Document rMX94Odm0y85G469O1Q8RoqE

2 HISTORICAL BACKGROUND TO THE USE OF ASBESTOS 2.1 INTRODUCTION Asbestos is a collective term for a group of naturally occurring fibrous silicates that are incombustible and separable into filaments: chrysotile (white asbestos), amosite (brown asbestos, cummingtonite, grunnerite), crocidolite (blue asbestos), anthophy llite, tremolite and actinolite1. Only the first three have widespread commercial use. In its natural state, asbestos occurs throughout much of the planet. It is found in two-thirds of the rocks in the earth's crust. The ancient Greeks first used chrysotile asbestos over two thousand years ago as wicks for oil-lamps and it was they who gave us the word asbestos, meaning "everlasting" or "non-extinguishable"2. There is evidence that it was used even earlier - some four thousand years ago - for strengthening clay pots in Finland. This non-flammable quality led ancient Greeks to manufacture asbestos lamp wicks. The Romans mined asbestos and left us with both non-flammable cremation cloths and records of an illness among slaves who may have worked with asbestos3. During the middle Ages, manuscripts in Europe mentioned diseases common to miners, but there was no mention of asbestos. A small asbestos textile industry developed in Russia during the time of Peter the Great (1675-1725) but asbestos use remained negligible until the time of the Industrial Revolution. The commercial exploitation of asbestos fibre in modem times occurred in the latter part of the 19th century, when experiments were successfully carried out in producing asbestos thread, which was woven to form asbestos cloth - important for thermal insulation and protective clothing. At the same time asbestos-cement building materials were being developed, thereby exploiting the reinforcement properties of the fibre in combination with cement. These developments led to the widespread introduction of manufacturing facilities for asbestoscement corrugated and flat sheets, and high pressure pipes, together with a wide range of associated products. Subsequently other applications of asbestos fibre were developed to include friction materials, jointing and packing and electrical insulation. In total, there are over 3 000 recorded different uses for asbestos. 2.2 ASBESTOS MINERALS Asbestos minerals may be broadly divided into two groups, namely: amphibole asbestos and serpentine asbestos1. 2.2.1 Amphibo le Asbestos Amphibole asbestos, which has a chain-like crystalline structure, comprises of mainly crocidolite (or blue asbestos) as well as amosite, tremolite, anthophy llite and actinolite. Because of their chemical structure and straight, needle like fibres, amphiboles are very dusty, as well as highly biopersistent. In some countries, and for some special applications, the amphiboles continue to be used: Crocidolite is the strongest of the asbestos fibres. It has high tensile strength and acid resistance. Long-fibre crocidolite is woven into fabrics used for boiler lagging, acid-resistant packing and gaskets. Historically the principal use of the shorter crocidolite fibres was in the manufacture of asbestos-cement products, although this is no longer the case. 15  Amosite is highly resistant to heat and quite flexible, but may be susceptible to strong acids and alkalis. It has less tensile strength than chrysotile or crocidolite and has only fair spinnability. Amosite asbestos has the longest fibre lengths. Its resistance to acids and seawater is greater than that of chrysotile, and it fuses at a much higher temperature than crocidolite. It is, however, somewhat more brittle. It is used in blanket form for felted insulation for high temperature applications. In compacted form it is applied as a covering for marine turbines, jet engines and similar applications. 2.2.2 Serpentine Asbestos Serpentine asbestos has a leafy or layered structure and is represented by chrysotile (also known as white asbestos), the most common serpentine fibre. Silky in texture, with curly fibres, serpentine asbestos is unlikely to remain suspended in the air. Chrysotile currently accounts for more than 98% of world asbestos consumption. Its fibres are characterised by high tensile strength, resistance to alkalis, high flexibility and good spinnability. Chrysotile's tensile strength and resistance to heat make it suitable for spinning and weaving and as counteraction to heat and fires. It is mainly used for asbestos textiles, friction linings and facings, asbestos cement and insulation products 2.3 GLOBAL ASBESTOS DEPOSITS Asbestos is a naturally occurring mineral fibre commercially available in most parts of the world. Supply is fairly diversified. Thus there is no strategic dependency on a single supply. Table 2 reflects worldwide reserves of asbestos4. T ABLE 2: W ORLDW IDE ASBESTOS RESERVES COUNTRY Canada South Africa USA China CIS Brazil Zimbabwe Others TYPE OF ASBESTOS Chrysotile Chrysotile Amosite Crocidolite Chrysotile Chrysotile Chrysotile Chrysotile Chrysotile Chrysotile Amosite Anthophllite RESERVE BASE 47 million tons 8.2 mllion tons Large Large Large M oderate M oderate Large Unfortunately, this source does not provide a definition of "large" versus "moderate" deposits, therefore, it is difficult to assess into which category South Africa's deposits fall. However, the fact that South Africa has deposits of all three major types of asbestos confirms that it has been an important international source of asbestos. 16 2.4 ASBESTOS PRODUCING COUNTRIES Figure 1 reflects an estimate of world asbestos mining production for the twentieth century5. Figure 1: world asbestos mining production - 1900 to 2001 6.000.0 00 5.000.0 00 4.000.0 00 3.000.0 00 2.000.0 00 1.000,0 00 0 MfcMWMMtMlMMlUtl ^^ ^^ ^ ^^ ^^ ^ ^ ^^ ^^ ^ ^ ^v' ^ ^ ^ ^ ^ ^ ^ This figure indicates that asbestos mining production peaked at 5 million tons in 1975 and has steadily declined to the current levels of approximately 2 million tons in 2000 and 2001. Table 3 reflects a schedule of asbestos producing countries5, with their production levels for the 1996 to 2000 period. Table 3: asbestos producing countries Argent ina Brazil Bulgaria Canada China Egypt Greece India Iran Japan Kazakhstan Russia Serbia and Montenegro South Africa Swaziland Zimbabwe TOTAL 1996 446 170,000 400 506,000 293,000 1,836 80,213 23,215 4,500 18,000 128,700 615,000 509 57,120 26,014 165,494 2,090,447 1997 400 170,000 300 455,000 288,000 2,000 80,000 25,051 4,300 18,000 125,000 710,000 360 49,986 25,888 144,959 2,099,244 1998 380 170,000 300 309,000 314,000 2,000 70,000 18,751 2,258 18,000 125,000 600,000 633 27,195 27,693 123,295 1,808,505 1999 350 170,000 350 337,366 247,000 2,000 60,000 20,000 2,000 18,000 125,000 675,000 361 18,700 28,000 115,000 1,819,127 2000 350 170,000 350 340,000 260,000 2,000 50,000 21,000 2,000 18,000 125,000 750,000 550 18,909 25,000 110,000 1,893,159 2000 CONTRIBUTION 0.02% 8.75% 0.02% 20.05% 14.44% 0.10% 3.50% 1.11% 0.16% 0.93% 6.47% 34.50% 0.02% 1.77% 1.37% 6.78% 17 These figures indicate that Russia, Canada, China, Brazil and Zimbabwe are the worlds largest asbestos mining countries and account for almost 85% of world supply. 2.5 ASBESTOS EXPORTING COUNTRIES Table 4 reflects a schedule of asbestos exporting countries, ranked according to volume of 1998 exports4, the latest date for which these statistics are available. T ABLE 4: ASBESTOS EXPORTING COUNTRIES Canada Zimbabwe USSR /Russia Brazil South Africa China Kazakhstan COUNTRY 1998 295, 000 117, 000 99, 000 63, 000 25, 000 14, 000 5, 000 % OF PRODUCTION EXPORTED 95% 95% 17% 35% 95% 4.5% 4% As would be expected, the largest mining countries are also the largest exporting countries. 2.6 ASBESTOS CONSUMING COUNTRIES Table 5 reflects a schedule of asbestos-consuming countries, ranked according) to their 1994 consumption levels, the latest date for which these statistics are available"5. Table 5: worldwide asbestos consumption CIS China Japan Brazil Thailand India South Korea Iran France Indonesia Mexico Colombia Spain USA Turkey Malaysia South Africa TOTAL 1994 700,000 220,000 195,000 190,000 164,000 123,000 85,000 65,000 44,000 43,000 38,000 30,000 29,000 29,000 25,000 21,000 20,000 2,021,000 34.6% 10.9% 9.6% 9.4% 8.1% 6.1% 4.2% 3.2% 2.2% 2.1% 1.9% 1.5% 1.4% 1.4% 1.2% 1.0% 1.0% 18 These statistics indicate that, even at this relatively recent stage, South Africa was already one of the smallest international consumers of asbestos. 2.7 PROPERTIES OF ASBESTOS The most important properties exhibited by asbestos, and which account for its widespread use in a broad range of asbestos-containing products include3: Tensile strength Resistance to high and low temperatures Fire, friction and acid resistance Chemical resistance - particularly to cement alkalinity Dielectrical resistance Resistance to bacteria, fungi, etc. Weather proofing, and Compatibility with cement as a binder The mining and processing of asbestos and its use in manufactured products constitutes a billion dollar industry. Asbestos has been acclaimed for its heat, friction and acidresistant properties. However, most asbestos is used as a cheap reinforcement agent: more than 70% of asbestos is used for reinforcing asbestos-cement in construction projects1. 2.8 ASBESTOS CONTAINING MATERIALS Up until the 1970s, some 3,000 products were made with asbestos fibres of all types. These included toasters, dryers, ironing boards and low-density friable insulation products. Today, some sixty countries still use asbestos, but only the chrysotile variety and primarily in cement building materials such as roofing materials, cladding and pipe. In a modern context, there are four common applications for asbestos1: Asbestos Cement Chrysotile asbestos is used in asbestos cement as it has good reinforcing properties. Products are mainly in the form of profile sheets and slates. 90% of the world production of chrysotile is used in the manufacture of chrysotilecement, in the form of pipes, sheets and slates. Asbestos-cement is valued principally for its excellent cost effectiveness and durability. Friction Materials Chrysotile asbestos has been used in friction materials because it is durable and resistant to heat and oil. Friction products represent about 7% of the chrysotile fibre used today. S eals and Gaskets The main uses are in: o Packing and seals - braided and laminated packing, proofed asbestos cloths and tapes, and moulded gland packing used to seal openings in a variety of industrial applications 19 o Gaskets - compressed asbestos fibre in a mixture of natural or synthetic rubber compounds that are used to seal joints in a variety of piping and pumps that transport liquids and gasses Insulation Materials The main chrysotile asbestos textiles are woven tapes, welting, cloths and yarns. Composites are generally asbestos fibre or cloth impregnated with resin and then formed into sheets, tubes, rods or shaped mouldings. These are used as insulation materials for temperature control purposes in a variety of industrial applications 2.9 CATEGORIES OF ASBESTOS-CONTAINING PRODUCTS Table 6 categorises asbestos-containing products according to the density of their asbestos content. Table 6: categories of asbestos-containing products Density Types of Asbestos Friability Applications Products LOW-DENSITY PRODUCTS HIGH DENSITY PRODUCTS > 20% asbestos content < 20% asbestos content Amphibole (until 1980) Serpentine Amphibole (until 1980) Serpentine Friable (W hen dry can be crumbled, pulverised or reduced to powder by hand pressure) Non friable Insulation Temperature control Fire protection Noise control Ornamental fittings Reinforcement Friction Resistance Textiles Packings Braided Packings Asbestos-Cement Products: Profiled sheets Slates Pipes M oulded goods (containers etc.) Brake Pads Clutch Plates Gaskets Valve Steim Seals This table indicates that most of the modern applications of asbestos are in high-density products where the risk of exposure to asbestos fibres is lower. 20