Caution urged as raised levels of pesticide found in public water supply

Uisce Éireann: 'By minimising pesticide use, we can protect water quality and help to deliver wider environmental benefits.'

Uisce Éireann has urged the public to be mindful of the potential effects on drinking water when spraying plants after raised levels of pesticide were found in the water supply for the first time in nearly a decade.

While the levels of pesticides in the drinking supply have decreased overall by more than 50% since 2017, 2024 saw those levels increase slightly on the tallies noted in 2023.

The water utility has said that everyone concerned “must make sustained efforts and be vigilant to protect drinking water quality”.

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

Several water catchment areas have currently been prioritised for action amid worrying findings of recurring pesticide measurements, the company, formerly known as Irish Water, said.

Those areas include Hacketstown in Co Carlow, Greenmount in Co Louth, and the Foynes Shannon estuary in Limerick, it said.

Similar recent targeted actions in Cavan and Mayo have succeeded in reducing the amount of pesticides in the water supply from their previously dangerous levels, the company said.

Dr Pat O’Sullivan, Uisce Éireann’s drinking water compliance senior manager, said a “concerning trend” currently being noticed is the number of pesticide exceedances above normal levels being seen outside the regular spraying season, particularly in winter.

Pesticide exceedances detected 66 times last year

“Last year, we detected pesticide exceedances 66 times in 22 public drinking water supplies,” Dr O’Sullivan said, a rise from the 52 seen in 2023. 

That 2023 figure itself represented an increase of 12 exceedances on those seen in 2022.

The National Pesticides and Drinking Water Action Group (NPDWAG) meanwhile urged both professionals like farmers and greenkeepers as well as residential pesticide users to take account of the “vulnerability” of community water supplies when choosing whether or not to spray herbicides or other plant treatments.

“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 30 kilometres away,” Dr O’Sullivan said.

“Pesticides should only be applied when essential and after considering alternative methods.

“By minimising pesticide use, we can protect water quality and help to deliver wider environmental benefits,” Uisce Éireann said, adding that leaving certain areas unsprayed can likewise allow native flowering plants to thrive, thus encouraging pollination.

If pesticides must be used, the utility said, then basic steps should be taken to minimise the risks to the civilian water supply, such as:

• Observing closed spray periods detailed on product information leaflets;
• Not spraying if rain is forecast within the following two days;
• Not filling a sprayer directly from a watercourse.

Tighter EU restrictions recently introduced on the permitted use of pesticides are seeking a reduction of 50% in the amount of substances used to control weeds and crop pests across the bloc by 2030.

That initiative has caused some consternation for tillage farmers who fear significant crop yield losses as a result of the more stringent protocols around pesticides.