
The three main decontamination methods that have been highly publicized through media reports are: the stripping away of surface soil from school playgrounds and athletic fields, the removal of mud accumulated in gutters, and the washing of roofs using high-pressure water cleaners. While the first method is considered effective, the remaining two have been found to be effective only to a certain point, and some especially warn against overestimating the effects of high-pressure water cleaners.
"It might make you feel like you're decontaminating, but there's a limit to the amount of radioactive cesium that's caked onto roofs that can be eliminated with high-pressure water cleaners," says Kunihiro Yamada, a professor of environmental science at Kyoto Seika University. "The water cleaners wash surface dirt off, but then that tainted water goes into sewers and can contaminate rivers, thereby affecting farm goods and seafood. If people in highly populated areas were to begin using water cleaners, we may end up finding people forcing tainted water onto each other."...........................
He illustrated the gravity of the situation and the dire need for decontamination efforts, saying: "The amount of radioactive materials that have been released in the latest nuclear disaster, if converted to uranium, is the equivalent of 20 of the atomic bomb that was dropped on Hiroshima."
http://mdn.mainichi.jp/features/news/20111007p2a00m0na018000c.html