Asbestos Concentrations in Lung Tissue.

One element in the asbestos debate that has received some scrutiny is that of asbestos concentrations in tissue. One study on point is called, "The optical and electron microscopic determination of pulmonary asbestos fibre concentration and its relation to the human pathological reaction" by T. Ashcroft, A. G. Heppleston - J Clin Pathol 1973;26:224-234. Here is an excerpt: "Abstract - The quantitative extraction of asbestos fibres from asbestotic lung by alkali digestion has been refined by maceration of the tissue without prior drying, the minimum use of centrifugation, and the adoption of phase contrast microscopy. Preliminary experiments suggested that, using this technique, asbestos fibre counts were accurate to within at least ± 20% and in most instances to within ± 10%.

The method was used to assess asbestos concentrations in lung tissue showing various degrees and forms of fibrosis. The results, as determined by light microscopy, indicated that uncoated fibres generally outnumbered coated fibres. In mild and moderate asbestosis there was a progressive increase in concentration of asbestos fibres, both coated and uncoated, with increasing severity of fibrosis, whereas in severe asbestosis no correlation existed between the fibre concentration and the form or the extent of the pathological reaction. It is suggested that the severe fibrosis results from the supervention of non-specific inflammatory processes.

Asbestos fibre diameter distributions, gauged by electron microscopy, were fairly constant irrespective of the degree of fibrosis. Optically visible fibres constituted between 12 and 30% of the total, so that an optical count may be said to give an approximate indication of the total asbestos concentration and, so far as asbestosis is concerned, may well serve for comparative purposes. The relation between asbestos and neoplasia will, however, require identification and quantitation of particular types of the mineral by microanalytical techniques."

Another interesting article is called, "The hygiene standard for chrysotile asbestos." by Peto J. - Lancet. 1978 Mar 4;1(8062):484-9. Here is an excerpt: "Previous studies, including the analysis on which the current 2 fibres/cm3 hygiene standard is based, may have underestimated the risk of morbidity or mortality following exposure to low levels of asbestos dust. Accurate dose-response data at levels below 2 fibres/cm3 are unlikely to be available for the foreseeable future, and the biologically plausible assumption that excess cancer mortality is approximately proportional to dust level should be provisionally accepted. It may be reasonable, however, to postulate a safe threshold for mortality from asbestosis. If excess mortality from asbestos-related disease is proportional to dust level for each cause, approximately 10% of male asbestos workers might, under certain assumptions, eventually die of asbestos-induced disease after 50 years' exposure at 2 fibres/cm3. Peritoneal mesothelioma is usually due to crocidolite (blue asbestos) or other amphiboles, but exposure to chrysotile (white asbestos) alone may lead to a substantial risk of pleural mesothelioma. These predictions are based on rather small numbers in a single factory, and further studies in other working environments are required. Fibre counts based on optical microscopy are likely to be less relevant than total counts by electron microscopy, and excess mortality is virtually confined to men first exposed more than 20 years ago, when little or no accurate data on dust levels were collected."

If you found any of these excerpts interesting, please read the studies in their entirety. We all owe a debt of gratitude to the people examining these important issues.

About the Author:

Monty Wrobleski is the author of this article on Mesothelioma Lawsuit Settlements. Find more information about Asbestos Lawsuit Settlement here.