Fish may find some water contaminants to their benefit as researchers have shown that a drug used to treat anxiety in humans reduces mortality rates in fish.
The results may have significant implications for existing standard ecotoxicological tests, which predominantly focus on harmful effects of water contaminants and ignore the potential benefits.
"A new, conceptual view of ecotoxicological testing should include the possibility that a substance can improve the health of an organism and make individuals affected by contamination more competitive than non-affected individuals," said Tomas Brodin from Umea University in Sweden.
In their study, the researchers retrieved a two-year-old Eurasian perch from a lake in Sweden and randomly exposed them to high and low concentrations of Oxazepam.
Oxazepam is a benzodiazepine which is commonly used to treat anxiety and insomnia in humans and regularly contaminates surface waters via treated wastewater effluent.
Results showed that mortality rates were significantly reduced by Oxazepam exposure in comparison to the control group of fish who were not exposed.
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"It is possible that similar effects could be induced by exposure to a whole range of pharmaceuticals that find their way into surface waters, such as antibiotics, pain killers, anti-inflammatory drugs, hormones and anti-depressants," Brodin added.
The study appeared in the journal Environmental Research Letters.