In India and Latin America, residues seep into rivers due to a lack of regulations in the pharmaceutical industry, but this is not the culprit in northern Europe. There is no comparable large-scale drug industry around the Baltic Sea. 

Instead, University of Tartu chemist and researcher Ivar Zekker points to ordinary consumers and veterinary medicine.

"Take painkillers, for example, which are ingested in the tens of tonnes every year in Estonia alone. Half of the residues of these medicines end up directly in the environment. The medicine does its work in the human body and then leaves the body in up to 90 percent undegraded form. This is why the problem is so widespread," he explained.

As well as waste products excreted by the human body, a large number of drugs come from agriculture and veterinary medicine. These include pesticides and antibiotics used to treat farm animals.

While human sewage undergoes treatment at water plants before reaching the environment, no one filters out remnants from manure used as fertilizer.

Zekker said the most common drug residues in the Baltic Sea come from painkillers such as ibuprofen, paracetamol and antibiotics. There have also been rises in antidepressants, cardiovascular and anti-epileptic drugs in recent years.

"Painkillers, antibiotics and anti-inflammatory drugs are mainly found in wastewater. Some of these have very complex structures. They contain aromatic nuclei and carbon-fluorine bonds. They are very difficult for nature to break down by self-purification," the researcher said.

Low concentrations of pharmaceutical residues are not directly toxic, but continuous exposure can cause a multitude of problems in living organisms. These include drug resistance, sex changes in fish, and large numbers of deaths among various animal species.

Drug resistance is particularly worrying as medicines may no longer be effective in the future and require newer and stronger active ingredients.

Medicinal residues can be broken down in wastewater

The researchers want to develop water purification systems to treat the drug traces using several types of bacteria. They are currently working with 31 types of residues.

"Our aim is to develop treatment techniques that do not drive up the price of water. One of the cheapest and easiest to implement methods is bacterial treatment, which allows the removal of various pharmaceutical residues by biofilms," Zekker explained.

While the researchers' plan may seem simple on paper, quickly and universally breaking down all residues is far from easy, Zekker said. It could take several years for traces to fully degrade in a natural environment.

To speed up decomposition, the researchers are growing new bacterial cultures and mixing them with others.

"For example, we have introduced anaerobic ammonium nitrate oxidizing bacteria. They belong to a family of bacteria that evolved on the seabed millions of years ago, forming a major part of the nitrogen cycle. It is this family that we are trying to use for the simultaneous removal of nitrogen and pharmaceutical residues, together with denitrifying bacteria," Zekker said.

The chemist and his colleagues are optimistic about the future of bacteria-based frameworks. For example, Zekker has already found that bacteria can break down complex residues.

Although the researchers are currently studying the process in the laboratory, it is hoped it could be used to treat wastewater for entire settlements.

"First we test these things out in the lab. Then it should be piloted in an institution that uses a large amount of drugs, such as a hospital or a nursing home," Zekker outlined. Following those trials, the project could be expanded to cities or settlements.

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