In a groundbreaking study, researchers have discovered that sharks living off the coast of Brazil have tested positive for cocaine, marking the first time the drug has been detected in free-ranging sharks. The study, conducted by scientists at the Oswaldo Cruz Foundation in Brazil, tested 13 Brazilian sharpnose sharks in the waters near Rio de Janeiro and found cocaine present in both their liver and muscle tissue.

The Brazilian sharpnose shark species was chosen for the study due to its small size and its habitat in a localized area of coastal waters, where it is subjected to significant contaminant discharges throughout its life cycle. The study revealed that cocaine levels were approximately three times higher in muscle tissue compared to liver tissue, and interestingly, female sharks exhibited higher concentrations of the drug in their muscle tissue than males.

The researchers attribute the presence of cocaine in the sea to sewage discharges from human drug users, as well as illegal cocaine production laboratories. According to Enrico Mendes Saggioro, an ecotoxicologist and co-author of the study, cocaine consumption has drastically increased worldwide in recent decades. The study highlights that around 22% of cocaine users reside in South America, with Brazil being the second largest consumer market in the region.

Poor sewage treatment infrastructure coupled with increased cocaine consumption has led to higher levels of the drug in the sea, explained the researchers. While previous research has suggested that drug traffickers dumping cocaine at sea contributes to contamination, this study indicates that the contamination is primarily caused by human sewage discharge rather than intentional disposal of narcotics.

The study also raises concerns about the potential health effects on sharks. Although no conclusive evidence exists regarding the impact of cocaine on sharks' health, previous research has demonstrated harmful effects on other marine animals such as fish and mussels. The researchers caution that exposure to cocaine could have physiological repercussions for sharks, as the drug targets the brain and has been known to induce hyperactive and erratic behavior in other animals.

Furthermore, Rachel Ann Hauser Davis, a biologist and co-author of the study, suggests that the prey of these sharks, including crustaceans and fish, may also be contaminated with cocaine. As sharks are routinely consumed by humans in Brazil and other countries, the potential effects on human health are challenging to establish.

Moving forward, the research team plans to expand their analysis to include other shark species as well as rays living in river estuaries. They also aim to study migratory fish, such as mullet, to determine if migratory behavior affects cocaine accumulation.

The study, published in the journal Science of the Total Environment, highlights an alarming environmental issue with potential implications for marine life and human consumption. With previous instances of drug contamination in freshwater shrimp and mussels, it underscores the need for further research and heightened awareness regarding the consequences of drug pollutants on aquatic ecosystems.