(CN) – Half of the world’s killer whale populations could collapse in the next century due to the buildup of toxic PCBs, and widespread chemical contamination means only killer whales living near the Arctic and the Antarctic will be left alive according to a new study published Thursday in the journal Science.
PCBs were banned in most parts of the world more than 30 years ago. But by then, they were already widespread in the environment due to heavy industrial use. The chemicals cause cancer, inhibit reproduction and harm the endocrine and immune systems.
Killer whales living of the coasts of Japan, Brazil, the northeast U.S., the Strait of Gibraltar and the United Kingdom are the most at risk, according to researchers.
In ideal conditions, killer whales can live up to 100 years. But they’re also threatened by the proliferation of heavy shipping vessels, which impair their ability to echolocate their prey and communicate with each other.
For those populations that rely primarily on fish, their prey has declined in number. One group – Southern Resident killer whales in the Salish Sea off the coast of Seattle – hasn’t had a calf survive in three years. Washington state Gov. Jay Inslee convened a task force to make recommendations on how to stave off the extinction of Southern residents.
For the study published Thursday, a group of scientists headed by Jean-Pierre Desforges analyzed data on known concentrations of PCBs in the blubber of killer whale populations. The team used a model to predict the transfer of the chemicals from mothers to their young, plus the amount of chemicals the young will encounter in the ocean and in their food. The model analyzed the effects of that exposure on the whales’ immune systems and ability to reproduce and used that to forecast the future of whale populations around the globe.
The results are sobering.
Over the next 100 years, half of the world’s population of killer whales could collapse, the authors say. Among whale populations with the lowest chemical exposure, PCBs could cause a 15 percent reduction in their population over the next century. Those populations will still grow, the authors say, but at a reduced rate.
But the groups living in the most toxic waters are headed for a complete collapse, according to the model. That includes 10 out of 19 killer whale populations for which data was available – those living near Japan, Brazil, the Northeast Pacific, the Strait of Gibraltar and the United Kingdom.
And that’s based on a model that measures the effects of just one of many human-created toxic chemicals that persist in the environment, regardless of whether they are still being produced. Other chemical the authors said are probably reducing reproductive rates among killer whales include flame retardants, perfluoroalkyl acids, which were used in carpets, clothing and water-resistant food packaging, as well as polychlorinated naphthalenes, which are common in older electrical devices.
PCB concentration is strongest in whales that live near heavily industrialized areas. Pods that live in the Arctic or the Antarctic, for example, have much lower accumulation rates than those off the northeast coast of the U.S.
Among those populations living in the most toxic waters, males have much higher accumulation rates than females do. Researchers say this is because mothers pass the toxins built up in their bodies to the bodies of their young. But this trend is waning in the most toxic of the toxic areas, and the researchers say that may be because the chemicals suppress reproduction rates, and therefore reducing female whale’s chances to get rid of their accumulated toxins.
Based on their findings, the researchers worry efforts to prevent the extinction of struggling killer whale populations will fail without a reduction of PCB contamination that goes beyond those currently underway based on the Stockholm Convention on Persistent Organic Pollutants.
“The status-quo efforts to protect killer whales from conservation threats are likely to be impeded because PCBs have remained at levels associated with adverse health effects in at-risk populations over the past decades,” the group wrote. “Concerted efforts beyond those listed under the Stockholm Convention on Persistent Organic Pollutants are urgently needed to reduce PCB exposure in vulnerable wildlife populations.”