Current risk of radiation-related health problems in Japan

What is the current risk of radiation-related health problems in Japan?

The actions proposed by the Government of Japan are in line with the existing recommendations based on public health expertise. The government is asking people living within 20 km of the Fukushima Daiichi nuclear power plant to evacuate and those between 20 km and 30 km away from the plant are asked to stay indoors in unventilated rooms. People living farther away are at lower risk than those who live nearby.

However, radiation-related health consequences will depend on exposure. Exposure in turn is dependent on the amount of radiation released from the reactor, weather conditions such as wind and rain at the time of the explosion, the distance someone is from the plant, and the amount of time someone is in irradiated areas.

The Fukushima nuclear plant in Japan is leaking radiation, and that sounds scary. Will it kill a lot of people?

Not likely. The World Health Organization says that in a nuclear power plant accident, the general population usually isn't exposed to doses high enough to cause acute effects, such as skin redness, hair loss and radiation burns.

But isn't radiation always dangerous?

People are exposed to natural radioactive materials every day from space (cosmic rays) and the soil, water and air. There also are manmade sources of radiation, such as X-rays and CT scans.

The radiation dose is expressed in units called a sievert (Sv). On average, a person is exposed to about 3.0 millisieverts a year. The radiation from a CT scan amounts to about 11 mSv.

What kind of radiation is leaking?

The materials are iodine-131 and caesium-137, and they can damage the thyroid gland and the blood system. The body parts most vulnerable to radiation damage are the blood and immune systems, reproductive organs, and the stomach and intestinal tract. Exposure to more than 2,000 millisieverts - equivalent to more than 180 CT scans - can have long-term and genetic effects.

Is everyone affected the same way?

Children and fetuses are most vulnerable because their cells are young and actively proliferating.