Killer whales that frequent the coastal waters of British Columbia and Washington state will not recover from historic PCB exposures until 2030 or later, according to new environmental modelling results published last month by Trent University’s Dr. Brendan Hickie and his colleagues in Environmental Science & Technology.

The study, entitled “Killer Whales Face Protracted Health Risks Associated with Lifetime Exposure to PCBs”, developed environmental models to estimate PCB concentrations in two populations of killer whales during the period from 1930 forward to 2030, both within a lifetime (about 50 years) and across generations, and then evaluated these in the context of health effects thresholds established for marine mammals.

“PCB concentrations in these killer whale populations likely peaked in the early 1970s when PCB production ceased with the onset of environmental regulations, but their concentrations have only declined slowly since then” explained Dr. Hickie, who is an assistant professor in the Environmental & Resource Studies program at Trent. “Concentrations in the threatened northern resident population may fall to acceptable levels by about 2030 while the endangered southern resident population may only reach that point by 2060.” Dr. Hickie and his colleagues conclude that persistent contaminants such as PCBs may hinder the recovery of endangered killer whale populations by increasing vulnerability to infectious disease, reducing reproductive performance, and impeding normal growth and development.

PCBs Passed On To Nursing Young

“Nursing mothers pass on PCBs in their fat-rich milk, so calves can have some of the highest concentrations found in these populations.” The study also found that first-born calves receive a larger dose of PCBs than their siblings, and that mothers deplete much of their store of PCBs in their blubber by passing them on to their offspring. Male killer whales have no similar mechanism to off-load PCBs and continue to accumulate them from their food throughout their long lives.

The use of environmental models such as those developed for this study are important tools for conservationists and regulators to establish benchmarks against which to evaluate the effectiveness of legislation and programs designed to protect wildlife species. Since 1995, Trent University has been home to the Canadian Environmental Modelling Centre which develops specialized computer programs to accurately predict the fate of chemicals in the natural environment.

Posted October 5, 2007