Today I’m going to talk about: Radiation effects I’ve divided my presentation into one parts: First I’d like to introduce radiation effects, and second I’ll dealwith the effects. So, let’s start with introduce radiation effects
Radiation Effects, effects observed when ionizing radiation strikes living tissue anddamages the molecules of cellular matter. Cellular function may betemporarily or permanently impaired from the radiation, or the cell may bedestroyed. The severity of the injury depends on the type of radiation, theabsorbed dose, the rate at which the dose was absorbed, and theradiosensitivity of the tissues involved. The effects are the same, whetherfrom a radiation source outside the body or from material within. 1) Biological, The biological effects of a large dose of radiation delivered rapidlydiffer greatly from those of the same dose delivered slowly. The effects ofrapid delivery are due to cell death, and they become apparent withinhours, days, or weeks. Protracted exposure is better tolerated because someof the damage is repaired while the exposure continues, even if the totaldose is relatively high. If the dose is sufficient to cause acute clinicaleffects, however, repair is less likely and may be slow even if it doesoccur. Exposure to doses of radiation too low to destroy cells can inducecellular changes that may be detectable clinically only after some years. 2) ACUTE EFFECTS High whole-body doses of radiation produce a characteristic pattern ofinjury. Doses are measured in grays or rads, 1 gray being equal to the doseabsorbed when one kilogram of matter absorbs one joule of ionizingradiation, and 100 rads being equal to 1 gray. Doses of more than 40 graysseverely damage the human vascular system, causing cerebral edema, whichleads to profound shock and neurological disturbances; death occurs within
48 hours. Whole-body doses of 10 to 40 grays cause less severe vasculardamage, but they lead to a loss of fluids and electrolytes into theintercellular spaces and the gastrointestinal tract; death occurs withinten days as a result of fluid and electrolyte imbalance, severe bone-marrowdamage, and terminal infection. 3) LATE EFFECTS Nonmalignant delayed effects of ionizing radiation are manifested inmany organs—particularly bone marrow, kidneys, lungs, and the lens of theeye—by degenerative changes and impaired function; these are largelysecondary to radiation-induced damage to blood vessels. The most importantlate effect of radiation exposure, however, is an increased incidence ofleukemia and other cancers. Statistically significant increases in leukemiaand of cancers of the thyroid, the lung, and the female breast have beendemonstrated in populations exposed to relatively high doses (greater than1 gray). 4) NONIONIZING RADIATION The radio-frequency radiation, or electromagnetic fields (EMFs), fromsources such as power lines, radar, communications networks, cellularphones, and microwave ovens is nonionizing, and for many years only highdoses of such radiation were known to be harmful, causing burns, cataracts,temporary sterility, and other effects. In the 1980s and early 1990s,however, with the proliferation of such devices, the possible effects oflong-term exposure to low levels of nonionizing radiation began to be amatter of scientific concern and controversy. Subtle biological effectswere reported in some studies, while other studies failed to find theseeffects