The only sharks found regularly in fresh water, bull sharks encounter treated wastewater near its source. This water may carry active drug ingredients, which humans excrete after taking medicine, or introduce by flushing unwanted pills. Pharmaceuticals slip through treatment plants, which are designed to clean up other contaminants, such as bacteria and viruses. Numerous U.S. streams have pharmaceutical pollution usually at low levels according to the U.S. Geological Survey. But scientists are only beginning to look for drugs in wild fish, and no one had tested wild sharks until now. The 2006-2007 study, led by scientist Jim Gelsleichter formerly of Mote's Center for Shark Research, found miniscule amounts of active ingredients from a birth control drug and five antidepressants, as well as indirect evidence of a sixth antidepressant, in newborn bull sharks' blood. "The levels in the river are not levels for which you'd anticipate health effects in any fish" or fisherman, said Gelsleichter. Rarely, he added, did a single bull shark's blood contain all seven drugs detected. "It's nothing for people to be Chicken Little about, and start saying that the sky is falling." Gelsleichter, who is now an assistant biology professor at the University of North Florida, and co-investigator Nancy Szabo of the Univeristy of Florida tested 30 newborn sharks by comparing blood samples from bull sharks in the Caloosahatchee River which has six wastewater treatment plants to blood samples taken from sharks in the Myakka River, which has no treatment plants. "When you look at Myakka River versus the Caloosahatchee, only the Caloosahatchee sharks had measurable evidence of human drugs," Gelsleichter said. Along with evidence of seven drugs in bull sharks, the researchers detected three drugs in Caloosahatchee surface water, and five in water entering the river from Fort Myers Advanced Wastewater Treatment Plant, including a birth control estrogen, antidepressants and an impotency drug. But the pharmaceuticals were diluted as spread out as a drop or two of water in an Olympic swimming pool. Gelsleichter recommends monitoring of common pharmaceuticals in rivers now, to avoid any surprises later. Access the full report (see pages 18-36). For further information, or to speak with study authors, contact Hayley Rutger at 941-388-4441, ext. 365, or hrutger@mote.org
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