Of all the creatures on Earth impacted by reckless human activity, polar bears are having a remarkably lousy time of it. First, climate change eats away at their habitat and makes it harder to hunt, and now it looks like chemical pollutants released into the atmosphere over previous decades are causing polar bears to experience weakness or even breakage in the most sensitive of bones. As one might imagine, this doesn’t bode especially well for the continued re-population of the species.

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So, first things first: penis bone? Yes, some mammals (though not humans, in case you were wondering) have bones in their penises. No one is entirely sure what they’re there for: as New Scientist explains, it “could be just a by-product of evolution, or it may help support the penis or stimulate the female during mating.” Regardless of its purpose, one thing’s for certain; if a male polar bear experiences weakening or fracturing of the penile bone, they’re going to have a tougher time procreating.

A team at Aarhus University, Denmark lead byChristian Sonne, found that a certain class of pollutants, organohalogens, when present a high levels, caused polar bears to have smaller testes and a smaller penis bone. Bad enough, but then they began to look at a specific class of organohalogens—polychlorinated biphenyls (PCBs)—and found that these chemicals can cause the penis bone to be less dense.

After 80 years of inclusion in paint and rubber products, PCBs were banned by a UN treaty in 2001. But the pollutants are slow to break down, and concentrate at higher levels in the cold, polar air. This leaves polar bears prone to far greater exposure to PCBs, which are a form ofEndocrine Disruptor (EDC). They are recognized as a carcinogen in animals and most likely also in humans.

Related: Climate Change Forces Polar Bears to Consume More Contaminants

Sonne’s team collaborated with researchers to gather and examine the penile bones of 279 polar bears from eight subpopulations born between 1990 and 2000. What they found was that polar bears in Canada had a larger and more dense penile bone, while polar bears that had greater exposure to PCBs had smaller and less dense penile bones; the North East Greenland subpopulation was found to be at the highest risk of having negative health effects.

Which is genuinely troubling news for the polar bears of North East Greenland, and others exposed to high levels of PCBs. These subpopulations may encounter difficulty reproducing in what is already an increasingly inhospitable environment. As Sonne explained to New Scientist, while we may not know what the penis bone is for, “if it breaks, you probably won’t have a bear which can copulate.”

Via New Scientist

Lead image and second image via Shutterstock