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 deal

with the effects.

So, let’s start with introduce radiation effects

Radiation Effects,

effects observed when ionizing radiation strikes living tissue and

damages the molecules of cellular matter. Cellular function may be

temporarily or permanently impaired from the radiation, or the cell may be

destroyed. The severity of the injury depends on the type of radiation, the

absorbed dose, the rate at which the dose was absorbed, and the

radiosensitivity of the tissues involved. The effects are the same, whether

from a radiation source outside the body or from material within.

1) Biological,

The biological effects of a large dose of radiation delivered rapidly

differ greatly from those of the same dose delivered slowly. The effects of

rapid delivery are due to cell death, and they become apparent within

hours, days, or weeks. Protracted exposure is better tolerated because some

of the damage is repaired while tthe exposure continues, even if the total

dose is relatively high. If the dose is sufficient to cause acute clinical

effects, however, repair is less likely and may be slow even if it does

occur. Exposure to doses of radiation too low to ddestroy cells can induce

cellular changes that may be detectable clinically only after some years.

2) ACUTE EFFECTS

High whole-body doses of radiation produce a characteristic pattern of

injury. Doses are measured in grays or rads, 1 gray being equal to the dose

absorbed when one kilogram of matter absorbs one joule of ionizing

radiation, and 100 rads being equal to 1 gray. Doses of more than 40 grays

severely damage the human vascular system, causing cerebral edema, which

leads to profound shock and neurological disturbances; death occurs within

48 hours. Whole-body doses of 10 to 40 grays cause less severe vascular

damage, but they lead to a loss of fluids and electrolytes into the

intercellular spaces and the gastrointestinal tract; death occurs within

ten days as a result of ffluid and electrolyte imbalance, severe bone-marrow

damage, and terminal infection.

3) LATE EFFECTS

Nonmalignant delayed effects of ionizing radiation are manifested in

many organs—particularly bone marrow, kidneys, lungs, and the lens of the

eye—by degenerative changes and impaired function; these are largely

secondary to radiation-induced damage to blood vessels. The most important

late effect of radiation exposure, however, is an increased incidence of

leukemia and other cancers. Statistically significant increases in leukemia

and of cancers of the thyroid, the lung, and the female breast have been

demonstrated in ppopulations exposed to relatively high doses (greater than

1 gray).

4) NONIONIZING RADIATION

The radio-frequency radiation, or electromagnetic fields (EMFs), from

sources such as power lines, radar, communications networks, cellular

phones, and microwave ovens is nonionizing, and for many years only high

doses 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 of

long-term exposure to low levels of nonionizing radiation began to be a

matter of scientific concern and controversy. Subtle biological effects

were reported in some studies, while other studies failed to find these

effects