'Cocaine Sharks' Make Waves Off Coast of Brazil

A new analysis from researchers at the Oswaldo Cruz Institute in Rio de Janeiro revealed that 13 wild sharpnose sharks have tested positive for cocaine, with 92 percent of muscle samples and 23 percent of liver samples found to contain high levels of the drug and its key metabolite.

Female sharks had higher concentrations of cocaine in their muscles compared to male sharks, which could suggest a correlation between a shark's weight and size and its ability to metabolize cocaine.

For the study, researchers analyzed wild sharks accidentally caught by fishing fleets off the coast of Recreio dos Bandeirantes between September 2021 and August 2023.

"We were actually dumbfounded," Rachel Ann Hauser Davis, a co-author of the study and a biologist, told the New York Times. "We were excited in a bad way, but it’s a novel report. It’s the first time this data has ever been found for any top predator."

This study is the first to report the presence of cocaine and benzoylecgonine in free-ranging sharks, suggesting that illegal drugs in the environment could have an impact on marine life.

As you may have guessed, human activities are the primary source of drugs entering water systems. Cocaine and other illegal substances can end up in the water when drug smugglers sink their own vessels to avoid being caught by the law. Sometimes, they sink accidentally.

Outside of smuggling, marijuana, cocaine and other illicit substances can be excreted by users and then enter sewage systems. Many wastewater treatment plants are not equipped to completely remove these contaminants, allowing them to pass through and eventually reach natural water bodies.

Beyond illegal drugs, pharmaceuticals used for medical purposes can also end up in water sources. People often dispose of unused or expired medications by flushing them down toilets or sinks. Hospitals and pharmaceutical factories can also contribute to this issue if their waste management practices are not adequately regulated.

Agricultural Runoff

Agriculture is another significant contributor to water pollution. The use of veterinary drugs in livestock farming can lead to residues being washed into nearby streams and rivers during rainfall.

Pesticides and fertilizers, often containing chemicals that can degrade into drug-like substances, also contribute to the contamination of water bodies.

Industrial Discharge

Some industries — particularly those involved in chemical manufacturing — release pollutants into water systems through improper waste disposal.

The pharmaceutical industry, for example, introduces active pharmaceutical ingredients (APIs) and antibiotics into aquatic environments primarily through the discharge of untreated or inadequately treated wastewater from manufacturing plants.

Due to their chemical stability, many drugs and their metabolites can persist for long periods once in the water. This persistence means that even low levels of contamination can accumulate over time, leading to significant concentrations that can affect marine life like Brazilian sharpnose sharks.

And this contamination is much more widespread than you think.

Numerous instances of drug contamination in marine life have been reported globally. In Puget Sound, a large estuary located in Washington State, researchers found opioids, cocaine, antidepressants and other pharmaceuticals in the tissues of juvenile Chinook salmon and staghorn sculpin.

Across the pond in England, researchers have detected MDMA, cocaine and antidepressants in shrimp, crab and other marine life in the English Channel. Over in Italy, researchers discovered traces of drugs, including cocaine and amphetamines, in the tissues of European eels, highlighting the widespread nature of this issue.

A 2024 study found high levels of pharmaceuticals in South African coastal waters, including efavirenz and sulfamethoxazole, which pose significant risks to the coastal environment due to their potency and concentration.

Addictive Behaviors in Fish

Aside from harming their health, this drug exposure can potentially lead to dependency in marine life.

In 2021, a study highlighted the growing threat of drug pollution to wildlife, noting instances where brown trout became "addicted" to methamphetamine, displaying altered behaviors such as increased preference for drug-contaminated water and signs of stress during withdrawal.

This study emphasized that the impact of drug pollution extends beyond immediate physiological effects, potentially altering fish behavior, feeding, and reproductive patterns, and even reducing their ability to evade predators.

Addressing drug contamination in water requires a multifaceted approach. Ultimately, improved wastewater treatment technologies are essential to remove these contaminants more effectively.

Stricter regulations and enforcement can help reduce industrial and agricultural contributions to water pollution. Collaborative efforts between governments, industries and communities are crucial to protect our water resources and the health of aquatic ecosystems.

Public awareness campaigns can educate people about the proper disposal of medications.

To properly dispose of medications, first check the label for specific disposal instructions. If none are provided, consider using a local drug take-back program.

These programs allow you to return unused or expired medications to authorized locations such as pharmacies, hospitals or law enforcement agencies for safe disposal. They ensure that medications are disposed of in a way that prevents them from entering water systems and causing environmental harm.

If a take-back program is not accessible, refer to the FDA's disposal guide for further guidance on safe disposal methods. This guide provides detailed instructions to ensure medications are disposed of responsibly, protecting both public health and the environment.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.