According to the IPSN or Institute for Nuclear Protection and Security, artificial radioactivity in the atmosphere produced by cesio 137 presents the lowest level of the last thirty-five years. The current level is 0.9 microbecquerel per cubic meter of air.
This artificial element that emits nuclear radiation has spread to the atmosphere since the tests carried out with nuclear weapons in the atmosphere and nobil accident. The concentration also varies depending on the time of year. In summer, the concentration is six or eight times smaller than in winter.