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Occupational characteristics of cases with asbestos-related diseases in The Netherlands.

OBJECTIVE: To describe the occupational background of cases with an asbestos-related disease and to present overall mesothelioma risks across industries with historical exposure to asbestos. METHODS: For the period 1990-2000, cases were collected from records held by two law firms. Information on jobs held, previous employers, activities performed and specific products used were obtained from patients themselves or next of kin. Branches of industry and occupations were coded and the likelihood of asbestos exposure was assessed. For each branch of industry, the overall risk of mesothelioma was calculated from the ratio of the observed number of mesothelioma cases and the cumulative population-at-risk in the period 1947-1960. In order to compare mesothelioma risks across different industries, risk ratios were calculated for the primary asbestos industry and asbestos user industries relative to all other branches of industry. RESULTS: In total, 710 mesotheliomas and 86 asbestosis cases were available. The average latency period was approximately 40 yr and the average duration of exposure was 22 yr. Ship building and maintenance contributed the largest number of cases (27%), followed by the construction industry (14%), the insulation industry (12%), and the navy and army, primarily related to ship building and maintenance (5%). In the insulation industry, the overall risk of mesothelioma was 5 out of 100 workers, and in the ship building industry, 1 out of 100 workers. The construction industry had an overall risk comparable with many other asbestos-using industries (7 per 10,000 workers), but due to its size claimed many mesothelioma cases. CONCLUSION: The majority of cases with asbestos-related diseases had experienced their first asbestos exposure prior to 1960. For cases with first asbestos exposure after 1960, a shift was observed from the primary asbestos industry towards asbestos-using industries, such as construction, petroleum refining, and train building and maintenance. Due to the long latency period, asbestos exposure from 1960 to 1980 will cause a considerable number of mesothelioma cases in the next two decades.

Adult↗

Brake mechanics, asbestos, and disease risk.

Health risks posed by inhalable asbestos fibers are known to exist in a variety of industrial and nonindustrial settings. Although early studies described an increased risk of asbestosis, lung cancer, and mesothelioma in asbestos-industry workers, subsequent research revealed the existence of a potential asbestos-related health hazard in nonasbestos industries such as the textile and railroad industries. Brake mechanics and garage workers constitute a large work force with potential exposures to levels of asbestos capable of producing disease. Unfortunately, the health risk faced by these workers has received little attention. This article briefly discusses currently available information on the asbestos health risks of workers in this setting, and highlights the need for further investigations of this occupational group.

Asbestos↗

Chronological assessment of asbestos exposure on cell composition in murine lung.

To elucidate immune pathogenic mechanisms in asbestosis, lung and spleen lymphoid cell populations were analyzed at defined time intervals (1, 2, 3, 6, and 12 weeks during exposure and 4, 24, and 48 weeks post-exposure) in asbestos-exposed and unexposed (control) mice. Polymorphonuclear leukocytes and macrophages were increased in the lung tissue histologic sections of asbestos-exposed mice compared to controls. No consistent changes were observed in percentages of lung or spleen helper, suppressor, or total lymphocyte populations after asbestos exposure. The numbers of B cells (identified by anti-IgG) in minced lung preparations of asbestos-exposed animals were increased after 12 weeks of exposure. There also was an increase in IgG production in asbestos-exposed mice after 12 weeks exposure and at 4 weeks post-exposure with a return to near baseline levels 24 and 48 weeks after initial exposure. Collectively, these studies demonstrate stimulatory effects of inhaled asbestos fibers on B cells and IgG production after 12 weeks of continuous inhalation of asbestos fibers in a dust generation chamber.

Animals↗

Asbestos-related benign disease and cancer: symptoms and treatment.

Long lasting occupational exposure to asbestos dust may cause skin corns, benign pleural effusion, hyaline plaques of the parietal pleura, diffuse thickening of the pulmonary pleura, and asbestosis, i.e. diffuse interstitial pulmonary fibrosis. Malignant disorders include lung cancer and mesothelioma of the pleura, peritoneum and pericardium. In general, many years elapse from first exposure to the appearance of symptoms. Almost all these diseases are the result of dusty working conditions more than 20 years ago. In spite of the fact that the general public is invariably exposed to small amounts of the material, asbestos is not a public health problem. Even living in a building containing sprayed asbestos is calculated to produce a lifetime risk of death which is negligible. There is no evidence to indicate that ingested asbestos fibres represent a major health problem.

Aged↗

The effect of cigarette smoking on the detection of small radiographic opacities in inorganic dust diseases.

Whether cigarette smoking can cause radiographic opacities indistinguishable from those due to pneumoconiosis remains controversial. The situation becomes clearer when one limits the abnormalities to those that can be standardized under the International Labour Office (ILO) classification system. The bulk of the evidence indicates that, using the ILO system, cigarette smoking alone is not associated with radiographic opacities that would be mistaken for pneumoconiosis with sufficient frequency to be of any practical importance. The effects of cigarette smoking, as a cofactor, in conjunction with occupational dust exposure depend on the type of dust. No relationship has been convincingly demonstrated for coal dust or silica. Only with asbestos exposure does there appear to be a significant cigarette smoking-associated increase in the frequency of irregular radiographic opacities. This increase does not appear to translate into a restrictive impairment in pulmonary function. The limited information available indicates that the features of asbestosis on high-resolution computed tomography are not similarly related to cigarette smoking. Additional research is needed to substantiate the relationship between smoking and occupational exposure to dust of many types, and also the possible imaging and pathophysiologic significance of their interactions.

Asbestosis↗

Biomarker assessments in asbestos-exposed workers as indicators for selective prevention of mesothelioma or bronchogenic carcinoma: rationale and practical implementations.

Asbestos-associated malignancies are one of the major industrial hazards of recent decades and will continue to be so until beyond the end of the century. It has been estimated that, in the United States alone, there will be 131,200 cancer deaths as a result of asbestos exposure. At present the early lesions are detected radiologically, by which time intervention is no longer effective. The aim of this study was to test the value of a battery of serum biomarkers in the early detection of malignancy and in distinguishing between the early stages of mesothelioma and bronchogenic carcinoma. Many of the biomarkers had no discriminating value but on the basis of four such markers (namely TPA, CEA, HA and ferritin) it has been possible to distinguish between the late stages of the two malignancies and asbestosis. The results are discussed in terms of their possible application to the detection of early pre-malignant lesions in a screened population of asbestos-exposed persons, with the aim of attempting to prevent cancer death in such early detected cases.

Antigens, Neoplasm↗

How the industrial physician can reduce mortality from asbestos-related diseases.

Risk indicators for asbestos-related diseases (cancers of the lung, larynx, and alimentary tract; mesothelioma; and asbestosis) and methods of early detection are reviewed and evaluated. The best medical means of reducing mortality from these diseases is to recognize particularly susceptible persons during a preemployment examination and to recommend that they not be hired for jobs involving asbestos exposure. Workers necessarily exposed to asbestos should be enrolled in a medical screening program and urged not to smoke.

Asbestosis↗

'B-readers' and asbestos medical surveillance.

"B-readers" certified in International Labor Office methodology interpret large numbers of randomly distributed asbestos medical surveillance roentgenograms of US Navy employees. Analysis of 23 participating observers, interpreting more than 105,000 radiographs, demonstrated a 300-fold prevalence range of perceived "definite" pulmonary parenchymal abnormalities. There was an evident geographic component to interpretation habits, with East and West Coast observers more likely to interpret films as abnormal than observers from the midcontinent. The most expert observers, a group who instruct the course leading to National Institute for Occupational Safety and Health certification in International Labor Office methodology, also perceived fewer abnormalities than other readers or coastal observers. Instructors still exhibited a sevenfold prevalence range of positive interpretation. Under usual surveillance conditions, the habits of B-readers appear to have a major impact upon the diagnosis of asbestosis from roentgenograms. Certification in B-reading should not be the only quality assurance for radiographic surveillance programs, medical decision-making, epidemiologic comparisons, nor related legal activities.

Asbestosis↗

Dust-induced interstitial lung disease in the tropics.

Inhalation of dusts is an important cause of interstitial lung disease in the tropical countries such as India. While dusts of organic origin, such as the cotton dust causing byssinosis, generally cause bronchial or bronchiolar involvement and hypersensitivity pneumonitis, inorganic metallic dusts cause progressive pulmonary fibrosis. Silicosis, coal workers' pneumoconiosis, and asbestosis are the three most commonly recognized forms of pneumoconiotic pulmonary fibrosis. Pulmonary tuberculosis is an important complication seen in up to 50% of patients of silicosis in some reports from India. The presentation is generally chronic, although acute and accelerated forms of silicosis are known when the exposures are heavy. Breathlessness, dry cough, and general constitutional symptoms are commonly seen. Patients with silicotuberculosis or other forms of infection may also have significant expectoration, hemoptysis, fever, and rapid progression. Respiratory failure and chronic cor pulmonale occur in the later stages. The diagnosis is easily established if the occupational history is available. Dense nodular opacities on chest roentgenograms, which may be large in patients with massive pulmonary fibrosis, are characteristic. Emphysematous changes generally appear in advanced stages or in patients who smoke. Bronchoalveolar lavage and/or lung biopsy may occasionally be required to establish or exclude other causes of interstitial lung disease. Treatment is largely palliative, although a variety of drugs including corticosteroids and procedures such as whole lung lavage have been tried. None of these methods has yet been found successful in the treatment. Preventive safety steps, including removal of the patient from the site of exposure, are the only effective strategies to control disease progression.

Asbestosis↗

Differences in mortality by radiation monitoring status in an expanded cohort of Portsmouth Naval Shipyard workers.

Studies of leukemia and lung cancer mortality at the Portsmouth Naval Shipyard (PNS) have yielded conflicting results. In an expanded cohort of PNS workers employed between 1952 and 1992 and followed through 1996, the all-cause standardized mortality ratio (SMR) was 0.95 (95% confidence interval, 0.93-0.96). Employment duration SMRs were elevated with confidence intervals excluding 1.00 for lung cancer, esophageal cancer, and all cancers combined. Leukemia mortality was as expected overall, but standardized rate ratio analyses showed a significant positive linear trend with increasing external radiation dose. The role of solvent exposures could not be evaluated. Findings differed by radiation monitoring subcohort, with excess asbestosis deaths limited to radiation workers and several smoking-related causes of death higher among nonmonitored workers. At PNS, asbestos exposure and possibly smoking could be nonrandomly distributed with respect to radiation exposure, suggesting potential for confounding in internal analyses of an occupational cohort.

Adult↗

The art of perpetuating a public health hazard.

OBJECTIVES: Canadian chrysotile (white asbestos) could be a paradigm for those agents that are successfully exploited commercially long after they have been found to be lethal. Mining started in the late 1870s, and reports of disability and death followed in Britain (1898), in France (1906), and Italy (1908), but it was not until 1955 that Canada acknowledged asbestosis in its asbestos miners and millers. Even when shortly after asbestos was shown to be carcinogenic, Canadian Public Relations experts assisted by their scientists exculpated chrysotile by deeming other agents to have been causal. RESULTS: The PR techniques that have been successfully used in the defense of chrysotile are reviewed, to forewarn scientists involved in formulating public health policy for similar agents, as to the tricks that will be played on them.

Animals↗

Pleural mesothelioma: an approach to diagnostic problems.

In the 1960s, a close relationship between heavy exposures to crocidolite asbestos and mesothelioma was established. The debate on the diagnosis of mesothelioma became complicated because of the possibility of litigation. Well differentiated mesothelioma cells are mucicarmine negative but alcian blue and periodic acid-Schiff (PAS) positive, which are removed by hyaluronidase and diastase digestion. By electron microscopy (EM), they show bush-like elongated, slender, and branching microvilli. By immunohistochemistry they express both keratin and vimentin but not carcinoembryonic antigenicity (CEA), B72.3, Ber-EP4, and Leu-M1. In poorly differentiated mesotheliomas, chromosomal and molecular biological alterations are common and complex but these alterations also overlap with that of poorly differentiated tumours of the lung and other organs. A poorly differentiated pleural tumour is most likely metastatic and needs good team work to locate the primary site. The diagnosis of a mesothelioma and asbestosis should be established separately. Future studies will be focused less on the phenotypic differences but more on the broad molecular and multi-phasic mechanisms of carcinogenesis, irrespective of the aetiological agents, in poorly differentiated tumours.

Asbestosis↗

Case study 1: asbestos--the TLV approach.

A review of the control of carcinogenic exposures using the TLV approach presents a prospect of limited effectiveness. With asbestos, as with any carcinogen, no threshold is known below which no health effect may be manifest. At best, we have only limited dose-response information at levels much above those of practical concern. In the case of asbestos, current exposures can only be described crudely at any level of exposure, and health effects are only known for past high, but ill-defined, exposures. Limited information exists on the effects of synergistic interactions with other materials. The current U.S. TLV, based on data concerned with occurrence of asbestosis, has not been evaluated with regard to possible effectiveness in the prevention of asbestos cancer. Yet cancer is the heart of the asbestos-hazard problem. Finally, enforcement of the existing TLV, especially for asbestos has been limited, frequently absent, and often ineffective. Workers are exposed in many situations to levels much above the current standard. As discouraging as this picture may seem, a TLV can be useful for stimulating the development and application of engineering-control procedures. The application of these procedures, however, must be specified and mandated in future standards to lower worker exposures to the minimum commensurate with existing technology. As technology is developed that makes lower exposure levels possible in a large part of the industry, TLVs should be reduced to take advantage of that technology.

Air Pollutants, Occupational↗

Asbestos disease in maintenance workers of the chemical industry.

In several large groups of workers employed in chemical plants, chest x-ray abnormalities (small irregular opacities and/or pleural changes) of the type known to be induced by asbestos were found in a proportion of those examined. A cross-sectional study of maintenance workers in a large chemical plant was undertaken to evaluate the prevalence of asbestosis; 185 workers were examined. Radiologic evidence of parenchymal interstitial fibrosis was found in 24% of those examined; in 10% of workers, parenchymal fibrosis was the only abnormality. Pleural fibrosis and/or calcification was found in the absence of parenchymal fibrosis in 14% of cases; in another 14% of workers, both parenchymal and pleural abnormalities were detected. The prevalence was significantly higher in those employed 20 or more years. Pleural abnormalities were more prevalent than were parenchymal changes. The increased risk of lung cancer and mesothelioma remains to be studied.

Adult↗

Analysis of asbestos fibers in lung parenchyma, pleural plaques, and mesothelioma tissues of North American insulation workers.

Asbestos fibers and ferruginous bodies (FBs) in lung parenchyma, lung cancer tissues, pleural plaques, and pleural and peritoneal mesothelioma tissues from 13 North American insulation workers were analyzed and quantified using an analytical transmission electron microscope and a polarized microscope. Diseases from which these workers suffered included asbestosis, lung cancer, and mesothelioma. They had been occupationally exposed to materials containing chrysotile and amosite; their pathological diagnoses, occupational and cigarette smoking histories, and clinical summaries have been reported. Large numbers of FBs were found in the lungs and small numbers found in extrapulmonary sites. Most of the FBs had cores of amosite fibers. In all instances, lung parenchyma and lung cancer tissues showed chrysotile and amosite fibers in high concentrations (63.1 x 10(6) and 150.2 x 10(6) fibers/g dry tissue as mean values, respectively). Crocidolite fibers were seen in seven of the 13 cases, but in much smaller numbers. Other amphiboles were rarely found. In pleural plaques and in pleural and peritoneal mesothelioma tissues, amosite fibers were markedly fewer in number, whereas chrysotile fibers were seen in similar numbers as in the lungs. No significant differences in the size distribution of asbestos fibers were seen in the different sites. However, the mean widths of chrysotile fibers were thinner than those of amosite fibers. These results strongly suggest that translocation of inhaled asbestos fibers from the lung to other tissues, such as the pleura and the peritoneum, occurs frequently, and that chrysotile may be more actively translocated from the lung, compared to amosite or amphibole asbestos. The likelihood of translocation seems to be strongly related to the thinness of the fibers. Translocated chrysotile fibers may play an important role in the induction of either malignant mesothelioma and/or hyaline plaques, since the asbestos fibers detected in both these sites were mainly chrysotile.

Adult↗

Asbestos: scientific developments and implications for public policy.

Asbestos is a commercial term for a group of fibrous minerals often associated with the development of pulmonary interstitial fibrosis (asbestosis), lung cancer, and malignant mesothelioma in occupationally exposed individuals. The pathogenicity of different forms of asbestos varies--long, thin amphibole fibers are most pathogenic, particularly in the induction of mesothelioma. Available data do not support the concept that low-level exposure to asbestos is a health hazard in buildings and schools. The concentration of asbestos fibers in air, type of asbestos, and size of fibers must be considered in evaluation of potential health risks.

Animals↗

Asbestos bodies in lungs at necropsy.

This study was made in Glasgow, Scotland, near an industrial area where ship building is an important industry. Asbestos bodies were found in 23% of 100 consecutive hospital necropsies, bodies were present in 37% of the 62 males, none were found in 38 females. These findings are compared with results of other similar surveys. In 85.4% of cases showing asbestos bodies, hyaline pleural plaques were found. There was one case of asbestosis and three of bronchial carcinoma in the cases showing asbestos bodies.

Adenocarcinoma↗

Mortality of chrysotile asbestos workers at the Balangero Mine, Northern Italy.

The mortality from 1946 to 1975 of over 900 North Italian chrysotile asbestos workers first employed between 1930 and 1965 has been studied. Nine deaths were certified as attributable to asbestosis, and eleven to lung cancer. One death was attributed to mesothelioma of pleura but this diagnosis was not supported by histological examination. Comparison with the national figures for all Italy did not reveal an excess of deaths from lung cancer but during the last quinquennium of observation, the SMR for lung cancer rose to 206. Simulation experiments enabled a dust index in fibre/years to be attached to each man in the cohort. All but two of the deaths from lung cancer occurred in the higher exposure group. The relative risk of lung cancer in this group was 2.89. The eleven workers who died from lung cancer were all cigarette smokers. A further period of observation is required to monitor the mortality of the surviving workers.

Asbestos↗