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Scientists To Assess Effects Of Pharmaceutical Pollutants On Bull Sharks

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GAINSVILLE, Florida -- Sending commonly prescribed medications down the drain may be taking a bite out of the environment — at least when it comes to shark habitat, University of Florida veterinary scientists say. In fact, the combination of flushing unused medications and the natural excretion of drug residue from antidepressants, cholesterol-regulating drugs and contraceptives into wastewater systems could be having repercussions on aquatic animal life in general.

Researchers at UF’s College of Veterinary Medicine’s Analytical Toxicology Core Laboratory, in collaboration with Mote Marine Laboratory in Sarasota, are studying the bull shark’s exposure to pharmaceutical drug residue found in the waters of the Caloosahatchee River near Fort Myers. Bull sharks leave the ocean to spend time in brackish rivers and estuaries, and the river serves as a nursery for their young.

“Because bull sharks have the unique ability to survive in both saltwater and freshwater environments, they are in close, frequent contact with people — and, as a result, are frequently exposed to wastewater pollutants found in freshwater basins,” said Jim Gelsleichter, senior scientist at Mote Marine Laboratory.

Scientists are trying to determine whether exposure to prescription residue contaminants from water treatment plants and other sources affects the sharks’ ability to grow and reproduce.

“Treatment plants were designed to remove pathogens like viruses and bacterial agents, and that they do very well,” said Nancy Szabo, Gelsleichter’s co-investigator and director of UF’s Analytical Toxicology Core Laboratory. But these facilities simply aren’t designed to deal with pharmaceuticals, she said.

Evidence suggests that low-level pharmaceutical pollution is widespread. In 1999 and 2000, the U.S. Geological Survey sampled 139 streams in 30 states for organic wastewater contaminants, including common pharmaceuticals. Eighty percent of the streams studied contained traces of chemical pollution. The consequences of such contamination are not yet fully known, although some research has shown even low levels of these contaminants affect several fish species.

Federal guidelines for proper disposal of prescription drugs recommend flushing them down the toilet only if the accompanying patient information specifically says it is safe to do so.

Gelsleichter is testing for the presence and levels of human drug contaminants in bull shark blood by tagging bull sharks in the river basin with passive sampling devices — silicone rubber discs that collect chemical samples in the water for later examination. When sharks are caught by local anglers or by the Mote team on subsequent research expeditions, the tags are retrieved and sent to UF’s Analytical Toxicology Core Laboratory for analysis.

When the blood and silicone-rubber discs from the bull sharks arrive at the laboratory, Szabo’s team analyzes the samples to determine the variety and concentration of chemicals present in the bull shark’s environment.

The UF laboratory specializes in non-routine analysis. Szabo’s team works with researchers both at UF and elsewhere to develop appropriate methods for measuring and analyzing whatever toxins are being examined. These techniques are tailored specifically to each client.

For the bull shark study, the UF laboratory has been able to use distinctive techniques to gauge chemical levels in bull shark blood. The laboratory worked with Mote not only to design the experiment but also to adapt the analytical methods used to ensure valid results are produced.

“The type of work we do requires a lot of effort, and one has to have the expertise available to know where to even begin,” Szabo said.

The bull shark study, which is funded through September 2008 by the Charlotte Harbor National Estuary Program and a federal grant to the National Shark Research Foundation, is the most recent collaboration between the UF laboratory and Mote. The two groups have worked together for the past nine years.

“Our collaborative efforts have provided new data on the environmental quality of essential fish habitat for the U.S. shark populations,” Gelsleichter added. “This information is necessary for NOAA (National Oceanic and Atmospheric Administration) fisheries to have so they can manage and conserve these populations from an ecosystem perspective.”

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