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VANCOUVER – Toxic chemicals banned during the 1970s will interfere with the reproductive success of B.C.’s northern and southern resident killer whales until at least 2030, a newly published study says.
Killer whales living in the waters off B.C. still retain high levels of toxic PCBs even though the chemicals have been out of use for 30 years, Trent University professor Brendan Hickie said. It will take another 20 to 50 years before the toxins fall to “acceptable concentrations,” he added.
Killer whale calves born off the West Coast have the highest levels of PCBs, according to a sophisticated environmental computer model developed by Mr. Hickie and his colleagues. The calves are born with PCB concentrations similar to their mothers. The same is true for humans, Mr. Hickie points out.
But whale mothers pass more PCBs stored in their blubber to their calves through fat-rich milk, “so calves can have some of the highest concentrations found in these populations,” he said, with first-born calves receiving the highest dose of all.
Males, with no way to eliminate the PCBs they take in from contaminated fish, build ever-higher accumulations throughout their lives, Mr. Hickie said.
PCBs, used in electrical equipment before they were banned by Canada in 1977, reduce reproductive success and leave the whales prone to infection. Mr. Hickie said killer whale populations will be at risk from the effects of these chemicals for decades to come.
When persistent contaminants like polychlorinated biphenyls enter the food chain, they tend to accumulate in predators such as whales, which feed on large amounts of fish. With no way to flush the contaminant from its body, the concentration of the toxin rises over time.
About 20 per cent of the northern resident population—which lives off northern B.C. and Alaska—shows PCB levels associated with health effects.
“We predict it will take until 2030 for their PCB levels to drop below the risk threshold,” Mr. Hickie said.
© The Ottawa Citizen 2007