The World Health Organisation website provide a useful selection of pages on radiation risks arising from the Japan earthquake.
1. Current risk http://www.who.int/hac/crises/jpn/faqs/en/index.html
2. Ionising radiation http://www.who.int/hac/crises/jpn/faqs/en/index1.html
3. Human exposure to ionising radiation http://www.who.int/hac/crises/jpn/faqs/en/index2.html
4. Travel advice http://www.who.int/hac/crises/jpn/faqs/en/index3.html
5. Health effects http://www.who.int/hac/crises/jpn/faqs/en/index4.html
6. Public health actions http://www.who.int/hac/crises/jpn/faqs/en/index5.html
7. Personal protective measures http://www.who.int/hac/crises/jpn/faqs/en/index6.html
8. Food safety http://www.who.int/hac/crises/jpn/faqs/en/index7.html
9. Water contamination http://www.who.int/hac/crises/jpn/faqs/en/index8.html
10. WHO’s response http://www.who.int/hac/crises/jpn/faqs/en/index9.html
In addition the WHO publishes regular situation reports regarding radiation exposure through air, drinking water and locally grown foodstuffs.