The poisonous chemical Polychlorinated biphenyl (PCB) has long been banned, but it continues to leak into the ocean. A new study has revealed that the chemical continues to pose a threat, particularly to the apex predators of the sea.
The new study published in the journal Science suggests that at least half of the killer whale population in the world may be wiped out before the end of the century due to chemical pollution in the ocean.
PCBs were once widely used in the production of carbonless copy paper and as coolants before they were discovered to be carcinogenic and toxic.
The production of the chemicals was halted in the United States in 1979 under a 2001 international treaty. Unfortunately, PCBs are still used in many parts of the world. The terms of the Stockholm Convention state that the chemical is not due to be completely phased out until the year 2025.
As a result, PCBs continue to seep into the ocean, where they pose a long-term risk to marine mammals at the top of the food chain.
One problem with PCBs is they can be passed to offspring of mammals through milk. Another is that these chemicals do not readily break down so they build up in the bodies of sea predators as they eat more fish that are contaminated with PCBs. Orcas are in the last link in the marine food chains, which makes them the most affected by the problem.
Study researcher Jean-Pierre Desforges, of Aarhus University in Denmark, and colleagues found that the levels of PCBs in the blubber of some orcas were as high as 1,300 milligrams per kilo. Studies have shown that a ratio of 50 milligrams per kilo can already cause immune system and fertility problems.
The researchers found that the effects of PCBs on the immunity and fertility of killer whales threaten their already devastated populations.
The new study, which looked at the prospects for orca populations over the next century, found that populations of orcas could vanish as early as within 30 years.
“PCB-mediated effects on reproduction and immune function threaten the long-term viability of >50% of the world’s killer whale populations,” the researchers wrote in their study.
Experts said that the findings showed that current efforts have not been effective enough to prevent the accumulation of PCBs.
“Our abysmal failures to control chemical pollution ending up in our oceans has caused a killer whale catastrophe on an epic scale,” Lucy Babey, deputy director at conservation group Orca, told The Guardian.