The proliferation of discarded plastics in the oceans is leading to problems with the ability of marine life to grow and reproduce, according to a new paper.

Polychlorinated biphenyls (PCBs) were used in many plastics before being banned globally in 2004.  Unfortunately, plastics made before the ban made their way into the oceans, and scientists found frightening evidence of the impact.

A pod of Orcas off the west coast of Scotland known to have high levels of PCBs has failed to produce a single calf in 25 years.  One female washed ashore, with researchers giving her the name "Lulu".  She had accumulated 957 milligrams of PCBs per liter of lipid tissue - a level that is 100 times above the threshold of toxicity.  Although she was of age, she was unable to calve.

"Lulu was barren, as if she was a juvenile," said Paul Jepson of the Zoological Society of London and a co-author of the paper published in the journal Proceedings of the Royal Society B: Biological Sciences.  "But she should have been in her prime," he added.

In fact, the problem could be even worse because Jepson says scientists don't know how different combinations of endocrine-disrupting chemicals (EDCs) impact wild populations.

"We do not know what proportion of chemicals are EDCs.  There is a very large proportion of chemicals that we use every day that we know very little about," said ecotoxicology Professor John Sumpter of Brunel University London and a co-author of the paper.  "There is a huge gap in our knowledge.  We just do not know what effect they are having."