Chrysotile asbestos in serpentinite quarries: a case study in Valmalenco, Central Alps, Northern Italy

Our plain-English summary of Chrysotile asbestos in serpentinite quarries: a case study in Valmalenco, Central Alps, Northern Italy, by A. Cavallo, B. Rimoldi (Environmental Science. Processes & Impacts, 2013).

The study

• Authors: A. Cavallo, B. Rimoldi
• Journal: Environmental Science. Processes & Impacts
• Published: 2013;15(7):1341-50
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The Valmalenco serpentinite (Central Alps, Northern Italy) is marketed worldwide as dimension and decorative stone. However, the same area was once subject to chrysotile asbestos mining, from the XIX century until 1975. Asbestos is a well-known carcinogen, and there is the possibility of releasing fibres during quarrying, subsequently exposing workers. From 2004 to 2011, extensive sampling and monitoring of quarry fronts, asbestos veins, commercial stones and airborne asbestos was carried out. Massive rock and vein samples were analyzed by a combined use of optical microscopy, X-ray powder diffraction (XRPD) and quantitative electron microscopy (SEM). Asbestos is concentrated almost exclusively in discrete horizons, that coincide with the main discontinuities of the rock mass. Commercial stones without fractures and veins are practically asbestos free, whereas there is a slight contamination (sometimes exceeding the 1000 ppm threshold) close to hydrothermal selvages. Quarry floors were always quite contaminated by chrysotile "beards" detached from the surface of the blocks. The airborne asbestos concentrations (PCM and SEM) were distributed over a wide range, mostly below the occupational exposure limit of 0.1 f ml(-1). Concentrations at the quarry property border or at the closest villages were always below the environmental exposure limit of 0.002 f ml(-1). The extreme thinness of chrysotile fibrils produced during quarrying activities, and the abundance of pseudo-fibrous antigorite cleavage fragments proved the SEM-EDS analytical procedure to be the most suitable. It is of crucial importance to avoid the interception of veins during quarrying and to remove all visible asbestos from the extracted blocks, before any further processing.

In plain English

From 2004 to 2011 the authors studied chrysotile asbestos in seven serpentinite quarries in Valmalenco, Northern Italy, where chrysotile was mined until 1975. They analyzed 74 rock, 85 vein and 21 cutting-sludge samples, plus 204 personal and 28 environmental air samples. Chrysotile occurred almost only in thin veins along main fractures. Estimated average quarry content ranged from 0.01 to 0.32 percent by weight. Commercial stone without visible fractures or veins, sampled at least 10 cm from veins, was virtually asbestos-free; rock 1 cm from veins sometimes exceeded 1000 ppm. Amphibole asbestos was never detected, though the authors said it could not be completely excluded, especially near talc veins. Worker exposures were mainly below the occupational limit, except 6 localized cases; the highest, 0.2074 fibres per ml, occurred during diamond wire cutting. Border and nearest-village readings were below the 0.002 fibres per ml environmental limit, except 2 values without statistical significance. Light microscopy (PCM) counts were mostly lower than electron microscopy counts. The authors concluded there was no evidence of pollution outside the quarries and that avoiding veins during quarrying is crucial.

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: Field and laboratory monitoring case study: geological surveys of quarries, mineralogical analysis of rock, vein and sludge samples, and personal and environmental air sampling
• Who was studied: Seven serpentinite quarries in Valmalenco, Central Alps, Northern Italy: five massive serpentinite and two schistose serpentinite. The area was mined for chrysotile until 1975. Samples comprised 74 rock, 85 mineralized vein and 21 cutting sludge samples, plus 204 personal air samples (41 PCM, 163 SEM-EDS) and 28 environmental air samples, collected from September 2004 to October 2011.
• Exposure: Naturally occurring chrysotile asbestos in serpentinite rock, released during quarrying activities (drilling, diamond wire cutting, and moving or handling material). Only chrysotile and non-asbestos antigorite cleavage fragments were found in air samples.
• Main results:
  • Chrysotile occurred almost exclusively in thin veins and lenses along the main fracture systems of the rock.
  • Estimated average asbestos content of the quarries ranged from 0.01 wt% (SC quarry) to 0.32 wt% (DF quarry).
  • Commercial stone samples were virtually asbestos-free, well below 1000 ppm. These samples had no visible fractures or veins and were taken at least 10 cm from vein selvages.
  • Rock 1 cm from vein selvages showed slight chrysotile contamination, sometimes above the 1000 ppm threshold. The highest values were near the biggest veins (VB and DF quarries), including in cutting sludge.
  • Amphibole asbestos was never detected. The authors noted that its presence could not be completely excluded, especially near talc veins, where fibrous tremolite had been reported.
  • Workers' occupational exposure levels were mainly below the occupational exposure limit, except for 6 localized cases.
  • During diamond wire cutting, a task that uses water, occasional high values reached up to 0.2074 fibres per ml (SEM-EDS personal samples).
  • The occupational limit was not exceeded during drilling.
  • Chrysotile concentrations in massive serpentinite quarries were generally higher than in schistose serpentinite quarries.
  • Chrysotile concentrations at quarry property borders and nearest villages were below the Italian environmental exposure limit of 0.002 fibres per ml, except for 2 values described as having no statistical significance.
  • PCM (light microscopy) results were mostly lower than SEM-EDS results. The authors attributed this to extremely thin chrysotile fibrils that PCM cannot detect. In one paired sample, PCM gave 0.025 fibres per ml where SEM-EDS gave the maximum of 0.2074.
• The authors' conclusion: The authors concluded that airborne asbestos concentrations varied widely but were generally higher in massive than schistose serpentinite quarries, and that there was no evidence of pollution outside the quarries. They also concluded that it is crucial to avoid intercepting veins during quarrying and to remove visible asbestos from blocks before further processing.
• Limitations the authors state:
  • The study did not consider asbestos occurring as micro-veins and micro-fractures outside the main discontinuities.
  • The findings cannot be fully applied to highly fractured rock masses.
  • Amphibole asbestos cannot be completely excluded, especially near talc veins where fibrous tremolite has been reported.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Serpentinite, Occupational Exposure, Environmental Exposure, Fibril, fibrous antigorite, Cleavage Fragment.

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• An update of cancer mortality among chrysotile asbestos miners in Balangero, northern Italy — G. Piolatto, E. Negri, et al. (1990)
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• Airborne fiber concentration and size distribution of mineral fibers in area with serpentinite outcrops in Aichi prefecture, Japan — K. Sakai, N. Hisanaga, et al. (2001)
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