Parenchymal Asbestosis Research Articles

Recognizing the pleura in asbestos-related pleuropulmonary disease: Known and new manifestations of pleural fibrosis.

Pleural thickening (PT) is a major consequence of exposure to all fiber types of asbestos. In recent decades, it is more prevalent than parenchymal asbestosis. Its manifestations occupy a full clinical and radiographic spectrum. Six major manifestations can be identified: (a) acute pleuritis generally with effusion; (b) diffuse PT or fibrous pleuritis; (c) rounded atelectasis; (d) circumscribed PT or plaques; (e) chronic pleuritic pain; and (f) mesothelioma. Review of the experience of workers and community members in Libby, MT to asbestiform fibers in vermiculite has confirmed the appearance of these previously known benign and malignant asbestos-related diseases as well as a unique pleuropulmonary disease characterized as lamellar PT and associated with progressive decline in pulmonary function and pleuritic pain. Despite previous literature asserting that PT represents a marker for asbestos exposure without significant effect on pulmonary function and physiology, the experience of Libby amphibole (LA) disease, along with other studies, indicates that PT plays a role in declining vital capacity in those with prolonged or unusual exposures such as those arising from LA.

Case-fatality study of workers and residents with radiographic asbestos disease in Libby, Montana.

BackgroundVermiculite ore from Libby, Montana contains on average 24% of a mixture of toxic and carcinogenic amphibole asbestiform fibers. These comprise primarily winchite (84%), with smaller quantities of richterite (11%) and tremolite (6%), which are together referred to as Libby amphibole (LA).Methods A total of 1883 individuals who were occupationally and/or environmentally exposed to LA and were diagnosed with asbestos‐related pleuropulmonary disease (ARPPD) following participation in communitywide screening programs supported by the Agency for Toxic Substances and Disease Registry (ATSDR) and followed up at the Center for Asbestos Related Disease (CARD) between 2000 and 2010. There were 203 deaths of patients with sufficient records and radiographs. Best clinical and radiologic evidence was used to determine the cause of death, which was compared with death certificates.ResultsAsbestos‐related mortality was 55% (n = 112) in this series of 203 patients. Of the 203 deaths, 34 (17%) were from asbestos‐related malignancy, 75 (37%) were from parenchymal asbestosis, often with pleural fibrosis, and 3 (1.5%) were from respiratory failure secondary to pleural thickening.ConclusionsAsbestos is the leading cause of mortality following both occupational and nonoccupational exposure to LA in those with asbestos‐related disease.

Parenchymal asbestosis due to primary asbestos exposure among ship-breaking workers: report of the first cases from Bangladesh

We report for the first time asbestosis among ship-breaking workers of Sitakunda in Bangladesh who were exposed to asbestos during ship-based and beach-based operations for at least 10 years. Asbestosis...

Asbestos and Its Toxicological Concern

phagocytosis. Further longer fibers are cleared only after fragmentation, splitting or dissolution and retained in the lungs for a long time. Due to the differences in structure and length, chrysotile has high affinity to be deposited in the upper airways of the respiratory tract and also cleared efficiently from the lungs compared with amphibole fibers [3]. Shorter fibers retained in the lungs for prolonged periods and further they penetrate the epithelial cells into the lymphatic system or the blood and simultaneously reach kidney and gets excreted. Asbestos enter into a person by breathing and deposited in lung tissues and accumulates over time and causes irritation, scarring and inflammation and eventually produces severe health implications [49]. Therefore, asbestos has been classified as human carcinogens. A history of asbestos exposure at occupational exposure is reported in about 70% to 80% of all cases of mesothelioma (a rare type of cancer of the mesothelium-the membrane that covers and protects most of the internal organs of the body). The main symptoms of mesothelioma of the lungs are shortness of breath, chest pain and abdominal mesothelioma include weight loss, swelling and pain in the abdomen, blood clotting abnormalities, bowel obstruction, anemia and fever. Continued exposure to high levels of asbestos in the occupational exposure scenario can also cause asbestosis (e.g., disease that can lead to disability and death and it scars the lungs and can cause the heart to enlarge). The primary symptoms of asbestosis are shortness of breath, persistent cough that produces mucus, chest tightness, chest pain, loss of appetite, dry, crackling sound in the lungs while inhaling followed by lung cancer with the symptoms of cough (including coughing up blood), wheezing, unexplained weight loss, difficulty breathing or shortness of breath, hoarseness and anemia. Clinical signs and symptoms of asbestosis include basal crackles on auscultation, dyspnea, cough and abnormal gas exchange, which may ultimately lead to death. The prolonged asbestos fiber particle exposure is associated with severe health illnesses including pulmonary fibrosis, bronchogenic carcinoma, diffuse malignant, parenchymal asbestosis (prolonged inflammatory response stimulated by the presence of fibres in the lung, leading to fibrosis of the lung parenchyma and permanent damage to the lung system), mesothelioma of the pleura and peritoneum, pleural abnormalities such as effusions (excessive fluid collections in lung tissues and chest cavity), pleural plaques/thickening (changes in lung membrane and visceral pleura and discrete fibrous or calcified thickened areas that arise from the surface of the parietal pleura which is observed in 20 to 60 percent of the occupationally exposed

Asbestos exposure and benign asbestos diseases in 772 formerly exposed workers: Dose–response relationships

Since previous studies have provided conflicting results, we investigated the relationship between the risk of benign asbestos-related diseases and different aspects of asbestos exposure in previous asbestos workers who underwent low-dose computed tomography (CT). CT scans were carried out in 772 subjects. A questionnaire was employed to collect data on smoking habits and duration, peak and cumulative exposure, and time since first exposure to asbestos. Multiple logistic regression models with stepwise selection of variables were used to evaluate the associations. Fourteen (1.8%) cases of asbestosis, 187 (24.2%) of pleural plaques (PP), and 50 (6.5%) of diffuse pleural thickening (DPT) were found. The significant risk factors were: cumulative exposure for asbestosis (P for trend = 0.004); time since first exposure (P for trend <0.001), and peak exposure (P for trend <0.001) for PP; and time since first exposure for DPT (P for trend = 0.024). Parenchymal asbestosis and PP are associated with different aspects of asbestos exposure. DPT appears to be less specific for asbestos exposure.

The past and present of pneumoconioses.

Pneumoconioses are still a common cause of chronic lung disease. In industrialized countries, improvements in working conditions and dust control measures have led to a decrease in the incidence of severe forms of silicosis, coal worker pneumoconiosis, and parenchymal asbestosis. However, the diversity of settings in which silica and asbestos are used fuels a continued input of cases, and the burden of cases related to remote exposures is still considerable. Overall, the clinical picture of the classic pneumoconioses and their complications has not changed substantially. However, their limits and links have expanded toward systemic and connective tissue disease, idiopathic pulmonary fibrosis, and antineutrophil cytoplasmic autoantibody-positive vasculitides. Immunologically mediated occupational lung diseases have emerged, such as berylliosis and hard-metal disease. Advances in imaging, mineralogic analysis of bronchoalveolar lavage fluid, and immunologic techniques have been instrumental in describing new patterns of disease and are helpful in litigious or difficult cases.

Conventional and High-Resolution CT in Asymptomatic Asbestos-Exposed Workers

To compare the value of conventional CT (CCT) and high-resolution CT (HRCT) to detect benign asbestos-related diseases, 159 exposed workers with a normal chest radiography were imaged by both techniques. Pleural plaques were detected in a total of 59 cases (37.1%). Ten cases (16.9%) were detected by CCT only and one case (1.7%) by HRCT only. Pulmonary lesions compatible with parenchymal asbestosis were detected by HRCT in 20 cases, whereas CCT showed abnormalities in 45% of these. Rounded atelectasis was equally recognized by both techniques. The results confirm that in a subject with a normal chest radiography, HRCT is a better diagnostic tool to demonstrate lesions of asbestosis. On the other hand, HRCT is insufficient to exclude the presence of pleural plaques. When HRCT does not reveal pleural abnormalities, CCT should be performed.

Is there an association between pleural plaques and lung cancer without asbestosis?

A recent review or meta-analysis of epidemiologic studies concluded that persons with asbestos-related pleural plaques do not have an increased risk of lung cancer in the absence of parenchymal asbestosis. The reviewer inferred that this conclusion provided indirect supportive evidence for the proposition that asbestosis is a necessary precursor of asbestos-related lung cancer. The objective of the present communication is to contest these claims. Finnish epidemiologic data and population statistics were used to estimate the apparent risk ratio of lung cancer associated with radiographic signs of pleural plaques. Power calculations were applied to compute the needed population sizes to demonstrate that the association is statistically significant. Unrealistically large population studies would be needed to observe the statistical relation between pleural plaques and lung cancer, quantitated as a risk ratio of 1.1, resulting from relatively low levels of environmental asbestos exposure. In realistic and valid epidemiologic studies on heavily exposed subpopulations, a two- or threefold risk can be identified. Uninformative studies should not be interpreted as providing suppressive evidence that pleural plaques are a noncausal risk indicator of lung cancer. Even for the null hypothesis, the inference that asbestosis is a necessary causal link between asbestos and lung cancer is illogical.

Early detection of interstitial lung disease in asbestos exposed non-smoking workers by mid-expiratory flow rate and high resolution computed tomography.

Ten years of lung function and radiological findings in six non-smoking asbestos exposed subjects who had increased mid-expiratory flow rate (FEF 25-75%) as the only functional abnormality were prospectively analysed. A biphasic change in FEF25-75% was noted. It initially increased up to the fifth year, and then a decrease was seen. In the final three years of the study, FEF25-75% reduction correlated well with a decrease in pulmonary capacity for CO (DLCO). During that time high resolution computed tomography (HRCT) probability scores correlated inversely with FEF25-75% and with DLCO, whereas chest radiography was unchanged (International Labour Organisation (ILO) profusion below 1/1). For five of the six subjects HRCT probability of asbestosis was intermediate. An increase in FEF25-75% in some asbestos exposed non-smoking workers may be one of the earliest functional signs indicative of future development of parenchymal asbestosis. Early asbestos related parenchymal abnormalities are seen more frequently on HRCT than on chest radiography.

Asbestos disease in sheet metal workers: II. Radiologic signs of asbestosis among active workers.

A review of chest x-rays of 707 currently employed New York metropolitan area sheet metal workers found that 29.3% of the workers with 20 years or more of union membership (a surrogate for years of exposure) had radiologic abnormalities characteristic of parenchymal and/or pleural asbestosis, with 18.6% having abnormalities characteristic of parenchymal asbestosis (International Labor Organization [ILO] classification 1/0 or higher) and 17.4% of pleural asbestosis. The prevalence of abnormalities characteristic of either parenchymal and/or pleural asbestosis in the group as a whole was 16.4%, with 10.9% exhibiting signs of parenchymal asbestosis and 9.2% of pleural asbestosis. There was a strong, statistically significant relationship between years in the trade and the prevalence of radiologic abnormalities. These findings underscore the need for medical surveillance of all asbestos-exposed construction workers, including retirees and workers who have had past exposure but who are no longer exposed.

Morphology of bronchogenic carcinoma in workers formerly exposed to crocidolite at Wittenoom Gorge in Western Australia.

Cytology and histology material from 46 bronchogenic carcinomas occurring in ex-workers from the Wittenoom crocidolite mine and mill in Western Australia and a matched random sample of 234 other bronchogenic carcinomas occurring in Western Australia over the same period were reviewed by a single histopathologist without knowledge of asbestos exposure status. Squamous-cell carcinomas formed 45.7% of the cancers in the asbestos-exposed group but only 32.5% of the cancers in the comparison group. This difference could not be explained by differences in smoking history between the two groups of lung cancer patients or in the type of histopathological material available for review. The excess of squamous-cell cancers was observed in subjects both with and without parenchymal asbestosis.

Asbestosis and Associated Medical Problems

Asbestos is a relatively indestructible. fibrous mineral, for which over 3,000 specific uses have been found (2). More than 100 companies in the United States alone manufacture asbestos textiles, tile, cement products, friction materials, paper, paint, and plastics. The largest known deposits of asbestos outside the Soviet Union are in an area approximately 75 miles long by 5 to 6 miles wide in Quebec, Canada (34). In this region eight companies mine and mill chrysotile, the most important commercial form of asbestos (Table I) (9). Chrysotile, extracted from serpentine rock, is a hydrated magnesium silicate. The long, blue-fibered crocidolite and the short-fibered amosite, mined in South Africa, are chemically similar to chrysotile but contain considerable iron instead of magnesium (21). Asbestos was first mined over 2,000 years ago in Crete, whence it was transported to Greece, Rome, and Egypt and woven into fire-resistant cloth (4). Awareness of the asbestos fiber and its unique properties was then lost and not regained until the latter part of the nineteenth century. The modern industry began in 1876 in Italy and in 1878 in Canada (37). Annual world production has risen from 500 tons in 1880 to over 3.5 million tons in 1964 (35). Asbestosis Material One hundred and eighty-seven asbestos workers employed in various insulating trades were examined in the Department of Radiology, Hahnemann Medical College Hospital. Approximately 30 per cent showed some pulmonary change which could be ascribed to the inhalation of asbestos dust. In none was a lung biopsy carried out. The roentgenologic findings are summarized in Table II. Pleural thickening was the most common finding. It was most often minimal or moderate (Fig. 1) but was quite extensive in a small percentage of workers (Fig. 2). Calcified pleural plaques were seen in 21.4 per cent of positive cases (Figs. 2 and 3). Pulmonary parenchymal fibrosis was not as common as pleural disease and rarely seen unassociated with pleural thickening (Fig. 4). Positive findings related both to the pleura and to the pulmonary parenchyma involved the lower lobes almost exclusively and were more common on the left side. A “shaggy heart,” noted in 19.6 per cent of the subjects, is a manifestation of the parenchymal fibrosis adjacent to the cardiac shadow (Fig. 5). Large hilar arteries, most often unilateral, were observed in over half the cases. Kerley's B lines were found in a minority of the 187 workers and not always associated with pleural or parenchymal asbestosis, and the relationship of these lines to the disease is not clear. Discussion Until the twentieth century there was considerable controversy in pathology circles concerning dust inhalation and possible pathological sequelae. In 1886 Virchow suggested that dust may cause discoloration of the lungs (37).The first significant report which dealt with asbestosis was by Merewether in 1933 (37).