Bioaccessibility by perspiration uptake of minerals from two different sulfurous peloids

Abstract

The risks associated with the use of peloids in thermal centers, spas, or at home, need to be tested to develop appropriate safety guidelines for peloids formulations and the release of high concern substances. Also, the beneficial effect of some elements on human health should be assessed, to assist in the interpretation of therapeutic action and effectiveness on dermatological or osteomuscular disorders, using pelotherapy. Hence, a methodology was developed to better understand the biogeochemical behavior of the elements in formulated peloids. Two peloids were formulated with the same clay and two different sulfurous mineral-medicinal waters, for 90 days, with light and stirring every 15 days. The clay used was bentonite, with high content of smectite, with Ca and Mg as the main exchangeable cations and with high heat capacity. The selected mineral-medicinal waters were collected from two Portuguese thermal centers, with recognized therapeutic efficacy for rheumatic, respiratory and dermatological pathologies. The peloids were used without drying, withdrawn directly of the maturation tank and a mixture of bentonite with demineralized water was prepared as a reference sample. A stabilized, ready-to-use, artificial perspiration test was used to simulate the peloids’ interaction with skin. Thirty-one elements extracted from the two prepared peloids were analyzed by ICP-MS. The data were analyzed and related to the mineralogical composition of the original clay and supernatant composition of the maturation tanks. The content of some potentially toxic elements and metals bioaccessibility by perspiration showed very low solubility and undetectable amounts extracted from the studied samples. This analytical method provided some reliable information on dermal exposure and the identification of some elements that may enter the systemic circulation and for which surveillance and control measures should be implemented.