The Concentration of Asbestos Fibers in Bulk Samples and Its Variation with Grain Size

Gaia M Militello,Elisa Sanguineti,Federico Mantovani,Adrián Yus González,Laura Gaggero

doi:10.3390/min9090539

Abstract

The aim of this work was to establish whether asbestos fibers homogeneously occur in the different fractions ground from naturally occurring asbestos lithotypes, and to calculate the contribution of fibers from each fraction to the overall concentration in the sample. Serpentinite, metabasalt, calc-schist, clay, debris material, and soil, were addressed. Grain size fractions below 20 mm were sieved at 2 mm and 0.106 mm; they were then were mechanically milled to obtain powders below 0.106 mm. The three powdered fractions were characterized using a scanning electron microscope coupled with energy dispersive spectroscopy following M.D. 06/09/94. The still in use (in some cases), Italian normative M.D. 161/2012 specifies that analyses must be performed on the <2 mm fraction and the concentration (mg/kg) correlated with the weight of the whole sample <20 mm. However, the fiber counts yielded asbestos concentrations 50–60% lower compared with total asbestos analyses according to the new R.P.D. 120/2017. Consequently, there is a need to standardize the normative worldwide regulations for the management of asbestos-containing materials, by re-evaluation of sample preparation and quantification of asbestos.

Highlights

Asbestos is a generic term encompassing a group of natural hydrated silicate minerals that grow in a fibrous form and that exhibit characteristics such as flexibility, high tensile strength, and resistance to heat and chemical degradation [1]
We addressed for the investigation samples from metamorphic rocks and sedimentary rocks/materials representative of an ophiolite succession and its covers, outcropping in the Sestri–Voltaggio area (Central Liguria, Northern Italy) (Figure 2) likely to contain asbestos
Six lithotypes were analyzed for asbestos fiber size distribution and content across the grain size fractions of interest

Summary

Introduction

Asbestos is a generic term encompassing a group of natural hydrated silicate minerals that grow in a fibrous form and that exhibit characteristics such as flexibility, high tensile strength, and resistance to heat and chemical degradation [1]. The Italian normative standard declares that asbestos fibers should have a length of >5 μm, a width of

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