Document DDnyNjbvyOKoryGegav5835Jn

FILE NAME: Welding (WELD) DATE: 1976 DOC#: WELD014 DOCUMENT DESCRIPTION: Journal Article - A Proportional Study of Cancer Registrations of Dockyard Workers British Journal o f Industrial Medieim , 1 4 7 6 , 3 3 , 108-1 14 A proportional study of cancer registrations of dockyard workers K. P. S. L U M L E Y Medical Research Unit, H.M. Naval Base, Devonport, Plymouth, Devon I.mnley, K. 1\ S. (1976). British Journal o f Industrial Medicine, 33, 108-114. A proportional study of cancer registrations of dockyard workers. Evidence of an occupational effect due to asbestos exposure was sought by comparing cancer registrations for dockyard workers with those for Plymouth men in the same age groups for 1960-69. The results show a significant excess of pleural tumours in the dockyard group but no significant excesses at other sites. Registrations for pleural mesothelioma were recorded for men with many dockyard occu pations and the observed mean interval between first exposure to asbestos and registration for a pleural tumour (37-6 years) indicates that cases of pleural mesothelioma may be expected to occur among these workers for many years, even though crocidolite is no longer used in naval ships. A trend of increasing annual excess of stomach and gastrointestinal registrations was observed in the dockyard group. No cases of peritoneal mesothelioma were recorded but it is likely that some did occur which were diagnosed as cancers arising from other sites. This may account for some of the excess of gastrointestinal registrations. The Royal Naval Base at Devonport, Plymouth, employs about 14 000 men, many of whom tire directly employed in refitting warships. Before strict precautions were introduced to control the use of asbestos in naval dockyards, many of these men had had varying amounts of exposure to crocidolite (blue), amosite, and chrysotile asbestos (Harries, 1968). A dust sampling survey (Harries, 1971a) also showed that there had been high concentrations of airborne asbestos dust in the ships during refits, and a radiological survey showed that the prevalence of abnormalities associated with asbestos was about 4",, in this population (Sheers and Templeton, 1968). The risk of developing lung cancer is increased in those exposed to asbestos. Epidemiological studies by Doll (1955) and Knox et at. (1968) suggested that the risk of developing lung cancer was high when the risk of developing asbestosis was high, but fell to (hat in the general population when asbestos exposure was low and unlikely to cause asbestosis. However, neither of these studies considers the elTect of sm ok ing. and SelikolT. Hammond, and C'hurg (1968) and Berry, New house, and Turok (1972) showed that smoking augments considerably the asbestos related risk of developing lung cancer. The risk of developing mesothelioma of the pleura and peritoneum is particularly associated with exposure to crocidolite but this risk is less certainly related to close (Wagner, et a t 1971). It is suspected that asbestos exposure may increase the risk of developing malignant tumours at other sites. Selikolf, C'hurg, and Hammond (1964) reported a threefold excess in mortality from gastro intestinal cancer in New York insulation workers. Times and Simpson (1971) also found an excess number of deaths from gastrointestinal cancers in Belfast insulation workers, and Newhouse (1973) reported a significant excess of deaths not only from thoracic cancers but also from 'other cancers' in men follow ed-up for 25 years after two or more years' exposure to asbestos. It has also been suggested that asbestos exposure may be implicated in the aetiology of cancers of the orophanyx (Selikolf, Hammond, and C'hurg, 1970), the larynx (Stell and McGill, 1973). haematopoietic tissue (Gerber, 1970), and the ovary (Keal, I960). 2/82/9 981/62) 00:S A proportional study o f cancer registrations o f dockyard worker 109 In this study evidence of an occupational effect due to asbestos exposure on the occurrence of malignant tumours in dockyard workers as a whole has been sought by comparing cancer registrations for male dockyard workers with those for all males living in the Plymouth area. Methods Population The cancer registrations recorded at the Plymouth ollice of the South Western Regional Cancer Registry between I960 and 1969 were examined, and all registrations for males aged 15 years and over whose addresses were in the Plymouth area at the time of registration were included in the study. The Plymouth area was defined as the City of Plymouth and the adjoining rural districts of Plympton and St Germans. Data recorded Full name, address, date of birth, year of registration, diagnosis, and occupation were recorded for each indi vidual. The occupation as stated on the death certificate was recorded for those who had died; this was usually available at the Cancer Registry, but if not, the occupation was obtained either from a copy of the death certificate or from the Returns of Deaths to Sanitary Authorities for Plymouth and Plympton. Dockyard workers were idemi'iable because of the addition of the letters HMD after the occupation recorded on the death certificate. Dock yard workers among those who had not died were identified by tracing them in the Naval Rase employment records. All the information was coded numerically for analysis, using the Fighth Revision of the International Statistical Classification o f Diseases (World Health Organization, 1967) to classify diagnosis. Analysis The registrations were divided into those for dockyard workers, both currently employed and retired, and all other Plymouth males. The registrations for these two groups were tabulated by age and diagnosis in live-year age groups for each year of the study and for 1960-69 combined. Because the age structure of the dockyard population was not known, expected numbers for that group were calculated using the proportional method proposed by the Registrar General ( 1968a). l or example, in Table I at age 55-59 years there were 189 registrations for thoracic cancers out of 602 registrations for all types of cancer in Plymouth males as a whole, and there were 195 regis trations for all types of cancer in dockyard workers, so that the expected number of registrations for thoracic cancers in dockyard workers would be 19.1 189 -- -- 60-6. 602 Fxpected numbers calculated by this method for each live-year age group were summed to obtain an expected number fur all ages over 15 years, and a Proportional Registration Ratio (PRR), which is die ratio of ihc observed to the expected number 100, was calculated. Thus, from Table 1, the PRR for thoracic cancers in ^ XK dockyard workers = ---- ; 100= 11T7. The devia- 347-4 lions below expected were not assessed for significance because, using this method, excess registrations for one site must be matched by deficiencies elsewhere. Results Between I960 and 1969, 4998 cancer registrations were recorded for Plymouth males aged 15 years and over, of which 1377 were for dockyard workers. Local comparison The observed and expected number of cancer regis trations for dockyard workers based on the cancer TABLE I C ancer R egistrations u rn D ocky ar d W orkers and A li. P lymouth M ales 1960-69 Aift- Thoracic cancers ............................................-............... Dockyard ( I S C 162-3) Plymouth 15 - 0 0 20 - 0 1 25- 0 I 30 -- 1 i 35- 1 5 40 3 15 45 - 20 62 50- 23 105 55-- 67 189 60 - 102 270 65- 82 242 70 - 50 178 75 : 39 147 All a g e s o v e r 15 yr s 388 1216 All earners U SC . . Dockyard 1-10-20V) Plymouth 2 16 5 17 4 27 4 39 16 72 23 109 49 206 74 333 19.3 602 258 766 241 858 216 813 292 1 140 1377 4998 C.xpcctcil no. of ihorm ic , oncers in dockyarif workers 0-3 (H 01 M 3-2 14-7 2 V3 60-6 90-9 68-0 47-3 37-7 347-4 ISC - Iincnmliomil Statistical Classification o f Diseases (1967) H O K. P. S. Mmley registrations for Plymouth males for 1060-69 are shown in Table 2. There was a very small excess o f cancers of the buccal cavity and pharynx, and a small excess of cancers of the gastrointestinal tract as a whole, which was associated within the gastrointestinal tract with excesses of stomach and pancreatic cancers, but none was significant. No excesses were found for cancers of the oesophagus, small intestine, colon, and rectum and the figures for these sites have been omitted from Table 2. N o registrations for peritoneal mesothelioma were recorded, There was a significant excess o f cancers o f the respiratory tract as a whole, but this was confined to cancers of the thoracic organs, and there was no significant excess o f cancers of the upperrespiratory tract and the larynx. On further analysis the significance of the excess of thoracic cancers was confined to the pleural tumours, and the excess of lung cancer was not significant, though it was numerically larger than that for the pleural tumours, A small insignificant excess was found for cancers for which no site was specified, but there was no excess of cancers o f haematopoietic tissue, lymphoid tissue, and cancers at `all other sites'. Pleural tumours The excess of pleural tumours was due to the registration of 22 cases of pleural mesothelioma and one case of pleural endothelioma for the dockyard workers compared with only three cases o f pleural mesothelioma in other Plymouth males. Details of the year and age at registration, age at death, occupation, and asbestos exposure where this information was available for the 26 men are given in Table 3. The mean ages were 60-3 years (range 39-82) at registration and 60 8 years (range 39-85) at death, For those for whom the information was available, the mean number of years between first exposure to asbestos and registration for a pleural tumour was 37-6 years (range 23-69; 19 men) and the mean number of years of asbestos exposure was 28-7 years (range 12-47; 18 men). The occupations of the men for whom details of asbestos exposure were not known suggested that they had also been exposed to asbestos. The population of the Plymouth area includes about 100 000 men aged 15 years and over, Estimates of the mesothelioma rates from Scotland (McEwen ct a!., 1970) and from Canada (McDonald ct al., 1970) give values of between 0-7 and one per million a year. Thus, the expected number in 10 years in Plymouth would be about one case. Even the railway fitter was known to have been exposed to asbestos, but it is of interest that one case of pleural mesothelioma in a bank employee was registered in 1970. Annual trends Evidence of annual trends of excesses was sought by calculating the annual excesses for stomach, gastrointestinal, lung, and pleural tumours in the dockyard workers for each year of the study. The results are shown in the figure. The numbers involved are relatively small, but they suggest a trend of increasing excesses of stomach and gastrointestinal registrations together with a decreasing trend for lung cancel for the dockyard workers during the period studied. TABLE 2 O b.sf.rved a n d E x pe c t e d C a n c e r R e g is tr a ti o ns a n d P r o p o r t i o n a l R e g is tr a ti o n R atios tor D o c k y a r d W o r k e r s C o m p a r e d w i t h P ly m ou th M ales 1960-69 Site Buccal cavity and pharynx Stomach Pancreas Gastrointestinal trad I 'pper respiratory tract l .arvnx I U tlfi Pleura Thoracic Respiratory tract l.vtuphoid tissue Ihiemutopoielic (issue Site unspecified All other sites ISC No. 140-9 151 157 150-9 160-1 161 162 163-0 I6">-T 160 A 200-2 200-9 199 170-198 Dock yard Observed Expected 55 51-3 179 157-1 46 42-2 416 408-5 24 22-5 20 IX-5 764 7780 23 8-1 788 347-4 412 *69-8 24 28-7 57 61-5 40 >3-2 799 451-9 PRR 107-7 1170 1090 101-8 106-7 108-1 107-4 282-7 1117 111-4 X4-8 92-7 120-5 88-7 /> NS NS NS NS NS NS NS 0-0001 002 O-r' - NS A proportional study o f cancer registrations o f dockyard workers 111 TABLE 3 Vi-.AR and Act-: at R egistration, Agi at D e a ii i , O gctji' a h on and Ashesios I \ imsi ri (where k n o w n ) eor P l ymouih M ai ls vviiii C ancer R egisirations iok Pe u iu a i . T umours (1960-69) .R-e-i-'i-st ra - tion -------- Vrar Age 1960 58 1964 58 1965 69 65 6-4 64 56 46 W67 65 61 78 55 80 53 60 59 39 1968 64 43 49 1969 61 50 82 Ai>e at death 58 58 7(1 66 64 65 56 46 66 62 79 56 80 53 61 59 39 64 43 49 61 50 85 Dockyard workers Occupation Boilermaker* Boilermaker assistant Skilled labourer Supers isor of shipss rights Shipwright Supervisor of boilermakers Shipw right Boilermakers assistant Instructor Technical ollicer Skilled labourer Draughtsman Shipwright Skilled labourer Hlecirical liner Supers ior of sveklers Welder blectrical liner Shipwright Caulker riveter Electrical liner Caulker riveter La bourer Asbestos e.\'i osure (years) Since first exposed Total exposure Not know n 32 Not known 49 Not know n Not known 34 28 35 31 57 35 59 Not know n 28 42 25 Not known 23 31 45 32 69 Not know n 31 23 Not known 34 Not know n Not know n 28 34 30 40 IX Not known Not known 28 41 24 Not known 23 30 12 3! 47 Other Plymouth males 1968 77 1969 58 56 77 Railway litter 59 Supers isor power station 56 Bookseller lex engine room branch Royal Navy) Registered as endothelioma. All oilier registrations were for mesothelioma. Not know n 22 37 Not know n 21 22 Stomach (ISC 151) Gastrointestinal (ISC ISO-9) Lunq (ISC 162) Pleura (ISC 163) IO *"i"h 1j i" i "i i i i t i-- r--? i i i i i i r~~i i i--i--i--i--i--r--i--i--i--i--j----i--i--j--i--i--i--i--i--'i--i--r~ I960 -I -2-3-4-5-6-7-8-9 1960-1-2-3-4-5-6-7-8-9 1960 -1-2 -3-4-5-6-7-8-9 1960 -1-2-3-4-5-6-7-8-9 figure Observed minus expected cancer registrations for dockyard workers aged 15 years and over by year and site 1960-69. 1 1 2 K. P. S. Lumley There were few pleural tumours recorded each year which may account for the absence o f any definable trend o f excess for these tumours. Death certificate registrations To make the registration of cancers as complete as possible the Plymouth office of the South Western Regional Cancer Registry is notified of all deaths of people living in the Plymouth area in which cancer is mentioned on the death certificate as one of the causes of death. These cases are recorded as `death certificate registrations' if they have not been registered previously. They tend to be recorded for elderly people and there is usually little or no ad ditional clinical or pathological information available in the Registry record to support the diagnosis. It was considered important to analyse these registrations separately to see if there were substantially more of them for the dockyard workers than for other Plymouth males. Between 1960 and 1969, 27.3 death certificate registrations were recorded for Plymouth males of which 72 were for dockyard workers. Table 4 shows no evidence of differences between dockyard workers and other Plymouth males. In fact the expected number of such eases among dockyard workers is 75-2, just more than the observed 72. The propor tions of these registrations, expressed as a percentage of the total number of registrations, were also similar for each site. It was interesting to find that stomach cancer was more commonly registered in this way than any of the other types of cancer. It was also found that, as expected, over half of the death certificate registrations were for men aged 75 years and over. Discussion A study of cancer registrations should give more information about the occurrence of cancer than a mortality study because people who develop cancer do not necessarily die of cancer. There is. however, the disadvantage that the registration of cancer may be incomplete. The Registrar General (1968b) reported evidence of variation in the completeness of cancer registration throughout England and Wales, showing in fact that the South Western Regional Cancer Registry was above average for registration. This study would be biased if the cancer registra tions for dockyard workers were more, or less, complete than those for other Plymouth males. There is no reason to believe this to be so, and the overall registration rates per 100 000 of the popu lation in Plymouth and in the South Western Region are similar suggesting that any such bias that may exist can only be small. Expected numbers for dockyard workers could also have been calculated on the basis of cancer registrations for all males aged 15 years and over in either the South Western Region or England and Wales for 1962-68. This would have been misleading. Table 5 shows that for stomach cancer registrations in dockyard workers the PRR is 144 when compared with the South Western Region. However, for other Plymouth males the corresponding PRR is 120 showing that stomach cancer registration is high in the Plymouth area anyway. The PRR for gastro intestinal cancers is also significantly higher in the Plymouth area whereas that for thoracic cancers is significantly lower, and the simple comparison with England and Wales would have shown an apparent, and erroneous, deficiency of thoracic cancers. For these reasons the findings from the local comparison with Plymouth males is thought to provide a better guide to the possible effects of asbestos exposure on the occurrence of cancers in the dockyard workers than a comparison based on cither regional or national cancer registrations. In a proportional mortality study by Harries ( 1971b) no significant excesses of thoracic and gastro intestinal cancers were found in the dockyard workers. In that study the pleural tumours could not TABLE 4 N ummi.k oi Di a h i C i r r i ica ti. R k u s i r a i i o n s w i t h P i r o n i ac;i s or A u . R k i i s t r a notes at E ach S i r . io r 1960-69 C ommini:!) Sin- u se So.) D ocks;! rd No. Other Plymouth males No. Stomach US I ) Pancreas US 71 .-1// other paMrointi rtiiial tract 28 7 10 ISTi 6-5 5-? hi 11 14 15-7 10-7 60 l.llll/.' (M2) 17 7-6 7 ft 4-4 Pleura I6.it) Site not .spa ified (W> /// other ( aueers Total cancers (140-20<s\ 2-8 0 16 72 Nil 5-0 5-2 0 7 52 20! Nil 8-6 .VI 5-6 A proportional study o f cancer npi.itrations o f dockyard workers 1 1 3 TABLE 5 P rOI'OK IIONAL REGISTRATION RATIOS IOk SlOMACTI. ( iASTKOIN Il-SITNA1. AND THORACIC C aNCIRS TOR P lymouth D ockyard W orkers and P i.ymou'ih M ai is 1960-69, Based on C ancer R e g is ir a iio n s in the South W estern R egion and in E ngland and W ait s eor 1962-68 Population Plymouth dockyard workers Pl> mouth males other than dockyard workers Sto/iuu h ( tinccr (/.VC No LU) .SIP Ration England one/ Wales 144 138 120 115 Gastrointestinal loncer u s e No. 150-9) .VIP Region Enplane! end Wales 11 > 109 108 106 / horaeic cancer (ISC No. 162-5) S 11' Ration England and Wales no 91 94 79 be analysed separately, and the main findings from the present study are that it confirms a significant excess of pleural tumours but does not show evidence of a significant excess of cancers at any other sites for the dockyard workers as a whole. The variety of occupations o f the dockyard men with registrations for pleural tumours shows that many were at risk of developing a mesothelioma, but it is of interest that none of them was an asbestos lagger or sprayer, who are most heavily exposed to asbestos. The range of occupations of the dockyard workers is also similar to that of the shipyard workers with mesothelial tumours reported by McEwen et al. (1970) in Scotland, Whitwell and Rawclilfe (1971) in the Liverpool area, and Stumphius (1971) in Holland. The mean number o f years of exposure to asbestos and the mean interval between'first exposure to asbestos and registration for a pleural tumour could be calculated from data for only 18 and 19 respec tively of the 26 men, but the values obtained agree fairly well with those found by Newhouse and Thompson (1965), Whitwell and Rawclilfe (1971), and Limes, McCaughey, and Wade (1965). The long mean interval between first exposure and registration also indicates that cases of pleural mesothelioma may be expected to occur among these dockyard workers for many years to come although strict precautions are now taken when working with all forms of asbestos which remain in naval ships, and only asbestos-free materials are now used for all new insulation. The fact that no cases of peritoneal mesothelioma were recorded is likely to be due to lack of awareness of this tumour in the early 1960s and also because a necropsy examination is required to confirm the diagnosis. One case o f peritoneal mesothelioma in a dockyard worker was suspected as a result of a peritoneal biopsy in 1971, but the diagnosis was not confirmed because no necropsy examination was made. A second case was diagnosed clinically in 1974 but this diagnosis has also yet to be fully confirmed. It is likely that other cases occurred previously which were diagnosed as cancers arising from other sites within the gastrointestinal tract. If so, this might help to account for some of the excess of registrations for cancers of the stomach and pancreas. Although no significant excesses were found for cancers at sites other than the pleura for dock)aid workers as a whole, one of the drawbacks of this study is that it was not possible to categorize the dockyard group according to their asbestos exposure, and it is likely that the risk of developing cancer is greater in those who have been more heavily exposed. As part o f an epidemiological study of the health o f the employees in all the Royal Naval bases in this country, a mortality study of past and present Devonport dockyard workers is being carried out in which it will be possible to relate causes of death to history of asbestos exposure obtained from employ ment records and occupational histories. The results of that study should provide more precise information about the relationship between asbestos exposure and cancer. I am grateful for the permission of the Medical Director General (Naval) to submit this article for publication, i also wish to thank Mr C. L. Rossiter and Surgeon Commander P. G. Harries for their advice, The Director of the South Western Regional Cancer Registry for his permission to study the records at the Plymouth Registry, Mrs E. M. Longstalle and her staff at the Plymouth Registry for their assistance, and Mrs M. Stevens and Mr G. LeCounl who recorded much of the data. References Berry, G., New'house, M. L., and Turok, M. (1972). Combined effect of asbestos exposure and smoking on mortality from lung cancer in factory workers. Lancet, 2, 476-479. Doll, R. (1955). Mortality from lung cancer in asbestos workers. British Journal o f Industrial Medicine, 12, 81-86. Elmes, P. C., McCaughey, W. T. E., and Wade, O. L. 1 1 4 K. P. S. Litniley (1965). 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Statistical Review o f England and Wales 1962-64. Supplement on Cancer, p. 2. HMSO, London. Sclikolf, I. J., Churg, J., and Hammond. E. ('. (1964). Asbestos exposure and neoplasia. Journal o f the American Medical Association, 188, 22-26. -----, Hammond, E. C , and Churg, J. (1968). Asbestos exposure, smoking, and neoplasia. Journal o f the American Medical Association, 204, 106-112. ----- , - --------------- , a n d ----------- . (1970). Mortality experiences of asbestos insulation workers 1943-68. In Pneumoconiosis: Proceedings o f the International Conference, Johannesburg, 1969, edited by H. A. Shapiro, pp. 180-186. Oxford University Press. London and Capetown. Sheers, G. and Templeton, A. R. (1968). Effects of asbestos in dockyard workers. British Medical Journal, 3, 574-579. Stcll, P. M. and McGill, T. (1973). Asbestos and laryngeal carcinoma. Lancet, 2, 416-417. Stumphius, .1. (1971). Epidemiology of mesothelioma on Walchcren Island. British Journal o f Industrial Medicine, 28, 59-66. Wagner, J. C., Gilson, J. C., Berry, C., and Timbu.ll, V. (1971). Epidemiology of asbestos cancers. British Medical Bulletin, 27, No. 1, 71-76. Whitwell, F. and Rawcliffe, R. M. (1971). Diffuse malignant pleural mesothelioma and asbestos exposure. Thorax, 26, 6-22. World Health Organization (1967). International Statistical Classification o f Diseases. WHO, Geneva. Received for publication 13 November 1975 Accepted for publication 26 February 1976