The cytotoxic/genotoxic role of impurities in soluble minerals: The case of natural (fibrous epsomite) versus synthetic (Epsom salt) magnesium sulphate

Epsomite and Epsom salt are very common mineral phases, and many known uses are found in agriculture, and in food and pharmaceutical industries. Natural epsomite can be fibrous and inhalable, potentially reaching the digestive tract after dissolving in mucus and saliva. Epsom salt is a common food additive (E 518) to which humans can be exposed daily, although its health effects are still debated. This study aims to (i) determine if natural epsomite (MP) and Epsom salt (SE) may be toxic to humans and (ii) identify and quantify the impurities in natural epsomite and try to ascertain their role in the toxicity of this mineral. In vitro experiments were performed on human colon epithelial cancer cells (Caco-2), enterocyte-like Caco-2-derived monolayers, human monocytic cell line THP-1, and THP-1-derived M0 macrophages. Generally, MP showed significantly higher toxicity in terms of oxidative stress, DNA damage and inflammation than SE, whose effects can be considered negligible. The higher pathogenicity of MP undoubtedly comes from the toxic elements of impurities, which are absent in pure SE. This research clarifies the role of impurities in the toxicity of natural epsomite, which may be higher than previously supposed. Moreover, considering its extensive use in the food industry, it represents a new step in assessing the safety of ingesting magnesium sulphate.