Drugs are no longer just a social problem, they are also an environmental problem. This is the conclusion of the scientists who published a study on Monday, April 20, 2026, demonstrating that salmon exposed to cocaine, increasingly present in rivers, travel longer distances than their congeners.
Salmon exposed to cocaine in the water travel longer distances than those not exposed to it, according to a joint study by Australian and Swedish universities. This study, published on Monday, April 20, 2026 by scientists from Griffith University in Australia and the Swedish University of Agricultural Sciences, examined how this drug affected the movements of wild fish in their natural habitat.
The researchers collected about a hundred wild Atlantic salmon in Lake Vättern, Sweden, and exposed them to both cocaine and benzoylecgonin, a metabolite formed by this drug in the liver, before following their movements. They found that fish under the grip of cocaine were 1.9 times longer than other specimens per week. The study also revealed that those exposed to the metabolite swam 12.3 kilometers more.
« A major and growing risk for biodiversity »
The researchers warned that water pollution by drugs or medicines represented « a major and growing risk to biodiversity ». « Any abnormal change in animal behavior is worrying, » Marcus Michelangeli, co-author of the study and researcher at the Australian Rivers Institute at Griffith University, told the Australian national channel ABC. « We are seeing increasingly high concentrations not only of illicit drugs, but also of all types of pharmaceuticals in our rivers, » he added.
For Professor Michael Bertram, of the Swedish University of Agricultural Sciences, the study demonstrates the need to improve the treatment and monitoring of wastewater. « Our study shows that drugs are not only a social problem, but also a concrete environmental challenge, » he stressed.
Wastewater reveals the increase in drug use
In Belgium, a wastewater analysis revealed in March the extent of drug use, including cocaine, present throughout the country, and ketamine, in full expansion. The Belgian study was published one year after a broader analysis in Europe in 128 cities in 26 countries, which showed, for 2024, an increase in the detections in wastewater of ecstasy, cocaine and amphetamine residues compared to 2023, and a decrease in cannabis.
source : ouest France
