By Abdulsalam Adigun,
Marine scientists have found that sharks in the Bahamas are consuming substances such as caffeine, painkillers and even cocaine, raising concerns about possible effects on their health and behaviour.
The study, conducted by an international team of marine biologists, analysed blood samples from 85 sharks across five species. The sharks were captured about four miles off the coast of a remote island and tested for 24 legal and illegal drugs.
Findings showed that 28 sharks had detectable levels of caffeine, common over-the-counter painkillers or, in one case, cocaine. Some of the sharks tested positive for multiple substances.
The researchers identified medications, illicit drugs and other chemicals as “contaminants of emerging concern” in marine environments, particularly in areas experiencing rapid urbanisation and tourism-driven development. They noted that this is the first study to examine such contamination in sharks in the Bahamas.
“While the detection of cocaine — an illicit substance — tends to draw immediate attention, the widespread presence of caffeine and pharmaceuticals in the blood of many analyzed sharks is equally alarming,” said lead author Natascha Wosnick, a zoologist and associate professor at the Brazil’s Federal University of Parana, in an email to CBS News. “These are legal substances, routinely consumed and often overlooked, yet their environmental footprint is clearly detectable. This underscores the need to critically reassess even our most normalized habits.”
The study also found that sharks with contaminated blood showed changes in metabolic markers linked to stress and metabolism. Although the long-term effects remain unclear, researchers warned that such exposure could lead to behavioural changes.
“Our primary concern is not an increase in aggression toward humans, but rather the potential implications for the health and stability of shark populations,” Wosnick said. “Chronic exposure to these anthropogenic compounds, many of which have no natural analogue in marine systems, may lead to negative effects that are still poorly understood.”
The team stressed the need for urgent action to tackle marine pollution, even in environments often considered pristine.
The findings build on previous research and observations. Tracy Fanara, a marine biologist involved in the Discovery TV programme “Cocaine Sharks”, earlier highlighted unusual behaviour linked to simulated cocaine exposure during experiments.
“My goal of this experiment was to shed light on the real problem of chemicals in our waterways and impacting our aquatic life and then eventually impacting us,” Fanara said in 2023. “But the goal of the study was basically to see if this is a research question worth exploring more. And I would say, yes, it is.”
In a separate 2024 study, scientists reported that sharks off the coast of Brazil also tested positive for cocaine and its primary metabolite, benzoylecgonine. All 13 sharks examined in that research showed high levels of the substance, with experts calling for further studies to understand the broader impact on marine life.