Effects of radioactivity The effect of nuclear radiation on non-living material is mainly due to two causes: the ionization and subsequent breaking of chemical bonds and the transmutation of nuclei in some other elements.
effects on materials Transmutation requires a careful choice of steels and alloys designed to operate in radioactive environments, because it changes the chemical composition and can make them lose the necessary mechanical strength, even the concrete meets the same problems, albeit less pronounced. In addition, the nuclei are transmuted in part also radioactive, so the material, if exposed to radiation on a permanent basis, with the passage of time accumulates inside becomes increasingly unstable isotopes and radioactive. This is the main reason why nuclear power plants have a lifetime limit set (several decades), after which it must be dismantled.
radioactivity was also able to render unusable an electronic circuit based on semiconductors, transmuting the atoms of silicon and altering the doping low concentrations of elements from which they derive their electronics skills. Biological effects
The biological effect is due to hand most of ionizing properties: breaking the bond between molecules, the radiation damages cells by generating free radicals. But mostly affect large macromolecules DNA and RNA, resulting in somatic and genetic damage, and this effect is mainly produced by gamma radiation, the most energetic and penetrating alpha and beta particles.
The time at which the cells are more vulnerable than ever to radiation is that of reproduction (mitosis or meiosis), in which DNA is being copied, the core structures are dissolved and the enzymes that ensure the integrity of the material gene can not operate. The most obvious macroscopic effect of radiation on cells, then, is the slow rate of reproduction: the populations of cells and reproduce very rapidly are more vulnerable than those who do so slowly. By virtue of this fact, the organs are more sensitive to radiation bone marrow hematopoietic and lymphatic system.
level instead of the whole organism, both in humans and higher animals we see a premature aging of the body related to the total dose of radiation absorbed, both with large doses snapshots that with prolonged exposure to low levels of radioactivity.
bone marrow and blood is the tissue of the body most affected. The first consequence of irradiation is the decrease of white blood cells (leukopenia), followed by a decrease in platelets, causing bleeding and, if the damage is very serious, from the red blood cells (anemia). If the damage is not completely exterminate the hematopoietic stem cells this tissue recovers more quickly after irradiation.
lymphatic system lymphatic system In the main consequence of the radiation is infection of the lymph nodes and spleen following the death of lymphocytes present.
Digestive System The small intestine is the portion of the gastrointestinal tract radiosensitive, while the esophagus and stomach are less so. With a slight injury, the intestinal mucosal cells begin to reproduce in a discontinuous manner and secrete more mucus, which together can lead to cell death to occlusions. With increasing dose ulcers that appear on the small number of white blood cells become infected easily.
genital organs The damage can be either somatic (sterility, permanent or otherwise) that genetic. Females are more sensitive than males. The damage consists of genetic mutations that can be transmitted to subsequent generations.
nervous system The central nervous system is among the less radiosensitive tissues, while the spinal cord and peripheral nerves are more so. With high doses can be absorbed ischemia, because of damage sustained by the brain capillaries.
Thyroid and endocrine The thyroid, the pituitary gland, the adrenal and other glands are not particularly radiosensitive. For metabolic reasons, however, concentrates in the thyroid itself almost all the iodine in the body, being the most common radioactive isotope 131I, this body can absorb massive amounts of radioactivity in the air if you breathe or ingest contaminated food.
Eye The retina is very radiosensitive, but the lens, composed of dead cells and therefore can not repair itself quickly loses its transparency increasing dose absorbed by developing a cataract.
Lungs The lungs come into contact with the outside air is directly affected by radioactive particles inhaled through breathing which is deposited in his pockets: it is therefore absolutely necessary to wear gas masks during the operation in areas contaminated by dust, fumes or radioactive gases. The main source of pulmonary contamination is radon, a radioactive gas that being, it can easily be inhaled and deposited (it or its decay products) in the lungs.
liver, kidneys, heart and circulatory system They are all very very radiosensitive organs. The liver and gallbladder can receive damages in case of contamination with specific radioactive isotopes such as gold, but in general there is a harm only with very high doses of radiation.
Skin and hair The skin has a particular vulnerability, because, if not protected, received all three types of radiation (alpha, beta and gamma). The damage it receives is much higher, the less penetrating radiation: is little affected by gamma rays and more rays alpha and beta. For low levels of radiation you develop a rash, can occur if the radiation increases epithelial neoplasia. The ability to repair the damage is very high.
The hair growth stops completely, and those present fall into more or less according to the dose absorbed. After a few weeks they begin to grow, sometimes with different characteristics than they had before.
Musculoskeletal muscles and skeleton are generally less in absolute tissue damaged by radiation, but some isotopes of strontium and plutonium are concentrated right in the bone marrow, in which case the damage can be severe and may lead to leukemia or other malignancies.
Note that not all animal and plant species have the same susceptibility to radiation: for example, cockroaches can withstand without serious damage levels of radioactivity well above those lethal to humans, and a bacterium, Deinococcus radiodurans, survive radiation doses 1000 times the lethal dose for humans.
Effects in humans The effects of ionizing radiation are divided into "deterministic" and "stochastic effects (ICRP 60 International Commission on Radiological Protection), depending on whether or not they are directly related to the absorbed dose. Because of susceptibility to breast cancer, women have 40% more likely to acknowledge stochastic effects than men.
deterministic - are directly attributable to radiation (there is a direct cause-effect);
- derive from the inactivation of the vital structures of the cell;
- is seen immediately after irradiation;
- only occur if the absorption exceeds a definite dose-called "threshold dose"
- Their severity increases with the dose absorbed (hence also known as "graduated effects").
deterministic effects are skin rash, dermatitis and specific (radiation dermatitis in fact), cataracts, anemia and leucopenia. In severe cases have mucosal bleeding and intestinal tract, hair loss and hair. If the absorbed dose was not lethal, the deterministic effects subside within a few weeks, with survival and recovery more or less
Stochastic effects - not depend on the dose Consumption;
- derive from damage to the cell nucleus and in particular to DNA
- not appear immediately, they can occur or not, sometime in the future;
After irradiation, the DNA can be damaged in a reversible or irreversible if the structure of DNA was not repaired (or repaired incorrectly), the cell would give rise to a progeny of genetically modified cells that after a certain period of latency may lead to diseases such as cancer or leukemia. This increases the likelihood that the patient, sooner or later be affected by certain types of cancer.
For more see: Wikipedia
Radioactivity
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