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ORIGINAL ARTICLE
Year : 2018  |  Volume : 41  |  Issue : 3  |  Page : 132-135  

Measurement of radon concentration in drinking water and estimation of radiation dose to the publics of Hassan city, Karnataka, India


1 Department of Physics, I.D.S.G Government College, Chikkamagaluru, Karnataka, India
2 Department of PG Studies and Research in Physics, Kuvempu University, Shimoga; Deparment of Science and Humanities, PES University, Bangalore, Karnataka, India
3 Department of PG Studies and Research in Physics, Kuvempu University, Shimoga, Karnataka, India
4 Research and Development Centre, Bharathiar University, Coimbatore, Tamil Nadu, India

Date of Submission20-Jun-2018
Date of Decision23-Aug-2018
Date of Acceptance24-Sep-2018
Date of Web Publication19-Nov-2018

Correspondence Address:
Dr. E Srinivasa
Department of Physics, I.D.S.G Government College, Chikkamagaluru, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/rpe.RPE_46_18

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  Abstract 


In the present paper, the radon concentration in drinking water samples of the Hassan city, Karnataka state, India, was analyzed using the radon emanometry technique. The measured radon concentrations ranged from 19.5 ± 1.5 to 121.8 ± 5.6 Bq/L with an average value of 61.4 ± 3.3 Bq/L. This study reveals that all the drinking water samples have radon concentration levels higher than the maximum contaminant level of 11 Bq/L as suggested by the Environmental Protection Agency, and 75% of the recorded radon concentration values were found to be well below the action level of 100 Bq/L recommended by the World Health Organization. The average annual effective dose to the population of the studied area was found to be slightly greater than the safe limit of 100 μSv/y recommended by the World Health Organization.

Keywords: Annual effective dose, drinking water, emanometry, ingestion dose, radon


How to cite this article:
Srinivasa E, Rangaswamy D R, Suresh S, Nagabhushana S R, Sannappa J, Umehsareddy K. Measurement of radon concentration in drinking water and estimation of radiation dose to the publics of Hassan city, Karnataka, India. Radiat Prot Environ 2018;41:132-5

How to cite this URL:
Srinivasa E, Rangaswamy D R, Suresh S, Nagabhushana S R, Sannappa J, Umehsareddy K. Measurement of radon concentration in drinking water and estimation of radiation dose to the publics of Hassan city, Karnataka, India. Radiat Prot Environ [serial online] 2018 [cited 2018 Dec 10];41:132-5. Available from: http://www.rpe.org.in/text.asp?2018/41/3/132/245799




  Introduction Top


Radon (222Rn) can be a significant source of radioactivity in indoor air. 222Rn, a noble radioactive gas produced by the decay of 226Ra, is a member of the 238U series which is present in almost all types of rocks, soil, and groundwater. Groundwater is usually found to be more radioactive than surface water because of dissolution of many minerals and radioactive substances while passing through rock and soil formations.[1],[2] When the groundwater reaches the surface by natural or human-made forces, some of the radon will be released into the air. The radon present in groundwater is considered to be the second largest source of environmental radon and is estimated to contribute to the global atmosphere.[2] High concentration of radon and its short-lived daughters in the indoor atmosphere and drinking water constitutes a major health hazard for humankind since it is considered as human carcinogen. The exposure of people to high concentrations of radon and its daughters for a long time leads to pathological effects.[3] The concentration of radon at any place depends on emanation capacity of the ground, the porosity of soil or rock, the barometric pressure gradient between the interfaces, soil moisture content, and extent of water saturation grade of the medium.[4] The aim of the present work is to measure the radon concentration in the available drinking water sources and estimating the radiation doses to the population resulting from its consumption.


  Materials and Methods Top


Determination of 222Rn by Bubbler method

The borewell, open well, hand pump, and public tap water samples were collected from 20 different selected locations in Hassan city during 2015–2017. From each location, three samples were taken for measuring radon concentration reproducibility. About 500 ml of water samples were collected in airtight plastic bottle with minimum disturbance. The plastic bottles were filled completely and carefully so that zero headspace was present. All the collected samples were analyzed within 24 h. The concentration of 222Rn in drinking water was estimated using the emanometry technique [Figure 1].[5]
Figure 1: Radon bubbler

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After collecting the water samples using the above standard procedure, the samples were brought to the laboratory, about 60 ml of the water samples were transferred into the bubbler using the vacuum transfer technique. The dissolved radon in the water was transferred into preevacuated and background-counted scintillation cell. The scintillation cell was stored for 3 h to allow radon to attain equilibrium with its daughters. Then, it was coupled to a photomultiplier tube and alpha counting assembly and counted for 17 min. The radon concentration in groundwater samples was calculated using the relationship (1).



Where D = total counts above background, V = volume of water (L), E = efficiency of the scintillation cell (74%), λ = decay constant for radon (2.098 × 10−6 s−1), Sc = counting delay after sampling (s), and St = counting duration (s).

The annual effective doses for inhalation and ingestion of radon in water were calculated using the parameter established in the UNSCEAR 2000[6] report as



Where DIn is the effective dose for inhalation, ARnW is the radon concentration in water (Bq/L or kBq/m3), CaW is the radon in air to the radon in water ratio (10−4), F is the equilibrium factor between radon and its progenies (0.4), I is the average indoor occupancy time per individual (7000 ha–1), and DCF is the dose conversion factor for radon exposure (9 nSv [Bq h m−3]−1). The ingestion dose is calculated using the following formula,



Where DIg is the effective dose for ingestion, ARnW is the radon concentration in water (Bq/L or kBq/m3), Cw is the weighted estimate of water consumption (60 la–1), and EDC is the effective dose coefficient for ingestion (3.5 nSvBq−1), respectively.


  Results and Discussion Top


[Table 1] gives the mean values of radon concentration of all the studied drinking water samples which vary from 19.5 ± 1.5 to 121.8 ± 5.6 Bq/L with an average value of 61.4 ± 3.3 Bq/L. [Figure 2] shows the graphical representation of the variation of radon concentration with different locations. In all the studied samples, the higher radon concentration in drinking water was observed in borewells, and hand pumps water. This is possibly because of its greater depth, which allows water to interact with a greater thickness of aquifer and thus more radon is expected in hand pumps and borewells. The US Environment Protection Agency has proposed that the allowed maximum contamination level (MCL) for radon concentration in water is 11 Bq/L.[6] This study reveals that all the drinking water samples have radon levels higher than the maximum contaminant level of 11 Bq/L recommended by the Environmental Protection Agency (EPA).[7] The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has suggested a value of radon concentration in water for human consumption between 4 and 40 Bq/L.[6] From this, it is evident that 70% water samples from borewells and hand pumps water have radon concentrations higher than 40 Bq/L. The recorded radon concentration values were compared with the European Commission recommendations[8] on the protection of the public against the exposure to radon in drinking water supplies, and the WHO recommended limit of radon in drinking water, which recommends the action level of 100 Bq/L for public water supplies. Except three samples, all the recorded values are found to be well below the action level and hence safe for drinking purposes.[9] The higher concentration of radon in borewell water was observed at Pension mohalla, Krishnarajapura, and Master control facility borewell water samples. This is because these regions are composed by the granites and metamorphic rocks. The lower radon activity concentration in drinking water was observed at Vijayanagara borewell water sample. This is due to the groundwater occurs in this area under phreatic condition in weathered zone of gneiss, and under semi-confined to confined conditions in joints and fractures of the formation at deeper level and these regions are attributed by schist, these rocks contain lower activity of radionuclides.[2] The estimated inhalation dose varied from 49.1 to 306.9 μSv/y with an average of 154.7 μSv/y. Ingestion dose received varied from 4.1 to 25.6 μSv/y with an average of 12.9 μSv/y. UNSCEAR has prescribed the level of mean radon in drinking water for inhalation as 25 μSv/y and for ingestion as 2 μSv/y. The mean radon inhalation dose and ingestion dose estimated from water are higher than those prescribed by UNSCEAR.[6] The result shows that the health hazard from water is mainly through inhalation of radon [Figure 3].[10] The total annual effective dose due to radon inhalation and ingestion ranges from 53.1 to 332.5 μSv/y with an average value of 167.5 μSv/y. The overall average dose value is slightly above the reference level of 100 μSv/y. This exposure levels to radon from the drinking water are not expected to pose any health problem.
Table 1: Average radon concentrations and estimated annual effective dose from drinking water samples

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Figure 2: The variation of radon concentration with different locations

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Figure 3: Variation of inhalation dose, ingestion dose, and total dose with locations

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  Conclusions Top


From this study, it is evident that the radon concentration in all samples actually used by the inhabitants of the study area is greater than the EPA suggested maximum contamination level of 11 Bq/L. The estimated average total annual effective dose of the studied area is found to be slightly above the safe limit of 100 μSv/y recommended by the WHO and EU Council. The study showed that only 15% water is unfit for drinking and 85% is safe for household use and drinking according to the WHO standard.[9] The results show no significant radiological risk for the inhabitants of the studied area.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
National Council on Radiation Protection and Measurements. Evaluation of Occupational and Environmental Exposures to Radon and Radon Daughters in the United States. NCRP Report No. 078. NCRP Publication 1984.  Back to cited text no. 1
    
2.
Rangaswamy DR, Srinivasa E, Srilatha MC, Sannappa J. Measurement of radon concentration in drinking water of Shimoga district, Karnataka, India. J Radioanal Nucl Chem 2016;307:907-16.  Back to cited text no. 2
    
3.
Umesha RK, Ningappa C, Sannappa J, Rangaswamy DR, Srinivasa E. Concentration of radon and physicochemical parameters in ground water around Kolar Gold Fields, Karnataka state, India. J Radioanal Nucl Chem 2017;314:907-15.  Back to cited text no. 3
    
4.
Niranjan RS, Ningappa C, Ashaswini TY, Chamaraja N, Rangaswamy DR, Sannappa J. Studies on radon concentration in drinking water around Hemavathi river basin, Karnataka state, India. J Radioanal Nucl Chem 2017;314:321-31.  Back to cited text no. 4
    
5.
Raghavayya M., Iyengar MA, Markose PM. Estimation of radium-226 by emanometry. Bull Radiat Prot 1980;3:11-4.  Back to cited text no. 5
    
6.
United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). The General Assembly with Scientific Annexure. United Nation; 2000.  Back to cited text no. 6
    
7.
United States Environmental Protection Agency (USEPA). National primary drinking water regulations for radionuclides. US, Governmental Printing Office, Washington EPA/570/9-91/700, 1991.  Back to cited text no. 7
    
8.
European Commission Commission recommendation of 20th December 2001 on the protection of the public against exposure to radon in drinking water. 2001/982/Euratom, L344/85. Official Journal of the European Commission, Geneva; 2001. p. 197-209.  Back to cited text no. 8
    
9.
World Health Organization. International Standards of Drinking Water. 3rd ed. Geneva: WHO; 1971.  Back to cited text no. 9
    
10.
United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). Sources and Effects of Ionising Radiation. New York: UNSCEAR, United Nations; 2008.  Back to cited text no. 10
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1]



 

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