Asbestos Exposure Levels and the Impact on Mortality Rates for Workers

Many statistical models have been developed over the years to help with research regarding mortality rates resulting from asbestos exposure.  One interesting study worth reading is called, "Exposures and mortality among chrysotile asbestos workers. Part I: Exposure estimates" by John M. Dement, PhD, Robert L. Harris Jr., PhD, Michael J. Symons, PhD, Dr PH Carl M. Shy, MD - University of North Carolina, School of Public Health, Chapel Hill - American Journal of Industrial Medicine - Volume 4 Issue 3, Pages 399 – 419 23 Jan 2007.  Here is an excerpt:  "Abstract - A detailed study of plant processes and dust control methods over the period 1930-1975 was conducted in an asbestos textile plant processing chrysotile. Linear statistical models for reconstructing historic dust exposure levels, taking into account textile processes, dust control measures, and job assignments, were developed. Parameters of these statistical models were estimated using 5,952 industrial hygiene sampling measurements covering the period 1930-1975. For most textile operations, exposure levels were significantly reduced by about 1940, when most engineering dust control measures were in place.

Results of the exposure estimates indicated precontrol exposure levels to range from 3 to 78 fibers/cc with typical levels well above 10 fibers/cc. After textile operations were provided with dust control measures, estimated exposure levels ranged from 3 to 17 fibers/cc and were usually in the range of 5 to 10 fibers/cc. These exposure estimates were combined with an assessment of mortality among workers at this plant to investigate exposure-response relationships. Exposure-response results are presented in the companion manuscript in this volume."

Another interesting article is called, "Penetration of Asbestos through the Digestive Tract of Rats" by R. D. Pontefract & H. M. Cunningham - Food Research Laboratories, Health Protection Branch, Department of National Health and Welfare, Ottawa - Nature 243, 352 - 353 (08 June 1973).  Here is an excerpt: "MESOTHELIOMAS of the pleura and peritoneum1−3 have been linked with the inhalation of asbestos fibres. We have shown4 that asbestos fibres are present in drinking water, beer, wine and other beverages. Asbestos fibres can penetrate the mucosa of the stomach and intestine5 and Telischi and Rubenstone6 have found asbestos material in a gastric carcinoma. Godwin and Jagatic7, reporting on mesotheliomas of the pleura caused by asbestos, noted that asbestos particles were widely distributed in various tissues. They suggested that particles may migrate from the lung through the blood and lymphatic system to all parts of the body. In the light of these reports, we surmised that asbestos consumed orally can pass through the gut into the blood stream and accumulate in various tissues."

A third article worth looking at is called, "The biological effects of magnesium-leached chrysotile asbestos." By Morgan A, Davies P, Wagner JC, Berry G, Holmes A. - Br J Exp Pathol. 1977 Oct;58(5):465-73.  Here is an excerpt:  "Chrysotile asbestos was leached in N hydrochloric acid for varying times to produce a range of magnesium-depleted samples. The protein adsorptive capacity, the haemolytic activity, and the capacity to cause selective release of acid hydrolases from macrophages were measured for the various samples in vitro. The carcinogenicity of the same materials was determined following intrapleural inoculation in rats. The adsorptive capacity for albumin decreased linearly with magnesium removal. The haemolytic activity also declined until about half the magnesium had been removed, after which there was little further change. The selective release of acid hydrolases from macrophages in culture increased up to the point at which half the magnesium had been removed but by 90% depletion had declined rapidly. The carcinogenicity of 50% -depleted chrysotile was similar to that of intact, but at 90% depletion the incidence of mesothelial tumours had fallen considerably. There was no evidence that the leached samples fragmented more than the unleached in vivo."