Radioactivity can be defined as the spontaneous disintegration of nucleus of an atom with an emission of alpha, beta particles and gamma ray. The radiation burden of the environment is constantly being enhanced by ionizing radiations from natural sources and their transfer to flora and faunas as have been noted by many researches (Badran, et al., 2003; Velasco, et al., 2004; Eyebiokin, et al., 2005 and Akinloye and Olomo, 1995).
Radiation plays an important and sometimes vital role in our everyday lives, every day we are exposed to naturally occurring quantities of radiation. We get exposed to naturally occurring radioactive materials (NORT) through the air we breathe, the food we eat, the soil we walk on and the water we drink and even within our bodies (Ademola 2008). Monitoring these radioactive materials is therefore of primary importance for human and environmental protection but rapid and accurate method for the assessment of radioactivity is essential (El-bahi 2004). There are over 60 radionuclide (radioactive elements) can be found in nature and are generally classified into three; the Primordial- those formed before the creation of the earth, the cosmogenic – formed as a result of cosmic rays interaction and the artificial radionuclide- these formed due to human action or activities (Eyebiokon et al., 2005)
The series naturally occurring radionuclide are found in food chain are Uranium -238 and Thorium 232 and their progenies while the non-series one is the Potassium-40 (40K). Potassium-40 is the principal naturally occurring source of internal radiation, despite it low isotopic abundance (ICRP, 1994). The deleterious radiological health hazard posed by human activity especially in energy production, research, medical application of nuclear facilities and oil and gas extraction and production have attracted great concern and tremendous interest in radiation protection (Arogunjo, et al., 2004).
Dietary paths ways become contaminated with radioactive materials from these man-made applications during routine operation. Since radioactivity was first discovered, there has been concern regarding the damage that it might pose to humans, living creatures and the environment. Many studies have been dedicated to monitoring amounts of radionuclides activity in food and nutritional supplements, particularly related to the human diet, seeking to determine the risks those amounts may bring Concern with radiation levels in food samples is also very important, because ingestion is one of the most common way radionuclides enter living organisms.
Radionuclides are chemical elements with unstable atomic structures called radioactive isotopes. The unstable structures breakdown to release or emit radiation energy from the nucleus or other parts of the atom. Three types of radiation can be released: alpha particles, beta particles and gamma rays (photons). Most naturally occurring radionuclides are alpha particle emitters (uranium-231 and radium-226), but some beta particle emitters also occur naturally (radium-228 and potassium-40). Manmade radionuclides are mainly beta and photon (gamma) emitters. Tritium is a beta particle emitter that may be formed naturally in the atmosphere or by human activities (OEPA, 2005). Radiation being energy emitted when a radionuclide decays, it can affect living tissue only when the energy is absorbed in that tissue. Radionuclides can be hazardous to living tissue when they are inside an organism where radiation released can be immediately absorbed. They may also be hazardous when they are outside of the organism but close enough for some radiation to be absorbed by the tissue. Radionuclides move through the environment and into the body through many different pathways: air, water (both groundwater and surface water) and the food chain. Knowing these pathways make it possible to take necessary control measure to reduce their intake by aquatic animals, terrestrial animals and human beings to minimal levels.
Radionuclides enter the human body through complex mechanism including foodstuffs via the food chain from natural sources. The season of the year determines to a great extent the magnitude of contamination of different foods (IAEA, 1989; Strand et al., 2002). Green leafy vegetables are very prone to external contamination during the raining season, while roots and tubers may also become contaminated (Badran et al., 2003). Grain are subjected to contamination mostly during storage and if fallout occurs during the growing season. Radionuclides may be transported into grains through the plant growth. The most predominant naturally occurring radionuclides in foodstuffs is 40K, Other contributions to the radio-nuclides in foods include deposited fallouts from fission and activation products released during nuclear accidents and constituents of weapons tests released after detonation. This work is aimed at assessing the radioactivity concentration of some staple food in Uvwie and Warri south local government areas in Delta State, Nigeria.
1.1. BACKGROUND OF STUDY
The radiation burden of the environment is constantly being enhanced by ionizing radiations from natural sources and their transfer to flora and faunas have been noted by many researchers (Badran, et al., 2003; Velasco, et al., 2004; Eyebiokin, et al., 2005 and Akinloye and Olomo, 1995). The deleterious radiological health hazards posed by human activities, especially in the production of energy (oil and gas exploration and exploitation), research and medical applications of nuclear facilities have attracted great concern and tremendous interest over the years in the field of radiation protection (Arogunjo, el al., 2005). Dietary pathways become contaminated with radioactive materials from naturally enhanced radionuclide and man-made applications during routine operation, accidents, and migration of radionuclide from radioactive waste deposal repositories into the biosphere (Tang, et al., 2003). This androgenic contribution gained prominence after the Chernobyl nuclear power plant accident on 26 April 1986 when large quantities of radioactive substances were released to the environment, which eventually found their way into the fishes organs from contaminated water bodies, soil and vegetation (Tang, et al., 2003, Rhaman and Voigt, 2004; Arogunjo et al., 2005). Contamination of the human food chain occurs as a result of direct deposition of this radionuclide on fauna from contaminated soil or water, and animas ingesting contaminated plants, soil or water. Considerable efforts are being made by researchers in many parts of the world to measure the activity of radionuclide in the rivers and sea faunas and the estimated of their deposition in human organs and tissues as a result of the consumption of these fauna from radionuclide contaminated water (Hakonson-Hayes, et al., 2002; Badran, et al., 2003; Tang, et al., 2003; Velasco, et al., 2004; Avwiri et al,. 2005; Uchida and Tagami, 2007). Some radioisotopes are only found on the earth as a result of human activity, they are Stontium-90 (90Sr), Cesium- 137 (137Cs), Iodine-131 (131I) and Technetium-99 (99TC), and some Isotope like Potassium-40 (40K) is only present due to natural processes, a few isotopes are present as a result of both natural processes and human activities e.g tritium (3H). The concentration and location of some natural isotopes, particularly Uranium-238 (238U), can be affected by human activity (Wikipedia, 2009). There have been claim of loss of endanger species of aquatic organisms, health problems due to the consumption of fish and other faunas from Worlds ocean, water pollution and other health related radiation and radioactivity induced sicknesses. The biological effects of radiation on marine animals will be essentially the same as they are humans. Both would have the same long-term risks, which are a very slight increase in the risk of cancer, all humans have a risk of dying from cancer. About 19% to 23% of us will die from cancer, even if we are never exposed to radiation levels above natural background levels. According to the American Cancer Society’s website there would be no giant or super sea creatures produced by the dilute amounts of natural, man-made radioactive material found in seawater. Also, there is essentially no increase in mutations in the generations the follow the exposure of the parent animals. Because the radioactive material in the ocean is so dilute and the water itself absorbs radiation and is a very good shielding material, very little if any exposure will be from the water outside the animal. Essentially all exposure will be from radioactive materials ingested by the animal.
1.2. STATEMENT OF PROBLEM
Radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is an atom that has excess nuclear energy, making it unstable. This excess energy can either create or emit from the nucleus, new radiation (gamma radiation) or a new particle (alpha particle or beta particle), or transfer this excess energy to one of its electrons, causing it to be ejected (conversion electron). Radionuclide which emit radiation are found naturally in air, water and soil. Natural radioactivity is common in materials that make up our planet, in waters and oceans, and rock. A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is an atom that has excess nuclear energy, making it unstable. This excess energy can be either emitted from the nucleus as gamma radiation, or create and emit from the nucleus a new particle (alpha particle or beta particle), or transfer this excess energy to one of its electrons, causing that electron to be ejected as a conversion electron. During those processes, the radionuclide is said to undergo radioactive decay. Radionuclides that find their way into the environment may cause harmful effects as radioactive contamination, Potential health damage from exposure to radionuclides depends on a number of factors, and can damage the functions of healthy tissue/organs. Radiation exposure can produce effects ranging from skin redness and hair loss, to radiation burns and acute radiation syndrome. Prolonged exposure can lead to cells being damaged and in turn lead to cancer. Signs of cancerous cells might not show up until years, or even decades, after exposure. (Ionizing radiation, health effects and protective measures“. World Health Organization. (2012; 2014).
Unplanned exposure to radionuclides generally has a harmful effect on living organisms including humans, although low levels of exposure occur naturally without harm. The degree of harm will depend on the nature and extent of the radiation produced, the amount and nature of exposure (close contact, inhalation or ingestion), and the biochemical properties of the element; with increased risk of cancer the most usual consequence. However, radionuclides with suitable properties are used in nuclear medicine for both diagnosis and treatment.
1.3 JUSTIFICATION OF THE STUDY
A preliminary assessment of Naturally Occurring Radioactive Material (NORM) found in staple food crops within Warri south local government would be the main purpose of the research work using the Gamma spectrometer (sodium iodide detector) for analysis of the thirteen (13) selected staple food to determine the background ionization radiation level of the study area and the food crops samples. The study would ascertain the level of rising radiation level as it affects the consumption of these staple foods though within the acceptable limit for the general public and within the safe limit for radiological workers. Other analytical methods of ascertaining the exposure rate such as Hyper Pure Germanium (HyGe) detector to know the specific radionuclide responsible for the contamination and pollution of these foodstuffs. The study hopes to establish the relevance of knowing the effect of Naturally Occurring Radioactive Material (Norm) on commonly consumed staple food and its effect on human after consumption of these food stuffs.
1.4 AIM & OBJECTIVES OF THE STUDY
This work is aimed at assessing the radioactivity concentration of some staple food consumed in Uvwie and Warri South local government and effect on human after consumption, with the following objectives;
- Ø To measure radioactive contaminants in some staple foodstuffs consumed in Uvwie and Warri south local government areas of Delta state.
- Ø Determination of naturally occurring radionuclide’s in foodstuffs sample.
- Ø Analyzing the result to ascertain the radiological implication on the people consuming these foods stuffs.
- Ø To make recommendation that will help guide the ongoing project.
- Better understanding of the nature of distribution of radionuclide’s in food stuff in Delta State.
Addition of new findings to existing baseline data.
1.5. LIMITATION OF THE STUDY
This research is born out of the concern for the increasing case of food related sicknesses which are mostly attributed to the content of staple food consumed. The radionuclide content of these food are becoming a growing concern also due to the indiscriminate application of fertilizers that are radionuclide laden. This research work therefore intended to examined as many as possible the most of the consumed stapled food. But for time and financial constraint, this work is restricted to only thirteen major staple food item in the studied area.
1.6. STUDY AREA
The study samples are restricted to staple food consumed in Uvwie and Warri south local government area of Delta state. Delta State is an oil and agricultural producing state of Nigeria, situated in the region known as the South-South geo-political zone with a population of over 4 million, the capital city is Asaba located at the Northern end of the state with an estimated area of 762 square kilometers (294sqm) while Warri is the economic nerve center of the state and also the most populated in the Southern end of the state. The state has a total land mass of about 18,050km2, of which more than 60% is land. The state covers approximately between the longitude 5000 and 6045’ east and latitude 5000 and 6030 north. It is bounded in the north and west by Edo state, the east by Anambra, Imo States, South East by Bayelsa state and on the southern flank is the Bight of Benin which covers about 160 kilometers of the state coastline. Delta State is generally low lying without remarkable hills. The state has a wide coastal belt inter-lace with rivulets and streams. Apart from oil Delta State is rich in agricultural produce. Warri is an important seaport in the country and the commercial nerve centre of delta state, the area is predominantly riverine with large expanses of mangrove forests and has a land area approximately 1,520 square kilometers. The local government area consist of several communities namely Ode-itsekiri, Agbassa, Orugbo, Ogunu, Obodo, Igbudu, Omadino, Edjeba, Ijala, Ekurede, Ugbori, Okere, Ikpisan, Ifie-kporo, Ubeji, Ajamimogha and Alders town. According to national population census warri has over 311,970 inhabitants who are drawn from the Urhobo, Itsekiri and Ijaw extraction but also host people from varied ethnic groups around delta state and Nigeria at large. Uvwie local government is proximal to Warri south local government area with a population of approximately 251,200 is an Urhobo speaking community within headquarters in Effurun, Uvwie is also use to describe the people and their language the local government area consist of several communities.