# biological effects of ionizing radiation

The cell can go into an irreversible state of dormancy, known as senescence. A dose unit more closely related to effects in biological tissue is called the roentgen equivalent man or rem and is defined to be the dose in rads multiplied by the relative biological effectiveness. For both cancer and genetic defects, the approach to safety has been to use the linear hypothesis, which is likely to be an overestimate of the risks of low doses. Any dose less than 100 mSv (10 rem) is called a low dose, 0.1 Sv to 1 Sv (10 to 100 rem) is called a moderate dose, and anything greater than 1 Sv (100 rem) is called a high dose. A radiation dose unit called the rad is defined in terms of the ionizing energy deposited per kilogram of tissue: $1 \, rad = 0.01 \, J/kg.$, The SI unit for radiation dose is the gray (Gy), which is defined to be $$1 \, Gy = 1 \, J/kg = 100 \, rad.$$, To account for the effect of the type of particle creating the ionization, we use the relative biological effectiveness (RBE) or quality factor (QF) given in, Particles that have short ranges or create large ionization densities have RBEs greater than unity. The effects of ionizing radiation may be directly proportional to the dose in rads, but they also depend on the type of radiation and the type of tissue. No biological effects in individuals have ever been documented as being due to levels of ionizing radiation employed for medical diagnosis. The cell can go into unregulated cell division leading to tumors and cancers. Fertilizers containing phosphates have potassium and uranium. Worst effects due to malfunction of small intestine and blood systems. Worse yet, plutonium has a long radioactive half-life and is not readily eliminated by the body, and so it will remain in the lungs. You need to follow certain steps for dose calculations, which are. For ionizing radiation, the kinetic energy of particles (photons, electrons, etc.) The rate of DNA repair depends on various factors such as the cell type and age of the cell. All effects of radiation are assumed to be directly proportional to the amount of ionization produced in the biological organism. 32.2: Biological Effects of Ionizing Radiation, [ "article:topic", "authorname:openstax", "quality factor", "high dose", "low dose", "moderate dose", "relative biological effectiveness (RBE)", "roentgen equivalent man (rem)", "gray (Gy)", "gray", "Gy", "linear hypothesis", "rad", "sievert", "relative biological effectiveness", "RBE", "rem", "hormesis", "license:ccby", "showtoc:no", "program:openstax" ], 32.3: Therapeutic Uses of Ionizing Radiation, Creative Commons Attribution License (by 4.0). This is called the linear hypothesis and it may be prudent, but it is controversial. The energy needed for a single ionization is a few eV, or less than $$10^{-18} \, J$$. Medical images with radiopharmaceuticals give doses ranging from 1 to 5 mSv, usually localized. Fatal within hours due to collapse of central nervous system. This work is licensed by OpenStax University Physics under a Creative Commons Attribution License (by 4.0). Thus, the exposure to the public can vary greatly, even within short distances. In human cells, we can have as many as a million individual instances of damage to DNA per cell per day. Doses from most medical diagnostics have decreased in recent years due to faster films that require less exposure time. Immediate effects are explained by the effects of radiation on cells and the sensitivity of rapidly reproducing cells to radiation. knowledge a reasonable presumption is that increased exposure to radiation carries an increased probability of subsequent "stochastic" health effects. (credit: Andrew Kuchling ) (b) Now that we know the effects of exposure to radioactive material, safety is a priority. Even the linear hypothesis estimates of the risks are relatively small, and the average person is not exposed to large amounts of radiation. For example, the eyes are more sensitive to radiation, because the cells of the lens do not repair themselves. Note that the RBEs are 1 for higher-energy $$\beta$$s, $$\gamma$$s, and x-rays, three of the most common types of radiation. Animal studies do not seem to correlate well with effects on humans and are not very helpful. Watch alpha particles escape from a polonium nucleus, causing radioactive alpha decay. How many Gy of exposure is needed to give a cancerous tumor a dose of 40 Sv if it is exposed to α activity? Laws regulate radiation doses to which people can be exposed. Oxygen involvement in thiol free radical reactions has been implicated in oxygen radiosensitization of cells to the lethal effects of radiation. Limited survival. By any standard, this yearly radiation dose is high and will have a devastating effect on the health of the worker. The isotope $$^{123}I$$ is more difficult to produce, but its short half-life limits thyroid exposure to about 15 mSv. The incidence of genetic defects induced by radiation is about one-third that of cancer deaths, but is much more poorly known. Its actual hazard depends on how likely it is to be spread out among a large population and then ingested. Cells in the lining of the digestive system also rapidly reproduce, and their destruction causes nausea. Diagnostic doses are generally low and have further lowered with improved techniques and faster films. Many countries have introduced limits on allowable radon concentrations in indoor air, often requiring the measurement of radon concentrations in a house prior to its sale. Positive effects may occur at low doses that could be a problem at high doses. Dose in rem is defined by 1 rad = 0.01 J/kg and rem = rad × RBE. The SI equivalent of the rem is the sievert (Sv), defined to be, Whole-body, single-exposure doses of 0.1 Sv or less are low doses while those of 0.1 to 1 Sv are moderate, and those over 1 Sv are high doses. Significant reduction in blood cell counts, brief nausea and vomiting. However, if the range of the radiation is small, as it is for $$\alpha$$ paticles, then the ionization and the damage created is more concentrated and harder for the organism to repair, as seen in Figure $$\PageIndex{1}$$. See how random decay times relate to the half life. The developing embryo and fetus are extremely sensitive to ionizing radiation. Concentrated damage is more difficult for biological organisms to repair than damage that is spread out, so short-range particles have greater biological effects. A short half-life will produce many more disintegrations per second. The isotope 123I is more difficult to produce, but its short half-life limits thyroid exposure to about 15 mSv. Recall that 1 mSv = 1 mGy × RBE(or 1 rem = 1 rad × RBE). As the average value a brief look at molecules within cells and how cells operate when an is! Of one or more steps, depending on the health of the radiation after if! 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