Gary7 said:
Certainly possible, but I wouldn't say its a certainty (or "undeniable") given the Swedish study that was linked. Firstly, the study says it does not take into account the ingestion of local produce, which presumably plays a significant role in internal exposure rates (and therefore cancer rates). I don't think the residents of that section of Tokyo are growing much of their own produce in that soil. Secondly, the highest level mentioned in Tokyo in your first link is for an extremely localized area in the northern part of Tokyo, while the Swedish study seems to be describing areas of far more widespread contamination. There could also be a bias induced by increased awareness and screening for cancer post-Chernobyl.
Just my two cents.
These are very fair observations, and I definitely considered some of these arguments before I posted.
Firstly, regarding local produce. As a resident of Tokyo, I can confirm that we are not consuming many products grown in Tokyo. However - and swl alludes to this - agricultural production in Japan is extremely localised. Due to strict import tariffs and government advocacy, more than 90% of what is on sale in Tokyo at the moment is produce from radiation affected areas. Fukushima cucumbers, Ibaraki Spinach, Chiba carrots. I am following the spirit of the IRSN recommendations regarding providence of produce, and I am struggling to find anything produced outside the wider contamination zone. At this point it comes down to how much faith one puts in the Japanese testing regime as compared to the limitations put in place in Sweden after Chernobyl.
As for the 'extremely localized' contamination figures for eastern Tokyo, I would point out that we are discussing these measurements due to the action of concerned citizens. These figures seem isolated due to that fact that no one is measuring on a systematic level - concerned parents in Koto-ku went out to the local park, sunk a spade and sent the soil away for testing. The fact that they stumbled upon such a hot spot suggest to me that, far from being 'extremely localized', the problems are in fact much more wide spread than has been admitted, although we can revisit this again when a more comprehensive survey has been undertaken. However I would bet you the price of a geiger counter that, by using the previously mentioned NNISTAR map along with the expanding citizen led mapping at safecast.jp, I could go out tomorrow and find you 10 soil samples bearing comparable levels of contamination in wider Eastern Tokyo.
Finally, it is worth noting that the Swedish study dealt with lower contamination levels - it broke contamination down into band of <3000, 3000-29 0000, 30 0000 - 39 000, 40 000 - 59 000, 60 000 - 79 000, 80 000 - 120 000 bq/m2. The results were surprisingly linear, so if (hypothetically) most of Koto-ku is 10 times less contaminated than the 200,000 bq/m2 hotspot in the public park in Oshima, the conclusion remains the same - cancer rates in parts of Tokyo can be expected to increase.