- I am a mathematician, Occupational and Environmental Health scientist, aerosol and inhaled particles researcher. Mor... moreI am a mathematician, Occupational and Environmental Health scientist, aerosol and inhaled particles researcher. More significantly, I am also a musician with a respectable number of compositions. In May 2017, I became a Professor Emeritus. Currently, I am devoting time to musical composition research in occupational and environmental health theory, such as reconstructing past exposures from theoretical models to be used in retrospective studies. These seminal efforts have been called Industrial archeologyin eedit
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This presentation was given at the 2002 American Industrial Hygiene Conference and Exhibition (AIHce) meeting in San Diego, CA
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Dustiness is a visually perceived phenomenon. In this paper, results of a quantification experiment for dustiness using a photometric method of measuring dust deposition and panel sampling techniques are reported. It was found that with... more
Dustiness is a visually perceived phenomenon. In this paper, results of a quantification experiment for dustiness using a photometric method of measuring dust deposition and panel sampling techniques are reported. It was found that with maximum contrast a 0.2% effective area coverage (EAC) by dust can be perceived against a clean background. The minimum perceivable difference between varying gradations of shading was a change of 0.45% EAC. The results also revealed that a dust deposition level of 0.7% EAC was required before the object so covered was deemed unfit to use. A telephone survey indicated that the minimum tolerable interval between household dusting was every four days. Combination of the telephone survey information with the level of dust coverage found to be objectionable implies that a dustfall rate of less than 0.17% EAC/day would be tolerable for the population at large.
Research Interests: Engineering, Visual perception, Adolescent, Medicine, Humans, and 5 moreAged, Middle Aged, Adult, Sampling Technique, and Dust
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The use of cadmium sulfide solar cells was proposed in order to solve a very pressing problem of the energy needs of this civilization. Extensive studies to ensure that the introduction of this new technology will not create environmental... more
The use of cadmium sulfide solar cells was proposed in order to solve a very pressing problem of the energy needs of this civilization. Extensive studies to ensure that the introduction of this new technology will not create environmental problems detrimental to the health and well being of the society have been undertaken. Cadmium is known to be a toxic substance and ought to be treated with respect. It is necessary to investigate first the possible routes of introduction of cadmium to the environment due to the development of the proposed technology. If cadmium is to be used in solar cells to a great extent, the first problem arises in the procurement and manufacturing operations.
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The reconstruction of worker exposures has been the mainstay of modem industrial epidemiologic studies. In most cases, the researchers are faced with the difficult dilemma created by the scarcity of the exposure measurement data vis-à-vis... more
The reconstruction of worker exposures has been the mainstay of modem industrial epidemiologic studies. In most cases, the researchers are faced with the difficult dilemma created by the scarcity of the exposure measurement data vis-à-vis the demands for refined quantification. The 4 industrial epidemiologic studies of workers exposed to acrylonitrile share many similarities to illustrate strengths and weaknesses of the current exposure reconstruction methodologies. The analysis of the reported exposure reconstruction methods and comparative analysis of some of the results suggest that there is a certain degree of conformity in the results of the exposure reconstruction processes in these 4 studies. At the same time, the same analysis invokes some questions with respect to the interpretation of the exposure reconstruction results.
Research Interests: Psychology, Occupational Epidemiology, Environmental Monitoring, Risk assessment, Medicine, and 15 moreHumans, United States, Female, Male, Occupational Exposure, Chemical Industry, Retrospective Studies, Reproducibility of Results, Risk Assessment, Sensitivity and Specificity, Acrylonitrile Research, Cohort Studies, Acrylonitrile Monomer, Acrylonitrile, and Epidemiological monitoring
In the occupational hygiene component of occupational epidemiological studies, the goal is to assign group average exposure levels that can be used to compute individual cumulative exposures. This task requires the availability of... more
In the occupational hygiene component of occupational epidemiological studies, the goal is to assign group average exposure levels that can be used to compute individual cumulative exposures. This task requires the availability of sufficient amounts of proper individual exposure level data. Typically, the required data are either sparse, completely lacking or happenstance data collected for purposes not suitable for the aims of the study. In the epidemiological study of mortality patterns among industrial workers exposed to chloroprene and other substances, we developed and used a process analysis and modeling based exposure reconstruction to augment, extrapolate, or interpolate the available exposure data. The models developed utilize equations based on the engineering principles and chemistry associated with the processes as determined from the process documentation and task performance habits as determined from interviews of knowledgeable personnel. The resulting equations are tractable and provide a general basis for calculating exposure levels for vapors. The validation of the results with available exposure measurements suggests that comprehensive process analysis and modeling may be used to reconstruct exposures or to evaluate exposure potential with scientifically defensible methods. Furthermore, even in the absence of validating data, the methodology developed has potentially very useful applications in predicting exposure levels to newly synthesized substances. Properly interpreted, the limitations of modelling can be minimized to obtain scientifically reasonable results.
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Esmen NA1 Author information Suppl 2:63-70 PMID: 9714514 Review Share this article Share with emailShare with twitterShare with linkedinShare with facebook Abstract The reconstruction of worker exposures has been the mainstay of modem... more
Esmen NA1
Author information
Suppl 2:63-70
PMID: 9714514
Review
Share this article Share with emailShare with twitterShare with linkedinShare with facebook
Abstract
The reconstruction of worker exposures has been the mainstay of modem industrial epidemiologic studies. In most cases, the researchers are faced with the difficult dilemma created by the scarcity of the exposure measurement data vis-à-vis the demands for refined quantification. The 4 industrial epidemiologic studies of workers exposed to acrylonitrile share many similarities to illustrate strengths and weaknesses of the current exposure reconstruction methodologies. The analysis of the reported exposure reconstruction methods and comparative analysis of some of the results suggest that there is a certain degree of conformity in the results of the exposure reconstruction processes in these 4 studies. At the same time, the same analysis invokes some questions with respect to the interpretation of the exposure reconstruction results
Author information
Suppl 2:63-70
PMID: 9714514
Review
Share this article Share with emailShare with twitterShare with linkedinShare with facebook
Abstract
The reconstruction of worker exposures has been the mainstay of modem industrial epidemiologic studies. In most cases, the researchers are faced with the difficult dilemma created by the scarcity of the exposure measurement data vis-à-vis the demands for refined quantification. The 4 industrial epidemiologic studies of workers exposed to acrylonitrile share many similarities to illustrate strengths and weaknesses of the current exposure reconstruction methodologies. The analysis of the reported exposure reconstruction methods and comparative analysis of some of the results suggest that there is a certain degree of conformity in the results of the exposure reconstruction processes in these 4 studies. At the same time, the same analysis invokes some questions with respect to the interpretation of the exposure reconstruction results
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Dustiness is a visually perceived phenomenon. In this paper, results of a quantification experiment for dustiness using a photometric method of measuring dust deposition and panel sampling techniques are reported. It was found that with... more
Dustiness is a visually perceived phenomenon. In this paper, results of a quantification experiment for dustiness using a photometric method of measuring dust deposition and panel sampling techniques are reported. It was found that with maximum contrast a
0.2% effective area coverage (EAC) by dust can be perceived
against a clean background. The minimum perceivable difference
between varying gradations of shading was a change of 0.45%
EAC. The results also revealed that a dust deposition level of
0.7% EAC was required before the object so covered was
deemed unfit to use. A telephone survey indicated that the minimum tolerable interval between household dusting was every four
days. Combination of the telephone survey information with the
level of dust coverage found to be objectionable implies that a
dustfall rate of less than 0.17% EAC/day would be tolerable for
the population at large.
0.2% effective area coverage (EAC) by dust can be perceived
against a clean background. The minimum perceivable difference
between varying gradations of shading was a change of 0.45%
EAC. The results also revealed that a dust deposition level of
0.7% EAC was required before the object so covered was
deemed unfit to use. A telephone survey indicated that the minimum tolerable interval between household dusting was every four
days. Combination of the telephone survey information with the
level of dust coverage found to be objectionable implies that a
dustfall rate of less than 0.17% EAC/day would be tolerable for
the population at large.
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developed by UK’s Health and Safety Executive to assess exposure. EASE computes estimated airborne concentrations based on a substance’s vapor pressure and the types of controls in the work area. Though EASE is intended only to make broad... more
developed by UK’s Health and Safety Executive to assess exposure. EASE computes estimated airborne concentrations based on a substance’s vapor pressure and the types of controls in the work area. Though EASE is intended only to make broad predictions of exposure from occupa-tional environments, some occupational hygienists might attempt to use EASE for individual exposure characterizations. This study investigated whether EASE would accurately predict actual sampling results from a chemical manufacturing process. Personal breathing zone time-weighted average (TWA) monitoring data for two volatile organic chemicals—a common solvent (toluene) and a specialty monomer (chloroprene)—present in this manufacturing process were compared to EASE-generated estimates. EASE-estimated concentrations for specific tasks were weighted by task durations reported in the monitoring record to yield TWA estimates from EASE that could be directly compared to the measured TWA data. Two hundred and six chl...
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Research Interests: Environmental Monitoring, Air pollution, Exposure Assessment, Environmental Sciences, Humans, and 12 moreFemale, Male, Oklahoma, Exposure, CHEMICAL SCIENCES, Middle Aged, Adult, Environmental Exposure, Global position ing system, Medical and Health Sciences, Epidemiological monitoring, and Population surveillance
The factors affecting the volatilization of trichloro-ethylene from a shower spray were assessed and modeled as a function of the distribution of drop sizes. For the 10 L/min shower-water flow system, the measured drop sizes were smaller... more
The factors affecting the volatilization of trichloro-ethylene from a shower spray were assessed and modeled as a function of the distribution of drop sizes. For the 10 L/min shower-water flow system, the measured drop sizes were smaller and initial velocities greater than those for ...
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Occupational and environmental hygiene sampling strategies are usually dictated by factors that limit sample sizes to relatively small numbers. Often, parameters estimated from small sample sizes are then used to make further estimates of... more
Occupational and environmental hygiene sampling strategies are usually dictated by factors that limit sample sizes to relatively small numbers. Often, parameters estimated from small sample sizes are then used to make further estimates of the occurrence of extreme events, which are governed by the underlying exposure distribution. We investigated the limitations superimposed by the number of samples in distinguishing an asymmetric (Lognormal) distribution through the rejection of a hypothesized symmetric (Normal) distribution. Sets of 5 to 250 synthetic samples from underlying Lognormal distributions with unit median were generated for 24 separate geometric standard deviations (GSDs), ranging from 1.25 to 7.00. Each simulated combination was repeated in blocks of 200 and each block was repeated tenfold. The synthetic samples were then tested for goodness of fit for Normality by using the Shapiro and Wilk's W Test. Results indicated that the number of samples required to distinguish between Normal and Lognormal distributions was inversely related to GSD. When GSD = 1.25, 169 samples were required for 90 percent distinction at alpha = 0.05. The criteria for success for GSD of 2.00 and 4.00 were 25 and 15 samples, respectively. These results led to the conclusion that the general inability to distinguish an underlying distribution may impose serious difficulties in the estimation of extreme events associated with occupational and environmental hygiene-related sampling.
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A multinational occupational epidemiological study is underway to investigate the total and cause-specific mortality of workers exposed to tungsten carbide with a cobalt binder (WCCo). The study includes 12 US and 9 European plants. The... more
A multinational occupational epidemiological study is underway to investigate the total and cause-specific mortality of workers exposed to tungsten carbide with a cobalt binder (WCCo). The study includes 12 US and 9 European plants. The objective of the exposure assessment component, coordinated by the University of Illinois at Chicago, is to reconstruct agent-specific exposure estimates for use in the epidemiological analyses. Quantitative occupational exposures are being generated through a process of modelling and validation using industrial hygiene data from study plants. Innovative semi-quantitative methods are being developed to extrapolate data for years in which it is missing, and are based on exposure changes due to manufacturing process changes over time (e.g., moving from manual to automated methods). Company work history information is being used to construct a job dictionary. The resulting exposure estimates and job dictionary will form the job-exposure matrix. The agen...
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Fibrous glass and mineral wool workers exposed to airborne man-made mineral fibers prior to 1964 were identified and followed for deaths caused by respiratory disease. Fiber exposure levels were estimated for each worker. Average fiber... more
Fibrous glass and mineral wool workers exposed to airborne man-made mineral fibers prior to 1964 were identified and followed for deaths caused by respiratory disease. Fiber exposure levels were estimated for each worker. Average fiber concentrations were very low in relation to a National Institute of Occupational Safety and Health recommendation that exposure to man-made mineral fibers less than 3.5 microns in diameter be limited to 3 fibers per cubic centimeter of air. Fibrous glass workers were exposed to about one hundredth and mineral wool workers to about one tenth of that amount. Respiratory cancer death rates were not excessive for the fibrous glass workers, but they were significantly elevated for the mineral wool workers. When respiratory cancer deaths were compared with fiber exposure levels, however, there was in no instance a strong positive correlation. There was a significant excess in nonmalignant respiratory disease deaths (excluding influenza and pneumonia) for fi...
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Research Interests: Epidemiology, Animal Studies, Fertility, Birth Weight, Humans, and 15 moreLow Birth Weight, Female, Animals, Male, Metaanalysis, Experimental Study, Meta Analysis, Adult, In Vitro Studies, Formaldehyde, Organogenesis, Occupational Diseases, Birth Defect, Developmental toxicity, and Pharmacology and pharmaceutical sciences
ABSTRACT
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To assess the possible relationship between formaldehyde exposure and mortality risk from pharyngeal cancer (PC), in particular nasopharyngeal cancer (NPC). Subjects were 7328 workers employed at a plastics-producing plant (1941-1984).... more
To assess the possible relationship between formaldehyde exposure and mortality risk from pharyngeal cancer (PC), in particular nasopharyngeal cancer (NPC). Subjects were 7328 workers employed at a plastics-producing plant (1941-1984). Vital status for 98% of the cohort and cause of death for 95% of 2872 deaths were determined. Reconstructed exposures to formaldehyde, particulates and pigment were used to compute several exposure measures. Standardized mortality ratios (SMRs) were computed for several demographic, work history and formaldehyde exposure variables. In a nested case-control study, seven cases of NPC and 15 cases of other PC were matched on race, sex, age and year of birth to four controls from the cohort. Among interviewed subjects, lifetime smoking history was determined using respondents or proxies for all but one control subject. Statistically significant 2.23-fold and fivefold excesses for PC and NPC, respectively, were observed. Fivefold range NPC excesses were observed for both short ( < 1 year) and long-term workers and were concentrated among workers hired during 1947-1956. Only three NPC cases were exposed to formaldehyde for longer than one year, and each had low average intensity of formaldehyde exposure (0.03-0.60 ppm). Only a few exposure measures revealed some evidence of an association with all PC or NPC. For all PC combined, adjustment for smoking and year-of-hire in the case-control study generally corroborated findings from the cohort study. Overall, the pattern of findings suggests that the large, persistent nasopharyngeal and other PC excesses observed among the Wallingford workforce are not associated with formaldehyde exposure, and may reflect the influence of nonoccupational risk factors or occupational risk factors associated with employment outside the Wallingford plant.
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A low flow, compact Parallel Stage Impactor was designed, constructed and calibrated. This instrument has six stages: one for total collection of air particulates, and the other five with cut-off sizes of 0.34 micrograms, 0.75 micrograms,... more
A low flow, compact Parallel Stage Impactor was designed, constructed and calibrated. This instrument has six stages: one for total collection of air particulates, and the other five with cut-off sizes of 0.34 micrograms, 0.75 micrograms, 1.90 micrograms, 3.12 micrograms and 7.43 micrograms aerodynamic equivalent diameter. Flow through the individual stages is controlled by adjustable needle valves, which act as critical orifices. Flow was 700 mL/min per stage, resulting in a total flow of 4.2 L/min. The instrument was calibrated using uranine test aerosols, photofluorescence and optical microscopy techniques. There was excellent agreement between theoretical calculations and observed performance. The instrument design details and performance suggest a rugged and reliable field instrument for particle size analysis.
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The fractionation of airborne particles according to aerodynamic size by a number of impactor stages operated in parallel offers significant advantages over the commonly employed cascade impaction technique when determining mass or... more
The fractionation of airborne particles according to aerodynamic size by a number of impactor stages operated in parallel offers significant advantages over the commonly employed cascade impaction technique when determining mass or chemical size distribution of an aerosol. A seven stage, round jet impactor based on the parallel stage concept was designed, manufactured, calibrated and tested. The stages operate at 25 liters per minute collecting fractions of zero to 0.35, 0.70, 2.0, 4.0 and 7.0 micrometers aerodynamic diameter. The last two stages have no impaction surface and collect aerosol over the entire size range. All stages are mounted on standard 47 mm filter holders. For each stage, particles larger than the cut-off size impact on a thick adhesive surface and are discarded while those smaller are collected on a filter. The ratio of the particle mass penetrating to the filter of a given stage to the mass of the entire aerosol represents the cumulative mass fraction associated with the cut-off diameter for that stage. Any losses associated with non-ideal behavior in the impactor become an inherent part of the calibration. Calibration of the impactor showed that stage cut-off sizes are close to the values predicted by impactor theory. A novel technique employing polydisperse aerosol was used in the calibration. Challenge of the impactor calibration with solid aerosols of known size distribution gave excellent results. Tests for particle bounce after four hours of operation in urban aerosol showed that accumulation of particles at the impaction surface does not increase bounce or blow-off. Microscopic examination of impaction surfaces immediately after sampling showed most of the particles to be embedded within the adhesive rather than on the surface.
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Investigations of the aerodynamic behavior of fibers, lung deposition studies which involve fibers and investigations which are concerned with the biological effects of fibers create the need for fibrous aerosols monodisperse with respect... more
Investigations of the aerodynamic behavior of fibers, lung deposition studies which involve fibers and investigations which are concerned with the biological effects of fibers create the need for fibrous aerosols monodisperse with respect to both fiber length and diameter. The method of preparation presented in this paper is primarily based on embedding the bulk quantity of fibers in a plastic histological preparation medium and subsequently cutting the fibers to the desired lengths. The slices which are obtained by the microtoming process are purified of the plastic medium by burning and ashing and the fibrous dust obtained in this manner is then cleared of any debris by liquid elutriation. The results show that gram quantities of nearly monodisperse glass fiber dust with lengths of up to 50 micrometers can be obtained.
Research Interests: Glass, Aerosols, Methods, Respiration, Particle Size, and 3 moreGlass Fiber, Dust, and Lung deposition
The true test of the long-term response of workers exposed to a hazardous agent is usually the epidemiological studies performed on same. This necessitates the long-term knowledge of exposure levels. Usually, the extent to which the... more
The true test of the long-term response of workers exposed to a hazardous agent is usually the epidemiological studies performed on same. This necessitates the long-term knowledge of exposure levels. Usually, the extent to which the exposures measured during recent experiences are representative of past exposures is difficult to assess as only limited historic measurements are available, and oftentimes the limited data are difficult to relate to today's measurement techniques. It is fallacious to assume that the conditions were worse in the past as it is fallacious to assume that they were better. The methodology of estimating past exposures to an agent based on industry-wide survey techniques is discussed.
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The inertial deposition is given considerable credit in the deposition of inhaled particulate matter in the upper respiratory tract. A determination of the parameters governing the impaction of fibers must be the basis of evaluating the... more
The inertial deposition is given considerable credit in the deposition of inhaled particulate matter in the upper respiratory tract. A determination of the parameters governing the impaction of fibers must be the basis of evaluating the role of impaction in the respirability of fibrous dusts. The study reported here describes an experimental method of defining the inertial behavior of fibers. The results of the experiments show that the aspect ratio of the fibers plays a much more important role than hitherto considered. The results of the experimental work gave an empirical mathematical model for the prediction of the impaction of fibers from the physical properties of fibers such as density, fiber diameters and aspect ratio. In addition an equivalent diameter based on inertial properties of the fiber is developed.
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To evaluate further elevated mortality risks from respiratory system cancer (RSC) and lymphatic and hematopoietic tissue cancers (LHTC) in a cohort of 1466 male workers employed full-time in pharmaceutical production. We computed... more
To evaluate further elevated mortality risks from respiratory system cancer (RSC) and lymphatic and hematopoietic tissue cancers (LHTC) in a cohort of 1466 male workers employed full-time in pharmaceutical production. We computed standardized mortality ratios, and in nested case-control studies of RSC and LHTC, evaluated mortality risks by plant exposures with adjustment for potential confounding factors. Subjects with potential plant exposure had no elevated RSC risk and a statistically significant LHTC excess. The case-control study found many RSC risks reduced with adjustment for smoking, and LHTC risks increased with increasing levels of average exposure to dimethyl-formamide. RSC mortality risks decreased, and we found limited evidence that positive confounding by smoking may explain some remaining excess risks. For LHTC, increased mortality risks and exposure-response patterns in the case-control study may indicate a possible workplace association.