Drugs, including antidepressants, widespread in Irish rivers, water study finds

The Liffey had the highest concentration of drugs© Getty Images

Caroline O'Doherty

Antidepressants and antibiotics are widespread in Irish rivers, some at ‘high-risk’ concentrations, a study has found.

All of the water samples analysed in the three-year study by Dublin City University (DCU) tested positive for pharmaceutical drugs.

The finding is worrying because current wastewater treatment systems are not equipped to screen out drugs so they will continue to build up in the environment.

Scientists involved in the study warn they pose potential harm for public health and a “serious ecological hazard”.

Sulfamethoxazole, an antibiotic, and the antidepressant Venlafaxine comprised the most detections but 16 widely used drugs tested for showed up in varying levels.

The commonly prescribed anti-inflammatory Diclofenac was also regularly detected, as was Metformin, a drug for diabetes patients.

Ciprofloxacin, a broad spectrum antibiotic used to treat abdominal, respiratory, skin and urinary tract infections, also featured widely.

Most of the drugs were found at low-level concentrations but 53 were rated high risk and 64 were moderate risk.

Four rivers flowing through multiple counties were studied extensively over the three years – the Liffey, Nore, Suir and Annalee.

The Liffey overall had the highest concentrations and number of detections out of all sample sites.

The Suir and the Annalee rivers were found to have elevated levels of sulfamethoxazole.

The Nore came up least affected but even there, some drugs were found in levels described as above ‘predicted no effect concentrations’.

Surface water samples were collected between September 2020 and March 2022 from sampling locations recommended by the Environmental Protection Agency (EPA) which part-funded the research with the Irish Research Council.

The findings were revealed by Professor Fiona Regan, director of the DCU Water Institute, at an Environment, Health and Wellbeing Conference hosted by the HSE, EPA and Royal College of Surgeons of Ireland.

“We analysed 16 pharmaceuticals based on their presence in European rivers and found them in all of the Irish rivers we sampled,” said Prof Regan, who led a team of 12 researchers on the project.

“The results have shown the effect of Covid-19 in leading to the increased use of pharmaceuticals – certain antidepressants and antibiotics increased during this time.

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

“Meanwhile, the presence of antidepressants and other pharmaceutically active products in rivers can, even at low concentrations, have negative impacts on metabolism in organisms and on levels of biodiversity.

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

The Irish Independent reported last month that pressure was growing at EU level to require water treatment plants to screen out pharmaceuticals but none of Ireland’s plants were equipped to take on the task.

A new directive proposes requiring ‘quaternary’ water treatment – a fourth phase of screening and cleaning that would catch and neutralise pharmaceuticals and chemicals – but almost two-thirds of Irish plants are not yet equipped to provide even tertiary or three-phase treatment.

The project team said: “Action needs to be taken to either phase out or replace problematic pharmaceuticals.”