Antidepressants in Wastewater Disrupt Fish Neurochemistry, Study Finds

Researchers at Japan’s Tokyo University of Science examined how common human antidepressants affect two native fish species—medaka and ayu. By cloning the genes that encode the fish versions of monoamine transporters (SERT, DAT, NET) and expressing them in engineered human cells, the team exposed the proteins to several widely-prescribed drugs, including Lexapro, Cymbalta, Prozac, mirtazapine and quetiapine. The study, published in *Environmental Science & Technology*, reports that the concentrations required to impair the fish proteins were often ten times lower than those needed to affect the human equivalents. The authors note that about one-in-six American adults are prescribed antidepressants, which are excreted largely unchanged and can enter rivers and oceans through wastewater treatment systems.

Vice NewsThe Independent

Laboratory tests showed that the fish serotonin transporter (SERT) was especially vulnerable, shutting down at drug levels up to tenfold lower than those that inhibit the human SERT. Some compounds that have minimal impact on human transporters—such as mirtazapine and quetiapine—still produced measurable blocking effects on the fish versions, suggesting “unforeseen side effects” for aquatic organisms. The researchers also found a direct correlation between the drug concentrations that disrupted fish proteins in the lab and pollutant levels previously measured in rivers and streams worldwide.

Vice NewsThe Independent

Because fish share the same neurotransmitters (serotonin, dopamine, norepinephrine) that antidepressants target in humans, the heightened sensitivity could alter behavior, reproduction and overall ecosystem health. The authors liken fish to “canaries in the coal mine,” warning that pharmaceutical contamination may have broader ramifications for marine and freshwater wildlife beyond the two species studied.

The Independent

Canadian researcher Sigal Balshine, who has conducted related studies, previously described fish as early warning indicators for environmental contaminants. Both scientists call for greater attention to pharmaceutical residues in wastewater.

The Independent

• “By demonstrating that key molecular targets in fish can be more sensitive than their human equivalents, our work offers crucial insights into the potential risks of pharmaceutical exposure to aquatic wildlife,” — Shinichi Miyagawa, a professor at Japan’s Tokyo University of Science

The Independent