Document zz6mZbQD1NBYVg49n46zELJyR

ie ; ..tack Meter: tra. CngUnd. * *V tuck ' "your ' i9 ' Rothwel 9 "Mb Ltd . Umittd. ' V!3. Imcotn, -: England. 372 f Atmoiphtrie Etwirontntnt Pcrgxmon Pres* 1973. VoL 7, pp. 481-483. Primed in Great Britain. . ASBESTOS FIBRES IN THE AIR OF TOWNS P. F. Holt and E>. K. Youno . Department of Chemistry, University of Reading, Berkshire, England (Firs! received 29 Jtmt 1972 and In finalform 11 August 1972) Abstract--Many observers have reported Ibat asbestos bodies are present in the lungs of town dwellers who have had do industrial exposure to asbestos, suggesting that asbestos may be a normal contaminant of the urban atmosphere. The air of several cities--London, Reading, Rochdale, Bochum, Dusseldorf, Prague, Pilsen, Johannesburg and Reykjavik--has been sampled using mDlipore filters. The samples were transferred to carbon film on a gt id and they were examined by electron microscopy. Asbestos fibres were found in samples from every town. They were mostly present as single fibrils but some were in agglomerates that contained many fibre*. Asbestos fibres that have been inhaled often become coated in the human lung with a material that is largely ferroprotein, giving characteristic structures called asbestos bodies. Some other fibrous materials may also become coated to give pseudo asbestos bodies. Cauka, Totten and Gross (1965) found asbestos bodies in 41 per cent of lung smears taken from 100 autopsies of adults who had bad no known connection with the asbestos industry. Thomson and Graves (1966) examined lung smears ob tained at 500 autopsies in Cape Town and 500 in Miami, Florida. The results were similar in the two cities, specimens from 30 per cent of the males and 20 per cent of the females showing asbestos bodies. Some 15 per cent of the positive cases bad very many asbestos bodies and it was considered that these had been exposed to an in dustrial risk. In 85 per cent of the positive cases there were few bodies and there were no associated pulmonary changes. Atod.vel and Tkurlbecc (1966) in Montreal found asbestos bodies in 48 of 100 random necropsies. They also found pseudo asbestos bodies but believed they could differentiate betweeo bodies produced from asbestos and those from other sources. Roberts (1967) found asbestos bodies in lung smears from 23 of 100 consecutive hospital necropsies in Glasgow, Scotland, near an industrial area where shipbuilding is an important industry, Ghezzi, Molteni and Puccetti (1967) found asbestos bodies in 51 out of 100 random subjects who died in Milan. Webster (1965) reported asbestos bodies in the lungs of 47 per cent of a group of patients who had bad no direct connexion with the asbestos industry. Tabershaw (1968) found asbestos bodies In 41 per cent of the lung smears he examined, and Polliack and Sacks (1968) in 26 per cent of 100 consecutive adult autopsies iD Jerusalem. Penman and Thomson (1970) obtained similar results in Dunedin, a town in New Zealand without heavy industries. They showed that the number of asbestos bodies found in a lung was related to the method of examination; presumably most lungs contain asbestos bodies. An examination (Um, 1971) of histological slides kept in the Central Histological Laboratory of the Archway Hospital, London, suggested that the number ofasbestos bodies in lungs is increasing; when 100 lung sections cut from blocks made in each of the years 1936, 1946,1956 and 1966 were examined, asbestos bodies were found in 0, 3, 14 and 20 per cent respectively. . In France, Bignon et al. (1970) found structures similar to asbestos bodies in tissue from every lung examined. In general, there were more such structures in the lungs of 481 . ' AL 7/t--A 'iJiry cct. 8060 139E persons who bad lived in Paris or Dear to a large factory manufacturing brake linings io which asbestos is used. The asbestos bodies in the lungs of persons not normally handling asbestos are presumably derived from fibres present in the urban atmosphere but the widespread reports suggest that most atmospheres are contaminated. We obtained samples of dust from the air of several cities by drawing about 50 I. of air through a millipore filter (type VF) by means of an Austin diaphragm pump. The filters were used face downwards to prevent large particles from settling on the membrane. Tbe specimens were transferred to grids by forming a carbon deposit about 200 A thick over the dust, transferring small pieces (1 *5 X 1-5 mm) cut from the filter onto the grids, carbon downwards, then dissolving the filter away with acetone. The dust was left on the carbon membrane on the grid. A careful search of these specimens was made with the electron microscope. Blank millipore filters treated in the same way were examined to ensure that the filters themselves were not contaminated. The sampling points chosen were well above street level and, so far as could be ascertained, away from any direct source of contamination. In London samples were taken from the top of a five-storey buildmg, in Reading from the top of a two-storey, building situated in a park and also inside the building. Sampling positions well above street level were also chosen in Rochdale, England, in Bochum and Diisseldorf in Germany, in Prague and Pilsen in Czechoslovakia, in Johannesburg, South Africa, and in Reykjavik, Iceland. Only Rochdale, which has the largest asbestos textile factory in Europe, can be regarded as having an important asbestos industry. - A cartful search of some of the grids revealed no true fibres, but on other gridsC there were fibres or agglomerates of fibres. It was seldom that more than one or two windows of a grid revealed fibres. Usually the fibres were single, but occasionally large agglomerates were observed. Some appeared to be coated with soot or other > material. Fibres were present in the specimens from every sampling point but no'- fibre was found on any blank filter. -Tr Cbrysotiie is the most widely used variety of asbestos. The chrysotile crystal has cr characteristic appearance in the electron microscope. Tbe lattice is in the form of a. tube that may be hollow or filled with amorphous material and the ultimate fibril has . diameter of about 0-03-0-06 pm. Electron diffraction studies made on some fibres*-- baving this appearance confirmed that they were in fact chrysotile asbestos. Other'; fibres were identified as amphibole asbestos. Amphibole asbestos was identified in the; air of Bochum and Johannesburg. - t. Compared with other contaminants the amount of asbestos is very smalL A part of. a grid as seen in {he electron microscope is showB in Flo. 1. Matty similar fields con-* tain do fibres. There appears to be no way in which the concentration of fibres can be expressed satisfactorily. Rickards and Badami (1971) found chrysotile asbestos* in the air of Rochdale and attempted to estimate the mass concentration by an X-ray. technique based on the measurement of the integrated area under the (002) peak. They were able to determine only the upper limit which was 100 /*g of chrysotile ; m"1 of air. Gadsden, Parker and Smith (1970) described an infra-red technique for the measurement of tbe mass concentration of asbestos dust in air but they found the ' concentration too low for the application of their method even in a car park with a foundation of asbestos waste and a tip used for dumping asbestos waste. They did however, detect fibres on their millipore filters by electron microscopy. ' v> , rf .' : ^gfrirrt l_____ __ 01 p m F*C. 2. A single fibre dorf. Mcnt fibres apj {Facing p. 4SD 000 13^3 PRODUCED BY PfiPn ;/has a 6ns of a fibril has me fibres K. Other iedialfee K pari of e!ds con* ibrrs can asbestos an X-ray > peak, hrj'iotile aique for ouod the rk ith a They did PRODUCED BY FOPn wmwii rfrtfiii 'M -VRS Fic. 5. An *K- 4- An **s**0fnera,e Of fibre* collected on a filter at the top of a buildin* in London. 8000 )395 PRODUCED BY POPn PRODUCED BY FORD i-WiVA Asbestos Fibres in the Air of Towns 483 Most of the asbestos found in our millipore filter samples was present as single fibres or as ultimate fibrils (Figs. 2 and 3). These could be estimated by counting except that some were obliterated by other contaminants. There were, however, some complex agglomerates (Figs. 4 and 5) and it is impossible to decide in any meaningful way how many particles such masses represent. Such a mass tends to brtalc up when the filter is extracted with acetone and there are far more fibres near an agglomerate than in the rest of the sample. Agglomerates might also break up when meeting surface active substances in the lung. These observations are offered as an indication that asbestos is a contaminaot in the air or cities and as an explanation of the asbestos bodies that have been found in the lungs of persons not industrially exposed to asbestos. The concentration of fibres is small and there is no indication whether the fibres are pathologically significant. Asbestos fibres are removed from the Jung by a mechanism (Botham and Holt, 19SS) that involves tbe production and eventual fragmentation of asbestos bodies. Evidence from animal experiments suggests that once a fibre is coated it is no longer pathogenic but that the uncoated fibres produce the pathological effects. Since the rate of coating depends on the nature of the fibre, chrysotile (and glass) fibres being coated more quickly than crocidolite and amosite, fibres of the amphiboles are . potentially more dangerous. Asbestos fibres in the lung are coaled in the cytoplasm of macrophages and giant cells, but if several fibres are retained by the same cel] only one is usually coated. Moreover, the number of macrophages in an area of lung is limited. Thus, while low concentrations of isolated fibres are likely to have minimal pathological significance, a high local concentration produced by the break up of an agglomerate of fibres, might represent a potential risk. . j Acknovlrdtemmsr--The author* are indebted to Dr. Fannaicm (Dtrueidorf), Mr. R_ RendALL (lohinnesburg), Miss Tmooatoao Thordadotter (Reykjavik) and Mr. J. Me K. Ellison (London) who provided millipore filler samples, and to Professor J. Tewnou (Prague) who provided facilities tor tempting. . - - . . REFERENCES Awavrt L and Thuruccc W. M. (1966) The incidence of asbestos bodies in the lungs at random necropsies In Montreal. Cm. med. Ass. J. PS, 1179-1182. ' Rionon Gohi J., Bokhaud O., Jaurand M. C, Dotour C. and Pinchon M. C. (1970) Incidence cf pulmonary ferruginous bodies in France. Emir. Res. 3,430-442. Botmav S. K. tod Holt P. F. (1968) The mechanism of formation of asbestos bodies. J. Path. Baet. 1i 6,443-453. Cauka D., Totten R, S. and Oaoss P. 0965) Asbestos bodies in human lungs at autopsy. J. Am. mtd. An. 192, 371-373. - Gadsden ). A., Parker J. and Smtth W. L. (1970) Determination of chrysotfle in airborne asbestos by an tnfra-rtd tpoctrometric technique. Atmospheric Emlronment 4, 667-670. Gkezzi I., Molteni O. and Puccsm U. (1967) Asbestos bodies in tbe lungs of inhabitants of Milan. Mtina Leo. 58,223-227. Penman H. O. and Thomson K_ J. (1970) Pulmonary asbestos in Dunedin, New Zealand, assessed by two methods. Patholopy 2, 175-182. Pdluack A. and Sacks M. I. (1968) Prevalence of asbestos bodies in basal lung smears. Israel J I Mtd. Set. 4,223-226. .- Rickards A. L. and Badami D. V, (1971) Chrysotile asbestos in urban air. Nature 234,93-94. ROBERTS C. H. (1967) Asbestos bodies In lungs at necropsy. /. elin. Path. 20, 570-573. Tabekjnaw I. R. (1968) Asbestos as an environmental hazard. J. aeeup. Med. 10, 32-37. i ! Thomson J. O. and Grave* W. M., Jr. (1966) Asbestos aa an urban air contaminant. Arch, falhiozy, ' . 45M64. . ,, Um C.-H. (1971) Study of the secular trend in asbestos bodies in lungs in London 1936-66. Br. sued. J. 2,248-252. V-' J I- 666 Discussion AUTHOR'S REPLY Tiaham the large intradiuroa) variation in turbidity I reported (Rakotmos 19711 has nn been normally observed hcoauve, in the United Stjlet, turbidity observations arc frc.|ucnll)' cnllccird only two or three limes daily (I'lowtn rr al., 1969), at local noon aiul > li before and after local noon, weather permitting. 1 believe that Ur. Ilullrich misinterpreted my second possible explanation for tlic iironn imradiurnal variation in turhiJiry. Tire selenium photocell in the sunphotomoicr is smsinvr from 0-J toO rg i< ttnd the wavelength of maximum intensity of xolnr ratliation shifts inw.ml o ' ,, ;n Hie air moss value increases (Moon, I'liOl. Thereby, (he idea was ttiac propotiinnaiels mote sol.tr radiation might be sensed by the sunplinti'mcter near 0-7/. rntlict than at 0-} ,, for pi - 5. 7 suit I, containing data provided by Fuming fl`172), supports Ihis conlcnlion; however. I would like tn point nut lli.it Dowers has recently shown iltal litis contribution is ttuiic small ami doesn't appear lo explain the observed imradiurnal variation in turbidity. Tamr I. Sot Alt ti.ux vs air mass am> waviiim.iii (ly min'') I i HI -- I III } /.(0 44-OT6 p) .1,(0 10-013 ?) l:H 4 04 x IO-> 70 X IO-` 17 x 10** 91} v I0-* 35 x IO-` 3 8 x 10** Dr. Bullrich has offered forwird scatter as another possible explanation for this iiitrndiurnal variation. To my knowledge, there arc no quantitative data available to permit an evaluation of Ihe contribution nf forward scalier lo local turbidity. A noteworthy study by I It mum (1941) showed that forward scalier can be greatly increased by the presence of dust and bare particles in the atmos phere. I ccitainly agree that forward scatter might explain a significant portion nf the imradiurnal variation in lutbidily I observed, using two Voli sunpholometers. If further study does explain forward scatter as the primary culprit, then if should be accounted for in the observations. Air Reteorches l/iboratory, Lai Vegas, Nevada 89114, US.A. D. Ranomson I. Asheslns bodes m.nenat- other thsr> resolution of (he nvl ettv duellers -and. v IVI: I'nit i v rr al. aslvst'iv bxsjj ewe It unnpte Rroearant c. :. 7 tie authors xeci fihttfs m :ur. Adnrlte Csi'iuaies van be m?.. three is |H>-oil le.t 1 ' ittsfUMtor fiir the pit and si/e of lihrih. ;n esample. nur carlv o (Sitikutr rr al., 197." Additionally, spcxifit tile*. r-LOwnu E C. (1972) Persona) commumcttioA. " rr- '-c * *' ' ' t- . Fiowru E C., McCormick R. A. and Kunris K. R. (1969) Atmospheric turbidity over Ihe United Stales, >961-1966. J. Appl. Meteor. 8, 955-962. Huiauar E O. (1941) Optics of atmospheric h. J. Opt. See. Aw. 31, 467-476. '........ ... Moon P. (1940) Proposed standard solar radiation curves for engineering ine. J. Franklin Inti. 230, 583-617. ' Randuson D. (1973) A summary of hourly turbidity measurements for Las Vegas, Nevada, during fall months. Atmospheric Environment 1,271-279. . . ..... 'T.t'^ .. . A-v' DISCUSSION i.v^f' * K* 4 ASBESTOS RBRES IN THE AIR OP TOWNS* Holt and vrotMO art unduly reseryed jiboirt the potential for quantitating the asbestos content of city air. Other studies have shownIbaiilBaimeasurement con provide very useful data concerning asbestos air pollution, even serving as a basis for Ihe implementation of abatement procedures. P. F. Hcx-T and D. K. Youno (1973). Atmospheric Encironmcnt 7, 481-483. "' Since these data 49 U.S. eiti arm hr .7. It is (tiflicilll IP > description. Snr e r< scanned visually nr > find, for example, tl What magnificatior more revealing.! It is evident that contamination by t correctly stale. i` occur with ouup* >. : ry1 a ., .... -.**.<- .v. * * - 7 * *'< ;I,i'i..r,'B-vrpvi >'w.*r*.7ei..v<'*"**# - .fv1 IP* .1..r''ws' AV".v .. . ' b..uw: r.i1*1 * n* -r . . > *' , i.' g?v> riQ. fitPQBO00 1396 * - -vr* -v. ** v.\*" 'C1' '' PRODUCED BY FORD G k. 19771 hot noi been equcnlly ciillrvicd only c and after local noun, the strong inlradiurnal front 0 7 to 0 68 /i and tit ihc iiir matt value lar radiation might be .mix I, containing data like lo point out that i appear lo explain Ihc 0- 0" 10" n for this inlradiurnal ' nil an evaluation of the luLturr (1941) showed , e particles in die almos lion of the inlradiurnal * tdy c^gcespbin forwaid . tOnsBo D. Ranmmon : ' - : v.K-v; - .iidity over (he United ` '-<76. i e. y. Franklin hut. ihr asbestos content if fnl ilaia concerning ' lent procedures. w; Discussion' 667 I. Asbestos bodice arc only the lip of the iceberg, representing only the largest fibres (including materials oilier than ;i*Iicsi<k), visible by optical microscopy, but missing fibres below the limit of resolution of the mclliiul. Rather, asbestos fibres and fibrils ean be directly sought by L'M in lungs of . cits dwellers--and, when they arc. found far mote frequently than coated biwlics (I.sm.ck ri <//.. 1971; Hi mi.IV r; at., I "70l. Moreover Ihetc need not be the insccuniy uinccrning the nature of Ihc asbestos body ente fl sv.ti rr /., 19711. As Moll and Young note. iy I.M chrysmile aslvslos has a unique appearance. We know ssliat we arc seeing. 2.1 he authors hviii icsiimcd lo being unal'lc in satisfaclutils express the cniccntralinn of asbestos fibics in an. Admittedly, this cannot be done with line precision. bm rather tellable and i. pimlucihlc C'limaies ean be made. (Duplicate analysis nf samples in out I aburanny imlnaie a lasloi of in or llnee is possible.) The Iceliniqucs they qnoir (X-ray diiliniiiun ami infrared s|>celroii`irs j ;ur bm insensitive foi Ihc purposes. On lltc oilier band, mass eons.durations can he ealenlaled fiom number and si/e of fibrils, and Ihc dcns/ly nf chrysonlc (Niriioi cin ri at. I'/'li. In die Uiuicd Stales for example, our early results showed the following concentrations io be found in the air of New York (Set nemr rt at., 1972; Seuxorr tt at., 1968). Tablx I. Cmbysotiu cosncsn or amiuint aim ik N.Y.C. gHiiiMiNAHS *tsuits Sample locaiions Asbestos air level in ICC* g nr* Manhattan lironx Droolt lyn Queens Stalcn island ... 2J-60 2^28 19-22 18-29 . 1, 1-21, - Additionally, specific sources of asbestos air pollution were defined from sampling near construction tiles. v. :: 91'* C*.:.. . Ta*U 2. ClIAYXJTlLf COWTEHT Of N.Y.C. At* fN v ' VICINITY Of IfRAY mf.fAOOriNO WITH AMCttOfr* * CONTAININO MATIMAU '' .V, - -. .. >y S",it,ev 1 (downwind from source) Asbestos tcwl in I0-* g nr* <$-180 < (downwind froinf source) tW? S (upwind from source) ' 20 " Dsese dait were oobSined ~We hasifquanfilared' af 49 U.S. cities and have found asbestos to he present in all. _' 7. It it difficult to comment upon the relevance nf comparative techniques, in the absence of detailed dctcrinlinn. Nome reservadons mielit be lifted with alterations in methods. l:or example, weic grids SSjsS&S' It Is evident that a pond deal is no* Vnowm of asbestos air pollution and consequent, lung etiultiiiuniiiion hy Ihc uhiqtiitnus lihrils. Wlut has nor yet been ilvciphcicd, ns Hull and tilling correctly state, is the disease potential of tuth general commundy asbevins air pollution. CatuTf may occur with occupational asbestos exposure, with that associated with neighborhood pollution 6 -'..I ' T . 5 6 - w > i .. . 00 0 RQ PRODUCED BY FORD ift - W itx I ^ I 668 Discussion bout asbestos works or in households oT asbestos workers, but these art presumably heavier exposures than we now observe in the general cnviionmcnl, and the cifrcl of general asbestos air pollution temains to he denned (ScLicoft et el.. 1912; Si.ucotr et at.. IvfiK). evidence Ih.i h;#* K df* not infoi Environmental Sciences Ijthorotary. Mount Sinor School of Medicine. The City University, >\cw York, N. r. 100:9. U.S.A. W. 3. Nioioi.son A. M. L.ano(k I. J. Skikoh i> it (rum h pointed up between mo I'rfMin* 4</ 1055 ( it-rrtb f tU`U\Ct. ( til KCPCRCNClS Lakosr A. M.. Sruvorr I. J. and Sashii. A. II9?|J C'hryoiiic asbestos in the lungs of persons in New Voik City. Arch. Environ, l/lth 22. T 111 o 11 -vi 1 the rruii'iki Lam.lk A. M., Ruiiin I. B. nnd Sm.ikoh I. J. (19721 Chcnuc.il chitracierisatinn of asbestos body cores by cle'Clron micfoprolie analysis. J. llisrorhcm. Crimm-m. 10, 72.S-7S4. Niciioi-son W. J,, Ron A. N. and FiRRami E. F. (1971) Asbestos air polliiliun in New York City. _e In /Viic. SccoiiiI Inlcrnnlinnal Cleon Air Congress (Edited by I.nulumj H. M. and Brnnv W. 1.) pp. 136-139. Aeadentie Press. New York. Pooti y I-. D.. Oi.diiasi P. n,, Um C. and Waunth 3. C. (IO'Oi The detection of asbestos in tissues. In Pwutnoctmiosis: Pmc. Imernniionol Cnf, Johannesburg. I9n9 (lidded by Siuriko II. A.) pp. I OH-I Hi. Osford University Press, Oxford Sil icon I. J., Nioioljo* W. J. and Lasolk A. M. (1972) Asbestos air pollution. Arch. Environ lllih 25. 1-13. SiLiriiir I. J. and Hammond E. C. (1968) Community effects of noil-occupational environmental asbestos exposure. Am. J. Pub. Hlllt 58, 1638-1666. coiiiamtn:il const..r.iK appc;it;m.i- have been I more likely O'Kfli v H 1 he indi arpc-iraner exislenvc Perhaps' and pattiev aibcstosiv" r asbestos w. and Clour M s, . I960)and! QuAwnTATivt results for the concentration or asbestos in New York City are valuable and a reprodu cibility indicated by a difference of only (wo or three times is impressive. Values for (he 49 other cities will be of great interest. The dilfcrcncc shown by these figures between concentrations of asbestos fibres near to a point at which asbestos was being sprayed and the concentrations found in the general atmosphere was Itllle ...more than the dilfcrcncc between duplicate samples estimated in the laboratory, except when the ^` sampling was carried out Immediate)/ downwind froci'*o6eot.'TWi jwwesthat there h.widespread and rapid dissipation of (he durt ftiorh'ftje'jioinl ' r- The neighbourhood hazard has again been emphasized in a report given by W. Douchd at the meet .. Ing of the International SocietiesJoe Hygiene. Preventive and SocialMedieUte. 1972. five report showed . ' not oocupa (Dalohus 1 he efTcv readily ren probably t similar rat -vj'other vTie Orots<i needed to in rats wit ihat,<4fc. I9C patienU with mesothelioma rtporiedln She city ofHaroburg, SJhd no known' '' ` Industrial 'exposure to asbestos "but had lived in the neighbourhood of asbestos factories. This indi-' cates the importance nf independent surveys of the type carried out by SclikoITand his collaborators. The object of our investigation was only to determine uhetlicr asbestos fibres are prcscnl in the ; tSeparrmei University Berkshire. atmosphere of towns where there is no asbestos industry. The result was positive in every case. fe-Vvir* Berkshire. Botham S Botham 3 crocido Dalqui'i t prciimii FtrteiitK Got i> C. Kivu.iot anth> Luvitiv a poi Ntwholg&SKSW* Stuiofi Am. .j.ks"|W "9nyrt gv, ... > %. * --p *.. ' ? 'v" PRODUCED BY FORD G,'.r exposures Mix air pollution W. i. Ninim sow A. M. Lancia I. J. Srmorr Discussion 669 evidence that it is mort common in cities than in runt environments. They do nnt review the evidence which has been puhlivhcd which liiggcsts that certain forms of axhcitov art relatively harmleu. They do not inform the Trader it hat they consider to be the sourer of the asbestos in rite uihan atmosphere: is it from brake linings or construction materials, for example? I would lie grateful if the authors pointed up the nature of the risk to which they allude and stress, if possible, nays of distinguishing between more harmful and less harmful asbestos fibres. Veterans Administration Hospital, 10SS C"letmust Street, Center, Colorado 80220, U.S.A. Root* S. Mnnirii AUTHORS' REPLY mg' of persons in i of asbestos body n New York City, ami Brany W. T.) isN-stos in tissues, y Shawau H. A.) in. Arch. Environ. nal environmental Me and a reprodothc 49 other cities I was little eept when the -re is widespread niche at the meet ly report showed 'thtul no known "' 5rics. This indi; his cotblnsralnrs. j are present in thcT.-'x-'.' . every ease. ... ' T itr. sound of (he asbestos fibres in urban air is still a matter of speculation. Rome 3 million tons of the matciial arc mined annually and nshesins has very many industrial applications so some perietal contamination of the air seems certain. Chrysolite is used in brake linings and brake linings ate being constantly disintegrated. However, the heat generated when brakes arc applied would alter tbc appearance of Ihc chrysoiilc fibre in the electron microscope. Some fibrils tn our samples appear to have been healed but most of the chtysotilc fibrils wc observed did not have this appearance and are mort likely to have been derived from building material. Photographs by Lumliv. 11 Atoms and O'Kelly (1971) iliusirate the production of dust from building materials. The individual fibrils seen in our samples probably have no pathological significance hut the appearance of large agglomerates in random samples is less reassuring. They suggest Ihc possible existence of localized sources where the conuiinuiaiion may he appreciable. Perhaps the titost disconcerting aspect of reports on Ihc incidence of a>l whwis and related diseases, and patiicularly mesothelioma, is tbc frequency with which a "neighbourbond hazard" nr "endemic asbcslosis" is mentioned, disease occurring in apparently innocent occupaimns or in members of an asbestos worker's family. Examples that may be quoted arc workers near luggers in Glasgow (Gold and CViiiiicrt, I9M). villagers near an asbestos mine in Italy (Vioiiani, 1 `Jt.'Z), Finland (Klvu.uoio, I960) and South Africa (Waunf.r, 1959; SuJh'orf, 196}),in carpenters (Fletcher, 1971) and persons not occupationally exposed to asbestos in London (Nlwhoum and Tssompson, 1965) and Hamburg ' (DAbout i n. Daimf.kt and Hinz, 1970). The effects of asbestos may be due, in part, to the morphology of the fibres but, because it is more readily removed from She respiratory part of the lung, chrysolite the commonest form,pf asbestos M_._ "probeblylhe least harmful (Botham and Holt, 1971a). Submicron gists fibre is atso removeslilia^S similar me to chrysolite (Botham and Holt, 1971b). Chrysolite can be readily distinguished from other varieties of asbestos with the electron microscope. Gross fibrosis is prohahly produced only by very high concentrations of asbestos but the amount needed to produce a carcinoma is not known. Stanion and Wrench (1972) produced mesothelioma in rats with amosilc, crocidolitc and chrysoiilc. . Department of Chemistry, University of Reading, F. F. Holt . ... .. D. K. Youno REFERENCES^, F. F. HoltJ: I :. z.-- v. - v 2 DothamTS'ICCT'ahivd Holt F. F. (1971a) The devdopment of gUssfibrelbodici wTneju tig**? pigs.y. FOf*. 10}, 149-156. . jBotham S. K. and Holt F.. F. (1971b) Development of tsbestos bodies oo tmosile, chrysoiilc and ciocidolile fibres in guinea-..pig.lun.gs. J. Path. 105.,159-167. '" ; ' . * ' Dalouixn P,, Damekt A. F. and Hinz 1. (1970) The epidemiology of pleural mesothelioma preliminary report on 119 eases from the Hamburg area. Gem. Med. Mon. 15 (2) 89-95. FinciirJi D. E. (1971) Asbestos-related chest disease In jointrs. Fzuc, R. Soe. Med. M, (8) 837--8. Gold C and CiffMautT J. (1966) Asbestos--A hazard to the community. Dab. Health 00 (6) 261-70. = "tioqju j YocotgtmoloelcaiRisW endemic - * rT1F.~S.',TWaiw FTC', and O'Kkuv F.YTI971) ttundlngs msulatedwuh sprayed asbesloaV ;7 55^ ;* a potential hazard. Ann. Occup. Hyt. 14, 255-257. Ncw ikhikl M. L, and Thompson H. (1965) Mesothelioma of pleura and pentnm >m following expo- jure lojasbcifc* in (he London are*. Br.f. itsdust. Med. 22 (4) 261-9. . 1 `^ -^^^AiMQHP^^utiTOrhmc j.*(1968) Asbeatog exposure, smoking and peopla^. ^lgvjiiiir.'Sl^j':-. `: ff-'-i;-,* j; 7 -- .^v.- . ... ; r d - .... -A--r'VAT-"-. e yyr y V, . "'- ; . " 1 . ` '` 1 f". i8iwr RQ8000 101; I PRODUCED BY FORD