Nuclear weapon test debris 'persists' in atmosphere
Date published: 21st January 2014
Previously, scientists believed that nuclear debris found high above the Earth would now be negligible.
However this research shows that plutonium and caesium isotopes are still present at surprisingly high concentrations.
Lead author Dr Jose Corcho Alvarado, from the Institute of Radiation Physics at Lausanne University Hospital in Switzerland, said: "Most of the radioactive particles are removed in the first few years after the explosion, but a fraction remains in the stratosphere for a few decades or even hundreds or thousands of years."
However, he said the levels were not high enough to pose a risk to human health.
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