Ireland has been found guilty of providing unsafe drinking water to thousands of people served by supplies tainted with a chemical compound linked to cancer.
Uisce Éireann says the majority of supplies referred to in the case have been brought up to standard since proceedings began in the European Court of Justice.
However, the Environmental Protection Agency (EPA) said there were other supplies similarly affected and the matter must remain a priority for Uisce Éireann.
The case was taken by the European Commission which warned Ireland in 2015 that 21 public water supplies and nine group water schemes were consistently breaching EU regulations on the presence of trihalomethanes (THMs).
THMs are a chemical compound that forms when organic particles such as bacteria and plant material left in water after filtering in water treatment plants reacts with chlorine disinfectant.
“THMs are of concern for human health and the environment since long-term exposure to high levels of these chemical compounds in drinking water may pose risks such as cancer risks, in particular bladder cancer and colon cancer, and cause gastrointestinal problems and skin irritation,” the court said it its ruling.
“Moreover, THMs, once released into the environment, may be toxic for aquatic wildlife, disrupt freshwater ecosystems and contribute to the formation of ‘dead zones’ in the oceans by encouraging excessive growth of algae.”
Ireland failed to show sufficient progress in addressing the issue and the European Commission referred the case to the court in 2021.
Ireland’s defence stated that it was difficult to reach the required standards in some drinking water sources because of the country’s geography, the presence of peatlands and higher than average rainfall.
The court rejected the argument and ordered the authorities to get the supplies up to the required standard and pay the as yet unspecified costs of the case.
Uisce Éireann said it had been working to address the problem and of 74 supplies referenced in the original European Commission complaint, five remained in breach.
“In all these cases Uisce Éireann is taking action to remove the risk of elevated levels of THMs forming in all public water supplies through a combination of plant upgrades and enhanced operational controls,” it said.
Laura Burke, director general of the EPA which reports on THM exceedances annually, said she expected the outstanding supplies referenced in the case would be compliant in 2026.
“This was absolutely one of the top priorities for Uisce Éireann to address, from our perspective,” she said.
“We need to give Uisce Éireann credit for the work done on this but other supplies also need attention.”
Friends of the Irish Environment which made the original complaint to the European Commission, welcomed the ruling but said households were still not being informed of the full dangers.
The group said showering in water with high levels of THMs presented a risk of inhaling the chemical compounds.
It also said households using supplies with THM exceedances who were also subject to boil water notices were at extra risk because of the steam created by bringing the water to the required “vigorous, rolling boil”.