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Research ArticleInhalation Dose and Source Term Studies ina Tribal Area of Wayanad Kerala India

Reshma Bhaskaran12 Ravikumar C Damodaran2

Visnuprasad Ashok Kumar3 Jojo Panakal John3

Danalakshmi Bangaru4 Chitra Natarajan4 Bala Sundar Sathiamurthy4

Jose Mundiyanikal Thomas4 and Rosaline Mishra5

1Government Medical College Kozhikode Kerala India2Department of Physics University of Calicut Malappuram Kerala India3Department of Physics Fatima Matha National College Kollam India4Radiological Safety Division Indira Gandhi Center for Atomic Research Kalpakkam India5Environmental Assessment Division Bhabha Atomic Research Center Mumbai India

Correspondence should be addressed to Reshma Bhaskaran bhaskaran_reshmayahoocoin

Received 20 December 2016 Revised 26 March 2017 Accepted 30 April 2017 Published 22 May 2017

Academic Editor Jong-Tae Lee

Copyright copy 2017 Reshma Bhaskaran et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Among radiation exposure pathways to human beings inhalation dose is themost prominent one Radon thoron and their progenycontribute more than 50 per cent to the annual effective dose due to natural radioactivity South west coast of India is classifiedas a High Natural Background Radioactivity Area and large scale data on natural radioactivity and dosimetry are available fromthese coastal regions including the Neendakara-Chavara belt in the south of Kerala However similar studies and reports fromthe northern part of Kerala are scarce The present study involves the data collection and analysis of radon thoron and progenyconcentration in the Wayanad district of Kerala The radon concentration was found to be within a range of 12ndash378 Bqm3 Thethoron concentration varied from 15 to 621 Bqm3 Progeny concentration of radon and thoron and the diurnal variation of radonwere also studied In order to assess source term wall and floor exhalation studies have been done for the houses showing elevatedconcentration of radon and thoronThe average values of radon thoron and their progeny are found to be above the Indian averageas well as the average values reported from the High Natural Background Radioactivity Areas of Kerala Exhalation studies of thesoil samples collected from the vicinity of the houses show that radonmass exhalation rate varied frombelow detectable limit (BDL)to a maximum of 80mBqkgh The thoron surface exhalation rate ranged from BDL to 17470 Bqm2h

1 Introduction

Among all the natural sources of radiation dose to mankindinhalation of radon (222Rn) thoron (220Rn) and theirprogeny contribute about 50 of global effective dose [1]Epidemiological studies enhance our understanding of thehealth risk to ionising radiation Initially the epidemiologicalstudies from the miners were used to assess the health riskfrom exposure to radon However in the recent past severalcase control studies of residential exposure to radon have alsobeen reported These studies also show an increasing risk of

lung cancerwith increasing exposure to radon [2]Thoron onthe other hand has not been studied in detail with referenceto lung cancer risk [3] Only recently the contribution ofthoron to the radiation dose has been recognised [4ndash7]The south west coast of India is very well studied in termsof both terrestrial radioactivity and the radon and thoronconcentrations [8 9] However studies in the northern part ofKerala especially the Malabar region are scarce No study ofterrestrial radioactivity or indoor radon thoron and progenyconcentration is so far reported from theWayanad district ofKeralaWayanad is one of the coldest high range tourist places

HindawiJournal of Environmental and Public HealthVolume 2017 Article ID 1930787 10 pageshttpsdoiorg10115520171930787

2 Journal of Environmental and Public Health

situated in the Western Ghats of southern India Severalstudies have proved the increase in the concentration ofindoor radon with decreasing temperature [10ndash12] Thesestudies have reported indoor radon thoron levels which arehigher than those seen in the High Natural BackgroundRadioactivity Areas (HNBRA) of Kerala Hence the presentinvestigations in Wayanad district are imperative to analysethe effect of temperature and ventilation on these gases withrespect to the warmer regions of Neendakara and Chavarawhich are one among the six HNBRAs of the world

The locationwe have chosen for the present investigationsis Bathery region of Wayanad This region has large numberof granite quarries and granite is already known to possesshigher radioactivity when compared to other types of rocks[13ndash15] It may be of interest to know the effect of granites interms of radiation dose when used as construction materialfor building Wayanad is the native place for a large popula-tion of tribal community of Kerala who belong to low incomegroup These people live in houses made of constructionmaterials likemud available locallyThe study aims to analysethe effect of the locally available construction materialscomprising granites and mud on the inhalation dose due toradon and thoron to the residents of Bathery Taluk

2 Materials and Methods

21 Geology Wayanad district is situated on the southern tipof the Deccan plateau and forms a part of theWestern GhatsThe geographical coordinates for the district are 11∘3610158401810158401015840Nand 76∘0410158405910158401015840E The population is 816558 as per the 2011census and the area is 2132 km2 The altitude ranges from 700to 2100 meters above sea level The mean annual temperatureis 238∘C During DecemberndashJanuary temperature lowers to15∘ C Bathery is located at 1167∘N 7628∘E It has an averageelevation of 907m Ambalavayal is part of Bathery and is oneof themain regions having a large number of granite quarriesThe Ambalavayal granite is of four types namely foliatedgranite pink granite grey granite and aplitic granite [16]These are composed of quartz pink feldspar hornblende andbiotite

22 Materials Indoor radon and thoronmeasurements weredivided into two phases of one year each In the first phase(2014-2015) pinhole dosimeters were used for the measure-ment of indoor radon and thoron concentrations This studyincluded all the villages in Bathery From this study spatialvariation of radon and thoron in Bathery was assessed Alongwith the indoor radon and thoron concentration studiessoil samples were collected from the top surface (of 15 cmthickness) from the vicinity of the houses These sampleswere analysed using gamma ray spectrometry for assessingterrestrial radioactivity Radon and thoron exhalation studieswere also done on the samples to obtain the mass exhalationrate for radon and the surface exhalation rate for thoronIn the second phase 19 houses in the Ambalavayal regionwere studied during 2015-2016 Out of these 10 houseswere intensively studied using both active and passive mea-surement techniques The second-phase study involved themeasurement of both radon and thoron concentrations as

well as their progeny The diurnal variation of radon andwall and floor exhalation was also studied by using activemeasurement techniques

221 Passive Measurement LR115 films based pinholedosimeters [17] were used for the passive measurement ofradon and thoron concentrationThis device has a single facefor gas entry and gives the time integrated measurement ofradon and thoron Pinhole dosimeters equipped with LR-115Type II Solid State Nuclear Track Detectors (SSNTD) with2 times 2 cm2 area were hung in a room of the houses (at least30 cm away from nearby wall) for a period of three monthsThe dosimeters were hung at a height of around 2m from thefloorThe principle working and processing of the dosimeterare discussed in detail elsewhere [17 18]The dosimeters werereplaced with new ones at the end of every threemonths untila cycle of 1 year was completed The retrieved dosimeterswere processed in the laboratory and the developed trackswere scanned using a spark counter by the standardisedprotocolTheminimum detectable limit for radon in pinholedosimeter is 2 Bqm3 and that for thoron is 6 Bqm3

Progeny measurements were done using the depositionbased Direct Radon Progeny Sensors and Direct ThoronProgeny Sensors (DRPSDTPS) [19] DTPS is made of LR-115SSNTDmounted with absorbers in 50120583m aluminised MylarThis detects the alpha particle emitted from 212Po (thoronprogeny with energy 878MeV) The radon progeny sensorDRPS is made of LR115 mounted with the absorber thickness37 120583m This detects 769MeV alpha particles emitted from214Po The minimum detectable limit for radon progeny inDRPS is 1 Bqm3 and that for thoron progeny in DTPS is01 Bqm3 The principle and method of measurement ofradon and thoron progeny is discussed in detail by Prasad etal [20]

222 Active Measurements The active measurements weredone using the state-of-the-art equipment the PortableRadon Monitor (SMART RnDuo) developed by BARC(Bhaba Atomic Research Center Mumbai) The detectorworks on the principle of scintillation counter by scintillationwith ZnS(Ag)The detection limit of Portable RadonMonitor(SMART RnDuo) is in between 8 Bqm3 and 50MBqm3(Operational Manual of Portable Radon MonitormdashSMARTRnDuo March 2015) The detector has a progeny filterthat eliminates the radon and thoron progenies For theestimation of radon concentration thoron is eliminated bythe diffusion time delay based thoron discriminator whichtakes advantage of the short half-life of thoron

For thoron monitoring program based sampling is car-ried out using a flow mode sampler connected to the pumpinlet of the monitor Each measurement cycle consists of15 minutes During this the pump is kept ON for the first5 minutes This gives a measure of the thoron and thebackground A delay of 5 minutes is maintained after thisto ensure the complete decay of thoron The last 5 minutesgives a measure of the background count for the cycle Thebackground count is subtracted from the total count of theinitial 5 minutes to get the thoron concentration

Journal of Environmental and Public Health 3

223 Gamma Ray Spectrometry and Exhalation Studies Soilsamples were collected from the top 15 cm of the surfacesoil These samples were then dried sieved and sealed in ahermetically tight container and kept for 30 days to attainsecular equilibrium between the radon and its parent nuclideNaI (Tl) scintillation detector available at the Radiologi-cal Safety Division of Indira Gandhi Center for AtomicResearch (IGCAR) was used for gamma ray spectrometryof the sources The method for estimation of the terrestrialradioactivity using NaI (Tl) detectors is discussed in detail inmany papers [21ndash23]

The radon and thoron exhalation studies were done byusing the enclosed sample method as explained by Petropou-los et al [24] RAD 7 detector [25 26] manufactured byDurridge Inc USA was used for the soil exhalation studiesIt detects the radon and thoron concentrations between4 and 400000 Bqm3 The methodology suggested by themanufacturer was followed The mass exhalation rate ofradon was calculated using the formula [22 27ndash29]

119869119872 = 1198620 sdot 119890minus120582sdot119905 +119862 sdot 119881

119872 sdot 119905sdot120582 sdot 119905

1 minus 119890minus120582sdot119905 (1)

where 1198620 is the initial radon concentration (Bqm3) 119862 isthe accumulated radon concentration and 119869119872 is the massexhalation rate (mBqkgh) Accumulated time is denoted by119905 (h)119881 is the effective volume inm3 (volume of the container+ volume of the detector minus volume of the sample)119872 is massof the sample in kg and 120582 denotes the effective decay constantof radon which is the sum of the leak rate (if existing) and theradioactive decay constant of radon (hminus1)

The thoron measurement is also done by keeping thesample in a closed chamber The thoron surface exhalationrate is calculated using the formula [29]

119869119904 =119862119879 sdot 119881 sdot 120582

119860 (2)

Here 119862119879 is the equilibrium thoron concentration which isattained in a short time period119881 is the residual air volume ofthe setup in m3 120582 is the thoron decay constant (00126 sminus1)and 119860 is the surface area (m2) of the sample

The soil gas radon activity measurements were done tostudy the contribution of the radon gas in the subsoil tothe indoor radon concentration The soil gas measurementwas done at a depth of 08m as it is already known fromthe literature that the activity concentration of radon in thesoil increases with increasing depth up to around 1m fromthe surface and then it reaches saturation [30 31] The soilgas radon activity measurements were done in ten houses(selected based on indoor radon and thoron concentra-tion availability of power point and safety of the equip-ment) where the active measurements were conducted usingPortable Radon Monitor SMART RnDuo A steel probe wasinserted into the soil for measurement The measurementcycle was set at 15minutes Soil gas was sampled for 2minutesusing a pump before starting themeasurementThemeasure-ment is continued for 1 hour to have a stabilised reading ofradon concentration

Table 1 Average concentration of radon and thoron in WayanadKerala India Result of phase 1 study

Radon [Bqm3] Thoron [Bqm3]Minimum 13 21Maximum 108 621Average 31 96Standard deviation 20 115Geometric mean 27 72Geometric standard deviation 2 2

The health effect due to radon and thoron exposure wasquantified in terms of the annual effective dose 119864 Annualeffective dose 119864 was calculated as [32]

119864 = 119862 times 119876 times 119865 times 119905 (3)

where 119862 (in Bqmminus3) is the concentration of isotope ofinterest 119876 (nSv per Bq hmminus3) the dose conversion factor(9 nSv per Bqhmminus3 for radon and 40 nSv per Bqhmminus3 forthoron) and 119865 the equilibrium factor (EF) for radon andthoron (119865119877 and 119865119879 resp) 119905 is the total time of exposurecalculated by using an indoor occupancy factor of 08 (119905 =7000 hry) 119865 is calculated as follows [20]

119865 =EEC119862 (4)

Here EEC is the equilibrium equivalent concentration ofradon and thoron (EERCandEETC resp) calculated as givenby Prasad et al [20]119862 is the concentration of radon or thoronas the case may be

3 Results

In the first phase 25 houses were studied in Bathery Theaverage of radon and thoron concentration for a year is asgiven in Table 1 The average ratio of thoron to radon is 33 Itis seen that the thoron concentration in one house is highlyelevated (annual average thoron concentration = 621 Bqm3)as compared to all the other houses As this house is veryclose to the granite quarries intensive study was planned inthe houses in the vicinity of this house and those near othergranite quarries The frequency distribution of both radonand thoron has a positive skewness as shown in Figures 1 and2 The Q-Q plot of the logarithm of radon concentration forthe 25 samples is shown in Figure 3 The same is repeatedfor thoron excluding the outlier and given in Figure 4 Thelinearity of the plots (Figures 3 and 4) confirms the lognormaldistribution of radon and thoron concentrations A similarobservation of lognormal distribution of radon and thoronconcentration was made in the HNBRA of Kerala and someother studies [8 33]

31 Radon Thoron and Progeny Measurements To find theconcentration of radon and thoron progeny in the secondphase measurements were carried out in the vicinity of thehouse showing high concentration of thoron as well as a fewhouses in the vicinity of other granite quarriesThe average of


00

25

50

75

100

125

Freq

uenc

y

2000 4000 6000 8000 10000 12000000Radon concentration

Figure 1 Distribution of radon concentration in phase 1 study

Thoron concentration

00

25

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100

125

Freq

uenc

y

50 450

400

650

550

600

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700

350

250

200

150

300

1000

Figure 2 Distribution of thoron concentration in phase 1 study

the radon thoron and progenymeasurements for the secondphase is as given in Table 2 The average equilibrium factordetermined for the region is 07 for radon and 004 for thoronThe EF is higher for radon as compared to the UNSCEARvalue of 04 The equilibrium factor for thoron is also greaterthan the value (002) given in UNSCEAR [34] Similar resultof higher EF for radon and thoron as compared to the worldaverage or the HNBRA of south west coast of India is foundin the Beijing area of China In the Chinese study it is seenthat the EF increases during the period of Haze-fog [35]

The inhalation dose for the residents of the region usingthe average equilibrium factor for radon and thoron is asgiven in Figure 5 From the study of the radon and thoronconcentration it is seen that out of the 44 houses studied onlyone house [23] showed radon concentration greater than

Expe

cted

nor

mal

4

3

2

1

0

12 14 16 18 20 2210Observed value

minus1

minus2

Figure 3 Q-Q plot for radon concentration

150 175 200 225125Observed value

minus3

minus2

minus1

0

1

2

3

Expe

cted

nor

mal

Figure 4 Q-Q plot for thoron concentration

the action limit prescribed by International Commission onRadiological Protection ICRP (300 Bqm3)

32 Active Measurements As the passive measurementsusing the pinhole dosimeters may be influenced by factorslike the bulk etching rate leakage from the cup and soforth [36] active measurements were done to ascertain andvalidate the concentration obtained using pinhole dosime-ters Ten houses including the houses showing higher radonand thoron concentrations were intensively studied Theactive measurements were done for a period of five daysin every house to study the diurnal variation Plot of thediurnal variation is as given in Figure 6 It is seen that theconcentration of radon reduces during the day time whenthe houses are more ventilated as compared to the nightThere is no particular pattern and the concentration keepsfluctuating during day time The maximum concentration ofradon is found aftermidnight and in the earlymorning hoursIn the house showing the highest concentration of radon thevalue increased to as high as 1533 Bqm3 at night (Figure 7)However the concentration dropped to levels shown during


Table 2 Average concentration of radon thoron and progeny in Wayanad Kerala India Result of phase 2 study

Maximum Minimum Average plusmn SD GM (GSD)Radon concentration [Bqm3] 379 20 68 plusmn 74 54 (2)Thoron concentration [Bqm3] 576 16 123plusmn 115 95 (2)EERC [Bqm3] 160 10 43 plusmn 30 37 (2)EETC [Bqm3] 8 1 3 plusmn 2 3 (2)119865Rn 089 043 069 plusmn 014 068 (124)119865Tn 014 001 004 plusmn 003 003 (183)

5 10 15 20 25 30 35 40

Sampling location number

0

2

4

6

8

10

12

14

16

18

Ann

ual e

ffect

ive d

ose (

mSv

)

Figure 5 Inhalation dose to the residents of Bathery WayanadKerala

700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

AM

700

PM

TimeRadonConc

0

10

20

30

40

50

60

70

80

Rado

n co

ncen

trat

ion

(BqＧ

3)

Figure 6 Diurnal variation of radon in one house for 5 days

the day time when the room had increased ventilation bykeeping the door of the room open overnight

Figure 7 shows the significant variation which ventilationcan make to the concentration of radon The maximumconcentration of radon decreased by a factor of 5 when the

Increasedventilation

0

200

400

600

800

1000

1200

1400

1600

Rado

n co

ncen

trat

ion

(BqＧ

3)

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PM

400

AM

400

PM

400

AM

400

PM

400

AM

400

PM

400

PM

400

AM

Time

Figure 7 Diurnal variation of radon in the house showing maxi-mum radon concentration

door was kept open along with the window opposite to it inthe corridor which opens to the outside environment

33 Exhalation Measurements As part of phase 1 studysoil samples were collected from the vicinity of the housesAs mentioned earlier since majority of the houses in thisarea are made up of mud blocks procured from the site ofconstruction itself the aim of collecting the soil samples wasto study the correlation if any between indoor radon thoronconcentration and the radon thoron exhalation rate from thesoil samples From the gamma ray spectrometry of 25 soilsamples it is observed that the 238Uconcentration varies frombelow detectable limit (BDL) to 68 Bqkg with an average of18 plusmn 15Bqkg The 232Th concentration ranges from BDL to112 Bqkg with an average of 40 plusmn 29Bqkg

Exhalation studies using RAD 7 were done on the 25samples Out of the 25 samples 14 had radonmass exhalationrate as BDL 12 samples also showed BDL values for thoronsurface exhalation rateThe radonmass exhalation rate variedfromBDL to amaximumof 80mBqkghThe thoron surfaceexhalation rate ranged from BDL to 17470 Bqm2h No cor-relation was found between the indoor radon concentrationand radon mass exhalation rate from soil Similarly nocorrelation was found between indoor thoron concentrationand the thoron surface exhalation rate No correlation was


0 20 40 60 80 100 120

Soil 232４Ｂ concentration (Bqkg)

R = 090

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Thor

on ex

halat

ion

rate

from

soil

(BqＧ

2s

)

Figure 8 232Thversus thoron exhalation rate in soil

found between radon exhalation rate from soil and 238Uconcentration in the soil However as seen in Figure 8 there isa good correlation between thoron exhalation rate and 232Thconcentration in soil

To analyse the source term for the relatively higherconcentration of radon and thoron exhalation studies weredone for the walls and floor in the houses showing thehighest concentration of radon and thoron The result of theexhalation studies for radon shows that the exhalation rateis more from the floor (439 plusmn 019Bqm2hr) as comparedto the walls (134 plusmn 012Bqm2hr) The house showing highconcentration of thoron was also studied by wall and floorexhalation It is found that the walls are the major sourceof thoron as compared to the floor (mean wall and floorcontribution being 581plusmn020 and 253plusmn018Bqm2s resp)

Soil gas radon activity measurements were done toanalyse the contribution of the soil gas under the houses tothe indoor radon concentration A maximum of 28 kBqm3radon concentration in the soil gas was found in the vicinityof the house showingmaximum indoor radon concentrationOnly marginal variation (22 kBqm3 to 28 kBqm3) wasfound in the radon concentration in the soil gas at the varioussitesThis value falls in the category of soil with normal radonpotential as per the Swedish criteria [37]

A study of the indoor concentration of radon andthoron with respect to the construction material shows thatthe mud houses have the highest concentration of radon(Figure 9) Both the houses which showed highest indoorradon and thoron concentration are mud houses with verypoor ventilation Ventilation estimation was done by takinginto consideration the number of doors and windows in theroom where the dosimeters were kept Rooms with only onedoor and no window were called poorly ventilated Mostof such houses had the door of the room facing anotherroom or corridor Thus the exchange of air from the outsideenvironment was comparatively less Rooms with one doorand one window which were kept open for a major part of aday were considered to bemoderately ventilated Roomswithmore than one door and more than one window which were

Con

cent

ratio

n (B

qＧ

3)

Mud block Brick Laterite Cement blockConstruction material

RadonThoron

0

10

20

30

40

50

60

70

80

90

100

110

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130

140

Figure 9 Variation of indoor radon and thoron concentration withconstruction material

kept open for a large fraction of a day were assumed to be wellventilated

4 Discussion

41 Radon Thoron and Progeny Measurements The initialstudy of the indoor radon and thoron concentration showsthat the thoron concentration in the region is higher com-pared to the radon concentration This may be due to thefact that majority of houses in this region are made up ofbuilding materials which are locally available The region isone of the major suppliers of the granite and mechanisedsand made out of crushed granite to Malabar as well asthe neighbouring districts of Tamil Nadu and Karnatakastates It is well known that the concentration of 232Th ishigher in granite due to the presence of monazite [14]Hence the higher concentration of thoron may be attributedto the presence of higher concentration of thorium in thebuilding materials The study of indoor radon and thoronconcentration in the Neendakara-Chavara region whichis one of the HNBRAs of the world shows a median of23 Bqm3 for radon and 24 Bqm3 for thoron [38] Eventhough Neendakara-Chavara region has very high terrestrialradioactivity due to the presence ofmonazite sand the indoorradon thoron levels are less as compared to the present studyThis result is in agreement with the discussion by Mishraand Sapra in the BARC newsletter [9] Here they argue thateven though the HNBRA of Kerala experiences 10 timesmore external gamma effective doses the inhalation dosesdue to indoor radon and thoron concentrations are similarto the Normal Background Radiation Areas (NBRA) Thereasons provided by them are the excessive ventilation andthe type of flooring which shields the radon from reachingthe indoor environment in the HNBRA Our study provesthat along with this the construction material of the housesin the HNBRA may also be contributing to the reduction inthe radon thoron concentrations as compared to the present


study Unlike Wayanad the construction material for thecoastal region of Neendakara-Chavara mainly consisting ofsand may be coming from outside the region which maynot be part of HNBRA Hence the radioactivity content inthese construction materials may not be as high as the sandin the HNBRA Even in the present study the average value ofradon and thoron concentration increases when the region ofinterest is concentrated near the granite quarriesTheworkersin the quarries mainly reside in this area Houses are of oldstyle made of mud blocks and with very less ventilation Thetemperature in the southern part of Kerala is higher (averageof 30∘C to 35∘C) as compared to the Wayanad district whichis one of the coldest tourist places in South India Due tothe colder climate people here opt for lesser ventilation ascompared to the houses in the warmer regions of KeralaHence lack of ventilation may also be one of the reasonsfor the increase in indoor radon thoron concentration ascompared to the HNBRA of Kerala Similar results areavailable from the Tehri-Garhwal regions of India which alsoare high altitude regions and hence colder places The radonconcentration in these places is reported to be an averageof 100 Bqm3 in winter and that of thoron is 1264 Bqm3[18] As seen in Table 2 the average EF for radon is more ascompared to the value given in UNSCEAR [23] The EERCvalues are effected by both natural andmechanical ventilation[39] The houses in the present study were selected based ontheir type of construction Majority of the houses had poorventilation for energy efficiencyThe life style in the area doesnot involve artificial ventilation or air conditioners Besidesas the study was done near the areas of the granite quarriesthe dust loading may also contribute to the accumulation ofprogeny in the houses This may be the reason for the higherEERC and hence higher EF of radon The thoron EF is alsomore as compared to the valuementioned inUNSCEAR [34]The concentration of thoron may be less at the centre of therooms as compared to the walls due to its very short half-life[40] As the pinhole dosimeters were hung in the center of theroom the concentration of thoron would have been less andnonuniform over the period of three months

The study shows that only one house has radon concen-tration greater than the limit prescribed by ICRP [41] Asno such limit is prescribed for thoron so far the concept ofequivalent radon concentration for thoron is used to estimatethe hazard due to thoron as suggested by Chen and Moir[42] The equivalent radon concentration 119877Tn is the radonconcentration that delivers the same annual effective dose asresulted from the thoron concentration 119862Tn

119877Tn =119862Tn times 119865Tn times 7000 times 40

119865Rn times 7000 times 9 (5)

The total indoor exposure to radon and thoron may beregarded as the sum of the radon concentration and theequivalent radon concentration for thoron This total expo-sure can then be compared to the radon guideline value Theequivalent radon concentration as given by Jing Chen andDeborah Moir was calculated for all the samples Out of the44 samples only two samples showed values for total exposureto radon and thoron greater than the limits prescribed by

5 10 15 20 25 30 35 40

Sample number

EPA guidelineICRP guideline

0

50

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200

250

300

350

400

Tota

l exp

osur

e to

Rn an

d Tn

conc

entr

atio

n(B

qＧ

3)

Figure 10 Distribution of exposure to total radon concentration(radon concentration + equivalent radon concentration for thoronconcentration)

Environmental ProtectionAgency US (150 Bqm3) Only onesample showed values greater than the limits for indoor radonconcentration prescribed by ICRP (Figure 10)

42 Active Measurements and Exhalation Studies From thegamma ray spectrometry of soil samples from vicinity ofhouses it was observed that the average thorium concen-tration is more as compared to the average uranium con-centration However no significant correlation was foundbetween the indoor radon concentration and the exhalationrate of radon from soil Similarly no significant correlationwas found between the exhalation rate of thoron and theindoor thoron concentration The reason for this may bethe variation in the ventilation condition of the housesSince the concentration of radon varies significantly with theventilation conditions even in houses with high exhalationrate of radon the concentration of indoor radon may not bevery high or may be even low if well ventilated

Besides this variation in the type of building and flooringmaterial may also affect the indoor radon concentration andhence the correlation may be lost In the case of thoron alongwith the factors mentioned for radon the short half-life mayalso contribute to the lack of correlation From Figure 8 wesee that very good correlation was found between 232Th andthoron surface exhalation rate whereas no such correlationwas found between 238U and radon mass exhalation rateSince radon is the daughter product of the 238U seriesa correlation between 238U and radon exhalation rate isexpected However no significant correlation was observedmost likely due to the small sample size

The diurnal variation shows that the concentration ofradon builds up at night when the ventilation in the housesis significantly reduced The maximum concentration wasfound in the early mornings In the house showing highestconcentration of radon the concentration increased duringthe early morning hours The concentration starts dropping


once the residents wake up and open the door to the room(which happens to be the only ventilation in the room) Asthe average radon concentration is higher than the limitsprescribed by International Commission for Radiation Pro-tection (ICRP) [41] the residents of the house were advisedto increase the ventilation in the room by affixing an exhaustfan Another room in the house was also studied using activemeasurements to check whether the concentration is thesame in all the rooms However this room showed lesserconcentration (average 161 Bqm3) The room showing thehighest concentration of radon had very large cracks in thefloor The exhalation studies of the walls and floor showedthat the major contribution to the radon concentrationcame from the floors Due to the closed room at night thetemperature inside the room will be higher as compared tothe outside environment This results in stack effect drawingthe radon inside the room The large cracks on the floorfurther assists in the flow of radon from soil gas to theindoor atmosphere due to the pressure variation between theindoor areas and the soil gas Besides this the room has onlyone door giving entry to another room and not the outsideenvironment Hence lack of air circulation from the outdoorenvironment may also be contributing to accumulation ofradon at night when the door was kept closed As the secondroom has intact floors and the door of the room faces theoutside environment the concentration of radon was not ashigh as seen in the first room This shows that in spite ofthe source (concentration of radon in the soil gas) being thesame cracks and openings in the floor and walls contributesignificantly to the increase of the radon concentration andhence the inhalation dose to the residents A similar effectwasseen in the case of thoron The exhalation study of the wallsand floors of the house showing higher thoron concentrationshowed that the contribution from the walls was more ascompared to the contribution from the floor In this casealso the cracks in the walls may be one of the reasons forthe excessive exhalation of thoron In this study nearly allthe houses had tiled roof or roof made of asbestos Hence thecontribution from roof was not taken into consideration

Comparison of the radon and thoron concentration withrespect to the construction material used showed that themaximum concentration of radon and thoron was foundin the houses made of mud blocks In most of the housesmud required for the mud blocks was taken from the site ofconstruction itself Wayanad district has a major populationof tribal community who are below poverty line and residein houses made of mud The architecture involves very lessventilation to conserve energy Hence a detailed study of theradon and thoron in the tribal villages may lead to betterunderstanding of the inhalation dose to the residents due toradon and thoron The modern houses are all well ventilatedand hence the radon thoron levels are within the permissiblelimits

5 Conclusion

The study of radon thoron and progeny concentration ofBathery region of Wayanad district shows that the averageconcentration of radon and thoron is greater than the values

observed in the HNBRA The average equilibrium factorfor radon as well as thoron is greater than the values ofworld average reported in UNSCEAR No correlation wasfound between indoor radon concentration and radon massexhalation rate of soilThe correlation between indoor thoronconcentration and thoron surface exhalation rate of soil wasalso found to be feeble The concentration of radon seemsto increase with decreasing ventilation Among the varioustypes of building materials mud houses show higher con-centration of both radon and thoron These results suggestthat the soil in the vicinity of the houses has very littlecontribution to the indoor radon thoron concentration ascompared to the type of building material and existingventilation conditions Radon and thoron concentration wasfound to be higher in houses close to granite quarries incomparison with those farther away or in urban area 25per cent of the houses showed radon concentration greaterthan the reference limit prescribed by ICRPThe study pointstowards the need for analysis of a larger sample to give a betterpicture of the radon thoron concentration in the whole ofWayanad district The Kalpetta region which is also famousfor the Kalpetta granites should also be studied in detail tounderstand the variation these granites make as comparedto the Ambalavayal granites to the indoor radon thoronconcentration when used as construction material

Conflicts of Interest

The authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

Reshma Bhaskaran acknowledges with gratitude fruitfuldiscussions with Dr A M Vinod Kumar during the project

References

[1] UNSCEAR ldquoSources and effects of ionising radiationunitednations scientific committee on effect of atomic radiationrdquoReport to the General Assembly 2000

[2] SENES Consultants Limited for Canadian Nuclear Safety Com-mission ldquoEstimation of the Range of Radiation Dose for aRadon Progeny Working Level Due to Physical Parametersrdquo2013

[3] J Wiegand and S Feige ldquoThoron ignored and underestimatedin the big shadow of radonmdashan example from ChinardquoGeofisicaInternacional vol 41 no 3 pp 261ndash264 2002

[4] B Shang B Chen Y Gao Y Wang H Cui and Z Li ldquoThoronlevels in traditional Chinese residential dwellingsrdquo Radiationand Environmental Biophysics vol 44 no 3 pp 193ndash199 2005

[5] R C Ramola G S Gusain B S Rautela et al ldquoLevels of thoronand progeny in high background radiation area of southeasterncoast of Odisha IndiardquoRadiation Protection Dosimetry vol 152no 1ndash3 pp 62ndash65 2012

[6] Saıdou S TokonamiM Janik B G Samuel Abdourahimi andN N Joseph Emmanuel ldquoRadon-thoron discriminative mea-surements in the high natural radiation areas of southwesternCameroonrdquo Journal of Environmental Radioactivity vol 150 pp242ndash246 2015


[7] S Tokonami ldquoWhy is 220RN (thoron) measurement impor-tantrdquo Radiation Protection Dosimetry vol 141 no 4 pp 335ndash339 2010

[8] M P Chougaonkar K P Eappen T V Ramachandran etal ldquoProfiles of doses to the population living in the highbackground radiation areas in Kerala Indiardquo Journal of Envi-ronmental Radioactivity vol 71 no 3 pp 275ndash297 2004

[9] R Mishra and B K Sapra ldquoApprehensions about inhalationexposures due to radon (222 Rn) and thoron (220 Rn) in highbackground radiation areas of indiardquoBARCNewsletter no July-August pp 3-4 2015

[10] M S Kandari and R C Ramola ldquoAnalysis of seasonal variationof indoor radon concentration in Tehri Garhwal NorthernIndiardquo Indian Journal of Physics vol 83 no 7 pp 1019ndash10232009

[11] M Prasad M Rawat A Dangwal G Prasad R Mishra and RC Ramola ldquoStudy of radiation exposure due to radon thoronand progeny in the indoor environment of yamuna and tonsvalleys of garhwal himalayardquo Radiation Protection Dosimetryvol 171 no 2 pp 187ndash191 2016

[12] R C Ramola V M Choubey Y Prasad G Prasad and SK Bartarya ldquoVariation in radon concentration and terrestrialgamma radiation dose rates in relation to the lithology in south-ern part of KumaonHimalaya Indiardquo RadiationMeasurementsvol 41 no 6 pp 714ndash720 2006

[13] C Ningappa K S Hamsa K U Reddy R S Niranjan D RRangaswamy and J Sannappa ldquoStudy on radon concentrationat the work places of mysuru bengaluru and kolar districts ofkarnataka state South Indiardquo Radiation Protection Dosimetryvol 171 no 2 pp 200ndash203 2016

[14] J Sannappa C Ningappa and K N P Narasimha ldquoNaturalradioactivity levels in granite regions of Karnataka Staterdquo IndianJournal of Pure and Applied Physics vol 48 pp 817ndash819 2010

[15] C Ningappa J Sannappa and N Karunakara ldquoStudy on radio-nuclides in granite quarries of Bangalore rural district Kar-nataka Indiardquo Radiation Protection Dosimetry vol 131 no 4pp 495ndash502 2008

[16] P S Anilkumar ADKVarma andMMNair ldquoDetailed stud-ies on acid intrusives of Kerala Part-Brdquo GSI Report 1993

[17] B K Sahoo B K Sapra S D Kanse J J Gaware and Y SMayya ldquoA new pin-hole discriminated 222Rn220Rn passivemeasurement device with single entry facerdquoRadiationMeasure-ments vol 58 pp 52ndash60 2013

[18] V Joshi S Dutt M Yadav R Mishra and R C Ramola ldquoMea-surement of radon thoron and their progeny concentrations inthe dwellings of pauri garhwal Uttarakhand Indiardquo RadiationProtection Dosimetry vol 171 no 2 pp 234ndash237 2016

[19] R Mishra R Rout R Prajith S Jalalluddin B K Sapra andY S Mayya ldquoInnovative easy-to-use passive technique For 222Rn And 220 Rn decay product detectionrdquo Radiation ProtectionDosimetry vol 171 no 2 pp 181ndash186 2016

[20] M Prasad M Rawat A Dangwal et al ldquoVariability of radonand thoron equilibrium factors in indoor environment ofGarhwalHimalayardquo Journal of Environmental Radioactivity vol151 pp 238ndash243 2016

[21] P Bangotra R Mehra K Kaur and R Jakhu ldquoStudy of naturalradioactivity (226Ra 232Th and 40K) in soil samples for theassessment of average effective dose and radiation hazardsrdquoRadiation Protection Dosimetry vol 83 no 2 74 pages 2016

[22] S Bala Sundar N Chitra I Vijayalakshmi et al ldquoSoil radioac-tivitymeasurements and estimation of radonthoron exhalation

rate in soil samples from Kalpakkam residential complexrdquoRadiation Protection Dosimetry vol 164 no 4 pp 569ndash5742015

[23] S Harb A E-B Abbady A E-H El-Kamel I I Saleh and AI Abd El-Mageed ldquoNatural radioactivity and their radiologicaleffects for different types of rocks fromEgyptrdquoRadiation Physicsand Chemistry vol 81 no 3 pp 221ndash225 2012

[24] N P Petropoulos M J Anagnostakis and S E SimopoulosldquoBuildingmaterials radon exhalation rate ERRICCA intercom-parison exercise resultsrdquo Science of the Total Environment vol272 no 1ndash3 pp 109ndash118 2001

[25] N Ahmad M S Jaafar S A Khan T Nasir S Ahmad and MRahim ldquoMeasurement of radon exhalation rate radium activityand annual effective dose from bricks and cement samplescollected from Dera Ismail Khanrdquo American Journal of AppliedSciences vol 11 no 2 pp 240ndash247 2013

[26] P Pant T Kandari M Prasad and R C Ramola ldquoA compara-tive study of diurnal variation of radon and thoron concentra-tions in indoor environmentrdquo Radiation Protection Dosimetryvol 171 no 2 pp 212ndash216 2016

[27] NM HassanM Hosoda K Iwaoka et al ldquoSimultaneousmea-surement of radon and thoron released from building materialsused in Japanrdquo Progress in Nuclear Science and Technology vol1 pp 404ndash407 2011

[28] N Mann A Kumar S Kumar and R P Chauhan ldquoMeasure-ment of indoor radon-thoron in air and exhalation from soil inthe environment of Western Haryana Indiardquo Radiation Protec-tion Dosimetry pp 1ndash6 2016

[29] L M Singh M Kumar B K Sahoo B K Sapra and R KumarldquoStudy of radon thoron exhalation and natural radioactivity incoal and fly ash samples of kota super thermal power plantRajasthan Indiardquo Radiation Protection Dosimetry pp 1ndash4 2016

[30] M Antonopoulos-Domis S Xanthos A Clouvas and DAlifrangis ldquoExperimental and theoretical study of radon distri-bution in soilrdquo Health Physics vol 97 no 4 pp 322ndash331 2009

[31] Y I Hafez and E-S Awad ldquoFinite element modeling of radondistribution in natural soils of different geophysical regionsrdquoCogent Physics vol 3 no 1 pp 1ndash16 2016

[32] UNSCEAR ldquoAnnex B Exposures from natural radiationsources united nations scientific committee on effect of atomicradiationrdquo Report to the General Assembly 2000

[33] Y Yamada Q Sun S Tokonami et al ldquoRadon-thoron dis-criminative measurements in Gansu province China andtheir implication for dose estimatesrdquo Journal of Toxicology andEnvironmental Health - Part A vol 69 no 7-8 pp 723ndash7342006

[34] UNSCEAR 2006 ANNEX E Sources-to-effects assessment forradon in homes and workplaces

[35] CHou B Shang Q ZhangH Cui YWu and J Deng ldquoImpactof haze-fog days to radon progeny equilibrium factor anddiscussion of related factorsrdquo Radiation and Environmental Bio-physics vol 54 no 4 pp 475ndash480 2015

[36] K P Eappen and Y S Mayya ldquoFactors affecting the registrationand counting of alpha tracks in solid state nuclear track detect-orsrdquo Indian Journal of Physics vol 83 no 6 pp 751ndash757 2009

[37] WHO ldquoMan-made Mineral Fibres and Radon IARC mono-graph Volume 43rdquo 1983

[38] C E Pereira V K Vaidyan M P Chougaonkar Y S MayyaB K Sahoo and P J Jojo ldquoIndoor radon and thoron levelsin Neendakara and chavara regions of southern coastal KeralaIndiardquoRadiation ProtectionDosimetry vol 150 no 3 Article IDncr399 pp 385ndash390 2012


[39] M Singh K Singh S Singh and Z Papp ldquoVariation of indoorradon progeny concentration and its role in dose assessmentrdquoJournal of Environmental Radioactivity vol 99 no 3 pp 539ndash545 2008

[40] TV Ramachandran ldquoEnvironmental thoron (220Rn) A reviewrdquoIranian Journal of Radiation Research vol 8 no 3 pp 129ndash1472010

[41] ldquoInternational Commission on Radiation Protectionrdquo ICRPPublication 103 Ann ICRP no 55 pp 49ndash79 2007

[42] J Chen and D Moir ldquoThe concept of equivalent radon con-centration for practical consideration of indoor exposure tothoronrdquo International Journal of Environmental Research andPublic Health vol 9 no 1 pp 286ndash293 2012

Submit your manuscripts athttpswwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


MEDIATORSINFLAMMATION

of


Behavioural Neurology

EndocrinologyInternational Journal of



Disease Markers


BioMed Research International

OncologyJournal of



Oxidative Medicine and Cellular Longevity


PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of



Computational and Mathematical Methods in Medicine

OphthalmologyJournal of


Diabetes ResearchJournal of



Research and TreatmentAIDS


Gastroenterology Research and Practice


Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


situated in the Western Ghats of southern India Severalstudies have proved the increase in the concentration ofindoor radon with decreasing temperature [10ndash12] Thesestudies have reported indoor radon thoron levels which arehigher than those seen in the High Natural BackgroundRadioactivity Areas (HNBRA) of Kerala Hence the presentinvestigations in Wayanad district are imperative to analysethe effect of temperature and ventilation on these gases withrespect to the warmer regions of Neendakara and Chavarawhich are one among the six HNBRAs of the world

The locationwe have chosen for the present investigationsis Bathery region of Wayanad This region has large numberof granite quarries and granite is already known to possesshigher radioactivity when compared to other types of rocks[13ndash15] It may be of interest to know the effect of granites interms of radiation dose when used as construction materialfor building Wayanad is the native place for a large popula-tion of tribal community of Kerala who belong to low incomegroup These people live in houses made of constructionmaterials likemud available locallyThe study aims to analysethe effect of the locally available construction materialscomprising granites and mud on the inhalation dose due toradon and thoron to the residents of Bathery Taluk

2 Materials and Methods

21 Geology Wayanad district is situated on the southern tipof the Deccan plateau and forms a part of theWestern GhatsThe geographical coordinates for the district are 11∘3610158401810158401015840Nand 76∘0410158405910158401015840E The population is 816558 as per the 2011census and the area is 2132 km2 The altitude ranges from 700to 2100 meters above sea level The mean annual temperatureis 238∘C During DecemberndashJanuary temperature lowers to15∘ C Bathery is located at 1167∘N 7628∘E It has an averageelevation of 907m Ambalavayal is part of Bathery and is oneof themain regions having a large number of granite quarriesThe Ambalavayal granite is of four types namely foliatedgranite pink granite grey granite and aplitic granite [16]These are composed of quartz pink feldspar hornblende andbiotite

22 Materials Indoor radon and thoronmeasurements weredivided into two phases of one year each In the first phase(2014-2015) pinhole dosimeters were used for the measure-ment of indoor radon and thoron concentrations This studyincluded all the villages in Bathery From this study spatialvariation of radon and thoron in Bathery was assessed Alongwith the indoor radon and thoron concentration studiessoil samples were collected from the top surface (of 15 cmthickness) from the vicinity of the houses These sampleswere analysed using gamma ray spectrometry for assessingterrestrial radioactivity Radon and thoron exhalation studieswere also done on the samples to obtain the mass exhalationrate for radon and the surface exhalation rate for thoronIn the second phase 19 houses in the Ambalavayal regionwere studied during 2015-2016 Out of these 10 houseswere intensively studied using both active and passive mea-surement techniques The second-phase study involved themeasurement of both radon and thoron concentrations as

well as their progeny The diurnal variation of radon andwall and floor exhalation was also studied by using activemeasurement techniques

221 Passive Measurement LR115 films based pinholedosimeters [17] were used for the passive measurement ofradon and thoron concentrationThis device has a single facefor gas entry and gives the time integrated measurement ofradon and thoron Pinhole dosimeters equipped with LR-115Type II Solid State Nuclear Track Detectors (SSNTD) with2 times 2 cm2 area were hung in a room of the houses (at least30 cm away from nearby wall) for a period of three monthsThe dosimeters were hung at a height of around 2m from thefloorThe principle working and processing of the dosimeterare discussed in detail elsewhere [17 18]The dosimeters werereplaced with new ones at the end of every threemonths untila cycle of 1 year was completed The retrieved dosimeterswere processed in the laboratory and the developed trackswere scanned using a spark counter by the standardisedprotocolTheminimum detectable limit for radon in pinholedosimeter is 2 Bqm3 and that for thoron is 6 Bqm3

Progeny measurements were done using the depositionbased Direct Radon Progeny Sensors and Direct ThoronProgeny Sensors (DRPSDTPS) [19] DTPS is made of LR-115SSNTDmounted with absorbers in 50120583m aluminised MylarThis detects the alpha particle emitted from 212Po (thoronprogeny with energy 878MeV) The radon progeny sensorDRPS is made of LR115 mounted with the absorber thickness37 120583m This detects 769MeV alpha particles emitted from214Po The minimum detectable limit for radon progeny inDRPS is 1 Bqm3 and that for thoron progeny in DTPS is01 Bqm3 The principle and method of measurement ofradon and thoron progeny is discussed in detail by Prasad etal [20]

222 Active Measurements The active measurements weredone using the state-of-the-art equipment the PortableRadon Monitor (SMART RnDuo) developed by BARC(Bhaba Atomic Research Center Mumbai) The detectorworks on the principle of scintillation counter by scintillationwith ZnS(Ag)The detection limit of Portable RadonMonitor(SMART RnDuo) is in between 8 Bqm3 and 50MBqm3(Operational Manual of Portable Radon MonitormdashSMARTRnDuo March 2015) The detector has a progeny filterthat eliminates the radon and thoron progenies For theestimation of radon concentration thoron is eliminated bythe diffusion time delay based thoron discriminator whichtakes advantage of the short half-life of thoron

For thoron monitoring program based sampling is car-ried out using a flow mode sampler connected to the pumpinlet of the monitor Each measurement cycle consists of15 minutes During this the pump is kept ON for the first5 minutes This gives a measure of the thoron and thebackground A delay of 5 minutes is maintained after thisto ensure the complete decay of thoron The last 5 minutesgives a measure of the background count for the cycle Thebackground count is subtracted from the total count of theinitial 5 minutes to get the thoron concentration





119872 sdot 119905sdot120582 sdot 119905

1 minus 119890minus120582sdot119905 (1)



119869119904 =119862119879 sdot 119881 sdot 120582

119860 (2)








119865 =EEC119862 (4)


3 Results




00

25

50

75

100

125

Freq

uenc

y




00

25

50

75

100

125

Freq

uenc

y

50 450

400

650

550

600

500

700

350

250

200

150

300

1000




Expe

cted

nor

mal

4

3

2

1

0

12 14 16 18 20 2210Observed value

minus1

minus2



minus3

minus2

minus1

0

1

2

3

Expe

cted

nor

mal







5 10 15 20 25 30 35 40


0

2

4

6

8

10

12

14

16

18

Ann

ual e

ffect

ive d

ose (

mSv

)


700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

AM

700

PM

TimeRadonConc

0

10

20

30

40

50

60

70

80

Rado

n co

ncen

trat

ion

(BqＧ

3)





0

200

400

600

800

1000

1200

1400

1600

Rado

n co

ncen

trat

ion

(BqＧ

3)

400

AM

400

PM

400

PM

400

AM

400

PM

400

AM

400

PM

400

AM

400

PM

400

PM

400

AM

Time






0 20 40 60 80 100 120


R = 090

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Thor

on ex

halat

ion

rate

from

soil

(BqＧ

2s

)






Con

cent

ratio

n (B

qＧ

3)


RadonThoron

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140



4 Discussion






119865Rn times 7000 times 9 (5)


5 10 15 20 25 30 35 40

Sample number


0

50

100

150

200

250

300

350

400

Tota

l exp

osur

e to

Rn an

d Tn

conc

entr

atio

n(B

qＧ

3)









5 Conclusion





Acknowledgments


References



















































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




















119872 sdot 119905sdot120582 sdot 119905

1 minus 119890minus120582sdot119905 (1)



119869119904 =119862119879 sdot 119881 sdot 120582

119860 (2)








119865 =EEC119862 (4)


3 Results




00

25

50

75

100

125

Freq

uenc

y




00

25

50

75

100

125

Freq

uenc

y

50 450

400

650

550

600

500

700

350

250

200

150

300

1000




Expe

cted

nor

mal

4

3

2

1

0

12 14 16 18 20 2210Observed value

minus1

minus2



minus3

minus2

minus1

0

1

2

3

Expe

cted

nor

mal







5 10 15 20 25 30 35 40


0

2

4

6

8

10

12

14

16

18

Ann

ual e

ffect

ive d

ose (

mSv

)


700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

AM

700

PM

TimeRadonConc

0

10

20

30

40

50

60

70

80

Rado

n co

ncen

trat

ion

(BqＧ

3)





0

200

400

600

800

1000

1200

1400

1600

Rado

n co

ncen

trat

ion

(BqＧ

3)

400

AM

400

PM

400

PM

400

AM

400

PM

400

AM

400

PM

400

AM

400

PM

400

PM

400

AM

Time






0 20 40 60 80 100 120


R = 090

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Thor

on ex

halat

ion

rate

from

soil

(BqＧ

2s

)






Con

cent

ratio

n (B

qＧ

3)


RadonThoron

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140



4 Discussion






119865Rn times 7000 times 9 (5)


5 10 15 20 25 30 35 40

Sample number


0

50

100

150

200

250

300

350

400

Tota

l exp

osur

e to

Rn an

d Tn

conc

entr

atio

n(B

qＧ

3)









5 Conclusion





Acknowledgments


References



















































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















00

25

50

75

100

125

Freq

uenc

y




00

25

50

75

100

125

Freq

uenc

y

50 450

400

650

550

600

500

700

350

250

200

150

300

1000




Expe

cted

nor

mal

4

3

2

1

0

12 14 16 18 20 2210Observed value

minus1

minus2



minus3

minus2

minus1

0

1

2

3

Expe

cted

nor

mal







5 10 15 20 25 30 35 40


0

2

4

6

8

10

12

14

16

18

Ann

ual e

ffect

ive d

ose (

mSv

)


700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

AM

700

PM

TimeRadonConc

0

10

20

30

40

50

60

70

80

Rado

n co

ncen

trat

ion

(BqＧ

3)





0

200

400

600

800

1000

1200

1400

1600

Rado

n co

ncen

trat

ion

(BqＧ

3)

400

AM

400

PM

400

PM

400

AM

400

PM

400

AM

400

PM

400

AM

400

PM

400

PM

400

AM

Time






0 20 40 60 80 100 120


R = 090

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Thor

on ex

halat

ion

rate

from

soil

(BqＧ

2s

)






Con

cent

ratio

n (B

qＧ

3)


RadonThoron

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140



4 Discussion






119865Rn times 7000 times 9 (5)


5 10 15 20 25 30 35 40

Sample number


0

50

100

150

200

250

300

350

400

Tota

l exp

osur

e to

Rn an

d Tn

conc

entr

atio

n(B

qＧ

3)









5 Conclusion





Acknowledgments


References



















































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of



















5 10 15 20 25 30 35 40


0

2

4

6

8

10

12

14

16

18

Ann

ual e

ffect

ive d

ose (

mSv

)


700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

PM700

AM

700

AM

700

PM

TimeRadonConc

0

10

20

30

40

50

60

70

80

Rado

n co

ncen

trat

ion

(BqＧ

3)





0

200

400

600

800

1000

1200

1400

1600

Rado

n co

ncen

trat

ion

(BqＧ

3)

400

AM

400

PM

400

PM

400

AM

400

PM

400

AM

400

PM

400

AM

400

PM

400

PM

400

AM

Time






0 20 40 60 80 100 120


R = 090

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Thor

on ex

halat

ion

rate

from

soil

(BqＧ

2s

)






Con

cent

ratio

n (B

qＧ

3)


RadonThoron

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140



4 Discussion






119865Rn times 7000 times 9 (5)


5 10 15 20 25 30 35 40

Sample number


0

50

100

150

200

250

300

350

400

Tota

l exp

osur

e to

Rn an

d Tn

conc

entr

atio

n(B

qＧ

3)









5 Conclusion





Acknowledgments


References



















































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















0 20 40 60 80 100 120


R = 090

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Thor

on ex

halat

ion

rate

from

soil

(BqＧ

2s

)






Con

cent

ratio

n (B

qＧ

3)


RadonThoron

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140



4 Discussion






119865Rn times 7000 times 9 (5)


5 10 15 20 25 30 35 40

Sample number


0

50

100

150

200

250

300

350

400

Tota

l exp

osur

e to

Rn an

d Tn

conc

entr

atio

n(B

qＧ

3)









5 Conclusion





Acknowledgments


References



















































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




















119865Rn times 7000 times 9 (5)


5 10 15 20 25 30 35 40

Sample number


0

50

100

150

200

250

300

350

400

Tota

l exp

osur

e to

Rn an

d Tn

conc

entr

atio

n(B

qＧ

3)









5 Conclusion





Acknowledgments


References



















































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of



















5 Conclusion





Acknowledgments


References



















































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















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