Assessment of the potential hazard represented by natural raw materials containing mineral fibres-The case of the feldspar from Orani, Sardinia (Italy)

Our plain-English summary of Assessment of the potential hazard represented by natural raw materials containing mineral fibres-The case of the feldspar from Orani, Sardinia (Italy), by A.F. Gualtieri, N.B. Gandolfi, S. Pollastri, et al (Journal of Hazardous Materials, 2018).

The study

• Authors: A.F. Gualtieri, N.B. Gandolfi, S. Pollastri, R. Rinaldi, O. Sala, G. Martinelli, T. Bacci, F. Paoli, A. Viani, R. Vigliaturo
• Journal: Journal of Hazardous Materials
• Published: 2018;350:76-87
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This work describes the nature of the potentially hazardous fibrous amphibole found in the Orani's feldspar mine (Sardinia, Italy). To identify its nature, a protocol of analysis including morphometric, chemical and crystallographic characterizations was applied. Thanks to this approach, it was possible to classify the observed fibres as tremolite after comparing chemical data, SEM/TEM observations, FTIR/ Raman spectra and X-ray diffraction data with those reported for a standard sample. The unit cell parameters of the investigated tremolite phase are a = 9.82(1) Å, b = 18.08(3) Å, c = 5.27(1) Å, and the angle β corresponds to 104.4(1)°. The mean concentration of asbestos tremolite in the Orani's feldspar is 0.28 wt%. Most of the fibres (0.26 wt%) are respirable 'regulated' fibres, representing a potential hazard. Because the total amount of tremolite in the sample is 0.6 wt%, a large fraction of it has a crystal habit other than fibrous-asbestiform or acicular. The obtained results allowed us to suggest possible solutions for a safe exploitation and mineral processing of the Orani's mine. The procedure proposed herein may be a general tool suitable to identify the mineralogical nature of fibrous minerals in raw materials and assess if they may represent a potential health/environmental hazard.

Copyright © 2018 Elsevier B.V. All rights reserved.

In plain English

This laboratory study examined rock samples collected around a feldspar mine at Orani, Sardinia (Italy), and a commercial feldspar product (labelled MM) once sold to Italian ceramics makers, to identify a fibrous mineral found there. The authors combined microscopy, X-ray diffraction, spectroscopy and electron microprobe analysis, and compared the fibres with a reference sample of tremolite asbestos. X-ray diffraction found an amphibole mineral in samples 1, 4 and MM. The authors classified the fibres as tremolite asbestos and found no other asbestos minerals. In the MM product, tremolite fibres made up on average 0.28% by weight. Fibres meeting World Health Organization counting criteria (regulated fibres) made up 0.26%. Total tremolite was 0.6%, so a large fraction of it had a crystal habit other than fibrous-asbestiform or acicular. Results depended on the sample-preparation method used. The authors concluded that tremolite asbestos is present as an impurity, that most of its fibres are respirable, and that only asbestos-free parts of the mine should be selectively worked. They noted that new air sampling is needed to learn how many fibres actually become airborne.

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 mineralogical characterization (morphometric, chemical and crystallographic analysis) of rock samples and a commercial product, compared with a tremolite asbestos reference standard
• Who was studied: Rock samples (1, 2, 3, 3-bis, 4) collected around the Orani feldspar mine (Nuoro, Sardinia, Italy), mined since the 1970s and impounded in late 2015, plus the commercial feldspar product MM
• Exposure: Tremolite asbestos occurring as a natural contaminant of a feldspar raw material used for traditional ceramics, glazes and sanitary ware. Earlier monitoring, cited by the authors and not done in this study, had reported regulated tremolite fibres of about 100(15) ff/l near grinding, mixing and bagging machinery.
• Main results:
  • X-ray diffraction screening found an amphibole phase in samples 1, 4 and MM (tremolite 1.3, 0.5 and 0.6 wt% respectively in Table 1)
  • The micro-Raman spectrum of fibres from the MM sample matched a standard tremolite specimen
  • All fibres examined had the same composition, which the authors said ruled out other asbestos minerals
  • By comparison with the HSE reference standard, the authors classified the fibrous component as asbestos tremolite
  • In sample MM, mean concentration was 2818 ppm (0.28%) for all tremolite fibres and 2646 ppm (0.26%) for regulated fibres
  • For regulated fibres, mean length ranged from 8.35 to 10.29 micrometres and mean diameter from 0.53 to 0.77 micrometres
  • Total tremolite in sample MM was 0.6 wt%, so a large fraction had a crystal habit other than fibrous-asbestiform or acicular
  • The Italian Ministerial Decree preparation method (Code 1) always gave lower fibre concentrations than the alternative method (Code 2)
  • The authors stated that the concentrations exceed the 0.1 wt% limit set by Italian Law 152/06 for free asbestos fibres in contaminated anthropogenic soils
• The authors' conclusion: The authors concluded that tremolite asbestos is present as an impurity in the Orani feldspar. They found that most of the tremolite fibres are respirable, although a large fraction of the tremolite does not display a fibrous-asbestiform crystal habit. They recommended selective exploitation of asbestos-free material, following the New Caledonia example, and new air sampling.
• Limitations the authors state:
  • X-ray diffraction cannot show crystal habit, and at this low amount it cannot reliably tell tremolite from other calcic or sodium-calcic amphiboles
  • SEM-EDS chemical analysis was not conclusive and needed electron microprobe confirmation
  • Fibre aggregates were unevenly distributed, which affected the quantitative SEM estimates
  • Chemical comparison with the HSE reference standard was not possible
  • The study did not measure how much of the fibre content becomes airborne
  • The full protocol is costly for most environmental monitoring laboratories

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Group, Tremolite, X-Ray Diffraction (XRD), Habit, Asbestiform, Acicular.

Related studies

• Minimising health hazards associated with derogated products and in-situ materials containing chrysotile contaminated with amphibole asbestos fibres — R.M. Howie (1999)
• Potential health hazards associated with exposures to asbestos-containing drywall accessory products: A state-of-the-science assessment — A.D. Phelka, B.L. Finley (2012)
• Occupational exposure in the removal and disposal of asbestos-containing materials in Italy — A. Scarselli, M. Corfiati, et al. (2016)
• Asbestos containing materials in schools of Rome and surrounding area (Italy) — A. Campopiano, A. Cannizzaro, et al. (2021)
• Potential health hazards of ceramic ring lining material — D.R. Davis (1987)
• Risk assessment of asbestos containing materials in a deteriorated dwelling area using four different methods — Y.L. Zhang, H.S. Byeon, et al. (2021)

Browse more research in Journal of Hazardous Materials, or return to medical research.