Asbestos and public health

Our plain-English summary of Asbestos and public health, by D. Liddell (Thorax, 1981).

The study

• Author: D. Liddell
• Journal: Thorax
• Published: 1981;36(4):241-4
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002015).

Summary of the article

This editorial summarised evidence on asbestos and health, concentrating on mortality, especially from lung cancer. The author drew heavily on a Quebec cohort of 10 939 men and 440 women who had worked at least a month in chrysotile mining and milling, some from 1904. They were followed to the end of 1975, with nearly 4500 deaths, and the study had job-by-job dust estimates and smoking histories. In Quebec the exposure-response relationship for lung cancer was effectively linear, and the author saw no evidence for a threshold or 'safe' dose. Most studies supported a 'fibre gradient': crocidolite had the most severe health effects, chrysotile the least, and amosite fell in between. The gradient was steepest for mesothelioma. The author considered that one new study of chrysotile textile workers, out of line with earlier reports, needed careful evaluation. He stated that current control limits for chrysotile were equivalent in carcinogenic potency to smoking three or four cigarettes a week. On a very gloomy interpretation of Rochdale factory data, 50 years' exposure at the UK limit of 1 f/ml would lead to 1.25% excess mortality from lung cancer. He recommended treating amosite like crocidolite and urged care when removing asbestos from buildings. He noted that no ill effects had been shown from asbestos in drinking water, food or the general atmosphere, and that substitutes resembling asbestos might be similarly harmful.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This 1981 editorial in Thorax was not a new study. It reviewed published research on asbestos and health, focusing mainly on deaths, especially from lung cancer, and covered mesothelioma briefly. It relied heavily on a Quebec chrysotile production cohort of 10 939 males and 440 females. In that cohort the relationship between accumulated dust exposure and lung cancer was effectively linear, and the author wrote that there seemed to be no evidence of a threshold or "safe" dose. Most studies appeared to support a "fibre gradient": crocidolite had the most severe effects, chrysotile the least, and amosite fell between. The gradient was almost certainly steepest for mesothelioma. Assuming a linear relationship and a conservative fibre-to-dust conversion ratio, the Quebec data meant that over a 50-year working life no lung cancer excess could have been detected with confidence below about 20 respirable fibres per millilitre. The 1981 UK limit for occupational exposure to chrysotile was 1 fibre per millilitre, which the author said did not guarantee absolute safety. The author suggested treating amosite the same way as crocidolite. No human study could measure actual dose.

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: editorial (narrative review of published studies)
• Who was studied: No new population was studied. The editorial drew mainly on a cohort of 10 939 males and 440 females who worked at least a month in Quebec chrysotile production, some from 1904, followed to the end of 1975 (nearly 4500 deaths). It also drew on other occupational studies, for example Rochdale, Nottingham and Western Australia.
• Exposure: Chrysotile and the amphiboles crocidolite and amosite, mainly in mining, milling and manufacturing. Non-occupational exposure, such as from building materials, was also discussed.
• Main results:
  • In the Quebec chrysotile cohort, the exposure-response relationship for lung cancer was effectively linear. The author wrote that there seemed to be no evidence for a threshold or safe dose.
  • Most studies appeared to support a fibre gradient: crocidolite most severe, chrysotile least, amosite in between. For mesothelioma the gradient was undoubted and almost certainly steeper than for any other outcome.
  • Chrysotile production (mining and milling) yielded a comparatively mild excess of lung cancer. The risk with pure crocidolite exposure was much higher in Nottingham, Eastern Canada and Western Australia.
  • From the Quebec data, on the linear hypothesis and with a conservative fibre/dust conversion ratio, no lung cancer excess could have been detected with any confidence for a 50-year working lifetime at concentrations below about 20 respirable fibres per millilitre. This was a limit of detection, not a demonstration of no risk. The proposed control limit of 1 f/ml is one-twentieth of that.
  • At Rochdale (mainly chrysotile, probably with some crocidolite), among those who entered after 1951, no relationship was found between lung cancer and exposure up to the equivalent of 8 f/ml for 50 years.
  • From the Quebec data, today's control limits for chrysotile were equivalent in carcinogenic potency to smoking three or four cigarettes per week.
  • Cancer of the larynx was unrelated to asbestos exposure in Quebec and London, but was associated with asbestos, probably amphibole, in a few other studies.
  • The peak level found in a UK survey of buildings containing asbestos materials was 0.08 f/ml.
  • The author stated that the 1981 UK regulations limiting occupational exposure to chrysotile to 1 f/ml do not guarantee absolute safety. Crocidolite was subject to much more stringent regulations.
  • The author regarded one 1980 symposium paper (on chrysotile textile workers) as completely out of line with previous findings and said it should await careful evaluation.
• The authors' conclusion: The author concluded that, because amosite is an amphibole and evidence against it is accumulating, it would seem sensible to treat it on the same lines as crocidolite, which is under much more stringent regulation.
• Limitations the authors state:
  • No human study can measure the dose reaching or retained in the target organ.
  • Most studies used duration of exposure as a stand-in for dose, which the author called of dubious validity.
  • Quantitative comparisons between fibre types are difficult.
  • Mesotheliomas were reviewed only cursorily.

Topics

Medical terms in this study, explained in our Lexicon: Lung Cancer, Chrysotile, Crocidolite, Amosite, Mesothelioma, Carcinogenic.

Related studies

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• The third wave of asbestos disease: exposure to asbestos in place. Public health control. Introduction — P.J. Landrigan (1991)
• Prevention of Asbestos Exposure in Latin America within a Global Public Health Perspective — E. Algranti, J.P. Ramos-Bonilla, et al. (2019)
• The origins of public concern with taconite and human health: Reserve Mining and the asbestos case — M.E. Berndt, W.C. Brice (2008)
• Adverse health effects of fluoro-edenitic fibers: epidemiological evidence and public health priorities — C. Bruno, P. Comba, et al. (2006)

Browse more research in Thorax, or return to medical research.