Illinois River Otters Loaded with PCBs and Pesticides: Persistence of Banned Chemicals

Chemicals such as polychlorinated biphenyls (PBCs) and certain pesticides may have been banned in the 1970s and 1980s, but they're still causing problems. Scientists have discovered that these chemicals are impacting river otters in Central Illinois, revealing the persistence of these pollutants in the environment.

In order to see what chemicals might be affecting otters, if any, the researchers examined the bodies of 23 river otters collected between 2009 and 2011. These animals were incidentally killed--either hit by cars or accidentally caught in traps. The scientists then looked at liver concentrations of 20 organohalogenated compounds once used in agriculture and industry.

So what did they find? It turns out that average concentrations of dieldrin, an insecticide that was used across the Midwest before being banned in 1987, actually exceeded those measured in eight river otters collected from 1984 to 1989. In other words, it seems as if concentrations are becoming greater over time rather than less. In addition, the researchers found liver concentrations of PCBs and DDE (a breakdown product of the banned DDT pesticide) that were similar to those in an earlier study.

"The PCBs, dieldrin and DDE were the contaminants that we detected in highest concentration, in terms of average concentrations," said Samantha Carpenter, one of the researchers, in a news release. "And male river otters had significantly higher concentrations of PCBs compared to females."

The fact that these contaminants are still persisting in the environment is worrisome. Some studies of dieldrin exposure have found links to cancer, Parkinson's disease and Alzheimer's. But perhaps most concerning is the fact that both dieldrin and PCBs can act as developmental neurtoxicants, which means that developing fetuses can be harmed at higher concentrations.

That said, there's still a lot to study when it comes to these contaminants. The chemicals occur in different concentrations in different areas, which means that species are affected differently depending on where they are or how much they move. In addition, the scientists need to study exactly how these contaminants interact with one another within a body.

"We don't know enough about how these contaminants behave synergistically," said Carpenter in a news release. "The cocktail of contaminants that we're exposed to here in the Midwest differs from what humans and wildlife are exposed to in eastern and western North America."

The findings are published in the journal Ecotoxicology and Environmental Safety.