Elevated Radiation Claimed At Tokyo 2020 Olympic Venues

An anonymous reader writes "A citizens' group in Tokyo claims to have found elevated levels of radioactivity at 39 sporting venues earmarked for the 2020 Olympic Games. Expert and organizers are cautious about the findings but see no problem, as the levels do not pose an immediate threat to human health. From the article: '"It is difficult to have this debate unless we know for sure whether this radiation is from Fukushima or whether it is naturally occurring background radiation," said Pieter Franken, founder of the Japan office of the environmental monitoring organization Safecast."

Comments

Here's the letter and data

[evilsofa]

This appears to be the letter and the data that started all this:

http://olympicsokuteikai.web.fc2.com/encontents.html

Perhaps the most crucial part of the letter is this:

"Just before the Fukushima power plant accident, the mean value of the atmospheric radiation in Tokyo was estimated as 0.04 Sv/h, and radioactive Cesium was almost non-existent. Therefore, atmospheric radiation value above this level can be regarded as the effect of the nuclear accident."

Is that a valid assumption?