Bloomberg News

Tokyo’s Setagaya Says Radiation Spike Unlikely From Fukushima

October 13, 2011

Oct. 13 (Bloomberg) -- Tokyo’s Setagaya district officials said an investigation today of a “high” radiation reading in the area indicates it may not have come from the crippled Fukushima reactors.

The district in the western part of the capital said earlier today it will expand tests in 258 locations after a local resident alerted authorities to a radiation spike that required partially blocking off a sidewalk to the public.

Investigators entered an unoccupied house alongside the sidewalk and radiation readings led them to remove floorboards where they found a case of unidentified substances in bottles, public broadcaster NHK reported.

“When a dosimeter was brought close to the bottles the radiation readings exceeded the limit of the device,” Setagaya Mayor Nobuto Hosaka said in a press conference carried by NHK. No further details were given on the possible contents of the bottles.

The reading was more than 30 microsieverts per hour, NHK reported, which equates to a dose of 157.7 millisieverts per year, or more than 150 times the internationally recommended safety level for the general public, according to a Science Ministry formula.

The discovery follows a flurry of reports this week on a rise in radiation readings in Tokyo and Yokohama, indicating fallout from the Fukushima nuclear disaster has formed “hot spots” in the cities.

Setagaya ward, a mostly residential district with a population of more than 840,000 people, earlier said radiation readings near the sidewalk in the Tsurumaki 5-chome area reached 2.7 microsieverts per hour. The ward, home to Komazawa park that hosted events in the 1964 Olympics, is 233 kilometers (145 miles) from the Fukushima reactors leaking radiation.

More Testing

Other areas in Tokyo and Yokohama have reported radiation readings requiring further investigation, with most originating from local residents using personal dosimeters.

Setagaya adjoins Ota ward where radiation levels exceeding the ward’s own safety standard of 0.25 microsieverts per hour were detected at 13 schools, the Ota ward board of education said today. The tests are continuing at the schools.

In Yokohama, officials are testing samples in an area of Kohoku ward after a resident removed sediment from an apartment building roof that laboratory tests showed contained strontium found in radioactive fallout.

“We received data from a resident about strontium and we are carrying out an investigation in the neighborhood by picking up samples for lab tests,” said Yokohama city official John Kuramochi. He declined to confirm if the first lab tests showed the sediment contained strontium 90.

Strontium 90 has a similar structure to calcium and tends to accumulate in bone and can cause bone cancer and leukemia, Hiroaki Koide, a nuclear physics scientist at Kyoto University, said on the phone today.

“It seems what was found in Yokohama is a relatively high radiation dose, so they need to thoroughly investigate.”

--Editor: Peter Langan

To contact the reporters on this story: Chisaki Watanabe in Tokyo at; Makoto Miyazaki in Tokyo at

To contact the editor responsible for this story: Peter Langan at

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