“Cocaine sharks” found off the coast of Brazil

In coastal Brazil, small sharpnose sharks have been found full of cocaine, raising concerns about environmental pollution. Marine toxicologist Gabriel de Farias Araujo and ecotoxicologist Enrico Mendes Saggioro at the Oswaldo Cruz Institute captured several sharpnose sharks near river estuaries and analyzed them in the laboratory to assess the impact of pollutants on overlooked species. Chromatography showed every shark contained cocaine plus massive doses of benzoylecgonine, the drug’s chief metabolite. Such levels point to chronic exposure to the drug, which probably arrived in the sea from rivers contaminated with city wastewater. Indeed, cocaine often ends up in wastewater after human use, and treatment plants are not designed to neutralize the drug. Moreover, smugglers frequently toss overboard discarded bales of the substance, and drug dealers throw residue from clandestine laboratories along rivers. The result is a steady flow of cocaine contaminating waters, plants, and wildlife, including sharks.
However, cocaine is only one element of a complex web of chemical pollution. For instance, researchers have found epilepsy drugs in British river otters and methamphetamines in Czech trout. Each chemical substance affects animal behaviour and metabolism in its way. Yet their mingling and interacting in the same waterways multiplies their negative effects. Araujo and Saggiorio said that enhanced monitoring is the first step to redress the situation, upgrading wastewater plants with activated carbon filters, cracking down on illegal dumping, and tracing pollution hot spots with environmental DNA surveys.