Asbestos cancer: past and future hazards

Our plain-English summary of Asbestos cancer: past and future hazards, by J.C. Gilson (Proceedings of the Royal Society of Medicine, 1973).

The study

• Author: J.C. Gilson
• Journal: Proceedings of the Royal Society of Medicine
• Published: 1973;66(4):395-403
• Type of article: Historical article
• Cited by: 26 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. 001303).

Summary of the article

In this Michael Williams Lecture, given to the Section of Epidemiology and Preventive Medicine of the Royal Society of Medicine on 10 February 1972 and published in abridged form, the author reviewed evidence on cancers linked with asbestos and on their prevention. He outlined the history of asbestos use, the stages of the industry where dust exposure occurs, and factors thought to influence cancer incidence, including dose, fibre type, fibre size and shape, time since first exposure, sex and cigarette smoking. Comparing prospective surveys of asbestos workers followed for 20 or more years, he reported that the excess of lung cancer varied widely. Risk was low among 12 000 Quebec chrysotile miners and millers and high in insulation workers, and it was dose related. He concluded that no single fibre type seemed especially important for lung carcinoma. For mesothelioma, the evidence suggested greater variation by fibre type, with the South African excess almost limited to the crocidolite mining area. Case-control studies in Scotland and Canada supported the link with asbestos. Confirmed mesothelioma deaths in the UK register rose from 6.2 per year in 1955-59 to 73 in 1968. He outlined Dr V Timbrell's hypothesis that fibre diameter and shape govern how far fibres penetrate the lung. He also described UK preventive measures, stressing continuing research and cost/benefit analysis.

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 1972 lecture, published in abridged form, reviewed surveys and case reports on asbestos-linked cancers. It drew mainly on other researchers' work, plus figures from the UK Register of Mesotheliomas. In the surveys of asbestos workers that the author compared, the lung cancer excess varied. It was low among Quebec chrysotile miners and millers, high among insulation workers. In cited UK studies of insulation and textile workers, lung cancer risk was related to dust exposure and length of exposure. For mesothelioma, the cited evidence suggested risk varied more with fiber type than lung cancer risk did. In South Africa, the excess was almost limited to the crocidolite mining area. Confirmed mesothelioma deaths on the UK register rose from 6.2 per year in 1955-59 to 73 in 1968. The author outlined a colleague's hypothesis that fiber diameter and shape affect how far fibers penetrate the lung. The author concluded that the dose needed to raise lung cancer risk materially was likely well above what the general public had encountered. The author also noted that smoking makes small excess risks hard to detect.

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: Narrative review given as a lecture (Michael Williams Lecture, abridged). It mainly brought together other researchers' published surveys and case reports. It also presented figures from the UK Register of Mesotheliomas without citing a published source.
• Who was studied: The lecture reviewed published surveys of asbestos miners and millers, manufacturing workers and insulation workers in several countries, with follow-up of 20 or more years from first exposure. It also covered mesothelioma case surveys (Scotland, Canada, South Africa) and cases on the UK Register of Mesotheliomas, which was started in 1962.
• Exposure: Occupational asbestos dust in mining and milling, manufacturing (insulation, textiles) and application or removal of insulation. Fiber types were chrysotile, amosite, crocidolite and anthophyllite, often in mixtures.
• Main results:
  • Across the reviewed surveys, the lung cancer excess varied considerably. The sharpest contrast was between the low risk in a survey of 12 000 chrysotile miners and millers in Quebec and the high risk in insulation workers exposed to fiber mixtures in the USA and UK.
  • The author's reading of the reviewed surveys was that no single fiber type stood out for lung cancer. The author suggested that the dose of respirable fiber of a particular size, diameter and perhaps shape mattered.
  • In the cited surveys, lung cancer risk was dose related. Among workers manufacturing insulation and textiles (chrysotile, amosite, crocidolite), the observed-to-expected lung cancer ratio was 1.5:1 with low or medium exposure and 6.1:1 with severe exposure in men. In women it was 6.7:1 and 13.4:1. Among Quebec chrysotile miners and millers, the excess risk was limited to those with the highest past dust exposures.
  • In the cited Newhouse et al. 1972 study of severely exposed workers, the lung cancer observed-to-expected ratio was 3.0 in men exposed under 2 years and 5.6 in men exposed over 2 years. In women it was 6.8 and 32.6. The excess rate per 100 000 subject years was 120 and 570 in men and 70 and 380 in women.
  • In a cited 'blind' case-control survey in Scotland, only 5% of mesothelioma cases gave no history of asbestos exposure.
  • The cited evidence showed a bigger variation of mesothelioma risk with fiber type than was found for lung cancer. In South Africa, surveillance found very few mesotheliomas from amosite mining and none from chrysotile, with the excess almost limited to the crocidolite area. No mesotheliomas had been found with anthophyllite in Finland.
  • The author put the proportion of deaths due to mesothelioma in the groups at greatest risk at about 5%. In a table of cited groups, mesothelioma accounted for 3 of 2413 deaths (0.12%) among 9981 Quebec chrysotile miners and millers. It accounted for 20 of 436 deaths (4.6%) among 4806 London insulation manufacturing workers, 22 of 380 deaths (5.8%) among 632 New York insulation workers, and 7 of 98 deaths (7.1%) among 165 Belfast insulation workers.
  • Confirmed mesothelioma deaths on the UK Register of Mesotheliomas rose over time: 17 in total before 1955, 6.2 per year in 1955-59, 17.4 per year in 1960-64, 24 in 1965, 28 in 1966, 43 in 1967 and 73 in 1968.
  • Under a hypothesis by the author's colleague Dr V Timbrell, fiber diameter and shape govern how deep fibers reach in the lung. Crocidolite was reported to have about one-third the diameter of amosite.
• The authors' conclusion: The author concluded that the surveys, taken with other evidence, suggest that the asbestos dose needed to increase lung cancer risk materially is likely to be well above what the general public had encountered up to then.
• Limitations the authors state:
  • The high lung cancer risk from cigarette smoking makes small excess risks from occupational or environmental causes hard to detect.
  • Information on dust dose and mesothelioma risk was only qualitative.
  • Pathologists' diagnoses of mesothelioma varied, and disagreements were expected.
  • The difference between the Scottish and Canadian mesothelioma survey findings was unexplained.

Topics

Medical terms in this study, explained in our Lexicon: Epidemiology, Lung Cancer, Quebec Chrysotile, Insulator, Carcinoma, Mesothelioma, Crocidolite.

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• Commentary: Past and current asbestos exposure and future mesothelioma risks in Britain — B. Terracini (2018)
• Past exposure to asbestos and combustion products and incidence of cancer among Finnish locomotive drivers — P. Nokso-Koivisto, E. Pukkala (1994)
• Dangerous and cancer-causing properties of products and chemicals in the oil refining and petrochemical industry: Part V--Asbestos-caused cancers and exposure of workers in the oil refining industry — M.A. Mehlman (1991)
• Asbestos and cancer: history and public policy — M.P. Weller (1993)

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