Records says 269 million people worldwide use drugs each year. After being used by humans’ methamphetamine enters waterways through sewage systems and discharges from wastewater treatment plants. Meth pollutes rivers all over the world, with concentrations of the drug ranging from a few nano grams to dozens of micrograms per litre of water says researches. Once in the environment, drugs and their by-products can affect wildlife.
A recent study has shown that illicit drug concentrations in waterways, could be detected in the brains of brown trout. They also looked at whether these concentrations were enough to cause the animals to become addicted. The trout were exposed to the drug in large tanks over eight weeks and then put into withdrawal, going “cold turkey” in drug-free tanks for ten days. During that time, the researchers tested the fish’s preference for fresh water or water containing methamphetamine and compared this with the responses of fish that had never been exposed to the drug.
The findings showed that methamphetamine-exposed fish preferred the water containing the drug, while no such preference was shown for the untreated fish. The study also revealed that the brain chemistry of the exposed fish differed from the unexposed.
This is not the first study to find illicit drugs in wildlife. In 2019, scientists in the UK reported cocaine in freshwater shrimp in all 15 rivers they sampled. Interestingly, they detected illicit drugs more often than some common pharmaceuticals. However, the wider effects of those drugs remain largely unknown.