The Environmental Protection Agency (EPA) has urged local authorities to assess the vulnerability of drinking water supplies to a deadly parasite that spreads a notifiable disease.
So far 363 risk assessments have been carried out for Cryptosporidium, which can cause fever, stomach upsets, weight loss and diarrhoea.
This means the drinking water of 59 per cent of consumers has been monitored.
According to a new report, published today by the EPA, it is now required that "risk assessments be carried out on the remaining public water supplies and that steps be taken to protect water supplies where risks are identified."
The report noted that the quality of drinking water supplied by sanitary authorities was satisfactory in 2004, with the overall rate of compliance with drinking water standards at 96.4 per cent.
Surface water quality (lakes and rivers) has improved slightly in recent years.
However, the authors point out "a worrying trend" in the decline in the number of river stations recording the highest biological water quality.
They recommend that efforts be stepped up if the State is to meet the water quality targets set out in the phosphorus regulations and by EU directives.
"Significant issues remain to be tackled in Ireland if we are to protect the environment and comply with European legislation," said the director of the EPA's office of environmental enforcement, Dara Lynott.
"But as a result of increased enforcement, new legislation and the work of a network of enforcement regulators, improvements are
happening."