Tuesday, March 15, 2011
Radiation's health effects
CBC News Posted: Mar 15, 2011:
We are all naturally exposed to background radiation from radon, a colourless, odourless gas found in soil, water and air. Unnatural sources of exposure such as medical X-rays deliver about 10 days' worth of naturally occurring radiation.
Symptoms of radiation sickness occur when the body is damaged by a very large dose of radiation over a short period of time. Workers at a nuclear power plant or emergency responders on site of a nuclear disaster are at greatest risk of exposure to high levels of radiation.
The more radiation a person absorbs, the sicker he or she will get. That's why the first step in preventing harm is to prevent exposure. In Japan, authorities expanded the evacuation zone for people living near the Fukushima Dai-ichi nuclear plant, which was damaged by the devastating March 11 earthquake and subsequent tsunami.
Once exposed, people are screened to establish how much radiation they were exposed to. Their bodies, clothes and shoes are then washed with soap and water.
Potassium iodide tablets are often given out to people at risk of contamination or who have been exposed. The compound prevents or reduces absorption of radioactive iodine, a byproduct of nuclear fission, through the thyroid gland, which uses iodine to produce thyroid hormones. But potassium iodide cannot prevent radioactive iodine from entering elsewhere in the body and does not affect the absorption of other radioactive elements, such as cesium, which stays in organs, tissue and the environment much longer than iodine.
Radiation sickness, also called radiation poisoning, is serious but rare. Since the Second World War, most cases of radiation sickness have resulted from industrial accidents, such as the Chornobyl meltdown in 1986.
Radiation dosage is measured in sieverts (Sv). Short-term exposure of the whole body to about 10,000 mSv or 10 Sv would cause immediate illness, such as nausea and decreased white blood cell count, and subsequent death within a few weeks, according to the World Nuclear Association.
People living in two villages near the Chornobyl plant were exposed to, on average, 300 mSv of radiation. The average cumulative exposure for the general population in various affected regions of Belarus, Russia and Ukraine over a 20-year period after the accident is estimated to be between 10 and 30 mSv, according to the Merck Manuals reference publication for health professionals.
The strength of the radiation itself and distance from it are key factors in the severity of radiation sickness. Read more>>