Scientists have discovered traces of cocaine, caffeine and painkillers in sharks swimming in waters around the Bahamas, marking the first time such drugs have been detected in these species. The study, published in Environmental Pollution, found that 28 out of 85 sharks tested positive for at least one of the substances, including cocaine, caffeine, acetaminophen (Tylenol) and diclofenac (Voltaren).
The drugs were detected in Caribbean Reef Sharks, Atlantic Nurse Sharks and Lemon Sharks, while Blacktip Sharks and Tiger Sharks were also studied but did not show contamination. Researchers warned that the findings highlight “emerging pollution risks in seemingly pristine ecosystems.”
Natascha Wosnick, a biologist at Federal University of Paraná in Brazil and co-author of the study, attributed the contamination to human activity. “It’s mostly because people are going there, peeing in the water and dumping their sewage in the water,” she told Science News. The research was conducted near remote Eleuthera Island and an inactive fish farm popular with divers.
The study noted changes in metabolic markers in contaminated sharks, including altered triglycerides, urea and lactate levels. Diclofenac can cause kidney disease in animals, while cocaine and caffeine have been linked to hyperglycemia and lactate accumulation. A young Lemon Shark that tested positive for cocaine was likely exposed shortly before sampling, possibly by ingesting a packet containing drug residues.
Wosnick previously detected cocaine and rare earth minerals in sharks off Rio de Janeiro, where levels were higher, though that study tested muscle tissue rather than blood. She emphasised that chemical pollution is often overlooked in the Bahamas compared to oil spills and plastic pollution. The researchers called for greater attention to pharmaceuticals and illicit drugs as contaminants of emerging concern in marine environments.
