Abstract
Radon in the household water collected from hand pumps is measured using a continuous radon monitor. Water samples are collected from 25 villages from the surrounding regions of the National Capital Power Cooperation (NTPC), Dadri. The radon concentration ranges from 17±1 to 68±3 Bql−1 with a mean value of 33±13 Bql−1. The measured radon concentration in all collected samples lies well within the limit of 100 Bql−1as set by the World Health Organization (WHO). The mean values of the annual effective dose due to ingestion of radon and due to the inhalation of radon released from water are 84±33 and 167±65 μSvy−1, respectively. In addition, the mean values of estimated total annual effective doses are found to be 167±65 μSvy−1. The mean value of total annual effective doses is found to be higher than the reference dose level of 100 μSvy−1 recommended by the WHO and the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). The mean values of effective doses per annum to the lungs and stomach are 9.9±3.9 and 10.1±3.9 μSv, respectively.
HIGHLIGHTS
SMART Rn Duo: A Continuous radon monitor.
Radon concentration present in the drinking groundwater is measured.
The annual effective ingestion, inhalation, and total dose of radon are measured.
Radon concentration is found to be below the recommended action level of 100 Bql−1 proposed by the EU and WHO.
The mean value of total annual effective dose is found to be higher compared to the safe limit recommended by the WHO.
Graphical Abstract
INTRODUCTION
Radon (222Rn) is a naturally occurring radioactive gas in the decay chain 238U. This gas is produced continuously and is commonly present in the pore space of rock and soil. A fraction of radon present in pore space is dissolved in groundwater depending upon the air–water partition coefficient. The consequences of radon in drinking water are twofold: (i) irradiation of stomach tissues and small intestine through ingestion and (ii) irradiation of lung tissues through inhalation. In terms of ingested radon, the radiation exposure is primarily due to radon gas itself (NRC 1999; Kendall & Smith 2002). The highest organ dose (>90%) from ingested radon is to the stomach (Kendall & Smith 2002). The US NAS (1999) assessed that the risk of stomach cancer caused by radon dissolved in drinking water is small compared to stomach cancer due to other causes. No definitive link between ingestion of drinking water containing radon with increased risk of stomach cancer (Auvinen et al. 2005) has been established. Still, worldwide efforts are ongoing to study the linear relationship between radon exposure and health risk due to the assumption of the Linear No Threshold (LNT) hypothesis in radiation risk assessment (WHO 2017). Based on the estimated risk to human health from the LNT model because of radiation protection, different radon levels have been introduced for radon in drinking water. In the European Union countries, the limit is between 100 and 1,000 Bql−1 (EURATOM 2013). Spanish legislation has set a limit of 500 Bql−1 (Gonzalez et al. 2018). In the United States, two different levels, a maximum contamination level of 11.1 Bql−1 and an alternative maximum contamination level of 148 Bql−1, are given (EPA 1999). The World Health Organization (WHO) and the European Commission (EU) set the guidance level to 100 Bql−1 (EU 2001; WHO 2008). The WHO (2008) has recommended a reference dose level (RDL) of 0.1 mSv due to the annual intake of drinking water. The RDL of 0.1 mSv is equal to 10% of the dose limit for the intervention level recommended by the ICRP (1991) and the International Basic Safety Standards (IAEA 1996).
Surface and underground water samples contain natural radionuclides in various concentrations depending on their origin. Radon gets released into waters due to the decay of its parent nuclide 226Ra contained in rock and soil. The amount of radon dissolved depends upon different factors such as radium content, radon emanation coefficient, air–water partition coefficient, and aquifer characteristics (Moreno et al. 2014). The groundwater generally has much higher concentrations of radon than surface water. In public water supplies derived from surface water, the mean radon concentration is usually less than 0.4 Bql−1 and its mean value is about 20 Bql−1 from groundwater sources (WHO 2008).
Various studies have been performed in different parts of India to measure the radon concentration in groundwater used for drinking purposes. In various states of India, the concentration of radon dissolved in groundwater ranged as follows: 0.87–6.73 Bql−1 in Himachal Pradesh (Singh et al. 2016), 0.4–74.37 Bql−1 in Jammu and Kashmir (Kumar et al. 2017a, 2017b, 2018; Kaur et al. 2019), 0.14–35 Bql−1 in Punjab (Kaur et al. 2017; Kumar et al. 2017c, 2019; Sharma et al. 2019, 2020; Pant et al. 2020), 0.60–57.35 Bql−1 in Haryana (Duggal et al. 2017; Panghal et al. 2017; Sharma et al. 2017a, 2017b; Singh et al. 2019), 0.50–861.5 Bql−1in Rajasthan (Mittal et al. 2016a, 2016b; Duggal et al. 2020a, 2020b), 0.19–160.18 Bql−1in Karnataka (Srinivasa et al. 2015, 2018, 2019; Rangaswamy et al. 2016; Niranjan et al. 2017; Reddy et al. 2017; Shilpa et al. 2017; Kaliprasad & Narayana 2018; Sannappa et al. 2020; Yashaswini et al. 2020), 0.12–28.20 Bql−1in Kerala (Nandakumaran et al. 2016; Divya & Prakash 2019), 0.07–40.7 Bql−1in Tamil Nadu (Singaraja et al. 2016), 1.04–10.02 Bql−1 in West Bengal (Krishna et al. 2015), 0.33–7.32 Bql−1 in Maharashtra (Raste et al. 2018), and 2–400 Bql−1 in Uttarakhand (Prasad et al. 2018). These available literature values show that the overall range in India varies from 0.07 to 861.5 Bql−1. Singaraja et al. (2016) have reported the minimum value of 0.07 Bql−1 in the Tuticorin district in Tamil Nadu state. Duggal et al. (2020a, 2020b) have reported the maximum value of 861.5 Bql−1 in the Khandela region of the Khetri Copper Belt of Rajasthan.
Coal-fired power plants are the sources of fly ash, which contains naturally occurring radioactive elements such as 238U, 232Th, and their decay products and other toxic elements. Fly ash is generally stored at coal power plants or placed in landfills. Ash stored or deposited outdoors may eventually leach radioactive elements (238U, 232Th, and their decay products) and other toxic composites into underground water aquifers. This may lead to contamination of underground water used for drinking purposes and may cause internal exposure to the public. One of the important radionuclides in drinking water causing internal exposure is the dissolved radon gas which originates from the 238U decay series. As per the WHO, internal exposure to radon is the second highest cause of lung cancer, next to smoking. In view of radiological importance of radon in drinking water, the present study was taken up to measure the concentration of dissolved radon in water and estimate the corresponding annual effective dose in water samples collected from hand pumps in the surrounding area of coal and natural gas-based power plant situated in the Gautam Buddha Nagar district, Uttar Pradesh, India. To the best of our information, the measured values for radon in drinking water and associated doses are the only data available for the studied region around the National Capital Power Cooperation (NTPC), Dadri. Some novelties of this study includes onsite measurements using a portable continuous radon monitoring system and a novel sampling technique to prevent loss of dissolved radon by aeration and air-contact, which is commonly faced by researchers.
MATERIALS AND METHODS
Study area
The area under study around the NTPC, Dadri power station, lies between 28.5568°–28.6419°N and 77.5476°–77.6521°E. This region comprises an aquifer system that forms a good repository of groundwater. These water repositories occur in granular zones constituted of fine to coarse and occasional gravel. Thick clay beds interlying with sand act as confining layers and separate the aquifers. Groundwater occurs in shallow aquifers down to the depth of 100 m below ground level under confined and semi-confined conditions and is safe for drinking. In the deeper zone, water becomes brackish to saline (Joshi 2008–2009). Figure 1 shows a map of the study region with sampling locations.
Locations of water samples in the surrounding region of the NTPC, Dadri.
Sample collection and instrument details
Samples were collected from hand pumps in the month of February 2020 from 25 villages from the surrounding region of the NTPC in a leak-tight bottle made up of low-permeability material having a volume of 60 ml. Sufficient precaution was taken during sampling to minimize aeration and prevent loss of dissolved radon in water sample. Measurements were carried out at the site within 3 h of sample collection to minimize the loss of radon due to the radioactive decay process.
A continuous activity monitor (SMART RnDuo), developed and calibrated by the Bhabha Atomic Research Centre, Mumbai (Gaware et al. 2011), was used to measure radon in water samples because of its very high sensitivity per unit activity concentration of radon (∼1.2 cph/Bq m−3) and less dilution due to low-detector volume (1.53 × 10−4 m3). A scintillation technique is employed to detect alpha particles of sampled radon and its progeny formed inside the detector volume. Alpha counts obtained in each interval get converted into the radon concentration through a novel in-built algorithm in the micro-controller. The measured values are always free from the effects of humidity and trace gases because this device does not have any interference from charge-neutralizing species (such as humidity, CO2, CH4, etc.).
The sampling bottle is attached to the SMART RnDuo monitor through a bubbler and tubes. Figure 2 shows a schematic of the experimental setup for measuring radon in the water. A fast mode with a counting interval time of 15 min and a pump on time of 5 min per interval is employed. The measurement was continued to about 1 h for obtaining converge reading of radon concentration in water sample.
Mathematical formalism


RESULTS AND DISCUSSION
Table 1 shows the radon concentration in drinking water samples, annual effective inhalation, ingestion, total dose, dose to lungs and stomach for the adult population living in the study area around the NTPC, Dadri.
Results of measured radon concentration in water samples collected from hand pump around the NTPC, Dadri and estimated annual effective doses
Sample code . | Village . | Sample location . | Radon concentration (Bql−1) . | Annual effective dose (μSvy−1) . | Annual effective dose to body organs (μSv) . | ||||
---|---|---|---|---|---|---|---|---|---|
Latitude . | Longitude . | Inhalation . | Ingestion . | Total . | Dlungs . | Dstomach . | |||
S01 | Dadupur Khatana | 28.5649 | 77.5956 | 42±2 | 63±4 | 64±4 | 126±6 | 7.5±0.5 | 7.6±0.5 |
S02 | Dhanibas | 28.5568 | 77.6170 | 30±2 | 106±5 | 107±5 | 213±7 | 12.7±0.6 | 12.9±0.6 |
S03 | Uplarasi | 28.5593 | 77.6253 | 17±1 | 75±4 | 76±4 | 152±6 | 9.1±0.5 | 9.2±0.5 |
S04 | Gulaothi Khurd | 28.5689 | 77.6321 | 42±2 | 43±3 | 43±3 | 86±5 | 5.1±0.4 | 5.2±0.4 |
S05 | Jarcha | 28.5708 | 77.6521 | 48±2 | 105±5 | 106±5 | 211±7 | 12.6±0.6 | 12.8±0.6 |
S06 | Unch Amirpur | 28.6057 | 77.6106 | 34±2 | 121±5 | 123±5 | 244±8 | 14.5±0.6 | 14.7±0.7 |
S07 | Khangoda | 28.5901 | 77.6278 | 43±2 | 86±4 | 87±4 | 173±6 | 10.3±0.5 | 10.5±0.5 |
S08 | Khatana Dhirkhera | 28.5587 | 77.5991 | 24±2 | 109±5 | 110±5 | 219±7 | 13.1±0.6 | 13.2±0.6 |
S09 | Daulatpur Dhikri | 28.6287 | 77.6371 | 18±1 | 60±4 | 61±4 | 122±6 | 7.2±0.5 | 7.3±0.5 |
S10 | Dhaulana | 28.6324 | 77.6479 | 19±1 | 44±3 | 45±4 | 90±5 | 5.3±0.4 | 5.4±0.4 |
S11 | Kakarana | 28.6419 | 77.6410 | 31±2 | 47±3 | 48±4 | 95±5 | 5.7±0.4 | 5.7±0.4 |
S12 | Saulana | 28.6084 | 77.6392 | 41±2 | 78±4 | 79±5 | 158±6 | 9.4±0.5 | 9.5±0.5 |
S13 | Iradatpur | 28.6009 | 77.5590 | 18±1 | 103±5 | 104±5 | 207±7 | 12.3±0.6 | 12.5±0.6 |
S14 | Bambawar | 28.6114 | 77.5476 | 17±1 | 46±3 | 47±3 | 93±5 | 5.5±0.4 | 5.6±0.4 |
S15 | Pyawali Tajpur | 28.6088 | 77.5820 | 53±2 | 42±3 | 43±3 | 85±5 | 5.0±0.4 | 5.1±0.4 |
S16 | Akilpur Jagir | 28.6150 | 77.5640 | 68±3 | 134±6 | 136±6 | 270±8 | 16.1±0.7 | 16.3±0.7 |
S17 | Hasanpur Lodha | 28.6354 | 77.5559 | 34±2 | 172±7 | 174±7 | 346±10 | 20.6±0.8 | 20.9±0.8 |
S18 | Sidipur | 28.6214 | 77.5934 | 32±2 | 85±5 | 86±5 | 171±7 | 10.2±0.6 | 10.4±0.6 |
S19 | Ranoli | 28.5783 | 77.5834 | 43±2 | 81±4 | 82±4 | 163±6 | 9.7±0.5 | 9.8±0.5 |
S20 | Salarpur Kalan | 28.5817 | 77.5991 | 35±2 | 107±5 | 109±5 | 216±7 | 12.9±0.6 | 13.0±0.6 |
S21 | Muthiyani | 28.5711 | 77.6203 | 21±1 | 88±5 | 90±5 | 178±7 | 10.6±0.6 | 10.7±0.6 |
S22 | Rasoolpur Dasana | 28.6036 | 77.5877 | 20±1 | 53±4 | 54±4 | 107±5 | 6.4±0.4 | 6.5±0.4 |
S23 | Chauna | 28.6328 | 77.5934 | 37±2 | 49±4 | 50±4 | 99±5 | 5.9±0.4 | 6.0±0.4 |
S24 | Tatarpur | 28.6267 | 77.6089 | 32±2 | 92±5 | 93±5 | 186±7 | 11.1±0.6 | 11.2±0.6 |
S25 | Bisahada | 28.5905 | 77.5705 | 25±2 | 81±4 | 82±4 | 163±6 | 9.7±0.5 | 9.8±0.5 |
Minimum | 17±1 | 42±3 | 43±3 | 85±5 | 5.0±0.4 | 5.1±0.4 | |||
Maximum | 68±3 | 172±7 | 174±7 | 346±10 | 20.6±0.8 | 20.9±0.8 | |||
Average±SD | 33±13 | 83±32 | 84±33 | 167±65 | 9.9±3.9 | 10.1±3.9 |
Sample code . | Village . | Sample location . | Radon concentration (Bql−1) . | Annual effective dose (μSvy−1) . | Annual effective dose to body organs (μSv) . | ||||
---|---|---|---|---|---|---|---|---|---|
Latitude . | Longitude . | Inhalation . | Ingestion . | Total . | Dlungs . | Dstomach . | |||
S01 | Dadupur Khatana | 28.5649 | 77.5956 | 42±2 | 63±4 | 64±4 | 126±6 | 7.5±0.5 | 7.6±0.5 |
S02 | Dhanibas | 28.5568 | 77.6170 | 30±2 | 106±5 | 107±5 | 213±7 | 12.7±0.6 | 12.9±0.6 |
S03 | Uplarasi | 28.5593 | 77.6253 | 17±1 | 75±4 | 76±4 | 152±6 | 9.1±0.5 | 9.2±0.5 |
S04 | Gulaothi Khurd | 28.5689 | 77.6321 | 42±2 | 43±3 | 43±3 | 86±5 | 5.1±0.4 | 5.2±0.4 |
S05 | Jarcha | 28.5708 | 77.6521 | 48±2 | 105±5 | 106±5 | 211±7 | 12.6±0.6 | 12.8±0.6 |
S06 | Unch Amirpur | 28.6057 | 77.6106 | 34±2 | 121±5 | 123±5 | 244±8 | 14.5±0.6 | 14.7±0.7 |
S07 | Khangoda | 28.5901 | 77.6278 | 43±2 | 86±4 | 87±4 | 173±6 | 10.3±0.5 | 10.5±0.5 |
S08 | Khatana Dhirkhera | 28.5587 | 77.5991 | 24±2 | 109±5 | 110±5 | 219±7 | 13.1±0.6 | 13.2±0.6 |
S09 | Daulatpur Dhikri | 28.6287 | 77.6371 | 18±1 | 60±4 | 61±4 | 122±6 | 7.2±0.5 | 7.3±0.5 |
S10 | Dhaulana | 28.6324 | 77.6479 | 19±1 | 44±3 | 45±4 | 90±5 | 5.3±0.4 | 5.4±0.4 |
S11 | Kakarana | 28.6419 | 77.6410 | 31±2 | 47±3 | 48±4 | 95±5 | 5.7±0.4 | 5.7±0.4 |
S12 | Saulana | 28.6084 | 77.6392 | 41±2 | 78±4 | 79±5 | 158±6 | 9.4±0.5 | 9.5±0.5 |
S13 | Iradatpur | 28.6009 | 77.5590 | 18±1 | 103±5 | 104±5 | 207±7 | 12.3±0.6 | 12.5±0.6 |
S14 | Bambawar | 28.6114 | 77.5476 | 17±1 | 46±3 | 47±3 | 93±5 | 5.5±0.4 | 5.6±0.4 |
S15 | Pyawali Tajpur | 28.6088 | 77.5820 | 53±2 | 42±3 | 43±3 | 85±5 | 5.0±0.4 | 5.1±0.4 |
S16 | Akilpur Jagir | 28.6150 | 77.5640 | 68±3 | 134±6 | 136±6 | 270±8 | 16.1±0.7 | 16.3±0.7 |
S17 | Hasanpur Lodha | 28.6354 | 77.5559 | 34±2 | 172±7 | 174±7 | 346±10 | 20.6±0.8 | 20.9±0.8 |
S18 | Sidipur | 28.6214 | 77.5934 | 32±2 | 85±5 | 86±5 | 171±7 | 10.2±0.6 | 10.4±0.6 |
S19 | Ranoli | 28.5783 | 77.5834 | 43±2 | 81±4 | 82±4 | 163±6 | 9.7±0.5 | 9.8±0.5 |
S20 | Salarpur Kalan | 28.5817 | 77.5991 | 35±2 | 107±5 | 109±5 | 216±7 | 12.9±0.6 | 13.0±0.6 |
S21 | Muthiyani | 28.5711 | 77.6203 | 21±1 | 88±5 | 90±5 | 178±7 | 10.6±0.6 | 10.7±0.6 |
S22 | Rasoolpur Dasana | 28.6036 | 77.5877 | 20±1 | 53±4 | 54±4 | 107±5 | 6.4±0.4 | 6.5±0.4 |
S23 | Chauna | 28.6328 | 77.5934 | 37±2 | 49±4 | 50±4 | 99±5 | 5.9±0.4 | 6.0±0.4 |
S24 | Tatarpur | 28.6267 | 77.6089 | 32±2 | 92±5 | 93±5 | 186±7 | 11.1±0.6 | 11.2±0.6 |
S25 | Bisahada | 28.5905 | 77.5705 | 25±2 | 81±4 | 82±4 | 163±6 | 9.7±0.5 | 9.8±0.5 |
Minimum | 17±1 | 42±3 | 43±3 | 85±5 | 5.0±0.4 | 5.1±0.4 | |||
Maximum | 68±3 | 172±7 | 174±7 | 346±10 | 20.6±0.8 | 20.9±0.8 | |||
Average±SD | 33±13 | 83±32 | 84±33 | 167±65 | 9.9±3.9 | 10.1±3.9 |
SD, standard deviation.
Radon concentration in water samples
The experimentally observed radon concentration in the water samples varies from 17±1 to 68±3 Bql−1. The arithmetic mean with one standard deviation is found to be 33±13 Bql−1.
Seventeen locations out of 25 have radon concentrations lower than the upper limit (40 Bql−1) recommended by the UNSCEAR (2008) in water for human consumption. Furthermore, all the samples have radon concentration much below the recommended action level of 100 Bql−1 proposed by the EU and the WHO (EU 2001; WHO 2008) and is also lower than the alternative maximum contamination level (AMCL) of 148 Bql−1 suggested by the Environmental Protection Agency (EPA) in the United States (EPA 1999).
Annual effective inhalation, ingestion, total effective dose, and dose to the body organs
The annual effective inhalation dose for the adult population around the NTPC varies from 42±3 to 172±7 μSv with an average value of 83±32 μSv. The effective ingestion dose ranges from 43±3 to 174±7 μSv with an average value of 84±33 μSv (Table 1). The contribution of inhalation dose due to waterborne radon and ingestion dose due to intake of water containing radon is almost equal in each study location around the plant.
The total annual effective dose, a sum of the inhalation and ingestion dose, varies from 85±5 to 346±10 μSv with an average value of 167±65 μSv (Table 1). In six locations of 25, the total annual effective dose received by the adult population is below the safe value (100 μSv) recommended by the WHO (WHO 2008, 2017), whereas in the rest of the locations it is higher than the safe value.
Table 1 also presents the effective dose per annum to the lungs due to inhaled air having radon released from water and the stomach due to ingestion of radon-containing water. The effective dose per annum to the lungs ranges from 5.0±0.4 to 20.6±0.8 μSv with an average value of 9.9±3.9 μSv. The effective dose per annum to the abdomen due to ingestion ranges from 5.1±0.4 to 20.9±0.8 μSv with a mean value of 10.1±3.9 μSv.
CONCLUSIONS
The radon concentration is minimum (17±1 Bql−1) in the Rajatpur village and maximum (68±3 Bql−1) in the Hasanpur Lodha village. The observed maximum value of radon concentration dissolved in water is about 31.5% lower than the recommended safe value of 100 Bql−1 by the EU (2001) and WHO (2008). Furthermore, the measured values in all the locations are well below the alternative maximum contamination level (148 Bql−1) suggested by the EPA (1999). Our measured values are also in the range (0.07–861.5 Bql−1) reported by various researchers in different parts of India. Therefore, it appears that the measured radon level in water is mainly from the geological attributes of the study region.
The mean value of the total annual effective dose due to inhalation of waterborne radon and ingestion of water is 167 μSv (0.17 mSv). This value is about 66.8% higher than the recommended RDL of 0.1 mSv from the possible total radioactive contamination of the annual drinking water consumption (WHO 2008). However, this value is only 17% of the intervention exemption level (1 mSv) recommended by the ICRP (1991). In view of this, it can be concluded that water collected from hand pumps for drinking purposes around the NTPC is safe as far as the radiological dose is concerned.
ACKNOWLEDGEMENTS
The authors acknowledge the financial support extended by the Board of Research in Nuclear Science (BRNS) for this project. We are also thankful to the villagers for their support and cooperation during sample collection process.
FUNDING
This work was supported by the Board of Research in Nuclear Science (BRNS), Department of Atomic Energy, Government of India [Project Ref. No.: 2013/36/59-BRNS/2468].
AUTHORS' CONTRIBUTION
P.K. carried out field measurements. A.A. has prepared tables and figures. M.K. drafted the article and supervised the research and measurements. B.K.S. reviewed and edited the manuscript.
DECLARATION OF COMPETING INTEREST
The authors declare that they have no known competition for financial interests or personal relationships that could have appeared to influence the work reported in this paper.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.