Document XR71K4VVJJwbkDX9pbO9DXKzg

FILE NAME: Welding (WELD) DATE: 1968 Sept 7 DOC#: WELD007 DOCUMENT DESCRIPTION: Journal Article - Effects of Asbestos Dockyard Workers 7 September 1968 Anticoagulant 'Tbcnpy-r-Borchgrevink et al. these two patients the difference between the treated and the control group would have been correspondingly greater. Tlte clinical condition of the survivors was fairly similar in the two groups ; significantly more control patients had no angina pectoris, but more control patients needed digitalis and diuretics. The same proportion of the survivors returned to work. It should be rcmcmlicicd, however, that 11 patients in the control group and two treated patients died before the end of the observation period. The mean Thrombotcst value achieved was 15.9%, which compares favourably with previous studies from Scandinavia (Bjcrkclund, 1957; Borchgrcvink, 1960, 1962 ; Harvald et al., 1962 ; Aspcnstrbm and Bcngtscn, 1964 ; Sorensen el al., 1968), but which is higher than that recently reported from Holland (Locliger el al., 1967). Half the tests were between 5 and 14% Thrombotcst, which is satisfactory. The bleeding complica tions were all trivial, and no patient had to be admitted to hospital or to stop treatment because of them. Our results are in agreement with those of Qaussen el al. (1961), Aspenstrom and Bengtscn (1964) and Sorensen ct U. / '968), but differ from those obtained by Bjerkelund (1957) 1 id the M.R.C. (1959), who did not find any beneficial -*fect of long-term anticoagulant therapy in female patients. I t is possible that differences in selection of patients may explain the difference in the results. Other statistically satisfactory studies on long-term anticoagulant therapy have included only men (Veterans Administration, 1965 ; Lovell et al., 1967) or have not given the morbidity or mortality separately for the two sexes (Harvald et id., 1962 ; Seaman et al., 1964), and hence cannot be compared with the present study. An editorial in the British M edical Journal (1964), while advocating long-term anticoagulant therapy in younger men, concluded: " . . . there seems to be little justification for giving women long-term anticoagulant therapy.** Nevertheless, there is no valid theoretical or practical reason for believing that the effect of long-term anticoagulant therapy is materially different in the two sexes. However, while in men the effect scei'.n to be more pronounced below the ages of 55 to 60 years, in women our study siiows that there is an effect on both the mortality and the rem.'arciion rate between the ages of 60 and 70. Our study docs not answer the question whether younger women would also benefit from long-term anti coagulant therapy, though there is a suggestion of an effect on the icmfarction rate. The present study cannot answer how long the therapy should last. The effect seems to be maximal during the first three months after discharge from hospital, but our results do noc rule out that the effect lasts longer. From our study and from recently published accounts we think it is logical to adopt the same policy on instituting and maintaining long-term anti coagulant therapy in women as in men. By carefully crossanu-ysing all the data we had hoped to be able to correlate the positive effect of the treatment with certain features in the parent's history. We were, however, unable to find any sub group of patients in whom the therapy was effective and other subgroups in whom it was ineffective. It may be argued, however, that with our method of selection we were already deal jig with a subgroup of female patients with myocardial Bequests for reprints should be sririrew ri to C hr. B trchcrcviak, D e p t VUp U ikval Hospital, O rio, Norway. lU rauB M C ss A spesF osn, G ., and B cngoen, 1C (1964). Acta mad. stand., 176. 543. B icracl-jnd, C hr J. (1957). Acta mad. su n d .t 158, SuppL Nol 350. B onru^rcviak, C hr. F . (1960). Acta mad. stand., 168, SuppL K a 359. B orsagrcriak, C hr. F . (1*62). Lancet, I , 449. B n u mad. J., 1964, 2, S31. C U a-iica, J., at al. (1961). Ugaskr. Lae*., 123, 987. H a rrilsi, H ildcn, T ., and Lund, E . (1962). Lancet, 2, 626. S o tcaica, O. H ., Frii$, T h-, Jorgensen, A. W ., Jorgensen, M . B , and N .ssen, N . 1. (1968). Ugeskr. L a g - 130, 318. Locu-rcr. . A ., ct aL (1967;. Acta mad. stand., 182, 549. L ovc^, R. R . H ., D enborough. M . A * N cstci, P. L , and C^oSe, A . J . (1967). Mad. J. A usl, 2. 97. M edical Research Council (1959). Brit. mad. J., 1, 803. S cao u a, A. J., G risw old, H. E ., Resum e, R . B. and B ig n -a , L . W (1964). J. Amar. mad. Ass., 189, 183. V enom s A dm inistration (1965) J. Amar. mad. A st^ 199, 929. Effects of Asbestos in Dockyard Workers \ GEOFFREY SHEERS,* m a ., m a . ; ANN R. TEMPLETON,t m a ., CHA. V\>l (W ith Special Plate r u n e Face 374] B rit, med. 7 - 1 9 , . 574A 7 Summary: T he prevalence of pleural and pulmonary Introduction abnormalities attributed to asbestos among 15,000 workers in a naval dockyard has been studied by means From 1958 onwards cases of pleural and pulmonary fibrosis of a one-in-ten sample. Ninety-four per cent, of the men have been discovered in men working at the Royal dockyard in the sample were examined. O f these, 3% had experi at Dcvonport, partly in the course of routine oL-niaations enced continuous occupational exposure to asbestos and in the dockyard and partly among patients with -rr.ptom* half of the remainder (representing approximately 6,800 referred to the local chest clinic. Further investii-.ion has men) bad been exposed intermittently. The prevalence confirmed an association between these conditions a n - o posure of pleural fibrosis ranged from 28% in continuously to asbestos, and by 1964, when the first case of pleu.--. meso- exposed workers to 1.9% in those with least exposure. t hriajma was identified, it was evident that a scrino, increase in the hazards arising from the use of this material had Most cases of pulmonary fibrosis occurred in taggers developed. and sprayers who had been continuously exposed for In 1966 it became practicable to carry out a large-scale between IS and 20 years. Pulmonary fibrosis was also survey with a radiographic technique of adequate quality, and seen in a variety of intermittently exposed trades, and had the opportunity was taken to incorporate a one-in-ten sample been preceded by extensive pleural thickening in some of workers. This paper is concerned mainly with the results cases. Ten cases of pleural mesothelioma have occurred of tnc survey, and in particular with the prevalence of r in the last three years and a Urge number of men appear abnormalities attributed to asbestos and their relation to to be potentially at risk. j i exposure. Consultant Chest Physician, Plym outh'General HospiaL t Msitin l Director, Maw Radiography C ram , Plymouth. .T- / Septem ber 1968 Anticoagulant Therapy--Borchgrevink et al. mwJTComu. 573 Matt of the observation period--that is, during the 14 daya after a long history'of angina pectoris before their first infarction. discharge from hospital while the anticoagulant therapy they Further analysis did not show that benefit front the treatment had had during the acute infarction was being tapered off. The was correlated with any other factor, such as the nature of the difference in mortality in patients between 60 and 70 years, infarction or the clinical situation at discharge from hospital. eight against one, is statistically significant (P<0.05). One of the two deaths in the treated group occurred in the T asca VU.--Cardiac D raft + Non-fetel Remferaion m Fattemi m ilk ar W ithout Angina fw iirii Fuor la Their Firn Infarction first month and the other in the fifth month. In the control "" i 1 group three patients died in the first month, three later in the a Tnsrsil CMI first quarter, two in the second quarter, and one in the fourth quarter. No. at rstkats No. Mi Cardiac Epaodca No. U h h fn No. Ml Cwdke Necropsy in three patients (all in the control group), tiro ffWlW 40 1 N It of whom had died suddenly, shotted widespread coronary N t piwtoui ongino . atherosclerosis. In two patients an old infarction was found, ItocM rit a i . as 12 7 a but no fresh infarction o r fresh coronary thrombus. In the third patient a fresh thrombus and infarction were found, aa well as the old infarction. Two patients in the treated group died at home after an T a sta V ili.--Cardiac Daalh aad Nan-fatal Relmferctnm m F a rin a with a History #/ Angina Pacioni af Moro or L o u Thon Orto Torn Bafora T krir P int i nfarction _________ acute attack of retrosternal pain, death being presumably due Tuoni Cimimi to recurrent infarction. Of the control patients in w h o a paai- . mortem examination was not carried mat, oae died suddenly, four had recurrent infarction clinically, and one died hi an attack of acute pulmonary oedema without retrosternal pain. Thus all deaths were presumably cardiac. Unglao Munii <1 jw kajlas gsnsiii alyw t No. of fOlllOII at I . NCoo. rwfkiteh No. ai Potato to M No. wfat SSatSm a Table V gives the number of patients who sustained recurrent infarction, and includes cases classified aa " definite " as well as " probable " infarctions by the different medical wards. The three patients who died suddenly are not included in this Sable. The difference in reinfarction (one and nine) between the two groups in patients aged 60 and over is statistically signifiratit (0.02>P>0.01). If both age groups are combined the differ ence'between treated and controls (4 and 16) it statistically significant a t the 1% level. T a sta V. " Number af Parianti W ith Definite and Probable Infardam i Both Petal end Non fetal Pigmea ni Parentheut Denote the Number of Recurrence! i M ow M yw n................... 6+ yamt............................ N adM nu - Treated Control 1.. i ................... a 7*<U(9)) Table VI shows the time interval between discharge from hospital and the first cardiac episode (reinfarction or death).. The effect of the treatment seems to be most pronounced in the first three months. T a s u VI.-- Tune Intereel Between Discharge from Hotpitel and First Cartbac Episode (Myocardial inf arction. Sudden Death. Ptdmonery Oedema Leading to Death). Flgurel m Parentheue Denote the Number ol Deaths 1 t Hfft 7 -t 10-U ra ............................. ....................... ............................................................................................... .W ........................................... No. ofta k a ta Trcoted Control t a (2) 2(1) 7 0 im 1(1) 2(2) I t 0 3(11 Trilles VII and V III express the correlation between the effect of therapy and the existence and duration of angina pectoris previous to the myocardial infarction. The results suggest thet the effect of anticoagulant therapy is better in patienta with previous angina pectoris. The number of patients who had had angina pectoris for more or less than one year is too small to allow definite conclusions to be drawn. But our data do not support the hypothesis that the effect of anti coagulant therapy is fetter in patients with a short than with l a the treated group 17% of patients reported bleeding . episodes, but no aerious episode occurred. None of there patients had to be admitted to hospital, and in no patient was the treatment stopped. In the control group 3% repotted THtTUTT (piw hl D beanioi Previous experience with long-term anticoagulant therapy in men showed clearly that this had better effect in patienta under the age of. 35 to 60 than in rider ones (Bjerkdund, 1937 ; M.R.C., 1959). Hence we classified our patients by age in order to secure the same number of treated and control patienta in women aged less than 60 and those aged 60 and over. A multicentre trial, such as the one reported here, always involves t certain problems. We tried to avoid some of these by having the registration and randomization of all patients from the five medical departments involved in the study done centrally, and by letting the Institute for Thrombosis Research perform all the Thrombotests, and control and secure a stable standard of treatment. This study, though dealing with only 159 patients, is the largest single study so far published on long-term anticoagulant therapy m women. The results have shown that this treatment has a significant effect both on the reinfarction rate and on the death rate in women aged 60 to 70. In patients under 60 treatment had no significant effect, but because of the method of selecting these patients the prognosis in control patients under 60 is so good that a much larger aeries would have been necessary to show a possible beneficial effect in this age group. Hence the apparent difference in effect in patients under 60 and those aged 60 and over may be artificial. Since the two groups were well matched prognosticate at the start of the" observation, it is reasonable to conclude that the anticoagulant therapy is responsible for the observed difference in morbidity (5% as against 20.8%) and mortality (2.5% as against 11.7%). So far as we can judge all death* were cardiac. Two patients in the control group died before the observation period started and are not included in the statistics! analyses. Nevertheless, since they died in a period when anticoagulants for their acute infarction episode were being tapered off we cannot rule out the possibility that continuous anticoagulant therapy would have changed,the prognosis. If we had included O. SHEERS AND ANN R. TEMPLETON: EFFECTS OF ASBESTOS IN DOCKYARD WORKERS rn ; 7 Septem ber 1968 P. J. HILTON ET A L .. NEPHROTIC SYNDROME WITH HEART DISEASE c -V flMN e u fw--m Vo. S. Va. 4 PM. 1.--Caac I. Q tonerular toft. Epithelial cell (top) haa km to f a t proccaeca. The ht t rmeni membrane la noraelj thickened to 920 t o (X34,6M .) Fia. 2. Ce I. Proximal coneoluted tubule. T h en it froaa ncu o latto t a i the epithelium, ritible alto in the b(bt macro tcope. The crtoplaim it electron-denie, and the cell appetr t * deicnerate. (X 3,710.) FM. 3.--Caae 1. Ftoximai couTohned tabule. T he tncnnlet Ue between adjacent epithelial e d it and communicate one with another. (X12,310J Flo. 4.--Caae 2. Qlomcntlar tot Epithelial cell (top) foot procreate are km . The baacmcnt membrane raiict la thick- near from 360 to 100 m*. (X 11,600.) A t, 3. Cata L Froelmai canunlmed tubule. The ccd etruetnre it well pcetcrr t d, in ecutreat to the tabular ed it is Cate 1. (X iA tO J 7 Septem ber 1968 Asbestos--Sheen and Templeton 575 Working Environment The conditions of work in Devonport Dockyard have been more fully described elsewhere (Harries, 1968). They can be summarized by comparison with methods of work in com mercial shipyards and by reference to changes in practice during the postwar years leading to the large increase in the amount of asbestos handled. A naval dockyard is concerned largely with refitting and modernization, and only to a lesser extent with new construc tion. A major refit is likely to require the removal of a large proportion of aU types of insulating material, and it is the stripping and remora] of old lagging rather than new applica tion which causes hazardous working conditions with very high dust counts. This work is done at the same time as many ether jobs, and aU these activities take place in small illventilated compartments. As a result workers in a variety of trades not directly concerned with the handling of asbestos are exposed to the same working conditions. Changes in practice arose from the demand for better insula tion to meet the need foe improved environmental conditions in tropical waters, lessening of fire risks, doted ventilation and recirculation of air during simulated atomic warfare, and improved efficiency in propulsion machinery. Three construc tional demands developed in the later war yean and continued into the early postwar period, resulting in a maximum level of exposure during refits between 1950 and 1963. AU types of asbestos fibre were used. Significant examples are the use of pirn amosite actions for high-temperature steam-pipe insula tion and the use of crocidolite to cover very large oreaa below the flight decks of aircraft carriers. It must be emphasized that these conditions no longer prevail, and that a drastic reorganization of working practice has been carried out in order to minimize the risks of using asbestos. Population Studied Methods The Navy Department employs some 21,000 civilians in the Plymouth area. AU activities connected with shipbuilding and refitting are confined to the main dockyard, comprising North and South Yards at Devonport. The number employed in the main dockyard is 15,765, and the relevant subdivisions of. the occupational structure are shown in Table I. T sars I.--Occupation*! Stru a m o i M tm f l o i g r i R e t r i a l . . TTT Finance iufT > .. Other female ttaff . . J Supervisory and clerical . . Occupation directly invoiced in shipbuilding and refitting: working afloat . . 0,000 \ Working ashore . . 4,130 / Supporting occupations . . . 24 1 7 (Bariudad Cram amplhig). 19.M0 (10% S a m p le -1,900 ,1 0 ,1 3 1*0 J Total employed in North and South Yard . 19.709 7,687 men were examined in this way. A more detailed study of 420 men, including all those known to have been con tinuously exposed, is being carried out concurrently aa a separate investigation. RcflpfiWM Efforts were made to trace every man in the 10% sample. In addition to the small number who were too ill to attend or who died near the time of the survey there were 25 who left die district without trace and a final residue of 59 men who refused to co-operate. The remaining 1,414 men were examined, indicating a response of 94% (Table O). T u u II.--ftasgaasa M H r linam i Men m the 10% sample recorded their industrial histories on a standard form, and the record was checked by a trained assntam at the time of radiographic examination. The initial radiograph in the majority a t cases was the 100 by 100 mm. photofluorograph produced by the Odclca camera / (which incorporates a stationary grid), coupled to a 200 mA -ray generator and photetimer. The 81ms were trad by both of us independently, and in any case where an abnormality was suspected by either reader the subject was recalled for confirmatory radiographic examination and for verification of the industrial history. Clinical examina tion was carried out in all cases in which an abnormality had been attributed to exposure to asbestos, and the pulmonary function was examined in all those in which there was any suspicion of involvement of the lung parenchyma. Analysis at fifiinure The measurement of exposure in terms of dust concentrations and time exposed was impracticable on account of the ride variations in working conditions. In the small group of men whose work involved continuous handling o f asbestos - the number of years spent in the job provided a fair basis for comparison, but for the great majority of men in the dockyard these conditions did not apply. Even after taking a most detailed industrial history it was often impossible to make a reasonable estimate of the proportion of working time that bad been spent under hazardous conditions. The analysis was therefore based on the trade in which each man had worked Men on the weekly pay roll of the North and South Yards are recorded numerically on a computer tape, and advantage was taken of this procedure to obtain a 10% sample. This method excluded managerial snd finance staff, and for the sake of simplicity 15 other female workers were also excluded. The remaining 15,040 men form the subject of the survey. The number working afloat at any one time is estimated to be 6,000, but on account of the constant interchange between work afloat and work ashore this can be only an approximation. Most of the exposure to asbestos dust occurs within this group, but the number exposed varies considerably from day to day. The average is in the neighbourhood of 2,000. The 10% sample, consisting of 1,504 men, was used for the study of prevalence and exposure. Chest radiography was also offered to all other workers jn the dockyard, and an additional c i . \ ^ 576 7 September 1968 Asbestos--Sheers and Templeton for the greater part ot his time in the dockyard. Two measure ments were made: firstly, the number of yean spent in the trade, and, secondly, the number of yean since first employ subsequent radiographs are likely to show evidence of pleural thickening, which may be of either the limited or. the extensive type. ment in the tnde. Tndes have been grouped in order to Extension of the pleural thickening upwards towards the provide numbers of sufficient size for analysis (Table III). lung apex was seen in a small number of cates, and it would The first-group consists of occupations which involved con seem that only the limitations of standard radiographic tech i tinuous exposure: Of these, the laggen and sprayers were the niques prevented more frequent demonstration of this reaction / most heavily exposed, but there were also a small number of on all aspects of the pleural surfaces. men who used asbestos cement and asbestos d o th or who Additional linear shadows, especially in the lower zones, are i i handled the material in stoics. Painters have been induded often seen in conjunction with extensile pleural thickening, and in this group, since their work is mainly below decks and deformity or displacement of the leaser fissure is common. regularly involves the deanmg of surfaces heavily contaminated These shadows seem likely to represent changes in the visceral by asbestos (exterior painting is done by men in the semiskilled pleura, but with progressive involvement the normal pulmonary category). pattern is increasingly obscured,; and it becomes unprofitable The other principal trades concerned in ship refitting have to attempt to discriminate between pleural and pulmonary been divided between the second and third groups. All these changes on radiographic evidence alone. occupations involved intermittent exposure to asbestos, and it Cases in which the radiographic features of pulmonary would be difficult io r the casual observer to detect large differ fibrosis predominate formed a small but clearly recognizable ences m the degree of exposure between one trade and another. group. Pleural changes were rarely absent fat this group, ban, Of the three bigger trades, the electrical fitters appeared to- provided these did net obscure the lung fields, the characteristic be at risk for a somewhat larger proportion of working time nodular and linear opacities could be satisfactorily ikmrantrastd than the shipwrights and engine fitters. By placing the two (Fig. 4, Special Plate). I i ( latter trades in a separate group it was hoped to gain an i impression of the range of prevalence of abnormalities expert- cnced by intcrmitttiuly exposed men. , The fourth group comprises many occupations, of which the majority do n e t involve significant exposure, but it includes Definition in purely radiographic terms is practicable for the a Urge number of semiskilled and unskilled Workers who are limited pleural plaque, but in alt other cases additional diag liable to frequent changes of job. Seme of these men worked nostic criteria are needed in order to differentiate those in which I ' Oasthaesrssiswtaenrtes etmo ptlroaydeedsminenstirniptphinegseacnodndcleaanrdingthuirpd lgargoguinpgs., tphreeliAmbiinoatricy rreeaqcutiiorenminenvot livnesaltlhecapseasrewncahsyamdaeqoufatteheevliudnegnsc:e oAf and were thus heavily exposed a t times. exposure to asbestos. The diagnosis of pulmonary fibrosis was accepted rally when the typical persistent basal cries were detected and when reduction in the gas transfer factor to less / than 70% of the predicted value was confirmed (CO single I Radiographk ftfjttaraufia breath technique). Cases in which any Other cause of pulmonary fibrosis was suspected have been excluded. f The term " pleural plaque " has been restricted to those cases f The commonest finding was .the limited plaque of pleural in which the extent of the pleural thickening did not exceed th ickening. T h u is best seen on the lateral chest wall, as in the equivalent of four rib interspaces cmeither side and in which < s this situation it it tangential to the x-ray beam. It is charac the degree of pleural thickening was insufficient to obscure die normal pulmonary vascular pattern. I teristically bilateral and does not involve the antophscruc angle d(Fiaigp.hr1a,gmSpaeticciaalndPlmateed).iastPilnaaqlupelseumraabyuatlasroe bdeiffpicruesltetnot obbnsetrhvee noCsiassoesf opfulmmoorneaeryxtfeinbsriovseispwleausranlotthiecsktaebnliinshgeidnwwehreicphlaaceddiaghi 4 1 cuhnelesstswoafllcamlcaiyficbdeceonmsitey.visPib-l'iequwehseonnotfhesiamnitlearriodreannsidtyp. osTtehreisoer abnordinertelirnmeecdaisaetseact abtoegthoruyp. peTr ahnisd lcoawteegrolriymitisn,eavnitdabinlypainrtciclnudlarsr may show the so-called holly-leaf outline, but can range from it includes casesin which there were good reasons for suspecting uniformly opaque, very dense shadows to faint groups of pulmonary fibrosis but in which all the diagnostic criteria were nreopdruelseesntwahniceharlmiearystabgee dinifftichueltprtoocesseseobf ufot cwalhdicehpopsirtoiobnabolyf nwohtastaittisifnierde.alTithyias pcoronbtilneumouissirnahnegreenint itnheanexytaetntet mofptthteorcelaacstsioifny J - calcium in the periphery of the plaque. This latter variety to a fibrogenic dust. can be a cause of difficulty in interpreting the pulmonary Cases showing opacities of calcific density have been included pattern. in the appropriate category according to the extent of the pleural More extensive pleural thickening was also seen. In these thickening. 1 L cases the peripheral opacity overlaps the lung field to a varying extent. The inner outline of the opacity may be quite well defined when the main area of thickening n situated laterally (Fig. 2, Special Plate), but is frequently indistinct, becoming progressively more faint as it fades into the central ares of the lung field. Involvement of the oostophrenic angle and lower zone is not uncommon, and this extension of the pleural reaction has been observed within a period of three months (Fi$. 3, Special Plate). It may be accompanied by a small effusion. Such coses may present in clinic practice, especially when associated with an acute episode of pleural pain, but others have developed insidiously. Larger effusions were seen occasionally, but the accompartying shortness of breath usually leads to referral to a clinic rather than to discovery in a routine examination. Resolution of the . fluid is usually uncomplicated fat the non-malignant cases, but Results fat the 11% Sasnplt Pulmonary Fibrosis.--There were four cases of pulmonary fibrosis, of which three were found in the small high-risk group of workers. All three had been taggers ; 13 years had elapsed since they started work in the trade, but none had been exposed for more than 20 years. The fourth was a labourer who had been employed for 29 yean, in the course of which he had cleared up lagging debris in an aircraft carrier. Exceptionally high dust counts have been recorded during this procedure. B xtsnsht Plsurat Thicktning,--Of the 11 cases fat this category two occurred in the high-risk group of trades o ne in a logger and the other in a painter. Seven occurred in trades with recognized intermittent exposure--five in group 2 and taro r T ! 7 Septem ber 1968 Asbestos--Sheers and Templeton u C a u S77 in group 3. Of the remaining two cases one had worked as a cleaner in the boilermakers' shop, and also, more significantly, clearing up lagging debris in an aircraft carrier. The other had 'worked in small craft only, but had previously been a naval engine-room rating for 22 years. In nine of the 11 cases the time since first exposure exceeded 30 years. Of the other two one had been a ship fitter for 18 years and the other had been an engine fitter for no more than 12 years but had previously worked as a ship's engineer. Lim ited Plagues.--There were 48 cases showing limited plaques til pleural thickening. Their distribution between the occupational groups was similar to that seen in cases with extensive pleural thickening ; 10 were in the high-risk gro u p ; 27 were in trades with intermittent exposure (17 la group 2 and 10 in group 3). The remaining 11 were in group 4. The time since first exposure was over 23 years in 33 of the 48 cases. It was under 13 years in six cases. Two of these were loggers, but one had also worked as a boilermaker for 27 yean. Of the other four one had previously spent 31 yean main taining steam turbo-generators in a power station, ewe had worked as a plumber for 11 yean before continuing in the tame trade in the dockyard, one was a palmer's assistant and. had probably been heavily exposed at times, and the fourth is men tioned below at an umtsunl ease of biapical calcificat ion. Calcification.--Opacities of calcific density were observed In seven cases and occurred in ah the occupational groups with recognized exposure. In all but one case the' first exposure had been more than 26 years previously, and the average wua 33 years. The other case was unusual. Calcification was limited to the extreme apical pleura on both sides symmetrically. The industrial history included 12 yens as an electrical finer in the dockyard, but this work was limited to the maintenance r of the telephone exchanges ashore. There was no satisfactory evidence of exposure either to asbestos or to talc in any previous occupation. The cause of the condition remains unexplained, except on the basis of environmental exposure. The relation between the three types of abnormality and the time since first exposure in all groups of workers is shown h t - H ; r r in Fig. 3. The number of laggcrs who have remained in employment for more than 23 yean since first exposure is to o ' small to influence the characteristics of the third column in ' this : l1 ( r Yor* line firit poiMf* Flo. 5.--Typ of iboonsafity rebttd to d o t itece Am ctpotun (til o p ow rt troop). Prevalence T he prevalence of all types of abnormality attributed to asbestos was 4.4% (63 cases in 1,414 men). A total of over 600 cases in the dockyard as a whole may therefore be expected. This figure gives an indication of the sire of the problem, but because of the wide variation in working conditions further breakdown is necessary before comparisons can be drawn. Fig. 6 relates the prevalence to the four exposure groups and also shows the distribution of the three types of abnor mality. These rates are subject to error on account of the small number of men in group 1 (only 3% of the total) a n d ' are not adjusted for differences in age structure. Analysis shows that the number ol men over 43 years of age is a little SO * 20-1 8 S , Pleural pteguut m s c ' H fulleoary flkrosls m 1 2 tsposun groups n n n o . S.--Types st afcow alhy retasad SO higher than would be expected in group 1 and substantially higher fit group 4. In group 3 the number in this age bracket is lower than would be expected, and the tame applies to men aged 33-64 in group 2 (Table IV). This difficulty can be largely overcome by relating the prevalence in cadi group to the time since first exposure (Fig. 7). Aw 15-24 25-54 55-44 45-54 55-44 45+ , Tul T w m V e-d p ih d .il to a m O m * 1 3 5 4 4 117 f ' 52 14 45 14 74 9 45 -- 4 44 105 74 1 74 144 44 14 45 174 2 14 42 555 355 444 M 320 330 293 314 375 34 MM The most obvious feature is the much higMr prevalence of all types of abnormality in men experiencing continuous occupational exposure (group I). The number in this group is too small to justify detailed analysis in a 10% sample, but it is important to note that the majority of cases of pulmonary fibrosis occurred within this group and that in consequence the number of men suffering disabling disease was amall in relation to the total number of men in the industry. . On the other hand, though the prevalence of pleural abnor malities in groups 2, 3, and 4 is relatively low, the numbers involved are large and indicate a total of little under 600 cases. The difference between group 2 and group 3 is small and probably of little significance. In both groups a sharp rise in prevalence occurred when the time factor exceeded 23 years. This applied equally to time since starting work and to time spent in the exposed occupation (Table V). The prevalence of pleural abnormalities in these two groups combined after 23 yean or more since first exposure was 14% (28 cases in 198 men). .1 578 7 Septem ber 1968 Asbestos--Sheers and Templeton In group 4 over half the worken experienced little mote than environmental exposure, and this it reflected in the prevalence rate of 1.9%. -- F n . 7.--P fenkaee mi tta m ilN ia b l tjycs) im rwpmiwr tnapm reiated to t a c siocc arat cspM M t The proportion of pleural abnormalities classified a t exttn sive pleural thickening was a little over one in sis. T bit proportion showed little variation between the four exposure groups but rote to one in four after 23 yean had elapsed since first exposure. ffiiu^Bm i/iv cu n Mesothelioma.--The first histologically confirmed case of mesothelioma of the pleura occurred in 1964 in a man who . had been a boilermaker for 31 years. On retrospective review it seems probable that other cases had occurred during the preceding decade. Since 1964 the numbers confirmed were: three in 1965, two in 1966, and five iir 1967. One case was found in the 1966 survey (not in the sample) with a small pleural reaction in the left costophrenic cnglc. In every case there had been intermittent exposure to asbestos of all types in the course of long periods of employment in the dockyard. The time since first exposure exceeded 30 years in all but one. Peritoneal involvement was not observed. Bronchogenic Carcinoma.--Two cases of bronchogenic carci noma were found in the sample, and this incidence happens to conform to the avenge figure of 20 cases expected in one year in dockyard worken under the age of 65. Insufficient evidence has as yet been accumulated to establish an association between tbit tumour and the effects of exposure to asbestos in the dockyard. Other Ahoonnalitka Pulmonary Tuberculosis.--One cate of sputum-positive tuberculoaia was found in the sample. Two others were given prophylactic chemotherapy for small, doubtfully healed lesions. The annual incidence of new cases of pulmonary tuberculosis in dockyard workers has fallen from 13 in 1962 to four in 1967. These rates are lower than those for other men between the ages of II and 64 living in the county borough of Plymouth. The rate for Plymouth is the same as the average rate for England and Wales (41 per 100,000 males aged 13 to 64). Care has been taken to exclude tuberculosis as a possible cause of pleural thickening. In cases where any doubt has risen on this point the abnormality has been recorded as postinfcctive pleural thickening and excluded from those attributed to 'asbestos. The number in the sample classified in- this way was 39. This is more than would be expected, and it is reason able to suspect that in seme cases asbestos may have been a factor. Pleural effusions presented a similar problem in differential diagnosis, but none occurred m the 10% sample. O ther Conditions.--Of the conditions stimulating pulmonary fibrosis, only two were identified within the 10% sample. One eras a case of sarcoidosis in which subsequent observation has shown partial resolution of the tiahite pul monary nodulation. The other was a previously diagnosed esie of complicated coal miner's pneumoconiosis. . The prevalence of bronchitis and emphysema is fortunately low in Plymouth, and in very few cases has airway obstruction interfered with riinirsl and functional aum m ent. The occupational structure and pattern of exposure to asbestos in the dockyard leads to the risk of the development of pleural abnormalities in a disproportionately large number of men. The prevalence and possible complications of these conditions are therefore of particular importance. The prevalence rates cover a wide range, corresponding to the variety of working conditions in so heterogeneous a labour force. At one end of the scale, on the basis of the 10% sample, the expected prevalence of pleural abnormalities among the 420 continuously exposed men (28%) is comparable with the rate of 24% observed in New York insulation workers (Selikoff, 1963). At the lower end of the range there are over 6,800 men with little exposure among whom the prevalence rate is 1.9%. In an environmentally exposed community living near the anthophyUite mines in Finland the highest rate vas slightly below 1% (Kiviluoto, 1960). Occupying an intermediate position there a the important group of approximately 2,000 skilled tradesmen with over 25 yean of intermittent exposure and a prevalence rate of 14%. Half the total of pleural abnor malities occur in this group, and these include 70 of the expected 110 cases of extensive pleural thickening. Necropsy studies suggest that only 13% of all pleural plaques can be detected radiographically, and that these are those most densely calcified (Hourihane, Lesaof, and Richardson, 1966). In recent repares an increasing number of less dense pleural i opacities have been described (Anton, 1967 ; Leathart, 1967), but it seems evident that a large proportion of pleural abnor malities remain undiscovered and that prevalence rates bated on radiographic surveys are considerably underestimated. Pulmonary fibrosis occurred in a variety of trades in which exposure was intermittent, and appeared to be a definite risk in some cases of extensive pleural thickening. In SO such cases seen locally during the last five years an attempt was made to apply the distinction drawn by Elmes (1966) between circumscribed hyaline fibrosis in the parietal pleura and a diffuse pleural thickening with ill-defined ntbrgms, most pro nounced over the lower lobes, which he relates to underlying parenchymal disease. There was considerable overlap between the two varieties in some of our cases, but it would be reason able to regard 26 as parietal pleural thickening and 24 as mainly diffuse lower-zone fibrosis. All five cases in which a diagnosis of pulmonary fibrosis was subsequently established occurred among the 24 with diffuse lower-zone fibrosis. A possible explanation for the predominance of pleural over / parenchymal changes is that the intermittent exposure cxperif meed in most of these cam has allowed sufficient time to v elapse for the appearance of pleural reactions, while the dust concentrations were insufficient to give rise to pulmonary fibrosis as the presenting feature. A further cause of anxiety is the possibility of a relation between pleural fibrosis and malignancy. O ur first case of mesothelioma was preceded by extensive parietal pleural thickening for mote than five yean. Others have developed in the neighbourhood of previously identified limited pleural plaques. In addition to those with recognized pleural fibrosis there are at present in the dockyard over 1,200 men whose first occupational exposure to asbestos was more than 30 yean ago, and a further 1,000 who have been environmentally exposed for a similar period. The large number of retired men living in the district must be added to these in order to gain an impression of the number who may be at risk. It is hoped that the long-term study of a series of all types of pleural thickening will help to assess the added risks of malignancy and morbidity from extending fibrosis. We would like to thank Surgeon-Commander P. G. Harries, Royal Navy, for his dose collaboration and for help with pulmonary function studies ; D r. J. C . Gilson for encouragement and valued advice ; the Admiral Superintendent of the Dockyard and his staff for their co-operation ; and the staff of the Mass Radiography Service for their skilled work. T h e investigation was supported by a research grant from the South-western Regional Hospital' Board. Anton, H. C (1967). Brit. J. R adial. 4 t, MS. Elmo, P. C. (1966). Pestered. m uL 7-, 42, i f f . Hartiet, P. G. (196*). Atm. co u p , ffye.,11, 235. Hounhsnc, D. O'B., Lesaef, L., and Richardson, P. C. (I960. Brit, m td. J ., 1, 1069. KMlooto, R. (i960). A tm R adi. (S u d * .). Sapai. No. 1M. Leathart, G. L. (1967). Unpublished. Scliksa, 1. J. (1965), A tm . N .Y . Acad. ScL. 132, 351. r\ J Chloroquine : Ophthalmological Safety, and Clinical Assessment in Rheumatoid Arthritis S. P. B. PERCIVAL,* m a , mu., DD. ; I. MEANOCK,f MJ, Mjlcf. ' Brit, mtd. J,, 1960, , 579-584 Summary : 272 patienta on long-term chloroquine therapy were assessed with respect to ocular toxicity and clinical benefit A simple scheme for rendering patients ophthaJmologicaily safe is presented, employing the recording of central fields to red, targets. Under this it was possible to diagnose a state of- premaculopathy, which was reversible on stopping treatm ent T h e inci dence of premaculopathy was 41% in 143 patienta w ho otherwise displayed no abnormality of the fundus ocnll and who had received a mean total dose of 410 g. of chloroquine phosphate or the hydroxychloroquine sul phate equivalent Under this joint ophthalmological and rhcumatological supervision it was considered that the minor side-effects that may be caused by chioroqnine are outweighed by Its therapeutic value. Introduction In spite of undoubted therapeutic value in certain disorders, the use of the antimalarials chloroquine phosphate (Avlochlor), hydroxychloroquine sulphate (Plaquenil), and chloroquine sulphate (Nivaquine) has been losing favour in clinical practice * Ophthalmic Rejituar, Roytl Berkshire Hospital, Reading. Present address : The Eye, Ear, tot1 Throat Hoipitsl* Shrewsbury. f Consultent Physician in charte ai Rheumatic Diseases and Physical Medicine Departments, Reading and District Hospitals Group, because of ocular toxicity. It is the purpose of this paper to show how antimalarials may be rendered ophthalmologically safe and to assess the clinical and functional status of a group of patients on continuous antimalarial therapy, the majority of whom had rheumatoid ritseaar, ,- M aterial and Methods T he 272 outpatients taking part in the eurvey were referred from the departments of rheumatology and dermatology to the ophthalmic outpatient department during 1964 and the early p a n c i 1965. Their age and sea are shown in Table L rm tenu 1 20-40 I T a a ta .--At "4 Sex Maie A etd Female A nd .41-40 41-40 20-40 41-40 41-45 7 j a 54 26 2S 11 57 295 Skin 1 * 4 1 1 T he etanderd daily dote of antimalarial was 250 mg. of chloro quine phosphate or 200 mg. of hydroxychloroquine sulphate. Five patients hsd also received courses of chloroquine sulphate. Ninetythree received double the daily dose during the first p an of their course,' and 43 received half the daily dose during the course when control et tbit level seemed satisfactory.