Published on March 13, 2014
INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org Asbestos exposure in asbestos insulation removal work John Cherrie, Andy Stelling, Alan Jones, Geoff Smith
Summary • What will we cover? • Changes over the last 70 years • Airborne fibre levels during removal • The bad old days • Control by wetting and enclosure • The impact of using power tools • How effective are respirators? • Bystanders were exposed • Exposure after work complete Photos from www.flickr.com/photos/asbestos_pix
Scope of paper… • Include: • removal, take out, remediation, disturbance, disrupt, damage, demolition and disposal of in- situ asbestos containing materials in buildings, ships and industrial plant or equipment • Exclude: • maintenance on gaskets, brakes, ceiling tiles, floor tiles etc • Only release into workplace air • Including both workers, bystanders and others
Seven decades of removal… <1940s Widespread use of asbestos insulation in buildings and ships 1945 Action taken… British Factory Inspectors express concern about conditions on ships
Seven decades of removal… 1950s Removal part of the insulators job. No serious attempt to control exposure 1960s Awareness of the very high exposure in shipbuilding and elsewhere 1965 Sunday Times article "Scientists track down killer dust” 1970s New regulations in Britain to deal with asbestos in factories etc. Asbestos remediation workers begin work
The seven ages of removal… 1970s Removal done inside enclosures Clearance testing begins (using hygiene standards as a benchmark) First Government and industry codes introduced 1980s Improved codes of practice for safe work introduced “Work with asbestos insulation and asbestos coating” (1981) Procedures progressively tightened
Seven decades of removal… 1990s Movement towards management in preference to removal 1992 Enforcement of wet removal as opposed to dry Closer supervision of removal work 2000+ Duty to manage Consolidation of control limits Removal of action levels as deemed „not safe‟
Limit values in Britain…
Changes in fibre measurement… • 1960s particle counting methods to membrane filter method • In 1972 IARC recommended that inter- laboratory trials be carried out • Trials in late 1970s showed average differences between laboratories could be up to 3x • Prior to 1980 there was little standardisation and inadequate quality assurance • It wasn‟t until the 1980s that measurement methods were harmonized Walton, W. H. et al. (1976). An international comparison of counts of airborne asbestos fibres sampled on membrane filters. Ann Occ Hyg, 19(3-4), 215–224.
Published studies • A systematic review of the literature • Search terms • Asbestos, chrysotile, crocidolite, amosite • Exposure, air concentration, fibres or fibers/ml, fibres/cc, mppcf • Removal, remediation, disturbance, damage • Retrieved 741 papers • Screened using title and abstract • 16 papers considered potentially informative • Data extracted from 7 papers • Also included other known informative sources
Surgeon Commander Harries… http://tinyurl.com/pflc58m Harries, P. G. (1968). Asbestos hazards in Naval Dockyards. The Annals of Occupational Hygiene, 11(2), 135–145.
Pipe lagging on ships… Harries, P. G. (1971). Asbestos dust concentrations in ship repairing: a practical approach to improving asbestos hygiene in naval dockyards. Ann Occup Hyg, 14(3), 241–254.
Sprayed asbestos removal… Harries, P. G. (1971). Asbestos dust concentrations in ship repairing: a practical approach to improving asbestos hygiene in naval dockyards. Ann Occup Hyg, 14(3), 241–254.
Balzer and Cooper in the USA Balzer, J. L., and Cooper, W. C. 1968. The work environment of insulating workers. Am. Ind. Hyg. Assoc. J. 29: 222–227.
Summary of IOM data… Howie, R. et al (1996). Workplace effectiveness of respiratory protective equipment for asbestos removal work (No. HSE CRR 112:90. ). Report (pp. 1–90). HSE.
Use of power tools… Howie, R. et al (1996). Workplace effectiveness of respiratory protective equipment for asbestos removal work (No. HSE CRR 112:90. ). Report (pp. 1–90). HSE.
The effectiveness of respirators • Sampling simultaneously inside and outside the respirator • Results expressed as a Protection Factor (PF) PF CA CM
The effectiveness of respirators Akkersdijk, H., et al(1989). Effect of respiratory protective equipment on exposure to asbestos fibres during removal of asbestos insulation. Ann Occ Hyg, 33(1), 113–116.
Workplace protection factors Howie, R. et al (1996). Workplace effectiveness of respiratory protective equipment for asbestos removal work (No. HSE CRR 112:90. ). Report (pp. 1–90). HSE.
Workers and bystanders • Exposure of bystanders will be lower than workers • Far-field vs Near-field exposure Cherrie, J. (1999). The effect of room size and general ventilation on the relationship between near and far-field concentrations. App Occup Env Hyg, 14(8), 539–546.
Modeling results… Cherrie, J. (1999). The effect of room size and general ventilation on the relationship between near and far-field concentrations. App Occup Env Hyg, 14(8), 539–546.
Levels near enclosures… Perkins, J. L., Rose, V. E., & Cleveland, M. S. (1992). Analyses of PCM asbestos air monitoring results for a major abatement project. Applied Occupational and …, 7(1), 27–32.
After removal work complete… • “Clearance test” began in the 1970s • 1970s – Used the OELs • 1980s – IOM started to use 0.05 fibres/ml as an in-house limit • 1983 – Clearance indicator of 0.01f/ml widely adopted (EH10) • 1987 – UK hygienists Code of Practice
Exposure during clearance tests Bailey, S., Conchie, A., Hiett, D. M., & Thomas, C. (1988). Personal exposure to asbestos dust during clearance certification. Annals of Occupational Hygiene, 32(3), 423–426.
Elevated levels post removal… Ryan, G. et al (1996). A longitudinal study of an american public building following asbestos removal. Applied Occupational and Environmental Hygiene, 11(12), 1417–1423.
Conclusions • Exposure levels were very high with dry stripping and when using power tools • Enclosures increase exposure levels • Wetting, use of fibre supressants, glove bags and other controls can help reduce levels below 1 fibre/ml • If correctly worn respirators probably reduce exposures well below 0.1 f/ml • Bystanders may have had high exposures • Airborne fibre levels remain slightly elevated post removal
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