Researcher Discovers Chemical Pollution In Brains of Beached Marine Animals

TAMPA, Fla. (May 20, 2009) -- A University of South Florida researcher has found contamination from PCBs, the residue of long-ago used DDT, and common flame retardant chemical in the brains and cerebrospinal fluid of marine mammals in a new study which raises concerns about the potential impact hazardous chemicals have on ocean life.


Eric Montie, a postdoctoral researcher at USF’s College of Marine Science, says the study is the first of its kind to report the presence of old toxic chemicals and still widely used PBDE flame retardants in marine mammals’ brains and cerebrospinal fluid. The ground-breaking report, five years in the making, is being published in the journal Environmental Pollution.


PBDEs – Polybrominated diphenyl ethers – are pervasive flame-retardant chemicals used in a wide array of consumer products including computers, furniture and textiles. In recent years, PBDEs have become a concern to scientists who have provided evidence that these chemicals can accumulate in wildlife, can disrupt the thyroid hormone system in experimental studies with rats, and can affect neurodevelopment.


Scientists have known that PCBs and DDTs – both banned in the 1970s because of their health effects on wildlife and humans – and PBDEs accumulate in the blubber of marine mammals.  But the new study highlights the accumulation of hydroxylated (OH) analogues of PCBs (OH-PCBs) and PBDEs in the brains of marine mammals.


“The fact that you find these PCB metabolites and flame retardants in the brains of marine mammals is a concern,” Montie said, noting the very high concentrations of OH-PCBs in the cerebrospinal fluid of an emaciated and diseased newborn gray seal found washed up on a Massachusetts beach in 2004.

 “There is evidence that these chemicals can affect brain development in rats by interacting with the thyroid hormone system,” he continued. “However, we have no idea whether this mixture may affect the development of the brain in marine mammals. As a scientific community, it’s important to assess this risk.”


The study is a collaboration with Chris Reddy and Mark Hahn of Woods Hole Oceanographic Institution; Robert Letcher of Environment Canada at Carleton University in Ottawa; and Katie Touhey of the Cape Cod Stranding Network. Montie began the project as a researcher at Woods Hole Oceanographic Institution before coming to USF where he now conducts his research under the tutelage of Professor David Mann, whose Marine Sensory Biology laboratory focuses on the neural mechanisms of hearing and sound production of marine mammals and fish. Montie is co-advised by Frances Gulland, Director of Veterinary Science at The Marine Mammal Center, on a neurotoxicology project with California sea lions.


Previous studies have found PCB metabolites in the liver of beluga whales, in the plasma of bottlenose dolphins and polar bears and in the blood of Pacific killer whales. But little was known about how these contaminants and their metabolites partition into the marine mammals’ brain compartments until now.


There is widespread concern about the use of PBDEs, the safety of which has been questioned since the early 1990s. The chemicals are ubiquitous – having been used in computers, furniture and fabrics and are now believed to be pervasive in the food supply, environment and even dust.


Previous studies have shown the greatest concern from PBDEs is their developmental neurotoxicity. Studies in lab rats have indicated pre- and post-natal exposure to PBDEs impairs motor activity and cognitive behavior.


In a related set of studies published earlier, the team used an MRI to examine the brains of a gray seal, two short-beaked common dolphins, and eight Atlantic white-sided dolphins found on Cape Cod between 2004 and 2005. Four of the Atlantic dolphins in the study were part of a mass stranding on a single day in February 2005.


The project did not seek to determine what killed the animals, but focused on measuring the presence of the chemical contaminants in the animals’ brains as a first step in determining whether animals like these can develop neurological issues resulting from chemical exposure.


Three years ago in his doctoral dissertation, Montie developed the use of magnetic resonance imaging (MRI) as a tool to investigate the potential neurological effects of environmental pollutants and naturally occurring neurotoxins on marine animals. Specifically, he said, he is interested in exploring how the contaminants and marine toxins (e.g., from red tide events) affect the brains and hearing in marine mammals.


The marine mammals Montie and the research group studied are exposed to the chemicals, which accumulate and magnify in the food chain. The chemicals are fairly resistant to metabolism and accumulate in the animals’ blubber. Young seals and dolphins are likely ingesting neurotoxicants that contaminate their mother’s milk, Montie added.


For dolphins, which depend on hearing and echolocation to find and catch food, the effect of those chemicals could have serious ramifications, he said.


In August, Montie, Mann, and former USF doctoral student Mandy Cook, working in collaboration with the National Oceanic and Atmospheric Administration, will embark on a new study to test the hearing of bottlenose dolphins living near a Superfund site in Georgia to see if PCBs have affected the animals’ hearing.


The larger concern, however, is that marine mammals are not just exposed to these harmful chemicals but rather what Montie and his fellow researchers call a “cocktail” of old chemicals, PCBs and their metabolites, and other neurotoxicants, such as lead, mercury and dioxins. 


The fact that chemicals like DDT and PCBs were banned from use more than 30 years ago does not mean that they do not continue to harm the environment. Now PBDEs are adding to that toxic cocktail, he said.


“What’s really unfortunate about this situation is that we are repeating previous mistakes, this time, with a different chemical,” Montie said of the flame-retardant contamination. “They could very well be the ‘PCB problem’ of the 21st century.”



The University of South Florida is one of the nation's top 63 public research universities and one of 39 community-engaged, four-year public universities as designated by the Carnegie Foundation for the Advancement of Teaching. USF was awarded more than $360 million in research contracts and grants in FY 2007/2008. The university offers 219 degree programs at the undergraduate, graduate, specialist and doctoral levels, including the doctor of medicine. The university has a $1.8 billion annual budget, an annual economic impact of $3.2 billion, and serves more than 46,000 students on institutions/campuses in Tampa, St. Petersburg, Sarasota-Manatee and Lakeland. USF is a member of the Big East Athletic Conference.