Asbestosis in Rhodesia*BY

MICHAEL GELFAND,C .B .E . , M .D . , F .R .C .P . , D . P . P 1 D . M . R .

Professor of Medicine {with special reference lo Africa), University College of Rhodesia. Chairman, Pneumoco­

niosis Medical Bureau, Rhodesia;

AND

S. ARCHIBALD MORTON.M .D ., C .M ., M .S ., F.A.C.R.

Visiting Professor o f Radiology, Salisbury, Rhodesia;American University of Beirut, Lebanon .

The purpose of this study was to investigate the effects of the inhalation of asbestos on employees (mostly African) in the Rhodesian mining in­dustry. Every effort was made to ensure that each worker investigated had been exposed to only this dust and had not worked in any other type of mine.

Asbestos is mined in the Shabani-Mashaba region in the southern part of Rhodesia. The variety occurring in this country is the fibrous modification of chrysotile, chemically a hydrated magnesium silicate. This fibrous nature coupled with heat resistance determines its value as an asbestos. The long fibre, blue asbestos, crocidolile, and the shorter fibre, amosite, mined in South Africa are not known to occur in Rhodesia. These two belong to the amphibole group of minerals and differ in chemical composition from chryso­tile. Crocidolite is a sodium/iron silicate and amosite is a magnesium/iron silicate.

On the surface, chrysotile asbestos is quarried, but underground mining is carried out by stan­dard methods. The use of water and adequate ventilation renders the hazard of lung disease almost negligible. Tn quarries wagon drills are employed to drill a line of long holes in benches 10 feet high and over. These holes are blasted electrically with no person present, and so the resulting dust cloud is harmlessly dispersed to the atmosphere. While drilling is in progress, dust generated is removed by an apparatus which sucks it from the drill hole and discharges it down wind at a safe distance from the drilling crew.

Vol. 15. No. 9. September, 1969

* Paper read at International Conference on Pneumo­coniosis held in Johannesburg in April, 1969.

As soon as dust forms in. the mills, special exhaust systems aspirate it throughout the plant. Many of the machines also operate under nega­tive air pressure to prevent the escape of dust to the atmosphere. The exhaust dust is led to bag filters which collect it and do not allow it to escape to the atmosphere. Water is added to the collected dust to form a “slurry” which is con­veyed. to a dump by conveyor belts. On the dump it forms a hard cake impervious to wind action. As the capital outlay of filtration is so great, the exhaust dust in. smaller mills is discharged from high chimneys and so dispersed to the atmosphere.

The standard of permissible dustiness in Rho­desia must be no more than 300 particles per cubic centimetre. No particle is to be longer than five microns and no fibre beyond 40 microns. The majority of particles are fibrous, varying from five microns in length to 40 microns; the non-librous portions are generally below five microns, hut if over they would not be counted.

The dust hazard underground is negligible and in quarries the methods of dust suppression are most effective. On the other hand, the dust hazard in milling originates from crushing, grind­ing and the transfer of material from one carriage belt to another, and consequently the hazard in this branch of the industry is much greater.

Asbestosis has been divided into three phases. In the first the asbestos body or fibre is deposited in the bronchiolar or bronchial wall. In the next phase there is a peribronchiolar or peribronchial oedema, and in the third, interstitial fibrosis (Fig. 1). The asbestos body inhaled varies from one to five microns in length and is said to become coaled with a ferritin-containing gela­tinous material which possibly protects the pulmonary tissues. The lesions which ensue may be caused by mechanical irritation, but it is also thought that liberation of silicic acid formed by the deposition of the asbestos fibre is ultimately responsible for the fibrous tissue laid down (Freundli'ch and Greening, 1967). An increased incidence of tuberculosis has also been said to follow exnosure to inhalation of asbestos fibre, but the evidence is conflicting (Webster, 1964).

As asbestos consists essentially of an interstitial fibrosis in the lung, the most functional change is a lowered diffusing capacity, together with a diminished ventilatory one, hyperventilation (often accompanied by desaturation) on exertion without evidence of air flow obstruction, unless complicated by asthma or emphysema. Further, these functional changes may be present inde­pendent of the physical signs and radiological

T h e C entral. A fr ic a nJ o u rn al o f M e d ic in e

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September, 1969 ASBESTOS IS IN RHODESIA T he C entral A m i canJ ou rn al o f M e d ic in e

Fig. 1—First stage asbcstosis. Increased reticulation, es­pecially right base.

Fig. 2—Second stage asbcstosis. Marked fibrosis. Right lower zone, plueral reaction in left side with shaggy heart appearance.

changes (Williams and Hugh-Jones, 1960) (Figs. 2 and 3).

Without doubt asbestosis occurs in the Rho­desian industry. We have good radiological evi­dence of this disease and it has also been found at autopsy in men who have served only in these mines. However, we cannot give a figure for the incidence of the disease since the bulk of the employees have worked in other mines, both in and outside Rhodesia, and we are not aware of the exact number of miners who have been engaged only in this industry. The average number of Europeans employed in asbestos mines

Fig. 3—Second stage with lesions mostly in middle zones. (In employ 192 months.)

from 1963 to 1967 was 712 in contrast to 7,624 Africans. In this period 235 men were certified as having the following diseases: tuberculosis alone, 76; tuberculosis with pneumoconiosis, 41; pneumoconiosis alone, 118. But this figure pro­vided us with no idea as to the frequency of the disease in those who had worked only in Rho­desian asbestos mines. Accordingly we had to take a fresh look at their places of employment to find out how many had been exposed only in asbestos mines in this country. In the period 1963-67 the Pneumoconiosis Bureau was con­cerned with 97 cases thought to have disease

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September, 1969 ASBESTOSIS IN RHODESIA T h e C e n t r a l Afr ic a nJ o u rn a l o f M e d ic in e

which could only be attributed to employment in these mines. We scrutinised these cases again and our new assessment excluded seven as being within normal limits and two as doubtful. The results are given in Table I.

Table 1

Cases D iscovered in Asbestos M ines O nly, F ive Year Period 1963-1967 96 Africans; 1 E uropean

Asbestos ........... 1st, IS; 2nd, 20; 3rd, !; total 39Tuberculosis or tuberculosis/asbcstosis ................... 48Carcinoma of the lung .......................... 1Doubtful ........................... —................. mm 2Probably no abnormality 7

One European out of 712 contracted asbestosis and 38 Africans out of 7,624. The subjects with asbestosis were examined by various medicalofficers at the different mines and therefore it is not possible to claim any uniformity in pro­cedure. Nevertheless, the paucity of these find­ings may add more to their value. The symptoms mentioned by the patients in order of frequency are shown in Table II.

Table IISymptoms in Uncomplicated

AsbestosisSymptom—

CoughShortness of breath

(In 5 the questionnaire was incomplete.In 10 no dyspnoea was noticed.)

Pain in chest .................. 19Haemoptysis ........................... 7Loss of weight ................... —* 3No symptoms ........... — — 5

Signs in 39 subjects with asbestosis—Rales -....... - ... — 19Rhonchi ..-................................. 7Dullness ................. - — 3Sputum positive for tuberculosis ... 0

The relative frequency of cough and shortness of breath on exertion does not call for special comment, but pains in the chest seem to be fairly common, being mentioned by 19 out of 39 sub­jects. This may be the result of pleural reaction and fibrous tissue formation which is apparently not an uncommon feature of the disease. Perhaps worthy of mention are the seven patients who complained of the presence of blood in the sputum. As tuberculosis was absent in these cases, could no! haemoptysis occur at times in a damaged lung with bronchiolar changes?

Table IIIT he C h e st E x p a n s io n i n I n c h e s

(In one case this finding was not recorded)Range of Expansion Number

0-1 121.1-2 212.1-3 33 plus 3

Table IVN u m b er of M o n t h s i n E m p l o y m e n t BeforeA sbestosis or T uberculosis W ere R ec ognised

The number of months the men had workedin the industry before they were found to haveasbestosis is shown in this table.

M o n t h s W orked by 39 M en W h e n F o u n d

to H ave A sbestosis

Months Number1-100 2101-200 11201-300 16301 -400 8401 -500 2

The 48 miners who had tuberculosis (with orwithout asbestosis) were discovered after employ-ment at the following periods:

Table VM o n t h s W orked in t h e I nd ustry by 48

M in e r s W h e n F o u n d to H aveT uberculosis

Months of Employ Number1-100 17101-200 17201-300 8301-400 6401-500 0

If we compare the two tables it will be seen that tuberculous disease apparently made its appearance in the majority of subjects within 16 ̂years, whereas most with asbestosis were dis­covered after this period (Fig. 4).

Cancer of t h e Br o n c h u s The first cases of lung cancer and asbestosis

were reported by Lynch and Smith (1935). There have been many allegations about the possible relationship between asbestosis and bronchial carcinoma apart from mesothelioma. Thus Demy and Adler (1967) in the U.S.A. were able to col­lect 37 proven cases of asbestosis and lung cancer, as well as 10 cases of mesothelioma. The pre­dominant cell type was the squamous cell carcinoma and the next most frequent adeno­carcinoma. Tn 1955 Doll in Britain reported 61 cases, one of which was mesothelioma (Doll, 1955, quoted by Wagner et al., 1960).

During the period of 1955-59 (inclusive) Dr. N. Walter, the Principal Medical Officer of the Shabanie Mine (personal communication), found

No. of subjects (total 39)

.... 2524

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September, 1969 ASBESTOSIS IN RHODESIA T h e Central AfricanJ ournal of Medicine

five cases of lung cancer among a total European population of the region of about 4,000. One was a miner from the Shabanie Asbestos Mine, one a small worker (gold) from Belingwe, two worked at Bannockburn station and the last case, a woman visitor, who had come to spend her last few days with her daughter. As this European hospital serves Shabani, Belingwe, Mashaba and Bannockburn, it is difficult to give a precise population figure, but Dr. Walker estimates it at about 4,000. The African population on the Shabanie Mine is about 4,000. The two European cases in the period 1960-65 (inclusive) were a miner from Mashaba and another from Shabani. During each of these periods three Africans de­veloped carcinoma of the lung.

Table VI

T otal N um ber of E uropean s and Af r ic a n s W ho D eveloped C arcino m a of t h e L u n g in

t h e S habani and M ashaba A reas

European African

1955-59 ............ 5 3

1960-65 ............ 2 3

Fig. 4— Third stage. Marked fibrosis in (he lungs with pleural reaction (192 months).

Fig. 5- Tuberculosis in an asbestos worker. Note plaque in left lung (360 months).

In our present series there was one probable case who had a carcinoma of the bronchus.

At the Mashaba Mine. Dr. A. G. Bradley reports in a personal communication that between June, 1961, and July, 1968, there were two cases of primary carcinoma of the lung noted in employees. One was an African found at Gaths Mine at autopsy to have had this lesion. The second case, a European, was found to have this disease in 1968. The Gaths Mine employs 1,650 Africans and 190 Europeans.

Again, at the Pangani Asbestos Mine in Fila- busi, which has been in operation since 1963, no case of lung cancer has been reported. There are about 44 Europeans and 428 Africans in employ­ment.

Thus in this study, while we are unable to show a relationship between the two diseases, we sus­pect that exposure to chrysotile may have some causal relation to the development of lung malignancy.

X -R ay A ppearances

Characteristic of the X-ray appearances of asbestosis is the ground glass mottling of the lung fields, especially in their lower sections, pleural thickening and a shaggy border of the heart. Some authorities report that calcified pleural plaques are frequently seen in asbestosis (Figs. 4, 5 and 6). For instance, Freundlich and Greening (1967) state that they occur in 21.4

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Sep i ember, 1969 ASBESTOS1S IN RHODESIA T i i k C r n r iiA L A f r i c a n

jO L 'IlN ’A L O F M FII1CI NIC

Fig. 6—Asbestosis with pleural calcification left side. (In employ 280 months.)

Fig- 7—Asbestosis. Severe pleural reaction on left side.

per cent, and a shaggy heart in 19.6 per cent, of cases. Other fairly frequent findings include Kerley’s B line in about 18 per cent, of workers, but this is not always associated with pleural or parenchymal, asbestosis.

Williams and Hugh-Jones (I960) report that in the majority of cases a higher degree of mottling is found in the lower zones than in the mid zones. There is little difference between the two sides. Although a shaggy border to the heart and a pleural reaction are regarded as common in asbestosis, these workers report them to be far less frequent than is commonly found.

Fig. 8—Note Ihe extensive fihrotic mass in each lung, proved histologically lo be due to asbestosis.

Hurwitz (1961) provides us with an excellent account of the radiological features of asbestosis in South Africa. Like other observers in America and elsewhere, he emphasises pleural changes in the form of uni- or bilateral parietal thickening to a varying degree. However, he brings to light a more specific pleural Jesion in the form of calcification in the typical pneumoconiotic plaques. These calcified plaques may be minimal or extensive, linear or distributed in irregular patterns. More often they are bilateral and more or less symmetrical, tending to occur mainly along the parietal pleurae, especially in the middle and lower zones. But he mentions that it is worth

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September, l% 9 ASBESTOS IS IN RHODESIA T h e C entral AfricanJ ournal of Medicine

noting that extensive areas of calcification may be observed along the anterior aspect. Further, both the diaphragmatic and mediastinal pleura are commonly involved. The plaques are different in appearance and character from silicotic ones, which, though not frequent, are located mainly in the upper zones towards the periphery of the lungs. Hurwitz also emphasises that in pure asbestosis associated '‘eggshell” lymph node cal­cification is singularly absent in contradistinction to that found in silicosis (Figs. 7 and 8).

The variability of the X-ray changes and the difficulty in trying to classify them into various stages has been stressed by others (Williams and Hugh-Jones, (960), Our X-ray findings were not quite the same as described by others. We did not see the frequent pleural thickening or pleural calcification that has been described in South Africa (SelikofT, 1965, and Sluis-Cremer, 1965). There were four cases somewhat similar in ap­pearance to those described by Selikoff. One had a marked left-sided pleural reaction. A few others had calcification, but in association with obvious old tuberculous disease, and the oosto- phrenic angles were not frequently impaired (right 9, left 14 in 96 patients). One case had a typical diaphragmatic adhesion. Emphysema was

big. 9—Tuberculosis in an asbestos miner. (In employ 215 months.)

noticed in the films of seven of the 39 cases with pure asbestosis.

The “shaggy appearance” of the heart is em­phasised by others (Pendergrass, 1958, and Webster, 1965). Only two rather equivocal examples of this were seen. No finding sug­gestive of cor pulmonale was encountered. In only five cases the heart shadow appeared ab­normal, looking like old hypertensive or valvular disease.

Nodules and infiltrates were seen quite fre­quently, but often in association with obvious tuberculous nodes, and in some cases seemed to be due solely to tuberculosis. There was little tendency for the nodules to coalesce, and when cavities were detected they seemed obviously of tuberculous origin rather than due to colliquative necrosis of large silicotic masses.

The association with tuberculosis was frequent and in some cases the entire appearance of the lung seemed best explained by tuberculosis alone (Figs. 9 and 10). Acid-fast bacilli were found in 29 out of 93 cases, in which the sputum was examined, Cavities were demonstrated in 22 cases and from the X-ray appearance alone the diagnosis of tuberculosis was made in 47 cases. The incidence of tuberculosis among asbestos miners does not seem to be greater than in non­mining male Africans ( Wester, personal communi­cation).

Significantly increased reticulation was noted in 39 cases, sometimes without and sometimes

Fig. 10—Tuberculosis in an asbestos miner.

September, 196y ASBESTOS IS IN RHODESIA Th e L knthai . A frican J ohknai . OF MKHIClilL

with noduialions. The ground glass appearance so frequently mentioned in the diagnosis of various forms of pneumoconiosis was seen in over half the cases and was usually patchy in appear­ance. There was nothing to suggest the presence of a pleural mesothelioma in any of these subjects and in only one case was the question raised of possible lung cancer; in all, old tubercu­lous nodes seemed more likely. This is in accord­ance with a report from Canada by Braun and Tracy (1958), who recorded no increase in the incidence of lung malignancy. In Canada, like in Rhodesia, the mineral is chrysotile. This does not agree with reports from South Africa (Col­lins, 1967; Sluis-Cremer, 1965, and Wagner el al., 1960).

T he Regions of I nvolvement We also studied radiologically the distribution

of the lesions of asbestosis in the lungs and com­pared these results with those found in miners considered to have tuberculosis who had worked at least five years in the asbestos industry.

Table VIIR adiological D istribu tio n of L e s io n s F o u n d in 24 M in er s W it h U ncom plicated A sbestosis

Right Left

Upper zone 4 3

Middle zone ............ ■ - - 15 14

Lower zone ............ ....... 18 12

Table VIIIR adiological D istribu tio n of L e s i o n s F o u n d i n 24 M in e r s Considered to H ave T ubercu­lo sis W it h F ive Y ears or O ver of Service in

A sbestos M in e s

Right Left

Upper zone ........................ 18 11

Middle zone ........................ 10 13

Lower zone .................... . 3 5

When one compares these two tables it will be observed that with pure asbestosis the lesions are found mostly in the middle and lower zones, whilst in tuberculosis they are mainly in the upper zones. Nevertheless, in many of the cases of pure asbestosis the lesions were fairly evenly distributed throughout the lungs.

In the seven cases of asbestosis in which the lesions were apparently confined to one lung, six were on the left side and one on the right. When asbestosis was accompanied hy tuberculosis the pattern changed to that shown in Table VIII.

Pendergrass (1958) reports a diminution in the superior-inferior distance of the chest in asbesto­sis. This finding was not noted in our cases.

S u m m a r y

(1) Our more frequent radiological findings were the presence of nodules, increased markings and a ground glass appearance in the lung fields. None of these seemed at all specific for asbestosis.

(2) Pleural involvement with or without cal­cification was not seen as frequently as we expected.

(3) The "shaggy heart" appearance is probably uncommon.

(4) No case of pleural mesothelioma was noted, nor was cancer of the lung of significance, as there was only one possible case in our series based on radiological evidence.

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Health, 17, 634.C o llin s , T. F. B. (1967). .S’. Afr. med. J., 41, 639. Dem y , N . G . & Adler, H. (1967). Amer. .1. Roentgen

and Radium Therapy, 100, 597.D oll, R. ( 1955), quoted in W agner, J. C., Sleggs, C. A,

and M akchand, P. (1960). Brit. J . indiist. M ed ., 17, 260.

F keundlich , I. M. & G reening , R. R.' (1967). Radio­logy, 89, 244.

H u r w itz , M. (1961). .4m,-i ./ Roentgen and RadiumTherapy, 85, 256.

Ly n ch , K . M . & Sm it h , W. A. (1935). Amer. .1. Cancer, 24, 56.

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Selikoee , I. J. (1965). Ann. New York Acad. Sci., 132, 215.

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623.W esTwater, M . L . PersoD.it com m unication.W illiam s, R. & H u g hJ o n es , P. (1960). Thorax, 15,

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