The first-of-its-kind study by Brazilian scientists has uncovered an alarming connection between human drug consumption and marine life contamination. Wild sharks caught off the coast of Brazil have tested positive for cocaine, with concentrations 100 times more than previously observed in other marine species. 

Conducted by the Oswaldo Cruz Foundation the study Cocaine Shark, published in the Science of the Total Environment, examined 13 sharpnosed sharks. All sharks tested positive, including three males and ten females, either juveniles or small adults measuring approximately 50 centimetres long.

The study’s co-author, Enrico Mendes Saggioro, a biologist at the Oswaldo Cruz Institute, told The Guardian: “Cocaine has a low half-life in the environment, so for us to find it in an animal like this, it means a lot of drugs are entering the biota.” 

The sample was caught in fishermen’s nets off a beach in Rio de Janeiro between September 2021 and August 2023. The study concludes all sharks were exposed to cocaine during their lifetimes, as the drug was detected in all muscle and liver samples. The source of the cocaine remains unclear, with runoff from illegal cocaine manufacturing plants and untreated sewage discharge thought to be the most likely causes. 

Various previous studies have found cocaine in rivers, sea, and sewage water. Last year, in England, scientists found traces of E-coli and cocaine in Hampshire waters. Campaigners continue to raise the issue of pollution incidents being unacceptably high in Britain’s waterways. 

According to the Global Report on Cocaine 2023 by the United Nations, global cocaine consumption has increased exponentially, with Brazil as the second largest consumer market. The report also points to the country being an important point of departure for vessels trafficking cocaine across the Atlantic. 

Although reported as less likely, another school of thought as to how the cocaine entered the sharks potentially stems from the drug being intentionally dumped overboard.

The study’s findings also correlate with observations of strange shark behaviour off the coast of Florida last year. Marine biologist and broadcaster Tom Hird noted these developments during the Discovery Channel’s Shark Week 2023 on the topic of Cocaine Sharks, he suggested a possible link between shark behaviour and illegal drugs in waterways. Drugs are commonly found worldwide at sea – in June, recreational boaters in the Florida Keys hauled in $1m worth of cocaine. 

While this scientific study is the first to positively test sharks, cocaine found in marine life is not new. Last year, the BBC reported that cocaine was evident in shrimp throughout several sampling points in Suffolk rivers, resulting from a study by the King’s College and the University of Suffolk.

The implications of these studies extend beyond environmental concerns. There are possibilities that illegal drugs that enter the water and subsequently the food chain – with sharp nose sharks a common part of Brazilian diets – could pass to humans.

The disturbing results serve as a reminder of the far-reaching consequences of human activities on marine ecosystems and the urgent need to address water pollution to protect both the oceans and health.

Main image is representative of sharks and is courtesy of U.S. Coast Guard Heartland.

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