That figure is an increase of over 80,000.
The number of people served 'at risk' public water increased by 80,000 last year.
That's among the findings of the EPA's latest report, which, despite 561,000 people using at risk water, the quality of Ireland's drinking water remains very high.
However, an Offaly area's water supply remains on the 'remedial action list' for failing the THM limit.
That's affecting over seven thousand people using the Clara/Ferbane supply, while the solution is Uisce Éireann's upgrading of the water treatment plant.
It says that project is moving through the final stages.
Programme Manager with the EPA, Noel Byrne, says the number of long-term boil water notices were up last year:
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