129I concentrations of mammalian thyroids in Taiwan

The 129I and 129I/127I ratios in mammalian thyroids were determined by neutron activation analysis to estimate the 129I concentrations in the biosphere due to fallout accumulation during the past decades in this island. The average 129I/127I ratio in thyroids of grazing animals, bovine and ovine, is about 1 x 10(-9), three times higher than that of hogs. The 129I/127I ratio in twin water collected during the same period was found to be as high as 1.7 x 10(-8) and it is supposed to be the predominant source of 129I in the biosphere. The 129I concentrations in these mammalian thyroids are similar to those of non-direct contamination areas of the world, where the terrestrial 129I contents are influenced by the global fallout.