Characterization of three types of chrysotile asbestos after aerosolization

Our plain-English summary of Characterization of three types of chrysotile asbestos after aerosolization, by K.E. Pinkerton, A.R. Brody, D.A. McLaurin, et al (Environmental Research, 1983).

The study

• Authors: K.E. Pinkerton, A.R. Brody, D.A. McLaurin, B. Adkins, R.W. O'Connor, P.C. Pratt, J.D. Crapo
• Journal: Environmental Research
• Published: 1983;31(1):32-53
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Jeffrey Mine and Coalinga Mine chrysotile, two asbestos samples prepared for experimental research by the National Institute of Environmental Health Sciences, and the UICC B chrysotile reference sample have been characterized in the aerosolized state using gravimetric measurements, light microscopy, scanning electron microscopy, and x-ray energy spectrometry. These methods revealed (1) a greater "respirable" mass fraction in the Jeffrey and UICC B preparations compared to the Coalinga sample, (2) for fibers greater than 5 microns in length and less than 3 microns in diameter, Jeffrey Mine chrysotile contained a significantly greater fraction of fibers longer than 40 microns in length compared to the UICC B or Coalinga Mine chrysotiles, and (3) Jeffrey and UICC B chrysotile contained no fibers or fiber clusters which exceeded 2 microns in diameter while Coalinga chrysotile contained numerous fibers and fiber clusters which were greater than 2 microns in diameter. The characterization of these chrysotile preparations in the aerosolized state, in particular the Coalinga Mine chrysotile, demonstrated different fiber length and fiber width distributions when compared with previous characterizations of samples that had been dispersed in a liquid medium by ultrasonification. These observations emphasize the importance of determining size distribution of fibers in the aerosolized state for inhalation studies and the size distribution of fibers in a liquid suspension for oral ingestion, instillation, or injection studies. Because of differences in length-width distributions, each of the studied chrysotile preparations would be expected to have different patterns of deposition in the alveolar regions of the lung after an inhalation exposure.

In plain English

This 1983 laboratory study examined three chrysotile asbestos samples dispersed as airborne dust in an exposure chamber. They were Jeffrey Mine chrysotile (Quebec), Coalinga Mine chrysotile (California) and the UICC B reference sample. No people or animals were studied. The authors weighed the dust and measured fibers by microscopy. With one sampler, the respirable share of dust was 87% for Jeffrey, 76% for UICC B and 42% for Coalinga. By light microscopy, among fibers longer than 5 micrometres and under 3 micrometres wide, Jeffrey had a significantly greater share longer than 40 micrometres than the others. By electron microscopy, no Jeffrey or UICC B fiber or fiber cluster was wider than 2 micrometres. Coalinga had many wider ones, which widened as they lengthened. In airborne Coalinga, 28.1% of all particles were longer than 10 micrometres. An earlier study of the same sample dispersed in liquid by ultrasonification found 2.1% of all chrysotile particles analyzed longer than 10 micrometres. The authors concluded that Jeffrey and UICC B were mixed short- and long-fiber preparations, and Coalinga a somewhat short-fiber preparation without very long respirable fibers.

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 airborne (aerosolized) asbestos fiber samples; no human or animal subjects
• Who was studied: Three chrysotile samples: Coalinga Mine chrysotile (California, Union Carbide, labelled COF-25), Jeffrey Mine chrysotile (Quebec, Canada, Johns-Manville, labelled Plastibest-20), and the UICC B chrysotile reference sample (a mix from eight Canadian mines). The two mine samples were prepared for experimental research by the National Institute of Environmental Health Sciences.
• Exposure: Chrysotile from each sample was dispersed into a dust cloud in a 5-cubic-metre stainless steel exposure chamber using a modified Timbrell generator. Samples of the chamber air were then weighed and examined by light microscopy, scanning electron microscopy and x-ray energy spectrometry.
• Main results:
  • Using the Casella sampler, the respirable share of the total chamber dust was 87% for Jeffrey and 76% for UICC B.
  • Using the Casella sampler, the authors described the respirable share as significantly lower for Coalinga, at 42%.
  • Using the Cascade impactor, a smaller share was respirable: 21% of total dust for Jeffrey and 5% for Coalinga. UICC B was not measured this way.
  • By light microscopy, counting fibers 5 micrometres or longer, more than 70% of counted fibers in all three samples were 5 to 30 micrometres long.
  • By light microscopy, among fibers longer than 5 micrometres and less than 3 micrometres in diameter, Jeffrey had a significantly greater share of fibers longer than 40 micrometres than UICC B or Coalinga. This applied to the 40-50, 50-100 and over-100 micrometre intervals, each at P less than 0.05.
  • By scanning electron microscopy, at least 92% of combined fibers and fiber clusters in Jeffrey and UICC B were shorter than 10 micrometres, compared with 66% in Coalinga.
  • No fiber or fiber cluster measured in Jeffrey or UICC B was wider than 2 micrometres in diameter.
  • In Coalinga, fibers and fiber clusters generally became wider as they became longer.
  • In airborne Coalinga, 34.0% of combined fibers and fiber clusters, or 28.1% of all particles (fibers, fiber clusters and nonfibrous particles), were longer than 10 micrometres.
  • The authors compared this with an earlier study (Campbell et al., 1980) of the Coalinga sample dispersed in liquid by ultrasonification. That study had reported that 2.1% of the total chrysotile particles analyzed were longer than 10 micrometres. The article's sentence is split by Table 7: the length criterion appears after the table as 'particles analyzed were greater than 10 pm in length'.
  • Among the 50 nonfibrous particles analyzed per sample, the share with a magnesium-to-silicon ratio matching chrysotile was 40% for Jeffrey, 52% for UICC B and 20% for Coalinga.
• The authors' conclusion: The authors concluded that, in terms of respirability, the airborne Jeffrey and UICC B fibers made up a mixed short- and long-fiber preparation. The airborne Coalinga fibers made up a somewhat short-fiber preparation in which very long respirable fibers were not present. They stressed measuring fiber sizes in the airborne state for inhalation studies.
• Limitations the authors state:
  • The definition of 'respirable mass concentration' was arbitrary and differed between the two sampling instruments.
  • Light microscopy and electron microscopy fiber counts used different counting rules, so they cannot be expected to agree closely.
  • Respirable mass by Cascade impactor was measured only for Jeffrey and Coalinga, not UICC B.
  • The Coalinga chamber mass concentration with the Cascade impactor was based on only three samples (and, per the table note, a single respirable sample).
  • Further grinding or fiber separation of these samples may change the fiber size distribution from what is reported here.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Jeffrey mine, Asbestos, Quebec
• Santa Rita mine, Joaquin Ridge near Coalinga, California

All asbestos mines

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Jeffrey Mine, UICC, Scanning Electron Microscopy (SEM), Fiber Length, Deposition.

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