Sharks in the Bahamas Test Positive for Drugs, Including Cocaine and Painkillers, in a New Study

Around one-third of the studied sharks had detectable levels of the analyzed drugs in their blood

Kunjal Bastola | Editorial Intern

March 30, 2026

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Sharks in the Bahamas are ingesting drugs—including cocaine, caffeine and painkillers—according to a study published in February in the journal Environmental Pollution. Scientists identified blood contamination in about one-third of tested animals, findings that further highlight how humans are harming marine environments.

“We’re talking about a very remote island in the Bahamas,” study co-author Natascha Wosnick, a biologist with the Federal University of Paraná in Brazil, tells Science News’ Joshua Rapp Learn.

Researchers have become increasingly aware of pharmaceuticals and other products entering marine habitats, where they’re called contaminants of emerging concern. Past studies have mainly focused on their effects on invertebrates and bony fish, but sharks—important players in ocean ecosystems—have been largely left out.  

So Wosnick and her colleagues captured 85 sharks representing five species near Eleuthera Island in the Bahamas. The researchers suspected that the tropical region’s tourism has led to an increase in pollution that ends up in local sharks.

The team collected blood samples from the animals and then released them. After that, they examined the specimens for about 20 different drugs, spanning classes including antibiotics, antidepressants and opioids. Analyses revealed that 28 sharks across three species—Caribbean reef sharks, nurse sharks and lemon sharks—had detectable levels of at least one of four drugs: cocaine, caffeine and the painkillers diclofenac and acetaminophen. 

“While the detection of cocaine—an illicit substance—tends to draw immediate attention, the widespread presence of caffeine and pharmaceuticals in the blood of many analyzed sharks is equally alarming,” Wosnick tells CBS News’ Kerry Breen in an email. “These are legal substances, routinely consumed and often overlooked, yet their environmental footprint is clearly detectable. This underscores the need to critically reassess even our most normalized habits.”

This isn’t the first time Wosnick has found pollutants in the ocean predators. In previous research, she and some of the same scientists identified cocaine in sharks near Rio de Janeiro in Brazil. However, in that study, published in 2024, the team tested the liver and muscle tissue of sharks. Blood, on the other hand, reflects more recent exposure to drugs, the researchers write in the paper.

The data also showed that the sharks with contaminated blood had changes in some biological markers, which can point to how tissues are functioning. Though the researchers don’t know if the alterations are detrimental, the team says they could lead to behavioral changes.

“Our primary concern is not an increase in aggression toward humans, but rather the potential implications for the health and stability of shark populations,” Wosnick tells CBS News. “Chronic exposure to these anthropogenic compounds, many of which have no natural analog in marine systems, may lead to negative effects that are still poorly understood.”

The work comes a few years after the release of the documentary Cocaine Sharks, in which scientists conducted experiments to see how sharks in the Florida Keys would react to a stimulant drug similar to cocaine. For instance, researchers wanted to know whether the animals would seek out the stimulant rather than food, Tracy Fanara, an oceanographer at the University of Florida who helped produce the show, told CBS News’ Caitlin O’Kane in 2023. They were motivated by the large amount of cocaine being brought to the United States from other countries, some of which has washed up on the Florida coast, she added.  

“The goal of the study was basically to see if this is a research question worth exploring more,” Fanara said. “And I would say, yes, it is.”

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Kunjal Bastola is an editorial intern with Smithsonian magazine.