TY - JOUR
AU1 - Fatoki, Olusola Odunayo
AU2 - Ademola, Janet Ayobami
AB - Abstract Radon-222 concentrations in groundwater from 10 local government areas (LGAs) of Ogun State were measured using AlphaGUARD radon detector and AquaKIT. The mean activity concentration of radon ranged from 1.23 ± 0.21 to 12.68 ± 18.11 Bq.l−1 corresponding to geometric means (GMs) of 1.22– 6.39 Bq.l−1. The radon concentrations of all the samples were below the World Health Organization and European Commission guidance level of 100 Bq.l−1, with 17% higher than 11.1 Bq.l−1, recommended by the United States Environmental Protection Agency. Mean annual effective dose due to ingestion ranged from 0.020 ± 0.004 to 0.254 ± 0.353 mSv.y−1 (adults), 0.041 ± 0.007 to 0.509 ± 0.705 mSv.y−1 (children) and 0.024 ± 0.004 to 0.297 ± 0.411 mSv.y−1 (infants). That of inhalation varied from 0.303 ± 0.053 to 3.108 ± 4.440 μSv.y−1. The mean annual effective doses of some of the LGAs were higher than the International Commission for Radiological Protection recommended reference dose level of committed effective dose of 0.1 mSv from 1-year consumption of drinking water. INTRODUCTION Radiation is a natural part of the environment, and man is exposed to naturally occurring radiation in soil, water, air and food. The largest fraction of exposure to natural radiation comes from a radioactive gas, radon(1,2). The three major isotopes of radon are Rn-219 (T½ = 3.96 s), Rn-220 (T½ = 0.927 m) and Rn-222 (T½ = 3.82 d). Of these three isotopes Rn-222 is the most stable and more of public health concern. Radon-222 is formed from the radioactive decay of Ra-226, a decay product of U-238. Uranium-238 and its decay products occur at low concentrations in the earth’s crust; therefore, there is continuous generation of radon in soils, rocks, etc., and it is present virtually everywhere on the earth. Radon-222 is a chemically inert gas. It cannot be detected with human senses because it is colorless, odorless and tasteless. When Ra-226 decays to Rn-222 in soil, some mixes with air by moving through pores in the soil to the surface and some remains in the ground and dissolved in underground water. Permeability of the soil and water characteristics influences radon concentration in water. Other factors include radium content and specific surface area of the aquifer(3). Surface water usually has low level of radon because the gas is easily released into the air. However, groundwater could have high concentration of radon and can significantly contribute to indoor radon(4–6). This contribution could be through the use of the water for showering, washing, laundry and other domestic uses. Exposure to radon in drinking water is through ingestion and inhalation(4), and this could cause stomach cancer and lung cancer, respectively, if the level is high(7,8). Lung cancer has been linked to inhalation of radon and stomach cancer weakly linked to ingestion of radon(9,10). The health effect of radon has led to proposals and recommendations by different international organizations on the limit of radon in water. The United States Environmental Protection Agency proposed alternative maximum contamination level (AMCL), 148 Bq.l−1 and maximum contamination level (MCL), 11.1 Bq.l−1for two different scenarios(4,11,12). The World Health Organization (WHO) guidance on radon in drinking water supplies recommends 100 Bq.l−1, and that control should be implemented if this is exceeded(1). In the same vein, the Commission of the European Communities also recommends that for radon-222 concentration <100 Bq.l−1, no remedial action is required(13). Water is essential for life, and the dependence of man on groundwater cannot be overemphasized. The result of a survey carried out in five local government areas (LGAs) of Ogun State of which four are in this study showed that larger percentage of the respondents (81%) obtained water from groundwater sources for domestic use(14). This study confirms the dependence of a larger percentage of the populace on groundwater for sustenance. The current study therefore is aimed at measuring the activity concentration of 222Rn in groundwater in Ogun State and evaluating the effective dose due to ingestion and inhalation of radon-222 concentrations in the water. MATERIALS AND METHODS Study area Ogun State with a total area of 16 409.26 km2 is located in the south-western part of Nigeria and comprises 20 LGAs. It is on Latitude 6.2°N to 7.8°N and Longitude 3.0°E to 5.0°E(15,16). The State shares boundaries in the west, east and south with Benin Republic, Ondo State and Lagos State, respectively, and in the north with Oyo and Osun States. The geological formation of the State consists of basement complex and sedimentary rocks, which underlie the remaining surface of the state. The sedimentary rocks are made of four formations: Abeokuta, Ewekoro, Ilaro and Oshosun. These formations are overlain by the coastal plain sands(16). The Northern part is dominated by basement rock that extends eastward. This consists of granite gneiss, porphyritic granite, undifferentiated schist, biotite granite, granodiorite, muscovite granite and migmatite, all of Archean age rock(16,17). Figures 1 and 2 are the maps of Ogun State showing the LGAs and the geological formation. Figure 1 Open in new tabDownload slide A map of Ogun State showing the LGAs Figure 2 Open in new tabDownload slide The geological map of Ogun State (Adopted from Olurin et al., 2016)(33) Water samples collection and measurement A total of 100 groundwater samples were collected from wells and boreholes in 10 LGAs of Ogun State. Global positioning system was used to obtain the geographical coordinates of the collection points. The water samples collected comprised of 63 boreholes water and 37 well water. Some of the water samples collected are not used for drinking but are, however, used for other domestic purposes. Reasons could be due to the taste, color or odor of the water. Water samples were collected into glass bottles of 490 ml. Water from boreholes was allowed to flow for some minutes before collection bucket was placed under the tap. The bucket was filled to overflow after which the sample bottle was immersed, filled to the brim and tightly capped at the bottom of the bucket. Bailer bucket (bucket with a long rope dip in a well to draw out water) was used to collect water from wells and bottles were carefully filled with water inside the bailer bucket. All the samples of water were collected at the fetching point in order to minimize the effect of aeration on the concentration of the dissolved radon. Radon measurements were done using AlphaGUARD radon monitor connected to AquaKIT. The AlphaGUARD is a portable, battery-operated radon monitor with a high storage capacity. It uses the principle of the pulse ionization chamber (alpha spectroscopy) with a linear response from 2 to 2 000 000 Bq.m−3, that is, it is suitable for monitoring radon concentrations between 2 and 2 000 000 Bq.m−3. It has high detection efficiency of 1 cpm at 20 Bq.m−3, fast response to concentration gradients as well as maintenance-free long-term operation. It measures and records radon concentrations simultaneously with the ambient temperature, relative humidity and atmospheric pressure with integrated sensors. The instrument is insensitive to both vibrations and shock(18). The background signal due to internal detector contamination is <1 Bq.m−3. The AlphaGUARD radon monitor was calibrated by SAPHYMO GmbH, Frankfurt/Main, Germany and the radon calibration is traceable to PTB/Germany, NIST/USA and NPL/UK. The measuring system consists of a vessel used for forced degassing the radon diluted in water samples, a security vessel for water drop deposition. The vessels and the AlphaGUARD are connected with plastic radon proof tubes. Radon gas in water is forced degas by circulating the air in the setup with the aid of a pump (AlphaPUMP). Water sample of 100 l volume was put into the appropriate system of glass vessels and connected to the detector through the air pump according to manufacturer’s recommendation(19). For each of the samples, two aliquots of water were taken for measurement, and the mean value was determined. Water samples measured after >4 hours of collection were corrected for decay(20,21). RESULTS AND DISCUSSION Radon concentration in groundwater The radon activity concentrations in the water samples were determined from the radon-222 in air degassed from the water (radon gas expelled from the water samples by means of the AlphaPUMP) using the equation below(19); $$\begin{equation} {C}_{\mathrm{water}}=\frac{C_{\mathrm{air}}\left(\frac{V_{\mathrm{system}}-{V}_{\mathrm{sample}}}{V_{\mathrm{sample}}}+\kappa \right)-{C}_{\mathrm{background}}}{1000}, \end{equation}$$(1) where radon-222 concentrations in the water and background radon concentration in the measuring equipment before sampling are Cwater (Bq.l−1) and Cbackground (Bq.m−3), respectively. The radon concentration in air after expelling the radon from water is Cair (Bq.m−3). The total volume of the measurement circuit is Vsystem given as 1102 ml(19) and Vsample is the volume of the water sample in ml. The diffusion coefficient, k, is given as 0.26 by the manufacturer in the AquaKIT manual(19). The sources of water and the activity concentrations of Rn-222 in all the groundwater samples are presented in Table 1. The table also shows the range, arithmetic mean (AM) and GM for each of the 10 LGAs. The mean radon concentration was highest for Abeokuta South LGA (12.68 ± 18.11 Bq.l−1), followed by Abeokuta North LGA (11.16 ± 10.87 Bq.l−1) and the least was for Ijebu Ode LGA (1.23 ± 0.21 Bq.l−1). The standard deviation (SD) in each of the mean value shows the spread of the radon concentration in water samples from the same LGA. There are wide variations in the radon concentrations in water samples from most of the LGAs with the exception of a few LGAs. This significant variation could be due to local differences in geology, which tend to influence the patterns of radon levels observed at specific locations(4). The GMs varied from 1.22 Bq.l−1 (Ijebu Ode LGA) to 8.54 Bq.l−1 (Sagamu LGA). The radon concentrations of all the samples were below the WHO (2008) and EC (2001) guidance level of 100 Bq.l−1(1,13). Seventeen out of 100 samples had radon concentration higher than the United States Environmental Protection Agency (USEPA) MCL of 11.1 Bq.l−1 with the highest concentration of 62.07 Bq.l−1 in water sample from Abeokuta South LGA. However the mean values for each of the LGA with the exception of one (Abeokuta South LGA) were less than MCL(11). Table 1 Activity concentrations of radon-222 in groundwater in Ogun State S/N . Source . Rn concentration degassed Cair (Bq.m−3) . Rn concentration Cwater (Bq.l−1) . Abeokuta North LGA  1 Boreholea 2036 ± 168 20.93 ± 1.72  2 Borehole 1240 ± 84 12.75 ± 0.86  3 Borehole 1440 ± 93 14.80 ± 0.96  4 Wella 756 ± 61 7.77 ± 0.63  5 Wella 902 ± 68 9.27 ± 0.70  6 Borehole 203 ± 28 2.09 ± 0.28  7 Borehole 331 ± 36 3.41 ± 0.37  8 Wella 394 ± 39 4.05 ± 0.41  9 Wella 2522 ± 186 36.20 ± 1.91  10 Borehole 30 ± 8 0.31 ± 0.09 Range 30–2522 0.13–36.20 AM ± SD 1085 ± 1058 11.16 ± 10.87 GM 608 6.26 Abeokuta South LGA  11 Wella 699 ± 55 7.18 ± 0.57  12 Wella 577 ± 52 5.93 ± 0.54  13 Borehole 6038 ± 282 62.07 ± 3.43  14 Borehole 168 ± 30 1.74 ± 0.31  15 Borehole 1866 ± 123 19.19 ± 1.27  16 Borehole 979 ± 80 10.07 ± 0.82  17 Borehole 940 ± 83 9.66 ± 0.85  18 Borehole 506 ± 56 5.21 ± 0.57  19 Wella 515 ± 43 5.29 ± 0.44  20 Borehole 46 ± 9 0.48 ± 0.09 Range 46–6038 0.48–62.07 AM ± SD 1233 ± 1762 12.68 ± 18.11 GM 620 6.39 Ewekoro LGA  21 Wella 1380 ± 84 14.18 ± 0.86  22 Wella 1660 ± 106 17.07 ± 1.09  23 Wella 1754 ± 115 18.03 ± 1.19  24 Wella 462 ± 49 4.75 ± 0.50  25 Borehole 177 ± 29 1.82 ± 0.29  26 Well 962 ± 79 9.88 ± 0.81  27 Wella 187 ± 31 1.92 ± 0.32  28 Borehole 509 ± 57 5.24 ± 0.56  29 Well 1512 ± 83 15.54 ± 0.89  30 Borehole 82 ± 15 0.84 ± 0.15 Range 82–1754 0.84–18.03 AM ± SD 869 ± 663 8.93 ± 6.81 GM 572 5.87 Ifo LGA  31 Borehole 84 ± 14 0.87 ± 0.15  32 Borehole 120 ± 19 1.24 ± 0.20  33 Boreholea 889 ± 68 9.14 ± 0.70  34 Wella 442 ± 46 4.54 ± 0.48  35 Well 440 ± 40 4.52 ± 0.41  36 Borehole 1268 ± 95 13.04 ± 0.98  37 Well 157 ± 27 1.61 ± 0.28  38 Borehole 144 ± 25 1.48 ± 0.26  39 Well 109 ± 15 1.12 ± 0.16  40 Wella 116 ± 23 1.19 ± 0.23 Range 84–1268 0.87–13.04 AM ± SD 377 ± 403 3.88 ± 4.14 GM 240 2.47 Ijebu North LGA  41 Well 155 ± 20 1.60 ± 0.21  42 Borehole 575 ± 51 5.91 ± 0.52  43 Well 128 ± 20 1.31 ± 0.20  44 Well 129 ± 20 1.32 ± 0.21  45 Well 155 ± 27 1.60 ± 0.23  46 Borehole 320 ± 37 3.29 ± 0.38  47 Borehole 351 ± 40 3.61 ± 0.41  48 Borehole 348 ± 41 3.58 ± 0.42  49 Borehole 109 ± 19 1.12 ± 0.20  50 Borehole 132 ± 21 1.36 ± 0.22 Range 109–575 1.12–5.91 AM ± SD 240 ± 153 2.47 ± 1.57 GM 205 2.10 Ijebu Ode LGA  51 Borehole 105 ± 16 1.08 ± 0.16  52 Borehole 99 ± 14 1.02 ± 0.14  53 Borehole 142 ± 23 1.46 ± 0.23  54 Borehole 135 ± 21 1.38 ± 0.22  55 Borehole 105 ± 17 1.08 ± 0.17  56 Borehole 165 ± 27 1.69 ± 0.27  57 Borehole 116 ± 22 1.19 ± 0.23  58 Borehole 103 ± 20 1.06 ± 0.21  59 Well 113 ± 17 1.16 ± 0.17  60 Wella 118 ± 22 1.22 ± 0.23 Range 99–165 1.02–1.69 AM ± SD 120 ± 21 1.23 ± 0.21 GM 119 1.22 Obafemi Owode LGA  61 Borehole 917 ± 56 9.43 ± 0.58  62 Borehole 715 ± 60 7.35 ± 0.62  63 Borehole 301 ± 35 3.10 ± 0.36  64 Borehole 388 ± 35 3.98 ± 0.36  65 Borehole 374 ± 40 3.84 ± 0.41  66 Borehole 964 ± 77 9.91 ± 0.80  67 Borehole 301 ± 38 3.10 ± 0.40  68 Wella 764 ± 66 7.85 ± 0.62  69 Borehole 364 ± 45 3.75 ± 0.46  70 Borehole 668 ± 59 6.88 ± 0.57 Range 301–964 3.10–9.91 AM ± SD 576 ± 259 5.92 ± 2.66 GM 523 5.38 Ota LGA  71 Borehole 79 ± 13 0.81 ± 0.13  72 Borehole 99 ± 17 1.02 ± 0.18  73 Borehole 367 ± 43 3.78 ± 0.43  74 Borehole 151 ± 24 1.56 ± 0.25  75 Borehole 80 ± 15 0.82 ± 0.15  76 Borehole 1000 ± 73 10.28 ± 0.76  77 Wella 470 ± 56 4.84 ± 0.57  78 Wella 354 ± 48 3.64 ± 0.49  79 Borehole 1932 ± 140 19.86 ± 1.44  80 Wella 39 ± 9 0.40 ± 0.09 Range 39–1932 0.40–19.86 AM ± SD 457 ± 594 4.70 ± 1.57 GM 231 2.38 Sagamu LGA  81 Wella 1550 ± 123 15.94 ± 1.27  82 Borehole 2282 ± 127 23.46 ± 1.32  83 Well 471 ± 49 4.84 ± 0.50  84 Wella 1289 ± 90 13.25 ± 0.93  85 Wella 885 ± 71 9.09 ± 0.73  86 Well 543 ± 56 5.58 ± 0.58  87 Borehole 506 ± 53 5.20 ± 0.54  88 Wella 607 ± 59 6.24 ± 0.60  89 Borehole 436 ± 48 4.48 ± 0.49  90 Borehole 1139 ± 91 11.71 ± 0.93 Range 436–2282 4.48–23.46 AM ± SD 971 ± 602 9.98 ± 6.19 GM 831 8.54 Yewa North LGA  91 Well 3145 ± 157 32.33 ± 1.62  92 Borehole 610 ± 55 6.28 ± 0.57  93 Borehole 215 ± 28 2.21 ± 0.28  94 Borehole 499 ± 46 5.13 ± 0.48  95 Wella 358 ± 38 3.68 ± 0.39  96 Borehole 160 ± 23 1.65 ± 0.24  97 Borehole 102 ± 20 1.07 ± 0.20  98 Well 155 ± 26 1.59 ± 0.31  99 Borehole 399 ± 48 4.10 ± 0.49  100 Borehole 701 ± 65 7.21 ± 0.67 Range 102–3145 1.07–32.33 AM ± SD 634 ± 905 6.53 ± 9.30 GM 373 3.84 S/N . Source . Rn concentration degassed Cair (Bq.m−3) . Rn concentration Cwater (Bq.l−1) . Abeokuta North LGA  1 Boreholea 2036 ± 168 20.93 ± 1.72  2 Borehole 1240 ± 84 12.75 ± 0.86  3 Borehole 1440 ± 93 14.80 ± 0.96  4 Wella 756 ± 61 7.77 ± 0.63  5 Wella 902 ± 68 9.27 ± 0.70  6 Borehole 203 ± 28 2.09 ± 0.28  7 Borehole 331 ± 36 3.41 ± 0.37  8 Wella 394 ± 39 4.05 ± 0.41  9 Wella 2522 ± 186 36.20 ± 1.91  10 Borehole 30 ± 8 0.31 ± 0.09 Range 30–2522 0.13–36.20 AM ± SD 1085 ± 1058 11.16 ± 10.87 GM 608 6.26 Abeokuta South LGA  11 Wella 699 ± 55 7.18 ± 0.57  12 Wella 577 ± 52 5.93 ± 0.54  13 Borehole 6038 ± 282 62.07 ± 3.43  14 Borehole 168 ± 30 1.74 ± 0.31  15 Borehole 1866 ± 123 19.19 ± 1.27  16 Borehole 979 ± 80 10.07 ± 0.82  17 Borehole 940 ± 83 9.66 ± 0.85  18 Borehole 506 ± 56 5.21 ± 0.57  19 Wella 515 ± 43 5.29 ± 0.44  20 Borehole 46 ± 9 0.48 ± 0.09 Range 46–6038 0.48–62.07 AM ± SD 1233 ± 1762 12.68 ± 18.11 GM 620 6.39 Ewekoro LGA  21 Wella 1380 ± 84 14.18 ± 0.86  22 Wella 1660 ± 106 17.07 ± 1.09  23 Wella 1754 ± 115 18.03 ± 1.19  24 Wella 462 ± 49 4.75 ± 0.50  25 Borehole 177 ± 29 1.82 ± 0.29  26 Well 962 ± 79 9.88 ± 0.81  27 Wella 187 ± 31 1.92 ± 0.32  28 Borehole 509 ± 57 5.24 ± 0.56  29 Well 1512 ± 83 15.54 ± 0.89  30 Borehole 82 ± 15 0.84 ± 0.15 Range 82–1754 0.84–18.03 AM ± SD 869 ± 663 8.93 ± 6.81 GM 572 5.87 Ifo LGA  31 Borehole 84 ± 14 0.87 ± 0.15  32 Borehole 120 ± 19 1.24 ± 0.20  33 Boreholea 889 ± 68 9.14 ± 0.70  34 Wella 442 ± 46 4.54 ± 0.48  35 Well 440 ± 40 4.52 ± 0.41  36 Borehole 1268 ± 95 13.04 ± 0.98  37 Well 157 ± 27 1.61 ± 0.28  38 Borehole 144 ± 25 1.48 ± 0.26  39 Well 109 ± 15 1.12 ± 0.16  40 Wella 116 ± 23 1.19 ± 0.23 Range 84–1268 0.87–13.04 AM ± SD 377 ± 403 3.88 ± 4.14 GM 240 2.47 Ijebu North LGA  41 Well 155 ± 20 1.60 ± 0.21  42 Borehole 575 ± 51 5.91 ± 0.52  43 Well 128 ± 20 1.31 ± 0.20  44 Well 129 ± 20 1.32 ± 0.21  45 Well 155 ± 27 1.60 ± 0.23  46 Borehole 320 ± 37 3.29 ± 0.38  47 Borehole 351 ± 40 3.61 ± 0.41  48 Borehole 348 ± 41 3.58 ± 0.42  49 Borehole 109 ± 19 1.12 ± 0.20  50 Borehole 132 ± 21 1.36 ± 0.22 Range 109–575 1.12–5.91 AM ± SD 240 ± 153 2.47 ± 1.57 GM 205 2.10 Ijebu Ode LGA  51 Borehole 105 ± 16 1.08 ± 0.16  52 Borehole 99 ± 14 1.02 ± 0.14  53 Borehole 142 ± 23 1.46 ± 0.23  54 Borehole 135 ± 21 1.38 ± 0.22  55 Borehole 105 ± 17 1.08 ± 0.17  56 Borehole 165 ± 27 1.69 ± 0.27  57 Borehole 116 ± 22 1.19 ± 0.23  58 Borehole 103 ± 20 1.06 ± 0.21  59 Well 113 ± 17 1.16 ± 0.17  60 Wella 118 ± 22 1.22 ± 0.23 Range 99–165 1.02–1.69 AM ± SD 120 ± 21 1.23 ± 0.21 GM 119 1.22 Obafemi Owode LGA  61 Borehole 917 ± 56 9.43 ± 0.58  62 Borehole 715 ± 60 7.35 ± 0.62  63 Borehole 301 ± 35 3.10 ± 0.36  64 Borehole 388 ± 35 3.98 ± 0.36  65 Borehole 374 ± 40 3.84 ± 0.41  66 Borehole 964 ± 77 9.91 ± 0.80  67 Borehole 301 ± 38 3.10 ± 0.40  68 Wella 764 ± 66 7.85 ± 0.62  69 Borehole 364 ± 45 3.75 ± 0.46  70 Borehole 668 ± 59 6.88 ± 0.57 Range 301–964 3.10–9.91 AM ± SD 576 ± 259 5.92 ± 2.66 GM 523 5.38 Ota LGA  71 Borehole 79 ± 13 0.81 ± 0.13  72 Borehole 99 ± 17 1.02 ± 0.18  73 Borehole 367 ± 43 3.78 ± 0.43  74 Borehole 151 ± 24 1.56 ± 0.25  75 Borehole 80 ± 15 0.82 ± 0.15  76 Borehole 1000 ± 73 10.28 ± 0.76  77 Wella 470 ± 56 4.84 ± 0.57  78 Wella 354 ± 48 3.64 ± 0.49  79 Borehole 1932 ± 140 19.86 ± 1.44  80 Wella 39 ± 9 0.40 ± 0.09 Range 39–1932 0.40–19.86 AM ± SD 457 ± 594 4.70 ± 1.57 GM 231 2.38 Sagamu LGA  81 Wella 1550 ± 123 15.94 ± 1.27  82 Borehole 2282 ± 127 23.46 ± 1.32  83 Well 471 ± 49 4.84 ± 0.50  84 Wella 1289 ± 90 13.25 ± 0.93  85 Wella 885 ± 71 9.09 ± 0.73  86 Well 543 ± 56 5.58 ± 0.58  87 Borehole 506 ± 53 5.20 ± 0.54  88 Wella 607 ± 59 6.24 ± 0.60  89 Borehole 436 ± 48 4.48 ± 0.49  90 Borehole 1139 ± 91 11.71 ± 0.93 Range 436–2282 4.48–23.46 AM ± SD 971 ± 602 9.98 ± 6.19 GM 831 8.54 Yewa North LGA  91 Well 3145 ± 157 32.33 ± 1.62  92 Borehole 610 ± 55 6.28 ± 0.57  93 Borehole 215 ± 28 2.21 ± 0.28  94 Borehole 499 ± 46 5.13 ± 0.48  95 Wella 358 ± 38 3.68 ± 0.39  96 Borehole 160 ± 23 1.65 ± 0.24  97 Borehole 102 ± 20 1.07 ± 0.20  98 Well 155 ± 26 1.59 ± 0.31  99 Borehole 399 ± 48 4.10 ± 0.49  100 Borehole 701 ± 65 7.21 ± 0.67 Range 102–3145 1.07–32.33 AM ± SD 634 ± 905 6.53 ± 9.30 GM 373 3.84 aNot for drinking. Open in new tab Table 1 Activity concentrations of radon-222 in groundwater in Ogun State S/N . Source . Rn concentration degassed Cair (Bq.m−3) . Rn concentration Cwater (Bq.l−1) . Abeokuta North LGA  1 Boreholea 2036 ± 168 20.93 ± 1.72  2 Borehole 1240 ± 84 12.75 ± 0.86  3 Borehole 1440 ± 93 14.80 ± 0.96  4 Wella 756 ± 61 7.77 ± 0.63  5 Wella 902 ± 68 9.27 ± 0.70  6 Borehole 203 ± 28 2.09 ± 0.28  7 Borehole 331 ± 36 3.41 ± 0.37  8 Wella 394 ± 39 4.05 ± 0.41  9 Wella 2522 ± 186 36.20 ± 1.91  10 Borehole 30 ± 8 0.31 ± 0.09 Range 30–2522 0.13–36.20 AM ± SD 1085 ± 1058 11.16 ± 10.87 GM 608 6.26 Abeokuta South LGA  11 Wella 699 ± 55 7.18 ± 0.57  12 Wella 577 ± 52 5.93 ± 0.54  13 Borehole 6038 ± 282 62.07 ± 3.43  14 Borehole 168 ± 30 1.74 ± 0.31  15 Borehole 1866 ± 123 19.19 ± 1.27  16 Borehole 979 ± 80 10.07 ± 0.82  17 Borehole 940 ± 83 9.66 ± 0.85  18 Borehole 506 ± 56 5.21 ± 0.57  19 Wella 515 ± 43 5.29 ± 0.44  20 Borehole 46 ± 9 0.48 ± 0.09 Range 46–6038 0.48–62.07 AM ± SD 1233 ± 1762 12.68 ± 18.11 GM 620 6.39 Ewekoro LGA  21 Wella 1380 ± 84 14.18 ± 0.86  22 Wella 1660 ± 106 17.07 ± 1.09  23 Wella 1754 ± 115 18.03 ± 1.19  24 Wella 462 ± 49 4.75 ± 0.50  25 Borehole 177 ± 29 1.82 ± 0.29  26 Well 962 ± 79 9.88 ± 0.81  27 Wella 187 ± 31 1.92 ± 0.32  28 Borehole 509 ± 57 5.24 ± 0.56  29 Well 1512 ± 83 15.54 ± 0.89  30 Borehole 82 ± 15 0.84 ± 0.15 Range 82–1754 0.84–18.03 AM ± SD 869 ± 663 8.93 ± 6.81 GM 572 5.87 Ifo LGA  31 Borehole 84 ± 14 0.87 ± 0.15  32 Borehole 120 ± 19 1.24 ± 0.20  33 Boreholea 889 ± 68 9.14 ± 0.70  34 Wella 442 ± 46 4.54 ± 0.48  35 Well 440 ± 40 4.52 ± 0.41  36 Borehole 1268 ± 95 13.04 ± 0.98  37 Well 157 ± 27 1.61 ± 0.28  38 Borehole 144 ± 25 1.48 ± 0.26  39 Well 109 ± 15 1.12 ± 0.16  40 Wella 116 ± 23 1.19 ± 0.23 Range 84–1268 0.87–13.04 AM ± SD 377 ± 403 3.88 ± 4.14 GM 240 2.47 Ijebu North LGA  41 Well 155 ± 20 1.60 ± 0.21  42 Borehole 575 ± 51 5.91 ± 0.52  43 Well 128 ± 20 1.31 ± 0.20  44 Well 129 ± 20 1.32 ± 0.21  45 Well 155 ± 27 1.60 ± 0.23  46 Borehole 320 ± 37 3.29 ± 0.38  47 Borehole 351 ± 40 3.61 ± 0.41  48 Borehole 348 ± 41 3.58 ± 0.42  49 Borehole 109 ± 19 1.12 ± 0.20  50 Borehole 132 ± 21 1.36 ± 0.22 Range 109–575 1.12–5.91 AM ± SD 240 ± 153 2.47 ± 1.57 GM 205 2.10 Ijebu Ode LGA  51 Borehole 105 ± 16 1.08 ± 0.16  52 Borehole 99 ± 14 1.02 ± 0.14  53 Borehole 142 ± 23 1.46 ± 0.23  54 Borehole 135 ± 21 1.38 ± 0.22  55 Borehole 105 ± 17 1.08 ± 0.17  56 Borehole 165 ± 27 1.69 ± 0.27  57 Borehole 116 ± 22 1.19 ± 0.23  58 Borehole 103 ± 20 1.06 ± 0.21  59 Well 113 ± 17 1.16 ± 0.17  60 Wella 118 ± 22 1.22 ± 0.23 Range 99–165 1.02–1.69 AM ± SD 120 ± 21 1.23 ± 0.21 GM 119 1.22 Obafemi Owode LGA  61 Borehole 917 ± 56 9.43 ± 0.58  62 Borehole 715 ± 60 7.35 ± 0.62  63 Borehole 301 ± 35 3.10 ± 0.36  64 Borehole 388 ± 35 3.98 ± 0.36  65 Borehole 374 ± 40 3.84 ± 0.41  66 Borehole 964 ± 77 9.91 ± 0.80  67 Borehole 301 ± 38 3.10 ± 0.40  68 Wella 764 ± 66 7.85 ± 0.62  69 Borehole 364 ± 45 3.75 ± 0.46  70 Borehole 668 ± 59 6.88 ± 0.57 Range 301–964 3.10–9.91 AM ± SD 576 ± 259 5.92 ± 2.66 GM 523 5.38 Ota LGA  71 Borehole 79 ± 13 0.81 ± 0.13  72 Borehole 99 ± 17 1.02 ± 0.18  73 Borehole 367 ± 43 3.78 ± 0.43  74 Borehole 151 ± 24 1.56 ± 0.25  75 Borehole 80 ± 15 0.82 ± 0.15  76 Borehole 1000 ± 73 10.28 ± 0.76  77 Wella 470 ± 56 4.84 ± 0.57  78 Wella 354 ± 48 3.64 ± 0.49  79 Borehole 1932 ± 140 19.86 ± 1.44  80 Wella 39 ± 9 0.40 ± 0.09 Range 39–1932 0.40–19.86 AM ± SD 457 ± 594 4.70 ± 1.57 GM 231 2.38 Sagamu LGA  81 Wella 1550 ± 123 15.94 ± 1.27  82 Borehole 2282 ± 127 23.46 ± 1.32  83 Well 471 ± 49 4.84 ± 0.50  84 Wella 1289 ± 90 13.25 ± 0.93  85 Wella 885 ± 71 9.09 ± 0.73  86 Well 543 ± 56 5.58 ± 0.58  87 Borehole 506 ± 53 5.20 ± 0.54  88 Wella 607 ± 59 6.24 ± 0.60  89 Borehole 436 ± 48 4.48 ± 0.49  90 Borehole 1139 ± 91 11.71 ± 0.93 Range 436–2282 4.48–23.46 AM ± SD 971 ± 602 9.98 ± 6.19 GM 831 8.54 Yewa North LGA  91 Well 3145 ± 157 32.33 ± 1.62  92 Borehole 610 ± 55 6.28 ± 0.57  93 Borehole 215 ± 28 2.21 ± 0.28  94 Borehole 499 ± 46 5.13 ± 0.48  95 Wella 358 ± 38 3.68 ± 0.39  96 Borehole 160 ± 23 1.65 ± 0.24  97 Borehole 102 ± 20 1.07 ± 0.20  98 Well 155 ± 26 1.59 ± 0.31  99 Borehole 399 ± 48 4.10 ± 0.49  100 Borehole 701 ± 65 7.21 ± 0.67 Range 102–3145 1.07–32.33 AM ± SD 634 ± 905 6.53 ± 9.30 GM 373 3.84 S/N . Source . Rn concentration degassed Cair (Bq.m−3) . Rn concentration Cwater (Bq.l−1) . Abeokuta North LGA  1 Boreholea 2036 ± 168 20.93 ± 1.72  2 Borehole 1240 ± 84 12.75 ± 0.86  3 Borehole 1440 ± 93 14.80 ± 0.96  4 Wella 756 ± 61 7.77 ± 0.63  5 Wella 902 ± 68 9.27 ± 0.70  6 Borehole 203 ± 28 2.09 ± 0.28  7 Borehole 331 ± 36 3.41 ± 0.37  8 Wella 394 ± 39 4.05 ± 0.41  9 Wella 2522 ± 186 36.20 ± 1.91  10 Borehole 30 ± 8 0.31 ± 0.09 Range 30–2522 0.13–36.20 AM ± SD 1085 ± 1058 11.16 ± 10.87 GM 608 6.26 Abeokuta South LGA  11 Wella 699 ± 55 7.18 ± 0.57  12 Wella 577 ± 52 5.93 ± 0.54  13 Borehole 6038 ± 282 62.07 ± 3.43  14 Borehole 168 ± 30 1.74 ± 0.31  15 Borehole 1866 ± 123 19.19 ± 1.27  16 Borehole 979 ± 80 10.07 ± 0.82  17 Borehole 940 ± 83 9.66 ± 0.85  18 Borehole 506 ± 56 5.21 ± 0.57  19 Wella 515 ± 43 5.29 ± 0.44  20 Borehole 46 ± 9 0.48 ± 0.09 Range 46–6038 0.48–62.07 AM ± SD 1233 ± 1762 12.68 ± 18.11 GM 620 6.39 Ewekoro LGA  21 Wella 1380 ± 84 14.18 ± 0.86  22 Wella 1660 ± 106 17.07 ± 1.09  23 Wella 1754 ± 115 18.03 ± 1.19  24 Wella 462 ± 49 4.75 ± 0.50  25 Borehole 177 ± 29 1.82 ± 0.29  26 Well 962 ± 79 9.88 ± 0.81  27 Wella 187 ± 31 1.92 ± 0.32  28 Borehole 509 ± 57 5.24 ± 0.56  29 Well 1512 ± 83 15.54 ± 0.89  30 Borehole 82 ± 15 0.84 ± 0.15 Range 82–1754 0.84–18.03 AM ± SD 869 ± 663 8.93 ± 6.81 GM 572 5.87 Ifo LGA  31 Borehole 84 ± 14 0.87 ± 0.15  32 Borehole 120 ± 19 1.24 ± 0.20  33 Boreholea 889 ± 68 9.14 ± 0.70  34 Wella 442 ± 46 4.54 ± 0.48  35 Well 440 ± 40 4.52 ± 0.41  36 Borehole 1268 ± 95 13.04 ± 0.98  37 Well 157 ± 27 1.61 ± 0.28  38 Borehole 144 ± 25 1.48 ± 0.26  39 Well 109 ± 15 1.12 ± 0.16  40 Wella 116 ± 23 1.19 ± 0.23 Range 84–1268 0.87–13.04 AM ± SD 377 ± 403 3.88 ± 4.14 GM 240 2.47 Ijebu North LGA  41 Well 155 ± 20 1.60 ± 0.21  42 Borehole 575 ± 51 5.91 ± 0.52  43 Well 128 ± 20 1.31 ± 0.20  44 Well 129 ± 20 1.32 ± 0.21  45 Well 155 ± 27 1.60 ± 0.23  46 Borehole 320 ± 37 3.29 ± 0.38  47 Borehole 351 ± 40 3.61 ± 0.41  48 Borehole 348 ± 41 3.58 ± 0.42  49 Borehole 109 ± 19 1.12 ± 0.20  50 Borehole 132 ± 21 1.36 ± 0.22 Range 109–575 1.12–5.91 AM ± SD 240 ± 153 2.47 ± 1.57 GM 205 2.10 Ijebu Ode LGA  51 Borehole 105 ± 16 1.08 ± 0.16  52 Borehole 99 ± 14 1.02 ± 0.14  53 Borehole 142 ± 23 1.46 ± 0.23  54 Borehole 135 ± 21 1.38 ± 0.22  55 Borehole 105 ± 17 1.08 ± 0.17  56 Borehole 165 ± 27 1.69 ± 0.27  57 Borehole 116 ± 22 1.19 ± 0.23  58 Borehole 103 ± 20 1.06 ± 0.21  59 Well 113 ± 17 1.16 ± 0.17  60 Wella 118 ± 22 1.22 ± 0.23 Range 99–165 1.02–1.69 AM ± SD 120 ± 21 1.23 ± 0.21 GM 119 1.22 Obafemi Owode LGA  61 Borehole 917 ± 56 9.43 ± 0.58  62 Borehole 715 ± 60 7.35 ± 0.62  63 Borehole 301 ± 35 3.10 ± 0.36  64 Borehole 388 ± 35 3.98 ± 0.36  65 Borehole 374 ± 40 3.84 ± 0.41  66 Borehole 964 ± 77 9.91 ± 0.80  67 Borehole 301 ± 38 3.10 ± 0.40  68 Wella 764 ± 66 7.85 ± 0.62  69 Borehole 364 ± 45 3.75 ± 0.46  70 Borehole 668 ± 59 6.88 ± 0.57 Range 301–964 3.10–9.91 AM ± SD 576 ± 259 5.92 ± 2.66 GM 523 5.38 Ota LGA  71 Borehole 79 ± 13 0.81 ± 0.13  72 Borehole 99 ± 17 1.02 ± 0.18  73 Borehole 367 ± 43 3.78 ± 0.43  74 Borehole 151 ± 24 1.56 ± 0.25  75 Borehole 80 ± 15 0.82 ± 0.15  76 Borehole 1000 ± 73 10.28 ± 0.76  77 Wella 470 ± 56 4.84 ± 0.57  78 Wella 354 ± 48 3.64 ± 0.49  79 Borehole 1932 ± 140 19.86 ± 1.44  80 Wella 39 ± 9 0.40 ± 0.09 Range 39–1932 0.40–19.86 AM ± SD 457 ± 594 4.70 ± 1.57 GM 231 2.38 Sagamu LGA  81 Wella 1550 ± 123 15.94 ± 1.27  82 Borehole 2282 ± 127 23.46 ± 1.32  83 Well 471 ± 49 4.84 ± 0.50  84 Wella 1289 ± 90 13.25 ± 0.93  85 Wella 885 ± 71 9.09 ± 0.73  86 Well 543 ± 56 5.58 ± 0.58  87 Borehole 506 ± 53 5.20 ± 0.54  88 Wella 607 ± 59 6.24 ± 0.60  89 Borehole 436 ± 48 4.48 ± 0.49  90 Borehole 1139 ± 91 11.71 ± 0.93 Range 436–2282 4.48–23.46 AM ± SD 971 ± 602 9.98 ± 6.19 GM 831 8.54 Yewa North LGA  91 Well 3145 ± 157 32.33 ± 1.62  92 Borehole 610 ± 55 6.28 ± 0.57  93 Borehole 215 ± 28 2.21 ± 0.28  94 Borehole 499 ± 46 5.13 ± 0.48  95 Wella 358 ± 38 3.68 ± 0.39  96 Borehole 160 ± 23 1.65 ± 0.24  97 Borehole 102 ± 20 1.07 ± 0.20  98 Well 155 ± 26 1.59 ± 0.31  99 Borehole 399 ± 48 4.10 ± 0.49  100 Borehole 701 ± 65 7.21 ± 0.67 Range 102–3145 1.07–32.33 AM ± SD 634 ± 905 6.53 ± 9.30 GM 373 3.84 aNot for drinking. Open in new tab Among the factors that might affect radon-222 concentration in groundwater is geological formation(22,23). The study area consists of different geology, and this could be responsible for the variations in the radon concentrations. The results of this study show a relationship between the mean radon concentrations of groundwater from LGAs with the same geological formation. For instance, Abeokuta South and Abeokuta North, which are of the same geology, had similar mean radon concentrations, and Ewekoro and Sagamu also had similar concentrations. Comparing the results obtained in this study with a similar study carried out in Lagos State, the mean radon concentration in groundwater obtained for the LGAs in Lagos State ranged between 0.138 ± 0.058 Bq.l−1 (Ifako-Ijaye LGA) and 0.411 ± 0.135 Bq.l−1 (Agege LGA), which are less than the minimum average (1.23 ± 0.21) for this study. This could also be a result of the differences in the geological formation of the two States(21). Ingestion and inhalation doses Annual effective dose due to the ingestion of radon-222 in the groundwater was estimated from the radon concentrations using equation 2(2,10,20,24,25): $$\begin{equation} {H}_{\mathrm{ing}}={C}_{\mathrm{water}}\times{D}_{\mathrm{ing}}\times W, \end{equation}$$(2) where the annual effective doses due to ingestion and radon concentration in water are Hing (Sv.y−1) and Cwater (Bq.l−1), respectively. Dose conversion coefficient from activity concentration to dose is Ding and W is the annual consumption of water. Dose conversion coefficients were considered for adults (1 × 10−8 Sv.Bq−1), children (2 × 10−8 Sv.Bq−1) and infants (7 × 10−8 Sv.Bq−1)(26). The volume of water intake for 365 d was taken as 4.5 l.d−1 for adults and children(27,28) and 0.75 l.d−1 for infants(27,29). The inhalation dose was obtained using the following equation(2,10,20,30): $$\begin{equation} {H}_{\mathrm{inh}}={C}_{\mathrm{air}}\times R\times F\times T\times DC \end{equation}$$(3) where Hinh (nSv.y−1) and Cair (Bq.m−3) are, respectively, the annual effective dose due to inhalation and radon-222 concentration of the degassed air from the water. Air–water concentration ratio, R is given as 10−4 and F, the equilibrium factor between indoor radon and its progeny is given as 0.4. The occupancy factor, T is taken as 7000 h y−1 and DC, the dose conversion coefficient is 9 nSv per Bq.h.m-3(2). The AM and GM of annual effective doses for adults, children and infants due to the ingestion of radon-222 in the groundwater samples collected from each of the LGAs are presented in Table 2. The annual effective doses due ingestion were obtained for only drinking water. The AM values ranged from 0.020 ± 0.004 to 0.254 ± 0.353 mSv.y−1 with a corresponding GM of 0.020 to 0.107 mSv.y−1 for adults. For children, the AM ranged from 0.041 ± 0.007 to 0.509 ± 0.705 mSv.y−1, which corresponds to GM from 0.040 to 0.214 mSv.y−1. The range of AM and GM for infants was between 0.024 ± 0.004 to 0.297 ± 0.0.411 mSv.y−1 and 0.023 to 0.0.125 mSv.y−1, respectively. However, the highest GMs; 0.123, 0.245 and 0.143 mSv.y−1 for adults, children and infants, respectively, do not correspond to the highest AMs. The SDs in the AM values depict the variations in the 222Rn concentrations of samples from the same LGA. There are large variations in the activity concentrations of radon in water from the same LGA. This is revealed in the GM values of samples from the same LGA. The reference dose level (RDL) of committed effective dose as recommended by the ICRP is 0.1 mSv from 1-year consumption of drinking water, and this comprises 10% of the intervention exemption level(1,31,32). The mean annual effective doses for some of the LGAs were higher than the RDL with the highest occurrence for children. The AM of the annual effective doses due to inhalation ranged between 0.303 ± 0.053 and 3.108 ± 4.440 μSv.y−1 with corresponding GMs of 0.299 and 1.563 μSv.y−1. The contribution of annual inhalation dose to the total annual effective dose is negligible compared to the annual ingestion dose. Table 2 Annual effective doses due to ingestion (Hing) and inhalation (Hinh) of radon −222 in groundwater in Ogun State LGA . Hing (mSv.y−1)a . Hinh (μSv.y−1) . Adults . Children . Infants . AM ± SD GM . AM ± SD GM . AM ± SD GM . AM ± SD GM . Abeokuta North 0.110 ± 0.109 0.055 0.219 ± 0.217 0.110 0.128 ± 0.127 0.064 2.735 ± 2.666 1.533 Abeokuta South 0.254 ± 0.353 0.107 0.509 ± 0.705 0.214 0.297 ± 0.411 0.125 3.108 ± 4.440 1.563 Ewekoro 0.109 ± 0.100 0.068 0.219 ± 0.200 0.136 0.128 ± 0.117 0.080 2.187 ± 1.670 1.441 Ifo 0.056 ± 0.073 0.034 0.112 ± 0.145 0.068 0.063 ± 0.085 0.040 0.950 ± 1.015 0.605 Ijebu North 0.041 ± 0.026 0.035 0.081 ± 0.052 0.069 0.047 ± 0.030 0.040 0.605 ± 0.039 0.515 Ijebu Ode 0.020 ± 0.004 0.020 0.041 ± 0.007 0.040 0.024 ± 0.004 0.023 0.303 ± 0.053 0.299 Obafemi Owode 0.094 ± 0.045 0.085 0.187 ± 0.090 0.170 `0.109 ± 0.052 0.099 1.451 ± 0.652 1.319 Ota 0.089 ± 0.118 0.043 0.179 ± 0.237 0.086 0.104 ± 0.138 0.050 1.152 ± 1.149 0.582 Sagamu 0.151 ± 0.123 0.123 0.303 ± 0.246 0.245 0.177 ± 0.143 0.143 2.446 ± 1.516 2.095 Yewa North 0.112 ± 0.161 0.063 0.225 ± 0.322 0.127 0.131 ± 0.188 0.074 1.599 ± 2.281 0.940 LGA . Hing (mSv.y−1)a . Hinh (μSv.y−1) . Adults . Children . Infants . AM ± SD GM . AM ± SD GM . AM ± SD GM . AM ± SD GM . Abeokuta North 0.110 ± 0.109 0.055 0.219 ± 0.217 0.110 0.128 ± 0.127 0.064 2.735 ± 2.666 1.533 Abeokuta South 0.254 ± 0.353 0.107 0.509 ± 0.705 0.214 0.297 ± 0.411 0.125 3.108 ± 4.440 1.563 Ewekoro 0.109 ± 0.100 0.068 0.219 ± 0.200 0.136 0.128 ± 0.117 0.080 2.187 ± 1.670 1.441 Ifo 0.056 ± 0.073 0.034 0.112 ± 0.145 0.068 0.063 ± 0.085 0.040 0.950 ± 1.015 0.605 Ijebu North 0.041 ± 0.026 0.035 0.081 ± 0.052 0.069 0.047 ± 0.030 0.040 0.605 ± 0.039 0.515 Ijebu Ode 0.020 ± 0.004 0.020 0.041 ± 0.007 0.040 0.024 ± 0.004 0.023 0.303 ± 0.053 0.299 Obafemi Owode 0.094 ± 0.045 0.085 0.187 ± 0.090 0.170 `0.109 ± 0.052 0.099 1.451 ± 0.652 1.319 Ota 0.089 ± 0.118 0.043 0.179 ± 0.237 0.086 0.104 ± 0.138 0.050 1.152 ± 1.149 0.582 Sagamu 0.151 ± 0.123 0.123 0.303 ± 0.246 0.245 0.177 ± 0.143 0.143 2.446 ± 1.516 2.095 Yewa North 0.112 ± 0.161 0.063 0.225 ± 0.322 0.127 0.131 ± 0.188 0.074 1.599 ± 2.281 0.940 aOnly drinking water. Open in new tab Table 2 Annual effective doses due to ingestion (Hing) and inhalation (Hinh) of radon −222 in groundwater in Ogun State LGA . Hing (mSv.y−1)a . Hinh (μSv.y−1) . Adults . Children . Infants . AM ± SD GM . AM ± SD GM . AM ± SD GM . AM ± SD GM . Abeokuta North 0.110 ± 0.109 0.055 0.219 ± 0.217 0.110 0.128 ± 0.127 0.064 2.735 ± 2.666 1.533 Abeokuta South 0.254 ± 0.353 0.107 0.509 ± 0.705 0.214 0.297 ± 0.411 0.125 3.108 ± 4.440 1.563 Ewekoro 0.109 ± 0.100 0.068 0.219 ± 0.200 0.136 0.128 ± 0.117 0.080 2.187 ± 1.670 1.441 Ifo 0.056 ± 0.073 0.034 0.112 ± 0.145 0.068 0.063 ± 0.085 0.040 0.950 ± 1.015 0.605 Ijebu North 0.041 ± 0.026 0.035 0.081 ± 0.052 0.069 0.047 ± 0.030 0.040 0.605 ± 0.039 0.515 Ijebu Ode 0.020 ± 0.004 0.020 0.041 ± 0.007 0.040 0.024 ± 0.004 0.023 0.303 ± 0.053 0.299 Obafemi Owode 0.094 ± 0.045 0.085 0.187 ± 0.090 0.170 `0.109 ± 0.052 0.099 1.451 ± 0.652 1.319 Ota 0.089 ± 0.118 0.043 0.179 ± 0.237 0.086 0.104 ± 0.138 0.050 1.152 ± 1.149 0.582 Sagamu 0.151 ± 0.123 0.123 0.303 ± 0.246 0.245 0.177 ± 0.143 0.143 2.446 ± 1.516 2.095 Yewa North 0.112 ± 0.161 0.063 0.225 ± 0.322 0.127 0.131 ± 0.188 0.074 1.599 ± 2.281 0.940 LGA . Hing (mSv.y−1)a . Hinh (μSv.y−1) . Adults . Children . Infants . AM ± SD GM . AM ± SD GM . AM ± SD GM . AM ± SD GM . Abeokuta North 0.110 ± 0.109 0.055 0.219 ± 0.217 0.110 0.128 ± 0.127 0.064 2.735 ± 2.666 1.533 Abeokuta South 0.254 ± 0.353 0.107 0.509 ± 0.705 0.214 0.297 ± 0.411 0.125 3.108 ± 4.440 1.563 Ewekoro 0.109 ± 0.100 0.068 0.219 ± 0.200 0.136 0.128 ± 0.117 0.080 2.187 ± 1.670 1.441 Ifo 0.056 ± 0.073 0.034 0.112 ± 0.145 0.068 0.063 ± 0.085 0.040 0.950 ± 1.015 0.605 Ijebu North 0.041 ± 0.026 0.035 0.081 ± 0.052 0.069 0.047 ± 0.030 0.040 0.605 ± 0.039 0.515 Ijebu Ode 0.020 ± 0.004 0.020 0.041 ± 0.007 0.040 0.024 ± 0.004 0.023 0.303 ± 0.053 0.299 Obafemi Owode 0.094 ± 0.045 0.085 0.187 ± 0.090 0.170 `0.109 ± 0.052 0.099 1.451 ± 0.652 1.319 Ota 0.089 ± 0.118 0.043 0.179 ± 0.237 0.086 0.104 ± 0.138 0.050 1.152 ± 1.149 0.582 Sagamu 0.151 ± 0.123 0.123 0.303 ± 0.246 0.245 0.177 ± 0.143 0.143 2.446 ± 1.516 2.095 Yewa North 0.112 ± 0.161 0.063 0.225 ± 0.322 0.127 0.131 ± 0.188 0.074 1.599 ± 2.281 0.940 aOnly drinking water. Open in new tab CONCLUSION The activity concentrations of radon-222 in 100 groundwater samples collected from 10 LGAs of Ogun State, Nigeria are presented in this study. The radon-222 concentrations of all the samples were lower than the WHO and EC limit of 100 Bq.l−1(1,13). Seventeen percent of the sampled water had radon concentrations higher than the MCL value of 11.1 Bq.l−1. However, the mean values for eight of the LGAs were less than the MCL value proposed by United States Environmental Protection Agency(11), but that of Abeokuta South LGA was ~14% higher than the MCL value. The mean annual effective doses due to ingestion of radon in groundwater of some of the LGAs exceeded the recommended 0.1 mSv.y−1 RDL from the annual consumption of water(1). ACKNOWLEDGEMENTS The authors appreciate the Alexander von Humboldt Foundation, Bonn, Germany for the donation of the AlphaGUARD and all the accessories. 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TI - OCCURRENCE AND DOSE FROM INTAKE OF RADON IN DRINKING GROUNDWATER IN OGUN STATE, NIGERIA
JF - Radiation Protection Dosimetry
DO - 10.1093/rpd/ncaa221
DA - 2020-12-30
UR - https://www.deepdyve.com/lp/oxford-university-press/occurrence-and-dose-from-intake-of-radon-in-drinking-groundwater-in-tD6eV5iRaa
SP - 421
EP - 429
VL - 192
IS - 4
DP - DeepDyve
ER -