"The PCBs, dieldrin and DDE were the contaminants that we detected in highest concentration, in terms of average concentrations," Carpenter said. "And male river otters had significantly higher concentrations of PCBs compared to females."
PCBs were once used as insulators and coolants in motors and electrical systems, but were banned in 1979 in the U.S. after studies found that exposure to these compounds caused cancer and other deleterious health effects in animals. PCBs are classified as "probable human carcinogens" and there are fish consumption advisories for this contaminant in many Illinois rivers.
DDT was banned in the U.S. in the early 1970s after decades of widespread use. Studies indicated that DDT and DDE contribute to eggshell thinning in several bird species and are toxic to fish, shellfish and other organisms. In mammals, these compounds can cause gene disruption and interfere with hormone function, particularly in a developing fetus.
Dieldrin was used extensively to kill crop pests, termites and mosquitoes before it was banned in 1987 in the U.S. Its use in the Midwest agricultural belt was particularly pronounced. Before these compounds were banned, U.S. farmers applied more than 15 million pounds of dieldrin and aldrin (its parent compound) to their crops every year -- much of it in the Midwest.
"Some studies (of dieldrin) exposure find links to cancer, Parkinson's disease and Alzheimer's and some do not," Carpenter said. "But perhaps most concerning is that both dieldrin and PCBs can act as developmental neurotoxicants, meaning that developing fetuses can be harmed at concentrations much smaller than those that can impact the health of adults."
Concentrations of contaminants in river otters ranged widely. One male had a concentration of PCBs in its liver of 3,450 parts per billion (ppb), while ano
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University of Illinois at Urbana-Champaign