The Impact of Radiation on the Human Body

This article explains the effects of various doses of radiation on the human body, and the levels of radiation we are exposed to in our daily lives.


Japan’s Safety Standards Stricter than IAEA and EU Requirements

Human beings in every corner of the globe are exposed to radiation from space, from the ground, and from the food they consume. Medical devices like CT scanners and X-ray machines use radiation to diagnose medical conditions. The International Commission on Radiological Protection has set 1 millisievert as the upper limit for annual radiological exposure, not including radiation from natural sources and medical devices.

Radiation is more dangerous if a person is exposed to a large dose all at once, which increases the risk of cancer and other diseases. Ill-effects start to appear after exposure to radiation levels of around 100 millisieverts; and exposure to 7,000 millisieverts or more is invariably fatal.

In Japan, the normal upper limit for radiation exposure for workers at nuclear power stations is 100 millisieverts, but this was raised to 250 millisieverts following the disaster at the Fukushima Daiichi Nuclear Power Station. Workers are issued with a radiation dose monitoring notebook in which to record their levels of exposure, the results of health checkups, and other information. Workers are not allowed to enter a radiation management zone such as the areas around a nuclear power station without this book.

There are two types of radiation exposure: external radiation exposure through contact on the body, and internal radiation exposure caused by ingestion of radioactive foods or liquids. Internal radiation exposure is of particular concern because until the radioactive substance disappears or is expelled, it will continue to expose the person to radiation.

In order to prevent internal radiation exposure, the Japanese government has stipulated provisional regulation values for radioactivity levels in food products. These ensure safety by preventing radioactive food and drinking water from entering the food chain. The regulations are extremely strict to ensure that radiation exposure will not approach the harmful level of 100 millisieverts even if the vegetables, milk, or other items in question are consumed every day for a year. Japan’s safety standards are even stricter than those set by the International Atomic Energy Agency or by EU countries in the wake of the Chernobyl disaster.

Shipments of spinach and other vegetables were halted when radiation levels exceeding these standards were detected on March 21. Most of the radiation was from radioactive iodine, which has a halflife of just eight days. By the end of April, the ban on shipments had been lifted from all agricultural products from Ibaraki, Tochigi, Gunma, and Chiba Prefectures. 

Provisional Iodine-131 Regulation Values for Food/Drink
  Japan IAEA EU
Drinking water 300 becquerels

3,000 becquerels

400 becquerels
Milk and dairy products 300 becquerels 500 becquerels
Vegetables (excluding root vegetables and potatoes)

2,000 becquerels

3,000 becquerels

Seafood 2,000 becquerels

* All values are per 1kg
* EU standards were established in 1987, the year after the Chernobyl disaster