Drinking water in north Dublin has been found to have lead levels that are almost 15 times above the legal limit.
Unsafe levels have been found in a number of locations in the north of the county.
On Tuesday, Dublin Live reported on a meeting of residents in Coolock, where levels were found to be 12 times over the legal limit.
And in Sutton, lead contamination was found to be almost 15 times above the legal limit.
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Within the Dublin City Council area on both the north and southside of the capital, lead levels over the legal limit were found in Cabra, Sandymount, Terenure, Beaumont, Drumcondra and Phibsborough.
According to HSE guidelines, long-term exposure to higher lead levels can affect development of babies in the womb and brain development in children.
It is classed as a probable carcinogen and can cause high blood pressure and problems to kidneys.
In a statement to Dublin Live, Irish Water said that they had been "working hard" to improve the quality and supply of their drinking water throughout Dublin and the rest of the country.
They said: "Irish Water has [written] to 38,000 people who we identified as having lead in their drinking water through our metering programme and our drinking water testing programme.
"We continue to write to people as we find lead services as part of our monitoring programmes with detailed information and advice."
They added that the water leaves their treatment plants "free from lead" and said "in the vast majority of cases, lead in the water comes from lead plumbing inside the private property boundary".
According to the company, lead plumbing was widely used in houses in Ireland up until the 1980s.
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They estimate that there are 180,000 properties in Ireland with lead plumbing.
Irish Water continued: "As water passes through private connections or internal plumbing made of lead, the lead can be dissolved into the water."
According to the company, if lead is present, the homeowner needs to replace their internal plumbing.
There is a Government grant scheme to help with this replacement and the company said that they had "replaced 22,000 lead service connections through our programmes of work".
Irish Water urges anyone who has concerns about their water to visit their website and homeowners can also check the water quality in their homes by entering their address in here .
