Document 1N1zppgyj6myak87BDyEjJ3Z

FILE NAME: Neighborhood Exposures (NE) DATE: 1963 Jan DOC#: NE005 DOCUMENT DESCRIPTION: Medical Journal Article - Asbestos as a Modern Urban Hazard s E a H J .T H j7 % S lan u arie 1963 S .A . T ydskrif vir G eneeskunde 77 " j ASBESTOS AS A MODERN URBAN HAZARD J. G. T homson, R. O. C. K aschula, and R. R. M acD onald Department of Pathology, Medical School, University of Cape Town reliminary report by one of us has been published he association between mesothelioma of pleura or oneum and a limited pulmonary asbestosis, confined le basal 1 cm. or so of the lower lobes, in people had no history of occupational or industrial exposure bestos.1 It was stressed that these cases had no clinical diological evidence of asbestosis, and that the limited asbestosis was usually missed at autopsy. Even if lungs were examined microscopically the local tosis would again be missed unless sections were i from the bases of the lower lobes. The association regarded as an actio'ogical one in that there was y an asbestosis of carcinogenic concentration, effective 16 pleura or on the peritoneum, which is no more a few millimetres distant over the diaphragm. No :hi of any size are present in this thin strip of basal only bronchioles without glands; and consequently mchial carcinoma, the more usual result in classical trial asbestosis, is Dot to be expected, bestos fibres in the lung, or some of them, are coni into asbestos bodies by the deposition of yellow les of protein and iron, producing an easily recognized juiie characteristic structure. But before this happens , if not most, of the very thin and sharp asbestos -nd to move down towards the bases, owing to J 'emcnts and gravity. Once the fibre has become bestos body it is unlikely to move further; it is too to be transported by lymphatics and its sharp points ow blunted by the protein globules. ___ s enormously increased world consumption of los, from 300,000 tons in 1934 to 2,400,000 tons in is used in a wide variety of industrial products, obvious ones such as asbestos roofing, roof tiies, gs, floor tiles, pipe insulation and electrical insulato less obvious ones where asbestos is added to all of plastic materials, cement, etc. It is possible for manufacturing, selling and using these products to : asbestos fibres, although their occupations are in al not labelled or recognized as ones in which os is a hazard to be anticipated. We do not knowpercentage of the world's consumption of asbestos id in factories other than those labelled asbestos ies, but suspect that it is becoming more and more icant 1her, it is possible that the inhalation of a relatively number of asbestos fibres over a long period, several or indeed a lifetime, may result in a focal con ation at the lung bases, in people who have no ational risk from asbestos, merely because asbestos inly used in towns and cities and is a likely conant of the air. were unable to find any figures in the literature ` frequency of asbestos bodies in the lungs in routine sies, and in I960 an investigation was started to see 'alation of asbestos was indeed an urban hazard, y and establish some sort of standard frequency imparison with any change in the future. materials and methods From each lung a smear was made on a 3 x l inch (7-5 by 2 5 cm.) microscope slide, usually consisting mainly of blood, and quite thick. This was air-dried, flooded with xylol, and mounted with balsam or balsam substitute under a large coverglass. Initially the smears were made from apex to base of lung, but the majority were from the bases of the lower lobes only. The golden-yellow asbestos bodies were readily seen with the low-power of the microscope (16 mm. objective), and confirmed by the 4 mm. objective. Counting (on one slide only) was done by low-power fields, and in those re corded as negative 300 low-power fields were examined. Rarely we saw a small black carbon particle with a yellow coating, usually circular in form and readily distinguished from the true asbestos body, and nothing was seen in these smears giving any real resemblance to a genuine asbestos body. Smears were taken from consecutive autopsies from the Groote Scbuur Hospital. Cape Town, on subjects aged 15 years and over to a total of 500, of which 60% were males. RESULTS The method used to demonstrate these asbestos bodies is subject to certain variables, the most important of which is the extent to which pulmonary oedema is present. When it is marked enough, fluid from a small number of air vesicles is sufficient to cover the slide, and a severe degree of basal pulmonary congestion will have a similar but less marked effect. None of the lungs thus examined was from medicolegal autopsies (many of these were for people dying suddenly), and few lungs in this series were without some pulmonary oedema and congestion. The amount of lung thus examined for asbestos bodies w-as trifling, and the positive findings should be assessed in that light. We suspect that the percentage of lungs showing these asbestos bodies could be brought to much higher figures if larger samples of lung juice were examined. Even so, the per centage positive is surprisingly high, and we can regard our suspicions that inhalation of asbestos is a hazard of modern urban life as having been confirmed. Over one-quarter of the lungs of 500 consecutive autopsies on subjects of 15 years and over showed asbestos bodies by the method used (26-4% -- 132 cases) -- a much higher figure than anticipated when the investigation was started. We expected a higher incidence in the male, and this was found (30%), but the proportion of females w-hose lungs were positive was also strikingly high (20%) (Tabic I). Further differences" were evident in th e'th re e racial groups in Cape Town, from 16% in the Whites to 58% in the Africans, with the Coloureds occupying an inter mediate position with 23-7% of autopsies positive for asbestos bodies. In males only (306 cases), these racial differences in frequency were more evident -- Whites 17-9%, Coloureds 29-2% and Africans 61-7%. In both sexes and in all three racial groups there is the anticipated rise in frequency with age (Table II), ranging from one positive in the under-25-years group (4-3 %) to approximately 30% in those over 65 years of age. One surprising feature is a lower frequency in the 45 - 54 year age group, present in both sexes, as shown in Fig. 1. 78 S.A. Medical J ournal 19 January 196J TABLE I. THE FREQUENCY OF ASBESTOS BODIES IN BASAL LUNG SMEARS IN THE THREE RACIAL GROUPS Whites Coloureds Male Cases examined.................................. 140 Cases p o s i t iv e ..................................17-9%(25) Female 84 14-3%<12) Total 224 I65%<37) Male 106 29-2% <31> Female 84 J6-7%(I4> Africans All races Mate Cases examined.................................. 60 Cases p o s i t iv e ..................................61-7% (37) Female 26 50% (13) Total 86 58-1 % (50) Male 306 30-4% (93) Female 94 20 0% (39) Total 190 23-7% (45) 4 Tota! i 26-4% (132) 5 Age groups (years) f Positive 15--24 t Negative f Positive 25--34 ( Negative 35-44 Positive Negative {("Positive 45--54 ( Negative Positive -- --Negative {f Positive Over 65 ( ^Negative TABLE II. THE FREQUENCY OF ASBESTOS BODIES IN BASAL LL'NG SMEARS IN AGE GROUPS Male 0% (0) 100% (4) 28-6% (2) 71-4% (5) 22-2% (2) 77-8% (7) & I% 3). 90 9% (30) 19-4% (7) 80-6% (29) 21-6% (11) 78-4% (40) Whites Female 0% (0) 100% (2) 33-3% (2) 66-7% (4) 0% (0) 100% (6) dl-1% O) 88-9% (8) 16% (4) 84% (21) 13-9% (5) 86-1% (31) Coloureds Total 0% (0) Male 0% (0) Female 0% (0) 100% (6) 100% (7) 100% (5) 30-8% (4) 13-3% (2) 12-5% (1) 69-2% (9) 86-7% (13) 87-5% (7) 13-3% (2) 38-2% (8) 9-5% (2) 86-7% (13) 61 8% (13) 90-5% (19) 9-5% (4) 20-0% (5) 6-7% (1) 90-5% (38) 80 0% (20) 93-3% (14) 18-0%(1J) _36:8% (7)__ - 29-4% (5)- 82-0% (50) 63-2% (12) 70-6% (12) 20-8% (16) 47-4% (9) 27-8% (5) 79-2% (71) 52-6% (10) 72-2% (13) Total 0 % (0) 100% (12); 13 0% (3) 87-0% (20) 23-8% (10). 76-2% (32) 15 0% (6)J 85 0% (34)4 33-3% (12) 66-7% (24)4 37-8% (14)i 62-2% (23); Age groups (years) f Positive 15--24 t Negative f Positive 25--34 < I Negative f Positive 35--44 ^Negative f Positive 45--54 ( (_Negative f Positive 55--64 ( (Negative f Positive Over 65( ( Negative Male 25-0% 0 ) 75 0% (3) 50% (4) 50% (4) 43-8% (7) 56-2% (9) 78-6% (11) 21-4% (3) 77-0% (10) 23-0% (3) 80-0% (4) 20-0% (1) Africans Female 0% (0) 100% (1) 33-3% (1) 66-7% (2) 60-0% (3) 40-0% (2) 28-6% (2) 71-4% (5) 57-2% (4) 42-8% (3) 100% (3) 0% (0) Total Male 20-0% (1)> 6-7% (I) 80-0% (4) 93-3% (14) 45-5% (5) 26-6 % (8) 54-5% (6) 73-4% (22) 47-6%"(10) *37-1% (17) 52-4% (U) 62-9% (29) 61-9% (13) 26-4% (19) 38-1 % (8) 73-6% (53) 70-0% (14) - 35-3% (24) 30-0% (6) 64-7% (44) 87-5 % (7) 32-0% (24) 12-5% (1) 68-0% (51) All races Female 0% (0) 100% (8) 23-5% (4) 76-5% (13) 15-6%' (5) 84-4% (27) 12-9% (4) 87-1% (27) 26-5% (13) 73-5% (36) 22-8% (13) 77-2% (44) Total 4-3% (I)| 95-6% (22| 25-6% (12)] 74-4% (3J)| 28-2% (22)] 71- 8% (56)i 22-4% (23? 77-6% m . -J 31-6% (37)] 68-4% (S); 28-0% (3# 72- 0% (9% 19 1963 S.A. T ydskrif vir G eneeskunde 79 Fig. I. Percentage of cases positive for asbestos bodies in age groups (all races). Fig. 2. Percentage of cases positive for asbestos bodies in age groups (males only). Ii nuicx only (306 cases) this is striking in Whites and v.loured', but in Africans the drop appears one decade carher iFig. 2). and is based on smaller numbers. The # ppc.iMives suggest that there are two curves: that of the . ung which, if extrapolated, would reach 100% by the i;c ot oD. and that of those two decades older who were .-s exposed to the inhalation of asbestos fibres in their ...:h and avoided the undue exposure from 45 years -i*.trds Otherwise we would have to presume that after -,f jge of 35 a significant number of formed asbestos lose their encrustation of protein and iron and to the state of asbestos fibres, in which form they uld not be seen or recognized in smears. Another .-svhihti. just as difficult to establish or to refute, is that the older age groups there is a less marked or slower Tispoitsc to the presence of asbestos fibres, and a smaller ' ,~ portion of those inhaled is converted ditto asbestos *sd C' I`ere can be little doubt that those under the age of - have had better. opportunities of inhaling asbestos_ : *"ts titan the older age groups in their first 35 years. * nji to the increased and more widespread use of ntvstos 1he world consumption of asbestos 35 years ago L-xx than one-eighth of what it is today, and the "rw's and public buildings in Cape Town generally '--toned relatively little asbestos. The city has since more doubled in size and population, and the new buildings, r-K.* and private, contain much larger quantities of to-'ses-ox in various forms. In addition, much of the in--'trx using asbestos in this area is of new growth or r.f.: development, as it is in almost every part of the rx'crm/ej world, in conformity with the marked increase in world consumption of asbestos in the last 30 years. It is not difficult to suggest reasons why those of 45 years and older at death did not inhale as many fibres as did those in the younger age groups in the same period of time. A higher proportion of these older people would not be employed in occupations involving hard physical work as is required in the manufacture, handling or use of many asbestos-containing products, more would be in administrative posts, and some would be retired. What are the possible means by which asbestos fibres are inhaled to produce the asbestos bodies? Firstly, we have those employed in asbestos factories or, in South Africa at least, as pointed out recently by Wagner et a l those who work in asbestos mines or who live in the vicinity of the mines or where the asbestos from the mines is treated or handled. This is of necessity a restricted group. Secondly, we have those who may be exposed to asbestos fibres in factories not designated asbestos factories, where asbestos is used. These constitute a surprisingly large and ever-increasing group, such as cement works (asbestos cement), and all the factories where asbestos is used in the manufacture of asbestos roofing, tiles, millboard, friction materials such as brake linings, ceiling boards, insulation and packing for pipes and boilers, for electrical insulation, and the many other ways in which asbestos is employed as an addition to all sorts of plastic materials. A much larger group of people who deal with or handle such materials may be similarly exposed to varying degrees, ranging from the occupational exposure of builders and builders' labourers to the handyman in his home work shop. For example, a garage worker would not ordinarily be regarded as a candidate for asbestosis of any degree, yet Brugsch and Bavley' reported recently pulmonary asbestosis in a garage worker employed in spraying underbody coating containing 50% of asbestos. We suspect that the number of people in a modern urban community who are thus theoreti cally or practically liable to inhale asbestos fibres is a very CONCENTRATION OF ASBESTOS BODIES IN BASAL LUNG SMEARS Whites 'Vsu, hi'ilx in 31-300 L.P.Fs. .. ''csi.xx hod> in 10-30 L.P.Fs. 'Vkos hodx in 2-9 L.P.Fs. *t S-Jn ' asbestos bodv per 2 L.P.Fs. Male Female Total Male 16 9 25 21 4 2 6 4 4 1 5 3 1 0 1 3 Africans i' :" Fodx in 31-300 L.P.Fs. ^'rsi. x b.vK in KhI> in 210-93L0.PL..FPs.F. s. an I asbestos bodx per 2 L.P.Fs. .... Male 21 9 5 - 2 L.P.Fs. Female 1) 2 0 0 Low-power fields. Total 32 11 5 2 Male 58 17 12 6 Coloureds Female 10 1 3 0 All races Female 30 5 4 0 Total 31 5 6 3 Total 88 22 16 6 80 S .A . Medical J ournal 19 January 196j significant percentage of the population, but cannot even put forward a guess as to what the figure is. Lastly, we have those with employments not obviously associated with asbestos. These constitute presumably the largest group of all, yet the results of this investigation clearly indicate that they also inhale asbestos fibres. To try and place our positive cases into these three groups would appear an impossible task, since details of occupation are meagre, and in any case many of the Coloureds and Africans have had varied occupations and only the last is noted. But in Cape Town the occupations of the three racial groups are restricted to a greater extent than in most cities. There are virtually no labourers who are White, and the occupations of the African males have a relatively narrow range; those of African females are narrower still. A crude assessment of the relative number of asbestos bodies is given in Table III. It should be stressed that these are quantitative only to the bases of the lungs and not to the lungs as a whole. In the great majority, over 80% of the positive cases, the bodies were scanty, one body in 10- 300 low-power fields. In 22 cases, 4-4% of those examined and 6% of the males, the asbestos bodies were numerous, from more than one per low-power field to 1 in 9 low-power fields. These are likely to be cases in which industrial or occupational exposure to asbestos has been present, and if that inference is correct, it is disturbing that 1 in 17 of the males of the hospital population of Cape Town of 15 years and over should be thus affected. The admissions to the Groote Schuur Hospital are fully representative of all ethnic groups in Cape Town, but not perhaps of all social groups in the Whites. In Cape Town African females are rarely employed except as domestic secants, -%nd, as expected, none are found in the group with abundant asbestos bodies. Only 4 were females, while 18 were males, a finding again in favour of occupational exposure as the explanation. Unfortunately tissue for microscopical examination was not taken as a routine from the bases of the lungs, and a precise correlation between the presence of asbestos bodies and a limited basal asbestosis is not possible. But in all cases sections frem the lungs were available for study, and 3 examples of ordinary classical asbestosis were found, 1 mild and 2 of moderate severity. In only 1 of these was a history of exposure to asbestos obtained, one year's employment in an asbestos factory 15 years before his death from lobar pneumonia, and that was obtained from relatives as a result of persistent enquiry. In 2 further cases sections had been taken from the lung bases and both showed a limited basal asbestosis with bilateral basal pleural thickening, but the lungs elsewhere were free from fibrosis, and showed very scanty asbestos bodies. Of the remaining 17 cases in this group we do not know howmany would have shown this basal asbestosis had sections from the lung bases been available for histological examination. All one can say is that in the sections of lung taken at autopsy from areas other than the bases, asbestos bodies, usually scanty, were demonstrated in 9, but in none was there fibrosis or pulmonary asbestosis. The fact that lung smears from these 17 cases showed asbestos bodies to be as numerous as in the smears from 3 cases of classical asbestosis and 2 of basal asbestosis, leads us to suspect that most would have shown the basal f asbestosis had sections been taken from the lung basts. We find it difficult to believe that the majority of those with abundant asbestos bodies worked in asbestos factories, though no investigation of their occupations during their lifetime was undertaken. Only 1 was a builder, and no other of the occupations given indicated clearly the possibility of exposure to asbestos. We presume that most of them at some time or other came into the second group, and had contact with asbestos or asbestos-containinj products in some of the varied occupations alreadj mentioned -- a conclusion that is significant enough. U they were not so exposed occupationally, the findingi are even more significant, and even more disturbing though it should be emphasized that only in the 2 ca$a of classical asbestosis of moderate severity pulmonary disability was present, and in none of the others were the pulmonary lesions in any way responsible for death. But perhaps the most significant finding is the larp proportion of cases in which fewer asbestos bodies wen demonstrated -- 1 in 4 of all the remaining autopsies. U most of these the bodies were scanty, but quite character istic, and we wisb to stress that there are no grounds fa regarding these as pseudo-asbestos bodies merely because their presence may be regarded as difficult to explain. We do not think that there is any difficulty in explaininj their presence, and indeed would go so far as to say that their absence would be the more remarkable finding it the average urban dweller of adult age in westernized communities. In recent years the term `asbestos body' ha been altered by some to `asbestosis body', an unfortunate and unwarranted change, because the great majority o! lungs which show- asbestos bodies have no pulmonan asbestosis at all, as these findings clearly demonstrate. The varying frequencies in the three racial groups and the two sexes give some indication of the means by whid the asbestos fibres are inhaled. The overall positive figures for the sexes are 30% male to 20% female. If we exclude those with abundant asbestos bodies as being the result of occupational exposure, the resulting figures show little variation between the sexes in Whites and Africans: Whitt males White females 13-3%; African males 57% African females 50%, but the difference in the Coloured! is increased: Coloured males 25%, Coloured females 13-6% i We find almost identical figures for the Whites, mak and female, and the female Coloureds -- 14-8%, 13-3% and 13-6,J.> respectively. Are we justified in presuming th* this is the environmental base-line in Cape Town, nd resulting from occupation, but determined entirely b? asbestos fibres in the air? The numbers on which the* figures are based are not large, but together are signifi cantly lower than the other 3 groups with higher fre quencies (P = < 001). And what are the explanation! of the much higher rates in Coloured males and African! of both sexes? Occupations with possible exposure asbestos, such as building, may account for both the male groups, but not for the African females. Then environment, largely restricted to native locations, is tlx only explanation left to us. i If we assume, as is likely, that most of those with scant; asbestos bodies did not develop them as a result of the* employment, we are left with the home and the air d 4 Januarie 1963 S . A . T Y D S K R I F VI R G E N E E S K U N D E 81 . city s the only possible sources for the asbestos res. !n the modern home there is no lack of theoretical ss:--'Ves- Asbestos roofing or roof tiles, ceilings and o. Js are common enough, and the last at least must subjected to wear and liberation of asbestos fibres, .bestos-insulated central heating pipes, so common in the rthem hemisphere, are virtually absent in Cape Town mes, but the asbestos-insulating pad in domestic irons almost universal and usually is made in a soft, friable i readily disintegrating form. But under ordinary conions it would seem unlikely that many asbestos fibres inhaled in the average home. The air of the street ms a more probable source. The average motor vehicle ars out 3 or 4 sets of brake linings in its lifetime, and y consist mainly of asbestos, which is ground to dust the linings wear. This alone would involve in most es the discharge of tons of asbestos dust in the streets ry year. The disintegration by natural weathering of estos-containing products from car underbody coating asbestos cement roofing must again result in asbestos es getting in the air of towns and cities, tut'perbaps the most important factor is that asbestos dually indestructible. It resists heat, alkalis, acids and er means by which materials are altered chemically or sically, and mechanical disintegration merely results he production of finer fibres, more liable to be inhaled, ! more dangerous when inhaled than larger fibres, wever one assesses the hazard of inhaling asbestos es, as it exists today, as a trifling matter or as a entially significant one, it must become greater with years. The half-life of strontium 90 is 28 years, but half-life of the asbestos fibre is an infinity of years, a * '5,000 tons of asbestos used each year are added th. .illions of tons used in previous years, and even 3 small proportion becomes available as an air-con.inant in towns, the actual amount will increase, as more estos accumulates ort the. surface of the earth. The jral weathering and disintegration of some asbestostaining products is likely to be very slow, but many relatively new, and may not be as long-lasting as ected. We can only guess what proportion of air-borne estos fibres is rendered innocuous by dispersal or re'ed by fresh or salt water, but whatever the proportion, ; likely to be one that is more or less fixed, and we not think that the total amount of air-borne asbestos es in cities will do other than increase. v'Ve do not know of any published figures from other s of the world with which our findings can be com- ' d, but the high frequency of asbestos bodies in routine 'psies is not confined to Cape Town. One of us ated a similar investigation in 1961 in Miami, Florida, V, and even higher positive figures are being obtained. - ; s almost to be expected since proportionately more hat city is of recent growth w'ith a high asbestos =nt of the buildings, and the United StaLes accounts roughly over a third of the world's consumption of stos. We would suspect that even higher figures would >btained in Los Angeles. is all too easy to go to extremes in discussing these !ngs. They could be dismissed as a pathological isity of no practical significance, supported by the fact that in only 3 of the 132 cases positive for asbestos bodies was there associated pulmonary fibrosis and dis ability. and in none was there an associated mesothelioma of pleura or peritoneum. But 5 such cases were seen in the same autopsy service in the previous 3 years, and, going to the other extreme, a lurid picture could be painted of what conditions might be in 30 years' lime, when the accumulation of so much asbestos in towns would lead to much higher concentrations of asbestos fibres in the air. The results of life-long inhalations of these fibres might be almost universal basal asbestosis in adults, and a frequency of mesothelioma of pleura or peritoneum higher than that of bronchial carcinoma today. It could be added that even if the hazard were then appreciated, and all mining and utilization of asbestos ceased, there might be no significant reduction of the air contamination, owing to the indestructibility of the asbestos already mined and used, and its inevitable weathering and disintegration with time. The present findings clearly demonstrate that asbestos fibres are being inhaled by urban dwellers, but not in amounts sufficient to produce pulmonary lesions or dis ability. In 6% of hospital autopsies in males aged 15 years and over, a high basal concentration of asbestos bodies is demonstrated, suggesting that industrial exposure to asbestos is more widespread than expected. It would seem almost inevitable that in the future the urban dweller will be exposed to a higher concentration of asbestos fibres. We do not anticipate that this will lead to aD increase in classical pulmonary asbestosis, but more cases of basal asbestosis would seem almost inevitable. Indeed, even if there is no significant increase in the amount of asbestos fibres in the air, the younger urban dweller will have a Hfetime's'r-i'xpoTlire available for concentration at the lung bases, unlike most of those of over 50 years of age today, who, in their earlier years, bad little opportunity of inhaling asbestos fibres. If we are correct in regarding basal asbestosis as the main aetiological factor in mesothelioma of pleura or peritoneum,1 an increase in this tumour would also follow. This possibility is the main justification for the title of this paper. SUMMARY In smears from lung bases from 500 consecutive autopsies in subjects of 15 years or over, asbestos bodies were found in 30'-. of the males and 20i of the females. In most cases this would appear to be the result of con tamination of the urban atmosphere, and the bodies were scanty and not associated with pulmonary changes. In 6% of the males the bodies were numerous and were presumably of occupational origin. An increase in the amount of urban air contamination w-ould seem inevitable in view of the increasing consumption and diversity of uses of asbestos, and of its virtual indestruc tibility. The tendency for asbestos fibres to concentrate in the bases --of the lower lobes of the lungs produces a cumulative effect, and an increase in the frequency of basal asbestosis is probable. This basal asbestosis does not result in pulmonary disease or disability, but appears to be of aetiological significance in mesothelioma of pleura or peritoneum. An increase in this tumour is forecast, and this is suggested as the main ground for regarding asbestos as an urban hazard. REFERENCES 1. Thom son. J. G . (1962): S.A fr. M ed. !.. Ai, 7S9. 2. W inner. J. C ., Slcggs, C . A. and M archand, P . (1960): Brit. J . Industr. Med. P . 260. 3. Bru^sch. H . G . and BarJey, H . 0961): New Engl. J. M ed., 265, 379.