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 226Ra 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 40K, 226Ra and 228Ra were 101 ± 8 to 240 ± 12, 276 ± 7 to 322 ± 12 and 20 ± 7 to 80 ± 10 Bq.kg−1, respectively. Higher activity concentrations of 226Ra and 228Ra 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 226Ra in water samples from different thermal baths were approximated to also be 0.42 ± 0.20 Bq.l−1. 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 ± 410 and 2450 ± 530 Bq.m−3 and the radon concentrations in the spa galleries were measured to be between 790 ± 135 and 1050 ± 120 Bq.m−3, 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−1, respectively, which is slightly over the national limit in Iran (5 mSv.yr−1). The exposure duration was estimated 15 and 1468 h per year for visitors and workers, respectively.
Highlights
Occurring radiation can be defined as the radiation that originates from all sources in the natural environment including soil, water, the atmosphere or even space
The annual effective dose of natural radiation that inhabitants in Ramsar (Iran) are exposed to is much higher than that of those in other parts of in Dehloran (Iran), due to high concentrations of Naturally Occurring Radioactive Materials (NORM) in Ramsar (Harjo and Fervid, 2009)
A large number of studies have been conducted on indoor radon concentrations in thermal spas, e.g. in the Middle-Slovakian region, Lądek-Zdroj in south-western Poland, the thermal spas of Rudas and Hevíz in Hungary, Jachymov in the Czech
Summary
Occurring radiation can be defined as the radiation that originates from all sources in the natural environment including soil, water, the atmosphere or even space. The largest fraction of the annual effective dose the general population is exposed to from natural radioactivity originates from radon, thoron and their short half-life decay products. The annual effective dose of natural radiation that inhabitants in Ramsar (Iran) are exposed to is much higher than that of those in other parts of Iran, due to high concentrations of Naturally Occurring Radioactive Materials (NORM) in Ramsar (Harjo and Fervid, 2009). The hot spring and its surrounding area is an example of an elevated source of natural radiation that includes increased concentrations of 222Rn, 226Ra and 228Ra. The water from the hot spring is used extensively for balneotherapy and in thermal baths. A large number of studies have been conducted on indoor radon concentrations in thermal spas, e.g. in the Middle-Slovakian region, Lądek-Zdroj in south-western Poland, the thermal spas of Rudas and Hevíz in Hungary, Jachymov in the Czech
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