Irish Water says pesticides were detected in three drinking water supplies in Kerry.
The public is being urged to consider the environment and alternatives to pesticides.
Irish Water says exceedances for pesticides, including Glyphosate and MCPA, were detected in water supplies in Kerry in 2019 and 2020.
The exceedances were found as part of Irish Water's routine public water supply monitoring programme.
Glyphosate was detected in Caragh Lake water supply last year.
Glyphosate was also found in Listowel water supply in 2019 and there were four separate MCPA exceedances in Listowel last year.
There was an exceedance for MCPA detected in Lyreacrompane water supply in 2019.
Irish Water's Regional Drinking Water Compliance Specialist, Deirdre O'Loughlin, said while their consultation with the HSE concluded the levels didn't represent a threat to public health, they are undesirable.
Ms O'Loughlin said it is imperative that users of pesticides including farmers, gardeners and those maintaining sports grounds are mindful of best practice when using such chemicals and to seek out alternatives.