{"id":520048,"date":"2026-06-26T19:53:18","date_gmt":"2026-06-26T19:53:18","guid":{"rendered":"https:\/\/www.newsbeep.com\/ie\/520048\/"},"modified":"2026-06-26T19:53:18","modified_gmt":"2026-06-26T19:53:18","slug":"scientists-find-antidepressant-in-the-brains-of-sharks-off-the-coast-of-rio-de-janeiro","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ie\/520048\/","title":{"rendered":"Scientists find antidepressant in the brains of sharks off the coast of Rio de Janeiro"},"content":{"rendered":"

Sertraline<\/a> is one of the most widely prescribed antidepressants in the world. Global sertraline sales are expected to keep growing, projected to expand from an estimated US$1.94 billion in 2025 to approximately US$3.13 billion by 2032<\/a>.<\/p>\n

In Brazil, a national survey<\/a> indicates that 10.2% of Brazilians were diagnosed with depression, and it is estimated that 4% used antidepressants<\/a>.<\/p>\n

But what few people know is that some of these pills take a second path after being metabolized by the body: They are excreted in urine, enter the sewage system, and go straight into the ocean.<\/p>\n

And in Rio de Janeiro, in addition to all the beauty of the ocean, there are also sharks.<\/p>\n

The finding no one expected<\/p>\n

The EcoShark Project<\/a>, which is coordinated by Mariana Alonso, a professor at the Carlos Chagas Filho Institute of Biophysics at UFRJ<\/a>, has been monitoring shark health along the Rio de Janeiro coast since 2018. This research also involved other scientists, such as Jos\u00e9 Souto-Neto<\/a> and Victor Alves, and is a pioneering initiative on emerging contaminants in elasmobranchs<\/a>.<\/p>\n

\"\"<\/p>\n

EcoShark biologists identifying and studying sharks along the southern coast of Rio de Janeiro. Personal archive.<\/p>\n

The study, to be submitted for publication, but already shared among UFRJ scientists, identified sertraline \u2014 the active ingredient in Zoloft and dozens of generic versions \u2014 in the brain tissue of hammerhead sharks (Sphyrna lewini<\/a> and S. zygaena<\/a>), classified as critically endangered species (IUCN<\/a>, Ibama)<\/p>\n

The hammerhead sharks tested had been accidentally caught in fishing nets off the coast of Recreio, Barra da Tijuca, and Copacabana beaches and sent to analysis thanks to a partnership between fishermen and researchers from UFRJ. As apex predators, sharks are highly susceptible to bioaccumulation and biomagnification of contaminants in the food chain. As a shark swims and feeds, it constantly takes in amounts of contaminants from the water and sediment, while it also absorbs all the contaminants its preys, like other fish and cephalopods (squids and octopus), took in before as they also swam and fed. And, increasingly, the contaminants in these food chains are the residues of our medications.<\/p>\n

The path of the medicine<\/p>\n

How does a human antidepressant reach a shark\u2019s brain? The path is less surprising than it seems.<\/p>\n

When a person takes sertraline, the body metabolizes most of the drug in the liver. Sertraline can be excreted unchanged or metabolized, and both forms end up in the sewage system.<\/p>\n

Conventional wastewater treatment plants were designed primarily to remove organic matter, nutrients, and microorganisms. And the removal of pharmaceutical compounds is often incomplete. As a result, traces of antidepressants and their metabolites are detected in treated effluents and in aquatic environments<\/a>.<\/p>\n

In the Brazilian state of Rio de Janeiro, only about 47% of the sewage generated is effectively treated, according to recent data from Brazil\u2019s National Sanitation Information System<\/a>.<\/p>\n

A significant portion of the sewage is discharged into the ocean via the Ipanema and Barra da Tijuca submarine outfalls. With only preliminary treatment, these systems fail to remove pharmaceuticals, releasing molecules into the coastal environment, where they are absorbed by fish and marine invertebrates directly from the water or through their food.<\/p>\n

In sharks, various contaminants accumulate in specific tissues, especially the liver. In the case of sertraline, its affinity for lipid-rich tissues and the nervous system may help explain its detection in the animals\u2019 brains.<\/p>\n

This is not an isolated case<\/p>\n

Rio de Janeiro is not alone on this map. In March 2026, a study published in the journal Environmental Pollution<\/a> revealed that 28 of 85 sharks sampled near Eleuthera Island, in the Bahamas, had detectable concentrations of cocaine, caffeine, and painkillers in their blood.<\/p>\n

\"\"<\/p>\n

Personal archive.<\/p>\n

Brazilian researchers tested samples and found painkillers and cocaine in sharks. The finding has shifted perceptions: If drugs are found in sharks off a Caribbean island with low urban density, what can we expect from those swimming less than 1 km (0.6 miles) from Rio\u2019s beaches? The study also detected physiological changes in the animals, suggesting that these substances may affect their biochemistry.<\/p>\n

Why the shark\u2019s brain is the problem<\/p>\n

Sertraline, which acts on serotonin in the human brain, was detected in shark brain tissue. This points to exposure and bioaccumulation. Since this serotonin transporter is very similar across vertebrates, the drug could theoretically interact with the animals\u2019 proteins. But detection alone does not yet allow us to conclude that there has been a behavioral or physiological change in the animals.<\/p>\n

Science already shows that sertraline can affect other marine animals: in the laboratory, zebrafish exposed to 0.1 \u00b5g\/L of sertraline \u2014 a concentration found in coastal waters \u2014 developed hypokinesia and learning delays, along with alterations in the serotonergic system.<\/p>\n

What is not yet known \u2014 and this is the question EcoShark is trying to answer \u2014 is what these compounds do to an elasmobranch. Sharks have neurochemistry distinct from that of bony fish, more similar to that of mammals. The answer, for now, is a question mark weighing hundreds of pounds.<\/p>\n

A question that cannot be ignored<\/p>\n

Brazil has the highest fatality rate from shark incidents in the world<\/a>. In 2021, the recorded mortality rate reached 30% \u2014 compared to 1% in the United States and 14% in Australia.<\/p>\n

\"\"<\/a><\/p>\n

Pesonal archive, Author provided (no reuse)<\/p>\n

No, we\u2019re not suggesting that antidepressants in the oceans cause attacks. But the question science has a duty to ask is another: If these drugs, at relevant concentrations, alter the behavior of fish in the lab, what actually happens to sharks chronically exposed to them in the world\u2019s most polluted coastal areas?<\/p>\n

What\u2019s at stake beyond the obvious<\/p>\n

The discovery of sertraline in the brains of hammerhead sharks in Rio de Janeiro touches on three crises that Brazil still treats as separate.<\/p>\n

The first is the mental health crisis. Antidepressant use in Brazil rose by 12.4% among adults aged 29 to 58 between 2023 and 2025<\/a>. This increase is not a problem in itself. It reflects progress in diagnosis and access to treatment. But each pill has a second destination that is not being monitored.<\/p>\n

The second is the sanitation crisis. As long as about half of Rio de Janeiro\u2019s sewage remains untreated \u2014 without a process capable of removing pharmaceutical compounds \u2014 the ocean will continue to serve as a dumping ground for our household medicine cabinets.<\/p>\n

The third crisis is one of conservation: The hammerhead shark, a critically endangered species, is essential to marine balance \u2014 its presence regulates and stabilizes the food chain. Altering this animal\u2019s neurochemistry is an involuntary and uncontrolled experiment.<\/p>\n

What needs to change<\/p>\n

Three actions are urgent and are not mutually exclusive. Brazil\u2019s environmental monitoring protocols must include the systematic tracking of pharmaceuticals in sharks, rays, and cetaceans. The methodology already exists \u2014 namely, the EcoShark and EcoDELFIS projects. What\u2019s missing? Ongoing funding and a public policy that values and recognizes pharmaceuticals as emerging pollutants.<\/p>\n

The country\u2019s wastewater treatment plants need to be modernized to remove pharmaceutical micropollutants.<\/p>\n

Funding for marine ecotoxicology research needs to be expanded. Brazil has a coastline of nearly 8,000 kilometers (5,000 miles), one of the planet\u2019s most biodiverse regions, and now, sharks with antidepressants in their brains. <\/p>\n

Sertraline was created to alleviate human suffering. The fact that it has reached the nervous system of a predator just a few kilometers from Copacabana beach is the clearest indication of the extent to which this generation is leaving its mark.<\/p>\n

The research was funded by PIBIC-UFRJ<\/a>, Capes<\/a>, and Faperj<\/a>. The implementation of the EcoShark Subproject within the Marine and Fisheries Research Project was a compensatory measure established by the Conduct Adjustment Agreement under the responsibility of the company PRIO<\/a>, led by the Federal Public Prosecutor\u2019s Office \u2013 MPF\/RJ<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"Sertraline is one of the most widely prescribed antidepressants in the world. Global sertraline sales are expected to…\n","protected":false},"author":2,"featured_media":520049,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[61,60,82,263],"class_list":["post-520048","post","type-post","status-publish","format-standard","has-post-thumbnail","category-wildlife","tag-ie","tag-ireland","tag-science","tag-wildlife"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/520048","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=520048"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/520048\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/520049"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=520048"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=520048"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=520048"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}