Waterborne asbestos: Good practices for surface waters analyses

Our plain-English summary of Waterborne asbestos: Good practices for surface waters analyses, by C. Avataneo, S. Capella, M. Luiso, et al (Frontiers in Chemistry, 2023).

The study

• Authors: C. Avataneo, S. Capella, M. Luiso, G. Marangoni, M. Lasagna, D.A. De Luca, M. Bergamini, E. Belluso, F. Turci
• Journal: Frontiers in Chemistry
• Published: 2023;11:1104569
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos occurrence has been mainly monitored in air so far and only limitedly considered in other matrices, such as water. Waterborne asbestos could originate from natural or anthropogenic sources, leading to non-conventional exposure scenarios. It could be a secondary source of airborne asbestos in case of water-to-air migration, particularly in case of surface moving water, such as in rivers and streams. The scarce attention dedicated to waterborne asbestos has led to a considerable fragmentation in regulatory approaches regarding the study of water samples possibly contaminated by mineral fibres. In this context, this study has been designed to test the reliability of an existing analytical method devoted to natural waters investigations. Following the operational protocol issued by the Piedmont (Italy) Environmental Protection Agency, Scanning Electron Microscopy analyses have been performed on a standard sample of waterborne chrysotile, mimicking stream water. The investigations have been performed by different operators and using different analytical setups, to verify whether the method applied has a good interlaboratory reproducibility and which could be the most error-prone analytical steps. Three data sets have been obtained on the same sample, showing a low reproducibility among each other. Possible reasons causing this discrepancy have been discussed in detail and good practices to perform reliable analyses on surface water samples containing asbestos have been proposed to help the regulatory organs to better define analytical protocols.

Copyright © 2023 Avataneo, Capella, Luiso, Marangoni, Lasagna, De Luca, Bergamini, Belluso and Turci.

In plain English

This study tested how consistently an existing Italian laboratory method, the Piedmont Environmental Protection Agency's U.RP.M842 rev.03 protocol, measures asbestos in surface water using scanning electron microscopy. It did not study people or health effects. The authors suspended chrysotile from the former Balangero mine in tap water in a stirred tank to mimic contaminated stream water, at a nominal 137.40 μg/L. One filter was cut into three portions. An operator in Lab 1 analysed one gold-coated portion. Another operator in Lab 2 analysed one graphite-coated and one gold-coated portion. Counting fibres longer than 5 µm, Lab 1 found 4.44 × 10^7 fibres per litre, against 2.85 × 10^7 and 3.21 × 10^7 for Lab 2, and the two labs' confidence ranges did not overlap. Lab 1 detected many more very thin fibres. Mass results ran the other way, with more overlapping error ranges: 39.49 ± 18.48 μg/L for Lab 1 versus 103.43 ± 25.93 and 66.60 ± 15.62 μg/L for Lab 2. The authors concluded that good interlaboratory reproducibility is not guaranteed with the methods currently available in Italy. They proposed practices such as gold coating, a minimum image resolution, and clearer rules for counting bundles.

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 method-comparison (interlaboratory reproducibility) study on a prepared water sample; no human subjects
• Who was studied: No people studied. One prepared water sample: chrysotile standard from the former Balangero mine (Italy) suspended in tap water in a 38.28 L tank. 0.05 L was filtered onto one membrane, cut into three portions and analysed by two laboratories (Lab 1; Lab 2).
• Exposure: Waterborne chrysotile (a 1:1 mix of medium-to-long and short fibre products) at a nominal concentration of 137.40 μg/L, intended as a worst-case contaminated stream
• Main results:
  • Counting only respirable (WHO) fibres longer than 5 µm, the concentration was 4.44 × 10^7 fibres per litre for Lab 1 (gold coating), 2.85 × 10^7 for Lab 2 (graphite coating) and 3.21 × 10^7 for Lab 2 (gold coating)
  • The 95% fiducial (confidence) limits of Lab 1's results did not overlap with those of Lab 2
  • Number of respirable fibres counted: 228 by Lab 1, against 126 (graphite-coated) and 142 (gold-coated) by Lab 2
  • When fibres of all lengths were counted, the results were closer: 4.97 × 10^7 fibres per litre for Lab 1 and 4.16 × 10^7 or 4.14 × 10^7 for Lab 2 (graphite and gold coating, respectively)
  • 95% of fibres detected by Lab 1 were thinner than 0.2 µm, against 59% (graphite-coated) and 50% (gold-coated) for Lab 2 according to Table 2
  • Mass concentrations for respirable fibres were higher for Lab 2 even though it counted fewer fibres. Table 2 gives 39.49 ± 18.48 μg/L for Lab 1, against 103.43 ± 25.93 μg/L (graphite-coated) and 66.60 ± 15.62 μg/L (gold-coated) for Lab 2.
  • For respirable fibres, the mass concentrations with their 95% confidence limits overlapped more among the three setups than the fibre counts did
  • Thinner fibres were detected on the gold-coated portions, which the authors considered gave the more reliable fibre-per-litre values
• The authors' conclusion: The authors concluded that good interlaboratory reproducibility is not guaranteed with the methods currently available in Italy. They called for regulators to define interlaboratory circuits, minimum instrument requirements and better counting rules, especially for bundles and aggregates.
• Limitations the authors state:
  • The authors could not determine whether the differences between data sets came mainly from the analytical setup and method or from the operator
  • Because fibre density was high, a smaller area than the usual 1 mm2 was examined, which might explain the difference between the two gold-coated data sets
  • The chrysotile powder could contain traces of other minerals that were not counted, one possible reason measured mass fell below the nominal concentration
  • More data would be needed to define a precise relation between the amount of chrysotile added and the measured concentration

Topics

Medical terms in this study, explained in our Lexicon: Scanning Electron Microscopy (SEM), Chrysotile.

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