Document 91V88kRrk3aJ5616nRqGN3enR

In late May, delegates from 60 countries met in Canada for the World Symposium on Asbestos to debate the scientific, economic, political, social, administrative_and ethical aspects of asbestos use. Tern' Nash, formerly with Cape Irrdustries'a'na now a healtn anjl safety consultant, gives his view of the issues raised. : ' i A Pf'V" - 6 OCT 1932 its use must be controlled The World Symposium on As bestos was originally planned as a bold attempt to involve scientists, management and labour in one major meeting to discuss the commercial future of asbestos. "To ban or not to ban?" That was the question. In the event, it was a curious mixture of science and politics, which blended exactly as the proverbial oil and water. It produced an emulsion which temporarily rendered the whole situation opaque, to settle out again almost as soon as the conference was over without either component appreciably affecting the other. Politics entered at the ear liest planning stages. The sym posium was organised and financed by the Canadian government, the provincial government of Quebec and the EEC, so that the potential taint of money from private industry was avoided. But, the province of Quebec mines al most as much asbestos as the rest of the world outside the USSR, so that its government, which has a controlling share in some of the mines, has a major interest in its promotion. Attempts to get the European trades unions to participate had been greeted with the cry of "Whitewash!". In the end, few attended. This was a great pity and, coupled to the polarisation of certain members of the scientific fraternity around one eminent speaker, it resulted in a less balanced approach than one would have expected from such an important conference. The scientific part of the proceedings provided little new material in research results and no new answers, but it did perhaps help to clari fy the four main points: - What is the nature of the dose response at low levels? Is there any evidence for a threshold dose below which asbestos has no adverse effects? - Are all three types of com mercially used asbestos equ ally bad, or should chrysotile be treated differently from the amphiboles (crocidolite and amosite)? - Are there any environmental effects of asbestos usage? What evidence is there that people other than those occ upationally exposed are* ad versely affected? - Are all respirable fibres equ ally suspect? What is known about other natural or man made fibres? Is the shape or the chemistry to blame for the asbestos tragedy? Dose response An almost audible sigh of relief came from the industry side when one of the first speakers at the opening session, Irving Selikoff of the United States, made it dear that he was not advocating a total ban on asbestos. He merely wanted adequate control. Corbett McDonald of Canada showed that the higher the fibre count multiplied by the years of work, the more deaths there were from lung cancer among asbestos wor kers. This straight-line relationship between cumu lative dose and response was based on reasonable data on exposure levels available in the studies. Professor McDonald em phasised that risks differed between different industrial situations and also between different fibres. Chrysotile was in his opinion much safer than crocidolite or amosite. He felt that chrysotile should be permitted to be used for friction materials, asbestoscement products and perhaps textiles, but not in insulation. He concluded by saying that the question of banning asbes tos must not be considered in isolation, since there was some evidence already that man made mineral fibre was not without risk. As regards the proposed European standard of one fibre/cc he said that wor kers exposed to this level of chrysotile were unlikely to show any detectable increase in lung cancer. For practical purposes, it was a "no-effect" level. Hans Weill also thought that there was evidence for dif ferences between chrysotile and the amphiboles (amosite and crocidolite) in the in cidence of asbestosis and mesothelioma, as well as lung cancer. He discussed the dif ficulties in diagnosing early as bestosis, where minimal changes on chest x-ray caused the highest disagreement be tween readers, and where smoking and age could on their own be responsible for the changes. In discussing pleural plaques, he pointed out that there was no evidence that they increased the mortality risk. He repeated the recom mendation of the American College of Pathologists that the term pleural asbestosis should be dropped. Finally, he quoted evidence from McDonald's figures to suggest that there will be no excess of lung cancer in those occupa tionally exposed to asbestos at levels low enough to eliminate the risk of asbestosis. The session ended with papers by two cancer experts, John Higginson and Dietrich Schmael, discussing the possibility of a threshold for asbestos-induced cancer. That is a level of fibre exposure which the body could tolerate without any cell damage of the type believed to be conducive to malignant change. Both believed that there was evidence in favour of the threshold concept. All of this was very encouraging for per sons exposed to the low levels demanded by current and proposed legislation. Chrysotile or amphibole? If the first session set a high scientific note, the second session was almost pure polit ics. The time set aside for panel discussion and questions was almost entirely filled with prepared speeches by interes ted parties - unions, manage ment, politicians and concer ned organisations. This was the pattern for all subsequent discussions. Political considerations were very evident in the disagreement between the producer unions (representing miners and millers) and the consumer unions (represent ing mainly construction wor kers) about whether or not as bestos should be banned. They were equally evident between Canadian and South African interests, when differences between fibre types were discussed, since Canada produces only chrysotile while the world's supply of both crocidolite and amosite now comes from South Africa. Little new evidence emer ged on different risks and modes of action between chrysotile and crocidolite, and the puzzles remain. Both McDonald and Weill had stated their belief that the epidemiological evidence demonstrated lower risks for chrysotile. Frederick Pooley of the UK and Alison McDonald ' of Canada discussed electron microscope findings which in dicated in both humans and animals that chrysotile tended to break up and disappear after deposition in the lungs, while amphibole remained. This was consistent with a case control 22 Health Safer* at Work August 1982 PLAINTIFF'S EXHIBIT 71757-66 PLAINTIFF'S I* EXHIBIT is \M- DICRII C-UK-MS-000200 study of mesotheliomas which showed a positive association only with amphibole, and the known rarity of mesothelioma attributable to chrysotile ex posure, in contrast - to crocidolite. The contrast be tween human epidemiology and animal experiments, in which chrysotile is more car cinogenic both when adminis tered by inhalation or by im plantation, was repeatedly emphasised but not explained. Both Bill Simpson for the UK and William Hunter for the EEC stood by the more stringent controls imposed on crocidolite, which is to be prohibited in Europe except for the manufacture of pipes and special seals; this met with general approval from all ex cept the South Africans. Nevertheless, certain ques tions remain. Arthur Langer, of the United States, in an interesting paper on physiochemical aspects, poin ted out the difference in sur face potential, that of am phibole being negative and chrysotile being positive. At the same time, he emphasised both the physical changes produced in the fibre by processing which may alter its toxic effects, and the factors such as surface area and falling velocity which influence the received dose. It remains a fact that there are no published series of membrane filter counts on manufacturing processes involving only crocidolite by which to judge true exposure levels in earlier years. The possibility that part of crocidolite's higher car cinogenicity is due to a higher count of very fine fibres for a given level of dustiness cannot be discounted. Environmental risks Discussion on asbestos in the environment produced an interesting contrast between theory and practice. Scientists tended to stress how very small a risk, if any, would result from fibre liberated into the en vironment in contemporary situations, while represen tatives of the various govern mental agencies tended to play safe and err on the side of caution in exercising their regulatory function. The conclusion was that, outside specific settings, for example, rooms with crumb ling sprayed crocidolite, no valid assumptions about risk The hazards of inhaling asbestos dust are said to be virtually eliminated by the use of Martindale positive pressure respirators, as seen at the Goodyear Tyre and Rubber Company factory, Drumchapel, Glasgow, where old as bestos insulation is being removed in the boilerhouse by Asbestos Protection Services (Photo: Mertindote Protean* Limited) could be made on the basis of industrial experience. Con firmation was also available in an important paper by Jack Siemiaticky of Canada who had carried out a mortality study of the Thetford and As bestos areas, where the Canadian mines are situated. Despite environmental asbes tos levels more than 100 times greater than normal urban areas, there was no increase in the mortality rate for females either from all causes, from cancer in general, or lung can cer specifically. Males showed a significant increase in lung cancer, but 70 per cent had worked at least some time in the mines and the excess was attributable to their asbestos exposure at work. Hazards of other fibres Andrew Pye of the UK gave a detailed survey of the range of substitutes available. He stressed that there was no sing le universal substitute for as bestos, and for this and other reasons most substitutes were more expensive and involved compromises between perfor mance and cost. Speakers from India and Zimbabwe, who followed, stressed the im portance of asbestos, and par ticularly asbestos cement, for the developing countries and their great advantages over substitutes on a cost-benefit analysis. Chris Wagner of the UK then gave a valuable survey of the possible health hazards of mineral substitutes. He divided them into four classes: man-made (vitreous) mineral fibre; other forms of asbestos (mainly tremolite); fibrous zeolites (erionites); and fibrous clays such as palygorscite, sepiolite and attapulgite which are now finding increas ing' use. Fine tremolite has probably been responsible for mesotheliomas in the in habitants of certain areas of Cyprus and Turkey, and erionite in Turkey, so that these materials should be viewed with suspicion. No such hazards have yet been demonstrated with either man-made mineral fibres or the fibrous clays, although cer tain notes of caution have been sounded over man-made mineral fibres, particularly over glass microfibres and ceramic fibres. Wagner did not discuss or ganic fibres, and questions were asked about the promis ing new aromatic polyamide (aramid) fibres manufactured by Du Pont under the trade names of Nomex and Kevlar. These are already finding many industrial uses as asbes tos substitutes, particularly in textiles and friction materials. A high proportion of these fibres are in the respirable range. While a Du Pont representative claimed that their investigations had shown them to be harmless, there is so far no published evidence of their effect in the lungs. What of the future? Gloomy predictions had bean made within the asbestos industry that the symposium would sound its death knell. In the event, however, it was clear that neither scientists nor the regulatory agencies were in favour of a complete ban. While the unions were divided according to whether they represented producer or user industries, even the most vociferous of the latter, once their prepared speeches had been delivered, appeared to accept the possibility that as bestos might continue to be used under control limits for the foreseeable future. Nevertheless, the momen tum of substitution in Europe at least is now so great that it is unlikely to stop before asbes tos is phased out in all but a few specialised areas. A majority of the Canadian mines and mills, hit by both recession and substitution, have already ceased production for three months this year. Proposals for legislation As far as the UK is concer ned, there have been new legislative proposals in the wings for some considerable time. The main report of the Advisory Committee on As bestos (ACA) made over 40 recommendations in 1978 backed up by two subsidiary reports - one on "Monitor ing", the other on "Thermal Insulation Work". Progress on both of these latter items app ears to have gone on quite well. A Central Reference Scheme for Asbestos Sam pling is well established and it is understood from an HSE spokesman that the final ther mal insulation proposals are soon to be placed before the HSC. On the broader front of new control limits and pro hibitions, the UK govern ment has patiently been await ing action in the European Community. Current progress on the asbestos directives has taken a decided tum for the better, helped apparently by decisions relating to the earlier lead directive which had been clogging the pipeline. Should European Community action fail to materialise, there is little doubt that the UK will now "go it alone" down the established route. It is becom ing an acute embarrassment to have had such a long delay with so little action since the evidence of the ACA was published, even though sub sequent consultation clarified many of the sticking points between the social partners. Health & Safety at Work August 1982 SC-UK-MS-000201