Document dajYgb70BnYx4o8YYr4E0Ryd9

468 NEWS AND VIEWS SouthAfricanJournalofScien.ee vot.oo zepiemvenuciooer 1992 deterrent to the inequitable remuneration of officials. Transparency and accountability should be further promoted through the publica tion of planning documents. Councils should be required to produce five-year rolling plans every year. Tangible, quan tifiable objectives should be identified and progress towards these goals reported annually. Aspects of efficiency and success should also be included and fin ancial statements made more comprehen sive and explicit. By making the various Councils' financial reports comparable with each other, using detailed guidelines provided by the Department of National Education, it will become feasible to judge their performance in achieving their objectives. The Research Councils constitute the backbone of the scientific system in South Africa. However, as for the rest of the scientific community there is no entit lement to continued support from public funds. The scientific enterprise must jus tify itself by visibly effective and effi cient use of resources and its contribution to society. 1. A System of Framework Autonomyfor Scientific Councils (1988). Department of National Educa tion, Science Planning, NATED 11-007 (88/04). Pretoria. 2. Rothschild (Lord) (1971). The Organisation and Management of Government RiD. Cmmd 4814. HMSO, London. 3. Rothschild (Lord) (1983). An Enquiry into the Social Science Research Council. Cmmd 8554. HMSO, London. 4. Pouris A. (1992). Perspectives on the institution al framework for science and technology policy making. S. Afr.JSci. 88,90-94 5. ASTEC (1990). Setting Directions for Austra lian Research. Australian Science and Technol ogy Council. Australian Government Publishing Service, Canberra. Tremolite in southern African chrysotile D. Rees, R.S.J. du Toit, R E G. Rendall, G.C.H. van Sittert and D.B.K. Rama It is possible that the presence of the amphibole tremolite in chrysotile ore may be the cause of mesotheliomas in miners exposed to this type of asbestos. This article is the first report of the presence of tremolite fibres in the lungs of miners who worked with chrysotile in southern Africa. Although significant exposure to tremolite was not detected, results support the case for a more detailed investigation of the potential health risk. Malignant mesothelioma, a tumour which arises from mesothelial cells, has been investigated extensively because of its association with asbestos exposure. Nev ertheless, important questions about asbestos and mesothelioma remain unan swered. One of these is the capacity for the different asbestos fibre types to cause mesothelioma in exposed individuals. The link between this tumour and the amphiboles, particularly crocidolite (blue asbestos), is well established but the role of chrysotile (white asbestos) in the development of the tumour is less clear. The mining and milling of Canadian chrysotile is associated with a small risk of mesothelioma1 and animal experi ments have shown convincingly that all the major asbestos varieties, including chrysotile, produce the cancer.2 Never theless, the causal association between chrysotile exposure and mesothelioma in humans is not established because certain chrysotile ores contain a small proportion of the amphibole tremolite and this fibre has been found in the lungs of chrysotile miners.3 It has been shown to cause mesothelioma in rats4 and has been im plicated as the causative agent of meso theliomas in workers exposed to vermiculite contaminated with tremolite.5 It has been suggested, therefore, that the fibrous tremolite, rather than the chrysotile itself, may be responsible for the disease in the majority, if not all, of the chrysotileexposed cases.1 If this hypothesis is correct, then chrysotile deposits which are not contaminated by fibrous tremolite would carry little if any mesothelioma risk. Despite its potential importance, information on the fibrous tremolite content of southern African chrysotile deposits is not available. To begin to rectify this gap in knowledge, a prelimin ary investigation to determine whether tremolite fibres are present in southern African chrysotile was conducted at the National Centre for Occupational Health (NCOH). The purpose of this preliminary investigation was to assess the need for a more detailed study of the extent and nature of amphibole in these deposits. Two methods were used in this investi gation; namely, a direct examination of milled chrysotile samples for tremolite, and an indirect approach in which lungs of miners with a recorded history of asbestos exposure exclusively on a chry sotile mine were examined for tremolite fibres. Samples of milled chrysotile mined at Shabanie mine (Zvishavane), Havelock, Kaapsehoop and African Chrysotile As bestos (ACA Msauli) mines were obtain ed from a local mining house. Addison and Davies's recently reported sulphuric acid digestion method for the analysis of amphibole asbestos in chrysotile and other minerals6 was adopted to concen trate any amphiboles contained in these samples. The authors report that their method improves the sensitivity of amphibole analysis greatly, giving detec tion limits of 0.01 to 0.05% in chrysotile by X-ray diffractometry (XRD). XRD, using a Phillips PW 1130/00 diffracto meter, and phase contrast optical micros copy (OM) and scanning electron micros copy (SEM) were used to analyse the concentrated samples for tremolite. Following inhalation, chrysotile is cleared from the lungs to a greater extent than amphiboles. Consequently, the am phibole fibres accumulate preferentially and may eventually become the predom inant fibre in the lung even if they made up only a small proportion of the total inhaled asbestos burden. This phenomen on has been observed in some Canadian chrysotile minersI>3-7 and was used in this study as an indirect method of determin ing the tremolite content of chrysotile ore. Lung tissue from four deceased miners with a history of exclusively chry sotile mining was identified using the PATHAUT database.8 The four ex miners had had autopsies at the NCOH and lung tissue had been stored in wax blocks. Asbestos fibre content of the lung tissue was determined by removing the wax with heat and xylene and digesting the lung tissue in 15% sodium hypochlor ite. The remaining material was suspen ded in distilled water and samples were then prepared for OM and SEM. A de tailed description of this procedure is contained in a thesis by Rendall.9 Results Milled chrysotile Tremolite could not be detected by XRD in any of the treated chrysotile samples. This negative finding was con firmed by an independent institution, the Council for Mineral Technology (Mintek). Examination of these samples under The authors are at the National Centre for Occupational Health, Department of National Health and Population Development, P.O. Box 4788, Johannesburg, 2000 South Africa. ntific lucaV04). i and 1814. > the 1554. ition>licy- istrahnolshing tec)tilc RD, ctoroscros the is tent amlally om- ladc otal icnlian this nin)tilc sed irythc cxOH vax jng the ing iorcncrc dc- is by itile >nthe in ter for nal O. iL-WO ANU vu_y*o 4W more detailed investigation. Such an Tabic 1. Cases by occupational history, diagnosi s and fibre analysis. Case Years of service on chrysoulc mines Mine Occupation Tremolite observed F:ibrc content . Diagnosis' of lung2 OM SEM 1 24 ACA Mill shiflsman Asbcslosis 697 000 No No Millwright : 22 Slolzburg Mill shiflsman Asbcslosis 411 000 No Yes Mill foreman l 22 ACA Mill shiflsman Asbcslosis 312 000 No Yes investigation should focus on two as pects. The fibre content of the lungs of deceased miners will provide data on the cumulative tremolite exposure over time from all sources within the mine and mill, while a systematic analysis of the tremolite content of raw and milled ore will clarify the current situation for speci fic localities. Mill foreman 1 22 ACA Underground Pleural 377 000 No skipman plaques Mill shiflsman 'tty NCOH specialist pathologist after post-mortem examination. 2Pcr gram of dry lung as determined by fibre counting under optical microscopy. 1. Churg A., Wiggs B., Depaoli L., Kampe B. and No Stevens B. (1984). Lung asbestos content in chrysotile workers with mesothelioma. Am. Rev. resp.Dis. 130,1042-1045. 2. Wagner J.C., Berry G. and Timbrell V. (1973). Mesothcliomata in rats after inoculation with asbestos and other materials. Br. J. Cancer 28, 173-185. OM at a magnification of X 450 con firmed the efficacy of the digestion process: only one fibre being observed in several Helds of vision. SEM showed that tremolite fibres were present but in very small numbers, being observed only with careful searching (at a magnification of X 1000). Lung analysis Selected characteristics of the four eases used for lung tissue examination arc presented in Table 1. Years of service in chrysotilc mining plus a summary of the jobs performed on the mine, the med ical diagnosis and fibre content of the lung tissue are shown in the Table. All four individuals had substantial service (exceeding 20 years) and had worked in doses being associated with increased risks.10 These factors were not examined in this investigation but are particularly pertinent for two reasons. Tremolite fibres in the lungs of the South African miners were scanty and much fewer than in Canadian miners, in whom tremolite fibres frequently exceed chrysotile fibres in lung tissue and can be very numerous: 10-100 million tremolite fibres per gram of dried lung was not unusual in one study.7 The second reason is that the tumour is not well documented in chrysotilc-exposed individuals in southern Afri ca. The register of mesothelioma cases maintained by the Pathology Department of the NCOH contains over 2 000 cases of mesothelioma, yet none has a history of asbestos exposure exclusively on a 3. Pooley F.D. (1976). An examination of the fibrous mineral content of asbestos lung tissue from the Canadian chrysotile mining industry. Envir. Res. 12, 281-298. 4. Wagner J.C., Chamberlain M., Brown R.C., Berry G., Pooley F.D., Davies R. and Griffiths D.M. (1982). Biological effects of tremolite. Br. J. Cancer 45, 352-360. 5. McDonald J.C., McDonald A.D., Armstrong B. and Sebastien P. (1986). Cohort study of mortal ity of vermiculite miners exposed to tremolite. Br. J. ind. Med. 43,436-444. 6. Addison J. and Davies L-S.T. (1990). Analysis of amphibole asbestos in chrysotile and other minerals. Ann. occup.Hyg. 34,159-175. 7. Rowlands N., Gibbs G.W. and McDonald A.D. (1982). Asbestos fibres in the lungs of chrysotile miners and millers -- a preliminary report. Ann. occup. Hyg. 26,411-415. 8. Hessel P.A., Goldstein B., Davies J.C.A., Web ster I., Hnisdo E. and Landau S. (1987). Patho logical findings in mine workers: 1. Description of the PATHAUT database. Am. J. ind. Med. 12, the mill -- usually the most dusty work site. Fibres most likely to be tremolite were not observed under OM, but SEM demonstrated fibres with the morphology and spectral characteristics of tremolite in chrysotilc mine (I. Webster, pers. commun., NCOH, 1992). It should be noted that an exposure history is not recorded in about 50% of these cases," thus reducing the significance of these 81-89. 9. Rendall R.E.G. (1988). The retention and clear ance of inhaled glass fibre and different varie ties of asbestos by the lung. M.Sc. thesis, Uni versity of Witwatersrand. 10. Stanton M.F., Layard M., Tegeris A., Miller E., two of the eases. These fibres were scan ty, one fibre appearing in approximately 20 fields at X 1000 magnification. In summary, a few tremolite fibres were found in milled southern African data. In conclusion, the results presented here do not confirm significant tremolite exposure in South African chrysotile miners but provide clear support for a May M., Morgan E. and Smith A. (1981). Rela tion of particle dimension to carcinogenicity in amphibole asbestos and other fibrous minerals. J. natn. Cancer Inst. 67, 965-975. 11. National Centre for Occupational Health. Annual reportfor 1990, Johannesburg. chrysotilc and in the lungs of two chryso tilc miners. These preliminary findings should be treated with caution and are certainly inadequate both to quantify the Xth Biennial Conference of the risk faced by exposed individuals or even to conclude that a tremolite hazard is Southern African Society for Quaternary Research definitely present. The XRD results suggest that the tremolite content was under 0.05% in all the samples but more extensive sampling may show that sub stantial variation in tremolite content exists within a particular mine. Further more, an improvement in the methodol ogy of isolating tremolite from chrysotile may facilitate identification and quantifi cation by X-ray diffractomctry. The mesothelioma risk from asbestos fibres is determined partly by the morph ology and the inhaled dose of the fibres, The papers that follow on pages 470 to 515 are selected contributions to the 10th biennial conference of the Southern African Society for Quat ernary Research, held from 2-5 July 1991 at the University of Port Elizabeth. The Society has an active membership of about 160, whose interests, as can be seen from these articles, range over palaeoanthropology, archaeology, palaeontology, palaeoclimatology, geology and related environmental studies. The balance of the conference proceedings will be published in a future issue of the journal. These articles were initially evaluated and prepared for publication under the direction of an editorial committee for the 10th conference proceedings consisting of Werner lllenberger and Jokl le Roux. with longer, thinner Hbres and increasing