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Radiation: When to worry

By Elizabeth Landau and Madison Park, CNN
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Avoiding nuclear exposure
STORY HIGHLIGHTS
  • Greater exposure leads to faster and more intense symptoms of radiation sickness
  • Exposure refers to high-energy beams from radioactive material
  • Radioactive iodine can cause thyroid problems and cancers

Editor's note: Tune in to CNN tonight at 9 ET for special editions of "In the Arena," "Piers Morgan Tonight" and "AC360║." Anderson Cooper, Dr. Sanjay Gupta and Soledad O'Brien report live from Japan on the quake and tsunami's catastrophic effects.

(CNN) -- Nuclear power has generally proved safe and nondetrimental to human health.

But when something goes wrong, it can result in widespread radioactive exposure and health hazards that turn an average power plant into a notorious name like Chernobyl.

The levels of radiation and potential health consequences were significantly worse at Chernobyl than at Tokyo Electric Power Company's Fukushima Daiichi nuclear power plant in Japan, which has has suffered numerous problems since Friday's earthquake and tsunami. .

The two accidents are not in the same realm, experts said.

On Monday, a hydrogen blast at at the Fukushima Daiichi plant injured 11 people and caused another reactor to malfunction, triggering new fears of a meltdown that could leak dangerous amounts of nuclear radiation.

As many as 160 people have tested positive for some level of radiation in the area. And 17 U.S. Navy helicopter crew members showed low levels of radioactivity after conducting disaster relief missions in Japan, the military said Monday. But after the crew members washed with soap and water, no further contamination was detected, the Navy said.

Radiation levels at the moment are low, but the next 24 to 48 hours will be critical, said David Brenner, director of the Center for Radiological Research at Columbia University.

As the public remains nervous about what will happen at the plant, it's important to keep in perspective the kinds of radiation that people are exposed to every day, and understand the real risks of too much radiation.

"I'm now concerned that we'll go into another nuclear winter, with public opinion turning against nuclear power," said Dr. James Thrall, president of the American College of Radiology and chief of radiology at Massachusetts General Hospital. "If you look at nuclear power objectively, it actually has fewer health consequences than any energy production with fossil fuels."

Contamination vs. exposure

Radiation is invisible; you cannot taste it, or smell it, or feel it on your fingers, Thrall said.

There are four primary kinds of ionizing radiation, which is light that has enough energy to ionize an atom, i.e. make it into a charged particle. Alpha particles are relatively heavy and, when emitted, cannot penetrate human skin or clothing, but are harmful if they get into the body otherwise. Beta radiation can cause skin injury and are also harmful to the body internally. Gamma and X-rays are high-energy invisible light that can damage tissue and are most hazardous to humans.

It's not possible to directly measure the amount of radiation exposure a person has had. Exposure refers to the energy the body has absorbed from radioactive material, the high-energy invisible light rays that unstable chemicals emit.

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When you see people with Geiger counters checking around a site like Fukushima Daiichi, they're measuring contamination -- which generally refers to actual radioactive particles.

Radiation all around us

A study from the National Council on Radiation Protection and Measurement found that nearly half of the radiation to which the U.S. population is exposed comes from medical sources such as CT scans, X-rays, and nuclear medicine, which is the use of radioactive chemicals in the treatment and diagnosis of health conditions. But there's also radiation coming from the sun, stars and soil.

The average radiation exposure a person gets from natural sources is about 3.1 millisieverts; in the United States, a person typically gets a total of 6.2 millisieverts because of medical diagnostic procedures and other man-made sources of radiation. The limit for occupational radiation exposure among workers who deal with radioactive material is 50 millisieverts.

To give you a sense of what that means, a chest X-ray delivers a dose of about .02 millisieverts, and a CT to the abdomen carries 8 millisieverts. But note that these procedures don't last very long; prolonged exposure would be more dangerous.

The farther away you are from the source of radiation, the less exposure you will have to damaging high-energy light beams such as gamma rays.

Radiation sickness

Generally, the greater exposure you've had, the faster and more intense the symptoms of radiation sickness will be.

Nausea and vomiting are usually the initial symptoms of radiation sickness. A very severe exposure can lead to them within 10 minutes; dizziness, weakness, and low blood pressure may begin immediately. If the radiation exposure is mild, a person might not start experiencing these symptoms for up to six hours. Check out this Mayo Clinic chart, under "symptoms" for more information about how various levels of radiation might affect a person.

The simple removal of clothes and shoes eliminates about 90% of external radiation contamination, according to the Mayo Clinic, and washing with soap and water takes radiation off the skin. This lowers your risk of breathing or ingesting radiation particles, or having them get into open wounds.

There may be damage to bone marrow, which can be treated with a protein called granulocyte colony-stimulating factor. Transfusions of red blood cells or blood platelets may also be necessary.

When there's a possibility of internal organs being damaged from radiation exposure, there are some treatments for specific types of radiation.

Radioactive iodine, which is hazardous to humans, is one of the biproducts of the chemical reaction involving uranium that takes place at the Fukushima Daiichi plant.

Since the thyroid is prone to taking up radioactive iodine, people at risk of this problem can benefit from potassium iodide, which contains the stable component of iodine. Potassium iodide can protect the thyroid from damage. The Japanese government is currently working to distribute potassium iodide to residents near the reactors.

There is also a type of dye called Prussian blue that binds to the radioactive particles of cesium and thalium, reducing the amount of radiation that cells may absorb, according to the Mayo Clinic. A chemical called diethylenetriamine pentaacetic acid binds to radioactive particles of plutonium, americium and curium.

The shadows of Chernobyl and Three Mile Island

In Chernobyl, the world's biggest nuclear accident, which occurred in 1986, 28 workers and firefighters died from radiation sickness months after they helped put out the fire.

Radioactive iodine also allegedly got into the general population through milk, Thrall said. This likely happened when milk-producing cows ate iodine-contaminated grass, he said.

Cancer can take decades to appear as a result of radiation exposure, and epidemiological studies have found an increased risk of cancer in people who were near Chernobyl at the time of the disaster.

The Japan situation probably won't get to the scale of Chernobyl, but it could be bigger than Three Mile Island, said. Three Mile Island is a nuclear power plant in Pennsylvania that, 32 years ago, had the worst nuclear power accident in the United States. But in the U.S. crisis, there was only a partial meltdown, and nuclear fuel never escaped the reactor vessels. There has been no evidence found of resulting long-term cancer risk in that area.

"At the levels that we're seeing in Japan I do not believe we'll see any cancer risk in the population," Thrall said.

How it differs from an atomic bomb

There is a big difference between the effects of the atomic bombs dropped in Hiroshima and Nagasaki at the end of World War II and possible spread of nuclear radiation from malfunctioning nuclear power plants, said Dr. John D. Boice, a radiation epidemiologist and scientific director of the International Epidemiology Institute.

In 1945, Americans dropped bombs in parachutes, and these detonated above the city -- not on the ground.

"The atomic bomb -- it was whole body exposure that lasted less than a second," he said. The radiation traveled through the body, similarly to how X-rays behave.

"The effects may be different, because it was such an immediate response," Boice said. "For the reactors, it's different. It's a gradual exposure over time. It might include radioactive elements such as iodine and cesium, which may be ingested."

Radioactive iodine can cause thyroid problems and cancers, and cesium can also increase cancer risk. If leaking occurs, the population could breathe or ingest contaminated foods with radioactive elements.

"These are different types of exposure -- they would involve the possibility of ingestion and staying in the body."

The effects of survivors of the Hiroshima and Nagasaki bombings have been followed through the Radiation Effects Research Foundation, a joint U.S.-Japan effort to study the impact. Studies found survivors had higher rates of leukemia and cancers in the breast, thyroid, lung, colon and stomach over time.

And today in Japan

Boice said he was concerned about workers who are having to deal with the emergency and work in a highly volatile situation at Fukushima Daiichi.

"They're dealing with the deaths of friends and families -- then to add on top of that, there is the possibility of a serious nuclear meltdown," Boice said. "How much can one country, one civilization bear?"

CNN's Elizabeth Cohen and Sabriya Rice contributed to this report.

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