Implementation of a multidisciplinary radon risk assessment of building materials in existing scenario in Sant'Agata de'Goti

Radon exposure is still a significant public health concern, particularly in regions where natural building materials are derived from high-radiation subsoils. This study proposes a multidisciplinary protocol for assessing radon risk in existing buildings, with a specific focus on the municipality of Sant'Agata de’ Goti (southern Italy), a historical town built entirely of Campanian Ignimbrite tuff. Indoor radon concentrations were monitored using CR-39 detectors in 20 locations over a one-year period, revealing that 70 % of the measured values exceeded the regulatory threshold of 300 Bq/m³. Complementary analyses were conducted on tuff samples used as Building Materials (BMs), including gamma spectrometry, electret ion chamber, X-ray fluorescence (XRF), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) measurements. High levels of Ra-226 and Th-232, along with elevated exhalation and emanation parameters, were observed. The study highlights how petrographic and mineralogical features - such as pumice porosity, zeolitization, and microstructure - enhance radon release beyond what is predicted by radionuclide content alone. The I index exceeded unity in both analyzed facies - the yellow one and the gray one of the Ignimbrite tuff - suggesting these materials pose a radiological hazard. The results highlight the need to integrate BMs characterization into National Radon Action Plans, particularly in areas with widespread historical use of volcanic tuff. This would include BMs already in use and not just those in pre-commercialization, as is required by current regulations. The proposed approach provides a replicable model for assessing radon risk in existing structures and supports targeted mitigation strategies based on multidisciplinary data.