Study of the secular trend in asbestos bodies in lungs in London 1936-66

Our plain-English summary of Study of the secular trend in asbestos bodies in lungs in London 1936-66, by C.H. Um (British Medical Journal, 1971).

The study

• Author: C.H. Um
• Journal: British Medical Journal
• Published: 1971;2(5756):248-51
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Thick sections (30mu unstained) cut from blocks of lung tissue from 100 consecutive necropsies for the years 1936, 1946, 1956, and 1966 at the Archway Hospital, London, have been searched for asbestos bodies. The incidence rose progressively-0, 3, 14, and 20% respectively. The rise was not explained by the increasing age of death in the later years or by the likely effects of changes in the areas within London in which the deaths occurred. There was no similar increase in the incidence of other bodies in the lungs which might be mistaken for asbestos bodies. The rising incidence is shown to fit reasonably with a model based on the hypothesis that the risk of inhaling asbestos increases in relation to the cumulative total of asbestos imported into the country from 1910 onwards. The rising incidence does not fit a model in which the risk depends simply on the current level of asbestos imports.

In plain English

This study asked whether asbestos bodies in Londoners' lungs became more common between 1936 and 1966. The author examined stored lung tissue from 127, 100, 100 and 100 consecutive autopsies on patients over 20 in 1936, 1946, 1956 and 1966, held by the Archway Hospital laboratory in London, which also served other London hospitals. The share of lungs with asbestos bodies was 0, 3, 14 and 20% respectively. Within each 10-year age group from 50 upward, the share generally rose, though numbers were small. The author wrote that it therefore appeared rising age at death did not explain the increase. Other bodies that might be mistaken for asbestos bodies showed no such trend. The rise did not fit a risk rising in line with yearly asbestos imports. It did fit a model linking risk to total asbestos imported into the UK since 1910: 37 positive cases were observed and 37.24 expected. The author could not identify the patients' occupations. Later cases came from hospitals farther from asbestos factories, so the author concluded the rise was likely an underestimate rather than an overestimate.

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: Retrospective autopsy (necropsy) study of archived lung tissue from four years. The material came from the records of the Central Histological Laboratory of the Archway Hospital, London. Until the National Health Service began in 1948, that laboratory served all former L.C.C. hospitals; after that it served a small group of hospitals.
• Who was studied: Consecutive necropsies on patients over age 20 with a block of lung tissue available: 127 from 1936, 100 from 1946, 100 from 1956 and 100 from 1966 (427 in total). They came from the hospitals served by the Archway Hospital laboratory, not from Archway Hospital alone.
• Exposure: General environmental exposure to asbestos in people from the general population, not asbestos workers. Fiber types were not distinguished. The findings were compared with UK imports of asbestos of all kinds.
• Main results:
  • The percentage of lungs with asbestos bodies was 0% in 1936, 3% in 1946, 14% in 1956 and 20% in 1966.
  • Among positive cases, the average number of asbestos bodies per section rose slightly: 1.0 in 1946, 1.2 in 1956 and 1.75 in 1966.
  • The number of asbestos bodies per unit volume of lung tissue examined increased progressively from 1946 to 1966.
  • In each 10-year age group from 50 to 90 and over, the percentage of positive lungs generally rose from 1936 to 1966, although the numbers were small.
  • From this, the author wrote that it appeared the increased age at death in later years was not the explanation for the rising prevalence.
  • Other bodies that superficially resembled asbestos bodies showed no trend over time.
  • UK asbestos imports rose nearly linearly from 20,000 tons in 1920 to about 150,000 tons in 1965.
  • A model with a risk that increased linearly over time, in line with yearly imports, did not fit. It would have required more positive cases in 1936 and fewer in 1966 than were found.
  • A model in which risk increased with the cumulative amount of asbestos imported since 1910 gave a satisfactory fit.
  • Across all 427 cases, 37 positive cases were observed under the cumulative-import model and 37.24 were expected.
• The authors' conclusion: The author concluded that the earlier samples were more likely to include men who had worked near asbestos factories. The rise in prevalence from 1936 to 1966 was therefore likely an underestimate rather than an overestimate of the general trend.
• Limitations the authors state:
  • The cumulative-import model predicted a less steep rise in cases than was observed.
  • The attempt to identify the occupations of the people studied failed.
  • Age and sex were not matched across years, and the selection of cases coming to necropsy changed over time.
  • The numbers within each age group were small.
  • The mean area of section scanned per case differed between years. The author said this could cause only small changes in the trend.
  • The site and lobe of the lung sampled varied or were not recorded. The author judged that this would not affect the results.

Topics

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

Related studies

• Correlation between fibre content of the lung and disease in east London asbestos factory workers — J.C. Wagner, M.L. Newhouse, et al. (1988)
• Correlation between fibre content of lung and disease in east London asbestos factory workers — R.M. Rudd (1989)
• Mortality of factory workers in east London 1933-80 — M.L. Newhouse, G. Berry, et al. (1985)
• Secular changes in asbestosis in an asbestos factory — W.J. Smither (1965)
• A procedure for the isolation of amosite asbestos and ferruginous bodies from lung tissue and sputum — M.G. Williams, R.F. Dodson, et al. (1982)
• Fibrous dust particles and ferruginous bodies. Methods for quantitating them and some results from the lungs of city dwellers — P. Gross, J. Tuma, et al. (1970)

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