Document Y8ZBRpXrdVQawgoX7jw0r6qk

AnoiCAa Journal of Industrial Mettidne 19rWl-l69 (1991) Chrysotile Asbestos and Health in Zimbabwe: (. Analysis of Miners and Millers Compensated for Asbestos-Related Diseases Since Independence (1980) Mark R. Cullen, ud, and Rabelan S. Baloyl, PhD ' Data on the health effects caused by locally mined daysodle asbestos in Zimbabwe have ' ' been very limited. Ihe prevailing local view has been that risk Is Cniiuir.al. In this: report we critically reassess die Cases of 51 individuals with asbestos exposure who have beet) Compensated by the Central Pneumoconiosis Bureau since independence in I960 Re suits demonstrate that the major health risks of exposure reported elsewhere--morbid asbescosls, DOnireahgnHut pleural disease, malignant mesothelioma, and lung cancer--all occur in .Zimbabwe, at least among workers in the asbestos mines and mills. It Is concluded that further investigation and control measurer in the industry are warranted. Key worth: aibetnii, pleura) disease, mesndieliona, lung cancer, chrysotile miners, thrysotHe railkrs INTRODUCTION As one of the world's major suppliers of chiysotilc asbestos and producer of several important asbestos products, Zimbabwe has a striable population exposed to the mineral, occupationally and environmentally. Currently, some 7.000 men are engaged in mining and milling of the major ore bodies in the Midlands, with another 3,000-4,000 engaged in the manufacture of asbestos construction materials (cement, asphalt, tiles) and automotive products (brakes, gaskets, clutches). An undetermined number of people are further exposed In the use, repair, and disposal of these ma terials. Some 40,000-45,000 people live within a few kilometers of the mills and mines; a large portion of the population lives and works in buildings made from asbestos materials. Despite these exposures, some of which have been ongoing for decades (the mines opening about 1910), there is general optimism among local observers that Yale New Haven Occupations! .Medtcme PiDgreTM, Yale University School of Medicine, New HLiven. CounccdcoL (M.R.C.). . Department ofOccupational Health, Safety ud Winkers' Compollution, Ministry of Labour, Manpower PUnning and Social Welfare, Harare, Zimbabwe (R.S.B.), Address reprint re<jUs re Dr, Mirk R. Cullen, Yale University School of Medicine. Occupational Medicine Program, 333 Cedar Street, New Haven. CT 06311 ' Accepted for publication June 20, 1990- 162 Cultett and Salojii ' health effects have been limited and a suggestion that the product itself--a hugely important export commodity---may be safer than nmphibole or even chiysotile as bestos mined and processed elsewhere in the world- Although some of this impression may result from perhaps premature acceptance of some published opinions from Europe and North America regarding the lesser toxicides of chiysotile generally [Cullen, 1987], at lean some opinion has been founded in observation, or rather lack of observations of anticipated sequelae, e.g., asbestosis, lung cancer, or mesothe lioma. . Four papers have been published on the subject- Gelfand and Morion [1969] reviewed the asbestos-associated cases certified by the Pneumoconiosis Bureau be tween 1963 and 1967. Only 37 cases met international criteria for asbestosis, once cases of apparent silicosis or tuberculosis were excluded. The authors, without critical analysis of their data source, extrapolate from the results quantitative evidence of a very low rate of asbestosis given the total numbers apparently at rule. In 1977, Walker, a mine physician, described the absence ofeven a single case of malignant mesothelioma either in his personal experience or, to his knowledge, anywhere in the country. He also commented on the rarity ofasbestosis and asbestos- related pleural disease in the mining populations be had cared for but did not provide quantitative information. ... Two.years later, Mostert and Meintjes [1979] reported Six cases of railwayman who had developed asbestosis (four cases) and ircsothelioma (two cases). Tbelr careful review of exposures, however, clearly documented that each man bad had some exposures to nonlocally mined ampbibotc fibere; indeed, each had worked during the time when crockfolite asbestos was being imported and used by the rail roads- In a note published in 1983, Mossup commented again on the rarity of asbestos- related diseases in his experience, claiming further that few cases were being iden tified by the Pneumoconiosis Bureau despite expansion of its role, He presented, as well, results ofa proportional cancermortality analysis of asbestos miners done using the cancer registry ofthe Mpilo Central Hospital, which draws referrals from the mine area. These data show that only 129b of all cancers registered among asbestos- exposed workers were primary bronchogenic, a rate similar to other occupational groups; this would suggest the absence of ns asbestos effect, which would be ex pected to elevate the proportion of lung cancers as well as die total incidence ofcancer cases (which could not be assessed by this method). In an as yet unpublished study, Armstrong and Firma) [1985] performed a cross-sectional survey of all active asbestos cement plant workers and a sample of asbestos mine and mill workers with mare than 10 years ofexposure. Among cement workers, for whom measured and extrapolated exposure levels were available, a clear dose-response of asbestos fiber on forced vital capacity and radiographic changes was demonstrated, consistent with previous studies of the cement industry in other coun tries . At the mines and mills, parenchymal radiographic abnormalities (ILO grade I/O or greater) were noted in 20% (mines) and 26% (mills), although the representative ness of the sample was not verified. As well, no dose-response could be shown on lung function using i surrogate index of exposure, years .of exposure. No actual or reconstructed air levels were available at that time for Ibo analysis. Given these very limited data sources, it was the aim ofthe present investigators to gain a dearer picture of the risks in the various exposure settings for malignant and Health Effects of Zimbabwean Asbestos 163 nontoelignant disorders most closely associated with exposures to asbestos in. other countries. Ideally, a mortality study using conventional techniques would have been proposed. However, given the very etude state of health statistics in the country generally, and the recognized fact that cause of death can rarely be ascertained for rural populations, such ait approach was rot feasible. On (he other hand, the nation has had a functioning Pneumoconiosis Bureau for almost 40 years. Despite obvious limitations to this existing source, h was determined that information at the Bureau could be utilized to maim certain qualitative and even semiquantitative judgements regarding the occurrence and rate of some disabling and lethal sequelae of asbestos exposure. The strategy, results, and interpretation of these data arc presented here. Subsequent to this effort, a cross-sectional health survey of current asbestos miners and millers was conducted to elucidate dose-response relationships for nonmalignanc respiiatory.disease; these data appear as a companion article [Cullen eta]., this issue], MATERIALS AND METHODS Pneumoconiosis Medical Bureau Practice Zimbabwe has had a Pneumoconiosis Bureau since 1949. In 1984, a law wax passed requiring universal surveillance of miners and others in "dusty trades," pri' manly those directly associated with mines; prior to that lime, X-rays were performed .primarily on more skilled or managerial personnel only. Chest X-rays representing ' "initial'* (first ever) Or "periodic" (routine follow-up) examinations ate obtained by employers and mailed to the central facility in Harare. Films ate accompanied by a briefquestionnaire and medical report, which generally provides age. summary work history, and job title. After registration, Dims and records are reviewed by a Medical Panel consisting ofa chest surgeon, a radiologist, a public health physician, and mine doctors. The purpose of the review is to certify: I) fitness for work; and 2) eligibility for compensation on a four-grade scale. Id addition to miners, workers from non reining Industries suspected of having pneumoconiosis may apply to the Bureau for compensation, although routine X-rays are required only at mining facilities; few ether industries routinely obtain them. Since this study would be limited to cases selected by the Medical Bureau, ihe selection process itself was investigated in a preliminary step. After observation of several working sessions, n sample of approximately 500 newly arrived (unread) films were blindly read using the 1LO system by one of the authors (M.R.C.), a NTOSH-certified B leader, and results were compared to subsequent leadings by tire Bureau- In this comparison, it became evident that fewer than 10% ofgrade I/O of 1/1 films (about 5% of total) were designated abnormal by die panel, whereas most films grade 1/2 or higher (about 1 % of films) were identified for compensation. Thus it was appreciated at the outset that the identified cases would, in general, reflect those of moderate or greater severity, at least radiographically, rather than the group of nil ' miners and millets with abnormal findings, Cone Selection Evaluation'and Analysis ' The records of all cases of occupational lung disorder certified since 1960 were reviewed to establish place of employment, All those from places in which asbestos was known to be mined, processed, or used were selected and an effort made to locate the full X-ray folder and compensation file. Once located, the entire case was re viewed in order to establish best diagnosis, using all available data sources, including 07/18/2002 09:02 FAX 757 628 5566 WILLCOX & SAVAGE NFLK VA 0006 vi-j.KSr'.'vl 164 CuIIcd and Btloyi the X-rays, demographic data, medical and occupational histories, and laboratory reports. The basis for best-evidence diagnoses and vital status when known.was also recorded. Final analysis was limited to eases meeting the following criteria. 1) Best evidence diagnosis was of ah asbestos-related disease (asbestosis, benign pleural disease, lung cancer, or malignant mesothelioma); 2) Exposure to asbestos occurred exclusively at a Zimbabwe asbestos mine or mill, since general knowledge of exposums to the total -workforce is available and because universal X-rays have been performed during the period of interest. RESULTS Among' the approximately 300 men certified by the Bureau as haring occupational lung disease since 1980, 54 were identified as having worked at some time at an asbestos mining or manufacturing facility. Complete Bureau records and X-ray files were available on 51 of these men, who thus formed the study population. An attempt was made first to assign a Clinical-radiologic diagnosis in each case, based on the records. In most cases, this was accomplished by radiographic inter pretation coupled with review of reports of physical examination and sputum smears and culture for acid-fast bacteria. This strategy was necessary because, io the majority of cases, no detailed clinical evaluation, e.g., functional studies, bronchoscopy, biopsy, etc., had ever been conducted and patients were dispersed geographically, Even among the 17 confirmed to have died, only five had received postmortem examinations, but two others had had premoitem lung biopsies. Notably, biopsy or autopsy results were the initial basis for compensation in six of these seven cases; only one man in the series had been certified for compensation on clinical grounds and subsequently had histologic (postmortem) confirmation of diagnosis, Using this classification strategy, diagnoses were as follows: Ten cases bad tuberculosis, smear- and culture-proven in six, suspected and treated Clinically in the other four. In none-of these cases could underlying pneumoconiosis be established. Eight cases met radiographic criteria for silicosis (l.c., symmetric small rounded opacities), simple in two and complicated lit six. Among the latter, two were dem onstrated to have superimposed pulmonary tuberculosis by culture or biopsy; the remainder had typical features of progressive massive fibrosis. Interestingly, in five cases, no exposure to dust other than asbestos mining or milling could be docu mented. Six cases appeared not to have diseases primarily associated with dust or fiber exposures. One had chronic obstructive pulmonary disuse demonstrated functionally and radiographically. A second had autopsy-documented adenocarcinoma ofthepros tate. Two had focal infiltrates most consistent with infectious pneumonitis. One had clinically recognized congestive cardiac failure. The last had a diffuse, symmetric profusion of thick irregular opacities (1LO U/U) associated with hilar and paratracfaeal node enlargement, most consistent with some granulomatous lung disease, likely sarcoidosis; insufficient data were available for better classification. This left 27 men with findings consistent with one or more of the asbestos- associated diseases. Detailed clinical and occupational data on these workers appears in Table I, The findings can he summarized as follows: . Health Effects of Zimbabwean Asbestos its 1. Three men, el] with exposure exclusively in Zimbabwean mines and/or mills, had evidence of asbestos-associated pleural plaques, without parenchymal changes. All were alive and working, apparently without impairment. 2. Three men with otherwise normal X-rays presented with clinical and radiographic features of chest malignancies. One case was proven ai open resection to be malignant mesothelioma. In the other two, no pathologic diagnosis was achieved--one radiographically resembled mesothelioma, the other a primary bronchogenic ttunOT. 3. Twenty-one men bad radiographic and/or pathologic evidence of asbestosis. Of these, one had been exposed making asbestos cement only, and 2 others bad been extensively exposed to asbestos outside Zimbabwe: the other IS had been exposed exclusively in the Zimbabwe mines and/or mills. The IS asbestosis cases associated with Zimbabwe mlne/tnill exposures only were further analyzed. Eight of these men were established to be dead by 1988, three from likely malignancies (one confirmed mesothelioma), five from progressive respiratory failure and/or cor pulmonale. Among ihc ten who survived, the severity level of disease, judged radiographically, was generally high, all but three being ILO profusion grade 1/2 or greater at the time of diagnosis. In general, exposures among these cases were of long duration, ranging from 17 to 37 years, with a mean of 22.3: latency prior to disease recognition was comparable (range 17-42 years, mean 27.2). DISCUSSION Despite the obvious limitations of a case series of the kind presented here, limited inferences may be drawn from these data, which could provide a rationale for some changes in clinical and public health practice in Zimbabwe as well as a basis for more substantial scientific inquiries in the future. Coupled with data from the cross sectionai study of the mining industry (Cuilen et ah. this issue], a more secure justification has been developed for undertaking these costly activities. Looking first at the shortcomings, the most obvious problem is the underrec ognition bias introduced by looking at a workers' compensation-derived series. Al though the active workers at the asbestos mines and mills have been under medical surveillance during the study period, there is no capacity in the system to follow-up - miners who have quit or retired from die industry, except for those who remain in the mining area and voluntarily utilize mining health services; the demographies of the workforce suggest (hat the majority return to their families in their region of origin. Among these, it is unlikely that most asbestos-related diseases would be recognized or a cue filed given general lack of awareness about the problem In most rural areas and the impediments to filing. The problem is compounded by the fact that lung cancer and mesothelioma have not been formally listed as compensable disorders, which could further reduce reporting for these conditions. That this bias is operating is suggested by the fact that over three-fourths of eases studied in (his series were actively working when first diagnosed. It is also clear that die series severely underrepresents workers or ex-workers with grade 1 parenchymal changes on X-ray. In the scries, only three nonfaial cases had changes below category 1/2, whereas eight had died, implying a highly skewed series in terms of case severity. That a large number of lower grade cases have TABUS l. Cases Certified by Zimbabwe pMWDwntosb lacew Between J>M and 1967 WUb Suspect Asbestos-Related Dbeatw A|e and Ok ycurof *0, d|ugMS Diagnosis } 33/WM AsbfcHMto Basil Tor dlagnirti* B top*y/poM mortem Exposure period 1965-1980 2 M/M7 Probable Cbesi X-rajr TTiesoLhalitHaD 1949-1982 J 64/IW7 AsbestosIfc MlCteit X-fiy; 1^2 F9fi9-l*J70 pUnral caltilrcibcm 4 si/ino Asbeskw-rclared Chetl X-njr 0/1 1947-J9RO pleurar dfteave Ulaknl pJaqves 5 44/19(2 AsbesLoiis w3ib calclficjiioiu Chert X*ny 2/2 lA 1937-1962 rtigtll pleunl Lhickeokg fi 53/1481 Artemwis in,Clot x-n) srt 1964-1986 bilateral 1 fiJ/1986 Aibcdoris Ckesl X-my 1/2 i/i 1949-1986 S Unknown/ AltcMoai; Lung biopsy; cbeti WB-1970 J9BO probable lung X-ray cuoei 9 51/198} Aibertosk Poimwciem 1462-1983 10 64/1985 Asbestos!* 11 65/1985 PrcbaMe lung ClKCI 12 72/1986 AAertou ii 46M986 Anbestotlt Chert X-ray 2/2 l biatemfc plaques Cheil X-ny 195I-J9S0 1932-L980 Cheat X-ny L/| ui bilateral pUqiict with <aJriBc*ilon (?wi X-ny ifOr j/q faltaasat jdiqm 1955-1971 1966-19*6 sLe Job Uric i 'Vi.ll laborer i Mill nweper t EtetfcrL-iaif 1 Mill opciMOt i Slmo drillec 2 Mine laborer Vrtal Sain* (>iktrathro) f ConancnlJ Dead (1982) Rapid progreiskMi 1980-82; lal chest X*uy 2/3 i/t with bilateral plaques wuuDeal 4.3987] Normal X-rays 1983; pleural noted prc-mortem; nu portmone* eKamioalion Alive wr-paPrior aura in shipyards, potter rtalicm, railroads bejficmlng 1943 Alive llcud 11983) DcitfoecrtiGrale; ctjc pvImouJc; no poaDuoctsn Alive Prior nickel, gold mine exposure l Mine lubura 1.2 M'me laborer L Mill operator 1 Mill rtlndtCK Alive Cte8 (19*0) Mw on X-ray in 1979, (legrtlve bronchoscopy, 1979; pe . iun$--flsbeiloiift; cuieer not ideoTrlked Dwd(l9S3) Premoflem X-rays of poor quality; porttratrictD revealed advanced Gbrcw with fenngiwui bodies Aliw 2 Mina laborer Unitoown 2 Underground manager Alive, 1.2 . Sanitation worker Alive Negative AF0 ilvdiu ir 1985; no follow-up available CreetidoUle mining J?5M9SS; Domibotoi mining 1953-1951 and 1971-1963 * CHSTtnal pleura iv^r-iwb 2 Mill Operator If UriknDwiV Asbestoux 1986. Cit*t X-rt)i 1/1, s/i 1952-1966 J Wtldfer, pl tmJkteral plrtpae IS Unknown Asbcslof-rdafisd Cbtsi X-ray 0*0, J962-J966 3 Mine bhortc 1995 pleural diaeeso bdricral plaques 17 7a't9W Aibeslwis Postmortem 1944-JM7 i Mine Mttrcr If Unknown/ Asbeiioals im dial X-4iy L/lr A I97I-19M Cemertf Sweeper normal pletira faclwy J9 52/1964 Malignant Hiopiy iwaoUmUniM J969-I9SI 2 H(tTM, turner 7B/I9S4 Ma&gnut ftuNiMflem meiolhcJforTtt i95M95J 4 Manager 31 Unknown/ Asbtllwk I9W Oitfi X-ray 20 ft, J9M-1973 5 Loader bJfllcral plaques 22 fi911983 Aitejtosis Chest X-ray 2/2 l/l, 19(^-1983 2 Lasher bilateral plaques 33 6211950 Asheitnsii Chest X-ray 1/2 r/q, 1957-J980 t Mil svwqier mnnal pleura 21 UiikcuTtTJt* Aabcskmls* Ctai X-ray JflJirt, I960-: 985 ] Gang leader I960 prnbaWe normal termlatl pjtura/pfeunl infile molhcUofliq 5 years later vs lung racer 23 33/IW1 AlbcBuSi! Chest X-cty Ul sfl 1960-1977 } Mill operator bilateral plaques 16 43/I9B2 Asbestos-related Choi X-ray (UD J9S6-I0B2 1,3 Bluiler pltuml dJsei&c (alcifcrf bilareraJ plsqpes 27 t,umi Afbnlosis Ota X-11)' in Hi WD-J95J 1 Dllltfi iwwi pteiiu. mfr*ag btomr "Sices: I, 2, stbetfot miues/mifli, 3-5, ctaed nbeaiot nrmct/rnlb. Dead (J987J No postmortem *Mjnltition Alive .' Alive Gold and copper mining expatuttt after J966 ' Dcid (J9B3) Prcieimmai X-ray 212 lAi diffusa pleural tfiicfceiwtg Alive UoknbWft Pfcoiadgnancy X-ray (1987} nonnoJ Dead C1954) PremslJgoaticy chol X-ray | /O^ s/c, aconil pleura (J971j Alive Heated apical raberctitoil* A lire AK re Dead Nodules rnWxepes; "mixed dual pneunoccmiasls No pHimnrtem examinallod Alt ue Alive Alive 07/16/2002 09:05 PA1 757 628 5566 wTi irnT & ssvsrrfi NFT.K VA El 010 ArV. 168 Cullen tod Baloyi escaped detection by this method has been proven by the findings in our own ctoss-scctionai study [Cullen et ah, this issue], in which 8.7% of wodaers with more than 10 years of exposure had such changes (categories 1/0 and 1/1), and in the previous study by Elmes end Armstrong [1985], who found over 20% in this category range. Given that each of (he approximately 3,000-4,000 active workers with this amount of experience has been X-rayed at least once, an additional 240-800 cases can be assumed to be missing from a theoretically complete series due to this bins alone. Another justifiable concern about the case series is (he accuracy of diagnoses given the limitations of the available data and (he use of a single clinician (M.R.C) as the diagnostic standard. This is especially true of the six apparent malignancies, of which only two (both malignant mesotheliomas) were pathologically confirmed. To a lesser extent, this is also a problem with the asbestosis cases, in which other, albdt less probable, causes could rarely be excluded from the records. Similarly, the ra diographic categorization may certainly be askew when based on the judgement of a single reader {Musch et al., 1985]. This is unlikely to introduce loo much overdiag nosis, however, since each film bad already beenjudged to represent asbestosis by the Medical Panel, These problems notwithstanding, the data appear to confirm that each of the major diseases associated with asbestos in other countries--asbestosis, mesothe lioma, nonmalignant pleural disease, and carcinoma of the lung--all occur among Zimbabweans exposed exclusively to the domestic chrysolite industry. Obviously very little can be said quantitatively about the cancers from this series, since case ascertainment and confirmation are so far from complete; even if they wore complete, comparisons would be difficult because ofthe lack of adequate morality data among up.exposcd men in the population from which the miners and millers were drawn. Nonetheless, ibis is the first report to confirm die occurrence of these most dread consequences of asbestos exposure and should serve to emphasize the need to develop diagnostic vigilance among physicians who beat exposed workers and enhanced surveillance strategies at the mines and nationally. ACKNOWLEDGMENTS This work was conducted with the support of the Department of Occupational Health, Safety and Workers Compensation, Ministry of Labour, Manpower Planning and Social Welfare, Harare, Zimbabwe, and the Kapnek Trust, directed by Dr. Rebecca Polland. It could not have proceeded without the cooperation of the staff of the Pneumoconiosis Bureau and its Medical Panel, chaired by Mr. Alex Graham. Barbara McGuire provided dedicated assistance in the preparation of the manuscript. REFERENCES . Antiitnjnj RH, Eboes PC (]9t3);"Asbeu and health in Zimbabwe A report or miners, millets and ubesuu cement workers. Unpublished minuterifiL CoIlea MR (1667)'. Cwurovtmta in uipertoueUied twig ennetr. Qccup Med Stale of die Ait Rev 22J9-272. CoIlea MR. Loper-CwriNo LT, AM 6, race PE, SbiUi SL, Bdoyl RS (1691): Cfrysocile asbestos and hold] Ja Zimbabwe, 11. Health slows survey df Active miners end miEea. Ant J Ind Med 17 [71--182. Gckfand M, MortonSA (1969): Aabeuoits It Rinduia. Cental African; Med 15:206-212.