The Preparatory Commission for the Comprehensive Nuclear-Test Treaty Organization (CTBTO) reported on Thursday that within nine days after the accident, the radioactive cloud had crossed North America, and
Three days later when a station in Iceland picked up radioactive materials, it was clear that the cloud had reached Europe.
The report notes that dangers from some radioactive particles decrease with distance, due to atmospheric dispersion rates and precipitation, and a limited half-life of days or weeks, which reduces radioactivity over time. However, other radioactive substances such as Plutonium can linger for thousands of years.
The cumulative effects of the hundreds of atmospheric nuclear tests released such vast amounts of radioactivity that the overall level of radioactivity in the Earth’s atmosphere increased to levels that even dwarfed the Chernobyl disaster. Radioactive isotopes could be traced in baby teeth of children born even at great distances from the test sites in these decades.
A wide range of emission sources can be detected by the CTBTO’s radionuclide stations, among them Iodine-131 and Caesium-137, and by determining ratios between the various radioactive isotopes, can pinpoint the source of radioactive emissions.
So sensitive are these monitoring stations that a rooftop detector at CTBTO’s Vienna headquarters still records trace emissions from Russia’s 1986 disaster at Chernobyl.
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