An individual’s work history is very important when trying to ascertain points of asbestos exposure. One question that many people are interested in is the relationship between exposure levels and the development of mesothelioma and other diseases.
One study worth taking a look at is called, “Exposures and mortality among chrysotile asbestos workers. Part II: Mortality” by John M. Dement, PhD, Robert L. Harris Jr., PhD, Michael J. Symons, PhD, DrPH Carl M. Shy, MD - American Journal of Industrial Medicine Volume 4 Issue 3, Pages 421 – 433 – 2007. Here is an excerpt: “A retrospective cohort mortality study was conducted among a cohort of 1,261 white males employed one or more months in chrysotile asbestos textile operations and followed between 1940 and 1975. Statistically significant excess mortality was observed for all causes combined (standardized mortality ratio [SMR] = 150), lung cancer (SMR = 135), diseases of the circulatory system (SMR = 125), nonmalignant respiratory diseases (SMR = 294), and accidents (SMR = 134). Using estimated fiber exposure levels in conjunction with detailed worker job histories, exposure-response relationships were investigated. Strong exposure-response relationships for lung cancer and asbestos related non-malignant respiratory diseases were observed. Compared with data for chrysotile miners and millers, chrysotile textile workers were found to experience significantly greater lung cancer mortality at lower lifetime cumulative exposure levels. Factors such as differences in airborne fiber characteristics may partially account for the large differences in exposure response between textile workers and miners and millers.”
Another interesting study is called, “Asbestos retention in human respiratory tissues: comparative measurements in lung parenchyma and in parietal pleura.” By Sebastien P, Janson X, Gaudichet A, Hirsch A, and Bignon J. - IARC Sci Publ. 1980;(30):237-46. Here is an excerpt: “Asbestos fibres in respiratory tissues from 29 cases diversely exposed to asbestos dusts have been characterized, sized and counted using a transmission electron microscope. Comparison of data obtained by measurement of fibres in lung parenchyma and in parietal pleura samples showed the following: -- In each case, the proportion of chrysotile fibres (as opposed to amphiboles) was higher in parietal pleura than in lung parenchyma. (The proportion of chrysotile in pleura was greater than 90% in 30 of the 40 samples.) -- Fibres encountered in parietal pleura were shorter than those in the parenchyma. -- There was no evident correlation between numerical concentrations of fibres in lung parenchyma and those in parietal pleura. This study has shown that characteristics of asbestos retention in parietal pleura cannot be derived from measurements in lung parenchyma. On the basis of the cases analysed here, who were exposed to mixed types of asbestos dust, chrysotile seems to be the asbestos type retained almost exclusively in parietal pleural tissues. These findings might be taken into account when assessing the risk of pleural diseases (especially mesothelioma) attributable to each type of asbestos fibre.”
A third study is called, “Deposition, clearance, and translocation of chrysotile asbestos from peripheral and central regions of the rat lung.” By Coin PG, Roggli VL, and Brody AR. - Environ Res. 1992 Jun;58(1):97-116. Here is an excerpt: “We investigated the pulmonary deposition, clearance, and translocation of chrysotile asbestos in the context of our previously developed model of asbestosis in the rat. Adult male rats were exposed for 3 hr to an aerosol of chrysotile asbestos. Subgroups were sacrificed up to 29 days postexposure and the lungs of the animals fixed. Peripheral and central regions of the left lung were resected, digested, and analyzed for fiber content by scanning electron microscopy. Pulmonary deposition did not differ between peripheral and central regions. There was no evidence of translocation of fibers from central to peripheral regions. The average diameter of retained fibers decreased over time, consistent with longitudinal splitting. The average length of retained fibers increased over time, consistent with slower clearance of longer fibers. We employed a novel counting scheme to ensure accurate fiber number measurements, allowing the calculation of clearance rates for fibers 0.5 to greater than or equal to 16 microns in length. Fibers of length greater than or equal to 16 microns were cleared slowly, if at all. These findings could have important implications for the pathogenesis of asbestos-related pleural disease. Many fibers are deposited in the peripheral region, and the longest (greater than or equal to 16 microns) will persist there for extended periods.”
If you found any of these excerpts interesting, please read them in their entirety.
Author Resource:
Thor Anderson is the author of this article on Mesothelioma Lawsuit Settlements .
Find more information about Asbestos Exposure here.
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