Radiation and Biological Effects - Research Paper Example

Radiation and its Biological Effects Radiation is energy that travels in the form of high-speed particles or waves. It may either occur naturally in sunlight as well as sound waves, or may be man-made. Some forms of radiation are useful for instance in X-rays and in the treatment of cancer, killing of unwanted pathogens or peering into the body. Other uses of man-made radiation are in generation of energy for daily use (in nuclear power plants) and in fabricating nuclear weapons. While some forms of radiation are useful or beneficial, other forms, particularly high dose radiations, are associated with adverse biological effects. This paper discusses radiation and it narrows down to the biological effects of radiation. Introduction When a nucleus of an atom emits high-energy photons and particles such as gamma rays, this kind of radiation is referred to as nuclear radiation. X-rays behave in a similar way as they do gamma rays, although unlike gamma rays, they do not involve the nucleus. For this reason, in describing nuclear radiation and x-rays, the term ionizing radiation is used. While non-ionizing radiation is vital to life, excessive exposures cause tissue damage. All ionizing radiation forms have adequate energy to ionize atoms that may in return destabilize molecules within cells ensuing into tissue damage (Francis & Kirkpatrick, 538). Although radiation is useful biologically as aforementioned, for instance in the treatment of cancer due to its ability to destroy cancerous tissues, exposure of human tissue to higher energies associated with nuclear radiation has adverse biological effects – it causes severe damage to the tissues (McCall, 213). Whenever any radiation passes through a matter, it deposits energy along its path, which leads to ionization, increased temperatures, and atomic excitations. The ionization that radiation passing through living tissue causes can lead to the damage of organic molecules if the electrons are involved in molecular binding. In the event that there is the destruction of too many molecules in this manner or in the event that there is the damaging of DNA molecules, cells may either become cancerous or die (Francis & Kirkpatrick, 538). In addition to cancer induction, other biological effects include changes in the central nervous system, heritable effects, formation of cataract and early effects on body organs as well as their function (National Research Council Staff, 2). Deliberate exposure of living tissues to radiation therefore is something to be avoided unless it is utterly necessary. In fact, the World Congress on Medical Physics and Biomedical Engineering 2009 documents that extreme care is not an option whenever radiation is used and the advantages of using radiation must always be greater than harm and risk from it (111). Radiations that are associated with nuclear explosions include gamma rays, neutrons, and to a much lesser extent, beta particles. During an explosion, most of the gammas and all the neutrons are essentially generated in fusion and fission reactions. The capture of neutrons in the surrounding air, water or earth as well as in the explosion-weapon debris generates additional gamma rays in addition to a large array of radioisotopes, which comprise the radioactive fallout. Normally, both gamma rays and neutrons are strongly absorbed all over the body thereby affecting all organs (Hafemeister, 5). Francis & Kirkpatrick point out that radiation’s outcome on people’s health is dependent on the amount of radiation that living tissue absorbs as well as the biological impacts linked with this absorption (538). To explain further, radiation’s harmful biological effects are attributable to destructive ionization generated within an exposed organism’s cell bodies. In animal tissues, both neutrons and gamma rays’ mean free paths are in the order of twenty centimeters, which is the range that inflicts maximum damage to the organism. In the event that the mean free path are a few millimeters or even less, the radiation would not reach vital body organs as it would be absorbed in the skin’s surface layers. Moreover, in case the mean free path are several meters or even more, there would be no damage to organs as most of the radiation would pass through the organism devoid of interaction (Hafemeister, 5). A Radiation Absorbed Dose (RAD) refers to the unit that designates the amount of energy that is deposited on a material. One RAD of radiation deposits 0.01 joule per kilogram of material (Francis & Kirkpatrick, 538). Owing to the fact that equal energy amounts from different radiation forms do not necessarily have similar biological effects, it is important to define a parameter known as the Relative Biological Effectiveness (RBE) for each radiation as well as for each effect. The RBE denotes the ratio of the absorbed gamma radiation dose at a given reference energy to the absorbed dose of the particular radiation in question that generates the same effect (Hafemeister, 5). A multiplication of the energy dose in RADs by the RBE yields the biological dose in REMs. This unit (REM – Radiation Equivalent in Mammals) was developed to show the biological effects that radiation brings about. Different radiations cause different impacts on our bodies. For instance, compared with electrons with the same amount of energy, alpha particles lead to more biological damage because they deposit more energy per centimeter of path. 1 rad of beta particles can lead to 1-1.7 rem of exposure, 1 rad of fast protons or neutrons can result in 10 rem, and one rad of alpha particles generates 10-20 rem. The rem and the rad are almost equal for photons. While talking about typical doses, the rad and the rem are roughly interchangeable because most human exposure has to do with electrons and photons (Francis & Kirkpatrick, 538). By definition, gamma rays’ RBE is unity at the reference energy, and usually, it is only slightly energy-dependent. Neutrons’ RBE varies not only with energy but also with the type of injury. However, for the nuclear weapons’ energy spectrum, the RBE of the neutrons that instigate acute radiation injury is near unity. For this reason, in most instances, one may use rads and rems interchangeably with minimal error. In certain injuries, for instance leukemia, genetic damage and cataracts, the RBE of neutrons is significantly greater than one (Hafemeister, 5). In biological systems’ radiation exposure, genetic material DNA’s damage is the most dangerous event. Exposing living organisms’ cells to radiation may bring about chromosome aberrations or cell replication failure, culminating into carcinogenesis or mutagenesis. Radiation damage to carbohydrates, proteins and lipids has applications in treatment of drugs and food through radiation where a point of major concern is the toxicity of radiation products. It is also relevant for such effects as inactivation of enzymes (Cuyper & Bulte, 262). Generally, biological effects of radiation fall into either of the following two categories namely deterministic effects and stochastic effects. Exposure to very large radiation doses results into deterministic effects, which have a threshold dose and whose severity rises with a rise in dose. Some good examples of deterministic effects include the acute radiation syndromes whose threshold is in the range of two hundred to three hundred rads (1-2 Gy) whole-body gamma or X- radiation, skin ulceration in the range of two thousand rads (20 Gy), and skin burns in the range of two hundred to three hundred rads (2-3 Gy). Causally, deterministic effects are clearly and indisputably associated with the radiation exposure (Cember & Johnson, 333). Hafemeister asserts that serious illness starts to appear at approximately 200 rems exposure and that the effects are fatal to majority of people with exposures above 600 rems (5). Stochastic effects on the other hand take place by chance and they appear both in exposed individuals and in unexposed individuals. For this reason, they are not definitely associated with exposure to radiation. These effects include genetic mutations and cancer. Evidently, chances of the occurrence of stochastic effects increase with exposure to radiation and the probability of their occurrence increases with increasing dose. It is important to point out that although there has been documentation of increased cancer incidence among particular populations under heavy exposure to radiation, for example the early radiologists, radiotherapy patients, and survivors of atomic bomb; never has any observations of increased incidence of heritable changes been made among any human population under exposure to radiation of any dose. Moreover, either in animals or in humans, observed stochastic effects are no different in any way from the effects observed in unirradiated populations (Cember & Johnson, 333). Exposing mammalian cells to 1 Gy of low-LET ionizing radiation causes the generation of roughly one thousand tracks with 2?105 ion pairs per cell nucleus, approximately two thousand of which may be generated within the DNA itself directly. While the same high-LET radiation dose generates roughly four tracks only per cell nucleus, more intense damage emanate from the extreme ionization within each track where the track interconnects the DNA. Additionally, other than this direct effect, free radicals generated in water close to DNA (around the DNA molecule in a radius of two nm) may indirectly cause radiation damage (Cuyper & Bulte, 263). In effect, one or more kinds of damage may affect the DNA including DNA base and sugar modification, single or multiple strand breaks, and dimerisation and cross-linking. Substantial amount of DNA damage is detectable immediately following irradiation. Approximates for a clinical dose of over a thousand base damages, roughly a thousand single-strand breaks, around forty double-strand breaks in addition to cross-links with nuclear proteins and between DNA strands are often quoted (Cuyper & Bulte, 263). It is important to note that during the first millisecond following an exposure to radiation, free radicals are engaged in an array of competitive reactions. Some of these reactions result into the fixation of damage while others culminate into the scavenging and inactivation of radicals. In addition to these chemical repair processes, rejoining of DNA breaks as well as their enzymatic repair reduces the damage further through the subsequent few hours. It is therefore clear that cells possess a considerably high ability to repair DNA damages that radiation induces (Cuyper & Bulte, 263). Conclusion In case an individual is exposed to small radiation amounts over a long period, it raises their risk of cancer and can as well cause mutations in their genes, which they could pass on to their offspring who come after their exposure to radiation. On the other hand, high radiation doses over a short period can cause burns or radiation sickness whose symptoms include weakness, nausea, skin burns hair loss, as well as reduced organ function. Some radiation exposures cause premature aging or even death. Considering the fact that radiation sources are present in a wide array of occupational settings, properly control of all forms of radiation is of paramount importance in order to alleviate chances of exposure of living organisms. Works Cited Cember, Herman and Thomas Edward Johnson. Introduction to Health Physics. New York: McGraw Hill Professional, 2009. Print. Cuyper, Marcel and Jeff W. M. Bulte. Physics and Chemistry Basis of Biotechnology. New York: Springer, 2001. Print. Hafemeister, David W. Physics and Nuclear Arms Today. New York: Springer, 1991. Print. Kirkpatrick, Larry D. and Gregory E. Francis. Physics: A World View. New York: Cengage Learning, 2006. Print. McCall, Richard Powell. Physics of the Human Body. Baltimore, MD: JHU Press, 2010. Print. National Research Council Staff. Radiation Hazards to Crews of Interplanetary Missions: Biological Issues and Research Strategies. Washington, D.C: National Academies Press, 1997. Print. World Congress on Medical Physics and Biomedical Engineering 2009, Munchen. World Congress on Medical Physics and Biomedical Engineering: Radiation Protection and Dosimetry, Biological Effects of Radiation. New York: Springer, 2009. Print. Read More