When asbestos is disturbed or damaged, small fibers can break away and float like dust into the air. If these fibers are inhaled, they can settle into the lungs and over several years cause life threatening health problems. One interesting study is called, "Radiological survey of men exposed to asbestos in naval dockyards" by P. G. Harries, F. A. F. Mackenzie, G. Sheers, J. H. Kemp, T. P. Oliver, D. S. Wright - Br J Ind Med 1972;29:274-279. Here is an excerpt: "Abstract - Radiological survey of men exposed to asbestos in naval dockyards. Asbestos related abnormalities were found in 3% of a 10% sample population in radiological surveys of the naval dockyards at Portsmouth, Chatham, and Rosyth. The prevalence of these abnormalities was related to the type of occupation and duration of exposure to asbestos. The results confirm the findings of an earlier survey at Devonport dockyard. No association between smoking, or the amount smoked, and the incidence of parenchymal or pleural disease due to asbestos was detected. Pleural abnormalities were found 10 times more frequently than parenchymal disease, and concern is felt over the uncertainty of the prognosis in men with pleural abnormalities, especially as 37 men have developed pleural mesothelioma at Devonport since 1965. More work is required to establish the true significance of pleural abnormalities caused by asbestos and to explore possible methods of treatment."
A second study is called, "Parietal pleural plaques, asbestos bodies, and neoplasia. A clinical, pathologic, and roentgenographic correlation of 25 consecutive cases by Wain SL, Roggli VL, Foster WL Jr. - Chest. 1984 Nov;86(5):707-13. Here is an excerpt: "Abstract - An investigation was made to correlate autopsy and roentgenographic findings of pleural plaques with occupational exposure to asbestos and occurrence of respiratory tract tumors. Of the 434 autopsies performed over a 2 1/2 year period, 25 (5.8 percent) had pleural plaques but no gross evidence of parenchymal fibrosis. Review of the posterior-anterior chest roentgenograms using the International Labor Office criteria for classification of pneumoconiosis (1980) revealed that only seven of the 25 cases had detectable pleural thickening or calcification, which demonstrates the poor sensitivity of standard x-ray films. There was no detectable difference in frequency of known or presumed exposure to asbestos between the pleural plaque cases and controls as determined by occupational information obtained from chart review. Asbestos bodies were identified in lung tissue digests from all 25 cases with pleural plaques, and exceeded the normal range for our laboratory in 14 cases (56 percent). Of the 25 cases with pleural plaques, four also had bronchogenic and three had laryngeal carcinoma. The prevalence of bronchogenic carcinoma in patients with plaques was not different from those without plaques (p greater than 0.50). However, the association between plaques and laryngeal carcinoma was highly significant (p = 0.004)."
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