Scientists have discovered traces of cocaine in wild sharks off the coast of Brazil, shedding light on the potential environmental impact of the illegal drug trade. The unprecedented study, published in the journal Science of the Total Environment, reveals that all 13 Brazilian sharpnose sharks tested positive for cocaine and its metabolite, benzoylecgonine.
Between September 2021 and August 2023, fishing fleets captured the sharks – three male and ten female – off the coast of Rio de Janeiro state in southeastern Brazil. Researchers found the drug and its metabolite in the sharks' muscle tissue and livers, raising concerns about the extent of drug pollution in marine ecosystems.
While the exact source of exposure remains unclear, scientists speculate that cocaine traces may have entered coastal waters through untreated sewage discharged from rivers and urban canals. Another potential source could be cocaine packages drifting in the water, posing a risk if sharks inadvertently bite into them.
"This is the first time cocaine has been detected in wild sharks worldwide," the study's authors noted. "Our findings point to the potential impacts of the presence of illicit drugs in environments."
The discovery draws parallels to the infamous "Cocaine Bear" incident in Georgia, where a black bear overdosed on cocaine believed to have been discarded by drug smugglers. However, unlike the fictionalized movie adaptation, the bear's actual fate was likely a swift overdose.
Researchers expressed concern about cocaine potentially reentering the food chain, as these sharks are often fished for their meat. The study also revealed that cocaine levels were three times higher in muscle tissue than in the liver, with female sharks showing higher concentrations compared to males.
The amount of cocaine and benzoylecgonine found in the sharks "exceeded levels reported in the literature for fish and other aquatic organisms by up to two orders of magnitude," according to the study.
This research adds to a growing body of evidence highlighting the presence of illegal drugs and pharmaceuticals in water bodies worldwide. Previous studies in São Paulo state detected cocaine contamination posing ecological threats to marine life, including mussels and oysters. In 2019, British researchers found freshwater shrimp exposed to cocaine and other pharmaceuticals in UK rivers.
The UN reports a significant increase in global cocaine consumption over recent decades, with Brazilians among the largest consumers in South America. The researchers chose to study the sharpnose shark due to its small size and habitat in areas susceptible to sewage contamination, making it an "environmental sentinel."
As this study unveils the extent of drug pollution in marine ecosystems, it underscores the urgent need for improved wastewater treatment and stricter measures to combat drug trafficking to protect marine life and public health.
