66 pesticide exceedances in public drinking water supplies in 2024 (2025)

66 pesticide exceedances were detected in public drinking water supplies in Ireland last year, compared to 52 exceedances in 2023, according to Uisce Éireann.

In 2024, the national water utility carried out 34,000 analyses of samples from public drinking water supplies.

The number of pesticide exceedances in public drinking water supplies in Ireland has decreased significantly since 2017, by more than 50%.

While the overall compliance rate remains very high, Uisce Éireann said that all stakeholders must make sustained efforts and be vigilant to protect drinking water quality.

The most frequently detected pesticide substance in Ireland’s drinking water is MCPA, an active substance in many herbicide products commonly used to control thistle, dock, and rush.

Pesticide

Currently, several catchment areas are prioritised for action, where Uisce Éireann has detected recurring pesticide exceedances through its monitoring programmes.

These include Hacketstown, Co. Carlow, Greenmount, Co. Louth, and Foynes Shannon Estuary, Co Limerick.

The National Pesticides and Drinking Water Action Group (NPDWAG) and local catchment-based focus groups, established to coordinate targeted actions at a local level, are prioritising these areas for further work in 2025.

Similar targeted action in recent years in areas such as Belturbet, Co. Cavan and Newport, Co. Mayo has successfully eliminated pesticide exceedances in those water supplies.

Dr. Pat O’Sullivan, Uisce Éireann’s drinking water compliance senior manager, emphasised the need for collective action.

“Last year, we detected pesticide exceedances 66 times in 22 public drinking water supplies. A concerning trend is the number of exceedances outside the spraying season for certain plant protection products, particularly in winter.

“We want to remind users to be mindful of water sources when using pesticides, as one drop of pesticide can be detected in a stream up to 30km away,” he said.

The NPDWAG has reminded all users of herbicides and other pesticide products to always take account of the vulnerability of their local drinking water supplies when making decisions about the possible use of pesticides and to be aware of how their actions could impact their community’s drinking water.

Dr. Aidan Moody, Department of Agriculture, Food and the Marine (DAFM) and chair of NPDWAG, said that an integrated pest management approach must be followed, in which the potential to use alternative control methods is fully considered.

“Users of pesticides must always consider the possibilities for alternative control methods in the first instance.

If pesticide application is considered essential, ensure they follow best practices to protect water quality. This approach is a win-win for water quality and biodiversity,” Dr. Moody said.

Farmers and other landholders dealing with the challenge of rushes should note and follow the DAFM guidance on the sustainable management of rushes.

This approach is based on the concepts of containment or suppression and aims to minimise the use of pesticides.

Correct usage

If pesticides must be used, Uisce Éireann highlighted the following basic steps to reduce risks to drinking water sources and the aquatic environment:

• Always read the product label carefully and only use product as directed on the label;
• Note that a closed spray period, during which product use is not permitted, is specified on the label for some products (e.g., products containing MCPA). Products containing MCPA are not approved for use in weed-wipers;
• Do not use pesticides if rain is forecast in the next 48 hours;
• Make sure you are aware of the location of all nearby watercourses, including drains, wells and springs;
• Comply with either a minimum 3m no-spray buffer zone for any watercourse subject to CAP conditionality, or a larger product-specific aquatic buffer zone specified on a product label if one has been set;
• Avoid spills, stay well back from open drains, and rinse empty containers three times into the sprayer;
• Store and dispose of pesticides and their containers properly;
• Never fill a sprayer directly from a watercourse or carry out mixing, loading, or other handling operations beside a watercourse;
• Never fill/wash a sprayer on concrete or sealed surface areas where spillage/runoff to drains/watercourses is possible;
• Never leave a sprayer unattended during filling or mixing/agitating, regardless of location.

Uisce Éireann has also launched a pilot study in Cavan’s Erne-Larah catchment to encourage farmers to consider the vulnerability of the water supplies to pesticide contamination.

This pilot study aims to assist Uisce Éireann with capturing new data and learnings on how different protection measures can improve water quality.