Better to read the site http://ex-skf.blogspot.com/
as he tries to keep up with all aspects of Japan dealing with nuclear power and fallout involving tea. seaweed, to cement, etc. Also. maybe check the Greenpeace site for information as they asked Japan for permission to test seawater and fish near the accident and were refused but try to keep track of the fallout.
On a sensor, the difference in readings from an adult holding it, to a child holding it, to laying on the ground can be 100 fold. Defenseless children are more susceptible to fallout just being nearer the ground as dust kicks up first to their level.