Polar bears are already seriously threatened by climate change, but according to a new study they’re also facing another significant threat to their survival — toxic pollutants.
For the study, which was just published in the journal Environmental Toxicology and Chemistry, researchers analyzed data from four decades of research on exposure to toxins in species including Arctic cod, ringed seals and polar bears.
Specifically, they were looking at a class of pollutants in the Arctic known as persistent organic pollutants (POPs) that stay in the environment for long periods, accumulate in humans and wildlife, and are known to be toxic to both. These POPs are able to spread widely throughout the environment, and make their way through the food chain from plankton all the way to polar bears, accumulating in highly toxic doses as they move through the system to larger animals.
Unfortunately, researchers found polar bears fared the worst, with exposures that were 100 times higher than what is considered safe for an adult bear. More concerning is that for cubs who are exposed to toxins through their mother’s milk, the risk was 1000 times greater. According to the study, these pollutants are known endocrine disrupters, which could have a serious impact on developing cubs.
“This work is the first attempt to quantify the overall risk of POPs for the Arctic ecosystem and to define a ranking in order to highlight the most dangerous chemicals in the mixture,” said Sara Villa, a toxicologist at Italy’s University of Milano Bicocca and co-lead author of the study.
Unlike PCBs, these pollutants are still in production. Some make their way into the environment through agriculture, while others are applied as industrial products, or created as byproducts in industrial production. POPs also change in composition and while some have been banned, new ones are still entering the environment. One in particular, perfluorooctane sulfonate, which was used as a fabric protector, among other things, is still posing a high risk to polar bears.
The study’s authors note that since the 1980s, control measures have helped decrease the risk to cubs, but they still hope that further mitigation and control measures will be implemented to stop POPs from becoming an even bigger problem, or one that will take generations to resolve.
“The results demonstrate that international control measures are effective at reducing the risk to ecosystems. Nevertheless it is fundamental to continuously implement the control of new and emerging contaminants,” added co-lead author Marco Vighi.
For polar bears, every measure to protect them will help. Even without taking this issue into account, another recently published study concluded that one-third of the world’s total polar bear population is going to disappear over the next 35 years as they continue to lose the sea ice they need to survive because of climate change.
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