Since the otters were collected from counties all over Central Illinois, the findings could indicate that some watersheds have a worse contamination problem than others, Carpenter said.
"For many of the contaminants we did detect a large range," she said. "This is a red flag. We need to understand more about what humans and wildlife are being exposed to in different watersheds."
More research is needed to understand the factors that contribute to the river otters' exposure to these chemicals, Mateus-Pinilla said.
"We don't have a good understanding of how much time they spend in a particular area, how long they stay there, how far they go or where they spend most of their time during the winter versus the summer," she said. "All of these can contribute to differences in exposure."
The researchers do not know why the male otters in the study carried a heavier burden of PCBs than the females, Carpenter said. It may be simply that the males are larger. They may range further than the females, picking up more toxins as they go. Or the females might transfer some of the contaminants to their offspring during nursing, as previous research suggests.
"Maternal transfer is particularly interesting," Novakofski said. "In some watersheds humans may have the same kind of risk because they're eating the same kinds of fish that the otters might be."
Studies have shown that PCBs and dieldrin can be transferred through breast milk, he said.
"We don't know enough about how these contaminants behave synergistically," Carpenter said, especially since "the cocktail of contaminants that we're exposed to here in the Midwest differs from what humans and wildlife are exposed to in eastern or western North America."
|Contact: Diana Yates|
University of Illinois at Urbana-Champaign