Document zXy8jMaLbD4LX38VQwBQzo0g

FILE NAME: Asbestos Information Association (AIA) DATE: 1973 Dec 18 DOC#: AIA006 DOCUMENT DESCRIPTION: Memo - Hazards of Heath Associated with Crocidolite and Amosite Asbestos with Cover Letter from North American Asbestos Corp ( 7N3OIRTH AMERICAN ASBESTOS CORPORATION 150 NORTH WACKER DRIVE. CHICAGO. ILLINOIS 60606 PHONE: (312) 726-8515 CABLES: NORAMCO. CHICAGO D e c e m b e r 18, 1973 Mr. R. H. M e r e n e s s Asbestos Information Association 1660 L Street, N. W. Washington, D. C. 20036 i PLAINTIFFS EXHIBIT Dea r Bob, During m y recent visit to your offices you will recall our discussion p e r taining to a position paper which C ape Asbestos asked permi s s i o n to submit to the A 1 A / N A . W e are enclosing copies of the d o c u m e n t as received today. W e believe there have been tendencies in s o m e areas to segregate Blue and A m o s i t e asbestos into a separate category, as opposed to Chrysotile, w h e n related to health hazards. F r o m this point of view, it would appear that C ape has endeavored to fairly and fully present all the k n o w n facts as regards Blue and A m o s i t e asbestos. These documents are for your files and information, and m a y be circulated to all m e m b e r s of the A I A / N A should you so desire. In the event you believe they would serve a useful purpose, copies m a y be distributed to selected people in O S H A . If you have any questions relative to this matter, please contact m e . Sincerely yours, N O RTH AMERICAN ASBESTOS CORPORATION CGMorgan/jc end. Memorandum from The Cape Asbestos Company Limited on Hazards to Health Associated with Crocidolite and Amosite Asbestos INTRODUCTION It is not infrequently suggested that special hazards may exist with crocidolite (blue) and amosite asbestos that are not so pronounced with chrysotile. As the largest producer and processer of amphibole asbestos, Cape is naturally concerned about this and, while being fully aware of its responsibility as a supplier of these materials, it is anxious that the facts relating to these forms of asbestos should be fully understood. It is unfortunately true that through an insufficient understanding of the hazards involved, workpeople in the past have suffered damage to their health through exposure to inadequately controlled concentrations of asbestos dust of all types. It is inevitable with problems of this kind that evidence relating incidence of disease to the type and intensity of exposure must largely be based upon the best assessment it is possible to make of what has happened in the past. With asbestos exposure this is particularly difficult since long periods of elapsed time are involved. Great efforts have been made to sift out the facts and with amphibole asbestos these are very fragmentary. It is suggested that the evidence particularly connecting mesothelioma with exposure to crocidolite is quite insufficient to justify the definite conclusion that is sometimes drawn. The evidence available certainly suggests that it is the particular uses to which crocidolite and amosite have been put in the past (in consequence of their individual properties) that has resulted in their special mention in the general health area rather than any exceptional biological hazard that may differentiate them from other types of asbestos. The background for these conclusions is set out in this memorandum. CROCIDOLITE (BLUE) ASBESTOS Chemistry and Mineralogy Crocidolite asbestos contains about 50% of combined silica and early 40% of combined ferrous and ferric iron as oxides. Tables I and II compare the physical and physico-chemical properties of both amphiboles with chrysotile asbestos and the chemical composition of these asbestos minerals. In addition to possessing the high bulking and structural characteristics of amosite, crocidolite is the strongest of asbestos fibres and has a high resistance to acids. It has been used extensively in place of chrysotile asbestos in textiles, insulation mattresses, packings and as a filler when resistance to acids is important. It was also used in spray insulation on account of its high bulk volume. Today, however, its use is predominantly in asbestos cement pressure pipes, acting both as a filter aid to speed production and as a reinforcement in the final structure. n JHM 0 1 0 2 6 -2- 2.2 Possible Association between Crocidolite and Mesothelioma 2.2.1. For some time there has been a belief, though not universallyaccepted, that there are greater risks to health from crocidolite than from other types of asbestos, especially chrysotile. This view predominated in the U.K. during the period when the U.K. Asbestos Regulations were being formulated and led to the inclusion of discriminatory provisions regarding the use of crocidolite. When the subsequent interpretive document establishing working guides for safe levels of exposure was prepared, this also included a separate standard for crocidolite based, it was admitted, on cn entirely arbitrary assumption that l/10th of the normal standard would ensure ample protection. At that time, the results of Harries' detailed and thorough investigations were not available and, as far as the U.K. was concerned, the principal and limited.use of crocidolite asbestos had been in the form of mattresses, thermal insulation and, especially, sprayed insulation. For mainly technical reasons, crocidolite was little used in the U.K. for A/C pressure pipe manufacture. The report of the Advisory Committee on Asbestos Cancers to the Director of the International Agency for Cancer Research (Lyon 1972) said "The risk (of mesothelioma) is greatest with crocidolite, less with amosite and apparently less with chrysotile". It also states that "there is evidence that all commercial types of asbestos except anthophyllite may be responsible". 2.2.2. The evidence upon which these beliefs are based rests heavily on the study in South Africa reported by Wagner in 1960. The results of further studies associating crocidolite with mesothelioma (particularly in manufacturing situations) are less specific but all of the significant evidence is reviewed below. 2.3 Mesothelioma in Association with Crocidolite Mines 2.3*1. Wagner (1960) (6) investigated an unusual frequency of the rare tumour, mesothelioma, in the Cape Province of South Africa. Of 33 cases, 8 had evidence of asbestosis, but, of the remaining 25, 24 had a probable exposure to crocidolite mostly through residence from birth or early age in the vicinity of crocidolite mines in N.W. Cape. Subsequent studies enlarged this study to 120 cases, 110 of which were said to have been exposed to crocidolite, more than half through living in the vicinity of mines and mills. 2.3.2. Wagner's is the only epidemiological study where there is no other type of asbestos than crocidolite known to be present. The conditions prevailing during the exposure period of his aeries, of which he says the average latent interval was 40 years, were extremely dusty - in a dry and arid region. The exposure level and the duration of exposure for the great majority of those living in the immediate neighbourhood, ploying and freely moving about the tailing dumps and stockpile areas, would have been considerable in those days. Hand cobbing (freeing fibres from the rock capping) was done by female labour accompanied by their children. /3 0102V -3- Subsequent surveys (Sluis-Cremer (33); Webster, Lyon 1972 (34)) and investigations by the South African Bureau of Mines have not produced evidence of a growth of cases corresponding to growth in production anticipated by Wagner. 360 cases have been reported, 155 with no known exposure, 117 with definite industrial or environment exposure. They have also indicated that, where there has been a positive exposure to asbestos in mining, the majority of cases (83 out of 88 reported since 1956) appear to be confined to the south and central part of the N.W. Cape crocidolite mining areas. In Canada, a research team led by Doctors Corbett and Alison McDonald, started in 1967 a study of the health cf workers in the Quebec asbestos mines and mills, with the primary purpose of assessing what risk of lung cancer there might be in persons exposed to Canadian chrysotile asbestos. Reports covering various aspects of the survey have been and will continue to be published, but a progress report issued by Dr. Corbett McDonald in 1970 (18) conveys an impression which does not seem to have ^een ''hanged materially by subsequent reports. The study of some 12,000 employees in the Quebec mines and mills bora between 1890 and 1920 showed a death rate for lung cancer among those in the highest category cf dust exposure three times greater than that cf employees with minimal exposure. The employees in the lowest dust categories apparently had little or no increased mortality from asbestos-related disease. ' As far as mesothelioma is concerned, few cases were found (13). Only 165 cases were recorded by pathologists in the entire country during the period 1960 - 1968 and only in a minority of these was there a definite history cf having worked with asbestos (11 definite, 9 probable). Ten of these, including 3 engaged in mining or milling, would apparently have only been exposed to chrysotile asbestos}, 10 were involved with insulation materials and so may have been exposed to other types of asbestos. In comparing McDcnaldts surveys in the Quebec mining.area with Wagnerrs findings in South Africa, it must be remembered that climatic and working conditions were entirely different. Comparison is further confused by the difficulty of retrospective case finding and diagnosis together with uncertainty of exposure history in such widely differing locations. Considerable efforts have been made to confirm more positively the association between crocidolite exposure and mesothelioma in the N.W, Cape. The results have been inconclusive, 7m extensive survey conducted by the Pneumoconiosis Research Unit throughout the N.V7. Cape in 1961/62 did not reveal new cases, and after .further extensive research, Professor I. Webster (35) has recently suggested that crocidolite "must be associated with another factor before malignant change occurs". There continues to be difficulty in establishing conclusive evidence in this area. As an example of this, experience at the crocidolite mine cf Cape Asbestos at Kocgas may be quoted. This is probably the eldest commercially significant mine, having been worked for 80 years and with many long serving employees. As with ail South African mines, regular health cheeks arc compulsory but, at the time of writing, no cases cf mesothelioma have been notified to us as from former employees and we are not aware of any. /A I \ -4- 2,4 Mesothelioma in Asbestos Manufacturing 2,4.1 Newhouse in 1964 (3) undertook the first attempt to investigate . a connection between crocidolitc and mesothelioma in a manufacturing situation. She looked for a possible connection with exposure to crocidolitc asbestos among mesothelioma cases recorded by a hospital in East London. Of 76 cases, she established that 23 had worked in asbestos factories, 7 had worked in the application of thermal insulation, 10 had probable-exposure of an indirect nature. 11 others lived within ij-mile of a large asbestos factory. The remaining I 25 had no traceable connection with asbestos. While the i positive or probable exposure was to asbestos of ell types, it was believed that in all cases crocidolite could have been present. Subsequent studies (1968 (9), 1972 (29), 1973 . (30)) all related to similar industrial exposure. 2.4.2. The further study by Newhouse (1972 (29)) of a group of 716 women employed between 1936 and 1942 revealed 11 nesothelial tumours; over 407. of those in the cohort had worked in textile processing departments and 107. in mattress making. Crocidolite and chrysotile were largely used in the former and amosita in addition to these in mattress making. 2.4,3. In another survey (30) of over 4,500 male workers in an asbestos factory making textiles, insulation products of various kinds, jointings and brake linings, Dr. Newhouse reported that there was no excess mortality among those who worked in jobs where exposure was low or moderate, though where work entailed heavy exposure, there was a significant excess from cancer of lung and pleura, in some cases where total period of employment had been less than two years. Occupations in these categories included insulation manufacture, textiles, fibre opening and disintegrating, mattress making, asbestos store and dust and waste collection. 2.4.4. Dr. Newhouse's work as a whole represents a very thorough study of the effect upon workpeople and those living in the vicinity, I of conditions in an asbestos factory where, it is now realised, there was insufficient control of asbestos dust in earlier years and particularly for a period during and immediately following.the last war. All types of asbestos were used in this factory - frequently on the same machines - and it is certainly not possible to pinpoint specific types of asbestos dust to which particular workers were exposed. For this reason, Dr. Newhouse's work cannot be used as a means of assessing relative hazards of different kinds of asbestos. 2.4.5. Dr. Gilson (31) refers to nine cases of mesothelioma in a group of workers employed in the assembly cf crocidolite asbestos filter pads in gas masks during the war. Information concerning the asbestos content of these filters is now imprecise but the nature of the process was such as to generate appreciable and possible heavy dust clouds in the immediate breathing zone of the operatives. Dr. Gilson also quotes information from Dr. Levinschn that a group of mesotheliomas were discovered among men working in a factory in the mid-20's where possible heavy exposure to crocidolite occurred. 2.4.6. Crocidolite has been used for at least fifty years throughout the T.;crld in the manufacture of asbestos cement, which accounts for the largest use cf asbestos, but two possible cases only have been reported from this sector of industry. Another use has been as reinforcement in plastics (e.g. battery boxes). Mo cases of mesothelioma are known to have occurred in this connection. /5 o:o y i Mesothelioma in Naval Dockyards nnd ether Shipyards Harries' (7) (22) studies of pleural mesotheliomas among workers in UK naval dockyards, indicated exposure to all types of asbestos. Heaviest concentrations recorded were in stripping sprayed asbestos, normally crocidolite which, up to that time, had been used in very large quantities for insulation in naval vessels. This was possibly the first study to recognise the very severe exposures to asbestos dust that occurred when asbestos insulation was stripped within confined spaces on ships. Dust levels exceeding 1,000 fibres/ml were recorded at some points. Subsequent work has confirmed this and the relationship between incidence cf mesothelioma in the country (U.K.) as a whole and areas where shipbuilding and ship repair work has been carried out has been illustrated on a map by Wagner (36). . Comments on the Evidence Concerning Crocidolite The only evidence based upon exposure to crocidolite alone is limt supplied in Wagner's pap^w. Subsequent work has not confirmed the conclusions that were at one time drawn from Wagner's findings. Other exposures that are quoted in this connection have been both mixed and heavy. No conclusions regarding the specific contribution of a particular type of asbestos can therefore be drawn. There is no evidence of mesothelioma in association with the use of crocidolite where the form of product or nature of use has not resulted in excessive dust. The idea that only minimal exposure is necessary to produce mesothelioma has developed by suspicion and there are no facts to substantiate this idea. A detailed study of cases of mesothelioma associated with exposure to asbestos throughout the world (excluding mining) (see Appendix A), which prompts the above reservations, ' indicates that, of 763 reported cases, 664 are said to be definitely associated with occupational exposure. (Most of these studies are, of course, cf groups of workers in occupations where an exposure tc asbestos dust is expected. This obviously, weights the sample heavily.) Of these,290 are positively stated to have occurred where chrysotile and crocidolite and/or amosite has been in usej in 361 cases, no details of the type of asbestos are given but it is apparent from the general references to the type cf exposure' that more than one type was likely to have been present. Further scrutiny of the occupations recorded in these studies also indicates that cf those listed as occupationally exposed, directly or indirectly, 553 were engaged in or in close association with insulation work, either on land installations or ship repair and construction. The remaining cases were also associated with manufacturing processes such as textile manufacture, mattress making and ether insulation manufacture, where dust concentrations were known tc have been heavy. /6 0.1 OJ 0 -6- AMOSITE Cenerei As indicated in Table If anoaite asbestos also contains approximately 507. silica, with about 407, of ferrous oxide. Its characteristic is the springiness of the fibres and the high bulk volume produced when processed. It is also highly resistant to corrosion. These characteristics made amosite fibre the preferred material for heat insulation applications and consequently the most frequently used by insulation workers. The preference for amosite-based thermal insulation material spread to most industrial countries, and such materials were used in greatly increased quantities from the mid-1940's to the late 1950's. Chrysotile asbestos was also used in this field as the reinforcing fibre in calcium silicate section and S57. magnesia. Amosite has come under particular scrutiny in the United States because of its extensive use as an insulating material during and after the war years. Amosite has not been associated with mesothelioma to the extent that has crocidolite and this probably results from the almost complete absence of any history of mesothelioma in the Northern Transvaal, the only area in which amosite is mined. The question to be decided is whether exposure to amosite involves a greater hazard than e::posure to chrysotile so far as asbestosis and lung cancer are concerned. Amosite and Insulation Workers The extensive investigations of Dr. Selikoff and his co-workers are well known and no attempt is made to summarise these in this memorandum. The important point for present consideration is that the workers upon whose history the investigations are based were involved in the thermal insulation industry. There are two sectors of this, the first being concerned with manufacture cf products and the second being concerned with the fitting and stripping of insulation on site. For a period during and immediately after the last war, a number of factories in the United States and Europe were involved in the manufacture of preformed insulating blocks, pipe sections and mattresses. In the United States, these materials were largely based either upon chrysotile asbestos in the form of "857, magnesia" (containing 157, of asbestos) or upon amosite in the form of "Unibestos" (containing 80 - 1007, of asbestos). It is now clear that conditions in many of these factories were very bad by today's standards. The products were in great demand during the war, particulariy by the U.S. navy. Hours were long and safety standards were relaxed in the interests cf obtaining vital materials in time of war. Dust concentrations were undoubtedly heavy and the health of many workpeople has suffered in consequence of this. Similar conditions have applied in the sector cf the industry concerned with the fitting and stripping cf insulation cither in the form of moulded pieces or as sprayed fibre. In the United Kingdom, such work was net subject to control by the U.K, Asbestos Industry Regulations 1931, and dust measurement (Harries 1968 (7)) shewed that even with calcium silicate insulation containing only 157, asbestos, together with asbestos n -7- rcpe, clcth and plastic nixes, moan concentrations in the general atnesphere in boiler rooms where lagging was taking place vzere 22.4 fibres/ml(. Sene individual operations concerned with fitting insulation give average breathing zone samples' as 256 fibres/ml, none was less than 43.1. In operations particularly associated with crocidolite, Harries' quotes mean concentrations of over 300 fibres/ml at the place of work, while in adjacent areas and passageways two or three decks away from the work site, evan concentrations in excess of 30 fibres/ml and as much as 177 fibres/ml were recorded. It is clear that men in occupations in no way connected with the asbestos work, and whose occupation would be assumed normally not to expose them to asbestos dust, would have been exposed to concentrations which would be considered very heavy in an asbestos factory. 3.2.4. Such concentrations are also likely to apply to such occurrences of asbestos related disease in areas cf shipyard repair and construction reported by McEvan (19), Stumphius (11), Bohlig (21) and others. Selikoff has suggested (28) that average dust concentrations . to which American insulation engineers had been exposed would have been low. He bases this cn some measurements of various operations commonly performed by these men quoting levels from 0.0 to 0.4 fibres/ml. He refers to similar results in another survey with higher levels noted during spraying; "average level of all operations approximated 6 fibres/Ql". He further assumes that, since observations in 1969 showed that asbestos materials constituted less than half of insulating materials then used, the time weighted average of ejrposure would be under 3 fibres/ml. ' The levels of dust concentrations quoted for such operations I bear no relation to those meticulously observed and measured l in the United Kingdom, notably by Harries and H.li. Factory I Inspectorate. In the same paper Selikoff himself agrees that I the effect cf peak exposures may be considerable, and that ten 1 minutes of hard work in an atmosphere of 100 fibres/ml may \ overslihdow the biological effect of- the rest of the working I - day.in environmental concentrations of 1 fibre/ml. This would I agree with personal observation of those who have practical I experience of fitting and stripping preformed insulation and \ asbestos spray work. Under conditions prevailing in the past, the nature of the work made it inevitable that there was frequent but irregular exposure to very high ccncentraticns of dust - at the moment of breaking away an old section of lagging, for example. The TLV used in the U.K. based on the recommendations of the 3.O.H.S. Standards of Hygiene for Chrysotile Asbestos Dust (32) fully recognise the significance cf peak closures and qualifies the average c-f 2 fibres/ml over four hours tc the extent that excess above 12 fibros/ml for any ten minute period is unacceptable. ' 4. CONCLUSIONS 4.1 Apart from the study by Wagner, which subsequent surveys suggest have not been repeated on the same scale in other crocidolite mining areas, there arc very few cases of masetholiema where the cause can be said with certainty to .relate exclusively to crocidolite exposure. * f\ ` i 0 * 1j,* /S If -8- 4.2 Cases of mesothelioma 'reported throughout the world where an occupational exposure to asbestos, usually both amphibole and chrysotile, is definite or possible, have invariably occurred where concentrations have been very heavy - much heavier than have occurred in U.IC. manufacturing industry for very many years. 4.3 Although there continues to be lack of satisfactory evidence, the suggestion is still occasionally made that mesothelioma can be associated with short duration of exposure. It is ' acknowledged that mesothelioma is "not always caused by asbestos and in the absence of an cccupational history, there is a temptation to attribute a particular case to some slight and often unspecified exposure in the past. Recent work (Newhouse (30)) indicates mesothelioma is dose related and it is believed that where asbestos is involved - and here again the type of asbestos cannot usually be specified with certainty - a high degree of exposure took place, possibly many years ago and in the early years of life. 4.4 Crocidolite and amosite fibres, by their nature, have tended to h the most favoured for use in thermal insulation, particularly during the war years and years of reconstruction after the war. The various diseases associated with asbestos use are clearly mostly found in areas where such work has been concentrated (Wagner (38)). The incidence of the various diseases are therefore more likely to be associated with the excessive concentrations and relatively uncontrolled working conditions, whether of chrysotile or amphiboles, than with, the type of asbestos. There does not seem to be any evidence that where such high concentrations are prevented or do not arise,, that there is any greater risk of asbestos-related disease with one kind of asbestos than with another. ;-',cr 11 t i l December L','72