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For vegetables, it is effective to wash or peel them as radioactive materials get attached to the surface. For fish, however, radioactive materials could be drawn into the body through seawater and feed, so they can be eliminated significantly by removing offal. It is also important to wash the fish because there may be some radioactive materials left on the surface. It is recommended to avoid eating fish skin.
I find it hard to believe that washing vegetables will make them "safe"?