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Occupational Safety and Health Administration (OSHA) regulations allow the use of an alternative sampling device for exposure monitoring provided the device has been demonstrated to be equivalent to the standard device. For example, the OSHA standard allows the use of an alternate cotton dust sampler that is equivalent to the Lumsden-Lynch vertical elutriator (VE); also, OSHA defines the accuracy of the monitoring device for measuring airborne chemicals such as benzene and sulfur dioxide. Typically, the OSHA criterion is that 90% of the readings of the sampling device should be within +/- 25% of the readings obtained by the standard device or within +/- 25% of the actual airborne chemical concentration. This article proposes two statistical tests for establishing that an alternative measuring device of airborne chemicals or dust is equivalent to the OSHA standard. The statistical tests are illustrated using an example.

Assumptions about the underlying distribution of occupational exposures are important to the practice of industrial hygiene. They affect decisions on exposure monitoring strategies, the interpretation of monitoring results, and the degree of protection provided by occupational exposure limits and action levels. However, there is little published data validating these assumptions. Strict exposure limits for three highly hazardous agents, asbestos, beryllium, and ionizing radiation, led to frequent monitoring of occupational exposure levels. Consequently, sets of hundreds to thousands of exposure measurements are available for analysis. Statistical analysis of these data sets indicates that within-worker variation, as measured by geometric standard deviation (GSD), tend to be higher than is generally assumed for occupational exposures. The success of health protection programs in identifying and controlling predictable sources of exposure through frequent monitoring is offered as a possible explanation for the relatively high variation observed in these data sets. Despite the high exposure variation, arithmetic mean levels and the percentage of measurements exceeding exposure limits were low, indicating that a large GSD does not imply that working conditions are unacceptable. However, more frequent monitoring is required to assure exposures are acceptable. This article also presents an adaptation of graphical methods, using probability plotting and linear regression, to estimate the distribution parameters of a data set that contains a high percentage of nondetected results.

Over the past 50 years significant strides have been made in reducing occupational exposure to airborne chemicals. To a large extent, the impetus behind the reductions has been the identification of presumably safe levels of exposure, or occupational exposure limits (OELs). Most of the reduction in exposure has been to chemicals such as hepatotoxins, neurotoxins, nephrotoxins, and carcinogens that cause frank toxic effects. Recently, however, a number of industrial hygiene and occupational medicine initiatives have sought to identify acceptable levels of exposure to sensory irritants and reduce exposure to this class of chemicals. This article presents an overview of the field with emphasis on the work presented at two symposia sponsored by the Chemical Manufacturers Association: "How Do We Set an Occupational Exposure Limit (OEL) for Irritation?" (1998) at the American Industrial Hygiene Conference and Exposition and "Respiratory Tract Irritation and Olfaction Conference" (1997). The two symposia reviewed clinical and experimental methods used to assess odor and sensory irritation, to increase understanding of the research needed to establish OELs for sensory irritants, and to discuss how to use this information to identify appropriate values. The symposia illustrated that research in this area is evolving quickly and that there is already sufficient understanding to permit scientists to identify chemicals likely to be sensory irritants. Further, there appears to be an ample number of research methods for identification of airborne concentrations that should protect most workers. This article summarizes some of the key points raised at these symposia and suggests areas deserving of future study.

A number of different protocols have been put forth for measuring reverse diffusion from diffusive samplers. The basic concept is that reverse diffusion tests, depending as they do on basic laws of mass transfer, are not independent of one another, but may give general information about the limits to the possible change that can occur if the conditions to measure reverse diffusion are changed. Laboratory measurements of the reverse diffusion of vinyl chloride, using 3M and SKC diffusive samplers, following both the National Institute for Occupational Safety and Health (NIOSH) and the European Union test protocols, support the mathematical analysis developed in this article. An important conclusion is that if in following the NIOSH protocol a diffusive sampler loses 10% of its analyte over a period of 4 hours, then the maximum loss expected from a sampler allowed to back-diffuse for 8 hours is 19%.

This case study was a critical investigation of the analytical methodology and exposure assessment components of an intervention that led to the closure of a polyurethane foaming plant in Glenola, N.C., where plant neighbors reported a wide range of adverse health effects. Resident complaints and reports of nuisance odors and health effects persisted for many years, coming to a head in late 1995 and early 1996. Central to state and federal agency activities was the determination of the concentrations of air contaminants including toluene diisocyanate (TDI) at the plant fence line to establish an empirical foundation for resident complaints. Well over 2000 air concentration measurements were collected in the 18-month period prior to intervention and plant closure in September 1997. Results showed that flawed methodology, including poor quality assurance and improper interpretation of the data, may have led to improper conclusions and the inappropriate closing of this facility. Agency data did not show that ambient air concentrations of TDI at the plant fence line exceeded any required or recommended concentration limit. Furthermore, the identity and concentration of other air contaminants were not thoroughly investigated. Key lessons learned are that such interventions must be based on well-designed and executed exposure assessments. Resultant risk determinations must be based on sound science and methods.

This article reviews the analytical methods for crystalline silica polymorphs and summarizes promising techniques for compliance with health-related regulations. X-ray diffraction analysis appears to be the most promising method of determining quartz and cristobalite content at this threshold in many bulk mineral and chemical systems. Other analytical techniques can be used in some mineral and chemical assemblages, but usually lack polymorph specificity or sensitivity. All analytical methods benefit from concentration techniques that do not alter crystalline properties of silicas. National Institute of Occupational Safety and Health (NIOSH) Analytical Method 7601 as written suffers from destruction of the mineral residue containing crystalline silica polymorphs after dissolution of many silicate minerals in phosphoric acid and may also include digestion-resistant silicate minerals, but it is a promising concentration method for other analytical methods such as NIOSH Analytical Method 7500 (X-ray diffraction).

The effects of exposure misclassification on the interpretation of results of occupational epidemiological studies has been widely investigated and reported. Usually, only the direct effects of misclassification have been considered or simple estimates of misclassification rates have been assigned to various types of exposure estimation processes. Lifelong job profile data obtained from a previously published case-control study provided complete or nearly complete job histories of 511 decedents. An analysis of these work histories and the comparison of exposures related to longest-held job to estimated total lifetime exposures suggest that single job-based exposure estimates may lead to significant exposure misclassification rates. In addition, the appearance of shorter duration jobs in a study population occurring predominantly early in the work history may exacerbate problems associated with exposure misclassification. While few specific suggestions emerge from this analysis, the inclusion of extensive recording of the work history of study subjects emerges as a reasonable basis for the investigation and potential reduction of secondary misclassification of exposures in occupational epidemiological studies.

This article (the second of a two-part series) provides a discussion of currently accepted methodology and possible future happenings regarding measurement of benzene in workplaces. The gap between occupational and environmental monitoring is becoming narrow. Environmental levels will always be lower than the occupational, but as the push for lower threshold limit values continues, the focus should be on the environmental aspect as the ultimate limiting factor with respect to measurement. The charcoal tube/carbon disulfide desorption procedure is slowly being stretched to its limit with respect to benzene. It may be time for serious consideration in North America regarding adoption of the proven European procedure of thermal desorption using a porous polymer tube for analysis of benzene.

Changes in urinary flow induce changes in urinary concentrations of toxic substances. The authors modified the conventional specific gravity adjustment method for measuring urinary concentration of toxic substances to compensate for the dilution effects from varying degrees of hydration. The conventional specific gravity adjustment method is a special case to the more general method proposed in this article. The conventional method generally does not correct the urinary concentration to the mean specific gravity of urine. It requires the assumption that a change in urine flow preserves the relative ratio between the mass of the xenobiotic and the mass of total dissolved solids. The derivation of the modified specific gravity adjustment method shows that a change in urine flow does not necessarily preserve this ratio. An experimental slope between urinary flow and urinary specific gravity was linear on a log scale. A ratio was formed between the experimental slope and Araki's "b" slopes for various substances to predict changes in urine concentrations due to changes in the specific gravity of a spot sample. Since excretion rates typically vary for different substances with changes in urinary flow, an appropriately weighted exponential adjustment factor is required for each substance to normalize its concentration to the standard specific gravity of urine.

This study assessed the exposure of coke-oven workers to polycyclic aromatic hydrocarbons (PAH) based on two methods of biological monitoring (urinary mutagenicity by Ames test and urinary 1-hydroxypyrene) and concentrations of benzo(a)pyrene in the air collected by personal sampling. The coke-oven workers were classified into four job categories. There was no significant correlation among three methods applied. According to all methods, the workers most exposed to PAH were those working at the topside area of the coke plant, Coke-oven workers excreted significantly more mutagenic substances and 1-hydroxypyrene (HpU) in urine than the controls. Mutagenic substances in urine of coke-oven workers and the control group were detected only with TA98 after metabolic activation. Median HpU levels of coke-oven workers classified into three job categories (A, B, C) exceeded the biological exposure limit. The effect of smoking on urinary mutagenicity and urinary 1-hydroxypyrene was statistically significant.

This study examined the field precision of National Institute for Occupational Safety and Health (NIOSH) Method 3500, also known as chromotropic acid method, in the range of exposure limit covers the Occupational Safety and Health Administration (OSHA) permissible exposure limit of 0.75 ppm and the OSHA action level of 0.5 ppm airborne formaldehyde. Using this method, 78 area samples (25 sets of replicate samples) were collected in a workplace and analyzed. The concentrations of formaldehyde ranged from 0.05 to 1.72 ppm with a mean +/- standard deviation of 0.95 +/- 0.31 ppm. The precision (coefficient of variation, CV) of 25 sets of replicated samples ranged from 0.03 to 0.24 with an overall (pooled) precision of 0.09, which is in agreement with that stated in NIOSH Method 3500. In 68% of replicate samples the precision was equal to or less than 0.09. The relative accuracy of the sampling and analytical procedure used in this study was evaluated by collecting 12 sets of side-by-side replicate samples using both NIOSH Method 3500 and OSHA Method 5.2 Method 53 was used to determine whether the concentrations of formaldehyde were within the desired range. The overall mean concentrations were 0.98 +/- 0.42 for Method 3500 and 0.78 +/- 0.28 ppm for Method 5.2. These were no statistically different. The pooled CVs were 0.114 and 0.076 for Method 3500 and Method 52, respectively.

Air samples were collected to examine physical and chemical characteristics of lead aerosols in different work environments in the airborne lead concentration range from 28-783 micrograms/m3. Size distribution of aerosols was measured using a Marple personal cascade impactor, and lead analysis was conducted using graphite atomic absorption spectrometry. Lead aerosol size distribution was found to be different from that of total particles. Such differences are not negligible and must be taken into account when estimating aerosol deposition within the human respiratory tract. Variation of MMAD (mass median aerodynamic diameter) and GSD (geometric standard deviation) of lead aerosols in the coarse mode wit total airborne concentration was found to be small, and the assumption that lead aerosol distribution is constant is reasonable for establishing the relationship between airborne lead concentration in all work areas of the three plants except the charging area of the capacitor plant. Therefore, it is expected that either total airborne lead or respirable airborne lead concentration can be used to correlate blood lead concentration.

A computer-based training program has been devised to promote better understanding of the recently revised National Institute for Occupational Safety and Health (NIOSH) test guidelines applicable to methods requiring on-site sample collection and laboratory sample analysis of airborne toxic substances. A statistics section explains the basis of the NIOSH accuracy criterion (NAC); an experiments section provides details on the evaluation experiments; and a calculations section calculates method statistics based on data entered by the user. The statistics section graphically explains concepts such as the NAC and limit of detection, allowing the user to experiment with some parameters to see how the results are affected. This section also provides background material to show how some of the performance criteria evolved. The experiments section provides a summary of the experiments used to generate the data for method evaluation. The calculations section has several screens that work like customized spreadsheets for the entry of data collected during the laboratory evaluation of a method. A separate screen then calculates the precision (relative standard deviation) of analytical results at each of four concentrations, tests to see if the precision values are statistically homogeneous, and combines the homogeneous data for calculation of the relative standard deviation. It does the same for bias, and combines the precision with method bias to arrive at an estimate of method accuracy. Other screens in the calculations section facilitate the determination of method limit of detection and sample storage stability.

This study investigated the possibility of making compliance data from the public and private sectors more amenable for multiple uses, by studying data from Occupational Safety and Health Administration (OSHA) inspections during 1979-1989. The potential association of five variables with mean and upper-end (in upper quartile) airborne exposures in similar exposure groups was investigated. The exposure groups reflected airborne exposures to lead in the battery manufacturing industry, to perchloroethylene among dry cleaners, and to iron oxide among welders in three metal fabrication industries. Variables examined were year, inspection type and scope, and size and union status of inspected establishments. Multiple linear regression and logistic regression models were used for the analyses. In small battery plants mean exposure levels were higher and the relative frequency of upper-end exposures (> 75th percentile) greater than in larger establishments. Evidence suggested a decline in mean lead exposures (5-9% per year). Neither type of inspection nor union status were associated with mean or upper-end levels of lead exposure, although the study's power to detect an association was sometimes modest. Some evidence showed that full scope inspections may be associated with higher mean exposures. Strong evidence showed a decline in mean perchloroethylene exposures among dry cleaners (7% per year), but no temporal trends for welder exposures to iron oxide. With few exceptions, the size, type, scope, and union variables were rarely associated with mean or upper-end exposure levels among dry cleaners or welders, although the power of the analyses to detect associations was at times modest. Results show that OSHA data is amenable to analysis that can provide valuable insights about workplace exposures. Several findings of the study are directly useful to the design of public policy.

This study investigated the potential for mineral oil mist to evaporate, during sampling, from filters and electrostatic precipitator substrates used to assess personal exposure. If sample evaporation occurs, reported mist concentrations will underestimate true exposure. Mineral oil used as a machining fluid is not normally considered volatile; however, when dispersed as mist its aggregate surface area is so high that significant evaporation can occur. National Institute for Occupational Safety and Health Method 5026 specifies that oil mist concentrations should be determined by collecting mist on filters of mixed cellulose esters (MCE) or polyvinyl chloride (PVC). Collected mist droplets remain dispersed on the filter surface and in contact with passing air while sampling continues, conditions that can lead to sample evaporation. Less evaporation should occur for samples taken with an electrostatic precipitator, where mist droplets are separated from the airflow by electrostatic force and coalesce on the precipitator wall to form a film with relatively low surface area. Collection of mineral oil mist was investigated using a precipitator designed for personal sampling and using either an MCE or a PVC filter. The amounts of oil mist collected using the precipitator were significantly higher than the amounts collected using the filters, p < 0.001. Further tests in which clean air passed through mist-loaded precipitators and filters showed that the precipitator retained substantially more collected mist than both filters, p < 0.001, and further suggested that the MCE filter retained more mist than the PVC filter, p = 0.059. Differences in sample collection and retention between the precipitator and the filters were particularly pronounced at mist loadings below 1 mg.

Several recent studies have compared worker personal aerosol exposures as measured by the current method with those obtained by a new approach based on collecting the inhalable fraction, intended to represent all the particles that are capable of entering through the nose and/or mouth during breathing. The present study investigated this relationship for a metal machining facility where aerosols were generated from severely refined, nonaqueous ("straight") cutting oils used during the lathe working of metal rod stock. Workers (n = 23) wore two personal aerosol samplers simulataneously, one of the 37-mm type (for "total" aerosol exposure, E37) and the other of the Institute of Occupational Medicine (IOM) type (for inhalable aerosol exposure, EIOM). The data were analyzed by weighted least squares linear regression to determine the coefficient S in the relation EIOM = S.E37. It was found that S = 2.96 +/- 0.60. This ratio-in which exposure to inhalable aerosol was greater than to "total" aerosol-is consistent with previous observations in other industries. The relative coarsenss of the oil mist aerosol, as estimated by cascade impactor measurements, probably explains the difference between the sampling methods. The collection of large "splash" droplets, may also contribute. Future occupational aerosol standards for metalworking fluids will be based on the new, health-related criteria, and exposures will be assessed on the basis of the inhalable fraction. Results of studies like that described here will enable assessment of the impact on future workplace aerosol exposure assessments of introducing new standards.

Diffusive sampler operation may be affected by a large number of factors. Interactions between the factors may also be important. A protocol for determining sampler performance has been developed by the National Institute for Occupational Safety and Health (NIOSH) that addresses sampler precision and accuracy when these factors vary within the ranges normally encountered in the field. However, it is costly, time-consuming, and often unnecessary to apply all of the tests to each sampler for every possible chemical hazard. A sampler shown to sample a specific vapor accurately may be assumed to require fewer tests to assure equal performance with related chemicals. The criteria used to define the reduced tests depends somewhat on sampler design, and the justification for applying the criteria must depend on information gained from validating a large selection of related chemicals using the full protocol. Thus, the full protocol remains the standard of reference for the lower validation level. Based on these considerations a "bilevel validation" approach was developed for the SKC 575 series diffusive sampler. Application of the bilevel approach to the NIOSH protocol is described, and the results are related to the full NIOSH protocol and also to a European validation protocol. The European protocol recognizes the validity of reduced tests for homologue validation. The conclusions are that (1) it is feasible to validate a sampler for a large number of organic vapors using the NIOSH protocol and that this number can be substantially increased by use of a bilevel approach, saving time and resources, and (2) samplers validated to either the NIOSH or European protocol should be accepted as meeting the requirements of the other.

A new reagent, 1-(9-anthracenylmethyl)piperzine (MAP), was used for the derivatization of airborne 1,6-hexamethylene diisocyanate (HDI) and polyisocyanates generated during spray-painting operations. The new reagent, which offers enhanced sensitivity and uniformity of response to both the monomeric and oligomeric forms of HDI, was compared directly with 1-(2-methoxyphenyl)piperazine (MOP), the currently employed derivatizing reagent used in the National Institute for Occupational Safety and Health Method 5521. Both the validity of the side-by-side sampling protocol and the efficacy of two derivatizing reagents were evaluated in field studies. The analytical results indicate that there is no significant difference at the 95% confidence level in the concentration of polyisocyanate in the aerosol as determined by two impingers containing MAP and a third containing MOP when these are positioned in a side-by-side-by-side arrangement.

Analytical reference standards generally are not available for non-monomeric isocyanate species, making accurate identification and quantitation by high-performance liquid chromatography (HPLC) difficult. A successful derivatizing reagent must react rapidly with all isocyanate groups, the derivatized isocyanate must be detectable selectively and at very low levels, and the detector used for quantitation must give a response proportional to the number of derivatized isocyanate groups present. A novel derivatizing reagent, 1-(9-anthracenylmethyl)piperazine (MAP), was prepared in an attempt to achieve these goals. Derivatives were prepared by reacting five mono- and difunctional isocyanates with MAP and three other established isocyanate derivatizing reagents. These reagents included 1-(2-methoxyphenyl)piperazine (MOPP),9-(methylaminomethyl)anthracene (MAMA), and tryptamine (TRYP). The relative reactivities of MAP, MOPP, TRYP, and MAMA with phenyl isocyanate were found to be 100, 88, 30, and 25, respectively. Average molar absorptivities at the absorbance maxima +/- compound-to-compound variabilities were, for MAP: 1.47 x 10(5) +/- 3.50%; MAMA: 1.38 x 10(5) +/- 7.07%: and TRYP: 3.98 x 10(4) +/- 13.1%. Average fluorescence responses were, for MAP: 100 +/- 32.6%; MAMA: 41.0 +/- 58.8%; and TRYP: 2.27 +/- 15.6%. A comparison of MAP and MOPP ureas by HPLC/ultraviolet (UV)/electrochemical (EC) gave average responses for UV, EC, and EC/UV for MAP: 117 +/- 7.3%, 52.1 +/- 6.6%, and 0.447 +/- 10.7%, respectively; for MOPP: 24.3 +/- 62.5%, 76.7 +/- 28.5%, and 4.28 +/- 59.1%, respectively. The favorable performance of MAP warrants its further study as a reagent for the determination of total isocyanate group in air.

The major occupational concern from bio-decontamination of equipment using vapor phase hydrogen peroxide (VHP) generation systems is potential operator exposure outside the protective barrier from possible VHP leaks or accidental releases from the sealed piece of equipment during decontamination. For this reason, different real time monitoring techniques were evaluated to determine their ability to accurately measure VHP at concentrations ranging from 0.5 ppm to 5 ppm. The results of this laboratory evaluation suggest that two of the four methods evaluated (the ion mobility spectrometer [IMS] and Polytron) will approximate the National Institute for Occupational Safety and Health +/- 25% accuracy requirements for measuring the concentration of VHP at and near the Occupational Safety and Health Administration permissible exposure limit of 1.0 ppm. Over the range of 0.5 ppm to 5.1 ppm VHP, the IMS had an approximate pooled method accuracy of +/- 21%, while the Polytron had a pooled method accuracy of +/- 22%. However, both instruments had false readings when exposed to nominal concentrations of methanol, bleach, and sulfur dioxide. The two additional VHP monitoring techniques evaluated (the single point monitor [SPM] and Draeger tube) were unable to accurately measure the concentration of VHP when the relative humidity was below 20%.

As part of a consideration of the sampling method for refractory ceramic fibers, calculations were carried out at the National Institute for Occupational Safety and Health to evaluate different approaches to fiber measurement. The most common technique for estimating fibers that can reach the lungs is to use an upper diameter limit of 3 microns in the phase contrast optical microscope counting rules. Calculations were carried out to estimate the aerodynamic diameter of fibers in several lognormal size distributions likely to occur in workplaces. Using these size distributions, the use of a 3 microns fiber diameter upper limit in the counting rules was compared with results expected from a sampler designed to collect fibers according to the thoracic definition, which is based on the aerodynamic diameter of compact particles. The other limits in the optical courting procedure, i.e., counting only fibers longer than 5 microns and thicker than 0.25 micron, were included in the calculations. The calculations indicate that the 3 microns upper diameter counting rule agrees with the thoracic definition within about +/- 25% for a wide range of possible fiber size distributions. The advantages of using a sampler designed to collect the thoracic fiber size fraction include reducing analyst decision making (all fibers collected would be counted) and reducing the nonthoracic particles on the sample, making the sample easier to analyze. Until thoracic samplers are available for fibrous aerosols, incorporating the 3 microns upper diameter limit as part of the criteria for counting fibers may serve as a surrogate for thoracic sampling.

The purpose of this study was to determine how two types of sampling data could be used for an exposure assessment in a beryllium shop at the Department of Energy's Rocky Flats Plant. Beryllium exposure was assessed via fixed airhead (FAH) sampling, in which the filter cassette was affixed to the machine, generally within a few feet of the worker's breathing zone. Approximately 500,000 FAH samples were collected for beryllium over three decades at the site. From 1984 to 1987, personal breathing zone (PBZ) samples also were collected as part of the evaluation of a new high velocity/lcw volume local exhaust ventilation system in the beryllium shop. FAH data indicated that four statistically different exposure periods existed from 1970 to 1988, as the FAH annual arithmetic means varied with changes in the local exhaust ventilation system and production levels. A matched comparison between the FAH and PBZ sample data found no direct linear correlation (R2 = 0.014); however, the mean PBZ results were higher than the mean FAH results (p = 0.0001). The mean PBZ level was 1.04 micrograms/m3 while the FAH average was 0.16 microgram/m3 (permissible exposure limit for beryllium: 2 micrograms/m3). A health surveillance program to identify cases of chronic beryllium disease (CBD) and beryllium sensitization has been implemented at Rocky Flats. To date, 53 cases of CBD and 86 cases of sensitivity to beryllium have been diagnosed. Continuing studies are evaluating semiquantitative dose response relationships for CBD using the exposure data discussed herein.

In 1974 the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration joined to complete exposure standards promulgated by federal regulations. In that effort NIOSH scientists developed an accuracy criterion (AC) and a statistical protocol for evaluating fulfillment of that AC by an analytical method. This article extends that foundation and proposes a new approach to accuracy analyses. It concentrates on the case of known bias, but attempts to bridge the procedures from that case to one in which the bias is estimated. The article emphasizes a general and flexible approach to the design and analysis of more informative and effective method accuracy studies. These empower the user/investigator to design and analyze studies to be most useful and informative for specific requirements.

A quantitative exposure-estimating algorithm for benzene and total hydrocarbons was developed for a case control study of petroleum marketing and distribution workers. The algorithm used a multiplicative model to adjust recently measured quantitative exposure data to past scenarios for which representative exposure measurement data did not exist. This was accomplished through the development of exposure modifiers to account for differences in the workplace, the materials handled, the environmental conditions, and the tasks performed. Values for exposure modifiers were obtained empirically and through physical/chemical relationships. Dates for changes that altered exposure potential were obtained from archive records, retired employee interviews, and from current operations personnel. Exposure modifiers were used multiplicatively, adjusting available measured data to represent the relevant exposure scenario and time period. Changes in exposure modifiers translated to step changes in exposure estimates. Though limited by availability of data, a validation exercise suggested that the algorithm provided accurate exposure estimates for benzene (compared with measured data in industrial hygiene survey reports); the estimates generally differed by an average of less than 20% from the measured values. This approach is proposed to quantify exposures retrospectively where there are sufficient data to develop reliable current era estimates and where a historical accounting of key exposure modifiers can be developed, but where there are insufficient historic exposure measurements to directly assess historic exposures.

Six models of audio dosimeters from five manufacturers were tested to determine the effect of radio frequency (r-f) interference caused by the operation of hand-held radios near the dosimeters on the measured average sound pressure level in a controlled noise field. Exposures were in a reverberant chamber at levels of 36, 80, and 92 dBA to an octave of noise centered at 1 kHz. Two walkie-talkie type radios, one operating at 160 mHz and the other operating at 460 mHz were used to generate the r-f field. The radios were operated on two duty cycles (2 or 3 cycles/min) during the recording period. Reported measures, such as average sound pressure level and peak sound pressure level, were compared for each noise exposure condition with and without operation of the hand-held radio. The results indicate that all makes and models of the dosimeters that were tested gave false readings under some conditions. These values always exceeded the reading in the noise alone control condition and varied by as much as 45 dB above the "true" level. Because each dosimeter behaved differently--including different samples of identical models--it was not Rather, steps are recommended to help users identify potential r-f contamination on dosimeter performance in the field.

Methods of environmental and biological monitoring were applied in order to evaluate exposure to methylene chloride in workers operating in a factory where this substance was used as a solvent. For the measurement of methylene chloride in environmental concentration, the ambient air was sampled by using personal passive dosimeters. The activated charcoal was desorbed with CS2 and injected into a gas chromatograph connected with a mass spectrometer. The biological monitoring of exposed workers was performed by determining the concentration of CO in alveolar air (CA, ppm) and methylene chloride in urine (Cu, mu/L). Immediately after the end of the exposure, a urine sample was collected avoiding solvent loss and using gas-tight samplers. Excretion level in urine was determined by using headspace gas chromatography linked to a mass spectrometer. The CO was determined at the end of the shift by using a portable instrument. A group of 20 workers (12 smokers and 8 nonsmokers) in the manufacturing plant were monitored. No significant correlation was observed among the CO of all subjects and the concentration of methylene chloride in ambient air. When those workers who smoked were removed from the analysis, a correlation between the methylene chloride concentration in air and the CO concentration in alveolar air was found. Significant linear correlation was found between the environmental concentration of methylene chloride in the breathing zone and methylene chloride concentration in urine.

In the Dutch animal feed industry, approximately 6000 workers are exposed to organic dust, originating mainly from raw materials such as grain, pulses (peas and beans), and waste products from the vegetable oil and starch industries. In this study, 79 stationary dust samples and 530 personal dust samples from eight animal feed production facilities were analyzed. The stationary total dust samples showed gravimetric concentrations ranging from 0.2 to 25 mg/m3 (geometric mean [GM] 1.3 mg/m3). Concentrations of smaller particle fractions (respirable, thoracic, and inspirable dust) were considerably lower. Personal inspirable dust concentrations were considerably higher than stationary concentrations and were strongly related to job titles. Pooled personal inspirable dust concentrations ranged from 0.2 to 450 mg/m3 (GM = 2.4 mg/m3). After adjusting for differences between inspirable and total dust, 25% of the measurements exceeded the Dutch maximum allowed concentration (MAC) for total nuisance dust (10 mg/m3) and 42% exceeded the American Conference of Governmental Industrial Hygienists' threshold limit value for grain dust (4 mg/m3). Endotoxin concentrations ranged from 0.2 to 1870 ng/m3 inspirable dust (GM = 5.1 ng/m3). Endotoxin appeared to be less prevalent in respirable dust than in larger dust fractions. Concentrations in dust appeared to be related to stages in the production process. Colony-forming units (cfu) of fungi ranged from 130 to 15,300 cfu/m3 (GM = 2300 cfu/m3) and were in parallel measurements more strongly related to endotoxin concentrations than to dust concentrations. Clearly, workers in the Dutch animal feed industry are frequently exposed to dust levels above recommended Dutch and American levels. Exposure levels to endotoxin and to fungi are quantified.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of the kinds of data used for the derivation of ambient air quality standards (AAQSs) for carbon monoxide and ozone shows that these values are based on the toxicology of the materials and thus are suitable for evaluating potential health effects of indoor environments, especially on the very young, the aged, and the infirm. A similar analysis shows that the AAQSs for suspended particulate matter, nitrogen dioxide, and sulfur dioxide are strictly empirical and that they should not be used for any but their first, intended purpose. The AAQSs for non-methane hydrocarbons are based on photochemical smog production, not injury of any kind, and have no utility for indoor environment evaluation.