Antibiotics on the plate, painkillers in the glass

Professor Kümmerer, how do drug residues get into water bodies?

Professor Dr Klaus Kümmerer: Residues of medicines such as the contraceptive pill, painkillers, psychotropic drugs or antibiotics enter waterways in different ways. For one thing, many people flush leftover medicines down the toilet at home, which is not the right thing to do and which causes them to end up in the sewage. In addition, the human body doesn’t completely absorb the active substances. Depending on the substance in question, between five and 95 per cent is excreted out again as active substance and this then comes into the environment. Another part of the residues, including those from antibiotics, is caused by animal farming.

How do these drug residues affect us humans?

Kümmerer: The active substances of drugs are dissolved as molecules in the water, which is why they’re not directly visible – unlike plastic particles. As a result, the problems they cause receive considerably less attention, even though we really should not by any means underestimate them. Pharmaceutical residues partly re-enter the food chain through drinking water or foodstuffs such as cereals. The problem is that we may potentially be ingesting these substances all our lives. The effects they may have on adults or on child development – especially where very low concentrations are concerned – have not yet been sufficiently researched. In addition, all previous risk assessments regarding active pharmaceutical ingredients only took into account individual substances. However, in almost all cases, several of these substances are present at the same time. We know that elderly people who take several drugs at the same time may experience significant negative interactions.

How do these residues affect animals and the environment?

Kümmerer: In the animal world, we’ve already gained some insights: for instance, hormones in the water cause fish stocks to become female, which is why they’re no longer able to reproduce properly. Painkillers like diclofenac damage the internal organs of fish. Shoal fish that ingest psychotropic drugs have been found to suddenly leave the shoal and become easy prey. We also know that even water spiders absorb these substances. As a result, the quality of their spider webs may decrease. Some cancer drugs even cause cancer themselves. What this means for aquatic organisms is something we just don’t know.

How do these substances affect smaller organisms?

Kümmerer: Antibiotics also have an effect against bacteria in water. However, these bacteria are not harmful, but important: they break down substances and are therefore essential for clean water and an intact ecosystem. Bacteria can become resistant to antibiotics. And antibiotics in the water can provide resistant bacteria with an advantage. However, this resistance can also be transferred to other bacteria and come back to us in this way.

How can drug residues create “negative cycles”?

Kümmerer: In agriculture, sewage sludge is often used as fertiliser. Some pharmaceuticals end up in the sewage sludge or, in the case of animal farming, in the liquid manure. Both are used as fertilisers and absorbed by plants in the soil. This is how residues end up in cereals, among other foods. This means that here, too, a synthetic substance that we humans have introduced into nature returns to us – with all the undesirable consequences that entails. Via the soil, residues can also enter groundwater, which is often used for drinking water.

Are there any cleaning procedures that can solve the problem, and what challenges are associated with them?

Kümmerer: Eighty percent of the world’s sewage is not treated. The remaining 20 percent is purified in sewage treatment plants. But the drug residues are not completely removed. In so-called advanced sewage treatment, the water is treated with chemicals such as ozone or hydrogen peroxide or with UV light in addition to traditional methods. This allows some substances to be broken down, albeit often incompletely. As a result, new substances emerge, which we are still completely unaware of and which may be more toxic than the starting substances. A further procedure using activated carbon doesn’t produce hazardous new substances, but for all that also only removes a fraction of the substances – and the carbon must be filtered out of the water during purification and reprocessed or incinerated. Since there are so many different active substances, a universal purification process that can filter all substances equally is virtually impossible. The properties of the drug molecules are too different for this purpose. Even within a substance or an application group, such as antibiotics, the purification result may vary considerably.

How will the situation of pharmaceutical residues in waters develop in the future?

Kümmerer: The wasteload through drug residues will continue to increase in the future. New substances are constantly entering the market, so that the range of substance properties is also increasing. The substances we’ve mainly studied up till now may no longer be of significance tomorrow. Of course, we don’t yet know anything about the properties of the new substances. But the number of existing active substances will also continue to increase. Demographic change and the increasing standard of living boost this development, because people are getting older and older and need more medicines.

Do you personally see any long-term solutions?

Kümmerer: To solve the problem in the long term, we need a radical change in thinking. This starts with the consumers. Better handling of medicines must become the norm. Doctors need to think about changing their prescription habits, while pharmacists should be paid for the advice they give. By now, our inhibition threshold for taking medicinal drugs has fallen considerably, although many diseases could be treated with home remedies or through a changed lifestyle, sufficient exercise or a balanced diet. Drug manufacturers need to change their ways of thinking too. Smaller package sizes could be a first step towards tackling the problem of leftover medicines that otherwise end up down the toilet. The trend should also be towards developing new business models, in which profits will no longer be achieved solely through sales volumes, but through the transfer of knowledge, training and advice.

Does this mean that pharmaceutical residues in sewage will remain a problem in the future?

Kümmerer: Of course we’ll still require medicines in the future, and this isn’t about banning them. However, we also know that some drugs are already easily and completely degradable in the environment. We’ve even been able to show that it’s possible to incorporate this property specifically into active substances from the very outset of their development, while still meeting all medical and pharmaceutical requirements. This can become the basis for a new business model – and an incentive for drug manufacturers. Of course, policy-makers at state level should also bring this about by means of appropriate legislation.

About Professor Dr Klaus Kümmerer

Dr Klaus Kümmerer is a professor at Leuphana University Lüneburg in Northern Germany, where he conducts research on sustainable chemistry, material resources and trace substances in the aquatic environment. In 2009, he received the Recipharm International Environmental Award for his research on pharmaceuticals in the environment and sustainable pharmacy; in 2015, he received the Water Resources Award from the Rüdiger Kurt Bode Foundation.