Background: Public perception of environmental (natural background) radiation represents an important challenge for public health communication, as risk perception is often influenced more by information quality and institutional trust than by objective exposure levels. Methods: A cross-sectional survey was conducted among 481 respondents using a structured questionnaire assessing self-perceived knowledge, information sources, perceived radiation risk, institutional trust, and health-related attitudes. Results: Significant gender differences were observed in self-reported knowledge about radioactivity, with men more frequently reporting higher knowledge levels than women (p < 0.001), while no significant differences emerged between urban and rural respondents; logistic regression analysis showed that lower perceived risk was associated with lack of medical information (OR = 0.32, 95% CI: 0.14–0.71) and absence of avoidance behavior (OR = 0.23, 95% CI: 0.11–0.47), whereas low trust in medical institutions was associated with higher odds of perceiving natural background radiation as dangerous (OR = 1.84, 95% CI: 1.21–2.80). Conclusions: Effective radiation risk communication requires more than the dissemination of information; it must also address public concerns, enhance institutional trust, and provide clear, credible, and accessible health-related messages. Tailored communication strategies are essential to bridge the gap between expert knowledge and public perception.

Background: Environmental ionizing radiation plays a major role in human radiation exposure. Natural background radiation originates from the Earth’s crust and outer space. The terrestrial component consists of primordial radioisotopes (⁴⁰K, ²³⁸U, ²³⁵U, ²³²Th), as well as elements of the uranium and thorium decay chains, of which, from a dosimetric perspective, ²²²Rn and its decay products carry the greatest weight. These account for more than half of the crustal component. Cosmic radiation consists of gamma rays, X-rays, and particles such as protons, electrons, neutrons, mesons, and hyperons. Methods: The main objective of our research is to determine the background radiation levels characteristic of various regions of Transylvania. In addition, we aim to determine the effects of local environmental, diurnal, and seasonal changes on radiation levels. Results: A statistically significant difference was observed between the values of the individual regions (p < 0.001). The values we measured ranged from 0.051 µSv/h to 0.285 µSv/h. Based on the results, we can conclude that there is a statistically significant difference (p < 0.05) between the median value dropped after ventilation (0.159 µSv/h), compared to the one before ventilation (0.164 µSv/h). According to our database, radiation levels are significantly (p < 0.01) higher during the fall and winter months. Conclusions: On this basis, Transylvania can be regarded as a safe and livable region in terms of natural background radiation levels. Nevertheless, it is important to maintain a healthy lifestyle, ventilate homes frequently, and spend as much time as possible outdoors in nature.