Fertility problems and more
In humans, PCBs are considered a neurotoxin and an endocrine disrupter, and exposure to high levels of the substances has been linked to low birth weights, delayed developmental milestones, and lower IQs in comparison with unexposed children. Overall, a number of studies have found that exposure to persistent pollutants such as PCBs during critical developmental periods is associated with a range of negative health effects in wildlife, experimental animals and humans.
In polar bears, "PCBs affect the bears' thyroid hormones, and in the worst case can reduce the animals' ability to survive in the tough Arctic environment," Bytingsvik adds. "There can be negative effects on the bears' ability to grow and thrive. The contaminants can also affect the ability of the animals to learn and may reduce their fertility."
From mother to cub
Polar bear milk is high in fat, which also unfortunately makes it perfect for transmitting PCBs from mothers to their cubs. Bytingsvik also looked at levels of OH-PCBs, which are toxic substances created by the body when PCBs are metabolized. While OH-PCBs are still harmful, they are more likely to bind to proteins rather than dissolve in fat, which means that they are more likely to be transferred by umbilical cord blood than by milk. Another source of exposure is the cubs own metabolic conversion of PCBs into OH-PCBs.
In her study, Bytingsvik was able to look at polar bear blood samples from mothers and cubs that were collected in 1997 and 1998 (which she considered as 1998 for statistical purposes) and 2008. All told, she had samples from 26 mother bears and 38 cubs from the different time periods.
The bears were all
|Contact: Bjrn Munro Jenssen|
Norwegian University of Science and Technology