Document GzGyqRQmo4ND9MJNLZY1Z14zq

FILE NAME: Asbestos in India (IND) DATE: 1971 DOC#: IND003 DOCUMENT DESCRIPTION: Book Excerpt - Asbestos & Asbestosis iv i ^ j / ' F t r i *"7 ^ c l'f / \ L L L (f r s .-c/ ASBESTOS AND ASBESTOSIS W. J. Smither The Forms and uses of asbestos Commercially important asbestos fibres fall into two main groups. The first of these is chrysotile, and the second comprises the amphiboles. Both groups are fibrous silicates, but they differ in geological origin, in chemical composition, in molecular structure, in fibre size and strength, and in other characteristics. Chrysotile., white asbestos, comes from many different places. There are slight chemical and physi cal variations in the fibres from different sources, but basicailv all have the same molecular structure. On the other hand, the amphiboles comprise at least three separate types, whose molecular structure is very similar, but whose chemi cal and physical properties differ more widely. Amosite (amber) and crocidolitc (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 the figure. Asbestos Annual world output--3,000,000 tons Chrysotile fwhitc) 2 'toom000/ tons Canada 1.250,000 USSR 750.000 S. Africa 250,000 USA 100,000 Europe 100,000 Others 351!,000 Crocidolitc (bluet (South Afric-.p 10,000 tons 3t% Amosite (South Africa) `10.000 tons -TO/O/ World production of asbestos 62 Anthophyllite !Fin land i in (too ' nas 63 The different characteristics of asbestos fibres dictate their uses, applications and their mode of packing and hand ling. For example, amosite can be pressure packed and palletized, whereas chrysotile lends itself more readily to con tainerization. By far the greatest use of chrysotile is in the asbestos cement industry. Amosite is used mainly in insuhtion and building products. Crocidolite, due to its excellent acid resistance, finds its major application in the manufac ture of baUcry bores in this country. It is added to the pitch mixture in unopened dissoluble bags. Very broadly it can be said that current friction mate rials, whether they be disc brake pads, passenger car and commercial vehicle brake linings or clutch facings, contain 50 per cent chrysotile asbestos. The new trends of develop ment, rv'.rticuiarly in the fields of disc brake pads and com mercial vehicle brake linings, indicate that the percentage of asbestos included in the mix is likely to decline. Some no.v materials now contain approximately 40 per cent asbestos, and newer mixes can be foreseen with an even lower percen tage, probably down to a minimum of 30 per cent. The pads for disc brakes require less asbestos fibre than conven tional drum brake linings. It is estimated that more and more missengcr 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 variations existing in the biological effects of the different types of asbestos is the subject of considerable interest and research, -md the extent to which the physical and chemical characteristics of the asbestos i t'elf influence biolowcnl effects is being investigated. The role of trace elements and contaminants associated with the fibres lias also to be considered. The chief biological effects of asbestos are confined to the lung and pleura, or lining of the lung and chest cavity, 64 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 of asbestos, if inhaled in fairly high concentra tions over a considerable period of time, may cause fibrosis of the lungs. This disease, called asbestosis. consists of thickening of (he lung membranes with resultant stiffening of the tissues and interference with oxygen uptake. The inter ference 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 mare debatable. It may be that shorter, less concentrated exposures, particularly in youth, leave this mark upon the pleura. In any event this particular effect of asbestos inhala tion causes little or no disability in itself. Exposure to ashe-tos may lead to further complication. c e.. heart milmc. cancer of the lung, or. rarely. ! ' malignant ch-ia.ms in the pleura or peritoneum, known as me,othdioina. Career cf the It.ng has been -Town to be more common in asbestos workers who `moke, just as it is in the general population. Mesotheliomas are \er.. uncommon droaghoul the world, but in some areas they have been associated more fre.;.;cnt]y with exposure to chrocidolite than to ehrysotile. amosite or anthophyllite. The reasons for Mis are at pre`c: : obscure, but are being sought intensively by investiga t e m many different countries. "T he A nnals of Occupational H ygilnl-- Vol. 13, No. 1 January 1970" PHENOL (C.H OH) AND ITS CARE Although, to-day. Phenol is a basic raw material, used in large quantities by many industries, it was originally used as an antiseptic. Later phenol found use in the synthesis 'W* 65 of dyes, the newly discovered aspirin, and one of the first high explosives, picric acid. Phenolic resins are now one of the most important ap plications of phenol. Their uses are wide and growing. They are used as moulding materials, laminates and adhesives ; other derivatives of phenol go into the manufacture of plas ticizers. pharmaceuticals, photographic chemicals, soaps, dyestuff's, germicides, preservatives, inks, paints, glues, tex tile-. explosives and weed killers. Phenol itself is v/idely used as a selective solvent in pertoleum refining. Phenol having a flash point of 80C, melts at -1041 C ant! boils at approximately 180-!82C at normal atmospheric pressure. Phenol is flammable and its vapours mixed v. ith air can be explosive. Phenol i, highly toxic and is readily absorbed even litivrah hv.ict (unbroken) skin The greater the urea '!' ski : ei .itaminated. the greater the Jangei. In contact a. ith skm. nheno! "dll cause painful or dangerous burns: and if laft. i: wilt be ah-orbed into bi v d stream. It is also to<ic when .-/allowed or when its vapom is inhaled A few serious and fatal accidents were caused due to it- improper handling and lack of knowledge regarding its to- ie:t'. ;:nil llar.i.ubility. Recently one worker died in a fcctorv while melting solid phenol contained in a drum without loosening its bung, on a naked flame. Precautions : 1. Corrosive toxic chemicals should always be handled carefully by operatives who are fully informed on the charac teristics of the materials and trained in the proper handling procedure. 2. Workmen who handle phenol should wear gas tight safety goggles or face mask, rubber gloves and rubber boots.