Abstract
Analysis of indoor radon level and its health risk parameters has been carried out in Borikiri (BT), Diobu (DR), and Rebisi (RB) towns in Port Harcourt, Rivers State, Nigeria. A pocket sized Corentium Arthings digital radon detector meter was used to record the indoor radon concentration levels. The geographical coordinates were recorded using a hand-held geographical positioning system (GPS) for the various sample points. A total of ten houses were measured for each town making a total of 30 sample points for the three communities. The results obtained show that for Borikiri town, the concentration level varied from 30.7100 - 19.9800 Bqm-3 with an average of 11.32 ± 2.59 Bqm-3 . The annual absorbed dose varied from 7.7478 - 1.1202 mSv/yr with a mean value of 2.59 ± 0.65 mSv/yr while the annual equivalent dose rate varied from 0.829 - 0.336 mSv/yr with an average of 0.69 ± 0.16 mSv/yr The excess life time cancer risk calculated for seventy years (70yrs) varied from 6.510 - 0.941 with an average of 2.45 ± 1.71. The results of the indoor concentration level for Diobu town ranged from 37.74 - 5.9200 Bqm ?3 with a mean value of 12.95 ± 2.91 Bqm-3 . The annual absorbed dose for the area ranged from 9.5214 - 1.1494 with an average of 3.26 ± 0.73 mSv/yr, the annual equivalent dose rate varied from 0.694-0.359 with a mean of 0.78±0.8, the excess life time cancer risk calculated for seventy years ranged from 8.000-1.725 with a mean of 2.91±0.61. The indoor concentration level for Rebisi town ranged from 12.9500?4.0700 Bqm-3 with an average of 8.55 ± 1.00, the annual absorbed dose ranged from 3.2671 - 1.0268 mSv/yr, the annual equivalent dose rate varied from 0.784 - 0.269 with an average of 0.52 ± 0.06, the excess life time cancer risk of 2.745 - 0.863 with an average of 1.82 ± 0.21. The results of the indoor concentration levels, the annual absorbed dose and the annual effective dose rate are all below the ICRP safe limit. However, the results of the excess life time cancer risk are all higher than the ICRP safe standard limit of 0.029 × 10-3 .
Highlights
Radon is a radioactive gas which is colourless, odourless and tasteless
Indoor radon concentration and their geographical coordinates for the three Borikiri, Diobu and Rebisi are presented in Tables 1, 2 and 3, respectively
The calculated values of the excess life time cancer risk calculated for life time of 70yrs, 60 yrs, 50 yrs, 40 yrs and 30 yrs are all higher than the set limit by International Commission on Radiological Protection (ICRP)
Summary
Radon is a radioactive gas which is colourless, odourless and tasteless. It is predominantly found in rock samples, bedrock formations, soil and ground water all over the world, [1]. Two of the radon progenies (daughters) Polonium-214 and Polonium-218 release the highest amount of alpha radiation dose to the lungs [6]. When these radioactive particles settle in a person’s lung they can cause damage to the mucosa linings of the lungs. The maximum amplitude of the voltage signal is detected and sampled by an analogue to digital converter (ADC) The amplitude of this signal is proportional to the energy of the alpha particle that hit the photodiode. The brain of the monitor is a micro-controller which registers the time and the energy of every detected particle This information is used to calculate the mean Radon concentration for, daily, weekly, monthly and yearly periods. The windows and doors were kept closed throughout the period of the measurement to ensure that the indoor air is not distorted to achieve accuracy within the period of 48 hours
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