Evaluation of asbestos dispersion during laser ablation of rocks containing Naturally Occurring Asbestos (NOA)

Our plain-English summary of Evaluation of asbestos dispersion during laser ablation of rocks containing Naturally Occurring Asbestos (NOA), by A. Bloise, F. Parisi, M.F. La Russa, et al (Heliyon, 2024).

The study

• Authors: A. Bloise, F. Parisi, M.F. La Russa, C. Apollaro, N. Godbert, I. Aiello, E. Giorno, A. Croce, L. Cagna, A.J. López, A. Ramil, D. Pereira
• Journal: Heliyon
• Published: 2024;10(21):e39624
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Health risks are often overlooked when the short-term consequences are not immediately apparent. During restoration work, cleaning actions can generate particles that pose health risks to workers through inhalation. This is particularly true in the case of asbestos fibres that might be spread out from the laser cleaning of buildings or heritage artifacts made of stone, such as serpentinite and other ultramafic rocks, that have a high probability of containing asbestos (e.g., chrysotile, tremolite asbestos, actinolite asbestos). To show workers the importance of wearing proper protection to prevent health injuries, several serpentinite samples, ascertained to contain asbestos minerals by specific investigations, have been laser ablated using ad hoc modified equipment in order to collocate a HEPA filter prone to collect all dust emitted during ablation. The powder deposited on the surface of these filters after laser ablation was analyzed, by Powder X -ray Diffraction (PXRD), Transmission Electron Microscopy combined with Energy Dispersive Spectroscopy (TEM/EDS), micro-Raman spectroscopy (μ-Raman) and Fourier-transform infrared spectroscopy (FTIR/ATR). The results confirmed the presence of asbestos fibres during the laser ablation of rocks containing Naturally Occurring Asbestos (NOA), emphasizing the importance of wearing appropriate personal protective equipment (PPE) during these procedures. Noteworthy, approximately 33 % of the analyzed fibres met the WHO criteria in size for respirable fibres. Furthermore, through our experiments, we also demonstrated that using tools that integrate filters into working tools would definitively further decrease the risk of fibres inhalation to workers.

© 2024 The Authors.

In plain English

This was a laboratory experiment. The authors took five slabs of commercial metabasite, serpentinite and ophicalcite from quarries of the Mount Reventino Unit in Calabria, southern Italy. They treated each slab with a laser for about 2 hours and collected the dust on a HEPA filter. They then examined that dust with X-ray diffraction, electron microscopy and two kinds of spectroscopy. Asbestos phases were found in all the collected dust samples. The asbestos fibres identified were tremolite asbestos, actinolite asbestos and chrysotile, and tremolite asbestos was the most abundant. About 40 fibres were measured for each sample, and 33.2% of the measured fibres fell within the WHO size criteria for respirable fibres. The fibres were up to 6.3 micrometres long, with an average length of about 0.98 micrometres, and averaged 0.13 micrometres wide. The laser left cross-wise fractures that were more evident in the amphibole fibres than in chrysotile. The authors concluded that building a filtration system into the laser equipment, along with workers wearing masks, can effectively reduce the risk of breathing in fibres. They called for further research on samples with higher concentrations of fibrous minerals.

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 experiment: laser ablation of asbestos-bearing rock samples, with the emitted dust collected on a HEPA filter and analysed by X-ray diffraction (PXRD), transmission electron microscopy with energy dispersive spectroscopy (TEM/EDS), micro-Raman and FTIR spectroscopy
• Who was studied: Five slabs of commercial rock: two metabasite (A19, A20, from Conflenti), one ophicalcite (R1) and two serpentinite (A, A18, from Reventino), all from quarries of the Mount Reventino Unit, Calabria, southern Italy. No humans or animals were studied.
• Exposure: Laser ablation of rocks containing naturally occurring asbestos (chrysotile, tremolite asbestos, actinolite asbestos). The laser ran at maximum power (4 W) over a 15 mm by 40 mm area, with the pattern repeated 20 times, for about 2 hours per sample.
• Main results:
  • Asbestos phases were found, in variable amounts, in the filter dust from all samples (PXRD)
  • The asbestos fibres detected in the filter dust were tremolite asbestos, actinolite asbestos and chrysotile
  • Tremolite asbestos was the most abundant asbestos phase, followed by chrysotile and actinolite asbestos
  • Of approximately 40 fibres measured per sample, 33.2% fell within the WHO criteria for respirable fibres
  • Measured fibres were up to a maximum of 6.3 μm long, with an average length of about 0.98 μm
  • Measured fibres were less than 0.5 μm wide, with an average width of 0.13 μm
  • Tremolite-actinolite asbestos fibres were wider than chrysotile fibres, and the longest fibres were chrysotile
  • The laser caused fractures across some fibres, and these were much more evident in the amphiboles (tremolite-actinolite) than in chrysotile
  • Micro-Raman spectroscopy distinguished actinolite asbestos from tremolite asbestos directly on the HEPA filters
• The authors' conclusion: The authors concluded that building a filtration system into laser ablation equipment, along with workers using masks, can effectively reduce the risk of fibre inhalation during cleaning of monuments and historical structures
• Limitations the authors state:
  • Laser settings were chosen to produce enough powder for laboratory analysis, not to match an optimised real-world laser cleaning technique
  • X-ray diffraction of the metabasite samples gave little information on asbestos phases
  • FTIR did not detect tremolite in samples R1 and A19, possibly because other minerals masked its signal
  • Amorphous spherical particles seen on the filters were not characterised
  • The authors stated that further research on samples with a higher concentration of fibrous minerals is needed

Topics

Medical terms in this study, explained in our Lexicon: naturally occurring asbestos (NOA), Serpentinite, Ultramafic Rocks, Chrysotile, Tremolite, Actinolite, Asbestos, Transmission Electron Microscopy (TEM).

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