U.S. EPA response to the Fukushima Daiichi Nuclear Power Plant accident.

During the spring of 2011, the U.S. Environmental Protection Agency (EPA) used its national radiation monitoring and sampling system, RadNet, to detect, identify, and inform the public about radioactive material in the United States resulting from Japan's Fukushima Daiichi Nuclear Power Plant release. The RadNet system monitors ambient air, drinking water, precipitation, and pasteurized milk for radionuclides. To supplement its existing stationary (fixed) continuous air monitoring system, EPA deployed additional air monitors to Saipan, Guam, and locations in the western United States. The Agency also accelerated the regular quarterly sampling of milk and drinking water and collected an additional round of samples. For two months, staff located at EPA's Headquarters Emergency Operations Center, west coast regional offices, and National Air and Radiation Environmental Lab worked seven days a week to handle the increased radiochemical sample analysis from air filters, precipitation, drinking water, and milk; provide interagency scientific input; and answer press and public inquiries. EPA's data was consistent with what was expected from the Fukushima Daiichi Nuclear Power Plant release. The levels of radioactivity were so low that the readings from the near-real-time RadNet air monitors stayed within normal background ranges. Detailed sample analyses were needed to identify the radionuclides associated with the release. Starting at the end of April and continuing through May 2011, levels of radioactive material decreased as expected.