Document oD793w7j5k9GVvdw5jRvVyJZ7

FILE NAME: Welding (WELD) DATE: 1971 DOC#: WELD011 DOCUMENT DESCRIPTION: Journal Article - Epidemiology of Mesothelioma on Walcheren Island IBnrdituisshtriJaol uMrneadl icoifne Volume 28, 1971 editor W. R. Lei? ASSISTANT EDITORS P. C. Eimes D. F. H eath j EDITOR CURRENT AWARI NESS SECTION K. S. W illiamson EDITORIAL COMMETTI E Sir Melville Arnott D. E. Broad be nt R. C. Browne E. A. Cheeseman A. G. Heppleston P. J. Lavvther Trevor Lloyd Davies C. R. Lowe A. E. M. M cLean A. Munii R. Murray R. S. F. Schilling T. S. Scott 1. Sutherland . A. B. Swan J. S. W einer Editor, British Medical Journal { t British Medical Association Tavistock Square London WC1 H 9JR I" Bril. J. induslr. Med., 1971, 28, 59-66 in in lead s -------------------- --------------------------------------------------------------------------------- ------------------------------------------------- rotopor- Epidem.iology of mesothelioma on Walcheren 'T,' Island i J.STUMPHIUS Bedrijfsarts van de N.V. Kon. Mij 'D e Scheld e', Scheepsw erf en M achinefabriek, Vlissingen, The Netherlands Stumpluus, J, (1971}. Brit. J. induslr. Med., 28, 59-66. Epidemiology of mesothelioma on Walcheren Island. The chance finding of asbestos bodies without `asbestosis' in the lungs of a shipyard worker who had not worked directly with asbestos led to this investigation into the relationship between asbestos bodies in the sputum, occupation, and mesothelioma in the shipyard at Vlissingen on Walcheren island. Examination of the sputum from a sample of 277 shipyard workers from various occupation groups (excluding insulation workers and others know n to work continuously with asbestos) showed `asbestos' bodies to be present in 60%. The frequency varied from 39% in workers with no obvious exposure to asbestos dust to 100%, among those with slight but definite exposure. By repeating the analysis using the occupations 5 to 10 years previously it was found that many of the workers currently employed in occupations not exposed to asbestos who had asbestos bodies in their sputum had been exposed in the past. Between 1962 and 1968, 25 cases of mesothelioma were discovered on Walcheren; of these, 22 cases had been employed in the shipyard at some time and their actual job was known in all but one case. The shipyard employs approximately 3 000 men so that the attack rate for mesothelioma was approximately 100 per 100 000 males per year. For Dutch provinces with heavy industry the rate is 10 per 100 000 per year. For the different occupational categories within the shipyard the rates varied from approximately 50 for `clean work' to 280 for men with some exposure to asbestos dust. Asbestos insulation workers were not included in the study and no cases of mesothelioma came from that occupational group. I Asbestos is a mineral widely used for an ever increasing number of purposes on account of its fibrous structure, its many practical applications, and its low cost. The medical consequences of contact with asbestos arc twofold, namely, asbestosis (frequently coupled with a high incidence of bronchial carcinoma) as a typical occupational disease of asbestos workers, and diffuse mesothelioma associated with slight exposure to asbestos in the distant past. In addition, asbestos leads to the formation of asbestos bodies and also of pleural plaques which appear (as yet) to be non-malignant. Diffuse mesotheliomas, until recently held to be extremely rare, have been reported in increasing numbers in the past few years. The majority of recent publications are of AngloSaxon origin and demonstrate some connexion cither direct or indirect - with the asbestos industry as such or with heavy industry in general (Wagner, Sleggs, and Marchand, 1960; Gilson, 1966). The Netherlands has never had a large asbestos industry but heavy industry is well represented, particularly in the western provinces of Zeeland. North Holland, and South Holland. Zeeland lies on the delta of the rivers Rhine and Scheldt, in the south-west of the country. It consists of a number of linked islands, a circumstance which has tended ov> .'tium(>htu\ & !o isolate it from the rest of (lie Netherlands. It is primarily an agricultural province. The most important island is Walcheren (90 000 inhabitants) witn the county seat of Middelburg at its centre and the port and industrial town of Vlissingcn on the south coast. Until recently, almost the only local industry was actually worked with asbestos, nor were welding electrodes covered with asbestos ever used by this firm. (2) In 1966, three cases of mesothelioma were diagnosed in men who had been employed in the shipyard. III iron expoemph IV M en. nol , carpei rcpaii the large shipyard and engineering works of N.V. Koninklijke Maatschappij 'de Schelde' (Royal Schelde) established in Vlissingcn a century ago. At present this firm has some 3 100 employees on its payroll. A considerable proportion of the in habitants of Walcheren work there and the labour turnover is relatively low. At the time when this investigation was carried Methods Sputum examination Workers were asked to briny fresh specimens of sputum for examination. They were encouraged to bring sputum produced during acute respiratory illnesses so that speci mens were obtained from men with and without a chronic productive cough. At least two thick smears were made, dried, and stained V Not . nor to This clas population study and n same men a yard 5 to 10 although th tendency fo> out the situation was as follows: For many years shipbuilding, including naval vessels, was the firm's main activity. More recently the emphasis has changed to other industrial pro ducts and to ship repairs. Asbestos had been widely used in shipbuilding, especially in the past, as it meets the high standards required for insulation and fire prevention in sea going vessels. Insulation work was never done by the firm's own employees. It was always carried out by the personnel of an insulating firm regularly engaged as sub contractor. Intensive occupational exposure of the Royal Schelde's own employees to asbestos dust did not occur. But of course asbestos cannot be excluded as a source of slight exposure in many departments of the firm. Asbestosis used seldom to be found in the Nether lands. Undoubtedly this was partly due to pro fessional unfamiliarity with the possibility of the disease. But the insulation workers had been exam ined and seven asbestosis cases were found out of a with Perl's iron stain. Only specimens of sputum con taining alveolar macrophages were examined for asbestos bodies. The slides were examined under low power, and suspected asbestos bodies were re-examined under higher magnification. When asbestos bodies were not found on the direct smear, specimens containing alveolar macro phages were re-examined after digestion with 1 sodium carbonate for 24 hours at 37 C. The sediment was separated by centrifuge and washed repeatedly with water before re-examination. No difficulty was encoun tered in distinguishing typical asbestos bodies from other iron pigment in the sputum. Sputum specimens were considered positiv e for asbestos bodies if any were found. No attempt vste- made to grade the specimens according to the number of bodies. Mesotheliomas Walcheren has a central pathology laboratory and, with the close cooperation of the pathologists and physicians on the island, it was possible to follow up and investigate fully many suspected cases of mesothelioma. Wherever possible the final diagnosis was made on postmortem findings but in some eases it rested on biopsy combine with typical clinical findings. The criteria for diagnosis cleaner jobs about the <n over 10 year Asbestos ho, During the sputum fro, examined. 57-8 %). In Table I are related t. of the invest, occupational A remark, found in th, rational hiextended to , 5 lo 10 years the latter bast dean work cat total of 24 workers. were those recommended by the UICC Working Group Among Royal Schelde employees the most detailed on Asbestos and Cancer in their 1965 report. investigation and examination had failed to bring even one case of asbestosis to light. Asbestos seemed to represent no danger to the firm's own employees until two discoveries were made which seemed to contradict this. (1) Necropsy performed on the body of an employee of the firm who had died as the result of an accident revealed countless asbestos bodies in the lungs. There was no fibrosis so that asbestosis was Occupational classification Because both in the sputum containing asbestos boditi and in the lungs of patients dying of mesothelioma lb asbestos bodies were always associated with other ironcontaining material, the workers were classified accordint to their exposure both to iron oxides or fumes and i; asbestos. The men employed by contractors on insulati were not studied so that no men were regarded as work ing with asbestos or as being heavily exposed to its dus l \po\ure gfoui (u'c text) I Inm vapour ll Rust and son; 1 not diagnosed. During his lifetime the man had never suffered from any serious illness of the respiratory tract. What was striking was the presence in the lungs of large quantities of iron pigment, both in the macrophages and in the form ofamorphousparticles. The origin of these was obvious. There is always a great deal of exposure to iron oxides in a shipyard. Moreover, the victim had spent years as an electric welder. Heavy occupational exposure to asbestos However, those craftsmen who were employed in finish ing ships inevitably had some exposure to asbestos dur because it was at this time that insulation work wasbeini done. Similarly, craftsmen doing repair work were alv exposed if insulation was being removed or replaced! the same time. The following categories were recognized I Iron vapour: Apparently negligible asbestos tv posure welders and cutters 11 Iron oxides (rust): Some exposure to asbestosfitters, welders, plumbers, etc. employed aftc asbestos III Iron vapour an. rust I ' Some asbestos ht. hlllc iron ' u p o u r or rns t'ic.in work I `Mai *, r elive of spui. **mined . . had not occurred. The man himself had never launching or during repairs A total wxjrkt: "tr. I '.pidemioloyy oj mesothelioma on Ualeheren /slant/ 61 ior were wehhn ever used by tlm esothelioma wete i employed in live % t) pecimens of sputum ged to bring sputum Inesses so that spew mi without a chrome le, dried, and staimsj ens of sputum cotn xamined for ashestm ndcr low power. aM 'imined under highrs s were not found o* ring alveolar mactw rfion with 1% sodium The sediment * ned repeatedly uittt ifficulty was cncoum os bodies from other d positive for asbestm ,n was made to gtiJi her of bodies. laboratory and, vutV ogists and physios** inv up and inveslip* a helioma. Where nade on postiiionc ; on biopsy comhmtrf wueria for diagm ICC Working Gnnf 65 report. lining asbestos bodm .<of mesothelioma it* iaied with other Hi# ere classified accord)** .ides or fumes and umtractors on insulaum ere regarded as wi*V . ily exposed to its tii** ere employed in trnni unsure to asbestos Ju* idation work was htw* repair work were *>*> removed or replaced * gories were recogniroi negligible asbestos * exposure to axbcsu etc. employed ah III Iron vapour and rust: apparently negligible asbestos `exposure - platers, shipwrights, and foundrymen employed on initial construction it Men exposed to other dust, including some asbestos, not exposed to iron vapour or rust: painters, carpenters, etc. employed after launching or during repairs V Not apparently exposed to iron vapour or rust nor to asbestos dust. This classification was applied to the total working Jopulation in the shipyard at the time of the sputum turfyand mesothelioma study. It was also applied to the men according to their occupation within theshipUrtl 5to 10years previously. This was necessary because uiiotjgh the turnover of labour was low there was a wrfeney for men to move within the firm to lighter and Csaner jobs as they grew older. The information available bCxit the occupational classification of the labour force srt 10 years before the investigation was incomplete. Results Wkstos bodies ttaing the five-year period specimens of alveolar mwium from 277 Royal Schelde employees were mined. Asbestos bodies were found in 160 -J*S\I. In Table 1 the results of the sputum examination m related to the occupation of the men at the time *1ihc investigation and to the total numbers in each wupational group. \ remarkably high proportion of positives are ItHcsi in the group `clean work' (V). The occuS#t>anal history of all those examined was eroded to cover the work they had been doing 10 years previously (Table 2). Classification on U* Utter basis showed a considerable shift from the tlkie work category to that of other exposure groups. Of the original 63 (39%) positives in group V, only 33 (26%) remained. In Table 2 the percentage of positive sputa in group V proved to difier significantly from that in groups 1 to IV ( y 104-1; D.F. 4: i> 0-001). There also proved to be significant differences between the four groups I to IV (%2 8-13, D.F. 3; p < 0-05). It is fair to assume that if the work history were extended to cover even more of the past an increasing number of the positives in group V would have to be re-classified. The variation between the four groups 1 to IV appears to he related to the possibility of exposure to asbestos in that groups II and IV contained the highest proportion of positives. The sputa from group II, in which rust exposure was combined with possible exposure to asbestos, all contained asbestos bodies. The findings are consistent with the suggestion that the high proportion of sputa positive for asbestos bodies found in this investigation were due to inhalation of asbestos at work. The frequency of positive sputa appears to be related to the extent of the exposure possibly augmented by inhalation of rust. Mesotheliomas Mesothelioma was diagnosed in 25 cases during the seven years 1962-68. Of these. 22 were confirmed histologically, 7 by both biopsy and necropsy, 4 by necropsy, and 11 by biopsy plus clinical findings. In the remaining 3 cases the diagnosis was based on typical clinical findings and course hut histological confirmation was not available. In all 11 necropsy cases numerous asbestos bodies were found in the TABLE 1 F inding o r A snrsios Bodies in S putum related to C urrent O cc u pa iio n $ group Wf Iftl) * ur iaJ some ****10% pour and % FcMos but i-V iion *#**wr or rust $ i.'fa)*nrk !*(> i jMwr*t of sputa MMuMt! ABC 2 0 0 7 0 0 61 0 0 40 0 161 1 0 235 1 0 20-29 30 -J 9 A B C A }i C 36 2 2 63 6 2 42 1 1 37 5 5 67 4 2 57 4 3 47 1 0 56 1 285 5 1 275 12 477 13 488 28 16 Age group 40-49 A I) C 136 12 0 54 4 4 114 13 II 79 7 6 469 44 13 852 80 43 50 59 A BC 75 3 3 35 5 5 99 21 18 50 -65 A B C 17 4 3 13 6 6 26 7 6 89 5 5 37 6 472 49 22 I 187 49 770 83 53 280 72 42 58 8 Total A B 329 27 188 21 424 4(! 31 20 1 K4l> 160 3 102 277 57 8 - tv*<41 working po pulation; B - n um b er o f men from whom sputa were positive of sputa t wa/uirn'il 70-4 100 80 2 85 39 4 62 J. Stumphius TABU 2 F inding of Asmisros Bourns in S putum r i l a i i i ) to O ccupation 5 to 10 Yi ars pki.vioi si i Exposure group (see text) I Iron vapour III Rust and some asbestos .. Ill Iron vapour and rust IV Some asbestos but little iron vapour or rust .. V Clean work Total % positive of sputa examined 15- 19 BC 00 00 00 00 10 10 0 20- 29 13 C 32 00 32 i0 62 13 6 46-2 30 39 Bc 84 55 43 10 10 4 28 16 57-1 Agi group 40 49 30 59 Bc Bc 12 10 4 4 55 66 20 16 26 23 66 88 37 6 39 12 80 43 83 53 53-8 63-9 60 65 Bc 43 66 17 14 it) 10 35 9 72 42 58-8 Total Bc , O positive o f sputa examined 31 23 74-2 22 22 100 70 82-9 26 24 92-3 128 33 25-8 277 If'O 57-8 B = number of men from whom sputa were examined; C number of sputa positive for asbestos bodies. underlying and in the contralateral lung in both section and smear. In 4 of the non-necropsy cases asbestos bodies were found in the sputum. A large quantity of iron pigment, other than that forming the asbestos bodies, was found in all these lungs and sputa. In 2 of the necropsy cases, asbestos bodies from the lung smears were examined with the electron microscope. Chrysotile and amphibole asbestos fibres were identified in each case (Stumphius and Meyer, 1968). In 19 of the 25 cases the tumour originated in the pleura, in 4 cases it originated in the peritoneum, and in 2 cases there was a combination tumour in both pleura and peritoneum and it was impossible to decide the site of origin. The clinical course of the illness in the pleural cases was usually associated with a characteristic posture (Figs 1 and 2). These illustrate a typical case of right-sided pleural mesothelioma in which symptoms started when the patient was aged 60; he died 18 months later. He was thought initially to have had a pulmonary embolism because of a blood-stained effusion with underlying lung atel ectasis. As the disease progressed and a thick rind of tumour formed around the lower part of the right lung, the right half of the thorax diminished in size. This was associated with a characteristic stoop due to a scoliosis to the right which is well shown in the photographs. Occupation and mesothelioma As the incubation period for this tumour may be 30 to 40 years from first exposure, directly relevant information about shipyard employment was not available. The information which was obtained is summarized in Table 3 and shows that 22 of the 25 cases had been employed in the shipyard at some time and 17 were employed there at the time of onset of their symptoms. Of the 7 cases who were employed in `clean' work recently or when they retired, 2 had done dustier work within the last 10 years and only 3 were always in `clean' occupations. Of the 5 cases who were no longer employed by the shipyard 4 had been employed in dusty work and in the other case (No. 17) the nature of his work was not known. The 3 men never employed in the shipy ard had all had dusty occupations but in only one (case 23) was there an obvious source of asbestos. Table 4 relates the number of cases in each exposure group to the total number of men employed by the shipyard at the time of the study. This gives an approximate estimate of the number of cases in relation to the population at risk. Occupational groups 11 and IV, both known to have had some exposure to asbestos, showed the greatest number of cases (I -6 and F9%). Groups 1 and 111 showed 0-6 and 0-9o whereas group V showed only 0-32,,. The mean number for all workers during the seven-year period was 0-68 %. For Holland as a whole the attack rate for primary pleural tumours was 0-63 per 100 000 men per year between 1958 and 1965. The attack rate for all the shipyard workers appears to be 0-68 in seven years or about 100 per 100 000 men per year. Those with some exposure to asbestos dust appear to have an attack rate at least twice this (group II 230 and group IV 280). Since the original analysis five further meso theliomas have been detected up to August 1970. two of which have not yet been confirmed histo logically, partly because of a reluctance to perforr biopsies which may cause distressing spread of tlx tumour. Three of the five cases had worked in th shipyard. HJSLY / positive I \ c eoxfasmpiuntead I 23 74-2 22 100 58 82-9 24 92-3 i 33 25-8 160 ie time of onset were employed retired, 2 had years and only Of the 5 cases shipyard 4 had the other case as not known, shipyard had all ne (case 23) was Table 4 relate* e group to the the shipyard at an approximate relation to the 'imps II and IV, isure to asbestos, s (1 -6 and 1-9"7). d 0-9% whereas mean number for r ear period was f k rate for primary 000 men per ycat k rate for all the 0-68% in seven per year. Those lust appear to hast (group II 230 and ive further meso to August 1970. i confirmed hislt* dance to perform sing spread ol It* had worked in the $ 1 ti ij'hlnwolo),'}- of tncfoflitiioiiiii on Wulchcrcii Islam! 63 IT ,,l ,T; )i no. 1. Patient born in 1906, started work in shipyard age 24 as a pipe worker in completion department (exposure group II). Remained in this work and was a foreman when lie developed his first symptoms early in 1966. Until that time he had enjoyed good health. Complained of cough and pain in right chest; chest radiograph showed free fluid and basal atelectasis. Large volume of bloody fluid removed, no malignant cells found, culture sterile. Pam and breathlessness were relieved temporarily but returned a few months later. More fluid was removed but no malignant cells were found. Bronchogram revealed collapse with no obstruc tion or bronchiectasis; the right hemithorax already showed a marked reduction in size. I.atcr the pleura became densely thickened and only small volumes of fluid (200 ml) were aspirated. Pleural biopsy confirmed the presence of a mesothelioma. By February 967 the right hemithorax was grossly contracted. He was re admitted to hospital in May 1967 with evidence of spread to the left lung and peritoneum. He died in June and necropsy confirmed the clinical and biopsy diagnosis. The lungs contained much iron pigment as well as asbestos bodies which were shown on electron microscopy to be formed on both chrysotile and amphiboly asbestos (Stumphius and Meyer, 1968). w# i Ei 1. T -J . r t 4.' ;; ' j ti j * *S \ i I C. ;V (>4 Sliimphiiix i: TABLE 3 M esothelioma C ases in W ai.chere n showing O ccup ation ano E xposure G roup on 2 Si itember 1967, or at D ate oi R etire.ment or D i a i i i , xnd Previous O ccupation and E x p osu o G roup M e s o n ,, Connexe Case Occupation on 2 Sept. 967, Exposure no. retirement or death group Previous occupation Exposure group Clini, al (/annosi hi.loi. continu i Royal Schelde employment (yr) 1 Welder plate-works 2 Welder completion dept. 3 Welder completion dept. 4 Pipefitter completion dept. 5 Foreman pipeworker com- pletion dept. . . 6 Cleaner shipbuilding dept. 7 Cleaner shipbuilding dept. 8 Painter . . 9 Ship's carpenter. . 10 Foreman ship's carpenter's completion dept. ] 1 Ship's carpenter 12 Painter preassembly dept. 13 Cabinet maker .. 14 Labourer stores 15 Checker . . 16 Turner 17 (Agriculture)* . . 18 (Disabled)* 19 (Waterworks)* . . 1 No change 1 n Welder plate-works I U No change II ti No change h n No change II V Shipwright m V Rivetcr/cutter hi IV No change IV IV No change IV IV No change IV IV No change IV 111 Painter completion dept. IV V 1919-47 ship's carpenter com- pletion dept. . . IV V Previously labourer engine works . . V V Up to 1955 plater III V Always turner V -- In 1946 K.M.S. 1 month -- Up to 1946 K.M.S. as labourer; in 1930s i month of lagging work . . V ami III -- Up to 1946 K.M.S. as a sealer . . III 40 so ' 20 I1 n 52 40 43 34 25 36 40 19 43 41 50 36 <i 15 7 to E xpos, grani I Iron vapi, II Rust am asbestoIII Iron vapo rasi IV Some aslx- filile ir vapour ^ Clean wort Total tven reporte, Harries, 1968 l niled King, has been i Dabbert, and -axes of mes 20 Machine woodworker . . 21 (Painter)* 22 (Asbestos lagger)* 23 (Kngine room mechanic)* V No change V -- Up to 1950 K.M.S. scaler painter IV -- Up to 1926 K.M.S. as a riveter III ___ No change 41 Wilhelmshave local naval do 19 4 Although _ insulation wo, 24 (Sand and grit blaster)* 25 (Foundry moulder)* No change No change -- mesothelioma svHingcst pat,, (occupation)* not at Royal Schelde (K.M.S.I. flu- present sit IHwsible that , primary brotu. igc at which t Discussion to asbestos and to have an excessive incidence of I he type oi mesothelioma. This may have been due to the move maieritds adhc I The investigation shows that the finding of asbestos ment of men from job to job (.hiring their years in metal particles. bodies in the sputum and of mesothelioma is more the shipyard, or it may be that the whole area was "> die aetiolos- * frequent among shipyard workers who are exposed sufficiently contaminated with asbestos to produce K<k\ 1965; C\ to asbestos dust at work. Asbestos insulation this elVect. I owe, Richai 1 workers were excluded from the study and occu The special search for cases of mesothelioma, Walclieren stu, pational enquiry indicated that none of the workers good medical arrangements for such a study, anda vules in the s surveyed had had heavy exposure to asbestos dust. relatively static population all contributed to a high " oikers and m 'j 2 Their exposure to dust appears to have occurred level of case finding. This and the diagnostic criteria 'lihough crock during completion or repair work when insulation used for the national mortality register mean that 'veil regarded a- 1a w'as being carried out. In one of the groups all the the local and national figures for these tumours art m humans tha, i sputa examined contained asbestos bodies and the not strictly comparable. However, there is no doubt it'liM) have shoe i attack rate for mesothelioma appears to have been that the local incidence of this tumour is far is 'u can cause i about 300 times that expected for Holland as a excess of the national incidence. This is consistent `'milling the inn whole. However, while these workers were exposed with other published figures for heavy intlusfn separately from l I to more asbestos than the rest, all groups of ship (Gilson, 1966). The relationship between meso On Walchereit j yard workers appeared to have had some exposure thelioma and asbestos exposure in shipyards hat mutation work l\piilt'tt)iolo)!y oj mesothelioma <>n II alclieicn Island 65 Sii'TEMBER 1967, i G roup eal MStS tal. nned Royal Schelde emplovmcni Or) 40 50 20 32 32 40 43 34 25 36 40 19 43 TABLE 4 Mi vimi i.ioma Cases with a Royai. Sem id i: C o s s i MON AND E X P O SU R E G lU H IP AC C O R D IN G io Nature of Work in tue Pasi tSposiirv group i Iron \apour $ Iu4\%t K*salOmSi some 1" l'un vapour and fust 1 A -rc aduvslos but little iron * vapour or (Van work rust No. of persons employed 2 Sept. mi 329 188 424 312 1,849 Told .. 3,102 /<> Nmoe.soo-f Attack rate (/idiomas ploetr) 10 5 2 0-61 61 3 1-59 13-6 4 0 94 too ft 59-8 ft too 21 t -92 0-32 Mean 0-68 41 50 <316 15 7 41 14 4 .essive incidence ti eon due to the men luring their year * ihe whole area * asbestos to prods** i of mesoiheliiHmi such a study, and ontributed to a hn# iie diagnostic criim \ register mean lit* or these turnout m cr, there is no diM* ns tumour is far ce. This is coiimviw lor heavy indm*' Hup between mtw ne in shipyard h* %m reported frequently (Elmes and Wade, 1965; **, 1968; Sheers and Templeton, 1968) from the ;i-iicd Kingdom. More recently a similar situation fctt tven reported from Hamburg (Dalqucn, fiVixit, and Hinz, 1969). Stossel (1970) found 27 met of mesothelioma between 1964 and 1969 in fcINclnishaven, the majority having worked in the nasal dockyard. Mthough asbestosis was found among the million workers in the shipyard there were no JwsMhcliomas in this occupational group. The : *twvfct patient with a mesothelioma detected in ; 'k* .went study was aged 57 when he died. It is i jwmMc that insulation workers die of asbestosis or tifltui) bronchial carcinoma before they reach the ** u liielt mesothelioma is most frequent, fit ispe of asbestos and the presence of other adherent to the asbestos dust, such as ix' (articles, mineral oils, etc., has been considered * aetiology of mesothelioma (Harington and 4u*. 1965; Commins and Gibbs, 1969; Dixon, Richards, and Stokingcr, 1969). The study shows large amounts of iron : *afe in the sputum and lungs of the shipyard , *nrt<n and in patients dying from mesothelioma. Wfcxjfh crocidolite contains more iron and has 'tm carded as more likely to cause mesothelioma * Suntans than other types, Wagner and Berry .(W'tluvc shown that both chrysotile and crocido9* cut cause mesotheliomas in animals. In ship- tlic iron vapour and rust can be inhaled *mtcly from the asbestos dust in many situations. it Walchcren the source of asbestos dust has been work in the shipyard, the spraying of asbestos (a technique much used formerly) being particularly responsible for the pollution of the atmosphere in ships. Current policy is to employ asbestos-free materials as far as possible. Stone wool, polyurethane foam, ceramic fibre material, etc. have proved feasible substitutes. But unfortunately the effect of this change has been counteracted by the increased tise of asbestos-containing materials for other purposes. Fireproof plaster board (c.g-, Marinite) which contains asbestos is used in the construction of living accommodation ieabins, dining saloons, etc.) on hoard ship. This work is done by carpenters and it is impossible to prevent the escape of asbestos into the atmosphere when this type of plaster board is being used. This in creases the group of workmen exposed to asbestos in tile shipyard. It is highly desirable that research he earned out to find a suitable substitute for asbestos in making equally strong fireproof board. Here lies a task for the present-day technologist. This is one example from the held of shipbuilding but plenty of others can be found as the uses of asbestos arc so manifold that the mineral can be encountered in the most unexpected places. it is not surprising that mesothelioma is now being found in relation to various industries; it is the consequence of occupational exposure 30 to 40 years ago. Since those days the use of asbestos has increased vastly. So many processes involve the use of asbestos that it is impossible to ensure that the mineral is never released into the atmosphere cither as a result of wear and tear or for some other reason. The author believes that this mineral, which is practically indestructible as far as the human organism is concerned, might become an environ mental factor for the whole population. He fears that because of this, in the near future, diffuse mesothelioma .will become more prevalent among groups of tlic population without direct industrial exposure to asbestos in the sense that this has been recognized in the past. In this situation the in crease in world production of asbestos from 0 5 to 4 million tons per year between 1940 and 1970 may give rise to concern in the future. Dr. R. L. Zielhuis, Professor of Industrial Hygiene at the University of Amsterdam lias been a great support to me. The continual interest and assistance of the path ologists, Drs. If. T. Plantcydt and F. B. Bronkhorst, have been indispensable. The same applies to the Waleheren physicians, Drs. L. P. Roegholt. P. H. Postma, B. Uyterlinden, and J. L. van Ligtcn. Mr. C. M. Zvveedijk and Mr. T. A. Toorenburgh, of the Royal Schelde medical service in Flushing (Neth.), liave carried out a great deal of exacting work on behalf of this inquiry. Mrs. M. . Quast of {-'lushing (Neth.), lias been responsible for the careful translation. 66 Stumphius References Commins, B. T., ami Gibbs, G. W. (I'Jh1)). Gontuminuling organic material in asbestos. Brit. J. Cancer, 23, 358-362. Dalqucn, P., Dabbert, A. I7., and llinz, I. (1969). Zur Epidemiologic dcr Pleuramcsothelionie. Prax. Pncumoi, 23, 547-558. Dixon, J. R., Lowe, D. B., Richards, D. I7., and Stokinger, H. E. (1969). The role of trace metals in chemical carcinogen.esis-asbcst.os cancers. In Trace Substances in Environmental Health, edited by Delbert D. Hemphill, vol. 2, pp. 547-558. University of Missouri. Elmes, P. C., and Wade, O. L. (1965). Relationship between exposure to asbestos and pleural malignancy in Belfast. Ann. N.Y. Acad. Sci., 132, art. 1, 549-557. Gilson, J. C. (1966). Health hazards of asbestos. Trans. Soc. occup. Med., 16, 62-74. Harington, J. S., and Roe, F. J. C. (1965), Studies of car cinogenesis of asbestos fibers and their natural oils. Ann. N.Y. Acad. Sci., 132, 439-450. Harries, P. Cr. (1968). Asbestos hazards tn naval dockyards, Ann. occup. Hyp., I I , 135-145. Sheers, G., and Templeton. A. R. (1968). I fleets of asbestos in dockyard workers. Brit. mcd. ./., 3, 574-579. Stosscl (1970). Personal communication. Stumphius, J., and Meyer. P. B. (1968). Asbestos bodies and mesothelioma. Ann. occup. Hyp., I I , 283-293. Wagner, J. C., and Berry. G. (1969). Mesotheliomas in rats following inoculation with asbestos. Brii. J . Cancer, 23, 567-581. ----- , Sleggs, C. A., and Marchand, P. (I960). Diffuse pleural mesothelioma and asbestos exposure in the north west ern Cape Province. Brit. J. industr. Mcd.. 17, 260-271. Working Group on Asbestos and Cancer (1965). Report and recommendations of the working group on Asbestos and Cancer convened under the auspices of the Geographical Pathology Committee of the International Union against Cancer, Arch, linvironm. Hlth, II, 221-229. Brit. J. industr. Mcd., 23, 165-171. Received for publication December 15. 1969. tint.,/. in,, Parar COOLE' CDaespearWtmeestn- Butlct rabbit mg/ k moro > up to param the chr were o explain The herbicu dipyridylium j been noted to interstitial inilm man following a Mmog and Tai (i.illngher, and Woodruff, and t the toxicity of p;; MeHligott, and producing the pi .ulministration . chemical. These production of pu, oral or inlrapon Uudcd that mon doc mainly to in. drink, because of bom the swallow or from licking tl We thought that d she ditikulties of o "r.ipcriloncal ror .tul.( 1966) with t; re the subject of t