Sharks on Cocaine: What Drug Pollution Is Revealing About Ocean Contamination

Redacción HC
01/11/2024

It sounds like the plot of a B-grade horror film—“Cocaine Shark.” But a new scientific study has revealed something equally alarming and all too real: sharks off the coast of Brazil have tested positive for cocaine and its primary metabolite, benzoylecgonine. This marks the first time such drugs have been detected in large marine predators.

Published in Science of the Total Environment (Oct. 2024), the study by Gabriel de Farias Araujo and colleagues sheds light on the growing presence of illicit drugs in ocean ecosystems. As cocaine residues increasingly flow from urban wastewater into coastal waters, researchers are beginning to understand the extent to which marine life is exposed—with troubling implications.

How Did Cocaine Reach the Sharks?

Urban sewage systems and clandestine drug disposal practices are introducing narcotics into the environment. Previous studies have shown traces of pharmaceuticals and even cocaine in freshwater and marine animals, but data on apex predators like sharks was nonexistent—until now.

The researchers set out to answer a key question:

Are sharks being exposed to cocaine in the wild, and if so, to what extent?

The study focuses on Rhizoprionodon lalandii, a small coastal shark common in the western Atlantic.

The Method: Tissue Analysis of Wild Sharks

Thirteen sharks were obtained from artisanal fishers near Rio de Janeiro. Samples of muscle and liver tissue were collected and analyzed using liquid chromatography–mass spectrometry (LC-MS/MS)—a sensitive method for detecting trace levels of chemical compounds.

What They Found:

• 100% of sharks tested positive for cocaine (COC).
• 92% tested positive for benzoylecgonine (BE), a key cocaine metabolite.
• Cocaine concentrations were 3x higher in muscle tissue (average 33.8 µg/kg) than in liver.
• Female sharks had significantly higher muscle concentrations (40.2 µg/kg) than males (12.4 µg/kg).

This data reveals a systemic bioaccumulation of drugs in shark bodies, hinting at metabolic and physiological differences by sex and reproductive status.

Why This Matters: Shocking Comparisons and Ecological Concerns

Comparisons to Other Marine Species

The study found that cocaine levels in these sharks were 100 times higher than what has previously been observed in species like mussels or small fish. That dramatic difference raises the stakes:

If a top predator is accumulating drugs at this scale, it suggests that the entire food web is contaminated, said one co-author.

Potential Impacts on Shark Health

Although the study did not assess behavioral or physiological effects, the implications are serious. Cocaine affects the central nervous system in humans and is known to disrupt neurological and cardiovascular function. Could similar effects be harming marine species?

Future research will need to explore:

• Neurological effects (e.g., disorientation, aggression)
• Reproductive impacts (e.g., hormone disruption)
• Long-term bioaccumulation consequences

Pollution Pathways: From Street Drugs to the Sea

The likely culprits? Urban wastewater, maritime drug trafficking routes, and poor waste management. In cities like Rio de Janeiro—where untreated sewage is often discharged into coastal waters—these contaminants can flow freely into shark habitats.

Even more troubling, such contamination is largely unregulated. Illicit drugs are not currently monitored in most water quality assessments or marine conservation protocols.

What Needs to Change: From Awareness to Action

Policy Implications

This research urges policymakers to:

• Classify illicit drugs as emerging environmental contaminants.
• Integrate narcotic residue tracking into marine pollution and water quality standards.
• Fund programs that trace contaminants from urban sources to marine endpoints.

Conservation Urgency

Sharks are vital to marine ecosystems, maintaining the balance of species and preventing overpopulation of prey. If narcotic exposure undermines their health or reproduction, the ripple effects could be devastating for biodiversity.

Regional Significance: A Wake-Up Call for Latin America

Latin American countries like Brazil, Peru, and Ecuador are already grappling with coastal contamination, illegal dumping, and poor wastewater infrastructure. This study suggests that marine drug pollution could be more widespread than previously imagined.

Protected marine areas, such as those in Peru’s Pacific coast, may be particularly vulnerable. These results could support expanded environmental monitoring, including the use of forensic tools to detect chemical fingerprints of human activity in the ocean.

Conclusion: The Tip of a Toxic Iceberg

The idea of sharks testing positive for cocaine may grab headlines, but the underlying message is even more urgent: our drug habits are polluting the ocean, silently affecting marine life in ways we’re only beginning to understand.

This study is a landmark warning about a new dimension of environmental contamination—one that merges urban behavior, public health, and ecosystem resilience.

The presence of cocaine in sharks underscores the importance of monitoring illicit drugs as environmental pollutants in marine ecosystems.

Topics of interest

Pollution