Pleural mesothelioma and lung cancer risks in relation to occupational history and asbestos lung burden

Our plain-English summary of Pleural mesothelioma and lung cancer risks in relation to occupational history and asbestos lung burden, by C. Gilham, C. Rake, G. Burdett, et al (Occupational and Environmental Medicine, 2016).

The study

• Authors: C. Gilham, C. Rake, G. Burdett, A.G. Nicholson, L. Davison, A. Franchini, J. Carpenter, J. Hodgson, A. Darnton, J. Peto
• Journal: Occupational and Environmental Medicine
• Published: 2016;73(5):290-9
• Cited by: 74 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: We have conducted a population-based study of pleural mesothelioma patients with occupational histories and measured asbestos lung burdens in occupationally exposed workers and in the general population. The relationship between lung burden and risk, particularly at environmental exposure levels, will enable future mesothelioma rates in people born after 1965 who never installed asbestos to be predicted from their asbestos lung burdens.

Methods: Following personal interview asbestos fibres longer than 5 µm were counted by transmission electron microscopy in lung samples obtained from 133 patients with mesothelioma and 262 patients with lung cancer. ORs for mesothelioma were converted to lifetime risks.

Results: Lifetime mesothelioma risk is approximately 0.02% per 1000 amphibole fibres per gram of dry lung tissue over a more than 100-fold range, from 1 to 4 in the most heavily exposed building workers to less than 1 in 500 in most of the population. The asbestos fibres counted were amosite (75%), crocidolite (18%), other amphiboles (5%) and chrysotile (2%).

Conclusions: The approximate linearity of the dose-response together with lung burden measurements in younger people will provide reasonably reliable predictions of future mesothelioma rates in those born since 1965 whose risks cannot yet be seen in national rates. Burdens in those born more recently will indicate the continuing occupational and environmental hazards under current asbestos control regulations. Our results confirm the major contribution of amosite to UK mesothelioma incidence and the substantial contribution of non-occupational exposure, particularly in women.

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In plain English

This British population-based study compared the amount of asbestos in the lungs of 133 people with pleural mesothelioma with that of 262 people who had surgery for lung cancer, who served as the comparison group. Patients were interviewed about their work histories. Asbestos fibres longer than 5 micrometres were counted by electron microscopy. Most fibres found were amosite (75%) or crocidolite (18%). Chrysotile made up 1.9%. Among men, the odds of mesothelioma rose with lung burden. In the highest group (1.0 million fibres per dry gram of lung or more), the odds ratio was 35.00 (95% CI 7.22 to 169.6) compared with the lowest group. The authors estimated lifetime mesothelioma risk at about 0.020% per 1000 asbestos fibres per gram of dry lung. All 27 male mesothelioma patients with burdens above 0.5 million fibres per gram had worked in high-risk jobs. Carpenters had the highest amosite levels. Burdens in women were much lower. The authors concluded that amosite contributed heavily to UK mesothelioma and that non-occupational exposure contributed substantially, particularly in women. There were too few women to analyse them separately.

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: Population-based case-control study of asbestos lung burden, comparing mesothelioma patients with resected lung cancer patients as controls, with a statistical dose-response model
• Who was studied: Lung samples from 133 mesothelioma patients (107 men, 26 women; postmortem samples) and 262 lung cancer patients (182 men, 80 women; tissue removed at surgery). Patients were recruited from hospitals throughout Britain and interviewed between 2001 and 2006. All were born since 1940 except 11 women with mesothelioma born 1925 to 1939. Only pleural mesotheliomas were included.
• Exposure: Asbestos lung burden: asbestos fibres longer than 5 micrometres per dry gram of lung, counted by transmission electron microscopy and typed (amosite, crocidolite, chrysotile, tremolite, anthophyllite, actinolite), together with lifetime occupational history from personal interview
• Main results:
  • In men, the mesothelioma odds ratio in the highest lung burden category (1.0 million fibres per dry gram or more) was 35.00 (95% CI 7.22 to 169.6), compared with the lowest category (under 0.025 million fibres per dry gram)
  • Under the linear model fitted to men, lifetime mesothelioma risk was estimated at 0.020% per 1000 asbestos fibres per gram of dry lung
  • Estimated lifetime excess risk due to asbestos in British men born in 1945 was 0.86% for mesothelioma and 0.47% for lung cancer
  • Of the asbestos fibres counted, 75% were amosite, 18% crocidolite and 1.9% chrysotile; the remainder were other amphiboles
  • 27 (25.2%) of male mesothelioma patients had lung burdens above 0.5 million fibres per gram. All 27 had a high-risk occupational history, and 16 had worked as a carpenter, plumber, electrician or decorator.
  • Only 6 (3.3%) of 182 male lung cancer patients, and none of the women (mesothelioma or lung cancer), had lung burdens above 0.5 million fibres per gram
  • Among male mesothelioma patients, the highest amosite levels were mostly in carpenters
  • Lung burdens were much lower in women; the highest levels were in women who reported domestic exposure
  • The best-fitting model treated one crocidolite fibre as equivalent to 1.3 (95% CI 0.4 to 3.3) amosite fibres for mesothelioma risk
• The authors' conclusion: The authors concluded that their results confirm the major contribution of amosite to UK mesothelioma incidence and the substantial contribution of non-occupational exposure, particularly in women. They also concluded that the roughly linear dose-response, combined with lung burden measurements in younger people, will allow reasonably reliable predictions of future mesothelioma rates in people born since 1965.
• Limitations the authors state:
  • There were too few women for separate analysis, so model-fitting was limited to men
  • Peritoneal mesotheliomas were not included
  • Chrysotile clears rapidly from the lung, so its effects could not be estimated
  • Spontaneous mesotheliomas unrelated to asbestos were ignored in the modelling; estimating them would need larger numbers and more sensitive electron microscopy
  • The estimated increase in lung cancer relative risk per million fibres per gram was imprecise
  • The data were not adjusted for clearance of fibres from the lung over time
  • If an alternative projection of national mesothelioma rates proves more accurate, the risk per 1000 fibres per gram would fall from 0.020% to 0.017%

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite, Chrysotile, Crocidolite, Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Lung Cancer, Occupational History, Environmental Exposure, Mesothelioma, Transmission Electron Microscopy (TEM), Amphibole Group, Amosite.

Related studies

• Past and current asbestos exposure and future mesothelioma risks in Britain: The Inhaled Particles Study (TIPS) — C. Gilham, C. Rake, et al. (2018)
• Pulmonary mineral fibers after occupational and environmental exposure to asbestos in the Russian chrysotile industry — A. Tossavainen, E. Kovalevsky, et al. (2000)
• Relation between lung asbestos fibre burden and exposure indices based on job history — K. Takahashi, B.W. Case, et al. (1994)
• Quantitative analysis of asbestos burden in women with mesothelioma — R.F. Dodson, M. O'Sullivan, et al. (2003)
• Tissue burden evaluation of elongated mineral particles in two individuals with mesothelioma and whose work history included manufacturing tile — R.F. Dodson, L.W. Poye (2020)
• Report of a recent "brake" through in the fiber burden-mesothelioma dialogue — D. Egilman (2012)

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