Scientists found the presence of cocaine in more than a dozen sharks tested off the coast of Brazil, in findings published in a study earlier this month. The exact cause is still unknown, but raises concerns about possible widespread ocean contamination.
Marine biologists with the Oswaldo Cruz Foundation made the first discovery of its kind after 13 Brazilian sharpnose sharks in coastal waters near Rio de Janeiro were found to have high levels of the drug in their muscle and liver tissue. The concentration of cocaine was said to be 100 times higher than traces of the drug previously recorded in aquatic life.
Experts have put forward several theories about the presence of cocaine in the bodies of sharks, which are commonly found in the tropical waters of the western Atlantic Ocean.
One possible explanation is that the cocaine is entering waterways directly through drainage from illegal drug labs where the cocaine is produced and refined. Another possible contributing factor is that the drug is entering waterways through the feces of drug users in untreated sewage, as cocaine has been found in the rivers and sewage of many countries, including Brazil.
Another, less likely explanation is that cocaine ends up in the ocean when drug traffickers lose packages or dump them on boats.
In both cases, Sara Novais, a marine ecotoxicologist from the Center for Marine and Environmental Sciences at the Polytechnic University of Leiria, said Science magazine that the findings are “very important and potentially troubling.” Novais, who was not involved in the study, cautions that more research is needed to determine whether the sharks are harmed by the exposure, let alone by predators that might eat them.
All female sharks in the study were found to be pregnant, but any potential consequences for the fetuses are still unknown.