Sharks Off Coast of Brazil Test Positive for Cocaine: Study

Ipanema beach in Rio de Janeiro in an undated file photograph. Mario Tama/Getty Images

Sharks off the coast of Brazil have tested positive for cocaine, marking the first time the drug has been found in free-ranging sharks, according to researchers.

In the study, titled “‘Cocaine Shark’: First report on cocaine and benzoylecgonine detection in sharks,” researchers at the Oswaldo Cruz Foundation in Rio de Janeiro analyzed cocaine (COC) and its main metabolite, benzoylecgonine (BE), in the muscle and liver tissues of 13 Brazilian sharpnose sharks.

Researchers said concentrations of cocaine and BE detected in the sharks exceeded levels reported in other studies for fish and other aquatic organisms “by up to two orders of magnitude.”

The sharks were captured by fishing fleets in the Recreio dos Bandeirantes neighborhood off the coast of Rio de Janeiro in south-eastern Brazil from September 2021 to August 2023.

Cocaine Detected in All 13 Specimens

Three of the sharks were males and 10 were females. Five of the 10 female sharks were pregnant, according to the study authors.

Researchers found cocaine present in both the liver and muscle tissue of all 13 specimens, while 12 out of the 13 sharks tested positive for BE.

The average concentration of cocaine in the animals was three times higher than the concentration of BE.

Cocaine levels were also around three times higher in muscle tissue compared to liver tissue, according to the study, while the female Brazilian sharpnose sharks had higher concentrations of the drug in their muscle tissue compared to males.

“The results indicate that all sharks were exposed to cocaine in their natural habitats,” the authors wrote.

Cocaine Use Soaring

Global cocaine consumption has soared in the last decades, the authors noted, pointing to data in the United Nations World Drug Report 2023.

According to that report, around 4.8 million–or roughly 22 percent–of the estimated 22 million cocaine users worldwide reside in South America as of 2021, with Brazil emerging as the second largest consumer market in the region.

“Indeed, in these regions, increasing COC usage rates coincide with inadequate sewage treatment infrastructure, with treatment rates ranging only at around 50 percent,” the researchers said.

The findings point to the potential impacts of the presence of illicit drugs in environments, the study authors said, noting that cocaine is categorized as “pseudo-persistent” due to its “continuous environmental release from inadequate sewage treatment facilities as well as from clandestine refining operations.”

Another reason the drug has been discovered in waters is because of “drifting cocaine packs not recovered by sellers or authorities,” which may become “intense point sources of cocaine to water and biota and potentially be bitten or swallowed by larger fish, including sharks,” the authors wrote.

Further research is needed to better understand how consuming cocaine may change the behavior of sharks, the authors said.

“[U]nderstanding the assimilation of drugs of abuse and other contaminants of emerging concern in this species can offer valuable insights regarding human health risk assessments and seafood consumption safety,” they concluded.