Diclofenac, a non-steroidal anti-inflammatory medicine, which is usually applied to the skin in the form of a gel, is one compound, which accumulates in bodies of water. Professor of Technology of Antimicrobial Compounds at the University of Tartu Tanel Tenson said, that drug residues usually enter the human environment via the soil or sewage.

"When we ingest a pill of some kind, often it does not fully break down in our body and so it then it ends up in the sewage system. From the sewage system it reaches the sewage treatment plant, and they do not directly remove pharmaceutical residues from our sewage. So, they can pass through that treatment and then end up in the environment around us," Tenson explained.

Pharmaceutical residues from water bodies can therefore also end up in drinking water. 

Tenson added, that these pharmaceutical residues can end up affecting people, when they lead to the development of antibiotic-resistant bacteria for example.

According to Raili Kärmas, CEO of the Estonian Water Works Association (EVEL) there are indeed pharmaceutical residues present in wastewater in Estonia, though much less than in other European countries. This is confirmed by Tenson, who points out that, per capita, Estonia is one of the lowest users of antibiotics in Europe.

"This does not mean, of course, that as the problems are not yet serious, nothing should be done about them. We also need to think through the strategy for Estonia carefully, so that we are able to maintain the status quo and not suddenly realize that we are in the middle of some kind of major problem," Tenson said.

Therefore, in Tenson's view, there is plenty of room for improvement. He pointed to the example of the use of sewage sludge and liquid manure in agriculture. In order to recycle sewage sludge, it still needs to be composted. That is, harmful substances have to be removed, so that its composition is not hazardous to human health.

Liquid manure, on the other hand, which may also contain antibiotic residues if the animal, which produced it, has been given medication, does not currently need to be processed in any way before use. However, a study conducted by Estonian scientists shows that the use of untreated liquid manure does release more antibiotic residues into the environment than when it has been treated.

Based on the previous study, the EVEL has also proposed a revision of the current limits in the draft waste management plan for 2022-2028, which is currently being prepared. If, for example, there is a desire to increase the use of sewage sludge in agriculture, are the current limits scientifically justified?

"In particular, the current limits for heavy metals, which we believe are not based on scientific evidence, should be reviewed. The distribution of heavy metals and their pathways should be assessed more accurately, to see where heavy metals actually end up in our environment and what the limits should be for sewage sludge in particular," Kärmas said.

Sigrid Soomlais, director of the Environmental Management Department at the Ministry of the Environment, said the limits must be sufficient to ensure that the waste water sludge being recycled is safe and of good quality.

"Our aim is certainly to look at how this sewage sludge can be recycled and under safe and controlled conditions. Although quite a lot of research has already been done in this area, we do not rule out the need for further research is needed, to establish all these parameters for example," Soomlais said.

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