Here are the maps of radiation measured by citizens at asphalt level in the nuclear-free Japanese territory.
Okinawa is an example of what we should normally see for the rest of Japan (and the world), which is unfortunately not the case, even in western Honshu. Data in Okinawa is statistically relevant and consistent with an average of roughly 0.05 uSv/h. Okinawa thus provides us with a valid control group.
Distribution of radiation remains relatively the same in western Japan, primarily due to the lack of new data. The Hyogo / Kansai / Shiga regions still display levels about twice as high as normal which contrast with Okinawa low levels. Although this is not an alarming situation, it does show that fall-out occasionnally visit this area. Besides, the small sample of measures which moreover tend to be outdated does not make for a comforting outlook. Notice the ultra-low level of 0.01 uSv/h measured on a ship at the tip of the Kii peninsula as a reference.
Hiroshima displays low levels, especially considered its nuclear history. However, readings are taken at asphalt level which of course does not date back to the American bombing.
More surprising are the relatively high values of about 0.20 uSv/h near the nuclear power plants in Shimane (Honshu) and in Nagasaki (Kyushu) prefectures. These may be more related to the poor ethics of the Japanese nuclear industry and its release of waste into the wild rather than the Fukushima disaster. Values for the rest of Kyushu compare to the rest of western Japan with about 0.10 uSv/h.
Although values differ, do they pose a danger for human health? According to Wikipedia, “The worldwide average background dose for a human being is about 2.4 mS/year”. Excluding the highest measured values found near nuclear power plants, the cumulated averaged dose is less than 1 mSv/year for western Honshu, which is usually regarded as the maximum limit for the general public. Still according to Wikipedia, this is 20 times less than the irradiation from a single CT scan. Therefore, if no waste was brought from Fukushima, the whole area could be considered relatively radio-safe based on these readings, even though the sampling size is small and although Shikoku provides no data at all.
SurvivalJapan will therefore report only on risk events, such as a fall-out forecasts on the area, exceptional conditions which may trigger more instability at Fukushima, and of course wild waste dumps rumors and continuous contaminated food distribution which remains the number 1 threat.