Wild orcas living in the northeast Pacific Ocean and waters around Japan, Brazil and the UK are particularly in danger because of a certain kind of pollution — and it's predicted that about half the planet's wild orcas could die because of it.
Many common products, like electronics, plastics and paints, that were produced from the 1930s to the 1970s and 1980s contained a certain type of chemicals, polychlorinated biphenyls, known as PCBs. When it was discovered just how incredibly harmful these chemicals were, they were banned.
"At first we rejoiced when the bans came into play across the world," Mark Simmonds, senior marine scientist for Humane Society International (HSI), told The Dodo. "PCBs turn out to be even more persistent than we feared, leaving orca populations sadly still very vulnerable."