Swimmers have been warned not to bathe at the south Dublin beaches of Killiney, Seapoint or Blackrock until Monday due to high levels of bacteria.
Dún Laoghaire -Rathdown County Council issued the ban on swimming and bathing along most of its shoreline due to the high levels of E.coli and enterococci present in the water.
E.coli lives in the digestive tracts of humans and animals.
Most types of the bacteria are harmless but some can cause diarrhoea. Some strains may also cause severe anaemia or kidney failure.
The council said the temporary prohibition notice would remain in place until Monday, when test results are due back.
The ‘no-bathing’ ban follows regular water quality tests conducted by the Council which discovered the high levels of contamination at Killiney beach, Blackrock and Seapoint bathing areas and swimmers are being asked to obey the notice.
Fianna Fáil councillor Cormac Devlin said: “We are fortunate, in one way that the weather is not forecast to be as warm and sunny as it has been however the fact that this has happened for yet again, for another summer is alarming.
“Daily and regular swimming is common along our coast and I have asked the officials of the council to try investigate the root cause of this recurring problem so it can be dealt with once and for all. The last prohibition notice was issued in January of this year.”
The council advises pet owners that the water quality at present at these locations can be equally harmful to animals and that they should keep their pets out of the water also.
Separately, on Thursday the council asked people who swim at beaches, lakes and rivers to report on water quality to assess whether the they need a new bathing water designation.
Local authorities must identify official bathing areas in their area every year so that they can be monitored for safety, water quality and their level of use.
Under European and Irish law, Irish local authorities must identify bathing waters each year so that these areas can be monitored to ensure they meet stringent microbiological water quality standards.
“In some cases, the official bathing areas are also the areas where local authorities focus their resources providing lifeguards during the summer season,” the council said.
The laws also require that the local authority prepares detailed descriptions or profiles for each of the identified bathing water sites that describe not just the bathing area but also areas in the surface waters catchment area that could be a source of pollution.
Regular swimmers are asked to report to the council on how their swimming area has been used up to now, how many people use the site, what facilities exist at the site and how accessible it is and any safety issues.
They may also propose their favourite beach or river as a new bathing water site.
The closing date for submissions is August 3rd. Further details are available on the council's website at dlrcoco.ie