Boiling what? Controversy over boil water notices due to presence of Trihalomethanes

24th March, 2016

‘Boil water’ notices that were issued to Irish water consumers  are being met with fresh scrutiny, with fears that boiling water could increase the potency of certain harmful chemicals.  The chemicals at the centre of the controversy are Trihalomethanes (THM’s), which are toxic compounds that occur in water due to the reaction of organic chemicals, when chlorine is added as a disinfectant.  Environmental NGO ‘Friends of the Irish Environment (FIE) previously called on Irish water to inform consumers of the health risks associated with exposure to THM’s, which include the development of certain cancers, harm to the central nervous system, and miscarriage among pregnant women.

While the European Ombudsman ruled that Irish water could not be forced to provide information on THM’s to consumers, there is concern that consumers may be boiling THM infested water.  This is due to a large number of ‘boil water’ notices that were issued to consumers across the country, due to the presence of cryptosporidium in the water. One example is in Galway, where ‘boil water’ notices remain in place in the area’s of Williamstown, Loughrea, Carraroe, and Tiernee/Lettermore.

A paradoxical situation has emerged, whereby consumers may be avoiding risk of exposure to cryptosporidium by boiling their water, but may be increasing their risk of exposure to THM’s.  As FIE director Tony Lowes states:  ”Boiling water that contains high level of THM’s creates an imminent danger to public health because the volatile chemicals are released and absorbed by the skin and through inhalation at a rate 5-15 times faster than drinking the water”.

About the Author

Brian Cunningham

Brian works as Communications Assistant with the Environmental Pillar. He has a background in sociology and recently graduated from an MA in International Relations and Conflict Studies.


  1. Trihalomethanes (THM’s) in basic vernacular are the death gases from shit bugs (E. Coli etc)… the chemical poison explodes the bugs and they release the THM’s. The people nearest the water poisoning plant get more THM’s than the last house on the line… If the ‘treatment’ was fair to the people then the people would be informed about the duration of the treatment and be formally asked to not use water for a while and then to ‘dump’ thm water for a while. But that’s not how it works now is it???

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