Pharmaceutical residues on the radar of the water sector

When we take medication, residues enter the sewer system through our urine and feces. Since sewage treatment plants cannot process all of these substances, some of it ends up in surface water. And this surface water is also used for drinking water production. It is therefore very important to have insight into the harmfulness of these pharmaceutical residues for humans and the environment. It was this question that KWR researcher Daniel Duarte wanted to answer with his doctoral research at Radboud University, Nijmegen (department of Environmental Science).

Case study

“For my research, I focused on the Vecht, a river that flows through both the Netherlands and Germany,” Duarte says. A good choice for this case study, not only because of international dimension, but also because the Vecht undergoes many human influences causing a broad palette of substances present. Duarte: “Besides the effect of pharmaceutical residues on humans, animals and plants, I also looked at local and global relationships between antibiotic pollution and antibiotic resistance in bacteria. The goal of my research was to better assess the risks of pharmaceutical residues so that the water sector can anticipate more effectively.”

KWR researcher Daniel Duarte received his PhD degree on 25 September at Radboud University, Nijmegen.

No threat

For his work, Duarte used risk assessment studies that included long-term effects. These show that current emissions in the Vecht River basin pose no eminent threat to human health. “However, you do have to take extreme circumstances into account, such as when people eat contaminated fish,” the researcher warns. “But comparatively speaking, the concentrations of pharmaceutical residues in surface water are lower here than elsewhere in the world.”

Effect of drought

What struck Duarte most about the study results was the effect of pharmaceutical residues on the environment during dry periods. “During a dry summer, as much as 98 percent of the Vecht exceeds safe environmental limits for aquatic life,” he says. Lower rainfall deacreses the discharge and causes the concentration of pharmaceutical residues to increase in the water, posing a danger to ecology. “To my knowledge, this is the first time such a detailed spatial ecological risk profile has been assessed under different climate scenarios. In doing so, we hope to have provided guidance for further research into targeted risk assessments by local, regional and national authorities.”

Antibiotic resistance

The recently published research is also groundbreaking on the effect of pharmaceutical residues on antibiotic resistance. Antibiotic resistance is the phenomenon of bacteria becoming insensitive to antibiotics, making these drugs ineffective. This is the first study to integrate scarce information on concentration of antibiotics and resistance genes in the environment and describe their relationship statistically, as the thesis states. Thus, it appears plausible that the number of microbes resistant to antibiotics grows once pharmaceutical residues exist in surface water. “A source of concern,” Duarte believes.

Raising awareness

With his work, the researcher hopes to raise awareness in the water sector. “In general, emerging substances such as PFAS are on the radar of drinking water companies. My research confirms that it is just as necessary to keep paying attention to pharmaceutical residues. I would also like to encourage drinking water companies to actively contribute to discussions on this topic. There are many factors involved in maintaining a healthy water cycle, pharmaceutical residues are an important link in this.”

Ensuring water quality

Researcher Daniel Duarte has only been with KWR for three months. As a specialist in chemical and microbiological water quality, he considers his new job as a logical next step in his career. “During my doctoral research, I regularly came across KWR researchers,” Duarte says. “It struck me how diverse the group of experts working at KWR is. Very inspiring. Gradually I ended up here in a very organic way. And I hope my knowledge and experience will be of added value. I’m looking forward to contributing to the development and optimization of methodologies that help stakeholders in the water sector to safeguard water quality. Because KWR is an ultimate networking organization, I expect that we can set up very interesting and useful collaborative projects.”

Daniel Duarte’s thesis, entitled ‘Pharmaceuticals, toxicity and antimicrobial resistance: Advancing human health and environmental risk assessment’, is available for download at this link.