Natural 210Po-rich fibrous epsomite: a human health issue?

Biopersistent fibrous minerals are often investigated due to their possible hazard to human health because they can remain in the lungs for a long time. On the contrary, very scarce knowledge exists on the accurate chemical composition and the possible effect of particulates and fibres with higher solubility (in water and biological environments), such as sulphate minerals and other phases. Natural fibrous epsomite from Perticara Mine (Central Italy) was investigated through SEM-EDS, XRPD, ICP-AES and alpha spectrometry measurements with the aim of reducing this lack of knowledge on a fibrous sulphate mineral. A significant number of small fibres with inhalable size for humans were observed on the epsomite sample through morphological and morphometrical investigations. The resulting equivalent aerodynamic diameter (Dae) of epsomite fibres is 5.09 μm. Accordingly, we can assume that the fraction of measured fibres that can penetrate the respiratory tract is not negligible and that the epsomite fibres can easily penetrate and be deposited in the laryngeal and bronchial respiratory tract. Chemical analysis revealed the presence of toxic elements (As, Co, Fe, Mn, Ni, Sr, Ti, Zn) and very high amounts of radioactive isotopes on epsomite crystals. In particular, a surprisingly high amount of 210Po (5.59 Bq/g) was detected. The first results of this study were recently published by Giordani et al. (2022). Due to the high solubility of epsomite under lung conditions (37°C and 100% relative humidity; Chipera & Vaniman, 2007), the inhaled fibres rapidly became a solution. Then, the entire load of hazardous elements could be quickly released into the lung environment and adsorbed from all parts of the respiratory tract, with consequent effects on human health. Epsomite is common in several natural and anthropic environments worldwide, such as caves, mines, geological outcrops, mineral springs, and efflorescence, and also has several medical and pharmaceutical applications (Ruiz-Agudo et al., 2008). For this reason, our findings suggest great caution in handling other natural epsomite samples. The present work can be considered a representative case study of the investigation of the interaction between soluble minerals and human health. These preliminary results can be the basis for further studies on the content of hazardous elements in building materials and on the toxic elements interaction with humans. Chipera S.J. & Vaniman D.T. (2007) - Experimental stability of magnesium sulfate hydrates that may be present on Mars. Geochim. Cosmochim. Acta, 71(1), 241-250. Giordani M., Meli M.A., Roselli C., Betti M., Peruzzi F., Taussi M., Valentini L., Fagiolino I. & Mattioli M. (2022) - Could soluble minerals be hazardous to human health? Evidence from fibrous epsomite. Environ. Res., 206. Ruiz-Agudo E., Putnis C.V. & Rodriguez-Navarro C. (2008) - Interaction between epsomite crystals and organic additives. Cryst. Growth Des., 8(8), 2665-2673.