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.
The workers are certainly facing extreme risks, particularly if the situation at the plant becomes even worse. And while a total dosage of 250 millisieverts should not cause radiation sickness, it does marginally increase the risk of cancer, which is why people miles away from the plant are being evacuated or told to take potassium iodide.
"They must be extremely worried about the long-term consequences to their health," said Michael Dobbs, who covered the Chernobyl disaster for the Washington Post. "They're prepared for a shorter life span, [though] I don't think they would fear dying in the immediate future."
During the Chernobyl disaster in 1986, a core group of workers stayed behind to try to cool the fuel rods, exposed to radiation far more intense that what the workers at Daiichi plant currently face. Within the first hours of the disaster, many of the Chernobyl workers were already experiencing the effects of intense radiation.
"They were suffering from nuclear tan. Their skin went black. Their skin was flaking, and blisters were appearing on their skin within a couple of hours. They began to vomit. Some of them died within two or three days," said Dobbs.
In all, 134 of the workers in the reactor got acute radiation sickness and 28 died.
Perhaps the most famous case of radiation sickness in recent years occurred to Alexander Litvinenko, a former KGB spy. British authorities determined that Litvinenko was poisoned with radioactive polonium-210, and he died after a short hospitalization. A photograph of Litvinenko in his hospital bed showed him balding and sickly, a shadow of his former self.
The Associated Press contributed to this report.