Peloids are healing muds used in pelotherapy worldwide since ancient times. They represent a complex mixture of fine-grained natural materials of geological and/or biological origin and mineral water. They can be formed in river, swamp, lake and sea sedimentation environments due to volcanic and hydrothermal activities.

The specificities of the peloids depend on the interaction of the inorganic and organic parts of the peloid with mineral water during the maturing process, as well as the physical and chemical characteristics of the starting solid materials and mineral water. Depending on their thermal, chemical and mechanical properties, they can be used for therapeutic, cosmetic and relaxation purposes.

Peloids are considered an economically valuable and renewable natural resource. The use of cold and hot mineral springs in Serbia has been known since Roman times. The modern development of spas began between the two world wars and continues today. Although peloids have been used for therapeutic purposes since ancient times, knowledge about them is limited, especially in Serbia.

The general goal of the PELAS project is the detailed physico-chemical, geochemical and eco- chemical characterisation of peloids used in Serbian spas, for three main reasons: determination of peloid properties, assessment of their suitability for use and assessment of ecosystem services of spa areas. Peloids from 15 spas in Serbia will be analysed within the PELAS project.