Mesotheliomas - Asbestosis Research - Threats

"Exposure to asbestos causes cellular damage, leading to asbestosis, bronchogenic carcinoma, and mesothelioma in humans. The pathogenesis of asbestos-related diseases is complicated and still poorly understood.

Studies on animal models and cell cultures have indicated that asbestos fibers generate reactive oxygen and nitrogen species (ROS/RNS) and cause oxidation and/or nitrosylation of proteins and DNA. The ionic state of iron and its ability to be mobilized determine the oxidant-inducing potential of pathogenic iron-containing asbestos types. In addition to their capacity to damage macromolecules, oxidants play important roles in the initiation of numerous signal transduction pathways that are linked to apoptosis, inflammation, and proliferation.

There is strong evidence supporting the premise that oxidants contribute to asbestos-induced lung injury; thus, strategies for reducing oxidant stress to pulmonary cells may attenuate the deleterious effects of asbestos."

"This paper outlines the asbestos hazard in Scotland and draws upon a systematic oral history project to analyze from the workers' perspective the nature of exposure, the limitations of government regulatory initiatives, and the ramifications of contracting asbestos-related diseases for sufferers and their families.

Current issues are investigated, stressing the agency of workers, trade unions, sympathetic local councils, and, especially, the victims' pressure groups. The occupational and environmental health threats of asbestos in Scotland remain significant, although recent E.U.- and U.K.-based decisions to ban further use of asbestos together with active campaigning by local activist groups have helped to reduce them.

Mesothelioma mortality rates remain high, due to historic exposures, and much work remains to be done to reduce the number and plight of asbestos-exposed workers."

"Asbestos-related neoplastic and nonneoplastic diseases of the lungs and pleura range from pleural effusion and pleural plaques to lung cancer and malignant mesothelioma. Pleural effusions are typically hemorrhagic exudates of mixed cellularity but do not typically contain asbestos bodies. The classic distribution of pleural plaques seen on chest radiographs is the posterolateral chest wall between the seventh and tenth ribs, lateral chest wall between the sixth and ninth ribs, the dome of the diaphragm, and the mediastinal pleura.

Computed tomographic (CT) findings support this distribution but also show anterior and paravertebral plaques not well shown at chest radiography. Imaging features of diffuse pleural thickening include a continuous sheet, often involving the costophrenic angles and apices, that rarely calcifies. The typical CT features of round atelectasis are of a round or oval mass that abuts the pleura, a "comet tail" of bronchovascular structures going into the mass, and thickening of the adjacent pleura. Features of asbestosis on chest radiographs include ground-glass opacification, small nodular opacities, "shaggy" cardiac silhouette, and ill-defined diaphragmatic contours. CT, however, is more sensitive in their detection.

Chest radiography in patients with malignant mesothelioma may show an effusion, pleural thickening, and as the tumor progresses, a more lobulated outline. CT can help identify the disease in its early stages. Asbestos-related cancers can occur anywhere in the lungs. Recognition of the clinical, radiologic, and pathologic features of these diseases will be important for some years to come."

"In spite of hard epidemiological and clinical evidence associating asbestos fibre with asbestosis and cancer, the issue is controversial and likely to remain so. The focus is now shifting to non-occupational exposure, differential risk to various asbestos fibre types and the relatively low level of carinogenicity of the chrysotile form. This creates further space for scientific debate and the opportunity to form a considered opinion. However, the situation may take a worrisome turn if some of these scientific inquiries are used by market forces to their advantage.

A look at the history of corporate activities in asbestos-related research reveals a disturbing trend. Information that was made available, through legal interventions, clearly shows how for half a century the asbestos industry in collaboration with some academic leaders of occupational medicine successfully suppressed evidence against asbestos. In developing countries, extensive and aggressive marketing continues by chrysotile producers, mainly Canadian companies. There is renewed pressure on this part of the world since new use of asbestos has been almost completely discontinued in the developed countries as a result of public pressure and state prohibitions. In this scenario, relaxation of public health control over any form of asbestos should be opposed.

It is extremely dangerous and scientifically untenable to say that chrysotile asbestos can be used without risk. It has been identified as a potent human carcinogen, and remains so. However, some restraint must be exercised while dealing with asbestos that has already been released into the environment. Disturbing it unnecessarily may cause more harm than good."

"Exposures to asbestos and synthetic fibers remain areas of great concern in the field of occupational lung disease. Despite extensive study, the health effects associated with fibers remains an area of substantial controversy. In particular, effects of fibers at relatively low doses, particularly for mesothelioma, remain a matter of evolving opinion, especially when integrated with the divergence of opinion on relative pathogenicity of different fiber types.

Mechanistic studies continue to provide a window into pathogenesis and some hope for understanding dose-response relationships at the lower levels seen in contemporary Western workplaces and the general environment. Changes in clinical assessment based on use of new chest imaging techniques beyond the traditional plain film are also an area of evolution and begin to challenge B-reading as the definitive tool for noninvasive assessment of disease. Public health concerns have to a great extent been transported to the developing world where there is a strong trend toward increased use of asbestos, although it has been virtually eliminated from commerce in most developed countries.

For nonasbestos fibers, the major unsettled issues are their relative potencies as carcinogens for the human lung and mesothelium and the need to sort out the relation between physical and chemical properties of these fibers and their pathogenicity. The recent discovery of "flock worker's lung" due to synthetic fibers once again alerts us to emerging diseases associated with new technologies."

"Asbestos has long been associated with a number of life threatening pulmonary diseases, including asbestosis and mesothelioma.

While the lung is the primary target organ for asbestos toxicity, a number of clinical and experimental studies over the past 30 years have shown that the immune system may also be altered by exposure to asbestos at occupationally relevant concentrations. Whereas early clinical studies generally focused on systemic observations of immune alteration, more recent studies have assessed the immunological changes occurring in the lung, the primary target organ of asbestos.

This review will focus on the investigations that examine the influence of asbestos on systemic and local immunity, as well as the role that the immune system may play in asbestos-related disease."

"Asbestos causes four diseases in humans: Lung fibrosis (asbestosis) follows heavy exposure and, in industrialized countries, is mainly a relic of past working conditions. The risk of pleural fibrosis and plaques is likely to be linearly dependent from time since first exposure and is present for all types of asbestos fibres.

The diagnostic uncertainties regarding pleural plaques and the substantial degree of misclassification make it difficult to precisely estimate the shape of the dose-response relationship. The risk of lung cancer seems to be linearly related to cumulative asbestos exposure, with an estimated increase in risk of 1% for each fibre/ml-year of exposure. All fibre types seem to exert a similar effect on lung cancer risk; a multiplicative interaction with tobacco smoking has been suggested.

Pleural mesothelioma is a malignant neoplasm which is specifically associated with asbestos exposure: the risk is linked with the cubic power of time since first exposure, after allowing for a latency period of 10 years, and depends on the fibre type, as the risk is about three times higher for amphiboles as compared to chrysotile. Environmental exposure to asbestos is also associated with mesothelioma risk."

"Asbestos-induced pleural disease has become the most common manifestation of asbestos exposure. Asbestos has an unusual affinity for the pleural space and leads to plaques, benign effusions, fibrosis, and malignant mesothelioma.

The explanation for its affinity for the pleura may lie in part with new evidence showing that asbestos fibers can accumulate in certain regions of the parietal pleura at higher concentrations than in the lung. With the control of industrial exposures to asbestos, the incidence of this disease should decrease, with the incidence of mesothelioma peaking in the years 2000 to 2020.

Nonetheless, the toxic features of asbestos including shape, chemical composition, and surface characteristics should be understood to avoid toxicity in fibers used to replace asbestos and to know the risks of low level exposures from asbestos currently in our environment."

Mesotheliomas - Asbestosis Research - Threats of Asbestos Exposure Links

Asbestos Case - The documented health threats regarding asbestos are well described.

Asbestos Diseases - Provides diagnosis information and treatment options for the asbestos victims.