Unprecedented Fiocruz research detects cocaine contamination in sharks

The Oswaldo Cruz Institute (IOC/Fiocruz) has detected, for the first time in the world, the contamination of sharks by cocaine and its metabolite, benzoylecgonium. The data draws attention to the high quantity of the drug that is consumed in the city and discharged into the sea via sanitary sewage. Conducted by the IOC's Environmental Health Assessment and Promotion Laboratory, the study identified the presence of cocaine in 13 animals of the species Rhizoprionodon lalandii, popularly known as the "Brazilian sharpnose shark", "cação rola rola" or “cação-frango”. The results were published in the scientific journal Science of The Total Environment.

Shark of the species Rhizoprionodon lalandii being analised 

The substance's main metabolite, benzoylecgonine, which results from the metabolization of cocaine in the body, was found in 12 of these animals. Collections were carried out in the Recreio dos Bandeirantes neighborhood, in the West Zone of Rio de Janeiro, between September 2021 and August 2023, as part of an effort to assess environmental health, with a focus on monitoring changes in the environment, whether they occur naturally or as a result of human interference – and their impacts on the various forms of marine life.

Experts throughout Brazil are dedicated, for example, to analyzing the presence of viruses and bacteria in sewage to identify and measure the possible silent circulation of disease-causing microorganisms. It is also common to study the contamination of soil and water by metals and pesticides such as mercury, lead and arsenic, which directly affect the health of people, animals and the environment.

"In Brazil, studies have already detected the contamination of water and a few aquatic beings by cocaine, such as mussels. Our analysis is the first to find the substance in sharks," says pharmacist Enrico Mendes Saggioro, one of the researchers behind the unprecedented finding, together with biologist Rachel Ann Hauser-Davis, both from the IOC's Environmental Health Assessment and Promotion Laboratory.

According to Rachel, sharks play a crucial role in the marine ecosystem, as do rays. As they are predators, they are central figures in the food chain and are assumed to be sentinel species for detecting environmental damage, including different forms of contamination. The Laboratory has been responsible for important environmental alerts, from studies that identified metal contamination in fish from the Doce River, in Espírito Santo, after the tragedy caused by the collapse of the Samarco mining dam; and in dogfish and rays collected in Rio de Janeiro.

Results

The latest World Drug Report, published in 2024 by the United Nations Office on Drugs and Crime (UNODC), places Brazil among the biggest global consumers of cocaine. According to available studies, the researchers believe that the main route by which the drug reaches the marine environment is the disposal of residues of the substance in sewage, which is thrown into the sea.

"Based on this finding in Brazil, our research group decided to investigate whether the animals that our laboratory had collected for studies involving other contaminants were also contaminated by cocaine. The result is impressive. We found the substance in all 13 sharks analyzed and only one of them was not detected benzoylecgonine, which is the main metabolite of the drug," adds Enrico.

Following the protocols of good research practice and with the appropriate authorizations from the Biodiversity Authorization and Information System (Sisbio) and the National Genetic Heritage Management System (SisGen), the researchers analyzed the muscle and liver of 13 sharks of the species Rhizoprionodon lalandii collected in Recreio dos Bandeirantes. Three were males and 10 were females. 

Using specific techniques, reagents and state-of-the-art equipment, the samples were analyzed at the Advanced Laboratory Section of Santa Catarina (SLAV/SC), a unit linked to the National Agricultural Laboratory of Rio Grande do Sul, which is part of the National Network of Agricultural Laboratories of the Ministry of Agriculture, Livestock and Supply (MAPA). This stage was led by pharmacist and biochemist Rodrigo Barcellos Hoff, who works at SLAV/SC.

All the muscle and liver samples tested positive for cocaine. Benzoylecgonine was detected in 12 muscle samples and 2 liver samples. The average concentration of cocaine in the animals was 3 times higher than the concentration of the metabolite. One of the researchers' hypotheses to explain this fact is that the animals were overexposed to the substance. Another finding that intrigued the experts was the higher concentration of cocaine in the muscles than in the liver of the animals analyzed.

"Just like in humans, the shark's liver is a metabolizing organ. Everything that is ingested is transformed by the liver and then excreted. To our surprise, cocaine was found in greater concentration in muscle, which is an accumulation tissue, which may indicate the abundant presence of the substance in the marine environment. The sharks could be contaminating themselves in different ways, either because they live in the area or because they feed on other contaminated animals," says Enrico.

Comparing the data from the current study with others published on the subject, referring to the contamination of other species, the average level of cocaine identified in sharks was higher than that detected in other animals, according to the experts. "As next steps, we intend to collect and analyze samples of water and other animals from this and other regions off the coast of Rio de Janeiro," says Rachel.

Health risks

The West Zone is the fastest-growing region in the municipality of Rio de Janeiro and also the most populous, with almost 3 million inhabitants, according to the 2022 demographic census. The scientists explain that the shark species analyzed has no migratory characteristics and lives close to the coast. Thus, the probable site of contamination was the coast of Rio de Janeiro.

"Specific studies need to be carried out to determine the exact consequences of this contamination on the animals. It is believed that there may be an impact on the growth, maturation and, potentially, fecundity of sharks, as the liver acts in the development of embryos," says Rachel.

Recently, a study conducted by the Federal University of São Paulo and Santa Cecília University in São Paulo found high concentrations of cocaine in the water of Santos Bay and indicated that the drug can cause problems in the cells and genetic material of mussels. Concerning human health, Rachel and Enrico believe that specific research is needed to answer this question.

"Bathers' contact with the water is sporadic and they do not use seawater to eat or drink. That is why we believe that the risk to humans is minimal," says Enrico.

"It is worth remembering that sharks are often marketed irregularly under the popular name of dogfish. We have already found various toxic metals in dogfish and rays, which are also sold and consumed. Now we have detected cocaine in sharks. Pollution and contamination of the environment directly affect animals and nature, but also impact human life in one way or another. The health of one is linked to the health of the other," Rachel ponders.

The research was carried out in partnership with the Sérgio Arouca National School of Public Health (Ensp/Fiocruz), the Federal University of Santa Catarina, the Federal University of Rio de Janeiro, the Advanced Laboratory Sector in Santa Catarina (SLAV/SC), the Rio de Janeiro Marine Aquarium Museum Institute (IMAM/AquaRio) and the Cape Eleuthera Institute (Bahamas). The work was funded by the Carlos Chagas Filho Foundation for Research Support in the State of Rio de Janeiro (Faperj), the Brazilian Biodiversity Fund (FUNBIO) and the National Council for Scientific and Technological Development (CNPq).