It's never safe

The Federal Court of Australia has ruled that two soldiers died of cancer
because they were exposed to low levels of radiation while occupying Hiroshima
in 1945. The decision last month backs the consensus among regulatory agencies
that there is no threshold below which radiation is safe—a view that is
increasingly challenged in the US and France. The soldiers received doses of
less than 5 millisieverts, while the international safety limit for workers is
20 millisieverts. “Even extremely low doses have an associated risk,” Donald
Higson of the Australian Radiation Protection Society told the court.