Drinking water pesticides limits were breached 23 times in 2023, which was increase of six on the previous year, the Environmental Protection Agency’s (EPA) latest drinking water quality report has found.

However, 99.85% of drinking water samples were within microbiological limits and 99.62% of samples complied with chemical limits.

E coli bacteria were found in four supplies tested last year.

The EPA called on Uisce Éireann to continue engaging with stakeholders to prevent pesticides entering supplies at source and to ensure water is properly treated where supplies are "persistently affected".

Herbicides - particularly MCPA, which made up over half of pesticide exceedances - are the most frequently exceeding pesticides detected in drinking water supplies in Ireland.

Where pesticide failures are found, monthly testing of water supplies is carried out between April and November.

Boil water notices

“Our public water quality remains very high, which means that the public can remain confident that drinking water supplied to their homes is safe to drink,” according to the EPA’s director Dr Tom Ryan.

“However, the resilience of drinking water supplies isn’t robust enough as evidenced by more ‘at-risk’ supplies being identified by the EPA and an almost doubling of long-term boil water notices in 2023.”

Last year saw 91 boil water notices and 12 water restrictions in place across areas supplying 254,000 people, with half of these notices in place for more than 30 days.

This is a doubling of long-term boil water notices on the previous year, which the EPA said must be reversed by Uisce Éireann.

Some 20,173 people were on boil water notices when the EPA released the results on Tuesday.

The EPA stated that Uisce Éireann must show progress on all action programmes in place for areas on the remedial action.

Uisce Éireann must ensure that water is free of bacteria and pesticides, while ensuring its water treatment plants are operating correctly, the agency said.