It’s no secret that some European rivers contain excessive levels of various drugs. When many people see descriptions like "drugs in rivers exceed legal limits," they may think that they were thrown in by criminals when they were escaping. Actually no, these drugs come from the excrement of addicts.
After an addict ingests drugs, the body will not absorb and metabolize all of them, and part of them will be excreted intact with the metabolic waste (in the form of feces or urine).
After urban sewage is treated, it will be discharged directly into the river. Drug compounds and metabolic waste compounds will not be "filtered" by the sewage treatment system, so they will eventually enter the river.
The drug residues in these rivers show that different types of drugs are prevalent in different parts of Europe.
Rivers in Western and Southern Europe oftencocaineExceeding the standard is obvious, while Central Europe is usuallyamphetaminesExceeding the standard is even more serious, and rivers in the Czech Republic and Slovakia aremethamphetamineExceeding the standard is more common.
A recent study from the Swedish University of Agricultural Sciences stated that,Even if there is only a trace amount of drug residue in the river, it is affecting the entire ecology.
This study trackedLake WetternThe activity trajectories of juvenile Atlantic salmon exposed to cocaine and its metabolites showed that the activities of these "cocaine salmon" were significantly different from those of normal salmon.
△ Lake Wettern
They have become bolder and less fearful of predators;
They swim faster - 20% faster than normal salmon, they swim almost twice as far per week, and their total dispersal distance is 12.3 kilometers further;
Additionally, they do not have a passive period when they completely stop swimming, but continue to move.
The researchers set up three control groups, one was normal, one was injected with cocaine, and one was injected withbenzoylecgonineof.
△ From top to bottom, normal, cocaine injection, benzoylecgonine injection
They found that the chemical that had the greatest impact on salmon was not cocaine;benzoylecgonine.
Benzoylecgonine is a urinary metabolite when humans ingest cocaine, so the discharge of this substance into the river is actually greater than that of cocaine, and the content is also higher.
In humans, benzoylecgonine is a urine test indicator of whether a person has ingested cocaine but is not considered a stimulant.
However, previous studies have found that benzoylecgonine can have significant effects on the behavior of aquatic aquatic invertebrates, including increasing their swimming speed.
This study shows that the degradation products of this drug also have a huge impact on the behavior of juvenile salmon.
Young salmon need to migrate to the ocean. Although substances such as benzoylecgonine make them swim faster and more active, in fact, for salmon, this has no advantages and only disadvantages.
Not to mention getting bolder, they will definitely become more vulnerable to being eaten by natural enemies. In fact, it is not good to have more activities and distances, becauseThe more activities you have and the further you run, the easier it is for you to encounter predators and consume your precious energy..
Atlantic salmon is an important economic fish in several countries in Northern Europe (including Sweden). However, after entering the 21st century, wild Atlantic salmon are becoming less and less.
In the past, experts generally believed that uncontrolled fishing, environmental pollution and other problems were the main reasons for the decline of Atlantic salmon. Now it seems that the increase in drug content in the river is also a potential reason.
It’s hard to imagine that every human “indulgence” may eventually pass through the toilet and turn into a nightmare for the fish world.
refer to:
https://doi.org/10.1016/j.cub.2026.03.026