Asbestos

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Common Name:Asbestos
Other Names
  • White Asbestos - chrysotile (a serpentine asbestos)
  • Blue Asbestos - crocidolite
  • Brown Asbestos - amosite
Chemical Information
Molecular Structure
Important Issues in Man
Chronic toxicity, particularly with crocidolite and amosite.
Relevant Clinical Literature
Other Wikis
Wikipedia on Asbestos (Less technical, ? quality control)
LogoKeyPointsBox.png
  • All forms of asbestos cause cancer
  • Safer substitutes exist for most indications
  • A classic public health problem with politics preventing adequate action in the third world[1]

A mineral fibre that has excellent insulation properties and that can be made into cloth/rope. It was used early in human civilisation as a fire resistant wick or cloth. It has however caused massive long term health problems in not only those directly exposed to it, but say relatives who washed the clothes of workers contaminated by the dust. It is the main cause of the epidemic of mesothelioma that will peak in the UK in around 2015[2] and a major risk factor for restrictive lung disease due to asbestosis and bronchial carcinoma.[3] It is associated with the formation of calcified pleural plaques easily seen on chest X-rays of some of those exposed. National historic asbestos consumption explains:[4]

  • 74% of deaths from mesothelioma in both sexes with each increase of 1kg per head per annum increasing mesothelioma death rate 30 years later by 2.4 (95% CI 2.0-2.9) fold in men
  • 79% of deaths from asbestosis in men with each increase of 1kg per head per annum increasing mesothelioma death rate 30 years later by 2.7 (95% CI 2.4-3.4) fold

Compared to silicosis which has a weak but definite association with lung malignancy asbestosis has ten times the risk.

Pathology

The fibres by themselves are extremely thin and can be hard to see microscopically. However, they often become coated by iron and calcium, the former can be stained with Perls' staining to bring out the fibres, as in this photomicrograph.

The asbestos fibres can be seen on histological specimens.

QuotationMarkLeft.png At exposure levels seen in occupational cohorts, it is concluded that the exposure specific risk of mesothelioma... is broadly in the ratio 1:100:500 for chrysolite, amosite and crocidolite respectively QuotationMarkRight.png[5].

History of use & regulation

By the middle of last century, asbestos was to be found in a wide range of industrial products, including car brake linings (so any exposed to road side dust!), buildings (for insulation and fire-proofing), warships and aircraft (for insulation and fire-proofing), ironing boards and electrical distribution systems. The chrysotile form is less dangerous with only just over twice the relative risk of lung cancer[6]and is still used and mined in the third world. Import, processing and manufacture of asbestos was only completely banned in the USA in 2007.[7] This was 4 years after Australia had a complete ban and 15 years after the UK.

Now it is banned in lots of places, but notably not usually where it is mined. Canada where it was discovered in 1876 gives a good case study in how industry lobbies on public health matters. A major problem exists in the second and third world where interest groups can more effectively suppress and distort public health issues with major economic impact and effective mechanisms such as litigation to drive change do not exist. Lifetime mesothelioma risk appears to be almost totally explained by accumulated lifetime exposure to crocidolite or amosite. It is interesting that the Western media 'over-reaction' to the scientific evidence of the late 1970s which resulted in most Western countries in a total ban has worked so well because at one stroke it controlled construction-worker exposure to amosite which was not being regulated as it was seen as a minor issue in plasterboard, rather than a major issue as the dust was being produced by cutting on the job. Further the media hype that resulted in the removal of asbestos from buildings often increased population exposure. Multiple companies have gone into bankruptcy with Trust funds of the order of billions often set up.

The history of the health related problems with asbestos is:[8]

  • Ancient History Strabo (Greek (63/4 BC - c. AD 24) and Pliny the Elder(Roman 23–79) observed a sickness of the lungs in the slaves that wove asbestos into cloth.
  • 1924 William E Cooke publishes the second death due to asbestosis in the British Medical Journal.
  • 1925 Thomas Oliver coins the term "asbestosis".
  • 1927 William E Cooke, Stuart McDonald and Thomas Oliver publish three linked papers in the British Medical Journal.
  • 1930 Edward Merewether confirms that inhalation of asbestos dust can cause a fatal disease. (Merewether and Price Report to UK government)
  • 1931 UK Asbestos Industry Regulations negotiated by Dr Thomas Legge, suppressing asbestos dust by 1933
  • 1935 Kenneth Lynch and W Atmar Smith identify a "possible relationship" between pulmonary asbestosis and carcinoma of the lung.[9]
  • 1955 Sir Richard Doll finds that certain asbestos workers face a "notably higher risk" of contracting lung cancer than the rest of the population.[10]
  • 1960 Wagner, Sleggs, and Marchand publish their first paper indicating a relationship between pleural mesothelioma and asbestos exposure.[11]
  • 1965 Irving Selikoff, Jacob Churg, and Hammond demonstrate that insulation contract workers face a health hazard resulting from asbestos exposure.[12]
  • 1969 First third party products liability suit claiming personal injury from asbestos was launched in the USA. UK Asbestos Regulations remove the word Industry.
  • 1970 Voluntary Asbestos Import Ban by the asbestos industry on the import into the UK of raw blue asbestos. (did not impact on total UK asbestos use !!!!)
  • 1972 Regulatory targets for exposure reduced in USA, from here on in a progressive manner a few years bind UK.
  • 1974 The Health & Safety at Work Act 1974, required UK employers to conduct their work in such a way that their employees will not be exposed to health and safety risks
  • 1980 Voluntary Asbestos Import Ban extended to brown asbestos. Impact questionable. Indeed the two bans fuelled a myth in UK that both blue and brown asbestos were dangerous, whereas white asbestos was safe.
  • 1983 In UK the Asbestos Licensing Regulations 1983, meant that contractors working with asbestos insulation or coating were required to get a license from the HSE.
  • 1985 The Asbestos Prohibition Regulations 1985, banned the UK import and use of blue and brown (crocidolite and amosite) asbestos, the supply and use of products containing them. The Asbestos Products Safety Regulations 1985 prohibited the spraying of asbestos (except car under seal) and installation of asbestos insulation.
  • 1987 Amendment to the UK regulations to require that any products containing asbestos, were labelled to serve as a warning that asbestos was present and to give details of precautions to be taken in handling the product. The Control of Asbestos at Work Regulations 1987, introduced statutory control procedures to prevent workers from exposure to asbestos in the workplace.
  • 1990 The UK Control of Asbestos in the Air Regulations 1990, imposed an emission limit of 0.1 mg/m3 for asbestos emissions to the air by industrial installations
  • 1992 The UK Control of Asbestos at Work (Amended) Regulations 1992, included tighter action on chrysotile asbestos, a requirement to retain health records for 40 rather than 30 years, and requirement to produce a written plan of work and risk assessment when work on asbestos was to be undertaken. The Asbestos Prohibition Regulations 1992 banned all import into the UK.
  • 1998 The UK Asbestos Licensing (Amended) Regulations 1998, extended to include asbestos insulation (insulating) board
  • 1999 The Asbestos Prohibition (Amended) (No.2) Regulations 1999, prohibited the import, supply and use of all vehicle (asbestos containing) brake linings, including those for motor cycles.
  • 2002 The UK Control of Asbestos at Work Regulations 2002 covered domestic work - full implementation 2004.
  • 2009 EU Directive on exposure to asbestos (Directive 2009/148/EC).
  • 2012 UK Control of Asbestos Regulations as EU took the view 1969 regulations insufficient


Info bulb.pngIn the UK old hospitals often have asbestos lagging in the tunnels and basement passages through which various services pass. Many health workers also pass thorough those passages and this accounts for an observed increased risk of mesothelioma in health workers according to their hospital experience. Exemption of such Crown properties from many health and safety rules until the latter C19 is a factor left for the reader to consider


References

  1. Ogunseitan OA. The asbestos paradox: global gaps in the translational science of disease prevention. Bulletin of the World Health Organization 2015;93:359-360. doi: http://dx.doi.org/10.2471/BLT.14.142307
  2. Hodgson JT, McElvenny DM, Darnton AJ, Price MJ, Peto J. The expected burden of mesothelioma mortality in Great Britain from 2002 to 2050. British journal of cancer. 2005 Feb 14; 92(3):587-93.(Link to article – subscription may be required.)
  3. McCormack V, Peto J, Byrnes G, Straif K, Boffetta P. Estimating the asbestos-related lung cancer burden from mesothelioma mortality. British journal of cancer. 2012 Jan 31; 106(3):575-84.(Link to article – subscription may be required.)
  4. Lin RT, Takahashi K, Karjalainen A, Hoshuyama T, Wilson D, Kameda T, Chan CC, Wen CP, Furuya S, Higashi T, Chien LC, Ohtaki M. Ecological association between asbestos-related diseases and historical asbestos consumption: an international analysis. Lancet. 2007 Mar 10; 369(9564):844-9.(Link to article – subscription may be required.)
  5. Hodgson JT, Darnton A. The quantitative risks of mesothelioma and lung cancer in relation to asbestos exposure. The Annals of occupational hygiene. 2000 Dec; 44(8):565-601.
  6. Li L, Sun TD, Zhang X, Li XY, Fan XJ, Kenji M. A meta-analysis of cohort studies on cancer mortality among workers exposure to chrysotile fiber alone Zhonghua Yu Fang Yi Xue Za Zhi. 2004;38(1):39-42
  7. http://www.govtrack.us/congress/billtext.xpd?bill=s110-742
  8. Bartrip PW. History of asbestos related disease. Postgraduate medical journal. 2004 Feb; 80(940):72-6.
  9. Lynch KM, Smith WA. Pulmonary asbestosis III: carcinoma of lung in asbesto-silicosis. Am J Cancer 1935;24:56–64.
  10. Doll R. Mortality from lung cancer in asbestos workers. Br J Ind Med 1955;12:81–6
  11. Wagner JC, Sleggs CA, Marchand P. Diffuse pleural mesothelioma and asbestos exposure in the North Western Cape province. Br J Ind Med 1960;17:260–71
  12. Selikoff IJ, Hammond EC, Churg J. The occurrence of asbestosis among insulation workers in the United States. Ann N Y Acad Sci 1965;132:139–55