In so doing, the neutron will slow down, and the nucleus will gain speed. The most common collision is with a hydrogen nucleus, a proton that can excite or ionize electrons in nearby atoms. All of these collisions and ionizations take place very quickly, in less than a second. It takes much longer for the biological effects to become apparent. If the damage is sufficient to kill the cell, the effect may become noticeable in hours or days.
Cell "death" can be of two types. First, the cell may no longer perform its function due to internal ionization; this requires a dose to the cell of about gray 10, rad.
This requires a dose of 2 gray rad , which will cause reproductive death in half the cells irradiated hence such a quantity is called a "mean lethal dose. Death may also result if cell reproduction ceases in parts of the body where cells are continuously being replaced at a high rate such as the blood cell-forming tissues and the lining of the intestinal tract. A very high dose of gray 10, rad to the entire body causes death within twenty-four to forty-eight hours; a whole-body dose of 2.
These effects were once called nonstochastic; they are now called deterministic. What long-term effects can radiation have? The effect of the radiation may not be to kill the cell, but to alter its DNA code in a way that leaves the cell alive but with an error in the DNA blueprint. The effect of this mutation will depend on the nature of the error and when it is read.
Since this is a random process, such effects are now called stochastic. How can ionizing radiation cause cancer? Cancer is produced if radiation does not kill the cell but creates an error in the DNA blueprint that contributes to eventual loss of control of cell division, and the cell begins dividing uncontrollably. This effect might not appear for many years. Cancers induced by radiation do not differ from cancers due to other causes, so there is no simple way to measure the rate of cancer due to radiation.
During the period studied by the Advisory Committee, great effort was devoted to studies of irradiated animals and exposed groups of people to develop better estimates of the risk of cancer due to radiation.
This type of research is complicated by the variety of cancers, which vary in radiosensitivity. For example, bone marrow is more sensitive than skin cells to radiation-induced cancer. Because the cancers can occur anytime in the exposed person's lifetime, these studies can take seventy years or more to complete.
For example, the largest and scientifically most valuable epidemiologic study of radiation effects has been the ongoing study of the Japanese atomic bomb survivors. Other important studies include studies of large groups exposed to radiation as a consequence of their occupation such as uranium miners or as a consequence of medical treatment. Radiation may alter the DNA within any cell. Cell damage and death that result from mutations in somatic cells occur only in the organism in which the mutation occurred and are therefore termed somatic or nonheritable effects.
Cancer is the most notable long-term somatic effect. However, very high doses of radiation can kill the cell completely. We use this property of radiation to kill cancer cells, and also harmful bacteria and other micro-organisms. The hazard symbol is shown on containers of radioactive substances to warn of the danger. The degree to which each different type of radiation is most dangerous to the body depends on whether the source is outside or inside the body.
If the radioactive source is inside the body , perhaps after being swallowed or breathed in:. High levels can kill you by causing damage to your internal organs. It's difficult to treat high radiation exposure. Exposure to radiation over a long time can cause cancer. It's thought that only emergency workers at the plant are at risk of harmful doses of radiation, but it's likely they are only being exposed for short lengths of time so there's less danger.
The level of exposure for people living close to the plant was a lot lower, and there should be little risk to people living further away. Should MPs be allowed to do another job? How Christmas can still sparkle with plastic-free glitter.
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