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Study Finds Chemical Cocktail in Brains of Marine Mammals

(Beyond Pesticides, May 27, 2009) A recent, extensive study which investigated a variety of different chemicals, including organochlorine pesticides, in animal tissues reveals that marine mammals harbor high concentrations of hazardous chemicals in their brains. The results lay the groundwork for understanding how environmental contaminants influence the central nervous system of marine mammals.

The study entitled “Organohalogen contaminants and metabolites in cerebrospinal fluid and cerebellum gray matter in short-beaked common dolphins and Atlantic white-sided dolphins from the western North Atlantic” is the first of its kind to find toxic chemicals in the brains of marine mammals. The study identified several contaminants including organochlorine pesticides like DDT, polychlorinated biphenyls (PCBs) and flame retardants in the cerebrospinal fluid and cerebellum gray matter of several species of marine mammals including the short-beaked common dolphins, Atlantic white-sided dolphins and the gray seal. PCBs were found in alarmingly high concentrations. Researchers found parts per million concentrations of PCBs in the cerebrospinal fluid of a gray seal.

“We found parts per million concentrations of hydroxylated PCBs in the cerebrospinal fluid of a gray seal. That is so worrisome for me. You rarely find parts per million levels of anything in the brain,” remarked researcher, Eric Montie, PhD.

Dr. Montie, lead author of the study, performed the research in collaboration with Mark Hahn and Chris Reddy of the Woods Hole Oceanographic Institution (WHOI) and Robert Letchre of Environment Canada.

“We don’t really know the effect of that level in these animals,” he says. “The first step was just to see if these chemicals were present in the brain. And they are. So how do you monitor that? And that’s something we’re trying to develop methods to see if these chemicals do have neurotoxilogical effects,” says Dr. Montie.

Dr. Montie plans to find out how these chemicals might impact marine mammal health. This summer, Dr. Montie will partner with scientists from NOAA to test the hearing in dolphins living near a Superfund site in Georgia and compare it to dolphins from locations where ambient concentrations of pollutants are significantly lower. The researchers view their work as the forefront of a new field of research, something that might be called neuro-ecotoxicology. Previous studies have been focused on how concentrations of marine pollutants affected the animal’s immune system or its hormone systems, however, the authors of this study say their results indicate that contaminants in the ocean can affect the neurological development of marine mammals.

DDT, which is currently banned in much of the world, has been shown to cause cancer and reproductive toxicity. While an overall reduction in contaminant levels in coastal waters of the U.S., studies have found DDT and other persistent pollutants in Arctic animals like whales, penguins, seals and birds. However, new concern over the concentrations of these chemicals in the oceans arise as DDT, its metabolites and other persistent organic pollutants, including PCBs and PBDEs are being released at high levels in melting glaciers, further threatening the health of marine animals. In 2007, the National Oceanic and Atmospheric Administration (NOAA) and the Environmental Protection Agency (EPA) reported extremely high concentrations of the pesticide DDT in fish caught in California’s Los Angeles county waters. According to the survey, the fish caught in the area contain the world’s highest-known DDT concentrations.

Source: Science Daily


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