I suppose it all comes down to trying to establish the ‘actual’ risk versus the ‘theoretical’ risk and what level we as individuals and officials are willing to accept. For instance everybody knows that UV in sunlight can cause melanomas, some people take the risk seriously and apply various precautions, others view the risk as less and take no precautions, similar with smoking.
A few years ago I visited the Nevada Test Site and was able to go to the Sedan Crater, it would be easy to assume that standing in the crater of a nuclear explosion would be very bad for your health but there was a sign there that said something like ‘You would have to stand here for 4 years to receive the same amount of radiation as a normal X-ray’

Sedan Crater http://en.wikipedia.org/wiki/Sedan_Crater