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Low level exposure to asbestos and risk


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A lecture given at the Weightmans Disease Conference, Birmingham 2010

Published in: Health & Medicine, Technology
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Low level exposure to asbestos and risk

  1. 1. The impact of environmental asbestos exposure and it's relevance in cases of low level occupational exposure<br />John Cherrie<br />Research Director<br /><br />
  2. 2. Summary…<br />Asbestos<br />Historical uses of asbestos and the consequences<br />Risk models<br />Changes over the last 40 years<br />Contaminated land<br />Low-level occupational exposure<br />Background levels<br />Conclusions? <br />
  3. 3. 3<br />Asbestos minerals<br />Serpentine<br />Chysotile (white asbestos)<br />Amphibole<br />Amosite (brown asbestos)<br />Crocidolite (blue asbestos)<br />Tremolite<br />Anthophyllite<br />Actinolite<br />
  4. 4. Fibres...<br />Fibres are harmful because:<br /><ul><li>they are thin (d < 3mm)
  5. 5. they are long (l > 5mm) and
  6. 6. because of their shape (l/d > 3)</li></ul>also because they are persistent in the lung<br />
  7. 7. 5<br />Health effects of asbestos exposure<br />Pleural Mesothelioma<br />Bronchogenic carcinoma<br />Pleural Plaque<br />Asbestosis<br />
  8. 8. The epidemiology and toxicology…<br />Doll (1955) lung cancer<br />Wagner et al (1960) mesothelioma<br />1964 New York conference<br />Stanton and Wrench(1972) and Pott and Friedrichs (1972) induction of mesothelioma in experiments<br />
  9. 9. HSE guidance from 1970<br />
  10. 10. A serious public health risk...<br />
  11. 11. HSE funded research…<br />No evidence of increased risk associated with non-industrial workplaces or ‘low risk’, including motor mechanics and workers handling gaskets and mats<br />Only non-occupational exposure associated with increased risk was living with an exposed worker<br />Increasing trend in female rates suggest mesothelioma with no known occupational or domestic exposure may be caused by environmental asbestos exposure<br />Peto et al. (2009) Occupational, domestic and environmental mesothelioma risks in Britain. Report RR696<br />
  12. 12. Occupations affected…<br />Historically, insulation workers, shipbuilders and locomotive engineers<br />Asbestos exposure was widespread<br />About 65% of males and 25% of females at risk worked in medium or higher risk jobs<br />The most frequent occupations on death certificates for mesothelioma include carpenters and joiners; plumbers, heating and ventilating engineers; and electricians and electrical fitters<br />
  13. 13. Low exposed jobs…<br />Motor mechanic, Draughtsmen, Engineers, Stores & warehousemen, Armed forces, Drivers & road transport workers<br />Cleaners, Retail workers, Doctors, nurses & hospital workers, Teachers & school workers, Kitchen workers, Office workers<br />
  14. 14. Asbestos exposures today...<br />
  15. 15. The risks...<br />for lung cancer<br />risk is proportional to cumulative exposure<br />1% increase in risk for each year at 1 fibre/ml<br />for mesothelioma<br />risk is related to cumulative exposure and age at first exposure<br />where n= 3.2 and KM = 3.10-8<br />
  16. 16. Hodgson and Darnton model…<br />
  17. 17. 15<br />Gas masks…<br />
  18. 18. 16<br />Death amongst gas mask workers…<br />1950 1960 1970 1980 1990 2000<br />
  19. 19. 17<br />Asbestos in soil – where? <br />In brown field sites<br />In green field sites<br />Gardens to be - on construction sites<br />Existing gardens on any brown field site <br />Gardens near major asbestos sites?<br />Gardens in rural areas adjacent to asbestos source?<br />
  20. 20. 18<br />Example of sampling site on tracks<br />
  21. 21.
  22. 22. 20<br />Air Sample analysis for low levels…<br />Samples analysed by electron microscopy (SEM or TEM) for asbestos fibres<br />Airborne asbestos concentrations calculated from each sample<br />Often need to combine results from several samples over several days to get the necessary sensitivity<br />
  23. 23. Mesothelioma risk…<br />
  24. 24. Arc chutes…<br />Arc chutes containing asbestos were fitted over and between the copper components<br />No visible dust but after handling arc chutes there was a white residue on his hands<br />No cutting or drilling required<br />“Sindanyo” - 50% chrysotile (white) asbestos and 50% Portland cement<br />Only 2-days per week in this work <br />Exposure probably < 0.1 fibres/ml<br />Hodgson and Darnton model suggests mesothelioma risk 30 per million<br />
  25. 25. Background levels in air…<br />
  26. 26. in the UK in 1980s…<br />Risk for children living near an asbestos factory could be between 2 in 10,000 to 2 in 1,000 <br />
  27. 27. Conclusions…<br />Mesothelioma epidemic is almost at its peak<br />Current incidence represents exposure in 1960s and 70s<br />As time goes on proportionately more cases will come from “low” or “moderate” jobs<br />Past environmental exposure may have been a risk for mesothelioma<br />In the past living with an asbestos work was also associated with a risk <br />
  28. 28. My slides are on…<br />