Science of the Total Environment, by Marco Kaltofen (Nuclear Science and Engineering Program, Department of Physics, Worcester Polytechnic Institute) and Arnie Gundersen (Fairewinds Energy Education), Dec 2017 (emphasis added): Radioactively-hot particles detected in dusts and soils from Northern Japan… Radioactive particles from Fukushima are tracked via dusts, soils, and sediments; Radioactive dust impacts are tracked in both Japan and the United States/Canada; Atypically-radioactive particles from reactor cores are identified in house dusts… After the March 11, 2011, nuclear reactor meltdowns at Fukushima Dai-ichi, 180 samples of Japanese particulate matter (dusts and surface soils) and 235 similar U.S. and Canadian samples were collected and analyzed… Samples were collected and analyzed over a five-year period, from 2011 to 2016. Detectable levels of 134Cs and 137Cs were found in 142 of 180 (80%) Japanese particulate matter samples… U.S. and Canadian samples had detectable 134Cs and 137Cs in one dust sample out of 32 collected, and four soils out of 74… The mean in Japan was skewed upward due to nine of the 180 (5%) samples with activities > 250 kBq kg− 1 [250,000 Bq/kg]… 300 individual radioactively-hot particles were identified in samples from Japan; composed of 1% or more of the elements cesium, americium, radium, polonium, thorium, tellurium, or strontium. Some particles reached specific activities in the MBq μg− 1 level and higher [1,000,000,000,000,000 Bq/kg]… Some of the hot particles detected in this study could cause significant radiation exposures to individuals if inhaled. Exposure models ignoring these isolated hot particles would potentially understate human radiation dose.

Fairewinds Press Release, Jul 27, 2017: Radioactively-Hot Particles in Japan; New Study Shows Full Radiation Risks are not Recorded… the article details the analysis of radioactively hot particles collected in Japan following the Fukushima Dai-ichi meltdowns. Based on 415 samples of radioactive dust from Japan, the USA, and Canada, the study identified a statistically meaningful number of samples that were considerably more radioactive than current radiation models anticipated. If ingested, these more radioactive particles increase the risk of suffering a future health problem…

Truthout, Aug 1, 2017: Radioactive Hot Particles Still Afloat Throughout Japan Six Year After Fukushima Meltdowns — Radioactive particles of uranium, thorium, radium, cesium, strontium, polonium, tellurium and americium are still afloat throughout Northern Japan more than six years after… three full-blown nuclear meltdowns. That was the conclusion reached by two of the world’s leading radiation experts after conducting an extensive five-year monitoring project… 108 of the Japanese samples were taken in 2016, while the other 72 were gathered in 2011… “A majority of these samples were collected from locations in decontaminated zones cleared for habitation by the National Government of Japan,” the study revealed… In contrast to external X-rays, gamma, beta or alpha rays, hot particles are small mobile pieces of radioactive elements that can be breathed in, drunk or eaten in food. The fragments can then become lodged in bodily tissue where they will emanate high-intensity ionizing radiation for months or years, damaging and twisting cells, potentially causing myriad diseases and cancer… “Comparing external radiation to hot particles inside the body is an inappropriate analogy,” Gundersen toldEnviroNewsin an email. “Hot particles deliver a lot of energy to a very localized group of cells that surround them and can therefore cause significant localized cell damage.”…

Watch video presentation on study here