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).”
A third study is called, “Malignant Mesothelioma and Occupational Exposure to Asbestos: A Clinicopathological Correlation of 1445 Cases” by Victor L. Roggli, Anupama Sharma, Kelly J. Butnor, Thomas Sporn and Robin T. Vollmer - Ultrastructural Pathology 2002, Vol. 26, No. 2, Pages 55-65. Here is an excerpt: “Asbestos exposure is indisputably associated with development of mesothelioma. However, relatively few studies have evaluated the type of occupational exposure in correlation with asbestos fiber content and type. This study reports findings in 1445 cases of mesothelioma with known exposure history; 268 of these also had fiber burden analysis. The 1445 cases of mesothelioma were subclassified into 23 predominant occupational or exposure categories. Asbestos body counts per gram of wet lung tissue were determined by light microscopy. Asbestos fiber content and type were determined by scanning electron microscopy and energy dispersive x-ray analysis. Results were compared with a control group of 19 lung tissue samples. Ninety-four percent of the cases occurred among 19 exposure categories. Median asbestos body counts and levels of commercial and noncommercial amphibole fibers showed elevated levels for each of these 19 categories. Chrysotile fibers were detectable in 36 of 268 cases. All but 2 of these also had above-background levels of commercial amphiboles. When compared to commercial amphiboles, the median values for noncommercial amphibole fibers were higher in 4 of the 19 exposure groups. Most mesotheliomas in the United States fall into a limited number of exposure categories. Although a predominant occupation was ascertained for each of these cases, there was a substantial overlap in exposure types. All but 1 of the occupational categories analyzed had above-background levels of commercial amphiboles. Commercial amphiboles are responsible for most of the mesothelioma cases observed in the United States.”
If you found any of these studies interesting, please read them in their entirety. We all owe a great deal of thanks to the people who are researching these important issues.