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PubMed2004

Changing patterns of pneumoconiosis mortality--United States, 1968-2000.

Pneumoconioses are caused by the inhalation and deposition of mineral dusts in the lungs, resulting in pulmonary fibrosis and other parenchymal changes. Many persons with early pneumoconiosis are asymptomatic, but advanced disease often is accompanied by disability and premature death. Known pneumoconioses include coal workers' pneumoconiosis (CWP), silicosis, asbestosis, mixed dust pneumoconiosis, graphitosis, and talcosis. No effective treatment for these diseases is available. This report describes the temporal patterns of pneumoconiosis mortality during 1968-2000, which indicates an overall decrease in pneumoconiosis mortality. However, asbestosis increased steadily and is now the most frequently recorded pneumoconiosis on death certificates. Increased awareness of this trend is needed among health-care providers, employers, workers, and public health agencies.

Humans↗
PubMedDate not supplied

[Benign pleuropathies due to asbestos: their clinical prognostic significance and the medicolegal aspects].

Benign pleural disease due to asbestos, which at present is frequently the sole lesion in asbestos-exposed subjects due to the fall in full-blown asbestosis, consists of a series of phenomena of increasing severity, from minor manifestations without functional impairment, to manifestations associated with proven functional damage due directly to or as a consequence of as yet undiagnosed parenchymal asbestosis. In assessing individual cases from a medico-legal viewpoint, benign pleural disease must always be considered as a morbid manifestation of asbestos exposure. The implications for prognosis and insurance purposes must, however, take account of various factors such as internal dose, whenever detectable, time elapsed since beginning of exposure, presence and extent of functional damage. The tendency of assessing pleural disease merely as an indicator of past asbestos exposure should in any case be abandoned.

Asbestos↗
PubMedDate not supplied

[Mesothelioma: the aetiological role of ultrathin fibres and repercussions on prevention and medical legal evaluation].

BACKGROUND: Mesothelioma has until now been considered to be a manifestation, occurring in the pleura and/or peritoneum, of the carcinogenic action of the total burden of inhaled asbestos fibres, in the same way as lung cancer. Because of the pathogenic potential of very low exposure levels, the fact that the onset of the neoplasm always occurs in the parietal pleura, and the absence of any synergism with smoking, which is typical in the case of carcinoma, it was suspected that aetiopathogenetic differences existed but the reasons for such differences still could not be explained. In the past experimental results indicated the oncogenicity of very thin fibres but mesothelioma in practice was not exclusively linked to this specific dimensional size class. OBJECTIVES: The paper proposes to take full advantage of the significant knowledge that must emerged from research carried out in recent years and use this knowledge to reconstruct the mosaic of the aetiopathogenesis of mesothelioma. Due consideration will also be given to the consequent new approach required in the field of medical-legal evaluation of cases and in the field of prevention. RESULTS: The most important knowledge that must today be taken as certain is the fact that mesothelioma is not caused, as is the case for asbestosis, by all the fibres that are inhaled but only by the ultrathin fraction of these fibres, having diameter of 0.2 microm and length of only a few microm. Only fibres of this class of size can cross the pulmonary-pleural barrier and are, therefore, the causal agent of mesothelioma and other benign pleural manifestations (plaques). Moreover the ultrathin fibres that translocate from the lung to the pleura are not distributed casually on the parietal and visceral surfaces but move over the surfaces, to concentrate around the lymphatic reabsorption stomata situated on the parietal pleura. Due to their shape, the fibres cannot easily be absorbed into the stoma via the lymphatic flow and so remain clustered for an indefinite period of time among the mesothelial cells that surround the stoma. The concentration of ultrathin fibres in punctiform areas of the parietal pleura and the extremely long biopersistence of the amphiboles now finally explain how very low exposures can cause mesothelioma in susceptible subjects and why the neoplasm always occurs on the parietal pleura. CONCLUSIONS: In medical-legal assessments of cases of mesothelioma the etiological importance of the ultrathin fraction of fibres means that any assumption of the disease being avoidable must be discarded, at least up to the second half of the 1980s because until then this class of fibres, which today must be considered as the true causal agent of the neoplasm, was not visible under the optical microscope, nor could such fibres be measured or eliminated from the atmosphere of working environments. The filter materials available both for fixed ventilation systems and for individual protective masks were not able to block the ultrathin fibres and were therefore only efficacious for the prevention of asbestosis and probably pulmonary carcinoma. It was only with the use of highly efficient HEPA filters and "absolute" filters towards the end of the 1980s that efficacious protection against all size classes of respirable fibres became possible in industrial plants. Preventive measures in the public hygiene area must also take account of the aetiological role of ultrathin fibres by making full use of electron microscope investigations and by using "absolute" filters for domestic purposes, in ventilation systems and above all in the filter systems of the mechanical devices used in town street cleaning operations.

Asbestos↗
PubMed1991

Mortality from respiratory and digestive cancers among asbestos cement workers in Italy.

A cohort study is presented on the mortality of blue-collar workers in an asbestos-cement production plant that has been operating since 1907. Use of both crocidolite and chrysotile is reported. The cohort includes 2608 men and 759 women who were employed in the plant on Jan. 1, 1950 and those who started to work between 1950 and 1980. Follow-up was terminated on April 15, 1986 with 97.9% traced. Expected deaths were estimated from the age- and sex-specific regional mortality rates for the years 1969 to 1981. The data have been analyzed for the period 1964 to 1986 based on person-years at risk: 43,000 for men and 14,494 for women. A statistically significant increase was found in both sexes for mortality from all causes. From 1964 to 1986, 728 men died from all causes (608 expected), 275 with cancer at any site (158 expected) 110 with lung cancer (41 expected), 28 with pleural tumors (1 expected) and 85 with asbestosis (less than 1 expected). Corresponding figures for women were--all causes: 136 deaths versus 102 expected; all cancers: 79 verses 32 expected; lung cancer: 7 versus 2 expected; pleural tumor: 15 versus 0 expected and asbestosis: 4 versus 0 expected. Deaths from digestive tract cancer were in excess only among women (18 observed versus 10 expected, p less than 0.01). No excess was found for deaths from laryngeal cancer. Standardized mortality rates (SMR) for lung cancer among males showed a clear increase in direct relationship with length of follow-up. SMR according to length of employment were 234 for length 10 to 19 years, 363 for 20 to 29 years, and 256 for 30 years or longer (p less than 0.05 and lower).

Adult↗
PubMed1991

Occupational lung disease.

The pneumoconioses, extrinsic allergic alveolitis, lung damage due to irritant gases, fumes, and smoke constitute the occupational lung diseases that affect the lung parenchyma. The pneumoconioses are diseases resulting from the accumulation of dust in the lungs. The ILO has established a standardized system for classification of these pneumoconioses that includes both descriptions of diffuse lung opacities and pleural disease. The most common of the fibrogenic pneumoconioses are silicosis, CWP, and asbestosis. The former two entities are characterized radiographically by the presence of small rounded opacities or nodules in the lung parenchyma. Eggshell calcification may occur in lymph nodes, and eventually the diseases may be complicated by the development of large massive areas of fibrosis in the upper lung zones. Asbestosis, on the other hand, demonstrates small irregular or linear opacities usually confined to the bases of the lungs. It is associated with significant respiratory symptoms and disability. High resolution CT has proved useful in characterizing the parenchymal changes and also in identifying early disease in all of these entities. Berylliosis is a systemic disorder that in its chronic form produces granulomatous disease in the lungs. Radiographically it is characterized by the development of either small rounded or occasionally irregular linear opacities usually confined to the bases. Chemical pneumonitis results from exposure to toxic fumes. The acute reaction may produce diffuse lung injury characterized by air-space disease typical of pulmonary edema. In the chronic form, bronchiolitis obliterans supervenes. This usually is associated with either a normal radiograph or evidence of hyperinflation. Finally, hypersensitivity pneumonitis or extrinsic allergic alveolitis is a response of the lung to inhalation of antigens that may be present in the workplace. Either acute, subacute, or chronic disease may result. In the chronic form, a diffuse reticulonodular pattern with or without associated lymphadenopathy is characteristic.

Alveolitis, Extrinsic Allergic↗
PubMed1989

IgG and IgA enhance the chrysotile-induced production of reactive oxygen metabolites by human polymorphonuclear leucocytes.

Chrysotile asbestos fibres induce a rapid generation of reactive oxygen metabolites by human polymorphonuclear leucocytes (PMNL) in vitro. This effect was markedly enhanced by the presence of 10-200 micrograms/ml of human gammaglobulin, purified polyclonal IgG, and monoclonal IgG and IgA myeloma proteins. Purified monoclonal IgD, IgM, kappa light chain proteins, and secretory IgA inhibited this chrysotile-induced response. No enhancing effect of IgG was observed when quartz dust or opsonized zymosan were used as stimulators of PMNL metabolism. The enhancing effect of IgG was shown to depend on opsonization of the asbestos fibre. We suggest that the IgG and IgA potentiating effect on the asbestos fibre-induced production of tissue-damaging reactive oxygen metabolites by inflammatory cells is dependent on a particle-specific binding of immunoglobulin to the fibre surface, with subsequent Fc receptor-mediated effects on cells. Such an interaction between certain immunoglobulins and asbestos may explain a number of in vivo phenomena in which immunological responses (hypergammaglobulinemia, circulating immune complexes, etc.) have been shown to relate to the progression of pulmonary asbestosis. The differences between various immunoglobulin classes and monoclonal immunoglobulins could represent an individual inflammation-modulating mechanism in the development of acute or chronic pulmonary asbestosis.

Asbestos↗
PubMed1989

[Occupational pneumoconiosis and x-ray check-ups performed by the National Board of Occupational Protection].

In Norway the Directorate of Labour Inspection's pneumoconiosis panel consists of two radiologists. Pneumoconioses are notifiable diseases, and doctors are required by law to notify suspected and confirmed cases to the Directorate of Labour Inspection. Chest films are sent to the Directorate. The pneumoconiosis panel reads and classifies the cases according to ILO-standards. During a 9 months' period, 177 chest films were examined, 162 of which were from persons exposed mainly to asbestos. In this group of 162, 96 persons had parietal pleural plaques only, and 21 or 17% had pleuropulmonary asbestosis with visceral pleural thickening from which fibrous streaks radiated into the lung. Ten persons had pulmonary asbestosis alone or combined with pleural plaques. This group included one mesothelioma. The notification form used by the doctors demands adequate information on occupational history and exposures. More specific information would facilitate the work of the panel.

Adult↗
PubMed1981

Asbestos and other ferruginous bodies: their formation and clinical significance.

Analyses of asbestos bodies from the general population have confirmed that these structures, like asbestos bodies from the lungs of asbestos workers, contain an asbestos core. In members of the general population this core is almost always an amphibole, whereas asbestos workers may have bodies formed on either amphibole or chrysotile. Most adults have a few bodies, and increasing numbers are seen in blue collar workers and others who handle small amounts of the fiber, with the highest levels being seen in asbestos workers. In men with minimal or extensive occupational exposure, asbestos bodies are formed on the commercial fibers, amosite and crocidolite, whereas women also form a significant number of bodies on the noncommercial fibers, anthophyllite and tremolite. These findings suggest that women may be exposed to specific asbestos-containing products, eg, cosmetic talc. The commercial fibers found in women and white collar men probably reflect atmospheric pollution with asbestos. At the highest levels of exposure, numbers of asbestos bodies correlate in a general way with the presence of asbestosis, although no precise value has been determined above which asbestosis is always found. In persons with much lower or environmental exposure, there does not appear to be any correlation between numbers of bodies and disease, in particular between numbers of bodies and carcinoma of the lung or gastrointestinal tract. The situation for mesothelioma is uncertain.

Asbestos↗
PubMed1982

In vitro depression of human lymphocyte mitogen response (phytohaemagglutinin) by asbestos fibres.

Asbestosis is a fibrotic lung disease associated with chronic inhalation of asbestos dust. The response of peripheral blood mononuclear cells (PBM) to phytohaemagglutinin (PHA) in asbestosis patients has been reported to be impaired, suggesting a disturbance in the cell-mediated response of chronically exposed individuals. We demonstrated that PHA responses of normal PBM are also depressed when exposed to various forms of asbestos fibres in vitro. Furthermore, we showed the primary effect of the fibres to be on lymphoid (non-adherent) populations rather than monocytes (adherent cells). Exposure as brief as 1 hr affected the subsequent PHA response of the cells. This effect did not appear to involve suppressor cell activation nor was it mediated by soluble factors. Our findings therefore offer an explanation for the alterations in the cellular immune response observed in humans as a result of lymphoid cells coming into transient contact with inhaled asbestos fibres residing in the lung.

Adult↗
PubMed1980

Clinical and radiological observations on asbestos-related pathology.

The papers in this session, which are summarized briefly, do not cover the wide range of radiological and clinical problems resulting from inhalation of asbestos dust. Pleural effusions are found in persons exposed occupationally to asbestos, even in the absence of asbestosis, but they are difficult to attribute to such exposure. Asbestosis of the lung shows no striking symptoms and can also be diagnosed only after all other possibilities have been excluded. There are no convincing or striking morphological peculiarities that suggest that an 'asbestos lung cancer' exists. Mesotheliomas of the pleura and of the peritoneum are usually resistant to therapy of any kind, although several possibilities are discussed. Radiological surveillance is presented as being still the most effective and reliable method for medical surveillance of asbestos workers. Circumscribed pleural thickening is benign but a good indicator of exposure to mineral dusts. Diffuse pleural thickening occurs frequently in nonexposed groups and cannot, therefore, be used as an indication of exposure; however, it cannot yet be ruled out as being significant epidemiologically.

Adult↗
PubMed1980

Lung cancer mortality in relation to measured dust levels in an asbestos textile factory.

A cohort of 255 men who entered this factory since the beginning of 1951, when routine dust sampling weas initiated, have been followed up to the end of 1978. Eight (1.62 expected) died of lung cancer over 20 years after first exposure (P less than 0.001). Earlier estimates of dust levels hve been revised to correspond to modern counting methods, and the average cumulative exposure of this cohort is now estimated to have been 200-300 fibres/ml-years. No deaths have yet been attributed to asbestosis, but a separate study of this group has reported that 10 of these men have been certified as asbestotic. An earlier analysis of lung cancer, mesothelioma and asbestosis incidence in men employed prior to 1951 suggested a dose-response relationship for lung cancer in relation to static sampler dust measurements that was probably approximately correct, but it is not clear whether personal sampling wound give similar results.

Aged↗
PubMed1993

Humoral immunological profile of workers exposed to asbestos in asbestos mines.

Humoral immunological profile including immunoglobulins IgG, IgA, IgM, C-reactive protein, rheumatoid factor, antinuclear antibodies and circulating immune complexes were studied in a representative sample of 36 workers suffering from asbestosis (group A), 35 workers who are exposed to asbestos but not having evidence of asbestosis (group B) and 28 control workers (group C). Mean IgG and IgA levels were found to be significantly higher in the two exposed groups than in the controls. Circulating immune complexes of IgG, IgA and IgM class were detected in a significant percentage of cases in exposed groups than in controls. In groups A and B, the percentage of positive ANF cases was much higher than in the controls. The results suggest that immunological changes are associated with exposure to asbestos and these may play an important role in the pathogenesis of the disease process.

Adult↗
PubMedDate not supplied

Problems in assessing the relative predictive value of internal markers versus external exposure in chronic disease epidemiology.

Epidemiology traditionally has relied on measures of "external" exposure in determining the association between exposure and disease. Recently, there has been increasing reliance on internal markers reflecting internal dose and/or early stages of disease. In the context of observational studies of chronic disease in which there is a known exposure-disease association, the question arises whether the external exposure or the internal marker is a better predictor of eventual disease outcome. Here we describe some simple approaches to evaluate the relative predictive value of the internal marker (or biomarker, defined in the most general sense) versus the exposure, as well as their limitations. The problems of assessing the predictive value of internal markers for chronic disease are illustrated via two examples: (a) carcinogens, cytogenetic outcomes, and cancer; and (b) asbestos, asbestosis, and lung cancer. We conclude that it is unlikely that observational epidemiology will allow a full assessment of the predictive value of cytogenetic outcomes versus exposure for cancer in humans exposed to known carcinogens in the near future, although animal studies could provide important complementary information. For asbestos, data to date indicate that the presence or absence of asbestosis is a better predictor of lung cancer in an exposed population than is the level of exposure to asbestos itself. In general, the most useful markers for predicting chronic disease are ones which persist over time.

Animals↗
PubMed1996

Occupational respiratory diseases in Singapore.

Occupational respiratory disease statistics in Singapore from 1970 to 1993 were reviewed. Silicosis was the most common occupational respiratory disease in the 1970s and 1980s. About 78% of the cases were from granite quarries. With progressive reduction in dust levels and the closure of some quarries, there has been a decline in cases. From 1990 to 1993, occupational asthma was the most common occupational respiratory disease and more cases are expected with increasing awareness of the condition. The most common causative agent was isocyanates accounting for about 34% of cases. Of the asbestosis and malignant mesothelioma cases, about 70%-80% were from the one and only asbestos cement factory. With the closure of this factory and the increasing restrictions on the use of asbestos, cases of asbestosis are expected to decline in the long term. However, malignant mesothelioma cases may continue to surface because of the long latent period and the potential risk with low and brief exposures to asbestos. It is important to probe for possible occupational exposures (both present and past) in a patient with respiratory symptoms or disease.

Data Collection↗
PubMedDate not supplied

Asbestos bodies in sputum of asbestos exposed workers.

The prevalence of asbestos bodies (AB) in sputum was studied in a group of 220 former or current asbestos workers, who came under observation because of a claim for compensation and who had, in most cases, high levels of exposure. Only one sputum specimen was obtained from each subject. The overall AB prevalence was 34%; it was 24.5% among workers exposed to chrysotile only, and 42% among workers also exposed to amphiboles, thus showing a statistically significant difference. No significant differences were found in AB prevalence either between current asbestos workers and former workers or between asbestosis cases and those without asbestosis. AB prevalence among current smokers was significantly lower than that observed among non-smokers and ex-smokers pooled together. The highest AB prevalence was found among currently exposed textile workers (65.7%), especially in male subjects (66.7%). As the exposure of these groups was heavy and included amphiboles, it may be concluded that although AB counts are highly specific they have low sensitivity.

Asbestos↗
PubMed1996

Unrecognized asbestos-induced disease.

It is being slowly recognized that there is serious under-reporting of cancers that are occupationally related, in the sense that they would not have occurred without the occupational exposure. Data from the Workers' Compensation Boards of New South Wales in Australia and British Columbia in Canada relating to disease attributable to asbestos exposure indicate that in both jurisdictions the ratio of lung cancer cases to mesothelioma cases is much lower than epidemiological studies indicate must be occurring. Over the period from 1980 to 1994, if both jurisdictions are considered together, about 1,207 cases of lung cancer that would not have occurred without asbestos exposure went unrecognized as occupationally related. The data also suggest that it is unlikely that radiological asbestosis should be regarded as a necessary condition for there to be an increased risk of lung cancer following asbestos exposure.

Asbestos↗
PubMed1996

Mortality of Carpenters' Union members employed in the U.S. construction or wood products industries, 1987-1990.

This study evaluated the mortality of 27,362 members of the U.S. Carpenters' Union who died in 1987-1990. Age-adjusted proportionate mortality ratios (PMRs) and proportionate cancer mortality ratios (PCMRs) were computed using the U.S. age-, gender-, and race-specific proportional mortality for the years of the study. For white male carpenters who were last employed while in construction industry locals, raised mortality was observed for lung cancer (PCMR = 107, CI = 103, 111), bone cancer (PMR = 181, CI = 107, 286), asbestosis (PMR = 283, CI = 158, 457), emphysema (PMR = 115, CI = 102, 130), transportation injuries (PMR = 121, CI = 109, 135), and falls (PMR = 122, CI = 104, 142). For white male carpenters who were last employed while in industrial wood products locals, significantly raised mortality occurred for stomach cancer (PMR = 187, CI = 136, 250), male breast cancer (PCMR = 469, CI = 128, 720), and transportation injuries (PMR = 136, CI = 110, 173). Excess breast cancer was associated with last employment inn wood machining trades. Nasal cancer mortality was not elevated. A total of 121 mesotheliomas were observed. Contributing cause of death analyses revealed raised mortality for these and additional causes; 4,594 (18%) death certificates mentioned occupational and other lung disease as a contributing factor, resulting in significantly elevated mortality. These data show that construction carpenters have moderately elevated mortality for the diseases caused by asbestos (lung cancer and malignant mesothelioma) and from traumatic injuries. The finding of elevated mortality for stomach, bone, and breast cancer was unexpected and requires further evaluation of possible occupational factors. This study confirms that construction carpentry is an extremely hazardous trade. The data suggest that additional preventive action guarding against asbestos exposure and occupational injury is urgently needed in this occupation.

Accidental Falls↗
PubMed1997

Loss of lung function among sheet metal workers: ten-year study.

One hundred and twenty-two sheet metal workers in New England were examined over a 10-year interval for loss of pulmonary function and the development of asbestosis or asbestos-related pleural fibrosis. Regression models using the generalized estimating equation (GEE) approach were created to investigate the relationship between exposure and pulmonary function after adjusting for smoking status, age, height, and asbestos-related x-ray changes. A history of shipyard work was a significant contributor to the loss of forced vital capacity (FVC). Among smokers, loss in forced expiratory volume at 1 sec (FEV1) also had a significant relationship to prior shipyard work. There was a borderline significant relationship between percentage predicted FEV1 and cumulative years of asbestos exposure in smokers, as well as years-since-initial-exposure in never-smokers. This study supports previous findings of obstructive airway changes in asbestos-exposed workers and identifies shipboard work as an important predictor of loss in pulmonary function even years after shipyard exposure to asbestos has ceased.

Adult↗