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.
Because the equator acts as a dividing line between the planet’s northern and southern air masses, radioactive materials from Daiichi
remain confined to the northern hemisphere.
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, is able to pinpoint the source of radioactive emissions.
Results from the current readings clearly indicate the radionuclide releases came from the disabled Daiichi nuclear power plant near Fukushima.
The group currently has 63 International Monitoring System (IMS) stations worldwide that are operational, with 80 planned. As of this week, more than 30 of the IMS radionuclide stations have provided data on the spread of radioactivity and noble gases
from the Daiichi catastrophe.
Using atmospheric nuclear testing done in the 1950s and 1960s that created widespread fallout and radiation-related diseases as comparison, CTBTO reports that
the levels detected at stations outside Japan up until April 7 have been far below levels that could cause harm to humans and the environment.
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.
Once completed, the IMS network will be comprised of 337 monitoring stations across the globe.