Sharks in waters around the Bahamas have tested positive for cocaine, caffeine and a slew of pharmaceutical drugs, according to a study published in the May 2026 issue of Environmental Pollution.
Researchers from the Bahamas, Brazil and Chile took blood samples from 85 sharks of five different species near Eleuthera Island in the Bahamas. The researchers tested the samples for over 20 different classes of legal and illegal drugs, including antibiotics, antidepressants, painkillers, caffeine, cocaine and opioids. They found that 28 of the sharks had detectable levels of at least one of four drugs in their system: caffeine, cocaine and the painkillers diclofenac and acetaminophen, which is the active ingredient in Tylenol.
The study also found changes in some “metabolic markers” of the sharks that tested positive for the drugs, including “altered triglycerides, urea and lactate levels.”
However, the researchers said they don’t know what impacts on their behavior, if any, these changes may cause.
It marks the first time caffeine and acetaminophen has been detected in any shark species worldwide, according to the researchers, and the first report of cocaine in sharks from the Bahamas. Trace amounts of cocaine has previously been in detected in sharks in waters off the coast of Brazil.
The study’s authors believe the contamination of Eleuthera’s once-pristine waters is a result of human pollution “through wastewater effluents, agricultural runoff, and urban discharges.”
“Pharmaceuticals and illicit drugs are increasingly recognized as contaminants of emerging concern in marine environments, particularly in areas undergoing rapid urbanization and tourism-driven development,” the researchers said, noting the “increase in the number of vacation homes and rental properties significantly heightens the volume and chemical complexity of local wastewater.”
Their finding highlight the emerging risks to marine ecosystems in an area seeing a growing influx of tourism, and “urgent” need to address the issue.
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