OCTOBER 31, 2003
"Drugs may harm frogs and fish in the wild"
Drugs may harm frogs and fish in the wild
ATHENS, Ga. - University of Georgia researchers have discovered developmental problems in frogs and fish exposed to minute quantities of common antidepressants that can pass from humans through sewage treatment systems into rivers and streams.
The scientists have been studying the toxicity of a widely used group of antidepressants called selective serotonin reuptake inhibitors, which are commonly prescribed for depression, anxiety, panic disorder, obsessive compulsive disorder, eating disorders and social phobia.
Some of the drugs, including Prozac, Zoloft, Paxil and Celexa, have been found in low concentrations in surface water, particularly wastewater.
"While these compounds are not acutely toxic at concentrations detected in the environment, our longer-term studies indicate delayed development (in fish) and delayed metamorphosis (in frogs)," said Marsha Black, a University of Georgia aquatic toxicologist who led the study.
The researchers found that low concentrations of fluoxetine - Prozac - the most commonly prescribed of the drugs, significantly slowed development in Gambusia, or mosquitofish, which are often used to study toxicity on aquatic organisms.
"We found that male sexual development slowed by two to four weeks," said Ted Henry, a researcher on the project.
When the fish were around 80-85 days old, the sexual maturity of those exposed to low levels of fluoxetine was significantly delayed, he said. But by the end of the study, when the fish were 145 days old, the same fish had caught up developmentally with the unexposed fish, Henry said.
"We're scratching our heads right now as to exactly what this means," Black said. "But we know that in water, timing is everything. Reproduction for some species is timed to coincide with algae blooms for example. And possibly if sexual development is delayed, timing of reproduction could be affected and you could see some population impact."
The researchers also found that metamorphosis in frogs exposed to low levels of fluoxetine took longer than usual. For frogs, particularly the land-based frogs of North America, such a delay could be a matter of life and death, because frog eggs are often laid in temporary pools that dry up, Black said.
If the water evaporates before the tadpoles change into frogs - a process called metamorphosis - they die, she said.
Black believes the results may indicate a disruption of thyroid functions and plans to explore that theory in future research. The thyroid gland regulates metabolism.
"We know that the thyroid levels peak with metamorphic climax, when the legs and arms form and the tail resorbs," Black said. "We believe that fluoxetine inhibits the thyroid so we're measuring the thyroid hormone levels next."
In the next phase, they'll also closely examine the reproductive tissue of the fish affected by fluoxetine to determine whether drug exposure affects reproduction and embryo production.
The results of their initial research, funded by a $523,000 grant from the Environmental Protection Agency, will be presented at the 24th Annual Meeting of the Society of Environmental Toxicity and Chemistry Nov. 9-13 in Austin, Texas.
The drugs in the Georgia study fall into a broad category known as "pharmaceuticals and personal care products" that have become an emerging environmental concern. They include prescription and over- the-counter drugs that are excreted in tiny amounts by humans and pass through treatment systems into streams.
One of the largest concerns so far has been possible hormonal disruption in fish by natural and man-made estrogen and the release of antibiotics that could lead to drug-resistant
A recent study by Baylor University toxicologist Bryan Brooks found traces of fluoxetine in the tissue of bluegills in a Texas creek fed by discharges from a wastewater treatment plant.
"Treated municipal drinking water should be fine, but pharmaceuticals may not be filtered out of wastewater," Black said. "We should be putting a high priority on implementing technologies that remove ... pharmaceuticals from municipal wastewater discharges."
SOURCE: http://www.kansascity.com/mld/kansascity/news/brea king_news/7151720.htm