Can Radiation Be Contagious?

The Truth and Misunderstandings About Radiation Fear

News reports say that radioactive materials such as iodine, cesium, and xenon released from the Fukushima nuclear power plant accident in Japan have been detected across South Korea. This has increased public anxiety.

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Of course, nuclear experts explain that the detected levels are not high enough to harm the human body, so there is no need for excessive fear. Still, it is understandable that many people feel uneasy.

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What Is the Difference Between Radiation, Radioactivity, and Radioactive Materials?

Radiation is a type of strong energy wave released when an atomic nucleus breaks down naturally. Radiation can be harmful because when it enters the human body, it may damage cells and DNA. This damage can turn normal cells into cancer cells or cause diseases such as leukemia.

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The ability to emit radiation is called radioactivity.

A radioactive material is a substance that has radioactivity, meaning it can release radiation. Uranium, which is used as fuel in nuclear power plants, is a typical example. Cesium and radioactive iodine released during the Fukushima accident are also radioactive materials.

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Radioactive materials can be more dangerous than radiation itself because they can stick to the body or enter the body and continue to emit radiation over time.

External exposure, such as radiation on the skin or clothing, can usually be removed by taking a shower or changing clothes. However, if radioactive materials enter the body through breathing or eating contaminated food, medical treatment may be required.

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Is Water Contaminated With Radioactive Materials Safe After Boiling?

When radioactive materials contaminate people, food, or the environment, this is called radioactive contamination. On March 23, the Japanese government announced that radioactive iodine levels of 210 becquerels (Bq) were detected in tap water in Tokyo. This exceeded the safety limit of 100 Bq for infants, so parents were advised not to give tap water to babies under 12 months old.

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For adults, the safety limit is 300 Bq, so drinking the water was considered acceptable. However, water contaminated with radioactive materials cannot be cleaned by home water filters or by boiling. These methods do not remove radioactive substances.

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The Tokyo metropolitan government explained that short-term consumption would not immediately affect health. Despite this, panic buying of bottled water occurred in many stores across Tokyo.

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How Much Radiation Exposure Is Dangerous?

Radiation exposure is measured in sieverts (Sv).

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1 sievert equals 1,000 millisieverts (mSv).

A person who gets an X-ray at a hospital is exposed to about 0.03–0.05 mSv of radiation. A chest X-ray is about 0.1 mSv.

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According to nuclear safety regulations, the annual radiation exposure limit for the general public is 1 mSv. For nuclear power plant workers, the limit is 50 mSv per year.

On March 15, shortly after the Fukushima accident, radiation levels at the Fukushima Daiichi Nuclear Power Plant rose to as high as 400 mSv per hour—thousands of times higher than normal levels before the accident.

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Can Radiation Spread Like a Cold?

Radiation does not spread from person to person like a cold or infectious disease. People are exposed to radiation mainly by breathing in radioactive materials, eating contaminated food, being in areas with high radiation levels (such as near nuclear facilities), or undergoing medical procedures like X-rays or CT scans.

Temporary medical exposure from X-rays or CT scans does not leave radioactive material inside the body. Even if radioactive materials remain in the body after breathing contaminated air or eating contaminated food, they do not spread to other people.

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Radioactive Materials From Fukushima Detected Across South Korea

The distance between Fukushima and South Korea is more than 1,000 kilometers, similar to the distance between Chernobyl and Sweden. After the Chernobyl nuclear accident, radioactive materials were detected in Sweden, raising concerns about health, food safety, and environmental pollution.

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However, the total radiation dose received by people in Sweden was about 0.2 mSv, which was even lower than the radiation people receive naturally. For this reason, experts believe that even if radioactive materials from Fukushima reach South Korea, the expected annual exposure for the public would be below 0.1 mSv.

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On March 28, radioactive materials were detected in the air at 12 monitoring stations in South Korea, including Seoul and Chuncheon. The level of radioactive iodine was measured at 0.049–0.356 Bq per cubic meter. When converted into radiation dose, this equals only one 200,000th to one 30,000th of the annual public exposure limit of 1 mSv.

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Although these levels are too low to affect human health, they show that the impact of the Fukushima accident reached South Korea. As a result, the Korea Institute of Nuclear Safety decided to strengthen radiation monitoring of the air and coastal areas around the Korean Peninsula.

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The Panic Buying of Iodine Tablets

Potassium iodide (KI), also known as stable iodine, is used to protect the thyroid gland from radioactive iodine-131 released during nuclear accidents. If taken within 24 hours before exposure—or within 15 minutes after exposure—it can help prevent or reduce thyroid damage.

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However, taking iodine tablets unnecessarily in areas with low radiation risk can be harmful to health. Eating iodine-rich foods such as seaweed, kelp, or laver also provides little protection against radioactive iodine exposure.

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