A new scientific study has revealed alarming traces of human pharmaceuticals and illicit drugs in the bloodstream of sharks inhabiting the coastal waters of the Bahamas, underscoring the pervasive impact of pollution on marine ecosystems once considered pristine.
Researchers analyzed blood samples from 85 sharks across five species including tiger sharks, blacktip sharks, Caribbean reef sharks, Atlantic nurse sharks, and lemon sharks captured near Eleuthera Island. Of these, 28 individuals (nearly one-third) tested positive for contaminants of emerging concern (CECs), with caffeine detected most frequently, followed by the over-the-counter anti-inflammatory painkillers acetaminophen and diclofenac. In one case, a baby lemon shark tested positive for cocaine, marking the first detection of the substance in Bahamian sharks.
This groundbreaking research, published in the journal Environmental Pollution, represents the first report of caffeine and acetaminophen in any shark species worldwide, and the first documentation of diclofenac and cocaine in sharks from the Bahamas.
Some sharks showed multiple substances in their systems, and those with detectable levels exhibited altered metabolic markers, including changes in triglycerides, urea, and lactate indicators that could signal potential impacts on health, energy balance, and overall physiology.
Lead researchers, including marine biologist Natasha Wosnick and collaborators from institutions in the Bahamas, Brazil, and Chile, suggest the contaminants likely enter the ocean through multiple human sources.
Caffeine and painkillers are commonly flushed into waterways via sewage and wastewater, while the cocaine trace is suspected to result from the shark ingesting a discarded or lost drug packet a phenomenon previously observed in other regions.
"The Bahamas is often portrayed as a paradise with crystal-clear waters, yet this study shows that even top predators like sharks are not immune to the chemicals we release into the environment," said a spokesperson for the research team. "Detecting these substances in blood rather than just tissue points to relatively recent exposure and raises important questions about long-term effects on shark behavior, reproduction, and survival."
Sharks play a critical role as apex predators in maintaining healthy ocean ecosystems. Any disruption to their health could have cascading effects on marine biodiversity.
The findings add to growing global evidence of pharmaceutical and drug pollution reaching even remote marine environments and call for enhanced wastewater treatment, stricter controls on pharmaceutical disposal, and international efforts to curb illicit drug trafficking at sea.
The study team emphasizes that the concentrations detected are trace levels and do not pose an immediate threat to human safety from shark encounters or seafood. However, they highlight the urgent need for further research into how these emerging contaminants may accumulate in the food chain and affect vulnerable species.
The research was conducted as part of a broader investigation into contaminants of emerging concern in Bahamian marine life and was published in Environmental Pollution (2026). Full details are available via the journal.