The Environmental Protection Agency (EPA) is to undertake an audit of Mayo's Lough Mask water treatment plant on Tuesday to try and determine the cause of cryptosporidium contamination there.
A boil water notice affecting some 46,500 people across half of Co Mayo remains in place, following detection of the microscopic parasite during routine sampling late last week.
Irish Water has said that until the EPA audit – described as "full and comprehensive" – is complete and all of the data is available, neither it nor Mayo County Council nor the Health Service Executive (HSE) will be able to "speculate as to when the boil water notice will be lifted".
The incubation period for cryptosporidiosis – a gastrointestinal illness caused by the cryptosporidium parasite — is up to 14 days.
“Up to this point in time, the HSE has not been notified of any confirmed cases within the community attributed to this result,” Irish Water said on Monday evening.
It is urging people to continue to follow the HSE advice on boiling water before consumption, and this extends to water used in preparing food and brushing teeth.
“Public health is the priority for all agencies involved and Irish Water and Mayo County Council would like to apologise for the inconvenience this has caused to families, businesses and the agricultural community,” the agency has said.
All major towns in the south of Taoiseach Enda Kenny's constituency, including Castlebar, Westport, Claremorris, Ballinrobe, Ballyhaunis and Knock, are affected.
The communities of Ballindine, Balla, Kilmaine, Cong and their associated hinterlands and a number of group water schemes are also covered by the boil water notice, which was issued on advice from the HSE.
Vast area
Due to the vast area of the county covered by the notice, delivery of water in tankers is not yet being considered, according to Mayo county manager Peter Hynes. Nor were there plans as yet for bottled water supply.
Independent Mayo councillor Michael Kilcoyne said bottled water should be made available to elderly people and families on a fixed income, given the added cost of boiling water.
“The kettle is the most expensive use of electricity, and you have children returning to school whose families may be experiencing hardship,” Cllr Kilcoyne said. “The Health Minister doesn’t want children drinking sugared drinks, but it could be that sugared drinks become a cheaper option if there is no assistance,” he said.
Irish Water regional information specialist Sean Corrigan said that "self-declared" priority customers supplied by the scheme had been contacted directly by telephone to make them fully aware of the situation, as public health was a "number one priority".
An incident management team involving Irish Water and the local authority met again on Monday and is continuing to monitor the situation.
Major healthcare institutions, including Mayo General Hospital, will have to take precautionary boil water measures for drinking water, any water used in preparing salads and similar foods, teeth brushing and ice making.
Boiled water should be covered and stored in a refrigerator or cold place, and domestic water filters will not render water safe to drink, Irish Water says.
It advises that ice cubes in fridges and freezers and any filtered water in fridges should be discarded.
It says water can be used for personal hygiene, including baths and toilet flushing, but caution should be taken when bathing children to ensure they do not swallow water.
Infant feeds should be prepared with water that has been brought to the boil once and cooled, and water should not be reboiled several times.
Parents of infants are also warned that some natural mineral water has a high sodium content and should not be used for preparing baby food. It advises that bottled water labels be checked to ensure the sodium content is “Na” or not greater than 200 mg per litre.
“If no other water is available, then use this water for as short a time as possible,” it says, given the importance of keeping babies hydrated.
Irish Water advises that anyone suffering from diarrhoea for more than two days should contact their general practitioner and provide a stool sample for testing. It says they should continue to drink plenty of boiled or bottled water.
In 2007, some 120,000 people were affected by a boil water notice in Galway city and county due to cryptosporidium contamination, and almost 250 confirmed cases of associated gastrointestinal illness were reported. It is estimated that there were almost 500 non-reported cases of illness.
The boil water notice lasted five months, and a recent report by NUI Galway estimated the cost of the contamination at €19 million.
A map and a list of the affected areas in south Mayo is on the websites of Irish Water and Mayo County Council.
Irish Water says that further information and additional advice is available on water.ie
