Gamma-emitting radionuclides in therapeutic muds of the Euganean Thermal District (Padua, Italy)

Mud therapy is a therapeutic tool which uses natural materials available in the environment for healing purposes (clays and thermal water). The use of natural remedies increases the compliance to the cure, and their success is increasing in the last decades, all over the world. As natural matters, also muds have a wide range of composition, so, their use for healing requires appropriate knowledge. One of the most important world reference area for mud therapy has been accessed for sampling in different thermal centers (28) and also the exploiting site of raw clay has been studied. High resolution gamma spectrometry measurements have been acquired, compared with previous published data and discussed considering other compositional parameters. A clear increase of radionuclides of the 238U series characterize therapeutic muds respect to raw materials, 226Ra in particular. The scavenging of Ra from thermal waters is considered to occur after the precipitation of sulfate minerals (gypsum, barite) into the mud matrix, and several lines of evidence suggest that the repeated contact with thermal water (mud recycling) enhance the enrichment of Ra. A different scenario can be drawn for workers and for patients, as their contact with the mud is different for type and time. The dose arising from working in the area of therapeutic muds preparation and the dose to the skin of patients have been calculated. Even if Euganean therapeutic muds are richer in 226Ra respect to other similar materials, no radiological hazards emerged for workers who manage the preparation area, even in the most cautionary scenario. Also for patients, the contribution of Euganean mud therapy to the annual equivalent dose to skin is negligible, according to the cautionary elaboration done. Also considering literature data on the transcutaneous passage of chemical elements with geochemical affinity with Ra, no radiological hazard is detectable.