DISCUSSION

Theodore Cooper, Moderator National Heart and Lung Institute

Bethesda, Maryland

DR. LORIN KERR (United Mine Workers, Washington, D.C.) : Dr. Mc- Lintock, do I understand you correctly that when you went back and did the second x-rays, if the man who had been x-rayed five years previously was not employed at the time of the second go-round, then there was nothing with which to make a comparison? Since there was a sharp decrease in employ- ment, there would be a large group of men who would have been seen the first time, but were not, the second.

DR. J. S. MCLINTOCK: You are perfectly correct, Dr. Kerr, insofar as our routine x-ray scheme of every colliery is concerned. In our research scheme, however, the investigators are trying to do it in relation to the 25 collieries that were in the program.

DR. KERR: What about those figures then? Are they any different than the ones that you’re showing here?

DR. MCLINTOCK: We haven’t collected enough of them to give you any valid data.

DR. HARVEY PHELPS (Pueblo, Colo.): I believe it disadvantageous that specific mining tasks and smoking habits are not segregated in prevalence data. Also, longwall coal faces present special problems.

DR. MCLINTOCK: May I say that I entirely agree with Dr. Phelps about the importance of looking at the occupations. However, in Great Britain, because of our system of working, we do not seem to have men remain as long as you do in America in one occupation. Also, I would not like to leave you with the belief that I consider that it is impossible to suppress dust on longwall coal faces. I’m only suggesting that it is quite a different problem from what you have on the short wall.

DR. COOPER: How about the smokers and nonsmokers? DR. MCLINTOCK: There seems to be a suggestion of a relationship between

dust exposure to respirable dust, which was all that we had measured, and chronic bronchitis in men under the age of 45. But after the age of 45, the effect of cigarette smoking seemed to overwhelm anything that we might be able to find on the dust side.

QUESTION TO DR. MCLINTOCK: In England, do you have excessive P M F in the retired miner?

DR. MCLINTOCK: Among employed miners, approximately 25 % of those with Category 2 or more have PMF. My colleagues on pneumoconiosis panels suggest that before these men die, 50% of them have PMF. I think that this accords with your findings, too.

DR. RICHARD NAEYE: Let me ask one more question about nutritional status. There have been a lot of data from Great Britain relating nutrition to social class. In the United States, one has to go to the very lowest economic class before one finds objective evidences of undernutrition, as in pregnant mothers in this class.

With British mothers, one finds evidences of undernutrition appearing at intermediate and somewhat higher levels of social classes. I’m wondering about the nutritional status of British coal workers versus ours, since there is a well known relationship between nutritional status and infection.

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DR. MCLINTOCK: If the delegation that was present yesterday morning was representative of American coal miners, ours are better nourished. Nutri- tion in general is pretty good in Britain; among males, it is very difficult to find any overt signs of malnutrition, any clinical biochemical indicators of mal- nutrition, unless one gets to the very lowest socioeconomic classes. And here, I’m speaking of the Doss House occupants, where even beri-beri is found in Britain.

On the other hand, there is a very definite difference i; physique among various regions of Britain, which is obvious from the medical examination boards for national service during wartime. Even in a recent study that we have done of new entrants to coal mines-and here I’m speaking of the late teenager-we still found differences in physique. The Welsh miner, I should mention, is the smallest, has the poorest lung function, and so on.

DR. COOPER: Dr. Zahorski, would you comment on the smoking habits of this group?

DR. WITOLD W. ZAHORSKI: In this group, 65-80% of the miners are smokers. We find that in smokers, ventilatory disturbances are greater. In simple pneumoconiosis without smoking, disturbances are in most cases not observed.

DR. COOPER: If the incidence of smoking is that high, how do you explain the difference between the figures from Great Britain and your own? Do you think there is a genetic basis or a difference in geological features?

DR. NAEYE: I gathered from your presentation that your workers have less pneumoconiosis than British workers, and yet they are dying at an earlier age. I’d like to ask why?

Also, I notice the very interesting correlation between the inclination of your coal seams and the incidence or prevalence of pneumoconiosis. We have the same phenomenon in Pennsylvania. The more inclined the seam, the more severe the pneumoconiosis. This often has been ascribed to the fact that when the seam is inclined, more sand is groiind underneath train wheels and the workers come in contact with silica through this mechanism. What do you think is the mechanism in Poland?

DR. ZAHORSKI: I have presented the figure of 1.7% as the prevalence of pneumoconiosis in Poland. This represents only 60% of all cases. Additional cases are seen, but they have had experience in West Europe before being examined in our survey and do not necessarily represent reactions to Polish conditions.

With regard to sloping, Dr. Naeye’s observation is most interesting. DR. MCLINTOCK: May I, sir, first of all compliment Dr. Zahorski on

having a better drawing office than I have. But may I also take him to task for comparing prevalence in Poland and prevalence in Great Britain. I am not prepared to accept that prevalence can be compared in this way unless the readers have been tested and one is sure that they are measuring the same thing. I think Dr. Pendergrass would bear me out that even if two separate groups of film readers take the ILO category, read it, discuss it among themselves, and decide what their standards are, when they come together it is likely that their standards will be different.

DR. ZAHORSKI: I compared our data with British statistics simply to indi- cate that we approach the same problems. We, too, are alert to the difficulties of interobserver variations.

MR. MAURICE DEUL (Bureau of Mines, Pittsburgh, Pa.) : I have a question

Cooper: Discussion 337

and some comments relating to the apparently greater incidence of pneumo- coniosis where the coal mines are in beds that are thinner, that are sloping. This relates, I think, to two or three things, and may have a cause and effect or another kind of relationship that needs further study. In coal beds that are of higher rank, the tendency is for coal to be more highly structured, i.e., more highly polymerized. And the more highly polymerized the coal generally, the less its reactivity.

On the other hand, mineral matter incorporated into higher ranked coals tends to change in structure, so that silicates particularly tend to become layered or needle-like.

Now, the question of solubility at interfaces between coal and internal fluids is an interesting one. I know little about this and would like this con- ference to consider it. Certainly the relationship or interrelationship between mineral matter, which tends to be polar, and the internal body fluids is great. There would tend to be more reactivity and more reaction between the very fine mineral matter and the internal fluids.

Everything else being equal, the greater the amount of coal dust, the greater the amount of rock dust, and the greater the amount that tends to be in the lungs. But since the particles are often very small, they may be more difficult to demonstrate and identify.

The greater the slope and the thinner the coal beds, the more effort has to be put into mining this coal, especially where nonmechanized methods are used. Also, the greater the slope, the greater the problems in roof control. Therefore, a great deal more rock work has to be done. So this might in part account for the difference that Dr. Zahorski and Dr. Naeye have mentioned. I wonder whether these variations have been observed in other places.

DR. ZAHORSKI: This was only observation. This was not the essential factor, but I suppose that they are factors which could influence the prevalence of pneumoconiosis.

DR. COOPER: Do the coal miners in Poland have an excess of deaths from other causes, such as cancer or heart disease?

DR. ZAHORSKI: We do not have this impression from our studies. DR. ROSCOE YOUNG (Howard University, Washington, D.C.): I’d like to

ask Dr. Sari6 if he surveyed the incidence of tuberculosis in his country, par- ticularly with respect to complicated pneumoconiosis?

DR. MARKO SARIC: This was done usually at the same time when a survey was organized, for example, in the mines. The incidence rate of tuberculosis varied from mine to mine, but was usually 1-1.5 per thousand.

DR. COOPER: How about the smoking habits of this population with a low incidence of disease?

DR. SARIC: I only have data about miners who were reexamined. In the two mines on which I reported, 65% of the miners smoked, 11% were exsmokers, and 23-24% had no history of smoking. The average age in these mines was 38 years. This is more or less the same in other mines.

DR. NAEYE: There were a couple of mines with rather high levels of silica in the dust. Yet there was almost no complicated pneumoconiosis. This is quite surprising on the basis of our experience. How many years had those miners been underground and how many years of mining exposure had they had?

DR. SARIC: I showed not only the percentage of free silica, but the average dust concentration levels. You probably noted that in some of the mines the

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dust concentration level was rather low. This can be a factor. As I mentioned, however, in some of the’mines we had people with 20 years of exposure or even more. On the average, our miners are much younger than yours in the United States. The average age of our miners is between 35 and 40 years. Obviously, this factor can have some influence on the results.

DR. COOPER: Do they retire at some earlier age, such as before 55? DR. SARI^: They do, because about ten years ago, a law passed in our

country provided that one year of underground work was to be considered 1.5 years of work. Therefore, miners retire much earlier. In general, in our country, workers are supposed to retire after 40 years of work, generally at the age of 60, for men.

DR. COOPER: What is the pulmonary status of the retired group, compared with the average young group that’s underground right now?

DR. SARI^: It is difficult to be sure. There is the problem that you may lose a certain number of miners among those who retire. On the other hand, there is a rather good health service in these communities, so that I should say that cases of complicated coal workers’ pneumoconiosis would be notified by local doctors, especially because there is a disability insurance scheme. Nevertheless, I can’t say that some cases of complicated coal workers’ pneu- moconiosis were not overlooked.

DR. N. LEROY LAPP: For my enlightenment, why cannot the Reid Index be used in the Bantu? Is this a morphological difference by race or is there some other factor?

DR. I. WEBSTER: Our findings in the Bantu were reported at the 1969 Conference in Johannesburg, and we found that no matter what the age of the Bantu was, and no matter whether there was a history of chronic bron- chitis or not, all of the measurements of the bronchi in the Bantu fitted into the range in which Dr. Lynne Reid would have considered it to be chronic bronchitis. There seems to be a hyperplasia of the bronchial glands in the Bantu, making the Reid Index invalid.

DR. YOUNG: Since we couldn’t tell how long the Bantu abstained from work history in the interval, I wonder whether there was any difference in the smoking habits of the Bantu as compared to the Caucasian.

DR. WEBSTER: The European miner is usually a very heavy smoker. Coal mines are fiery, and the miners are not allowed to smoke underground. The Bantu does smoke and more of them are smoking today than before. But they do not smoke nearly as much as the white miners, although some of them use snuff quite extensively. But I would say that they smoke less than the white miners. Dr. Harington is here, and he would know a little bit more than I do about that.

DR. JOHN S. HARINGTON: I would entirely agree in principle about the smoking habits. I wish to discuss further the point which the previous ques- tioner raised. There is no doubt that the European habit of smoking the ordi- nary commercial cigarette as we know it is not practiced to any considerable extent among Africans, whether miners or not. They do, however, vary con- siderably by tribe. Quite a large proportion of miners might be expected to smoke various combinations of tobacco, such as handrolled cigarettes containing pipe tobacco. Certain groups would use pipes only. Or, again, combinations of these habits would be found. So one is faced here with a rather complex smoking pattern. As Dr. Webster has said, however, there is no really heavy smoking pattern such as we see in the European miner.

DR. IRVING J. SELIKOFF: Dr. Webster, is there any difference in the material

Cooper: Discussion 339

from the Bantu and the white miner populations that are received by your unit? Does the Bantu tend to be at work at time of death and the white miner perhaps not always at work at time of death, or is the duration from last employment the same in the two groups?

DR. WEBSTER: That’s a very good question. The Bantu does not have to be a t work for an autopsy examination to be carried out. But when they leave the mines, they go to their homelands, and in these distant regions an autopsy examination often may not be carried out. The chances of a n autopsy being carried out on a white miner are greater than for the Bantu, if they have left the mines. Still, quite often we d o get specimens from the various homeland regions which have been sent from an autopsy done in the country.

DR. COOPER: Did you indicate the causes of death of the 3,000 cases- were these pulmonary deaths that were autopsied?

DR. WEBSTER: No, sir. They were all deaths. We only received the cardio- respiratory organs. The causes of death are sometimes given to us, but they are usually fairly unreliable, and we haven’t analyzed them.

DR. COOPER: Is there a system of clinical observations of the two groups, or the whole group, from which subsequent anatomical correlation could be made?

DR. WEBSTER: N o white miner in South Africa can work in our mines unless he has a certificate of fitness from the Miners’ Medical Bureau. And in order to keep that valid, the miner has to be examined every year. The Bantu are examined when they apply for employment, and they are examined during their employment. The Bantu would not normally be currently examined in their homelands to the same extent as the white miners.

DR. PHILIP C. PRATT: I’m sure that the specimens in which you’ve described the morphology have also been analyzed chemically for total dust content and silica.

DR. WEBSTER: I regret very much, Dr. Pratt, that we have not examined these for silica content. This is in our research program, but has not been done.

DR. NAEYE: The incidence or prevalence of tuberculosis in the Bantu miners is certainly higher than that reported by anybody else here, or perhaps reported by anybody else in modern times. I’m curious to know whether this is incurred while a t work, or a t home. And i f it is incurred at work, is this due to the unique working conditons that your miners have, your Bantu miners, that have been so well publicized around the world?

DR. WEBSTER: Mr. Chairman, I’d just like to point out again, that of the tuberculous lesions I have reported here, the majority would not be detected on radiological examination. They are microscopic foci found in the lymph glands. They may be well-arrested tuberculous lesions and could not be diag- nosed clinically. It is because of the microscopic sections that we take that we find this higher incidence. I’m certain that if such sections were taken in the other populations, one would not find a difference in the tuberculous lesions. Most of the lesions are old and probably had been contracted before the men joined the mining industry.

DR. COOPER: What is the average age in the two groups? DR. WEBSTER: It is very difficult to tell the age of the Bantu. The average

age of the white miner would be somewhere around about 50 when he dies. DR. WARFIELD GARSON (United Mine Workers Retirement Fund, Pittsburgh,

P a , ) : Dr. Webster, with the observations you have made of the coal cuffing around the small vessels in the lung, I wonder if you have had occasion, there- fore, to look for more than just cor pultnonale as an end-stage, but have traced

340 Annals New York Academy of Sciences

backwards the effect of coal cuffing on blood vessels, particularly as it relates to breathlessness as a manifestation of coal workers’ pneumoconiosis in those miners in whom we find little or no x-ray evidence of a problem.

DR. WEBSTER: We do have cor pirlmonale as a cause of death, but this is usually found when emphysema is severe. One can find quite marked peri- vascular cuffing both in the coal worker and in the gold miner without any evidence of enlargement or hypertrophy of the right side of the heart.

DR. A. G. HEPPLESTON: I would like to take up the point that Dr. Garson has just raised. In coal workers’ simple pneumoconiosis, the dust that may be related to vessels and, secondly, to respiratory bronchials does not lead to vascular obstruction at that site. However, in the complicated pneumoconiosis of coal workers, extensive vascular occlusion can be demonstrated by injection techniques, and I think we ought to distinguish between the simple and the complicated forms because it’s in the latter that you’re more likely to develop chronic cor pulmonale.

DR. WEBSTER: I fully agree. DR. HARINGTON: I wonder if Dr. Webster could tell us whether there was

any evidence of other occupations, particularly other mining, in the two groups he’s considered.

DR. WEBSTER: We excluded as far as possible those cases of white miners with a history of other mining. We have not included here any white miner for whom there had been gold or platinum or asbestos service.

Where we found mixed service in the Bantu, that has also been excluded from this series. But I think, as Dr. Harington himself will realize, the history which we get from the Bantu very often does not disclose previous mining service.

DR. GARSON: I would like to pursue, both with Dr. Webster and with Dr. Heppleston, the vascular problem, particularly because they point out that in simple pneumoconiosis there is no obstruction of the blood vessels. I’m much more concerned about the problem that the miner has in breathing than with the ability to show obstruction such as one finds in PMF. I’m reminded that in a series in mid-Appalachia, at Beckley, a series of 150 unselected autopsies in soft coal workers showed 40% with massive right heart enlarge- ment or ventricular hypertrophy. That was by weight measurement. The clinical diagnosis of right ventricular failure was made in 30%. Approximately one out of every five of these people studied had no explanation for their heart changes other than the one abnormality one could find, simple pneumoconiosis. This might be a simple association, but in view of the location of the coal dust, in view of the likelihood of hypertension, particularly on exercise, I suggest that we need to explore this further. I do realize this is controversial. I wonder if in South Africa you have done cardiac catheterizations and exercising of living coal miners with minimal x-ray findings but maximal ventilatory com- plaints, to see if there was any correlation.

DR. WEBSTER: We have not carried out any catheterization studies on the miners coming to the Miners’ Medical Bureau. Certain physiological tests are carried out at the Central Miners’ Medical Bureau. At the subbureau in Dundee, which is one of the centers of the Natal Coal Fields, physiological tests are not carried out. From some other areas, if the miner comes to the Central Bureau, there are physiological tests, but I haven’t those records with me.

We will get into the analysis of the state of the heart in all of these cases, and I could let Dr. Garson know of our findings.

Cooper: Discussion 341

DR. W. K. C. MORGAN: We have done cardiac-catheterization, in 47 miners at rest and exercise. They were deliberately selected from southern West Virginia where these other cases came from, and many had been studied there previously. Not all of them showed pneumoconiosis on x-ray and most of them had normal ventilatory studies. But they did all complain of symptoms.

When we catheterized them, we could only find three subjects who had minimal elevations of pulmonary pressure either at rest or exercise in whom you could not account for this on the basis either of progressive massive fibrosis or of obstructive airways disease. I think these findings have been substantiated by Dr. Kremer, by Dr. Navratil in Czechoslovakia and by others. In fact, we are substantiating their findings, since they had already done this.

DR. COOPER: You feel there is no deficit in circulatory reserve except in the presence of PMF?

DR. MORGAN: Or obstructive airways disease. DR. M. GLICK: Perhaps I could add to that. We haven’t done any studies

in live miners, but in our postmortem series we did discover that people with simple pneumoconiosis had no increase in the thickness of the right ventricular wall unless some other factor was present, such as chronic obstructive disease, pulmonary fibrosis from previous inflammatory disease, old inactive tuberculosis or pleural adhesions.

QUESTION TO DR. WEBSTER: Is there any respiratory diseases associated with diamond mining?

DR. WEBSTER: We’ve found one very doubtful case where there was nodulation in a miner inhaling Kimberly dust, but I think in retrospect that that was a healed tuberculous lesion. We have inoculated Kimberly dust and also dust from the Premiere Diamond Mine and the Finch Diamond Mine, and we can usually produce, with the Kimberly, some change: some of the animals did show a grade three lesion. So Kimberly dust could be fibrogenic, although one would have to have long exposure. So far, none of our diamond miners have shown this.

DR. NAEYE: I notice that you referred to both panacinar and centrilobular emphysema in your cases. The pathogenesis of the emphysema in the United States is a very controversial matter. How do you differentiate between panacinar emphysema and consolidated or confluent centrilobular emphysema? This has great importance because one can make a case for relationship between dust exposure and centrilobular emphysema, but not really for panacinar.

DR. GLICK: Well, panacinar emphysema is the emphysema which we find in the whole of the community, but it also, of course, occurs in coal miners. The Gough dust focal emphysema is the one on which we concentrate insofar as coal dust exposure is concerned. We do accept the fact that this can be aggravated by chronic bronchitis into centrilobular emphysema.

DR. NAEYE: Are you saying that the coal miner has a greater prevalence of chronic bronchitis and of both forms of emphysema than the general population, that it is going down in New South Wales, but in the general population it’s going up?

DR. GLICK: No, I’m just saying the occurrence of emphysema is not an uncommon thing outside coal miners.

DR. COOPER: Do you experience what Dr. Enterline showed this morning- that there is a higher excess death rate from a variety of causes besides pulmo- nary in the coal miner?

DR. GLICK: This is not an impression we have.