Minimising health hazards associated with derogated products and in-situ materials containing chrysotile contaminated with amphibole asbestos fibres

Our plain-English summary of Minimising health hazards associated with derogated products and in-situ materials containing chrysotile contaminated with amphibole asbestos fibres, by R.M. Howie (The Annals of Occupational Hygiene, 1999).

The study

• Author: R.M. Howie
• Journal: The Annals of Occupational Hygiene
• Published: 1999;43(7):493-8
• Type of article: Letter
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This letter to the editor is not a research study and reports no new data. Writing as UK regulations banning chrysotile were expected, with exemptions for seven safety-critical uses (all time-limited except chlor-alkali diaphragms), the author argued chrysotile is often naturally contaminated with amphibole asbestos such as tremolite. Citing other studies' Quebec data, the letter noted mesothelioma made up 0.71% of deaths in the central Thetford mines, where tremolite can be higher, against 0.24% at Asbestos. From cited studies, the author estimated tremolite and crocidolite are about 100 times as potent as chrysotile for mesothelioma, so a 1% content would double the hazard compared with amphibole-free chrysotile. Citing a South African study finding tremolite below 0.05% in chrysotile from four mines, the author proposed amphibole in derogated imports be as low as reasonably practicable and at most 0.05% of asbestos fibre weight. The author proposed treating asbestos materials, including asbestos cement, as containing amphibole unless tested below a limit, with only licensed contractors doing contracted work above it. The author noted the import limit depended on reliable testing and available low-tremolite chrysotile.

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: Letter to the editor: an opinion and policy proposal drawing on previously published studies, with no new data
• Who was studied: No study population. The letter concerns expected UK (and EU) regulations prohibiting chrysotile, with derogations for seven safety-critical uses. All derogations were to be time-bound except diaphragms for the chlor-alkali industry. The letter also concerns existing in-place asbestos materials such as asbestos cement.
• Exposure: Chrysotile asbestos naturally contaminated with amphibole asbestos fibres (actinolite, anthophyllite or tremolite), and crocidolite added to chrysotile in UK asbestos cement products
• Main results:
  • Cited from other studies (McDonald et al. 1997, McDonald and McDonald 1997, Liddell et al. 1997): the proportion of total deaths due to mesothelioma was 0.71% in the central mines at Thetford, Quebec, compared with 0.24% at Asbestos, Quebec.
  • The author's own inference from the cited data: tremolite and crocidolite have similar potency for inducing mesothelioma, about 100 times that of chrysotile.
  • The author's estimate: compared with amphibole-free chrysotile, a 1% crocidolite or tremolite content would double the mesothelioma hazard, and a 6.9% tremolite content would increase it 8-fold.
  • Cited from Rees et al. (1992): no tremolite was detected in chrysotile samples from four South African mines, meaning a tremolite content below 0.05%.
  • The author's estimate: in 1950 and 1960, crocidolite made up 1.3% and 3.1% of the chrysotile used in UK asbestos cement products. If incorporated uniformly, this would raise the mesothelioma hazard by factors of about 2 and 4 respectively, compared with amphibole-free chrysotile.
• The authors' conclusion: The author proposed that the fibrous amphibole content of chrysotile imported under derogation be as low as reasonably practicable and in any case not more than 0.05% of asbestos fibre weight, certified by accredited independent laboratories. The author also proposed that all asbestos-containing materials, including asbestos cement, be treated as containing amphibole unless shown to be below a specified limit (0.05% pending public consultation). Only licensed contractors would be permitted to undertake contracted work on materials above that limit.
• Limitations the authors state:
  • The author stated that the import limit would only be practicable if a reliable method existed for measuring amphibole content below 1% of the fibrous material, and if low-tremolite chrysotile were available.

Topics

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

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

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