Nature, structure, and properties of asbestos cement dust

Our plain-English summary of Nature, structure, and properties of asbestos cement dust, by J. Baeten, J. Helsen, A. Deruyttere (British Journal of Industrial Medicine, 1980).

The study

• Authors: J. Baeten, J. Helsen, A. Deruyttere
• Journal: British Journal of Industrial Medicine
• Published: 1980;37(1):33-41
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy.

Abstract

ABSTRACT Total dust samples produced by machining three commercial asbestos-cement products (autoclaved sheet, non-autoclaved sheet, pipe) were examined for their dimensional, surface, and physicochemical characteristics. Microscopic inspection of dust fractions with different settling characteristics in air allowed determination of the simple dimensional features that apply to respirable fibres—that is, the true diameter, length, and aspect ratio and the coil diameter, coil length, and coil aspect ratio. The respirable fraction as a percentage of the total dust varied with the type of machined product: 8·5% for non-autoclaved sheet, 10·5% for autoclaved sheet, and 35% for pipe. Quantitative x-ray diffraction of different granulometric fractions showed that the asbestos content decreases with fraction size (thus the asbestos content will change with distance from the dust source). Electron microscopic examination of fine dust (aerodynamic diameter < 7 μm) showed that only about 10% of the inspected particles were optically virgin. From these observations it has been calculated that the threshold limit value of 2 fibres per cm3 of air corresponds to a total dust concentration of 1·2, 0·6, and 0·1 mg/m3 and to a maximum admissible respirable dust content of 0·1, 0·06, and 0·04 mg/m3 for non-autoclaved sheet, autoclaved sheet, and pipe respectively. The surface of optically virgin fibres may still be contaminated by calcium containing particles, as shown by analytical transmission and scanning electron microscope. Dust from the autoclaved product contains fewer calcium coated fibres. The physicochemical behaviour of dust, as shown by dissolution kinetics and absorption of carcinogens from tobacco smoke, is comparable to the behaviour of cement rather than of pure asbestos. In general, asbestos cement dust differs consistently from pure asbestos. Conclusions, drawn from studies on pure asbestos, cannot be applied as such to asbestos cement dust.

In plain English

This was a laboratory study of dust from asbestos-cement products. The authors collected about 1 kg of dust from each of three machining operations at an asbestos-cement plant: sawing NA-sheet and A-sheet, and lathe-machining pipe. Fine dust (aerodynamic diameter under 7 micrometres) made up 12.5, 19 and 52 percent by weight of the NA-sheet, A-sheet and pipe dust. Electron microscopy found optically pure asbestos fibres, cement particles and asbestos-cement aggregates. Chrysotile fibres from asbestos-cement dust, unlike pure asbestos, showed calcium in X-ray analysis. The authors concluded this layer probably consists of very small particles. All fibres examined from NA-sheet and pipe dust showed this layer, but not all A-sheet fibres did. The sheet dusts took up benzo[a]pyrene about as much as hydrated cement and much less than pure chrysotile. Asbestos-cement dust took up more maleic acid hydrazide than chrysotile. The authors' final sentence cautioned that conclusions about pure asbestos dust should not automatically be applied to asbestos-cement dust. The word 'automatically' is damaged in the scan, but it is the likely reading.

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: laboratory characterization study of dust samples (particle sizing, electron microscopy with X-ray analysis, adsorption tests)
• Who was studied: dust samples of about 1 kg collected from three machining operations in an asbestos-cement production plant: sawing of NA-sheet and A-sheet, and lathe machining of pipe; plant location and date not given
• Exposure: asbestos-cement dust from machined sheet and pipe; fibres analysed were chrysotile; compared with pure (virgin) chrysotile dust and hydrated cement dust
• Main results:
  • Fine dust (aerodynamic diameter under 7 micrometres) was 12.5% of NA-sheet dust, 19% of A-sheet dust and 52% of pipe dust
  • Transmission electron microscopy found three particle types in the dust: optically pure asbestos fibres, cement particles and asbestos-cement aggregates
  • X-ray analysis showed a calcium peak on 'optically pure' chrysotile fibres from asbestos-cement dust that was not present in pure asbestos
  • The authors concluded that the calcium-containing layer on these fibres probably consists of very small particles
  • All fibres examined from NA-sheet and pipe dust showed a calcium layer, but not all fibres from A-sheet dust did. The authors related this to differences in composition and fabrication process
  • Adsorption of benzo[a]pyrene by NA-sheet and A-sheet dust was close to that of hydrated cement dust and much smaller than that of pure chrysotile dust
  • Adsorption of maleic acid hydrazide by asbestos-cement dust was again similar to that of hydrated cement, but was larger than in chrysotile
• The authors' conclusion: The authors concluded that most asbestos fibres in asbestos-cement dust form aggregates with cement particles. They cautioned that conclusions reached for pure asbestos dust should not automatically be applied to asbestos-cement dust. The qualifying word is OCR-damaged ('mtc-uully'); 'automatically' is its likely reading.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Aspect Ratio (Length-to-diameter ratio), Respirable Fraction, X-Ray Diffraction (XRD), Threshold Limit Value (TLV).

Related studies

• Variation of properties of chrysotile asbestos subjected to milling — A.M. Langer, M.S. Wolff, et al. (1978)
• Asbestos cement dust inhalation by hamsters — A.P. Wehner, G.E. Dagle, et al. (1978)
• Small airways disease and mineral dust exposure. Prevalence, structure, and function — A. Churg, J.L. Wright, et al. (1985)
• The nature, hazards and assessment of occupational exposure to airborne asbestos dust: a review — W.H. Walton (1982)
• Some biological properties of respirable iron ore dust — D. Keast, N.P. Sheppard, et al. (1987)
• Exposure to cement dust, related occupational groups and laryngeal cancer risk: results of a population based case-control study — A. Dietz, H. Ramroth, et al. (2004)

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