Document 0g15JBVjbJ8g61aQqvEp6qbxV

FILE NAME: Asbestos Information Association (AIA) DATE: DOC#: / DOCUMENT DESCRIPTION:DZ,Z,Z ZZZZZ>ZEZ ZZ .- 150 NORTH WACKER DRIVE, CHICAGO, IWNOIS 60606 PHONE: (312) 726-8515 CABLES: NORAMCO, CHICAGO December 18, 1973 Mr. R. H. Mereness Asbestos Information Association 1660 L Street, N.-W. Washington, D. C. 20036 PLAINTIFF'S EXHIBIT ~s4 Dear l?ob, During my recent visit to your offices you will rec2-ll our discussion pertaining to a position paper which Cape Asbestos asked permission to submit to the AJ.A/NA. We are enclosing copies of the document as received today. We believe there have been tendencies in some areas to segregate Blue and Amosite asbestos into a separate category, as opposed to Chrysotile, when related to health hazards. From this point of view, it would appear that Cape has endeavored to fairly and fully present all the known facts as regards Blue and Amosite asbestos. These documents are for your files and information, and may be circulated to all members of the AJ.A/NA should you so desire. In the event you believe they would serve a useful purpose, copies may be distributed to selected people in OSHA. If you have any questions relative to this matter, please contact me. Sincerely yours, NORTH Alv!ERICAN ASBESTOS CORPORATION 7 ~-')/::. _l1, / ) ' 7 ii:'7 ~~~- ----- ~ ~- / ' Vice President/ G~"'e-i-.1.L..Manag er CGMorgan/ jc encl. ,.~\-:;~ t ' ' ..... . i--- . , ~: , ~":,,:;;.~t:l, . .Jj,;;,'.~-...,, Memorandum from The Cape Asbestos Company Limited on Hazards to Health Associated with Crocidolite and Amosite Asbestos ---------------------------~-----------------------~ 1. INTRODUCTION It is not infrequently suggested that special hazarda may exist with crocidolite (blue) and amosite asbestos that are not so pronounced with chrysotile. A.s 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 J 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 .-ipbibole asbestos these are very fragmentary. It is suggested that the evidence particularly connecting mesothelioma with ~.osure to crocidolite. is <t':!i.t~ insufficient to justify the definite conclusion that is sometimes dxawn. The evidence aVQilable 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 secial mention in the general health area rather than anx exceptional biological hazard that aay differentiate them from other typ~s of asbestos. The bacq~ound for these conclusions is set out in this memorandum. 2. CROCIOOL!TE (BLU!) ASBESTOS 2.1 Chemistry and Mineralop; Crocidolite asbestos contains about 50'Z. of combined silica and taearly 40i of combined ferrous and ferric iron as oxides. Tables I and II compare the physical and physicochemical properties of both amphiboles with chry~otile asbest~s and the chemical composition of these asbestos minerals. In addition to possessing the high buiking and structural characteristics of amosite, crocidolit~ is the strongest of asbestos fibres and has a hi&h resistance to acids. It has .P~en used extensively in place of chrysotile asbestos in textiles, insulation mattresses, packings and as a filler when resistance to acidsts 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. /2 JHM 01026 ..... --- --------- - - .. -2- 2.2 2.2.1. 2.2.2. 2.3 2.3.l. 2.3.2. Possible Association between Crocidolitc ~nd Mesothelioma For some time there has been a belief, though not universally accepted,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 crocidolitc. When the subsequent interpretive document establishing working guides for safe levels of exposure was prepared, this also included a s~par.:ite st.'.lndard for crocidolite based, it was adr.u.tted, on cu entirely arbitrary assumption that 1/lOth 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 i~ul~tion. For mainly technical reasonsF crocidolite was little used in the U.K. for A/C pressure pipe manuZu\;l;u.1..1;. 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". The evidence upcn which these beliefs are based rests heavily on the study in South Afric~ reported by Wagner in 1960. The results of further studies associating crocidolite with mesothelioma (pa:tic~larly in manufacturing situations) are less specific but ell of the significant evidence is reviewed below. Mesothelicma in Association with Crocidclite Mines Wagner (1960) (6) investigated an unusual frequency of the rare tumour, mesothelicma, 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. Wagner's is the only cpidcmfological study where there is no other type of asbestos than crocidolitc known to be present. The conditions prevailing durinr the exposure period of his aeries, cf which he says the aver.::ige latent interval wcs 40 years, were extrcr:iely dusty - in a dry and .irid region. The exposure level ond the clurction of exposure for the great majority of those living in the ir..mcdiatc neighbourhoo<l, playing and freely coving obout the tailing dumps and stockpile areas, uould have been considcrnblc in those d~ys. H~nd cobbin~ (freeing fibres frurn the rock c:.pping) was d,ma by female labour accompanied by their children. /3 0102'? -.3- 2.3.3. Subsequent surveys (Sluis-Cremer (33); Hebster, Lyon 1972 (34)) and ir.vcstigo.tions by the South African Bureau of Hines have not produced evidence of a growth cf cases corrcspontling to growth in production anticipated by Wagner. 360 cases have been reported, 155 with no known exposure, 117 with definite industrial or cnviron:nent exposure. They have also indicated that, where there has bean n positive exposure to asbestos in minin6, the majority of ccses (83 out of 88 reported since 1956) nppeo.r 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 a:id Alison McDonald, started in 1967 a study of the health cf workers in the Quebec csbestos mines and mills, with the primary purpose of assessing what risk of lung cancer there eight be in persons exposed to C~nadi~n chrysctile asbestos. Reports covering various aspects of the su=vcy have been and will continue to be published, but a progress report issued bj Dr. Corbett McDonald in 1970 (18) conveys an impression which dcic.:; ~.:;!: seem to have 'heen rha!lE>""-.:! wa~e!'iall~ by Sl\hsequ~nt reports. The study of scoe 12,000 ecployees in the Quebec mines and mills born between 1890 end 1920 showed a death rate for lung cancer amcng those in the highest category cf dust expcsure three times greater than thnt cf employees with mini::ial exposure. The employees in the lowest dust categories ap?arcntly had little or no increased mortality from asbestos-related disease. As far as oesothelioma is concerned, few cases were found (13). Only 165 cases were recorded by pathologists in the entire country during t~e period 1960 - 1968 and only in~ minorit"/ of these was there a definite history cf having wcrkec: with asbestos (11 definite, 9 probable). Ten of these, including 3 engaged in mining or milling, would apparently have cnly been exposed to chrysotilc asbestos;_. 10 ,1ere involved with insulation materials and sc may have been exp~sed to other types of nsbcstos. In comp:1ring McDcnald"s surveys in the Quebec mining .area with Wagner's findings in South Africa,. it must be remcmbcrec1 that clim.itic and wc,rking conditions ~ere entirely different. Comparison is fu:-ther confused by the difficulty of retrospective. case finding and diagnosis together with unccrtninty of exposure bisto:)' in such widely differing locations. Considerable efforts have been made to confirn more pcsitively the .:isscci:ltion betw~cn crocid.:ilite exposure a:-id cesothelicr.ia in lhc N.H. Cape. Th~ results have been inc.cuc.lusiv~. /..n extensive surv~y ccnducted by the Pneumoconiosis R~search Unit thro11eh~ut the N.W. C.:ipe in 1961/62 c!id not reveal new cascs 1 and .'.lfter.further extensive rcse~rch, Professor I. Webster (35) hns -recently suggested that crocidolite "must be ~sscciatec! with ,:mother fnctor before m.11ign.:mt change occurs". T~crc continues to be difficulty in establishing conclusive evidence in this .::irc.:i.. ,\!:. on ax.'.lI:lplc of this, experience .:it the.: crocid~litc mir.c cf Ccpc ..-\sbcst.:is at Kocgas m.1y be c;u:::itcd. This is prob::bly th~ c-lclcst ccr.u:ie:rcially sisnific~nt mi~c, h~ving be.en ,,:ork..;cl fn SO ycnrs ~nd with rn.:my long sc:-ving cnployces. .:..S with ~ll South Airicnn min~s, rctular h~clth che:d-.:; ~re CQt::pulsory but, .:t the time of w-ritint., n.::> c.:izcs cf rncsothdicrn.: h.:i\c b~cn nctificcl to us .:is from for:ncr cmployl)cs and we arc not ~i:nrc uf .'.lny. /4 . ' 2.4.2. 2.4.4. 2.4.5. 2.4.6. l-!esothclio1.1.::i in l'..sbcstos !-fanu(~icturin0 Newhouse in 1964 (3) und~~tock the first attempt to investigate a connection between crocidolitc and mesothcliomn in a m~nufacturing situnticn. She looked for a possible connection with exposure to crocid~litc asbestos runong roesothcliorna cases recorded by c hospital ~n Enst London. Of 76 cases, she establishad that 23 had worked in asbestos factories, 7 had worked in the application of thermal insulation, 10 had prcbablec}:?Osurc of en in~ir~ct n~tcrc. 11 others lived within ~-mile of a large asbestos f~ctory. The rel!laining 25 had no traceable connection with asbestos. While the positive or probable exposure was to asbestos of all types, it was believed tnat in all cases crocidolite could have been present. Subsequent studies (1968 (9), 1972 (29), 1973 (30)) all relatad to similar industrial exposure. The further study by Newhouse (1972 (29)) of a group of 716 wocen employed between 1936 and 1942 revealed 11 ~esothelial tumours; over 40% of those in the cohort hud worked in textile processing tlepartments and 10% in mattress making. Crocidolit~ &nd chrysotilc were l~rgely used in the former and amosita in e1.:!:;.:cn to th~se in r.u:ittrPSf\ r.::.!-:.::.::~. In another survey (30) of over 4,500 male workers in an asbestos factory maktng textiles, insulation products of various kinds, jcintings and brake linings, Dr. Newhouse reported that there was no excess mortality among those who worked in jobs where exposure was low er moderate, though where ~ork entailed heavy exposure, there was a significant excess from cancer of lung and pleura, in some cases where total period of emplo1inent had been less than two years. Occupations in these categories included insu~ation manufacture, textiles, fibre opening and disintag=eting, cattress making, asbestos store and dust and waste collection. Dr. Newhouse's work as a whole represents a very thorough study of the effect upon workpeoplc and those living in the vicinity, 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 en the same machines - and it is certainly not possible to pinpoint specific types of asbestos dust to which particular workers were exposed. For this roason, Dr. Ue-;;house's work cannot be used as a means of assessing relative hazards of different kinds of asbestos. Dr. Gilson (31) refers to nine c~ses of mesctheliom~ in a group cf workers er.ployed in the essembly cf crociC:olite asbestos filter per.ls in gas ;:-ic.sl~s curing the ~1c:r. Information concerni:ig the asbi:::s::.:Js content of these filters is now ir.:pracise but the ncturc of the process was such c?.S to geni2rntc ~ppreciablc ar.d pos~ible henvy dust clouds in the immediate breathing zone of the cpcr~tivcs. Dr. Gilson also quot~s inform.ition frco Dr. Lcwinschn thct a group of me.sotheliomas were cisc.:>vcrcd .:.mong ncn working in .1 f.::ictcry in the r.1id-20' s whi?rc possible lwavy c;(pcsurc to crocidolitc occurred. Crocidolitc hns b~cc used fur at lc.'.lst fifty ye.'.lr3 t~roughcut the i1~-rld in the m.:muf .:icturc of as bes t::.i5 cc:.icnt, which .-?.ccou~ts for the lcrgcst use cf asbestcs~ but two po5siblc c~sQs only hove been rcrort~d from this sector of industry. I.nether use hws b~cn ~s rcinf~rccr..cnt in ~l.:istics (~.g. b.'.lttcry bcxcs). No coses of rncsotlli;.lior.i:i :ir..:i kc(.'Wn to h.'.lvc occurred in this c~nnccti.;n. /5 -----------, .........,,_~....--- - -- ~----- ----~---- . ,._,..____ ' ...,t ;. ( ).!' ( 'I'l'w(,\, -5- 2.5 Hesothalicm~ in Nnval Docky~r~s an<l ether Shipvards Harries' (7) (ZZ) studies of pleuTnl nescthcliornas ~~~ng .workers in UK naval dockyards, indicated exposure to oll types of asbestos. Hc.:iviest conccnt-r.:itions recorded were in stripping sprayed asbestos, norrndly croci<lolite which, up to that time, h.:i<l be~n used in very large ~uantities for insulation in navai vessels. This was possibly the first study to recognise the very severe exposures to asbestos dust thc1t occurred when asbestos insul.:!.tion was strippad within confined spaces on ships. Dust levels excceC:ing 1,000 fibras/ml were recorded at some point!i. Subsequent work has co:ifimed this e.nd the rel~tionship between incide~ca cf rnesothelioma in the country (U.K.) as e. whole ond areas where shipbuilding and ship repair work has been carried out has be2n illustr~ted o~ a map by Wagner (36). 2.6 Con:me~ts on the Evidence Concernin~ Crocidclite The only evidence based upon exposure to crociclolite alone is -.l,ii.i:. SU?plie-:! in 1:!egner' ~ ~~:,:; ..... - Subse(!11ent work has not ccnfirced the conclusiocs that were at ona time drawn from Wagner's findings. Other exposures that ara quoted in this connection have been both mixed and heav,;. No conclusions regarding the specific contribution of a particular type of asbestos can therefore be drawn. There is no evidence of mcscthaliooa in association with the use of crocidolitc where the foro cf product or nature -of use has not resulted _in excessive dust. The iGca that only miniwil exposure is necessary tc produce mesothelioma has developed by suspicion and there are no facts to substantiate this idea. A detailed study of cases of rnesothelicma associatec with exposure to asoestos throughcut the world (excluding mining) (see Ap.pendi~ A), which prompts the above reservations, indicates that, of-763 reported cases, 664 are said to ba definitely associated with occupational eA7osure. (Most of tl1esc studies arc, of course, cf groups of workers in occupations where en eX?csurc tc asbestos dust is expected. This obviously. weights the s&1plc heavily.) Of thcse,290 . I I er~ positively stated to have occurred where chrysotile and crocidolite and/or amosite has been in use; in 361 cases, no details of the type of csbestos are givcP- but it is apparent fr~m the general r~fer~aces to the type cf exposure thct more th~n one 'type was likely to have been present. Further scrutiny of the occupaticns recorded in these studies nlso indicates that cf th~se listed as occu2ationally cxr,>oscd, directly er indirectly, 553 were engaged in or in close association with insulation wcrl~, either on land inst~ll.1tions or ship rcp.:iir and const:::uction. The rerncining cases \1ere also associated with rncnufacturing processes such as textile ~anufacture, mattress m.:ildng anc.! ether insulation m.:muf.:.cture, where dust conccntrcticns were kncw-n to h.:iv-:: been hc.:iv-;. /6 0 .: 0 .JO 3. 3.1 3.1.2. 3.2 3.2.l. 3.2.2. /J:OSITE Gcncrd As indicated in Tabla I, ac~3itc asbestos also contnins epproxim~tely 50k silica, with cbout 40% of fcrrcu$ oxide. Its charactaristic is the springiness of the fibres ancl the high bulk volume produced when processed. It is also highly rasistnnt to corrosion. These characteristics made nmosite fibre the prcfc=red mate~i~l =o~ he~t insulation epplications and consequently the most f~equently used by insulation workers. The prcfi:!rer.ce for ar.:osite-based thermal insulation ~atcri~l spre~d to most industrial countries, and such materials were used in gr~atly increas~d qu~ntitics from the mid-194O 1 s to the late l96O's. Chrysotile asbestos was else used in this field as th~ reinforci~g fibre in calcium silicate section anc 85% magnesia. Amosite has come under particular scrutiny in the United St~tcs because of its ~~tensive use as an insulati~g material during and after the war years. Acosite hes not been associatec with mcsotheli~ma to the extent that has crocictolite and thi~ probably r~sults r~om the almost complete absence of any history of mesothelicma in the Northern Transvaal, th~ only erea in whic!l .i:nos::.te is mined. The questicn to be decided is whct~e~ ex;,,osure to amosite involves a groater hazard than e::r,osu=e to chrysotile so far as asbestosis and lung cn~cer ere ccncerne<l. Amosite and Insulation Workers The extensive investigaticns of Dr. Sclikoff and his co-workers are well known and n.:, a::t~;,t is m.:!dc to su~rise these in this memoronduc. The io::?ortant pc:;.nt :for present consideration is that the wcrkcrs '..lpon ,-;hose history the investigations are based were 1.nvolvecl in the thcroal insulation industry. There ere tuo sectors of this, the first being concerned with monufacture cf pro<lu~ts end the second being concerned with the fitting and st:r::.J.)ping of insulaticn on site. For a period during and immediately after the last war, n number of factories in the Un:.ted Stctes and Europe were involved in the manufacture of preforoed insulating blocks, pipe sections anc rnatt~~sses. In the United States, these materials were l.:irgely based either upon chrysotile asbestos in the form of "857. magnesic" (containing 157. of as'!.,estos) or upon arncsite i.i the form of "Uni'bestos" (containing 80 - 100% of csbcstcs). It is now cle~r th~t conditions in many of these factories ware very bad by today's standards. The prcducts were in er-,at dcQ:l!ld du:-ing t!1c u.:i=, p<al::t:iculi:i::ly by the U.S. navy. Hol.!rs w~re long .:me saZety s:andards we:-e relcxed in the interest~ cf o~t~ining vital @atc=icl$ in tim~ cf war. Dust concentr.:itions ,1:-.re unr~oubtadly hccvy ~ncl the he.:ilth of many l1orkpeoplc has su:f:r.~c.rl in con$cquencc of this. Similar conditions have applied in the sector cf the industry concerned with the fitting and st:ri~?ing cf insulation cith~r in the forr:t of r.ioulc.!,:d pi-.1c0s or cs s'">::~v,:C.: f :.0:-c. In thc Unite<l Kingdom, such wcrk W~$ n~t sub}cc~ :o ccn~rol by the U.K. Asb~stos Industry Rcgul~ti~cs lSJl, ~n<l ~ust mcasurcm3nt (lkrrics 1968 (7)) showed th~:t even w::.:h cdciL:;:i silic.itc insulation containing only 15i ~s0cstos, tcecthc~ with a~bestcs /7 -7- rcpe, ckth .:.nd plc.stic r.,ixcs 1 rnc'.ln ccnccntr~tions iu tha general .:ltr.icsr,here in boiler ro~:ns ,,,1herc l.:igging w.cts tal;ing pl.ice were 22.t. fibres/ml,, S::i.le in<livic.!ud oper~tions concerned with fittine insul~ti::}n give ~vcr.'.lge breathing zone samples ns 256 fibres/ml, none was less tha~ 43.1. In cperotions particularly cssociat~d with crocidolite, Harries quo~es mean co~ccntrations of over 300 fibres/ml at the place of wort~, whil~ in .J.cj accnt are.as and passageways two or three clacks e.~-,ay frcm the wcrk site, C1""~n conccntrctions in excess of 30 fibr~s/ml and cs much as 177 f~bres/ml were recorded. It is cle~r that oen in occupations in no way connected with the asbestos work, and whose occupation would be assumed nomally not to expose th~~ to asbestos dust, would have been cxpc~~d to concentretions which ~ould be considered very heavy in an .J.Sbestos factory. 3.2.4. Such concentrations are alsc likely to apply to such occurrences of asbestos rel~ted cisease in ~re~s cf shipyard repair and ccnstructicn reported by McE~an (19), Stur.:phius (11), Bohlig (21) and others. Selikoff has suggested (28) that average dust concentrations to which Amcric~n insulation engineers had been exposed would have been low. He bases this en some measurements of v~ricus operations co~only perforn:cd by th~se men quoting levels from 0.3 to C.4 fibres/ml. He refers to sirailar results in another survey .ti.th higher levels noted curing spraying; 11 averagc level of all operations approx.imc:.ted 6 fibres/ml". He further ess~es thot, sir:.cc observaticns in 1969 showed that asbestos materials constituted less than half cf insulating materials then usec, the ticc weighted nveragC:! of e,=i)Osure woul'd be under 3 f ilrrzsJml. The levels of dust ccncentrations quctec for such operations benr no relation to those meticulously observed and ~easurctl in the United Kingdo~, notsbly by Harries and H.H. Fectory Inspactoratc. ln the same pc'.lper Selikoff hiffiself egrecs th~t the effect cf peck e}:posurcs m~y be considerable, and that ten l!linutes of hard work in an at~cspher~ of 100 fibres/~l mey overshadow the biclogical effect of the rest of the working day.in environmental concentrations of l fibre/ml. This would ~ee wit!:l parsonal observation of those who have practical experiellce of fitting and stripping preformed insulation and 45bestos sprey work. U'ndcr conditions prevailing in the past, the natl.!rc of the work me.de it inevitc'.lblc that there was frequant but irregular exposure to very high ccncentraticns of dust - ~t the moment cf b:caking away an old section of 1&8ging, for cy...:nplc. The TLV used in the U.K. based on the reccmmcndaticns of the B.O.H.S. Standards of Hygiene fer Chrysotile: Asbestos Du:;t (32) folly recognise the significc'.lncc of peck c:9csure:; and qunlifies the average cf 2 fibres/ml over four hours tc the extent that excess .:.bcvc 12 fibrcs/nl for ~ny ten minute period is unaccc?tablc. 4. COHCLUSim~s 4.1 Apart fro~ th~ study by Wa~ncr, which subsGquent surveys suggest h.'.lVC not b~cu repc~tcd on the s~~~ sc~lc in other crccidolit~ r.1inin3 arc~s, there .'.lrc very fei; case1s of r:i~scthe:licr.i:. ,1here the c.'.lusc C.'.ln be s~id with ccrt~inty to.rcl~tc exclusively to crocidolitc cxr,osurc. /S - . - - -,. -"' ~<- ... , ........- - -8- 4.2 Cc1ses of r.iesot.heliorna reported throughout the wo;ld where nn occupa~ional exposure to asbestos, usunlly both am~hibole and chrysotile, is d~finite or p.ossiblc, hav~ invariably occurred where coc.centrations have l.>een ve::y h~a1y - r:iuc:1 h~avier than have occurred in U.K. rr..::mufactu.:ing ~ndustry for very many years. 4.3 Althou8h there continues to be l.ick of satisfactory evidence, the suggestion is still occ.1sion.:.lly ~ade that mesotheliooa can be associnted ~1i~n short clur.:.tion or c:x:posu;::e. It is acknowledged that rncsoti1elior.1a is i.:.c.t ab1ays caused by asbestos and in the absence of an cccupational history, there is a ter.?ptation to e.t~ributc a pa-rticular case to soae slight and often unspecified e:~osure in the pcst. accent work (Newhouse (3C)) indicates h.esoth2lio~a i~ <lose related ancl it is balieved that where .:1sbesi:os is involved - and h(:re again the type of asbestos c~nnot usually be specified with certainty - a high degree of e>-.-posi.;re took place, pozsibly m~ny years ago and in the early years oi life. 4.4 Crocidolite and omositc fibres, by their nature, have tended tn l--'? the most favoured for use in thcroal insulation, particula-rly during the wa-:- years and years of t1.:i.:vnst:i:uct!.on after the war. Th:? various diseases associated with asbestos use are clearly mostly found in areas where such wo.rk has been concentrated (Wagner (36)). Th2 ii.1.cideric~ of the various diseases are therefore more likely to be associated with the excessive concentrations and relativaly unco!ltrolicd uorkir.g coilditions, whethe:::- of chrysotile or smphiboles, than with the type of asbestos. The-re coes not seem to be any evidence that where such high conccntraticn:; are preventecl or do not arise,. that there is any g-reat~r risk of asbesto!l-rclated disease with enc kind of ~sbest.os the.:i uith another. }~C/l.l.':./t: f G ll t ii rJ\!,:<.:~).~;:- l'i7.; ..... ................._ --4- --- ----4--