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Great Lakes Article:

Drugs in Waterways are Harming Aquatic Life

August 7, 2002 (ENS) - The overuse of antibiotics and other drugs may be harming zooplankton, tiny organisms that support the health of all freshwater ecosystems.

"Pharmaceuticals can be detected in many surface water streams and lakes, yet we know little about how these strongly biologically active chemicals affect the ecology of aquatic organisms," said Stanley Dodson, a zoologist specializing in freshwater ecology at the University of Wisconsin-Madison.

This pollution, argues Colleen Flaherty, a UW-Madison zoologist, has direct ties to humans, either through the improper disposal of unwanted pharmaceuticals or through the ingestion of the drugs.

"Up to 80 percent of drugs taken by humans and domesticated animals can be excreted in their biologically active form," Flaherty explained. This means that the antibiotics, antidepressants and anti-inflammatory pills that humans take or throw out can end up polluting the environment and harming the organisms that live in it.

Flaherty's research is the first to look at the effects of common prescription drugs on Daphnia, a zooplankton that is integral to freshwater ecosystems. She will present findings from her study on Thursday at the annual meeting of the Ecological Society of America in Tucson.

"Daphnia play a key ecological role in freshwater sources," Flaherty said. "They are an intermediate organism in these ecosystems - they eat the algae and are eaten by the fish. If something happens to Daphnia, it could affect both the algae and the fish populations."

To determine the influence of pharmaceuticals on this key freshwater species, Flaherty tested Daphnia's biological response to drugs that have been found in European and U.S. waters, including cholesterol lowering clofibric acid, an antidepressant called fluoxetine, and five antibiotics.

Flaherty performed short and long term studies to find out what happens to a female Daphnia and her offspring when exposed to a particular drug. The effects she found varied.

In the short term studies, the antibiotics and cholesterol drug at concentrations of just 10 parts per billion appear to stunt growth and result in more male offspring.

In the long term studies, these differences were diminished: offspring exposed to the antibiotics tended to have longer lifespans, while those exposed to the cholesterol lowering drug showed no apparent effects.

Exposure to the antidepressant produced no differences in the shorter trials, but did result in a greater number of offspring in the longer studies.

"When Daphnia were exposed to a single pharmaceutical throughout their entire [30 day] life span, as in the long term studies, they seemed to become acclimated to the polluted environment," Flaherty said.

But, Flaherty pointed out, Daphnia swim in waters tainted with not just one drug, but many.

"Some of these drugs may not have significant effects by themselves," she said, "but, when you combine them in a 'pharmaceutical cocktail,' the effects can be lethal."

When Flaherty exposed the organisms to a combination of the cholesterol drug and the antidepressant during the short term studies, up to 90 percent of them died. Their offspring were more likely to be female, and to have deformities that hinder swimming.

"I never expected that two drugs that had virtually no individual effects could be so lethal when combined," Flaherty said.

Because of these findings, Flaherty argues that scientists must look at not just one chemical, but combinations of them, to understand the ecological effects of pharmaceuticals or other manmade chemicals on freshwater ecosystems.


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