INTRODUCTION
1.1: BACKGROUND OF STUDY
Centuries of dreaming, study, speculation, and experimentation preceded the first successful flight. The ancient legends contain numerous references to the possibility of movement through the air. Philosophers believed that it could be accomplished by imitating the wing motions of birds, and by using smoke or other lighter-than-air media1
. The first form of aircraft made was the kite, about the 5th century bc. In the 13th century, the English monk Roger Bacon conducted studies that led him to the conclusion that air could support a craft in the same manner that water supports boats. At the beginning of the 16th century, Leonardo da Vinci1,2
gathered data on the flight of birds and anticipated developments that subsequently became practical. Among his important contributions to the development of aviation were his invention of the airscrew, or propeller, and the parachute. He conceived three different types of heavier-than-air craft: an ornithopter, a machine with mechanical wings designed to flap like those of a bird; a helicopter, designed to rise by the revolving of a rotor on a vertical axis; and a glider, consisting of a wing fixed to a frame on which a person might coast on the air. Leonardo’s concepts involved the use of human muscular power, quite inadequate to produce flight with the craft that he pictured. Nevertheless, he was important because he was the first to make scientific proposals.The practical development of aviation took various paths during the 19th century, especially through the Wright brothers who pioneered the first flight1,2
. Since then, improvements have been continually made resulting to the present Boeing787 aircraft with a passenger capacity of about 250. But as we know that every good thing has its disadvantages, aviation also has its down sides which include but are not limited to Air crashes, flight- induced illnesses and above normal exposure to cosmic radiation- which we shall focus on in this study.
People are exposed to low doses of radiation almost every day of their lives; from the use of X-ray based equipment for the early diagnosis of disease
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, to radiation workers who make use of radiation equipments in industries; mobile phone users, to patients in the radiology department and frequent fliers who receive higher doses of radiation than infrequent fliers7
.Ionizing radiation, such as X-rays, has proved to be a double-edged sword since its discovery in 1895. Radiation is a potent mutagen (meaning it can alter genetic activity) and a carcinogen (a cancer-causing agent); however, it is also used in the diagnosis and treatment of human diseases.
Background radiation, or radiation levels in the environment, consists of cosmic radiation and radiation emitted from radioactive substances present in the ground and commercial sources7
. Thus, all living organisms are constantly receiving background radiation.Cosmic radiation is also a form of ionizing radiation and it consists primary particles (protons, electrons, alpha particles and other heavy ions) and secondary particles (neutrons). Cosmic radiation contributes to about 13 percent of natural background radiation level which is about 1 mSv per year8
. In contrast to radiation workers in nuclear industry or patients receiving diagnostic procedures who primarily receive x-rays or gamma-rays, the air crews, pilots, and frequent flyers receive radiation doses in which about 50 percent is from neutron radiation. Research has shown that neutron radiation is more damaging than x-rays or gamma-rays. The dose rate in the aircraft flying at high altitude is about 0.005 mSv/ hour. A frequent flyer travelling around 100 hours per year would receive an additional dose of about 0.5mSv.1.2: Statement of Problem
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.1.3: General Objective of Study
1.3.1: Specific Objective of Study
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1.4: Significance of Study
1.5: Scope of Study
1.6: Hypothesis
1.7: Operational Definition of Terms
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