Friends of the Irish Environment [FIE] pointed out Irish Water and the Environmental Protection Agency had already admitted high levels of trihalomethanes is piped to homes of 10% of the population.
In some cases the level of the toxin is up to three times the figure considered safe by the World Health Organisation.
FIE, making a call for more public information, said it was not happy with Irish Water’s response to the issue, after the utility said it was developing a national plan for trihalomethanes.
Trihalomethanes are compounds that occur when organic materials in water react with chlorine which is added as a disinfectant for drinking water.
“Irish Water, the EPA, and the Health and Safety Authority have tried to convince the public that it would be dangerous and irresponsible to stop chlorinating to avoid the risk of the disinfectant by-product created, the more than 60 chemicals classed as THMs, trihalomethanes,” FIE said in a statement.
FIE said that Ireland was criticised by Europe in 2002 for the levels of contamination of drinking water.
“Ireland chose to disinfect its water by the use of chlorine, in spite of the commission warning them privately that chlorine was not really suitable for Ireland because two of the biggest threats biologically and chemically to Irish water are not addressed by chlorine — cryptosporidium and THMs,” the group said.
“Consumers should not be fooled by authorities who say that dangerous disinfectant by products like THMs are inevitable if our water supplies are to be protected.
“Irish Water customers are paying the price now for the refusal of the Irish State to listen to good advice in 2002, instead taking the “cheap and easy” way out,” the group said.