Assessment of radioactivity of different types of houses in Imphal city, Manipur, India

Abstract

An assessment of radioactivity concentration of different types of houses was conducted at 437 houses of Imphal City, Manipur, India. The average annual effective doses of gamma radiation level in indoor and outdoor were determined as 1.22 ± 0.09 (range: 0.79–1.41) mSvy-1 and 0.79 ± 0.08 (range: 0.57–1.07) mSvy-1 for reinforced cement concrete houses, followed by 1.06 ± 0.08 (range: 0.84–1.27) mSvy-1 and 0.78 ± 0.08 (range: 0.59–0.94) mSvy-1 for Assam-typed (AT) brick houses, 0.85 ± 0.08 (range: 0.63–1.28) mSvy-1 and 0.76 ± 0.08 (range: 0.52-1.01) mSvy-1 for AT mud houses, 0.77 ± 0.08 (range: 0.58–0.96) mSvy-1 and 0.73 ± 0.07 (range: 0.65–0.85) mSvy-1 for AT katcha houses, and 1.04 ± 0.07 (range: 0.88–1.22) mSvy-1 and 0.73 ± 0.07 (range: 0.65–0.84) mSvy-1 for adobe laid earthen houses, respectively. Moreover, the annual effective dose conceived from building materials was recorded as 1.8 mSvy-1 from sand, 1.5 mSvy-1 from brick, and 1.0 mSvy-1 from Portland cement. The worldwide average indoor dose limit of radon conceiving and its decay product by inhalation is 1.15 mSvy-1 prescribed by the UNSCEAR (2000).

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26 © 2020 Radiation Protection and Environment | Published by Wolters Kluwer - Medknow
Assessment of radioactivity of different types of houses in
Imphal city, Manipur, India
Sanasam Suranjit1, Oinam Shashikumar Singh1, S. Nabadwip Singh2, B. Arunkumar Sharma3
1Department of Zoology, D. M. College of Science, 2Department of Physics, Oriental College (Autonomous), 3Department of Radiaon
Oncology, Regional Instute of Medical Sciences, Imphal, Manipur, India
Original Article
INTRODUCTION
Terrestrial background radiations
The level of terrestrial radiation differs from place to place
around the world, as the concentration of materials in the
earth’s crust varies[1] and depends on their emanation rate
from the soil, meteorological, geological, and geographical
factors and height above the ground surface.[2] The main
radionuclides in building materials are from the 238U and
232Th decay chains and 40K.
Radon is an inert, naturally occurring radioactive gas,[3] which
is considered the second leading cause of lung cancer;[4,5]
besides, it can be more concentrated in indoor than
outdoor. The exposure to radon is due to the emanation by
decaying terrestrial radionuclide 238U and 232Th. The gamma
radiation arising from the walls, oors, and ceilings is the
major source of gamma radiation exposure[6] due to the
materials used for building construction containing elevated
levels of radioactivity.[7] Most of the people spending their
maximum time (approximately 80%) of a day in indoor.[8,9]
The average indoor effective dose due to gamma rays from
building materials is estimated to be about 0.4 mSvy-1.[10]
A study on building materials showed that granite and
phosphogypsum are the highly radioactive materials which
An assessment of radioactivity concentration of different types of houses was conducted at 437
houses of Imphal City, Manipur, India. The average annual effective doses of gamma radiation level
in indoor and outdoor were determined as 1.22 ± 0.09 (range: 0.79–1.41) mSvy‑1 and 0.79 ± 0.08
(range: 0.57–1.07) mSvy‑1 for reinforced cement concrete houses, followed by 1.06 ± 0.08 (range: 0.84–1.27)
mSvy‑1 and 0.78 ± 0.08 (range: 0.59–0.94) mSvy‑1 for Assam‑typed (AT) brick houses, 0.85 ± 0.08 (range:
0.63–1.28) mSvy‑1 and 0.76 ± 0.08 (range: 0.52‑1.01) mSvy‑1 for AT mud houses, 0.77 ± 0.08 (range:
0.58–0.96) mSvy‑1 and 0.73 ± 0.07 (range: 0.65–0.85) mSvy‑1 for AT katcha houses, and 1.04 ± 0.07 (range:
0.88–1.22) mSvy‑1 and 0.73 ± 0.07 (range: 0.65–0.84) mSvy‑1 for adobe laid earthen houses, respectively.
Moreover, the annual effective dose conceived from building materials was recorded as 1.8 mSvy‑1 from
sand, 1.5 mSvy‑1 from brick, and 1.0 mSvy‑1 from Portland cement. The worldwide average indoor dose limit
of radon conceiving and its decay product by inhalation is 1.15 mSvy‑1 prescribed by the UNSCEAR (2000).
Keywords: Different house types, effective dose, Imphal, Meitei Yumjao, radioactivity
Abstract
Address for correspondence: Dr. B. Arunkumar Sharma, Department of Radiaon Oncology, Regional Instute of Medical Sciences, Imphal, Manipur, India.
E‑mail: arunsb2000@yahoo.co.uk
Submied: 28‑Dec‑2019 Revised: 20‑Jan‑2020 Accepted: 18‑Mar‑2020 Published: 13‑May‑2020
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DOI:
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How to cite this article: Suranjit S, Singh OS, Singh SN, Sharma BA.
Assessment of radioactivity of dierent types of houses in Imphal city,
Manipur, India. Radiat Prot Environ 2020;43:26-30.
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Suranjit, et al.: Assessment of radioactivity of houses
Radiation Protection and Environment | Volume 43 | Issue 1 | January‑March 2020 27
enhance indoor absorbed dose rate up to ve times than
the dose criterion.[11] Another study showed that building
materials collected from Yan’an, China, may be used safely
as construction materials.[12] This suggests that the effective
radiation dose rate in indoor depends on the level of
radioactivity in the soil, rock, and industrial by-products
from where these building materials are derived. Hence,
the knowledge of the level of natural radioactivity in
building materials is, thus, become important to assess any
possible radiological risk to human health and develop any
precautionary measures in using building materials.
The present study area, Imphal City, is the capital of
Manipur and it includes two valley districts, namely,
Imphal-East and Imphal-West. Radioactive contaminants
as well as indoor and outdoor radiation dose rates for
ve different types of houses available in this area were
studied. As per census of 2011, Imphal-West district
is the most populous district, which has a population
density of 930 inhabitants per square kilometer (km2)
with a total population of 517,992 and covers a total area
of 558 km2. It is located at 24°49’N, 93°54’E,[13] whereas
Imphal-East district is the second most populous district
having a population density of 638 inhabitants per square
kilometer with a total population of 452,661 and covers a
total area of 710 km2. It is located at 24°48’N, 93°57’E.[14]
Besides, Imphal City is about 300 km away from Domiasiat
in Meghalaya which is known for huge deposited area of
heavy minerals in the country.[15]
MATERIALS AND METHODS
In‑house survey by survey meter
Indoor and outdoor background gamma radiations of
different types of houses were measured using a NaI (Tl)
scintillator-based microroentgen survey meter (SM)
manufactured by Nucleonix Systems Pvt. Ltd., Hyderabad,
India, having a sensitivity of 1 µ Rh-1. It was used for
instantaneous measurement of dose rate by keeping the
SM at a height of about 1 m above the ground surface.
Repeated measurements not <10 times for each spot were
taken. The average value for all these ten measurements
was assumed to be the dose rate for that particular area.[9]
Total measurements of 437 different houses were covered
during the study.
Radiological analysis of building materials
A total of 9 samples of building materials from Imphal City
were collected and crushed into small sizes. The samples
were subjected to dry in a hot air oven at 110°C for 24 h.
The Portland cement samples were also dried at 60°C.
Then, ground into ne powder, homogenized, and sieved
through a mesh size of 0.45mm;[16] sealed and stored it
carefully for a period of 4 weeks at room temperature to
reach secular equilibrium.[7,15]
A 3”X3” NaI (Tl) scintillation detector based Gamma
spectrometer was employed with adequate shielding (about
10 cm lead). The efciency calibration of the gamma
ray spectrometer was made using different energy peaks
covering the range up to ≈ 2000 keV. Measurements were
performed using calibrated standard source samples,
which contain a known activity of gamma ray emitters
radionuclides namely 133Ba (356.1 keV), 137Cs (661.6 keV),
60Co (1173 KeV and 1332 KeV) and 226Ra (1764.5 keV).
The activity concentrations of 226Ra, 232Th, and 40K in the
sample of 300 g were determined with adequate shielding.
The counting time was preset at 36,000 s.[18] The activities
concentration of 226Ra was determined from the average
activity concentration obtained from the prominent gamma
lines of 214Bi and 214Pb and that of 232Th was obtained from
the average concentration obtained from the gamma lines
of 212Bi, 228Ac, 208Tl, respectively. however, 40K was evaluated
from its own gamma photopeak.[15,16,19]
The activity concentrations of 238U, 232Th series, and 40K
were calculated using the following equation;[20]
A (Bqkg-1) = N/M (1)
Where N = the net gamma counting rate (counts per
second),  = the detector efficiency of the specific
gamma-ray, β = the absolute transition probability of
gamma decay, and M = the mass of the sample (kg).
The relative concentration and distribution of 226Ra, 232Th,
and 40K did not uniform in environment and not found to
be uniform in building materials. Radium equivalent (Raeq)
activity index is introduced to represent the specic activity
of 226Ra, 232Th and 40K by a single quantity.[7,21,22] The index
parameter Raeq is related to exposure to radiation and dened
to compare the specific activity of material containing
different activities of 238U, 232Th, and 40K.[23] Thus, radium
equivalent activity (Raeq) is computed using the equation:[10,24]
Raeq = ARa + 1.4ATh + 0.077AK (2)
Where ARa, ATh, and AK are the specic activities of 226Ra,
232Th, and 40K in Bqkg−1, respectively.
Activity concentration index, or gamma index I, is dened
in order to examine the applicability of using building
materials in construction. It is dened by the following
expression:[25]
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Suranjit, et al.: Assessment of radioactivity of houses
28 Radiation Protection and Environment | Volume 43 | Issue 1 | January‑March 2020
I = ARa/300 + ATh/200 + AK/300 ≤ 1 (3)
This is a simple criterion of the applicability of a building
material.
Adsorbed dose rate (D): The absorbed Dose Rate due to
gamma radiation in air for a standard room dimensions and
for common building materials with naturally occurring
radionuclides 226Ra, 232Th and 40K was calculated using the
guidelines given in UNSCEAR (2000):[10]
D (nGyh-1) = (0.92 × ARa) + (1.1 × ATh) + (0.08 × AK) (4)
The annual effective dose (Deff) was calculated by applying
the dose conversion factor of 0.7 SvGy-1 from the absorbed
dose in air received by an adult and a value of 0.8 as an
indoor occupancy factor (assuming 80% of an individual
time is spending in indoor).[10,22,26] The annual effective
dose (Deff) due to gamma radiation from building materials
was evaluated as:
Deff(mSv/y) = D(nGyh-1) × 8760 h × 0.8 × 0.7SvGy-1
× 10-6 (5)
RESULTS AND DISCUSSION
Background gamma dose rate and corresponding annual
effective dose rate of different types of houses were estimated
at 437 houses in Imphal City, Manipur, NE, India. During
the survey, approximately ve different types of houses were
classied, which is based on their building materials utilized
which are derived from soils and rocks in and around Imphal
City. The classied houses are shown in Figure 1.
In the survey, the average annual effective dose rates
of gamma radiation level in indoor and outdoor
were determined [Table 1] as 1.22 ± 0.09 mSvy-1
and 0.79 ± 0.08 mSvy-1 for RCC houses, followed by
1.06 ± 0.08 mSvy-1 and 0.78 ± 0.08 mSvy-1 for AT
brick houses, 0.85 ± 0.08 mSvy-1 and 0.76 ± 0.08
mSvy-1 for AT mud houses, 0.77 ± 0.08 mSvy-1 and
0.73 ± 0.07 mSvy-1 for AT katcha houses, and 1.04 ± 0.07
mSvy-1 and 0.73 ± 0.07 mSvy-1 for adobe laid earthen
house, respectively.
Meanwhile, the annual effective dose from building
materials was recorded as 1.76 mSvy-1 from sand, followed
by 1.53 mSvy-1 from brick and 1.04 mSvy-1 from Portland
cement [Table 2]. The average gamma index of bricks and
sand was observed higher than unity.
Average annual effective dose of 1.22 ± 0.09 mSvy-1
of RCC houses was slightly higher than the maximum
permissible dose limit for nonradionuclide industrial
workers and the public as 1 mSvy-1 recommended by
International Commission on Radiological Protection.[27]
The average effective dose rate from RCC houses as
evaluated from its building materials, namely, sand,
cement, and bricks, was also obtained as 1.44 ± 0.36
mSvy-1.
The adobe laid earthen typed houses are gradually
decreased in its number because of the modernization of
building materials and urbanization. The indoor average
effective dose rate of such type of houses as evaluated by
SM was 1.04 ± 0.07 mSvy-1. However, the annual effective
dose rate evaluated from soil of Imphal City as reported
earlier[15] was 1.1 mSvy-1.
The Assam-type brick houses are less in number compared
with RCC houses. The indoor average effective dose
rate of such type of houses as evaluated by SM was
1.06 ± 0.08 mSvy-1. The effective dose rates of the
remaining Assam-type mud houses and Assam-type
katcha houses were observed as 0.85 ± 0.08 mSvy-1 and
0.77 ± 0.08 mSvy-1, respectively.
The outdoor effective dose rate of the Imphal City was
observed in the range of 0.52–1.07 mSvy-1, which is in
agreement with the earlier study of Sharma et al.[15]
Figure 1: Illustration of different types of houses which is available in
the Imphal, Manipur, India. (a) Typical picture of reinforced cement
concrete house. (b) Typical picture of Assam‑typed brick house.
Typical picture of Assam‑typed mud house. (d) Typical picture of
Assam‑typed katcha house. (e) Typical picture of adobe laid earthen
house (an indigenous‑traditional house of Manipur) so called as Meitei
Yemjao in Imphal
d
c
b
a
e
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Suranjit, et al.: Assessment of radioactivity of houses
Radiation Protection and Environment | Volume 43 | Issue 1 | January‑March 2020 29
CONCLUSIONS
The average radioactive contaminant of building materials
available in different types of houses of Imphal City were
found: for bricks, 226Ra – 32.86 Bqkg−1, 232Th – 140.19
Bqkg−1, and 40K – 1596.41 Bqkg−1; for sand, 226Ra – 46.62
Bqkg−1, 232Th – 129.36 Bqkg−1, and 40K – 2159.62 Bqkg−1;
and for cement, 226Ra – 34.96 Bqkg−1, 232Th – 34.12 Bqkg-1,
and 40K – 1766.53 Bqkg-1. Indoor effective dose rate of
RCC houses is observed higher than other remaining types
of houses. Assam-type katcha houses and mud houses
show minimal effective dose rates.
Acknowledgments
The present study is the outcome of investigations carried
out by the authors. The authors express their gratefulness
to the Institutional Biotech Hub Laboratory, D. M.
College of Science, Imphal, Manipur, under Department
of Biotechnology, Ministry of Science and Technology,
Government of India, New Delhi, and Environment
Radiation Dosimetry Laboratory, Oriental College
(Autonomous), under Atomic Energy Regulatory Board
(AERB), Bombay, Government of India, New Delhi, for
providing the laboratory support necessary for this study.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conicts of interest.
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Table 1: Annual effective dose of different types of houses in Imphal City
Types of house Indoor (mSvy−1) Outdoor (mSvy−1)
Minimum Maximum Average Minimum Maximum Average
RCC house 0.79±0.06 1.41±0.08 1.22±0.09 0.57±0.08 1.07±0.10 0.79±0.08
AT brick house 0.84±0.09 1.27±0.09 1.06±0.08 0.59±0.08 0.94±0.06 0.78±0.08
AT mud house 0.63±0.06 1.28±0.10 0.85±0.08 0.52±0.07 1.01±0.07 0.76±0.08
AT katcha house 0.58±0.05 0.96±0.07 0.77±0.08 0.65±0.05 0.85±0.06 0.73±0.07
Adobe laid earthen house 0.88±0.09 1.22±0.07 1.04±0.07 0.65±0.08 0.84±0.08 0.74±0.07
RCC: Reinforced cement concrete, AT: Assam typed
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I D (nGyh−1) Deff (mSvy−1)
226Ra 232Th 40K
Brick sample
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Brick‑2 24.5±1.4 75.6±6.8 1561.3±124.8 252.9 1. 0 230.6 1.1
Brick‑3 44.3±3.9 156.8±12.5 2143.9±171.4 433.6 1. 6 384.7 1. 9
Average value 32.9±1.6 140.2±5.6 1596.4±125.4 356.3 1.3 312.2 1.5
Sand sample
Sand‑1 36.8±1.8 44.2±1.8 2236.9±189.5 272.2 1.1 261.3 1.3
Sand‑2 41.8±3.8 129.8±10.2 2109.3±168.7 389.8 1.5 350.0 1. 7
Sand‑3 61.4±2.9 214.1±17.1 2132.7±106.8 531.7 2.0 462.6 2.3
Average value 46.6±2.7 129.4±7.7 2159.6±150.9 397.9 1. 5 358.0 1. 8
Cement sample
Cement‑1 22.1±1.0 60.2±4.8 1234.6±61.8 203.2 0.8 185.3 0.9
Cement‑2 47.0±3.2 21.8±1.7 1719.4±154.9 210.6 0.8 204.8 1.0
Cement‑3 35.8±1.5 20.4±1.9 2345.7±164.9 245.6 1. 0 243.0 1.2
Average value 35.0±2.1 34.1±2.5 1766.5±157.5 219.8 0.9 211. 0 1. 0
Soil sample
Average value[15] 94.1±8.5 146.5±10.2 1222.9±85.5 397.7 1. 5 345.6 1.7
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