British Columbia - New research says Orca's face long term health effects for early exposure to PCB's. Polychlorinated biphenyl's, also known as PCB's, have declined in ecosystems since laws were first passed in the 1970's. But, for animals that live a long time like Orca's, the PCBs take much longer to leave their bodies.
British Columbia - New research says Orca's face long term health effects for early exposure to PCB's.
Polychlorinated biphenyl's, also known as PCB's, have declined in ecosystems since laws were first passed in the 1970's. But, for animals that live a long time like Orca's, the PCBs take much longer to leave their bodies.
Orca's are both endangered, and highly contaminated with PCB's. They live in the Northeastern Pacific Ocean. To investigate the influence of life history on PCB-related health risks, scientists developed models to estimate PCB concentrations in killer whales during the period from 1930 forward to 2030, both within a lifetime (~50 years) and across generations, and then evaluated these in the context of health effects thresholds established for marine mammals.
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When researchers modeled PCB concentrations in killer whales, they found the animals responded slowly to changes in PCB levels in the environment. Researchers saw slower accumulation and lower magnitude increases in PCB concentrations from their food supply, and a delayed decline in PCB levels in their bodies, something particularly evident in adult males.
Since PCBs attained peak levels well above the effects threshold (17 mg/kg lipid) in 1969, estimated concentrations in both the northern and the more contaminated southern resident populations have declined gradually.
Researchers say that the northern resident Orca's could largely fall below the threshold concentration by 2030 while the endangered southern residents may not do so until at least 2063 - a good 50 years. Their conclusion: long-lived sea mammals are not protected from PCBs by current dietary residue guidelines and policy.
The research was done by scientists at, Trent University, Canada, the Institute of Ocean Sciences, Fisheries and Oceans Canada, and the Pacific Biological Station, Fisheries and Oceans Canada, in Nanaimo British Columbia, Canada.
Revised manuscript received May 8, 2007
Accepted July 18, 2007
Abstract:
