Measurements of airborne asbestos fibres during refurbishing

Our plain-English summary of Measurements of airborne asbestos fibres during refurbishing, by T.K. Ervik, S.E. Hammer, N.P. Skaugset, et al (Annals of Work Exposures and Health, 2023).

The study

• Authors: T.K. Ervik, S.E. Hammer, N.P. Skaugset, P. Graff
• Journal: Annals of Work Exposures and Health
• Published: 2023;67(8):952-964
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Although the use of asbestos fibres in building materials has been prohibited in Norway since 1985, asbestos-containing materials (ACMs) are still found in many buildings. Lack of knowledge and awareness of these materials may lead to exposure during refurbishing. The aim of this study was to investigate the airborne fibre concentration and classify fibres found during the abatement of various ACMs. The release of fibres during short-term work tasks, such as drilling and sawing, was also investigated. Parallel air samples were collected during asbestos abetment of different building materials and analysed with scanning electron microscope (SEM) and phase-contrast microscope (PCM), respectively. Material samples were analysed with SEM. A real-time fibre monitor was used to measure asbestos during short-term work. The highest fibre concentrations were measured for samples collected during the removal of asbestos insulating boards (1.5-4.5 fibres/cm3 [f/cm3]), and the numbers were relatively similar for SEM and PCM. A large difference in asbestos concentrations was found between SEM and PCM when analysing floor materials, which were probably caused by a high number of gypsum fibres that the PCM operator counted. Thin fibres (<0.2 µm in width) were included in the SEM count and constituted up to 50% of the total fibre concentration for the asbestos cement materials. The presence of other inorganic and organic fibres on these samples probably led to similar results between SEM and PCM. Short-term work led to peak concentrations above 30 f/cm3.

© The Author(s) 2023. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

In plain English

This Norwegian study measured airborne fibres while workers removed asbestos-containing building materials. Air samples were taken in workers' breathing zones and at fixed points; 27 pairs were analysed by both scanning electron microscopy (SEM) and phase-contrast microscopy (PCM). The highest levels were measured during removal of asbestos insulating boards (1.5–4.5 fibres/cm3), a material in which amosite was the dominant fibre type. Eight floor-removal samples were rejected because their filters were overloaded; every floor sample quantified by SEM was below the asbestos detection limit. The four parallel PCM samples ranged from 0.4 to 2.1 f/cm3, which the authors attributed to gypsum fibres probably miscounted as asbestos by PCM. In samples from asbestos cement wall and roof removal, where chrysotile was the main fibre type, up to 50 per cent of fibres were thinner than 0.2 µm. Short tasks such as drilling and sawing produced peaks above 30 f/cm3 on a real-time fibre monitor. The authors note that this monitor may also have counted non-asbestos fibres. The authors concluded that PCM is not recommended when many non-asbestos fibres are present.

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: Field measurement study of airborne fibres during asbestos abatement work. It used personal and stationary air samples, parallel SEM and PCM analysis, SEM analysis of material samples, and a real-time fibre monitor during short tasks.
• Who was studied: Air samples from asbestos abatement work in Norway. There were 57 air samples for SEM (41 personal, 16 stationary). After 11 overloaded samples were rejected, 35 personal and 11 stationary samples remained, and 27 SEM/PCM parallel pairs could be compared. Most exterior samples came from a single-family house built in 1942 and fitted with asbestos-containing materials in the 1960s. A few came from a 1960s residential house in central Norway and a 1970s hotel on the west coast. The sampling dates are not stated.
• Exposure: Removal of interior materials: asbestos insulating boards (Asbestolux), pipe insulation, PVC vinyl tiles and one cork board floor. Removal of exterior asbestos cement materials: corrugated roof sheets, roof slate shingles and wall shingles (Eternit). Also 1-minute drilling or bayonet sawing, and breaking or friction of wall and roof materials.
• Main results:
  • The highest airborne fibre concentrations were measured during removal of asbestos insulating boards: 1.5–4.5 fibres/cm3.
  • In the asbestos insulating board material sample, amosite was the dominant fibre type.
  • During asbestos insulating board removal, thin fibres (under 0.2 µm) accounted for 5–15% of the asbestos fibres in the SEM count.
  • All indoor floor removal and floor grinding samples that could be quantified by SEM were below the asbestos detection limit. The detection limit was 0.04 f/cm3 for the personal floor samples. Eight further floor-removal samples were rejected because their filters were overloaded.
  • For floor materials, the four parallel PCM samples ranged from 0.4 to 2.1 f/cm3, while the matching SEM samples were all below the detection limit.
  • The authors explained the floor discrepancy by resuspended gypsum fibres that were probably counted as asbestos by the PCM operator.
  • For the single pipe insulation removal sample, PCM gave 0.1 f/cm3 and SEM gave 0.02 f/cm3.
  • Chrysotile was the main asbestos fibre type in the exterior asbestos cement material samples. Amosite and crocidolite were also identified.
  • Up to 50 per cent of fibres in samples from exterior wall and roof removal were thin fibres (under 0.2 µm).
  • Background levels of 0.05 f/cm3 were measured during the enclosed exterior abatement. The authors took this to indicate a risk of local asbestos contamination.
  • Airborne asbestos levels during roofing felt removal were comparable to those during roof removal, although the felt itself contained no asbestos. The authors attributed this probably to fibres from the deteriorated cement roof.
  • In asbestos cement samples, other inorganic fibres were present in relatively high amounts. The authors suggest some may have been included in the PCM count.
  • Short-term work on asbestos cement materials produced peak fibre concentrations above 30 f/cm3 on the real-time monitor.
  • Of the short-term tasks, the bayonet saw gave the highest peaks.
  • Breaking wall or roof shingles, or rubbing them together, gave peaks of about 1.0 f/cm3.
• The authors' conclusion: The authors concluded that PCM is not recommended when many non-asbestos fibres occur in samples, because common non-asbestos fibres such as calcium sulphate can lead to erroneous PCM counts.
• Limitations the authors state:
  • Indoor samples were taken in negative-pressure enclosures, which may have led to underestimated fibre concentrations, especially for stationary samples.
  • Eleven samples were rejected because the filters were overloaded: 8 from floor removal and 3 from roof felt and batten removal.
  • Short fibres may have been missed in SEM counting when other particles covered them.
  • The real-time fibre monitor may have counted non-asbestos fibres.
  • Organic fibres were removed during SEM preparation, so how common they were is unknown.
  • Fibres detected during pipe insulation removal may have come from settled dust rather than from the removal itself.
  • The asbestos content of the material samples was not quantified.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Containing Material (ACM), Abatement, Asbestos-Cement.

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• Personal and static sample measurements of asbestos fibres during two abatement projects — A. Dufresne, C. Dion, et al. (2009)
• Trends in Airborne Chrysotile Asbestos Fibre Concentrations in Asbestos Cement Manufacturing Factories in Zimbabwe from 1996 to 2016 — B. Mutetwa, D. Moyo, et al. (2021)
• A study of the size distributions of airborne amosite fibres in the manufacture of asbestos insulation boards — S.T. Beckett, J.L. Jarvis (1979)
• Measurement of airborne fibers: a review — P.A. Baron (2001)

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