As someone who has basic understanding/education in physics and how radiation works, there is something that is confusing me and which I would like to shed some light on (I posted about this previously, but the discussion diverted to the risk of radiation in North America from the Fukushima incident, rather than the biological processes of ingesting radioactive particles).
With background radiation, and even relatively high levels of surrounding radiation, I understand that the risk is non-existant to very minimal. However, it seems that lately, people and officials are saying that food near and even in Fukushima is completely safe to eat.
In the case of surrounding radiation, sitting next to something that reads 3000 μSv/h is completely different to eating food that also emits 3000 μSv/h of radiation. In the former situation, once you walk off, the exposure stops. In the latter, radiation is constantly emitted inside your body.
Even more, the amount of radiation is not absorbed by the body equally, but it is usually very concentrated in a particular area of the body, as the particles lodge somewhere and sometimes bioaccumulate. From my understanding, the exposure to the surrounding cells is therefore more intense and prolonged.
To what degree is ingesting radioactive particles in food considered safe (or if at all), such as those in food near Fukushima, when taking into consideration that a concentrated and continuous source of radiation is different from an external one?