High level of natural ionizing radiation at a thermal bath in Dehloran, Iran

Abstract

It has been proven that more than half of the exposure to natural background radiation originates from radon isotopes and their decay products. The inhalation of radon and its decay products causes the irradiation of respiratory tracts, thus increasing the risk of lung cancer. In this study, the concentrations of radon and thoron in thermal baths at a spa in Dehloran (Iran) were investigated. The concentrations of dissolved 226 Ra in samples of water from thermal baths were also measured. Additionally, the activity concentrations of abundant naturally occurring radionuclides in farmland soils irrigated with water from hot springs was measured and compared with other soil samples irrigated with water from other sources to estimate possible radioecological effects of natural radiation staff, patients and tourists at the spa are exposed to. In addition, the search for a link between the concentration of naturally occurring radionuclides in soil and the use of water from hot springs for irrigation was one of the main goals of the study. The activity concentrations of three major naturally occurring radionuclides in soil samples were measured; the ranges for 40 K, 226 Ra and 228 Ra were 101 AE 8 to 240 AE 12, 276 AE 7 to 322 AE 12 and 20 AE 7 to 80 AE 10 Bq.kg À1 , respectively. Higher activity concentrations of 226 Ra and 228 Ra were recorded in soil samples irrigated with hot spring water. The water from the same spring was used in all thermal baths so concentrations of dissolved 226 Ra in water samples from different thermal baths were approximated to also be 0.42 AE 0.20 Bq.l À1 . The indoor radon concentrations in the private thermal baths over a period of 45 days (including both occupied and vacant time) were measured to be between 1880 AE 410 and 2450 AE 530 Bq.m À3 and the radon concentrations in the spa galleries were measured to be between 790 AE 135 and 1050 AE 120 Bq.m À3 , however, thoron concentrations were below the detection limit. The ventilation and centralized heating systems at the spa under investigation are inefficient so the radon concentrations in the therapy rooms and baths are high.The maximum radiation doses originating from the inhalation of radon for tourists and the staff were estimated to be 0.13 and 5.5 mSv.yr À1 , respectively, which is slightly over the national limit in Iran (5 mSv.yr À1 ). The exposure duration was estimated 15 and 1468 h per year for visitors and workers, respectively.

Radiological Assessment of Indoor Radon and Thoron Concentrations and Indoor Radon Map of Dwellings in Mashhad, Iran

“…To determine the indoor radon and thoron concentrations, RADUET, a commercially available passive integrated radon–thoron discriminative detector, was used. These detectors consist of two diffusion chambers with different ventilation rates, and each chamber contains a CR-39 chip with the dimensions of 10 × 10 mm 2 (RADUET, Radosys Ltd., Budapest, Hungary) for detecting the alpha particles emitted from radon and thoron as well as their progenies [ 29 , 30 ]. All detectors were hung at a height of 1–2 m above the ground using hard wire and positioned at least 20 cm away from any of the wall surfaces in the living rooms of the houses.…”

“…The etching condition for CR-39 was as follows: Solution: 6.0 M NaOH; Temperature: 90 °C; Time: 3 h. The track densities were counted using an optical transmission microscope and image analysis software. The calibration factors were determined as a result of exposure tests using radon and thoron calibration chambers at the Institute of Radiochemistry and Radioecology of the University of Pannonia, Hungary, and is comprehensively described in [ 30 , 31 , 32 ].…”

A brief radiological survey and associated occupational exposure to radiation in an open pit slate mine in Kashan, Iran

“…The evaluation process, Fig. 2 Graphic image of radon exhalation measurement including the etching and counting of the tracks, has been intensely discussed in our previous publications [15][16][17]. The average concentration of radon exposure was calculated from counted tracks and Eq.…”

Characteristics of Thoron (220Rn) and Its Progeny in the Indoor Environment

“…PADC, commercially CR-39, is used as the detecting material. This monitor and its prototype have been widely used in various countries [ 27 , 28 , 29 , 30 ]. The above two monitors can be calibrated in the calibration chamber at Hirosaki University Institute of Radiation Emergency Medicine, Japan [ 31 ].…”