TOKYO (Dow Jones)--Radiation levels in the Tokyo area were around typical background levels on Friday afternoon, while in areas close to the quake-damaged Fukushima nuclear power plant they remained high but still below levels that would pose a threat to human health, officials said.
In a separate move, the International Atomic Energy Agency will begin measuring radiation levels, staring with Tokyo, as early as Friday night, said Yukiya Amano, director general of IAEA.
The Tokyo Metropolitan Government said Friday on its website that radiation levels in downtown Tokyo stood at 0.047 microsievert an hour around 1000 GMT. That compares with the 0.035 microsievert an hour a person would typically be exposed to in Shinjuku district of downtown Tokyo due to background radiation... A chest X-ray typically exposes the patient to a radiation dose of around 100 microsieverts, according to the Radiological Society of North America. The U.S. Nuclear Regulatory Commission sets the annual occupational dosage limit for workers who deal with radiation at 50,000 microsieverts and the limit per nuclear event at 10,000 microsieverts. The U.S. Environmental Protection Agency advises that a dose of 500,000 microsieverts can cause nausea, while 4 million microsieverts can be fatal without major medical care.
Separately, Fukushima Prefecture said on its website that it measured radiation of 10.80 microsieverts around 1100 GMT Friday in Fukushima City, about 60 kilometers northwest of the plant. It said it detected 2.46 microsieverts an hour in Koriyama City, around 60 kilometers west of the plant, and 1.00 in Iwaki City, about 40 kilometers southwest of the plant, around 1100 GMT. Normal levels at these locations range between 0.04 and 0.06 microsieverts.
http://online.wsj.com/article/BT-CO-20110318-708293.htmlToday, the IAEA began to take independent readings in Japan, beginning with Tokyo.