Abstract
A significant contribution to natural exposure of humans is radon gas, which emanates from the soil and may concentrate in dwellings. The level of radon exposure varies around the globe, but limited data are available on the daily variations of indoor radon concentrations. In this study, indoor radon measurements were performed continuously within one week at six different places in Dalat, Vietnam using the real time Smart Radon Detector Radon Eye+. The indoor radon behavior in a day follows a sine pattern, with peak values in the early morning and lowest values in the late afternoon. There are also some fluctuations at specific times due to different weather conditions. Indoor radon concentrations in the Dalat regions were found to exceed the recommended guidelines and thresholds; excessive radon levels warranting health concern were found (150.7-340.0 Bq/m3). Some corrective actions to reduce indoor radon concentrations were recommended. Annual effective doses on different age categories were also calculated.
Highlights
Radon is a radioactive gas which presents in terrestrial soils, rocks and building materials
During the weekdays, the indoor radon concentration continuously decreases from the peak level in the early morning to the lowest level in the late afternoon, and increases until the morning
Ventilation has been demonstrated as a major factor that influences indoor radon concentration
Summary
Radon is a radioactive gas which presents in terrestrial soils, rocks and building materials. Rn-222 has a half-life of 3.82 days and is formed from Ra-226, which is the decay product of U-238. Rn-222 is very significant for radiation exposure indoors because of the relatively high concentrations of U-238 in the ground. Rn-220 is found in the decay chain of Th-232; it has a short half-life of 55.6 seconds and can migrate a short distance before decay. Rn-219 has a short half-life of 3.96 seconds, and is a decay product of U-235 whose low concentrations can be found in soils. Exposure from Rn-222, Rn-220 and their decay products are mainly from alpha particles and some beta particles; gamma radiation is emitted. The basic quantity used to express radon concentration in air is Bq/m3- the radioactivity within a volume of space 2.
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