Radiation Sickness

The Nuclear Crisis in Japan

You've probably heard of radiation sickness after the recent problems at two nuclear power plants in Japan. People you know may be talking about whether they should worry about radiation getting into the air or food.

The good news is, there's no reason for most people to worry. Only people who live within a few miles of the Japanese nuclear plants need to take special steps to protect themselves.

Here's why:

Things to Know About Radiation

Radiation sickness is rare. People need to be exposed to a lot of radiation to get sick. Even if a nuclear plant releases large amounts of radiation, the farther away that radiation travels from the source, the more it disperses into the atmosphere. So even if radiation from Japan reaches the shores of Hawaii, Alaska, or other parts of the United States, health officials say the possibility of getting sick from these trace amounts is "essentially zero."

Food can be contaminated by radiation, but it's not something to worry about in the case of Japan. Experts know that radiation can cause health problems if too much gets into the vegetables, fruit, milk, meat, fish, and other foods we eat. That's why regulators in Japan, the United States, and elsewhere are working hard to ensure the food supply stays safe.

So just what is radiation? And how can it affect people?

What Is Radiation?

In just the right amounts, radiation is a good thing — and very necessary for life. In fact, radiation is a natural process. It's found in small amounts just about everywhere: in soil, water, food, and even our bodies. We're exposed to this kind of "background radiation" every day.

In the broadest sense, radiation is the act of giving off energy. The sun is one energy source that gives off (or "radiates") energy through its ultraviolet rays.

The two types of radiation are:

  1. Non-ionizing radiation. This type of energy is mostly emitted through "waves" — like sound waves, radio waves, and ultraviolet (heat) waves. It's what makes things like cell phones, light bulbs, microwave ovens and diagnostic ultrasound machines work. Although non-ionizing radiation can be harmful in very high doses, this type of radiation cannot change the molecular chemistry of a person or thing.
  2. Ionizing radiation. Some natural sources of ionizing radiation are cosmic rays from the sun and stars, and radon (an element found in soil). Manmade sources include X-ray machines and radiation therapy for cancer treatment. Ionizing radiation is powerful enough to split an atom and change the molecular chemistry of a person or thing. It can be useful (like when it's used for cancer therapy). But ionizing radiation can also be harmful if a person is exposed to too much. It's this type of radiation that can lead to radiation sickness — and even death if the amount of radiation is really high.

How Do People Get Exposed to Too Much Radiation?

It's rare to be exposed to dangerously high doses of radiation in everyday life. But people can be exposed to high doses if there's a nuclear attack or a nuclear power plant failure.

People who are within a few miles of a nuclear disaster are at risk of being exposed to increased levels of ionizing radiation. But unless someone is standing inside a nuclear reactor building when an explosion or meltdown happens, the chances of developing radiation sickness or dying suddenly are low. The further away from the source of radiation a person is, the lower the risk of radiation sickness.

What Happens to Someone With Radiation Sickness?

Radiation sickness usually only happens to people who are exposed to 300 or more times the average yearly dose of background radiation. A person exposed to such high doses of radiation may have:

  • a drop in blood cell counts
  • hair loss
  • nausea
  • vomiting
  • diarrhea
  • skin burns
  • an eventual increased risk for blood and thyroid cancers
  • eventual death as a result of organ failure

How severe these problems are and when they show up depends on how much radiation the person was exposed to. It also depends on whether the person was exposed to radiation over a short or long period of time.

When exposure is sudden and 100 or more times the average yearly dose, symptoms can be severe and appear within a few hours. A lower dose of radiation over a longer period of time is less likely to cause symptoms right away, but will still increase the risk of cancer later in life.


The health problems caused by dangerously high levels of radiation can be treated. But people who are exposed to near-fatal amounts of radiation and still survive can have lifelong health problems. They have an increased risk for developing certain types of cancer.

Usually a medical team of doctors with different health specialties will work together to treat the different areas of the body that were damaged by radiation. If medical personnel are able to treat people quickly (within 24 hours) after a radiation crisis, they may be able to prescribe medications to reduce the chances of certain cancers.

Effects to the Food Supply and Environment

After a nuclear incident, radiation particles can travel on wind currents and settle in water sources, plant life, and soil. That means that livestock and food crops that live and grow in these areas are likely to be affected.

Sometimes the level of radiation in food is so small that it poses no risk. Other times, it rises above safety levels. That's why scientists test the levels of radiation in the soil after a nuclear disaster. It helps them decide how high the risk really is. If scientists think a food is unsafe, regulators ban it from being sold or distributed until radiation levels decrease. It can take time for radiation to get back to acceptable levels. Depending on what happened, it may be weeks, months, or even years.

People can avoid eating contaminated food, but wild animals can't do that. Studies from previous nuclear disasters have found that some animals in affected areas might be harmed, but most do not suffer long-term health problems.

After a nuclear incident, there's no way of knowing how much environmental damage has been done until months or even years later. Scientists will be monitoring the area of Japan where the nuclear crisis happened for many years to come.

Reviewed by: Sharon W. Gould, MD
Date reviewed: March 2011

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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

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