When people take medication, some of the active substances are excreted through urine and faeces.
The substances end up at wastewater treatment plants, but not all of them are removed, DR reports, citing an analysis by the Danish think tank Tænketanken Hav.
Experiments conducted by Roskilde University in Denmark show that antidepressants can alter the behaviour of worms living on the seabed.
The worms become less responsive when predatory fish approach. Fewer worms could also mean less food for fish.
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Other types of medication can also affect aquatic life.
According to Tænketanken Hav, residues from contraceptive pills can affect sexual development in male fish, while painkillers can affect mussels and oysters.
How serious is the problem?
It is still difficult to determine exactly how serious the problem is.
The figures are based on calculations rather than direct measurements of pharmaceutical residues in the sea and marine animals.
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According to senior researcher John Jensen of Aarhus University in Denmark, pharmaceuticals are, among other things, broken down and diluted in the water.
At the same time, pharmaceuticals are just one of many forms of chemical pollution in the marine environment.
The EU's new wastewater rules mean that larger wastewater treatment plants will in future be required to remove ten selected pharmaceutical substances. The rules must be fully implemented by 2045.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.