137Cs, 40K and 210Po in marine mammals from the southern Baltic Sea

•Marine mammals from the Polish coast contain high levels of 137Cs.•Marine mammals are good sentinels of 137Cs contamination of the Baltic Sea.•Radiation doses from the naturally occurring 40K and 210Pb were higher than those from 137Cs.•Dose assessments did not imply health effects from 137Cs exposure in Baltic mammals.

This study provides information on baseline concentrations of the radionuclides Cesium-137, Potassium-40 and Polonium-210 in sea mammals from the Baltic Sea. The radionuclides were analyzed in the liver, kidney and muscle of harbor porpoises, striped dolphins, and gray and ringed seals from the Polish coast by γ- and α-spectrometry. Median 137Cs activities were 14.8, 13.2 and 23.2 Bq kg− 1 w.w. in the liver, kidney and muscles, respectively. Activities of 40K and 210Po in the respective tissues were found to be 79.1, 79.8 and 111 Bq kg− 1 for 40K and 58.1, 59.2 and 32.9 Bq kg− 1 for 210Po. The measured 137Cs concentrations were extraordinarily high in comparison to those reported in sea mammals from other locations. However, dose assessments did not imply health effects from 137Cs exposure in Baltic Sea mammals. Correlations between 137Cs tissue activities and reported sea water concentrations highlight the potential use of marine mammals for biomonitoring purposes.