Perhaps there is no health question so political as this one.
Japanese scientist Shunichi Yamashita claims in this interview with Der Spiegle that there is no statistically significant increase in cancer from exposures levels of 100 millisieverts or less despite the article providing a statistic of a cancer rate of 1 in 100 at 100millisieverts of exposure
Yamashit cites "research in Hiroshima, Nagasaki, and Chernobyl" as evidence for his claim of statistical insignificance, although he does agree that biological [laboratory] research on radiation shows that lower levels can affect DNA and cells.
[nowhere in the interview is a distinction made between adult and children's exposure effects, which alone should raise a red flag since kids are far more susceptible to damage than adults unless the adults are ill or old]
What I've learned from studying the research on Hiroshima, Nagasaki, and Chernobyl is that the research is full of contradictions, bias, and outright censorship.
I've posted many links to studies, reviews, and editorials arguing that the official statistics for all of these events are significantly skewed lower.
Here is one more example of a critical examination of official statistics, this example focuses on Chernobyl. This article is very accessible and provides a comprehensive overview. The radiation dose equivalent calculator here may be helpful http://online.unitconverterpro.com/unit-conversion/convert-group/convert.php?cat=radiation---dose-equivalent
Effects of the Chernobyl Catastrophe-Literature Review-
Alex Rosen Heinrich-Heine UniversityDüsseldorf, Germany
January of 2006