Biomedical subjects
J Dement
Publications and source records attributed to J Dement.
Three perspectives on work-related injury surveillance systems.
This paper reviews surveillance approaches for occupational injuries and evaluates three emerging methodologies for the enhancement of work-related injury surveillance: (1) narrative data analysis, (2) data set linkage, and (3) comprehensive company-wide surveillance systems. All three methods are the result of new applications of computer hardware and software that have apparent strengths and limitations. A major strength is the improved description of work exposures and related injuries leading to better understanding of injury etiology. This understanding, however, is limited by the data quality and completeness entered on records at the time of the injury. We recommend (1) more widespread inclusion of narrative text in databases, analyses of which can be a valuable supplement to injury coded data; (2) the increased use of data set linkage studies to combine injury and work-history data; and (3) the development of comprehensive company-wide surveillance systems to expedite the use of epidemiologic data for occupational injury prevention activities. Further development of these methods and others is encouraged, especially in light of technological advancements in data capture, analysis and presentation. Only through such efforts can we best apply epidemiologic principles to preventing injuries in the workplace.
Exposure and mineralogical correlates of pulmonary fibrosis in chrysotile asbestos workers.
OBJECTIVES: The relation between lifetime cumulative exposure to asbestos, pathological grade of pulmonary fibrosis, and lung burden of asbestos at death, was explored in a necropsy population of former workers in a chrysotile asbestos textile plant in South Carolina. METHODS: Estimates of cumulative, mean, and peak exposures to asbestos were available for 54 workers. Necropsy records and lung tissue samples were obtained from hospital files. Matched control cases were selected from consecutive necropsies performed at the same hospitals. The extent and severity of pulmonary fibrosis was graded on tissue sections. Mineral fibres in lung tissue were characterised by transmission electron microscopy combined with x ray spectroscopy. RESULTS: A significant positive correlation (r = 0.67, P < 0.0001) was found between lifetime cumulative exposure to asbestos and total lung burden of asbestos fibres. This relation was also found for the individual types of asbestos associated with the exposure: chrysotile and tremolite. Pulmonary fibrosis was correlated with both cumulative exposure to asbestos (r = 0.60, P < 0.01) and the concentration of asbestos fibres in the lung (r = 0.62, P < 0.0001). The concentration of tremolite fibres in the lung provided a better estimate of lung fibrosis than did the concentration of chrysotile. Asbestosis was usually present in asbestos textile workers with more than 20 fibre-years cumulative exposure. The lengths and aspect ratios of chrysotile asbestos, but not amphibole asbestos, were greater in the lungs of asbestos fibre workers than in the control population. Textile workers with lung cancer had significantly greater cumulative exposures and fibrosis scores than workers without lung cancer. CONCLUSIONS: Both cumulative exposure to asbestos and lung fibre burden are strongly correlated with severity of asbestosis. The data also support the hypothesis that the high prevalence of asbestosis and lung cancer in this population resulted from exposure to long fibres of chrysotile asbestos in the workplace.
Exposure-response analysis of risk of respiratory disease associated with occupational exposure to chrysotile asbestos.
OBJECTIVES: To evaluate alternative models and estimate risk of mortality from lung cancer and asbestosis after occupational exposure to chrysotile asbestos. METHODS: Data were used from a recent update of a cohort mortality study of workers in a South Carolina textile factory. Alternative exposure-response models were evaluated with Poisson regression. A model designed to evaluate evidence of a threshold response was also fitted. Lifetime risks of lung cancer and asbestosis were estimated with an actuarial approach that accounts for competing causes of death. RESULTS: A highly significant exposure-response relation was found for both lung cancer and asbestosis. The exposure-response relation for lung cancer seemed to be linear on a multiplicative scale, which is consistent with previous analyses of lung cancer and exposure to asbestos. In contrast, the exposure-response relation for asbestosis seemed to be nonlinear on a multiplicative scale in this analysis. There was no significant evidence for a threshold in models of either the lung cancer or asbestosis. The excess lifetime risk for white men exposed for 45 years at the recently revised OSHA standard of 0.1 fibre/ml was predicted to be about 5/1000 for lung cancer, and 2/1000 for asbestosis. CONCLUSIONS: This study confirms the findings from previous investigations of a strong exposure-response relation between exposure to chrysotile asbestos and mortality from lung cancer, and asbestosis. The risk estimates for lung cancer derived from this analysis are higher than those derived from other populations exposed to chrysotile asbestos. Possible reasons for this discrepancy are discussed.
Fibrous glass and cancer.
Some argue that fibrous glass (glass wool) should not be considered as a likely human carcinogen and hence should not be listed in the Seventh Annual Report on Carcinogens (ARC) prepared by the National Toxicology Program (NTP) and mandated by the U.S. Congress. In examining this issue, data from both laboratory experiments (animal studies) and epidemiologic studies (human data) are reviewed with the results evaluated according to the criteria established by the International Agency for Research on Cancer (IARC) and adopted in slightly modified form by the NTP for classifying substances as human carcinogens or likely human carcinogens. From our comprehensive review of the available information, we conclude that fibrous glass materials are carcinogenic, and in view of the NTP and IARC definitions should be listed in the ARC. Our review then examines the carcinogenic potency of glass fibers to humans in comparison with asbestos fibers and concludes that on a fiber-per-fiber basis, glass fibers may be as potent or even more potent than asbestos. The implications of these findings are then presented for regulatory purposes in the occupational setting.
Design and conduct of occupational epidemiology studies: III. Design aspects of case-control studies.
Currently available approaches for the design of occupational case-control studies are reviewed. An accompanying paper reviews methods of analysis. We commence by drawing a distinction between cohort-based and registry-based studies. Methods for selecting cases and controls are then reviewed, including cumulative incidence and incidence density sampling, matching, sources of controls, and issues in control selection. Finally, the advantages and disadvantages of the case-control approach are summarized.
Design and conduct of occupational epidemiology studies: IV. The analysis of case-control data.
This paper reviews the basic methods of analysis of data from case-control studies. The standard analytic methods are outlined first for a single stratum. The discussion is then extended to stratified analysis, multiple exposure levels, and analyses allowing for disease induction and latency periods. Finally, logistic regression is discussed as an extension of the more basic forms of analysis. The methods are illustrated with data from a study of lung cancer among asbestos textile plant workers.
Training under Superfund.
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Exponential models for analyses of time-related factors, illustrated with asbestos textile worker mortality data.
In any study based on an occupational cohort, it is important to consider the variation in risk factors over time. Cumulative exposure is the most important time-related factor for exposure-response analyses, whereas other time-related factors such as age at risk, year at risk, and length of follow-up may be confounders and effect modifiers. This paper examines the family of exponential models which can be used for time-related analyses of studies based on an occupational cohort. Analyses using Poisson regression, the proportional hazards model, and the logistic model are presented, and their interrelationships explored. These models are illustrated with data from a cohort study of lung cancer mortality among asbestos textile plant workers. All three approaches yielded similar effect estimates. In particular, Poisson regression and the proportional hazards model yielded very similar findings, but Poisson regression has some conceptual and computational advantages.
Salud Ocupacional.
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