MONTREAL - The fish swimming through waterways around big cities could be subjected to doses of humans' "happy hormone," a new study suggests.
Significant quantities of anti-depressants are finding their way into the water around Montreal and affecting the fishes' tissue and brain activity, says Dr. Sebastien Sauve, the study's lead researcher.
He said the phenomenon detected in the St-Lawrence River likely exists around other cities, and called for more research into the long-term ecological effects of of fish being stuffed with anti-depressants.
The controlled study involved brook trout exposed to varying amounts of effluent Montreal water over a three-month period.
Sauve, who works in the Universite de Montreal's chemistry department, said researchers measured a biomarker -- a synapse activity in the brain tissue -- and there was a clear reduction in that activity from the fish being exposed to wastewater.
"We have data that does show that anti-depressant drugs do accumulate in fish tissues -- there's significantly more in the liver than in the muscle but there's also more in the brain tissues," Sauve told The Canadian Press.
"This (the brain) is a bit more of a cause for concern because we have a molecule that's known and used for brain alteration functions in humans, so if we do have an accumulation in fish brain, it raises a question of what the impact is on the fish."
Sauve said the study revealed that ozone treatment reduces the level of antidepressants in the wastewater as it leaves the plant. Montreal is experimenting with that kind of treatment.
The study shows the phenomenon is likely found around many cities in the world because Montreal has a typical sewage-treatment system.
But the structure of that type of medication makes it difficult to remove its traces, even with a high-tech treatment facility, Sauve noted.
In Montreal, one in four people are believed to consume some type of anti-psychotic or anti-depressant drug. It's a number researchers based on pharmaceutical sale numbers and Health Department estimates of 555 million pills sold in Quebec each year.
Sauve said the impact on humans is negligible. They wouldn't drink or bathe in wastewater so exposure is "ridiculously small and not a cause for concern for humans."
Even eating the fish wouldn't be a huge cause for concern. The study showed most of the drug's impact is in the liver and brain, but the muscle was largely unaffected in the part people would eat.
"If we do a comparison with the exposure to humans from the traces of those compounds that remain in drinking water, the risk is really minimal," Sauve said.
"If someone was to drink two litres of tap water a day, everyday, for 70 years, they would have had the equivalent of . . . a small fraction of a pill."
Sauve said the actual amount of the drugs in the ecosystem is quite small, despite the potential impact.
"The amount of anti-depressants being released into our (St. Lawrence) River works out to roughly the equivalent of a grain of salt in an Olympic-size swimming pool," said Sauve said.
"Nevertheless, we are seeing an impact on the river's ecosystem, which should concern cities everywhere."
The peer-reviewed study received funding from Health Canada, the St. Lawrence Action Plan and the Canadian Foundation for Innovation. It was published online by Chemosphere on January 5, 2011.
