Understanding Radiation Sickness: What Can Happen in the Worst Case?

Despite danger for Japan nuclear workers, radiation sickness not yet a threat.

ByABC News
March 17, 2011, 4:40 PM

March 17, 2011— -- As the situation at Japan's nuclear reactors continues to deteriorate, many in Japan and around the world are confronting real fears about the effects of radiation.

Based largely on misinformation and confusion, potassium iodine pills have flown off the shelves in the United States, and in China, panicked shoppers have bought up iodized salt, mistakenly believing that it offers protection.

Radiation sickness is very rare, and it is triggered only when humans are exposed to extremely strong doses of radiation, far higher than presently found even close to the damaged plant, more than 150 miles north of Tokyo.

"We will see increases in dose levels in Tokyo, but I am confident it will be low enough to be not a health risk," said Dr. Peter Hosemann, an assistant professor of nuclear engineering at UC Berkeley.

Still, while most experts agree that the situation in Sendai presents no immediate threat even to most of Japan's population, fears are understandable given the serious effects of radiation sickness and concerns of an increased risk of cancer.

According to the National Institutes of Health, radiation sickness can be caused when the total body is exposed to 1000 of radiation. If humans are exposed to more than 4000 millisieverts of radiation, half are likely to die. Any more that 6000 millisieverts, doctors say, is untreatable and leads to almost certain death.

The health effects of radiation sickness are particularly brutal. The radiation causes chemical changes in the body, destroying cells. This results in symptoms that include bleeding, hair loss, skin burns and open sores.

Initial symptoms after exposure are often nausea and vomiting, and according to the Mayo Clinic, the earlier these symptoms appear, the more severe the exposure. After an exposure of 1000 millisieverts, such symptoms often occur within six hours.

In Japan, even the "Fukushmima 50," the group of 180 volunteers working to contain the crippled nuclear reactors, have apparently not yet been exposed to enough radiation to trigger acute radiation sickness. The Japanese government has upped the limit on total exposure for workers to an annual dose as high as 250 millisieverts.