Document 0g99O48pgdwoQqzngk2jKLGm

SUMMARY AND EVALUATION Subject: Brief discussion of the various forms of asbestos and their effects on health. Of some interest. Evaluation: This very short paper, running to three printed pages, was presented to provide background information to a conference on possible asbestos exposure to maintenance workers on auto brakes and clutches in Britain. The author points out that currently disc brake pads, brake lining6 and clutch facings contain 50 percent chrysotile asbestos. However never developments indicate that the percentage of asbestos in the mix is likely to decline, perhaps down to a minimum of 30-percent asbestos. Disc brakes require less asbestos fiber than drum brake linings, and it is estimated that more and more passenger cars produced in the U.K. will be eouiped with disc brakes. Adviser, Cape Asbestos Company). Journal: Annals of Occupational Hygiene (British), January 1970 Title: "Asbestos and Asbestosls." Summary: As. given above. SCF-FA-6348 Atm. Omr. Hit- Vol. U. PP. J-3. Hwno" Pro* l. htoied to Greet Britain ' ASBESTOS AND ASBESTOSJS* ' W. J. Smithlh ' Group Medic*) Adviser, Cape Asbestos Company. 114 Park Street, London W.l. THE FORMS AND USES OF ASBESTOS Commlrctai.lv important asbestos fibres Tall into two main groups. The first of these is chrysotilc, and the second comprises the amphiboles. Both groups arc _ fibrous silicates, but they differ .in geological origin, in chemical composition, in molecular structure, in fibre size and strength, and in other characteristics. Chrysolite, white asbestos, comes from many different places. There are slight chemical and physical variations in the fibres from different sources, but basically all have the same molecular structure. On the other hand, the amphibotes comprise at least three separate types, whose molecular structure is very similar, but whose chemical and physical properties differ more widely. Amostte (amber) and crocidolite (blue) are of commercial importance in this country, whereas anthophyllite is a Finnish fibre not used here. . The relative amounts of each fibre in world production is shown in Fig. I and the areas of main use in Fig. 2. ' . Chrysolite (white) 2.600,003 lorn tux Asbestos. Annuel world out pin -3,000.000 tom 1 AmosHe (South A(rieo) Creeidelite ' 90000 ions (blue) 3% South Alneo) . "ItOJBOOlwn 3-i* Ant hnphvlIHc (Fmlondl 10,000 tons iIv*. Conode * USSR ' S. Airies USA Europe Others 1,250.000 TSO.OOO 250.000 100.000 109,000 350.000 Fig. 1. World production of asbestos. 'This paper was originally presented at a Conference on Exposure to Asbestos during Drake and Clutch Maintenance, hekl ai Dientwood, Esses, March, 1969. 3 4 W. J. Sniniiu Mm M ISMCP Mlmtoi , . .. . :AjmmoI cntownplian-SjDOOiOOOtene WhcraH tn mraaS ' ' ChryteliU bcienn* Itotj Franc* JAPAN UK Germans orhart USA 5auth*rn Africa USSR " * USA . . 1 USSR ConaJa Blur Cracidolilt Amotiit 4Mhop*ytlrt t | SAlr.ee i ****** Fio. 2. Arcat el use of asbestos. The different characteristics of asbestos fibres dictate their uses, their applications and their mode of packing and handling. For example, ainositc can be pressure packed and palletized, whereas chrysotile lends itself more readily to containerization. By far the greatest use of chrysotile is in the asbestos ccmcm industry. Ainositc is used mainly in insulation and building products. Crocidolite, due to its excellent acid resistance, finds its major application in the manufacture of battery boxes in'this country. It is added to the pitch mixture in unopened dissoluble bags. ,; br co in P no wl pa hi be is i pin is i the linii cav; beci peri sists into the: 1 calci cone any itself E of th niBC work unco i frequ The . invesi cations tessure uuiion. osiic is :nl acid in this Asbestos and asbcstotb 5 Very broadly it can be said that current friction materials, whether they be disc - brake pads, passenger car and commercial vehicle brake linings or 'dutch facings, contain SO per cent chrysolite asbestos. The new trends of development, particularly in the fields of disc brake pads and commercial vehicle brake linings;, indicate that the percentage of asbestos included in the mix is likely to decline. Some new materials . now contain approximately 40 per cent asbestos, and newer mixes can be foreseen with an even lower percentage, probably down to a minimum of 30 per cent. The pads for disc brakes require less asbestos fibre than conventional drum brake linings. It is estimated that more and more passenger ears produced in the U.K.. will in future be equipped with disc brakes, particularly on the front wheels. THE BIOLOGICAL EFFECTS OF ASBESTOS The variation existing in the biological effects of the different types of asbestos is the subject of considerable interest and research, and the extent to which the physical and chemical characteristics of the asbestos itself influence biological effects is being investigated. The role of trace elements and contaminants associated with the fibres has also to be considered. The chief biological effects of asbestos are confined to the lung and the pleura, or lining or the lung and chest cavity, and to the peritoneum, or lining of the abdominal cavity. A few cases of skin corns have occured in asbestos workers, but these are - becoming much less common. - All types or asbestos, if inhaled in fairly high concentrations over a considerable period of time, may cause fibrosis of the lungs. This disease, called asbestosis, con* sists of thickening of the lung membranes with resultant stiffening of the tissues and interference with oxygen uptake. The interference with gas transfer is the reason for the shortness of breath which causes the disability associated with asbestosis. The amount of exposure required to produce fibrosis of the pleura, with or without calcium deposition in the scars, is more debatable. It may be that shorter, less concentrated exposures, particular))' in youth, leave this mark upon the pleura. In any event this particular effect of asbestos inhalation causes little or no disability in itself Exposure to asbestos may lead to further complications, e.g., heart failure, cancer or the lung, or, rarely, to malignant changes in the pleura or peritoneum, known as mesothelioma. Cancer ofThe lung Ijaybecn tsbown to -be more common m -asbestos workers who smoke, just as it is in the general population. Mesotheliomas arc very- uncommon throughout the world, but in some areas they have been associated more frequently with exposure io crocidolite than to chrysolite, amosilc or anthophyllitc. The reasons, for this arc at present obscure, but arc being sought intensively by investigators in many different countries. BftAXb LIMING DECOMPOSITION PRODUCTS In recent years, some individuals have pointed at brake lining wear as a pro bable source of asbestos contamination of the ambient air. In this paper, Jeremiah R. Lynch of `the National Center for Urban and Industrial Health, HEW, refutes this theory by showing that in all but a few extremely severe automobile braking tests, less than one percent asbestos fiber could be found in the collected dust. He concludes that brake lining wear is "an inconsequential health factor in urban air pollution."