Document 2NzpOL5RjvK5R3y11pvmDDMdb

FILE NAME: Neighborhood Exposures (NE) DATE: 1963 DOC#: NE006 DOCUMENT DESCRIPTION: Medical Journal Editorial - Pulmonary Asbestosis \x:can M edical x June 1963 SA.ftuJ.J- Jou rn al : Su id-A rik aanse Tydskxif vir G enecskunde Volume 37 No. 24 Dccl 37 Kaapstad, 15 Junie 1963 EDITORIAL : VAN DIE REDAKSIE PULMONARY pneumoconioses or dust diseases, asbestosis would be the mi"l serious from many points of view, ow a relatively short exposure-- months instead s in silicosis--and while the morbidity rate, as J by radiological means, has been much re measures to lessen the inhalation of asbestos factories, it can still be very high--44-5Ys workers with 20 or more years' exposure and iosc with 10-15 years' exposure.1 union in frequency of pulmonary tuberculosis t-war era. and the equally striking increase in r in most countries, makes it difficult to assess ,ed iiahility of present-day sufferers from asbes--se two complications. Clearly the data obtained ;re years ago have little validity now. while carcinoma has such a range o f frequency in oumries that conclusions based on world avertrdly acceptable. In the case of pulmonary tuber: British figure for the association of this disease cases of asbestosis in the years 1932 - 39 was :ile in die same period the figure was 57-1 e/ 0 in ' f silicosis.1 But in one part of Germany, , recent findings published in 1960 snow that is as a complication of silicosis was still very -- 34-6% --while the association with asbestosis little more than twice the tuberculosis figure bole population in that region.' ig-cancer rate in silicosis is not appreciably n in the general population, but in asbestosis its is estimated to be about ten times that of simiiups. both in Britain* and in Germany.1 it years the matter has been extended by the ptance by most pathologists of malignant mexos an entity, and the even more tardy appreciamesotbeiioma of the pleura may be associated stosix.11'1 nations where pneumoconiosis o f mineral origin d. those affected are normally the miners and 'y the workers handling the material in bulk. there is no danger as a rule to those who deal nanufactured goods containing the raw material . With asbestos it is otherwise. In Canada, where ee-quaners of the v.-orld's production of asbestos the miners would appear to suffer little as;d show no significantly increased cancer of the in South Airica at least, the miners, and even g in the vicinity of the mines, may develop asd pieurui mesothelioma.1'* ses of asbestosis, however, result not from min- m employment in asbestos factories. Today *sed in so many industries and is a constituent ny manufactured goods that the occupations estos "is a potential hazard are too many to here. Workers at risk include such unlikely ie garage worker^ employed in under-body _car ASBESTOSIS spraying.1* and more obvious ones such as those employed in lagging pipes w-ith asbestos, or those concerned with the manufacture of asbestos cement, roof and floor tiles, ceiling boards. etc_ or with the m e of them, such as builders and builders' labourers. While the modem use of asbestos expands the field of potential inhalers of asbestos fibres, the risk of asbes tosis is limited, and it is unlikely that these occupations will lead to a marked increase in pulmonary asbestosis. The effect of the inhalation of a small quantity* of asbesios fibres, insufficient to produce pulmonary asbestosis. but possible in many o f the occupations indicated, has been put on quite a different footing by two recent papers by Thomson and his colleagues in this Journal.'"'"' In the first paper" Thomson described 6 cases of mesothelioma, pleural and peritoneal, where there wax no diffuse pul monary asbestosis of the ordinary type, but only a few small foci of asbestosis at the bases of the lower lobes. It was stressed that this limited basal asbestosis produced no signs or symptoms and was likely to be overlooked at autopsy, unless sections from the lung bases were ex amined microscopically. In only one of these cases was there a history of exposure to asbesios. This paper was followed by what appears to be the first investigation into the extent to which urban dwellers are exposed to the inhalation of asbestos fibres. Thomson et alJ* examined the bases of lungs for asbesios bodies by a simple smear technique, and found that more than a quarter of the subjects over the age of 15 years in the autopsy services of the Groote Schuur Hospital. Cape Town, showed asbestos bodies, supporting their conten tion that the inhalation of asbestos fibres was now an urban hazard. They did not find_that it was a significant hazard today, and were more concerned with what might happen in the future. They emphasized that the world's production of asbestos is increasing at a staggering rate, and is now eight times w'nat it was 35 years ago. and that today asbestos-containing products arc ubiquitous, especially in urban areas. Thomson et a l also drew attention, to a simple but important fact which seems to have been overlooked so far from the medical and public health points of view. Tnis is that the very reason for the use of asbestos in in dustry-- its resistance to heat, acid, alkali, oxidation and reduction; in fact, its virtual indestructibility--is the reason why it may become progressively more dangerous to man. Wind and water may disperse ashestos fibres, but they cannot destroy them. Asbestos is now accumulating on the surface of the earth, mainly in the cities.-at the rate of 2.400.000 long tons per annum; motor, vehicles are discharging asbestos dust from brake drums, clutches, silencers and under-body coatings, and modem builcimrs may contain asbestos products from the roof to the base ment. The indestructibility of asbestos makes this to someextent cumulative, and in effect we may be creating such 629 an asbestos environment m cities that in the future hasal asbestos may become almost universal in urban dwellers and mesothelioma of the pleura and peritoneum may become common lumours. These observations and opinions arc new and we await confirmation of these findings from other countries: they may well be confirmed as regards the frequency of asbestos bodies in the lungs of urban dwellers. It would seem a hard turn of fate that the avoidance of ordinary pul* monary asbestosis might lead to an increased frequency of mesothelioma of the pleura or peritoneum, presumably because the patient lives longer and the carcinogenic action of asbestos has a longer lime to act. We hope the fears for the future expressed by Thomson cl aL'~ 3re unjusti fied. but it may be desirable to pa> hen1 their warnings, at least 10 the extent ul restricting unnecessary and possibly dangerous uses of asbestos 1. boLIic. H .. G. aJ H. <!**"**. /a- A/>*-\u*** **-* / Stuitirait: Thicme. Z . Sutherland C. L. US40: lu itc c t. ! . i . WkJi. J. H**o0>: O f t . n # .1 4. D oll. R. flVS5i: Brl. J. Imiuftr. M ed.. 12. *1. 5. Cjirucr. f. rt*S2>: Arch. lnduir. H y#.. 5. 2tw. t>. V*n ckur School. H . C. M . (1952): N 4. T , Ocnc*k.. J2. IIT* 7. Warner. J. Sic**. C. A . and M^rchand. h UVoO: lin i i . 1 . Med., 17. 260. Braun. O. anJ Truu. P. ilV.'fci: Arch. Induiir. H ti;.. 17. **4 V. Skrfga. C . A .. M sr c lu td . P . and W<yncr, J. C . (tv 1): Si. 4!# J.. 35. iS . !*'*. B rutw h. H . G . *tul BavWr. H . HMtrli: N w tnvtl. J. Md . 2a4 1!. T hom son. J. G . i|v n 2 l: 5*. Air. M cJ. J.. 3%. 75*. 12. TK om snr. i . G .. K a w h u U . R . O C . a*J K * / W h 27. 77. BAKTERIELE CENETIKA Daar was "n tyd loe dit aanvaar was dal die klassieke genetiese wette en beginscls nie op mikro-organismes. en vera! bakterie. van locpassing was nie. Bakierice reproduxeer vegetatief en hui mikroskopiese grootte het hlle ongeskik vir sitologicsc studics gemaak. Vir baie jare was dit aanvaar dar daar fundamcntele vcrskillc. beide geneties cn fisiologies. tussen hoer dicre cn mikro-organismes bcstaan en dat die wette w'at op die een van locpassing is. nie vir dis ander gdd nie. Maar, gesien in die lig van die moderne fundamcntele eenvormigheid tussen alle biologicse wetenskappe. is dit duidelik dat hierdie opvattmg verkeerd was. Gcmeenskaplike grond is gevind deur die inlensiewe Studie van bakterielle Genetika wat slegs in die aaste twee dekades op die voorgrond getrec het. Vandag is hierdie vak die brandpunt van die biologicsc^wetenskappe en het al selfs sover gevorder dat dit amper die tergendc vtaag .wat is lewe-.'", kan vcrkJaar. Jacob en Wollman' verdcel die historiese omwikkeling van bakteriele genetika in sekere tydvakke: Gcdurendc die laaste helfte van die 19de ceu is mikrobiologie as ekspenrnenteie weienskap ingesteJ en aandag is hoofsaaklik bestee aan die isolasie en morfologiese beskrywing van nuwe spesies. Van 1900 tot 1940 is 'n groot aantal variasies van bakteriee geidenfiseer, bestudeer en beskrywe. en hieruit is die vak baktcriele genetika gebore. ln die laaste tydvak. beginnende 194. word baktcriele oorerwing onticed en gckoordincer in eie lig van die klassieke gcnctiese tcoriee. Klassieke genetika ontlecd die aard van kompldcse, dikwels nic-essensicle, eienskappe. In teenstelling daarmec analiseer bakteriele genetika op die molekuiere vlak en gee 'n beter begrip van basiesc scllulcre meganismcs. Ook dien dit as `n hndige instrument waarmee die struktuur en funksic van bioiogiese sisteme bepaal kan word. Treffende besvys. dat daar 'n chemiese basis vir oorerwir.g bestaun, is gelewer toe 'n bakteriele ei'cnskan omvorm is deur desoksicribonukleiensuur (D.N.S.). wat uit 'n pncumokokkalc rnutaor berci is. Soortgelyke ingrypendc waamemings is in die ^fgclopc 20 jaar met bakitrie gedoen waarvoor verskeie faktore verantwoordelik is. Om slegs `rt paar te noem: Bakterie kan. wecns hlle ongeewenaarde voortpiantingsnelheid in 'n kort tyd tot enorme gelalle aangroei. Die bakteriele sei se oorerwingsfaktorc is vasgcle deur 'n enkele liniere struktuur. die bakterieie chromosoom. beslaande uit D.N.S. wat die makromolckulcrc patroon van die bakierium beheer. Bak terie se gcnctiese matcriaal is relaticf onstabiel. Mutasies kom spontaan voor in `n g eg en c gene m een un . honderd miijocn scl-vcrd d in gs. Ekspcrimcntelc r.a in bakteriele genetika tref deur hui cenvoud. akkura. en berekenbaarheid waarm ee analicse uitgevocr kan D ie fundam cntele problcm e van genetika het hi.-.,, binne die bcstek van die nie-genctikus geval. \ _r merkw-aardigste bvdraes op hierdie gebied is indii.;. gemaak deur fisici en biochem ici. ln 1953 he'sW atson cn C rick / N o b e lp r > e n n e r s van 19<i2. die . tuur van D .N .S.. gehascer op chem iese analicse en kr.lografiese studies, wat allcrwce as 'p. hiochrmtesc t: aanvaar is. H icrsolgens sou D .N .S . bestuan uit in u nukleoticd-kem ngs w at spiraalseewy-sc rondom n *e; as gedraai is. D ie ruegraat van elke spiraai be-*;_-j fosfodiester-bande. D ie hasisse. op `n geeewe die een ketting. word met beliuin van waterstnliat..' bind aan ba.sissc op die m 'iccnvirm m cm lc vljt ander ketting. W alerstofhm dings kan. wt-e-ns sir... redes, net plaasvmd tussen die hasfs-pare adcnie-r. ; cn guanicnsiuiMcn sodat die een ketting dan dabeeid van die ander is. Dit is verbasend waiter Kcl. bioiogiese gevolgtrekkingr van hierdie model gen*._. w-ord: Dit lewer bew ys van D .N .S . se moleknirr. kasie; die aaneenlopende liniere Vivlgorde van hjgee aanieiding tot 'n hepaalde gcnctiese U>de tn teit. terwyl dit ook 'n verklaring vir muijsics ^ nana gec. Hierdie m oitel dien verder as v.Mrh.. 'n nuwC studicrigting. naamfik <uu!.kuteridaargestei is hoofsaaklik deur die toedoen van Ken virus-genetika. H o c ver uns reeds vandag gev. van die klassieke sito lo cie hlyk uit die leit iL' genetika van dterlikc som atiese solle up hierdie . ontwikkel moct w ord, dit dan 'n direkte m ir ,, baktcriele en virus-genetika ts. wat weer up i,u. hlle ontsiaan aan w eeiselkuhure tc danke hei D ie scnirale fx'sisie wat atoom fisika v a n i . fisiese wetenskappe beklce. kan uns vergehk n. kulere biologic in die bioiogiese wetenskappe. tcorie is die praktyk van m ore, ln hoevrrre genetika die natuurwette gaan bcinvked. hatte .. sukses waarm ee die teorice. wat sodanig vt -`. . ander bioiogiese sistem e toegepas kan wtrd. t. Jacrth. F. cn W ulhiufl. i*. 1 . iia rirr s. . A. jJcm is l'ie. S * \ u u l t i .~n.i 2. Ascry. (J T .. Mwl cU. C. M . cn NUC -ul.%. M. . 1*^^. 71. 1J7. : NVairun J . D . rn Crick. F. H. C. I*i53i: N^iurc *1 *..