Review: Fish in drug tainted water suffer reaction


What happens to fish that swim in waters tainted by traces of drugs that people take? When it's an anti-anxiety drug, they become hyper, anti-social and aggressive, a study found. They even get the munchies.

The findings, published online Thursday in the journal Science, add to the mounting evidence that minuscule amounts of medicines in rivers and streams can alter the biology and behavior of fish and other marine animals.

Calling their results alarming, the Swedish researchers who did the study suspect the little drugged fish could become easier targets for bigger fish because they are more likely to venture alone into unfamiliar places.

Researchers around the world have been taking a close look at the effects of pharmaceuticals in extremely low concentrations, measured in parts per billion. Such drugs have turned up in waterways in Europe, the U.S. and elsewhere over the past decade.

They come mostly from humans and farm animals; the drugs pass through their bodies in unmetabolized form. These drug traces are then piped to water treatment plants, which are not designed to remove them from the cleaned water that flows back into streams and rivers.

The research team at Sweden's Umea University used minute concentrations of 2 parts per billion of the anti-anxiety drug oxazepam, similar to concentrations found in real waters. The drug belongs to a widely used class of medicines known as benzodiazepines that includes Valium and Librium.

Most previous research on trace drugs and marine life has focused on biological changes, such as male fish that take on female characteristics. However, a 2009 study found that tiny concentrations of antidepressants made fathead minnows more vulnerable to predators.

Another possibility, the researchers said, is that more aggressive feeding by the perch on zooplankton could reduce the numbers of these tiny creatures. Since zooplankton feed on algae, a drop in their numbers could allow algae to grow unchecked.



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