2.2. Measurement of Residential Radon Levels

Residential radon levels were measured at two locations in each study home where individuals tend to spend most of their time: the living room and the bedroom. Alpha-track detectors (Raduet Model RSV-8; Radosys Ltd., Budapest, Hungary) were used as a passive radon measuring device. The measuring devices were positioned away from household electrical appliances, windows, or sealed drawers. The measurements were made over 3 months, and the average of measurements at both locations in the house was taken. Given that indoor radon levels are highest in the winter and lowest in the summer, seasonal corrections were made with average temperature, wind speed, and other factors taken into consideration [17]. The residential radon levels were dichotomized into high (≥100 Bq/m³) or low (<100 Bq/m³) according to World Health Organization reference data [18].