Icelandic orcas (IMAGE) McGill University Caption These killer whales may appear healthy, but a new study has found extremely high levels of PCB contamination in some of the whales. There was a 300-fold difference between the levels of PCBs among the most contaminated orcas compared to the least contaminated ones. The variation was mainly due to their eating habits. Credit Filipa Samarra - Icelandic Orca Project 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.