Tokyo radiation hotspot 'not linked to Fukushima'
Elevated levels of radiation found in a residential area of Tokyo are almost certainly not connected to the stricken Fukushima nuclear plant, say officials.
The reading, taken on a small area of pavement in Setagaya ward, had fuelled fears about the possible effects of radiation from the plant.
But Japan's science minister said the radiation had been traced to material stored in the basement of a house.
Local residents had been told the radiation was no threat to health.
The hotspot was detected at height of about one metre above the pavement, after Setagaya residents who had been monitoring radiation levels alerted the authorities.
The ward is more than 200km (124 miles) from the Fukushima nuclear plant, which was damaged by an earthquake and tsunami in March, so the discovery led to fears that radiation from the damaged plant had spread further than previously thought and at higher levels.
"I've been measuring radiation levels throughout the metropolitan Tokyo areas, but I have never seen such a high level of radiation [as] I found here," one member of a nuclear action group told reporters.Old bottles
The area was cordoned off as a precaution and checks carried out while nuclear experts tried to establish why such a small area was affected.
These instances say more about the concern that people have about radiation here in Japan than the actual spread of radiation from the Fukushima nuclear plant.
Sales of Geiger counters have soared in recent months - people are going around checking their neighbourhood. That is how this hotspot in Setagaya was found. Had these worried people not been patrolling the streets, it might not have been discovered at all.
Signs of people's concern are visible all over Tokyo - labels have appeared in supermarkets showing where produce is from because some people are trying not to eat food from anywhere in the Fukushima region.
Nerves are still strained as the crisis to stabilise the nuclear plant drags on into a seventh month.
Other sections of the pavement - which is regularly used by children at a nearby school and nursery - were unaffected, said the Kyodo news agency.
"The readings were found in a very small area and we will take measures to resolve residents' concerns," a spokesman for the ward, Michio Hirasawa, told Bloomberg.
Setagaya Mayor Nobuto Hosaka said washing the pavement with water had not dispersed the radiation, Reuters reported.
There were suggestions that contaminated rainwater could have collected on a rooftop before dripping on to the pavement. Officials said radiation tests would be carried out in 258 parks in the ward.
However, they said the reading of 3.35 microsieverts per hour was no threat to public health.
A person who stayed by the spot for eight hours a day for one year would receive a dose of about 17 millisieverts, said Kyodo.
The allowable limit set by Japan's government is 20 millisieverts a year, while most people are exposed to background radiation of 2 millisieverts every year.
But officials later said they were almost certain that the radiation had not come from Fukushima, after the source was traced to the basement of a nearby house, where an unknown material was being stored in old bottles in a wooden box.
Tests are now being carried out to confirm the bottles are to blame and to establish what they contain.
Health effects of radiation
- Most people are exposed to background radiation of about 2 millisieverts per year (mSv/yr)
- The lowest level at which any long-term increase in cancer risk is clearly evident is 100 mSv/yr
- Exposure to high levels of radiation can induce radiation sickness with nausea, headaches and vomiting
- Cancer is the biggest long-term risk of radiation exposure
- The extent of the damage depends on how long people are exposed to radiation, and at what level
The BBC's Roland Buerk in Tokyo says the alarm over the reading is a sign of the concern felt by people in Japan about contamination, as efforts to stabilise the Fukushima plant drag on.
The discovery in Setagaya follows reports that Strontium-90, which is linked to leukaemia, had been found on a rooftop in Yokohama, even further away from Fukushima.
Another hotpot was detected at a park in Chiba.
Last week, health workers began checking more than 300,000 children living near the Fukushima nuclear plant for thyroid abnormalities.
Parents have expressed concern about a link between thyroid abnormalities and radiation, citing reports of a rise after Chernobyl in 1986.
The Fukushima plant was crippled by the earthquake and tsunami in March which killed 20,000 people. Japan's government says the recovery and decontamination effort could take years.