USGS Measures Fallout from Fukushima in US NADP Precipitation Samples Radioactive Rain In 15 States

USGS and the National Atmospheric Deposition Program (NADP) networks measured fission-product isotopes in the U.S. from the Fukushima Dai-ichi nuclear power facility atmospheric release incidents, which occurred March 12 and 14, 2011 near Sendai, Japan. This project added to the body of knowledge about radioactive fallout from the March 12-14, 2011 incident and exhibited the capabilities of the USGS and NADP to respond to an unexpected atmospheric release. 

Following the disaster, radioactive iodine and radioactive caesium were detected in precipitation samples collected in the U.S. at NADP sites. Detectable quantities of Iodine-131, Cesium-137 and Cesium-134 were observed at approximately 20% of the NADP locations where precipitation was sampled between March 15 and April 5, 2011.  Radioactive iodine and caesium are often some of the largest contributors to human radiation doses after an accident at a nuclear reactor.  Fallout amounts measured in precipitation by NADP were similar to amounts measured by other organizations, which were determined to be well below any level of public health concern.