redOrbit Staff & Wire Reports – Your Universe Online
North American river otters in central Illinois are being exposed to chemical substances that had been banned for use in the US at least three decades ago, according to research published in the latest edition of the journal Ecotoxicology and Environmental Safety.
Between 2009 and 2011, the Illinois Department of Natural Resources collected 23 river otter carcasses after the creatures had been accidentally killed. Their bodies were analyzed by experts at the Illinois Natural History Survey (INHS) and autopsies were performed by members of the University of Illinois Veterinary Diagnostic Laboratory.
Wildlife technical assistant Samantha Carpenter and wildlife veterinary epidemiologist Nohra Mateus-Pinilla of the INHS, as well as Jan Novakofski, an animal sciences professor at the university, looked at the liver concentration of 20 organohalogenated contaminates (OHC) that had been used by agricultural and industrial workers – all but one of which were banned in the 1970s and 1980s.
The toxicology tests revealed that the otters were being exposed to both polychlorinated biphenyls (PCBs) and banned pesticides. In fact, the authors found that the average concentration of the compound dieldrin – an insecticide and the byproduct of the pesticide aldrin – was higher than those found in eight river otters collected in Illinois in both 1984 and 1989. The substance has been banned since 1987, the researchers said.
In addition, the researchers found that liver concentrations of PCBs, which had been used as coolants and insulators in motors and electrical systems before being banned in 1979, and DDE — a byproduct of the prohibited pesticide DDT — which has not been used in the US since the early 1970s, were similar to those in the earlier analysis. PCBs were found to be potentially carcinogenic to humans, and DDT/DDE were found to contribute eggshell thinning in some species of birds, and are toxic to fish and other forms of marine life.
“The PCBs, dieldrin and DDE were the contaminants that we detected in highest concentration, in terms of average concentrations,” Carpenter said.
Dieldrin was banned in 1987, and had previously been used to kill crop pests, termites and mosquitoes – especially in the Midwest agricultural region. Before this compound was banned in 1987, it (and parent compound aldrin) were applied to over 15 million pounds of crops annually.
“Some studies (of dieldrin) exposure find links to cancer, Parkinson’s disease and Alzheimer’s and some do not,” the technical assistant added. “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.”
The concentrations of contaminants found in the river otters varied greatly, though the researchers said that male river otters typically had significantly higher PCB concentrations than their female counterparts. One male otter was found with 3,450 parts per billion (ppb) worth of PCBs in its liver, while another had just 30 ppb. Dieldrin concentrations ranged from 14.4 to 534 ppb.
“For many of the contaminants we did detect a large range. This is a red flag. We need to understand more about what humans and wildlife are being exposed to in different watersheds,” Carpenter 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.”
“All of these can contribute to differences in exposure,” she added. “We don’t know enough about how these contaminants behave synergistically… [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.”