Joint research between Trinity College Dublin and Teagasc has been conducted to determine the presence of veterinary drugs in Irish groundwaters.

Anthelmintics – used to control parasitic worms (called helminths) in food-producing animals on pasture-based diets – and anticoccidials – used to treat coccidiosis, an intestinal parasitic disease predominant in poultry – were the focus of the research.

The work was carried out by Trinity College Dublin researcher, Damien Mooney from the Irish Centre for Research in Applied Geosciences.

The use of these medicines is commonplace on Irish farms but there is little known about their environmental impact.

According to the researcher, the administration of these substances can potentially lead to their occurrence in environmental waters, primarily as a result of excretion in faeces and urine.

In fact, up to 90% of the administered dose can be excreted by the animal into the environment – directly onto the land or by spreading manure – he said.

The researcher points to a number of reasons why information on these products is so scarce:

  • There has been a lack of suitably sensitive analytical methodologies for detecting these contaminants;
  • There is no regulatory monitoring of these drugs in environmental waters;
  • There is no definitive legislative limits specific to natural waters or drinking water.

Research – veterinary drugs

As part of the research two highly sensitive analytical methods were developed to investigate the occurrence of 40 anthelmintics and 26 anticoccidials, respectively, Damien explained.

A range of rural groundwater sites across the country were sampled, including water bodies abstracted for potable use by Irish Water and by privately sourced group water schemes (GWSs).


Seventeen different anthelmintic compounds were detected across 22% of the 106 sites, including 22 GWSs that were sampled in 2017. The concentrations ranged from 1-41 parts per trillion.

Monthly sampling was carried out over 13 months, at eight karstic springs, including four from which GWSs abstract their raw water.

The results showed seasonal variation, with increased frequency and concentration of anthelmintics in groundwater between March-April and again during August-September.

The research highlighted the importance of anthelmintic usage patterns (as well as extreme rainfall events) in understanding the occurrence of anthelmintics in groundwaters that are most sensitive to contamination.


In a separate study in 2018, 109 sites (including 11 GWSs) were sampled for the 26 anticoccidials.

Seven different compounds were detected at 24% of sites, with concentrations in the range of 1-386 parts per trillion. The anticoccidials detected were in line with expected usage.

Statistical analysis shows that the presence of poultry farms and poultry manure land-spreading – within the zone of contribution of the groundwater source – is a significant driver of the occurrence of anticoccidial compounds in groundwaters.

Legislative limits

Commenting, Damien said:

“Although there are no legislative limits set to determine the safe levels of these contaminants in water, the detected concentrations in this study were an order of magnitude lower than the levels permissible in foods of animal origin that are intended for human consumption.

“Even so, this study highlights the fact that these veterinary pharmaceuticals are occurring in our groundwaters and may, therefore, need to be considered with regard to potential groundwater quality and environmental concerns.

“This is especially so given that their use is anticipated to continue, and possibly increase, as a result of agricultural intensification and climate change.”

The above research was conducted at Johnstown Castle Environment Research Centre, Wexford and Ashtown Food Research Centre, Dublin.

Two papers have been published by Damien Mooney as a result of this research:
Investigating veterinary antiparasitic drugs as emerging contaminants in Irish groundwater, which is available here.
An investigation of anticoccidial veterinary drugs as emerging organic contaminants in groundwater, which is available here.

More details can be found on the National Federation of Group Water Schemes website here.