Nature of exposure to chrysotile

Our plain-English summary of Nature of exposure to chrysotile, by M. Lippmann (The Annals of Occupational Hygiene, 1994).

The study

• Author: M. Lippmann
• Journal: The Annals of Occupational Hygiene
• Published: 1994;38(4):459-67, 408
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Fibres in general, and chrysotile fibres in particular, have properties that set them apart from other airborne particles in terms of their aerodynamic behaviour and the nature of their interactions with cells and fluids in vivo. Their lengths and diameters are primary determinants of their penetration through conductive airways to deposition sites within the lungs, and to their access into translocation pathways; their surface properties and biopersistence affect their retention times and the biological responses that can lead to chronic disease. In the absence of sufficiently detailed knowledge of the specific ranges of lengths, diameters, surface properties and biopersistence of the long, thin fibres most closely related to hazard potential, crude surrogates of relevant exposure have been used. These include: (i) the number concentration of fibres (aspect ratio > 3) longer than 5 microns, as measured by optical microscopes lacking the ability to resolve thin (< 0.25 micron dia.) fibres; or (ii) by electron microscopy of mostly short, thin fibres by scanning a small fraction of the surface of the filter on which they have been collected. The conventional electron microscopy analytical protocols lack the ability to determine the presence of a statistically relevant number of the long fibres having the greatest hazard potential. A strategy for determining the distribution of long fibres of all thicknesses is outlined.

In plain English

This paper was a review the author presented at a 1993 workshop on health risks of chrysotile asbestos. It reported no new data from people or animals. It summarized existing knowledge about how airborne chrysotile fibres behave and how they are measured. The author stated that the size and shape of airborne chrysotile fibres depend on the specific situation, so general answers cannot be given and fibres need to be measured at each site. The phase-contrast optical microscope, the author noted, cannot resolve fibres thinner than about 0.25 micrometres, which the author described as those most closely linked to mesothelioma risk. It also cannot tell asbestos types apart. The author wrote that electron microscopy analyses usually include few or no fibres longer than 5 micrometres. Citing a rat study by other researchers, the author reported that longer chrysotile fibres appeared to be cleared more slowly. The author outlined an electron microscopy strategy for counting long fibres in U.S. buildings and concluded that more experimental data and better prediction models are needed.

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: Narrative review (workshop paper) summarizing existing knowledge on the nature of exposure to airborne chrysotile; no original data
• Who was studied: No people or animals were studied directly; the paper reviewed published work on airborne chrysotile fibres, their deposition in the lungs, and microscopy methods for measuring them
• Exposure: Airborne chrysotile asbestos fibres, particularly their length, diameter and shape, and how these are measured
• Main results:
  • The author stated that the size and shape of airborne chrysotile fibres depend on the particular exposure situation, so general answers cannot be given and they need to be measured for each site
  • The author noted that the phase-contrast optical microscope cannot resolve fibres thinner than about 0.25 micrometres, described as those most closely associated with mesothelioma risk
  • The author noted that the phase-contrast optical microscope cannot distinguish between asbestos types or between asbestos and other fibres
  • According to the author, electron microscopy analyses examine small fractions of the filter, so few SEM or TEM data give useful information on the long fibres usually most related to hazard
  • Reviewing a comparison by Cherrie et al. (1989), the author reported that TEM gave higher total fibre counts than SEM, which in turn gave higher counts than phase-contrast optical microscopy
  • Reviewing a rat study by Coin et al. (1992), the author reported that the average length of retained chrysotile fibres increased over time, consistent with slower clearance of longer fibres
  • The author stated that the ICRP and NCRP regional lung deposition models predict different deposition efficiencies and cannot be considered definitive for quantitative risk assessment
  • The author outlined a strategy, developed for a Health Effects Institute-Asbestos Research programme in U.S. public and commercial buildings, using low-magnification TEM screening of large filter areas to count long fibres
• The authors' conclusion: The author concluded that more experimental data and better prediction models are needed to define the dose of inhaled fibres within critical fibre size ranges

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Deposition, Translocation, biopersistence, Retention TIme, Aspect Ratio (Length-to-diameter ratio).

Related studies

• Pulmonary mineral fibers after occupational and environmental exposure to asbestos in the Russian chrysotile industry — A. Tossavainen, E. Kovalevsky, et al. (2000)
• The nature, hazards and assessment of occupational exposure to airborne asbestos dust: a review — W.H. Walton (1982)
• Nonoccupational exposure to chrysotile asbestos and the risk of lung cancer — M. Camus, J. Siemiatycki, et al. (1998)
• Mesothelioma from chrysotile asbestos: update — M.S. Kanarek (2011)
• Mesothelioma in a worker who spun chrysotile asbestos at home during childhood — E. Yano, Z.M. Wang, et al. (2009)
• Biological indicators of chrysotile exposure — B.W. Case (1994)

Browse more research in The Annals of Occupational Hygiene, or return to medical research.