Analysis of data from sensitive U.S. monitoring stations for the Fukushima Dai-ichi nuclear reactor accident, Journal of Environmental Radioactivity: [A] major nuclear event at the Fukushima Dai-ichi nuclear power station… resulted in a breach of the nuclear fuel integrity and release of radioactive fission products to the environment. Fission products started to arrive in the United States via atmospheric transport on March 15, 2011… Atmospheric activity concentrations of 131I reached levels of 3 x 10^-2 Bq/m³ [30,592 microBq/m³] in Melbourne, FL. The noble gas 133Xe reached atmospheric activity concentrations in Ashland, KS of 17 Bq/m³… [These levels] were well above the detection capability of the radionuclide monitoring systems within the International Monitoring System [IMS] of the Comprehensive Nuclear-Test-Ban Treaty [CTBTO]… it should be noted that non-IMS stations located in Richland, WA detected the event one day earlier than any other systems within the US IMS network… The iodine detections reported in this manuscript are solely representative of the particulate iodine atmospheric activity concentration. It is recognized that the gas phase iodine was not collected via aerosol filtration [which] would be useful to assess the event and to quantify the total radioiodine atmospheric activity concentration.

According to remarks included with CTBTO data recently released by the United Nations Scientific Committee on the Effects of Atomic Radiation, the total iodine-131 in the air was up to 500% of the amount shown.

CTBTO Particulate air monitoring data (.xls file), July 2014: The PTS [Provisional Technical Secretariat] itself issued a number of comments and caveats on the data:… “Since the IMS stations use paper filters to collect the particulate radionuclides in the air, part of the iodine in gaseous form passes through the filter easily. It is estimated that only 20-50% of total iodine (from all forms) was collected in the samples.”

Of the more than 1,500 measurements in the CTBTO data taken since Fukushima began, iodine-131 levels detected in Florida were the highest of anywhere in the world outside of Japan. Florida also recorded 4 of the top 10 daily measurements.

Before the U.N. made this data public, an ENENews report from April 2011 noted that for the specific date of March 22, Florida recorded the highest I-131 level of any  CTBTO monitoring station in the world. See: Melbourne, Florida had highest iodine-131 reading of any CTBTO monitoring station in the world from March 22-23 (CHART)