Document zbxK8D6M6MbwGrDpv9k7yn3Zg

enter of crocldollte lining In Veetern Australia, reached a peak populalon of about 1,000 In tha I960*a. At present the population la down to bout 200 and the Vest Australian Stats Government haa suggested that losing of the town and evacuation^ of the residents because of conInulng risks of airborne aabeatoav dust ([Chmieal Veok, December 8, 9?8, p. 25). The risk of mesothelioma anong the residents of the town ho were not employed by mines la demonstrated by the case of e 27-yearld woman who had an environmental childhood exposure to crocldollte Unglols at at., 1978), SUMMARY roductlon Of the six forma of asbestos, only four have been used to any aiglflcnr.t degree In comaerce. These are amoslte, crocldollte, anthophyllte, and chrysotlle. Although asbestos was used by Stone Age man, it as not until the latter part of the 19th century that It came Into 'Meapread use In the Industrialised world. The modern Industry began n Italy and England after 1860, with Quebec being the main supplier of he crude fiber. By 1900 two to three hundred thousand metric tonnes had een mined, mostly In Quebec. By 1980 ever 100 million tonnes had been lned worldwide of which about 90 percent wae of the chrysotlle variety, pproxlmately 75 percent of all asbestos sver mined has come from just hree ehryootlle mining localities, Quebec, Canada, and the central and -outhem Urals of the Soviet Union. The chrysotlle producing countries .n order of Importance are the Soviet Union (46.1 percent of the world's :etnl asbestos production In 1978), Canada (28.9Z), Zimbabwe (3.8Z), :Una 0.8Z), Italy (2.9Z). South Afrlea (2.1Z), Brasil (1.8Z), O.S.A. :i.7Z), and Australia (1.0Z). Two to three percent of the world's asbestos production has been m crocldollte variety, most of which came from South Africa. Veatern stralla vas a minor producer of croeldollte between 1944 and 1966. All aoslte has been mined la the Transvaal frovlnca of South Africa and accounts for about two to three percent of all asbestos ever produced, rbe only significant authophylllte production came from Finland, Where 130,000 tonnes was mined between 1918 and 1966. Total production of vis 8005 0069 antbophylllte asbestos probably accounts for no more than 0.5 percent of . the world's total asbestos production to data. Deposits of commercial asbestos are found In four types of rocks: (I) alpine-type ultramaflc rocks. Including ophlolltes (chrysotlle, snthophylllte, and trcmollte); (II) stratiform ultramaflc Intrusions (chrysotlle and tremollte); (III) serpentlnlsed limestone (chrysotlle); and (IV) banded Ironstones (amoslte and crocldollte). Type I deposits are by far the most Important and probably account for over 85 percent of the asbestos ever mined. The tost Important Type I deposits are those of Quebec and the Urals. Type II deposits are found mostly In South Africa, Swaziland, and Zimbabwe. These furnish mostly chrysotlle asbestos. Type III deposits are small In size; the sat notable of these are located In Globe, Arizona, and In the Carolina area of the Transvaal Province of South Africa. Type IV depoalts are found only In the Frecambrlan banded Ironstones of the Transvaal and Capa Provinces of South Africa and of Western Australia. Only r*-.c South African deposits are still In produc- tlon. There Is considerable geologic evidence that-cosmerclal asbestos deposits form only where there la a favorable atress environment, ouch as where folding or faulting occurs. Asbestos and health The three principal dlseaaes which are related to asbeatos exposure are (1) lung cancer, (2) cancer of the pleural and peritoneal membranes (mesothelioma), and (3) asbestosls, a condition In which the lung tissue becomes fibrous and thus loses Its ability to function. Lung cancer can be caused by exposure to chrysotlle, anthophylllte, amoslte, and crocl dollte asbeatos; however. Increased risk of this 'disease Is probably found only In those who also smoke cigarettes. Asbestosls Is also caused by heavy and prolonged exposure to all four forms of asbestos. Mesothe lioma Is caused principally by exposure to crocldollte asbestos. There Is good evidence that snthophylllte and chrysotlle asbestos do not cause any significant increase In mesothelioma mortality, even after heavy . 117 PRODUCED BY FORD