Biological Radiation Hazards PDF

Biological Radiation Hazards Lec 4 & Lec 5 ‫ آيه محمد كنانه‬.‫د‬ 5.Leukemia Leukemia: is cancer of the white blood cells. White blood cells help your body fight infections. Blood cells are made in the bone marrow. In leukemia,however, the bone marrow produces abnormal white blood ce...

Biological Radiation Hazards Lec 4 & Lec 5 ‫ آيه محمد كنانه‬.‫د‬ 5.Leukemia Leukemia: is cancer of the white blood cells. White blood cells help your body fight infections. Blood cells are made in the bone marrow. In leukemia,however, the bone marrow produces abnormal white blood cells. These cells crowd out healthy blood cells, making it hard for blood to do its work. The incidence of radiation leukemia is influenced by age at the time of exposure. The youngest person at the time of exposure, the shorter the latency and the risk period for developing leukemia. The incidence of leukemia decreases with increasing age at the time of exposure; however, the increased risk of the older individual is for a greater period of time. When leukemia develops, the body produces large numbers of abnormal blood cells. Leukemia can arise in either of the two main types of white blood cells. When leukemia affects lymphoid cells, it is called lymphocytic leukemia. When myeloid cells are affected, the disease is called myeloid or myelogenous leukemia. Leukemia development cells blood spread rapidly and destroy living tissue. It grows/invades the bone marrow which is the factory of blood and replaces normal blood elements with cancer cells. Cancer cells replace all bone marrow cells which causes infection and bleeding problems. Blood cancer is basically white blood cells that don't work well and cause trouble. Healthy blood Leukemia Fig1: Normal blood vs leukemia Characteristic chromosomal aberrations and alterations in gene expression induced by radiation have been identified in patients with a variety of leukemias. Leukemia first appeared in the atomic bomb survivors 2 to 3 years after the nuclear detonations and reached a peak incidence 10 to 15 years after irradiation. The average latency period for leukemia is thought to be 2 to 20 years. Radiation dose has been described as a double edged sword. On the one hand, radiation itself is a useful tool for research; medical diagnosis and therapy, and on the other hand, radiation exposures, especially at high levels, can lead to increased frequencies or severities of various adverse health effects. Leukemia cells also can collect in the testicles and cause swelling. Also, some patients develop sores in the eyes or on the skin. Leukemia also can affect the digestive tract, kidneys, lungs, or other parts of the body. Latency period : The time between being exposed to radiation and having symptoms depending on the intensity dose. Leukemia induction etiology Thorotrast exposure has also been linked to leukemia induction. Thorotrast is a contrast medium, that contains thorium-22 and decays by radiation emission. It was used in diagnostic radiological procedures between until 1955. Also gamma radiation exposure, can also induce leukemia. Leukemia types In most types of leukemia, the abnormal cells are white blood cells. There are several types of leukemia. They are grouped in two methods, one way is by how quickly the disease develops and gets worse, the other way is by the type of blood cell that is affected. The exposure to high doses of radiation over short periods of time producing acute or short term effects. -acute leukemia: rapid increse in immature blood cells. (High doses can kill so many cells that tissues and organs are damaged.This in turn may cause a rapid whole body response often called the Acute Radiation Syndrome). The exposure to low doses of radiation over an extended period of time producing chronic or long term effects. - chronic leukemia: excessive build up of relatively mature.( low doses tend to damage or change cells. Low doses spread out over long periods of time don’t cause an immediate problem to any body organ. The effects of low doses of radiation occur at the level of the cell, and the results may not be observed for many years). Deterministic effects of ionising radiation Deterministic effects (non-stochastic) is the relationship between the absorbed radiation dose and the effect intensity, has a threshold (0.1 Gy and higher). Includes this type of effects : 1.Local tissue damage: only part of the body is irradiated, in contrast with whole-body irradiation, appear after months from the initial exposure or several years after a sequence of exposures, depending on the type of tissue and dose intensity. The severity of a deterministic effect increases as the dose of exposure increases and considers a minimum threshold, below which no detectable clinical effects occur. This type of effect is predictable and reproducible. For example, localized doses to certain parts of the body at increasing levels will result in the same biological effects. These effects are caused by severe cell damage or death. Individuals who experience the physical effects of this cell death do so when it is large enough to cause significant tissue or organ impairment. The deterministic effects in tissue are short-term, adverse tissue reactions resulting from a dose that is significantly high enough to damage living tissues. The severity of a deterministic effect increases with radiation dose above a threshold, below which the detectable tissue reactions are not observed. Radiation energy is not spread diffusely throughout the tissue; rather, the energy radiation penetrate into localized areas of tissue, affecting only the cells contacted by the rays. Whether a cell dies immediately or develops molecular changes depends upon the dose of radiation and the length of exposure. Molecular changes in a cell are reflected in its ability to grow and divide ability. When the radiation dose is high, cell death is rapid and extensive; there is usually no reserve tissue left to replace that damaged. The local tissues most affected by radiation such as, the lining of the gastrointestinal tract,the other slower-growing tissues, such as those of the brain and liver, require either high doses of radiation or longed exposure before they show symptoms of degeneration. To produce a radiation response in humans within a few days to months, the dose must be high, such a response is called an early effect of radiation exposure. Early radiation responses are described as deterministic, those that exhibit increasing severity with increasing radiation dose. The overall direct complications of radiation: Cell depletion and inability to reproduce new tissue. Lessened body resistance to infections. Body poisons from tissue breakdown, and a slower blood-clotting time. Anemia. 2. Somatic effects: are harm that extends to the level of the body's organs, such as sterility, cataract and severe and direct damage to the internal organs of the body. 3. Hematologic effects: The usual stae of blood reaction to radiation is leukopenia, but may effect on other types of blood cells cases some damagesm such as ,anemia, lymphopenia, and loss of specific immune response. The radiation dose–response relationship It is relationship between exposure and response , describes the magnitude of the response of an organism, as a function of exposure after a certain exposure time. Stochastic Deterministic effects effects No effect Fig2: Dose–response relationships curves. 4. Temporary Epilation (hair loss): Epilation (hair loss) results from depletion of the germinal layers of hair follicles. Single doses of 3 – 6 Gy might result in temporary loss of hair after about 3 weeks. Re-growth occurs after approximately 8-12 weeks. The doses in excess of 7 Gy may irreversibly damage the hair follicle, and permanent epilation of the affected follicles ensues. 5. Dry Desquamation: If the radiation dose exceeds about 8 – 12 Gy, the main Erythema may progress to dry desquamation of the skin within 25-30 days. 6. Moist Desquamation: If the radiation dose is even higher i.e 15 – 20 Gy, blistering and sloughing of the superficial skin (moist desquamation) occurs within 20-28 days. At radiation dose above 25 Gy necrosis develops in 3 weeks.