There is good news for polar bears living on the Norwegian archipelago of Svalbard. Researchers from the Norwegian University of Science and Technology have found less PCBs and related contaminants in cubs. Levels have dropped by as much as 59% between 1998 and 2008. Mother bears also show a significant drop in PCB contamination. The compounds were banned by many industrialized countries 30 years ago. They were once ubiquitous, used as coolants and insulators in electric motors and transformers. Production of PCBs has been banned since May 2004 by the Convention on Persistent Organic Pollutants. Levels are still considered too high for the bears' health since they affect thyroid hormones and may also reduce fertility. Polar bear milk is very high in fat content which allows polychlorinated biphenyls to be easily passed on to nursing cubs. Their favorite prey animal, seals, are also high in fat. In humans, PCBs have been linked to delayed development and lower IQs. The 2008 concentrations of PCBs in cubs was about 100-150 times higher than those known to affect thyroid hormones in human babies. Polar bears live and develop in a high stress environment where food is sparse and weather conditions often extreme. About 500 bears inhabit the main islands. A potent, man-made toxin in their habitat only makes survival more difficult. Still the results are encouraging and show once again that nature will heal itself if man cooperates.