Popular swimming spots on the southside of Dublin have had swimming restrictions put in place until Sunday.
The Forty Foot, Seapoint, White Rock, Sandycove and Killiney may have become polluted after heavy rain.
While the water quality may also have been affected at Velvet Strand in Portmarnock.
The potential pollution warnings have also been issued for Killiney, White Rock and Seapoint with the water quality deemed at risk until Monday.
Those most at risk of illness are pregnant women and anyone with an open wound or weakened immune system. Councils are warning they should avoid these waters.