Drinking water in three supplies in Ireland was found to have at least 10 times the maximum allowable limit of lead last year.
11 times the limit was detected in Dublin City Council's Leixlip supply - which serves much of the north and west of the capital.
And there were similar results on the Roundwood Reservoir supply and the Castlerea Public Water Supply in Co. Roscommon.
There were a total of 23 lead breaches across the country in Irish Water's most recent inspections, according to Freedom of Information files.
Environmental consultant Jack O'Sullivan says the results are a major concern: '10 and 11 times above normal is absolutely horrific. Lead in water can affect children because they absorb 4 or 5 times the amount of lead that an adult would and it's also harmful to the unborn'.