Asbestos and the urban dweller

Our plain-English summary of Asbestos and the urban dweller, by J.G. Thomson (Annals of the New York Academy of Sciences, 1965).

The study

• Author: J.G. Thomson
• Journal: Annals of the New York Academy of Sciences
• Published: 1965;132(1):196-214
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002511).

Abstract

The extent of inhalation of asbestos fibers by urban dwellers was investigated by counting asbestos bodies in smears from the lung bases from 500 consecutive autopsies in subjects over the age of 15 in Cape Town, South Africa, and 500 in Miami, Florida. The results were similar in the two cities, and no less than 30 per cent of the males and 20 per cent of the females showed asbestos bodies. In 85 per cent of the positive cases the bodies were scanty, were not associated with pulmonary changes, and were regarded as the result of contamination of the urban atmosphere. In six per cent of all the males examined the bodies were numerous and were presumably of occupational origin.

The tendency for asbestos fibers too long to be phagocytosed to move downwards by gravity before they become asbestos bodies leads to concentration at the lung bases, and small doses can have a cumulative effect. An increase in the amount of urban air contamination would seem inevitable in view of the increasing consumption and diversity of uses of asbestos and of its virtual indestructibility, and an increase in basal asbestosis is suggested as a possible future development. As a limited basal asbestosis may be associated with malignant mesothelioma of pleura and peritoneum an increase in this tumour is forecast as the main ground for regarding asbestos as a potential urban hazard. While that view is conjectural, the finding of abundant asbestos bodies in the lung bases of 1 in 17 of the male hospital population suggests that the occupational hazard from asbestos is greater and more diversified than is at present realized.

The main object of this work is to draw attention to the effects of a relatively new development, the widespread use of asbestos in cities, and to stimulate the obtaining of comparable figures from other parts of the world, to establish the baselines of urban asbestos inhalation of today, and enable us to detect increases in the future.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

The author looked for asbestos bodies (protein-coated asbestos fibers) in lungs at autopsy to learn how far city dwellers inhale asbestos. Lung-base smears were examined at 500 consecutive autopsies of people over 15 in Cape Town, South Africa, and 500 in Miami, Florida; not all were urban dwellers. In Cape Town, 26.4 per cent (132 cases) were positive: 30 per cent of males and 20 per cent of females. Positives were 16 per cent in Whites, 23.7 per cent in Coloureds and 58 per cent in Africans. The author linked this mainly to occupation, and for African women to asbestos-roofed homes without ceilings. In Miami, 31.6 per cent of males and 20.4 per cent of females were positive. Bodies were scanty in 85 per cent of positive cases. Of 40 cases with numerous bodies, 36 were men and four had classical asbestosis. The author judged scanty bodies of no significance as a cause of lung fibrosis or disability. Whether small amounts left 30 years or more cause cancer was called the main unknown. A possible future rise in mesothelioma was called conjectural.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Autopsy survey: counting asbestos bodies in smears taken from the lung bases at consecutive autopsies in two cities
• Who was studied: 500 consecutive autopsies of people over age 15 in Cape Town, South Africa (begun 1960): 306 males and 194 females; 224 Whites (Caucasians), 190 Coloureds, 86 Africans (Bantu). Also 500 consecutive autopsies in Miami, Florida (begun 1961): 304 males and 196 females, about one-quarter Negro. Not all patients were urban dwellers; some came from outlying villages and districts.
• Exposure: Exposure was not measured. Asbestos bodies in the lung bases were used as a marker that asbestos fibers had been inhaled. No fiber type was identified. The author discussed possible sources, including occupations using asbestos products, asbestos roofing in homes, and brake and clutch linings wearing down in city streets.
• Main results:
  • Cape Town, all 500 autopsies: 26.4 per cent (132 cases) had asbestos bodies.
  • Cape Town by sex: 30 per cent of males and 20 per cent of females were positive.
  • Cape Town by race: 16 per cent of Whites, 23.7 per cent of Coloureds and 58 per cent of Africans were positive.
  • Cape Town males only: Whites 17.9 per cent, Coloureds 29.2 per cent (printed as '208'; Table 1 gives 29.2%), African Bantu 61.7 per cent.
  • Cape Town African (Bantu) females: 50 per cent were positive, all with scanty or very scanty bodies. The author put forward homes with corrugated asbestos roofing and no ceilings as the probable source.
  • Miami, 500 autopsies: 31.6 per cent of males and 20.4 per cent of females had asbestos bodies.
  • Both cities combined: in 85 per cent of positive cases the bodies were scanty or very scanty. In 40 cases (four per cent of those examined, six per cent of males) the bodies were numerous. Four of these 40 were females, all from Cape Town, and 36 were males.
  • Four of the 40 cases with numerous bodies had classical asbestosis (three from Cape Town; one from Miami, a mining engineer with lung carcinoma). A history of asbestos exposure was obtained in only one of the four.
  • Positive findings rose with age, from 4.3 per cent in the under-25 group to about 30 per cent in those over 65 (Cape Town).
• The authors' conclusion: The author concluded that people in both cities were inhaling asbestos fibers. Cases with numerous bodies were presumed to be of occupational origin. The author regarded the scanty bodies as of no significance as a cause of pulmonary fibrosis or disability. If they came mainly from city air contamination, the author regarded that contamination as of no significance at the moment. The author called it the main unknown whether a small amount of asbestos in the lung bases, pleura or peritoneum, present for 30 years or more, is an effective carcinogen. The author forecast a possible increase in basal asbestosis and mesothelioma, while describing that view as conjectural.
• Limitations the authors state:
  • The findings do not show how much asbestos dust was inhaled, only fibers long enough to be converted into asbestos bodies. The author regarded the positive findings as minimal ones for urban dwellers.
  • The method varied with the amount of fluid, blood or exudate in the lung bases, which affected how much lung was examined.
  • Not all patients were urban dwellers; some came from outlying villages and districts.
  • Lung-base tissue was not routinely taken for microscopic examination, so asbestos bodies could not be correlated with limited basal asbestosis.
  • The occupations and environment of the men with abundant asbestos bodies were not investigated during life.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Bodies, Mesothelioma, Pleura, Peritoneum.

Related studies

• Asbestosis in South Africa--certain geographical and environmental considerations — G.K. Sluis-Cremer (1965)
• Ferruginous (asbestos) bodies in the lungs of rural dwellers, urban dwellers, and patients with pulmonary neoplasms — P.H. Breedin, D.H. Buss (1976)
• Ethnic differences in lung function: evidence for proportional differences — C.E. Rossiter, H. Weill (1974)
• Polymorphism of glutathione S-transferase M1 and lung cancer risk among African-Americans and Caucasians in Los Angeles County, California — S.J. London, A.K. Daly, et al. (1995)
• Silicosis among foundry workers. Implication for the need to revise the OSHA standard — K.D. Rosenman, M.J. Reilly, et al. (1996)
• Lung cancer risk in relation to the CYP2E1 Rsa I genetic polymorphism among African-Americans and Caucasians in Los Angeles County — S.J. London, A.K. Daly, et al. (1996)

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