Human body radiation damage

Radiation damage to life depends on whether the radioactive parent nuclides are already in the human hody or outside the human hody. If the radioactive nuclides are inside the human body, the damage effect is similar to that on crystal stmctures more massive particles are more damaging. For radioactive nuclides not inside the human body, the more massive particles cannot penetrate much distance, and could be stopped by cloth or paper, and hence do not cause much damage to life tissues. The less massive P-particles and y-rays are much more penetrating and can hence deliver energy to life tissues. 

Gamma radiation can penetrate most substances because of its high energy (lead is the best barrier against gamma radiation). Gamma radiation can penetrate the human body and damage cells, which could lead to cancer later in life. 

Because nuclear radiation varies considerably in energy, the potential to cause damage cannot be assessed simply by counting the number of emissions. The energy of emissions must also be taken into account. Furthermore, the three different t T)es of nuclear radiation affect human cells to different extents. When the amount, energy content, and t T)e of radiation are taken into account, the result is a measure of the effect of radiation on the human body. This is expressed using a unit called the rem. 

The human body is equipped to deal with nominal levels of radiation doses. Background (natural) radiation from radon gas, cosmic sources, soil, and water produces an average dose of about 0.3 rem (0.003 Sv) per year.4 However, large doses of radiation generated after a terrorist attack can overwhelm the body s ability to repair damage, leading to stochastic or acute health effects. 

In a different arena, a new sunscreen is under development from chemical compounds produced by reef-building corals. Corals living in a reef cannot move about, and in shallow water they are continually exposed to the sun s ultraviolet rays. This radiation can be as harmful to corals as to humans, so it seemed likely that sedentary corals must somehow limit radiation damage to their bodies. Pursuing this idea in the laboratory, investigators found that corals synthesize a family of ultraviolet-absorbing compounds. 

Electron beam processors generate two types of ionizing radiation their primary product is high-energy electrons, and their secondary product is x-rays resulting from their interaction with matter. The ionizing radiation is damaging because of its capability of penetration into the human body. 

Many radiopharmaceuticals for PET are labelled with 18F. 18F decays with emission of a positron with a relative low energy which limits its range in the body and thus enhances the resolution of a PET study. A second advantage of 18F is the half-life of 110 minutes which allows synthesis and PET studies, and allows use in humans, not causing radiation damage. 

Skin constitutes the interface between the human body and the environment. It represents a major target of oxidative stress since it is exposed to external oxidant aggressions like UV radiation, ozone, chemicals or pollution. Continuous exposure to such damaging effects and/or deficiency of the antioxidant protection systems result in skin premature aging and contribute to the development of cutaneous diseases and cancers [23]. Electrochemical studies dealing with the effect... 

After a low-LET dose of 3 Gy, every cell in the human body contains 3000 single strand and some 100 double strand breaks if given in a short time the cell (and organism) has great difficulties in repairing this damage (resulting in death in the case of no medical treatment). However, spread out over a week only chromosomal abberations will be noted. In the subsequent sections, we shall discuss macroscopic effects of various kinds and doses of radiation. 

Because radiation exposure can be cumulative, there are no truly safe levels of exposure to radioactive materials. Radiation does not cause any specific diseases. Symptoms of radiation exposure may be the same as those from exposure to cancer-causing materials. The tolerable limits for exposure to radiation that have been proposed by some scientists are arbitrary. Scientists concur that some radiation damage can be repaired by the human body. Therefore, tolerable limits are considered acceptable risks when the activity benefits outweigh the potential risks. The maximum annual radiation exposure for an individual person in the United States is 0.1 REM. Workers in the nuclear industry have a maximum exposure of 5 REMs per year. An emergency exposure of 25 REMs has been established by The National Institute of Standards and Technology for response personnel. This type of exposure should be attempted under only the most dire circumstances and should occur only once in a lifetime. 

When radioactive substances pass into the body by inhalation of radioactive vapors, gases (e.g., radon) or dusts, or by ingestion, such substances may accumulate and deposit in the bone. They incorporate in the bone matter the ionizing radiations damage cells and cause cancer. Cancer in lungs, bones, and lymphatic systems are known to occur in humans as a result of radiation exposures. 

Beta particles are subatomic particles that are ejected from the nucleus of unstable atoms. Beta particles can travel through several layers of human skin, and exposure to large sources of beta radiation can cause burns or skin reddening. Beta particles that enter the body can damage cells, which may lead to cell death or, later in life, to cancer. 

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