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Human Meds Harm Plankton in Water

Drugs take aquatic ecosystems on a bad trip

WEDNESDAY, Aug. 7, 2002 (HealthDayNews) -- Human drugs are a real downer for the tiny creatures that are essential to the health of freshwater ecosystems.

That's what a study by University of Wisconsin-Madison zoologist Colleen Flaherty has found.

Lakes and streams are being flooded with all kinds of common drugs, from caffeine to anticancer medicines, which are affecting minute organisms called zooplankton.

This steady flow of medicated pollution comes from the improper disposal of unwanted pharmaceuticals and from human waste.

"Up to 80 percent of drugs taken by humans and domesticated animals can be excreted in their biologically active form," Flaherty says.

That includes such things as antidepressants, antibiotics and anti-inflammatory medicines.

Flaherty's study is the first to document the effects of this kind of pollution on a type of zooplankton called Daphnia. She presented her study today at the annual meeting of the Ecological Society of America.

"Daphnia play a key ecological role in freshwater sources. 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," Flaherty says.

She researched both the effects of short- and long-term drug exposure on female Daphnia and their offspring.

In short-term studies, she found antibiotic and cholesterol drug concentrations of 10 parts per billion stunted Daphnia growth and produced more male offspring.

In long-term studies, she found Daphnia offspring exposed to antibiotics tended to have longer lifespans, and there were no apparent effects on Daphnia exposed to cholesterol-lowering drugs.

"When Daphnia were exposed to a single pharmaceutical throughout their entire lifespan, as in the long-term studies, they seemed to become acclimated to the polluted environment," Flaherty says.

However, she notes Daphnia living in lakes and rivers are exposed to many different drugs.

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

More information

Here's more information on zooplankton.

SOURCE: University of Wisconsin-Madison, news release, Aug. 7, 2002
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