A new experimental method to predict the dispersion of Elongated Mineral Particles in the environment

Abstract

<p>The occurrence of asbestos and asbestos-like minerals in natural sites may pose a risk to human health and the environment when rocks and soils are mobilized. Weathering and anthropic activities favour the liberation of potentially hazardous Elongated Mineral Particles (EMP, NIOSH 2011). The definition of EMP includes both asbestos and other fibrous minerals. The latter share several physical-chemical properties with asbestos, but their toxicological profile is still unknown. The assessment of risk requires the quantification of the occurrence and the estimation of the potential emissivity of EMP from the hosting matrix.</p><p>We quantitatively described the potency of a rock to disperse EMPs in the environment with a quantitative parameter namely the “liberability factor” (Lf). Lf was measured for 40 meta-ophiolite fragments from the NOA-bearing units of Liguria (Voltri Group and Sestri-Voltaggio Zone) and Calabria (Gimigliano-Monte Reventino Unit, Southern Ligurian Domain). The mineral–petrographic characterization of these rocks showed the presence of veins of chrysotile, fibrous tremolite-actinolite, fibrous sepiolite and fibrous antigorite.</p><p>By adapting the UNI EN 12457-2:2004 method for solid waste, we designed a weathering simulation test to quantify the EMPs and the fibres (according to the World Health Organization) possibly liberated by applying to the rock a standardized mechanical stress. Waterborne EMPs were filtered on membranes and counted by electron microscopy (SEM-EDS), by adapting the Italian Regional Agency for the Protection of the Environment (ARPA) procedure for waterborne asbestos (ARPA Piemonte, 2016). We obtained Lf values as the number of waterborne fibres suspended per unit volume of water (fibres/Litre). All analysed rock samples showed Lf values ranging from 30 Mf/L to 21’000 Mf/L. Chrysotile, tremolite, sepiolite, and antigorite, with asbestos-like habit, were detected.</p><p>Lf proved to be a reliable, easy to use method for the characterization and prediction of EMP and fibre dispersion in the environment from NOA-bearing rocks subjected to a standardized mechanical stress. This study is part of the BRIC 2019 project (grant number ID 57.1) supported by INAIL (Italian National Institute for Insurance against Accidents at Work).</p><p> </p><p>References</p><ul><li>ARPA Piemonte 2016. U.RP. M842 rev.03. Asbestos in water by Scanning Electron Microscopy.</li> <li>NIOSH, 2011. Asbestos fibers and other elongate mineral particles. Current Intelligence Bulletin 62.</li> <li>WHO, 1997. Determination of Airborne Fibre Number Concentrations. ISBN 92 4 154496 1</li> </ul>