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Made F, Kandala NB, Brouwer D. Compliance Testing and Homogenous Exposure Group Assessment in the South African Coal Mining Industry. Ann Work Expo Health 2021; 65:955-965. [PMID: 34089331 DOI: 10.1093/annweh/wxab030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 03/26/2021] [Accepted: 04/01/2021] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES Globally, several strategies for compliance testing and within-group exposure variability have been suggested. This study aimed to evaluate the performance of the South African Mining Industry Code of Practice (SAMI CoP) approach for grouping and compliance testing against international standards. METHODS A total of 28 homogenous exposure groups (HEGs) with 728 underground coal mine workers' eight-hour time-weighted average coal dust concentration data were obtained. Compliance testing was assessed using 10% exceedance above occupational exposure limit (OEL) for SAMI CoP, and the 95th percentile of the lognormal distribution was computed for the European Standardization Committee (CEN) and American Industrial Hygiene Association (AIHA). Comparison of the homogeneity of the HEGs was done between SAMI CoP which mandates that both the arithmetic mean (AM) and 90th percentile must fall in the same exposure band to certify homogeneity and the global geometric standard deviation (GSD) and Rappaport ratio (R-ratio) with specific acceptability criteria. To test the homogeneity of exposure within job titles, eight non-homogenous HEGs that have two or more job titles with three measurements were investigated using GSD and the SAMI CoP criteria. RESULTS A total of 21 HEGs out of 28 were non-compliant to the OEL across SAMI CoP, CEN, and AIHA criteria. Compliance to the OEL was observed for seven HEGs according to the SAMI CoP approach, whereas only one HEG was compliant according to both the SAMI CoP and CEN approaches. The GSD criterion and SAMI CoP revealed that 11 and 6 HEGs were homogenous, respectively, and only on 4 occasions, the 2 approaches agreed. The job titles of the majority of non-homogenous HEGs in both SAMI CoP and GSD were actually homogenous. Five out of 10 sub-groups have their AM above that of HEG B. Other HEGs had at least one of their AM and 90th percentile values above that of their respective parent HEGs. CONCLUSIONS All three approaches mainly confirmed non-compliance of HEGs. SAMI CoP tended to show compliance of HEGs more than CEN. Non-homogenous HEGs had many job titles that were homogenous according to both SAMI CoP and GSD criteria. There was no perfect agreement of homogeneity by all the indicators. For both future constitutions of HEGs as well as a retrospective assessment of high exposure groups, homogeneity can be improved by using job titles.
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Affiliation(s)
- Felix Made
- Division of Occupational Health and Epidemiology, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Gauteng Province, South Africa.,Epidemiology and Surveillance Section, National Institute for Occupational Health, National Health Laboratory Services, Johannesburg, Gauteng Province, South Africa
| | - Ngianga-Bakwin Kandala
- Division of Occupational Health and Epidemiology, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Gauteng Province, South Africa
| | - Derk Brouwer
- Division of Occupational Health and Epidemiology, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Gauteng Province, South Africa
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Marsh GM, Youk AO, Buchanich JM, Cassidy LD, Lucas LJ, Esmen NA, Gathuru IM. Pharyngeal cancer mortality among chemical plant workers exposed to formaldehyde. Toxicol Ind Health 2016; 18:257-68. [PMID: 14992463 DOI: 10.1191/0748233702th149oa] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Objectives: To assess the possible relationship between formaldehyde exposure and mortality risk from pharyngeal cancer (PC), in particular nasopharyngeal cancer (NPC). Methods: 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. Results: Statistically significant 2.23-fold and fivefold excesses for PC and NPC, respectively, were observed. Fivefold range NPC excesses were observed for both short (B / 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. Conclusions: 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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Affiliation(s)
- Gary M Marsh
- Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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Chen YC, Ramachandran G, Alexander BH, Mandel JH. Retrospective exposure assessment in a chemical research and development facility. ENVIRONMENT INTERNATIONAL 2012; 39:111-121. [PMID: 22208749 DOI: 10.1016/j.envint.2011.10.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Revised: 07/22/2011] [Accepted: 10/19/2011] [Indexed: 05/31/2023]
Abstract
The objective of this exposure assessment was to reconstruct cumulative historical exposures for workers who have been exposed to multiple chemicals and chemical groups to better understand a cluster of brain cancers within a research and development lab. Chemicals of interest, including acrylates, bis-chloromethyl ether (BCME), chloromethyl methyl ether (CMME), isothiazolones and nitrosoamines, were selected on the basis of the plausibility of penetrating the blood-brain barrier and the uniqueness of the chemical's biological activity. In a complicated exposure setting such as a chemical R&D facility, multiple exposure estimation methods were needed. First, similarly exposure groups (SEGs) were created for these materials based on department group, time period of the department's existence and function associated with job titles. A probabilistic framework for assessing exposures was developed using Bayesian analysis of historical monitoring data, mathematical exposure modeling and professional judgments of current and former industrial hygienists at the facility were used to reconstruct the exposure history for acrylates, BCME and CMME for each SEG over the time period of interest. Since sufficient measurement data for isothiazolones and nitrosoamines were not available, the exposure histories for each SEG for these chemicals were estimated. This was done using objective formaldehyde levels and subjective employee interviews. The interviews assessed workplace determinants of exposure as distinct surrogates for estimating inhalation and dermal exposures. The exposure assessments by these methods were compared against each other to estimate the potential for exposure misclassification. A job exposure matrix (JEM) was constructed that contained the exposures obtained from above multiple approaches for each of these chemical groups for each SEG for each year of interest. The combination of methods used in this work is a unique and potentially helpful framework that can be used in analogous workplace settings involving multiple exposures with incomplete objective measurement information.
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Affiliation(s)
- Yu-Cheng Chen
- University of Minnesota, Division of Environmental Health Science, School of Public Health, Minneapolis, Minnesota 55455, USA
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Gómez MR, Rawls G. Conference on Occupational Exposure Databases: A Report and Look at the Future. ACTA ACUST UNITED AC 2011. [DOI: 10.1080/1047322x.1995.10389030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Affiliation(s)
- Manuel R. Gomez
- Occupational Studies Section, Epidemiology and Biostatistics Program, EPB, National Cancer Institute, Executive Plaza North, Room 418, Rockville, Maryland, 20892, USA
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Olsen E, Jensen B. On the Concept of the “Normal” Day: Quality Control of Occupational Hygiene Measurements. ACTA ACUST UNITED AC 2011. [DOI: 10.1080/1047322x.1994.10388308] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Sahmel J, Devlin K, Paustenbach D, Hollins D, Gaffney S. The role of exposure reconstruction in occupational human health risk assessment: current methods and a recommended framework. Crit Rev Toxicol 2010; 40:799-843. [PMID: 20722488 DOI: 10.3109/10408444.2010.501052] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Exposure reconstruction for substances of interest to human health is a process that has been used, with various levels of sophistication, as far back as the 1930s. The importance of robust and high-quality exposure reconstruction has been recognized by many researchers. It has been noted that misclassification of reconstructed exposures is relatively common and can result in potentially significant effects on the conclusions of a human health risk assessment or epidemiology study. In this analysis, a review of the key exposure reconstruction approaches described in over 400 papers in the peer-reviewed literature is presented. These approaches have been critically evaluated and classified according to quantitative, semiquantitative, and qualitative approaches. Our analysis indicates that much can still be done to improve the overall quality and consistency of exposure reconstructions and that a systematic framework would help to standardize the exposure reconstruction process in the future. The seven recommended steps in the exposure reconstruction process include identifying the goals of the reconstruction, organizing and ranking the available data, identifying key data gaps, selecting the best information sources and methodology for the reconstruction, incorporating probabilistic methods into the reconstruction, conducting an uncertainty analysis, and validating the results of the reconstruction. Influential emerging techniques, such as Bayesian data analysis, are highlighted. Important issues that will likely influence the conduct of exposure reconstruction into the future include improving statistical analysis methods, addressing the issue of chemical mixtures, evaluating aggregate exposures, and ensuring transparency with respect to variability and uncertainty in the reconstruction effort.
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Marsh GM, Esmen NA, Buchanich JM, Youk AO. Mortality patterns among workers exposed to arsenic, cadmium, and other substances in a copper smelter. Am J Ind Med 2009; 52:633-44. [PMID: 19533624 DOI: 10.1002/ajim.20714] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
OBJECTIVE To evaluate the long-term mortality experience of workers exposed to arsenic, cadmium, and other substances at a copper mine and smelter in Copperhill, Tennessee studied earlier as part of an industry-wide study. METHODS Subjects were 2,422 male workers employed three or more years in the smelter or mill between 1/1/46 until the plant strike and scale-down of operations in April 1996. Vital status was determined through 2000 for 99.4% of subjects and cause of death for 91.3% of 878 deaths. Historical exposures were estimated for lead, SO(2), arsenic, cadmium, dust, and cobalt. We computed standardized mortality ratios (SMRs) based on U.S. and local county rates and modeled internal relative risks (RRs). RESULTS We observed overall deficits in deaths based on national and local county comparisons from all causes, all cancers and most of the cause of death categories examined. We found limited evidence of increasing mortality risks from cerebrovascular disease with increasing duration and cumulative arsenic exposure, but no evidence of an exposure-response relationship for cadmium exposure and bronchitis. CONCLUSIONS Our limited evidence of an association between inhaled arsenic exposure and CVD is an exploratory finding not observed in other epidemiology studies of more highly exposed occupational populations. Possible alternative explanations include chance alone and uncontrolled confounding or effect modification by co-exposures or other factors correlated with arsenic exposure and unique to the Copperhill facility.
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Affiliation(s)
- Gary M Marsh
- Department of Biostatistics, Center for Occupational Biostatistics and Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania PA15261, USA.
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He Y, Liang Y, Fu H. Application of bayesian methods to exposure assessment of area concentrations at a rubber factory. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2009; 6:622-34. [PMID: 19440405 PMCID: PMC2672369 DOI: 10.3390/ijerph6020622] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Accepted: 02/05/2009] [Indexed: 11/26/2022]
Abstract
The present study estimated area concentrations of airborne benzene in several workshops using Bayesian methods based on available historical measurements. A rubber products factory utilizing benzene was investigated. Historical measurements of benzene concentrations, expert experiences, and deterministic modeling were utilized in a Bayesian Method to estimate area concentrations. Historical concentrations (n=124) were available with the geometric mean of 15.3 mg/m(3). The geometric mean of the current field measurements on the workstations ranged from 0.7 to 89.0 mg/m(3). One of the seven historical geometric means by work locations significantly differed from the field measurements for equivalent locations, but none of the geometric means of Bayesian estimates were significantly different from the field measurement results. The Bayesian methods based on the historical measurements appeared to be a useful tool for more closely estimating area concentrations shown by field data than that predicted only using historical measurements.
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Affiliation(s)
| | | | - Hua Fu
- School of Public Health, Fudan University /Box 288, No 130, Dong’an Road, Shanghai 200032, PR China
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Conceptual Model for Assessment of Inhalation Exposure: Defining Modifying Factors. ACTA ACUST UNITED AC 2008; 52:577-86. [DOI: 10.1093/annhyg/men059] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Esmen NA, Hall TA, Phillips ML, Marsh GM. Chemical process based reconstruction of exposures for an epidemiological study. Chem Biol Interact 2007; 166:254-63. [PMID: 17010327 DOI: 10.1016/j.cbi.2006.08.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
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 modeling can be minimized to obtain scientifically reasonable results.
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Affiliation(s)
- Nurtan A Esmen
- University of Illinois at Chicago, School of Public Health (SPHW), MC 922, Environmental and Occupational Health Sciences, 2121 W. Taylor St., Chicago, IL 60612, USA.
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Marsh GM, Youk AO, Esmen NA, Buchanich JM. Mortality patterns among workers in a US pharmaceutical production plant. Ann Epidemiol 2005; 15:112-22. [PMID: 15652716 DOI: 10.1016/j.annepidem.2004.05.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2003] [Accepted: 05/28/2004] [Indexed: 10/26/2022]
Abstract
PURPOSE To examine mortality among workers in a pharmaceutical production plant and to address community concerns about 1980 to 1990 increases in local county cancer mortality rates. METHODS Subjects were 1999 workers with some full-time employment during the period between 1970 and 1996. We identified deaths through the year 2000 and reconstructed exposures to nine chemical agents with available exposure measurements. Data analyses included standardized mortality ratios (SMRs) and time trends in local cancer mortality rates. RESULTS We observed deficits in deaths from all causes combined, all cancers combined, and most cause of death categories examined. Male workers with potential plant exposure had excesses in deaths from all lymphatic-hematopoietic tissue cancers (LHTC), in particular non-Hodgkin's lymphoma (NHL), and respiratory system cancers (RSC) that were larger among long-term workers, but the pattern of findings suggested the excesses were probably not related to occupational factors at the plant. The increase in local county cancer mortality rates was simply the upward cycle of a periodic trend that peaked in 1990 and returned to 1980 levels in 2000. CONCLUSIONS With the possible exceptions of LHTC, in particular NHL, and RSC, this study provided no evidence of elevated total or cause-specific cohort mortality risks. It does not appear that plant factors played a role in the 1980 to 1990 increases in local county cancer mortality rates.
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Affiliation(s)
- Gary M Marsh
- Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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Esmen NA, Corn M. Airborne fiber concentrations during splitting open and boxing bags of asbestos. Toxicol Ind Health 1998; 14:843-56. [PMID: 9891915 DOI: 10.1177/074823379801400606] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Measured airborne concentrations of asbestos are often unavailable to assess different epidemiologic estimates of past personal exposure levels or concentrations near specific operations involving handling asbestos. The purpose of this study was to assess the potential use of a laboratory study in estimating exposure to asbestos in operations that ceased for many years. The asbestos transfer operations were simulated by splitting and boxing 4.5-kg paper bags of chrysotile asbestos in an enclosed chamber ventilated at 28.2 air changes per hour (ACH). Two recirculation fans achieved chamber air mixing. The airborne concentration of asbestos fibers was determined by sampling air through membrane filters at a rate of 10 l/min and by analysing fibers by phase contrast optical microscopy to determine 15-min average airborne concentrations. Samplers were located at four equidistant locations from the operation. Opening a maximum of seven bags in 15 min was associated with an asbestos-in-air concentration of less than 2 x 10(-6) fibers/m3 (f/m3) in splitting open and boxing and less than 0.85 x 10(-6) f/m3 in boxing of pre-split bags. The measured airborne asbestos concentration exhibited a linear trend with the number of bags opened per 15 min. The empirical results were utilised to model fiber concentrations for various ventilation rates. It was concluded that the distribution of the operation within the workday and the ventilation rate are the two most important variables in the determination of the estimated time-weighted average concentration. Splitting open and boxing 32 bags of asbestos over an 8-h period at a rate of 4 bags/h over an 8-h period results in a calculated time-weighted average exposure of about 1 x 10(-6) f/m3 in a work space with 20 ACH and approximately 7 x 10(-6) f/m3 in a work space with 2 ACH. Splitting open and boxing at a rate of 12 bags/h for 2 h and 45 min yielded calculated concentrations less than one-half of the above mentioned values. These results should serve as a useful benchmark for epidemiologists concerned with the magnitude of exposure in historically dusty industrial tasks.
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Affiliation(s)
- N A Esmen
- Health Sciences Center, University of Oklahoma, Oklahoma City, USA. nurtan-esmen@ouhsc
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Tharr D, Baldwin M, Mergler D, Julien D. Workplace Exposures beyond the Workplace: Exposure Assessment for a Pilot Study of Effects of Workplace Exposures on Family Life. ACTA ACUST UNITED AC 1998. [DOI: 10.1080/1047322x.1998.10390128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Symanski E, Kupper LL, Rappaport SM. Comprehensive evaluation of long-term trends in occupational exposure: Part 1. Description of the database. Occup Environ Med 1998; 55:300-9. [PMID: 9764107 PMCID: PMC1757580 DOI: 10.1136/oem.55.5.300] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVES To conduct a comprehensive evaluation of long term changes in occupational exposure among a broad cross section of industries worldwide. METHODS A review of the scientific literature identified studies that reported historical changes in exposure. About 700 sets of data from 119 published and several unpublished sources were compiled. Data were published over a 30 year period in 25 journals that spanned a range of disciplines. For each data set, the average exposure level was compiled for each period and details on the contaminant, the industry and location, changes in the threshold limit value (TLV), as well as the type of sampling method were recorded. Spearman rank correlation coefficients were used to identify monotonic changes in exposure over time and simple linear regression analyses were used to characterise trends in exposure. RESULTS About 78% of the natural log transformed data showed linear trends towards lower exposure levels whereas 22% indicated increasing trends. (The Spearman rank correlation analyses produced a similar breakdown between exposures monotonically increasing or decreasing over time.) Although the rates of reduction for the data showing downward trends ranged from -1% to -62% per year, most exposures declined at rates between -4% and -14% per year (the interquartile range), with a median value of -8% per year. Exposures seemed to increase at rates that were slightly lower than those of exposures which have declined over time. Data sets that showed downward (versus upward) trends were influenced by several factors including type and carcinogenicity of the contaminant, type of monitoring, historical changes in the threshold limit values (TLVs), and period of sampling. CONCLUSIONS This review supports the notion that occupational exposures are generally lower today than they were years or decades ago. However, such trends seem to have been affected by factors related to the contaminant, as well as to the period and type of sampling.
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Affiliation(s)
- E Symanski
- University of Texas Health Science Center, Houston, School of Public Health 77030, USA
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Gómez MR. Factors associated with exposure in Occupational Safety and Health Administration data. AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL 1997; 58:186-95. [PMID: 9075309 DOI: 10.1080/15428119791012838] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
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.
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Affiliation(s)
- M R Gómez
- U.S. Environmental Protection Agency, National Center for Environmental Assessment, Office of Research and Development, Washington, DC 20460, USA
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Stewart PA, Zey JN, Hornung R, Herrick RF, Dosemeci M, Zaebst D, Pottern LM. Exposure Assessment for a Study of Workers Exposed to Acrylonitrile. III: Evaluation of Exposure Assessment Methods. ACTA ACUST UNITED AC 1996. [DOI: 10.1080/1047322x.1996.10389418] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Marsh GM, Stone RA, Esmen NA, Henderson VL, Lee KY. Mortality among chemical workers in a factory where formaldehyde was used. Occup Environ Med 1996; 53:613-27. [PMID: 8882119 PMCID: PMC1128558 DOI: 10.1136/oem.53.9.613] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVES An independent and updated historical cohort mortality study was conducted among chemical plant workers to investigate further an association between exposures to formaldehyde and particulates and cancers of the nasopharynx and lung reported in an earlier National Cancer Institute study of the same plant. METHODS Subjects were 7359 workers who were first employed between 1941 and 1984 in a factory in Wallingford, Connecticut where formaldehyde was used. Vital status was determined on 31 December 1984 for 96% of the cohort and death certificates were obtained for 93% of 1531 known deaths. Exposures of individual workers were estimated quantitatively for formaldehyde, product particulates, and non-product particulates, and qualitatively for pigment. Statistical analyses focused on 6039 white men in 1945-84. Cohort data that could not have been included in the National Cancer Institute study were also analysed separately. RESULTS Mortality among long term workers (employed > or = 1 y) was generally similar to or more favourable than that of the general population, and there was little evidence of a relation between either rates of lung cancer or standardised mortality ratios (SMRs) and several measures of exposure to formaldehyde, particulates, and pigment. For several causes including lung cancer, death rates among short term workers (employed < 1 y) were significantly increased. Short term workers did not seem to differ from long term workers for the exposures considered. Among all white men, a significant SMR of 550 (local comparison) for nasopharyngeal cancer (NPC) was based on the same four index cases identified in the earlier study of this plant. Only one case of nasopharyngeal cancer had any appreciable exposure to formaldehyde. No new cases of nasopharyngeal cancers were found among the cohort data that could not have been included in the National Cancer Institute study--that is, extended observation time and additional study members. CONCLUSIONS Among workers employed for at least one year, this study provides little evidence that the risk of lung cancer is associated with exposure to formaldehyde alone or in combination with particulates or pigment. The significant increases in both the rates and SMRs for lung cancer seem to be primarily a phenomenon of short term workers, but the possibility remains that unmeasured occupational or non-occupational factors may have played a part.
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Affiliation(s)
- G M Marsh
- Department of Biostatistics, University of Pittsburgh, PA 15261, USA
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Seixas NS, Checkoway H. Exposure assessment in industry specific retrospective occupational epidemiology studies. Occup Environ Med 1995; 52:625-33. [PMID: 7489051 PMCID: PMC1128326 DOI: 10.1136/oem.52.10.625] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Quantitative estimation of exposure for occupational epidemiology studies has received increasing attention in recent years and, as a result, a body of methodological literature has begun to take form. This paper reviews the generic issues in the methodology of exposure assessment, particularly methods for quantitative retrospective assessment studies. A simple framework, termed an exposure data matrix (EDM), for defining and analysing exposure data is proposed and discussed in terms of the definition of matrix dimensions and scales. Several methods for estimation, interpolation, and extrapolation, ranging from subjective ratings to quantitative statistical modelling are presented and discussed. The various approaches to exposure assessment based on the EDM concept are illustrated with studies of lung disease among coal miners and other dust and chemically induced chronic occupational diseases. The advantages of validated statistical models are emphasised. The importance of analysis and control of errors in exposure assessments, and integration of the exposure assessment and exposure-response processes, especially for emerging occupational health issues, is emphasised.
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Affiliation(s)
- N S Seixas
- Department of Environmental Health, University of Washington, Seattle 98195-7234, USA
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Stewart PA, Stewart WF. Occupational case-control studies: II. Recommendations for exposure assessment. Am J Ind Med 1994; 26:313-26. [PMID: 7977405 DOI: 10.1002/ajim.4700260305] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Obtaining valid and reliable quantitative exposure estimates is a significant challenge in community-based case-control studies in part, because industrial hygiene monitoring data are usually not available and detailed information on the job and work environment is usually not systematically obtained or assessed. To improve the quality and credibility of disease risk information obtained from occupational case-control studies, we recommend that standardized exposure assessment methods be used to derive quantitative exposure estimates. We identify sources of variation inherent to the assessment process, including: the quality of the information reported on the job, industry, activities, and materials; the industrial hygienist's familiarity with the reported job/industry; the probability that the job/industry was exposed, which depends on plant preferences for particular substances, on process technology, and on customer specifications; and variability in workplace characteristics. To improve the reliability of estimating job-related exposures both within and between studies, we recommend that the epidemiologic analyses be conducted with and without data rated to be of poor quality; that contact be made with experts when the study industrial hygienist is unfamiliar with the manufacturing process in question; that existing data bases be used to estimate the probability of exposure; that a data base be developed that describes manufacturing processes; and that explicit criteria based on industrial hygiene principles be used to evaluate workplace characteristics. In addition, a procedure is described for deriving quantitative exposure estimates by using a reference scale of frequently monitored jobs with their associated mean exposure levels. Areas of research are identified to improve exposure assessment in community-based case-control studies.
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Affiliation(s)
- P A Stewart
- Environmental Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892
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Shore RE, Iyer V, Altshuler B, Pasternack BS. Use of human data in quantitative risk assessment of carcinogens: impact on epidemiologic practice and the regulatory process. Regul Toxicol Pharmacol 1992; 15:180-221. [PMID: 1626069 DOI: 10.1016/0273-2300(92)90049-f] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Epidemiologic data are increasingly being used to assess cancer risk from chemicals as their value is recognized and as more and better studies become available. Weight-of-evidence approaches are now available for classifying the experimental and epidemiological evidence regarding human carcinogenicity. When the human data are extensive and of good quality, they should be given substantial weight in assessing risk. Both the positive and the negative epidemiologic data should be used in a quantitative risk assessment (QRA), because only then can an unbiased risk assessment be derived. Good-quality epidemiological studies are those with sound methodology, lack of bias, long enough follow-up times to observe a carcinogenic response, adequate exposure information, and dose-response information. Before a lack of carcinogenicity can be inferred, it is essential that the exposures be of substantial duration and intensity, and that the number of exposed persons be reasonably large. Epidemiologists need to give more attention to exposure assessment, because lack of quantitative exposure information is often the limiting factor that prevents the use of epidemiologic data in QRA. Development of methods to estimate historical workplace exposure intensities from surrogate industrial hygiene variables should receive high research priority, since they have the potential to increase the usefulness in QRA of many epidemiologic studies that have limited exposure information. Several frequently used surrogates for exposure measurements have limitations or pitfalls in their use. In particular, the use of "ever/never" exposed has a large potential to produce falsely negative results by means of a "dilution" effect, especially in the common case where the exposure distribution is skewed. Duration of exposure (rather than duration x intensity) may also give misleading results. There is little information to suggest that synergistic exposures to multiple toxicants in an industrial environment are likely to invalidate QRAs, probably because few studies have identified a group of workers with major workplace exposures to multiple carcinogens that cause the same type of cancer. Most of the interactive effects which have been identified to date are between smoking and some occupational carcinogen, so this possibility needs careful evaluation for smoking-related diseases. It is important to evaluate dose-response gradients in a QRA to obtain maximum precision and accuracy in the resulting risk coefficient. The analysis should take into account an appropriate cancer induction period. Various methods to account for cancer induction times are compared; those that incorporate a lag period or model the induction-time distribution are superior to other methods.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R E Shore
- Institute of Environmental Medicine, New York University Medical Center, New York 10010-2598
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Abstract
Exposure data may be inadequate mainly for two reasons; they may not comply with a reasonable exposure-effect model or they may be biased. In the use of historical data it is essential to keep track of what the data were supposed to mean when collected in the first place. Most measurements of air contaminants in work places are probably carried out to establish compliance or non-compliance with limit values. Sometimes measurements are also made to evaluate control measures. Unfortunately, measurement data acquired in this way may have very little to do with the true average exposure of employees. The influence of trends and variations in production on the exposure level is substantial. This influence is similar and coincidental in widely different industries. In addition the variations attributed to production levels, there can be important variations due to season.
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Affiliation(s)
- U Ulfvarson
- Department of Work Science, Royal Institute of Technology, Stockholm, Sweden
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Stewart PA, Lee JS, Marano DE, Spirtas R, Forbes CD, Blair A. Retrospective cohort mortality study of workers at an aircraft maintenance facility. II. Exposures and their assessment. BRITISH JOURNAL OF INDUSTRIAL MEDICINE 1991; 48:531-537. [PMID: 1878309 PMCID: PMC1035414 DOI: 10.1136/oem.48.8.531] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Methods are presented that were used for assessing exposures in a cohort mortality study of 15,000 employees who held 150,000 jobs at an Air Force base from 1939 to 1982. Standardisation of the word order and spelling of the job titles identified 43,000 unique job title organisation combinations. Walkthrough surveys were conducted, long term employees were interviewed, and available industrial hygiene data were collected to evaluate historic exposures. Because of difficulties linking air monitoring data and use of specific chemicals to the departments identified in the work histories, position descriptions were used to identify the tasks in each job. From knowledge of the tasks and the chemicals used in those tasks the presence or absence of 23 chemicals or groups of chemicals were designated for each job organisation combination. Also, estimates of levels of exposure were made for trichloroethylene and for mixed solvents, a category comprising several solvents including trichloroethylene, Stoddard solvent, carbon tetrachloride, JP4 gasoline, freon, alcohols, 1,1,1-trichloroethane, acetone, toluene, methyl ethyl ketone, methylene chloride, o-dichlorobenzene, perchloroethylene, chloroform, styrene, and xylene.
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Stewart PA, Blair A, Dosemeci M, Gomez M. Collection of Exposure Data for Retrospective Occupational Epidemiologic Studies. ACTA ACUST UNITED AC 1991. [DOI: 10.1080/1047322x.1991.10387881] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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27
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A study of exposure, health effects and mortality of workers engaged in the manufacture and formulation of the insecticides aldrin and dieldrin. Toxicol Lett 1991. [DOI: 10.1016/0378-4274(91)90002-n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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28
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Weinkam JJ, Rosenbaum WL, Sterling TD. A practical approach to estimating the true effect of exposure despite imprecise exposure classification. Am J Ind Med 1991; 19:587-601. [PMID: 2053577 DOI: 10.1002/ajim.4700190504] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Accurate information on actual exposure to some possibly toxic agent usually is not available in long-term occupational studies. Any strategy for assigning exposure levels or categories necessarily results in misclassification, where some individuals classified as exposed have no real exposure and some individuals classified as not exposed have some exposure to the agent. Both misclassification errors serve to reduce the estimate of risk associated with exposure. The question arises, "How much does the true risk depart from the observed estimate given an assumed level of misclassification?" This paper quantifies the effect of such misclassification on several forms of standardized risk ratios. Our results express the true risk as a function of the apparent risk based on imprecise exposure classification and parameters representing the proportion of each of the groups that are correctly classified. In any practical situation, the apparent risk can be computed based on whatever classification scheme is being used. On the other hand, the proportions of the imprecisely classified groups actually exposed cannot. However, the investigator may have information or may make assumptions for likely ranges of values for these proportions. Given the apparent risk, estimated true risks can be calculated and plotted or represented in tabular form as a function of the proportions of actual exposure. The resulting graph or table enables the investigator to read off the range of possible true risk values based on what he is prepared to believe or what other information indicates about the range of proportions of misclassified subjects. For instance, results for a typical value of apparent risk of 1.8 show that the true risk may be twice the apparent risk with only 23% misclassification in each exposure group. The value of the true risk that would be necessary to be consistent with a given apparent risk increases rapidly as the extent of misclassification increases. We also show that, if the extent of misclassification is large, the apparent relative risk is close to 1.0 regardless of the actual value of the true risk. Therefore, a small apparent risk does not necessarily indicate that there is no occupational hazard.
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Affiliation(s)
- J J Weinkam
- Faculty of Applied Sciences, School of Computing Science, Simon Fraser University, Burnaby, British Columbia, Canada
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Dosemeci M, Stewart PA, Blair A. Three Proposals for Retrospective, Semiquantitative Exposure Assessments and their Comparison with the other Assessment Methods. ACTA ACUST UNITED AC 1990. [DOI: 10.1080/1047322x.1990.10389588] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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30
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Gérin M. Recent approaches to retrospective exposure assessment in occupational cancer epidemiology. Recent Results Cancer Res 1990; 120:39-49. [PMID: 2236877 DOI: 10.1007/978-3-642-84068-5_3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- M Gérin
- Département de Médecine du Travail et d'Hygiène du Milieu, Faculté de Médecine, Université de Montréal, Québec, Canada
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Wong O. An industry wide mortality study of chemical workers occupationally exposed to benzene. II. Dose response analyses. BRITISH JOURNAL OF INDUSTRIAL MEDICINE 1987; 44:382-95. [PMID: 3606967 PMCID: PMC1007839 DOI: 10.1136/oem.44.6.382] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The data presented in this paper show statistically significant dose response relations between cumulative exposure to benzene (ppm-months) and mortality from both all lymphopoietic cancer combined and leukaemia. Chemical workers with a cumulative exposure to benzene of at least 720 ppm-months experienced a relative risk of 3.93 for lymphatic and haematopoietic cancer when compared with workers with no occupational exposure. The dose response relation between cumulative exposure and non-Hodgkin's lymphopoietic cancer was of borderline statistical significance (p = 0.06). No dose response relation was detected for any other causes of death.
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Stewart PA, Blair A, Cubit DA, Bales RE, Kaplan SA, Ward J, Gaffey W, O'Berg MT, Walrath J. Estimating Historical Exposures to Formaldehyde in a Retrospective Mortality Study. ACTA ACUST UNITED AC 1986. [DOI: 10.1080/08828032.1986.10390441] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Ulfvarson U. Limitations to the use of employee exposure data on air contaminants in epidemiologic studies. Int Arch Occup Environ Health 1983; 52:285-300. [PMID: 6642692 DOI: 10.1007/bf02226895] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The bias in the estimation of uptake of substances in the human body from exposure data gathered from ordinary workplace check-ups is discussed. It is concluded that most exposure is probably overrated. This means that exposure limits based on these premises will tend to be too high. To counteract this bias in the future, filed exposure data should be accompanied with information on a number of circumstances which prevailed at the sampling.
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Dement JM, Harris RL, Symons MJ, Shy CM. Exposures and mortality among chrysotile asbestos workers. Part I: exposure estimates. Am J Ind Med 1983; 4:399-419. [PMID: 6846338 DOI: 10.1002/ajim.4700040303] [Citation(s) in RCA: 78] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
A detailed study of plant processes and dust control methods over the period 1930-1975 was conducted in an asbestos textile plant processing chrysotile. Linear statistical models for reconstructing historic dust exposure levels, taking into account textile processes, dust control measures, and job assignments, were developed. Parameters of these statistical models were estimated using 5,952 industrial hygiene sampling measurements covering the period 1930-1975. For most textile operations, exposure levels were significantly reduced by about 1940, when most engineering dust control measures were in place. Results of the exposure estimates indicated "precontrol" exposure levels to range from 3 to 78 fibers/cc with typical levels well above 10 fibers/cc. After textile operations were provided with dust control measures, estimated exposure levels ranged from 3 to 17 fibers/cc and were usually in the range of 5 to 10 fibers/cc. These exposure estimates were combined with an assessment of mortality among workers at this plant to investigate exposure-response relationships. Exposure-response results are presented in the companion manuscript in this volume.
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