PCBs (polychlorinated biphenyls) were widely used as cooling fluids and insulators in transformers and electric motors in our not-so-distant past. Studies found that PCBs acted as a neurotoxin and endocrine disruptor in humans and animals, and exposure to the pollutant resulted in low birth weights and developmental delays.
The chemicals were fat-soluble and were more concentrated the higher up in the food chain you looked. As a result, industrialized nations began banning PCBs thirty years ago. Then in the era of solar panels and global warming, they were banned in May 2004 from global production by the Stockholm Convention on Persistent Organic Pollutants.
Polar bears suffered from PCBs in particular, because they needed great stores of fat to survive the arctic winters. Added to that was the problem that their primary food source, seal, was also high in fat. This hit polar bear cubs particularly hard, because their mother’s milk was very fatty. The beleaguered species was already being affected by melting Arctic ice and shrinking habitat, and environmental pollutants were one more item to add to the list. Now there’s a flicker of hope in polar bear futures with the latest environmental news; PCB levels seem to be falling.
“The levels of PCB compounds in blood samples from females are on the decline,” says Jenny Bytingsvik, a biologist at Norwegian University of Science and Technology (NTNU) who is completing her doctoral dissertation on the findings. “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.”
In a study of polar bear cubs from Svalbard, Norwegian researchers discovered that PCBs and other pollutants in cub blood levels had decreased 59% from 1998 to 2008. There had also been a significant drop of 55% in their mother’s blood levels as well. The levels were still too high to be considered healthy, but there was significant evidence that proved the ban is effective.
Less PCBs meant that polar bear fertility rates may be on the rise as their thyroids are less affected by the chemical. Without the pollutant hurting their ability to grow and thrive, they’ll be able to cope better with the other challenges ahead. Even more importantly, the decreased levels of PCBs are evidence that a unified policy against a harmful contaminant is possible, and that humans can change this world for the better.
Photo Credit: Martin Lopatka