Rainbow trout or salmon trout Oncorhynchus mykiss close-up underwater
Matt Parker, University of Portsmouth and Alex Ford, University of Portsmouth
Around 269 million people worldwide use drugs every year. Often forgotten in this story is a basic biology problem. What comes in has to go out. The sewers become flooded with drugs that are eliminated from the body, along with the broken down chemical components, which have effects similar to the drugs themselves.
Sewage treatment plants don’t filter out these things – that’s never what they are designed for. If left untreated, a lot of wastewater also ends up in rivers and coastal waters. Once in the environment, drugs and their by-products can affect wildlife. In a study recently published in the Journal of Experimental Biology, researchers in the Czech Republic looked at how methamphetamine – a stimulant with a growing number of users around the world – could affect wild brown trout.
They investigated whether concentrations of methamphetamine and one of its by-products, amphetamine, could be detected in the brain of brown trout, which were estimated from other studies measuring the concentration of illicit drugs in water bodies. They also looked to see if these concentrations were enough to make the animals addictive.
white crystals medication methamphetamine
The trout were exposed to the drug in large tanks for eight weeks and then deprived of drug-free tanks for ten days. During this time, the researchers tested the fish’s fondness for freshwater or water containing methamphetamine and compared this to the reactions of fish that had never been exposed to the drug.
Your findings were fascinating. The methamphetamine-exposed fish preferred the water containing the drug, while no such preference was shown for the untreated fish. The researchers also found that the methamphetamine-exposed trout moved less during their wait. The researchers interpreted this as a sign of anxiety or stress – typical signs of drug withdrawal in humans.
The brain chemistry of the exposed fish also differed from the unexposed fish, with several proven changes in brain chemistry corresponding to what is observed in human addiction. Even after the behavioral effects had subsided after ten days of withdrawal, these markers were still present in the brain. This suggests that methamphetamine exposure could have long-term effects, similar to those seen in humans.
How drugs affect ecosystems and fish biology
Why should we care if trout become addicted to drugs? There are several reasons.
When the trout “enjoy” the medication, as appears in the most recent study, they may have a tendency to hang around in pipes where the sewage is discharged. We know that fish can behave in a similar way to people with addictions, not only from this experiment, but also from several studies on different fish species. One of the hallmarks of drug addiction is loss of interest in other activities, including those that are usually highly motivated, such as eating or reproducing. It is possible for the fish to begin to change their natural behavior, causing problems with their feeding, breeding, and ultimately their survival. For example, you are less likely to be able to dodge predators.
Drug exposure affects not only the fish themselves, but also their offspring. In fish, the addiction can be inherited over several generations. This could have long-term effects on ecosystems even if the problem were resolved now.
This isn’t the first study to find illegal drugs in wildlife. In 2019, British scientists reported cocaine in freshwater shrimp in all 15 rivers they sampled. Interestingly, they discovered illegal drugs more often than some common medicines.
But the broader effects of these drugs remain largely unknown. However, there are extensive studies on the effects of drugs in rivers.
Read more: Five Reasons Pisces Are More Like People Than You Think
Pharmaceutical pollution
Medicines are also not completely broken down in our body and end up in sewage treatment plants with faeces and urine. Most are discharged with sewage, but some end up in rivers by seepage from landfills or agricultural fields where human sewage is used as fertilizer. Wildlife living in rivers and coastal waters into which sewage is discharged are exposed to drug cocktails ranging from pain relievers to antidepressants.
Caged fish downstream of some water treatment plants switched sex from male to female within a few weeks due to exposure to hormone-disrupting chemicals in contraceptive pills. Recent studies have shown that antidepressants can cause a variety of behavioral changes in aquatic organisms, from aggression, attraction to the light, and increasing audacity.
Drug addiction is a global health problem that can devastate communities and its environmental impacts are costly to combat. One study has estimated that it would cost over $ 50 billion (£ 36 billion) to upgrade sewage treatment plants in England and Wales to remove these chemicals.
Sewer pipe in canal and sea
It may seem obvious that prescribed and illegal drugs designed to change human behavior change the behavior of wildlife as well. However, this problem is potentially more widespread and complex. We don’t even know if synthetic chemicals in everyday household products like cosmetics, clothing, and detergents can affect the behavior of humans and other animal species. An international group of scientists has asked companies and regulatory authorities to conduct risk assessments of new chemicals to assess their toxic effects on behavior.
We need to get a grip on the amount of medicine in our waterways. The world is far from solving the problems of addiction and illicit drug use. But at least more should be done to improve filtration in sewage treatment plants and force water companies to take more responsibility for ensuring that sewage does not affect wildlife.
Matt Parker, Senior Lecturer in Neuroscience and Psychopharmacology, University of Portsmouth and Alex Ford, Professor of Biology, University of Portsmouth
This article was republished by The Conversation under a Creative Commons license. Read the original article.
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