ESTIMATION OF RADIATION DOSES DUE TO EXPOSURE TO GAMMA RADIATION FROM FOOD SPICES

ESTIMATION OF RADIATION DOSES DUE TO EXPOSURE TO GAMMA RADIATION FROM FOOD SPICES

ABSTRACT: An external background ionization radiation has been carried out on food spices within two markets in Port Harcourt. This study was carried out in mile one market and mile three market, Port Harcourt. These background radiation readings were taken using the Radiation Alert meter and a Geographical Positioning System (GPS). The estimated values for the excess lifetime cancer risk from the two markets are higher than the required standard; also the Annual effective dose equivalent from mile one market is low, while mile three market is higher than the world accepted value. The average absorbed dose rates are higher than the world accepted value which is 84nGy/h. The average exposure rate from the two markets is higher than the world acceptable standard which is 0.013 mR/h. The absorbed dose rate and excess lifetime cancer risk exceeded the safe limit for the general public.

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CHAPTER ONE

INTRODUCTION

• Background of the Study

Encountered in everyday activities in various forms and different intensities is radiation. Radiation has been found to be beneficial and harmful. Some of the harmful effects are: cataract, gene mutation, destruction of bones and blood cells and it cause the death of an individual (Jwanbot, 2011). These radiations come from three main sources namely: Cosmic radiation, terrestrial radiation and radioactivity in the human body (Ike, 2003). It is the spontaneous decay of the nucleus of heavy isotope that leads to the emission of radiation. Some of these decay include radium which is a radioactive element with the isotopy of. The Radon is broken down into radium to emit electron with a higher amount of energy liberated in the system, the Thorium is decomposing to pallidum with the emission of a higher amount of energy some uranium the decompose to Thorium and Helium in the presence with a high amount of energy.    

In Nigeria, outdoor background ionizing radiation profile has received much attention than indoor background ionizing radiation, even though studies have established the presence of dangerous background ionizing radiation within a building.

Some of the materials used in the construction of a building are known to be radioactive (Hayambu et al: 1995). Indoor air often contains the harmful radioactive gas, radon (²²²Rn). Generally, indoor air has a higher concentration of radon than outdoor air.

Due to a change in lifestyle, people spend in more time indoor than outdoor. Surveys taken by the World Health Organization (WHO 1997) and the interaction commission of Radiological protection (ICRP 1993) show that residents of temperate climates spend only about 20% of their outdoors and  80% indoors (their home, officers, schools, and buildings) (Chad-Umoren et al; 2007). The implication of these statistics is obvious; the probability of exposure to dangerous radiation is higher indoors than outdoors.

Indoor background ionizing radiation profiles of a building are therefore crucial since they enable us to assess the level of risk of exposure to the regular users of such buildings. It has been established that chronic exposure to even how dose rate of nuclear radiations from an irradiated building has the potential to induce cytogenetic damage in human beings (Chad-Umoren et al, 2007), of particular concern for indoor background ionizing radiation is the incidence of the invisible, odourless, colourless, radioactive gas ²²²Rn which is a member of the uranium radioactive series. Estimates show that of the 2.4m SV/yr annual exposure from all ionizing sources. 40% is contributed by internal exposure to radon between radon exposures (inhalation) and the prevalence of lung cancer has also been reported (Chad-Umoren et al 2007, Anyakorah, 2010).

Radon -222 results from the radioactivity of Uranium-238 and itself decays with a half-life of 3.82 days. When it is inhaled it penetrates into the lung. Its most dangerous daughters are the two emitter ²¹⁸Po and ²¹⁴Po which emits two particulars with the energy of 6.0 MeV and 7.69Mev respectively. The continuous deposition and interaction of such high energy particles with the lung lends to its damage and the incidence of lung cancer. ²²²Rn kinds its way convection and through the soil hinder the building.

Human beings are exposed o background radiation that stems both from natural and man-made source. In general, approximately 85% of the annual total radiation dose of any person comes from natural radionuclides of both terrestrial and Cosmogenic origin (Believermis et al 2010; NCRP 1994; UNSCEAR 2000)

Soil radionuclide activity concentration is one of the main determinants of the natural background radiation a number of decay products of Th and U series and ⁴⁰k is the main component of external gamma radiation which exposes the public is attributed to the progeny of U series and ²²²Rn. The worldwide annual effective dose from natural sources is estimated to be 2.4 mSv (UNSCEAR 2000).

Natural radionuclide of the uranium –radium and the thorium series, as well as ⁴⁰k, are distributed in the soil almost homogenously, regardless of the depth, their concentration depends on local geological conditions. Each year there are seasonal changes in the gamma radiation dose rate value. Additionally, daily changes and changes caused by precipitation are observed. Their changes are due to differences in an exhalation of radon from soil and in the case of precipitation- washing out radon Isotopes from the air and deposition on the soil surface (Bienaoka et al; 2004).

As a result, a nuclear explosion carried out in the earth’s atmosphere are Chernobyl nuclear power station accidents, the world has become polluted with radionuclides of artificial origin. Some of these long-lived isotopes (e.g ¹³⁷Cs) are still eminent in the environment predominantly in surface soil, as a result of radioactive fallout from the atmosphere (Celit et al; 2008).

Radioisotopes that are present in soil significantly affect terrestrial gamma radiation levels. In the last decade, severe studies were carried out to assess the average outdoor terrestrial gamma dose rate air (Taskin et al., 2009; Radenkovic et al., 2009, Beliermis et al., 2010; Baykara and Dogru 2009; lee et al., 2009; Raheem et al., 2008; Ngachinetal. 2008; Jankovic et al., 2008; Degerlier et al., 2008; Psichoudak and papaefthymmiou, 2008; El-Taher et al., 2010; Al-Hamarneh and Awadallah 2009; Nada et al., 2009).

• Statement of the Problem

All forms of energy harnessed to support human activities which cause an environmental impact in one form or the other.

In this research, the rate at which some food spices were exposing and most time attracting flies or making the buyers sneeze when purchasing the spices for consumption, which sometimes causes serious health problems the body.

• Aim and Objectives

The aim of this work is to measure radiation exposure area of food spices area of some major markets in Obio/Akpor Local Government Area in order to quantify radiation doses to organs of exposed this can be achieved through the following objectives:

1. In-site measurement of radiation exposure rate of food spices area of some markets in Obio/Akpor L.G.A
2. Assessment of some radiological health risks parameter i.e absorbed dose, annual effective dose, equivalent dose excess lifetime cancer risk.
3. Radiation contour mapping of the area.

• Importance of the Study

The study of radiation can be emitted by a radioactive substance or generated electrically. This treatment is very significant in the use of improving food and food spices safety by extending products by preservation, reducing the risk of foodborne illness, delaying or eliminating sprouting, sterilization of food and food spices as a means of controlling insect and invasive pest. Food Irradiation primarily destroys organisms responsible for spoilage and foodborne illness and inhibiting sprouting. The food and drug administration (FDA) still requires that the specific food be thoroughly tested for irradiation safety.

• Scope of the Study

The work is to determine the background radiation from food spices in mile one and mile three market and to measure their radiological parameter, so as to ascertain the level of exposure to radiation.

• Study Area

The study was carried out in mile one and mile three market Port Harcourt, Rivers State to measure the exposure rate on food spices. The area lies along latitude 4⁰ 47’ N & 4⁰ 48’ N and longitude 6⁰ 59’ E and 6⁰ 59’ E. The area experiences wet and dry seasons which are typical seasons in Nigeria.

FIG 1.1: Map of the Study Area.