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Tuesday, 16 July 2013

Cancer asbestos exposure Wallpaper Photos Pictures Pics Images 2013

Cancer asbestos exposure Biogarphy

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Although tobacco smoking affects the total lung cancer risk, this effect does not detract from the risk of lung cancer attributable to asbestos exposure. No attempt has been made in this report to apportion the relative contributions of asbestos exposure and tobacco smoking
Prevention and screening
Screening of asbestos-exposed populations can be carried out for practical and scientific purposes. There are 4 goals of screening: (i) to identify high risk groups, (ii) to target preventive actions, (iii) to discover occupational diseases, and (iv) to develop improved tools for treatment, rehabilitation and prevention. Screening should aim to prevent asbestos-related diseases and therefore lead to gained healthy years of life among the screened or among those in similar risk situations. The benefits to the individual person should be viewed cautiously. The substantial morbidity and mortality related to asbestos exposure argue for continued efforts to increase the preventive power of screening.
Any screening for purely scientific purposes requires appropriate methods and criteria (eg, low cost and high predictive value). Before a screening program is initiated, the ethical, financial, and legislative aspects need to be considered. These aspects may include patient notification, data protection, allocation of costs, and follow-up of identified abnormalities. In addition, provision should be made for epidemiologic analyses, quality control, primary and secondary prevention, and the assessment of program effectiveness.
As tools for screening, questionnaires and personal interviews should include items related to asbestos exposure, smoking, and other contributing factors. Questionnaires should preferably be validated for smoking habits and occupational histories. When possible, questionnaires should be applied nationally to permit epidemiologic analysis of the results.
Chest X-ray examinations can include frontal and lateral roentgenograms. Appropriate lung function tests can measure respiratory flow volumes and rates. In spirometry, attention should be given to careful calibration, acceptable performance efforts, and reproducibility.
The prevention strategies of asbestos-related diseases can be based on the identification of exposure sources and exposed people. There are 3 main targets for prevention: (i) an individual worker, (ii) a selected group of workers, and (iii) the work environment. At the level of the individual worker, the tools for prevention include health education and the introduction of safe work practices, the avoidance of tobacco smoking, and careful follow-up of health by surveillance. The group level methods are in part the same as at the individual level (ie, health information, education, and recommendations including the use of respiratory protective equipment).
The work environment is the most important target for preventive measures, starting from avoiding the use of asbestos, carefully controlling dust emissions using wet techniques, and controlling passive smoking at the workplace. Many countries have prohibited the use of asbestos, but there are still substantial amounts of asbestos in consumer products and in buildings that can expose workers in repair and removal work. Some countries have permitted asbestos work only under special authorization, training, and protective measures.
From the knowledge on potential exposures to asbestos, high-risk populations can be identified among persons exposed 10 or more years ago. The availability of registers—union, workers` compensation, and employment records—can be explored for this purpose.
Subjects can be assigned to subgroups for intervention or screening as defined by their risk (eg, the current risk of lung cancer and risk projected to given time windows in the future). Criteria for inclusion in each intervention or screening group should be established in the study protocol. Subsequently, the members of each subgroup can serve as separate targets for group-based and individual intervention programs.
Protocols for intervention should be designed in such a way that they serve each subject and subgroup optimally in terms of promoting individual health and the early detection of asbestos-related diseases. Data on these subgroups can also form a basis for more specific studies of disease outcome or various biomarkers. Identified abnormalities should be followed by the best clinical and occupational practices.
Reserach needs
There are several issues that still require clarification and further study. The following list of recommendations and future directions is not intended to be exhaustive.
• Improvement in the assessment and quantification of exposure to asbestos, to include specific worker groups, with collation of data and the development of an international standardized protocol for the assessment of exposure.
• Further analysis of job-exposure data and further studies on asbestos fiber burdens in tissue in relation to various asbestos-related disorders.
• Studies on chrysotile fiber burdens in lung tissue relative to the risk of lung cancer (also to include experimental investigations).
• Lung cancer relative to the lung tissue burdens of mineral fibers other than asbestos (eg, refractory ceramic fibers and zeolites).
• Improvement of the ILO system for the radiological diagnosis and categorization of pleural abnormalities.
• Development of a standardized system for the reporting of HRCT scans of asbestos-related disorders, analogous to the ILO system.
• Studies on the specificity of lesions of the pleura visualized by CT as markers of asbestos exposure and studies on the prognosis of diffuse pleural abnormalities.
• Improvement in ultrasound imaging of the pleura.
• Development of new digital imaging techniques for the investigation of asbestos-related diseases.
• Standardization of the approach to lung crepitations with the use of special auditory devices.
• Investigation of mesothelioma as a potential outcome of exposure to mineral fibers other than asbestos—such as refractory ceramic fibers—to include experimental studies and a series of mesothelioma patients without exposure to asbestos or erionite, supported by lung tissue fiber analysis.
• Multicenter studies on biomarkers for the detection of early asbestos diseases and the assessment of the response to new treatment modalities.
• Investigation of asbestos-associated tumors other than lung cancer and mesothelioma (eg, laryngeal carcinoma and renal carcinoma).
• Further studies on the effectiveness of screening programs.
Participants: Douglas W. Henderson (Flinders Medical Centre, Australia), Jorma Rantanen (Finnish Institute of Occupational Health, Finland), Scott Barnhart (University of Washington, United States), John M Dement (Duke University Medical Center, United States), Paul De Vuyst (Cliniques Universitaires de Bruxelles, Hopital Erasme, Belgium), Gunnar Hillerdal (Karolinska Hospital, Sweden), Matti S Huuskonen (Finnish Institute of Occupational Health, Finland), Leena Kivisaari (Helsinki University Central Hospital, Finland), Yukinori Kusaka (Fukui Medical School, Japan), Aarne Lahdensuo (Tampere University Hospital, Finland), Sverre Langård (The National Hospital, Norway), Gunnar Mowe (Department of Social Insurance Medicine, University of Oslo, Norway), Toshiteru Okubo (University of Occupational and Environmental Health, Japan), John E Parker (National Institute for Occupational Safety and Health, United States), Victor L Roggli (Duke University Medical Center, United States), Klaus Rödelsperger (Justus-Liebig University, Germany), Joachim Rösler (Justus-Liebig University, Germany), Antti Tossavainen (Finnish Institute of Occupational Health, Finland), Hans-Joachim Woitowitz (Justus-Liebig University, Germany).
The article by Mollo and coworkers[1] examines the criteria for attribution of lung cancers to asbestos exposure, suggesting that the number of asbestos-related lung cancers in Italy might be underestimated. Their review of 924 consecutive lobectomies and pneumonectomies for lung cancer in northwest Italy included light microscopic asbestos body counts for asbestos body concentration in addition to histologic examination for asbestosis and asbestos bodies. Their interpretation is that 6% of the lung cancers in their series are attributable to asbestos exposure because of histologic diagnosis of asbestosis. However, they also conclude that another 0.5% of their cases had interstitial fibrosis without asbestos bodies on histologic section but an elevated asbestos body concentration on digestion study. Mollo and coworkers[1] raise the possibility that these cases also may be asbestos-related lung cancers.
The great majority of lung cancers are caused by tobacco smoke, but a minority of lung cancers are caused by asbestos exposure, virtually always in association with tobacco smoke exposure. One reason to identify the lung cancers caused by asbestos exposure is for establishing occupational and public health policies regarding asbestos or for investigation of lung cancer pathogenesis that, in turn, may provide a basis for new lung cancer therapies. In the individual case, the major reason to determine whether asbestos contributed to the development of a lung cancer is for purposes of compensation, which, in the United States, often is through litigation. Accurate identification of patients deserving compensation is also a primary concern of Mollo and coworkers.[1]
Before proceeding, we should remind ourselves that risk of a disease and actually having a disease due to that risk are two different things. This is a rather simple observation, but it is important if one is addressing etiology of a disease. Risk has to do with populations studied for relative likelihood of disease due to a common factor not present in a control population. Any membes of the at-risk population may not develop the disease under investigation and may have many individual factors that may modify the risk from the studied factor, be a confounding factor for the risk factor under study, or put them at risk for other diseases. An example can be found with the relationship of tobacco smoke to lung cancer. On the one hand, about 10% of tobacco smokers develop lung cancer as a result of their tobacco smoking. This is a considerably greater risk than the population of never smokers who have a background risk of lung cancer that is less than 1%, probably considerably so. On the other hand, even though most smokers do not develop lung cancer, about 90% of all lung cancers are caused by tobacco smoking.[2]
A smoker has a risk of lung cancer because of smoking that is much greater than that of individuals who have never smoked, but, even so, that person has a fairly good chance of not developing a lung cancer based on the risk seen in the population of all smokers. If that smoker does develop lung cancer, the lung cancer will be caused by the tobacco smoke and could have been avoided if the person had never smoked. If we look closer at the population of smokers with a risk of lung cancer, we can identify criteria that select those with the most risk of developing lung cancer based on the cumulative dose of tobacco smoke that they are exposed to and to factors of individual susceptibility.[3-5] However, the causal association between tobacco smoke and lung cancer is so strong that we seldom do more than obtain a smoking history and do not require a detailed analysis of corroborating evidence to link a smokers lung cancer to tobacco smoke in the vast majority of cases.
As rightly pointed out by Mollo et al,[1] many studies examine only the risk of lung cancer for asbestos-exposed populations and do not investigate the criteria for ascribing an individuals lung cancer to asbestos exposure. Studies have demonstrated that certain occupations and populations of workers commonly have higher asbestos exposures and greater risks of asbestos-related diseases than others.[6,7] For compensation, however, a worker must substantiate the individual claim.
Unlike the situation with tobacco smoke and lung cancer, at least 2 factors necessitate clearly defined criteria for linking a lung cancer to asbestos in the individual case. First, most workers with asbestos exposures will not develop lung cancers, indicating that there are differences between workers and/or their asbestos exposures in regard to lung cancer risk. Second, as already noted, tobacco smoke is the primary cause of lung cancers and is sufficient by itself to cause the great majority of lung cancers. As a result, tobacco smoke exposure is a powerful confounding factor in most cases of lung cancers in workers with asbestos exposures.
In regard to the first factor, studies indicate that everyone is exposed to background levels of asbestos in the ambient air. Studies have shown that members of the general (nonoccupationally exposed) population have tens of thousands to hundreds of thousands of asbestos fibers in each gram of dry lung tissue, which translates into millions of fibers and tens of thousands of asbestos bodies in every persons lungs.[6,7] However, the general population does not have an increased risk of asbestos-related lung cancers despite these background levels. Individuals with occupational exposures to asbestos have tissue burdens of asbestos that are higher than background levels. A number of studies have failed to show an increased risk of lung cancer in populations with comparatively low levels of asbestos exposure.[8] Therefore, the level of cumulative asbestos exposure, reported as asbestos dose or asbestos tissue burden, must be one of the factors that determine lung cancer risk. However, considering that millions of workers have had occupational exposure to asbestos and that only some of these individuals develop lung cancer, there must be other factors that separate those who develop asbestos-related lung cancer from those who do not. As with other types of exposures that carry risk of disease, including tobacco smoke, factors related to individual susceptibility also must have a role in whether an asbestos-related lung cancer develops in an individual once the requisite asbestos tissue burden is present.
The second factor creating a need for attribution criteria is the confounding factor of tobacco smoke. As previously stated, current or former active tobacco smoking accounts for 90% of all lung cancers in the United States. Secondhand environmental smoke accounts for a sizable percentage of the remainder, for a total of more than 150,000 new lung cancers in the United States each year due to tobacco smoke.[2] In contrast, asbestos is estimated to account for 2% to 5%, or about 3,400 to 8,500 new lung cancers in the United States each year.[9,10] Thus, there are anywhere from 20 to 50 tobacco-related lung cancers for every asbestos-related lung cancer. Tobacco smoke contains some 4,000 to 5,000 chemicals, including many known and suspected carcinogens, both initiators and promoters. As a result, tobacco smoke is sufficient by itself to cause the great majority of lung cancers without the additional contribution of any other agent.
Virtually all workers with lung cancers and asbestos exposure also are tobacco smokers or former smokers and, therefore, have 2 potential etiologic agents for their lung cancers. There is a synergistic effect of asbestos with tobacco smoke, and both of these potential etiologic agents are responsible for lung cancers in some workers. Other workers may have had asbestos exposure, but their lung cancers are due exclusively to their tobacco smoke exposure, like the overwhelming majority of patients with lung cancer in the general population. Specific criteria are needed to separate workers with purely tobacco-related lung cancers from those with lung cancers attributable to both tobacco and asbestos.
As noted, no increased risk of asbestos-related lung cancer from background levels of asbestos has been demonstrated in the general population, and a number of studies have failed to demonstrate an increased risk of lung cancer in populations with increased but comparatively low levels of asbestos exposure.[6-8] Various tissue burden studies report thousands of asbestos bodies and millions of asbestos fibers per gram of dried lung tissue in asbestos workers with lung cancer. In industrial hygiene terms, cumulative asbestos exposure of 25 fibers per cubic centimeter yea

Cancer asbestos exposure Wallpaper Photos Pictures Pics Images 2013