Glyphosate, the main ingredient in Roundup, was also found along with bentazone and other chemicals used in large scale food crop production as well as those applied to ornamental plants.
Irish Water said even where exceedances were detected, they were not high enough to pose any “immediate risk” to health.
But John Leamy, the utility’s head of drinking water compliance, said they were still “undesirable” to have in drinking water.
“It is therefore imperative that users of pesticides are mindful of best practices when using herbicides and pesticides and seek out alternatives,” he said.
Six catchment areas are of particular concern with frequent pesticide breaches detected.
A number of exceedances for the pesticide MCPA have been detected in the Longford Central drinking water supply while one exceedance was detected in the Granard.
Pesticide levels in public drinking water supplies breached regulations 81 times last year independent.ie - get the latest breaking news, showbiz & celebrity photos, sport news & rumours, viral videos and top stories from independent.ie Daily Mail and Mail on Sunday newspapers.
4 pesticide exceedances in Leitrim drinking water supplies in 2020 leitrimobserver.ie - get the latest breaking news, showbiz & celebrity photos, sport news & rumours, viral videos and top stories from leitrimobserver.ie Daily Mail and Mail on Sunday newspapers.