Polar Bear Cubs (IMAGE) Norwegian University of Science and Technology Caption A comparative study from researchers at the Norwegian University of Science and Technology of PCB levels in polar bear cubs over the last decade shows a decline in blood levels that researchers believe is due to real decreases in PCB levels in the environment and in polar bear mothers. Credit Jenny Bytingsvik, NTNU Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.