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Radioactivity in the United States From Japanese Nuclear Plants


Should I be worried about radioactivity coming to the United States from the failed Japanese nuclear reactors?

No, there is no need for concern. The information we have now tells us that no harmful levels1 of radioactivity have arrived in the United States from the failed Japanese nuclear power plants. Radioactive plumes2 that are being generated are dissipating with time as they cross the vastness of the Pacific Ocean.

In spite of this reassurance, thousands of people purchased potassium iodide (KI), a substance that blocks radioactive iodine (which was present in the airborne plumes and is a potential cause of cancer) from accumulating in the thyroid gland. Medical experts state that there is no need for that in the United States. In fact, use of KI could have an adverse medical effect on people with specific allergies and other ailments.

The ocean plume was expected to reach the west coast of the United States in 2014. Some dire predictions have been made over this. However, the testing that has been done shows little or no Fukushima fallout in the ocean or on the shore. The testing does show the natural radioactive minerals that are in all oceans. That is, the oceans are already naturally radioactive.  Testing up and down the west coast is continuing.

For more information on the Japanese nuclear reactors, see our Fukushima section on our Health Physics Society Website.

For more information on radiation, see Radiation Answers.

1 "Harmful level" means enough radiation to cause harm to the human body.
2 "Plume" means any of the reactor emissions that go into the air.

What types of radioactivity are being released from the nuclear plants and why is that of concern?

Radioactivity (or radioactive material) comes from the nuclear fuel in the plants. We call the radioactive compounds that are being released fission products. They include a number of radioactive noble gases, radioactive isotopes of iodine, and radioactive isotopes of other elements such as cesium.

Some of these materials emit radiation (gamma and beta rays) and, if in the surrounding air or deposited on the ground or other surface, can irradiate our bodies from the outside (externally).

In addition, if these materials are taken into the body by breathing or in food they have the potential of exposing body cells internally.


Are the amounts of radiation that are being released from the plant enough to cause radiation exposures to people?

Geiger counters and other radiation-detection instruments are sensitive enough to detect radiation if you have as few as 50 to several hundred radioactive atoms on your skin. We know from detector readings that some of the evacuated residents and plant workers had some radioactive contamination on their clothing, but we do not yet have validated data on the level of radiation exposure to the individuals wearing the clothing.


Aren't we exposed to other sources of radiation in our everyday lives?

Yes, from many sources. Our bodies contain some naturally radioactive potassium; our environment contains some naturally occurring radioactivity like uranium, radium, and radon; and there are consumer products containing radioactive materials, including smoke detectors, antique pottery called Fiesta ware, and some lantern mantles (typically used in lanterns when camping). If you want more information on radioactivity in consumer products, take a look at


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