São Paulo, Brazil — Researchers in Brazil have identified traces of cocaine and its metabolite, benzoylecgonine, in 13 sharks off the coast of Rio de Janeiro.
According to researchers, the finding points to the high quantity of the drug in the city’s waste water, which enters tributaries that empty into the Atlantic ocean, impacting marine fauna and flora. The study, conducted by the Oswaldo Cruz Foundation (Fiocruz), one of Brazil’s most important research institutions, was published in the journal Science of The Total Environment.
“In Brazil, studies had already detected cocaine contamination in water and a few aquatic organisms, such as mussels. Our analysis was the first one to find the substance in sharks,” said pharmacist and researcher Enrico Mendes Saggioro. The 13 contaminated animals tested were Rhizoprionodon lalandii, also known as the Brazilian sharpnose shark.
The study was carried out between September 2021 and August 2023 with the aim of identifying whether changes in the marine environment occurred naturally or through human interference. Researchers analyzed the muscle tissue and liver of 13 Rhizoprionodon lalandii sharks collected in Rio de Janeiro’s west region – three males and 10 females.
All muscle and liver samples tested positive for the presence of cocaine. Benzoylecgonine was detected in 12 muscle samples and two liver samples. One finding that really intrigued the specialists was the higher concentration of cocaine in the muscles than in the liver.
“Similar to humans, the shark’s liver is a metabolizing organ. Everything ingested is processed by the liver before being excreted. To our surprise, cocaine was found in higher concentrations in the muscle, which is an accumulation tissue, potentially signaling the abundance of the substance in the marine environment,” explained Saggioro.
According to Saggioro, the sharks might be getting contaminated in many ways, either by inhabiting the region or feeding on other contaminated animals.
The area where the sharks were collected is the fastest-growing in Rio de Janeiro and also the most populous, with nearly 3 million people. Scientists explained that the shark species analyzed does not have migratory characteristics and lives close to the coast. Therefore, the probable place of contamination was indeed the city’s coastline.
Also, comparing these data with others published on the subject, regarding contamination of other species, the average level of cocaine identified in the sharks was higher than that detected in other animals, according to Fiocruz. The next step of the study will be to analyze water samples and other animals from the same region in Rio de Janeiro.
Do the animals get high?
Cocaine is a stimulant that increases alertness and causes euphoria. The side effects on the human body are tachycardia, agitation, and muscle spasms. However, researchers still do not know if these same effects impact animals.
Despite this, they believe there are impacts on the health and even reproduction of the contaminated species. “It is necessary to conduct specific studies to determine the exact consequences of this contamination on the animals,” said biologist and researcher Rachel Ann Hauser-Davis.
“But it is believed that there may be an impact on the growth, maturation, and potentially the fecundity of the sharks, as the liver plays a role in embryo development,” she added.
Are there risks to human health?
Researchers believe it is too early to pinpoint potential health risks for the population living on the beaches of Rio de Janeiro, especially because the swimmers’ contact with the water is sporadic, and people normally don’t use seawater for food or drinking. “Therefore, we believe the risk to humans is minimal,” said Saggioro.
The problem, according to Hauser-Davis, might lie in the consumption of meat from animals contaminated with cocaine. The Rhizoprionodon lalandii shark, popularly known as “cação,” is a traditional species in Brazilian cuisine.
“Pollution and environmental contamination 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,” said the biologist.
