Radioactive cesium from the crippled Fukushima No. 1 nuclear plant probably reached as far as Hokkaido, Shikoku and the Chugoku region in the west, according to a recent simulation by an international research team based on data after March 20, a week after the hydrogen explosions.
Large areas of eastern and northeastern Japan were probably contaminated, with concentrations of cesium-137 exceeding 1,000 becquerels per kilogram of soil in some places, says the study, which was posted Monday on the website of the National Academy of Sciences.
Researchers for the U.S.-based organization said the study, based on the partial data readings, is the first to estimate potential cesium contamination across the country. But the scientists also played down the impact of the fallout on the three distant regions.