A team of researchers with Brazil’s Oswaldo Cruz Institute has detected cocaine in 13 specimens of the Brazilian sharpnose shark found off the coast of Rio de Janeiro. 

The researchers examined specimens found near the city’s West Zone from September 2021 through August 2023. While previous studies have found cocaine contamination in the water and other species, such as mussels, the newest study is the first to detect cocaine in sharks, the institute said Tuesday.

The main way cocaine gets into the water and into the sharks is through the city’s sewage. 

“Probably the main source would be human use of cocaine and metabolization and urine and feces discharge, and the second source would be from illegal refining labs,” Oswaldo Cruz Institute scientist Rachel Hauser-Davis, one of the researchers behind the study, told NPR.

The sharks were contaminated with amounts of the drug as much as 100 times higher than in previously researched specimens from the sea, according to The New York Times.

The scientists also found that, contrary to their expectations, more cocaine was detected in the muscles of the sharks than in the liver, which processes such substances.

“To our surprise, cocaine was found in higher concentrations in muscle, which is an accumulation tissue, which may signal the abundance of the substance in the marine environment. The sharks would be contaminating themselves in different ways, whether because they inhabit the region or feed on other contaminated animals,” fellow researcher Enrico Mendes Saggioro said in the institute’s news release.

The sharpnose sharks are a local, non-migratory species that stays close to the coast, and researchers are investigating whether their cocaine contamination has any major side effects.

“It is believed that there may be an impact on the growth, maturation and, potentially, the fecundity of sharks, since the liver plays a role in the development of embryos,” Ms. Hauser-Davis said.

• Brad Matthews can be reached at bmatthews@washingtontimes.com.