Researchers studying fish from the Niagara River have found that human antidepressants and remnants of these drugs are building up in the fishes' brains.

The concentration of human drugs was discovered by scientists from University at Buffalo, Buffalo State and two Thai universities, Ramkhamhaeng University and Khon Kaen University.

Active ingredients and metabolized remnants of Zoloft, Celexa, Prozac and Sarafem — drugs that have seen a sharp spike in prescriptions in North America — were found in 10 fish species.

Diana Aga, professor of chemistry at University at Buffalo, says these drugs are found in human urine and are not stripped out by wastewater treatment.

Could affect fish behaviour

"It is a threat to biodiversity, and we should be very concerned," Aga said in a release from the university.

Fish in the Niagara River show concentrations of antidepressants in their brains higher than levels in the river itself. (David Duprey/The Associated Press)

"These drugs could affect fish behaviour. We didn't look at behaviour in our study, but other research teams have shown that antidepressants can affect the feeding behaviour of fish or their survival instincts. Some fish won't acknowledge the presence of predators as much."

The Niagara River, which carries water from Lake Erie to Lake Ontario, is already under stress, with reports this summer of untreated wastewater released into the river.

Fish are receiving this cocktail of drugs 24 hours a day, and we are now finding these drugs in their brains - Diana Aga, study author

The research, published in the journal Environmental Science & Technology, found levels of antidepressants in fish brains that were several times higher than levels in the river itself, indicating that the chemicals are accumulating over time.

The study set out to look for a variety of pharmaceutical and personal care product chemicals in the organs and muscles of 10 fish species: smallmouth bass, largemouth bass, rudd, rock bass, white bass, white perch, walleye, bowfin, steelhead and yellow perch.

Antidepressants stood out as the major problem.

Rock bass had high concentrations

The rock bass had the highest concentrations of antidepressants, but several fish had a medley of drugs in their bodies.

Aga said she did not believe the chemicals were a threat to humans, as people do not usually eat fish brains. However, she was concerned about the health of fish species who are continually subjected to an influx of chemicals, as well as the delicate balance among species.

Aga said wastewater treatment plants have not kept up with the times in attempting to remove drugs from their effluent.

Between 1999-2002 and 2011-14, the number of U.S. residents using antidepressants rose by 65 per cent, according to the National Center for Health Statistics.

Wastewater treatment focuses on killing disease-causing bacteria and on extracting solid matter but not on removing chemicals that might be found in human urine, Aga said.

"These plants are focused on removing nitrogen, phosphorus, and dissolved organic carbon but there are so many other chemicals that are not prioritized that impact our environment," she said. "As a result, wildlife is exposed to all of these chemicals. Fish are receiving this cocktail of drugs 24 hours a day, and we are now finding these drugs in their brains."