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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteResearchers detected cocaine in all 13 Brazilian sharpnose sharks they tested off Rio de Janeiro, but the study did not show that the sharks were intoxicated or “high.” It found drug residues in tissue—not altered behavior or a demonstrated health effect.
What did the researchers find?
The peer-reviewed study, “Cocaine Shark”: First report on cocaine and benzoylecgonine detection in sharks, examined 13 Brazilian sharpnose sharks (Rhizoprionodon lalandii) caught by artisanal fishing fleets off Recreio dos Bandeirantes, a neighborhood in Rio de Janeiro. The sharks were sampled between September 2021 and August 2023. Researchers analyzed muscle and liver tissue using liquid chromatography–tandem mass spectrometry (LC-MS/MS). The paper was published in Science of the Total Environment on October 20, 2024.
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| Finding | Study result |
|---|---|
| Sharks with cocaine detected | 13 of 13 tested, Araujo et al., 2024 |
| Sharks with benzoylecgonine detected | 12 of 13 tested, Araujo et al., 2024 |
| Mean cocaine concentration | 23.0 μg/kg, as reported in the study abstract, Araujo et al., 2024 |
| Mean benzoylecgonine concentration | 7.0 μg/kg, as reported in the study abstract, Araujo et al., 2024 |
| Difference by tissue | Cocaine concentrations were about three times higher in muscle than in liver, Araujo et al., 2024 |
Benzoylecgonine is cocaine’s main metabolite. Finding it in tissue, alongside cocaine, is evidence of chemical exposure; it does not by itself reveal how the chemicals entered each shark or what biological effects they had.
Does this mean the sharks were “high”?
No. “Getting high” suggests intoxication or a change in behavior, neither of which this study measured. The researchers tested tissue for chemical residues; they did not observe or experimentally assess the sharks’ behavior, and the study did not establish a health effect. “Sharks exposed to cocaine” or “cocaine detected in shark tissue” is therefore more accurate than saying the animals were high.
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How could cocaine get into coastal water?
The researchers discussed sewage and other human-linked releases as plausible routes for cocaine and its metabolite to reach coastal waters. The Oswaldo Cruz Institute (Fiocruz) also described drug residues discharged through sewage as a concern. But the shark study did not trace the chemicals to a particular sewage outlet, drug laboratory, or other source, so the route remains a possibility rather than a proven explanation for these samples.
Fiocruz researcher Rachel Ann Hauser-Davis said: “Following this finding in the national territory, our research group decided to investigate whether the animals that our laboratory had collected for studies involving other contaminants were also contaminated by cocaine.” Her comment, reported by Fiocruz, explains the motivation for related investigation; it is not a finding that those other animals tested positive.
What the results can—and cannot—tell us
Detection is not an estimate for all sharks
All 13 sampled sharks tested positive for cocaine, but they came from one coastal area and were caught over the period from September 2021 to August 2023. This small, local sample cannot establish how widespread contamination is among sharks elsewhere in Brazil or estimate the proportion of the country’s shark population exposed.
Tissue residues do not establish harm
The study reported sex- and tissue-related differences and correlations, but those observations do not establish cause and effect. Because the researchers did not assess shark health or behavior, the measured concentrations cannot be used to conclude that the sharks suffered a particular injury, were impaired, or changed their behavior.
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More sampling is needed to answer the open questions
Fiocruz described water and animal sampling as intended next steps. Broader sampling could help clarify how often cocaine residues occur in coastal waters and marine animals; determining effects on sharks would require evidence specifically addressing health or behavior, not tissue detection alone.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why this finding matters
The study is a documented detection of cocaine and benzoylecgonine in sharks from one area off Rio de Janeiro, and it raises questions about how human-linked contaminants reach coastal ecosystems. It is not evidence that Brazil’s sharks generally are intoxicated. The distinction matters: detecting a contaminant establishes exposure in the sampled animals, while prevalence, source attribution, and biological effects require separate evidence.
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