Drinking water supplies in 13 counties were found to have a high level of an environmental pollutant, which is linked to cancer.
Trihalomethanes are usually formed as a result of adding chlorine to water.
Some studies suggest long-term exposure to high levels of THMs may be linked to cancer.
Irish Water tested 791 samples of drinking water this year to see if they had under the allowed limit of the environmental pollutants.
There were 59 failures across 13 different counties, with several in counties like Donegal, Clare and Louth. Three of the samples from Radestown, Kilkenny are understood to be among them.
However, many supplies had multiple failures.
Dr Michelle Minihan is a senior inspector with the Environmental Protection Agency, she says “Our view is that exposure to THMs should be minimised and kept at an absolute minimum, the way we’ve gone about addressing that is that where we identify supplies where the level of THMs in them is above the regulatory limit and where that’s a persistent occurrence we take action & add those to our remedial action list and that means Irish Water has to identify an action programme to address the THM exceedances”.
Irish Water says it has a programme in place to address all inadequacies in drinking water, including THMs.