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DOI: 10.14738/aivp.86.9119

Publication Date: 18th October, 2020

URL: http://dx.doi.org/10.14738/aivp.86.9119

Assessment of Ionizing Radiation Dose and Risk Levels

associated with Radioactivity in Oraifite, Nigeria

Anekwe, U.L.

Department of Physics, Federal University Otuoke, Bayelsa State, Nigeria.

uzanekwe@yahoo.co.uk

ABSTRACT

Radioactivity has been natural occurrence in human environment and its adverse effects are highly

undesirable. This study assessed radiation risk levels associated with radioactivity in Oraifite using

gamma ray (Ɣ-ray) spectrometry and radiation survey meter. The mean value of background ionizing

radiation (BIR) exposure rate ranged from 0.011 to 0.014mRh-1

. The mean activities of 226Ra, 232Th, 40K

ranged from 23.54±4.89 to 41.03±4.28 BqKg-1

, 9.69±1.88 to 11.34±1.86 BqKg-1

, 419.22±3.41 to

737.91±4.78 BqKg-1 respectively. Mean values of radium equivalent (Raeq), absorbed dose (D), Igamma

(IƔ), internal hazard index (Hin), external hazard index (Hex) and annual effective dose equivalent

(AEDE), were 60.05Bqkg-1

, 55.75nGh-1

, 0.86, 0.41, 0.30 and 0.07mSvy-1 respectively. Excess lifetime

cancer risk (ELCR) which is estimation of the probability of cancer incidence in a population of

individuals for a specific lifetime had a mean value of 0.25x10-3 and this is lower than the world

permissible limit of 0.29x10-3

. The average dose to human organs/tissues; lungs, ovaries, bone

marrow, testes, kidney, liver and whole body were 0.033, 0.028, 0.033, 0.040, 0.028, 0.023, and 0.033

mSvy-1 respectively, meaning that all the computed organ dose were far much lower than the

maximum allowable standard value of 1.0 mSvy-1

. Virtually all hazard indices were below the ICRP

recommended values and in general the residents of Oraifite are not under ionizing radiation threat.

Keywords: Spectrometry, Radiation Dose, Assessment, Health risk, Activity concentration

1 Introduction

Human beings are constantly exposed to radiations, basically to Ionizing and Non ionizing radiations.

The health implications of radiation exposure have been of great public concern. These two major

types of radiation are electromagnetic in nature. Ionizing radiation has high energy that can cause the

atoms of the matter through which it passes to be electrically charge and ejects electrons from the

atom it interacts with. This process actually results to gamma radioactivity. Radioactivity for so many

decades has been known to be spontaneous emission of radiation in the form of particles or photon

energy. It is a spontaneous disintegration of the nuclei of some isotopes with the emission of alpha

(α) or beta (β) particles or gamma (γ) rays. This phenomenon occurs in all human-environment for

which Oraifite community is not an exception. The earth and its atmosphere contain radioactive

materials that are natural since the “Big Bang” era. In their natural state they are called naturally

occurring radioactive materials, NORMs. Natural radioactivity is wide spread in the earth’s

environment and it exists in various geological formations in soil, rocks, plants, water and air [1].

Radionuclides include elements in the 238U, 235U, 232Th series and their respective decay daughters, as

well as 40K. A significant part of the total dose contribution in the form of natural sources comes from

terrestrial gamma radionuclides. Only nuclides with half−lives comparable with the age of the earth

or their corresponding decay products, existing in terrestrial materials, such as 40K, 238U and 232Th

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European Journal of Applied Sciences, Volume 8 No. 6, December 2020

Services for Science and Education, United Kingdom 13

radionuclides, are of great interest [2].When these are concentrated by human activity, the naturally- occurring radioactive materials become technologically-enhanced NORMs or simply called TENORMs.

Technologically occurring radioactive material represents the unintentional exposure to natural

sources of radiation which would not exist without the technological activity [3].

Non-ionizing radiation has low energy that is not sufficient to knock off an orbital electron from the

atom of matter through which it passes, though the electrons can be taken to higher energy level.

Examples are radio frequency waves such as the third, fourth and fifth generation frequencies (3G,

4G, 5G), infrared and visible light radiations. The World Health Organization (WHO) and the

International Telecommunication Union (ITU) recommended adoption of the radio-frequency

exposure limits developed by the International Commission on Non-Ionizing Radiation Protection

(ICNIRP) as reviewed and updated in 2018. Expert groups and public health agencies such as WHO and

ICNIRP broadly agreed that no health risks have been established from exposure to low radio signals

used for mobile communications [4]. Antenna Bureau in the Netherlands has refuted conspiracy

theorist that 5G tests harmed birds [4]. However, according to [5], the laboratory tests performed

provided the best scientific understanding of the effects of wireless radiation, but did not reflect the

real-life environment in which wireless radiation systems operate, hence they reported that high

frequency, radiofrequency spectrum from recent reviews can result in carcinogenicity. This assertion

is not in agreement with WHO, ICNIRP, ITU, positions. In recent time many cancer related illnesses are

being associated to all forms of non ionizing radiations but it has been speculations and without

scientific proof.

It is only ionizing radiation that has the ability to penetrate a living cell and to damage the chemical

compositions of the cells resulting in carcinogenicity. NORMs can be found in (1) Human bodies, (2)

Living-places, (3) domestic products, and (4) in the food we eat. Soil, water and air, are the common

media for naturally occurring radioactive materials transfer process. The primary sources of natural

ionizing radiations are the cosmic rays and terrestrial radiation. Radon gas can find its way into human

body through ingestion and inhalation. The Cosmic rays from the Sun and galaxy, terrestrial radiation

from the Earth crust, and incorporation of radioisotopes from the biosphere summarize the

undesirable exposure all over the world [6]. The exposure of human beings to ionizing radiation from

natural sources is a continuing and inescapable feature of life on earth and it exceeds that from all

man-made (artificial) sources combined [6]. Artificial sources include industrial, medical and nuclear

fuel cycle. Scientists have conducted studies on exposures and activity concentrations at different

locations and reports of such previous studies are found in [7], [8], [9], [10], [11]. The Assessment of

Ionizing Radiation Risks associated with Gamma Radioactivity in Oraifite is an original research work

and has not been previously conducted hence the primary aim of the study was to investigate certain

health parameters. Hence the need to evaluate radiological indices in that locality to provide useful

base line data through measurement of background ionizing radiation (BIR) and activity concentration

in soil samples. Therefore in agreement with [12], measurement of natural radioactivity in soil is very

important to determine the amount of change of the natural background activity with time as a result

of any radioactivity release that may alter the natural ecosystem.

2 Materials and Methods.

2.1 Study Area

Oraifite is politically located in Anambra State of the South East of Nigeria. Geographically, it lies

between Latitude 5.90 o and 6.04o N to 6.00o and 6.87o E and geologically Oraifite is in Nanka Formation

under Bende Ameki Group. The Ameki Group and the overlying Ogwashi-Asaba Formation in the

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Anekwe, U.L. Assessment of Ionizing Radiation Dose and Risk Levels associated with Radioactivity in Oraifite,

Nigeria. European Journal of Applied Sciences, Volume 8 No 6, Dec 2020; pp:12-26

URL: http://dx.doi.org/10.14738/aivp.86.9119 14

Southern Benue Trough and Anambra Basin are correlative with the Agbada Formation in the Niger

Delta [13]. Ameki Group is in the Niger Delta and there are three principal lithostratographic units

based on the dominant environment of deposition in ascending order of Akata, Agbada and Benin.

The Agbada Formation mainly consists of sequence of sandstones and shales. The sandy unit

constitutes the hydrocarbon reservoir in the Niger Delta oil fields while the shales form the seal [14].

This Formation consists of sand in which grain size increases upwards and the gamma radiation from

natural radionuclides in the upper layer is often higher than in the underlying marine clays [15]. Oil

exploration took place in Oraifite along the Unodu coastal area in the 1990s but there was no evidence

of hydrocarbon deposit in commercial quantity. According to [16] the Niger Delta has the same

geomorphology as the region of Bight of Biafra for which Oraifite is a part. The study area is made up

of four quarters or districts for convenience namely; Unodu, Ezumeri, Irefi and Ifite with sample codes

UNO, EZU, IRE and IFI respectively. Socio-politically, the ancient natives were mainly peasant farmers,

wine tappers, fishermen and petty traders. At the moment, with high level of western education a lot

of people have abandoned the traditional farming and other work practices and are involved in oil and

gas activities and corporate business as they migrate to cities. Industrial and economic activities in the

area include bottled and Sachet water packaging, saw-milling, wine tapping, ion welding and

fabrication, etc. Figure i is the Google map showing the study area.

Figure-1: Google map of the study area

2.2 Background ionizing radiation measurement

The BIR exposure rate measurement was done in situ in accordance with the world best standard

procedure as applied by [17]. A Radalert 100X radiation monitoring meter with Geiger counter was

used. The meter detects alpha, beta, gamma and X-ray radiations. The meter detector is a halogen- quenched Geiger-Mueller tube with mica end window LND712 of density 1.5 - 2.0 mg/cm2 and side

wall of 0.012 inches #446 stainless steel. Its maximum alpha and beta efficiencies are 10% and 15%

respectively and it operates within temperature range of -20o C to 50o C and -4o to 122o

F. The radiation

meter manufactured by S.E. International Incorporation, Summer Town, USA was calibrated with a

137Cs source of specific energy with high accuracy display switchable to count per minute (CPM), milli

Roentgen per hour (mR/hr) and micro Sievert per hour (μSv/hr). As a choice the meter was set to