-coated filter should satisfactorily collect isocyanate aerosols and vapors. Tsalev (B7) reviewed the past 10 years of progress in using electrothermal atomic absorption spectrometry in the application area of occupational and environmental health practice. The 350R
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review includes the development of direct procedures and simple pretreatment techniques, the selection of chemical m o d ~ e r and s reaction media, some practical problems, and the rational combination of the graphite atomizer with preconcentration and speciation techniques. Low-level particle sampling was reviewed by Schneider (B8). Surface sampling methods were presented, and the importance of including surface contamination in an indoor environment quality assessment was discussed. A review by Leichnitz (B9) considers European standards’ performance requirements for detector tubes, which are manufactured in accordance with a certified quality assurance system, making possible the stipulation of a range of applications for each type of tube prior to use. MONITORING INSTRUMENTS
Statistical Considerations and Multigas Analyzers. Several basic underlying principles that must be considered in any field evaluation of instrument performance are discussed and appropriate statistical methods available to assess them are summarized in an article by Kinney and Thurston ( C l ) . Operational characteristics of the Perkin-Elmer Model STS 25 sequential tube sampler and the Illinois Institute of Technology Research Institute/Illinois Institute of Technology (IITRI/IlT) total isolated-by-microenvironment exposure (TIME) monitor were evaluated by Pollok et al. (C2). Both units use multisorbent carbon-based sampling tubes to collect volatile organic compounds (VOCs) in ambient air and an analytical procedure that does not require cryogens for analysis. A Perkin-Elmer auto thermal desorption system (Model ATD 400) was used to process the collection tubes for analysis of the VOCs listed in the EPA 0-14 method. The Model STS 25 is designed to sample air with up to 24 tubes, one at a time for a preset period of time. The TIME monitor is designed to measure total exposure to VOCs and apportion the exposure into its microenvironmental components. The TIME unit uses ultrasound reflection to identify a subject’s location. Very good precision for collection and analysis of these VOCs was achieved. The Bruel-Kjaer 1302 multigas monitor (MGM), a portable photoacoustic analyzer, was evaluated in the laboratory and in the field, monitoring NzO and Forane. Results were compared with data obtained using a gas chromatograph connected to a mass-selective detector and personal passive samplers. Correlation between both methods was excellent. The linear range of the MGM was more than adequate for the sample concentrations determined in this study (C3). Instruments for Gases and Aerosols. Chemical gas analyzers based on indicator tubes have been used by Pochenkova et al. for monitoring CO, COS, NO,, SOz, HzS, and 02 in coal and ore mines and have been described in a Russian article (C4). Advantages over other types of gas detectors are discussed. A static sampler for the measurement of inhalable aerosol in the ambient atmosphere, with special reference to polycyclic aromatic hydrocarbons, is described by Mark et al. The instrument collects the respirable fraction of aerosols (C5). A test system has been developed by Botham et al. (C6) which evaluates the performances of total aerosol samplers for use in workplaces. It consists of a life-size mannequin mounted on a trolley so that it can be moved around in workplaces. It can be made to simulate a range of worker movements, orientations, and attitudes, under joystick control, and has an electronically controlled breathing
machine inside, providing a range of typical breathing parameters for the mannequin. The breathing machine pump also provides air movement for a number of personal samplers that are mounted on the torso of the mannequin and tested in that position. Comparisons are made of the aerosol collected by the sampler with that inhaled by the mannequin and collected on filters inside its head. The US. Bureau of Mines personal diesel exhaust aerosol sampler uses three consecutive stages to separate and collect respirable mineral and diesel aerosols from air,collecting fractions greater than 10pm using a cyclone separator acting as a respirable preclassifer, an impactor that collects aerosol of '0.8 pm, and an afteriilter assembly that collects aerosol of 10.8pm, in a report by McCartney and Cantrell (C7). An aerodynamic particle sizer (APS) can be used to make realtime measurements of the aerodynamic particle size distribution at 0.5-32 pm. The instrument, described by Heitbrink and Baron, is very useful in conducting health-related aerosol measurements involving aerosol generation, respirator efficiency, and particulate sampling efficiency (C8). Performance standards for aerosol samplers are described by John (C9), in a review of standards developed by the US. EPA for PM-10 sampling and the American Conference of Governmental Industrial Hygienists for sizeselective particle sampling in the workplace, and are under development by the European Economic Community. An apparatus for monitoring the air quality with regard to metallic aerosol concentrations of ultrahe powders of metal, dust, and fly ash on-line and in real time is described by Nore et al. (C1O). Pollutants are atomized, excited, and ionized in an inductively coupled plasma and then identified by their optical spectra. Results for detecting beryllium, cadmium, cobalt, and lead are given, and detection limits are below threshold limit values for the metals tested. Kenny and Bradley evaluated the Perspec multifraction aerosol sampler. Experimental data were used to devise a method for subdividing the filter into respirable, thoracic, and inhalable aerosol fractions (C11). A real-time instrument with high resolution is a time-of-flight instrument which includes an aerodynamic particle sizer (APS33B) and an Aerosizer. The APS33B can resolve particles in the size range 0.5-3@pm aerodynamic diameter using subsonic jet expansion flow, as described by Cheng et al. (C12). Baron reviewed direct-reading instruments for aerosols in air (C13). Among those reviewed were a miniaturized condensation nucleus counter used to estimate fit factors for respirators, a fiber monitor used for monitoring asbestos, especially in asbestos abatement operations, and optical particle counters used for lowconcentration aerosols, especially in clean rooms. Aerosol research instruments are used to evaluate and improve field instrumentation, such as respirable, thoracic, and inhalable samplers and cascade impactors. Several such direct-reading instruments are now commercially available and can rapidly measure aerosol concentration and size distribution and can also be used to make field measurements. Vincent reviewed the measurement of fine aerosols in workplaces ((34). Recent recommendations of the International Standards Organization, the American Conference of Governmental Industrial Hygienists, and the Comite Europeen de Normalization define the thoracic fraction (inhaled particles that penetrate into the lung) and the respirable fraction (inhaled particles that
penetrate further into the alveolar region). Additional criteria for sampler acceptability are needed, based on sampled mass in addition to particle size selectivity. Versatile devices capable of providing information about more than one fraction simultaneously are proposed and are finding increasing use as study tools for industrial hygienists. Vincent also reviewed the measurement of coarse aerosols in workplaces (0. There is substantial agreement on a single curve describing the probability of inhalation as a function of particle aerodynamic diameter. Experiments in wind tunnels to investigate the performances of previous samplers for total aerosol show that most of them do not satisfactorily match the inhalability criterion. A small number of samplers designed specifically for the inhalable fraction have been proposed. A modified personal air sampler with an inhalable entry efficiency for collecting pesticide aerosols and vapors simultaneously was studied by Brouwer et al. (C16). An XAD2 cartridge was constructed to fit into the sampler housing, and the vapor trapping efficiency of the cartridge was determined for three pesticides using a dynamic U-tube test system. Trapping efficiency varied from 87 to 100%for dichlorvos and methomyl, but was slightly lower for chlorothalonil(72-79%). No breakthrough was observed. The efficiency was not affected by humidity, temperature, pesticide loading, or sampling duration. This sampler enables adequate simultaneous sampling of pesticide aerosols and vapors. An instrument developed for the semicontinuous measurement of aerosol mass and its categorization into three classes is described by Spagnolo and Paoletti (C17). The instrument samples through three probes, with cut points of 15,5, and 2 pm. Airborne particles are collected on circular membrane filters. The increase in weight is measured by ,&ray attenuation by the particles collected on the filters. The performance of a porous sintered stainless steel disk used as a compact diffusion denuder has been experimentally and theoretically evaluated by Poon et al. (C18). Using a 1%sodium carbonate/glycerin coating, the collection efficiencies for sulfur dioxide and nitric acid gas are 99.6 k 0.4 and 93.4 f 2.5%, respectively. The porous metal used as a denuder is very efficient in collecting gas, and its small size makes possible the design.of a very compact atmospheric and/or indoor denuder sampling system. Instruments for Dusts and Fumes. A calibration method involving sideby-side comparative air sampling with a gravimetric sampling apparatus at constant environmental tobacco smoke respirable suspended particulate concentration has been developed by Ross and Sterling for testing nephelometric particle mass monitors (C19). A bench-top apparatus was developed by Cawley and k i t h to examine factors that affect dust generation (CZO).The apparatus consists of a dust generation section and a dust measurement section. Materials are introduced to the generation section at various drop heights and flows, by an injection slide. Dust is generated by the impact of the falling material and the release of air entrained with the falling stream of material. The generated dust is drawn through an elutriator, which removes particles 25 pm and greater in aerodynamic diameter. The size distribution of the residual dust is measured for particles between 1.4 and 15 pm with a cascade impactor. The effects of material drop height, mass flow, and moisture content were investigated for four granular materials: ground limestone, titanium dioxide, glass Analytical Chemistry, Vol. 67, No. 12, June 15, 1995
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beads, and lactose. For each material, a simple model was developed to describe the size-specific dust generation rate. Several designs of personal samplers were tested for collecting cotton dust, in a report by Ogden et al. ((221). The IOM personal inhalable-dust sampler was selected because of its wellcharacterized collection of the whole inhalable fraction and its practicality. This instrument uses a large static sampler. A battery-powered PM-10 respirable particle sampler developed by a joint US. EPA-Chinese venture, reported by Hams et al. (CZZ), was used to monitor indoor air in homes with unvented coal-fired appliances, with inconclusive results. A method using the size-classifying properties of partially penetrating filters was developed by Liebhaber and Willeke (C23) to calibrate optical particle counters quickly and easily, using fibrous filtering material cut from a single-use respirator. Filter calibration correlated well for particle sizes of ’1 pm, where inertia is the primary aerodynamic deposition mechanism, compared to the standard calibration method of impaction. An automated system to minimize variability in an aerosol concentration over time in an animal exposure chamber was developed by O’Shaughnessy and Hemenway (C24l. The system includes a microprocessor-controlled stepper motor to regulate the speed of a dust generator, a real-time aerosol monitor to instantaneously measure chamber aerosol concentrations, and a personal computer with an analog-to-digital converter, serial port, and relay board for signal input and output. The system produces a chamber concentration of dust near a level chosen by the operator. Beutling and Rudolf described the design, flow control, power supply, and handling of a new dust sampling device which was used to measure diesel soot at work places, in a German article (0. A computer-based, improved version of an airborne dust concentration monitor was presented by Urbanski et al. (C26). The principle of operation is based on the measurement of p absorption by the dust mass deposited on an air filter from an air volume that is proportional to the pumping time. Measurements of fume generation rates from a gas metal arc welding process were carried out in a large test chamber in a report by Jin (C27). The particle size distribution and fume generation rate were measured by a laser particle counter. Most of the measured fume particles had a size of < lpm, with the mass median diameters of the fume particles being 0.15-0.25 pm. Specific Techniques. (a) Znfiared. A portable FT-IR, the Midac Model 2400 open-path instrument, was the most compact high-resolution (0.5 cm-l) instrument in commercial production when this paper was presented at the annual meeting of the Air and Waste Management Association in 1992. The results of a field test conducted for the US. Air Force to assess firefighter toxic gas exposure during fire training exercises are discussed by Schell et al. (C28). Spellicy et al. present the results of two evaluation tests: (1) a fence-line monitoring program at a petroleum refinery and (2) an office building monitoring effort at a university. The equipment and layout used, examples of data collected, results from limited intercomparisons performed with canister/sorbent tubes, and detection limits for various compounds are presented (C29). A new approach for factor analysis of mid-infrared spectra is proposed and applied to 15 mixtures of three potential workplace pollutants by Gurden et al. (C30). The process is used to yield one pure spectrum for each component in the mixture. 352R
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(b) Other Spectrophotometric Techniques. Molecular recognition devices that optically detect and discriminate odors were described by Akiyama et al. in a Japanese article (C31). They used solvatochromic dye films that caused changes in absorption wavelength and color-former films that caused changes in absorbance. Changes in the optical characteristics of four dye films were detected by photodiodes, and the outputs were treated by a personal computer to give information for the discrimination of odors. (c) Mass Spectrometry. An empirical rulebased pattern recognition/expert system to classify, estimate molecular weights, and identify low-resolution mass spectra of toxic and other organic compounds has been developed and evaluated by Scott (C32). The system consists of a classifier followed by molecular weight estimators, filters, and identification modules. Target classes are non-halobenzenes, chlorobenzenes, bromo- and bromochloroalkanedalkenes, mono- and dichloroalkanes/alkenes,and tri-, tetraand pentachloroalkanes/alkenes. Classification and identification performance was very good with accuracies of 95-97%. (d) Gas Chromatography. An injection system for sampled and enriched air pollutants that allows cryofocusing temperatures of -180 “C and a sample injection temperature of 5400 “C for splitless injection into a dynamic headspace gas chromatograph was developed by Schlegemilch and is described in a German article (C33). The design and operation of the KA-D injection system are given, together with examples from exhaled air. (e) Chemometrics. Chemometrics is the application of advanced statistical and mathematical techniques to the field of analytical chemistry. Schlager and Beemster have written a review of these techniques coupled with smart analyzers (C34). This technology makes it possible to incorporate sophisticated pattern recognition algorithms into these analytical instruments, liberating them from the laboratory and turning them into “smart analyzers” that are capable of a variety of real-time chemical identification, quantification, control, and alarm tasks. Examples presented include on-line W/visible/near-IR absorption spectrometers for the analysis of organic compounds, in situ atomic emission analyzers for metals, and surface acoustic wave (SAW) detectors for gas analysis, which have important implications in environmental monitoring. Smart analyzers will make possible inexpensive environmental monitoring at more frequent intervals without the need for direct participation by scientific personnel and with results available instantaneously. (j9 Radionuclide Analysis. Continuous vent stack sampling for monitoring of radionuclide discharge is described in a report by Scheller et al. (C35). The continuous stripper consists of a point source radionuclide extraction system that includes an isokinetic probe, collection traps, a pump, a sample flowmeter, and a vent stack flow monitor. The system continuosly withdraws a representative measured sample of stack gas which is passed through traps of activated alumina that are subsequently analyzed for total uranium, U-235, Tc-99, and reactive fluoride. (g) Sulface Analysis. A surface contaminated with toxic materials to be tested or monitored is sampled using a probe that has a rectangular opening typically of several square inches in cross section, in a report published by Carlon (C36). A pliable gasket of a suitable heat-resistant material is used to cushion and seal the probe in contact with the surface, but small holes are provided of sufficient size and are positioned close enough to the surface to be tested, to allow ambient air to be drawn at a desired volumetric flow rate through a sampling tube, which also forms
the handle of the probe and is connected through a flexible tube or hose to a suitable detector and vacuum pump. The detector and pump can be combined in a single unit. The detector can be a vapor detector, e.g., a flame photometer or a gas chromatograph. A lamp that provides intense heat (e.g., a quartz tube lamp) is mounted within the probe and is mounted in such a position that it is close to the surface when the probe gasket is in contact with the surface. A polished reflector can be used to focus the radiation uniformly across the surface. Specific Compounds. (a) Carbon Monoxide. The US. Bureau of Mines developed an intrinsically safe CO monitoring system for mines by coupling a fiber-optic data telemetry system with a prototype electrochemical CO monitor, in a report by Chilton and Carpenter (C37). The system can be used in a coal mine as a component of an early fire-warning system. Personal exposure monitors, a commercial electrochemical monitor, and a CO passive sampler were compared with a nondispersive infrared analyzer and a gas chromatograph-flame ionization detector for accuracy, response time, and environmental effects by Lee et al. (C38). The miniature electrochemical monitors can measure personal exposures accurately. The passive samplers can measure integrated CO concentrations of 5-45 ppm with an accuracy of 98%and is suitable for determining instantaneous concentrations. A new analytical method, combining hollow fiber membrane, cryofocusing, and thermal desorption technologies has been developed by Yang et al. (C67) to allow rapid routine analysis and long-term continuous monitoring of volatile organic compounds in various environmental matrices. The method of membrane extraction with a sorbent interface (MESI) minimizes the loss of analytes by interfacing the membrane extraction module directly to a capillary gas chromatograph. The sensitivity of the system is significantly enhanced with the cryogenic sorbent
trap due to high sample throughput. The instrument consists of a hollow fiber membrane module, a cryofocusing and thermal desorption sorbent interface, an isothermal capillary GC, and a computer. Analytes of interest diffuse across the membrane and are collected at the cryogenic trap. A heat pulse desorbs all collected analytes at the trap and produces a narrow concentration band at the front of the GC column. The limit of detection for trichloroethane in water was 1 pg/L ( f 3 % relative standard deviation). Several environmental applications were demonstrated, including the analysis of volatile organic contaminants in clean water, wastewater, and laboratory air. GAS MONITORING SENSORS Gas monitoring sensors are used universally to identify and detect airborne contaminants because of their sensitivity, selectivity, response time, and cost. Many are equipped with alarms and multiple sampling ports to continuously monitor operations in different areas. The main types of gas sensors are based on electrochemical, semiconductor, paper-tape, flame emission spectrometry, Fourier transform infrared spectrometry, and mass spectroscopy. All of these sensors offer the capability for monitoring a wide range of process gases. Products of combustion seem to be the major contaminants for air monitoring sensors because they indicate the early stages of a fire and can give advance warning. Semiconductor gas sensors seem to be the most reliable sensors for detecting products of combustion as reported in the two articles (01,02). Specific gas sensors for toxic gases and vapors such as sulfur dioxide, nitrogen oxide, ammonia, ethanol, and styrene are reported in refs D3-D7. Sensors impregnated with functional polymers, platinium metals, and ceramic films also have been reported to provide high selectivity in monitoring organic molecules in air (08-010). Electrochemical sensors represent an expanding field of analytical chemistry for chemical detection with numerous a p plications in monitoring industrial and environmental atmospheres (011). These detectors can be made to respond quickly to contaminants by using novel designs (012). A mass-sensitive quartz sensor coated with tetraazacyclophanes offers a unique procedure for monitoring solvent vapors without cross sensitivity (013). Infrared evanescent wave fiber-optic sensors are another method that is reported to give accumulated exposure detection to organic vapors such as benzene (014). Fourier transform infrared remote sensors were reported to be a powerful tool for monitoring chemical emissions at a hazardous waste treatment, storage, and disposal facility (015). An excellent review article (016) gives an update on portable, multigas monitors for air quality evaluation. Another article with several references (017)gives an update on biosensors and test strips for environmental analysis. Finally, an oxygen ion-conductive sensor is reported which is useful for oxygen concentration monitoring to prevent harm to human life due to lack of oxygen (018). All these sensors are unique examples of some of the most recent innovative techniques for monitoring airborne contaminants and essential gases. AEROSOLS, DUSTS, AND FIBERS Aerosols. An aerosol containing a mixture of fatty acids at a nominal concentration of 100 mg/m3 was passed through filters
for respirators and the efficiency of filtration was tested using light
scattering as reported by Carlon et al. (El). Performance parameters for assessing the acceptability of aerosol sampling equipment are presented in a draft test procedure by the European Standardization Organization (CEN) , described by Liden (E2).The procedure gives the requirements for personal sampling pumps for dust sampling. Sampling and chemical characterization of aerosols in workplace air and the outside atmosphere are discussed by Hetland and Thomassen. Sampling methods and the chemical composition of samples are discussed in relation to analytical methods such as atomic absorption spectrometry and flame and electrothermal methods (E3). A Retsch precision high-volume cascade impactor was used as part of an epidemiological study which determined particle size distribution of an aerosol and its s u b fractions in gold, uranium, and nickel mines using dry drilling techniques (E4). A two-stage personal cascade impactor with median size cutoffs of 9.8 and 3.5 pm, plus a backup filter, was used to assess the current metal-working fluid exposures at three locations that manufacture automotive parts, in a report by Woskie et al. ( E a . Comparison of the results obtained from personal impactor samples with predictions from an aerosol-depositionmodel for the human respiratory tract showed high correlation. Optical microscopy and phase-contrast optical microscopy were used as standard procedures for the approximate determination of fibrous dust concentrations in workplace environments by Spumy ( E a . The methods with the best available technology and the methods of choice are scanning electron microscopy (SEW and transmission electron microscopy 0. Spurny’s paper describes and evaluates some commercially available equipment, presents the capabilities, accuracy, sensitivity, and detection limits of all of the methods mentioned, and compares them with one another. A preliminary study of personal exposure to blood-containing aerosols in the operating room is presented by Heinsohn and Jewett ( E a . A personal threestage cascade impactor corresponding to effective cutoff aerodynamic diameters of 14.8,3.5,and 0.52 pm was used to monitor the breathing zones of primary and assistant surgeons. These data showed that the mucous membrane lining of the upper respiratory tract and alveolar macrophages in the gas-exchange region of the lung are likely to be exposed to aerosolized blood in the operating room. The use of respirators instead of surgical masks was recommended in the operating room. Measurements of aerosol vapor and droplets were made in spray booths where base coat paint and clear coat finish are applied to automobile bodies as reported in an article by Cohen et al. (E@. Charcoal tubes, diffusion monitors, and glass fiber filters followed by charcoal tubes were used to monitor test stand and personnel, with xylene and toluene as representative solvents. The particle size distribution of automobile paint sprays was studied by Brousseau et al. (E9).They evaluated the particle sizerelated collection efficiency of particles traveling through charcoal tubes, measured the aerosol size distribution of spray paint in an automobile manufacturing facility, and predicted inhalation hazards associated with solvent-containingpaint spray droplets. The results of this study substantiated the need for periodic aerosol size distribution measurements and the use of prefiltered charcoal sorbent tubes for routine solvent tubes for routine solvent exposure sampling in paint spray environments. Analytical Chemistty, Vol. 67, No. 12, June 15, 1995
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Dusts. Exposure of Finnish bakery workers to airborne dust and a-amylase, an Aspergillus enzyme, was evaluated by Jauhiainen et al. (ElO). A spectrophotometric enzymic method was used to analyze a-amylase activity in flour dust. Burdorf et al. studied exposure to inhalable flour dust in Swedish bakeries ( E l l ) and found that workers were at risk of developing respiratory symptoms such as asthma and rhinitis. Concentrations of airborne inhalable flour dust were measured with the IOM personal inspirable dust sampler, and the particle size distribution was assessed using the IOM personal inspirable aerosol spectrometer. The fractions of a-amylase, water-soluble protein, and total protein in flour dust were determined. Chrysotile, quartz, cristobalite, and talc were determined in fine and coarse dusts using infrared and X-ray diffraction techniques in a Hungarian article by Hlavay et al. (El2). The method recommended by the U.K. Health and Safety Executive for the analysis of cristobalite in respirable airborne dust is discussed in an article by Chisholm (El3). Cotton was used as a model of organic dust to illustrate the application of exposure assessment: to develop a dose-response relationship between aerosolized dust and specific health effects, to evaluate the effects of process change on gravimetric dust levels and for compliance with the cotton dust standards, and to identify specific biologically active components in the dust as discussed in a report by Jacobs (El4). Potential health risks were found in the chicken hanging rooms of poultry processing facilities due to exposure to airborne organic dust containing endotoxins. Five out of six dust samples exceeded 100 ng/m3, 10 times the recommended limit, a level associated with spirometric evidence of acute airway obstruction, according to a NIOSH Health Hazard Evaluation Report by Lenhart and Humphries (E15).Dust was measured in iron mines in China in a Chinese article by Peng and Wu (El6),in a study to determine the causes of lung cancer among workers. They measured dust concentration including respirable silica, chemical elements, 17 polycyclic aromatic hydrocarbons (PAHs),and radon in four iron mines. One-third of the total dust was respirable, and concentrations of iron dust, nickel, and PAHs were high. Improved analytical and sampling methods were developed for the determination of pesticides in indoor air by Roinestad et al. (El 7). They sampled the air by adsorption of the pesticide dust in 1m3 of air onto Tenax TA with an air sampling pump, desorbed the Tenax with acetone, and analyzed the solution by gas chromatography/mass spectrometry with chemical ionization on an ion trap mass spectrometer. Limits of detection ranged from 0.5 ppt (w/w) for chlorpyrifos and diazinon to 30 ppt for o-phenylphenol. They also developed a method for the detection of pesticides in dust, by emptying the contents of a vacuum cleaner bag into a standard household food processor and extracting 1 g of homogenized dust with acetone before GC/MS analysis. Limits of detection by this method were 25-100 ppb due to interferences by common household chemicals. Pesticide concentrations were higher in dust than in air, so dust analysis is a better indicator of indoor pesticide exposure. An extensive assessment of the short-term (15-min STEL) and daily (&h TWA) dust and boron exposures of workers in a sodium borate production facility was done by Woskie et al. (El8). A real-time continuous aerosol monitor was used with an in-line filter to collect a &h gravimetric sample with a data logger to store the continuous aerosol data. Over 10000 15-min averages were collected over 430 person-days. Based on boron measurements, 356R
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a substantial portion of a total dust air sample is nonborate material such as cigarette smoke, vehicle exhaust, ambient dust, or hydration mass. Total dust measurements are an overestimate of the actual borate exposure level. The tannin concentration of hard- and softwood dust was determined in dust powder and in samples on filters by Bianco and Savolainen (El9) and varied from 1.6 i 0.3 mg/g for fir to 80 f 30 mg/g for oak. A spectrophotometric method with a low detection limit of 1.5 pg/sample was developed. Since hardwoods have a higher tannin concentration than softwoods, tannin concentration analyses in wood dust can be used as an indicator of exposure to hardwood dust, which is generally more toxic than softwood dust. Another study, by Wallingford et al., involved an industrial hygiene survey of a woodworking company to determine worker exposure to wood dust, organic vapors, formaldehyde, and noise (EZO). The major problem in this shop was exposure to wood dust during hand sanding and insufficient ventilation of several woodworking machines. Exposures to the other chemicals were controlled. Refractory products containing zirconium silicates or oxides are used in the glassmaking and steel industries. During their production in the ceramic industry, dust particles can be inhaled by workers. Since Zr minerals contain uranium and thorium from 0.1 to 1000 ppm, Castello et al. (E21) studied radiation safety for exposed workers in Italy. The activity due to radioactive isotopes in the minerals was measured by y spectrometry in samples of raw materials from various sources, and doses due to dust inhalation were evaluated. Dose absorption was measured by spectrophotometric determination of the Zr by the alizarin sulfonate method at 525 nm, and atomic absorption analysis at the 60.1-nm line was used. The asbestos, quartz, calcite, and albite content of dusts collected in coal mine workers were determined by Hlavay and Wesemann (E22) and were found to be much higher than those permitted in Hungary. Exposure to dust, endotoxins, and fungi in the animal feed industry was studied by Smid et al. in The Netherlands (E23). Twenty-five percent of the measurements exceeded the Dutch maximum allowed concentration for total nuisance dust (10 mg/m3). Endotoxin concentrations and colonyforming units of fungi were also measured. Two methods of sampling and analysis for silica (free crystalline silica a-quartz) were compared by Verma et al. (E24 in an underground gold mine. The methods compared were the X-ray diffraction method recommended by the Ontario Ministry of Labor (OML) and the NIOSH 7602 infrared spectrophotometric method. The two methods are equivalent when Ottawa silica sand is used as the calibration standard. The OML method showed a positive bias of 24-30% vs the NIOSH method when NBSSRM 1878 silica was used to calibrated the NIOSH method. A German article by Bauer et al. (E25) describes the analysis of elemental and organic carbon in respirable dusts in diesel engine exhaust gases. After sampling respirable dusts, volatile organic compounds are desorbed at 500 "C under nitrogen and the residual carbon is oxidized at 800 "C in an oxygen atmosphere. Carbon dioxide from each stage of the method is determined coulometrically. Airborne dust was selectively sampled in three ferrous foundries by Perrault et al. (E26). The dusts were analyzed for total dust, crystalline silica, and metal fumes, such as lead.
Laser microprobe mass spectrometry was used by Tourmann and Kaufmann to characterize individual particles of coal mine dusts (E27), shedding new light on the speciilc harmfulness of such dusts. Gauger (E28) measured cumulative exposure to air pollutants in a rubber processing plant. This German article uses two methods to characterize the dusts: British method MDHS 47 for total dust and a cyclohexane-soluble fraction, and BIA procedure No. 8000, which is used to evaluate the aerosol and gaseous phases in the air. The BIA procedure cannot be applied to determining total organic dust. Hlavay et al. (E29) collected airborne dusts in a two-stage sampler on an electrically activated filter, separating inhalable particles (55 ym) with a cyclone separator. The particle size distribution of quartz, calcite, albite, lead, cadmium, chromium, and cobalt was determined, using infrared and atomic absorption spectroscopy. The toxic metals were 5-12 times more prevalent in the h e fractions vs the coarse ones, with potentially greater effect on worker health. Greskevitch et al. analyzed bulk dust samples for quartz in an extensive, &year study of 491 mines conducted during the National Occupational Health Survey of Mining by NIOSH (E30). The goal of the survey was to inventory and characterize all of the healthrelated agents to which US. miners are potentially exposed. The potential exposure data are related to the percentage of quartz in bulk dust samples. Out of 272 000 miners, 78 000 (29%) were potentially exposed to bulk dust containing an average of > 12% quartz. Fibers. A comparison between phase-contrast microscopy (PCM) and scanning electron microscopy for the analysis of airborne asbestos fibers in office environments is found in an Italian article by Marconi et al. (E31). If counts are limited to fibers of >5 ym, good correlation exists between the two methods. The effectiveness of glovebags to control asbestos exposures was evaluated by Froehlich and Hollett (E32). Samples were collected and anlyzed by PCM. In this study, the glovebags did not completely contain the asbestos being removed, with workers being exposed to airborne asbestos above the NIOSH recommended exposure limit and the OSHA permissible exposure limit. Asbestos concentrations determined by aggressive sampling and E M indicated a higher level of contamination after removal than before in five of the eight rooms evaluated. Because of the uncertainty in controlling exposures during the use of glovebags, it is essential to provide a backup containment system (e.g., isolation, barriers, negative air), personal protective equipment (e.g., disposable coveralls), and respiratory protection. Asbestos release during the removal of valve packing was studied by Millette and Mount (E33). In a controlled, contained area within a steam power plant, personal and area air samples were collected before and during removal of asbestos packing material from valves that had been used at the plant. Results ranged from 0.2 to 1.3 fibers/mL by PCM and 1.5 to 4.2 fibers/ mL by TEM for all diameter fibers greater than 5 ym in length. Airborne aluminum-silicate ceramic fiber concentrations and fiber sizes in work environments were measured by Hori et al. in fiber manufacturing and processing workplaces, using PCM and SEM
(E34). Exposure to high concentrations of ceramic fibers has shown carcinogenic potential in laboratory rodents. Potential exposure to higher concentrations of fibers has been observed in US. industrial furnaces during the manual removal of ceramic insulation. An article by van den Bergen et al. (E39 presents the results
of a monitoring program for ceramic fibers and other respiratory hazards (dust, quartz, nickel, chromium) during replacement of the refractory lining inside a large furnace at the Shell Rotterdam (The Netherlands) refinery. They found that potential exposure of workers could be high and in excess of occupational exposure limits. Preventive measures and personal protection are described. A comment by Cheme and Johnston (E36) on an article by Robbins (E33 suggests that the difference in size of man-made mineral fibers on the cowl for Nuclepore polycarbonate filters vs the Gelman DM800 filters may be due to electrostatic charge on the filters. Nearly 1200 air samples were collected and analyzed gravimetrically or by PCM or SEM to describe worker exposure during installation of residential insulation products containing man-made vitreous fibers (E38). Most workers' 8-h TWA results were
