Japan’s Nuclear Crisis: Are There Serious Health Implications?

Japan’s nuclear crisis has raised many questions about the health implications of exposure to ionizing radiation. In this article, we discuss the current safety of food and water in Japan.

AsianScientist (Apr. 17, 2011) – After a series of 52 quakes with a magnitude of 6 or greater in North-east Japan since the initial 9.0 quake that caused a tsunami, with close to 30,000 people either dead or missing, Japan is now bracing itself with a nuclear crisis on a par with the 1986 Chernobyl accident.

Just this Tuesday, Japan raised the crisis level at its beleaguered Fukushima Dai-Ichi nuclear plant from 5 to 7 – the highest level on the International Atomic Energy Agency’s scale for rating nuclear accidents.

Japan’s nuclear crisis has raised many questions about the health implications of exposure to ionizing radiation. In this article, we answer a few of these questions, as well as discuss the current safety of food and water in Japan.
 

Human Exposure to Ionizing Radiation

Some definitions

Ionizing Radiation: The type of energy released when certain atoms disintegrate. This energy can travel as either electromagnetic waves (i.e. gamma or X-rays) or as particles (i.e. alpha, beta or neutrons). Ionizing radiation is commonly used in medicine for diagnostic testing, i.e. X-Ray and CT scans.

Radionuclides: Atoms that emit radiation e.g. radioactive iodine, caesium, plutonium, strontium.

Q: Are people normally exposed to ionizing radiation?

A: Yes, we are. We are exposed to two sources of radiation: natural and man-made.

Natural radiation (also known as background radiation) comes from space, for example, cosmic rays, as well as from naturally occurring radioactive materials found in the soil, water and air. The main source of natural radiation is radon gas, a naturally-occurring substance. Levels of exposure to natural radiation differ due to local geology. People in some areas can be exposed to more than 200 times the global average.

The most common sources of man-made radiation are X-ray machines and CT scanners.

Q: How is the degree of radiation expressed?

A: In Sievert (Sv) units. On average, a person is exposed to approximately 3.0 milli Sieverts (mSv)/year, of which 80 percent (2.4 mSv) is due to naturally-occurring sources while the remaining 20 percent is from man-made sources of radiation.

Q: How are people exposed to ionizing radiation?

A: Exposure can be internal or external. External irradiation occurs when a person is exposed to external sources (e.g. X-rays) or when radioactive material becomes attached to skin or clothes (e.g. via dust, liquid, or aerosols). Internal contamination may result from breathing in or swallowing radioactive material or through contamination of wounds.

Q: What is the current risk of radiation-related health problems in Japan for those residing near the reactor in comparison to those in other parts of Japan?

A: The health consequences of radiation exposure will depend on the degree of exposure. This in turn is dependent on several things, including: the amount and type of radiation released from the reactor; weather conditions, such as wind and rain; a person’s proximity to the plant, and the amount of time spent in irradiated areas.

The Japanese government has evacuated individuals who were living within a 20 kilometer radius around the Fukushima Dai-Ichi plant. Those living between 20 km and 30 km from the plant have been asked to evacuate voluntarily.

Q: What are the potential health effects of radioactive exposure?

A: The health consequences vary depending on the type of radionuclide a person is exposed to and the degree of exposure. Of all the radionuclides released from the Fukushima Dai-Ichi reactors, the following four are the most concerning ones.

  • Iodine-131: This isotope has a half-life of 8 days. It accumulates in the thyroid gland and causes cell apoptosis and mutations which may eventually lead to thyroid cancer. Out of the four, this is the easiest to protect against – the risk of accumulating this isotope can be reduced by the ingestion of potassium iodide which saturates the thyroid with normal iodine, thus preventing the uptake of radioactive iodine by the thyroid gland.
  • Strontium-90: This isotope has a half-life of 29 years. If ingested, it becomes incorporated into bones and teeth, increasing one’s risk of leukemia and bone cancer.
  • Caesium-137: The half-life of Caesium-137 is 30 years. Unlike Iodine-131 and Strontium-90, Caesium-137 does not accumulate as effectively in the body. If inhaled or ingested, it continues to emit radiation inside the body, increasing one’s risk of many forms of cancer.
  • Plutonium-239: This isotope not only has a long half life of 24,000 years, but is also extremely toxic. If inhaled, it can increase one’s risk of lung cancer once the total dose equivalent of inhaled radiation exceeds 400 mSv. Once inhaled, Plutonium-239 can enter the bloodstream and get deposited in various organs, where it stays for decades and continuously exposes surrounding tissues to radiation. This increases one’s risk of various cancers.

 

Water Safety

Q: Can I drink the tap water in Japan?

A: At present, drinking tap water in Japan poses no immediate health risk, but conditions will differ based on location and may fluctuate. Essential hydration should not be compromised in an attempt to reduce exposure to radionuclide contamination.

Currently, radioactive iodine is the most common detected contaminant. The standard for adults is 300 Becquerels* per liter in drinking-water. In the very unlikely scenario that drinking-water was contaminated and consumed for an entire year at this level, the additional radiation exposure from this water would be equivalent to being exposed to background radiation for one year. (* One Becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second)

Q: Can radioactive contamination be removed from water?

A: Yes, it can. This may be accomplished by standard water treatment procedures, as well as through controlled dilution of contaminated water with non-contaminated water. Radioactive iodine cannot be removed by boiling water.

 

Food Safety

Q: Is there a risk of radioactive exposure from food contamination?

A: Yes, there is. Foods become contaminated with radioactive materials released from the nuclear plant which fall from the air or are carried in rain water or snow. Also, over time, radioactivity can accumulate within food through radionuclides being transferred through the soil into crops or animals. Seafood can also be contaminated when radioactive materials are washed into rivers, lakes and the sea where fish and seafood could take up the radionuclides. The severity of the contamination is dependent on the level of contaminant released, as well as the mix of radionuclides.

Currently, the presence of radioactivity in some vegetables and milk has been confirmed and some of the initial food monitoring results show radioactive iodine and caesium detected in concentrations above Japanese regulatory limits.

Q: What general advice can be given to food consumers and producers in the event of a nuclear emergency?

  • Cover food in plastic sheets or impermeable tarpaulins. This protects against radioactive contamination.
  • Minimize radioactive contamination of livestock by moving animals into a shed or barn.
  • Greenhouses should have their ventilation system closed to protect growing vegetables.
  • Avoid consumption of agricultural produce, livestock and seafood from affected areas.

Q: Can food produced in other countries be affected by the events in Japan?

A: This is unlikely. At present, amounts of radioactive caesium and iodine detected in other countries are well below acceptable levels and would not pose a health concern to those who eat the food.

Q: What actions are being taken to monitor the safety of food from Japan?

A: Japanese authorities have instituted monitoring of food products and have restricted the consumption and distribution of some products in certain prefectures.

Other countries have implemented food control measures mirroring that of the Japanese authorities.  In some cases, food imports from the affected prefectures in Japan have been temporarily banned.

Q: Are there health risks to people living outside of Japan from radiation emitted into the atmosphere from damaged Japanese nuclear power plants?

A: No. Thus far, the radiation levels measured in other countries are far below the level of background radiation that most people are exposed to in every day circumstances.

Radiation levels are being monitored by the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), which operates 63 surveillance stations around the world.

Related Articles:
Japan May Be “Sinking” Due To Earthquake Damage.
APEC Secretariat Offers Condolences And Solidarity To Japan.

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Source: World Health Organization.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Rebecca Lim is a Singaporean-born medical doctor practising in Melbourne, Austraia. She earned her MBBS degree from Monash University, Australia.

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