Pathogenic Potential of Respirable Spodumene Cleavage Fragments following Application of Regulatory Counting Criteria for Asbestiform Fibres

Our plain-English summary of Pathogenic Potential of Respirable Spodumene Cleavage Fragments following Application of Regulatory Counting Criteria for Asbestiform Fibres, by M. Gardner, M. Cross, S. Reed, et al (International Journal of Environmental Research and Public Health, 2022).

The study

• Authors: M. Gardner, M. Cross, S. Reed, M. Davidson, R. Hughes, J. Oosthuizen
• Journal: International Journal of Environmental Research and Public Health
• Published: 2022;19(24)
• Read it: PubMed · Publisher · Free full text

Abstract

Health risks from exposure to lithium-bearing spodumene cleavage fragments are unknown. While asbestiform fibres can lead to fibrosis, mesothelioma and lung cancer, controversy remains whether non-asbestiform cleavage fragments, having equivalent dimensions, elicit similar pathologic responses. The mineralogy of respirable particles from two alpha (α)-spodumene concentrate grades (chemical and technical) were characterised using semi-quantitative X-ray diffraction (XRD). Particles were measured using scanning electron microscopy (SEM) and the dimensions (length [L], diameter [D], aspect ratio [AR]) applied to regulatory counting criteria for asbestiform fibres. Application of the current World Health Organization (WHO) and National Occupational Health and Safety Commission (NOHSC) counting criteria, L ˃ 5 µm, D ˂ 3 µm, AR ˃ 3:1, to 10 SEM images of each grade identified 47 countable particles in the chemical and 37 in the technical concentrate test samples. Of these particles, 17 and 16 in the chemical and technical test samples, respectively, satisfied the more rigorous, previously used Mines Safety and Inspection Regulations 1995 (Western Australia [WA]) criteria, L ˃ 5 µm and D ≤ 1 µm. The majority of the countable particles were consistent with α-spodumene cleavage fragments. These results suggest elongated α-spodumene particles may pose a health risk. It is recommended the precautionary principle be applied to respirable α-spodumene particles and the identification and control of dust hazards in spodumene extraction, handling and processing industries be implemented.

In plain English

This laboratory study examined mineral dust. It did not test people, animals or cells. The authors collected two grades, chemical and technical, of crushed α-spodumene concentrate (a lithium ore) from a mining and processing facility in Western Australia. X-ray analysis found spodumene made up 42% of the chemical grade and 25% of the technical grade, with quartz at 14% and 12%. No asbestiform minerals were identified. The authors separated out respirable particles and measured them in 10 electron-microscope images per grade. Under the WHO and Australian NOHSC fibre-counting rules (longer than 5 µm, narrower than 3 µm, more than three times as long as wide), 47 chemical-grade and 37 technical-grade particles counted. Of these, 17 and 16 met a stricter former Western Australian mining rule (longer than 5 µm, 1 µm wide or less). Most countable particles were consistent with spodumene cleavage fragments. None met the size the earlier "Stanton Hypothesis" links most strongly to tumours. The authors concluded that spodumene processing may generate harmful dust, and they recommended precautionary dust control. They also pointed to the quartz content.

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 mineral characterisation of bulk ore samples: X-ray diffraction to identify minerals and scanning electron microscopy to measure particle sizes, which were then compared against regulatory fibre-counting criteria. No human, animal or cell testing was done.
• Who was studied: Two grades of α-spodumene concentrate (chemical grade and technical grade), about 1.5 kg of each, collected from processing conveyors at a spodumene mining and processing facility in Western Australia. The ore came from a single pegmatite deposit. Ten SEM images were examined per grade.
• Exposure: Respirable particles from crushed and ground (comminuted) α-spodumene concentrate, extracted by elutriation (particles with an equivalent aerodynamic diameter of 4 µm or less). Particles were measured for length, diameter and aspect ratio.
• Main results:
  • Chemical grade: spodumene was the most abundant mineral at 42%, followed by quartz at 14%.
  • Technical grade: nontronite was the most abundant mineral at 52%, followed by spodumene at 25% and quartz at 12%.
  • No asbestiform minerals were identified in either grade.
  • Chemical grade, 10 images: 47 particles met the WHO (1997) and NOHSC (2005) criteria (L > 5 µm, D < 3 µm, AR > 3:1). Of these, 17 met the Mines Safety and Inspection Regulations 1995 (WA) criteria (L > 5 µm, D 1 µm or less).
  • Technical grade, 10 images: 37 particles met the WHO and NOHSC criteria. Of these, 16 met the Mines Safety and Inspection Regulations 1995 (WA) criteria.
  • Under the WHO and NOHSC criteria, mean particle length was 7.9 µm in the chemical grade and 7.6 µm in the technical grade. Mean diameter was 1.1 µm in both. Mean aspect ratio was 9:1 (chemical) and 10:1 (technical).
  • In both grades, most countable particles were consistent with α-spodumene cleavage fragments. In the chemical grade, a small number of countable particles had a fibre-like shape indicative of holmquistite, an amphibole.
  • No countable particle in either grade met the optimal tumour-inducing dimensions of the "Stanton Hypothesis" (from earlier animal research): longer than 8 µm and 0.25 µm or less in diameter.
  • Among WHO and NOHSC countable particles, 70.2% (chemical grade) and 75.7% (technical grade) were longer than 4 µm and narrower than 1.5 µm. Stanton et al. (1981) had reported these dimensions as correlating with a relatively high probability of carcinogenicity.
  • 12.8% of countable particles in the chemical grade and 8.1% in the technical grade were longer than 10 µm.
  • 4.3% of countable particles in the chemical grade and 8.1% in the technical grade met the width criteria taken from Wylie et al. (2020) and Korchevskiy and Wylie (2021).
• The authors' conclusion: The authors concluded that extracting, handling and processing α-spodumene may generate harmful mineral dust that puts workers at increased risk of permanent respiratory disease. They recommended applying the precautionary principle, monitoring in line with asbestiform fibre standards, and controlling dust. They also noted the significant quartz (crystalline silica) content.
• Limitations the authors state:
  • Because of low concentrations, the amphibole and the sodium magnesium aluminium oxide in both grades could not be fully characterised with certainty.
  • X-ray diffraction detects only crystalline materials. Amorphous material is not identified.
  • The authors acknowledged that the evidence that α-spodumene cleavage fragments are pathogenic may be limited.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Cleavage Fragment, Asbestiform, Fibrosis, Mesothelioma, Lung Cancer, Non-Asbestiform, Mineralogy, X-Ray Diffraction (XRD).

Related studies

• Assessment of the pathogenic potential of asbestiform vs. nonasbestiform particulates (cleavage fragments) in in vitro (cell or organ culture) models and bioassays — B.T. Mossman (2008)
• Dimensions of elongated mineral particles: a study of more than 570 fibers from more than 90 cases with implications for pathogenicity and classification as asbestiform vs. cleavage fragments — V.L. Roggli, C.L. Green (2019)
• Measuring EMPs in the lung what can be measured in the lung: Asbestiform minerals and cleavage fragments — V.L. Roggli (2018)
• Comments on "Dimensions of elongated mineral particles with implications for pathogenicity and classification as asbestiform versus cleavage fragments" — M.M. Finkelstein (2019)
• An inter-laboratory study to determine the effectiveness of procedures for discriminating amphibole asbestos fibers from amphibole cleavage fragments in fiber counting by phase-contrast microscopy — M. Harper, E.G. Lee, et al. (2012)
• Evaluation of the genotoxic and transformation potential induced by asbestos compared to cleavage fragments — S. La Maestra, G.M. Militello, et al. (2025)

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