Updated July 24, 2024 at 10:59 AM ET
Scientists in Brazil have come up with the first evidence that sharks are being exposed to cocaine.
Rachel Ann Hauser Davis, a biologist who worked on the study at Brazil's Oswaldo Cruz Foundation, told NPR that they dissected 13 wild sharpnose sharks caught near Rio de Janeiro. All tested positive for cocaine in their muscles and livers.
"The key findings of the study are the presence of cocaine in sharks," Hauser Davis says. "The actual high levels of cocaine detected in muscle is indicative of chronic exposure."
Narcotraffickers being chased in the high seas often toss bales of cocaine overboard. But Hauser Davis says it's more likely the sharks in the study were exposed to Rio de Janeiro wastewater contaminated with the drug.
"Probably the main source would be human use of cocaine and metabolization and urine and feces discharge, and the second source would be from illegal refining labs," she says.
Hauser Davis points out that cocaine affects the brain and could lead to hyperactive behavior among sharks — though she says the issue needs more research.
The findings in Brazil add to a growing body of research on marine wildlife and cocaine. For example, a 2018 study in the United Kingdom found that eels exposed to cocaine were having trouble mating.
Tracy Fanara, an environmental engineer at the University of Florida, told NPR the findings aren't surprising.
"Exposure to recreational drugs can slow down their processes to the point where they miss migration periods that are essential for the survival of their species," Fanara says.
She took part in a documentary last year called Cocaine Sharks in which scuba divers tried to determine whether sharks were being exposed to the drug.
Cocaine isn't the biggest problem sharks face. But Fanara says, the documentary was an excuse to remind people that all kinds of human pollution are wreaking havoc on ocean life.
"You know this could be really catastrophic, but cocaine does a good job of getting people's attention."
Copyright 2025 NPR
