Drug pollution – Not all bad

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Human-made pharmaceuticals are bound to find their way out into the ecosystem. This usually causes problems with the local wild life that has trouble with a newly introduced substance and usually cause harm. New research from Umeå University has studied this drug pollution in a new way, the results was anything other than fishy.

The usual way to test if a substance have detrimental effects when studying effects on fish is to start with a control population of fish grown in a lab to have 100% survival rate. Since the control group has 100% survival rate it is hard to observe any positive effect that drug pollution that contaminates the environment might have, this is of course rarely studied.

Klaminder and colleagues took a different approach to study possible effects of pharmaceuticals on the Eurasian perch (Perca fluviatilis). They took 2 year old fish from a newly thawed lake and fish eggs containing embryos undergoing sensitive development steps. The fish was divided into groups and exposed to the drug Oxazepam, a type of Benzodiazepine. In high concentration: 1000 micrograms / litre low concentration: 1 micro gram/ litre or no exposure at all. The low point concentration was based on actual measurements in an urban area.

Fishing for results

Mortality was high in the untreated fish. Exposure to the high concentration of the drug actually increased the survival rate of the embryos compared to both the untreated fish and those only exposed to the lower concentration of the drug. Regardless of the exposure, 1000 or 1 micro gram, it also improved the survival in mature fish.

Klaminder and his colleagues are unsure as to what causes this effect in the fish. One theory is that the fish grow bolder and spend less time with their buddies and more time foraging for food. Which increases their survival rate compared to unexposed fish. More research is needed on other types of drugs to ascertain if this drug pollution is the only one with some positive effects on certain species of if the phenomenon has a wider scope. Regardless its probably a bad idea to throw out your old prescription drugs.