Phil from the world nomads.com safety hub here. Apart from a 24 hour period around March 16th, the radiation levels in Tokyo have been near normal and well within internationally accepted "safe"levels. Some people are concerned about cesium levels in the drinking water and are sticking to bottled water, although there's no clear evidence the water is contaminated. There are concerns about contaminated food in Tokyo. The government has banned all beef from the Fukushima prefecture after high levels of Cesium were found in 650 cows that had been grazing within the 30 kilometer exclusion zone! - some of the beef made it onto the supermarket shelves. However, one official said it would be necessary to eat the contaminated meat at every meal for a year before it approached abnormal levels in your body. Obviously the contaminated meat has been withdrawn from sale, why meat from Fukushima wasn't already banned is a mystery.
Personally I think the risk of radiation exposure during a short visit is extremely low (I might think differently if I lived there permanently), and I'd have no hesitation in going to Tokyo. However each person has to make their own judgement on the level of risk they're prepared to accept. about 7 years ago