In a study of polar bear cubs in Svalbard, researchers found blood levels of PCBs and related contaminants appear to have dropped by as much as 59 per cent between 1998 and 2008, the Norwegian University of Science and Technology reported Thursday.
Levels in the cubs' mothers were as much as 55 percent reduced, the researchers said.
"The levels of PCB compounds in blood samples from females are on the decline," university biologist Jenny Bytingsvik said. "For newborn, vulnerable cubs, this is a very positive trend. Reduced levels of PCBs in the mother bears' blood mean that there is also less contamination in their milk. Even though the PCB levels we found are still too high, this shows that international agreements to ban PCBs have had an effect."
PCBs -- polychlorinated biphenyls -- were once widely used as cooling fluids and insulators in transformers and electric motors. Many industrialized countries banned them 30 years ago because of harmful effects on humans and animals.
Polar bears are particularly threatened by the pollutants, the researchers said, because the chemicals are fat-soluble and increase in concentration at the higher reaches of the food chain. Polar bear are at the top of the food chain and their preferred foods, like seals, tend to be very rich in fat, the researchers said.