A group of Tokyo parents filed a request Tuesday asking the metropolitan government to change the way it determines radiation levels in the capital after their own study found relatively high levels of contamination around Koto Ward.
"No! Hoshano Koto Kodomo Mamoru Kai" ("No! Radioactivity — The Group to Save Children in Koto") found that some areas in Koto Ward, located in the eastern part of the capital, had a maximum hourly reading of 0.18 microsievert of radiation.
That number is a fraction of the level in Fukushima Prefecture, which hit about 1.6 microsieverts per hour on Tuesday.
Nevertheless, the group warned, their findings indicate that some Tokyo children are in danger of being exposed to more than 1 millisievert of radiation per year, the nonbonding limit set by the education ministry for Fukushima Prefecture students.
"This should be taken as a sign that a grave (contamination) is in progress in Tokyo," Ayako Ishikawa, the leader of the group, said during a news conference.
The metropolitan government checks levels of radioactivity at an elevation of 18 meters in Shinjuku Ward, where the maximum hourly reading was about 0.06 microsievert on Tuesday.
But Ishikawa insists such readings are unreliable and should be taken at about 1 meter above the ground.
"We request that the Tokyo government and Koto Ward properly check the radiation levels, especially around school areas and parks," she said.
According to Ishikawa, her group, which has about 35 members, checked the soil and air in Koto Ward for contaminants between May 21 and 25 with the help of Kobe University professor Tomoya Yamauchi.
Yamauchi, an expert on radiation physics, said high levels of contamination were detected in soil, especially around a plant in Koto Ward that produces sludge, an ingredient in cement, where the level reached 2,300 becquerels per kilogram.
That level is about a third of the 6,550 becquerels per kilogram detected at a schoolyard in Fukushima Prefecture in April.
"But I can say that I wouldn't let my child play baseball at the ballpark, which is located near the sludge factory," Yamauchi said, adding there is concern the factory itself could be releasing radioactive particles.
"The metropolitan government should reveal the safety measures taken in the factory, and conduct proper radiation level checks at the facility, including the chimney," Yamauchi added.