Concern as low levels of antidepressants and antibiotics found in Irish rivers

Dublin's River Liffey registered both the highest concentrations and number of detections of all the sites included in the study. Picture: Gareth Chaney/Collins Photos

A "concerning" new study has found Irish rivers contain low levels of antidepressants and antibiotics, with current wastewater treatment processes not sufficient to remove them.

Between September 2020 and March 2022, researchers from Dublin City University (DCU) collected water samples from dozens of sites recommended by the Environmental Protection Agency (EPA) along the River Liffey, the River Suir, the River Nore, and the River Analee.

At each site, the team, which involved several DCU academics and PHD student Dylan O’Flynn tested for the presence of 16 different pharmaceuticals. The chemicals tested for were chosen due to their presence in European rivers, as reported in other similar studies.

The researchers say the pharmaceuticals tested for are also "ubiquitous within the Irish healthcare system" and recognised as being potentially harmful substances for aquatic organisms. Several appear on the European Commission's surface water chemical 'watch list'.

Results Pharmaceuticals were found in all four of the rivers tested, with sulfamethoxazole, an antibiotic, and Venlafaxine, an antidepressant, comprising the majority of individual detections.

Dublin's River Liffey registered both the highest concentrations and number of detections of all the sites included in the study. The River Suir and River Analee were found to have elevated levels of Sulfamethoxazole.

The River Nore had the lowest concentrations and number of detections out of all sample sites though, venlafaxine and its metabolite O-Desmethylvenlafaxine were observed there.

15 of the 16 pharmaceuticals tested were detected and quantifiable in surface waters, and the most frequently detected pharmaceuticals were:

• Diclofenac, an anti-inflammatory;
• Sulfamethoxazole;
• Metformin, a diabetes medication;
• Trimethoprim, an antibiotic;
• Ciprofloxacin, an antibiotic used to treat bacterial infections;
• venlafaxine;
• O-Desvenlafaxine, an antidepressant;
• and Carbamazepine, a medication most commonly used to treat epilepsy 

Results

Overall, the team identified 53 sites with a "high risk" presence of pharmaceuticals, and a further 64 sites were flagged as being of "moderate risk."

The team behind the survey said that there is "a significant knowledge gap on the presence of pharmaceuticals in Irish surface waters."

The research was led by Professor Fiona Regan the director of DCU's Water Institute. She said that current wastewater treatment processes are not equipped to remove such pharmaceuticals.

The presence of antibiotics in rivers is important and concerning because of increasing worries about antibiotic resistance in humans and animals.

"We didn't have any really monitoring data these chemicals in Irish rivers, so we were interested to see would we find them," said Prof Regan.

She said the presence of such pharmaceuticals in rivers can, even at low concentrations, have negative impacts on the metabolism of organisms and various levels of biodiversity.

Indeed, the researchers note in their study that some of the chemicals may pose a "serious ecological hazard" and that further research is needed "to expand the list of pharmaceuticals being tested."

Prof Regan also said it was likely these chemicals would be found in other Irish rivers, beyond those included in the study.

"We have these pharmaceuticals in our surface water," she said.

"We need to monitor for a longer time to confirm where exactly they are, and we need to see how they can be removed from surface water."

“The wastewater processes that we have in place are not fit for purpose to remove pharmaceuticals. This needs to be addressed.” 

 As for how this could be done, Prof Regan said "tertiary treatment" is required.

"We need advanced treatment on our wastewater treatment systems, but we also know that this is really expensive. It will need investment, for sure."

The study's findings are due to be presented at the Environment, Health and Wellbeing Conference 2023 hosted by the HSE, EPA and RCSI at the Royal College of Physicians on Wednesday afternoon.