Real-time detection of airborne asbestos by light scattering from magnetically re-aligned fibers

Our plain-English summary of Real-time detection of airborne asbestos by light scattering from magnetically re-aligned fibers, by C. Stopford, P.H. Kaye, R.S. Greenaway, et al (Optics Express, 2013).

The study

• Authors: C. Stopford, P.H. Kaye, R.S. Greenaway, E. Hirst, Z. Ulanowski, W.R. Stanley
• Journal: Optics Express
• Published: 2013;21(9):11356-67
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Inadvertent inhalation of asbestos fibers and the subsequent development of incurable cancers is a leading cause of work-related deaths worldwide. Currently, there is no real-time in situ method for detecting airborne asbestos. We describe an optical method that seeks to address this deficiency. It is based on the use of laser light scattering patterns to determine the change in angular alignment of individual airborne fibers under the influence of an applied magnetic field. Detection sensitivity estimates are given for both crocidolite (blue) and chrysotile (white) asbestos. The method has been developed with the aim of providing a low-cost warning device to trades people and others at risk from inadvertent exposure to airborne asbestos.

In plain English

This laboratory study described developing and testing an optical instrument to detect airborne asbestos in real time. The instrument shines laser light on single airborne particles and uses the scattered-light pattern to tell fibers from other particles. It then measures how far each fiber turns in a magnetic field. Asbestos, the authors explained, is almost unique among fibrous materials in turning this way. They built a single-beam version, then a dual-beam version measuring each fiber before and after the field. In dual-beam laboratory tests, crocidolite fibers were about 32 times more likely than gypsum fibers to turn more than 20 degrees. Statistical analyses suggested crocidolite could be detected with greater than 99% confidence if it made up at least about 11% (plus or minus 2%) of fibers present. For chrysotile, which turned less, the figure was about 45% (plus or minus 5%). Preliminary field tests at UK clearance or renovation sites gave correct positive or null responses. The authors concluded that airborne asbestos can be rapidly detected this way. They noted reliability depends on how many non-asbestos fibers 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: Laboratory development and testing of an optical detection instrument (single-beam, then dual-beam laser light-scattering systems), with preliminary field testing
• Who was studied: Laboratory-generated aerosols of asbestos (UICC respirable reference crocidolite and chrysotile) and of non-asbestos materials, including fibrous and non-fibrous aerosols such as gypsum. Also background air at an asbestos-free building renovation site, and preliminary field tests at various UK asbestos clearance or renovation locations.
• Exposure: Not a health-exposure study. Crocidolite and chrysotile asbestos fibers and non-asbestos fibers (e.g. gypsum) were passed through a magnetic field. The method relies on asbestos being almost uniquely turned by magnetic fields among fibrous materials.
• Main results:
  • In the fiber-versus-non-fiber test (a peak-to-mean ratio above 10 counted as a fiber), about 2% of particles at the asbestos-free renovation site scored as fibers
  • In the same test, about 40% of chrysotile particles scored as fibers and about 60% did not, which the authors attributed to clumping
  • More than 70% of crocidolite particles scored as fibers (peak-to-mean ratio above 10)
  • In the single-beam system, the magnetic field shifted the alignment distribution of crocidolite fibers by about 7 degrees (2,380 fibers with the field, 2,393 without)
  • In the single-beam system, a fiber detected at an alignment angle greater than +20 degrees was about 6 times more likely to be asbestos than a non-asbestos fiber
  • In the dual-beam system, the best discrimination came with magnets at 90 degrees to the airflow rather than at the 45 degrees predicted by theory
  • In the dual-beam system, crocidolite fibers were about 32 times more likely than gypsum fibers to be re-aligned more than 20 degrees (some 2,300 fibers in each group)
  • Statistical analyses suggested crocidolite could be detected with greater than 99% confidence if crocidolite made up at least about 11% (plus or minus 2%) of all fibers present
  • If only crocidolite fibers were present, the analysis suggested detection could be made with as few as 5 to 10 fiber measurements
  • For 99% confidence detection of chrysotile, chrysotile should make up at least about 45% (plus or minus 5%) of the fibers present
  • If only chrysotile fibers were present, 30 to 40 fiber measurements would be needed for 99% confidence
  • In preliminary field testing at UK sites where earlier surveys had already established whether asbestos was present, the prototypes correctly gave positive or null responses
• The authors' conclusion: The authors concluded that airborne asbestos fibers can be rapidly detected by analysing light-scattering patterns from individual particles carried through a magnetic field
• Limitations the authors state:
  • Whether a re-aligned fiber can be judged to be asbestos depends on the relative concentrations of asbestos and non-asbestos fibers in the air
  • In the single-beam system, a higher concentration of non-asbestos fibers than asbestos fibers would raise the risk of falsely detecting asbestos
  • The single-beam system was limited because each fiber's alignment before entering the magnetic field was not accurately known
  • Chrysotile fibers tend to clump, so many were not counted as fibers by the fiber test
  • The method was not intended to reproduce the statutory filter-based and EDAX procedures for assessing permitted post-clearance asbestos levels
  • Field testing was preliminary and was still continuing

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Chrysotile.

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