Sharks test positive for cocaine in Brazil’s drug-polluted waters. Photo: Bruna Prado/Getty Images

The Brazilian sharpnose sharks were captured by fishing fleets off the coast of the state of Rio de Janeiro in southeastern Brazil between September 2021 and August 2023. The 13 sharks — three male and 10 female — all tested positive for cocaine, researchers said in a study published in the journal Science of the Total Environment.

The drug, along with benzoylecgonine, the major metabolite of cocaine, was found in their muscle tissue and livers.

Researchers don’t know exactly how the sharks were exposed to the drug. But they suspect that traces of cocaine were probably discharged into the coastal region through raw sewage in rivers and urban canals.

Another potential source of exposure, according to scientists, is cocaine packs drifting in water and not discovered by drug smugglers or authorities, which pose a risk if sharks bite into them.

That was the case with another apex predator, Cocaine Bear, a 500-pound black bear in Georgia that overdosed on cocaine thought to have been tossed from a drug smuggler’s plane. The bear’s skeletal remains were discovered in 1985 by narcotics investigators. The story was loosely translated into a 2023 horror movie in which the bear went berserk. (In reality, authorities believed the bear probably overdosed swiftly.)

Researchers said this is the first time cocaine has been detected in wild sharks worldwide, and their findings “point to the potential impacts of the presence of illicit drugs in environments.”

Researchers also worry about cocaine reentering the food chain; the sharks are fished for their meat.

Previous studies have found illegal drugs, and legal medications, are accumulating in waters around the world, including in São Paulo state, where scientists say cocaine contamination is posing an ecological threat to marine life including mussels and oysters.

Researchers previously found that the level of cocaine in waters around São Paulo, home to Brazil’s most populous city, was similar to the amount of caffeine in coffee and tea, which they described as a “huge concentration.” It has also been detected in the state’s drinking water.

In 2019, British researchers found freshwater shrimp were being exposed to cocaine and other pharmaceuticals in the country’s rivers.

Global cocaine consumption has soared in recent decades, according to the United Nations. Brazilians are among the biggest consumers of the drug in South America, according to the study’s authors.

The Brazilian researchers chose to study the sharpnose shark because of its small size and the fact that it inhabits an area that is subject to significant contamination from sewage, making it an “environmental sentinel.”

They found that cocaine levels were three times higher in the muscle than in the liver, and that the female sharks had higher cocaine concentrations in muscle tissue 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.”