Document 7BgZYOdZNzLMVrja01xYN6ZR

FILE NAME: Welding (WELD) DATE: 1968 DOC#: WELD009 DOCUMENT DESCRIPTION: Journal Article - Asbestos Hazards in Dock Workers 4iut Occup Hyg. Vol. 11, pp. 135-145. Pergamon Presst 1968. Printed in Great Britain ASBESTOS HAZARDS IN NAVAL DOCKYARDS* P. G . H arries H.M. Dockyard, Devonport Abstract--A brief description is given of the types of asbestos materials, and their uses in shipbuilding and ship repairing in Naval Dockyards. An outline of the problems to be faced and a description of preventive methods is followed by a series of questions intended to stimulate practical solutions to the problems of using asbestos materials safely in the industry. So much has been written and spoken about asbestos in the last five years that it might seem irrelevant to add any more to the vast mountain o f words, facts and figures already expounded. 1 know that there is a keen awareness in Newcastle of the problems associated with asbestos in the shipbuilding industry and that a great deal of work has been, and is being done, by the Department of Occupational Medicine to further knowledge of the disease and to suggest a suitable code of practice for the use of asbestos in the industry. With this knowledge in mind it was with great trepidation that I approached the preparation of this paper. After some thought 1 came to the conclusion that it would not be very much good trying to tell you anything, but that here was a wonderful opportunity to see if you could answer some of the questions that we face in the Royal Navy as we search for the current solutions to the problems associated with ihe use of asbestos in building, repairing and refitting ships. I have come to Newcastle hoping to learn, and I hope to put specific questions to you, the answers to which we must know if we are to deal effectively with the problems of using asbestos safely. I think it fair to begin by outlining the problems as I see them, to describe what the Navy is doing about them, and then to ask for your solutions to them. THE INDUSTRY There are four Royal Dockyards in this country, at Portsmouth, Devonport, Chatham and Rosyth, and a small amount of refitting work is done in Singapore and Gibraltar. These remark s are confined to the four home dockyards who between them employ some 50,000 civilians. About 17,000 men work afloat on the ships while the remainder work in the shops, factories and docksides. Less than 450 men are classed as asbestos workers and only the 50 men who work in the asbestos mattress shops are subject to the Asbestos Industry Regulations. This paper was originally presented at the 22nd Conference of the British Occupational Hygiene, Society, Newcastle upon Tyne, September, 1967. 135 136 P. G. H arriks Most of the work carried out in the Royal Yards is refitting and repairing ships, rather than shipbuilding which accounts for most of the work undertaken in the civilian yards. The extent of the refits also differs in that naval refits are usually much more extensive and often involve the removal and replacement of nearly all the insulating material in machinery spaces. As the removal of lagging material gives rise to more dust than its application these are very important differences. For these reasons, and for the many engineering and constructional differences between naval and merchant ships, 1 believe that the overall exposure to asbestos is likely to be higher in the Naval dockyards than in their civilian counterparts. Materials The asbestos materials used in Naval ships are largely the same as those used in the Merchant Fleet. Changes have occurred in the amounts and types of material used which I think may help to explain the emergence of asbestosis in the dockyards as a problem at this time. From the start of this century to about 1950 most of the machinery insulation was in the form of asbestos mattresses, 85 per cent magnesia sections containing 15 per cent amosite, and asbestos cloth. A certain amount of crocidolite was used in fibre form for mattresses, and in some asbestos board. From 1950 onwards more efficient insulation was required and magnesia sections were replaced by massive amosite sections consisting almost entirely of asbestos. The dwindling stock of amosite sectional lagging is still being used in small amounts but calcium silicate section containing only 12-15 per cent amosite has been in creasingly used since 1963. The use of large amounts of amosite section from 1950 onwards has meant that there has been a great increase in the amount of asbestos exposure over the last seventeen years. f The sprayed asbestos process was used extensively in naval ships from the end / of the war until 1963 when it was discontinued, largely for reasons of weight. Nearly \ all the fibre used in this process was blue, but amosite fibre was sometimes used. There are very many other uses of asbestos containing materials in ships and it is difficult to find a compartment in which there is no asbestos. Table 1 indicates most of the asbestos materials used in the dockyards, and they have been sub-divided into those giving rise to dust in their manipulation and those not usually giving rise to dust unless they are ground, polished or sawn. It will be realised that most of the asbestos is used for heat insulation although extensive use has also been made of asbestos sound and electrical insulating materials. Processes Mattress making. In each dockyard this is carried out in shops equipped with exhaust ventilation cowls in which the mattresses are filled with amosite fibre. Working conditions are good and dust concentrations are low. Some crocidolite has occasionally been used in the past and the men preferred it to amosite as it was less dusty and less spiky than amosite. Wyers (1946) has previously commented on the workers dislike of amosite asbestos. Asbestos hazards in Naval Dockyards 137 4 T able 1. Asbestos materials used in N aval D ockyards Dusty Non dusty Asbestos: Blankets Cement Cloth (untreated) Cord Fibre Millboard Packing fibre Rope Soft sound insulation Asbestos: Cloth (treated) Condenser packing Sheets (compressed fibre) Gaskets Oilproof jointing Compressed fibre jointing Graphited packing Rings Compressed sound insulation Jointing strips Tape Tubing Twine Webbing Washers Coated electric wire Calcium silicate sectional lagging (up to 15 per cent asbestos) Amosite sectional lagging (over 90 per cent asbestos) Magnesia compound (up to 15 per cent asbestos) Lagging. The application and removal of heat insulating materials is mainly ..ncentrated in the machinery spaces aboard ships and present practice is to lag all >t faces above 150F with calcium silicate sections covered with asbestos cloth, t cuing and fixing sections, rope and cloth does give rise to localized high dust f .. ncentrations, but the highest dust concentrations occur during removal of old seeing material. Hot and cold water pipes and ventilation trunking throughout the ships have previously been covered with asbestos cloth, but this is now replaced by cork, felt ;;;J canvas. , Asbestos spraying. This process was extensively used for environmental insulation ' .vul 1963 when it was completely discontinued. The existing material is extensively ..noved during refits and is being replaced by glass fibre. The dust concentrations :_:ing removing the dry material are very high. Application o f sound insulation. Asbestos boards of various types and thicknesses -_i.e been sawn and fitted for sound insulation and removed during subsequent c:.tv This work is done by joiners, and again the highest dust concentrations occur ;,,:ing removal of the old material. There are many other minor processes involving the fitting or removal of asbestos tria ls some of which do produce dust. Examples are the fitting and removal of b:sios in galley equipment; sawing and fitting friable asbestos board for ironing . jfils, cleaning with wire brushes, pipes and glands previously lagged with asbestos. M-'>t of these procedures are carried out intermittently by men who are not con::ied to be "asbestos workers" . v men first impressions of the problem would suggest that only those men continuously v riing with asbestos are at risk. In the dockyards these men would be the mattress ! 3 * ***** **,!!!p!*t ti ' ''N-k At-.. 1J/ I 138 P. G. H arries workers, laggers, sailmakers working with asbestos cloth, asbestos sprayers and strippers, and storeman. Experience has shown, and further consideration of the industry and processes should suggest, that many other men have been at risk. As most of the asbestos has been applied and removed in machinery spaces it is amongst men working mainly in these compartments that we might expect to find evidence of the disease. Table 2 shows the occupations of men in Devonport Dock yard who are NOT recognised asbestos workers, and who have been accepted by the T able 2. O ccupations of men with asbestosis* (D evonport D ockyard) Boilermaker Electrical fitter Engine fitter Engineer Iron caulker Joiner Plumber Rivetter Shipwright Shotblaster Stoker Welder Other than asbestos workers. Pneumoconiosis Panel as suffering from Asbestosis in the last year. All these, with the exception of the joiner and shot blaster, work on ships mainly in machinery spaces. The joiner cuts, fits and tears down Acoustic insulation periodically. The shot blaster spent years cleaning and blasting asbestos coated pipes. Table 3 shows the occupations of men histologically proven to have been suffering from pleural mesothelioma in Devonport Dockyard. It will be seen that none of these is a recognised asbestos worker but that they have all had considerable asbestos exposure on ships under refit. T able 3. O ccupations of men with pleural mesothelioma (D evonport D ockyard) Boilermaker Fitter Labourer on ships Shipwright Welder The diseases We are concerned with three disease processes. Asbestosis; carcinoma of the lung associated with asbestosis or asbestos exposure; and pleural or peritoneal mesothelioma associated with asbestos exposure. All three conditions take a long time to cause symptoms and have insidious onsets, and this makes it more difficult Asbestos hazards in Naval Dockyards 139 ! enforce preventive measures, as the need for them is often not realised. All three .-case processes are occurring in Devonport Dockyard and there is no reason to relieve that the situation is very different in the other Royal Dockyards. Husl Asbestos dust is liberated during manipulation, and especially during vigorous .caringdown of most of the asbestos materials used in the dockyard. The main problem - to contain the dust and prevent dispersal throughout the ship. In machinery spaces :he asbestos insulation is applied to a maze of pipes and machinery much of which .es in awkward and inaccessible positions. For these reasons efficient exhaust emilation at the source of dust emission is difficult, and, as the work is progressive the exhaust system has to be portable. The question of discharge of the exhaust also poses problems as often the machinery spaces are many decks below an exit to the -pen air. The long and difficult access to machinery spaces is one reason against wetting the insulation prior to or during its removal. Trials of infusing the lagging with probes, and spraying with low pressure water spray during removal showed that not , nly did these methods very considerably slow the progress of the work, but they nude the asbestos debris three times as heavy when wet as when in the dry state. \s it all has to be manhandled out of the ship, weight is a very important factor. As the dust arising from most of the materials used is mixed dust 1 am employing :Mth gravimetric and fibre counting methods to give an idea of the amount of dust _nd the content of fibre. Dr. V. Timbrell of the P.R.U., Penarth, has kindly provided ~,c with M.R.E. gravimetric samplers which I use in pairs, one being adapted to simple "total" dust, the other " respirable" dust. Fibre counts are carried out using v.ethods recommended by the Asbestosis Research Council (Holmes, 1965). Table 4 shows the range of fibre counts in various occupations but I must emphasize that these results are examples only and it will be some time yet before 1 Table 4. Ranges of dust concentrations Process Range (fibres/cma) Storerooms Application of amosite sections Application and stitching asbestos cloth Removal of amosite sections (boiler room) Removal of blue sprayed asbestos Removal of asbestos acoustic board Bagging asbestos debris 01 -- 9 -- 005 -- 29 -- 112 -- 48 -- 106 -- 36 40 0-26 1040 1906 683 3815 Membrane Filter samples taken by Drager hand pump, Austen Dymax Pump or Hunt Personal j pier. Technique of evaluation as described by Asbestosis Research Council 1964 (Holmes, 1965). ;,c enough data to give a more detailed picture of the situation. I think it is obvious ugh that it is in the removal, or tearing down of asbestos materials that the .-.test dust concentrations are to be found, but we need a lot more sampling rcnence before we can build up an accurate picture of the exposures during -plication of lagging. 140 P. G. H arries TH E PRO BLEM S A N D C U R R E N T A C TIO N IN H.M. D O CK YA R DS men that these measures 1 I have attempted to show that as an industry the Navy uses large amounts of desirable that we should many different products containing asbestos in varied and difficult working conditions. employ more appropriate The work often gives rise to high dust concentrations and many people working near A Medical Research the different processes may be exposed to the hazard. We know that men other than Unit at Penarth has been those working directly with asbestos are contracting asbestosis. of the risks more clearly< At present the uses of all asbestos containing materials are being studied with a varying asbestos exposure view to using alternative materials, and crocidolite is being excluded from ships. employees is under way, I Where substitution is not possible and asbestos materials are used, or existing asbestos some idea of the dust ex materials are removed, the following precautions are taken. in the dockyards. As far as possible the work is isolated and only those actually involved in the process of lagging or stripping are allowed into the compartment. Where possible, supply and exhaust ventilation through a filter is provided but satisfactory ventilation Questions to be answered systems are most difficult to arrange. As dust suppression is not possible we have to rely almost entirely on personal Asbestos is a very use shipbuilding industry, bi protection. Where large amounts of machinery lagging, sound insulation, and know the answers to nia f --5 particularly sprayed asbestos is to be removed then the men wear impervious overalls found after close co-open Ik 4 made either of P.V.C. or rubber, and an air line P.V.C. hood supplying fresh air via industrial hygienists, thei the dockyard compressed air lines. Despite the difficulties of the work, and the Engineers and constrt discomfort of the overalls, the men have removed over 500,000 ft2 of sprayed and whether or not an J crocidolite asbestos from H.M.S. Ark Royal using this form of protection. At as cheaply. | present we also have on trial Positive Pressure Powered respirators manufactured by Martindale Electric Co. Ltd., which are proving very popular with the men. They have the advantage of supplying adequate filtered air making them very comfortable to wear, and do not have the disadvantage of the trailing ail hoses which are difficult to untangle in the confines of a boiler room. For the application of lagging or sound insulation materials, and in the store:, when moving or cleaning asbestos, Siebe Gorman Mark VIII dust respirators are worn together with Bri-nylon overalls. Experiments are planned to lag the pipes in Management must b< that the minimum numbj Men must be asked ti handled carelessly. ] Physicians probably ! 1. What exposure in in motion the disease pr envisage long continuous the shop and fit them ready lagged. The asbestos debris is bagged in paper sacks, sealed and carried off the ship after the end of normal working hours. The bag is then pierced with a probe, filled with due to asbestosis, or is q to develop? The latter hi C u t h b e r t (1 9 6 6 ). Is tli water, and placed in a barge from which it is eventually dumped at sea. The ship's compartments are cleaned with industrial vacuum cleaners by men wearing full protective clothing. All the men who are expected to work most of their time with asbestos have initial and annual medical examinations and chest X-ray at the dockyard medical centres, and this has been the procedure from the beginning of lagging in the dock yard. What we are doing is to limit the amount of asbestos used, to limit the number of men exposed to the dust and as far as possible to protect those who have to be exposed to the dust. All this is expensive. Refit schedules are now planned to exclude other trades from compartments in which removal of lagging or sprayed asbestos is proceeding. The use of uncomfortable and sometimes cumbersome overalls and air hoods has slightly slowed down the rate of work. It is to the credit of both the management and only be employed as suq' 2. What are the crip to achieve anything usej first indication of impe^ (1965) has suggested thj result of finding early iiq shown further deteriorat' At present to advise' early signs of impaired ( the Pneumoconiosis Pad real dilemma. If we \y fairly rapidly and soon ^ from exposure at an eaif at such a slow rate'tha? Asbestos hazards in Naval Dockyards 141 ; that these measures have been proved to be possible, but 1 think that it is highly irable that we should attempt to more clearly define the risks, so that we can :- rloy more appropriate preventive methods. A Medical Research Unit working closely with the Pneumoconiosis Research ,.t at Penarth has been set up in Devonport Dockyard to attempt to define some : the risks more clearly. Work is proceeding on a detailed study of 420 men with ..rying asbestos exposure. Mortality studies of asbestos workers and other dockyard .-Tployees is under way, and a dust sampling programme is being carried out to give v.me idea of the dust exposure of most of the procedures producing asbestos dust :. the dockyards. Questions to be answered Asbestos is a very useful material and for some purposes it is irreplaceable in the .hipbuilding industry, but in order that we can continue to use it safely we must mow the answers to many questions. The solution to these problems will only be :',>und after close co-operation between marine engineers and constructors, physicians, industrial hygienists, the Asbestos industry, management and men. Engineers and constructors must be asked why asbestos is specified in their ships, nJ whether or not an alternative material would perform as well, more safely and cheaply. Management must be asked to plan the work of building or refitting a ship so .ii.it the minimum number of men is exposed to asbestos. Men must be asked to treat with respect a material which can be dangerous when ..cidled carelessly. Physicians probably have to answer more difficult questions. 1. What exposure in terms of dust concentration and duration is required to set i motion the disease process manifesting itself as asbestosis? Is it still necessary to -.usage long continuous exposure before we think that pulmonary fibrosis may be to asbestosis, or is a short exposure sufficient given enough time for the disease - develop? The latter has already been suggested by McVittie (1965) and Gold and i. thbert (1966). Is this an argument against the suggestion that laggers should -sly be employed as such for limited period of time? 2. What are the criteria for making an early diagnosis of asbestosis? If we are achieve anything useful from periodical medical examinations then surely at the n indication of impending asbestosis exposure to asbestos should cease? Hunt ;v05) has suggested that men removed from further exposure to asbestos as the \ ,cli of finding early impairment of lung function at routine examination have not ...Mien further deterioration. At present to advise a lagger to seek alternative employment because he shows ,\sfly sips of impaired lung function, and before he is considered compensatable by Pneumoconiosis Panel means a serious financial loss for the man. This is a very d dilemma. If we wait until the diagnosis is certain the disease may progress ,.r!y rapidly and soon become " compensatable" . If on the other hand he is removed mexposure at an early stage he may not show further deterioration, or may do so -uch a slow rate that we may never be certain of the accuracy of the diagnosis. 142 P. G. H a r h ii.s Surely this must be our aim, to reduce to the minimum the number of cases of prows compensatable asbestosis. Enlightened management and unions must seek ways: retrain and re-employ these men without financial loss and at no further risk to the health. 3. Js it safe to use crocidolite in any amount where air borne dust is produced The experiences in our dockyards over the next two decades may partly help t answer this question. Occupational hygienists together with physicists and ventilation engineers vm, have to help in answering these questions and the further problems arising from then, 1. We want to know the most suitable method for sampling asbestos dust? 2. What standards are we to aim at in dust control ? 3. What are the best methods of dust control for our industry? We want to know what dust levels are produced by the different processes aia what protective measures must be taken by the men doing the work. Is it justifiabk to allow other men to work without respiratory protection in a boiler room where lagging is being applied ? How long after lagging or stripping has finished do we hau te wait before it is safe for other work to proceed without respiratory protection' Are there suitable, effective, portable dust extraction units for use in ships? The Asbestos Industry is undertaking intensive research into most of then problems. Can the industry produce insulating material which does not emit asbesto- dust? 1 have told you what we are doing to face up to the problems as we see them in tin light of present knowledge, and 1 have put to you some of the questions we warn answered. Can you help us? REFERENCES G old, C. and Cuthbert, J. (1966) Publ. Hlth, Lond. 80, 261. Holmes, S. (1965) Ann. N. Y. Acad. Sci. 132, 288. Hunt, R. (1965) Ibid. 132, 406. McVittie, J. C. (1965) ibid. 132, 128. Wyers, H. (1946) A thesis presented to the University of Glasgow for the degree of Doctor of Medicine. D IS C U S S IO N Dr. Hickish said that the Society had a Standards Committee dealing with asbestos, and it v,a-> hoped that a comprehensive standard would be produced later this year. Dr. Gaze (The Asbestosis Research Council and The Cape Asbestos Company) said that the asbestos industry was anxious that its products should be used safely and that the true facts con cerning the hazards should be brought to light. For that reason they very much welcomed the author's clear and objective account of his investigation, and this opportunity to discuss it. The conditions that the author had described had clearly been unsatisfactory in the past; as far as he could judge, they corresponded approximately to the conditions which prevailed in the factories in the asbestos industry 30-40 years ago. It was at that time that it was first realised that there were hazards associated with the inhalation of asbestos dust. It was reassuring to know that, apart from Ithe precautions which had been mentioned, things would be vastly better in the future, became asbestos spray was no longer used in Her Majesty's ships, and the types of insulating material that were now used for lagging in engine rooms contained very much less asbestos than the materials that were used ten years ago. ft was true that there would continue to be a problem in the stripping of lagging, but this would diminish as new materials came into use. The author had lci/ards that existei Eo questions and aiuwcr many of the he would comment The first set of q The obtaining of ar slow. However, the were now records o: lactones were very possible to relate th The next series i medical aspects, bu much earlier than \ clearly established, the asbestos industr the word 'e a rly " v consensus of opinio as possible from e\| there were human t The next questii the form oi asbesto: had decided that it asbestos, with the < essential and irrepl should be used at a The final questi asbestos dust. It v Perhaps the best w; achieve precisely th than hitherto had t certain applications crucial applications International Regul io be essential. Ft essential that indust Dr. M urray sai so afraid of asbest within the industry now learning somet it should be used w! approach in the mo was essential. The hear that Dr. Gaze t ships. But there wc that in any circums: The trade union used. He was grate he was able to denv of certain methods The wearing of pro clothing, but if pec were necessary tmd lion. The problem Dr. F letcher s before a ship went the regulations'.'" a first man there got answer seemed to t Asbestos hazards in Naval Dockyards 143 The author had challenged them by asking some extremely pertinent questions about the health wards that existed with asbestos and what could be done about them. There were about thirteen questions and the asbestos industry, from its own experience, was in a position to attempt to , ,wr many of them. Dr. Gaze said that time did not allow him to discuss them all at length, but would comment on some. The first set of questions dealt with the relationship of exposure to dust and the onset of asbestosis. . :.e obtaining of an answer had been bedevilled by the difficulty that the onset of asbestosis was so *. However, the industry was in a good position to try and help because in many factories there . ::e now records of dust concentrations over a long period, and the medical records in most asbestos -ories were very complete. A pattern was now emerging as a result of which it was becoming , vible to relate the onset of asbestosis with time and concentration of asbestos dust. Tne next series of questions concerned early diagnosis. He did not pretend to be an expert on the cdical aspects, but it appeared to him that they were now in a position to diagnose asbestosis very ,.h earlier than was possible five years ago. The techniques for diagnosis were now reasonably ..carl> established, although many of them were still somewhat subjective. However, in the view of casbestos industry, the earlier that diagnosis could be obtained, the better. Much hinged on how c word "early" was interpreted; there was always a point at which one had to speculate. The . nsensus of opinion was that it was better to remove workers who were suspect at as early a stage possible from exposure to asbestos, although this was a clinical answer and it was appreciated that ere were human difficulties which could occur. The next question concerned crocidolite, blue asbestos. It was suspected that blue asbestos was :.e form of asbestos principally associated with mesothelioma. The asbestos industry in this country :.jJ decided that it would exercise a voluntary control on the importation and use of crocidolite j.besios, with the object of confining it to those applications where its unique properties made it ;,sential and irreplaceable. As far as he was aware, there was now no reason why blue asbestos . auld be used at any point in Her Majesty's ships or in any shipyard. The final question was whether the industry could produce an insulation that would not emit asbestos dust. It was difficult to give an answer, yes or no, without considerable qualification. Perhaps the best way of answering would be to say that the industry was working hard in order to ..hieve precisely that end. In recent years, forms of insulation containing very much less asbestos jii hitherto had been successfully manufactured and used. Asbestos continued to be essential in .criam applications, particularly in the control of spread of fire at sea. This was one of the most .mcial applications of asbestos products; in order fully to comply with the requirements of the i.-.ternational Regulations concerned with the prevention of fire at sea, the use of asbestos continued be essential. For such purposes asbestos would continue to be essential, and it was equally c-emial that industry should find the safest way of manufacturing and using it. Dr. Murray said that the position in the trade unions varied. There were some people who were afraid of asbestos that they wanted the material banned altogether, while there were others, . :hin the industry particularly, who appeared to handle it with impunity. The trade unions were a learning something about the technical aspects of the use of asbestos and they did not see why should be used where alternatives were possible. He was glad to see that the author was using this arproaeh in the naval dockyards. He agreed that there were certain applications in which asbestos a' essential. The position in regard to crocidolite was particularly worrying, and he was glad to ear that Dr. Gaze thought that it was not necessary to use crocidolite asbestos in any of H er Majesty's But there was the question whether the technical properties of crocidolite asbestos were such jt in any circumstances at all it was necessary to use it. The trade unions appreciated that there were certain circumstances in which protection had to be e.i. He was grateful to Mr. Sanderson for doing some work on a building site in Glasgow in which : .,js able to demonstrate to the satisfaction of the building workers, after a strike, that by the use .ertain methods it was possible to control the asbestos in the atmosphere to a reasonable level. ; wearing of protective clothing had to be regarded in this light. Nobody liked wearing protective :nmg, but if people had explained to them the reasons why certain types of protective clothing necessary under certain circumstances, then they would wear it with intelligence and co-opera. The problem of the use of asbestos would remain for a long time. Dr. Fletcher said that nobody who had ever been in the engine room in the last two months re a ship went to sea could regard the issue as being one of, ``How are we going to comply with . regulations?" as long as asbestos was in use. Pipes were put in willy-nilly, without planning. The - man there got his pipe in. Pre-formed insulation for engine room pipes was non-existent. The . A.r seemed to be to use only a selected number of workers to do the work, and then to close the I- t- 1 1 J a-- 144 I*. G . HARRIES engine room space when it was done, vacuum cleaning the space twice a day. Care had to be taker, to see what happened to the air. As regards mesothelioma, there seemed to be some doubt as to what caused it. He was not happ, that the present respirators were sufficient protection. Management had no idea what to do about n iT h e use of respirators would add thousands of pounds to the construction of an engine room, and J there would also be delay. 1 As a substitute for asbestos, there was a fibre from sugar cane. Once that could be economical!;, ft L produced, it would be an answer for the bulkhead ceilings. V Dr. G lover said that on the one hand there was asbestosis which fibrosed the lungs; this had been known for many years, and occurred in asbestos workers. On the other hand, mesothelioma seemed to occur in those who had no diiect contact, such as the woman who washed factory overall, but appeared to be rare among asbestos workers. Was there some mutual exclusion? Was a person who got asbestosis less likely to get mesothelioma? He thought there was no case at all for using crocidolite in lagging. This blue, straight, brink fibre asbestos is not very suitable for weaving and could, perhaps, be banned entirely. Dr. Smither (Cape Asbestos Co.) said that it was not true that there were more cases of meso thelioma occurring outside asbestos workers than inside. Unhappily, cases of mesothelioma were still arising. It was hoped that in the future those cases would be fewer, because no blue asbestos was now being used by his company; blue asbestos was not now being used in cloth. Every time that mesothelioma was mentioned, the unfortunate woman who washed overalls was quoted. She had three daughters who worked for the Cape Asbestos Company; they would not accept the service offered by the company but took their overalls home for mother to wash. When one held up an overall and dusted it, a much greater cloud of asbestos was produced than any worker produced anywhere in the industry. Such people, far from getting minimum exposures, were getting maximum exposures, much higher than the average worker got at any one time. Miss Newhouse now accepted that this exposure was heavy; she said : " In most of the patients, exposure occurred before the introduction of controls into the industry, and even with short periods of employment exposure may have been very heavy." Past conditions and their results should not be extrapolated to future predictions without real justification. Dr. D. L. Cran (Pneumoconiosis Medical Panel) replied to Dr. Glover that mesothelioma din occur in cases of asbestosis, so they were not mutually exclusive. However, it was true that the vast majority of cases of mesothelioma which he saw weie not cases of asbestosis. The main difference appeared to be that asbestosis required long periods of exposure, while mesothelioma could occur long after a short intensive exposure. Continued exposure could produce mesothelioma and at the same time produce asbestosis. Dr. S. Holmes (Asbestosis Research Council) said, in reply to Dr. Glover's statement, that ver; little blue fibre was used in asbestos textiles. The main use in textiles used to be in the making of railway engine mattresses, and that trade had almost gone with the introduction of diesel and electric engines. Protective clothing was now made from white asbestos. Dr. C. N. D avies commented on the simultaneous occurrence of asbestosis and mesothelioma. The chemical analysis of particles and fibres might be the same, but the association of asbestosis with particles was rather devious. Recent work suggested that mesothelioma was associated with the leeching out of metallic constituents, and this could occur from pariicles or fibres, possibly irre spective of the place of deposition in the lung. One had to consider whether for asbestosis fibres were necessary, whereas in mesothelioma particles might be just as effective as fibres. Dr. Cran said that he had recently had a case of a man with mesothelioma completely confined to the abdomen and not to the chest. How a man could get that when he breathed in asbestos fibres, nobody knew. Dr. Smither said that it was difficult to see the role of fibres in the peritoneum. His own experience was that peritoneal mesothelioma was as common as pleural mesothelioma, and he had heard recently that in America they were now finding a very much higher proportion of peritoneal mesothelioma than was expected. He pointed out that the fibres went into the nose and throat; some went into the mouth and were spat out; some were trapped in the nose. A great many of the fibres that went into the trachea were swallowed. He had no difficulty in imagining the route by which the fibres got down. One could talk about amorphous asbestos, but under the electron microscope, jOiestos was not t!.c phagocslc w e.agoxomc. and i.rrc tickling aw, vcilular biochenn articles. When particle broke up phagocyte to lurr Dr. Davies sa tiicre. He drew l>cre was far m particles took pt As regard p e... (Asbe It is repeatedly asbestosis or meso lather conflicting tn chrysotile and moderate amount periods do not Many of us in b> epidemiological uncontrolled and enormous counts to this view. Asbestos hazards in Naval Dockyards 145 i 'ciios was not amorphous, it was nearly all fibrous; it was intra-cellular. It had been shown that j c phagocyte would ingest asbestos; pictures existed showing bits of asbestos held within the | jgosome, and the leucocyte giving up asbestos. The Old idea of a mechanical irritation, with a j -re tickling away at the lung, was not believed nowadays. It was known that this was an intra ocular biochemical process, and it could occur with small particles; it could also occur with long vneles. When the longer particle was in the gut, there seemed to be a delay period before that reticle broke up. It was ingested by the phagocyte upon which it acted biochemically and caused the pugocyte to turn into a fibroblast and produce extra-cellular fibrous tissue. Dr. Davies said that one had to go back a stage further in the process, and say how the fibre got re. He drew the comparison with silicosis. In asbestosis of the lungs was little mobility; hence .ere was far more dissemination in the general picture than with silicosis where focalisation of rankles took place because silica particles were moved by phagocytes. As regard peritoneal mesothelioma, might this not be due to fibres which had been swallowed evi then penetrated the gut ? Written contribution by Dr. R. Gaze (Asbestosis Research Council and The Cape Asbestos Company Limited) It is repeatedly alleged that quite small and possibly brief exposure to asbestos dust may cause , -taosis or mesothelioma many years later. Although the evidence in regard to crocidolite is still conflicting, there is a great deal of evidence from medically supervised long service employees chrysotile and amosite mines, and in factories using these fibres, that lengthy exposures to low or -derate amounts of dust (say less than 5 fibres/c5) or exposures to large amounts of dust over short .-nods do not cause injury or even detectable morbidity. Many of us in the Industry have believed for a long time that most of the cases of diseases found -. epidemiological surveys and thought to be due to minor exposure have in fact been caused by ..-controlled and severe exposures on occasions of which there may be no record, and Dr. Harries' irormous counts of air-borne fibres during stripping of old insulation add considerable support this view. r77T