This chart provides an excellent explanation of the dangers of radiation exposure. There are also several links to radiation level maps in Japan and related videos.

Radiation Effects Fukushima Japan

Radiations Monographie Effets sante valeurs millisieverts mSv Japon

The Wall Street Journal was providing an excellent interactive map of radiation levels in Japan up until April 2011 and then stopped reporting further details. Wonder why?

A map of citizen measured radiation levels shows radioactivity is distributed in a complex pattern reflecting the mountainous terrain and the shifting winds across a broad area of Japan north of Tokyo which is in the center of the of bottom of the map. Radiation limits begin to be exceeded at just above 0.1 microsieverts/ hour blue. Red is about fifty times the civilian radiation limit at 5.0 microsieverts/hour. Because children are much more sensitive than adults, these results are a great concern for parents of young children in potentially affected areas.

Radiation readings in Japan Map

Radiation readings in Japan Map

Radiation Level Map of North America

Radiation Map of North America

Real time World Map of Jet Stream

Jet Stream Map

List of Radiation And Jet Stream Forecast Monitoring Sites around the World courtesy of Rense.com

Fukushima radiation nuclear fallout map

Fukushima Japan radiation testing