Assessment of dose due to natural radio

Volume 12, No 3
International Journal of Radiation Research, July 2014
Assessment of dose due to natural radio-nuclides
in vegetables of high background radiation area in
south-eastern part of Bangladesh
A. Islam1*, A. Begum2, S. Yeasmin2, M.S. Sultana1
1DepartmentofEnvironmentalSciences,JahangirnagarUniversity,Savar,Dhaka-1342,Bangladesh
2HealthPhysicsDivision,AtomicEnergyCentre,Dhaka-1000,Bangladesh
ABSTRACT
► Short report
*Correspondingauthor:
Dr.AshnaIslam,
E‐mail:[email protected]
Received: May 2013
Accepted: Aug. 2013
Int. J. Radiat. Res., July 2014;
12(3): 271-275
Background: The aims of the study are to determine the radioac vity
concentra ons of 226Ra, 238U, 232Th and 40K in vegetables of a recently found
high background radia on area of south‐eastern part of Bangladesh and to
detect the radiological risks to human from intake of these vegetables.
Materials and Method: 10 plant samples were collected randomly from
diﬀerent loca ons of the study area. The radio‐nuclides in papaya were
measured by direct γ‐ray spectrometry using HPGe detector. Results: The
average ac vity concentra ons of 226Ra, 238U, 232Th and 40K in papaya samples
were 80.95±13.61, 64.77±38.47, 83.53±20.50 and 1691.45±244.98 Bq kg‐1
respec vely. The annual eﬀec ve inges on dose due to intake of papaya was
1.1 mSv Y‐1. Conclusion: The concentra ons of radio‐nuclides in the papaya
samples found in present study were higher than the world average values
suggested by the UNSCEAR. The annual eﬀec ve inges on dose was found 3.8
mes higher than total exposure per person resul ng from the inges on of
terrestrial radioisotopes.
Keywords: Natural radioactivity, vegetables, HPGe detector, effective ingestion
dose.
and 40K in vegetables of the
areainorderto indouttheingestiondosetothe
public due to intake of the food. This study will
Highlevelofnaturalradioactivityhasalready
provideabaselinedataofthenaturalradioactivbeen found in soil of Tulatoli village of Teknaf
ity concentration in food of the area for further
upazila at Cox’s Bazar District of Bangladesh. It
research.
is an old beach zone where high amount of
heavy minerals have been found as placer Papayahaschosenasthevegetableforstudy.
Because in the environment of Bangladesh it
depositsandnowbecomeawellpopulatedarea
growsroundtheyearandmasspeoplegenerally
(1). Plants are the primary recipients of the
grow it by the yard corner‐ side of their
radio‐nuclides from soil. These radio‐nuclides
residences. Thus, round the year it is a widely
can get transferred into plants along with the
takenfoodformasspeople.
nutrientsduringmineraluptakeandaccumulate
invariouspartsandevenreachedibleportions.
Studies on the radioactivity of the consumable
INTRODUCTION
226Ra, 238U, 232Th
MATERIALSANDMETHODS
parts of a vegetable assume importance as it is
necessary to estimate the ingestion dose to the
(2)
Descriptionofthestudyarea
public .
So, the aim of the present study is to TheTulatolivillageofTeknafupazilaatCox’s
determine the radioactivity concentrations of
Bazardistrictisthestudyareawhichissituated
Islam et al. / Natural Radio-nuclides in Vegetables
Radioactivitymeasurement
at the south‐eastern part of Bangladesh.
The activity concentration of gamma ray
Geologicallytheareaisanoldsandybeachzone,
emitting
radioisotopes in the samples were
characteristically enriched with heavy mineral‐
measured by using a gamma ray spectrometer
sands including good presence of thorium
(232Th) bearing monazite. The whole area iswith a high‐resolution HPGe coaxial detector
coupled with a Silena Emcaplus multichannel
covered by a thin layer of top soil. Human
analyzer (MCA). The effective volume of the
habitation in the area is moderate. The activity
detector was 83.469 cm3 and energy resolution
226
238
232
concentrationsof Ra, Uand Thinsoilof
the study area were found 9, 5.5 and 8 times ofthe1.33MeVenergypeakfor 60Cowasfound
respectively higher than the world average as1.69keVatfullwidthhalfmaximum(FWHM)
with a relative ef iciency of 19.6%. All samples
values(1).
werecountedfor5000s.Theactivityconcentra‐
tionof226Rawascalculatedthrough609.3keVof
Samplecollectionandpreparation
214Bi. 238Uwascalculatedthrough351.92keVof
The geographic location of the study area is
214Pband1120.3keV,1764.5keVof 214Bi. 232Th
shown in igure 1. Papaya (Carica papaya) was
activity was calculated through and 238.63 keV
selected as the vegetable for study. 10 samples
of 212Pb, 583.14 keV 208Tl, 911.07 keV, 969.11
were collected randomly from different
keV of 228Ac respectively. The 40K activity was
locations of the Tulatoli village. Each plant
calculated through 1460.75 keV. The
sample was approximately 2 kg of weight (wet
radioactivityconcentrationof eachradionuclide
weight).Allthesampleswereprocessedfollow‐
wascalculatedusingtheequation(i)(3).
ingthestandardproceduresasperInternational
AtomicEnergyAgency(IAEA)guidelines (3).The
(i)
plant samples were dried at 105°‐110° C Ai(Bqkg‐1)=N/(W×ԑ×Pγ)
temperature.Thenthesesamplesweresmashed
Where Ai is the activity concentration of each
with mortar and pestle, homogenized, screened
radionuclideinthesample,Nisthenetcountof
with laboratory test sieve of aperture 425
eachradionuclidewhichisfoundbysubtracting
micrometer and weighted. The weight of the
the sample radionuclide activity counting from
plant samples were in between 35 to 90 gm.
background activity counting, ε is the detector
Then all samples were packed individually into
ef iciencyofthespeci icγray,Pγisthetransition
cylindricalplasticcontainers(7.3cmdiameter×
probability of the speci ic γ ray and W is the
8.9 cm height), sealed tightly and were kept at
weightofthesample(kg).
room temperature for about 30 days to ensure
that 238U and its daughter products were in
Calculation of annual effective dose of
secularequilibrium(3).
radio‐nuclidesfromingestedvegetables
Radiationdosestopopulationfromintakeof
radio nuclides in foods can be calculated from
theformula(ii)reportedinUNSCEAR2000(4).
D=CAR
(ii)
WhereDistheeffectivedosebyingestionofthe
radionuclide(SvY‐1),Aistheactivityconcentra‐
tionoftheradio‐nuclidesinthesample(Bqkg‐1),
C is the internal dose conversion coef icient by
ingestionoftheradio‐nuclides(SvBq‐1)andRis
the annual intake of papaya (kg Y‐1) which
dependsonagivenage(5).
Figure 1. Geographic loca on of the study area.
Int. J. Radiat. Res., Vol. 12 No. 3, July 2014
272
Islam et al. / Natural Radio-nuclides in Vegetables
concentrationof40Kwasfoundveryhigh.
RESULTS
Annual effective dose of radio‐nuclides from
Activity concentrations (Bq kg‐1) of
ingestedvegetables
radio‐nuclides
Annual effective ingestion dose due to
Activity concentrations of radio‐nuclides in
vegetables consumption strongly depends on
papaya samples have shown in table 1. The
the vegetables consumption. The consumption
concentrations of 226Ra in papaya samples
ratewasde inedusingFAOde inition (6).Inthis
‐1
ranged from 41.82 to 120.08 Bq kg with an
study the annual consumption rate of papaya
average of 80.95±13.61 Bq kg‐1. The
consumedbytheadultswas20kgY‐1.
concentrations of 238U ranged from 18.57 to
The annual effective ingestion dose due to
110.98 Bq kg‐1 with an average of 64.77±38.47
intake of radio‐nuclides is shown in table 2.
Bqkg‐1.Theconcentrationsof232Thrangedfrom
Results show that the total average effective
39.58 to 127.48 Bq kg‐1 with an average of
ingestiondoseduetoannualintakeof226Ra,238U,
‐1
40
232Th and 40K from papaya was 1.1 mSv Y‐1 of
83.53±20.50 Bq kg and the concentrations K
rangedfrom1030.88to2352.02Bqkg‐1 withan
which0.21mSvwasfrom 40Kand0.89mSvwas
average of 1691.45±244.98 Bq kg‐1. The
from226Ra,238Uand232Th.
Table 1. Ac vity concentra ons (Bq kg‐1) of radio‐nuclides in papaya samples.
Sample ID
P1
P2
P3
P4
P5
P6
P7
P8
P9
P10
Range
Mean
226
Ra
41.82
111.5
63.57
92.80
120
86.03
47.79
49.10
76.81
66.64
41.82‐120
80.95±13.61
238
U
18.57
68.86
25.37
38.72
111
35.73
28.59
41.40
76.50
61.07
18.57‐111
64.77±38.47
232
Th
57.43
127.5
123.76
108
107.9
89.15
58.18
39.58
84.57
80.51
39.58‐127.5
83.53±20.50
40
K
1259
1088
1632
1892
1907
1951
1642
1030
1470
2352
1030‐2352
1691±245
Table 2. Annual eﬀec ve inges on dose due to intake of radio‐nuclides from papaya.
Radio‐nuclides
Ra
Maximum
Minimum
Average
238
U
Maximum
Minimum
Average
232
Th
Maximum
Minimum
Average
Maximum
40
Minimum
K
Average
226
Total inges on dose from papaya
273
Annual eﬀec ve inges on dose (mSv Y‐1)
0.67
0.23
0.45
0.10
0.02
0.06
0.59
0.18
0.38
0.13
0.29
0.21
Dose conversion coeﬃcient (Sv/Bq) (Adults)
2.8×10‐7
4.5×10‐8
2.3×10‐7
6.2×10‐9
1.1 mSv Y‐1
Int. J. Radiat. Res., Vol. 12 No. 3, July 2014
Islam et al. / Natural Radio-nuclides in Vegetables
DISCUSSION
CONCLUSION
The average activity concentration of 226Ra,
238U, 232Th and 40K in papaya samples were
80.95±13.61, 64.77±38.47, 83.53±20.50 and
1691.45±244.98 Bq kg‐1 respectively. A
comparisonoftheobtainedvaluehasdonewith
the activity concentration (Bq kg‐1) of the
natural radio‐nuclides in plants of different
districtsofBangladeshwhichisgivenintable3.
It shows that papaya of the study area has
higher radioactivity concentration than the
otherpartsofBangladeshaswellasthanworld
average value for root vegetables and fruits
suggested by UNSCEAR. Potassium is a
macronutrient,sotheconcentrationcanbehigh
invegetables (8).Besidethis,beachsoilcontains
high amount of salts due to regression of sea
water,whichmayalsocausehighconcentration
of40Kinpapayaofthisarea.
AccordingtoareportbyUNSCER (4),thetotal
exposureperpersonresultingfromingestionof
terrestrial radioisotopes should be 0.29 mSv, of
which0.17mSvisfrom40Kand0.12mSvisfrom
thorium and uranium series. The annual
effectiveingestiondose duetointakeofpapaya
was 1.1 mSv Y‐1 which was found 3.8 times
higher than world safe value of total exposure
per person resulting from the ingestion of
terrestrialradioisotopes(table4).
Aradiologicalstudywasperformedtoobtain
the annual effective dose of natural radio‐
nuclides(226Ra,238Uand 232Th)intohumanbody
due to intake of vegetables from a high
backgroundradiationareainsouth‐easternpart
of Bangladesh. The radioactivity concentrations
in papaya samples were higher than the world
average value. The annual effective ingestion
dosetohumanbodyduetointakeofpapayawas
also found 3.8 times higher than the world safe
value of total exposure per person resulting
from the ingestion of terrestrial radioisotopes.
The data derived from this study represent a
baselinedatabaseofdoselevelsthatcanserveas
areferencepointforfuturestudies.
ACKNOWLEDGEMENT
The author would like to thank the Health
Physics Division of Bangladesh Atomic Energy
Centre, Dhaka, Bangladesh for allowing the
experimenttobeconductedintheirlaboratories.
REFERENCES
1. Ashna Islam, Mahfuza Sharifa Sultana, Aleya Begum, Selina
Table 3. Comparison of ac vity concentra on (Bq kg‐1) of natural radio‐nuclides in root vegetables/fruits with diﬀerent districts
of Bangladesh.
Region
226
Vegetables
Ra
238
232
U
Th
40
K
Reference
Jamalpur
Ladies finger
‐
5.5‐74
8‐248
1274‐4860
(7)
Kus a
Red amaranth
‐
4.22‐20
5.5‐23
870‐2531
”
Tangail
Red amaranth
‐
9.4‐18.3
9‐23.6
1109‐1383
”
Jessor
Red amaranth
‐
9‐36
4‐19
204‐366
”
Tulatoli
village,Teknaf
Papaya
80.95
64.77
83.53
1691
Present
study
World average
value
Root vegetables/
fruits
0.03
0.003
0.0005
‐
UNSCEAR (4)
Table 4.Comparison of annual eﬀec ve inges on dose with world safe value.
Obtained value
1.1 mSv Y‐1
World safe value (4)
0.29 mSv Y‐1
Int. J. Radiat. Res., Vol. 12 No. 3, July 2014
274
Islam et al. / Natural Radio-nuclides in Vegetables
Yesmin (2013) Radioac vity level in soil of palaeo beach in
south‐eastern part of Bangladesh and evalua on of
radia on hazard. Radiat Prot Dosim, Doi: 10.1093/rpd/
nct135.
2. Jibiri N N, Farai I P, and Alausa S K (2007) Ac vity
concentra on of 226Ra, 228Th and 40K in diﬀerent food crops
from a high background radia on area in Bitsichi, Jos
Plateau, Nigeria. Radiat Environ Biophys, 53–59.
3. IAEA (1989) Measurement of radionuclides in food and the
environment. Interna onal Atomic Energy Agency,
Technical Reports Series no 295.
4. UNSCEAR (2000) Sources and Eﬀects of Ionizing Radia on,
United Na ons Scien fic Commi ee on the Eﬀects of
Atomic Radia on, United Na ons, New York.
5. ICRP (1996) Interna onal Commission on Radiological
275
Protec on, Age ‐ dependent doses to members of the
public from intake of radionuclides Part5: Compila on of
inges on and inhala on coeﬃcients ICR Publica on 72,
Oxford: Pergamon Press.
6. FAO (2000) Food Balance Sheets, Food and Agriculture
Organiza on of the United Na ons.
7. Selina Yeasmin, Aleya Begum (2012) Distribu on of
radioac vity levels of environmental samples from
diﬀerent upazillas of Bangladesh. Bangladesh Journal of
Physics, 11.
8. Shanthi G, Maniyan C G, Allan Gnana Raj G and Thampi
Thanka Kumaran J (2009) Radioac vity in food crops from
high background radia on area in southwest India.
Current Science, (97)9: 1331‐1335.
Int. J. Radiat. Res., Vol. 12 No. 3, July 2014

Download Report