137Cs and 210Po in Pacific walrus and bearded seal from St. Lawrence Island, Alaska

Abstract

The activity concentration of Cesium-137 ( 137Cs) and naturally-occurring Polonium-210 ( 210Po) were measured in the muscle tissue, kidney and liver of Pacific walrus ( Odobenus rosmarus divergens) and bearded seal ( Erignathus barbatus) collected by native hunters from the Bering Sea during May 1996. The mean 137Cs concentrations in muscle, liver and kidney of Pacific walrus were 0.07, 0.09 and 0.07 Bq kg −1 ( n = 5, wet weight), respectively, and 0.17, 0.10, and 0.17 Bq kg −1 ( n = 2, wet weight), respectively, in bearded seal. In general, 137Cs tissue concentrations are significantly lower than those previously reported for mammals from other regions. By comparison, 210Po activity concentrations are more variable and appear to be higher level compared with mammal data from other regions. The mean 210Po concentration in the muscle tissue, liver and kidney of Pacific walrus ( n = 5, wet weight) were 28.7, 189, and 174 Bq kg −1, respectively. This compares with 210Po concentration values ( n = 2, wet weight) of 27, 207 and 68 Bq kg −1 measured in the muscle tissue, liver and kidney, of bearded seal, respectively. Estimated concentration factors—as defined by the radionuclide concentration ratio between the target tissue to that in sea water—were two to three orders of magnitude higher for 210Po that those of 137Cs. We conclude from radiological dose estimates that ingestion of 137Cs in foods derived from walrus and seal will pose no threat to human health. This work has important implications for assessment of risks of Alaskan coastal communities concerned about the dumping of nuclear waste in the Russia Arctic.