In what could have been the unlikely plot of a low-budget thriller but is, in fact, a scientific study, traces of cocaine were found in sharpnose sharks off the coast of Brazil. It’s a worrying discovery that speaks to a rising environmental issue that reaches beyond usual suspects such as microplastics and oil pollution.
In part, the discovery team says, this cocaine in marine life may be because of increased drug use in Brazil, combined with low sewage treatment, runoff from cocaine production, and bags of the drug floating in the ocean. These may contribute to how the drug finally ends up in coastal waters, a potential danger to wildlife.
Sharks are apex predators of marine ecosystems, which could be used as a bio-indicator of environmental pollution. From September 2021 to August 2023, researchers sampled thirteen Brazilian sharpnose sharks that fishermen caught off the coast of Rio De Janeiro. This species was selected because it inhabits coastal environments through its entire lifecycle and, therefore, presumably has been exposed to human-induced pollution.
The sharks were weighed and measured before being dissected for samples from their muscles and livers. Samples were tested, with astonishing results: every shark tested positive for cocaine, while 92% of the muscle samples and 23% of the liver samples showed traces of benzoylecgonine, which is the primary metabolite of cocaine. This is the first incident of cocaine being found in free-ranging sharks.
While the study did not determine whether cocaine exposure affects the sharks, previous research on other fish species had established that cocaine can disrupt important proteins, alter skin, and interfere with hormone function; an example includes eels and zebrafish. The researchers are calling for more extensive testing to see if the same problems might be affecting sharks and other sea creatures too.
Anna Capaldo, an endocrinologist and specialist in environmental pollution at the University of Naples Federico II, not involved in the research, says cocaine pollution is becoming increasingly dangerous. She said that toxicants in shark livers might inhibit the production of vitellogenin necessary for the formation of egg yolk. All the female sharks in the research were pregnant, but how cocaine affected their fetuses is yet to be determined.
Cocaine in sharks also poses a risk to human health. Shark consumption is typical in Brazil and represents if contaminated by cocaine, a serious health risk for consumers. Although no maximum admissible concentrations for cocaine or benzoylecgonine have so far been defined in foodstuffs, results show that there may be a potential risk to human health.
The authors suggest that wider environmental monitoring studies be conducted along the Brazilian coast and a detailed investigation into the impact of drug contamination on environmental health. They raise the need for proactive measures to mitigate the ecological and public health risks associated with cocaine contamination in marine environments.
The research highlights the fact that it is long past time when action to protect health and balance in coastal ecosystems is urgently needed. Results of the research are published in the journal Science of the Total Environment.