ASBESTOS BODIES IN HUMAN LUNGS AT AUTOPSY

Asbestos and the lung: highlights of a detrimental relationship

“Asbestos” is a term used to characterise a number of natural mineral fibres of silica that can be categorised according to their structure in the serpentine-type fibres, mainly represented by chrysotile, and the amphibole-type fibres, which include crocidolite, amosite, anthophyllite, actinolite and tremolite [1]. Due to its remarkable durability and fire resistance, asbestos has been used in pottery and clothing since for at least 4500 years. However, modern commercial production of asbestos began during the second half of the 19th century when industry started to exploit its unique chemical characteristics for manufacturing various products, such as pipe insulation, brake linings, cement pipes, protective clothing, etc. With the increasing use of such materials, individuals working in the construction (e.g. builders, plumbers, etc.) and ship building (e.g. dockyard workers) industries began to be exposed to high concentrations of inhaled asbestos fibres. Approximately 50–70 years after the introduction of asbestos in commercial use, the first reports of asbestos-related diseases emerged [1]. Since then, multiple studies have connected asbestos exposure with a variety of malignant and non-malignant lung disorders.

Novel aspects of the pathogenesis of asbestos-related diseases are still coming to lighthttp://ow.ly/EPDa30e8JqK

Applying definitions of "asbestos" to environmental and "low-dose" exposure levels and health effects, particularly malignant mesothelioma

Although asbestos research has been ongoing for decades, this increased knowledge has not led to consensus in many areas of the field. Two such areas of controversy include the specific definitions of asbestos, and limitations in understanding exposure-response relationships for various asbestos types and exposure levels and disease. This document reviews the current regulatory and mineralogical definitions and how variability in these definitions has led to difficulties in the discussion and comparison of both experimental laboratory and human epidemiological studies for asbestos. This review also examines the issues of exposure measurement in both animal and human studies, and discusses the impact of these issues on determination of cause for asbestos-related diseases. Limitations include the lack of detailed characterization and limited quantification of the fibers in most studies. Associated data gaps and research needs are also enumerated in this review.

Changing attitudes and opinions regarding asbestos and cancer 1934-1965

Literature published in the years 1934-1965 was reviewed to determine attitudes and opinions of scientists as to whether asbestos is a cause of cancer. In Germany, the issue was decided in 1943 when the government decreed that lung cancer, when associated with asbestosis (of any degree), was an occupational disease. In the United States, however, there was no consensus on the issue until 1964. Opinions of scientists over a 22 year period are shown and the contributions of various cultural, social, economic and political factors to these opinions are discussed. A lack of experimental and epidemiological evidence played a major role in delaying a consensus. Other important factors included a rejection of science conducted outside of the U.S. during this period, particularly a rejection of German scientific thought during and after WWII, and a rejection of clinical evidence in favor of epidemiological investigations. Individual writers rarely changed their minds on the subject of asbestos as a cause of cancer.

A theory of carcinogenesis based on an analysis of the effects of carcinogens

Carcinogenic stimuli appear to act on target cells (and their daughters) by one or more of three mechanisms. The first is by oxidation of membrane component molecules on the extracellular surfaces of their plasma membranes. The second is by chronic and continuous impingement of electrons on the extracellular surfaces of their plasma membranes and the third is by relocation of predominantly basic molecules to the cytoplasmic surfaces of their plasma membranes. This latter effect in turn causes electrostatic attraction of image charged acidic molecules to the extracellular surfaces to balance the transmembrane charge of the target cells. Each of the above mechanisms results in a condition of increased electronegativity of the extracellular surfaces of plasma membranes of the target cells and their daughters. A theory of transformation is advanced based on the above related modes of action and it is used to explain some previously unexplainable properties of tumors.

Lung response to particulates with emphasis on asbestos and other fibrous dusts

Many theories have been proposed to explain asbestosis and asbestos-related pulmonary disease. However, none of the theories give a completely plausible explanation for the pathogenesis. Recently, attention has been drawn to a theory that the fibrogenicity or carcinogenicity of fibrous dust particles is related to fiber diameter and length rather than to chemical properties. This theory may help partially elucidate the disease process but is still far from solving the enigma of pulmonary fibrosis or carcinogenesis. The theory cannot explain the absence of these pathological effects among fiberglass workers or experimental animals exposed by inhalation (even though mesotheliomas are induced by intrapleural implantation and fiber dimension-related fibrogenicity is demonstrated by intratracheal injection). Little information regarding the pulmonary response to manmade fibrous particles is available in animals following inhalation exposure. Attempts should be made to confirm the absence of adverse effects using animal inhalation experiments even though to this point there is no conclusive evidence that either lung cancer or pulmonary diseases can be produced among employees in manmade fiber industries. A new research trend seems concentrated on testing the durability of asbestos or manmade fibers. This is based on the concept that biological effects of fibrous particles are the result of relative durability and that particles which can be fragmented or shortened may be less pathogenic. In the last two decades, considerable understanding about pulmonary fibrosis and carcinogenesis of asbestos has been achieved by clinical and animal experiments. In vitro tests including cytotoxicity, hemolysis, immunology, and enzyme biochemistry have provided important information on the interrelationships among these various biological effects of asbestos.

Pulmonary asbestos and dust content in East Anglia

Measurements were made of the asbestos fibre and dust content of samples from 96 surgically excised lungs; 42 necropsies on patients with lung cancer, 11 necropsies on patients with non-pulmonary malignancies, and 59 necropsies on patients without any malignant disease. The patients' ages ranged from 45 to 74 years at the time of study. None of the patients had asbestosis. The distribution of fibres and dust content of the lungs showed a log-normal distribution. There was no significant difference in fibre counts or dust content between men and women, and between lung cancer and non-cancer patients. The only group with an association with a high asbestos fibre count was four necropsy cases of pleural mesothelioma. There was no significant relationship between asbestos fibre count and dust content of the lung. The present data suggest that asbestos fibre counts below 100,000 per gram of dried lung are not related to specific asbestos disease, although in the surgical cases who were closely questioned on their residential and occupational histories most of those with fibre counts above 30,000 per gram dried lung had had occasions of definite or very likely asbestos exposure.

Asbestos exposure and related neoplasia. The 28 year experience of a major urban hospital

In a retrospective study of 49 cases of asbestosis, a steady increase in the frequency of diagnosis of asbestosis and asbestos-related neoplasia is documented from a major urban hospital since 1960. Although in the majority of cases the subjects were exposed to asbestos in a neighboring shipyard, in 20 per cent of the cases, asbestos exposure was in industries not related to shipbuilding, reflecting its widespread use. This selective population of patients with asbestosis more often than not had an associated neoplasm. The most likely accompanying tumor was pleural mesothelioma, and among cell types of lung cancer, adenocarcinoma was notably frequent.

Unsuspected exposure to asbestos and bronchogenic carcinoma

Two hundred and fifty men admitted to a thoracic surgical centre and matched controls were questioned in detail about their occupations after leaving school and their smoking habits. Of 201 men with confirmed bronchial carcinoma 58 gave a history of occupational exposure to asbestos, whereas only 29 out of 201 men matched for age and residential area who were admitted with other diseases gave such a history. This difference was statistically highly significant. The usual association of bronchial carcinoma with heavy smoking was observed, but asbestos exposure increased the risk of carcinoma whatever the level of smoking. These results are consistent with the hypothesis that asbestos exposure and the level of smoking act independently in causing bronchial carcinoma. The patients with carcinoma who had been exposed to asbestos presented on average three years earlier than those who had not been exposed. Asbestos regulations have eliminated the risk of exposure to workers in scheduled industries, so asbestos-induced diseases will probably be increasingly found among the many workers who have had incidental exposure to asbestos. It is therefore important to take a full occupational history.

Pleural calcification associated with exposure to chrysotile asbestos in southeast Turkey

In this study, pleural calcifications prevailing in the inhabitants of some villages and towns around Diyarbakir, a city in southeast Turkey, have been found to be caused by the inhalation of chrysotile asbestos, the mineral commonly used indiscriminately to paint the walls and floors of houses. There were no industrial establishments in the area, except some local mining, and asbestos deposits were even not included on the mining map of the country. Chest roentgenograms from the Chest Hospital and the tuberculosis dispensaries were screened: and, additionally, 15,239 photofluorograms were obtained during a survey. Of all these, 511 patients were found to have pleural calcifications, some with pericardial and diaphragmatic involvement. Forty-four percent (28) of the 64 patients who had examinations of samples of their sputa had asbestos bodies, and asbestosis was also induced in rabbits by administration of the raw material.

The pathology of parietal pleural plaques

The incidence, morbid anatomy, histology, and relationship of hyaline pleural plaques to exposure to asbestos has been studied. Plaques were found in 12.3% of 334 hospital necropsies (in an urban population in Glasgow, 41 cases). In 85.3% (35 cases) asbestos bodies were found in the lungs. There is evidence of a dose-response relationship between the number of asbestos bodies found in the lungs and the presence of pleural plaques. The selective distribution of plaques within the pleural cavities suggests that mechanical factors play a part in their localization. Histological examination contributed little to understanding the mechanism of plaque formation; that asbestos bodies have been detected in only a few cases suggest that their presence in the parietal pleura is not essential to plaque formation. The suggested mechanisms of plaque formation are discussed.

Correlation between lung asbestos count at necropsy and radiological appearances

In the first 100 of a series of 600 consecutive necropsies for which a chest x-ray film had been taken within a year of death the features of asbestosis were observed in eight of the nine cases where the asbestos count at subsequent necropsy exceeded 40. In only one of these cases had the diagnosis of asbestosis been suggested during life. The higher the asbestos count the greater the likelihood of radiographic abnormalities, particularly calcified and non-calcified pleural plaques on the chest wall and diaphragm.

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.

Pathological aspects of asbestosis

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