Epidemiological Approach and the Risks of Asbestos Exposure
One interesting study is called, "Determinants of restrictive lung function in asbestos-induced pleural fibrosis" by D
. A. Schwartz, J. R. Galvin, C. S. Dayton, W. Stanford, J. A. Merchant and G. W. Hunninghake - Department of Internal Medicine, University of Iowa, Iowa City 52242. J Appl Physiol 68: 1932-1937, 1990. Here is an excerpt: "We evaluated whether restrictive lung function among asbestos-exposed individuals with pleural fibrosis was caused by radiographically inapparent parenchymal inflammation and/or parenchymal fibrosis. All 24 study participants were sheet metal workers who were nonsmokers with normal parenchyma on posteroanterior chest radiograph. These subjects had either normal pleura (n = 7), circumscribed plaques (n = 9), or diffuse pleural thickening (n = 8). After controlling for age, years in the trade, and pack-years of smoking, we found that sheet metal workers with diffuse pleural thickening had a lower forced vital capacity (P less than 0.001), total lung capacity (P less than 0.01), and CO-diffusing capacity of the lung (P less than 0.05) than those with normal pleura. Similarly, sheet metal workers with circumscribed plaques were found to have a reduced forced vital capacity; however, because of the small number of study subjects, this difference (regression coefficient = -11.0) was only marginally significant (P = 0.06). Although circumscribed plaque and diffuse pleural thickening were both associated with a lymphocytic alveolitis and a higher prevalence of parenchymal fibrosis on high-resolution computerized tomography (HRCT) scan, neither a lymphocytic alveolitis nor the finding of parenchymal fibrosis on HRCT scan influenced the relationship between pleural fibrosis and restrictive lung function. We conclude that pleural fibrosis is associated with restrictive lung function and abnormally low diffusion that appears to be independent of our measures of parenchymal injury (chest X-ray, bronchoalveolar lavage, and HRCT scan)."
Another interesting study is called, "A Follow-Up Study of Workers from an Asbestos Factory" by P. C. Elwood, A. L. Cochrane - Br J Ind Med 1964;21:304-307. Here is an excerpt: "Abstract - Associations between exposure to asbestos and carcinoma of the lung, diffuse mesothelioma of the pleura, and diffuse abdominal tumours have been demonstrated. Only by an epidemiological approach can the total risks of exposure to asbestos be estimated, and such a study is reported here. This suggests that white asbestos (chrysotile) may not be a serious hazard as far as mesothelioma or abdominal tumours are concerned, though there is some evidence of an excess in the number of deaths from carcinoma of the lung and bronchus."
Another study is called, "Bivariate Lognormal Distribution for Characterizing Asbestos Fiber Aerosols" by Yung-Sung Chenga - Aerosol Science and Technology, Volume 5, Issue 3 1986 , pages 359 368. Here is an excerpt: "Abstract - The width and length distributions of fiber aerosols were successfully correlated using a lognormal distribution, and the joint distribution could be described by a bivariate lognormal distribution. Means and variances of the length and width for the joint distribution were the same as those for individual marginal distributions, and the correlation between the width and length was between 0.1 and 0.5. Based on the bivariate lognormal distribution, other physical properties of fiber aerosols of the form Q = aWbLc such as aspect ratio, surface area, volume, and aerodynamic diameter were also shown to be lognormally distributed. The mean and variance of In Q can be estimated from parameters in the bivariate analysis. The result shows the usefulness of this analysis in deriving aspect ratio, volume, and aerodynamic diameter from the basic length-width distribution. It also provides a simple way to convert the number concentration to surface area and mass concentration."
We all owe a debt of gratitude to these fine researchers for their important work. If you found any of these excerpts helpful, please read the studies in their entirety.
Epidemiological Approach and the Risks of Asbestos Exposure
By: Montwrobleski77
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