The evolution of85Kr concentrations in the atmosphere has been followed in the Northern hemisphere (France) from June 1966 to February 1979
and in the Southern hemisphere from March 1968 to October 1977 (Tahiti and Terre Adélie). The growth observed during the years
1966–1968 (1.8 pCi·m−3 per year) in the Northern hemisphere did not continue in 1969, 1970, 1971, during which period a constant level at 14.8 pCi·m−3 per year and even a decrease (12.9 pCi·m−3 in 1971) were noticed; this was followed by a new increase of about 0.9 pCi·m−3 per year. In the Southern hemisphere, a regular groth from 1968 to 1974 (0.9 pCi·m−3 per year) was followed by values stabilized around 14.5 pCi·m−3. The curve illustrating the evolution of the Krypton specific activity in the Northern hemisphere from 1954 to February 1979
shows that this increased in a discontinuous way from 1 to 40 disintegrations per minute; nevertheless the present atmospheric
activity is very low with a value of only 8·10−5 MPC.