Natural Radioactivity Of Some Local Food Material Like Millet, Local Rice, Guinea Corn, Maize, Beans, Dry Yam, Dry Cassava And Soya Beans

Description

ABSTRACT

The radioactivity measurements in food crops in Nigeria have been carried out in order to determine the concentration levels of natural radioactivity (⁴⁰K, ²²⁶Ra and ²³²Th). The activity concentrations of the natural radioactivity in the samples were determined via gamma-ray spectrometry using a 76 mm × 76 mm NaI(Tl) detector. Different common food crops representing the major sources of dietary requirements to the local population were collected for the measurements. The collected food crops were prepared into their different derivable composite diets using preparation techniques locale to the population. Using available food consumption data and the activity concentrations of the radioactivity, the ingestion effective doses were evaluated for the food crops like millet, local rice, guinea corn, maize, beans, dry  yam, dry cassava and soya beans, and diet types per preparation techniques. Results of the study indicate that method of diet preparation is seen to play a major role in population ingestion dose reduction especially for tuberous crops than in non-tuberous crops. The study also showed that more ingestion dose could be incurred in diets prepared by roasting techniques. The result of the study will serve as a useful radiometric data for future epidemiological studies in the area and for food safety regulations and policy implementations in the country.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• AIM/OBJECTIVE OF THE STUDY
• SIGNIFICANCE OF THE STUDY
• LIMITATION OF THE STUDY
• SUN–FREE SOURCE OF UV
• USES FOR ULTRAVIOLET LIGHT

CHAPTER TWO

LITERATURE REVIEW

• DIFFERENT METHOD OF STERILISATION
• DESCRIPTION OF ULTRAVIOLET LIGHT
• DISCOVERY OF ULTRAVIOLET LIGHT

CHAPTER THREE

METHODOLOGY

• MODE OF ACTION
• METHOD OF OPERATION
• EFFECTIVENESS UV LIGHT
• INACTIVATION OF MICROORGANISMS
• DESCRIPTION OF MAJOR COMPONENTS USED

CHAPTER FOUR

4.0      SAFETY OF THE UV LIGHT

• MAINTENANCE REQUIREMENTS FOR UV UNITS
• MONITORING UV DOSAGE
• UV RECIRCULATION SYSTEMS
• TESTING OF SYSTEM OPERATION
• SAFETY ADVANTAGES OF UV LIGHT STERILISTION
• RESULTS AND DISCUSSION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.1                                          INTRODUCTION

Natural ionizing radiation is emitted as a result of spontaneous nuclear transformations of unstable radionuclides naturally occurring in the earth’s crust (i.e. terrestrial origin) as well as those coming from outer space into the atmosphere (i.e. extraterrestrial origin). Natural radioactive materials under certain conditions can reach hazardous radiological levels. So, it is felt necessary to study the natural radioactivity in soil to assess the dose to the population in order to know the health risks and to have a baseline for future changes in the environmental radioactivity in human activities. The basic component of our life support system is considered to be in the soil, water, plants and air. These environmental components contain measurable amount of radioactivity. The specific metabolic character of the plant species may lead to accumulation of radio-nuclides in their organs which may further depend upon the physico-chemical characteristics of the soil. Therefore, there may be increased risk to human population via food chain.

The radioactivity from the phosphate ore was not grossly affected by processing during fertilizer production. They are therefore likely to be transferred to the plants when applied to them. According to the United Nations Scientific Committee on Effects of Atomic Radiation report. the greatest contribution to mankind’s exposure comes from natural background radiation.The study of natural radioactivity is usually done in order to gain the information about the present levels of harmful pollutants discharged to the environment itself or in the living creatures. It is also important to understand the behavior of natural radionuclides in the environment, because such information can be used as the associated parameter values for the radiological assessments. The soil radioactivity is usually important for the purposes of establishing baseline data for the future radiation impact assessment, radiation protection and exploration.

The fertilizers are essential in agriculture as they supply nutrients to the farming fields. The fertilizers used for plantation contain different elements including some natural radionuclides with their daughter decay products. Fertilizer use is a key factor for increasing agricultural production in Nigeria and its utilization has increased rapidly in the last four decades, mainly due to adoption of high yielding and expanding nutrient responsive cultivated land in large parts of the country. Phosphate rocks are the starting materials for the production of all phosphate fertilizers. Soil and fertilizers consists of naturally occurring radionuclides with their daughter decay products. Relatively large concentrations of natural radionuclides present in phosphate fertilizers contaminate the environment and agricultural lands during cultivation that leads to natural radioactivity of food crops like millet, local rice, guinea corn, maize, beans, dry  yam, dry cassava and soya beans. Fertilizers are considered as technologically enhanced natural radiation, which increase the environmental uranium and partially thorium concentrations in the environment.  The primary sources of elements from the environment to plants are: air, water and the soil. The radionuclides present in the environment transfer to plants through (i) uptake from soil through roots, and (ii) direct absorption through aerial parts of the plants. Presence of radioactivity in plant organs has been reviewed by various workers. There are two major pathways for human exposure to soil contamination: soil–plant–human (food chain pathway) and soil–human (incidental soil ingestion) pathways. Migration and accumulation of contaminants in the soil-plant system is complex, and assessment models commonly utilize a soil-plant concentration ratio, referred to as a transfer factor (TF), to estimate the transportation of radionuclides through the food chain. This ratio describes the amount of radionuclide expected to enter a plant from soil. The study of natural radioactivity in plants and associated radiation exposure through the specific food materials is an important study. Plant roots are naturally associated with micro-organisms, and these associations can have direct or indirect effects on the mobility, availability and acquisition of elements by plants. There are different kinds of vegetables which may be roots, stems, leaves, fruits or seeds. The radiological impact of the use of fertilizers in soil is due to the internal irradiation of the lung by the alpha particles, short lived radon-thoron progeny and the external irradiation of the body by gamma rays emitted from the radionuclides. Radon is carcinogenic to humans and responsible for main natural radiation exposure to human being.

1.2                               OBJECTIVE OF THE STUDY

The objective of the study was to estimate the value of the natural radiation of some local food material like millet, local rice, guinea corn, maize, beans, dry yam, dry cassava and soya beans.

1.3                                                   SCOPE OF THE STUDY

Natural radioactivity of food crops are the main sources of internal radiation exposure in humans. The study was carried out to evaluate the natural radioactivity concentration in several food crops grown in Bangka and Belitung Islands. Food samples collected were analyzed by means of a gamma spectroscopy for natural radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K. The annual intake of the food was estimated on the basis of their average annual consumption. Calculations were also made to determine the effective dose to an individual consuming such diets. The intakes of these radionuclides were calculated using the concentrations in foods and annual consumption rates of these food. Annual intakes of these radionuclides were as follows: ²²⁶Ra = 190.00; ²³²Th = 633.79 and ⁴⁰K = 2065.10 Bq/year.

1.4   DIFFERENCE BETWEEN NATURAL AND ARTIFICIAL RADIOACTIVITY

Some points of difference between natural and artificial radioactivity are as follows:

Natural Radioactivity                                                             Artificial Radioactivity

1. It involves spontaneous                                          1. Stable nuclei are bombarded

Disintegration of unstable                                           with high energy particles

nuclei with emission of a                                            to produce radioactive

or 13 particles or y-radiations                                     nuclides.

giving rise to new nuclide.

2. It cannot be controlled.                                       2. It can be controlled by controlling                                                                             the speed of the                                                                                         bombarding projectiles.
3. It is shown by heavy                                              3. It can be induced even in the

elements i.e., elements                                               lighter elements.

with high atomic number

and mass· number.

1.5                                              UNITS OF RADIOACTIVITY

The SI unit of radioactivity is, Bacqueral (Bq) which is defined as one disintegration per second ( dps). Earlier, radioactivity was expressed in terms of curies (C;). One curie refers to the activity of one gram of radium, and is equal to 3.7 x 1010 disintegrations per second.

1Ci = 3.7 x 10¹⁰ dps = 3.7 x 10¹⁰ Bq.

1 millicurie ( m Ci) = 3.7 x 10⁷ dps and 1 microcurie ( µ Ci) = 3.7 x 10⁴ dps

A more recent unit of-radioactivity is Rutherford (Rd).

1 Rd = 10⁶ dps.

1.6                                     NATURAL TYPES OF RADIOACTIVITY

The three common natural types of radiation from nuclear decay are;

α radiation (alpha)  – a helium atom nucleus. This is a “slow” moving particle,  with a short range in air.  Alpha particles are extremely dangerous inside the body but not very dangerous outside as they cannot penetrate the skin. The speed of αradiation is about 0.1 of the speed of light.

The radiation has two elementary positive charges and the particle has considerable mass.

β radiation (beta) – an electron  or β- ejected from the nucleus when a neutron changes spontaneously to a proton. These are moving fast, about 0.9 of the speed of light, they can get through skin and have a reasonably long range in air (about one metre ). These have only a little mass, and are negatively charged. βradiation is dangerous if ingested.

γ radiation (gamma)  ; this is a very energetic form of electromagnetic radiation. Compared to light , each bit (photon) has 1 million times as much energy ( or 1 thousand times more energy than an X-ray photon).

They travel at the speed of light. They happily travel through centimetres of lead and travel easily through air. They are a danger to the human body even when not ingested due to this penetrative ability.

Gamma radiation has no charge associated with it. Nuclear decays and reactions produce other forms of radiation as well. Some are from artificial elements, some are products of splitting atoms.

Neutrinos, antineutrinos,  , ; weird neutral particles which are emitted with electrons in beta decay. They can be ignored for the purpose of this course.

β+ ; an antielectron or positron  . It has all the same characteristics of a normal electron except for having the same charge as the proton and the disconcerting habit, if it meets an ordinary electron, of turning itself and the electron into gamma rays! (All “antimatter” will do this on meeting the matter counterpart!)

n; a neutron,- emitted as a side product of nuclear fission. Solo neutrons have a half life of about 10 minutes. They easily pass through steel plating and large doses finally have deadly consequences. Neutron bombs are fission bombs with less blast but more leaky neutrons. They therefore do less damage to factories but kill very satisfactorily.

All radiation can be absorbed to “negligible” levels by sufficient material and, of course, the further one is from the source, the smaller the received dosage.  (Recall that radiation means spreading out from a centre.  The further from that centre you are the more the radiation energy has spread out.)

Because of the energy of the radiation, radioactive sources can fog photographic film.  This technique is used to crudely monitor dosage for people who work with the materials.